AME 73:17-28 (2014)  -  DOI:

Response of under-ice prokaryotes to experimental sea-ice DOM enrichment

Andrea Niemi*, Guillaume Meisterhans, Christine Michel

Fisheries and Oceans Canada, Freshwater Institute, 501 University Crescent, Winnipeg, Manitoba R3T 2N6, Canada
*Corresponding author:

ABSTRACT: Marine dissolved organic matter (DOM) plays a key role in the global carbon cycle. In this study we show experimentally that Arctic sea-ice DOM can stimulate prokaryotic activity when added to surface waters. Time-series and dose-response enrichment microcosm experiments were conducted, in which first-year, sea-ice DOM was added to surface waters from Resolute Passage, Canadian Arctic Archipelago. Sea-ice DOM concentrations in this productive region averaged nearly 2000 µmol l-1 in May 2011 and 2012. The abundance, activity (high [HNA] versus low [LNA] nucleic acid cells) and apparent size of surface water prokaryotes were quantified along with dissolved organic carbon (DOC) and dissolved nitrogen (DN) concentrations during the experiments. Following a 4 d lag, prokaryotic abundance increased more than 30× in the time-series enrichment experiment and the proportion of HNA cells increased from 60 to >99% of total prokaryote abundance. DOM dose-response experiments conducted in 2011 and 2012 yielded prokaryotic growth rate estimates between 0.35 and 0.67 d-1 in response to the addition of sea-ice DOM. On average, 20% of the sea-ice DOC pool was utilized by the surface water prokaryotes and the observed increase in cell abundance and individual cell size indicated a release from carbon limitation of initial in situ conditions. Prokaryotic growth yields ranged from 0.02 to 0.07 cell µmol l-1 DOC and 0.01 to 0.06 cell µmol l-1 DN and experimental conditions shifted from net autotrophic to net heterotrophic. Heterotrophic activity at the ice-water boundary layer upon the release of labile first-year ice DOM is likely to impact current and future carbon flux estimates as seasonal ice becomes the predominant ice type in the Arctic.

KEY WORDS: Dissolved organic carbon · Prokaryotes · Sea ice · Melt · Heterotrophy · Arctic

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Cite this article as: Niemi A, Meisterhans G, Michel C (2014) Response of under-ice prokaryotes to experimental sea-ice DOM enrichment. Aquat Microb Ecol 73:17-28.

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