TRENTON - Rapid development is killing New Jersey's waterways by dumping tons of fertilizer, pesticides, and other pollutants into rivers, bays, and the Atlantic Ocean, according to a report released Wednesday by the state's leading environmental groups.

The study, mainly written by Environment New Jersey, called for the state to limit the nitrogen in fertilizer, reduce storm-water runoff into drains, and improve water treatment plants.

The report says nitrogen runoff leads to algae blooms that choke off aquatic life and feed the rapid growth of stinging jellyfish.

The groups say runoff pollution forces the closing of beaches, kills fish and clams, and threatens the Shore's multibillion-dollar tourism industry.

Calling Barnegat Bay the state's most heavily used body of water, with 100,000 boaters on an average summer weekend and $100 billion worth of property around it, Nicole Dallara of the New Jersey chapter of the Sierra Club said: "If we don't change things, the bay will die."

"The Shore is raising a red flag that we cannot afford to ignore," added Dena Mottola Jaborska, Environment New Jersey's executive director. "Nitrogen pollution creates the cancer that is putting the Barnegat Bay in critical condition."

The state is considering measures that would reduce nitrogen in fertilizer, but faces opposition from manufacturers.

Building on natural areas increases impervious surfaces such as roads, parking lots, and roofs, which channel pollution into waterways instead of absorbing storm water.

In 1972, development covered 18 percent of the Barnegat Bay-Little Egg Harbor watershed. Now more than 30 percent of the watershed is developed. What's more, zoning in municipalities surrounding the bay would allow a further 50 percent increase in development.

The U.S. Geological Survey estimates that 66 percent of the nitrogen pollution flowing into the two bays comes from surface water. Those two bays, along with the Great Bay at the mouth of the Mullica River, are susceptible to frequent algae blooms that deprive water of oxygen.

The number of beach-closing days rose from 79 in 2005 to 180 in 2009, mostly due to bacterial contamination from storm-water runoff or sewage overflow.

Barnegat Bay and Little Egg Harbor, as well as rivers including the Manasquan and Metedeconk, have been inundated with stinging jellyfish since 2000.

Nitrogen-based pollution in the water helps the jellyfish thrive.

The report also said the hard clam population in Barnegat Bay and Little Egg Harbor had been devastated, with harvests down 99 percent between the early 1970s and 2000.

In addition, bay scallops are virtually nonexistent, and eelgrass and other sea grasses, which provide shelter and food for a variety of fish, are in steep decline.

The environmentalists also called on the state to require the Oyster Creek nuclear power plant to build one or more cooling towers to replace its current system of sucking bay water through large pipes to cool the reactor, then releasing warmed water back into the bay.

A decision on the cooling towers could come as soon as Thursday.