While a 2-degree increase in the temperature of waters near Antarctica will not make much of a difference for humans, it may cause the extinction of native fish species.
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A research group led by Thomas Near, Yale associate professor of ecology and evolutionary biology, outlined the evolutionary history of Antarctic fish, which developed antifreeze proteins tens of millions of years ago to survive in subzero polar conditions. The study, published online Feb. 13 in the journal Proceedings of the National Academy of Sciences, warned that these fish may be threatened by the rise of water temperatures in the region. Environmental experts said that polar ecosystems are very vulnerable to even slight temperature changes.
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“The development of polar climatic conditions that shaped the [evolution] of Antarctic fish is now reversing,” Near said. “The increasing temperature of the Southern Ocean, with the potential for the arrival of invasive species and disruption of food webs, is the greatest threat to the survival of this unparalleled [diversity].”
Tens of millions of years ago, rapid cooling in the Antarctic led to the mass extinction of fish acclimated to warmer temperatures, with the surviving fish developing antifreeze proteins. The study shows that new species arose as the fish adapted to fill the ecological gaps left by the extinction. This process eventually gave rise to the 100 species of fish now living in Antarctic waters, which all possess the ability to withstand cold temperatures.
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But Near said that these polar adaptations have rendered Antarctic fish unusually sensitive to warmer water temperatures, making climate change a dire threat to Antarctica’s fish populations. A decline in the fish population would cripple the rest of the ecosystem by removing a major food source for penguins and seals, he added.
Sarah Gille ’88, a professor at the Scripps Institution of Oceanography, said that even small temperature changes in certain regions near Antarctica could allow the influx of invasive species more adapted to warmer water. She added that Antarctic waters were by no means the only ecosystem threatened by climate change.
“Species and ecosystems evolve over tens of millions of years in response to changing environmental conditions,” Gille said. “The concern about modern climate change is that it might happen faster than ecosystem response times, and the result could lead to a catastrophic decrease in biodiversity.”
David Barnes, a scientist in the British Antarctic Survey, said the study was important because it explained how fish adapted to living in hostile environments.
He added that while climate change represents a major threat to fish and other fauna native to Antarctica, the exact mechanism endangering them is still unknown, since patterns of marine warming and other effects of climate change are so complex.
He said that it is likely that in the long run climate change will create new ecological balances and ecosystems in unpredictable ways, as the mass extinction of Antarctic fish before the development of the antifreeze protein did millions of years ago.
The study was funded by grants from the National Science Foundation.