Archaea: Unicellular microorganisms that constitute one of the three domains of life: bacteria, archaea, and eukaryotes. Like bacteria, archaea have no true nucleus; however, archaea are considered to be more closely related than bacteria to eukaryotes, organisms with a true nucleus.

Black smokers: A type of hydrothermal vent found on the ocean floor that emits black colored fluids rich in iron sulfides.

Benthos: The collection of organisms living on the sea floor or the bottom of other bodies of water.

Biofilms: Associations of microorganism attach to surfaces that form a protective extracellular matrix.

Biogeography: Large scale geographical distributions of individual organisms and groups of organisms.

Biomass: The mass of living matter within a defined area or habitat.

Chemosynthesis: The use of chemical energy rather than sunlight as the energy source for the production of organic compounds from inorganic sources.

Chimney: The geological structure that forms over hydrothermal vents as minerals precipitate from vent fluids once they come in contact with ocean waters.

Chitin: A polysaccharide found in the cell walls of fungi, insects, and other organisms such as tubes of Vestimentiferan worms.

Deposit feeders: Organisms that feed on the detritus, bacteria, and other organic material found in the sediments.

Ecological succession: The process in which the community of organisms changes over time as an unoccupied habitat progresses towards a stable community.

Endosymbionts: An organism living inside a separate organism in a mutually beneficial relationship.

Episymbionts: An organisms living on the surface of another organism in a mutually beneficial relationship.

Hydrogen sulfide: A common chemical found in the fluids of hydrothermal vents. When seawater is exposed to the sulfate in volcanic rock below the ocean floor, hydrogen sulfide is formed.

Larval exchange: The dispersal of mobile larvae from their natal site to the environments which they inhabit as adults.

Metabolites: The chemical constituents either produced by or taken apart in the process of metabolism.

Peridotite: An igneous rock consisting mostly of the mineral olivine and pyroxene.

Photoreceptors: The neurons that are specialized for the perception of light.

Plume: The fluid formation that is created as hydrothermal vent waters are injected into the ocean from the sea floor.

Polychaetes: Worms from one of the three classes of the phylum Annelida. The worms are bristled and possess leg like parapodia.

Primary producers: Organisms that posses the capacity to produce organic compounds from inorganic material, with the aid of light or a chemically derived energy source. Primary producers compose the bottom of various food chains.

Productivity (biological): The rate at which photosynthetic or chemical energy is used by organisms to create organic substances.

Symbionts: Organisms that are living in a mutually beneficial association with organisms from another species.

Symbiosis: An association between organisms of separate species that is of mutual benefit to both organisms, or is beneficial to one organism and does not harm the other.

Taxa: The plural form of taxon. Pertaining to the classification of organisms into systems of relationship based on genetic and morphological similarities.

Tectonic: The study of the processes of change and formation of the earth's crust.

Thermophilic: Organisms such as bacteria that require a high temperature environment for normal development.

Throphosome: A specialized organ found within vestimiferan worms that serves as a home to the symbiotic bacteria that live in association with the tube worms and chemosynthetically produce the organic compounds that tube worms require for growth.

Trophic structure: The relationship of an organism to other organisms in the context of a food web.

Vacuoles: Spaces in cells surrounded by a single membrane that are used storage.

Vesicomyid: A group of bivalves from the family Vesicomyidae.

Vestimentiferans: A phylum of marine tubeworms that lack a digestive system and depend on chemoautotrophic organisms to supply nutrients.