Zooplankton dynamics and pesticide influence in a stream basin affected by land use change in the Argentine Espinal region

Abstract

Watercourses in agricultural areas often receive diffuse pesticide inputs through drift, runoff, infiltration, and erosion. Weassessed the qualitative and quantitative response of the zooplankton community to pesticide exposure in the Estacas streambasin, Argentina, over two years at seven sites. Surface water and zooplankton were sampled every two months, and 125pesticides were screened and classified by detection frequency. A total of 24 pesticides and the AMPA metabolite weredetected. Dominant pesticides included atrazine, glyphosate, and AMPA in the first year, and metolachlor and S-metolachlorin the second. Sixty-three zooplankton taxa were identified, primarily rotifers (65%) and cladocerans (35%), with peak richnessat one site during spring of the second year. Copepods were present but less frequent, with Cyclopoida being the mostcommon. Microzooplankton dominated across sites, with higher densities in the first year. Canonical Correlation Analysisshowed that glyphosate and atrazine were probably associated with microzooplankton abundance in the first year, whilemetolachlor and S-metolachlor were associated with copepod and rotifer populations in the second. This study representsthe first report on zooplankton community responses to pesticide gradients in this basin, providing crucial information onthis bioindicator’s sensitivity to land use changes and pesticide application timing. These insights can help the developmentof environmentally sustainable agricultural practices.