ARCTIC CHANGES IMPACT GRAY WHALES AND OTHER SPECIES

ARCTIC CHANGES IMPACTING GRAY WHALES AND OTHER SPECIES.

SCIENCE NEWS

LOWEST SO FAR The smallest remnant of Arctic sea ice left after a summer of melting (since satellites started monitoring in the 1970s) was this tattered bit recorded September 16, 2012. The yellow line shows the second-lowest minimum, recorded in 2007 (2015 had the fourth-lowest minimum); the black line shows the median for the annual minimum for 1979 through 2000.

NOAA CLIMATE.GOV

Of perhaps more popular interest than transplanted diatoms are potentially Arctic-crossing whales. Gray whales persist in the Pacific but went extinct in the Atlantic more than two centuries ago.

In 2010, a marine-mammal monitoring program photographed a gray whale off the coast of Israel. “It was really a huge surprise to everybody,” says Elizabeth Alter of York College CUNY in Jamaica, N.Y., a coauthor with McKeon on the new paper. “There was discussion at first of whether the photos might have been photoshopped.” (They were not, it turned out.)

In 2013, a monitoring group sighted another gray whale along the coast of Namibia. It seems improbable that gray whales from the northern Pacific had looped down to the Southern Hemisphere to swim around continents and then into the Atlantic, Alter says. She suspects the whales were feeding along the Arctic coastline as they normally do, and without much ice to block their progress, inadvertently hugged the coast all the way to the Atlantic side.

Should gray whales eventually re­colonize the Atlantic, McKeon expects that their new neighbors would notice. Unlike similar whales with baleen plates in their mouths, grays gulp whale-sized mouthfuls of soft sea-bottom gunk to savor its hidden crustaceans. In the course of dining, the whales stir up sediment, scattering clouds of invertebrates that other species eat and leaving behind whale-gouges as habitat. It’s impossible to know the impacts, but McKeon speculates on what could happen to the blue crabs that bury themselves in the mud at the mouth of the Chesapeake Bay in winter: “I can’t imagine anything much better as a snack for a wintering gray whale than sleepy blue crabs.”

Melting may also bring new opportunities to another whale species, the bowheads, which live in the Arctic full time. “They can break ice that’s 2 feet thick with their heads,” Alter says. The Atlantic and Pacific bowhead populations have shared genes over the last several thousand years, Alter’s DNA studies show. And in 2010, biologists tracking both populations by satellite found a whale from each population feeding near each other. After about a week, the whales retreated in opposite directions, but left clear evidence that the melting Arctic permits populations from separate oceans to mix.

Also on McKeon’s list of possible vanguards of Arctic crossovers is a northern gannet, a plunge-diving, fish-eating seabird that soars over the Atlantic with a wingspan of about 2 meters. “What every gull dreams of being,” he says. In 2011, one of these gannets showed up off the coast of Alaska. Possibly the same bird reached the Farallon Islands along northern California. The most plausible explanation, McKeon says, is that the bird had worked its way through some avian northwest passage with open water for fishing along its flight path.

Open water in the Arctic could also move animals indirectly. As summer sea ice shrinks more and more, shipping could boom along Arctic routes. These ships take on ballast water in one place and release the ballast in another, letting animals (smaller than whales) catch a lift, says Jacqueline Grebmeier of the University of Maryland Center for Environmental Science. The prevailing wisdom has been that stowaways wouldn’t survive the harsh Arctic, but as the Arctic climate changes, Grebmeier can imagine circumstances now in which ballast creatures might. Whales and charismatic seabirds may be easier to spot when they switch oceans, but ballast stowaways may turn out to be more common. And as important.


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