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| Christaki, Urania; Gueneugues, Audrey; Liu, Yan; Blain, Stéphane; Catala, Philippe; Colombet, Jonathan; Debeljak, Pavla; Jardillier, Ludwig; Irion, Solène; Planchon, Frederic; Sassenhagen, Ingrid; Sime Ngando, Telesphore; Obernosterer, Ingrid. |
| Spatial and seasonal dynamics of microbial loop fluxes were investigated in contrasting productivity regimes in the Indian sector of the Southern Ocean. Observations carried out in late summer (February–March 2018; project MOBYDICK) revealed higher microbial biomasses and fluxes in the naturally iron‐fertilized surface waters of Kerguelen island in comparison to surrounding off‐plateau waters. Differences were most pronounced for bacterial heterotrophic production (2.3‐fold), the abundance of heterotrophic nanoflagellates (HNF; 2.7‐fold). Independent of site, grazing by HNF was the main loss process of bacterial production (80–100%), while virus‐induced mortality was low (< 9%). Combining these results with observations from previous investigations... |
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| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00649/76109/77064.pdf |
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| Irion, Solène; Jardillier, Ludwig; Sassenhagen, Ingrid; Christaki, Urania. |
| In the Southern Ocean, diatom blooms have attracted a lot of attention, while other small nonsilicified phytoplankton groups have been less studied. Here, small phytoplankton (< 20 μ m, including small diatoms and nonsilicified small phytoplankton) are focused on in two contrasting areas: the productive Kerguelen plateau and its surrounding low productivity waters. To assess the diversity and spatial structuration of phytoplankton, discrete plankton samples (0–300 m layer) of two size fractions (< 20 and 20–100 μ m) were analyzed with 18S rDNA amplicon sequencing in late summer. Phytoplankton seasonal succession was described using flow cytometry, pigments, and environmental data, from two previous cruises (during the onset and decline of the diatom... |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00635/74746/74854.pdf |
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| Irion, Solène; Christaki, Urania; Berthelot, Hugo; L’helguen, Stéphane; Jardillier, Ludwig. |
| Phytoplankton is composed of a broad-sized spectrum of phylogenetically diverse microorganisms. Assessing CO2-fixation intra- and inter-group variability is crucial in understanding how the carbon pump functions, as each group of phytoplankton may be characterized by diverse efficiencies in carbon fixation and export to the deep ocean. We measured the CO2-fixation of different groups of phytoplankton at the single-cell level around the naturally iron-fertilized Kerguelen plateau (Southern Ocean), known for intense diatoms blooms suspected to enhance CO2 sequestration. After the bloom, small cells (<20 µm) composed of phylogenetically distant taxa (prymnesiophytes, prasinophytes, and small diatoms) were growing faster (0.37 ± 0.13 and 0.22 ± 0.09... |
| Tipo: Text |
Palavras-chave: Biogeochemistry; Microbial ecology; Stable isotope analysis. |
| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00684/79595/82286.pdf |
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