Viruses and Protists Induced-mortality of Prokaryotes around the Antarctic
Peninsula during the Austral Summer
#MMPMID28303119
Vaqué D
; Boras JA
; Torrent-Llagostera F
; Agustí S
; Arrieta JM
; Lara E
; Castillo YM
; Duarte CM
; Sala MM
Front Microbiol
2017[]; 8
(?): 241
PMID28303119
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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 ×
10(7) viruses ml(-1) d(-1) in the Bellingshausen Sea to1.3 ± 0.7 × 10(7) viruses
ml(-1) d(-1) in the Bransfield Strait, while lysogeny, when detectable, recorded
the lowest value in the Bellingshausen Sea (0.05 ± 0.05 × 10(7) viruses ml(-1)
d(-1)) and the highest in the Weddell Sea (4.3 ± 3.5 × 10(7) viruses ml(-1)
d(-1)). Average mortality rates due to viruses ranged from 9.7 ± 6.1 × 10(4)
cells ml(-1) d(-1) in the Weddell Sea to 14.3 ± 4.0 × 10(4) cells ml(-1) d(-1) in
the Bellingshausen Sea, and were higher than averaged grazing rates in the
Weddell Sea (5.9 ± 1.1 × 10(4) cells ml(-1) d(-1)) and in the Bellingshausen Sea
(6.8 ± 0.9 × 10(4) cells ml(-1) d(-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 × 10(4) cells ml(-1) d(-1) and 6.5 ± 3.9 × 10(4)
cells ml(-1) d(-1) in the Weddell Sea; 22.1 ± 9.6 × 10(4) cells ml(-1) d(-1) and
11.6 ± 1.4 × 10(4) cells ml(-1) d(-1) in the Bransfield Strait; and 16.1 ± 5.7 ×
10(4) cells ml(-1) d(-1) and 7.9 ± 2.6 × 10(4) cells ml(-1) d(-1) in 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.
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