Anacostia Riverkeeper has worked on Citizen Science Water Quality Monitoring, measuring levels of E. coli for the past five years. As we have collected samples across the watershed, both in District of Columbia waters as well as for smaller monitoring programs in Montgomery and Prince George’s County, we have frequently fielded questions on where the E. coli we find might be coming from. We know it’s there- but how is it getting introduced into our water, and what might be done to thwart it?
E. coli is a bacteria that naturally grows in the guts of warm-blooded animals (birds, dogs, mammals, and even humans!) and the high levels of E. coli that are sometimes found in the Anacostia River can make it unsafe for recreation. Microbial source tracking (MST) is a lab procedure that allows scientists to distinguish the source of fecal contaminants in a water source. Using MST lab procedures, scientists can analyze the E. coli found in the river to identify what types of fecal waste might be entering the waterway.
DOEE (DC’s Department of Energy & Environment) scientist Amir Sharifi recently partnered with a group of scientists at the federal Environmental Protection Agency (EPA) to conduct an MST study in seven tributary catchments in southeast DC (see included map). In this study, published in January of 2023, identified sources of E. coli found in samples collected from November 2019-2020.
Overall, they found the highest levels of E. coli in the summer, particularly after heavy rain events. 44.6% of samples collected had high amounts of E. coli and therefore failed to meet the acceptable use threshold (<410 cfu of E. coli per sample). Similar to what we find in our Citizen Science Water Quality Monitoring, most of these failing events occur after heavy summer rainstorms. Using MST methods, DOEE and EPA scientists were able to gain insights into the sources of E. coli during these failing events.
Overall, these findings were an interesting insight into the sources of microbial pollution in the Anacostia River. We look forward to DOEE’s continued efforts in MST sampling, as we expect results in the mainstem of the Anacostia to be quite different as these are impacted by the cities’ combined sewer outflows (CSOs).
We are initiating MST studies in Maryland’s Anacostia tributaries across Montgomery and Prince George’s county in partnership with University of Maryland professor Dr. Amy Sapkota to fully understand the sources of E. coli across our watershed and help advocate for plans to reduce bacterial levels so the watershed can be safe for all to recreate.
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