Chesapeake Bay Monitoring

​Bottom Dwellers (Benthos)

Illustration of Polychaetes

Benthic animals, such as these polychaetes, live in or on the bottom.

Animals that live in or on the bottom of the Bay are called the benthic community. Examples of some benthic animals that live in Chesapeake Bay sediments include:

Benthic macroinvertebrates are used as biological indicators because they are reliable and sensitive indicators of habitat quality in aquatic environments and they are ecologically important components of the Chesapeake Bay’s food web.

The long-term benthic sampling program has two components:

Probability samples are collected during the summer at 150 randomly-selected sites in 6 major regions of the Chesapeake Bay mainstem and tributaries in Maryland. Results from the probability sampling are used to determine the number of acres that meet the Chesapeake Bay Benthic Restoration Goals. These goals define a healthy benthic macroinvertebrate community.

The second component of the program samples 27 fixed sites to see if management actions designed to improve water quality are resulting in healthier benthic communities. Benthic community health serves as a measure of water quality that is integrated over time because it captures the effect of water quality problem such as low dissolved oxygen that occurred prior to the time of sampling.

For more information on the Maryland Chesapeake Bay Long-Term Benthic Monitoring and Assessment Program visit: