| Summary: | Trabajo presentado en Arctic Frontiers 2011, Arctic Tipping Points, celebrado en Tromso (Noruega), del 23 al 28 de enero de 2011. El libro de abstracts se publicó como: 2011 Abstracts. Arctic Frontiers. The Arctic in the Earth System Perspective: the role of tiping points. Tromso: [University of Tromso, 2011] The Arctic region is experiencing the steepest warming rate on Earth, which is three times faster than the global mean. In order to solve which is the effect of global warming affecting Arctic microbial communities, we examine the effect of increasing temperatures on prokaryotes production, and mortality (by bacterivores and viruses) as well as changes in the community composition of protist from two contrasting Arctic marine systems. During July 2009, we collected Arctic, and Atlantic influenced waters to carry out two mesocosms experiment along 10 days each and at 7 increasing temperatures from 1.5 to 10ºC. Different responses at increasing temperatures were found for the microbial communities from different systems. Thus, for the Arctic microbial community, adapted to live at ¿ 1.5º C, we have detected that all microbial abundances as well as bacterial production and fluxes of bacterial carbon due to grazers and viruses achieved maximum values around 4.5º- 6ºC experimental temperature, and maintained high values even at higher experimental temperatures. In addition, ciliates community composition showed a shift, increasing heterotrophic and bacterivores organisms at increasing temperatures. The biomass of phototrophs, has also shown maximum values at ca. 5ºC and a clear decrease at temperatures higher than 5ºC. In contrast, in the Atlantic-influenced community living at temperatures around 4ºC no clear response to increasing temperature was found. Our results indicate that communities used to to live at very low temperatures would suffer a higher impact than communities living at higher temperatures. Peer Reviewed
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