At its peak, the algae bloom extended from Penobscot Bay to Martha's Vineyard.
Lobster fishermen work at sunrise on Sept. 8, 2022, off Kennebunkport. Credit: Robert F. Bukaty / AP

An unusually large algae bloom in the Gulf of Maine has researchers trying to understand its cause and possible effects.

At its peak, the algae bloom extended from Penobscot Bay to Martha’s Vineyard. The bloom is comprised of a naturally occurring phytoplankton that is not toxic to humans or animals.

University of New Hampshire scientists first noticed the bloom in April when they recorded the lowest carbon dioxide and highest pH levels in their 20 years of monitoring.

Nicole Poulton of the Bigelow Laboratory for Ocean Sciences said it’s hard to know what’s causing it, but the rapidly warming waters of the Gulf of Maine could be playing a role.

“We do know that the gulf is changing quite rapidly. And it could be a variety of things,” Poulton said. “Both the increasing temperatures in the Gulf of Maine, as well as increased rainfall into the gulf as well.”

Poulton said a dozen research groups from Maine to Rhode Island are collaborating to understand the event. One concern is the possibility that the algae will deplete oxygen in parts of the gulf when it dies and decomposes.

This article appears through a media partnership with Maine Public.