P. J. Herring.

Journal of the Marine Biological Association of the United Kingdom, Vol. 86, No. 1, 2006, pp. 125-128.

Two types of alvinocaridid shrimp postlarvae were taken at plume depth over the Kairei and Edmond hydrothermal vent fields in the south-west Indian Ocean. These postlarvae were superficially indistinguishable from similar postlarvae taken previously over hydrothermal vents in the Atlantic. The micronekton invertebrate taxa in the water column over the Kairei and Edmond sites were similar to those in the Atlantic. The most frequently taken deep-water fish at Kairei was an unidentified cyemid snipe eel, whereas in the Atlantic its place was taken by Gonostoma bathyphilum and species of the melamphaeid Scopeloberyx. Previous sampling over East Pacific Rise hydrothermal sites at 13 degree N failed to take any alvinocaridid postlarvae, but the ostracod Gigantocypris agassizi was a major component of the micronekton.

Eric G. DeChaine and Colleen M. Cavanaugh.

Progress in.molecular and subcellular biology, Vol. 41, 2006, pp. 227-249.

The symbioses between invertebrates and chemosynthetic bacteria allow both host and symbiont to colonize and thrive in otherwise inhospitable deep-sea habitats. Given the global distribution of the bathymodioline symbioses, this association is an excellent model for evaluating co-speciation and evolution of symbioses. Thus far, the methanotroph and chemoautotroph endosymbionts of mussels are tightly clustered within two independent clades of gamma Proteobacteria, respectively. Further physiological and genomic studies will elucidate the ecological and evolutionary roles that these bacterial clades play in the symbiosis and chemosynthetic community. Due to the overall abundance of the methanotrophic symbioses at hydrothermal vents and hydrocarbon seeps, they likely play a significant, but as of yet unquantified, role in the biogeochemical cycling of methane. With this in mind, the search for methanotrophic symbioses should not be restricted to these known deep-sea habitats, but rather should be expanded to include methane-rich coastal marine and freshwater environments inhabited by methanotrophs and bivalves. Our current understanding of the bathymodioline symbioses provides a strong foundation for future explorations into the origin, ecology, and evolution of methanotroph symbioses, which are now becoming possible through a combination of classical and advanced molecular techniques.

J. L. Salerno, S. A. Macko and S. J. Hallam, et al.

Biological Bulletin, Marine Biological Laboratory, Woods Hole, Vol. 208, No. 2, Apr 2005, pp. 145-155.

The densities of chemoautotrophic and methanotrophic symbiont morphotypes were determined in life-history stages (post-larvae, juveniles, adults) of two species of mussels (Bathymodiolus azoricus and B. heckerae) from deep-sea chemosynthetic environments (the Lucky Strike hydrothermal vent and the Blake Ridge cold seep) in the Atlantic Ocean. Both symbiont morphotypes were observed in all specimens and in the same relative proportions, regardless of life-history stage. The relative abundance of symbiont morphotypes, determined by transmission electron microscopy, was different in the two species: chemoautotrophs were dominant (13:1-18:1) in B. azoricus from the vent site; methanotrophs were dominant (2:1-3:1) in B. heckerae from the seep site. The ratio of CH sub(4):H sub(2)S is proposed as a determinant of the relative abundance of symbiont types: where CH sub(4):H sub(2)S is less than 1, as at the Lucky Strike site, chemoautotrophic symbionts dominate; where CH sub(4):H sub(2)S is greater than 2, as at the seep site, methanotrophs dominate. Organic carbon and nitrogen isotopic compositions of B. azoricus ( delta super(13)C = -30ppt; delta super(15)N = -9ppt) and B. heckerae ( delta super(13)C = -56ppt; delta super(15)N = -2ppt) varied little among life-history stages and provided no record of a larval diet of photosynthetically derived organic material in the post-larval and juvenile stages.

T. Wolff.

Cahiers de Biologie Marine, Vol. 46, No. 2, 2005, pp. 97-104.

Based on enumerations from 1997/1998 and personal records, an up-to-date survey of the hydrothermal vent fauna is presented with number of species, genera and families of various taxa. The number of recorded species is 712 and includes species known exclusively from vents (71%), also occurring in cold seeps and/or whale falls (5%), also recorded from non-vent/non-seep environments (9%) or mainly referred to genus only (15%). The number of genera is 373, of families 185. Molluscs, arthropods and polychaetes are the prevailing groups (36, 34 and 18%, respectively). Prosobranch gastropods number almost three fourths of 257 mollusc species, copepods more than one third of 225 crustaceans and phyllodocid polychaetes more than half of 129 polychaetes. Calculation of vent endemism (after deduction of 103 species of doubtful status) shows values far exceeding those found elsewhere in the marine environment. On species level it is 83.4%,with maximum values found in cirripeds (100%), copepods (98%), prosobranch gastropods (89%), and polychaetes (86%).The percentage of endemic genera is 45. All six cirriped and most vestimentiferan genera are endemic, and other high values are within copepods (66%), gastropods (58%), polychaetes (51%) and decapod crustaceans (43%). Fourteen among the families (8%) are found in vents exclusively, eight also in seeps.Original Abstract: Fondee sur les listes publiees en 1997 et 1998 et sur des donnees personnelles, une liste mise a jour de la faune des sources hydrothermales est presentee. Le nombre total d'especes signalees est 712, nombre qui inclut les especes exclusivement infeodees aux sources hydrothermales (71%), celles egalement presentes dans les zones de suintements froids ou sur les carcasses de baleines (5%), celles egalement trouvees dans d'autres types de milieux (9%), enfin celles identifiees seulement au niveau generique (15%). Le nombre total de genres est de 373, et celui des familles de 185. Mollusques, Arthropodes et Polychetes sont les groupes predominants (respectivement 36, 34 et 18% du total). Le nombre de Gasteropodes prosobranches represente a peu pres les trois quarts des 257 especes de Mollusques, les Copepodes plus d'un tiers des 225 Crustaces et les Phyllodocides plus de la moitie des 129 Polychetes. Une fois soustraites les 103 especes de statut douteux, le taux d'endemisme de la faune des sources hydrothermales atteint des valeurs qui excedent toutes celles trouvees dans d'autres environnements marins. Le taux d'endemisme au niveau specifique est de 83 %, avec des valeurs maximales chez les Cirripedes (100%), les Copepodes(98%), les Gasteropodes (89%) et les Polychetes (86%). Le pourcentage de genres endemiques est de 45%. Les six genres de Cirripedes et la plupart des genres de Vestimentiferes sont endemiques; d'autres valeurs elevees ont ete trouvees chez les Copepodes (66%), les Gasteropodes (58%), les Polychetes (51%) et les Decapodes (43%). Quatorze familles (8%) sont endemiques des sources hydrothermales.

V. G. Tarasov, A. V. Gebruk, A. N. Mironov and L. I. Moskalev.

Chemical Geology, Vol. 224, No. 1-3, 15 Dec 2005, pp. 5-39.

Hydrothermal vent communities from 76 areas lying at depths from 0 to 4100 m were split into two groups - "deep" and "shallow-water", based on the occurrence of vent obligate (restricted to hydrothermal vents) taxa of a high rank (genus and family). The two groups were then compared based on a large set of environmental, faunistic and community parameters. The degree of obligacy of fauna sharply changes at the depth of approximately 200 m. In 21 shallow-water areas, located at depths 200 m) hydrothermal communities differ from shallow-water ones (<200 m) in a much higher ratio of vent obligate taxa. Deep-sea vent communities are also distinguished by the lack of diatom and algae-bacterial mats, phytoplankton, lower species richness, the development of large sulphide structures, higher role of active vents in structuring communities in space, replication of a set of dominant taxa in communities within large regions reproduced through the succession at newly formed vent fields, more pronounced concentric and vertical zonality, higher biomass of macrofauna, the important role of symbiotrophic forms dominating the biomass. The ratio of species with a "point" species range (endemic to small areas) is higher in the deep sea. There are no significant differences between the vent and non-vent biogeography both in shallow-waters and the deep ocean. Modern deep-sea hydrothermal vent communities have a longer evolutionary history than their shallow-water counterparts. To explain major differences between deep and shallow-water hot vent communities, evolutionary processes need to be analysed over long geological periods and within global vertical zones. It is suggested that the proportion of organic matter derived from chemosynthesis and photosynthesis plays a crucial role in evolution. When calculated for global zones this proportion increases with depth to a certain critical level that separates deep and shallow-water hot vent communities and fauna. Vertical zonation in the distribution of obligate taxa in hydrothermal vent communities indicates that this level is reached at approximately 200 m depth. Differences between deep and shallow-water hydrothermal vent communities are significant enough to distinguish the two different phenomena. The principle differences are a higher ratio of vent obligate taxa and a dominance of symbiotrophic forms in deep-sea hydrothermal vent communities.

J. C. Dreyer, K. E. Knick, W. B. Flickinger and C. L. Van Dover.

Marine Ecology Progress Series, 121-134. 2005, pp. Vol. 302, p.

Comparisons of macrofaunal community structure (species composition, abundance, biovolume, rank order, species richness, diversity) in hydrothermal vent mussel beds at 9 degree 50'N (9N) on the East Pacific Rise were made from analysis of multiple quantitative samples collected in 1999 and 2001 from each of 3 mussel beds of known age (4 to 8 yr in 1999). In addition to this time series approach, a chronosequence based on 2001 samples from 4 mussel beds at 9N and 1 mussel bed at 11 degree 25'N (11N) allowed comparison of macrofaunal community structure for mussel beds ranging in age from 6 to >14 yr. Many aspects of community structure (rank abundance patterns, dominant species, and diversity) were similar in 1999 and 2001 samples. Young (6 to 7 yr) and old (10 to 14 yr) mussel beds sampled in 2001 could be distinguished using multivariate analyses, based on species abundance and species biovolume matrices, but the differences were in the relative abundance of the dominant species rather than in any substantial changes in the identity of the dominant species. The limpet Lepetodrilus elevatus was the dominant species at all sites in terms of abundance and biovolume; it and other dominant species may have slightly greater fitness compared to other species that allows them to persist as dominants regardless of the age or location of mussel beds. Decreasing biovolume of macrofaunal communities sampled at 9N and 11N in 2001 was correlated with increasing age of the mussel beds and is postulated to be largely a response to biological processes; including competition for inorganic substrates by free living and symbiotic chemoautotrophs and mussel induced mortality of larvae of macrofaunal species, rather than the result of waning hydrothermal activity.

Satoshi Nakagawa, Ken Takai and Fumio Inagaki, et al.

Environmental microbiology, Vol. 7, No. 10, Oct 2005, pp. 1619-1632.

