Effect of Monsoonal Spates on Macroinvertebrate Assemblages in a Subtropical Basin pp. 87-96
Authors: (L.M. Mesa, Instituto Nacional de Limnología (INALI-CONICET), Ciudad Universitaria, Santa Fe, Argentina)
Abstract: The monsoon causes major spates events in streams of Tucumán province in the northwestern of Argentina. I assessed seasonal change in macroinvertebrate community at eleven streams in Lules River basin. Invertebrate samples were collected during dry (September) and wet (March) seasons across two years. I evaluated changes in invertebrate density, taxa number and the reciprocal of Simpson‘s index between periods using ANOVA. Changes in community composition was also explored by non-metric multidimensional scaling. Indicator species analysis was used to evaluate the significance of the association of each taxon with each season. Variability in presence-absence and abundance data of lotic invertebrates between periods was determinated using Bray-Curtis distance. A significant reduction in benthic density and taxa number occurred between seasons, so those community parameters were already low after the monsoon. Community composition showed strong temporal patterns reflecting two clearly distinct groups associated with each period. Twelve taxa were indicative of low flow season, while Camelobaetidius penai, Corydalus sp. and Austrelmis sp. (adult) dominated in high water period. Variability in presence-absence data was lower than abundance reflecting that the main influence of season occurred not in the species composition but in the way in which abundance was distributed among species.