Structure of benthic macroinvertebrate assemblages on a gradient of environmental integrity in Neotropical streams

Marcia Thais Suriano,Alaide Aparecida Fonseca-Gessner

doi:10.1590/s2179-975x2013000400007

Abstract

AIM: This study investigated the taxonomic composition of the benthic macroinvertebrates in streams to evaluate how this fauna reflects the various uses of the soil and to identify which groups of macroinvertebrates might be taken as characterizing each situation under study. METHODS: To achieve these objectives, 29 streams were collected and inserted in regions with different conservation using Surber sampler. Analyzes were performed of environmental variables (Principal Components Analysis - PCA) and taxonomic structure of the community (taxon richness, numerical abundance and Multidimensional scaling - MDS). RESULTS: EPT group (orders Ephemeroptera, Plecoptera and Trichoptera) and the Coleoptera exhibited greater numerical abundance and taxon richness in streams located in reference areas. In contrast, dipteran larvae, especially the chironomids, along with immature odonates, were more abundant in streams in areas suffering from a lack of riparian forest. Multidimensional scaling analysis (MDS) revealed an environmental gradient, on which the streams within the Atlantic forest formed a tightly clustered group, as did those in semideciduous forests. However, the latter group occupied an intermediate position between the Atlantic forest streams and those in areas disturbed by human activity. Among these areas there were no specific clusters by monoculture. CONCLUSIONS: Among the groups of streams defined by the types of land use in the adjacent areas, the state of integrity was found to decline from Atlantic rainforest, through semi-deciduous forest and then pasture, to the monocultures of eucalypts and sugarcane.

Highlights

Aquatic systems in a given area of land acquire unique functions that relate to the characteristics of the drainage basin involved
There is a clear pattern of separation of the streams located in low-impact areas in the Conservation Units (Cus), characterized by high dissolved oxygen content, hard beds of boulder, gravel and sand and fast-flowing water, from those in areas dominated by extensive monoculture or cattle-grazing (Figure 2)
Turbellaria and Gastropoda were prominent in streams running through fields of pasture. It was evident from the results of principal components analysis (PCA) that physical characteristics such as the composition of the stream bed and the current velocity were determining factors in the separation of the streams into two groups: those classified as well conserved and those subject to human interference

Summary

Introduction

Aquatic systems in a given area of land acquire unique functions that relate to the characteristics of the drainage basin involved. Those characteristics, in turn, depend on the local geomorphology, climate of the region, type of vegetation and amount of human activity in the zones adjacent to the watercourses (Wetzel and Likens, 1991). The environmental factors are correlated with each other and determine the composition and taxon richness of the biological community. Both biological and ecological data are needed for an understanding of the relations among species and between them and their habitat. With the aid of such observations it is possible to determine the degree of sensitivity of organisms in lotic habitats to various types of anthropic disturbance, for the purpose of assessing the state of conservation of the environment under the impact of the different land uses, especially where the integrity of riparian forest is affected

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Conclusion