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Old Carbon in Arctic Rivers Utilized by Microbes


The thawing permafrost of the Arctic is releasing old carbon to fluvial systems. But the ancient carbon in the river water was undetectable because of microbes. Researchers found that the old dissolved organic carbon (DOC) is highly biolabile. Microbes can selectively “eat” the old DOC in a very short time.

Climate change has induced permafrost thawing in high latitude regions. It was hypothesis that ancient carbon is released from active soil layer to the river systems associated with permafrost degradation. However, many studies found more young DOC from high-order fluvial systems (downstream, like river mouth) from Arctic rivers. Can these results indicate the old carbon of the permafrost is less vulnerable? The answer is no. A study from the headwaters of Kolyma river found that microbial communities can use millennial-aged carbon (Mann et al., 2015). Mann et al. used bioincubation and carbon isotope analyses methods and shown that thaw stream DOC was utilized by microorganisms during short-term (28 days).

More information: Fellman, J. B., et al. (2014), Dissolved organic carbon biolability decreases along with its modernization in fluvial networks in an ancient landscape. Ecology, 95: 2622–2632. DOI:10.1890/13-1360.1.

Mann, P. J., et al. (2015). Utilization of ancient permafrost carbon in headwaters of Arctic fluvial networks. Nat. Commun. 6:7856 DOI: 10.1038/ncomms8856.

Spencer, RGM., et al. (2015). Detecting the signature of permafrost thaw in Arctic rivers. Geophys. Res. Lett., 42, 2830–2835. DOI: 10.1002/2015GL063498.

Vonk, J. E., et al. (2013). High biolability of ancient permafrost carbon upon thaw, Geophys. Res. Lett., 40, 2689–2693, DOI:10.1002/grl.50348.

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categories: CARBON  tags: river carbon  carbon cycle  old carbon