Phytoplankton productivity down in Gulf of Maine

The Gulf of Maine is growing warmer and saltier, and those changes have led to a substantial decrease in the productivity of phytoplankton that are the center of the marine food web. Specifically, phytoplankton in the gulf are now about 65 percent less productive than they were two decades ago, scientists from Bigelow Laboratory for Ocean Sciences reported in research published on June 7, 2022.

The Gulf of Maine helps fuel New England’s marine ecosystems and maritime economy. Like plants on land, phytoplankton absorb carbon dioxide from the atmosphere and use sunlight to grow via photosynthesis; they then become food for other organisms. Disruptions to the productivity of these microscopic organisms can lead to adverse effects on the region’s fisheries and the communities that depend on them.

Research published in 2021 showed that the Gulf of Maine has been warming faster than most ocean basins. In the new effort from Bigelow, funded in part by NASA, scientists showed how that warming has affected the phytoplankton.

The natural-color image above shows the northwest Atlantic Ocean blooming with phytoplankton on June 5, 2022, as observed by the Moderate Resolution Imaging Spectroradiometer on NASA’s Aqua satellite.

“Phytoplankton are at the base of the marine food web on which all of life in the ocean depends, so it’s incredibly significant that its productivity has decreased,” said William Balch, a Bigelow Laboratory scientist who co-led the study. “A drop of 65 percent will undoubtedly have an effect on the carbon flowing through the marine food web, through phytoplankton-eating zooplankton, and up to fish and apex predators.”

The findings are the result of an analysis of the Gulf of Maine North Atlantic Time Series (GNATS), a 23-year sampling program that has measured the temperature, salinity, and other chemical, biological, and optical properties of the gulf. Balch says the changes that they are recording show an intricate connection between the gulf and the greater Atlantic Ocean.

NASA Earth Observatory, 5 June 2022. Press release.

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