Cold Spring Harbor faces outbreak of toxic algae

Cold Spring Harbor is facing an outbreak of red algae, first detected last week, that might imperil shellfish.

If this variety of red tide, called dinophysis, should infest shellfish, the grounds where they grow would have to be closed because it can cause gastrointestinal poisoning in people.

"This one can get into shellfish; so far there is no evidence that’s happened yet — but we’re going to be testing for that," said Christopher Gobler, endowed chair of coastal ecology and conservation and principal investigator with the Gobler Laboratory at Stony Brook University.

While researchers say they do not yet fully understand what this algae may do to the shellfish, they do agree one primary cause — the excess nitrogen fueling these harmful algae blooms — comes from the watershed around Cold Spring Harbor, around 30 miles east of midtown Manhattan.

"We’re obviously very concerned that the testing is done, and that it makes sure the clams are safe, and hopefully, it will be a one-off" occurrence, said Robert Wemyss, secretary, North Oyster Bay Baymen's Association.

Previous red tides also have flared in Northport Harbor, about six miles east of Cold Spring Harbor on the North Shore of Long Island.

"Aging and failing septic systems," along with pet and animal waste, as well as fertilizer, are the sources of the excess nitrogen, said Nassau County spokeswoman Vicki DiStefano in an email.

As a result, explained Gobler: "When you do get a big rainfall event … it is going to push out the ground water, and also lead to a lot of water runoff."

The boundary between Nassau, where 90% of properties have sewers, and Suffolk, where only 30% of properties do, runs through the harbor.

"An estimated 66 percent of the nitrogen entering Cold Spring Harbor from Suffolk County emanates from unsewered wastewater sources," Walter Dawydiak, director of environmental quality with Suffolk County's Department of Health Services, said by email.

The Nassau side of Cold Spring Harbor also mainly lacks sewers, DiStefano said.

Suffolk first saw "discolored" water in Cold Spring Harbor on July 20; the Gobler Laboratory then confirmed the red tide. Dawydiak said no discolored water has been seen since then.

The counties have not closed beaches.

"Our monitoring is to protect human health" by frequently checking bacteria levels, said Mary Ellen Laurain, a spokeswoman with the Nassau County Department of Health. "If we see, while out there testing, algae blooms, any type of red tide, we would report that to the Department of Environmental Conservation as that's under their jurisdiction."

The state's Department of Environmental Conservation said it was making "generational investments to reduce nitrogen pollution," citing the Long Island Nitrogen Action Plan, which in recent years has helped fund more than $879 million for 209 projects in Nassau and Suffolk. In addition to that, a $439 million project will divert sewage out of Reynolds Channel and into the ocean by laying miles of pipe under Sunrise Highway.

The red tide can thrive in smaller bays, where cleansing tides are less powerful.

"These areas that have high nitrogen loading and low tidal flushing are the most vulnerable," Gobler said.

At least Long Island — unlike New York City, Westchester County and Connecticut — does not have sewers that mix rainwater with untreated sewage that can spill directly into waterways during storms, officials said.

Those systems, scientists say, help give the western Long Island Sound a "dead zone," where oxygen levels have plunged.

Spending $2.5 billion on upgrading wastewater treatment cut the size of that zone to 94 miles in 2020, based on a five-year-rolling average, from 205 square miles from 1987 to 2000, the U.S. Environmental Protection Agency said in May.

Red tides usually peak in July, and the weather will help determine how long this one lasts.

"Once it gets too warm," Gobler said, "they are done, so to speak, but if the temperature stays right, and there is some heavy rainfall, that could keep it around longer."

While the worst brown tide in years recently flared in the Great South Bay, it appears to have died off. Yet another harmful algae bloom may take its place — especially if the rest of the summer is hot.

Said Gobler: "That’s what we are keeping an eye out for. … That's the one that likes the hotter summer temperatures."

Read more about algae blooms and see temporary shellfish closures at the Department of Environmental Conservation's official website.