Avaliação da condição ambiental de reservatórios da região semiárida através de métricas taxonômicas e funcionais de Chironomidae (Insecta: Diptera)

Abstract

Reservoirs are artificial systems created to store water for various social and economic purposes. However, intense anthropogenic pressures in these environments can lead to the loss of ecosystem services. Therefore, it is essential to adapt tools to assess the environmental condition of these ecosystems. The objective of this study was to adapt an Integrated Disturbance Index (IDI) to establish less and more disturbed sites, and thus select taxonomic and functional metrics of Chironomidae for an assessment of the environmental condition of reservoirs in the Brazilian semiarid region. We used a database from the Benthic Ecology laboratory of UEPB, based on collections conducted in six semiarid reservoirs: Sabugí, Cruzetas, Passagem das Traíras, belonging to the Piancó-Piranhas-Açu river basin, and Poções, Sumé, and Cordeiro, belonging to the Paraíba River basin. Collections were made in June and September of the years 2014 and 2019. To compose the IDI, we combined local variables (phosphorus, % nitrogen, % organic matter, and % silt+clay) and variables from a 100m buffer around each sampling site (% built area, % agriculture, % pasture, % exposed soil) to obtain a disturbance gradient of the sites. After establishing the least and most disturbed sites, we used PERMANOVA analysis to distinguish the sites based on the considered taxonomic and functional metrics. Individual abundance, taxonomic richness, Margalef index, and filter-feeding trophic group were the most sensitive metrics in 2014, and only body size G2 (2.5 - 5mm) showed significant differences between the least and most disturbed condition in 2019. Changes occurring during the period of extreme drought resulted in local alterations within and around the reservoirs between 2014 and 2019, causing changes in site conditions. Thus, we conclude that the Integrated Disturbance Index was a robust tool capable of selecting biological metrics sensitive to anthropogenic alterations at different spatial scales. This is a first and essential step toward the development of effective biomonitoring tools and the advancement of conservation and management measures for reservoirs in the Brazilian semiarid region.