This aerial photograph from Stony Brook University marine science professor...

This aerial photograph from Stony Brook University marine science professor Christopher Gobler shows a damaging brown tide on June 3, 2015, that emerged in May of that year across much of Great South Bay and Moriches Bay and intensified. Credit: Christopher J. Gobler

A brown tide crossing the western section of the Great South Bay that emerged earlier this month has intensified this week, raising experts’ concerns about the shellfish population in the area.

The murky brown water, caused by algae blooms, has appeared before — only this time, marine biologists warn that the environmental event is occurring more than one month earlier than expected and has similar characteristics to the long, damaging blooms that occurred in 2000 and 2008 and killed shellfish and eelgrass.

“The outbreak of brown tide in this part of Great South Bay this early in the season is a troubling sign for Long Island.” said Christopher Gobler, professor of marine science at Stony Brook University. “Given the steady, ongoing rise of brown tide in eastern Great South Bay, Moriches Bay and Shinnecock Bay, the entire South Shore could be ‘in bloom’ in a matter of days to weeks.”

Gobler and his team of researchers regularly monitor and track various water-quality indicators on Long Island. Brown algae, Aureococcus anophagefferens, poses no health risk to humans but is lethal to shellfish.

The severity of an algae bloom is measured by its cell density. At 50,000 cells per milliliter, it is harmful to marine life, particularly clams.

A sample collected off of Bay Shore on Monday showed levels were elevated 10 times, 500,000 cells per milliliter, Gobler said.

Typically, brown algae blooms begin in mid- to late June and last for a few weeks. Gobler believes this event could last all summer and extend as far east as Shinnecock Bay.

A picture of the brown tide at the Quogue Canal...

A picture of the brown tide at the Quogue Canal bridge in Quogue take June 23, 2016 when more than one million cells per milliliter were recorded. Credit: School of Marine and Atmospheric / Christopher J. Gobler

Carl LoBue, New York Oceans Progam director for the Nature Conservancy, said he was out fishing on Sunday when he noticed the brown tide.

“You can really see that the water is terrible-looking. It looks like coffee with skim milk,” he said.

LoBue, who monitors the waters in the state’s bays and harbors, said the recent brown tide is just another reason why there are increased efforts to remove nitrogen leaching into the water in Suffolk County. Nitrogen from cesspools and septic systems get into the water. There are about 360,000 residential septic systems and about 100,000 non-residential septic systems in the county.

“It’s why doing all those things is so important,” he said.

In 2008, after appearing first in the western Great South Bay in May, the brown tide spread across all of the South Shore, from the Robert Moses Bridge to Southampton, killing the hard clam population.

Brown algae also has been blamed for the demise of the largest bay scallop fishery on the East Coast in the Peconic Estuary, the loss of eelgrass across the Island and the slow recovery of the hard clam population in the Great South Bay, Gobler said.

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