Washington,
Sep 8 - More than
a million king crabs, known for their crushing claws and ecosystem-altering
habits, have shown up in the warming waters of a deep basin in the Antarctic
continental shelf, a finding scientists say could be the first sign of an
ecological disaster.
ÒIt looks like a pretty negative consequence
of climate warming in the Antarctic,Ó said Craig Smith, a professor of
oceanography at the University
of Hawaii at Manoa, who
led the research into the crabs, estimated at 1.6 million, in the Palmer Deep.
This species of crab, Neolithodes yaldwyni, is
known to populate Antarctica's Ross Sea, which lies south of New Zealand. The Palmer Deep, a
pocket in the relatively shallow continental shelf, lies south of South America.
The discovery of a king crab population there
suggests that, after millennia of apparently being held at bay by the cold
water of the continental shelf, the dangerous predators can now cross it,
LiveScience reported.
The worry is that king crabs will threaten the
unusual, isolated animal life established on the seafloor of the shelf.
The research team saw evidence of this when
they deployed a remotely operated vehicle to survey the Palmer Deep. While they
found no evidence that the invasive species was living on the shallower, colder
shelf, they warned that it could take hold there within two decades.
In the Palmer Deep, they saw that the crabs
had disturbed sediment on the basin seafloor by digging for worms and other
creatures, an alteration that affects other animals' habitat.
The predatory crabs also
feed on other invertebrates, like sea lilies and basket stars. These and other
creatures were absent from depths below 3,117 feet (950 meters) where the crabs
were found, the researchers wrote in the journal Proceedings of the Royal Society
B.
The deeper
the water, the warmer it is, the result of warmer water coming in from the
north, Smith explained. The incoming water is saltier and denser, so it sinks
below the cooler waters.
It appears the crabs are limited by
temperatures approaching 34.5 F, though the team found crabs living in basin
waters colder than 34.5 degrees Fahrenheit (1.4 degrees Celsius) and there is
evidence that some members of this species can live at even colder
temperatures.
The Palmer Deep is located near the West Antarctic Peninsula, an area experiencing rapid
warming. Below 2,625 feet in the Palmer Deep, temperatures have been increasing
at a rate of about 0.01 degrees Celsius per year for almost 30 years.
Given the warming trend, these crabs could
move up onto the shelf within one to two decades, the researchers said.
The crab population in
the Palmer Deep Òis likely to serve as an important model for the potential
invasive impacts of crushing predators,Ó they added.
No comments:
Post a Comment