Discovery Guides Areas


Freshwater Mussels: Engineering Ecosystems One Shell at a Time
(Released August 2011)

  by Natalie Abram  


Key Citations




Key Citations Short Format Full Format
  1. Assessing the toxicity of sodium chloride to the glochidia of freshwater mussels: Implications for salinization of surface waters

    Patricia L. Gillis.

    Environmental Pollution, Vol. 159, No. 6, Jun 2011, pp. 1702-1708.

    Chloride concentrations in surface waters have increased significantly, a rise attributed to road salt use. In Canada, this may be a concern for endangered freshwater mussels, many with ranges limited to southern Ontario, Canadaas most road-dense region. The acute toxicity of NaCl was determined for glochidia, the musselas larval stage. The 24h EC50s of four (including two Canadian endangered) species ranged from 113a1430mgClLa1 (reconstituted water, 100mg CaCO3 La1). To determine how mussels would respond to a chloride pulse, natural river water (hardness 278a322mg CaCO3 La1) was augmented with salt. Lampsilis fasciola glochidia were significantly less sensitive to salt in natural water (EC50s 1265a1559mg Cl La1) than in reconstituted water (EC50 285mgLa1). Chloride data from mussel habitats revealed chloride reaches levels acutely toxic to glochidia (1300mgLa1). The increased salinization of freshwater could negatively impact freshwater mussels, including numerous species at risk. Highlights ao Compared to other aquatic organisms glochidia are very sensitive to chloride. ao Glochidia were less sensitive to salt in natural water than in reconstituted water. ao Glochidia were less sensitive to salt in hard water than in soft water. ao Road salt runoff may pose a threat to the reproduction of freshwater mussels. ao Salinization of freshwater could negatively impact numerous species at risk. Freshwater mussel larvae were acutely sensitive to sodium chloride, such that chloride levels in some Canadian rivers may pose a threat to the survival of this early life stage.

  2. Coextirpation of host-affiliate relationships in rivers: the role of climate change, water withdrawal, and host-specificity

    D. Spooner, M. Xenopoulos, C. Schneider and D. Woolnough.

    Global Change Biology, Vol. 17, No. 4, Apr 2011, pp. 1720.

    The role of climate-related disturbances on complex host-affiliate relationships remains understudied, largely because affiliate species vary in host use and are often differentially susceptible to disturbance relative to their hosts. Here we report the first set of host-affiliate species-discharge relationships (SDR) in freshwater and examine how anticipated shifts in water availability (flow) will impact coextirpations. We used SDR for freshwater mussels and fish across 11 regions (over 350 rivers) in the continental United States that we coupled to future water availability (2070) to model mussel and fish coextirpations. We also used river-specific host-affiliate matrices (presence-absence) to evaluate how host-specificity (mean number of hosts used by an affiliate) and host-overlap (extent to which affiliates share hosts) relate to extirpation vulnerability. We found that the strength and predictability of SDR models vary geographically and that mussels were more susceptible to flow alterations than fish. These patterns of extirpations were strongest in the southeast where: (1) flow reductions are expected to be greatest; (2) more species are lost per unit flow; (3) and more mussels are expected to be lost per unit of fish. We also found that overall mussel losses associated with reduction in habitat (water availability) were greater than those associated with loss of fish hosts which we assumed to be a function of host redundancy. These findings highlight the utility of SDR as a tool for conservation efforts but they also demonstrate the potential severity of reductions in mussel and fish richness as consequence of climate change and water use. Mussels provide key ecosystem services but face multiple pronged attacks from reductions in flow, habitat, and fish hosts. These losses in biodiversity and ecosystem functions can translate into major effects on food webs and nutrient recycling. [PUBLICATION ABSTRACT]

  3. A DNA-barcoding approach to identifying juvenile freshwater mussels (Bivalvia:Unionidae) recovered from naturally infested fishes

    Sarah L. Boyer, Alexander A. Howe, Nathan W. Juergens and Mark C. Hove.

    Journal of the North American Benthological Society, Vol. 30, No. 1, 11 Jan 2011, pp. 182-194.

    We developed a multilocus deoxyribonucleic acid (DNA)-barcoding approach to identify newly transformed juvenile mussels collected from naturally infested fishes in a federally protected waterway that is home to a diverse mussel community, the St Croix River (Minnesota/Wisconsin, USA). We used new and publicly available data downloaded from GenBank to build reference databases for identified adult mussels. We assessed the efficacy of the mitochondrial loci cytochrome oxidase c subunit I (COI) and nicotinamide adenine dinucleotide dehydrogenase subunit 1 (ND1) for DNA barcoding. We concluded that the barcoding gap between average intra- and interspecific genetic distances is wider for ND1 than for COI, but both loci perform well for species identification in character-based phylogenetic analyses. Almost every species formed a monospecific clade with high bootstrap and posterior-probability support. We obtained newly transformed juvenile mussels by collecting individuals of 3 different fish species that were infested with unionid larvae. We held the fish in aquaria until the mussels emerged naturally. We then extracted DNA and sequenced our loci of interest. When sequences from the juveniles were included in phylogenetic analyses, they grouped with single species (or, in one case, a pair of closely related species) with high bootstrap and posterior-probability support. Identifying juveniles using morphology alone is difficult and, in some cases, impossible. Therefore, our approach will be useful to researchers interested in the relationship between unionid mussels and their fish hosts.

  4. An evaluation of the factors influencing freshwater mussel capture probability, survival, and temporary emigration in a large lowland river

    Jason R. Meador, James T. Peterson and Jason M. Wisniewski.

    Journal of the North American Benthological Society, Vol. 30, No. 2, 29 Mar 2011, pp. 507-521.

    The decline of freshwater mussels in the southeastern US emphasizes the need to evaluate the current status of mussel populations. We used the Robust Design, which is a captureaarecapture sampling design, to estimate demographic parameters (apparent survival and temporary emigration) and capture probabilities of Alasmidonta arcula, Lampsilis dolabraeformis, Lampsilis splendida, and Pyganodon gibbosa in a large lowland river in Georgia. Mussels were sampled in individual habitat units using line-transect methods at a14a146-wk intervals from summer 2006aa2007. We used an information-theoretic approach to evaluate the relative importance of maximum river discharge, habitat characteristics, mussel species, and season on temporary emigration (i.e., proportion of mussels not at the surface), apparent survival, and capture probability. The best-supported models indicated that apparent survival and capture probability varied positively with mussel shell length and among habitat types. Apparent survival (6-wk interval) ranged from 94 to 99% and was greatest in slackwater and lowest in swiftwater habitat. Capture probability ranged from 8 to 20% and was greatest in slackwater and lowest in swiftwater habitat. Temporary emigration also varied among species and season and appeared to be related to reproductive behavior, with the largest proportion of mussels occurring at the surface when mussels appeared to be reproductively active. A comparison of catch-per-unit-effort indices to population estimates suggested that the reliability of catch-per-unit-effort indices was influenced by vertical migration behavior and other factors affecting mussel capture probability.

  5. Food Habits and Fish Prey Size Selection of a Newly Colonizing Population of River Otters (Lontra canadensis) in Eastern North Dakota

    Cory R. Stearns and Thomas L. Serfass.

    American Midland Naturalist, Vol. 165, No. 1, Jan 2011, pp. 169-184.

    The food habits of river otters (Lontra canadensis) on three rivers in the Red River of the North drainage of eastern North Dakota were evaluated using an analysis of 569 scats collected between 4 Oct. 2006 and 26 Nov. 2007. Fish and crayfish were the primary prey items, occurring in 83.0% and 51.1% of scats, respectively. Other prey included insects (26.7%), birds (7.9%), amphibians (6.7%), mammals (6.0%) and freshwater mussels (0.2%). Fish of Cyprinidae (carp and minnows) were the most prominent fish in the diet, occurring in 64.7% of scats. Other relatively common fish in the diet included Ictaluridae (catfish, 17.4% frequency of occurrence), Catostomidae (suckers, 13.0%), and Centrarchidae (sunfish, 11.2%). The diet of river otters changed seasonally, including a decline in the frequency of fish in the summer diet, and a corresponding increase in the occurrence of crayfish. Consumed fish ranged from 3.5 to 71.0cm total length, with a mean of 20.7cm (se plus or minus 0.5, n = 658). Fish 10.1-20.0cm were the most frequently consumed size class (36.5% relative frequency), with the majority of other consumed fish being less than or equal to 10.0cm (24.6%), 20.1-30.0cm (14.1%), 30.1-40.0cm (14.0%), or 40.1-50.0cm (8.2%). The size of consumed fish changed seasonally, with spring having the largest mean prey size.

  6. Growth and longevity in freshwater mussels: evolutionary and conservation implications

    Wendell R. Haag and Andrew L. Rypel.

    Biological Reviews, Vol. 86, No. 1, 2011, pp. 225.

    The amount of energy allocated to growth versus other functions is a fundamental feature of an organism's life history. Constraints on energy availability result in characteristic trade-offs among life-history traits and reflect strategies by which organisms adapt to their environments. Freshwater mussels are a diverse and imperiled component of aquatic ecosystems but little is known about their growth and longevity. Generalized depictions of freshwater mussels as 'long-lived and slow-growing' may give an unrealistically narrow view of life-history diversity which is incongruent with the taxonomic diversity of the group and can result in development of inappropriate conservation strategies. We investigated relationships among growth, longevity, and size in 57 species and 146 populations of freshwater mussels using original data and literature sources. In contrast to generalized depictions, longevity spanned nearly two orders of magnitude, ranging from 4 to 190 years, and the von Bertalanffy growth constant, K, spanned a similar range (0.02-1.01). Median longevity and K differed among phylogenetic groups but groups overlapped widely in these traits. Longevity, K, and size also varied among populations; in some cases, longevity and K differed between populations by a factor of two or more. Growth differed between sexes in some species and males typically reached larger sizes than females. In addition, a population of Quadrula asperata exhibited two distinctly different growth trajectories. Most individuals in this population had a low-to-moderate value of K (0.15) and intermediate longevity (27 years) but other individuals showed extremely slow growth (K = 0.05) and reached advanced ages (72 years). Overall, longevity was related negatively to the growth rate, K, and K explained a high percentage of variation in longevity. By contrast, size and relative shell mass (g length) explained little variation in longevity. These patterns remained when data were corrected for phylogenetic relationships among species. Path analysis supported the conclusion that K was the most important factor influencing longevity both directly and indirectly through its effect on shell mass. The great variability in age and growth among and within species shows that allocation to growth is highly plastic in freshwater mussels. The strong negative relationship between growth and longevity suggests this is an important trade-off describing widely divergent life-history strategies. Although life-history strategies may be constrained somewhat by phylogeny, plasticity in growth among populations indicates that growth characteristics cannot be generalized within a species and management and conservation efforts should be based on data specific to a population of interest. (ProQuest: ... denotes formulae/symbols omitted.)

  7. Measured and modelled tritium concentrations in freshwater Barnes mussels (Elliptio complanata) exposed to an abrupt increase in ambient tritium levels

    TL Yankovich, SB Kim, F. Baumgaertner, et al.

    Journal of environmental radioactivity, Vol. 102, No. 1, Jan 2011, pp. 26-34.

    To improve understanding of environmental tritium behaviour, the International Atomic Energy Agency (IAEA) included a Tritium and C-14 Working Group (WG) in its EMRAS (Environmental Modelling for Radiation Safety) program. One scenario considered by the WG involved the prediction of time-dependent tritium concentrations in freshwater mussels that were subjected to an abrupt increase in ambient tritium levels. The experimental data used in the scenario were obtained from a study in which freshwater Barnes mussels (Elliptio complanata) were transplanted from an area with background tritium concentrations to a small Canadian Shield lake that contains elevated tritium. The mussels were then sampled over 88 days, and concentrations of free-water tritium (HTO) and organically-bound tritium (OBT) were measured in the soft tissues to follow the build-up of tritium in the mussels over time. The HTO concentration in the mussels reached steady state with the concentration in lake water within one or two hours. Most models predicted a longer time (up to a few days) to equilibrium. All models under-predicted the OBT concentration in the mussels one hour after transplantation, but over-predicted the rate of OBT formation over the next 24 h. Subsequent dynamics were not well modelled, although all participants predicted OBT concentrations that were within a factor of three of the observation at the end of the study period. The concentration at the final time point was over-predicted by all but one of the models. The relatively low observed concentration at this time was likely due to the loss of OBT by mussels during reproduction.

  8. Seasonal and species-specific patterns in abundance of freshwater mussel glochidia in stream drift

    JJacob Culp, Wendell R. Haag, DAlbrey Arrington and Thomas B. Kennedy.

    Journal of the North American Benthological Society, Vol. 30, No. 2, 15 Mar 2011, pp. 436-445.

    We examined seasonal patterns of abundance of mussel larvae (glochidia) in stream drift in a diverse, large-stream mussel assemblage in the Sipsey River, Alabama, across 1 y. We used recently developed techniques for glochidial identification combined with information about mussel fecundity and benthic assemblages to evaluate how well observed glochidial abundance corresponded to expected abundance based on glochidial production. Glochidia from short-term brooding species (Amblema plicata, Elliptio arca, Fusconaia cerina, Pleurobema decisum, Obliquaria reflexa, and Quadrula asperata) were abundant from May to August but did not occur in drift between November and the end of April. Long-term brooders (Lampsilis spp., Medionidus acutissimus, Obovaria unicolor, and Villosa spp.) occurred in several short peaks in spring, summer, and autumn, but generally were less abundant than short-term brooders. We estimated that the benthic assemblage at our study site produced >500,000 glochidia/m2 annually and production varied widely among species. Abundance of species in the drift was positively related to benthic abundance but was only weakly related to glochidial production. The poor relationship between glochidial production and abundance in the drift suggests that release and transport of glochidia are influenced by a wide variety of abiotic and biotic factors.

  9. Biodiversity Losses and Ecosystem Function in Freshwaters: Emerging Conclusions and Research Directions

    C. Vaughn.

    Bioscience, Vol. 60, No. 1, Jan 2010, pp. 25.

    Six conclusions have emerged from recent research that complicate the ability to predict how biodiversity losses may affect ecosystem function: (1) species traits determine ecosystem function, (2) species within functional groups are not always ecological equivalents, (3) biodiversity losses include declines in the abundance of common species, (4) biodiversity losses affect whole food webs, (5) the effects of biodiversity losses depend on abiotic and biotic context and spatial and temporal scales, and (6) successfully predicting linkages between biodiversity and ecosystem function requires using multiple empirical approaches across scales. Nutrient recycling by freshwater mussel communities illustrates these conclusions. Nutrient excretion rates depend on the expression of mussel species traits, which vary with flow, temperature, and community structure. Nutrient contributions from mussels depend on which mussel species are dominant, but common species of mussels are declining, leading to shifts in species dominance patterns and thus nutrient recycling. These changes are very likely affecting the rest of the benthic food web because mussel excretion stimulates primary, and subsequently secondary, production. [PUBLICATION ABSTRACT]

  10. Climate effects on inter-annual variation in growth of the freshwater mussel (Anodonta beringiana) in an Alaskan lake


    Freshwater Biology, Vol. 55, No. 11, Nov 2010, pp. 2339-2346.

    Summary1. Warming trends are evident in many parts of the globe but are especially marked at higher latitudes, with complex effects on the biota that include direct effects on growth potential and indirect effects through food webs.2. Air temperatures have been increasing over the past 50 years in southwestern Alaska, affecting the growth and population dynamics of many organisms, including a variety of aquatic species such as the freshwater mussel Anodonta beringiana.3. We collected freshwater mussels from Iliamna Lake, in the Bristol Bay region of Alaska, and measured their shells to examine climatic effects on growth patterns.4. Linear mixed effects models and ordinary least square linear regressions revealed strong positive correlations between local air temperatures (especially in May, October and the summer months) and inter-annual variation in mussel growth. Slower mussel growth was also significantly correlated with later date of ice break-up, which was linked to air temperatures in late spring.

  11. Comparative toxicity of single and combined mixtures of selected pollutants among larval stages of the native freshwater mussels (Unio elongatulus) and the invasive zebra mussel (Dreissena polymorpha)

    Melissa Faria, Miguel Angel Lopez, Maria Fernandez-Sanjuan, Silvia Lacorte and Carlos Barata.

    Science of the Total Environment, Vol. 408, No. 12, 15 May 2010, pp. 2452-2458.

    This study evaluated the impact of biocides (tributyltin, chlorthalonil and Irgarol 1051) and of pollutants (copper, inorganic and methyl mercury and 4-nonylphenol) occurring in Ebro River (NE Spain) on early developmental stages of native Spanish freshwater and invasive zebra mussels. Toxicity tests were conducted with embryos and glochidia of zebra mussel (Dreissena polymorpha) and the naiad species Unio elongatulus, respectively. Toxicity was quantified in terms of median effective concentration (EC50) impairing embryogenesis and glochidia viability in single and combined mixture exposures. Irgarol 1051 was not toxic at concentrations below 40A-103nM. Zebra mussel embryos were on average 50 fold more sensitive to the studied pollutants than glochidia. Tributyltin was the most toxic compound with EC50s for zebra mussel embryos and glochidia, respectively, of 1.24 and 47.93nM, followed by chlorothalonil (3.65, 176.58nM), methyl mercury (7.06, 156.4nM), inorganic mercury (3.64, 518.28nM), copper (19.73, 1358.55nM) and 4-nonylphenol (33.99, 1221.48nM). Combined toxicity of Ebro River pollutants (copper, inorganic and methyl mercury and 4-nonylphenol) was greater than additive in zebra mussel embryos and additive in glochidia. These results indicated that contaminant levels that affect zebra mussel embryos are not toxic to early life stages of the naiad mussel species U. elongatulus.

  12. Complex hydraulic and substrate variables limit freshwater mussel species richness and abundance

    Daniel C. Allen and Caryn C. Vaughn.

    Journal of the North American Benthological Society, Vol. 29, No. 2, 16 Feb 2010, pp. 383-394.

    We examined how substrate and complex hydraulic variables limit the distribution of freshwater mussels. We sampled mussels and measured substrate and hydraulic variables (at low and high flows) at 6 sites in the Little River, Oklahoma. To test which variables were most limiting to mussel species richness and abundance, we evaluated univariate and multiple 95th-, 90th-, and 85th-quantile regression models using a model selection approach. Across all 3 quantiles analyzed, hydraulic variables related to substrate stability (relative shear stress ratio [RSS] and shear stress) at high flows most limited mussel species richness and abundance. High-flow substrate stability models performed the best, but models that used substrate variables (substrate size and heterogeneity) also performed relatively well. Models that used complex hydraulic variables estimated at low flows performed poorly compared to those using the same variables estimated at high flows, a result suggesting that hydraulic conditions at low flows do not limit mussel habitat in our system. Our results demonstrate that substrate stability at high flows is an important factor governing mussel distributions. Last, our quantile regression approach successfully quantified the limiting-factor relationships of substrate and hydraulic characteristics on mussel habitat, and this approach could be used in other studies investigating habitat requirements of aquatic organisms.

