Despite a year of above average rainfall and record heat, the overall health of Chesapeake Bay held steady in 2013, according to scientists at the University of Maryland Center for Environmental Science. Overall, the Chesapeake scored a C, nearly the same score as the previous year, which was up from a D+ and C- in previous years.
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Variations in the health of waterways on either side of the Bay indicate that effective stormwater runoff strategies—such as forest buffers cover crops, and upgraded wastewater treatment facilities—can make a difference and should continue to be implemented.
“Nutrient and sediment pollution carried by stormwater are important factors in Chesapeake Bay health,” said Bill Dennison of the University of Maryland Center for Environmental Science. “Based on patterns in rainfall and report card grades for several reporting regions, we conclude that it is not the rain that affects the report card scores; it is what the rain carries.”
For example, the James River at the southern end of the Bay is showing a positive trend. This watershed has a higher percentage of forested land cover, which acts as a buffer to prevent pollution from entering waterways during rain events, and upgrades to its wastewater treatment plants are helping to remove excess nitrogen and phosphorus. Western Shore tributaries such as the Patapsco and Back Rivers and the Elizabeth River also generally improved last year, following wastewater treatment plant upgrades and a decline in atmospheric nitrogen deposition triggered by the implementation of the Clean Air Act.
On the other end of the spectrum, there is continuing degradation of the Eastern Shore waterways bordered by agricultural lands. The Choptank River (C-) and the Upper Eastern Shore tributaries (D), such as the Elk, Sassafras, Chester and Miles Rivers, had poor grades last year, due in part to rainfall in excess of 50 inches on the Delmarva peninsula and the resulting runoff of fertilizer and chicken manure applied to the fields.
“On the bright side, the rivers west of the Chesapeake Bay generally improved last year, in part due to the success of wastewater treatment plant upgrades,” said Dennison. “While the overall grade for the Bay did not change, we are seeing a continuing degradation of the Eastern Shore waterways that are dominated by agriculture. This tells us the importance of local management actions for our rivers and streams.”
Fisheries indicators are variable over time, but generally are showing improving scores. Bay anchovy, one of the most abundant schooling fishes in the Bay and an important food source for top predators, scored a 100% in 2013. Blue crabs, both predator and prey in the Bay's food web, scored a 68% in 2013, a moderately good score based on the amount of adult female blue crabs in the Bay. Striped bass, Maryland’s state fish and a key top predator in the Bay, scored a 100%. (While the three-year average population of striped bass is down, 2013 was an improved population number.)
On the whole, Chesapeake Bay is becoming murkier, measured as water clarity. In 2012, there were some improvements in water clarity in contrast to the long-term trends, but 2013 was another year of poor water clarity. The heavy rainfall in 2013 contributed to the murkier water conditions, in addition to a higher amount of chlorophyll. Total nitrogen scores are improving over time, while aquatic grasses rebounded from lower scores assessed in 2012.
The report card rates 15 reporting regions of the Bay using seven indicators that are combined into a single overarching index of health.
This year’s report card also introduces a Climate Change Resilience Index to measure the resilience of the Chesapeake Bay to the impacts of climate change. Resiliency is the ability of an ecosystem to withstand change in its environment. For example, how well will coastal wetlands withstand sea level rise? How well will underwater plants that provide habitat for fish and crabs survive higher water temperatures? These are important questions to ask now so that we may protect and restore Chesapeake Bay in the face of climate change.
The Climate Change Resilience Index addresses several climate change impacts including sea level rise, increasing water temperatures and rainfall, increasing storm frequency and intensity, and ocean acidification. Additional indicators include the impact on coastal wetlands, submerged aquatic vegetation, bacteria and other pathogens, and fish and shellfish recruitment.
The University of Maryland Center for Environmental Science’s Integration and Application Network produces several annual report cards to assess the health of Chesapeake Bay waterways to enhance and support the science, management and restoration of Chesapeake Bay. For more information about the 2013 Chesapeake Bay Health Report Card including region-specific data and downloadable graphics, visit www.chesapeakebayreportcard.org.
