Influence of watershed land use and riparian characteristics on biological indicators of stream water quality in southeastern Brazil

Abstract

Land use changes and riparian corridor degradation strongly influence the water quality of low-order streams at different spatial scales. Stream water quality can be analyzed by chemical and biological indicators, but which are generally evaluated separately. Here, we evaluated if anthropogenic alterations at distinct spatial scales (estimated by land use, riparian zone composition, and riparian forest structure) influenced stream water quality according to chemical and biological (e.g., fish and macroinvertebrate) indicators in a tropical rural landscape (SE Brazil). We found higher total nitrogen concentrations and electric conductivity in streams with land use dominated by pasture and narrower riparian forests, higher diversity of macroinvertebrates and dissolved oxygen concentrations in streams with higher cover and width of riparian forests although land use was dominated by sugarcane, whereas fish diversity was related with natural vegetation cover at the watershed scale. Thus, stream water quality indicators responded to variation at both scales studied, with interactions between land use and riparian corridor characteristics. These results suggest that different degradation drivers may account for variation of different types of indicators (chemical vs. fishes vs. macroinvertebrates) at distinct spatial scales.