March 9, 2013

Changing ecosystem concerns fishermen

They're not alone: As Gulf of Maine waters become warmer and more acidic, scientists too worry about the implications for the region's fisheries.

By North Cairn
Staff Writer

Humans are dumping so much carbon dioxide into the oceans so fast that seawater -- even in the Gulf of Maine -- is getting warmer and more acidic, according to marine and climate researchers.

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Jeff Runge, professor of oceanography in the School of Marine Sciences at the University of Maine and a researcher at the Gulf of Maine Research Institute, examines plankton samples to test acidity in the ocean. “It’s starting to be recognized as a serious issue. But it’s very complex,” he said.

Gabe Souza/Staff Photographer

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Scientists aren't sure yet how the trend, which is believed to be tied to human-induced climate change, will affect ocean life in the gulf. But there is rising concern -- especially among fishermen -- that changes in the ocean ecosystem could severely damage some of the fisheries that are the backbone of the region's seafood industry.

The effects of warming and acidification are showing up all over the world, including in and along the gulf.

"We've seen levels of acid that rival some of the highest levels recorded anywhere," said professor of marine science Mark Green, whose work at St. Joseph's College in Standish has focused exclusively on ocean acidification. "Many coastal areas are increasing three times faster than open ocean."

Lobsters are up, cod down. The herring caught in the gulf are much smaller than they were 20 years ago, marine scientists have observed. Northern right whales might leave altogether if populations of plankton are reduced enough to affect the whales' food supply.

Ocean acidification is a long, slow process in which seas absorb excessive amounts of carbon dioxide, enough to alter pH levels (the percentage of hydrogen, which is a measure of acidity and alkalinity).

Global surface waters have an average pH of 8.1, according to the National Oceanic and Atmospheric Administration. But scientists believe that level could drop in the next 50 years to as low as 7.8, a huge change.

The impacts of increased carbon dioxide go far beyond making the water warmer and more acidic. Many species are weakened by the loss of oxygen and the spread of infectious diseases can speed up when water temperatures rise. Higher carbon dioxide levels in the ocean lead to an increase in carbonic acid, which reduces the availability of structural materials that mollusks and crustaceans need to form their shells.

The ranges of many species of sea life have been changed. Green crabs, for example, have moved in on shellfish beds in Maine from the more southerly waters they have traditionally inhabited.

"That's the really compelling story -- that there will be winners and losers," said Rick Wahle, research associate professor in the School of Marine Sciences at the University of Maine.

Absorption of carbon dioxide from the atmosphere into the ocean waters has increased to about 100 times what it was 600 years ago, Green said. On average, ocean carbon dioxide levels are up 30 percent, most of it absorbed in the past 50 years. Exacerbating the problem is runoff from rivers polluted by fertilizer and soil erosion, and millions of tons of untreated sewage pumped into coastal waters, including Casco Bay.

Debate swirls about which stressors are to blame for which consequences, but one fact is undeniable: Ocean temperatures are rising and the water is becoming more acidic. The increased carbon dioxide in air and water comes largely from the burning of fossil fuels and emissions from factories, cars and power plants, most scientists say.


Some of the early evidence has been revealed by testing of pH levels in costal seawater and the monitoring of water and air temperatures over the past 15 years or so.

"I consider it to be an issue that merits better understanding," said Jeff Runge, professor of oceanography in the School of Marine Sciences at the University of Maine and a researcher at the Gulf of Maine Research Institute in Portland.

"It's starting to be recognized as a serious issue," he said. "But it's very complex. We're just not doing a very good job yet in understanding the biological and ecosystem effects in the Gulf of Maine."

(Continued on page 2)

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