Epsilon-Proteobacteria is increasingly recognized as an ecologically significant group of bacteria, particularly in deep-sea hydrothermal environments. In this study, we studied the spatial distribution, diversity and physiological characteristics of the epsilon-Proteobacteria in various microbial habitats in the vicinity of a deep-sea hydrothermal vent occurring in the Iheya North field in the Mid-Okinawa Trough, by using culture-dependent and -independent approaches. The habitats studied were inside and outside hydrothermal plume, and annelid polychaete tubes. In addition, we deployed colonization devices near the vent emission. The polychaete tubes harboured physiologically and phylogenetically diverse microbial community. The in situ samplers were predominantly colonized by epsilon-Proteobacteria. Energy metabolism of epsilon-Proteobacteria isolates was highly versatile. Tree topology generated from the metabolic traits was significantly different (P = 0.000) from that of 16S rRNA tree, indicating current 16S rRNA gene-based analyses do not provide sufficient information to infer the physiological characteristics of epsilon-Proteobacteria. Nevertheless, culturability of epsilon-Proteobacteria in various microbial habitats differed among the phylogenetic subgroups. Members of Sulfurimonas were characterized by the robust culturability, and the other phylogenetic subgroups appeared to lose culturability in seawater, probably because of the sensitivity to oxygen. These results provide new insight into the ecophysiological characteristics of the deep-sea hydrothermal vent epsilon-Proteobacteria, which has never been assessed by comparative analysis of the 16S rRNA genes.

Breea Govenar, Nadine Le Bris and Sabine Gollner, et al.

Marine Ecology Progress Series, 67-77. 2005, pp. Vol. 305, p.

The vestimentiferan tubeworm Riftia pachyptila (Polychaeta: Sibloglinidae) often dominates early succession stages and high productivity habitats at low-temperature hydrothermal vents on the East Pacific Rise. We collected 8 aggregations of R. pachyptila and the associated epifaunal community at 2 discrete sites of diffuse hydrothermal activity, in December 2001 and December 2002. Because of the high spatial and temporal variability of the biotic and abiotic factors related to hydrothermal vent activity, significant differences in the structure and the composition of the community were expected to occur at the scale of either 1 yr or 500 m distance between very different sites. There was no significant difference in the temperature ranges of the diffuse flow between sites or years, even though the environmental conditions were very different at the 2 sites. At 1 site (Riftia Field), the diffuse hydrothermal fluids had relatively low concentrations of sulfide, low pH, and high concentrations of iron. At the other site (Tica), the diffuse hydrothermal fluids had higher sulfide concentrations, the pH was closer to neutral, and iron was undetectable. The physiological condition of R. pachyptila appeared to reflect the availability of sulfide at each site. However, the structure and the composition of the epifaunal community were remarkably similar between sites and years, with the exception of a few species. Aggregations of R. pachyptila support high local species diversity relative to the surrounding seafloor and high community similarity in different hydrothermal vent habitats.

J. R. Voight.

Journal of the Marine Biological Association of the United Kingdom, Vol. 85, No. 4, 2005, pp. 985-988.

A feeding frenzy of 12 octopuses of Vulcanoctopus hydrothermalis was observed from the manned submersible Alvin at Parigo, a 2620 m deep hydrothermal vent on the East Pacific Rise. The aggregated benthic octopuses at the active vent used their arms and webs to forage on bathypelagic amphipods, apparently targeting their attacks based on contract with the swarming amphipods. Individual octopuses wrapped their arms around the mantles of smaller octopuses, apparently in competition for prey. Although members of the prey species, Halice hesmonectes, are individually small (<5 mm long), the density of their swarms may make them attractive prey for the octopus. Inactive sulphide spires encircled part of this vent site; octopuses that climbed these spires had easy access to the dense prey swarms. The presence of the spires may uniquely enable this site to support simultaneous foraging by large numbers of octopuses.

Antje Boetius.

Science (Washington), Vol. 307, No. 5714, 4 Mar 2005, pp. 1420-1422.

A new type of hydrothermal vent field in the Atlantic Ocean called Lost City was discovered in 2000. As Boetius describes in her Perspective, recent detailed mapping of this hydrothermal vent field as well as chemical and microbial analyses (Kelley et al.) reveal that an extraordinary array of micro- and macro-organisms inhabit the giant white carbonate chimneys of Lost City.

Edda Hahlbeck, Mark A. Pospesel, Franck Zal, James J. Childress and Horst Felbeck.

Deep Sea Research (Part I, Oceanographic Research Papers), Vol. 52, No. 10, Oct 2005, pp. 1885-1895.

Riftia pachyptila lives in the unstable environment at hydrothermal vent sites along oceanic spreading zones in the Eastern Pacific. The tubeworm has a symbiosis with intracellular carbon-fixing and sulfide-oxidizing bacteria. Nitrate is the main source of nitrogen available from their habitat. This compound serves as a substrate either for nitrate respiration or for biosynthesis after transformation into ammonia. Very high nitrate (up to 3.2 mM) and nitrite (up to 0.8 mM) concentrations in vascular blood of R. pachyptila indicate a novel uptake mechanism. The dialysis experiments reported here demonstrate the binding and transport of nitrate to the symbionts by high molecular weight components in the blood, most likely hemoglobin. The extent to which nitrate is bound differed markedly between blood from different animals. In addition, a strong inverse correlation was found between the concentrations of sulfide and nitrate in vascular blood, as well as between the sulfur content of trophosome and the nitrate content of vascular blood. Specimens with low sulfur stores showed much lower nitrate levels than those with pale green trophosome due to high levels of elemental sulfur.

Amanda E. Bates, Verena Tunnicliffe and Raymond W. Lee.

Marine Ecology Progress Series, 2005, Vol. 305, pp. 1-15

Habitat selection by 3 Juan de Fuca Ridge gastropod species relates to their thermal environment. Both collections and images taken along transects document the small-scale abundance patterns of each species with respect to temperature and distance from vent flows. Lepetodrilus fucensis and Depressigyra globulus were most abundant at distances from vent flows of 0 to 25 cm in warm fluids with high temperature variability (10 +/- 5 degree C) over several time scales. Both species were also abundant at 26 to 50 cm, where temperatures were lower with less variability (4 +/- 1 degree C). Provanna variabilis was most abundant from 51 to 75 cm, where temperatures were stable (3 +/- 0.5 degree C). All species were absent where maximum fluid temperatures reached 18 degree C and their substratum coverage was related to temperature. When presented with a choice in vent fluids from 10 to 2 degree C, L. fucensis and D. globulus moved to areas with temperatures above 5 degree C, while P. variabilis showed no preference. In species-specific temperature preference experiments, L. fucensis and D. globulus aggregated between 5 and 13 degree C, while P. variabilis occupied areas with significantly lower temperatures from 4 to 11 degree C. These experimental temperature preferences correspond with their thermal environments. Upper temperature limits are moderate; extreme abiotic variability in higher temperature fluids may constrain these 3 species. We conclude thermal conditions are a primary determinant of habitat selection, thereby driving gastropod abundance patterns. However, other factors likely contribute. Space competition nearest vent flows may result in the displacement of individuals of these species to low quality habitats.

G. Sancho, C. R. Fisher and S. Mills, et al.

Deep Sea Research (Part I, Oceanographic Research Papers), Vol. 52, No. 5, May 2005, pp. 837-844.

This study investigates predation by the vent zoarcid fish Thermarces cerberus through gastrointestinal analyses of 27 specimens collected with the submersible ALVIN at vents at 950'N on the East Pacific Rise. T. cerberus fed most frequently on gastropod mollusks (mainly Lepetodrilus elevatus) and amphipod crustaceans (mainly Ventiella sulfuris). Species found occasionally in high abundance included the swarming amphipod Halice hesmonectes and the snail Cyathermia naticoides. Other items also found in gastrointestinal tracts, but in very low numbers, included polychaete worms, crustaceans and unidentified tissue clumps. The comparison between the size distribution of L. elevatus limpets ingested by T. cerberus and those found attached to vestimentiferan tubes suggest that the fish may selectively prey on large limpets. If the selective removal of large Lepetodrilus spp. limpets by T. cerberus does occur, then it would have potential community-level consequences at hydrothermal vents, since these mobile gastropods appear to inhibit the settlement of sessile vent species, including tube-building worms. Our results suggest possible direct and indirect effects of T. cerberus on benthic community structure at hydrothermal vents on the East Pacific Rise.

Deborah S. Kelley, Jeffrey A. Karson and Gretchen L. Fruh-Green, et al.

Science (Washington), Vol. 307, No. 5714, 4 Mar 2005, pp. 1428-1434.

The serpentinite-hosted Lost City hydrothermal field is a remarkable submarine ecosystem in which geological, chemical, and biological processes are intimately interlinked. Reactions between seawater and upper mantle peridotite produce methane-and hydrogen-rich fluids, with temperatures ranging from <40 degree to 90 degree C at pH 9 to 11, and carbonate chimneys 30 to 60 meters tall. A low diversity of microorganisms related to methane-cycling Archaea thrive in the warm porous interiors of the edifices. Macrofaunal communities show a degree of species diversity at least as high as that of black smoker vent sites along the Mid-Atlantic Ridge, but they lack the high biomasses of chemosynthetic organisms that are typical of volcanically driven systems.

A. Hilario, C. M. Young and P. A. Tyler.

Biological Bulletin, Marine Biological Laboratory, Woods Hole, Vol. 208, No. 1, Feb 2005, pp. 20-28.

Vestimentiferan tubeworms are ecologically important members of deep-sea chemosynthetic communities, including hydrothermal vents and cold seeps. Some are community dominants and others are primary colonists of new vent sites; they include some of the longest living and fastest growing marine invertebrates. Their mechanisms of propagation, dispersal, and genetic exchange have been widely discussed. Direct sperm transfer from males to females has been documented in one species, Ridgeia piscesae, but others are known to discharge what are apparently primary oocytes. Brooding of embryos has never been observed in any vestimentiferan. These observations have led to the supposition that fertilization might be external in most species. Here we report sperm storage at the posterior end of the oviduct in five species, including tubeworms from both vents and seeps. We show experimentally that most eggs are inseminated internally, that fertilization rate is typically lower than 100%, that meiosis is completed after eggs are released from the female, and that the dispersal phase includes the entire embryonic period.

Z. P. McKiness and C. M. Cavanaugh.

Marine Ecology Progress Series, Vol. , No. 23 Jun 2005, pp. Vol. 295, pp. 183-190

The discovery and exploration of hydrothermal vents on the Central Indian Ridge (CIR) yielded invaluable samples for further resolution of the biogeography of chemoautotrophic symbioses. Mytilid mussels were collected from 2 CIR hydrothermal vent fields and preliminary molecular analyses suggested phylogenetic affinity with the western Pacific vent mussel Bathymodiolus brevior. Resolving whether this mussel, designated B. aff. brevior, hosts a dual symbiosis, as characterized for the 2 Mid-Atlantic Ridge hydrothermal vent mussel species, or a single chemoautotrophic symbiosis, as seen in the Pacific vent mussel species, will provide insight into the evolutionary history of mytilid symbioses. Ultrastructural, physiological, and molecular evidence are reported herein which support the presence of a single endosymbiont phylotype with chemoautotrophic metabolism. Phylogenetic analyses placed this symbiont in the same clade as the vesicomyid clam symbionts, prompting discussion regarding the evolutionary origin of chemoautotrophic symbioses in vent bivalves.

