Scientists Are 'Troubled' By A New Lowered-Oxygen Zone In Coastal Mass. Waters

The Massachusetts Water Resources Authority is reporting an area of lowered oxygen saturation near the ocean floor about 10–15 miles outside Stellwagen Bank National Marine Sanctuary. The MWRA reports "no adverse impact to marine life."

The MWRA detected the low-oxygen zone during routine a water monitoring survey on Sept. 8, and reported it to the Environmental Protection Agency (EPA) in a letter on Sept. 24.

The MWRA monitors this area of ocean to ensure that discharge from the Deer Island Wastewater Treatment Plant doesn't overstimulate algae growth, which can deplete ocean oxygen. However, because the low-oxygen zone was detected nearly 11 miles away from the end of the discharge pipe, the MWRA said in the letter that there is "no evidence" that the drop in oxygen was influenced by the facility.

This zone does not seem to be related to — or as serious as — the low-oxygen "blobs" that have appeared in Cape Cod Bay in recent years, killing lobsters and fish. But its appearance is "troubling," and is is probably related to climate change, said Matthew Liebman, an environmental biologist with EPA New England.

"This is first time this has happened in over 20 years," Liebman said. "The Gulf of Maine is warming a lot this year and that the decline in [dissolved oxygen] over time at the site looks like it's outside the bounds of all the data collected over the last 20-plus years."

The oxygen saturation level at the Stellwagen Basin location was 66.3%  -- "pretty low," according to Liebman. Any level below 75% triggers a warning.

"It just really scares me because this hasn't happened in New England before," said Glen Gawarkiewicz, an oceanographer at the Woods Hole Oceanographic Institution. "It's just like, holy moly! Is this the start of a whole string of these things?"

Gawarkiewicz said researchers aren't yet sure what's been causing the spate of lower-oxygen zones in recent years. But he points out that rapid ocean warming and extreme rainfall have changed the density of various layers of the ocean, making them more stratified. This can deter oxygen-rich layers from mixing with oxygen-poor ones.

"It's going to take dedicated studies and probably networks of oxygen sensors to figure this out," says Gawarkiewicz. "We're not treating the base of the food chain very well. And it's going to come back and bite us."