7 September 2011 | Alan Bouquet
Biodiversity, Climate Change, Antarctica

 

The red king crab is the culprit

Global warming is affecting the Polar Regions disproportionately faster than elsewhere and as a result foreign species are severely altering the biodiversity of the region. The journal Proceedings B reports that a survey of the Palmer Deep basin on the Antarctic coast has been invaded by Neolithodes yaldwyni or King Crab.

It is likely that 1 or more influx of warm waters from South America was swept into the basin, bringing with it the crabs which are not native to the area. Crabs of different species have been known to venture as far south as the Antarctic Peninsula and surrounding islands but this is the first sighting of crabs near the continent itself. Scientists believe there are now around 1.5 million King crabs in the area.

The crabs can only survive in waters warmer than 1.4 degrees Celsius (which only exists at depth in the Antarctic due to an inverse thermocline), which means that they cannot move onto the continental shelf itself, which is cooler than the deeper basin area, but with current trends of warming it is likely that the shelf will exceed this temperature in the next few decades.

Whilst this story is rather remarkable, the adverse impact on the biodiversity of the region is staggering. Below 500m, where the water is warm enough for crabs, there is a bare ocean floor with little flora or fauna, whereas above this point and onto the shelf, there is a wide variety of local ocean life. An expansion of the crab’s extent could therefore lead to local extinctions. It has long been suspected that these crabs could drastically alter the ecology of the region, but this is the first evidence of it in action.

Whilst fishing in the region is not currently permitted, in future it might be necessary to harvest the crabs to keep their numbers down and preserve the Antarctic ecosystems.

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