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Tropical Plankton Invade Arctic Waters
http://www.earth.columbia.edu/articles/view/2993[font face=Serif][font size=5]Tropical Plankton Invade Arctic Waters[/font]
[font size=4]Researchers See Natural Cycle; But Questions Arise on Climate Change[/font]
2012-07-24
[font size=3]For the first time, scientists have identified tropical and subtropical species of marine protozoa living in the Arctic Ocean. Apparently, they traveled thousands of miles on Atlantic currents and ended up above Norway with an unusual—but naturally cyclic—pulse of warm water, not as a direct result of overall warming climate, say the researchers. On the other hand: arctic waters are warming rapidly, and such pulses are predicted to grow as global climate change causes shifts in long-distance currents. Thus, colleagues wonder if the exotic creatures offers a preview of climate-induced changes already overtaking the oceans and land, causing redistributions of species and shifts in ecology. The study, by a team from the United States, Norway and Russia, was just published in the British Journal of Micropalaeontology.
The creatures in question are radiolaria—microscopic one-celled plankton that envelop themselves in ornate glassy shells and graze on marine algae, bacteria and other tiny prey. Different species inhabit characteristic temperature ranges, and their shells coat much of the world’s ocean bottoms in a deep ooze going back millions of years; thus climate scientists routinely analyze layers of them to plot swings in ocean temperatures in the past. The new study looks at where radiolarians are living now.
In 2010, a ship operated by the Norwegian Polar Institute netted plankton samples northwest of the Norwegian archipelago of Svalbard, about midway between the European mainland and the North Pole. When the coauthors analyzed the samples, they were startled to find that of the 145 taxa they spotted, 98 had come from much farther south—some as far as the tropics. Furthermore, the southern radiolaria were in different sizes and apparently different stages of growth for each species, indicating they were reproducing, despite the harsh conditions. It was the first time since modern arctic oceanographic research began in the early 20th century that researchers had spotted a living population of such creatures in the northern ocean.
Coauthor O. Roger Anderson, a specialist in one-celled organisms at Columbia University’s Lamont-Doherty Earth Observatory, said, “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.” He said the invaders were apparently swept up in the warm Gulf Stream, which travels from the Caribbean into the north Atlantic, but usually peters out somewhere between Greenland and Europe. Oceanographers have previously shown that sometimes pulses of warm water penetrate along the Norwegian coast and into the arctic basin; such pulses have occurred in the 1920s, 1930s and 1950s. Further, the authors say that well-dated fossils of foraminifera—protozoans closely related to radiolaria—found on the arctic seafloor suggest that warm-water plankton may have temporarily established themselves at least several times before—around 4200 and 4100 BC, and again around 220, 370 and 1100 AD. “All the evidence is that this isn’t necessarily immediate evidence of global warming of the ocean,” said Anderson. Lead author Kjell Bjørklund, of the University of Oslo Natural History Museum said of the invaders, “This doesn’t happen continuously—but it happens.”
...[/font][/font]
[font size=4]Researchers See Natural Cycle; But Questions Arise on Climate Change[/font]
2012-07-24
[font size=3]For the first time, scientists have identified tropical and subtropical species of marine protozoa living in the Arctic Ocean. Apparently, they traveled thousands of miles on Atlantic currents and ended up above Norway with an unusual—but naturally cyclic—pulse of warm water, not as a direct result of overall warming climate, say the researchers. On the other hand: arctic waters are warming rapidly, and such pulses are predicted to grow as global climate change causes shifts in long-distance currents. Thus, colleagues wonder if the exotic creatures offers a preview of climate-induced changes already overtaking the oceans and land, causing redistributions of species and shifts in ecology. The study, by a team from the United States, Norway and Russia, was just published in the British Journal of Micropalaeontology.
The creatures in question are radiolaria—microscopic one-celled plankton that envelop themselves in ornate glassy shells and graze on marine algae, bacteria and other tiny prey. Different species inhabit characteristic temperature ranges, and their shells coat much of the world’s ocean bottoms in a deep ooze going back millions of years; thus climate scientists routinely analyze layers of them to plot swings in ocean temperatures in the past. The new study looks at where radiolarians are living now.
In 2010, a ship operated by the Norwegian Polar Institute netted plankton samples northwest of the Norwegian archipelago of Svalbard, about midway between the European mainland and the North Pole. When the coauthors analyzed the samples, they were startled to find that of the 145 taxa they spotted, 98 had come from much farther south—some as far as the tropics. Furthermore, the southern radiolaria were in different sizes and apparently different stages of growth for each species, indicating they were reproducing, despite the harsh conditions. It was the first time since modern arctic oceanographic research began in the early 20th century that researchers had spotted a living population of such creatures in the northern ocean.
Coauthor O. Roger Anderson, a specialist in one-celled organisms at Columbia University’s Lamont-Doherty Earth Observatory, said, “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.” He said the invaders were apparently swept up in the warm Gulf Stream, which travels from the Caribbean into the north Atlantic, but usually peters out somewhere between Greenland and Europe. Oceanographers have previously shown that sometimes pulses of warm water penetrate along the Norwegian coast and into the arctic basin; such pulses have occurred in the 1920s, 1930s and 1950s. Further, the authors say that well-dated fossils of foraminifera—protozoans closely related to radiolaria—found on the arctic seafloor suggest that warm-water plankton may have temporarily established themselves at least several times before—around 4200 and 4100 BC, and again around 220, 370 and 1100 AD. “All the evidence is that this isn’t necessarily immediate evidence of global warming of the ocean,” said Anderson. Lead author Kjell Bjørklund, of the University of Oslo Natural History Museum said of the invaders, “This doesn’t happen continuously—but it happens.”
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