Plankton-sampling nets used to detect tropical and subtropical species in northern waters. (Photo: Beth Stauffer/Lamont-Doherty Earth Observatory)
Tropical microorganisms found in Arctic Ocean
Wednesday, July 25, 2012, 23:30 (GMT + 9)
Scientists have identified tropical and subtropical species of marine protozoa in the Arctic Ocean for the first time. These protozoa seem to have made their way from the tropics on the Gulf Stream current and ended up above Norway with a naturally cyclic, as opposed to climate change-caused, pulse of warm water.
As arctic waters continue to warm quickly, such pulses are predicted to increase as global climate change brings shifts in long-distance currents. Researchers thus wonder if the tropical protozoa offer a preview of climate-induced changes already taking over the oceans and land and pushing redistributions of species and shifts in ecology.
The study, conducted by a team from the US, Norway and Russia, was published in the British Journal of Micropalaeontology.
The protozoa are radiolaria -- microscopic one-celled plankton that wrap themselves in ornate glassy shells and feed on marine algae, bacteria and other tiny organisms, ScienceDaily reports.
In 2010, a vessel operated by the Norwegian Polar Institute caught plankton samples northwest of the Norwegian archipelago of Svalbard, halfway between the European mainland and the North Pole. Of the 145 taxa they spotted, researchers saw that 98 had come from as far as the tropics.
Further, the southern radiolaria were in different sizes and stages of growth, indicating they were reproducing despite the hostile environment. It was the first time since the early 20th century that researchers had spotted a living population of such creatures in the northern part of the globe.
Oceanographers showed that such pulses have occurred in the 1920s, 1930s and 1950s. Also, the authors say that fossils of protozoans foraminifera found on the arctic seafloor suggest that warm-water plankton may have temporarily established themselves many times before.
"This doesn't happen continuously -- but it happens," lead author Kjell Bjørklund, of the University of Oslo Natural History Museum said.
At the same time, oceanographers admit that such pulses seem to be increasing and growing, which is to be expected from global warming, said Rainer Froese, an oceanographer at the Helmholtz Centre for Ocean Research.
Changes in global ocean ecology and warming waters are already being detected in many places.
A 2011 global study found that many marine species are into deeper, cooler waters in response to warming along the US east coast, the Bering Sea and off Australia, among other places.
In the arctic, earlier and faster melting of sea ice in the summer may be shifting plankton species assemblages toward smaller types, which could ultimately damage the food web that sustains creatures including seals and whales, said Jody Deming, a biologist at the University of Washington who studies arctic microbes.
Bjørklund said his team is anxious to receive new samples of the southerly radiolarian and discover whether they adapt or perish.
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By Natalia Real