Over the past month, the Peconic Estuary has been hit with one environmental blow after another, a Stony Brook biologist and marine researcher said, thanks in part to rising temperatures in East End waterways.
Since the end of July, local waters have been affected by rust tide, a type of algal growth that produces toxins harmful to marine life; mosquito fern, a plant that is covering parts of the Peconic River; and blue-green algae, which can be dangerous to humans and their pets.
While most of the problems don’t pose an immediate threat, the blooms point to serious issues, said Christopher Gobler, associate dean of research at Stony Brook University’s School of Marine and Atmospheric Sciences.
“These events are definitely temperature-driven,” he said of the algal blooms now spreading in the estuary. He said the overload of nutrients like nitrogen and phosphorus from septic systems, fertilizer and rain runoff is also a “big factor.”
The most dangerous bloom is the blue-green algae, technically known as cyanobacteria, which was spotted in the upper Peconic River in Calverton and Riverhead for the first time in August, Mr. Gobler said.
His lab found that water samples taken from the Peconic River showed levels of bacteria that were 10 times the safe limits set by the county health department. That algae can prove dangerous because it produces microcystin, a toxin that can cause skin irritation in humans and serious harm to pets.
Last year, two dogs on the East End were sickened by microcystin from blue-green algae and, in 2012, a dog in East Hampton died after ingesting the toxins from Georgica Pond, according to media reports.
While the algae can grow easily in stagnant waters, it has never before been seen in the Peconic River because the water there normally moves too quickly, Mr. Gobler said.
“Usually flowing water bodies are less likely to accumulate blue-green algae,” he said. “The water normally flushes out.” But due to a drought that has affected all of Long Island for more than a year, water isn’t draining into the river as frequently, which slows the water’s speed.
The county health department issued a notice last week warning swimmers to stay away from that area of the river. Mr. Gobler said the algae can concentrate along the shorelines and can stick to the fur of pets.
“If the water looks green, best to keep you and your pets away,” he suggested.
The rust tide — so called because of the algae’s rusty red color — first sprouted on the East End in a few isolated locations in late July, he said.
“Since that time it’s just sort of progressively ramped up,” Mr. Gobler said.
The last big bloom was in 2012, with two more mild summers delaying the growths. The algae that causes red tide only begins to grow when the water is warm enough, said Stephen Schott, a marine botany and habitat restoration specialist with Cornell Cooperative Extension.
“A lot has to do with water temperature,” Mr. Schott said. “It definitely likes the warmer water. Rainfall can trigger it in the summer time.”
Rust tide was rarely spotted on the East End before 2004, Mr. Gobler said. At that time, temperatures in Peconic Bay rarely got close to 75 degrees Fahrenheit, the ideal growing temperature for the algae. But since then, water temperatures regularly exceed 75 degrees and the algal blooms have returned almost every summer.
Rust tide — like its relative “mahogany tide” — has a distinctive color as well as a smell similar to “rotting ketchup,” Mr. Gobler said. However, it poses no threat to human swimmers, Mr. Schott said.
“It’s kind of creepy,” he added. “The water has a distinct reddish tinge as you’re swimming around in it. It’s almost like a red filter on a camera.”
But the blooms do pose threats to marine animal life, Mr. Gobler said. The sheer density of the blooms, which can spread over vast areas of open water, can tax the regional ecosystem. At night, when the algae breathe and suck in oxygen, the mass of organisms can suck oxygen right out of the water.
This creates dead zones where fish or other plant life can literally suffocate and die. The rust tide has other side effects on fish and shellfish as well, thanks to highly reactive chemical substances the algae release called “reactive oxygen series,” Mr. Gobler said.
These short-lived compounds — also known as free radicals — “essentially destroy proteins that they’re exposed to,” he explained. All living marine organisms have natural anti-oxidant mechanisms that filter out free radicals. But when assaulted by a dense cloud of the substances caused by the algal bloom, the marine life’s natural defenses are overwhelmed.
That means a fish’s gills or vital parts of a shellfish can be fatally damaged, Mr. Gobler said.
Though the free radicals themselves are invisible to the naked eye, Mr. Gobler said the red coloring of the water associated with rust tide is “tens of thousands of [algal] cells in a milliliter of water cranking out that stuff that does the damage.”
Finally, an unusual plant has spread across the water’s surface on the Peconic River near downtown Riverhead. The red-colored plants are called mosquito fern, Mr. Gobler said, and have coated much of the area.
While the plants don’t pose a direct threat to humans or animal life, the mosquito fern can further retard water movement, which can lead to other types of algal growth, he said. The ferns also disrupt the natural habitat and can make it difficult for marine life to hunt prey.
“These things are overgrowing what would be otherwise natural habitat,” he said.
As the plant and algal growths spread, Mr. Gobler said there’s little to be done that can directly limit the blooms once they begin. Until the fall, when temperatures drop again, scientists will continue monitoring the Peconic Estuary.
A quick fix, he said, won’t be coming. But if septic systems are improved and if property owners cut back on fertilizers, the nitrogen that fuels these plant and algal blooms can be reduced, which would limit the effects of future problems, Mr. Gobler said.