Development endangers St. Mary's River, study shows

Jessie Ditillo of St. Mary's College kayaks in the St. Mary's River, where water quality has dropped.
Jessie Ditillo of St. Mary's College kayaks in the St. Mary's River, where water quality has dropped. (James A. Parcell For The Washington Post)
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By Christy Goodman
Washington Post Staff Writer
Sunday, November 22, 2009

Water clarity and oxygen levels in the St. Mary's River are at failing levels, largely because of development.

Data collected by the St. Mary's Watershed Association and other scientists show that between 2000 and 2008, water quality has decreased in streams that feed into the St. Mary's River near the Lexington Park development district, including fewer macroinvertibrates, tiny organisms that live in the bottoms of streams and rivers.

"Generally speaking, most of the streams in the upper area of the development district have gone down in quality," while impervious surfaces have increased, said Bob Lewis, executive director of the Watershed Association.

The St. Mary's and Wicomico rivers are considered to be the most degraded of lower Potomac tributaries, according to a 2008 report by the Interstate Commission on the Potomac River Basin, Lewis said.

Robert Paul, biology professor and director of the St. Mary's River study project at St. Mary's College of Maryland, used Church Point as an example of conditions throughout the river. The college has 10 years of data from the point.

The studies found that, during summers, the levels of dissolved oxygen at the bottom of the river is nonexistent and that aquatic vegetation is dying at high rates, Paul said. That's especially true in wet summers, when more harmful nutrients wash off lawns, pavement and developed areas and into waterways, creating algae blooms and sediment that block sunlight, he said.

"Not only are you killing the organisms outright due to lack of oxygen, you are also killing habitat," Paul said.

Another indicator of the river's health is its oyster population, he said. In 1974, there were about 90,000 bushels of oysters harvested from the St. Mary's River. Since 2000, about 1,500 bushels were harvested.

In about 20 years, the development district's population should double, doubling the pressure on the stream systems, Lewis said.

The Watershed Association is working on the St. Mary's River Watershed Action Strategy to combat the onslaught of sediment and other harmful actions to the river.

Association President Joe Anderson said that once the plan is completed, the county will be at the forefront of others in the area and will have a solid plan to back grants from local, state and federal sources.

Because the St. Mary's River Watershed covers more than 45,000 acres and is entirely in St. Mary's, the county has the ability to protect and improve the watershed. The county can make changes and "essentially act as a model [of how] to do things the right way," Anderson said.

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