Domestic Sewage and Oil Spills in Streams: Effects on Edaphic Invertebrates in Flooded Forest, Manaus, Amazonas, Brazil

Abstract

The influence of the aquatic environment on the terrestrial environment in areas subject to natural seasonal flooding has been little studied; especially lacking are studies that include anthropogenic impacts on these areas. Soil samples (including a superficial layer of litter) were collected between September 2000 and May 2001 on the banks of three streams in Manaus, Amazonas, Brazil in four seasons of the year, as determined by the flood pulse of the Rio Negro. The objectives of this study were to verify how an oil spill and urban sewage affect the abundance and richness of edaphic invertebrates on the stream banks and if these forms of pollution also influence the effect of the flood pulse on the natural community. Our results suggest reductions in the abundance and richness of edaphic invertebrates in the impacted areas and changes in the composition of edaphic invertebrate communities show a disturbance gradient from the banks of the unimpacted stream (Cristalino) to the banks of the stream that was impacted by the oil spill (Cururu), with more similar patterns occurring in impacted streams. The streams also showed effects of the flood pulse. Acarina, Entomobryidae, Formicidae, Staphylinidae and Carabidae were the only taxa that occurred in all three of the areas studied and in all of the sampling periods.