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| Leruste, A; Guilhaumon, F; De Wit, R; Malet, Nathalie; Collos, Y; Bec, Beatrice. |
| We studied a mesotrophic and a hypertrophic Mediterranean coastal lagoon, both of which had been simultaneously subjected to a nutrient input reduction for 9 yr. We compared these 2 lagoons to an oligotrophic coastal lagoon. Using bioassays comprising 24 h incubations with added phosphorus and/or ammonium, we investigated the response of the phytoplankton communities to nutrient enrichment during summer in terms of biomass, size class structure, abundance and growth. For nitrogen and phosphorus, we identified which nutrient limited phytoplankton growth, and what strategies of nutrient exploitation the communities adopted to cope with these limitations. Ultraphytoplankton dominated the 3 communities, but it differed in composition among the lagoons. Green... |
| Tipo: Text |
Palavras-chave: Growth rate; Nutrient limitation; Dilution experiment; HPLC. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00508/61978/66084.pdf |
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| Mathieu, M; Leflaive, J; Ten Hage, L; De Wit, R; Buffan Dubau, E. |
| The aim of the present study was to examine the effects of biofilm-dwelling nematode activity on the oxygen turnover of cultured diatom biofilms. Oxygen microprofiles were simultaneously measured using the microelectrode technique in biofilms incubated with and without nematodes during short-term (24 h) and medium-term (6 d) experiments. During 24 h nycthemeral incubations, maximum oxygen concentrations and oxygen peak depths of microprofiles, as well as net oxygen production rates, were significantly higher in the diatom biofilms with nematodes. These effects might be dependent on the densities of nematodes. In the present study, significant effects were observed at nematode densities exceeding 100 ind. cm(-2), but not at a density <50 ind. cm(-2).... |
| Tipo: Text |
Palavras-chave: Bioturbation; Grazing; Net production rate; Oxygen community metabolism; Microelectrode; Oxygen microprofile; Nematodes; Diatom biofilms. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-3607.pdf |
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| Bianchi, A; Calafat, A; De Wit, R; Garcin, J; Tholosan, O; Cacho, I; Canals, M; Fabres, J; Grout, H; Masque, P; Sanchez-cabeza, Ja; Sempere, R. |
| Microbiological and biogeochemical studies were carried out in sediments and near bottom waters in the upwelling area off the Malaga coast and in the Almeria-Oran frontal zone. In these nutrient-rich conditions, metabolic activity is potentially limited by oxygen availability through the sediment depth. In the surficial sediments of the frontal zone, however, oxygen penetrated to a depth of 4 cm, allowing oxic mineralisation processes to occur throughout the layer. In the surficial sediments of the upwelling area, oxygen penetration was limited to the top 2.5 cm, leading to anoxic conditions. Glutamate respiration and global oxygen uptake rates were clearly higher than in the frontal zone. In the superficial sediments of the frontal zone, bacteria were... |
| Tipo: Text |
Palavras-chave: Taux de minéralisation; Sédiments; Eaux profondes; Méditerranée occidentale; Bacteria; Mineralisation rate; Sediments; Deep-sea; Western Mediterranean. |
| Ano: 2002 |
URL: http://archimer.ifremer.fr/doc/00322/43298/43034.pdf |
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