By Judy Benson
The New London Day 1/20/2015

Five years of water quality testing at four estuaries in Mystic and Stonington have revealed that Wequetequock and Pequotsepos coves are particularly stressed by high levels of polluted runoff and low dissolved oxygen in the summer.

The two narrow coves both received a “poor” aquatic health score – a measure of inorganic and organic nitrogen levels, microscopic algae and dissolved oxygen that impact aquatic life – due to inadequate tidal flushing and constricted flows. High inorganic nitrogen levels, which spur overproduction of algae, are elevated due to runoff laden with chemical fertilizers, discharges from boats, poorly maintained septic systems and roadways, among other sources. Organic nitrogen comes from decaying plants and animals. Water quality in the coves is especially poor when freshwater flows are low during dry months. Wequetequock Cove connects into Little Narragansett Bay, while Pequotsepos Cove enters Mystic Harbor.

Stonington Harbor’s overall “Aquatic Health Index” score was rated “good,” while the mouth of the Mystic River was labeled “good to fair” and upstream, the river received a “fair-minus” rating. The Aquatic Health Index scores water quality on a scale of zero to 100.

Those were the conclusions of a report released last week by CUSH, Clean Up Sound & Harbors. It presents the findings of the nonprofit group’s water quality testing project from 2008 to 2013, in which 16 to 22 volunteers collected water samples at 12 locations in the four estuaries. The samples were tested by the University of Rhode Island’s Watershed Watch program. Grants from Connecticut Sea Grant, the Long Island Sound Futures Fund, among other sources, paid for the testing.

“What this provides is actual hard numbers and evidence,” Claire Gavin, former director of the water quality testing program, said Monday. “The coves just aren’t getting any fresh water input.”

Since it was established five years ago, one of CUSH’s main initiatives has been offering workshops to promote the use of organic lawn and gardening practices and raise awareness about the impact of “non-point source” pollutants – those from multiple, disparate origins – on coastal waters in Stonington and Mystic. Frances Hoffman, past president of CUSH and now head of the group’s Sound Friendly Yards program, said the testing confirms that the group has been putting its efforts in the right place.

The test results, she said, also highlight the need to better manage runoff so that more is filtered through soils rather than being directly discharged into waterways, and to reopen constricted coves to tidal flows.

The report has been shared with Stonington’s Planning and Zoning Commission, so that it can consider the findings as it revises the town’s plan of conservation and development, she said. She would also like to share it with Amtrak and the state Department of Transportation, so that bridges over the two coves could be widened the next time rebuilding projects are underway.

Gavin said that while the report’s conclusions largely reinforced what the group already knew, it highlighted the strong influence of tidal flushing on the health of the estuaries. That points to the importance of working to improve marine water quality as well as freshwater runoff, according to the report.

“The way to protect Stonington Harbor in the long term is not only to reduce surface runoff, but also to ensure the health of Block Island Sound, because the harbor is only as good as the water that enters it twice a day,” the report states.

Gavin said the report will be posted on the group’s website in the next few days. It sums up the reports conclusions in two major findings:

• “When estuaries are well flushed with oxygen-rich water, as in Stonington harbor and the Mystic River, aquatic life can be well supported even in the presence of nitrogen pollution – as long as nitrogen input does not overwhelm the flushing capacity.”

•”When both fresh and saltwater flows are weak, as in our flow-restricted coves, poor flushing will allow pollutants to accumulate, and good water quality can only be achieved by limiting the amount of nitrogen that enters the water.”

Restoring natural tidal flows is a “long-term effort,” the report states, but people can take stapes to reduce nitrogen pollution by using organic lawn and garden practices, eliminating sources of bacteria and excess nitrogen such as septic and pet wastes and runoff, and using pumpout facilities when boating, among other steps.

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