Attenuation of insecticide impact by a small wetland in a streamdraining a horticultural basin in Argentina

Abstract

Horticulture has greatly increased in Argentina in recent decadesmainly due to increasing greenhouse utilization and agrochemical consumption, thus representing a threat to adjacent water bodies. Riparianwetlands, however, could attenuate agrochemical contamination. The present work therefore compared insecticide concentrations in bottomsediments in addition to sediment toxicity to the amphipod Hyalella curvispina and investigated the macroinvertebrate composition upstreamand downstreamfroma naturalwetland in a small streamdraining a basin undergoing intense horticultural production. The wetland surface was covered by macrophytes, mainly Thypha sp., and the insecticide concentrations measured downstream from the wetland were significantly lower, at roughly 19% of the upstream values. The growth rates of H. curvispina were significantly higher when exposed to the sediments downstream fromthe wetland,while themacroinvertebrate-assemblage composition was significantly different upstream and downstream: the snail Pomacea canaliculata was the dominant species upstream while the amphipod H. curvispina was dominant downstream. Pomacea canaliculata is often the dominant species in the regional streams draining agriculture and horticultural basins. Hyalella curvispina is sensitive to pesticide toxicity and is often dominant in streams draining extensive livestock basins and within a biosphere reserve.We conclude that riparianwetlands effectively attenuate horticulture contamination in pampean streams and should therefore be preserved and restored.