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 Chesapeake 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 comprises a wide range of plants, animals and bacteria from all levels of the food web.
What Types of Organisms Are Part of the Benthos?
There are two groups of benthic organisms, based on their habitat:
- Infauna are animals and bacteria of any size that live in bottom sediments. Worms and clams are considered infauna. Within bottom sediments, infauna form their own community structures that are connected to the water by tubes and tunnels.
- Epifauna are animals that live either attached to a hard surface (such as rocks, shells and pilings) or on the surface of the Bay's bottom. Epifauna include oysters, mussels, barnacles, snails, starfish, sponges and sea squirts.
An oyster reef and the many species it supports is an example of a benthic community. The roots and lower stems of underwater bay grasses also provide a solid surface for some epifauna to attach themselves to.
How Is the Benthic Community Important to the Chesapeake Bay?
Benthic invertebrate communities provide a good snapshot of environmental conditions in the Chesapeake Bay because they:
- Cannot move very far and thus are unable to avoid polluted or unhealthy water conditions.
- Live in bottom sediments where they are exposed to environmental stressors, such as chemical contaminants and low 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 (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, are food for important recreational and commercial fish species such as spot, croaker, blue crabs and juvenile striped bass.