Microbial food web dynamics during spring phytoplankton blooms in the naturally iron-fertilized Kerguelen area (Southern Ocean)
|Author(s)||Christaki U.1, Lefevre D.2, Georges C.1, Colombet J.3, Catala P.4, 5, Courties C.6, 7, Sime-Ngando T.3, Blain S.4, 5, Obernosterer I.4, 5|
|Affiliation(s)||1 : ULCO, LOG, UMR8187, INSU CNRS, F-62930 Wimereux, France.
2 : Aix Marseille Univ, CNRS INSU, IRD, MIO,UM110, F-13288 Marseille, France.
3 : Univ Clermont Ferrand, Clermont Univ, LMGE, INEE CNRS,UMR6023, F-63177 Aubiere, France.
4 : CNRS, Lab Oceanog Microbienne, Observ Oceanol, UMR7621, F-66650 Banyuls Sur Mer, France.
5 : UPMC Univ Paris 06, Univ Paris 04, UMR7621, Lab Oceanog Microbienne,Observ Oceanogol, F-66650 Banyuls Sur Mer, France.
6 : CNRS, UMS2348, Lab Oceanog Microbienne, Observ Oceanol, F-66650 Banyuls Sur Mer, France.
7 : UPMC Univ Paris 06, Univ Paris 04, UMS2348, Lab Oceanog Microbienne,Observ Oceanol, F-66650 Banyuls Sur Mer, France.
|Source||Biogeosciences (1726-4170) (Copernicus Gesellschaft Mbh), 2014-12-05 , Vol. 11 , N. 23 , P. 6739-6753|
|WOS© Times Cited||45|
|Note||Special issue : KEOPS2: Kerguelen Ocean and Plateau Study 2Editor(s): S. Blain, I. Obernosterer, B. Queguiner, T. Trull, and G. Herndl|
|Abstract||Microbial food web dynamics were determined during the onset of several spring phytoplankton blooms induced by natural iron fertilization off Kerguelen Island in the Southern Ocean (KEOPS2). The abundances of heterotrophic bacteria and heterotrophic nanoflagellates, bacterial heterotrophic production, bacterial respiration, and bacterial growth efficiency, were consistently higher in surface waters of the iron-fertilized sites than at the reference site in HNLC (high nutrient low chlorophyll) waters. The abundance of virus-like particles remained unchanged, but viral production increased by a factor of 6 in iron-fertilized waters. Bacterial heterotrophic production was significantly related to heterotrophic nanoflagellate abundance and viral production across all sites, with bacterial production explaining about 70 and 85 %, respectively, of the variance of each in the mixed layer (ML). Estimated rates of grazing and viral lysis, however, indicated that heterotrophic nanoflagellates accounted for a substantially higher loss of bacterial production (50 %) than viruses (11 %). Combining these results with rates of primary production and export determined for the study area, a budget for the flow of carbon through the microbial food web and higher trophic levels during the early (KEOPS2) and the late phase (KEOPS1) of the Kerguelen bloom is provided.|