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| Schapira, Mathilde; Seuront, Laurent. |
| Despite ample evidence of micro- and small-scale (i.e., millimeter- to meter-scale) phytoplankton and zooplankton patchiness in the ocean, direct observations of nutrient distributions and the ecological importance of this phenomenon are still relatively scarce. In this context, we first describe a simple procedure to continuously sample nutrients in surface waters, and subsequently provide evidence of the existence of microscale distribution of ammonium in the ocean. We further show that ammonium is never homogeneously distributed, even under very high conditions of turbulence. Instead, turbulence intensity appears to control nutrient patchiness, with a more homogeneous or a more heterogeneous distribution observed under high and low turbulence... |
| Tipo: Text |
Palavras-chave: Nutrient patchiness; Turbulence; Phytoplankton; Surge uptake; Nutrient depletion; Turbulent history. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00643/75527/76435.pdf |
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| Schapira, Mathilde; Buscot, Marie-jeanne; Pollet, Thomas; Leterme, Sophie; Seuront, Laurent. |
| Background Picophytoplankton (i.e. cyanobacteria and pico-eukaryotes) are abundant and ecologically critical components of the autotrophic communities in the pelagic realm. These micro-organisms colonized a variety of extreme environments including high salinity waters. However, the distribution of these organisms along strong salinity gradient has barely been investigated. The abundance and community structure of cyanobacteria and pico-eukaryotes were investigated along a natural continuous salinity gradient (1.8% to 15.5%) using flow cytometry. Results Highest picophytoplankton abundances were recorded under salinity conditions ranging between 8.0% and 11.0% (1.3 × 106 to 1.4 × 106 cells ml-1). Two populations of picocyanobacteria (likely Synechococcus... |
| Tipo: Text |
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| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00174/28548/26932.pdf |
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| Pollet, Thoams; Schapira, Mathilde; Buscot, Marie-jeanne; Leterme, Sophie; Mitchell, James G; Seuront, Laurent. |
| he distribution and aminopeptidase activity of prokaryotes were investigated along a natural continuous salinity gradient in a hypersaline coastal lagoon, the Coorong, South Australia. The abundance of prokaryotes significantly increased from brackish to hypersaline waters and different sub-populations, defined by flow cytometry, were observed along the salinity gradient. While four sub-populations were found at each station, three additional ones were observed for 8.3% and 13.4%, suggesting a potential modification in the composition of the prokaryotic communities and/or a variation of their activity level along the salinity gradient. The aminopeptidase activity highly increased along the gradient and salinity appeared as the main factor favouring this... |
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| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00174/28549/26933.pdf |
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