Estrutura e função de comunidades de insetos aquáticos em um sistema fluvial de Mata Atlântica no sudeste brasileiro, com especial referência à avaliação do conceito de continuidade de rios (CCR)

Abstract

The present work intends to contribute to the understanding of a middle-sized river ecosystem placed in the Atlantic Forest of southeastern Brazil. A brief review of some concepts about communities is presented. First, as well as the description of the major models that explain river ecosystem function, especially the River Continuum Concept from VANNOTE et. al (1980). The general foundations of these models are displayed in a way that allows an easy comparison with the results presented herein. Next, the results about the composition and structure of the aquatic insects communities along the longitudinal gradient of the Macaé river basin are exhibited. The spatial distribution of these communities, from a ritral section about 11 0üm high to a potamal area at about 20m high, were ali analysed by means of Multivariate Analysis (Correspondence Analysis and Cluster Analysis). The results indicate that the aquatic macroinvertebrate fauna of the Macaé river exhibits a gradual change of species along its profile, being divided in two distinct portions: a characteristic community from the higher section, from the 1 s t to the 4 th orders (sensu Strahler) and another typical of the lower orders (5th and 6th). The highest biological diversities for the severa! aquatic insects were found between the 2 nd and 4 th orders. The community has not exhibited a temporal replacement of its constituent species, nor a significant change in the community structure during the year, reflecting a highly stable organization. The analysis of the distribuition over the different substrates has shown a disarrangement of the fauna at the beggining of the rainy season, as a result of the disturbance caused by the intensa rains. At last, the adequacy of the Macaé river basin to the RCC was analysed through the evaluation of some of its predictions. The results showed that several assumptions of the RCC were partially confirmed, such as: the highest diversity was observed in sections where there is a transition from a predominantly heterotrophic zone to an autotrophic one (4th order). lt was seen that there is a trend in increasing the fine particulate organic matter as well as a decreasing in the coarse particulate organic matter, along the longitudinal gradient of the river. The biomass variation of the trophic functional categorias has shown a picture similar to the modifications predicted by the RCC, according to the increase in size of the river.