Richness and abundance of aquatic macroinvertebrates associated with different phytophisiognomies on Barreiras Formation

Abstract

In association with expansion of cities and urban centers and increasing human population and agribusiness activities, we observe that the consumption of water has increased while its quality decreases. The consequences of human activities on rivers, streams and creeks have been measured using the communities of aquatic macroinvertebrates as bioindicators. The objective of this study was to evaluate the effect of vegetation type on the benthic macroinvertebrate assemblages associated with leaf litter in streams crossing altered and conserved areas. The survey was conducted in August 2014 in streams within and surrounding the area of the Reserva Natural Vale. Samples of organic substrate (litter) were collected in the three different vegetation types (pasture, forest and transition) over the sampled streams. One control stream within forest areas was used. In each sampled point were colected three replicates of litter, totaling 24 samples. Temperature, pH, conductivity, turbidity, dissolved oxygen, total dissolved solids and salinity were measured in water at each point, using a portable multiparameter. Samples of macroinvertebrates associated with leaf litter were collected using Surber colector. In the laboratory, the samples were washed and macroinvertebrates were identified. The statistical analysis used was the Kruskal-Wallis. The physico-chemical variables did not show significant variations in relation to the vegetation type, except for pH, and between the water bodies sampled, except for percentage of O2 saturation. The pH values showed an increase in direction to forests and this may be related to acid-base buffer substances present in this environment. A total of 454 specimens were collected belonging to 15 taxa of Arthropoda (Insecta, Arachnida, Malacostraca), Annelida (Hirundinea and Oligochaeta) and Mollusca (Gastropoda). The community of benthic macroinvertebrates showed higher richness and abundance in the forest, mainly in respect to Ephemeroptera, Plecoptera and Trichoptera groups, which are indicators of good quality of aquatic environments. In the areas of pasture, the highest abundance was Chironomidea and Oligochaeta, considered Macroinvertebrates associated with impacted environments. The data obtained in this study may be related to the fact that forest areas have higher heterogeneity of microhabitats and promote the improvement of water quality, contributing to the maintenance of higher richness and abundance of species, including taxa that are sensitive to environmental changes.