for National Geographic News
After a thousand years, blue musselshelped along by warmer water temperatureshave returned to high-Arctic seas.
Their comeback could have serious implications for Arctic ecosystems and may be a sign of climate change, according to scientists.
"We are heading into uncharted waters in terms of future climate, and indicators, such as these mussels, are telling us clearly that we had better pay attention, because entire ecosystems are going to be disrupted," said Raymond Bradley, a climatologist at the University of Massachusetts in Amherst.
Since the mollusks require relatively warm temperatures to thrive, many scientists consider blue mussels to be reliable indicators of global warming.
Some scientists, though, think the creatures can survive in cold waters too.
Over the past 120,000 years the global climate system has oscillated from warm to cold and back again.
During one such warm spellbetween about 10,700 and 7,700 years agosummer temperatures on the surface of Arctic seas reached almost 46ºF (8ºC).
Fossil records show that during the subsequent cooling period, the blue mussel population around the Norwegian island chain of Svalbard gradually dwindled.
About a thousand years ago it disappeared completely.
Then in August 2004 the blue mussels reappeared in Svalbard, according to findings published in the November 21 issue of the journal Marine Ecology Progress Series.
Based on the size of the newly discovered mussels and the absence of larvae, researchers concluded that the mollusks were at least a year old and therefore had survived at least one Arctic winter.
SOURCES AND RELATED WEB SITES