Increasing levels of nitrogen have caused a dramatic disappearance of eel grass in Buzzards Bay, and forests and stream buffers have declined in the watershed, according to the State of the Bay report by the Coalition for Buzzards Bay.

Increasing levels of nitrogen have caused a dramatic disappearance of eel grass in Buzzards Bay, and forests and stream buffers have declined in the watershed, according to the State of the Bay report by the Coalition for Buzzards Bay.

In Westport, the east branch of the Westport River is among the most unhealthy waterways in the bay area, the report says. The inlet to the river, however, is one of the healthier areas, and the inner west branch of the river is rated “fair.”

More than half of Buzzards Bay’s harbors and coves show a decline in the quality of sea life because of high levels of nitrogen, which typically comes from residential septic systems, according to the report. The rise in nitrogen, largely the result of residential growth in the area, according to the coalition, generally leads to higher algae growth and occasional fish kills.

In the report to the Board of Selectmen Monday, the coalition’s executive director, Mark Rasmussen, recommended localized waste treatment plants for areas like Westport Point and the Head of Westport that can treat nitrogen. Most home systems, even those that pass state guidelines, don’t treat nitrogen, Rasmussen said.

He also mentioned how other towns in the watershed have adopted 50- or 60-foot wetlands buffers, which he called “the most important part of the watershed.” Westport has traditionally enforced a 25-foot wetlands buffer.

There is “still time to act despite (the) disturbing trend,” the report says. The coalition suggests that homeowners consider upgrading to nitrogen-reducing septic systems, reduce the use of lawn fertilizers, reduce stormwater runoff, and convert to nontoxic, environmentally friendly house and garden products.

The report also encourages the preservation of forests, wetlands and stream buffers in the 17-town Buzzards Bay watershed. Impervious surfaces like paved areas and rooftops have increased by 42 percent between 1985 and 2002, according to a study cited in the report.

“If you live near a stream, create as wide a buffer of native vegetation as feasible along the stream’s edge,” the report says. It also suggests supporting efforts to improve fish passage and restore herring populations, and the adoption of 100-foot no-build wetlands setbacks.

Bacteria levels have climbed so high that 44 percent of the bay’s most productive shellfish beds are too polluted to permit commercial and recreational shellfishing, the report says. “This represents an ongoing threat to human health and economic losses in many parts of Buzzards Bay,” the report says.

One of the few positives in the report was a decrease in toxic pollution. Since 2003, “we have had three more years of groundwater treatment, which has reduced the toxic plume flowing into the bay from the Massachusetts Military Reservation,” the report says, “and Fairhaven eliminated the use and discharge of toxic chlorine for sewage disinfection.”

The town’s Board of Health and Conservation Commission, and the Westport River Watershed Alliance attended the coalition’s meeting with selectmen, but no remarks were made.

Members of the Coalition for Buzzards Bay met with the Board of Selectmen as part of an effort to meet with town officials throughout the watershed after releasing the report.

E-mail Grant Welker of the Herald News (Fall River, Mass.) at gwelker@heraldnews.com.