Trends in Fixed Site Benthic Condition

Forty-eight sites in areas targeted for pollution abatement and other management actions are monitored annually by the Benthic Monitoring Program to assess whether benthic community condition is changing.  The illustration below shows where significant improving (green) and degrading (red) trends have been observed in summer Chesapeake Bay benthic condition between 1985 and 2010.

Summary results:
• Maryland Trends Discussion

Individual site results:
• Interactive Map
• Site Locations (Coordinates)

Statistically significant B-IBI trends (p<0.1) were detected at 10 of the 27 sites currently monitored for trends. Trends in benthic community condition declined at 8 sites (significantly decreasing B-IBI trend) and improved at 2 sites. Four trends disappeared in 2010 and 4 trends emerged as new. All of the new trends were declining trends, and all of the trends that were significant through 2009 but disappeared in 2010 were improving trends. Thus changes in trend direction and magnitude in 2010 indicated generally degrading benthic conditions in Chesapeake Bay.

Sites with improving condition were located in the mainstem of the Bay (Station 26) and the Back River (Station 203). Sites with declining condition were located in Baltimore Harbor (Station 22), Curtis Creek (Station 202), Patuxent River at Holland Cliff (Station 77), Patuxent River at Broomes Island (Station 71), tidal fresh Potomac River (Station 36), mesohaline Potomac River at Morgantown (Stations 43 and 44), and Nanticoke River (Station 62). The most important changes in 2010 were the appearance of new degrading B-IBI trends, reversing conditions in the Potomac River at Morgantown (Station 44), and the disappearance of previously improving benthic condition trends in the Choptank River (Station 64), North Beach (Station 15), Bear Creek (Station 201), and Elk River (Station 29). This was reflected in a general decline in benthic community status at a majority of the fixed sites. Major effects of hypoxia in the last few years were suggested by a decline in abundance and species numbers at sites in the mainstem and lower reaches of tributaries since 2005, and, on average, lower abundance values and species numbers for the 1998-2010 time period.

Benthic organisms respond to long-term patterns in water quality parameters, such as dissolved oxygen concentrations, water column chlorophyll, total nitrogen, sediment loading, and organic loading, in addition to natural fluctuations in salinity and temperature. Improving trends likely reflect undergoing basin-wide changes resulting from management actions. Degrading trends reflect the cumulative impacts of nutrient loading and hypoxia in regions with significant problems that do not yet respond to pollution abatement.