  13. Effect of imperfect detectability on adaptive and conventional sampling: simulated sampling of freshwater mussels in the upper Mississippi River

    David R. Smith, Brian R. Gray, Teresa J. Newton and Doug Nichols.

    Environmental monitoring and assessment, Vol. 170, No. 1-4, Nov 2010, pp. 499-507.

    Adaptive sampling designs are recommended where, as is typical with freshwater mussels, the outcome of interest is rare and clustered. However, the performance of adaptive designs has not been investigated when outcomes are not only rare and clustered but also imperfectly detected. We address this combination of challenges using data simulated to mimic properties of freshwater mussels from a reach of the upper Mississippi River. Simulations were conducted under a range of sample sizes and detection probabilities. Under perfect detection, efficiency of the adaptive sampling design increased relative to the conventional design as sample size increased and as density decreased. Also, the probability of sampling occupied habitat was four times higher for adaptive than conventional sampling of the lowest density population examined. However, imperfect detection resulted in substantial biases in sample means and variances under both adaptive sampling and conventional designs. The efficiency of adaptive sampling declined with decreasing detectability. Also, the probability of encountering an occupied unit during adaptive sampling, relative to conventional sampling declined with decreasing detectability. Thus, the potential gains in the application of adaptive sampling to rare and clustered populations relative to conventional sampling are reduced when detection is imperfect. The results highlight the need to increase or estimate detection to improve performance of conventional and adaptive sampling designs.

  14. The effect of natural dissolved organic carbon on the acute toxicity of copper to larval freshwater mussels (glochidia)

    Patricia L. Gillis, James C. McGeer, Gerald L. Mackie, Michael P. Wilkie and Josef D. Ackerman.

    Environmental Toxicology and Chemistry, Vol. 29, No. 11, 1 Nov 2010, pp. 2519-2528.

    The present study examined the effect of dissolved organic carbon (DOC), both added and inherent, on Cu toxicity in glochidia, the larvae of freshwater mussels. Using incremental additions of natural DOC concentrate and reconstituted water, a series of acute copper toxicity tests were conducted. An increase in DOC from 0.7 to 4.4 mg C/L resulted in a fourfold increase (36-150 μg Cu/L) in the 24-h median effective concentration (EC50) and a significant linear relationship (r super(2) = 0.98, p = 0.0008) between the DOC concentration and the Cu EC50 of Lampsilis siliquoidea glochidia. The ameliorating effect of added DOC on Cu toxicity was confirmed using a second mussel species, the endangered (in Canada) Lampsilis fasciola. The effect of inherent (i.e., not added) DOC on Cu toxicity was also assessed in eight natural waters (DOC 5-15 mg C/L). These experiments revealed a significant relationship between the EC50 and the concentration of inherent DOC (r super(2) = 0.79, p = 0.0031) with EC50s ranging from 27 to 111 μg Cu/L. These laboratory tests have demonstrated that DOC provides glochidia with significant protection from acute Cu toxicity. The potential risk that Cu poses to mussel populations was assessed by comparing Cu and DOC concentrations from significant mussel habitats in Ontario to the EC50s. Although overall mean Cu concentration in the mussel's habitat was well below the acutely toxic level given the concentration of DOC, episodic Cu releases in low DOC waters may be a concern for the recovery of endangered freshwater mussels. The results are examined in the context of current Cu water quality regulations including the U.S. Environmental Protection Agency's (U.S. EPA) biotic ligand model.

  15. Effects of nitrate nitrogen pollution on Central European unionid bivalves revealed by distributional data and acute toxicity testing

    Karel Douda.

    Aquatic Conservation: Marine and Freshwater Ecosystems, Vol. 20, No. 2, Mar-Apr 2010, pp. 189-197.

    1. Studies from Central Europe have shown a relationship between the impaired population status of threatened freshwater mussel species and elevated nitrate nitrogen (N-NO) concentrations in running waters. 2. Causal mechanisms, however, remain unknown, and no experimental data or comprehensive studies involving more species are available, which causes uncertainty in prioritizing conservation actions. 3. This study uses both descriptive and experimental approaches to identify the effects of nitrates on freshwater mussels and demonstrates the need for integrating different research methods for development of conservation strategies for threatened species. 4. Spatial co-occurrence of five native freshwater mussel species (Anodonta anatina, Pseudanodonta complanata, Unio pictorum, Unio tumidus, Unio crassus) and N-NO concentrations were examined in a 7th-order river catchment (Lunice River, Czech Republic) with anthropogenically-induced increasing N-NO levels and declining populations of these species during the 20th century. 5. Acute toxicity of N-NO was then estimated for artificially reared juveniles of A. anatina and U. crassus using both lethal and sublethal test endpoints. 6. Results showed that the probability of occurrence of all species was significantly reduced in reaches with elevated N-NO levels. 7. In contrast, the results of toxicity testing revealed that the juvenile stages of the two tested species were less sensitive to N-NO than most previously tested freshwater macroinvertebrates. The detected 96-h median lethal N-NO concentrations were two orders of magnitude higher than the limits derived from distributional data. 8. Despite the probable absence of a direct negative effect of N-NO on freshwater mussel populations, N-NO has potential to be used as an effective indicator of biotope conditions. Identification of causal mechanisms responsible for the observed relationship between unionids and N-NO will require further research.

  16. An evaluation of the influence of substrate on the response of juvenile freshwater mussels (fatmucket, Lampsilis siliquoidea) in acute water exposures to ammonia

    Jingjing Miao, MChristopher Barnhart, Eric L. Brunson, Douglas K. Hardesty, Christopher G. Ingersoll and Ning Wang.

    Environmental Toxicology and Chemistry, Vol. 29, No. 9, 1 Sep 2010, pp. 2112-2116.

    Acute 96-h ammonia toxicity to three-month-old juvenile mussels (Lampsilis siliquoidea) was evaluated in four treatments (water-only, water-only with feeding, water and soil, and water and sand) using an exposure unit designed to maintain consistent pH and ammonia concentrations in overlying water and in pore water surrounding the substrates. Median effect concentrations (EC50s) for total ammonia nitrogen in the four treatments ranged from 5.6 to 7.7 mg/L and median lethal concentrations (LC50s) ranged from 7.0 to 11 mg/L at a mean pH of 8.4. Similar EC50s or LC50s with overlapping 95% confidence intervals among treatments indicated no influence of substrate on the response of mussels in acute exposures to ammonia.

  17. Mussel Remains from Prehistoric Salt Works, Clarke County, Alabama

    Stuart W. McGregor and Ashley A. Dumas.

    Southeastern Naturalist, Vol. 9, No. 1, Mar 2010, pp. 105-118.

    Archaeological research at salt springs in Clarke County, AL (Tombigbee River drainage), documented bivalve mollusk exploitation by late prehistoric American Indians. A total of 582 valves representing 19 species of freshwater mussels (Unionidae) and an estuarine clam (Mactridae) from the Lower Salt Works Site (ca. A.D. 900-1550) and 41 valve fragments representing 6 mussel species from the Stimpson Site (ca. A.D. 1200-1550) were documented. The Lower Salt Works fauna was dominated numerically by Fusconaia ebena and Quadrula asperata, the dominant species reported during recent local surveys. The mussel species represented are known from medium to large streams in sand and gravel habitats and include four federally protected species and other species of conservation concern in Alabama. Results offer comparative data for other archaeological and ecological studies in the region.

  18. Native Dreissena freshwater mussels in the Balkans: in and out of ancient lakes

    T. Wilke, R. Schultheiss, C. Albrecht, N. Bornmann, S. Trajanovski and T. Kevrekidis.

    Biogeosciences, Vol. 7, No. 10, 11 Oct 2010, pp. 3051-3065.

    The Balkans is a biogeographically highly diverse region and a worldwide hotspot of endemic freshwater diversity. A substantial part of this diversity is attributed to well recognized and potential ancient lakes in its southwestern part. However, despite considerable research efforts, faunal relationships among those lakes are not well understood. Therefore, genetic information from native representatives of the mussel genus Dreissena is here used to test the biogeographical zonation of the southwestern Balkans, to relate demographic changes to environmental changes, to assess the degree of eco-insularity, to reconstruct their evolutionary history, and to explore the potential of native taxa for becoming invasive. Phylogeographical and population genetic analyses indicate that most studied populations belong to two native species: D. presbensis (including the distinct genetic subgroup from Lake Ohrid, "D. stankovici") and D. blanci. In addition, the first confirmed record of invasive D. polymorpha in the southwestern Balkan is presented. The distribution of native Dreissena spp. generally coincides with the biogeographical zonations previously suggested based on fish data. However, there is disagreement on the assignment of the ancient lakes in the area to respective biogeographical regions. The data for Lake Ohrid are not conclusive. A closer biogeographical connection to lakes of the Vardar region and possibly the northern Ionian region is, however, suggested for Lake Prespa. The reconstruction of the evolutionary history of Dreissena spp. suggests that populations underwent demographic and spatial expansions in the recent past. Expansions started around 320 000-300 000 years ago in "D. stankovici", 160 000-140 000 years ago in D. blanci, and 110 000-70 000 years ago in D. presbensis. These time frames are discussed within the context of available paleogeological data for lakes Ohrid and Prespa. It is suggested that regional environmental changes may have had pronounced effects on the population histories of native Dreissena spp., though the high buffer capacity of Lake Ohrid may have lessened these effects in " D. stankovici". In addition, local events influencing individual lakes had very likely considerable effects on the demographic histories of Dreissena spp. as well. The observed patterns of immigration and emigration in and out of ancient lakes may suggest that limited gene flow enabled the survival of few isolated subpopulations and that later on eco-insularity (selective advantages of locally adopted groups) may have prevented excessive hybridization and sympatry of closely related taxa. As for the potential invasiveness of native Dreissena spp., the inferred spatial expansions are not human-mediated and all taxa still appear to be restricted to their native ranges. A concern, however, is that today D. presbensis and D. blanci also occur in artificial water bodies, and that invasive D. polymorpha has reached the area.

  19. Neurochemical effects of benzodiazepine and morphine on freshwater mussels

    F. Gagne, C. Andre and M. Gelinas.

    Comparative Biochemistry and Physiology, Part C: Toxicology & Pharmacology, Vol. 152, No. 2, Aug 2010, pp. 207-214.

    The purpose of this study was to examine the neurochemical effects of morphine, diazepam, a common benzodiazepine, and an effluent concentrate on the endemic freshwater mussel Elliptio complanata. Mussels were exposed to the drugs and to the solid-phase concentrate of a municipal effluent and left to stand at 15 degree C for 48 h. Neurochemical effects were determined by monitoring changes in dopamine, serotonin, glutamate and gamma-aminobutyric acid (GABA) levels in the visceral mass (containing the nerve ganglia) of mussels. The activities of acetylcholinesterase (AChE), dopamine and serotonin-dependent adenylyl cyclase (ADC) were also determined in the mussels. Oxidative stress was determined by tracking changes in lipid peroxidation (LPO) in the mitochondrial and post-mitochondrial fractions. The results revealed that the drugs and the effluent extract were biologically active in mussels. Morphine reduced serotonin and increased dopamine in mussel tissues while reducing AChE activity and increasing GABA levels. This suggests the induction of a relaxation state in mussels. Diazepam also reduced serotonin levels but produced no change in dopamine levels. However, dopamine-sensitive ADC activity was readily activated, indicating the potential effect on opiate signaling. Diazepam increased glutamate levels slightly, but AChE remained stable. The increase in both dopamine ADC activity and glutamate concentrations was also associated with greater oxidative stress on the mitochondrial and post-mitochondrial fractions in cells. A comparison of the global response pattern of these drugs with those of the effluent extract revealed only a relative proximity to morphine. In conclusion, the data warrant more studies on the analysis of opiates and benzodiazepines in municipal effluents to better address the potential environmental hazard of these neuroactive drug classes to aquatic organisms.

  20. Phenotypic plasticity and genetic isolation-by-distance in the freshwater mussel Unio pictorum (Mollusca: Unionoida)

    A. Zieritz, JI Hoffman, W. Amos and DC Aldridge.

    Evolutionary Ecology, Vol. 24, No. 4, Jul 2010, pp. 923-938.

    Freshwater mussels (Unionoida) show high intraspecific morphological variability, and some shell morphological traits are believed to be associated with habitat conditions. It is not known whether and which of these ecophenotypic differences reflect underlying genetic differentiation or are the result of phenotypic plasticity. Using 103 amplified fragment length polymorphism (AFLP) markers, we studied population genetics of three paired Unio pictorum populations sampled from two different habitat types (marina and river) along the River Thames. We found genetic differences along the Thames which were consistent with a pattern of isolation by distance and probably reflect limited dispersal via host fish species upon which unionoid larvae are obligate parasites. No consistent genetic differences were found between the two different habitat types suggesting that morphological differences in the degree of shell elongation and the shape of dorso-posterior margin are caused by phenotypic plasticity. Our study provides the first good evidence for phenotypic plasticity of shell shape in a European unionoid and illustrates the need to include genetic data in order properly to interpret geographic patterns of morphological variation.

  21. Priority Wetland Invertebrates as Conservation Surrogates

    S. Ormerod, I. Durance, A. Terrier and A. Swanson.

    Conservation Biology, Vol. 24, No. 2, Apr 2010, pp. 573.

    Invertebrates are important functionally in most ecosystems, but seldom appraised as surrogate indicators of biological diversity. Priority species might be good candidates; thus, here we evaluated whether three freshwater invertebrates listed in the U.K. Biodiversity Action Plan indicated the richness, composition, and conservation importance of associated wetland organisms as defined respectively by their alpha diversity, beta diversity, and threat status. Sites occupied by each of the gastropods Segmentina nitida, Anisus vorticulus, and Valvata macrostoma had greater species richness of gastropods and greater conservation importance than other sites. Each also characterized species assemblages associated with significant variations between locations in alpha or beta diversity among other mollusks and aquatic macrophytes. Because of their distinct resource requirements, conserving the three priority species extended the range of wetland types under management for nature conservation by 18% and the associated gastropod niche-space by around 33%. Although nonpriority species indicated variations in richness, composition, and conservation importance among other organisms as effectively as priority species, none characterized such a wide range of high-quality wetland types. We conclude that priority invertebrates are no more effective than nonpriority species as indicators of alpha and beta diversity or conservation importance among associated organisms. Nevertheless, conserving priority species can extend the array of distinct environments that are protected for their specialized biodiversity and environmental quality. We suggest that this is a key role for priority species and conservation surrogates more generally, and, on our evidence, can best be delivered through multiple species with contrasting habitat requirements. [PUBLICATION ABSTRACT]

  22. Sensitivity of early life stages of freshwater mussels (Unionidae) to acute and chronic toxicity of lead, cadmium, and zinc in water

    Ning Wang, Christopher G. Ingersoll, Christopher D. Ivey, et al.

    Environmental Toxicology and Chemistry, Vol. 29, No. 9, 1 Sep 2010, pp. 2053-2063.

    Toxicity of lead, cadmium, or zinc to early life stages of freshwater mussels (fatmucket, Lampsilis siliquoidea; Neosho mucket, L. rafinesqueana) was evaluated in 48-h exposures with mussel larvae (glochidia), in 96-h exposures with newly transformed (5-d-old) and two- or six-month-old juvenile mussels, or in 28-d exposures with two- or four-month-old mussels in reconstituted soft water. The 24-h median effect concentrations (EC50s) for fatmucket glochidia (>299 μg Pb/L, >227 μg Cd/L, 2,685 μg Zn/L) and 96-h EC50s for two- or six-month-old fatmucket (>426 μg Pb/L, 199 μg Cd/L, 1,700 μg Zn/L) were much higher than 96-h EC50s for newly transformed fatmucket (142 and 298 μg Pb/L, 16 μg Cd/L, 151 and 175 μg Zn/L) and Neosho mucket (188 μg Pb/L, 20 μg Cd/L, 145 μg Zn/L). Chronic values for fatmucket were 10 μg Pb/L, 6.0 μg Cd/L, and 63 and 68 μg Zn/L. When mussel data from the present study and the literature were included in updated databases for deriving U.S. Environmental Protection Agency water quality criteria, mussel genus mean acute values were in the lower percentiles of the sensitivity distribution of all freshwater species for Pb (the 26th percentile), Cd (the 15th to 29th percentile), or Zn (the 12th to 21st percentile). The mussel (Lampsilis) genus mean chronic value was the lowest value ever reported for Pb (the 9th percentile) but was near the middle of the sensitivity distribution for Cd (the 61st percentile) or Zn (the 44th percentile). These results indicate that mussels were relatively sensitive to the acute toxicity of these three metals and to the chronic toxicity of Pb, but were moderately sensitive to the chronic toxicity of Cd or Zn compared to other freshwater species.

  23. Spatial Variability in Growth-Increment Chronologies of Long-Lived Freshwater Mussels: Implications for Climate Impacts and Reconstructions

    Bryan A. Black, Jason B. Dunham, Brett W. Blundon, Mark F. Raggon and Daniela Zima.

    Ecoscience, Vol. 17, No. 3, Sep 2010, pp. 240-250.

    Estimates of historical variability in river ecosystems are often lacking, but long-lived freshwater mussels could provide unique opportunities to understand past conditions in these environments. We applied dendrochronology techniques to quantify historical variability in growth-increment widths in valves (shells) of western pearlshell freshwater mussels (Margaritifera falcata). A total of 3 growth-increment chronologies, spanning 19 to 26 y in length, were developed. Growth was highly synchronous among individuals within each site, and to a lesser extent, chronologies were synchronous among sites. All 3 chronologies negatively related to instrumental records of stream discharge, while correlations with measures of water temperature were consistently positive but weaker. A reconstruction of stream discharge was performed using linear regressions based on a mussel growth chronology and the regional Palmer Drought Severity Index (PDSI). Models based on mussel growth and PDSI yielded similar coefficients of prediction (R2Pred) of 0.73 and 0.77, respectively, for predicting out-ofsample observations. From an ecological perspective, we found that mussel chronologies provided a rich source of information for understanding climate impacts. Responses of mussels to changes in climate and stream ecosystems can be very site- and process-specific, underscoring the complex nature of biotic responses to climate change and the need to understand both regional and local processes in projecting climate impacts on freshwater species.