L. S. Mullineaux, S. W. Mills, A. K. Sweetman, A. H. Beaudreau, A. Metaxas and H. L. Hunt.

Marine Ecology Progress Series, 2 Jun 2005, pp. Vol. 293, pp. 1-16

We examined larval abundance patterns near deep-sea hydrothermal vents along the East Pacific Rise to investigate how physical transport processes and larval behavior may interact to influence larval dispersal from, and supply to, vent populations. We characterized vertical and lateral distributions and temporal variation of larvae of vent species using high-volume pumps that recovered larvae in good condition (some still alive) and in high numbers (up to 450 individuals sample super(-1)). Moorings supported pumps at heights of 1, 20, and 175 m above the seafloor, and were positioned directly above and at 10s to 100s of meters away from vent communities. Sampling was conducted on 4 cruises between November 1998 and May 2000. Larvae of 22 benthic species, including gastropods, a bivalve, polychaetes, and a crab, were identified unequivocally as vent species, and 15 additional species, or species-groups, comprised larvae of probable vent origin. For most taxa, abundances decreased significantly with increasing height above bottom. When vent sites within the confines of the axial valley were considered, larval abundances were significantly higher on-vent than off, suggesting that larvae may be retained within the valley. Abundances of all vent species varied significantly among sample dates; the variation was not synchronized among taxa, except for consistently low abundances during November 1998. Lateral distributions did not vary among major larval groups (gastropods, polychaetes and bivalves), although polychaetes showed anomalously high abundances off-vent at 1 m above bottom. Lateral patterns also did not vary among species of gastropods, indicating that hydrodynamic processes may be transporting diverse species in similar ways. However, the species-level differences in temporal patterns indicate that there is substantial discontinuity in the abundance of individual species at vent communities, possibly due to timing of spawning and/or behavioral interactions with flow.

S. C. Cary, B. J. Campbell and A. Ghadiri, et al.

Marine Ecology Progress Series, Vol. 284, 2004, pp. 237-251

The shrimp Rimicaris exoculata dominates the megafauna of some Mid-Atlantic Ridge hydrothermal vent fields. This species harbours a rich bacterial epibiosis inside its gill chamber. At the 'Rainbow' vent site (36' 14.0'N), the epibionts are associated with iron oxide deposits. Investigation of both bacteria and minerals by scanning electron microscopy (SEM) and X-ray microanalysis (EDX) revealed 3 distinct compartments in the gill chamber: (1) the lower pre-branchial chamber, housing bacteria but devoid of minerals; (2) the 'true' branchial chamber, containing the gills and devoid of both bacteria and minerals; and (3) the upper pre-branchial chamber, housing the main ectosymbiotic bacterial community and associated mineral deposits. Our chemical and temperature data indicated that abiotic iron oxidation appears to be kinetically inhibited in the environment of the shrimps, which would explain the lack of iron oxide deposits in the first 2 compartments. We propose that iron oxidation is microbially promoted in the third area. The discrepancy between the spatial distribution of bacteria and minerals suggests that different bacterial metabolisms are involved in the first and third compartments. A possible explanation lies in the modification of physico-chemical conditions downstream of the gills that would reduce the oxygen content and favours the development of bacterial iron-oxidizers in this Fell-rich environment. A potential role of such iron-oxidizing symbionts in the shrimp diet is suggested. This would be unusual for hydrothermal ecosystems, in which most previously described symbioses rely on sulphide or methane as an energy source.

M. Turnipseed, C. D. Jenkins and C. L. Van Dover.

Marine Biology, Vol. 145, No. 1, Jul 2004, pp. 121-132.

Comparisons between invertebrate communities hosted by similar foundation species under different environmental conditions permit identification of patterns of species distributions that might be characteristic of the different ecosystems. Similarities and differences in community structure between two major types of chemosynthetic ecosystems were assessed by analyzing samples of invertebrates associated with Bathymodiolus heckerae Gustafson et al. mussel beds at the Florida Escarpment seep (Gulf of Mexico, 26 degree 01.8N; 84 degree 54.9W; October 2000) and B. puteoserpentis von Cosel et al. mussel beds at the Snake Pit vent (Mid-Atlantic Ridge, 23 degree 22.1N; 44 degree 56.9W; July 2001). Macrofaunal species richness was nearly twice as high in the seep mussel bed compared to the vent mussel bed, and only a single morphospecies, the ophiuroid Ophioctenella acies Tyler et al., was shared between the sites. Similarities between the two faunas at higher taxonomic levels (genus and family) were evident for only a small percentage of the total number of taxa, suggesting that evolutionary histories of many of these seep and vent macrofaunal taxa are not shared. The taxonomic distinctiveness of the seep and vent mussel-bed macrofaunal communities supports the hypothesis that environmental and oceanographic barriers prevent most taxa from occupying both types of habitats. Macrofaunal community heterogeneity among samples was similar in seep and vent mussel beds, indicating that spatial scales of processes regulating community variability may be similar in the two types of ecosystems. Suspension feeders were not represented in the macrofauna of seep or vent mussel beds. Primary consumers (deposit feeders and grazers) contributed more to the total abundance of macrofauna of seep mussel beds than vent mussel beds; secondary consumers (polychaetes and shrimp) were more abundant in the vent mussel beds.

B. Govenar, M. Freeman, D. C. Bergquist, G. A. Johnson and C. R. Fisher.

Biological Bulletin, Vol. 207, No. 3, December, 2004 2004, pp. 177-182.

Following eruptions on the East Pacific Rise, tubeworms Tevnia jerichonana and Riftia pachyptila quickly colonize the basalt-hosted hydrothermal vents, soon growing to dominate these habitats. Colonization by the vent mussel Bathymodiolus thermophilus follows, with the mussels eventually overgrowing the tubeworms. Tubeworms and mussels harbor sulfur-oxidizing chemoautotrophic endosymbionts, which provide the bulk of their nutrition. Mussels have maintained the ability to filter-feed, allowing them to occupy a wider range of conditions, tolerating declining hydrothermal vent activity better than the tubeworms. An experiment to understand the mechanism of ecological succession in these vent habitats was recently undertaken. A manipulative experiment tested the hypothesis that the mussels prevent further colonization by tubeworms. In May 1998, six aggregations of tubeworms were cleared from a site, with location, source of diffuse flow, and venting fluid temperatures recorded. Six hundred nearby mussels were collected; 200 were deployed over each of three cleared sources of diffuse flow to test the mussels' effects on the subsequent colonization by the tubeworms. Observations were made after 1 year; growth rates of R. pachyptila were estimated from tube length. Colonization rates on the cleared sources of diffuse flow were similar to those on basalt blocks. There was an abundance of gastropods in this community, though as grazers and scavengers, none relied on the tubeworms for nutrition. None of the transplanted mussels persisted on the cleared sources of diffuse flow. Situated above the venting source, the juvenile mussels were exposed to less concentrated hydrothermal flow, the temperatures and concentrations of reduced chemicals were lower, and the oxygen concentration was higher than in the fluids emanating from the basalt. Results indicate that R. pachyptila may modify the vent habitat to facilitate the colonization of other species in the diffuse-flow habitat of basalt-hosted hydrothermal vents.

M. Zbinden, N. Le Bris, F. Gaill and P. Compere.

Marine Ecology Progress Series, 2004, pp. Vol. 284, pp. 237-251

The shrimp Rimicaris exoculata dominates the megafauna of some Mid-Atlantic Ridge hydrothermal vent fields. This species harbours a rich bacterial epibiosis inside its gill chamber. At the 'Rainbow' vent site (36' 14.0'N), the epibionts are associated with iron oxide deposits. Investigation of both bacteria and minerals by scanning electron microscopy (SEM) and X-ray microanalysis (EDX) revealed 3 distinct compartments in the gill chamber: (1) the lower pre-branchial chamber, housing bacteria but devoid of minerals; (2) the 'true' branchial chamber, containing the gills and devoid of both bacteria and minerals; and (3) the upper pre-branchial chamber, housing the main ectosymbiotic bacterial community and associated mineral deposits. Our chemical and temperature data indicated that abiotic iron oxidation appears to be kinetically inhibited in the environment of the shrimps, which would explain the lack of iron oxide deposits in the first 2 compartments. We propose that iron oxidation is microbially promoted in the third area. The discrepancy between the spatial distribution of bacteria and minerals suggests that different bacterial metabolisms are involved in the first and third compartments. A possible explanation lies in the modification of physico-chemical conditions downstream of the gills that would reduce the oxygen content and favours the development of bacterial iron-oxidizers in this Fell-rich environment. A potential role of such iron-oxidizing symbionts in the shrimp diet is suggested. This would be unusual for hydrothermal ecosystems, in which most previously described symbioses rely on sulphide or methane as an energy source.

C. T. S. Little, T. Danelian, R. J. Herrington and R. M. Haymon.

Journal of Paleontology, Vol. 78, No. 3, May 2004, pp. 542-559.

The Figueroa sulfide deposit located in Franciscan Complex rocks in the San Rafael Mountains, California, contains the only known Jurassic hydrothermal vent community. Based on radiolarian biostratigraphy it is Pliensbachian (early Jurassic) in age. The Figueroa fossil organisms lived at a deepwater, high temperature vent site located on a mid-ocean ridge or seamount at an equatorial latitude. The vent site was then translated northeastward by the motion of the Farallon Plate and was subsequently accreted to its present location. The vent fossils are preserved as molds of pyrite and there is no remaining shell or tube material. The fossil assemblage is specimen rich, but of low diversity, and comprises, in order of decreasing abundance, vestimentiferan worm tubes, rhynchonellide brachiopods (Anarhynchia cf. gabbi), and trochoidean gastropods (Francisciconcha maslennikovi new genus and species). These fossils represent only primary consuming organisms, some of which may have had chemosynthetic microbial endosymbionts, like many modern dominant vent animals. The Figueroa vent assemblage shares vestimentiferan tube worms and gastropods with other fossil and modern vent communities, but is unique in having rhynchonellide brachiopods. It shares this feature with contemporary Mesozoic cold seep communities. Many other taxonomic groups found at modern vent sites are missing from the Figueroa assemblage. The presence of vestimentiferan tube worm fossils in the Figueroa deposit is at odds with the supposed time of origin of the modern vestimentiferans ( similar to 100 Ma), based on molecular data.

C. L. Van Dover and R. A. Lutz.

Journal of experimental marine biology and ecology, Vol. 300, No. 1-2, Mar 2004, pp. 273-307.

