1. Comparison of the Effects of Two Herbicides and an Insecticide on Tropical Freshwater Plankton in Microcosms
- Author
-
Philippe Cecchi, Laurence Amalric, Christophe Leboulanger, G. Sarazin, Agnès Bouchez, Marc Bouvy, Marc Pagano, Claire Carré, Ecosystèmes lagunaires : organisation biologique et fonctionnement (ECOLAG), Université Montpellier 2 - Sciences et Techniques (UM2)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de géochimie des Eaux (LGE), Université Paris Diderot - Paris 7 (UPD7)-Institut de Physique du Globe de Paris, Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Centre Alpin de Recherche sur les Réseaux Trophiques et Ecosystèmes Limniques (CARRTEL), Institut National de la Recherche Agronomique (INRA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry]), Cyanobactéries des milieux aquatiques tropicaux peu profonds. Rôles et contrôles (CYROCO), This paper is a contribution to the ECOMET project, funded by the French Ministry of Ecology, Energy, Sustainable Development, and Sea (MEEDDM), grant no. CV070000783. The authors would like to thank the Forestry and Agriculture Office at Mamoudzou (DAF Mayotte) and SOGEA-Mayotte for their help with fieldwork. We are grateful to the staff of the Gite du Mont Combani for their support during our stay. Anonymous referees are acknowledged for improvement of an earlier version of the manuscript., and Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut National de la Recherche Agronomique (INRA)
- Subjects
Paraquat ,0106 biological sciences ,Insecticides ,Food Chain ,Health, Toxicology and Mutagenesis ,[SDU.STU]Sciences of the Universe [physics]/Earth Sciences ,010501 environmental sciences ,Biology ,01 natural sciences ,Zooplankton ,Fenitrothion ,chemistry.chemical_compound ,Phytoplankton ,Animals ,Biomass ,Mozambique ,0105 earth and related environmental sciences ,2. Zero hunger ,Herbicides ,010604 marine biology & hydrobiology ,fungi ,General Medicine ,Bacterioplankton ,Plankton ,Pesticide ,environmental monitoring/analysis ,Pollution ,[SDE.ES]Environmental Sciences/Environmental and Society ,6. Clean water ,chemistry ,13. Climate action ,Diuron ,Environmental chemistry ,environmental sciences and ecology ,Microcosm ,natural plankton communities ,tropical freshwater reservoir ,Water Pollutants, Chemical ,Environmental Monitoring ,toxicology - Abstract
International audience; Natural plankton communities from a tropical freshwater reservoir (Combani Reservoir, Mayotte Island, Mozambique Channel) were exposed, in 20-l nutrient-enriched microcosms, to two nominal concentrations of three pesticides: the herbicides diuron (2.2 and 11 mu g/l) and paraquat (10 and 40.5 mu g/l) and the insecticide fenitrothion (10 and 100 mu g/l), commonly used in the tropics for agriculture and disease vector control. Bacterioplankton, phytoplankton, and zooplankton communities were monitored for 5 days after exposure, and the concentrations of toxicant and major nutrients were measured. Bacterioplankton growth was noticeable in all systems and was slightly affected by pesticide at any concentration. A transitory increase in thymidine-based bacterial production was observed in diuron- and fenitrothion-treated microcosms, followed by a marked decrease in all microcosms after 5 days. The functional diversity of bacterioplankton, evaluated using BIOLOG ECO (R) microplates, was reduced by exposure to the highest pesticide concentrations. Phytoplankton was affected by pesticides in different ways. Chlorophyll biomass and biovolumes were increased by diuron addition and decreased by paraquat, whereas fenitrothion-treated microcosms remained unaffected relative to controls. Phytoplankton taxonomic diversity was decreased by paraquat and high doses of fenitrothion but was unaffected by addition of diuron. The decrease in diversity was due to a reduction in the number of species, whereas the density of small cells increased, especially after addition of paraquat. Heterotrophic flagellates were sensitive to paraquat and to the highest diuron concentration; a reduction in biomass of up to 90% was observed for 40.5 mu g/l paraquat. Zooplankton, dominated by Thermocyclops decipiens and Diaphanosoma excisum, was slightly sensitive to diuron, and very sensitive to paraquat. High concentrations of the insecticide fenitrothion were effective only on young stages. The potential direct and indirect effects of pesticide contamination on such a simplified plankton food web, typical of newly constructed reservoirs, appear to differ significantly depending on the biological compartment considered. The overall sensitivity of tropical plankton is comparable to the sensitivity for temperate systems, and direct and indirect effects appeared rapidly, within 5 days of exposure.
- Published
- 2011