  24. Urbanization and a threatened freshwater mussel: evidence from landscape scale studies

    Kenneth M. Brown, Gerald George and Wesley Daniel.

    Hydrobiologia, Vol. 655, No. 1, 2010, pp. 189-196.

    The inflated heelsplitter, Potamilus inflatus, a federally listed freshwater bivalve, has been eradicated from northern portions of its range in the Amite River in Louisiana, USA. We hypothesized that the remaining populations of Potamilus inflatus in the southern part of the Amite River are being affected by increased urbanization of the watershed caused by growth of the surrounding Baton Rouge metropolitan area. Comparison of catch per unit effort in 2007 with a study conducted in 1994 indicated a significant drop in CPUE from 1.76 heelsplitters per site to 0.87. The size distribution of heelsplitters also had decreased in mean shell length from 116 to 97 mm, owing either to dislodgement of larger individuals in spates, or die-offs of larger males. Logistic regression suggested that site variables like substrate type and current velocity were not as important as landscape scale variables in predicting heelsplitter presence at a site. Heelsplitter presence was positively related to the amount of wetland riparian forest, and negatively related to the amount of residential development at the reach (1 km upstream) scale. Our results are significant because we show (1) that statistical models of GIS-based land use can predict the distribution of threatened mussel species, and that (2) conservation of endangered freshwater mussels will require more emphasis on the integrity of the riparian corridor.[PUBLICATION ABSTRACT]

  25. What a difference a species makes: a meta-analysis of dreissenid mussel impacts on freshwater ecosystems

    S. Higgins and M. Vander Zanden.

    Ecological Monographs, Vol. 80, No. 2, May 2010, pp. 179.

    We performed a meta-analysis of published studies and long-term monitoring data sets to evaluate the effects of dreissenid mussels (Dreissena polymorpha and D. rostriformis bugensis), two of the world's most problematic biological invaders, on the biogeochemistry, flora, and fauna of lakes and rivers across North America and Eurasia. Dreissenid effects were structured along two distinct energy pathways. For the pelagic-profundal pathway, large mean reductions in phytoplankton (-35% to -78%) and zooplankton (-40% to -77%) biomass occurred and were dependent on habitat type. The largest effects were found in rivers, followed by littoral and pelagic habitats in lakes. In contrast, benthic energy pathways within littoral habitats of lakes and rivers showed dramatic increases in mean benthic algal and macrophyte biomass (+170% to +180%), sediment-associated bacteria (about +2000%), non-dreissenid zoobenthic biomass (+160% to +210%), and total zoobenthic biomass, which includes dreissenid mussel soft tissues (+2000%). Our study quantifies the remarkable ability of these invasive mussels to shift aquatic food webs and energy flow from pelagic-profundal to benthic-littoral energy pathways, and it provides a basis for forecasting their impacts in diverse freshwater ecosystems. Our meta-analysis approach was a powerful tool for moving beyond the idiosyncrasies of individual case studies and may be equally powerful for assessing impacts of other biological invaders. [PUBLICATION ABSTRACT]

  26. Biodynamics, Subcellular Partitioning, and Ultrastructural Effects of Organic Selenium in a Freshwater Bivalve

    C. Adam-Guillermin, E. Fournier, M. Floriani, V. Camilleri, J. Massabuau and J. Garnier-Laplace.

    Environmental science & technology, Vol. 43, No. 6, Mar 15 2009, pp. 2112.

    Selenium is a trace element characterized by concentrations that narrowly range between being essential and being toxic. Even though inorganic selenite and selenate are the predominant chemical forms of Se in surface waters, the toxicity of Se to aquatic organisms is mostly governed by the bioavailability of organic selenium within food webs. The present study was designed to evaluate organic selenium bioaccumulation and toxicity patterns in the freshwater sentinel species Corbicula fluminea. Waterborne selenomethionine (SeMet) exposure was used to mimic dietary organo-Se uptake. Our results demonstrate that SeMet is accumulated to a relatively high extent with a concentration factor of 770 (wet weight basis). Higher uptake than depuration rates suggest that bivalves deal with high Se amounts using a strategy of detoxification based on Se sequestration that could involve granules, as shown by a strong increase of Se in the particulate subcellular fraction. Selenium is persistent in the cytosol of bivalves exposed to SeMet where it is found in proteins of a wide range of molecular mass, indicating a possible replacement of methionine by selenomethionine. A subsequent alteration of protein function might be one of the mechanisms of Se toxicity that could explain the histopathological effects we observed in gills by using transmission electronic microscopy. Those analyses showed changes in gill filament ultrastructure and suggested mitochondria as the first target for SeMet cytotoxicity, with alterations of the outer membrane and of cristae morphology. Organo-Se would thus not only be toxic via indirect mechanisms of maternal transfer as it was suggested for fish but also directly. Our results on Se distribution agree with studies that used dietary Se transfer, and highlight the relevance (and less expensive way) of using SeMet water-only exposure protocols to mimic the real environment. [PUBLICATION ABSTRACT]

  27. Developing Predictive Models for Freshwater Mussels (Mollusca: Unionidae) in the Appalachians: Limitations and Directions for Future Research

    Alison Mynsberge, Michael Strager, Jacquelyn Strager and Patricia Mazik.

    Ecoscience, Vol. 16, No. 3, 2009, pp. 387-398.

    Eastern North America contains the greatest diversity of freshwater mussels in the world. Additional information on threats and on habitat requirements and distributions of freshwater mussels is necessary to preserve diverse freshwater mussel communities, as many species are in decline. Models of freshwater mussels can predict species distributions by determining natural and anthropogenic environmental factors within the watershed, riparian area, or upstream that may influence occurrences. Subwatershed-based models developed for Elliptio complanata and E. dilatata in the Mid-Atlantic and Ohio drainage regions of the United States using existing survey data performed well on training datasets but did not accurately predict independent species occurrences. Additional studies are necessary to evaluate the quality of existing data, the utility of subwatershed-based models, and the feasibility of modelling freshwater mussel distributions across large extents.

  28. Evaluation of Acute Copper Toxicity to Juvenile Freshwater Mussels (Fatmucket, Lampsilis Siliquoidea) in Natural and Reconstituted Waters

    N. Wang, C. Mebane, J. Kunz, et al.

    Environmental Toxicology and Chemistry, Vol. 28, No. 11, Nov 2009, pp. 2367.

    The influence of dissolved organic carbon (DOC) and water composition on the toxicity of copper to juvenile freshwater mussels (fatmucket, Lampsilis siliquoidea) were evaluated in natural and reconstituted waters. Acute 96-h copper toxicity tests were conducted at four nominal DOC concentrations (0, 2.5, 5, and 10 mg/L as carbon [C]) in dilutions of natural waters and in American Society for Testing and Materials (ASTM) reconstituted hard water. Toxicity tests also were conducted in ASTM soft, moderately hard, hard, and very hard reconstituted waters (nominal hardness 45-300 mg/L as CaCO^sub 3^). Three natural surface waters (9.5-11 mg/L DOC) were diluted to obtain a series of DOC concentrations with diluted well water, and an extract of natural organic matter and commercial humic acid was mixed with ASTM hard water to prepare a series of DOC concentrations for toxicity testing. Median effective concentrations (EC50s) for dissolved copper varied >40-fold (9.9 to >396 μg Cu/L) over all 21 treatments in various DOC waters. Within a particular type of DOC water, EC50s increased 5- to 12-fold across DOC concentrations of 0.3 to up to 11 mg C/L. However, EC50s increased by only a factor of 1.4 (21-30 μg Cu/L) in the four ASTM waters with wide range of water hardness (52300 mg CaCO^sub 3^/L). Predictions from the biotic ligand model (BLM) for copper explained nearly 90% of the variability in EC50s. Nearly 70% of BLM-normalized EC50s for fatmucket tested in natural waters were below the final acute value used to derive the U.S. Environmental Protection Agency acute water quality criterion for copper, indicating that the criterion might not be protective of fatmucket and perhaps other mussel species. [PUBLICATION ABSTRACT]

  29. Extreme longevity in freshwater mussels revisited: sources of bias in age estimates derived from mark-recapture experiments

    Wendell Haag.

    Freshwater Biology, Vol. 54, No. 7, 2009, pp. 1474-1486.

    Summary1. There may be bias associated with mark-recapture experiments used to estimate age and growth of freshwater mussels. Using subsets of a mark-recapture dataset for Quadrula pustulosa, I examined how age and growth parameter estimates are affected by (i) the range and skew of the data and (ii) growth reduction due to handling. I compared predictions from von Bertalanffy growth models based on mark-recapture data with direct observation of mussel age and growth inferred from validated shell rings.2. Growth models based on a dataset that included observations from a wide range of length classes (spanning greater than or equal to the upper 50% of the population length range) produced only slightly biased age estimates for small and medium-sized individuals (overestimated by 1-2 years relative to estimates from validated shell rings) but estimates became increasingly biased for larger individuals. Growth models using data that included only observations of larger animals (< the upper 50% of length range) overestimated age for all length classes, and estimated maximum age was two to six times greater than the maximum age observed in the population (47 years). Similarly, growth models using a left-skewed dataset overestimated age.3. Reductions of growth due to repeated handling also resulted in overestimates of age. The estimated age of mussels that were handled in two consecutive years was as much as twice that of mussels that were handled only once over the same period. Assuming a constant reduction in the annual rate of growth, handling an individual for five consecutive years could result in an estimated age that is five times too high.4. These findings show that mark-recapture methods have serious limitations for estimating mussel age and growth. A previous paper (Freshwater Biology, 46, 2001, 1349) presented longevity estimates for three mussel species that were an order of magnitude higher than estimates inferred from shell rings. Because those estimates of extreme longevity were based on mark-recapture methods and subject to multiple, additive sources of bias, they cannot be considered accurate representations of life span and cannot be used to conclude that traditional methods of bivalve ageing by interpretation of shell rings are flawed.

  30. Infectious Diseases of Freshwater Mussels and Other Freshwater Bivalve Mollusks

    J. Grizzle and C. Brunner.

    Reviews in Fisheries Science, Vol. 17, No. 4, 2009, pp. 425.

    Numerous species of freshwater mussels (order Unionoida) are imperiled in the wild, and unionoids and other freshwater bivalves are important components of many ecosystems. Freshwater mussels also are propagated in captivity for production of pearls and enhancement of wild populations. However, infectious diseases of these mollusks have received relatively little attention. Unionidae is the most diverse family of freshwater bivalves, and most of the information available for this review is about species in this family. Eukaryotic organisms, especially trematodes, mites, and Conchophthirus spp. (Ciliata) are common inhabitants of unionids, and some have the potential to decrease the fitness of the host unionid. Several species of potentially pathogenic bacteria have been isolated from freshwater bivalves, but their role in diseases of bivalves has not been established. Evidence for viral diseases has been found in only one species of freshwater bivalve, a Chinese pearl mussel, Hyriopsis cumingii. The potential for some pathogens to cause greater harm to freshwater bivalves during periods of suboptimal conditions has not been evaluated adequately. Additional research is also needed to determine whether other types of pathogens are present in freshwater bivalves. [PUBLICATION ABSTRACT]

  31. Mussel Shell Evaluation as Bioindicator For Heavy Metals

    Avacir Casanova Andrello, Fabio Lopes and Tiago Dutra Gavao.

    Proceedings of the 32nd Workshop, Vol. 1245, No. , Sep 11 2009, pp. 110-113.

    Recently, in Brazil, it has appeared a new and unusual 'plague' in lazer and commercial fishing. It is caused by the parasitic larval phase of certain native bivalve mollusks of fresh water known as 'Naiades' and its involves the presence of big bivalve of fresh water, mainly Anodontites trapesialis, in the tanks and dams of the fish creation. These bivalve mollusks belong to the Unionoida Order, Mycetopodidae Family. The objective of the present work was to analyze the shells of these mollusks to verify the possibility of use as bioindicators for heavy metals in freshwater. The mollusks shells were collected in a commercial fishing at Londrina-PR. A qualitative analysis was made to determine the chemical composition of the shells and verify a possible correlation with existent heavy metals in the aquatic environment. In the inner part of the shells were identified the elements Ca, P, Fe, Mn and Sr and in the outer part were identified Ca, P, Fe, Mn, Sr and Cu. The Ca ratio of the outer part by inner part of the analyzed shells is around of 1, as expected, because Ca is the main compound of mollusks shells. The ratio of P, Fe, Mn, and Sr to the Ca were constant in all analyzed shells, being close to 0.015. The ratio Cu/Ca varied among the shells, showing that this mollusk is sensitive to concentration of this element in the aquatic environment.

  32. Non-indigenous invasive bivalves as ecosystem engineers

    Ronaldo Sousa, Jorge L. Gutiérrez and David C. Aldridge.

    Biological Invasions, Vol. 11, No. 10, 2009, pp. 2367-2385.

    Several non-indigenous bivalve species have been colonising aquatic ecosystems worldwide, in some cases with great ecological and economic impacts. In this paper, we focus on the ecosystem engineering attributes of non-indigenous invasive bivalves (i.e., the capacities of these organisms to directly or indirectly affect the availability of resources to other species by physically modifying the environment). By reviewing the ecology of several invasive bivalves we identify a variety of mechanisms via which they modify, maintain and/or create habitats. Given the usually high densities and broad spatial distributions of such bivalves, their engineering activities can significantly alter ecosystem structure and functioning (e.g., changes in sediment chemistry, grain size, and organic matter content via bioturbation, increased light penetration into the water column due to filter feeding, changes in near bed flows and shear stress due to the presence of shells, provision of colonisable substrate and refuges by shells). In addition, changes in ecosystem structure and functioning due to engineering by invasive bivalves often have very large economic impacts. Given the worldwide spread of non-indigenous bivalves and the varied ways in which they physically modify habitats, their engineering effects should receive more serious consideration in restoration and management initiatives. [PUBLICATION ABSTRACT]

  33. Not Knowing, Not Recording, Not Listing: Numerous Unnoticed Mollusk Extinctions

    C. Régnier, B. Fontaine and P. Bouchet.

    Conservation Biology, Vol. 23, No. 5, Oct 2009, pp. 1214.

    Mollusks are the group most affected by extinction according to the 2007 International Union for Conservation of Nature (IUCN) Red List, despite the group having not been evaluated since 2000 and the quality of information for invertebrates being far lower than for vertebrates. Altogether 302 species and 11 subspecies are listed as extinct on the IUCN Red List. We reevaluated mollusk species listed as extinct through bibliographic research and consultation with experts. We found that the number of known mollusk extinctions is almost double that of the IUCN Red List. Marine habitats seem to have experienced few extinctions, which suggests that marine species may be less extinction prone than terrestrial and freshwater species. Some geographic and ecologic biases appeared. For instance, the majority of extinctions in freshwater occurred in the United States. More than 70% of known mollusk extinctions took place on oceanic islands, and a one-third of these extinctions may have been caused precipitously by introduction of the predatory snail Euglandina rosea. We suggest that assessment of the conservation status of invertebrate species is neglected in the IUCN Red List and not managed in the same way as for vertebrate species. [PUBLICATION ABSTRACT]

  34. Predicting Dietborne Metal Toxicity from Metal Influxes

    M. Croteau and S. Luoma.

    Environmental science & technology, Vol. 43, No. 13, Jul 1 2009, pp. 4915.

    Dietborne metal uptake prevails for many species in nature. However, the links between dietary metal exposure and toxicity are not well understood. Sources of uncertainty include the lack of suitable tracers to quantify exposure for metals such as copper, the difficulty to assess dietary processes such as food ingestion rate, and the complexity to link metal bioaccumulation and effects. We characterized dietborne copper, nickel, and cadmium influxes in a freshwater gastropod exposed to diatoms labeled with enriched stable metal isotopes. Metal influxes in Lymnaea stagnalis correlated linearly with dietborne metal concentrations over a range encompassing most environmental exposures. Dietary Cd and Ni uptake rate constants (k...) were, respectively, 3.3 and 2.3 times higher than that for Cu. Detoxification rate constants (k...) were similar among metals and appeared 100 times higher than efflux rate constants (k...). Extremely high Cu concentrations reduced feeding rates, causing the relationship between exposure and influx to deviate from linearity; i.e., Cu uptake rates leveled off between 1500 and 1800 nmol g... day.... L. stagnalis rapidly takes up Cu, Cd, and Ni from food but detoxifies the accumulated metals, instead of reducing uptake or intensifying excretion. Above a threshold uptake rate, however, the detoxification capabilities of L. stagnalis are overwhelmed. (ProQuest: ... denotes formulae/symbols omitted.)

  35. Species richness and temperature influence mussel biomass: a partitioning approach applied to natural communities

    D. Spooner and C. Vaughn.

    Ecology, Vol. 90, No. 3, Mar 2009, pp. 781.

    To increase the generality of biodiversity-ecosystem function theory, studies must be expanded to include real communities in a variety of systems. We modified J. W. Fox's approach to partition the influence of species richness on standing crop biomass (net biodiversity effect) of 21 freshwater mussel communities into trait-independent complementarity, trait-dependent complementarity (species with particular traits dominate without impacting other species), and dominance effects (species with particular traits dominate at the expense of others). Overall, species-rich mussel communities have greater biomass than predicted based on average biomass across the region. This effect is largely due to trait-independent complementarity with less abundant species having higher body condition and reduced metabolic rates in species-rich communities. These measures are positively correlated with spatial and temporal thermal variation, suggesting that use of thermal niches as habitat may be important to species coexistence and performance, and emphasizing that knowledge of species traits and environmental context are important to understanding biodiversity-ecosystem function dynamics. [PUBLICATION ABSTRACT]

  36. Genetic and environmental implications of reintroducing laboratory-raised unionid mussels to the wild

    E. Hoftyzer, J. Ackerman, T. Morris and G. Mackie.

    Canadian Journal of Fisheries and Aquatic Sciences, Vol. 65, No. 6, Jun 2008, pp. 1217.

