Influence of landscape on assemblages of Chironomidae in Neotropical streams

Abstract

Landscape is important in determining the composition of aquatic assemblage, and benthic in- vertebrates, particularly Chironomidae, are often used as bioindicators of environmental quality because their occurrence and distribution are influenced by different land uses. The objective of this study was to evaluate the influence of different land uses, considering three landscape scales (drainage basins, riparian buffer and streams), on chironomid assemblage. We sampled streams located in an agricultural matrix by collecting chir- onomid larvae and water samples and performed a landscape analysis using Geographical Information System techniques. The drainage basins had a high percentage of agricultural land use; in all of the drainage basins studied, 79% of the riparian buffer was not in accordance with Brazilian law. Cricotopus proved to be a good indicator of the agricultural conditions, whereas Thienemanniella and Rheotanytarsus proved to be indicators of exposed soil. Lopescladius was more sensitive to disturbance and was positively correlated with the presence of riparian vegetation. Although the variables at the local scale (stream) were responsible for a major change in the assemblage, the landscape attributes at large scales (drainage basin and riparian buffer) generated significant effects on Chironomidae fauna. Our results suggest the importance of the conservation of two larger landscape scales to support the equilibrium and maintenance of aquatic assemblage.