Long Island's summer of 2021 brought algae and sharks

Algae and sharks sure found Long Island’s summer of 2021 to their liking — for entirely different reasons.

The algae flourished in warm, nitrogen-polluted waters in streams and bays, scientists said. The sharks were chasing recovering bunker fish populations toward shore.

At least the rust tide, one of the last outbreaks still infesting bays, including the East End's Peconic and Shinnecock, should die off as waters cool by month's end, said Christopher Gobler, who holds the endowed chair of coastal ecology and conservation and is principal investigator with the Gobler Laboratory at Stony Brook University.

And Long Island's shellfish for the second year in a row were spared a devastating outbreak of paralytic shellfish poisoning, said Debra Barnes, shellfisheries bureau chief for the state Department of Environmental Conservation.

Yet next summer probably will have more algae flare-ups, said Gobler, "Unless we stem the flow of nutrients coming from the land."

Algae blooms, though somewhat unpredictable, tend to recur in the same spots. After summer, these plantlike visitors can become dormant. "And then, in the spring, as we have nutrients added and increased sunlight, it will start to generate, and then, depending on what the conditions are, may reproduce and come into a bloom," Barnes said.

This summer's extraordinary rainfall sent the excess nitrogen the various colored tides of algae thrive on gushing into the Great South Bay and Long Island Sound — and the waters warmed to the 70-degree range some species favor, scientists said.

After all, it was the hottest meteorological summer for the lower 48 states since the 1936 Dust Bowl, with the average temperature rising 2.6 degrees above average to 74, the National Oceanic and Atmospheric Administration said Thursday.

Both the Great South Bay and Long Island Sound are cleaner — another shark- and bunker fish-appealing factor — due to wastewater plant improvements in New York City, Westchester and Connecticut. Yet powerful storms — like Henri and Ida of 2021 — can release sewage with rainwater, so advocates call for stricter limits.

Boaters can be polluters as well. Every year, the DEC issues two to three violations to boaters in Nassau and Suffolk for violating pump-out regulations, spokeswoman Maureen Wren said. This problem has arisen in Sag Harbor, for example, after complaints about "vessels over 75 feet that had a history of not going to pump-outs and discharging into the harbor," she said.

Fred Uvena, Huntington's marine services interim director and senior harbormaster, estimated 2,100 gallons of waste were pumped by his crews from some of the as many as 1,500 boats that moored in the harbor over the Labor Day weekend. "We keep a close watch on that around the holiday," he said, noting the state preemptively closes some shellfish spots ahead of holiday boat traffic.

To some extent, Long Island’s geography works against it. The aquifer system, its sole source of drinking water, lies just 600 feet or so below ground on the North Shore and at its deepest, 2,000 feet on the South Shore, the U.S. Geological Service calculated.

Aquifers store groundwater; how long it takes to reach the Sound and the Great South Bay varies markedly, from as little as 20 years around the Twin Forks to hundreds of years in the middle of Long Island, estimated Gobler.

This vast difference in travel time means the Twin Forks might improve more quickly, rather like Long Island Sound. Its "dead zone," where oxygen levels fall critically low, has shrunk in the past two decades as wastewater plants were forced to upgrade.

In 2020, the dead zone covered 63 square miles, 25 less than in 2019, said Long Island Sound Study, conducted by the U.S. Environmental Protection Agency, New York and Connecticut.

Much of Long Island's groundwater, however, researchers say, still is being polluted by all the nitrogen-laden fertilizers poured on lawns for decades. In Suffolk, where about 70% of homes are not connected to sewers, leaks from the home septic systems can exacerbate that pollution.

The problem, of course, with intense rainfall is that once the ground is sodden bacteria, pesticides, fertilizers, oil, animal waste and debris can contaminate rainwater.

Stormwater runoff is the main source of water pollution in Nassau, Mary Ellen Johanson Laurain, a county health department spokeswoman, said by email. "Microbiological contamination generally increases after a rainfall and dissipates after approximately two tide cycles."

Suffolk pointed to another problem: storm surges. Grace Kelly-McGovern, a county Department of Health Services spokeswoman, said: "Most existing local studies that have evaluated pathogen sources to surface water, concluded that feces from waterfowl or other wildlife are the primary source of pathogen contamination, in most instances."