Short-term bacterial reactivity of nitrogen-enriched seawater of a eutrophic lagoon |
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| Authors: | F Van Wambeke MA Bianchi G Cahet |
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| Institution: | 1. Laboratoire de Microbiologie du Milieu Marin, C.N.R.S. ER 223, Université de Provence. 13331 Marseille Cedex 3 France;2. Laboratoire Arago, 66650 Banyuls-sur-Mer, France |
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| Abstract: | We carried out, in September, a 24 h experiment to determine the potential reactivity of bacterial communities found in the sea water in Arcachon Basin (France). To create eutrophic systems, batches of seawater were enriched with 30 mgl?1 of either ammonium chloride or amino acids. Samples were taken every 3 h. Quantitative measurements were made of direct counts (AODC), biomass and ATP content. The heterotrophic bacterial communities were defined in terms of their catabolic potentialities and ‘specific’ diversity. Bacterial heterotrophic activity was established by measuring heterotrophic uptake and the mineralization percentage of labelled glucose or amino acids. From these data, ratios of AMP/ATP and P/B were calculated where P is the uptake of labelled substrate and B is the biomass.After the nitrogen enrichment an increase of the respiration was seen at first. After 6 h, a biomass peak appeared associated with a continuous increase in the number of cells. Bacterial growth was concurrent with a qualitative modification of the community: UAI increased, and diversity dropped. A less diversified community resulted suggesting an immature ecological state (zymogenous bacterial). Low values of respiration percentage (20%) characterized high growth yields. |
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| Keywords: | nitrogen bacteria diversity index community |
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