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 2017 sampling sites.

The overall condition of Chesapeake Bay improved in 2017, with 59% of the Bay’s tidal bottom meeting the Benthic Community Restoration Goals (41% failing), up from 55% in 2016. There was no statically significant change in percent area degraded over the 1985-2017 time series. However, benthic community condition in the Bay has improved in the last four years of monitoring relative to previous years.

The improvement in 2017 was associated with better oxygen conditions in the Bay’s waters. Hypoxic volume (waters with low oxygen content) was below the long-term average July through September, and overall lower in 2017 than in 2016. Summer hypoxic volume and the timing of hypoxia play important roles in determining benthic community condition. Despite improvements, a large portion of the Bay remains degraded.

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: September 25, 2018

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