In situ and laboratory experiments conducted over the past quarter of a century have greatly increased our understanding of the ecology of deep-sea hydrothermal systems. Early experiments suggested that chemosynthetic primary production constituted the principal source of organic matter for biological communities associated with vents, although subsequent studies have revealed many complexities associated with interactions between microbes and higher organisms inhabiting these ecosystems. A diversity of host-microbial symbiont relationships has been identified and experimental studies have revealed the exquisite physiological adaptations within the giant tubeworm, Riftia pachyptila, for the uptake, fixation, and assimilation of carbon. In vitro experiments demonstrated the unusual sulfide binding properties of tubeworm hemoglobin that prevent inhibition of the cytochrome-c oxidase enzyme system during transport of sulfide to symbiont-bearing tissues. Studies of respiration and growth of several species of vent organisms conducted over the past two decades transformed earlier views that low metabolism and slow growth are characteristics of all organisms inhabiting all deep-sea environments. Results of recent experiments suggest that metabolic rates correlate with the degree of mobility of the organisms rather than with any specific attribute of the deep- sea environment itself, and growth rates of certain vent organisms (e.g. R. pachyptila) were found to be among the highest in any marine environments. While extreme thermal tolerance has been suggested as characteristic of certain vent fauna (e.g. alvinellid polychaetes and alvinocarid shrimp), the majority of vent metazoans live at temperatures below 20 degree C and additional experiments are necessary to reconcile field experiments documenting thermal tolerance in situ, thermal tolerance in vivo, and thermal sensitivity of biochemical constituents of vent organisms. Transplantation and clearance experiments, as well as in situ characterization of vent fluid chemistry, have greatly increased our understanding of organism-environment interactions. Early analyses of metazoan egg size and larval morphology, coupled with in vivo larval culture experiments, available physical oceanographic data, and genetic studies of gene flow, have contributed greatly to our understanding of mechanisms of dispersal between widely separated vent sites. The documentation of invertebrate colonization and succession of new vents following a volcanic eruption, and a series of manipulative field experiments, provide considerable insights into the relative roles of abiotic conditions and biotic interactions in structuring vent communities. Recent and emerging technological developments, such as in situ chemical analyzers, observatory approaches, and laboratory-based pressure culture systems, should provide invaluable new experimental tools for tackling many remaining questions concerning the ecology of deep-sea hydrothermal systems.

M. -S Jeng, N. K. Ng and P. K. L. Ng.

Nature, Vol. 432, No. 7020, 23 Dec 2004, pp. 969.

The crab Xenograpsus testudinatus lives at enormously high densities around the sulphur-rich hydrothermal vents found in shallow waters off Taiwan, even though this acidic environment is low in nutrients. Here we show that these crabs swarm out of their crevices at slack water and feed on the vast numbers of zooplankton that are killed by the vents' sulphurous plumes, and that rain down like marine 'snow'. This opportunistic feeding behaviour explains how the crabs are able to survive in the adverse toxic environment of these shallow hydrothermal vents.

S. K. Goffredi, A. Waren, V. J. Orphan, C. L. Van Dover and R. C. Vrijenhoek.

Applied and Environmental Microbiology, Vol. 70, No. 5, May 2004, pp. 3082-3090.

Here we describe novel forms of structural integration between endo- and episymbiotic microbes and an unusual new species of snail from hydrothermal vents in the Indian Ocean. The snail houses a dense population of gamma -proteobacteria within the cells of its greatly enlarged esophageal gland. This tissue setting differs from that of all other vent mollusks, which harbor sulfur-oxidizing endosymbionts in their gills. The significantly reduced digestive tract, the isotopic signatures of the snail tissues, and the presence of internal bacteria suggest a dependence on chemoautotrophy for nutrition. Most notably, this snail is unique in having a dense coat of mineralized scales covering the sides of its foot, a feature seen in no other living metazoan. The scales are coated with iron sulfides (pyrite and greigite) and heavily colonized by epsilon - and delta -proteobacteria, likely participating in mineralization of the sclerites. This novel metazoan-microbial collaboration illustrates the great potential of organismal adaptation in chemically and physically challenging deep-sea environments.

T. Nakagawa, S. Nakagawa, F. Inagaki, K. Takai and K. Horikoshi.

FEMS microbiology letters, Vol. 232, No. 2, 19 Mar 2004, pp. 145-152.

The phylogenetic diversity of sulfate-reducing prokaryotes occurring in active deep-sea hydrothermal vent chimney structures was characterized based on the deduced amino acid sequence analysis of the polymerase chain reaction-amplified dissimilatory sulfite reductase (DSR) gene. The DSR genes were successfully amplified from microbial assemblages of the chimney structures, derived from three geographically and geologically distinct deep-sea hydrothermal systems in the Central Indian Ridge (CIR), in the Izu-Bonin Arc (IBA), and the Okinawa Trough (OT), respectively. Phylogenetic analysis revealed seven major phylogenetic groups. More than half of the clones from the CIR chimney structure were related to DSR amino acid sequences of the hyperthermophilic archaeal members of the genus Archaeoglobus, and those of environmental DSR clones within the class Thermodesulfobacteria. From the OT chimney structure, a different group was obtained, which comprised a novel, deep lineage associated with the DSRs of the thermophilic sulfate-reducing bacterium Thermodesulfovibrio. Most of the DSR clones from the IBA chimney structure were phylogenetically associated with the delta -proteobacterial sulfate-reducing bacteria represented by the genus Desulfobulbus. Sequence analysis of DSR clones demonstrated a diverse sulfate-reducing prokaryotic community in the active deep-sea hydrothermal chimney structures.

Carol A. Di Meo-Savoie, George W. Luther III and S. Craig Cary.

Geochimica et Cosmochimica Acta, Vol. 68, No. 9, May 2004, pp. 2055-2066.

Alvinella pompejana is a polychaetous annelid that inhabits narrow tubes along the walls of high-temperature hydrothermal vent chimneys. The worm hosts a rich community of epibiotic bacteria that coats its dorsal surface. Although the worm tube microhabitat is a challenging environment to sample, characterizing the thermal and geochemical regime is important for understanding the ecology of the worm and its bacteria, as the worm spends most of its time inside the tube. We characterized the physicochemical conditions of diffuse hydrothermal flow inside inhabited worm tubes using in situ analysis and wet chemical analysis of discrete water samples. Thermistor probes deployed inside worm tubes measured temperatures ranging from 28.6 degrees C to 84.0 degrees C, while temperatures at tube orifices ranged from 7.5 degrees C to 40.0 degrees C. In situ electrochemical analysis of tube fluids revealed undetectable oxygen (<5 mu M) and surprisingly low levels of free H (sub 2) S (<0.2 mu M), with most of the sulfide existing as aqueous FeS molecular clusters. Acid-volatile sulfide measured on discrete samples of tube fluids ranged from 62.9 to 359.3 mu M, while free sulfide (H (sub 2) S) ranged from undetectable (<0.2 mu M) to 46.5 mu M. The pH ranged from 5.33 to 6.40, and sulfate ranged from 22.5 mM to 27.5 mM. Nitrate ranged from 13.9 to 20.0 mu M, whereas ammonium ranged from 2.5 to 9.7 mu M. Total Fe ranged from 72.1 to 730.2 mu M. Mn, Zn, Ni, V, P, and Cu were present in micromolar amounts; Pb, Cd, Co, and Ag were present in nanomolar levels. The worm tube fluids contained between 72% to 91% of Mg concentrations typically found in deep seawater. Plots of Mg concentrations vs. other fluid components showed that the tube fluid is geochemically altered from theoretical mixing values. Values of SO (sub 4) (super 2-) were enriched inside the worm tube fluids, whereas NO (sub 3) (super -) , Sr, Mn, Fe, Zn, and acid-volatile sulfide were depleted. The geochemistry of the tube microhabitat likely influences the structure of resident microbial communities.

A. Metaxas.

Limnology and Oceanography, Vol. 49, No. 6, Nov 2004, pp. 1949-1956.

Larval supply in marine benthic invertebrates influences patterns of settlement and recruitment to adult populations. To successfully colonize newly formed or distant hydrothermal vents, which are discontinuous and ephemeral habitats, larvae of vent invertebrates must possess long-range dispersal abilities. However, a significant proportion of locally produced larvae must remain within the adult habitat to maintain the observed dense assemblages of invertebrates. I compared spatial and temporal patterns in larval availability (flux and abundance) at hydrothermal vents within and between ridge segments in the northeast Pacific ocean at Axial Seamount and Endeavour Segment on the Juan de Fuca Ridge and at Magic Mountain on Explorer Ridge. Near-bottom (within 50 cm) larval supply (individuals m super(-2) d super(-1)) at five vents on Axial Seamount, measured with passively collecting traps in 2000 and 2001, varied temporally by an order of magnitude, but not spatially at scales of tens of meters to kilometers. The most abundant larval taxa were gastropods (particularly the limpet Lepetodrilus fucensis) and polychaetes. Larval abundance in the water column within the axial valley was measured with net tows by the remotely operated vehicle ROPOS at the three ridge segments: Axial Seamount (2000, 2001); Endeavour Segment (2001, 2002); Magic Mountain (2002). Abundance was greater by an order of magnitude at the Endeavour Segment than at Axial Seamount and Magic Mountain, and it did not differ between on-vent (within tens of meters) and off-vent (up to 5 km from the venting source) locations within the axial valley. The uniformly high abundance of larvae within axial valleys suggests that larval supply within a ridge segment is most likely localized, implying significant larval retention on the scale of vent fields and possibly ridge segments.

Patrice Piccino, Frederique Viard, Pierre-Marie Sarradin, Nadine Le Bris, Dominique Le Guen and Didier Jollivet.

Proceedings of the Royal Society of London, Series B: Biological Sciences, Vol. 271, No. 1555, 22 Nov 2004, pp. 2351-2359.

Alvinella pompejana lives on the top of chimneys at deep-sea hydrothermal vents of the East Pacific Rise. It is thought to be one of the most thermotolerant and eurythermal metazoans. Our experimental approach combines methods of population genetics and biochemistry, considering temperature as a potential selective factor. Phosphoglucomutase (Pgm-1 locus) is one of the most polymorphic loci of A. pompejana and exhibits four alleles, from which alleles 90 and 100 dominate with frequencies of approximately 0.5 in populations. Results from previous studies suggested that allele 90 might be more thermostable than allele 100. Significant genetic differentiation was found by comparing contrasted microhabitats, especially the young, still hot, versus older and colder chimneys, with allele 90 being at highest frequency on young chimneys. Moreover the frequency of allele 90 was positively correlated with mean temperature at the opening of Alvinella tubes. In parallel, thermostability and thermal optimum experiments demonstrated that allele 90 is more thermostable and more active at higher temperatures than allele 100. This dataset supports an additive model of diversifying selection in which allele 90 is favored on young hot chimneys but counterbalanced over the whole metapopulation by the dynamics of the vent ecosystem.

