Development and validation of a Biotic Index for evaluation of environmental quality in the central region of Argentina

The Suquia River (Cordoba, Argentina) has become an important issue because it flows into Mar Chiquita Lake, one of the largest saline lakes in the world. This water body, together with the expansive swamps of the Dulce River on the northern shore and the mouth of Suquia and Xanaes River, is considered one of the most important wetlands in Argentina in terms of biodiversity in a range of freshwater to very saline environments. Nevertheless, the presence of densely populated urban settlements and the increasing environmental impact due to anthropogenic activities characterize the central and lower sections of Suquia River Basin. Fishes are particularly affected and change their distribution and abundance as a consequence of the environmental deterioration. We collected information on fish fauna to develop and validate a Biotic Index to assess degradation of the Suquia River Basin. We classified fish species according to their sensitiveness or tolerance to environmental degradation, based on their distribution and abundance variations along a water quality gradient in order to design a Biotic Index for Suquia River Basin. The set of metrics used in the Biotic Index calculation was conformed by: the abundance of Astyanax eigenmanniorum, Rineloricaria catamarcensis, Gambusia affinis and Cnesterodon decemmacultus, the proportion of sensitive species richness, and the proportion of tolerant species richness. They clearly distinguished between the impaired and referenced sites. We demonstrated that it is possible to use fish as indicators of water quality in Cordoba Province (central part of Argentina) in order to carry out rapid and relatively inexpensive monitoring and conservation programs. The application of this Biotic Index showed that fish assemblages reflect the watershed conditions and are sensitive to changes in water quality across the environmental gradient.