Adaptation of the biotic index for macroinvertebrates in tributaries of the Itacaiúnas River

Abstract

The streams in the Amazon region play a pivotal role in maintaining biodiversity and providing ecosystem services, but they are vulnerable to a range of anthropogenic impacts. The objective of this study is to develop a biotic index based on macroinvertebrate communities for the purpose of assessing the ecological integrity of streams in the Tapirapé-Aquiri National Forest, an area that is threatened by mining and livestock activities. Sampling was conducted in 16 streams with varying degrees of impact over the course of two dry seasons in years of 2022 and 2023. Macroinvertebrates were collected from leaf litter habitats using a kick-net collector. Environmental conditions were evaluated through the adapted habitat integrity protocol and the calculation of integrated disturbance indices. The final index was composed of: genus richness, percentage of predators, and percentage of scrapers. No stream was classified as "preserved", with seven streams rated as "acceptable", eight as "impacted", and one as "severely impacted". The analysis indicated that activities such as mining and livestock farming are strongly associated with environmental degradation of high-altitude streams in the Amazon. Although the index showed moderate accuracy in cross-validation, it proved to be a promising tool for monitoring environmental quality in tropical regions. Future studies should consider integrating additional factors, such as habitat connectivity and hydrological dynamics, to enhance the index's sensitivity and support conservation policies.