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Aquatic Microbial Ecology

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AME 70:17-32 (2013)  -  DOI:

Experimental evaluation of the warming effect on viral, bacterial and protistan communities in two contrasting Arctic systems

Elena Lara1,*, Jesús M. Arrieta2, Iñigo Garcia-Zarandona2, Julia A. Boras1, Carlos M. Duarte2,3, Susana Agustí2,3,4, Paul F. Wassmann5, Dolors Vaqué1

1Departament de Biologia Marina i Oceanografia, Institut de Ciències del Mar (CSIC), Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Spain
2Global Change Research Department, Institut Mediterráni d’ Estudis Avançats (CSIC-UIB), Miquel Marquès 21, 07190 Esporles, Illes Balears, Spain
3The UWA Oceans Institute, and 4School of Plant Biology, University of Western Australia, 35 Stirling Highway, 6009 Crawley, Western Australia, Australia
5Department of Arctic and Marine Biology (AMB), Faculty of Biosciences, Fisheries and Economics, University of Tromsø, 9037 Tromsø, Norway

ABSTRACT: The effect of Arctic warming, which is 3 times faster than the global average, on microbial communities was evaluated experimentally to determine how increasing temperatures affect bacterial and viral abundance and production, protist community composition, and bacterial loss rates (bacterivory and lysis) in 2 contrasting Arctic marine systems. In July 2009, we collected samples from open Arctic waters in the Barents Sea and Atlantic-influenced waters in Isfjorden, Svalbard Islands (Fjord waters). The samples were used in 2 microcosm experiments at 7 temperatures, ranging from 1.0 to 10.0°C. In the open Arctic microbial community, collected at <1.0°C, bacterial and viral abundances, bacterial production and grazing rates due to protists increased significantly above 5.5°C, and remained at high values at even higher experimental temperatures. The abundance of protists, such as some heterotrophic pico/nanoflagellates, as well as some ciliates, also increased with warming. In contrast, the biomass of phototrophs decreased above 5.5°C. The water temperature in Fjord waters was 6.2°C at the time of sampling, and the microbial community showed smaller variations than the Arctic community. These results indicate that increases in temperature stimulate heterotrophic microbial biomass and activity compared to that of phototrophs, which has important implications for carbon and nutrient cycling in the system. In addition, open Arctic communities were more vulnerable to warming than those already adapted to the warmer Fjord waters influenced by Atlantic seawater.

KEY WORDS: Virus · Bacteria · Protists · Viral production · Grazing · Global warming

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Cite this article as: Lara E, Arrieta JM, Garcia-Zarandona I, Boras JA and others (2013) Experimental evaluation of the warming effect on viral, bacterial and protistan communities in two contrasting Arctic systems. Aquat Microb Ecol 70:17-32.

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