Relações de fatores ambientais de habitats físicos com riqueza, distribuição e conteúdo alimentar de macroinvertebrados bentônicos em riachos decabeceira no Cerrado

Abstract

Stream ecosystems are heterogeneous and complex. The physical conditions vary from headwater to mouth, including characteristics of width, depth, slope, flow velocity, temperature and energy. These variations and nutrient dynamics contribute to determine the functional composition and distribution of macroinvertebrates. The objectives of this thesis were to assess how environmental variables of physical habitats explain (i) the richness and distribution of Ephemeroptera, Plecoptera and Trichoptera (EPT) and (ii) the food items found in the stomach contents of larvae of Phylloicus (Plecoptera: Calamoceratidae). We sampled benthic macroinvertebrates cummunities, quantified physical habitats an measured physicochemical variables of water quality in 80 randomly selected sampling sites in two watersheds in the Cerrado (Upper Araguari River Basin and Upper São Francisco River Basin), southeastern Brazil. Habitat metrics bankfull width, percentage of pebbles, proportion of shelters, slope, percentage of slow flow, wetted area width and dissolved oxygen were selected by multiple regression models (MLR) and contributed significantly to explain the EPT richness in both basins. Physical habitats metrics were more important than water quality variables in the structuring EPT genera in the two basins. We studied the diet of Phylloicus considering five instars and six categories of food items in the gut content (CPOM - coarse particulate organic matter, FPOM - fine particulate organic matter, algae, animal tissue, plant tissue and mineral material). We showed through our statistical analyses that CPOM content was higher in the Phylloicus larvae of streams of Upper São Francisco River Basin, and it varied between streams and between instars larval in the two basins. FPOM was higher in the larvae of streams of Upper Araguari River Basin and varied between streams in the two basins; mineral material content was higher in the larvae of streams of upper Araguari and varied between streams in the two basins. The main physical habitat metrics related to food items were mean bankfull width, mean width x depth, percentage of total organic matter, riparian cover and shelter as the presence of large wood debris. Phylloicus larvae showed different feeding strategies in the two basins. This thesis showed the importance of physical habitats in the distribution of EPT richness and relations of habitats with the gut contents of Phylloicus larvae. The results of this thesis contribute with information regarding the influences of physical habitat for structuring benthic macroinvertebrate communities and functional trophic groups in aquatic ecosystems.