The algae cochlodinium has been spotted in Sengekontacket Pond, Vineyard marine biologists confirmed.

Cochlodinium is harmful to shellfish but not humans and shellfish biologists have been monitoring it closely since it was first detected last month in Cape Pogue Pond. Rick Karney, director of the Martha’s Vineyard Shellfish Group, confirmed the spotting this week in Major’s Cove in Sengekontacket. He said Paul Bagnall, shellfish constable for Edgartown, brought a water sample to the shellfish hatchery late last month. By testing the water and putting the sample under a microscope, Mr. Karney was able to identify it as cochlodinium. “It is quite distinctive under the scope,” Mr. Karney said. Subsequent aerial photographs of Sengekontacket showed that the algae bloom had spread into the Oak Bluffs side of the pond.

Cochlodinium has been seen in recent weeks on Nantucket as well.

“I am hearing it is all around here and up and down the East Coast,” Mr. Karney said.