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| Registros recuperados: 68 | |
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| Hermin, M; Daumas, R; Drogue, N. |
| The bacterial activity of the superficial sediment layer was evaluated by incorporation super(14)C-labelled amino-acids mixed an hydrolysate of chlorella cells. Estimation of super(14)C-CO sub(2) super(14)C and super(14)C-A.A. by H.P.L.C. give some informations on the utilization of free dissolved. A.A. and on the transport of labelled compounds from water to sediment. The adsorption mechanism of A.A. on the mineral particles draw to the sediment a larger part of A.A. in the first period; but 28% of this adsorbed A.A. were discharged by an acid treatment. A part of super(14)C-A.A. was incorporated in unhydrolysable organic matter. Di-COOH A.A. are more resistant to bacterial degradation than the other A.A., but arginine is completely metabolized in ten... |
| Tipo: Text |
Palavras-chave: Biogeochemistry; Bacteria; Chromatographic techniques; Metabolism; Amino acids; Sediment water exchanges. |
| Ano: 1984 |
URL: http://archimer.ifremer.fr/doc/1984/acte-945.pdf |
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| Bertoni, R. |
| The radiochemical methods proposed for evaluating heterotrophic activity in waters have been severely criticized in recent years because they are not considered to be sufficiently realistic. Thus, the possibility of directly measuring the heterotrophic consumption of naturally occurring Organic Carbon (OC) in fresh water samples incubated under controlled conditions has been evaluated. The analytical performances of two OC analyzers utilizable for this purpose are discussed here, and some examples of the results obtained by the direct measurement of OC consumption are presented. The consumption rates thus measured ranged from 11.6 to 50.2 mu gC/ 1.h. Although the technique discussed here is less sensitive than radiochemical methods, the few assumptions... |
| Tipo: Text |
Palavras-chave: Biogeochemistry; Microbiology; Carbon cycle; Organic carbon; Water; Heterotrophic organisms; Analytical techniques. |
| Ano: 1984 |
URL: http://archimer.ifremer.fr/doc/1984/acte-950.pdf |
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| Hoppe, H. |
| Extracellular enzymes mediate the decomposition of polymeric organic compounds in natural waters. In many cases these enzymes comprise a component linked to the bacterial fraction of the aquatic community and react in close association with these cells. An annual survey of microbial activities in a brackish water fjord exhibited an excellent correlation between V sub(m) of proteases (ability to split the substrate analogue methylumbelliferyl-leucine) and V sub(m) as well as T sub(R) for leucine uptake by microorganisms. Hydrolysis rates (H sub(R)) for the decomposition of naturally occurring competitive substrate analogues of the model substrates (methylumbelliferyl-(MUF)-leucine, MUF- alpha -D-glucose, MUF-N-acetyl-glucosamine, MUF-phosphate) drastically... |
| Tipo: Text |
Palavras-chave: Biogeochemistry; Fjords; Bacteria; Brackishwater environment; Seasonal variations; Dissolved organic matter; Interspecific relationships; Hydrolysis; Enzymes. |
| Ano: 1984 |
URL: http://archimer.ifremer.fr/doc/1984/acte-952.pdf |
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| Morita, R; Jones, R. |
| The nitrifying bacteria were found to survive 24 weeks in the absence of ammonium without decreasing their number of cell size. Because H sub(2), CO, and CH sub(4) are present in the marine environment, these substrates were investigated as a possible source of the energy of maintenance for the nitrifying bacteria. super(14)CO and super(14)CH sub(4) were found to be oxidized by the nitrifiers. N-serve was found to inhibit the oxidation of CO. Using the nitrifiers' ability to oxide CO, a method for the determination of the nitrification rate was developed. The ability of nitrifiers to oxidize CO may play a significant role in the cycling of CO sub(2) in the marine environment. Whether CO and CH sub(4) oxidation play a role in the survival of nitrifiers in... |
| Tipo: Text |
Palavras-chave: Methane; Carbon dioxide; Survival; Bacteria; Nitrification; Nitrogen cycle; Oxidation; Carbon cycle; Biogeochemistry; Metabolism. |
| Ano: 1984 |
URL: http://archimer.ifremer.fr/doc/1984/acte-975.pdf |
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| Herbert, R. |
| Seasonal data and depth profiles using super(15)N-labelled NO sub(3)u- show that denitrification (77-90% of NO sub(3)u- respired) rather than NO sub(3)u- dissimilation to NH sub(4)u+ was the principal route of nitrate reduction in Kingoodie Bay sediments. Populations of both groups of NO sub(3)u- reducing bacteria were highest in the 0-20 mm horizon in those sediments where highest rates of NO sub(3)u- respiration were recorded (28.56 mu g N.d super(-1) dry wt. sediment super(-1)). Autotrophic nitrification rates shared a marked seasonality with highest rates (0.92 mu g N.d super(-1).g dry wt. sediment super(-1)) occurring during the summer. Maximum populations of autotrophic nitrifying bacteria were also found in the 0-20 mm sediment horizon and these... |
| Tipo: Text |
Palavras-chave: Seasonal variations; Bacteria; Estuaries; Sediment chemistry; Biogeochemistry; Ammonia; Nitrates; Nitrogen cycle. |
| Ano: 1984 |
URL: http://archimer.ifremer.fr/doc/1984/acte-971.pdf |
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| Michel, Pierre. |
| Arsenic levels of in the marine environment are high in comparison with other contaminants. Over the past twenty years, a large number of arsenic organic compounds have been identified in the water, sediments and living species. This document constitutes a synthesis of current knowledge on arsenic sources, and contamination levels, on its biogeochemical cycle as well as its toxic effects on human and marine fauna. This paper highlights in particular the effects of phosynthesis on arsenic speciation and its distribution throughout the marine environment. Problems of toxicity in the case of certain phyto- and zooplankton species are identified. Bioaccumulation in seaweeds, molluscs and fishes is documented as well, with special attention to the species... |
| Tipo: Text |
Palavras-chave: Ecotoxicology; Contamination; Biogeochemistry; Arsenic; Ecotoxicologie; Contamination; Biogéochimie; Arsenic. |
| Ano: 1993 |
URL: http://archimer.ifremer.fr/doc/1993/rapport-1448.pdf |
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| Registros recuperados: 68 | |
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