In hot water

Rising ocean temperatures threaten lobster larvae
Photo by Jesica Waller

Lobster larvae are more responsive to a 2–3 degree increase in temperature than they are to the near doubling of the carbon dioxide projected for the Gulf of Maine by the end of the century. That temperature rise could mean trouble for lobsters and the lobster industry, according to research conducted at the University of Maine Darling Marine Center and Bigelow Laboratory for Ocean Sciences.

The research is the only published study focused on how larvae of the American lobster will be affected by two aspects of climate change — ocean acidification and warming.

The study found acidification had almost no effect on survival of young lobsters, but did cause changes in larval size and behavior. But lobster larvae reared in water 3 degrees Celsius higher in temperature, which is predicted by 2100 in the Gulf of Maine, struggled to survive compared to lobster larvae in water that matched current gulf temperatures.

“With lobsters now comprising over 80 percent of the state’s overall fishery value, Maine’s coastal economy is perilously dependent on this single fishery.” Rick Wahle

“They developed twice as fast as they did in the current temperature of 16 C (61 F), and they had noticeably lower survival,” says Jesica Waller, a graduate student at the DMC and lead author of the study published in the ICES Journal of Marine Science. “Really only a handful made it to the last larval stage. We saw more dead larvae in the tank,” she says. “We recognized this could be really important to Maine and may help us understand the future of the lobster industry.

These short-term experiments, though, don’t account for the possibility that lobster populations may adapt to changing conditions over generations.

“We need to do much more research to understand that,” she says. Waller’s co-adviser and co-author of the paper, UMaine research professor Rick Wahle, says last year Maine harvested nearly half a billion dollars in lobsters. “It’s critical to know how climate change will affect the future of our most important fishery,” he says.

At the Bigelow Laboratory for Ocean Sciences in nearby East Boothbay Harbor, UMaine graduate student researcher Jesica Waller raised more than 3,000 lobster larvae. She took measurements daily for a month, assessing their survival rate, development time, length, weight, respiration rate, feeding rate and swimming speed.

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