, Volume 35, Issue 5, pp 785-794
Date: 09 Oct 2011

Evidence of heterotrophic prokaryotic activity limitation by nitrogen in the Western Arctic Ocean during summer

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Global warming in the Arctic Ocean may result in changes to the stock and dynamics of nutrients that drive the activity of heterotrophic prokaryotes, a key component of the microbial food web. We performed 14 enrichment experiments during summer in the Beaufort and Chukchi Seas (Western Arctic Ocean), with C (acetate and/or glucose), N (nitrate and/or ammonium) and P (phosphate) amendments. In 8 out of 11 experiments performed with surface waters, prokaryotic heterotrophic production was limited by N, either alone (5 experiments) or in co-limitation with C (3 experiments). This contrasted with the experiments performed using waters from the chlorophyll maxima, where N was never limiting. Diversity analyses (DNA- and RNA-based fingerprinting) suggest that limitation was not restricted to specific operational taxonomic units but common to the different groups. This is the first report of N limitation of prokaryotic heterotrophic production in Arctic surface waters. This control by N may gain importance in future scenarios of higher productivity in the area.