Huge crabs more than a metre across have invaded the Antarctic abyss, wiped out the local wildlife and now threaten to ruin ecosystems that have evolved over 14 million years.
Three years ago, researchers predicted that as the deep waters of the Southern Ocean warmed, king crabs would invade Antarctica within 100 years.
But video taken by a remotely operated submersible shows that more than a million Neolithodes yaldwyni have already colonised Palmer Deep, a basin that forms a hollow in the Antarctic Peninsula continental shelf.
They are laying waste to the landscape.
Video footage taken by the submersible shows how the crabs prod, probe, gash and puncture delicate sediments with the tips of their long legs.
"This is likely to alter sediment processes, such as the rate at which organic matter is buried, which will affect the diversity of animal communities living in the sediments," says Craig Smith of the University of Hawaii at Manoa, whose team discovered the scarlet invaders.
The crabs come from further north and moved in as Antarctic waters have warmed, probably swept into Palmer Deep as larvae in warm ocean currents. They now occupy the deepest regions of Palmer Deep, between 1400 and 950 metres.
In 1982, the minimum temperature there was 1.2 °C – too cold for king crabs – but by last year it had risen to a balmier 1.47 °C.