From: Rebecca Kessler, Yale 360
Published November 26, 2013 09:08 AM

Climate change signals a whale of a shift in feeding patterns

Every summer and fall, endangered North Atlantic right whales congregate in the Bay of Fundy between Nova Scotia and New Brunswick to gorge on zooplankton. Researchers have documented the annual feast since 1980, and well over 100 whales typically attend, a significant portion of the entire species. Only this year, they didn't. Just a dozen right whales trickled in—a record low in the New England Aquarium's 34-year-old monitoring program. And that comes on the heels of two other low-turnout years, 2010 and 2012.

 

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Numbers of the critically endangered marine mammal have been ticking up in recent years just past 500 individuals, so no one thinks the low turnout in the Bay of Fundy augurs a decline in the species as a whole. The right whales must have gone elsewhere. But where? And more importantly, why?

"Our whales have been missing in their normal habitat areas, where we’ve learned to expect them over three and a half decades," says Moira Brown, a senior scientist at the aquarium who runs the monitoring program. "It's quite shocking when you go out there day after day after day and you don’t see any right whales."

This change in North Atlantic right whale behavior is occurring against a backdrop of major climate-related ecosystem shifts taking place throughout the northwest Atlantic Ocean. While Brown and other right whale researchers are not ready to attribute changes in the species' feeding or migratory patterns to any one factor, including global warming, what is clear to them is that the right whales' new itinerary must signal a shifting food supply. A zooplankton species called Calanus finmarchicus is the whales’ mainstay. Researchers reported an unusual scarcity of the zooplankton in the Bay of Fundy this summer. By the same token, in Cape Cod Bay, where right whales have been unusually plentiful, other scientists have been documenting increasing concentrations — so much so that the normally invisible creatures noticeably color the water.

Other ecosystem shifts are afoot in the northwest Atlantic off the eastern coasts of the United States and Canada. Sea surface temperatures in waters such as the Gulf of Maine are rising and various marine species, including cod and red hake, are shifting their ranges northward, according to recent studies. Increasing precipitation, the rapid disappearance of Arctic sea ice, and the melting of ice sheets in Greenland and Canada are all expected to pour more freshwater into the northwest Atlantic, causing increased stratification of ocean waters and changes in the abundance and distribution of phytoplankton and zooplankton at the bottom of the food chain, studies show.

Read more at Yale Environment 360.

Whale image via Shutterstock.

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