PARENT SESSION
49 - Predicting Pollution Effects in the Field
8:00 AM to 6:30 PM, Tuesday, 14 May 2002
Exhibition Area

(49-10) Assessment of the effects of herbicides in aquatic pond mesocosms: combination of metrics measured at the individual, population and community levels in invertebrates.

CAQUET, Thierry^*,1, LAGADIC, Laurent¹, JUMEL, Audrey¹, HEYDORFF, Micheline¹, ¹ INRA,UMR 985 Ecobiology and Quality of Continental Hydrosystems, ENSAR,65 rue de Saint-Brieuc, RENNES CEDEX, FRANCE

ABSTRACT- The effects of triazine (atrazine ; nominal concentrations : 5, 25 and 125 g/l), diphenyl ether (fomesafen, nominal concentration 40 g/l), and mixture of fomesafen and polyethoxylated nonylphenols (nominal concentrations 40 and 90 g/l, respectively) on macroinvertebrates were assessed using outdoor freshwater pond mesocosms. Criteria were measured at increasing biological organization levels, ranging from individuals to community, in macroinvertebrates. Individual-level parameters (biomarkers) were measured in freshwater snails of the genus Lymnaea (detoxication enzymes, bioenergetic parameters) and in the isopod Asellus aquaticus (adenylate energy charge). Quantification of key processes of population dynamics (individual growth, fecundity, fertility) was performed in freshwater snails. Data on the structure (abundance of the different taxonomic groups) and function (abundance of the different functional feeding groups) of the macroinvertebrate community were also collected. Organisms were either caged in the mesocosms (for freshwater snails and isopods) or sampled using a stratified sampling strategy. Additional laboratory studies were also performed to improve interpretation of the data collected in the ponds. Both herbicides had significant effects on some of the biomarkers and demographic criteria measured in freswhater snails. Community-level analysis indicates that atrazine reduced the abundance of some herbivorous taxa (midges of the subfamily Orthocladiinae). Several invertebrate taxa were also significantly affected by fomesafen and by the mixture fomesafen-polyethoxylated nonylphenols. These results suggest that herbicide may have both direct and indirect effects on freshwater macroinvertebrates. Furthermore, the simultaneous use of multi-level metrics in mesocosms may improve risk assessment procedures by linking individual effects and consequences at population or community levels.

Key words: aquatic mesocosms, herbicides, invertebrates