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(49-06) How to link bioassays in the laboratory and changes at the population level in the field. GEFFARD, ALAIN1,2, GEFFARD, OLIVIER*,1,3, MENASRIA, REDA1,4, BEAUPOIL, R.1,5, AMIARD-TRIQUET, CLAUDE1,2, 1 CNRS/GRD 1117, Faculté des Sciences, 2 rue de la Houssinière BP 92208, Nantes, France, France2 ISOMer, SMAB, Faculté des Sciences, 2 rue de la Houssinière BP 92208, Nantes, France, France3 LPTC, Université de Bordeaux I 351 cours de la Libération, Bordeaux, France, France4 Institut Océanographique, 195 rue Saint-jacques, Paris, France, France5 Station de Biologie Marine du MNHN, Place de la Croix, Concarneau, France, France ABSTRACT- Biomonitoring programmes have two majors aims:to determine the levels and trends of contaminants; to assess the effects of contaminants on biota. With regards to this second aim, the present study has been designed in order to link mobility of sediment-bound metals (Cd, Cu, Zn), ecotoxicity of sediments to invertebrate larvae and variations of recruitment on artificial hard substrates. In the metal-rich Gironde estuary, Fr., from March to October 1997, superficial sediments were analysed monthly for metal levels and desorption tests were carried out to quantify the fraction easily re-mobilized. The ecotoxicity of these sediments was determined using oysters, sea-urchins and copepods larvae exposed to elutriates and/or raw sediments. Artificial substrates were immerged in the estuary and recovered monthly to determine the relative surface occupied by barnacles and hydroids. The total quantity of metals which can be re-mobilized was higher in summer and autumn than in spring. Concomitantly, invertebrate larvae belonging to the three test species showed a higher sensitivity to sediments sampled in summer and autumn than in spring. Concerning the recruitment, the most striking feature was the decreased settlement of the hydroid Laomedea flexuosa in summer and autumn compared to spring, although abiotic factors were not unfavorable to the requirements of this species. The similarities of the temporal trends of both the chemical factors and the biological responses is discussed. Key words: Trace metals, Bioassays, Population effects, Estuary |