D. Desbruyeres and Commission Internationale pour l'Exploration de la Mer Mediterranee - CIESM, Monaco.

Monaco (Monaco): CIESM, 2003

The discovery of hydrothermal vents, followed by that of cold seeps, has been one of the great interdisciplinary successes of oceanography in at least the last 25 years. One can hardly imagine a greater contrast to the typical soft-sediment deep sea than the exuberant oases of life at hydrothennal vents and cold seeps areas. With the steep gradient of chemistry and the high biological primary production, the ecology of vent invertebrates is probably more closely similar to that of intertidal communities than to the "regular" deep sea ones. These oases of life are small-sized and discontinuous in space and cannot be observed and studied without the use of deep-sea submersibles. The direct linkage between fluid emission and bacterial chemo-autotrophic production makes them also discontinuous in time at different scales.

R. E. Thomson, S. F. Mihaly, A. B. Rabinovich, R. E. Mcduff, S. R. Veirs and F. R. Stahr.

Nature, Vol. 424, No. 6948, 31 Jul 2003, pp. 545-549.

Understanding how larvae from extant hydrothermal vent fields colonize neighbouring regions of the mid-ocean ridge system remains a major challenge in oceanic research. Among the factors considered important in the recruitment of deep-sea larvae are metabolic lifespan, the connectivity of the seafloor topography, and the characteristics of the currents. Here we use current velocity measurements from Endeavour ridge to examine the role of topographically constrained circulation on larval transport along-ridge. We show that the dominant tidal and wind-generated currents in the region are strongly attenuated within the rift valley that splits the ridge crest, and that hydrothermal plumes rising from vent fields in the valley drive a steady near- bottom inflow within the valley. Extrapolation of these findings suggests that the suppression of oscillatory currents within rift valleys of mid-ocean ridges shields larvae from cross-axis dispersal into the inhospitable deep ocean. This effect, augmented by plume-driven circulation within rift valleys having active hydrothermal venting, helps retain larvae near their source. Larvae are then exported preferentially down-ridge during regional flow events that intermittently over-ride the currents within the valley.

A. Metaxas and Commission Internationale pour l'Exploration de la Mer Mediterranee - CIESM, Monaco.

Monaco (Monaco): CIESM, 2003

The discovery of hydrothermal vents in 1977 impacted profoundly our preconceptions of structure and function of marine biological communities. These extreme habitats harbour communities of exceedingly high biomass but relatively low diversity, consisting mostly of endemic, newly discovered species. The luxuriant communities at vents are sustained by chemoautotrophic production by microbes, using CO sub(2) as substrate and energy derived from the oxidation of hydrogen sulfide (H sub(2)S). Over the last 25 years, research on the geological, physical, chemical and biological properties of hydrothermal vents has expanded significantly our understanding of these systems. Presently we are faced with our next challenge: to move forward in our understanding, we must adopt a combination of traditional approaches, which have been used in other systems for several decades, and innovative technologies, which currently are under development.

T. Shank, D. Fornari and D. Yoerger, et al.

EOS, Transactions, American Geophysical Union, Vol. 84, No. 41, 14 Oct 2003, pp. 430-432.

For over 25 years, hydrothermal vent communities discovered at the Galapagos Rift near 86 degree W have provided the foundation of deep-sea vent biology as their study has led to fundamental discoveries of chemoautorophy and novel symbioses in the deep sea. Since 1979, numerous physiological and geochemical investigations of the Rose Garden vent community have been made possible through routine access to this deep sea floor site, provided by the deep submergence vehicle Alvin. This research revolutionized our understanding of basic biological and chemical processes in the deep ocean.

P. A. Tyler and C. M. Young.

Hydrobiologia, Vol. 503, No. 1-3, Aug 2003, pp. 9-19.

The discovery of hydrothermal vents along the Galapagos Rift in 1977 opened up one of the most dynamic and productive research themes in marine biology. In the intervening 25 years, hydrothermal vent faunas have been described from the eastern, northeastern and western Pacific, the mid-Atlantic Ridge and the Indian Ocean in the region of the Rodriguez Triple Junction. In addition, there is evidence of hydrothermal signals from the Gakkel Ridge in the Arctic, the central and southwest Indian Ridges and the Scotia Arc in Antarctica. Although often perceived as a continuous linear structure, there are many discontinuities that have given rise to separate biogeographic provinces. In addition, the intervening 25 years have seen a massive increase in our understanding of the biological processes at hydrothermal vents. However, how vents are maintained, and how new vents are colonised has been relatively poorly understood until recently. This review addresses the known larval development of vent-endemic invertebrates. The distribution of larvae in relation to the hydrothermal plume, and the ocean ridge in general, are discussed and the experimental evidence of larval longevity and transport are discussed using such variables as gene flow and larval development rates. The concept of larval dispersal along the mid-ocean ridge is discussed in relation to dispersal barriers and relates the known biogeography of hydrothermal vent systems to both local and evolutionary processes.

Maia Tsurumi, R. C. De Graaf and V. Tunnicliffe.

Journal of the Marine Biological Association of the United Kingdom, Vol. 83, No. 3, 2003, pp. 469-477.

The abundance patterns of copepods on the Juan de Fuca Ridge was examined. One species was studied in detail. Twelve non-parasitic species are recorded from the Juan de Fuca, but only three dirivultid species and some unidentified harpacticoids are abundant in collections. Densities are estimated at 0.5 copepod cm super(-2) on vestimentiferan tubes to over 8 cm super(-2) on chimney surfaces. Aphotopontius forcipatus is most abundant at new vents and Benthoxynus spiculifer is most abundant at mature vents. Vents with reduced or undetectable fluid flow have higher diversity of copepod fauna. The life cycle of the siphonostome Stygiopontius quadrispinosus begins with a centrolecithal egg brooded singly or doubly on the female. Hatching and naupliar stages are unknown in benthic samples. The pre-adult stage (copepodite V) recruits to the vent habitat. Pre-adult males attach to pre-adult females and fertilize at the final copepodite VI moult. As the sex ratio is highly skewed in favour of females, males probably inseminate many females and there may be mate competition in populations where males are rare. Reproduction is probably continuous or semi-continuous. Abundance is greatest on sulphide edifices near the points of hot water egress. This copepod co-occurs with the alvinellid polychaete Paralvinella sulfincola.

M. Tsurumi.

Global Ecology and Biogeography, Vol. 12, No. 3, May 2003, pp. 181-190.

To describe patterns of hydrothermal vent community diversity and dispersion at the intersegment scale (> 100 km). The area discussed is an approximately 170 km portion of the Juan de Fuca Ridge, a mid-ocean ridge in the north-east Pacific Ocean. Samples of benthic invertebrates from hydrothermal vents on three segments of the Juan de Fuca are examined for community characteristics such as diversity, abundance and distribution. Species richness (55 species) and evenness are low. If the macrofauna only are considered, species richness is about 30% lower than when meiofauna are also considered. The geometric series describes the species-abundance distribution. The relationship between vent species' distribution and abundance is significantly positive (r super(2) = 0.818; P < 0.001). Alpha diversity is lower in patchy habitat than continuous habitat and gamma diversity is similar for both habitat types. Beta diversity is higher in patchy habitat. Local diversity is linearly related to regional diversity. Species richness is comparable to other highly disturbed systems. The geometric series species abundance model implies some degree of niche pre-emption in the vent community and is consistent with the suggestion that the geometric series distribution can be found in species-poor environments that experience harsh conditions and are structured by relatively few environmental factors. Species distribution and abundance are highly correlated. The regional species pool affects local vent diversity. Vent diversity studies should be conducted on at least the ridge scale.

B. J. Campbell, J. L. Stein and S. C. Cary.

Applied and Environmental Microbiology, Vol. 69, No. 9, Sep 2003, pp. 5070-5078.

The deep-sea polychaete Alvinella pompejana colonizes tubes on the sides of black smoker chimneys along the East Pacific Rise. A diverse, yet phylogenetically constrained episymbiotic community is obligately associated with its dorsal surface. The morphologically and phylogenetically distinct dominant episymbionts have not yet been cultured, and there are no clearly defined roles for these bacteria in this symbiosis. A large insert fosmid library was screened for the presence of the two dominant phylotypes. Two fosmids, 35.2 and 38 kb, containing phylotype-specific 16S ribosmal DNA sequences were fully sequenced. Each fosmid had a gene encoding ATP citrate lyase, a key enzyme in the reverse tricarboxylic acid (rTCA) cycle, a CO sub(2) fixation pathway. A selection of episymbiont communities from various geographic locations and vent sites were screened for the presence, diversity, and expression (via reverse transcription-PCR) of the ATP citrate lyase gene. Our results indicate that the ATP citrate lyase gene is not only a consistent presence in these episymbiont communities but is also expressed. Phylogenetically distinct forms of ATP citrate lyase were also found associated with and expressed by bacteria extracted from the tubes of A. pompejana. Utilizing PCR with degenerate primers based on a second key enzyme in the rTCA cycle, 2-oxoglutarate:acceptor oxidoreductase, we also demonstrated the persistent presence and expression of this gene in the episymbiont community. Our results suggest that members of both the episymbiont and the surrounding free-living communities display a chemolithoautotrophic form of growth and therefore contribute fixed carbon to other organisms in the vent community.

C. Levesque, S. K. Juniper and J. Marcus.

Marine Ecology Progress Series, 2003, pp. Vol. 246, pp. 173-182

Biotic communities in highly variable, frequently perturbed habitats are usually expected to be structured mainly by abiotic factors. In the highly variable deep-sea hydrothermal vent environment, physical and chemical factors are known to play an important role in limiting the distribution and abundance of species, but the importance of biotic interactions remains largely unresolved. The high density and biomass attained by the vent macrofauna suggest that resource partitioning and competition may be significant in these communities. This study of food resource utilisation at northeast Pacific deep-sea hydrothermal vents uses an approach based on stable carbon and nitrogen isotope analyses to characterise trophic interactions between the 3 dominant alvinellid polychaetes, Paralvinella palmiformis, P. sulfincola, and P. pandorae. We also examine size structure in sympatric and allopatric populations of P. palmiformis and P. pandorae. Results indicate that food resource partitioning occurs both intra- and interspecifically in P. palmiformis and P. sulfincola, and we advocate that this process contributes to explaining their co-existence at very high densities. In contrast, P. pandorae has a much more restricted trophic niche, overlaps P. palmiformis in diet and is much smaller in size when found in sympatry with P. palmiformis. P. pandorae is the most likely of the 3 species to be affected by intra- and/or interspecific competition for food, and this may explain the drastic change in the population size structure observed between successive years. Our work indicates that within the limits imposed by environmental conditions, biotic interactions such as food resource partitioning and competition can be significant factors structuring deep-sea hydrothermal vent communities.

