Beavers Are Changing the Microbes of Arctic Ponds and Streams

The North American beaver has moved onto the tundra of Alaska in recent decades, helped by more favorable habitat and a population rebound after centuries of overtrapping. Beavers build ponds, and ponds change how water flows, how carbon and nutrients cycle and how fast permafrost thaws. A 2023 study asked a question no one had answered: what do beaver ponds do to the Arctic's microscopic life?

A beaver pond in Alaska.

The comparison

Researchers sampled sediments from beaver ponds along tundra streams in northwestern Alaska and compared them with tundra lakes and streams in north-central Alaska that beavers have not reached. They examined bacteria, archaea and fungi, and measured an enzyme (β-glucosidase) that indicates how readily cellulose is broken down.

What was different

Beaver ponds had fewer of the archaea groups Crenarchaeota and Euryarchaeota and fewer typically anaerobic bacteria, suggesting differences in how fast organic matter is broken down by fermentation and in methane production. They also had fewer Chytridiomycota fungi and more Basidiomycota fungi that live in partnership with plants.

Why it matters

Beavers were already known to change the chemistry of Arctic streams, and those changes are likely tied to the microbes living in pond sediments. This study gives the first look at the microbiology of far-northern beaver ponds — a new setting in a rapidly changing Arctic.

Sources

Based on "How beavers are changing Arctic pond and stream microbiology" from the National Park Service, a work of the United States government in the public domain, summarizing Shannon, K. C., N. R. Christman, B. C. Crump, M. P. Carey, J. Koch, L. L. Lapham, J. A. O'Donnell, B. A. Poulin, K. D. Tape, J. A. Clark and F. S. Colwell (2023), a comparison of sediment microbial communities in Arctic beaver ponds and tundra lakes and streams.