In-situ microcosms, a tool for assessment of pesticide impacts on oyster spat (Crassostrea gigas)

• Published in: Ecotoxicology
• Main Authors: Stachowski Haberkorn, S, Quiniou, Francoise, Nedelec, M, Robert, Rene, Limon, G, De La Broise, D
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer 2008
• Subjects: Epoxiconazole; Bentazon; Pesticide; Toxicity; Oyster; Microcosm; Crassostrea gigas
• Online Access: https://archimer.ifremer.fr/doc/2008/publication-4134.pdf; https://doi.org/10.1007/s10646-007-0190-9; https://archimer.ifremer.fr/doc/00000/4134/

Effects of the herbicide Basamais (bentazon) and the fungicide Opus (epoxiconazole) on oyster spat (Crassostrea gigas) were assessed using in-situ microcosms in a field experiment lasting 13 days. Six-week-old hatchery spat (mean size 1.1 mm), previously collected on PVC plates, was immersed in glass bottles filled with 200 mu m filtered seawater. Bottles were maintained underwater at 6 m depth and their water content changed every other day. Growth, measured as shell area index increase, was 126 +/- 4% in the control bottles. While no growth differences were observed between control and individual pesticide treatments at 10 mu g l(-1), oysters treated with a mix of 10 mu g l(-1) Opus and 10 mu g l(-1) Basamais showed a 50% growth reduction compared with the control (P < 0.0001), suggesting a synergistic effect of these contaminants. Laboratory controls in microcosms maintained in a water bath with filtered natural light, were not significantly different from in-situ microcosm controls in the field, for organic weight content or growth. This in-situ experiment in microcosms allowed us to conclude that: (1) oyster spat can achieve significant growth in bottles immersed in situ without supplementary food; (2) this microcosm system is reliable and easy to use for environmental toxicity tests with C. gigas spat; (3) such microcosm systems can also be run in a laboratory water bath instead of more technically difficult immersed field experiments; (4) the synergistic effect observed here, at a concentration simulating a peak agricultural runoff event, suggests that the impacts of pesticides could be a real threat for oysters in estuarine areas.