A new study by the U.S. Geological Survey finds levels of nitrogen and phosphorous are either dropping or holding steady in most New Jersey waterways.

“What it shows us is our strategies in enhancing water quality have been working,” said Larry Hajna, a spokesman for the New Jersey Department of Environmental Protection.

He said this is particularly encouraging because “this is the most comprehensive long-term study of water quality that has ever been undertaken in New Jersey, going back four decades, really.”

Hajna said what we’ve seen is the development of wastewater treatment plants, from smaller, local facilities into more modernized, regionalized plants. And that "has led to a reduction in the types of nutrients that can impair our waterways, specifically phosphorous and nitrogen.”

He added the study results also show “our strategies that we’ve enacted over the decades to better control stormwater pollution are having an impact as well.”

Stormwater carries fertilizers that contain nutrients that get into storm-water discharge systems, and ultimately, into our creeks, rivers and bays. A number of programs have been enacted on the local level to better control storm-water discharge, and collect it before it creates a problem.

Hajna also said New Jersey has enacted tough fertilizer laws that require steps be taken to improve the formulation of fertilizers and to make sure applicators are certified.

“There’s a lot of programs that have been in place for a number of years that this study is showing has worked really well.”

Hajna said if there is too much nitrogen present in the water, and “there’s too much algae in the water, it consumes oxygen as it dies — and that depletes the waterway of oxygen that aquatic life needs."

It can also make water taste "off."

The survey found that 25 of the 28 study sites, concentrations of phosphorous and nitrogen decreased or did not change significantly.

A statement by the DEP said an upward trend in phosphorous levels was observed at a station at the West Branch of the Wading River in Woodland Township, Burlington County. Nitrogen levels increased at just two stations — one at the Toms River in Toms River, Ocean County, and the other at the Cohansey River in Upper Deerfield, Cumberland County.

Hajna said the study will enable the DEP to take a close look those areas in an effort to determine why phosphorous and nitrogen levels are rising.

Researchers also found elevated levels of salt in the water at four sites along the Delaware River. The USGS notes studies in other northeastern state have found similar increases.

You can contact reporter David Matthau at David.Matthau@townsquaremedia.com.

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