In this Sept. 13, 2017, file photo, a lobster fishing boat heads out to sea at sunrise off shore from Portland. Credit: Robert F. Bukaty / AP

Recent research shows that plankton growth rates in the Gulf of Maine are slowing down, posing challenges for the rest of the ecosystem.

Plankton — phytoplankton in particular — are at the foundation of the Gulf of Maine’s highly productive ecosystems, turning the sun’s energy into food consumed by other creatures higher up the food chain. For 23 years, scientists at East Boothbay’s Bigelow Laboratory for Ocean Sciences have been measuring plankton productivity across the Gulf.

“Over the 20 years that we’re describing,” said Barney Balch, a senior scientist at Bigelow, “the productivity of the Gulf of Maine has dropped to about a third of what it used to be in the late ‘90s.”

Balch said changes in the circulation of ocean currents are bringing warmer, saltier water into the Gulf of Maine and suppressing overall plankton growth.

“When you start warming the water mass, lots of things can start changing,” he said, “like the chemistry can change, the ocean acidification properties can change and the nutrients have been changing, which are critical for the growth of these phytoplankton. So it’s a complex picture, but we’ve always known that the Gulf is a complicated place.”

Balch said that there has been improvement in plankton productivity since a big drop in the early 2000s, when extreme rain sent colored material into the water, filtering sunlight available for photosynthesis.

This article appears through a media partnership with Maine Public.