June 11, 2012 — Increased rainfall in New England over recent years has sent a surge of sediment into the Gulf of Maine, producing a vast, cloudy film across much of the ocean that threatens the microscopic, single-celled plants that form the foundation of the marine food chain, according to a new study.
Researchers at Bigelow Laboratory for Ocean Sciences in Maine and the US Geological Survey found significant changes in the Gulf of Maine ecosystem, which they linked to record rains in the past seven years in Maine and the resulting greater volumes of water from local rivers.
About 4.5 feet of rain fell over those years on average, about a foot more than the average annual rainfall over the past century, and the scientists attributed the increase to climate change. More precipitation is predicted as one result of warming temperatures in New England.
In a study published this month in the Marine Ecology Progress Series, the scientists documented a five-fold decline in the growth rate of phytoplankton, the single-celled plants that support life throughout the region’s waters, including everything from lobster to cod.
“The Gulf of Maine has been the recipient of extraordinary amounts of runoff from land over the past few years,” said Barney Balch, a senior research scientist at Bigelow and lead author of the study. “While the reasons for this dramatic decrease in marine primary production are complex, the ramifications are not particularly complicated.”
The researchers said it could take years before the decline in phytoplankton affects the supply of commercial fish species, because the plants serve as food for larval fish.
They said increased amounts of river water flowing into the ocean appears to be blocking deep, North Atlantic water, which carries silicate and other nutrients essential for phytoplankton growth, from entering the Gulf of Maine. The additional fresh water has also led to an increase in the amount of detritus and organic matter in the water, reducing the amount of light available for phytoplankton photosynthesis and growth.
“You can’t drop the primary production of an ecosystem by a factor of five and not have an impact on other parts of the marine food web that depend on it,” Balch said.