Evaluation of freshwater benthic communities: a case study in an urban

Abstract

The environmental damage suffered by urban water bodies and the need for public water supply result in a greater interest in techniques that enable water treatment in an efficient and ecological way, such as River Bank Filtration (RBF). This technique uses the soil as a filtering medium, as well as the biological activities of organisms that dwell in the Hyporheic Zone (HZ), the zone of interaction between the surface water body and its underlying aquifer. Knowledge of sediments and hyporheic organisms is indispensable to study RBF. The present paper aimed to characterize the HZ of the middle section of Beberibe river (Pernambuco State, Brazil) in its sedimentological and biological aspects, with sampling druing the rainy and dry seasons, in two distinct sampling sites, one in a conserved area and the other in a highly urbanized area. Biological characterization was performed at the level of large taxonomic groups of meiofauna, accounting for 982 individuals, with the three most abundant taxa being Nematoda, Annelida, and Rotifera. Permutational Analysis of Variance (PERMANOVA) statistical tests were performed, showing significant differences for the season and point factors (p < 0.05) in relation to abundance. The highest concentration of individuals and total organic matter were seen in the rainy season, especially at the point located in the urbanized area. With sedimentological characterization by grain size tests of the hyporheic sediments, the predominance of silt was observed during the rainy season, and sandy during the dry season. It was concluded that the main factor that influenced the structure of the meiofauna community was the release of domestic effluents. The information obtained by the present work helps to understand some features of the HZ, which is essential for RBF or other techniques that use the interstitial matrix.