M. E. Ward, C. D. Jenkins and C. L. M. Dover.

Canadian Journal of Zoology/Revue Canadienne de Zoologie, Vol. 81, No. 4, 2003, pp. 582-590.

Polychaetes are a large component of deep-sea hydrothermal-vent invertebrate faunas, yet little is known about the trophic ecology of most species. In this study, the feeding mode of a common and widespread vent polychaete, Archinome rosacea (order Amphinomida), is investigated through morphological studies and gut-content analyses. The foregut of this polychaete is similar in structure to that of other shallow-water Amphinomida. Prey capture is facilitated by a ventral muscular eversible proboscis with two glandular lateral-lip structures. Extracellular digestion is suggested by packets of digestive enzymes observed to be discharged from the apical ends of the midgut epithelial cells into the lumen. Midgut tissues also contain inclusions resembling spherocrystals, possibly sites where toxic materials are sequestered. Gut-content analyses indicate a preference for mobile prey, including polychaetes and crustaceans. We propose that predation and scavenging are important trophic strategies for A. rosacea.Original Abstract: Les polychetes sont une composante importante de la faune des cheminees hydrothermales dans la zone profonde des oceans et pourtant, on connait peu de choses au sujet de l'ecologie trophique de la plupart des especes. Nous etudions ici le mode d'alimentation d'un polychete commun dans les cheminees hydrothermales, Archinome rosacea (ordre Amphinomida), par examen morphologique et par analyse des contenus stomacaux. La partie anterieure du tube digestif est de structure semblable a celle d'autres Amphinomida d'eaux peu profondes. La capture des proies est assuree par le proboscis ventral, musculeux, reversible, qui porte deux structures laterales glandulaires en forme de levres. La digestion semble extracellulaire, vu la presence de paquets d'enzymes digestives liberes dans la lumiere aux extremites apicales des cellules epitheliales de la partie mediane du tube digestif. Les tissus de cette partie du tube contiennent aussi des inclusions ressemblant a des cristaux spheriques qui servent peut-etre a l'entreposage de matieres toxiques. Les analyses de contenus stomacaux ont revele une preference pour les proies mobiles, notamment des polychetes et des crustaces. Il semble qu'A. rosacea soit a la fois predatrice et detritivore, deux strategies alimentaires importantes pour cette espece.

I. A. Urcuyo, G. J. Massoth, D. Julian and C. R. Fisher.

Deep-Sea Research (Part I, Oceanographic Research Papers), Vol. 50, No. 6, Jun 2003, pp. 763-780.

The vestimentiferan tubeworm Ridgeia piscesae is an ecosystem- structuring organism in the hydrothermal vent environments of the Northeast Pacific. During this study, a single representative aggregation of the long- skinny morphotype of R. piscesae from the main endeavor segment was monitored for 3 yr before being collected in its entirety with a hydraulically actuated collection device manipulated in situ by a research vehicle. Vestimentiferan growth rates in this aggregation were determined by staining the exterior of the tubes and measuring newly deposited tube sections. The average growth rate of R. piscesae in this aggregation was very low in both years of the growth study (3.2 mm yr super(-1)). Although the incidence of plume damage from partial predation was very high (>95%), mortality was very low (<4% yr super(-1)). The distribution and the very tight clustering of recently recruited individuals indicated gregarious settlement behavior that is hypothesized to be partly due to biotic cues from settled larvae. Coupled measurements of vent fluid sulfide concentration and temperature were used to calculate the exposure of the vestimentiferans to sulfide from short- and long-term temperature monitoring. Plume-level temperature records indicate that most of the time individuals in this aggregation were exposed to extremely low levels of vent fluid, and therefore sulfide (<0.1 mu M), while their posterior sections were consistently exposed to sulfide concentrations in the 100 mu M range. A rootball-like structure formed the common base of the aggregation. In contrast to the anterior sections of the tubeworm tubes, the portions of the tubes within the 'rootball' were freely permeable to sulfide. The results of this study show that R. piscesae, unlike vestimentiferans from the East Pacific Rise, can survive and grow in areas of low diffuse vent flow with very low plume-level exposure to sulfide. We propose that this morphotype of R. piscesae has the ability to acquire sulfide from sources near their posterior ends, similar to some species of cold seep vestimentiferans from the Gulf of Mexico. The ability of this single species of vestimentiferan to survive low exposure to vent flow with low mortality coupled with sulfide uptake across posterior tube sections may help explain the occurrence of a single vent vestimentiferan species in a wide variety of habitat conditions at hydrothermal vent sites in the Northeast Pacific.

M. O. Schrenk, D. S. Kelley, J. R. Delaney and J. A. Baross.

Applied and Environmental Microbiology, Vol. 69, No. 6, Jun 2003, pp. 3580-3592.

A large, intact sulfide chimney, designated Finn, was recovered from the Mothra Vent Field on the Juan de Fuca Ridge in 1998. Finn was venting 302 degree C fluids on the seafloor and contained complex mineralogical zones surrounding a large open central conduit. Examination of microorganisms within these zones, followed by community analysis with oligonucleotide probes, showed that there were variations in the abundance and diversity of eubacteria and archaea from the exterior to the interior of the chimney. The microbial abundance based upon epifluorescence microscopy and quantitative fatty acid analyses varied from >10 cells/g of sulfide 2 to 10 cm within the chimney wall to <10 cells/g in interior zones. Direct microscopic observation indicated that microorganisms were attached to mineral surfaces throughout the structure. Whole-cell hybridization results revealed that there was a transition from a mixed community of eubacteria and archaea near the cool exterior of the chimney to primarily archaea near the warm interior. Archaeal diversity was examined in three zones of Finn by cloning and sequencing of the 16S rRNA gene. The majority of sequences from the exterior of the chimney were related to marine group I of the Crenarchaeota and uncultured Euryarchaeota from benthic marine environments. In contrast, clone libraries from interior regions of the chimney contained sequences closely related to methanogens, Thermococcales, and Archaeoglobales, in addition to uncultured crenarchaeal phylotypes obtained from deep subsurface sites. These observations of microbial communities within an active hydrothermal chimney provide insight into the microbial ecology within such structures and may facilitate follow-up exploration into expanding the known upper temperature limits of life.

R. A. Lutz, T. M. Shank and D. J. Fornari.

Journal of Shellfish Research, Vol. 22, No. 1, Jun 2003, pp. 341-342.

In April, 1991 a volcanic eruption obliterated existing biological communities within extensive regions along the crest of the East Pacific Rise between 9 degree 45'N and 9 degree 52'N (depth 2520 m). The initiation of hydrothermal venting during the eruptive process afforded the unique opportunity to follow, over a 10+ year period, temporal changes in biological community structure from the "birth" of numerous hydrothermal vents. Vestimentiferan tubeworms, amphipods, copepods, octopods, and galatheid and brachyruan crabs gradually colonized the vents during the first 2 years. Noticeably absent during this time was any evidence of the mussel Bathymodiolus thermophilus. Small mussels (5 cm were common in the region and had begun to colonize the tubes of Riftia pachyptila, concomitant with declining concentrations of H2S in the venting diffuse flow fluids. Over the next 5-6 years, the abundance of mussels increased dramatically until most of the existing communities previously dominated (in biomass) by tubeworms were now dominated by extensive populations of mussels.

R. W. Lee.

Biological Bulletin, Marine Biological Laboratory, Woods Hole, Vol. 205, No. 2, 1 Oct 2003, pp. 98-101.

M. Tsurumi and V. Tunnicliffe.

Deep Sea Research (Part I, Oceanographic Research Papers), Vol. 50, No. 5, May 2003, pp. 611-629.

Hydrothermal vent communities on a mid-ocean ridge crest can be separated by large distances on separate segments. Heat sources, vent character, fluid chemistry and current patterns may differ markedly. This study examines whether vent community characteristics on three of the four southern segments of the Juan de Fuca Ridge are significantly different. Taxonomic composition and relative abundance of the fauna over 1 mm in size associated with vestimentiferan tubeworm bushes are examined from fifty-one collections. Among nearly 350, 000 specimens, 37 taxa are recognized, most to species level. Another 14 taxa are meiofaunal in size classification. Species richness and selected diversity indicators are highest on Axial Volcano while animal density within the bushes does not differ significantly. Cluster analysis does not group collections by location, year of collection or vent temperature; collection substratum--basalt or sulphide--may influence clustering. The architecture of the tubes of tubeworm bushes appears to affect the numbers of species present and the resultant clusters. The tightly interwoven, knotted Ridgeia piscesae tubes found on Axial host twice as many species as tubeworm bushes with a less complex structure. Four species dominate most of the collections: two gastropods (Lepetodrilus fucensis and Depressigyra globulus) and two polychaetes (Paralvinella pandorae and Amphisamytha galapagensis). Other vent species are low in abundance (<1% relative abundance) and patchy in distribution. Four collections with no visible flow had markedly different assemblages representing a transition state from vent assemblages to normal deep-sea fauna. There are differences in community structure among the segments, but the causes for these differences are unclear. Higher diversity on Axial Volcano may be supported by a greater time of sustained venting, a larger venting area, water circulation contained within the caldera, or flow conditions that sponsor growth of more complex habitat.

C. L. Van Dover.

Marine Ecology Progress Series, 2003, pp. Vol. 253, pp. 55-66

Patterns in invertebrate community structure associated with mussel beds at 3 hydrothermal vents on the northern East Pacific Rise (NEPR) were explored using quantitative, replicate sampling methods and were compared to those of southern East Pacific Rise (SEPR) mussel beds (~63000 km apart). Univariate measures of diversity (H super('), J super(')) did not differ among 3 NEPR mussel beds. Diversity by most estimates was lower at NEPR mussel beds than at SEPR mussel beds. Invertebrate faunas of NEPR and SEPR mussel beds belong to the same biogeographic province, and the numerically dominant species at NEPR mussel beds were also numerical dominants at SEPR mussel beds. Patterns of community structure within and among NEPR mussel beds, between NEPR and SEPR mussel beds, and between 'young' 8 yr) mussel beds could be differentiated using multivariate techniques based on species-abundance matrices. Overall, these observations suggest that NEPR and SEPR mussel-bed communities are remarkably similar, differing primarily in the relative abundances of their shared, numerically dominant species and in the composition of the rare species.

Craig L. Moyer and Jeffrey J. Engebretson.

EOS, Transactions, American Geophysical Union, Vol. 83, No. 47, Suppl, 19 Nov 2002, pp. 1472.

N. Wery, M. A. Cambon-Bonavita, F. Lesongeur and G. Barbier.

FEMS microbiology ecology, Vol. 41, No. 2, Aug 2002, pp. 105-114.

