The impact of pesticides on the macroinvertebrate community in the water channels of the Río Negro and Neuquén Valley, North Patagonia (Argentina)

Abstract

Agriculture represents the second most important economic activity in the North Patagonian Region of Argentina and nonselectiveinsecticides are still being used with significant implications to the quality of the environment. The range of concentrations(μg/L) determined for azinphosmethyl, chlorpyrifos, and carbaryl in drainage channels were from non-detected to 1.02,1.45, and 11.21, respectively. Macroinvertebrate abundance and taxon richness in drainage channels were significantly lower inNovember compared to the other sampling months (October, February). The decrease in taxon richness observed in Novemberwas associated with chlorpyrifos and azinphosmethyl peak concentrations. The most remarkable changes were the decrease insensitive taxa such as Baetidae and the increase in some tolerant taxa such as Chironomidae and Gastropoda.For all three pesticides, the acute hazard quotient exceeded the risk criteria for invertebrates. The effects of the three pesticideson aquatic organisms, characterized by joint probability curves, showed that the LC50 of 10% of the species were exceeded fiveand three times by the concentrations of azinphosmethyl and chlorpyrifos during the study period, respectively. However, thecorrelation between the pesticide concentrations and both taxon richness and abundance of macroinvertebrates at each site(irrigation and drainage channels) was indicative that only chlorpyrifos was negatively correlated with both parameters(Spearman r2 − 0.61, p = 0.0051 and Spearman r2 − 0.59, p = 0.0068 for taxon richness and abundance correlation, respectively). We conclude that macroinvertebrate assemblages in drainage channels were highly affected by chlorpyrifos levels.