Arctic rivers as climate change forecasters

TEXAS A&M (US)—Scientists may be able to gauge the effects of climate change in the polar regions by monitoring bacterial communities in six large Arctic rivers, new research shows.

A study led by Rainer Amon, marine science professor at Texas A&M University, and Byron Crump, a researcher at the University of Maryland Center for Environmental Science, found that bacterial communities in the six rivers shifted synchronously over time, correlating with seasonal shifts in hydrology and biogeochemistry.

“Our results demonstrate that synchrony, seasonality, and annual reassembly in planktonic bacterial communities occur on global scales,” says Crump. The researchers reported their findings in the Proceedings of the National Academy of Sciences Early Edition.

“Since bacterial communities in big arctic rivers shift predictably with circumpolar seasonal changes in environmental conditions, they may serve as sensitive indicators of climate change in the Arctic.”

The study documents patterns through a three-year, circumpolar study of planktonic bacterial communities in the six largest rivers of the pan-Arctic watershed: the Ob’, Yenisey, Lena, Kolyma, Yukon, and Mackenzie Rivers.

“These six river systems we studied are comparable in size to the Mississippi River in the United States,” says Amon.

“One of the things we learned is the bacteria communities in all six of them seem to be very similar. There are many questions still to be answered, such as how these bacteria communities might respond to a continued increase in temperature. Many parts of these river systems are warming up faster than any other region on the planet.

“What can we expect if this area continues to go through such warming phases? What are the long-term consequences? Could these communities ultimately affect atmospheric conditions?

“This research may allow us to look into the future and see how these communities might respond to such changes. There has been very little research done previously on these river systems, so our work has contributed to the body of knowledge on this area. It gives us a better understanding of what is taking place in these bacteria communities and how we can proceed from there.”

The researchers say the synchrony indicates that hemisphere-scale variation in seasonal climate sets the pace of variation in microbial diversity. Moreover, these seasonal communities reassembled each year in all six rivers, suggesting a long-term, predictable succession in the composition of big river bacterial communities.

Divergence from this synchronous pattern may provide an early signal of climate change in some regions of the Arctic, and may result in changes to river microbial communities and the biogeochemical transformations they carry out.

Data was collected through the Partners program, a collaboration among scientists from the United States, Canada, and Russia examining the largest rivers of the pan-arctic watershed.

By including five of the world’s 25 largest rivers in the study, the results provide a unique perspective on global-scale patterns in bacterial diversity.

The work was supported by the the National Science Foundation.

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