    The reintroduction of endangered species is a potentially useful conservation strategy, which in the case of freshwater unionid mussels, must be preceded by the successful laboratory rearing of juvenile mussels on their host fishes. However, an understanding of the genetic and environmental implications of reintroductions of artificially propagated mussels is required. Unfortunately, there is a dearth of information on these issues with respect to freshwater mussels. In general, regarding the genetic effects of reintroductions, small founder populations may lead to low heterozygosity (reduced genetic variability) in the reintroduced populations, which can make them more susceptible to extinction. Captive breeding programs may also alter the genetic composition of species through artificial selection, whether intentional or unintentional. Captive breeding may also affect an individual's interactions with conspecifics or predators by altering behaviour. Genetic problems in reintroduced populations also have the potential to affect wild populations, particularly by reducing variability among populations of the same species and eliminating local adaptation. There is also the possibility that diseases, parasites, or exotic species may be spread when populations are relocated or augmented. Recommendations related to the minimization of these impacts are presented for freshwater mussels, with the recognition that many of the issues will require additional study. [PUBLICATION ABSTRACT]

  37. Models and model selection uncertainty in estimating growth rates of endangered freshwater mussel populations

    Y. Jiao, R. Neves and J. Jones.

    Canadian Journal of Fisheries and Aquatic Sciences, Vol. 65, No. 11, Nov 2008, pp. 2389.

    Appropriate inference of population status for endangered species is extremely important. Using a single model for estimating population growth rates is typically inadequate for assessing endangered species because inferences based on only one "best" model ignore model uncertainty. In this study, the endangered dromedary pearlymussel (Dromus dromas) in the Clinch and Powell rivers of eastern Tennessee, USA, was used as an example to demonstrate the importance of multiple models, with consideration of environmental noises for evaluating population growth. Our results showed that more than one model deserves consideration in making inferences of population growth rate. A Bayesian model averaging approach was used to make inferences by weighting each model using the deviance information criterion. To test the uncertainty resulting from model selection and the efficiency of the Bayesian averaging approach, a simulation study was conducted on the dromedary pearlymussel populations, which showed that model selection uncertainty is very high. The results of these tests lead us to recommend using Bayesian model averaging to assess population growth status for endangered species, by balancing goodness-of-fit and selection uncertainty among alternate models. [PUBLICATION ABSTRACT]

  38. Population genetics and phylogeography of freshwater mussels in North America, Elliptio dilatata and Actinonaias ligamentina (Bivalvia: Unionidae)

    C. Elderkin, A. Christian, J. Metcalfe-Smith and D. Berg.

    Molecular ecology, Vol. 17, No. 9, May 2008, pp. 2149.

    Extrinsic and intrinsic forces combined shape the population structure of every species differently. Freshwater mussels are obligate parasites to a host fish during a juvenile stage (glochidia). Elliptio dilatata (ED) and Actinonaias ligamentina (AL) are co-occurring freshwater mussel taxa with similar North American distribution and share some potential host fish. Using mitochondrial DNA, we determined the genotypes of 190 + individuals from collection sites in at least two tributaries in the Lake Erie and Ohio River watersheds, along with the Ouachita and Strawberry rivers in the southeast. Both species had followed a stepping-stone model of dispersal, with greater pairwise genetic structure among collection sites of ED. Also, phylogeographical analysis for ED found significant geographical structuring of haplotype diversity. Overall, within-population variation increased significantly from north to south, with low genetic diversity in the Strawberry River. We calculated significant among-population structure for both species (ED: [Phi]ST = 0.62, P < 0.001; AL: [Phi]ST = 0.16, P < 0.001). Genetic analysis identified the Ouachita River as an area of significant reproductive isolation for both species. Results for AL indicated dispersal into northern areas from two genetically distinct glacial refugia, where results for ED indicated dispersal followed by low gene flow in northern areas. The conservation strategies for mussels that co-occur in the same 'bed' could be species specific. Species such as ED have management units on the population scale, where AL has a more homogeneous genetic structure across its range. [PUBLICATION ABSTRACT]

  39. Testing the assumption of annual shell ring deposition in freshwater mussels

    W. Haag and A. Commens-Carson.

    Canadian Journal of Fisheries and Aquatic Sciences, Vol. 65, No. 3, Mar 2008, pp. 493.

    We tested the assumption of annual shell ring deposition by freshwater mussels in three rivers using 17 species. In 2000, we notched shell margins, returned animals to the water, and retrieved them in 2001. In 2003, we measured shells, affixed numbered tags, returned animals, and retrieved them in 2004 and 2005. We validated deposition of a single internal annulus per year in all species and in 94% of specimens. Most unvalidated shells were old individuals with tightly crowded rings. Handling produced a conspicuous disturbance ring in all specimens and often resulted in shell damage. Observed growth was similar to but slightly lower than growth predicted by von Bertalanffy length-at-age models developed independently from shell annuli; further, handling specimens in 2 consecutive years reduced growth more than handling only once. These results show that mussels are extremely sensitive to handling. Brief handling does not likely increase short-term mortality, but repeated handling could decrease long-term fitness. Handling effects should be considered in sampling programs or when interpreting results of mark-recapture studies designed to estimate mussel growth. Production of annual shell rings is a pervasive phenomenon across species, space, and time, and validated shell rings can provide accurate estimates of age and growth. [PUBLICATION ABSTRACT]

  40. Validation of annual growth rings in freshwater mussel shells using cross dating

    A. Rypel, W. Haag and R. Findlay.

    Canadian Journal of Fisheries and Aquatic Sciences, Vol. 65, No. 10, Oct 2008, pp. 2224.

    We examined the usefulness of dendrochronological cross-dating methods for studying long-term, interannual growth patterns in freshwater mussels, including validation of annual shell ring formation. Using 13 species from three rivers, we measured increment widths between putative annual rings on shell thin sections and then removed age-related variation by standardizing measurement time series using cubic splines. Initially, cross dating was a valuable quality control technique allowing us to correct interpretive and measurement errors in 16% of specimens. For all species, growth varied among years but was highly synchronous among individuals. Standardized measurement time series of 94% of individuals were significantly correlated with species master chronologies, and mean interseries correlations ranged from 0.37 to 0.96. Growth was also synchronous among species, even from different rivers, and growth was negatively correlated with mean annual streamflow for most species except Quadrula pustulosa from a regulated dam tailrace. Highly synchronous growth and the strong relationship to streamflow showed that large-scale environmental signals generated non-age-related variation in mussel growth giving strong support for annual formation of the growth increments we measured. Cross dating can be a valuable technique for studying freshwater mussel growth providing quality control, validation of annual rings, and reconstruction of long-term growth histories. [PUBLICATION ABSTRACT]

  41. Acute and Chronic Toxicity of Technical-Grade Pesticides to Glochidia and Juveniles of Freshwater Mussels (Unionidae)

    Robert B. Bringolf, W. Gregory Cope, Chris B. Eads and Peter R. Lazaro.

    Environmental Toxicology and Chemistry, Vol. 26, No. 10, Oct 2007, pp. 2086.

    Chemical contaminants are among many potential factors involved in the decline of freshwater mussel populations in North America, and the effects of pesticides on early life stages of unionid mussels are largely unknown. The objective of this study was to determine the toxicity of technical-grade current-use pesticides to glochidia and juvenile life stages of freshwater mussels. We performed acute toxicity tests with glochidia (five species) and juveniles (two species) exposed to a suite of current-use pesticides including herbicides (atrazine and pendimethalin), insecticides (fipronil and permethrin), and a reference toxicant (NaCl). Because of limited availability of test organisms, not all species were tested with all pesticides. Toxicity tests with fungicides (chlorothalonil, propiconazole, and pyraclostrobin) were performed with one species (Lampsilis siliquoidea). Lampsilis siliquoidea glochidia and juveniles were highly sensitive to the fungicides tested but the technical-grade herbicides and insecticides, at concentrations approaching water solubility, were not acutely toxic to this or the other unionid species. In a 21-d chronic test with four-month-old juvenile L. siliquoidea, the 21-d median effective concentration (EC50) with atrazine was 4.3 mg/L and in atrazine treatments e3.8 mg/L mussel growth was significantly less than controls. The relatively high sensitivity of L. siliquoidea to chlorothalonil, propiconazole, and pyraclostrobin is similar to that reported for other aquatic organisms commonly used for toxicity testing. The relative risk associated with acute exposure of early life stages of mussels to technical-grade atrazine, pendimethalin, fipronil, and permethrin is likely low; however, survival and growth results with juvenile L. siliquoidea indicate that chronic exposure to high concentrations (e3.8 mg/L) of atrazine may have the potential to impact mussel populations and warrants further investigation. [PUBLICATION ABSTRACT] Chemical contaminants are among many potential factors involved in the decline of freshwater mussel populations in North America, and the effects of pesticides on early life stages of unionid mussels are largely unknown. The objective of this study was to determine the toxicity of technical-grade current-use pesticides to glochidia and juvenile life stages of freshwater mussels. We performed acute toxicity tests with glochidia (five species) and juveniles (two species) exposed to a suite of current-use pesticides including herbicides (atrazine and pendimethalin), insecticides (fipronil and permethrin), and a reference toxicant (NaCl). Because of limited availability of test organisms, not all species were tested with all pesticides. Toxicity tests with fungicides (chlorothalonil, propiconazole, and pyraclostrobin) were performed with one species (Lampsilis siliquoidea). Lampsilis siliquoidea glochidia and juveniles were highly sensitive to the fungicides tested but the technical-grade herbicides and insecticides, at concentrations approaching water solubility, were not acutely toxic to this or the other unionid species. In a 21-d chronic test with four-month-old juvenile L. siliquoidea, the 21-d median effective concentration (EC50) with atrazine was 4.3 mg/L and in atrazine treatments >or=3.8 mg/L mussel growth was significantly less than controls. The relatively high sensitivity of L. siliquoidea to chlorothalonil, propiconazole, and pyraclostrobin is similar to that reported for other aquatic organisms commonly used for toxicity testing. The relative risk associated with acute exposure of early life stages of mussels to technical-grade atrazine, pendimethalin, fipronil, and permethrin is likely low; however, survival and growth results with juvenile L. siliquoidea indicate that chronic exposure to high concentrations (>/=3.8 mg/L) of atrazine may have the potential to impact mussel populations and warrants further investigation.

  42. Correlation Between Unionid Mussel Density and EPA Habitat-assessment Parameters

    Laura Nicklin and Michael Balas.

    Northeastern Naturalist, Vol. 14, No. 2, 2007, pp. 225-234.

    Freshwater mussels (Bivalvia: Unionidae) are sensitive to pollution of stream habitats. However, there has been no analysis of whether mussel density is correlated with measurements from commonly used rapid water assessment protocols. This study tested which water quality parameters are correlated with the density of freshwater mussels found in selected locations of the middle Allegheny River, PA. No correlation was found between mussel density and either temperature or chemical water quality parameters. However, there was a strong positive correlation between mussel density and the modified EPA physical habitat parameters tested. These results suggest that the physical habitat variables are a useful tool to assess the suitability of stream habitat for unionid mussels, and should help ecosystem managers make informed decisions about the maintenance or restoration of the ecosystem function that these mussels perform. [PUBLICATION ABSTRACT]

  43. Declining Populations of Freshwater Pearl Mussels (Margaritifera margaritifera) Are Burdened with Heavy Metals and DDT/DDE

    Hartmut Frank and Silke Gerstmann.

    Ambio, Vol. 36, No. 7, 2007, pp. 571-4.

    Many aquatic mollusks, such as the freshwater pearl mussel (Margaritifera margaritifera), are in decline throughout Europe. The reasons are largely unknown; factors that have been suggested to contribute are river bed compaction due to agricultural practices, eutrophication, or pollutants of various natures. Brittle shells of recently deceased pearl mussels from northern Bavaria with weak calcium incrustations point to the possibility that calcium metabolism is affected. It is known that certain persistent organic pollutants and some heavy metals may induce calcium deficiency in wildlife. Elevated levels of the organochlorine insecticide DDT and its metabolite DDE, as well as of cadmium and some other heavy metals, have been found in pearl mussels. Both classes of environmental pollutants are known to potentially interfere with calcium homeostasis. [PUBLICATION ABSTRACT]

  44. Effects of zebra mussels (Dreissena polymorpha) on native bivalves: the beginning of the end or the end of the beginning?

    D. Strayer and H. Malcom.

    Journal of the North American Benthological Society, Vol. 26, No. 1, Mar 01 2007, pp. 111-122.

    The long-term effects of an alien species may differ from transient effects that occur shortly after its invasion of a new ecosystem. Conservationists fear that the invasion of North America by the zebra mussel since 1985 may lead to the extinction of many populations and species of native bivalves. The appearance of zebra mussels in the Hudson River estuary in 1991 was followed by steep declines (65-100%) in population size of all species of native bivalves between 1992 and 1999. The body condition of all unionids and growth and recruitment of young unionids also declined significantly. Initial declines in population size and body condition were correlated primarily with the filtration rate of the zebra mussel population but not with fouling of native bivalves by zebra mussels. However, samples taken since 2000 have shown that populations of all 4 common native bivalves have stabilized or even recovered, although the zebra mussel population has not declined. The mechanisms underlying this apparent reversal of fortune are not clear. Recruitment and growth of young mussels have shown limited recovery, but the body condition of adults has not. We found no evidence that spatial refuges contributed to this reversal of population declines. Simple statistical models project now that native bivalves may persist at population densities about an order of magnitude below their preinvasion densities. These results offer a slender hope that zebra mussels may coexist with unionids and sphaeriids in North America, as they do in Europe.

  45. An Evaluation of Freshwater Mussel Toxicity Data in the Derivation of Water Quality Guidance and Standards for Copper

    Ferrella A. March, F. James Dwyer, Tom Augspurger and Christopher G. Ingersoll.

    Environmental Toxicology and Chemistry, Vol. 26, No. 10, Oct 2007, pp. 2066.

    The state of Oklahoma has designated several areas as freshwater mussel sanctuaries in an attempt to provide freshwater mussel species a degree of protection and to facilitate their reproduction. We evaluated the protection afforded freshwater mussels by the U.S. Environmental Protection Agency (U.S. EPA) hardness-based 1996 ambient copper water quality criteria, the 2007 U.S. EPA water quality criteria based on the biotic ligand model and the 2005 state of Oklahoma copper water quality standards. Both the criterion maximum concentration and criterion continuous concentration were evaluated. Published acute and chronic copper toxicity data that met American Society for Testing and Materials guidance for test acceptability were obtained for exposures conducted with glochidia or juvenile freshwater mussels. We tabulated toxicity data for glochidia and juveniles to calculate 20 species mean acute values for freshwater mussels. Generally, freshwater mussel species mean acute values were similar to those of the more sensitive species included in the U.S. EPA water quality derivation database. When added to the database of genus mean acute values used in deriving 1996 copper water quality criteria, 14 freshwater mussel genus mean acute values included 10 of the lowest 15 genus mean acute values, with three mussel species having the lowest values. Chronic exposure and sublethal effects freshwater mussel data available for four species and acute to chronic ratios were used to evaluate the criterion continuous concentration. On the basis of the freshwater mussel toxicity data used in this assessment, the hardness-based 1996 U.S. EPA water quality criteria, the 2005 Oklahoma water quality standards, and the 2007 U.S. EPA water quality criteria based on the biotic ligand model might need to be revised to afford protection to freshwater mussels. [PUBLICATION ABSTRACT] The state of Oklahoma has designated several areas as freshwater mussel sanctuaries in an attempt to provide freshwater mussel species a degree of protection and to facilitate their reproduction. We evaluated the protection afforded freshwater mussels by the U.S. Environmental Protection Agency (U.S. EPA) hardness-based 1996 ambient copper water quality criteria, the 2007 U.S. EPA water quality criteria based on the biotic ligand model and the 2005 state of Oklahoma copper water quality standards. Both the criterion maximum concentration and criterion continuous concentration were evaluated. Published acute and chronic copper toxicity data that met American Society for Testing and Materials guidance for test acceptability were obtained for exposures conducted with glochidia or juvenile freshwater mussels. We tabulated toxicity data for glochidia and juveniles to calculate 20 species mean acute values for freshwater mussels. Generally, freshwater mussel species mean acute values were similar to those of the more sensitive species included in the U.S. EPA water quality derivation database. When added to the database of genus mean acute values used in deriving 1996 copper water quality criteria, 14 freshwater mussel genus mean acute values included 10 of the lowest 15 genus mean acute values, with three mussel species having the lowest values. Chronic exposure and sublethal effects freshwater mussel data available for four species and acute to chronic ratios were used to evaluate the criterion continuous concentration. On the basis of the freshwater mussel toxicity data used in this assessment, the hardness-based 1996 U.S. EPA water quality criteria, the 2005 Oklahoma water quality standards, and the 2007 U.S. EPA water quality criteria based on the biotic ligand model might need to be revised to afford protection to freshwater mussels.

  46. Fecundity as a Basis for Risk Assessment of Nonindigenous Freshwater Molluscs

    Reuben P. Keller, John M. Drake and David M. Lodge.

    Conservation Biology, Vol. 21, No. 1, Feb 2007, pp. 191.

    The most efficient way to reduce future damages from nonindigenous species is to prevent the introduction of harmful species. Although ecologists have long sought to predict the identity of such species, recent methodological advances promise success where previous attempts failed. We applied recently developed risk assessment approaches to nonindigenous freshwater molluscs at two geographic scales: the Laurentian Great Lakes basin and the 48 contiguous states of the United States. We used data on natural history and biogeography to discriminate between established freshwater molluscs that are benign and those that constitute nuisances (i.e., cause environmental and/or economic damage). Two statistical techniques, logistic regression and categorical tree analysis, showed that nuisance status was positively associated with fecundity. Other aspects of natural history and biogeography did not significantly affect likelihood of becoming a nuisance. We then used the derived statistical models to predict the chance that 15 mollusc species not yet in natural ecosystems would cause damage if they become established. We also tested whether time since establishment is related to the likelihood that nonindigenous mollusc species in the Great Lakes and United States would cause negative impacts. No significant relationship was evident at the U.S. scale, but recently established molluscs within the Great Lakes were more likely to cause negative impacts. This may reflect changing environmental conditions, changing patterns of trade, or may be an indication of "invasional meltdown." Our quantitative analyses could be extended to other taxa and ecosystems and offer a number of improvements over the qualitative risk assessments currently used by U.S. (and other) government agencies. [PUBLICATION ABSTRACT]

  47. Review of the systematics and global diversity of freshwater mussel species (Bivalvia: Unionoida)

    Daniel L. Graf and Kevin S. Cummings.

    The Journal of Molluscan Studies, Vol. 73, No. 4, 2007, pp. 291-314.

