Glossary

Bathymetry - Relating to the depth of the ocean.

Benthos - Organisms that live on top of or within the substrate that comprises the seafloor. On occasion, this term is used to refer the seafloor, itself. "Benthic" is the adjective that is used to refer to the benthos.

Bryozoa - A phylum of moss-like, marine animals that are typically colonial and live in the benthic zone. Colonies of bryzoans found on Georges Bank either have an erect, branching form (e.g., "bushy bryozoa") or a low, encrusting forms (e.g., "encrusting bryozoa").

Economic Exclusive Zone (EEZ) - The area within 200 nautical miles of a coastline where activities, such as fishing, offshore mining, and scientific research, are regulated by the state or federal government.

Epifauna - Benthic organisms that live on top of the substrate that comprises the seafloor.

Essential fish habitat (EFH) - Any habitat that a finfish or shellfish species depends upon in order to feed itself, grow to maturity, or reproduce. In 1996, the U.S. Congress passed a law mandating the identification and conservation of EFH.

Evenness - A measure of whether the abundance of species within a community is equitably distributed or whether the community contains a few, very abundant species.

Hydroids - Marine organisms within the phylum Cnidaria that have life cycles in which they alternate between a plant-like, polyp stage and a medusa stage. During their polyp phase, individual hydroids tend to come together to form colonies. These colonies are commonly seen in bottom photographs from Georges Bank.

Megafauna - Benthic organisms that are generally larger than 2.0 cm. In contrast to smaller categories of benthic organisms (i.e., macrofauna, meiofauna, and microfauna), megafauna can be easily seen with the naked eye.

Polychaetes - Marine worms that have segmented bodies and leg-like appendages called parapodia.

Primary production - The process by which organisms generate living material through photosynthesis or chemosynthesis. Since primary producers are at the bottom of the food chain, their productivity impacts the amount of food available for all other organisms within an ecological community.

Remotely operated vehicle (ROV) - An underwater, maneuverable robot whose movements are directed by an individual aboard a research vessel. ROVs are generally equipped with lights and video cameras, but may also contain specialized sensors and mechanical arms, which are used to survey and collect samples from deep sea environments.

Sessile - An organism that does not move from a fixed location except during a brief, dispersal phase. Some examples of sessile organisms include mussels, barnacles, and sponges.

Side scan sonar - A sonar system attached to a towfish that is dragged behind a research vessel. The sonar produces sound energy that bounces off of the seafloor and is then picked up by a receiver. This reflected energy is used to create a picture of the changing bathymetry (e.g., underwater topography) of the area.

Spawning stock biomass - The total weight of all mature fish within a particular population.

Species diversity - In this context, this term refers to an index of a biological community's diversity that takes into account both species richness (i.e., the number of species present) and evenness (i.e., whether the abundance of species is equitably distributed throughout the community).

Species richness - The absolute number of species present within a community.