Impacts of sediment-bound synthetic pyrethroids on non-target aquatic macroinvertebrates

BOYLE, R.; LONG, S.; MARSHALL, S.; BALLESTEROS, M.L; PETTIGROVE, V.; HOFFMANN, A.A.,

Brisbane

Congreso; 2nd SETAC Australasia Conference; 2012

Synthetic pyrethroid pesticides enter waterways through drift or in runoff, and rapidly bind to sediment, where they potentially threaten macroinvertebrates through chronic exposure. While these pesticides are highly acutely toxic to macroinvertebrates, the effects of chronic exposure are less well understood. There is also a need for biomonitoring tools that identify synthetic pyrethroid contamination, especially subcellular biomarkers that can be linked to organism and community level effects. The aim of the study is to identify and link the effects of two synthetic pyrethroids at these three organizational levels. Laboratory toxicity tests and field microcosms examined the effects of sediment‐bound bifenthrin and permethrin on survival and life cycle parameters of aquatic macroinvertebrates. This dual‐pronged approach incorporates exposure in both controlled and natural conditions. In laboratory toxicity tests, clean field‐collected sediment was spiked with bifenthrin or permethrin at nominal concentrations of 12.5 ‐ 50 μg/kg. Second instar Chironomus tepperi larvae were exposed to the spiked sediment. At 50 μg/kg of bifenthrin, the number of larvae surviving after five days was lower than that of the controls, however the body length of surviving larvae was not affected. Two weeks of exposure to bifenthrin did not affect the number or sex ratio of emerged adults. Results for permethrin will be discussed, as will results of lab exposures to contaminated field‐collected sediment with comparable concentrations of pesticides. In the microcosm experiments, clean sediment was spiked with permethrin/bifenthrin at 8.9 μg/kg to 500 μg/kg. This sediment was placed in wetland microcosms and colonised by macroinvertebrates. Emerged adults were collected over several weeks and identified to species level. The chironomid Paratanytarsus grimmii showed significantly reduced emergence at concentrations of permethrin above 35.5 μg/kg. Results for bifenthrin will be discussed, as will the links between subcellular biomarkers and effects on whole organism parameters and community composition.