Assessing disruption of longitudinal connectivity on macroinvertebrate assemblages in a semiarid lowland river

Marta Leiva, Mercedes Marchese, Liliana Diodato, Héctor Tévez, María Eugenia Espeche


 Aim: Our aim in this study was evaluate the effects of flow regulation for irrigation on the macroinvertebrate assemblages in a semiarid river. Methods: We sampled two reaches in Dulce River, one of the selected reaches was placed upstream the diversion dam Los Quiroga and the other downstream in the assessment of the fluvial discontinuity.

We assess the differences among reaches and stations, environmental variables, invertebrate density, richness and Shannon-Wiener index applying non-parametric analyses of variance Kruskal Wallis. The similarity percentage analysis (SIMPER) was used to identify which species contributed to the dissimilarities on macroinvertebrate assemblages structure. Canonical correspondence analysis (CCA) was performed with the total set of samples to explore macroinvertebrate distribution in reaches and associations of the assemblages with habitat variables. Results:  The density, richness and Shannon index values did not show differences between the reaches upstream and downstream of derivation dam. Beta diversity (Whittaker) was 0.72 among upstream sites, 0.56 among dowstream sites and higher species turnover (0.73) was obtained between both reaches. The Canonical Correspondence Analysis explained 43.15% of the variance differentiating upstream sites explained by higher values of organic matter of bottom sediments and discharge, high density of  Nais communis, Bothrioneurum americanum, Pelomus, Stephensoniana trivandrana, Pristina menoni, P. jenkinae, P.longidentata,  P. americana, Dero obtusa , Endotribelos, Heleobia and Turbellaria. The downstream stations  were associated to coarser substratum and higher density of Lopescladius, Polypedilum, Cricotopus, Thienamaniella, Cryptochironomus, Baetidae, Nematoda and  Corbicula fluminea. Conclusions: The low-flow disturbance had effects on the composition on the benthic invertebrate assemblages, but also attributes (such as density and richness) showed a lower variability probably because of taxa replacement. 


flow regulation; water deviation; river ecology; macroinvertebrates diversity; Dulce River

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