Limnetica 42

Changes in land use due to human activities lead to disturbances related to sedimentation in aquatic ecosystems. Furthermore, the construction of dams in streams raises concerns about their safety, and the rupture of these structures implies significant impacts. Thus, this article assessed the effects of sedimentation and dam failure on the aquatic macroinvertebrate community in a tropical stream and verified its influence on the structural and functional composition of this assemblage of organisms. Water physical-chemical parameters and macroinvertebrate fauna data were obtained from monitoring data for both the pre- and post-rupture period. Macroinvertebrates were identified at the family level and classified according to functional feeding groups. Structural and functional biological indexes were applied, and data were analyzed using comparison tests, correla­tion matrix, correspondence, and cluster analysis. The results showed that sedimentation resulted in the impoverishment of macroinvertebrate fauna, with the loss of important functional feeding groups, indicating a low environmental quality. Dam failure changed the composition of the fauna, leading to the disappearance of important orders, the appearance of organisms belonging to the order Coleoptera, and the loss of feeding groups with consequent loss of ecological functions. The dam failure was not the only stressor for the studied stream, because it already suffered from small and medium scale disturbances related to sedimentation. However, the rupture of the structure resulted in greater environmental losses, and is considered large scale, implying the need to implement recovery measures in the area.