Chesapeake Bay Benthic Monitoring Program

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How's the Bay Doing?

Benthic community condition in Chesapeake Bay is assessed using a benthic index of biotic integrity (B-IBI), which evaluates the ecological condition of a sample by comparing values of key benthic community attributes to reference values expected under non-degraded conditions in similar habitat types. Probability-based sampling and the B-IBI are used to estimate the area of Chesapeake Bay with degraded bottom habitat condition.

Click here to see a map of the bottom habitat condition for each of the 2012 sampling sites.

The area with degraded benthic community condition (failing the Restoration Goals) in the Maryland portion of the Chesapeake Bay increased in 2012, from 65% to 73%, whereas the area with degraded benthos in Virginia decreased. The Patuxent River and the Maryland western tributaries were in worst condition. Overall, the area with degraded benthos in the Chesapeake Bay remained the same in 2012, with 55% of the Bay’s tidal waters failing the Restoration Goals.

The increase in degradation in the Maryland portion of the Bay in 2012 may be attributed to Tropical Storm Lee the previous fall. Dissolved oxygen conditions were moderate to good during the summer of 2012; however, hypoxia occurred earlier than ever in the monitoring record. Large amounts of organic matter delivered by Tropical Storm Lee in combination with higher than normal water temperatures in the winter and spring of 2012 may have been responsible for the early hypoxia. The development of hypoxia early in the year is likely to have severe effects on the benthic community during the sensitive period of species recruitment and growth.

See results at right for further detail.

Patterns of condition within each stratum can be explored from the interactive stratum map below. 

Click on the stratum name or area for detailed results


      Summary of Results

      Baywide Results Graph

      Sampling Strata


Strata Comparison for Wet and Dry Years

      Areas Failing Goals

      Fixed Station Trends

   Recent Research Results


Benthic Feeding Habitats of Seaducks


Low dissolved oxygen and benthic production



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Revised: Sept 10, 2013

Upper Bay Western Tribs Eastern Tribs Mainstem Patuxent Potomac Upper Bay Western Tribs Eastern Tribs Mainstem Patuxent Potomac