    ABSTRACT Freshwater mussels (Bivalvia: Unionoida) are interesting because of their unique life cycles, global aggregate distribution and ancient origin. They are also of practical importance due to their worldwide, imperiled status. Of utmost utility for their continued study are a modern assessment of global and regional species diversity and a natural classification that reflects phylogenetic patterns. The freshwater malacological community has taken steps toward satisfying the latter of these requirements, but a consensus census of mussel species has not been published since Fritz Haas's revisions of the late 1960s. We set out to describe the species-level diversity of the Unionoida by reviewing the secondary literature and developing a comprehensive taxonomic database. Each valid species was assigned to one or more geographical regions (i.e. Nearctica, Neotropica, Afrotropica, Palearctica, Indotropica and Australasia) and one or more subregions, and each valid genus was assigned to the lowest possible level in a classification derived from our own, recent phylogenetic analyses. Based upon a consensus of numerous regional works, our global estimate of freshwater mussel diversity is 840 species. Regional diversity was determined as follows: Nearctica: 302 spp., Neotropica: 172, Afrotropica: 85, Palearctica: 45, Indotropica: 219 and Australasia: 33. The largest family is the Unionidae, with 674 species. However, the classification of that taxon is currently in flux, and many genera (corresponding to 225 spp.) were assigned to incertae sedis geographical assemblages. Diversity patterns are discussed, and it is suggested that reevaluation of these faunas with modern methods will likely increase recognized species diversity, especially on the southern continents. Our checklist and classification of freshwater mussel species is included as an appendix and mirrored on the MUSSEL Project Web Site ( ).


    Sara Ward, Tom Augspurger, F. Dwyer, Cindy Kane and Christopher Ingersoll.

    Environmental Toxicology and Chemistry, Vol. 26, No. 10, 2007, pp. 2075-85.

    Water quality data were collected from three drainages supporting the endangered Carolina heelsplitter (Lasmigona decorata) and dwarf wedgemussel (Alasmidonta heterodon) to determine the potential for impaired water quality to limit the recovery of these freshwater mussels in North Carolina, USA. Total recoverable copper, total residual chlorine, and total ammonia nitrogen were measured every two months for approximately a year at sites bracketing wastewater sources and mussel habitat. These data and state monitoring datasets were compared with ecological screening values, including estimates of chemical concentrations likely to be protective of mussels, and federal ambient water quality criteria to assess site risks following a hazard quotient approach. In one drainage, the site-specific ammonia ecological screening value for acute exposures was exceeded in 6% of the samples, and 15% of samples exceeded the chronic ecological screening value; however, ammonia concentrations were generally below levels of concern in other drainages. In all drainages, copper concentrations were higher than ecological screening values most frequently (exceeding the ecological screening values for acute exposures in 65-94% of the samples). Chlorine concentrations exceeding the acute water quality criterion were observed in 14 and 35% of samples in two of three drainages. The ecological screening values were exceeded most frequently in Goose Creek and the Upper Tar River drainages; concentrations rarely exceeded ecological screening values in the Swift Creek drainage except for copper. The site-specific risk assessment approach provides valuable information (including site-specific risk estimates and ecological screening values for protection) that can be applied through regulatory and nonregulatory means to improve water quality for mussels where risks are indicated and pollutant threats persist. [PUBLICATION ABSTRACT]

  49. Buckets of muckets: A compact system for rearing juvenile freshwater mussels

    M. C. Barnhart.

    Aquaculture, Vol. 254, No. 1-4, Apr 28 2006, pp. 227.

    A novel system was developed for the culture of juvenile freshwater mussels (Unionidae). The system can be replicated economically to provide statistical power for experimental investigations of culture conditions. Two nested buckets partition a water volume of 18 l into upper and lower compartments. Water moves from the lower to the upper compartment via a small submersible pump, and returns to the lower compartment through screen-capped chambers containing the juveniles. Each bucket system includes 7 chambers, each of which can accommodate 2000 juveniles (14,000 total). Newly transformed juvenile unionids of 8 species were held in these systems for 9 to 12 wk and continuously drip-fed a monoculture of Neochloris oleoabundans. Survival rates were generally higher than those previously reported for newly metamorphosed unionids and exceeded 95% over 2 mo for Lampsilis siliquoidea and L. reeveiana. Mean growth rates varied among 5 species from 4.2 to 12.5 micro m/d at 22 degrees C. These growth rates are within the range previously reported for lampsiline juveniles in recirculating systems. The bucket rearing system may be particularly useful for conducting studies of water quality and feeding regimes that require replication to account for container effects. It is also useful for short-term culture of juveniles to be used in toxicity testing. [PUBLICATION ABSTRACT]

  50. Extirpation of Freshwater Mussels (Bivalvia: Unionidae) Following the Invasion of Dreissenid Mussels in an Interconnecting River of the Laurentian Great Lakes

    Don W. Schloesser, Janice L. Metcalfe-Smith, William P. Kovalak, Gary D. Longton and Rick D. Smithee.

    The American Midland Naturalist, Vol. 155, No. 2, Apr 2006, pp. 307.

    Previous (1992-1994) surveys for native freshwater mussels (Unionidae) along main channels of the Detroit River showed that unionids had been extirpated from all but four sites in the upper reaches of the river due to impacts of dreissenid mussels (Dreissena polymorpha and D. bugensis). These four sites were surveyed again in 1998 using the same sampling method (timed-random searches) to determine if they may serve as "refugia" where unionids and dreissenids co-exist. Two additional sites were sampled using additional methods (excavated-quadrat and line-transect searches) for comparison with unpublished data collected in 1987 and 1990. A total of four individuals of four species (Actinonaias ligamentina, Cyclonaias tuberculata, Lasmigona complanata and Pleurobema sintoxia) were found by timed-random searches at four sites in 1998 compared to 720 individuals of 24 species in 1992 and 39 individuals of 13 species in 1994. Excavated-quadrat and line-transect searches at the two additional sites yielded only one live specimen of Ptychobranchus fasciolaris compared to 288 individuals of 18 species in 1987 and 1990. Results of this study suggest that remaining densities of unionids in channels of the Detroit River are too low to support viable reproducing populations of any species. Therefore, we conclude that unionids have been extirpated from main channels of the Detroit River due to dreissenid infestation. As the Detroit River was one of the first water bodies in North America to be invaded by dreissenids, it is likely that unionids will also be extirpated from many other rivers and lakes across eastern North America over the next few decades. Resource agencies should be encouraged to implement active management programs to protect remaining unionid populations from zebra mussels. [PUBLICATION ABSTRACT]

  51. Molecular ecology of zebra mussel invasions

    Gemma E. May, Gregory W. Gelembiuk, Vadim E. Panov, Marina I. Orlova and Carol Eunmi Lee.

    Molecular ecology, Vol. 15, No. 4, Apr 2006, pp. 1021.

    The invasion of the zebra mussel, Dreissena polymorpha, into North American waters has resulted in profound ecological disturbances and large monetary losses. This study examined the invasion history and patterns of genetic diversity among endemic and invading populations of zebra mussels using DNA sequences from the mitochondrial cytochrome oxidase I (COI) gene. Patterns of haplotype frequency indicate that all invasive populations of zebra mussels from North America and Europe originated from the Ponto-Caspian Sea region. The distribution of haplotypes was consistent with invasive populations arising from the Black Sea drainage, but could not exclude the possibility of an origin from the Caspian Sea drainage. Similar haplotype frequencies among North American populations of D. polymorpha suggest colonization by a single founding population. There was no evidence of invasive populations arising from tectonic lakes in Turkey, while lakes in Greece and Macedonia contained only Dreissena stankovici . Populations in Turkey might be members of a sibling species complex of D. polymorpha. Ponto-Caspian derived populations of D. polymorpha (Beta=0.0011) and Dreissena bugensis (one haplotype) exhibited low levels of genetic diversity at the COI gene, perhaps as a result of repeated population bottlenecks. In contrast, geographically isolated tectonic lake populations exhibited relatively high levels of genetic diversity (Beta=0.0032 to 0.0134). It is possible that the fluctuating environment of the Ponto-Caspian basin facilitated the colonizing habit of invasive populations of D. polymorpha and D. bugensis. Our findings were concordant with the general trend of destructive freshwater invaders in the Great Lakes arising from the Ponto-Caspian Sea basin. [PUBLICATION ABSTRACT]

  52. Sex and the Single Freshwater Mussel

    L. J. Davenport.

    Alabama Heritage, Vol. , No. 80, Spring 2006, pp. 41.

    If male, then your internal organs produce vast quantities of sperm, which are released to the water, then taken into a female's body through her incurrent aperture and carried to eggs waiting in her gills. sections of these gills then serve as brood pouches or marsupta, producing parasitic larvae (glochidta) to be discharged into the water column. Streamside deforestation (with accompanying loss of cooling shade) leads to higher water temperatures, while strip mining and overdevelopment of watersheds result in choking sediment loads.

  53. The Curious Case of the Fat Pocketbook Mussel, Potamilus capax

    Andrew Miller and Barry Payne.

    Endangered Species Update, Vol. 22, No. 2, 2005, pp. 61-70,50.

    Native freshwater mussels (Family: Unionidae), often referred to as the most 'endangered' organisms in North America, typically reach their greatest abundance in gravelly shoals in medium-sized to large rivers in the United States. However, one species, the endangered fat pocketbook mussel, Potamilus capax Green 1832, is very common in deep deposits of fine-grained sediments in man-made ditches or in slow moving rivers, streams, sloughs, and bayous in the St. Francis Watershed in Arkansas. An early study reported the status of this species as 'tenuous;' however, research conducted in the last 20 years indicate that in appropriate habitat P. capax usually exhibits good evidence of recent recruitment and can comprise more than 10% of the mussel assemblage. Hundreds or even thousands of individuals can occur in 1- to 5-km-long reaches of rivers or ditches. Endangered species management should take advantage of accurate information on distribution, abundance, and life history. Confusion and misinformation about this mussel must be overcome to improve management plans and decisions concerning this species. In this article we examine the status of P. capax based on a review of the literature and our recent surveys in the St. Francis Watershed. [PUBLICATION ABSTRACT]

  54. Development and Assessment of a Sampling Design for Mussel Assemblages in Large Streams

    Alan D. Christian and John L. Harris.

    The American Midland Naturalist, Vol. 153, No. 2, Apr 2005, pp. 284.

    Freshwater mussel beds of the lower 68 km of the Cache River, Arkansas, were delineated, sampled using dive techniques and a stratified random sampling methodology and analyzed for density and species richness. A total of 38 mussel beds were delineated, 14 major beds (Mbeds) and 24 minor beds (mbeds), and defined by areal extent and mussel density. Analysis of our sampling precision indicated 80% or better confidence levels for a majority of our sites and suggested that a sample size of 15 1-m^sup 2^ quadrats is sufficient to obtain 80% or better confidence. Our large river diver-assisted sampling methodology has been shown to be a useful and appropriate methodology for obtaining large geographic scale baseline distribution (bed and species), species richness, density and population and community numerical standing crop estimates information where tradeoffs are required in order to complete a project within time and budget constraints. [PUBLICATION ABSTRACT]

  55. Freshwater mussel shells as environmental chronicles: Geochemical and taphonomic signatures of mercury-related extirpations in the North Fork Holston River, Virginia

    Megan E. Brown, Michal Kowalewski, Richard J. Neves, Donald S. Cherry and Madeline E. Schreiber.

    Environmental science & technology, Vol. 39, No. 6, Mar 15 2005, pp. 1455.

    This study utilized freshwater mussel shells to assess mercury (Hg) contamination in the North Fork Holston River that extirpated (caused local extinctions of) a diverse mussel fauna. Shells (n = 366) were collected from five sites situated upstream (two sites), just below (one site), and downstream (two sites) of the town of Saltville, Virginia, where Hg was used to produce chlorine and caustic soda from 1950 to 1972. Shell samples were used to test the (1) utility of geochemical signatures of shells for assessing the spatial variation in Hg levels in the river relative to the contamination source and (2) value of taphonomy (postmortem shell alteration) for distinguishing sites that differ in extirpation histories. Geochemical signatures of 40 shells, analyzed using atomic absorption spectroscopy, indicated a strong longitudinal pattern. All shells from the two upstream sites had low Hg concentrations (less than 5-31 ug/kg), shells directly below Saltville had variable, but dramatically higher concentrations (234637 mug/kg), and shells from the two downstream sites displayed intermediate Hg levels (less than 5-115 mug/kg) that declined with distance from Saltville. Two pre-industrial shells, collected at Saltville in 1917, yielded very low Hg estimates (5-6 mug/kg), Hg signatures were consistent among mussel species, suggesting that Hg concentrations were invariant to species type; most likely, highly variable Hg levels, both across sites and through time, overwhelmed any interspecific differences in Hg acquisition, Also, a notable postmortem incorporation of Hg in mussel shells seemed unlikely, as the Hg content was not correlated with shell taphonomy (r = 0.18; p = 0.28). The taphonomic analysis (n = 366) showed that the degree of shell alteration reliably distinguished sites with different extirpation histories. At Saltville, where live mussels have been absent for at least 30 years, shells were most heavily altered and fragmented. Conversely, fresh-looking shells abounded upstream, where reproducing mussel populations are still present. In summary, relic shells offered valuable spatiotemporal data on Hg concentrations in a polluted ecosystem, and shell taphonomic signatures discriminated sites with different extirpation histories. The shell-based strategies exemplified here do not require sampling live specimens and may augment more standard strategies applied to environmental monitoring. The approach should prove especially useful in areas with unknown extirpation and pollution histories. [PUBLICATION ABSTRACT]

  56. Genetic diversity and differentiation of central European freshwater pearl mussel (Margaritifera margaritifera L.) populations: implications for conservation and management

    G. E. I. S. T. Juergen and K. U. E. H. N. Ralph.

    Molecular ecology, Vol. 14, No. 2, Feb 2005, pp. 425.

    Despite the fact that mollusc species play an important role in many aquatic ecosystems, little is known about their biodiversity and conservation genetics. Freshwater pearl mussel (Margaritifera margaritifera L.) populations are seriously declining all over Europe and a variety of conservation programs are being established to support the remaining endangered central European populations. In order to provide guidelines for conservation strategies and management programs, we investigated the genetic structure of 24 freshwater pearl mussel populations originating from five major central European drainages including Elbe, Danube, Rhine, Maas and Weser, representing the last and most important populations in this area. We present a nondestructive sampling method of haemolymph for DNA analyses, which is applicable for endangered bivalves. The analyses of nine microsatellite loci with different levels of polymorphism revealed a high degree of fragmented population structure and very different levels of genetic diversity within populations. These patterns can be explained by historical and demographic effects and have been enforced by anthropogenic activities. Even within drainages, distinct conservation units were detected, as revealed from high FST values, private alleles and genetic distance measures. Populations sampled close to contact zones between main drainage systems showed lowest levels of correct assignment to present-day drainage systems. Populations with high priority for conservation should not only be selected by means of census population size and geographical distance to other populations. Instead, detailed genetic analyses are mandatory for revealing differentiation and diversity parameters, which should be combined with ecological criteria for sustainable conservation and recovery programs. [PUBLICATION ABSTRACT]

  57. The Effect of Size-limited Brood Capacity on Brood Size in a Freshwater Bivalve

    Mark A. Beekey and Daniel J. Hornbach.

    The American Midland Naturalist, Vol. 151, No. 2, Apr 2004, pp. 274.

    Size limited brood capacity is common among species with hard exoskeletons or shells. In these species, brood size is limited by the physical capacity to hold offspring. Here we present evidence that brood size is limited by physical constraints in Sphaerium striatinum, a small brooding bivalve. Sphaerium striatinum is a sequential brooder and produces offspring throughout the year. Offspring are brooded in marsupial sacs located on the inner demibranch. In an unconstrained brooder one would predict that brood size would increase as a function of adult length cubed, a volumetric relationship. In S. striatinum, brood size increases as less than a function of adult length squared. We demonstrate that brood size is limited by two general constraints: marsupial sacs and the retention of extra-marsupial offspring. The number of marsupial sacs increases as less than a function of adult length squared. This relationship may be a result of physiological process such as feeding and respiration. Offspring size at independence is a crucial factor in determining offspring survivorship. The retention of extra-marsupial offspring promotes growth inside a safe environment and increases survivorship upon independence. However, the exponent relating brood size to adult length is significantly less for adults that contain extra-marsupial offspring than compared to adults that do not contain extra-marsupial offspring. Although the evolution of brooding in S. striatinum has resulted in severe constraints on brood size, the benefits of brooding outweigh the cost of limited brood capacity. We discuss our results in relation to brooding strategies and size limited brood capacity in other brooding bivalves. [PUBLICATION ABSTRACT]

  58. The endocrine disrupting effect of municipal effluent on the zebra mussel (Dreissena polymorpha)

    B. Quinn, F. Gagne, M. Costello, C. McKenzie, J. Wilson and C. Mothersill.

    Aquatic Toxicology, Vol. 66, No. 3, 25 Feb 2004, pp. 279-292.

    Municipal effluents have been shown to contain a cocktail of endocrine disrupting chemicals (EDCs). The estrogenic effect of these effluents has been demonstrated on both vertebrate and invertebrate species by the feminisation of the exposed males. This effect was investigated on the freshwater zebra mussel (Dreissena polymorpha) after exposure to tertiary treated effluent from a municipal sewage treatment works (STW). Mussels were exposed to the effluent in situ for 112 days during gametogenesis (December to mid-March). Levels of vitellin (Vn)-like proteins (the major protein found in oocytes) were measured indirectly using the alkali-labile phosphate (ALP) technique and confirmed by gel electrophoresis. Significant increases (P0.05) in Vn-like proteins were found in both male and female mussels after exposure to the effluent, indicating that endocrine disruption (ED) had occurred. Using High-performance thin layer chromatography (HPTLC) levels of the mussels main steroid, cholesterol were found to more than double after effluent exposure. General physiological (survival, condition, etc.) and histological effects were also investigated. Histological effects observed included a large increase in interstitial tissue between the seminiferous tubules of the gonad in male mussels exposed to effluent. Effluent samples were tested for estrogenic compounds using the toxicity identification and evaluation method (TIE). A complex mixture of compounds with estrogenic activity was found with 17 beta -estradiol, 17 alpha -ethynlestradiol and bisphenol A accounting for the majority of the effluents estrogenic activity. Results indicate that the zebra mussel is a suitable bioindicator of endocrine disruption in freshwater environments.

  59. Estimating Survival and Recruitment in a Freshwater Mussel Population Using Mark-recapture Techniques

    R. F. Villella, D. R. Smith and D. P. Lemarie.

    The American Midland Naturalist, Vol. 151, No. 1, Jan 2004, pp. 114.

