Local scientists say the low quality of Long Island water is damaging marine life.

Dr. Christopher Gobler, a professor at Stony Brook's Marine Sciences Center, announced his findings after monitoring at 30 different locations this summer and fall.

Gobler says 70 percent of the sites being monitored had oxygen levels that were well below the state's standard for where fish can survive. One of them is in Riverhead's Peconic River. Lake Ronkonkoma, Long Island's largest freshwater lake, is one of 10 spots in Suffolk that had toxic blue green algae.

Experts say nitrogen pollution from septic tanks and fertilizers are mostly to blame for the poor quality of water.

Chris Clapp, a marine scientist from the Nature Conservancy, called the pollution "the largest public and environmental challenge of our generation."

Clapp says knowing there's a problem is just the first step. He says fixing it will take time and money.