Species at Risk (SPEAR) index indicates effects of insecticides on stream invertebrate communities in soy production regions of the Argentine Pampas

HUNT, L; C. BONETTO; N. MARROCHI; SCALISE, A; FANELLI, S.; LIESS, ; M. LYDY; M. LIU; V. RESH

THE SCIENCE OF TOTAL ENVIRONMENT

Elsevier

Año: 2017 vol. 580 p. 699 - 709

0048-9697

Weinvestigated relationships among insecticides and aquatic invertebrate communities in 22 streams of two soyproduction regions of the Argentine Pampas over three growing seasons. Chlorpyrifos, endosulfan, cypermethrin,and lambda-cyhalothrinwere the insecticides most frequently detected in streamsediments. The Species at Risk(SPEAR) pesticide bioassessment index (SPEARpesticides) was adapted and applied to evaluate relationships betweensediment insecticide toxic units (TUs) and invertebrate communities associated with both benthic habitatsand emergent vegetation habitats. SPEARpesticides was the only response metric that was significantlycorrelated with total insecticide TU values for all three averaged data sets, consistently showing a trend of decreasingvalues with increasing TU values (r2 = 0.35 to 0.42, p-value = 0.001 to 0.03). Although pyrethroidswere the insecticides that contributed the highest TU values, toxicity calculated based on all insecticideswas betterat predicting changes in invertebrate communities than toxicity of pyrethroids alone. Crustaceans, particularlythe amphipod Hyalella spp., which are relatively sensitive to pesticides, played a large role in the performanceof SPEARpesticides, and the relative abundance of all crustaceans also showed a significant decreasing trend withincreasing insecticide TUs for two of three data sets (r2 = 0.30 to 0.57, p-value = 0.003 to 0.04) examined. Forall data sets, total insecticide TU was the most important variable in explaining variance in the SPEARpesticidesindex. The present study was the first application of the SPEAR index in South America, and the first one to useit to evaluate effects of pesticides on invertebrate communities associated with aquatic vegetation.