King Crab and the Palmer Deep

King Crab (Neolithodes yaldwyni)

While scouring the internet in search of some interesting invasive species to showcase, I came across an article published in the biological research journal ‘Proceedings B’ (The Royal Society)  regarding the recent discovery of a species of deep-sea King Crab (Neolithodes yaldwyni) in Palmer Deep, a basin cut into the Antarctic continental shelf.  

King Crab
(Neolithodes yaldwyni)

The population of crabs are estimated to be up to 1.5 million, at a population density of 10 600 km², living at the depth of 850m. What is remarkable about this discovery is that these Lithodid crabs are thought to have been excluded from the arctic continental shelf waters for more than 14 million years due to their intolerance of water colder than 1.4C.  The crabs are thought to have crossed the Antarctic shelf to reach Palmer Deep.

With the warming of the oceans, it had been hypothesised that the fragile Antarctic ecosystem was at risk from future lithodid invasion. Nevertheless, this discovery has come as a surprise and indicated that the waters of the west Antarctic Peninsula are warming faster than previously thought. Indeed, the warming of the Antarctic waters has allowed these predators to establish themselves in this challenging environment (National Geographic).

While currently confined to dwelling at a depth of 850m, it is estimated that the peninsula shelf waters are warming at approximately 0.01°C yr⁻¹. The project leader of the team which discovered the crab colony, Professor Craig Smith of the University of Hawaii, told the BBC that that the species could spread up onto the shelf itself, to shallower depths, within the next decade or two.

Should the crabs spread to shallower waters, their impact on the ecosystem would be devastating. Not only do many of the native species – from brittle stars, urchins to sea lilies – not have resistance to the predatory crabs after 14 million years of isolation, but the crab has been termed an “ecosystem engineer” digging deep into soft sediments, preying on seafloor animals and altering basic habitat structure at the ocean bottom. Immediately above the 850m crab dwelling zone, the researchers found very few of the creatures they would have expected to have been in abundance at 50-100m depth. 

Perhaps this is a only a taste of what is to come?