Comparison of the Effects of Two Herbicides and an Insecticide on Tropical Freshwater Plankton in Microcosms

• Published in: Archives of environmental contamination and toxicology Vol. 61; no. 4; pp. 599 - 613
• Main Authors: Leboulanger, C., Bouvy, M., Carré, C., Cecchi, P., Amalric, L., Bouchez, A., Pagano, M., Sarazin, G.
• Format: Journal Article
• Language: English
• Published: New York Springer-Verlag 01.11.2011; Springer; Springer Nature B.V; Springer Verlag
• Subjects: Animal, plant and microbial ecology; Animals; Applied ecology; Aquatic ecosystems; Bacteria; Biological and medical sciences; Biomass; Diuron; Diuron - toxicity; Earth and Environmental Science; Earth Sciences; Ecotoxicology; Ecotoxicology, biological effects of pollution; Environment; Environment and Society; Environmental Chemistry; Environmental Health; Environmental Monitoring; Environmental Sciences; Fenitrothion - toxicity; Food Chain; Food chains; Fundamental and applied biological sciences. Psychology; General aspects; Herbicides; Herbicides - toxicity; Indicator organisms; Insecticides; Insecticides - toxicity; Laboratories; Microcosms; Monitoring/Environmental Analysis; Mozambique; Nutrient concentrations; Paraquat; Paraquat - toxicity; Pesticides; Phytoplankton; Plankton; Plankton - drug effects; Plankton - growth & development; Pollution; Reservoirs; Sciences of the Universe; Soil Science & Conservation; Studies; Toxicants; Toxicity; Tropical environments; Water Pollutants, Chemical - toxicity; Water pollution; Zooplankton; Mozambique; France; Phytoplankton; Paraquat; Dissolve Inorganic Carbon; Soluble Reactive Phosphorus; LDPE; Pollution; Insecticide; Ecotoxicology; Plankton; Toxicity; Tropical zone; Pesticides; Fresh water; Microcosm; Environment; Climatic zone; Herbicide; environmental sciences and ecology; toxicology; natural plankton communities; environmental monitoring/analysis; tropical freshwater reservoir
• ISSN: 0090-4341; 1432-0703
• DOI: 10.1007/s00244-011-9653-3

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 μg/l) and paraquat (10 and 40.5 μg/l) and the insecticide fenitrothion (10 and 100 μg/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 ® 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 μg/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.