Record Year For ‘Rust Tide’ Algae Scourge

Rust tide in Peconic Bay. TIM CORWIN

The red algae that has earned the nickname “rust tide” has continued to bloom in deadly reddish-brown ribbons into the month of October for the first time on record, Stony Brook University scientists say — an ignominious milestone that threatens fish and shellfish species in Shinnecock and Peconic bays.

The blooms of the algae first appeared in early August and have raged on most days since, through this week. Spurred on by heavy rains, which flush nutrients that feed the blooms, and a warm start to the autumn, the destructive algae now appears poised to persist in 2021 longer than they ever have before.

“In some years, it’s just be a blip — it will just pop up for a week or 10 days — but this year it’s hung on for a long time,” said Dr. Christopher Gobler, who leads the team of Stony Brook researchers who monitor harmful algae blooms across Long Island each summer. “This summer we had a lot of heavy rainfall events with these tropical storms … and the nutrients that come with that pulse of freshwater gives it a boost.”

Dr. Gobler said that in previous years with bad rust tide outbreaks, the blooms lasted until there is an extended cold snap: temps that dip into the 40s at night for a few days or more. That has yet to happen this late summer and early fall.

“I don’t think it’s ever gone all the way to October,” the Stony Brook professor said.

The rust tide has been the worst this year in Great Peconic Bay and some of its tributaries and in eastern Shinnecock Bay, but has also been seen in Flanders Bay and western Shinnecock Bay, Stony Brook researchers have found.

The rust tide algae is distinctive for the tiger-striped ribbons its single-cell dinoflagellates create when they swim into the upper water column during the day.

The cells emit a natural toxin that can be deadly to fish and shellfish if they are exposed to it for too long.

Thus far, there have not been any signs of major fish-kills or other impacts, Dr. Gobler said — save for smatterings of small dead fish scientists have found along the shorelines of eastern Shinnecock Bay and in the Shinnecock Canal.

But the blooms have been blamed for die-offs of bay scallops in the past and shellfish researchers are already monitoring a massive die-off of adult scallops and have expressed concerns that a major rust tide could decimate the young-of-the-year that pose perhaps the only hope for the species in 2022.