Toxic Rust Tide Returns for 11th Year

Three Mile Harbor/Photo: Rob Grambau, Flickr Creative Commons

For the 11th summer in a row, the “rust tide” has returned to Eastern Long Island, beginning this time in the waters off Sag Harbor it has been reported in News12 Long Island as well as Newsday. The current algae bloom has also been detected in Accabonac Harbor and Three Mile Harbor. In past seasons the bloom has originated in the Peconic and Shinnecock Bays, according to a press release from the Stony Brook South Hampton School of Marine and Atmospheric Sciences.

The rust tide is caused by a bloom of algae that thrives on nitrogen from sewage and fertilizer in water above 60 degrees. The cause of the rusty colored algae is Cochlodinium. It can be lethal to marine life in concentrations of more than 500 cells per milliliter. Levels as high as 30,000 cells per milliliter have been detected this year in waters off Sag Harbor. Last year, the level of concentration was a cause of alarm and the Stony Brook Southampton School of Marine and Atmospheric Sciences issued a press release advising the public to be cautious when levels of 1,000 cells per milliliter or more were detected. The level presently being reported is thirty times higher.

The rust tide is responsible for the death of finfish and shellfish. In the press release Professor Christopher Gobler explained that his laboratory has learned how the algae blooms propagate and become an annual occurrence.

“In the last year,” Dr. Gobler explained “we have published two important, new discoveries that help explain the chronic recurrence of these events. First, we have discovered the organism makes cysts or seeds which wait at the bottom of the bay and emerge each summer to start a new bloom. At the end of the bloom, they turn back into cysts and settle back to the bay bottom. This allows for the blooms to return every year. Second, we have found that nitrogen loading makes these blooms more intense and more toxic. As nitrogen loading has increased into our bays, these events have intensified.”

Experiments conducted in the Gobler Lab have demonstrated that these algae blooms can kill fish in hours and shellfish in days. In the autumn of 2012, bay scallop densities in the Peconic Estuary declined tenfold in some regions during the rust tide. The impacts of this year’s bloom will likely depend on its duration.

Dr. Gobler told News12 Long Island that left unchecked, the rust tide could kill Long Island’s multibillion-dollar fishing and shellfishing industry and urged lawmakers to enact regulations to restrict the flow of nitrogen nutrients from storm run-off, septic systems and fertilizers, into the waters of Eastern Long Island.

The rust tide is not toxic to humans, but swimmers should avoid it whenever possible. Scientists urge bathers to use common sense and avoid swimming in waters that are discolored.

The bloom typically flourishes until the water temperatures drop below 60 degrees, Dr. Gobler said.