Neolithodes yaldwyni may alter the local ecosystem in Antarctica. (Photo: NIWA Peter Marriott/NOAA)
King crabs threaten Antarctic ecosystem: study
Thursday, September 08, 2011, 15:20 (GMT + 9)
Scientists have found a great reproductive population of king crabs (Neolithodes yaldwyni) on the edge of Antarctica. They are attributing the crustaceans’ march south to rapidly warming waters and warn that the crabs may overwhelmingly alter the local ecosystem.
Published in the journal Proceedings B, the scientists’ findings point to a population of these king crabs and related species around islands off the Antarctic Peninsula and on the outer edge of the continental shelf.
"Our best guess is there was an event, or maybe more than one, where warmer water flushed up across the shelf and carried some of the larvae into the basin," said project leader Craig Smith from the University of Hawaii, BBC reports.
Because these giant skeleton-crushing crabs are at the top of the food chain, scientists expect that if and when they spread further, they will have a powerful effect on the ecosystem.
"They can crush clams and other kinds of animals with hard shells so they are very voracious predators," Smith stated, ABC reports.
The crabs were discovered via the Genesis, a submersible remotely operated vehicle (ROV) from the University of Ghent in Belgium that was sent into the Palmer Deep in March 2010.
The scientists estimate there may be 1.5 million crabs in the basin. A female crab they retrieved was carrying mature eggs and larvae.
Researchers believe the species cannot survive in waters below 1.4C. Where they were found, the seas get warmer with depth, and the crabs were all found below 850m.
The scientists speculate they probably ventured there only 30-40 years ago, as before that the water would have been too cold.
"If you look at the rate at which the seas are warming, (the continental shelf) should be above 1.4C within a couple of decades, so the crabs are likely then to come into shallower waters," Smith noted.
The upper limit of where the crabs were found, 850m, marks the line between copious seabed life above and depleted life below.
Above, the scientists found a high abundance and diversity of plants and animals, including brittlestars, sea lilies and sea cucumbers -- all known prey of king crabs -- according to Smith.
"We found none of them in the crab zone itself, and when we went 50-100m above we found very few - so we think the crabs are venturing up into shallow waters to feed. We would expect (local) extinctions in some of these organisms," he stressed.
Smith said the crabs are not only lowering biodiversity but also altering the geochemistry of the sediment as they eat the animals in it -- and they work quickly.
By Natalia Real