    We used a mark-recapture method and model averaging to estimate apparent survival, recruitment and rate of population growth in a native freshwater mussel population at a site on the Cacapon River, which is a tributary to the Potomac River. Over 2200 Elliptio complanata, E. fisheriana and Lampsilis cariosa were uniquely tagged over a period of 4 y. Recapture probabilities were higher in spring and summer than in winter except for L. cariosa which had a low probability of recapture regardless of time of year. All three species had high annual adult survival rates (>90%) with lower estimated survival of small (<55 mm) mussels (43%-69%). The variation in apparent survival over time was similar for all three species. This suggests that whatever environmental variables affect survival of mussels in this site affected all three species the same. Recruitment rates were low (1-4%) for both E. complanata and L. cariosa, with E. fisheriana having several periods of high (15-23%) recruitment. Distribution within the site was affected by both downstream and upstream movement, though movement rates were generally <1%. Average population growth rates for E. complanata ([lambda] = 0.996, SE = 0.053), L. cariosa ([lambda] = 0.993, SE = 0.076) and E. fisheriana ([lambda] = 1.084, SE = 0.276) indicated static populations. Population growth rate approximating 1.0 suggests this site supports a stable freshwater mussel population through a life history strategy of low but constant recruitment and high annual adult survival. [PUBLICATION ABSTRACT]

  60. The Global Decline of Nonmarine Mollusks

    Charles Lydeard, Robert H. Cowie, Winston F. Ponder and Arthur E. Bogan.

    Bioscience, Vol. 54, No. 4, Apr 2004, pp. 321.

    Invertebrate species represent more than 99% of animal diversity; however, they receive much less publicity and attract disproportionately minor research effort relative to vertebrates. Nonmarine mollusks (i.e., terrestrial and freshwater) are one of the most diverse and imperiled groups of animals, although not many people other than a few specialists who study the group seem to be aware of their plight. Nonmarine mollusks include a number of phylogenetically disparate lineages and species-rich assemblages that represent two molluscan classes, Bivalvia (clams and mussels) and Gastropoda (snails, slugs, and limpets). In this article we provide an overview of global nonmarine molluscan biodiversity and conservation status, including several case studies documenting the diversity and global decline of nonmarine mollusks. We conclude with a discussion of the roles that mollusks and malacologists should play in conservation, including research, conservation management strategies, and education and outreach. [PUBLICATION ABSTRACT] Keywords: nonmarine mollusks, biodiversity, gastropods, endangered species, hotspots

  61. Reducing risks of maintenance dredging on freshwater mussels (Unionidae) in the Big Sunflower River, Mississippi

    Andrew C. Miller and Barry S. Payne.

    Journal of environmental management, Vol. 73, No. 2, Nov 2004, pp. 147.

    In response to proposed dredging in a 122-km reach of the Big Sunflower River, Mississippi, we studied freshwater mussels (family: Unionidae) using qualitative, semi-quantitative, and quantitative (0.25 m2 total substratum removal) methods in 1987, 1993, 1994, 2001, 2002, and 2003. Our objectives were to identify important mussel resources, to devise methods for minimizing dredging risks, and to identify habitat improvement features. Approximately 60% of the fauna was located on two high-density shoals characterized by extreme dominance of the commercially valuable threeridge (Amblema plicata). Shallow nearshore and main channel areas comprised approximately 10 and 88% of the aquatic habitat in the project area; however, these areas were of less importance for mussels and supported densities of approximately 5 and 0.5 individuals/m2, respectively. Throughout the project area the mussel fauna exhibited little or no evidence of recent recruitment, dominance of relatively few species (either A. plicata, or the bank climber Plectomerus dombeyanus), and low species diversity (H?) and evenness. No federally listed endangered or threatened mussels were found, although the pyramid pigtoe (Pleurobema pyramidatum), a species listed as endangered in Mississippi, was collected in and upstream of the project area. Two other state-listed species, Plethobasus cyphyus (sheepnose) and Quadrula cylindrica (rabbitsfoot), were only found on gravelly shoals upriver of the project area. Maintenance plans were redesigned to minimize environmental damage; a hydraulic cutterhead dredge will be used in most of the mainstem to reduce risk to nearshore habitats. High-density assemblages on four shoals will not be dredged and 150 and 100 m buffer zones will be left immediately up and downriver. Enhancements for aquatic biota will be created with gravel substratum and wing dams. [PUBLICATION ABSTRACT]

  62. Assessing pollution in coastal ecosystems: a preliminary survey using the micronucleus test in the mussel Mytilus edulis

    JI Izquierdo, G. Machado, F. Ayllon, et al.

    Ecotoxicology and environmental safety, Vol. 55, No. 1, May 2003, pp. 24-29.

    Mussels Mytilus edulis were sampled at increasing distances from urban effluents in two very different locations, Gijon (northern Spain, Europe, 43 degree N) and Puerto Madryn (Argentina, South America, 43 degree S), and from an industry effluent in Puerto Madryn. The micronucleus test was performed on branchial cells. For the three situations, a statistically significant negative association was found between the distance of sampling site from the effluent and the mean number of micronuclei per 1000 cell counts, in a range of distances as short as 300m. The micronucleus test in Mytilidae, here revealed to be sensitive enough to monitor urban pollution, is proposed for routine surveys of pollution as a bioindicator of choice for coastal ecosystems.

  63. DDT is still a problem in developed countries: the heavy pollution of Lake Maggiore

    A. Binelli and A. Provini.

    Chemosphere, Vol. 52, No. 4, Jul 2003, pp. 717-723.

    The zebra mussel (Dreissena polymorpha), one of the most widely used bioindicators of persistent organic pollutants, trace metals and radionuclides in several worldwide freshwater ecosystems, has been used to monitor DDT contamination trends in Lake Maggiore since 1996, caused by industrial effluents on a tributary of the River Toce, one of the major affluents of the lake. Dreissena specimens were collected at two sampling sites, one within the Baveno Bay, where the River Toce flows, and the other outside (Villa Taranto). Total DDT levels (3119.6 ng/g lipids at Baveno and 1351.2 ng/g lipids at Villa Taranto) in the soft tissues of the zebra mussel decreased at both stations by about 30-50% in the first year after the closure of the chemical plant reaching an almost steady-state condition. The high concentrations measured in Zebra mussel specimens of Baveno Bay in 2000 (1947 ng/g lipids) and the percentage of pp'DDE in comparison with total DDT concentration, which showed a slight increase in the last years, clearly indicate that a contamination source is still present, deriving probably from the lacustrine sediments and the River Toce. Data show that the environmental risk is very high within the Baveno Bay and the recovery time should be longer than in the other parts of the lake, where DDT levels in Dreissena are presently two times higher than those measured in the other Italian subalpine lakes.

  64. Planktonic invaders of the St. Lawrence estuarine transition zone: environmental factors controlling the distribution of zebra mussel veligers

    Christine Barnard, Jean-Jacques Frenette and Warwick F. Vincent.

    Canadian Journal of Fisheries and Aquatic Sciences, Vol. 60, No. 10, Oct 2003, pp. 1245.

    The St. Lawrence estuarine transition zone (ETZ) is a productive ecosystem supporting a larval fish nursery. Since 1994, Dreissena polymorpha veligers have become the dominant Zooplankton (up to 260 individuals-L^sup -1^). The environmental factors controlling their distribution across the ETZ and their potential impact on the plankton were determined. Their horizontal distribution was limited by salinity, with maximum decreases in concentration at 2[per thousand]. A sharp decline in prey availability at >2[per thousand] may be a secondary Stressor for the veligers, in addition to the direct effects of salinity. Their vertical distribution was homogeneous throughout the water column, even in the presence of a pycnocline. Redundancy analysis showed that veliger concentrations were positively correlated with temperature and turbidity and negatively correlated with salinity and total phosphorus. Veligers were also positively correlated with chlorophyll a and picophytoplankton concentrations, suggesting little effect on their phytoplankton prey. Moreover, the veligers were positively correlated with the sestonic ratio of paniculate to total phosphorus, indicating their positive association with good food quality. The veligers appear to have no severe negative impacts on the ETZ plankton community and are restricted to favourable conditions for their survival in the upstream, low salinity region of the ETZ. [PUBLICATION ABSTRACT]

  65. The application of the endangered species act to the protection of freshwater mussels: a case study

    E. Biber.

    Environmental Law (Portland), Vol. 32, No. 1, 2002, pp. [91]-166.

    Freshwater mussels are the most endangered group of animals in the United States, and the success or failure of the Endangered Species Act (ESA) in protecting mussels provides an important case study of the overall strengths and weaknesses of the Act. The case study is based on 1) interviews with United States Fish and Wildlife Service biologists in charge of enforcing the Act with respect to mussels and with conservation biologists who have extensively studied freshwater mussels, 2) recovery plans, listing documents, and biological opinions created by the Fish and Wildlife Service as part of its implementation of the Act, and 3) quantitative data on recovery and listing efforts for mussel species. Based on this data, this Comment concludes that the Act is being substantially under-enforced with respect to mussels, especially in the areas of designation of critical habitat and section 9's prohibition on takings, and that the Act has had very limited success in restoring mussel populations. These results are due to 1) delayed recovery efforts for many mussel species, 2) gaps in the law that leave species vulnerable to aquatic pollution, and 3) a systematic bias against the protection of invertebrates. The case study thus shows that, contrary to one of the standard criticisms of the ESA, the administration of the Act already prioritizes enforcement and recovery efforts among various species based on perceived social value. The stringent requirements of the ESA may be essential to ensuring that species such as mussels receive even the limited protection they currently enjoy.

  66. Using Mussel Isotope Ratios to Assess Anthropogenic Nitrogen Inputs to Freshwater Ecosystems

    R. A. Mckinney, J. L. Lake, M. A. Charpentier and S. Ryba.

    Environmental monitoring and assessment, Vol. 74, No. 2, 2002, pp. 167-92.

    Stable nitrogen isotope ratios (d^sup 15^N) of freshwater mussels from a series of lakes and ponds wererelated to watershed land use characteristics to assess their utility in determining the source ofnitrogen inputs to inland water bodies. Nitrogen isotope ratiosmeasured in freshwater musselsfrom 19 lakes and ponds in Rhode Island, U.S.A., ranged from4.9-12.6[per thousand] and were found tosignificantly correlate with the fraction of residential development in 100 and 200 m bufferzones around the ponds. Mussel d^sup 15^N values in 12 of the 19 ponds also showed significantcorrelation with average dissolved nitrate concentrations, which ranged from 23-327 μg L^sup -1^.These observations, in light of previous studies which link elevatedd^sup 15^N values of nitrogenderived from septic wastewater with those seen in biota, suggest that mussel isotope ratios mayreflect nitrogen source in freshwater ecosystems. We followed aniterative approach usingmultiple regression analysis to assess the relationship between musseld^sup 15^N and the land usecategories fraction residential development, fraction feedlotagriculture, fraction row-cropagriculture, and fraction natural vegetation in 100 and 200 m bufferzones and pond watersheds.From this we developed a simple regression model to predict musseld^sup 15^N from the fraction ofresidential development in the 200 m buffer zone around the pond.Subsequent testing with datafrom 16 additional sites in the same ecoregion led us to refine themodel by incorporating thefraction of natural vegetation. The overall average absolute differencebetween measured andpredicted d^sup 15^N values using the two-parameter model was 1.6[per thousand]. Potential sources of error inthe model include differences in the scale and categorization ofland-use data used to generate andtest the model, differences in physical characteristics, such asretention time and range ofresidential development, and exclusion of sources of enrichednitrogen such as runoff from feedlot operations or increased nitrogen loading from inefficient or failed septic systems.[PUBLICATION ABSTRACT]

  67. Zebra Mussels (Dreissena polymorpha) as Indicators of Freshwater Contamination with Lindane

    P. Berny, O. Lachaux, T. Buronfosse, M. Mazallon and C. Gillet.

    Environmental research, Vol. 90, No. 2, Oct 2002, pp. 142-151.

    Zebra mussels are common freshwater mollusks in many European lakes and rivers. Their abundance, wide distribution, and filtering activity make them good candidates to evaluate the contamination of freshwaters with environmental contaminants. The purpose of this work was to determine the kinetics of lindane in zebra mussels and compare laboratory results with in situ measurements. Exposure was conducted in small tanks, under controlled experimental conditions. Our results indicated that mussels accumulated lindane with a bioconcentration factor around 10. They generally reached equilibrium within 4 days. Elimination was rapid but biphasic and the terminal elimination half-life was long (>168 h). Age of the mussels and temperature also affected the kinetics of lindane in mussels. In the Lake of Geneva, zebra mussels were sampled and showed that mussels accumulated it to significant values (up to 900 ng/g fresh weight) depending on the site and period of sampling. The in situ results, together with the laboratory exposures, showed that freshwater mussels could be used to monitor point sources of pollutants such as lindane over short periods of time (1 week).

  68. Culture of glochidia of the freshwater pearl mussel Hyriopsis myersiana (Lea, 1856) in artificial media

    Kovitvadhi Uthaiwan, Napavarn Noparatnaraporn and Jorge Machado.

    Aquaculture, Vol. 195, No. 1/2, Apr 2 2001, pp. 61.

    The freshwater pearl mussel, Hyriopsis myersiana (Limnoscapha) (Lea, 1856) was cultured in two artificial media at 23 +/- 2degreesC. Each artificial medium contained a mixture of M199, (Life Technologies, No. 71N0262) horse serum or fish (Oreochromis niloticus) artificial medium plasma as a protein source, and antibiotics/antimycotics at a ratio of 2:1:0.5.

  69. Decline and regional extirpation of freshwater mussels (Unionidae) in a small river system invaded by Dreissena polymorpha: the Rideau River, 1993-2000

    Andre Martel, Diane Pathy, Jacqueline Madill, Claude Renaud and et al.

    Canadian journal of zoology, Vol. 79, No. 12, 2001, pp. 2181-2191.

    Data pertaining to the ecological impact of the exotic zebra mussel, Dreissena polymorpha, on benthic fauna in small river systems are scarce. We conducted a long-term study to assess the impacts of the D. polymorpha invasion in a small river system (100 km) in eastern Ontario during an 8-year period (1993-2000).

  70. Exploitation trajectory of a declining fauna: A century of freshwater mussel fisheries in North America

    James Anthony and John Downing.

    Canadian Journal of Fisheries and Aquatic Sciences, Vol. 58, No. 10, 2001, pp. 2071-2090.

    Freshwater mussels (Bivalvia: Unionidae) have been an economically valuable biological resource in North America sicne the mid-1800s. Although the industries based upon mussel harvest are quite distinct from one another, the trends apparent in harvest statistics are remarkably similar among each successive harvest era.

  71. Antioxidant Biomarkers in Freshwater Bivalves, Unio tumidus, in Response to Different Contamination Profiles of Aquatic Sediments

    C. Cossu, A. Doyotte, M. Babut, A. Exinger and P. Vasseur.

    Ecotoxicology and environmental safety, Vol. 45, No. 2, 2000, pp. 106-121.

    Antioxidant systems were studied in the freshwater bivalve Unio tumidus transplanted from a control site to four different contaminated areas, in order to study the biological response according to the contamination characteristics. Reduced and oxidized glutathione (GSH, GSSG), the activities of antioxidant enzymes such as selenium-dependent and non-selenium-dependent glutathione peroxidases (SeGPx and non-SeGPx), and glutathione reductase (GRd) were measured in the gills and the digestive gland of the mussels after 15 days of exposure at different sites. Lipid peroxidation (LPO) was evaluated by means of malondialdehyde measurements (MDA). The four sites investigated were located in the valleys of Fensch (F), Moselle (M), Lot et Garonne (LG), and Sarthe (S). At each site, the bivalves were placed upstream (Up) from an identified pollution source (a cokery, a laundry, or a foundry) and downstream (Do), close to the effluent outfall (Do sub(1)) or farther (Do sub(2)). The goal was to study the antioxidant response in relation to the pollution gradient. Metals and congeners of PAHs, PCBs, and organochlorinated pesticides were analyzed in the river sediments of each station. The exposure of the bivalves at the most highly polluted sites or close to the pollution source led to a sharp depletion in some antioxidant parameters, namely GRd, SeGPx, and GSH. The decrease in enzyme activities could reach 80% for GRd and 70% for SeGPx, while GSH depletion could yield 70%, leading then in an induction of lipid peroxidation, either in the digestive gland or in the gills. The higher the MDA concentrations, the lower the activity of these three antioxidant parameters, suggesting that they could be biomarkers for toxicity. Yet, a depletion in these parameters was sometimes insufficient for cytotoxicity to be induced, since lipid peroxidation failed to appear in some cases where antioxidant depletion was clear, although not so severe. The response of the gills and the digestive gland was not always paralleled, which can be explained by differences in the bioavailability of pollutants. In some cases, a relationship was not found between the antioxidant response and the degree and the type of contamination in sediments, suggesting that the effects could result from nonidentified pollutants or/and be indicators of bio-availability. Copyright 2000 Academic Press.

  72. Transformation of freshwater ecosystmes by bivalves

    David L. Strayer, Nina F. Caraco, Jonathan J. Cole, Stuart Findlay and Michael L. Pace.

    Bioscience, Vol. 49, No. 1, Jan 1999, pp. 19.

    Strayer et al study zebra mussels in the Hudson River to discover the impact of human activities on the density and composition of bivalve communities. This impact often transforms ecosystem structure and function.

  73. To reproduce, mussels go fishing

    Adele Conover.

    Smithsonian, Vol. 28, No. 10, 1998, pp. 64-71.

    The reproduction of the freshwater mussel is examined. "Pearlers" who dive for cultured pearls produced by mussels in the waters of the Southeastern states have noticed a decrease in the mussel population.

  74. Characterization of metallothionein-like proteins from zebra mussels (Dreissena polymorpha)

    KA High, VJ Barthet, JW McLaren and J-S Blais.

    Environmental Toxicology and Chemistry, Vol. 16, No. 6, Jun 1997, pp. 1111-1118.

