An emerging science known as source-tracking may soon identify for scientists the sources of bacteria pollution in the Chesapeake Bay.
The method isolates the bacteria in water samples and compares them with those found in samples from known sources. A match between samples determines the origin of the waste in the water sample.
Common sources of bacteria include waste from dogs, wild geese, deer and humans. If scientists can figure out the source of the bacteria, then health officials can conduct public awareness campaigns so people will clean up after their pets, or municipalities will work harder to retrofit stormwater or encourage septic upgrades.
"In a creek where you have a community that's concerned, and you show it could be dogs, then hopefully they'll provide on-site ways to deal with pet waste," said Kathy Brohawn, chief of the bacteriological assessment division at the Maryland Department of the Environment.
Since 2008, the MDE has partnered with Salisbury University to track the sources of bacteria found in impaired waterways, many of them in Anne Arundel County. Researchers there are using antibiotic resistance technology to determine the sources. Brohawn said the department is hoping to build a library of samples so they can compare what they find in water samples with common sources. It will also help let them know which sources are perennial problems in particular creeks.
Antibiotic resistance testing is inexpensive, and can be replicated across multiple streams. A more precise test would be to look at the bacteria's DNA, according to Sally Hornor, a microbiologist at Anne Arundel Community College who specializes in water testing. But Brohawn said that is too expensive.
Virginia has been looking at the source of pollution as well. At Old Dominion University, Professor Fred Dobbs has been trying to determine the source of different bacteria in local creeks and rivers using the DNA methods. Dobbs directs the university's graduate program for Ocean, Earth and Atmospheric Sciences. He is partnering with colleagues in New Hampshire to run sophisticated tests on the bacteria.
It's likely Chesapeake residents will be hearing more about source-tracking as the methods improve.
"We're asking questions of bacteria," Dobbs said. "We're doing it in the context of public health."