Etude des modifications du métabolisme respiratoire de populations d'Acartia clausi (Crustacea: Copepoda) après passage dans le circuit de refroidissement d'une centrale thermo-électrique

Abstract

The respiratory metabolism of the copepod Acartia clausi, the most abundant species of zooplankton in the area investigated (Gulf of Fos, Mediterranean Sea, France) was studied at different temperatures during an annual cycle. Copepods were collected from three different stations: first the intake area, where sea water was pumped into the cooling circuit of a power plant; second, the outlet area of this circuit, where the heated effluents were discharged with an average Δt of 6°C; third, a small protected bay directly influenced by the flow of the heated waters. Seasonal variations in respiration intensity were observed, with a spring maximum. Specimens collected from the heated effluents exhibited comparatively reduced metabolism. Q₁₀ varied with temperature and time of year, suggesting seasonal regulation of metabolism. Except in March, where metabolic curves differed markedly according to the origin of the sample (species from the heated effluents displaying a metabolic curve of the summer type), the principal difference in shape of the respiration-temperature curves appeared in the range of 10° to 14°C, where reduced respiration was observed in specimens from the heated effluents. When A. clausi from external areas were exposed to artificial thermal stress, they displayed a respiratory metabolism pattern similar to that of specimens sampled from the heated effluents. Experiments performed with warm-acclimated copepods revealed respiratory modifications similar to those observed in copepods from the heated effluent. These results are discussed in relation to the thermal conditions prevailing at the investigated site.