    Zebra mussels (Dreissena polymorpha) are freshwater mollusks that have recently infested the Great Lakes ecosystem. Possessing a large capacity for filtration, these mussel populations act as bioconcentrators for contaminants, such as heavy metals, found in the Great Lakes ecosystem. Metallothionein is a low-molecular-weight, heavy metal-binding protein found in most living organisms. Characterization and partial purification of metallothionein-like Cd-binding proteins from zebra mussels were performed. Zebra mussels were exposed to 500 mu g/L Cd for 14 d. During the exposure period, two mussels were removed on alternate days for analysis of Cd-binding proteins. Gel-filtration high-performance liquid chromatography-microatomization-atomic absorption spectrophotometry results showed a single Cd-binding molecular weight protein fraction after 2 d of Cd exposure. After 10 d of Cd exposure, however, mussels exhibited an additional, higher molecular weight, Cd-binding protein fraction. The lower molecular weight metallothionein-like Cd-binding protein was further isolated and purified by acetone fractionation, Sephadex G75, and diethylaminoethyl anion-exchange chromatography. The quantities of Zn, Cu, and Cd in the anion-exchange metallothionein-like protein isoforms were determined by inductively coupled plasma-mass spectrometry. The ability to bioconcentrate heavy metals in a metallothionein-like form coupled with their large population in the Great Lakes make zebra mussels suitable for use in a freshwater biomonitoring program for aquatic metal contamination.

  75. The micronucleus assay in the zebra mussel, Dreissena polymorpha, to in situ monitor genotoxicity in freshwater environments

    J. Mersch and M-N Beauvais.

    Mutation Research-Genetic Toxicology and Environmental Mutagenesis, Vol. 393, No. 1-2, Sep 1997, pp. 141-149.

    Caged zebra mussels, Dreissena polymorpha, were transplanted to 6 monitoring sites receiving industrial effluents suspected of containing genotoxic chemicals. After a residence time of 2 months, the induction of micronuclei (MN) in haemocytes was determined as a criterion for genetic damage. The mean MN frequencies observed in mussels exposed to effluents ranged between 5.0 and 8.8ppt. These rates were significantly higher than the baseline level of 2.0ppt recorded in a concurrent control mussel group reintroduced at the reference location. Biological fitness descriptors (mortality, attachment biotest, condition index, gonadic index) revealed no relationship between the general well-being of the mussels exposed under contrasted environmental conditions and the frequency of MN induced in their haemocytes. The biological feasibility of the transfer technique of zebra mussels, together with a moderate, but significant, inducibility of MN, are major features towards the development of a first tool for in situ monitoring of genotoxicity in freshwater environments using a common indicator species.

  76. Mussel bound

    Augusta Dwyer.

    Canadian Geographic, Vol. 117, No. 6, 1997, pp. 26-32.

    Beneath the frozen surface of Wakeham Bay, the people of Kangiqsujuaq Quebec Canada pick mussels for a rare winter treat. When the tide goes out, the people gather mussels from caverns under the ice, being careful to not be loud or stay too long.

  77. Northern redistribution of freshwater pearly mussels (Bivalvia: Unionoidea) during Wisconsin deglaciation in the Sothern Glacial Lake Agassiz region: A review

    Daniel L. Graf.

    The American Midland Naturalist, Vol. 138, No. 1, Jul 1997, pp. 37.

    The chronology of the reinvasion of freshwater pearly mussels into the southern Glacial Lake Agassiz region is reconstructed from the published record of the latest Pleistocene (Wisconsin) deglaciation of the region and known spatial and temporal distributions.

  78. Fish hosts for four species of freshwater mussels (Pelecypoda: Unionidae) in the upper Tennessee River drainage

    Bruce L. Yeager and Charles F. Saylor.

    The American Midland Naturalist, Vol. 133, No. 1, Jan 1995, pp. 1.

    Fish hosts were identified for glochidia of four freshwater unionid mussel species from the upper Tennessee River drainage. Host fishes for all four species were fast-water species occupying the same riffle habitats.

  79. Acute Toxicity of Several Pesticides, Organic Compounds, and a Wastewater Effluent of the Freshwater Mussels, Anodonta imbecilis, Ceriodaphnia dubia, and Pimephales promelas

    AE Keller.

    Bulletin of Environmental Contamination and Toxicology BECTA6, p 696-702, November 1993, pp. 19 ref.

    Protection of endangered species may someday go as far as establishment of restricted areas for prohibition of pesticides usage. Many species of freshwater (unionid) mussels have been listed as endangered or are being considered for listing, so it is important to assess the impact of pesticides, herbicides and other organic pollutants on these sensitive species. The acute toxicity of several pesticides, organic compounds and an organic effluent was determined for juvenile Anodonta imbecilis mussels. The sensitivity of A. imbecilis was compared to common test organisms such as Daphnia magna, Ceriodaphnia dubia and Pimephales promelas, the fathead minnow. The toxic effects due to the presence or absence of sediment were compared in studies with toxaphene and chlordane in A. imbecilis. A group of eight organic compounds including methanol, acetone, sodium dodecylsulfate, hydrothol, ethylenediaminetetraacetic acid, pentachlorophenol (PCP), chlordane and toxaphene were chosen for acute toxicity studies. Forty-eight hour LC50s for A. imbecilis exposed to effluent concentrations of a single organic toxic component showed that the least toxic of these compounds was methanol and the most toxic was PCP. A study of a Jacksonville, Florida wastewater treatment facility effluent proved A. imbecilis less sensitive than C. dubia; and much less sensitive than P. promelas, which all died within 24 h in the lowest effluent concentrations. Sediment-sorption of chlordane and toxaphene seems to play an important role in survival rate of A. imbecilis in the studies with or without sediment in the chamber. Since A. imbecilis was found to be no more sensitive to the tested organic pollutants after a 48-h exposure than D. magna, mussels may be adequately protected by current water quality standards. (Martini-PTT) 35 090209000

  80. Density and Ecomorphology of a Freshwater Mussel (Elliptio complanata, Bivalvia:Unionidae) in a Rhode Island Lake

    DH Kesler and RC Bailey.

    Journal of the North American Benthological Society JNASEC, p 259-264, September 1993, pp. 18 ref.

    Densities of freshwater mussel species in a small (430 ha), shallow (maximum depth=1.8 m) lake (Worden Pond) in Rhode Island were determined by a SCUBA survey. The three dominant mussel species included Elliptio complanata, Lampsilis radiata and Ligumia nasuta. Anodonta cataracta was found rarely in shallow, sandy areas. A morphological analysis of E. complanata showed that individuals living in silt substratum were larger, older, and narrower relative to those in sand. Growth rates, calculated using data on size (length, height, and width of shell) and age (determined by thin section), showed faster growth in the silt substratum. These results conflict with other ecomorphological analyses of E. complanata and other unionid species. The sand habitat may be worse and/or the silt habitat better for mussel growth, relative to similar contrasts made previously. (Author's abstract)

  81. Freshwater bivalve extinctions (Mollusca: Unionoida): A search for causes

    Arthur E. Bogan.

    American Zoologist, Vol. 33, No. 6, 1993, pp. 599.

    Freshwater bivalves are classified in six families and about 165 genera worldwide. The worldwide rate of extinction and causes are discussed.

  82. Impact of the zebra mussel, a bivalve invader

    Michael L. Ludyanskiy, Derek McDonald and David MacNeill.

    Bioscience, Vol. 43, No. 8, Sep 1993, pp. 533.

    The freshwater bivalve mollusk Dreissena polymorpha, better known as the zebra mussel, is a native of southern Russia and is spreading throughout the waterways of the US and Canada. The positive and negative impacts of the zebra mussel and its distribution in North America are discussed.

  83. Juvenile Freshwater Mussel (Bivalvia:unionidae) Responses to Acute Toxicity Testing with Copper

    PJ Jacobson, JL Farris, DS Cherry and RJ Neves.

    Environmental Toxicology and Chemistry ETOCDK, p 879-883, May 1993, pp. 23 ref.

    The sensitivities of newly metamorphosed juveniles of Villosa iris and Anodonta grandis to copper were determined using 24 hr static bioassays. Two methods of assessing post-exposure response were compared: direct visual examination and the use of vital staining with neutral red. Both species responded to copper exposures, exhibiting valve closure at concentrations as low as 24 microgm Cu/L for V. iris and 17 microgm Cu/L for A. grandis. EC50 values of 27 microgm Cu/L (V. iris) and 33 microgm Cu/L (A. grandis) were calculated on the basis of the valve closure response. Use of vital staining with neutral red provided an EC50 of 29 microgm C/L for V. iris. The amber coloration of A. grandis valves prevented determination of an EC50 using the vital staining. LC50 values of 83 microgm Cu/L (V. iris) and 44 microgm Cu/L (A. grandis) were calculated from the results of vital staining. Neutral red was found to be effective in assessing post-exposure mortality and sublethal responses after acute exposures to copper. (Author's abstract) 35 032787064

  84. Marohabitats of Freshwater Mussels (Bivalvia:Unionacea) in Streams of the Northern Atlantic Slope

    DL Strayer.

    Journal of the North American Benthological Society JNASEC, p 236-246, September 1993, pp. 41 ref.

    When predicting the broad-scale (1-10 km) distributions of freshwater mussels from readily available macrohabitat descriptors, all six of the descriptors used (stream size, stream gradient, hydrologic variability, calcium concentration, physiographic province, and the presence or absence of a tide) were found to have some predictive power. However, stream size and tidal influence were the most effective predictors of mussel distributions. Unexpectedly, several mussel species typically occurred in calcium-poor waters, a situation which was tentatively interpreted as evidence that these species might not tolerate eutrophication. In general, the macrohabitat distributions of mussel species identified in this study correspond only moderately well to previously published, subjective assessments of mussel habitat use. (Author's abstract) 35 020272001

  85. Metal Regulation in Two Species of Freshwater Bivalves

    MH Kraak, M. Toussaint, EA Bleeker and D. Lavy.

    IN: Ecotoxicology of Metals in Invertebrates. Proceedings of a session at the First Society of Environmental Toxicology and Chemistry-Europe Conference held in Sheffield, England

    To examine whether and to what extent the freshwater mussels Dreissena polymorpha and Unio pictorum are able to regulate their body and/or internal tissue Cu concentrations these species were exposed to a range of dissolved sublethal Cu concentrations. In addition, the regulation and accumulation of Zn and Cd in D. polymorpha were studied. For D. polymorpha, total soft tissues were analyzed; for Unio pictorum the soft tissues of each mussel were divided into digestive gland, kidney, gill, mantle, and gonads before analyzing for Cu. Both species were able to regulate their internal concentration of the essential metal Cu. D. polymorpha was able to regulate the essential metal Zn up to a higher external concentration (191 microg/L) than Cu (28 microg/L), while the nonessential metal Cd could not be regulated. The different organs of U. pictorum exhibited different No Observed Effect Concentrations (NOEC accumulation) for Cu: gill (34 microg/L) 121 microg/L) and gonads (> 121 microg/L). After exposure to the highest Cu concentration tested (nominal 200 microg/L), the highest internal Cu concentrations were observed in the gill and the digestive gland. No significant accumulation took place in the kidney and gonads in these acute experiments. The concentration in an animal or tissue is not only determined by the exposure level, but also by the regulation capability (NOEC accumulation), the accumulation rate once the NOEC accumulation is exceeded, and the exposure time. (See also W94-00818) (Author's abstract)

  86. Metal Uptake, Regulation, and Excretion in Freshwater Invertebrates

    PS Rainbow and R. Dallinger.

    IN: Ecotoxicology of Metals in Invertebrates. Proceedings of a session at the First Society of Environmental Toxicology and Chemistry-Europe Conference held in Sheffield, England

    The processes of metal accumulation may be different in marine and freshwater invertebrates due to the inherent difference in the physicochemical properties of freshwater as opposed to salt water. Metal uptake by freshwater invertebrates may be by passive mechanisms such as diffusion, membrane transport, and the incorporation of metals into inorganic and organic ligands. Under unusual circumstances, direct passage through the lipid membrane is probably the route of uptake of metals bound in lipophilic organometallic compounds. The second possible uptake mechanism of metals into freshwater invertebrates involves the incorporation of dissolved trace metals into active pumps available for the major ions. The active pump route is under physiological control, as is the case for calcium and cadmium. The high requirement for calcium by freshwater invertebrates may increase the relative importance of Cd entry via the calcium pump. Constant body concentrations of metals in specimens of a species collected from many different sites of different metal bioavailabilities provides some indication that metal regulation is occurring. Regulation at the whole body level is not a common metal accumulation strategy of invertebrates, apparently being restricted to certain essential trace metals, particularly Zn and Cu, and perhaps to particular invertebrate taxa especially decapod crustaceans. Partial regulators which show little net accumulation of metal are exemplified by mussels, in the case of Zn. Oysters, on the other hand, are strong accumulators of Zn. Metal excretion needs to balance metal uptake if regulation is to be achieved. Increases in tegument impermeability in freshwater decapods and amphipods restricts osmotic entry of water and may regulate metal accumulation. Adoption of the freshwater habit by malacostracan crustaceans might also increase metal uptake by active pump routes. Freshwater mussels appear to regulate soft tissue concentrations. Losses of Zn and Cd were associated with cast exuvia at molting in chironomid larvae, but net accumulation of both metals still occurred. Sediment-feeding mayfly larvae excrete Zn, Cd, and Pb accumulated originally from sediment as food. (See also W94-00818) (Author's abstract) 35 004133047

  87. Microhabitat Use by an Assemblage of Stream-Dwelling Unionaceans (Bivalvia), Including Two Rare Species of Alasmidonta

    DL Strayer and J. Ralley.

    Journal of the North American Benthological Society JNASEC, p 247-258, September 1993, pp. 36 ref.

    The microhabitats of six species of freshwater mussels were studied, including two rare species of Alasmidonta, in the Neversink River, New York. In each of 270, 1-sq m quadrats, water depth, current speed, bottom roughness, spatial variation in current speed, distance to shore, presence or absence of macrophytes, presence or absence of an overhead canopy, the extent of patches of fine sediment, and sediment granulometry, were measured alone with a recording of the mussels present. Mussel populations in the Neversink are dense (mean=3.2/sq m) and highly clumped. Stepwise discriminant analyses showed that current speed and spatial variation in current speed were the most useful predictors of the occurrence of mussels in quadrats. Alasmidonta heterodon was found most frequently at moderate current speeds and in quadrats that contained many patches of fine sediments. Alasmidonta varicosa occurred most frequently at moderate current speeds and in sediments with a high proportion of medium sands (0.25-1 mm). Nevertheless, the predictive power of discriminant models based on microhabitat variables is so low that the adequacy of a traditional microhabitat approach to unionacean ecology can be questioned. Therefore, including geomorphological descriptors of the streambed or working at spatial scales of hundreds of meters might be more useful than a traditional microhabitat approach for predicting the distribution of freshwater mussels in streams. (Author's abstract) 35 020272001

  88. Mussels: The Forgotten Fauna of Regulated Rivers. A Case Study of the Caney Fork River

    JB Layzer, ME Gordon and RM Anderson.

    Regulated Rivers Research & Management RRRMEP, p 63-71, May 1993, pp. 33 ref.

    During the past century freshwater mussel populations have declined precipitously throughout North America. Much of this loss has resulted from the construction of dams. In the Cumberland River system, 23% (22 species) of the historic mussel fauna is extinct or listed as endangered. Several additional species have either been extirpated from the Cumberland River or exist only in small, non-reproducing populations. Mussels of headwater streams have been severely affected by coal mining and poor land use practices. An intensive survey was conducted in the Caney Fork River, a major tributary to the Cumberland River, to determine the historic and extant mussel fauna. The results indicate that at least 37 species of mussels have been extirpated from the Caney Fork River, mainly as a result of the construction and operation of the Center Hill Dam. Among the species extirpated, two are now extinct, five are endangered and five are candidates for listing as threatened or endangered. Effects associated with this dam include the inundation of 102 km of riverine habitat, the discharge of hypolimnetic water (which limits mussel reproduction) and an alternating pattern of stream bed scouring and dewatering. The recognition of mussel life history requirements during preconstruction could have reduced many of these effects. (Author's abstract) 35 084846000

  89. Shell Growth of the Freshwater Unionid Unio crassus from Estonian Rivers

    H. Timm and H. Mutvei.

    Proceedings of the Estonian Academy of Sciences-Biology ETATAW, p 55-67, 1993, pp. 9 ref.

    Studies were conducted to determine the growth rate and chemistry of shells of the freshwater unionid Unio crassus, from Estonian rivers. Growth rate was compared to the current mean summer air temperature, and to the amount of precipitation of the previous year. Maximum age of fully grown mussels varied between 15 and 90 years, 38+/-6 on the average. Shell length was highly variable in different localities. It was positively correlated to shell weight but not to age of the mussel. Summer mean temperature was not positively correlated to annual shell growth rates. Three individuals from the Velise River showed a positive correlation between growth rate and amount of precipitation of the previous year. No significant correlations were found in the case of the other twelve rivers. No significant differences between the three hydrochemical regions of Estonian small rivers were detected on the basis of shell growth parameters. The significant increase of annual growth rate during the last 10-12 yrs, found in mussels from the Soodla River, seemed to be caused by an increase of phytoplankton biomass due to the construction of a reservoir. Urban pollution 10 km downstream of the town of Jogeva, probably affected the mussel population in the Pedja River resulting in a short life span and rapid decrease of growth rate. Mussels from the agriculturally influenced Pedja and Mudajogi Rivers had short life spans and high annual growth rates. (Lantz-PTT)

  90. Spatial Aggregation, Body Size, and Reproductive Success in the Freshwater Mussel Elliptio complanata

    JA Downing, Y. Rochon, M. Perusse and H. Harvey.

    Journal of the North American Benthological Society JNASEC, Vol. p 148-156, No. , June 1993, pp. 38 ref.

    The reproductive ecology of the freshwater, unionid mussel Elliptio complanata was investigated by mapping a 6-m x 7-m segment of a population found in a uniform area of the sandy littoral zone of Lac de l'Achigan, Quebec. The contents of the marsupia were examined in mussels collected between spawning and larval release. Although unrelated to spatial aggregation, the number of ova carried by mussels varied with body size in a manner that suggested extremely late maturation followed by reproductive senescence in the largest mussels. Egg production was 1-2 orders of magnitude greater than that of other poikilotherms of equivalent mass. Fertilization success was strongly correlated with spatial aggregation, with complete fertilization failure found at local densities of 50% successful when local densities were > 18 mussels/sq m, and 100% successful only in patches where local densities exceeded 40 mussels/sq m. Fertilization failure is probably frequent at mussel densities found in most lakes. These data suggest that perturbation altering the density, aggregation or size distribution of mussel populations may have serious consequences for the maintenance of viable populations. (Author's abstract)

  91. Ageing Studies on Three Species of Freshwater Mussels from a Metal-Polluted Watershed in Nova Scotia, Canada

    JL Smith and RH Green.

