Coastal Bays Benthic Community

Benthic animals are faring poorly in creeks and better in open bays

Benthic animals, or those that live on or in the bay sediment, are a diverse group consisting of shellfish, crustaceans, snails and worms.  These organisms play an important role as food for fish for bottom feeding fish, ducks and marsh birds and in maintaining sediment and water quality (e.g. filtration of water by oysters).  Benthic animals are also important in cycling nutrients between the sediment and the water column. Since these communities are generally not very mobile, they are good indicators of ecosystem health, providing an integrated sample over time.

The overall health of benthic communities are assessed using a benthic index. The health of benthic communities are also linked to sediment toxicity and sediment chemistry. To learn more about how these topics read the following chapters in the 2004 Ecosystem Health Assessment Report: 'Ambient toxicity of sediment from the Maryland Coastal Bays' and 'A synthesis of sediment contaminant studies in the Maryland Coastal Bays' or check out the public State of the Coastal Bays report.

 

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Benthic Index

The relative proportion of the different groups of benthic animals is an indicator of system health.  The benthic index developed for the Mid-Atlantic Integrated Assessment incorporates changes in diversity and populations of indicator species to distinguish degraded benthic habitats from undegraded benthic habitats.  This index reflects the diversity and abundance of pollution-tollerant and pollution-sensitive species.  The accepted threshold for this index is a value greater than 3 on a scale from 1 (severely degraded) to 5 (meets all goals for healthy benthic community). 

The benthic condition data presented in the maps and reports below were collected by VERSAR Inc. as part of the EPA National Coastal Assessment, NCA, Program.

  • The 2000 NCA data showed that the open bays were in good condition but the upper tributaries were degraded (Trappe Creek, Manklin Creek and Grey's Creek) to severely degraded (Bishopville Prong, Shingle Landing Prong, upper Herring and Turville Creeks).  click here for the full 2000 benthic report (516 KB)

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  • The 2001 NCA data had 39% of the 54 sites sampled declared degraded by the index.. click here for the complete 2001 benthic report (511 KB)

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  • Of the 124 sites sampled by NCA in 2002, 95 sites (77%) exhibited healthy benthic communities and 29 (23%) exhibited degraded benthos.  click here for the full 2002 benthic report (1.1 MB) Appendix with complete Benthic inventory (232 KB)

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  • Of the 152 sites sampled by National Coastal Assessment in 2003, 136 sites (89.5%) exhibited healthy benthos. click here for the complete 2003 benthic report (1.6MB)

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  • The 2004 NCA data showed 84% of sites (46 out of 55) had healthy benthic communities.  click here for the full 2004 benthic report (538 KB)

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  • Benthic samples were collected at 21 sites in Marylands Coastal bays and at 18 sites in the Chesapeake Bay during 2005.  Of the 39 sites sampled, 26 sites exhibited healthy benthic communities.  2005 benthic report (912 KB)

If you have any questions about Maryland's Coastal Bays,
please feel free to e-mail, Cathy Wazniak, or call (410) 260-8638.
 

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