Researchers at Stony Brook Southampton said this week that rust tide has spread throughout the Peconic Bays. | Courtesy SCERP

An algae bloom that began in the western Peconic Bays in mid-August has spread east, and now covers waters as far from its origins in Flanders Bay and MeetingHouse Creek as Accabonac Harbor in Springs and Gardiners Bay, east of Shelter Island, according to researchers at Stony Brook’s Southampton Coastal and Estuarine Research Program.

The rust tide algae, a dinoflagellate called Cochlodinium, can be toxic to finfish and shellfish at densities above 500 cells per milliliter, while the East End’s other most problematic algae, brown tide, isn’t harmful to marine life until it reaches concentrations of 50,000 cells per milliliter. Rust tide is a different organism from red tide, which is toxic to humans who ingest shellfish contaminated by the algae. Rust tide is, however, believed by some scientists to have been responsible for a die-off of scallops and other marine life last fall.

Rust tide is also different in appearance from other algae blooms. It often appears in bands of dark red water, in contrast to the bluer water surrounding it.

The researchers said Wednesday that, in addition to in the open bays, they have found rust tide in East Creek in Jamesport, North Sea Harbor, Fish Cove in Noyac, Sag Harbor Cove, Coecles Harbor on Shelter Island, and Three Mile Harbor and Northwest Creek in East Hampton, and believe it may be present in other untested waters.

Rust tide has appeared on a smaller scale in East End waters for about a decade. SCERP researcher Chris Gobler has been studying the way cysts formed by the rust tide algae allow the blooms to recur year after year.

“In the last year, we have published two important, new discoveries that help explain the chronic recurrence of these events,” he said in a recent press release. “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.”

Rust tide begins to dissipate in the fall when the water temperature falls below 60 degrees.

Beth Young
Beth Young is an award-winning local journalist who has been covering the East End since the 1990s. She began her career at the Sag Harbor Express and, after receiving her Masters from the Columbia University Graduate School of Journalism, has reported for the Southampton Press, the East Hampton Press and the Times/Review Media Group. She founded the East End Beacon website in 2013, and a print edition in 2017. Beth was born and raised on the North Fork. In her spare time, she tinkers with bicycles, tries not to drown in the Peconic Bay and hopes to grow the perfect tomato. You can send her a message at editor@eastendbeacon.com

4 thoughts on “Rust tide spreads throughout bays

  1. Just to clarify, neither species of algae referred to in this article are “toxic to humans who ingest shellfish contaminated by it”. Cochlodinium blooms are highly toxic to finfish and shellfish (but not humans) and the ‘brown tide’, the notorious Aureococcus anophagefferens that wiped out the scallops, eelgrass and clams decades ago, harm marine life by a number of mechanisms. There are plenty of other ‘red tides-rust tides- and brown tides’ referred to as HABS or harmful algae blooms, that are toxic to humans who ingest shellfish or other seafood contaminated by it. Good thing they are not here now.

    1. I’m a little bit confused. This article refers to three types of algae, only one of which is harmful to humans. Are you saying red tide isn’t harmful to humans? The CDC says otherwise.

  2. Im pretty sure ‘rust tide’ is a new term…which currently refers to ‘rust’ colored algal blooms. Cochlodinium was commonly referred to as a species that caused a red tide-(just last year, in fact) but now I guess it is being called a rust tide. Many algae blooms are harmful to humans-red ones- blue ones, green ones…many algal species can be called a red tide organism, or a species that causes brown tide ….I just wanted to clarify that the 2 species I thought the article was referring to (Cochlodinium and Aureococcus) are not toxic to humans if they ingest marine life contaminated with it. We did have Alexandrium here in the past- which is toxic to humans, and was called a ‘red tide’. My bad if I misunderstood the red/rust/brown thing.

    1. No problem. I think there’s a lot of confusion in the media right now about the different types of algae, and I’d hate to add to that confusion. I’ll reword that paragraph to make it a little more clear. To my knowledge there have been small outbreaks of Alexandrium in Flanders Bay and Mattituck Inlet in recent years, but not in broader areas of the bay. (Thank god!)

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