Evaluating macroinvertebrate metrics for ecological assessment of large saline rivers (Argentina)

Benthic macroinvertebrates have been used around the world as indicators of the biological quality of freshwater habitats. Because of the intensive deterioration of waterbodies as a result of different land uses, indicators are used for environmental monitoring, control and remediation. The aim of this study was to assess (1) the sensitivity of taxonomical metrics and (2) functional traits to select the most appropriate for evaluating environmental impacts on rivers with high salinity and (3) to propose a multimetric index based on the selected metrics. Information from a preexisting database on twenty-eight sites in the Salado River basin (Argentina) was used. One hundred and twenty-three metrics were calculated to assess sensitivity to different land uses along the gradient of habitat condition, from low-disturbed (reference), to medium-disturbed (agricultural and industrial) and high-disturbed (agricultural, industrial and urban). This gradient was defined by available information in original articles and by quantifying the percentage of the different land uses. Filtering collectors (%), Gathering collectors (%), Ostracoda density, Limnodrilus hoffmeisteri/Total density, Naididae (%), Tubifex/Total density and Pristina/Total density were the metrics that distinguished the different land uses along the gradient of habitat condition. These metrics were used to propose a macroinvertebrate multimetric index in saline rivers: Index of Benthic Invertebrates in Saline Rivers (IBIS). Thus, this study provides a useful tool for management and monitoring of saline rivers and diagnoses of salinized environments.