During the 'MARVEL' oceanographical cruise performed in September 1997, samples were collected from the deep-sea vents of hydrothermal sites on the Mid-Atlantic Ridge. Eighty-four thermophilic and hyperthermophilic heterotrophic microorganisms were isolated using different culture media containing cellobiose, xylan, starch, lipidic or proteic substrates. These isolates were obtained in anaerobic conditions, at 65 degree C, 85 degree C and 95 degree C. Fifty of them were classified using amplified ribosomal DNA restriction analysis, random amplified polymorphic DNA and 16S rDNA sequencing. The strains classified have been assigned to the archaeal order Thermococcales and to the bacterial orders Thermotogales and Clostridiales. Variations in growth temperature and carbon sources were efficient enough to generate taxonomic diversity within enrichment cultures. Presumptive new genera and new species were isolated. Two isolates were confirmed as type strains of new species of new genera recently described: Marinitoga camini and Caloranaerobacter azorensis.

M. Tsurumi.

Dissertation Abstracts International Part B: Science and Engineering, Vol. 62, No. 10, Apr 2002, pp. 4337.

A. Reysenbach and E. Shock.

Science (Washington), Vol. 296, No. 5570, 10 May 2002, pp. 1077-1082.

Thermophilic microbial inhabitants of active seafloor and continental hot springs populate the deepest branches of the universal phylogenetic tree, making hydrothermal ecosystems the most ancient continuously inhabited ecosystems on Earth. Geochemical consequences of hot water-rock interactions render these environments habitable and supply a diverse array of energy sources. Clues to the strategies for how life thrives in these dynamic ecosystems are beginning to be elucidated through a confluence of biogeochemistry, microbiology, ecology, molecular biology, and genomics. These efforts have the potential to reveal how ecosystems originate, the extent of the subsurface biosphere, and the driving forces of evolution.

AM Wargo Rub, DJ Wright and JA Jones.

Roscoff (France): Station Biologique de Roscoff, 2002, 307-311. [Cah. Biol. Mar.]

A. Colaco, F. Dehairs and D. Desbruyeres.

Deep-Sea Research (Part I, Oceanographic Research Papers), Vol. 49, No. 2, Feb 2002, pp. 395-412.

Nutritional relations among invertebrates from the hydrothermal vent fields at the Mid Atlantic Ridge (MAR) were studied via the carbon and nitrogen stable isotope approach. A large number of specimens of different vent species from different MAR vent fields were analysed, providing a general picture of the community structure. The isotopic composition at each vent field presents the same general trend. There is an obvious dichotomy of the trophic structure, with the mussels being significantly depleted in super(13)C and shrimps being significantly enriched in super(13)C. MAR and Pacific vent fields present the same picture, despite a different species composition. Primary consumers are divided into main groups according to their delta super(13)C signature: > -15 (shrimps) and < -20ppt (mussels). Vent predators are tightly linked to one or the other group, but a mixed diet cannot be excluded. Bathyal species are top predators, making incursions into the vent fields to profit from the large biomass. Taking into account the above associations, a descriptive trophic model was elaborated. At the base of the food chain the chemolithotrophic bacteria predominate. Four trophic levels were then distinguished: primary consumers, feeding only on bacteria; mixotrophs feeding on bacteria and small invertebrates; vent predators feeding only on small invertebrates; and finally top predators that are mainly constituted by deep-sea fauna.

H. Yamamoto, K. Fujikura, A. Hiraishi, K. Kato and Y. Maki.

Marine Ecology Progress Series, 2002, Vol. 245, pp. 61-67

Molecular phylogenetics for endosymbiotic bacteria recovered from vestimentiferan tubeworm Lamellibrachia satsuma from Kagoshima Bay, vesicomyid clam Calyptogena laubieri from the Nankai Trough and mytilid mussel Bathymodiolus from the Mariana Back-arc Basin, were examined by PCR-aided 16S rDNA cloning and sequencing, and quinone profiling. The 16SrRNA clones of the endosymbionts from the 3 organisms fall within gamma -Proteobacteria and showed distinct lines of descent specific to their respective host. The 16S rRNA gene phylogeny confirms the host endosymbiont specificity in the coevolutionary process. Ubiquinones with 9 isoprene units (Q-9) or Q-10 were found as the major quinones in all test tissues of the host. Larger amounts of Q-8 were detectable only in those host body parts (gill or trophosome) harboring the endosymbiotic bacteria. These observations suggest that Q-8 is the major quinone of the endosymbionts. Based on the bacterial quinone concentration, the population densities of the bacteria present were estimated to be 10 super(10) to 10 super(11) cells/g wet wt of host tissue. The quantitative determination of quinones may provide information about physiological activity of the chemosynthetic communities as well as their biomass production.

F. Micheli, C. H. Peterson and G. A. Johnson, et al.

Ecological Monographs, Vol. 72, No. 3, Aug 2002, pp. 365-382.

The structure and dynamics of natural communities result from the interplay of abiotic and biotic factors. We used manipulative field experiments to determine the relative roles of abiotic conditions and biotic interactions in structuring deep-sea (2500 m depth) communities along environmental gradients around hydrothermal vents of the eastern tropical Pacific Ocean (East Pacific Rise, at 9 degree 50 degree N). We tested (1) whether predation by crabs and fishes affects the recruitment of benthic species and subsequent community structure and (2) whether the effects of predation vary along the steep gradients of temperature, oxygen, sulfide, and metal concentrations near vents. Recruitment substrates (basalt cubic blocks, roughly 10 cm on a side), both uncaged and caged to exclude predators (crabs, fishes, whelks, and octopi), were deployed along a decreasing vent fluid-flux gradient. The exclusion of predators for 8 mo increased the abundance of small mobile gastropods and amphipod crustaceans but decreased the abundance of sessile invertebrates, including juvenile vestimentiferan worms, tubiculous polychaetes, and mussels. Effects of predation were strongest nearest to hydrothermal vents, where abiotic environmental conditions were most extreme but productivity and the overall abundances of benthic invertebrates and mobile predators were the greatest. Additional 5-mo experiments conducted at three different locations showed similar trends at all sites, indicating that these effects of predation on benthic community structure are repeatable. Stomach-content analyses of the most abundant predators found at vents indicated that the zoarcid fish (Thermarces cerberus) primarily feeds on the vent snail Cyathermia naticoides, the limpet Lepetodrilus elevatus, and the amphipod crustacean Ventiella sulfuris, the very species that showed the greatest increase following predator exclusion. In contrast, brachyuran (Bythograea thermydron) and galatheid (Munidopsis subsquamosa) crab stomachs did not contain small mobile grazers, and crabs presented with arrays of the most common vent invertebrate species preferred mussels and vestimentiferans over limpets. Our results indicate that predation by large mobile predators influences the structure of hydrothermal vent communities, directly by reducing the abundance of gastropod prey species, and indirectly by reducing gastropod grazing and by bulldozing of recruits of sessile invertebrates.

S. K. Goffredi and J. P. Barry.

Marine Ecology Progress Series, Vol. 225, Jan 2002, pp. 227-238.

Symbioses involving sulfide-oxidizing bacteria and metazoan phyla dominate invertebrate assemblages at cold seeps and hydrothermal vents worldwide. The predominant species inhabiting cold seeps in Monterey Bay are the vesicomyid clams Calyptogena kilmeri and C. pacifica. The growth and survival of these clams depend directly upon the productivity of their chemoautotrophic endosymbionts, which is fueled by the oxidation of sulfide. For this reason, sulfide availability and sulfide-related physiology are thought to be the most influential factors governing the productivity of these associations. Both species inhabit sulfide-rich sediments and depend nutritionally on their symbionts, yet many aspects of their life histories differ considerably. Our results indicate that C. pacifica, which inhabits areas with lower environmental sulfide levels, is physiologically poised for the uptake and transport of sulfide, indicated by increased sulfide consumption rates, sulfide-binding ability, and internal sulfide levels. C. pacifica also has a greater potential for symbiont energy turnover, supported by increased sulfide oxidation potential, enzymes involved in sulfur metabolism, and bacterial densities. Conversely, C. kilmeri demonstrates a less effective sulfide uptake mechanism and, therefore, a specific need for higher environmental sulfide levels. It appears that the abilities of these 2 species to process sulfide differ greatly and reflect not only the environments in which they are found but also the capabilities of their symbionts. This research represents the first comparative investigation of the physiological functioning of closely related species in chemosynthetic symbioses and elucidates the constraints and advantages posed by different modes of sulfide (energy) uptake and assimilation in these, and perhaps other, symbiotic organisms.

AL Vereshchaka and ME Vinogradov.

Roscoff (France): Station Biologique de Roscoff, 2002, pp. 303-305. [Cah. Biol. Mar.]

BW Govenar, DC Bergquist, IA Urcuyo, JT Eckner and CR Fisher.

Roscoff (France): Station Biologique de Roscoff, 2002, pp. 247-252. [Cah. Biol. Mar.]

C. L. Van Dover.

Marine Biology, Vol. 141, No. 4, 2002, pp. 761-772.

Exploration of hydrothermal vent systems in locations remote from well-studied sites allows ecologists to determine the degree of site-specific variation in trophic relationships among communities. A preliminary outline of the trophic structure of the Kairei hydrothermal vent community on the Central Indian Ridge (25 degree 19.23'S; 70~'02.42'E) is provided here, based on analysis of collections from an April 2001 expedition. Invertebrate biomass at Kairei is dominated by organic carbon with a delta super(13)C isotopic value of about - 13 ppt, due to the abundance of primary consumers (shrimp: Rimicaris aff. exoculata) and secondary consumers (anemones: Marianactis) with this isotopic composition. Filamentous thiotrophic episymbionts on shrimp have been interpreted to be the major diet items of the shrimp and hence are the dominant primary producers within the community. Free-living autotrophic microorganisms are implicated as the dietary base for other invertebrate species. Four trophic groups are identified within the Kairei invertebrates based on carbon- and nitrogen-isotope ratios, but these groups do not always define discrete trophic levels. Ontogenetic shifts in diet are documented for R. aff. exoculata and brachyuran crabs (Austinograea). Diets of symbiont-bearing mussels (Bathymodiolus aff. brevior) and two species of gastropods are isotopically constant throughout the range of sizes analyzed. There is a consistent but unexplained pattern of increasing nitrogen isotopic composition with increasing carbon isotopic composition in vent communities from geographically disjunct oceanic regions. Given the assumptions associated with interpretations of isotopic data, there remains a missing pool of carbon (presumably unsampled bacterial biomass) that contributes to the maintenance of the super(13)C- and super(15)N-enriched primary consumers in these ecosystems. Electronic supplemen- tary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/ 10. 1007/s00227-002-0865-y.

P. A. Tyler, C. R. German, E. Ramirez-Llodra and C. L. Van Dover.

Oceanologica Acta, Vol. 25, No. 5, 2002, pp. 227-241.

