title: Viruses and Protists Induced-mortality of Prokaryotes around the Antarctic Peninsula during the Austral Summer.
abstract: During the Austral summer 2009 we studied three areas surrounding the Antarctic Peninsula: the Bellingshausen Sea, the Bransfield Strait and the Weddell Sea. We aimed to investigate, whether viruses or protists were the main agents inducing prokaryotic mortality rates, and the sensitivity to temperature of prokaryotic heterotrophic production and mortality based on the activation energy (Ea) for each process. Seawater samples were taken at seven depths (0.1-100 m) to quantify viruses, prokaryotes and protists abundances, and heterotrophic prokaryotic production (PHP). Viral lytic production, lysogeny, and mortality rates of prokaryotes due to viruses and protists were estimated at surface (0.1-1 m) and at the Deep Fluorescence Maximum (DFM, 12-55 m) at eight representative stations of the three areas. The average viral lytic production ranged from 1.0 ± 0.3 × 107viruses ml-1d-1in the Bellingshausen Sea to1.3 ± 0.7 × 107viruses ml-1d-1in the Bransfield Strait, while lysogeny, when detectable, recorded the lowest value in the Bellingshausen Sea (0.05 ± 0.05 × 107viruses ml-1d-1) and the highest in the Weddell Sea (4.3 ± 3.5 × 107viruses ml-1d-1). Average mortality rates due to viruses ranged from 9.7 ± 6.1 × 104cells ml-1d-1in the Weddell Sea to 14.3 ± 4.0 × 104cells ml-1d-1in the Bellingshausen Sea, and were higher than averaged grazing rates in the Weddell Sea (5.9 ± 1.1 × 104cells ml-1d-1) and in the Bellingshausen Sea (6.8 ± 0.9 × 104cells ml-1d-1). The highest impact on prokaryotes by viruses and main differences between viral and protists activities were observed in surface samples: 17.8 ± 6.8 × 104cells ml-1d-1and 6.5 ± 3.9 × 104cells ml-1d-1in the Weddell Sea; 22.1 ± 9.6 × 104cells ml-1d-1and 11.6 ± 1.4 × 104cells ml-1d-1in the Bransfield Strait; and 16.1 ± 5.7 × 104cells ml-1d-1and 7.9 ± 2.6 × 104cells ml-1d-1in the Bellingshausen Sea, respectively. Furthermore, the rate of lysed cells and PHP showed higher sensitivity to temperature than grazing rates by protists. We conclude that viruses were more important mortality agents than protists mainly in surface waters and that viral activity has a higher sensitivity to temperature than grazing rates. This suggests a reduction of the carbon transferred through the microbial food-web that could have implications in the biogeochemical cycles in a future warmer ocean scenario.
authors.affiliation: Institut de Ciències del Mar (CSIC), Consejo Superior de Investigaciones Científicas Barcelona, Spain.
authors.forename: Dolors
authors.initials: D
authors.lastname: Vaqué
authors.affiliation: Institut de Ciències del Mar (CSIC), Consejo Superior de Investigaciones Científicas Barcelona, Spain.
authors.forename: Julia A
authors.initials: JA
authors.lastname: Boras
authors.affiliation: Institut de Ciències del Mar (CSIC), Consejo Superior de Investigaciones Científicas Barcelona, Spain.
authors.forename: Francesc
authors.initials: F
authors.lastname: Torrent-Llagostera
authors.affiliation: King Abdullah University of Sciences and Technology Thuwal, Saudi Arabia.
authors.forename: Susana
authors.initials: S
authors.lastname: Agustí
authors.affiliation: King Abdullah University of Sciences and Technology Thuwal, Saudi Arabia.
authors.forename: Jesús M
authors.initials: JM
authors.lastname: Arrieta
authors.affiliation: Institut de Ciències del Mar (CSIC), Consejo Superior de Investigaciones CientíficasBarcelona, Spain; Institute of Marine Sciences (CNR-ISMAR), National Research CouncilVenezia, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Lara
authors.affiliation: Institut de Ciències del Mar (CSIC), Consejo Superior de Investigaciones Científicas Barcelona, Spain.
authors.forename: Yaiza M
authors.initials: YM
authors.lastname: Castillo
authors.affiliation: King Abdullah University of Sciences and Technology Thuwal, Saudi Arabia.
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Duarte
authors.affiliation: Institut de Ciències del Mar (CSIC), Consejo Superior de Investigaciones Científicas Barcelona, Spain.
authors.forename: Maria M
authors.initials: MM
authors.lastname: Sala
keywords: Antarctic waters; lysis; lysogeny; mortality; prokaryotes; protists; temperature; viruses