Land use effect on invertebrate assemblages in Pampasic streams (Buenos Aires, Argentina)

Abstract

Agriculture and livestock may contribute towater quality degradation in adjacent waterbodies andproduce changes in the resident invertebrate composition.The objective of the present study was to assessland use effects on the stream invertebrate assemblagesin rural areas of the Argentine Pampa. The four samplingevents were performed at six sites in four streamsof the Pampa plain; two streams were sampled inside abiosphere reserve, and another one was surrounded byextensive livestock fields. The fourth stream was sampledat three sites; the upstream site was adjacent toagricultural plots, the following site was adjacent to anintensive livestock plot and the downstream site wasadjacent to extensive breeding cattle plots. Higher pesticideconcentrations were found at the site adjacent toagricultural plots and higher nutrient concentrations atthe sites adjacent to agricultural and intensive breedingcattle plots. The invertebrate fauna were also different atthese sites. Multivariate analysis showed a relationshipbetween nutrient concentrations and taxonomic composition. Amphipoda (Hyalella curvispina)wasthe dominant group in the reserve and extensive breedingcattle sites, but was not present in the agriculturalsite. Also, Chironomidae were absent from the agriculturalsite while present at other sites. Gasteropoda(Biomphalaria peregrina), Zygoptera, and Hirudineawere dominant at the most impacted agricultural andintensive breeding cattle sites.