Potential habitats versus functional habitats in a lowland braided river (Cordoba, Argentina)

摘要

The benthic community of a braided reach of a lowland river was studied with the aim to identifyfunctional habitats through the assessment of potential habitats. Functional habitats were defined consideringphysical and biological characteristics. Three reaches of the Chocancharava River (Cordoba, Argentina)were selected and six potential habitats were sampled during high and low water periods. Hydraulic and en-vironmental variables were also registered in each sampling occasion. Taxonomic composition, macro-invertebrate abundance, richness, diversity and evenness were estimated for each identified functional habitat.TWINSPAN analysis was applied separately for two data sets (high water and low water period). This analy-sis showed that samples of the low water period were mainly grouped in relation to three habitats units:vegetated habitats, unvegetated habitats and habitats related to bars. These three habitats were consideredfunctional habitats. The whole biological and environmental data sets were ordinated by CanonicalCorrespondence Analysis (CCA) showing a significant relationship between benthic assemblages and en-vironmental variables. This analysis grouped samples in relation to the functional habitats identified byTWINSPAN and indicated that the most influential environmental variables explaining the ordination were:current velocity, depth, substrate size and cover percent of rooted emergent macrophytes. Faunal compositiondetermined by CCA for each functional habitat was in agreement with the results obtained by the RelativePreference Index (RPI). Factorial ANOVAs showed that abundance, taxonomic richness, diversity and even-ness were different among the functional habitats and that the community attributes were influenced by theeffect of the hydrological period and habitat. As the functional habitat approach provides useful tools inmanagement and river rehabilitation the use of this methodology may allow to develop more appropriaterestoration strategies to be applied in altered lowland reaches.