SEASIDE PARK — The fragile Barnegat Bay-Little Egg Harbor ecosystem is getting worse and will continue to decline unless development and storm water runoff into the bay are reduced, according to a new Rutgers University study.

The study, released Wednesday, finds Barnegat Bay to be highly stressed due to decades of nitrogen and phosphorus entering the waterway from lawns, parking lots and driveways and sewer system overflows.

"This study paints a rather bleak picture," said Michael Kennish, the study's lead investigator.

He said the bay system has endured low dissolved oxygen concentrations, harmful algae blooms, loss of habitat, diminishing hard clam populations and other detrimental effects. Since 2004, eelgrass beds, which are home to crabs, fish and other wildlife, have continually declined, to a low point in 2010.

Kennish said many things need to be done including improving storm water control systems, preserving open space, limiting fertilizer runoff and planning development so it has less impact on the waterways.

New Jersey has taken steps to limit pollutants in the bay, still a popular spot for fishing and recreational boating, but environmentalists say they fall far short of what is needed.

"This report is an alarm bell going off that Barnegat Bay will die unless strong programs are put in place to protect the bay," said Jeff Tittel, director of the New Jersey Sierra Club environmental group.

He and other environmentalists want New Jersey to declare that the bay has reached a fragile enough condition that warrants placing a daily limit on how much pollution can be allowed to enter the waterway. Republican Gov. Chris Christie vetoed a bill that would have imposed such a requirement.

Tittel said that when Christie vetoed the bill "he killed a real chance to clean up the bay."

Christie spokesman Michael Drewniak noted that Tittel was among those applauding protections the governor put into place two years ago for the bay, including the early closure of the Oyster Creek Nuclear Generating Station and the adoption of the nation's strictest limits on nitrogen content in fertilizer.

"Tittel is an overwrought fear-mongerer," Drewniak said. "He's even forgotten his own unqualified praise of the governor on Barnegat Bay protections enacted by this administration. This contradiction from Tittel would be hilarious if not so ignorant and irresponsible."

He said the improvements included in the governor's 10-point plan to help Barnegat Bay were enacted in January 2011, at the end of the two-decade period covered by the Rutgers study.

"We are committed to the health and recovery of Barnegat Bay," Drewniak said.

Land on the edge of and near Barnegat Bay has undergone tremendous residential and commercial development in recent decades. Where there once were wooded areas or grassy shorelines, there now are freshly manicured lawns where nitrogen-laden fertilizer washes into the bay. There are paved driveways and parking lots that rush storm water runoff into the water, along with multiple pollutants it picks up along the way.

One result of the pollution has been an explosion in the population of jellyfish in the bay, rendering large parts of it unfit for swimming for area residents.

"You walk in, and they just cling to you," said Bill Neveil, of Middlesex Borough, who was crabbing with his grandson on a dock in Seaside Heights on Wednesday. "I got stung a lot. Then no one wanted to go in the water."

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• Gov. Christie to sign clean water bill along Barnegat Bay