Animal Waste Accounts for Two-thirds of Bacteria in 2 Watersheds
A study by the Maryland Department of the Environment (MDE) and Salisbury University finds that pets and wildlife are significant sources of bacteria in the watersheds of eight Anne Arundel County waterways, MDE announced. Another study by these organizations suggests that bacteria are present in sediment and sand and may contribute to elevated bacteria levels in water.
The studies were conducted to determine the sources of bacteria in surface waters. Researchers found that waste from dogs and from such wildlife as fox and deer accounted for about two-thirds of the bacteria in the watersheds of both Furnace Creek and Marley Creeks, two Glen Burnie-area waterways where bacteria standards are not being met.
The findings suggest that failing to clean up after pets can have a significant effect on water quality in the watersheds. While further investigation is needed to determine ways to reduce human sources of bacteria in these waters, the study provides a beginning for local communities and governments to examine and prioritize ways to minimize bacteria in their waters. The study results, along with the findings from the MDE-SU study of bacteria in beach sand, will be used in connection with on-going efforts to reduce bacteria loads in Maryland waters.
MDE’s science services director, Rich Eskin, said: “We are constantly striving to improve our data so we can target our work to reduce pollution throughout Maryland. These studies can be used as models for determining the sources of bacteria in other waterways throughout the state.”
For several years, MDE has partnered with Salisbury University to develop Bacteria Source Tracking (BST) for all bacteria-impaired waters in Maryland. This latest round of BST work was completed in July and submitted to MDE by researchers Mark Frana and Elichia Venso of Salisbury University.
BST was conducted in watersheds in Anne Arundel County as part of the total maximum daily load (TMDL) determination for bacteria. A TMDL establishes the maximum amount of an impairing substance or stressor that a body of water can assimilate and still meet water quality standards and allocates that load among pollution contributors.
Researchers studied eight Anne Arundel County watersheds: Furnace Creek, Magothy River, Rhode River, Marley Creek, Severn River, South River, West River, and along Anne Arundel’s Chesapeake Bay coast. They collected samples in areas of the watersheds where bacteria standards are not being met.
Overall, the major contributor to bacteria in the eight watersheds was wildlife, followed by pets (primarily in the form of dog waste), humans, and lastly, livestock. A summary of the study findings for all eight watersheds is attached. The studies measured “indicator” bacteria, which are common in all warm blooded animals, including humans, and are generally not harmful. The presence of indicator bacteria in water, sediment, and sand does not necessarily mean that bacterial pathogens are present. Because pathogenic bacteria are infrequent and difficult to monitor, MDE and county health departments monitor indicator bacteria and use the results to determine whether waters meet water quality standards, whether shellfish harvesting waters should be closed, and whether swimming advisories are necessary.
The other MDE-Salisbury University study suggests that indicator bacteria are present in sediment and sand and may contribute to elevated indicator bacteria levels in water. Researchers in the Great Lakes, on the west coast, and in Florida have shown that indicator bacteria can thrive in beach sand in the absence of pollution sources, raising the question of whether sand rather than runoff or other discharges could be the source of elevated bacteria levels in the water.
MDE partnered with Frana and Venso to investigate whether the same thing happens in our region and to begin to try and understand how this may relate to health risk. To account for the variety of conditions found in our region, the study looked at four sites: an ocean beach in Sussex County, Del.; a coastal bay at Assateague Island National Sea Shore in Worcester County; Granary Creek, a small tributary of the Wye River in Talbot County; and the Chesapeake Bay at Sandy Point State Park in Anne Arundel County. For one year, water, sediment, and sand samples were collected monthly at each site to test for the presence of indicator bacteria. All samples were screened for human pathogens.
None of the sites were impacted directly by pollution sources and, like all of Maryland’s beaches, all of the sites were potentially impacted by non-point sources. Researchers found no bacterial pathogens normally associated with pollution sources in the water samples. They found only one potential human pathogen, which is naturally occurring and known to cause mild intestinal illness, in one sediment sample.
The absence of bacterial pathogens associated with pollution sources, in water samples whose indicator bacteria levels are increased by their presence in sediment and sand suggests that the current water quality standard is conservative and that the combination of shoreline surveys to address known pollution sources and routine monitoring are effective for adequately protecting public health.
For more information, visit www.salisbury.edu.