Organic matter from Arctic sea-ice loss alters bacterial community structure and function

• Published in: Nature Climate Change
• Main Authors: Underwood, G. J. C., Michel, C., Meisterhans, G., Niemi, A., Belzile, C., Witt, Matthias, Dumbrell, A. J., Koch, Boris P.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Nature 2019
• Subjects: Arctic; Arctic Ocean; ice pack; Sea ice
• Online Access: https://epic.awi.de/id/eprint/49015/; https://epic.awi.de/id/eprint/49015/1/Underwood_et_al_2019.pdf; https://hdl.handle.net/10013/epic.9f1909ba-f74b-4308-9816-08db1e9e6706

Continuing losses of multi-year sea ice (MYI) across the Arctic are causing first-year sea ice (FYI) to dominate the Arctic ice pack. Melting FYI provides a strong seasonal pulse of dissolved organic matter (DOM) into surface waters; however, the biological impact of this DOM input is unknown. Here we show that DOM additions cause important and contrasting changes in under-ice bacterioplankton abundance, production and species composition. Utilization of DOM was influenced by molecular size, with 10–100 kDa and >100 kDa DOM fractions promoting rapid growth of particular taxa, while uptake of sulfur and nitrogen-rich low molecular weight organic compounds shifted bacterial community composition. These results demonstrate the ecological impacts of DOM released from melting FYI, with wide-ranging consequences for the cycling of organic matter across regions of the Arctic Ocean transitioning from multi-year to seasonal sea ice as the climate continues to warm.