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 2015 sampling sites.

The overall condition of Chesapeake Bay improved in 2015, with 62% of the Bay’s tidal bottom meeting the Benthic Community Restoration Goals (38% failing), up from 59% in 2014. The extent of both the degraded and the severely degraded condition was the lowest since baywide monitoring began in 1996. The largest improvement occurred in the Maryland portion of the Chesapeake Bay, with 47% of its tidal bottom meeting the Restoration Goals (53% failing) in 2015, up from 40% in 2014.

Improvements in benthic condition in 2015 were associated with low hypoxic volumes (waters with low oxygen content). Low hypoxic volumes were likely the result of overall low spring flows and nutrient runoff into Chesapeake Bay. Notwithstanding this improvement, benthic communities in Chesapeake Bay remain in poor condition, with species diversity and biomass-dominant species declining over the 1995-2015 time period.

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: August 29, 2016

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