    Canadian Journal of Zoology CJZOAG, p 1284-1291, July 1992, pp. 29 ref.

    Freshwater mussels are increasingly used to monitor metal pollution in freshwater systems. Mussels are long-lived, and age is a factor that may influence metal concentrations in their tissues. Precise age estimates are also needed for determining the effects of contamination on population parameters such as growth rate. Elliptio complanata, Anodonta implicata, and Alasmidonta undulata (family Unionidae) were collected from two Nova Scotia (Canada) lakes contaminated with arsenic and mercury. Mussel shells were weighed, measured, and sectioned, and two independent counts of internal growth bands were made. External rings were also counted for A. implicata. Age estimates based on internal bands were most precise for E. complanata (r-squared = 0 71 vs. 0.35 for A. implicata and 0.29 for A. undulata). Estimates based on external rings were more precise (r-squared = 0.69) than those based on internal bands for A. implicata, but were believed to include disturbance rings. Shell length and weight were similarly correlated with age for a given species and population, but relationships were less clear in the lake with the more variable habitat. Elliptio complanata were much smaller at a given age in the more contaminated lake. (Author's abstract)

  92. Organochlorine Residues and Physiological Condition of the Freshwater Mussel Anodonta anatina Caged in River Pielinen, Eastern Finland, Receiving Pulp Mill Effluent

    TP Makela, P. Lindstrom-Seppa and AOJ Oikari.

    Aqua Fennica AQFEDI, p 49-58, 1992, pp. 50 ref.

    Freshwater mussels, Anodonta anatina L., were incubated at sites 5-40 km downstream from a bleached kraft pulp mill and at a control area upstream from the mill sewer for four months in the Pielinen River, Eastern Finland. Organochlorine residues were measured as extractable organically bound chlorine (EOCl or EOX) and as individual chlorinated phenolics. The residues were related to the following biological parameters: growth, nutritional reserves, glutathione-S-transferase (GST), and reproduction. Analysis of dry weight based EOCl in total mussel soft tissue did not show a clear distance related relationship. In the digestive gland, chlorinated phenolics could be detected only at the closest incubation site (3 km; 2,3,4,6-tetrachlorophenol 3.2 microg/g dw). EOX in the digestive gland had the highest value at a site where the primary production was highest, indicating that bioavailability from particulate material or filtering activity may play an important role in organochlorine accumulation. None of the biological parameters studied showed distance related effects caused by pulp mill effluent. On the other hand GST was decreased by about 20% at 20 Km but not at 5 km from the pulp mill sewer compared to the upstream site. (Author's abstract) 35 080743001

  93. Sublethal Effects of Cadmium on Physiological Responses in the Pocketbook Mussel, Lampsilis ventricosa

    TJ Naimo, GJ Atchison and LE Holland-Bartels.

    Environmental Toxicology and Chemistry ETOCDK, p 1013-1021, July 1992, pp. 40 ref.

    Recent studies indicate that the density and diversity of freshwater mussels are declining in many large river systems, probably from low-level chemical contamination. Exposure of Lampsilis ventricosa (pocketbook mussel) to 0, 22, 111, and 305 micrograms/L of cadmium for 28 d in a proportional diluter resulted in a significant decrease in respiration rate as cadmium rate increased. Although variations in cadmium concentrations did not significantly affect food clearance rates or ammonia excretion rates, mussels exposed to 305 micrograms Cd/L showed a decrease in ammonia excretion rates and a decrease in food clearance rates over the 28-d study. Assimilation efficiencies increased during the test in al treatments. Oxygen-to-nitrogen ratios were significantly increased in mussels exposed to either 111 or 305 micrograms Cd/L by day 28. Tissue condition index values were significantly lower in mussels in the toxicity test than those in a field sample. The significant change in respiration rate after only a 28-d exposure to Cd suggests that freshwater mussels may be sensitive indicators of sublethal contaminant exposure. However, the large variability in other physiological responses indicates that the study of contaminant effects requires careful selection of appropriate physiological indicators. (Author's abstract)

  94. Accumulation and Depuration of Chlorinated Phenolics in the Freshwater Mussel (Anodonta anatina L.)

    T. Makela, T. Petanen, J. Kukkonen and AOJ Oikari.

    Ecotoxicology and Environmental Safety EESADV, p 153-163, October 1991, pp. 25 ref.

    The duck mussel (Anodonta anatina), a widely distributed member of the family Unionidae, has been tested in bioindicator research in Finland. Uptake from ambient water and the depuration of five chlorinated phenolics, two chloroguaiacols (3 ,4,5-tri and tetrachloroguaiacol), and three chlorophenols (2,4 ,6-tri, 2,3,4,5-tetra and pentachlorophenol) were studied in the duck mussel. Groups of animals were exposed at four acclimation temperatures (3, 8, 13, and 18 C) to four chlorophenolic concentrations (total 6 to 56 micrograms/L). The depuration was monitored for 72 hours. For the analysis of individual chlorophenolics by the gas chromatographic/electron capture detection (GC/ECD) technique, the soft tissue of mussels was homogenized, spiked with internal standard, acetylated and extracted with n-hexane. The bioconcentration factors (BCF; concentration in animal wet weight per concentration in water) were determined for mussel soft tissue. The highest BCF was found for pentachlorophenol (81 to 461) and the lowest for trichlorophenol (14 to 125). Neither water temperature nor exposure concentration affected the BCFs. The compounds studied were depurated rapidly and their depuration half-lives in soft tissue were generally less than 24 hours. The BCFs for phenolics can differ two to threefold from one exposure group of animals to another. The values are so constant, however, that the contamination level in water can be back-calculated by tissue analyses within quite a large range of concentrations. (Author's abstract) 35 080743001

  95. Cross-Channel Distribution Patterns of Zoobenthos in a Regulated Reach of the Tennessee River

    KH Haag and JH Thorp.

    Regulated Rivers Research & Management RRRMEP, p 225-233, July/September 1991, pp. 45 ref. US Army Corps of Engineers Contract DACW89.

    The importance of substrate type and water depth was investigated in a regulated reach of a large, navigable river in the USA. Benthic grab samples were collected in June and August 1989, along two shore-to-shore transects in the lower Tennessee River, approximately 1.5 km downstream from Kentucky Lock and Dam. Diversity, averaged over all samples, was not significantly different from June to August. River depth of the samples, which ranged from 3.1 m to 6.5 m, significantly influenced macroinvertebrate density, but had no detectable effect on the total number of taxa collected. Densities of flatworms, Asiatic clams, snails, isopods, and mayflies increased significantly with increasing depth, whereas the abundance of native mussels (Unionidae) and caddisflies decreased with depth. Substrate type (sand through cobble) influenced both the total number of taxa and the total number of organisms collected. Sample areas dominated by cobble contained significantly fewer individuals than areas composed predominantly of gravel substrate. Asiatic clams, the single most abundant species collected, were consistently more numerous on intermediate substrate sizes. In contrast, densities of native mussels, snails, and mayflies were not correlated with bottom type. Sample areas included relatively little mud and sand, resulting in relatively low numbers of oligochaetes and midges in the collections. (Author's abstract) 35 006832030

  96. Changes in Freshwater Mussel Populations of the Ohio River: 1 ,000 BP to Recent Times

    R. Taylor.

    Ohio Journal of Science OJSCA9 Vol.89, No.5, p 188-191, December 1989.3 tab, 19 ref., 1989.

    Through the use of literature records and new data, it was possible to compile a list of species of freshwater mussels that inhabited the upper Ohio River (Ohio River Mile 0-300) around a thousand years ago. This information was derived from specimens found associated with Indian middens located along the banks of the Ohio. Analysis of these data indicates that at least 31 species of mussels were present in the river. Arnold Ortmann recorded 37 species from the same area as a result of his many years of collecting around the turn of the 20th century. Thirty-three species have been collectively documented as currently residing in limited numbers in the river. The number of species present has remained essentially unchanged through time. There have been, however, significant changes in species composition and total numbers of individual mussels present. Occasionally, healthy populations can be found presently but much of the upper Ohio River is devoid of mussel life. Several large-river species have become established in this reach of the river as a consequence of damming and the resulting increase in depth, greater siltation and slowed rate of flow. Seventeen species known to have previously inhabited the upper Ohio River are listed as presumed to no longer survive there. (Author 's abstract)

  97. Evaluation of a Skimmer Dredge for Collecting Freshwater Mussels

    A. Miller, R. Whiting and D. Wilcox.

    Journal of Freshwater Ecology JFREDW Vol.5, No.2, p 151-154, December 1989.1 fig, 1 tab, 10 ref., 1989.

    A skimmer dredge was used effectively to collect freshwater mussels from sand-silt substrate in the upper Mississippi River. The skimmer dredge used was a smaller version of a marine dredge without hydraulic jets. This dredge was made with 0.63 cm mild steel plate and weighed 34.5 kg. Runners were 10 cm wide and 105 cm long. The skimmer blade was 43 cm wide with a set of forward-pointing 0.6 cm diameter tines spaced 1.9 cm apart that extended 2.5 cm beyond the leading edge of the blade. The blade and ramp assembly could be adjusted to alter dredging depth. Effectiveness was determined by comparing the numbers of mussels collected by the dredge to the total number present. The dredge obtained 62.3 % of the mussels in its path and provided good estimates of species richness, diversity, and relative species abundance. It caused 10 % mortality of thin-shelled species but did not damage thick-shelled species. In suitable substrate the skimmer dredge is preferable to a brail for exploratory surveys. (Mertz-PTT)

  98. Physiological Background for Using Freshwater Mussels in Monitoring Copper and Lead Pollution

    J. Salanki and K. Balogh.

    Hydrobiologia HYDRB8 Vol.188/89, p 445-454, December 1989.4 fig, 2 tab, 19 ref., 1989.

    In studying the effect of copper (10 +/-0.57 microg Cu/L and 100 +/-3.01 microg Cu/L) and lead (50 +/-1.12 microg Pb/L and 500 +/-12.5 microg Pb/L) on the filtration activity of Anodonta cygnea L., it was found that both heavy metals resulted in significant shortening of the active periods, but little change occurred in the length of the rest periods. The concentrations of copper and lead were measured in the gill, foot, mantle, adductor muscle and kidney for 840 hours of exposure to 10.9 +/-5 microg Cu/L and 57.0 +/-19 microg Pb/L as well as during subsequent depuration. Uptake was observed after 72 hours of exposure. The highest copper concentration (59.1 +/-16.2 microg Cu/g) was measured at 672 hr in the mantle, and the highest lead value (143 +/-26.1 microg Pb/g) was obtained in the kidney. Depuration of copper was fastest from the foot, and from the adductor muscle for lead. The gill had the longest half-depuration time (>840 hr for copper and >672 hr for lead). (Author 's abstract)

  99. Use of Freshwater Mussels (Bivalvia: Unionidae) to Monitor the Nearshore Environment of Lakes

    R. Green, R. Bailey, S. Hinch, J. Metcalfe and V. Young.

    Journal of Great Lakes Research JGLRDE Vol.15, No.4, p 635-644, 1989.3 tab, 42 ref., 1989.

    A combination of observational studies and manipulative field, mesocosm, and laboratory experiments have shown that lentic populations of unionid mussels, in particular Lampsilis radiata and Elliptio complanata, respond to environmental variation in several ways. Thus, mussels may be useful as monitors of their environment. Shell morphology, degree of shell etching, and shell growth rates vary along a gradient of exposure to water energy. These phenotypic responses to environmental variation appear to have little genetic basis. Two polymorphic allozyme loci were examined with electrophoresis, and allelic frequencies showed little spatial pattern. The heritability of shell size and shape was assessed and found to be quite low. However, in transplant experiments mussels moved to different environments were strongly influenced by the environment from which they came. For example, growth rate and tissue metal burdens at the end of a 1-year transplant study are determined much more by the source lake than by destination lake. This ' source effect ' can be explained by: (a) slowly reversing acclimation of a common genotype to contrasting habitats (e.g., north shore Lake Erie and adjacent waters), or (b) underlying but as yet undetected genetic differences which are a product of selection in genetically isolated populations (e.g., separate lakes on an acidity gradient in the Muskoka/Haliburton region). Attempts to use contaminant levels in the mussel shell as an environmental monitor were not successful. However, the research does demonstrate that changes in density and growth rate parameters may be attributable to pollution, despite the potentially confounding effects of natural environmental variation. (Author 's abstract)

  100. Valve Movement Response of Mussels: A Tool in Biological Monitoring

    KJM Kramer, HA Jenner and D. de Zwart.

    Hydrobiologia HYDRB8 Vol.188/89, p 433-443, December 1989.5 fig, 3 tab, 45 ref., 1989.

    Biological sensors are becoming more important for monitoring the quality of the aquatic environment. A method using the valve movement response of freshwater (Dreissena polymorpha) and marine (Mytilus edulis) mussels as a tool in monitoring studies was developed. Possible applications of the technique include: (1) effluent monitoring; (2) general water quality monitoring; (3) monitoring of water inlets (drinking water, aquaculture); (4) early warning system (alarm function, triggering a water sampler for chemical proof); (5) toxicity testing; and (6) physiological and behavioral studies. The electronic induction system developed for measuring valve movement has several advantages: (1) The electronic interface facilitates automated data collection and data interpretation; (2) Since transmitting and receiving coils attached to the mussel are quite small, and the connecting wires are thin and supple, burrowing bivalves are free to move to some extent; and (3) The small size and rigidity of the system allows its use both under laboratory and (semi) field conditions, the latter being essential for the application in an Early Warning system. (Author 's abstract)

  101. Rationale and Sampling Designs for Freshwater Mussels Unionidae in Streams, Large Rivers, Impoundments, and Lakes

    B. Isom and C. Gooch.

    Rationale for Sampling and Interpretation of Ecological Data in the Assessment of Freshwater Ecosystems.American Society for Testing and Materials, Philadelphia PA.1986.p 46-59, 1 fig, 9 tab, 23 ref., 1986.

    Historically, the rationale for sampling freshwater mussels was almost entirely for purposes of taxonomy, natural history surveys, and conservation and propagation efforts following a decline of the pearl button industry in the early 1900s. The concept of quantitative sampling of freshwater mussels is almost unknown in historical literature. Except for some proprietary or unpublished quantitative studies, the first study designed primarily to quantitatively sample freshwater mussels was by Scruggs followed by Isom, Bates, and Isom, and Dennis and Bates. An earlier concept paper on quantitative sampling of mollusks and crustaceans can be found in Wurtz. Quantitative sampling methods for freshwater mussels within the context of varied study objectives, for example water pollution surveys are described. An example of a quantitative site-specific mussel study on the Cumberland River, Tennessee, is included. Difficulties with this study 's design and application are discussed in some detail, along with site-specific studies on Kentucky Reservoir, Tennessee River, and Clinch River, Tennessee. (See also W89-01599) (Author 's abstract)

  102. Sampling Effort Required to Find Rare Species of Freshwater Mussels

    W. Kovalak, S. Dennis and J. Bates.

    Rationale for Sampling and Interpretation of Ecological Data in the Assessment of Freshwater Ecosystems.American Society for Testing and Materials, Philadelphia PA.1986.p 34-45, 4 fig, 4 tab, 5 ref., 1986.

    Several approaches for determining the sampling effort required to find rare species of freshwater mussels were examined. Methods based on the relationship between number of species and number of individuals collected may provide a basis for estimating sampling effort, but more research is required to verify their applicability. Collections of dead shells (from lake shores or river banks) cannot be used because dead shells do not accumulate in proportion to the occurrence of live specimens in adjacent waters. Methods based on quantitative sampling are most promising. However, several methodological problems must be overcome to make quantitative sampling cost-effective. A tentative protocol for searching for rare species is presented. A preliminary survey using qualitative methods is used to determine the distribution of mussels in a habitat. These data are used to stratify the habitat for quantitative sampling, preferably using quadrats. The number of samples taken depends on the scope of the study. Sample number may be set by some predetermined target density that must be detected or by funding. (See also W89-01599) (Author 's abstract)

  103. Instruction Report on Freshwater Mussels

    A. Miller and DA Nelson.

    Instruction Report EL-83-2 September 1983.Final Report.198 p, 22 Fig, 42 Tab, 394 Ref., 1983.

    This report contains information on the following topics: collecting, preserving, and identifying freshwater mussels; methods for relocating and creating habitat for mussels; the commercial shell industry; and the technical literature concerning mussels. This information will aid in performing impact assessments and endangered species surveys. Techniques for determining the number of samples required to provide a fairly accurate estimate of a population mean are discussed. The simplest and fastest is to calculate cumulative means for a particular species collected in a series of samples. The resulting curve will eventually stabilize near the mean of the population. A more accurate technique is to conduct a pilot survey, determine the average and standard deviation of the sample, and decide what degree of precision is required. Based upon the pilot survey, it is possible to make an estimate of the number of samples needed to satisfy the particular criteria desired. The diversity of the habitat and likelihood of capturing additional, less common, species can be determined by plotting cumulative species versus cumulative individuals. A computer program has been developed which can provide assistance in determining the number of samples required. The program can simulate cluster, random, or uniform distribution patterns. Using random numbers, the program then ' samples ' the array and calculates sample means and standard deviation.

  104. The Changing Molluscan Community

    S. Fuller.

    The Freshwater Potomac, Aquatic Communities and Environmental Stresses, Proceedings of a Symposium January 1977, College Park, Maryland, Flynn, K.C.and Mason, W.T., Eds., 1978.p 124-131, 1 tab, 62 ref., 1978.

    An environmental survey of the middle Potomac River was conducted from 1956 to 1976 on behalf of the Potomac Electric Power Company (Pepco) and its steam electric station at Dickerson, Montgomery County, Maryland. Mollusks were selected for study because they are a predominant element of the fresh-water macrobenthos, and are widely adaptable to environmental changes. In addition to studying the changes in the mollusk population, the effects of thermal effluents on these invertebrates were examined. Information concerning the numbers of animals present, the location and state of the environment, symbiosis, and condition of the animal is presented for numerous bivalves and gastropods. The severe decline of these populations over the years is attributed to sedimentation, heightened water temperature, symbiotic relationships, and toxins. Significant changes occurred in 1967 or 1968, and most of the affected mollusks were extirpated or their populations were diminished below recruitment level. At present the inadequate environmental conditions persisting consist of sedimentation, adverse water temperature, the onslaught of exotic organisms, and the effects of toxic pollutants. Thermal effects are local and no longer affect the composition of the community which has been reduced to a core of species notoriously tolerant of environmental disturbances. (Davison-IPA)