Assessing combined impacts of agrochemicals: Aquatic macroinvertebrate population responses in outdoor mesocosms

• Published in: The Science of the total environment Vol. 631-632; pp. 341 - 347
• Main Authors: Barmentlo, S. Henrik, Schrama, Maarten, Hunting, Ellard R., Heutink, Roel, van Bodegom, Peter M., de Snoo, Geert R., Vijver, Martina G.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-08-2018
• Subjects: Agrochemicals; Aquatic invertebrates; Mesocosm; Mixtures; Outdoor testing; Outdoor testing; Mesocosm; Aquatic invertebrates; Agrochemicals; Mixtures
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2018.03.021

Agricultural ditches host a diverse community of species. These species often are unwarrantedly exposed to fertilizers and a wide-array of pesticides (hereafter: agrochemicals). Standardized ecotoxicological research provides valuable information to predict whether these pesticides possibly pose a threat to the organisms living within these ditches, in particular macro-invertebrates. However, knowledge on how mixtures of these agrochemicals affect macro-invertebrates under realistic abiotic conditions and with population and community complexity is mostly lacking. Therefore we examined here, using a full factorial design, the population responses of macroinvertebrate species assemblages exposed to environmentally relevant concentrations of three commonly used agrochemicals (for 35days) in an outdoor experiment. The agrochemicals selected were an insecticide (imidacloprid), herbicide (terbuthylazine) and nutrients (NPK), all having a widespread usage and often detected together in watersheds. Effects on species abundance and body length caused by binary mixture combinations could be described from single substance exposure. However, when agrochemicals were applied as tertiary mixtures, as they are commonly found in agricultural waters, species' abundance often deviated from expectations made based on the three single treatments. This indicates that pesticide-mixture induced toxicity to population relevant endpoints are difficult to extrapolate to field conditions. As in agricultural ditches often a multitude (approx. up to 7) of agrochemicals residues are detected, we call other scientist to verify the ecological complexity of non-additive induced shifts in natural aquatic invertebrate populations and aquatic species assemblages.
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•Combined effects of agrochemicals were assessed in outdoor mesocosms inoculated with aquatic invertebrate assemblages.•Environmentally realistic concentrations of binary mixtures showed additive species’ responses.•Tertiary mixtures affected species’ responses indescribable from cumulative responses of the single exposures treatments.•This indicates that in agricultural ditches, non-additive induced shifts in aquatic invertebrate assemblages might occur.