ChEss is a recently-funded Census of marine life programme aimed at improving our knowledge of the biogeography of deepwater chemosynthetically driven ecosystems by promoting an international field phase of discovery and exploration. The main objectives are to assess and explain the diversity, distribution and abundance of hydrothermal vent and cold seep species. With the global mid-ocean ridge system extending ~65 000 km, it is unlikely that its entire length would be examined in detail. The ChEss programme proposes to select a limited number of target areas chosen for the discovery of new vents and seeps. The intention is to identify the maximum scientific return that could be achieved from detailed investigation of the minimum number of sites at key locations. To narrow the field for exploration, a number of starting hypotheses and goals have been identified. A bio- and geo-referenced database for hydrothermal vent and cold seep species will be created. This database will be integrated with the Ocean Biogeographic Information System (OBIS). An international scientific committee will coordinate the programme, facilitate collaboration between participants, promote ship-time applications at national level and stimulate scientific innovation from a wider community.Original Abstract: ChEss est un des programmes les plus recents du Recensement de la vie marine (CoML). Il doit accroitre notre connaissance de la biogeographie des ecosystemes chemosynthetiques profonds en mettant en place une recherche internationale de terrain. L'objectif est de definir et d'expliquer la diversite, la distribution et l'abondance des especes des events hydrothermaux et des suintements froids. Avec un systeme de ride medio-oceanique s'etendant sur 65000 kilometres, une etude fine est hors de propos. Le programme ChEss propose de selectionner un nombre limite d'aires-cibles choisies pour la decouverte de nouveaux events ou sources. L'objectif est de tirer un benefice maximum d'une etude detaillee d'un nombre reduit de sites choisis dans des positions-clefs. Pour focaliser le champ de recherche, quelques hypotheses et themes ont ete identifies. Une base de donnees biologiques et geologiques pour les especes de ces aires sera creee ; elle sera integree a Obis (Ocean buiogeographic information system). Un Comite scientifique international coordonnera le programme, facilitera les cooperations, appuiera l'attribution de temps-bateau au niveau national et stimulera l'innovation scientifique pour une communaute elargie.

S. Durand, M. Le Bel and KS Juniper.

Roscoff (France): Station Biologique de Roscoff, 2002, 235-240. [Cah. Biol. Mar.]

C. L. Van Dover, S. E. Humphris and D. Fornari, et al.

Science (Washington), Vol. 294, No. 5543, 26 Oct 2001, pp. 818-823.

Within the endemic invertebrate faunas of hydrothermal vents, five biogeographic provinces are recognized. Invertebrates at two Indian Ocean vent fields (Kairei and Edmond) belong to a sixth province, despite ecological settings and invertebrate-bacterial symbioses similar to those of both western Pacific and Atlantic vents. Most organisms found at these Indian Ocean vent fields have evolutionary affinities with western Pacific vent faunas, but a shrimp that ecologically dominates Indian Ocean vents closely resembles its Mid-Atlantic counterpart. These findings contribute to a global assessment of the biogeography of chemosynthetic faunas and indicate that the Indian Ocean vent community follows asymmetric assembly rules biased toward Pacific evolutionary alliances.

K. Takai, T. Komatsu, F. Inagaki and K. Horikoshi.

Applied and Environmental Microbiology, Vol. 67, No. 8, Aug 2001, pp. 3618-3629.

Archaeal community structures in microhabitats in a deep-sea hydrothermal vent chimney structure were evaluated through the combined use of culture-independent molecular analyses and enrichment culture methods. A black smoker chimney was obtained from the PACMANUS site in the Manus Basin near Papua New Guinea, and subsamples were obtained from vertical and horizontal sections. The elemental composition of the chimney was analyzed in different subsamples by scanning electron microscopy and energy-dispersive X-ray spectroscopy, indicating that zinc and sulfur were major components while an increased amount of elemental oxygen in exterior materials represented the presence of oxidized materials on the outer surface of the chimney. Terminal restriction fragment length polymorphism analysis revealed that a shift in archaeal ribotype structure occurred in the chimney structure. Through sequencing of ribosomal DNA (rDNA) clones from archaeal rDNA clone libraries, it was demonstrated that the archaeal communities in the chimney structure consisted for the most part of hyperthermophilic members and extreme halophiles and that the distribution of such extremophiles in different microhabitats of the chimney varied. The results of the culture-dependent analysis supported in part the view that changes in archaeal community structures in these microhabitats are associated with the geochemical and physical dynamics in the black smoker chimney.

Jun Hashimoto, Suguru Ohta and Toshitaka Gamo, et al.

Zoological Science, Vol. 18, No. 5, Jul 2001, pp. 717-721.

Thriving chemosynthetic communities were located for the first time in the Indian Ocean between 2420 and 2450 m, on a volcanic knoll at the eastern crest of an axial valley, approximately 22 km north of the Rodriguez Triple Junction. The communities were distributed in a 40m by 80m field around the knoll. At least seven active vent sites, including black smoker complexes that were emitting superheated water at 360 degree C, were observed at the field. The faunal composition of the Indian Ocean hydrothermal vent communities had links to both Pacific and Atlantic vent assemblages. This discovery supports the hypothesis that there is significant communication between vent faunas in the Pacific and Atlantic Oceans via active ridges in the Indian Ocean.

A. G. Marsh, L. S. Mullineaux, C. M. Young and D. T. Manahan.

Nature, Vol. 411, No. 6833, 3 May 2001, pp. 77-80.

Hydrothermal vents are ephemeral because of frequent volcanic and tectonic activities associated with crust formation. Although the larvae of hydrothermal vent fauna can rapidly colonize new vent sites separated by tens to hundreds of kilometres, the mechanisms by which these larvae disperse and recruit are not understood. Here we integrate physiological, developmental and hydrodynamic data to estimate the dispersal potential of larvae of the giant tubeworm Riftia pachyptila. At in situ temperatures and pressures (2 degree C and 250 atm), we estimate that the metabolic lifespan for a larva of R. pachyptila averages 38 days. In the measured flow regime at a fast-spreading ridge axis (9 degree 50'N; East Pacific Rise), this lifespan results in potential along-ridge dispersal distances that rarely exceed 100 km. This limited dispersal results not from the physiological performance of the embryos and larvae, but instead from transport limitations imposed by periodic reversals in along-ridge flows and sustained episodes of across-ridge flow. The lifespan presented for these larvae can now be used to predict dispersal under current regimes at other hydrothermal vent sites.

R. A. Lutz, T. M. Shank and R. Evans.

American Scientist, Vol. 89, No. 5, Sep-Oct 2001, pp. 422-431.

The first examples of life forms not dependent on solar energy were discovered by scientists using towed cameras and the submersible Alvin in 1977 along hydrothermal vents of the Galapagos Rift. Since then, investigators have made hundreds of dives aboard Alvin to learn more about these unusual ecological communities. In the spring of 1991, Alvin and its tender, Atlantis II, happened to be on station above the East Pacific Rise between 9 and 10 degrees north latitude only a few days after the axial summit trough 2,550 meters below the surface erupted, obliterating a thriving vent community. The authors made numerous dives on the 9N Biotransect over the ensuing 10 years. Their article describes the return of life to the vents and the ecological succession they witnessed.

D. S. Kelley, J. A. Karson and D. K. Blackman, et al.

Nature, Vol. 412, No. 6843, 12 Jul 2001, pp. 145-149.

Evidence is growing that hydrothermal venting occurs not only along mid-ocean ridges but also on old regions of the oceanic crust away from spreading centres. Here we report the discovery of an extensive hydrothermal field at 30 degree N near the eastern intersection of the Mid-Atlantic Ridge and the Atlantis fracture zone. The vent field - named "Lost City" - is distinctly different from all other known sea-floor hydrothermal fields in that it is located on 1.5-Myr-old crust, nearly 15 km from the spreading axis, and may be driven by the heat of exothermic serpentinization reactions between sea water and mantle rocks. It is located on a dome-like massif and is dominated by steep-sided carbonate chimneys, rather than the sulphide structures typical of "black smoker" hydrothermal fields. We found that vent fluids are relatively cool (40-75 degree C) and alkaline (pH 9.0-9.8), supporting dense microbial communities that include anaerobic thermophiles. Because the geological characteristics of the Atlantis massif are similar to numerous areas of old crust along the Mid-Atlantic, Indian and Arctic ridges, these results indicate that a much larger portion of the oceanic crust may support hydrothermal activity and microbial life than previously thought.

S. Ohta and D. Kim.

Journal of Oceanography, Vol. 57, No. 6, Dec 2001, pp. 663-677.

During the Dives Nos. 409, 410, 480 and 481 of the Japanese submersible Shinkai 2000, conducted on June 10 and 11, 1989 and on May 16 and 17, 1990, several hydrothermal vents and prosperous vent associated biological communities were found on the northern slope of the Iheya Ridge in the Mid-Okinawa Trough (27 degree 32.5' N, 126 degree 58.5' E: depth 1,400 m). The first site we found, the "Calyptogena Site", was characterized by a relatively thick blanket of sediments, pleated and/or laminated lava flows, with occasional lobate pillows and white and yellow stains. Although no remarkable shimmering water and thermal anomalies were detected during the observations, the extraordinarily dense community must be related to hydrothermal activities. The community was dominated by the giant white clam, Calyptogena okutanii, in biomass, and by Neolepas-type primitive scalpellids and slender vestimentiferan tube-worms in number. The second site, the "Pyramid Site", situated only 200 m northward from the Calyptogena Site has typical clear smokers emitting hot water over 200 degree C, and is characterized by a hard substratum of volcanic rocks and hydrothermal slabs. No noteworthy succession was perceived at the Calyptogena Site over a year. Many of the vent members occurred at both sites. However, Calyptogena okutanii, which were confined to the sediment bottom, Neolepas spp. and larger vestimentiferan tube-worms were found to thrive only at the Calyptogena Site, being only minor elements in the Pyramid Site. The global distribution of several groups of organisms is discussed preliminarily in zoogeographical terms based on comparison with other submersible missions and surveys done by surface vessels.

B. Shillito, D. Jollivet and P. -M Sarradin, et al.

Marine Ecology Progress Series, Vol. 216, 6 Jul 2001, pp. 141-149.

For the first time, in vivo heat-exposure experiments were conducted on the hydrothermal vent polychaete Hesiolyra bergi from the hottest part of the vent biotope. Using a pressurised incubator equipped with video-facilities, we found that H. bergi, which forages around and in the tubes of the thermophilic Alvinella sp., became hyperactive once temperature exceeded 35 degree C and further lost co-ordination in the 41 to 46 degree C interval, just before death occurred. Another exposure experiment at 39 degree C for 3 to 4 h led to 80% mortality (max) 9 h after heat shock, and 100% thereafter. In view of the much higher temperatures recorded in this organism's habitat, these results suggest that tolerance to high temperatures (exceeding 40 degree C) is not a pre-requisite for life among alvinellid tubes. Behavioural responses (escape from heat) may suffice.