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Shell crushing crabs threaten ecosystem

Posted by: Saving Water SA (Cape Town, South Africa) – partnered with Water Rhapsody conservation systems – 09 February 2011

Warming waters along the Antarctic peninsula have opened the door to shell-crushing king crabs that threaten a unique ecosystem on the seafloor, according to new research by a U.S.-Sweden team of marine researchers.

Crabs haven't lived in coastal Antarctic waters for the past 40 million years.

On a two-month voyage of the Swedish icebreaker Oden and U.S. research vessel Nathaniel B. Palmer, marine biologists collected digital images of hundreds of crabs moving closer to the shallow coastal waters that have been protected from predators with pincers for more than 40 million years. They are the same kind of deep-water crabs with big red claws that you might find at the seafood counter.

“Along the western Antarctica peninsula we have found large populations over like 30 miles of transects. It was quite impressive,” said Sven Thatje, an evolutionary biologist at the University of Southampton in England and chief scientist on the cruise.

Finding crabs on the bottom of the ocean isn’t that big a deal. But here in Antarctica, crabs haven’t lived in coastal waters for the past 40 million years. Until now, it’s been too cold.

Bottom-dwelling creatures like mussels, brittle stars and sea urchins have not developed any defenses. They have thinner shells, for example. For the same reason, filter feeders, like clams and worms, burrow underground in most regions. The lack of predators has led to a thick canopy of sorts, much like a submarine jungle comprised of flowery feather stars, tube worms and squirming sea spiders.

During an interview on board the Oden just after it docked at the main U.S. base in Antarctica, Thatje described how the crabs are moving closer to an ecosystem with no defenses.

“The Antarctic shelf communities are quite unique,” Thatje said. “This is the result of tens of millions of years of evolution in isolation.” Continue reading Shell crushing crabs threaten ecosystem