Plum Island Underwater Survey Shows Abundance

Pictured Above: A northern star coral found during the survey (dead; live samples were also found)

Over five days last September, a team of divers and marine scientists conducted a first-of-its-kind marine survey of the underwater habitats around Plum Island. 

They spent the winter and spring poring over their field notes, photographs, samples, and data, and have now compiled their findings into a report titled “Initial Survey of Plum Island’s Marine Habitats.”

The study, supported by Save the Sound, New York Natural Heritage Program and New York State Department of Environmental Conservation and funded by an anonymous donor, reveals an abundance of animal and plant life in a wide range of habitat types.

“I have seen many parts of Long Island Sound over my long diving career, and I have never seen anything quite like it, particularly on the northern side of the island,” said Steve Resler of InnerSpace Scientific Diving, who helped conduct the survey. “Every centimeter of hard substrate was covered with plant and animal life, and some of the boulders were four meters across. It was extraordinary and thrilling for me.”

“Most people think of exotic tropical reefs when they think of coral, but we are lucky enough to have a species of shallow-water coral in Long Island Sound,” said Emily Runnells, a marine scientist for the New York Natural Heritage Program. “It’s great that we’ve discovered the northern star coral living around Plum Island, which is one of the few places in New York that has the shallow, rocky habitat it needs. This same kind of coral also lives in the tropics, so if we can learn the reasons for its adaptability to the range of temperatures it experiences in Long Island Sound, that knowledge may someday allow us to help struggling tropical coral reefs. More study needs to be done, and Plum Island’s waters could be a living laboratory for that work.”

The report describes communities of sponges, bryozoans, and tube worms covering the immense boulder fields, and near the surface, blue mussels. The researchers encountered gray seals, including one that nipped a diver’s swim fin. Plant communities consisted of various species of red and green algae, along with sugar kelp around most of the island.

“We thought that kelp may be growing in significant quantities around Plum Island—and we found it,” said Resler. “Here though, the kelp doesn’t stand in tall vertical columns like in the Pacific Northwest. Instead it sways almost horizontally due to the very strong tidal currents around the island.”

“Plum Island is part of an important coastal ecosystem, and we need to know what’s in the waters around the island in order to protect it,” explained Matt Schlesinger, chief zoologist with the New York Natural Heritage Program and principal investigator of the dive project. 

This pilot study lays the groundwork for a further in-depth study of Plum Island’s marine habitats and wildlife, currently planned for the summer of 2021.

The full dive report is online here.

Beth Young

Beth Young built her first boat out of driftwood tied together with phragmites behind her family’s apartment above the old Mill Creek Inn in Southold. Nowadays, she spends most of her time kayaking, learning about shellfish, writing newspaper stories, trying to sail a Sunfish, and watching the way the bay changes from day to day. You can send her a message at

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