Nutrient and oxygen exchanges at the water–sediment interface in a shellfish farming lagoon (Thau, France)

• Published in: Journal of experimental marine biology and ecology Vol. 205; no. 1; pp. 91 - 113
• Main Authors: Mazouni, Nabila, Gaertner, Jean-Claude, Deslous-Paoli, Jean-Marc, Landrein, Sonia, Geringer d'Oedenberg, Malgorsata
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.11.1996
• Subjects: Benthic fluxes; Bottom anoxia; Crassostrea gigas; Marine; Nutrient; Oxygen; Sediment; Water; MED, France, Languedoc-Roussillon, Thau Lagoon; Water; Bottom anoxia; Nutrient; Oxygen; Sediment; Benthic fluxes
• ISSN: 0022-0981; 1879-1697
• DOI: 10.1016/S0022-0981(96)02594-4

The Etang de Thau (France) is a shallow lagoon characterised by the semi-intensive farming of oysters ( Crassostrea gigas, Thunberg) cultured in suspension on frames. Analysis of the benthic fluxes of inorganic nutrients and oxygen over a period of a year has provided a basis for describing the dynamics of the water–sediment interface in the lagoon. Monthly measurements of fluxes at the water–sediment interface at two stations have been compared. One station (UC) is located under a culture table, and is subject to intensive accumulation of organic matter (biodeposition); the other (OC) is located outside the area directly under the impact of the culture activities. Oxygen consumption ranged from 288.24 to 1026.85 μmol·m −2·h −1 according to the season and the station. Ammonium production was maximal at station UC in Summer (600 μmol·m −2·h −1) and minimal at station OC in the Autumn (30 μmol·m −2·h −1). In general, the fluxes recorded at station UC were 1.8–3 times higher than those recorded at station OC for oxygen and 1–5 times higher for ammonium. Nevertheless, the variability between stations was lower than the seasonal variability. Using a Multiple Correspondence Analysis (MCA), it was possible to point out the occurrence of an atypical event that was responsible for the disruption of the seasonal cycle. This event was a state of hypoxia known locally under the generic name of malaı̈gue. The dystrophic crisis consists of a major perturbation of the ecosystem, responsible for a massive mortality affecting both the benthos and the reared stocks.