Benthos
Blennies are one type of fish that are commonly found living in and around Bay oyster reefs, part of the Bay's benthic community. Image courtesy: Mike Land
The organisms that live on and in the Bay's bottom sediments are known as benthos, a name derived from the Greek word meaning “depths of the sea.” The benthic community is complex and is composed of a wide range of plants, animals and bacteria from all levels of the food web.
What types of organisms are part of the benthos?
Benthic organisms can be differentiated by their habitat.
- Infauna are animals and bacteria of any size that live in bottom sediments. Worms and clams are considered infauna. They form their own community structures within bottom sediments, connected to the water by tubes and tunnels.
- Epifauna are animals that live either attached to a hard surface (for example, on rocks or pilings) or move on the surface of bottom sediments. Epifauna include oysters, mussels, barnacles, snails, starfish, sponges and sea squirts.
An oyster bar, including the many species it supports, is an example of a benthic community. The roots and lower portions of underwater bay grasses also provide an attachment surface for a variety of epifauna.
Why is the benthic community important to the Bay?
Benthic invertebrate communities provide a good snapshot of environmental conditions in the Bay because they:
- Have limited mobility and thus are unable to avoid adverse conditions.
- Live in bottom sediments where they are exposed to environmental stressors, such as chemical contaminants and low dissolved oxygen levels.
- Have long enough life spans to reflect the effects of environmental stressors.
- Are diverse enough to respond to multiple types of stress.
Benthic species play other important roles in the Bay ecosystem.
- Benthic organisms link the primary producers (such as phytoplankton) with higher trophic levels (such as fish and blue crabs) by consuming phytoplankton and then being consumed by larger organisms.
- Benthic organisms play a major role in breaking down organic material.
- Many benthic organisms, particularly clams and worms, provide food for important recreational and commercial species like spot, croaker, blue crabs and juvenile striped bass.