To solve the puzzle of the mussels' comeback, scientists at the University Centre at Svalbard looked at seasonal changes in ocean temperature and North Atlantic currents.
Using temperature data, biological samples, and knowledge of the life spans of blue mussel larvae, biologist Philos Jørgen Berge and his colleagues came up with a theory.
Warm water surging in from the North Atlantic created favorable conditions for the mussels, the researchers determined. Mussels had spawned in the North Atlantic, and their larvae rode the unusually warm currents that brought them to Svalbard.
"The establishment of these mussels was made possible only through a simultaneous occurrence of a set of independent environmental factors such as increased northward mass-transport [of warm Atlantic water], favorable local wind conditions, and a generally high sea-surface temperature in the North Atlantic," Berge said.
Computer simulations by Berge and his colleagues appeared to back up their theory.
Berge thinks that ocean currents could be the mussels' only mode of transportation into Svalbard.
The population, he says, is too large to have ridden in on floating debris. And the mussels couldn't have been carried in ships' ballast waterSvalbard is too far away from the nearest ports, Berge says.
The return of blue mussels to Svalbard could be just the beginning of a wholesale transformation of the high Arctic.
"Species composition in the area will change," Berge wrote in Marine Ecology Progress Series.
If temperatures continue to increase around Svalbard, he explained, larvae brought in by currents from warmer habitats will establish themselves in the region.
"The implications are significant," agreed James Carlton, a marine science professor at Williams College in Williamstown, Massachusetts.
"The appearance of blue mussels and the periwinkle snaila species not cited by the [study] authorsis probably the tip of the iceberg," Carlton said.
"Depending on the species, we could easily see the beginning of the reshaping of shallow-water Arctic marine ecosystems within our lifetimes."
According to Bradley, the University of Massachusetts climatologist, "All of these changes simply reinforce the conclusions that large climate changes are taking place at an unprecedented rate, leading to conditions not seen for thousands of years."
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