title: In-situ microcosms, a tool for assessment of pesticide impacts on oyster spat (Crassostrea gigas).
abstract: Effects of the herbicide Basamaïs (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 mum 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 microg l(-1), oysters treated with a mix of 10 microg l(-1) Opus and 10 microg l(-1) Basamaïs 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.
authors.affiliation: Lumaq, Université de Bretagne Occidentale, Quimper 29334, France.
authors.forename: Sabine
authors.initials: S
authors.lastname: Stachowski-Haberkorn
authors.forename: Françoise
authors.initials: F
authors.lastname: Quiniou
authors.forename: Morgane
authors.initials: M
authors.lastname: Nedelec
authors.forename: René
authors.initials: R
authors.lastname: Robert
authors.forename: Gwendolina
authors.initials: G
authors.lastname: Limon
authors.forename: Denis
authors.initials: D
authors.lastname: de la Broise
mesh_terms: D000818:Animals; D001581:Benzothiadiazines / Q000633:toxicity*; D049896:Crassostrea / Q000187:drug effects*; D004852:Epoxy Compounds / Q000633:toxicity*; D005659:Fungicides, Industrial / Q000633:toxicity*; D006540:Herbicides / Q000633:toxicity*; D018675:Toxicity Tests / Q000379:methods*; D014230:Triazoles / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D001581:Benzothiadiazines; D004852:Epoxy Compounds; D005659:Fungicides, Industrial; D006540:Herbicides; D014230:Triazoles; D014874:Water Pollutants, Chemical; C002003:bentazone; C109476:epoxiconazole