Tropical Plankton Invade Arctic Waters

By Chelsea Whyte on July 26, 2012 2:30 AM EDT

plankton
Dictyocoryne truncatum, normally found near the equator, was one of nearly 100 species of protozoa found living in the arctic ocean in 2010. (Photo: Bjorklund et al., Jnl of Micro)

Tropical plankton usually found in warm climates have been observed living in the Arctic Ocean off the northwest coast of Svalbard. This is the first time tropical and subtropical species of marine protozoa have been found living so for north.

In 2010, a ship operated by the Norwegian Polar Institute collected plankton samples northwest of the Norwegian archipelago of Svalbard in the Arctic Ocean. Of the 145 types of organisms in these samples, 98 came from farther south, as far as the tropics, reports Mother Nature Network.

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Researchers said the microscopic organisms traveled thousands of miles on Atlantic currents and ended up above Norway with an unusual-but naturally cyclic-pulse of warm water. They said the warm water is not a direct result of overall warming climate, but with Arctic waters warming rapidly, pulses like this are predicted to grow, which could mean this migration is a preview of changes to come due to global warming.

"When we suddenly find tropical plankton in the arctic, the issue of global warming comes right up, and possible inferences about it can become very charged. So, it's important to examine critically the evidence to account for the observations," said study co-author O. Roger Anderson, a one-celled organism specialist from Columbia University's Lamont-Doherty Earth Observatory.

These creatures are called radiolaria-microscopic one-celled plankton that surround themselves in ornate glassy shells and graze on marine algae, bacteria and other tiny prey. Their shells coat much of the world's ocean bottoms in a deep ooze going back millions of years, a layer which is routinely analyzed by climate scientists to plot swings in ocean temperatures in the past. 

These tiny invaders were swept up in the warm Gulf Stream, which flows from the Carribean into the north Atlantic. It usually peters out somewhere between Greenland and Europe, but oceanographers have previously shown that occasional pulses of warm water move along the Norwegian coast.

The journey far outside their usual balmy habitat may be extraordinary, but the warm water jets that carried them north aren't. These pulses have happened periodically in the 1920s, 1930s and 1950s.

"This doesn't happen continuously - but it happens," said lead researcher Kjell Bjørklund, of the University of Oslo Natural History Museum, according to Live Science.

So what brought these critters north? Arnold Gordon, head of Lamont's division of ocean and climate physics, who was not involved in the research, suggests that warming climates could slow down the countercurrent that normally wards off the Gulf Stream in the north.

Gordon said Atlantic currents might also respond to changing wind patterns, or to the increasing fresh water now pouring into the northern ocean from melting sea ice and glaciers. Either of these phenomenon would draw more water north.

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