A turbidez como fator determinante na estruturação do fitoplâncton do rio Doce após o rompimento da barragem de Fundão

Abstract

In 2015, Brazil experienced its worst environmental catastrophe with the collapse of the Fundão tailings dam in the waters of the Rio Doce basin. In this context, this study assessed the phytoplankton in sections of the Doce, Santo Antônio, Piranga, and Carmo rivers. We selected points at the headwaters of the Rio Doce, pairs in lotic environments (upstream and downstream of tributaries), and ten points in lentic and semi-lentic environments formed by the Risoleta Neves, Baguari, Aimorés, and Porto Estrela Hydroelectric Plants (UHEs). Samples were collected quarterly from April 2022 to January 2023. Qualitative analysis revealed differences between samples collected in rivers and reservoirs, as well as variations in phytoplankton composition and diversity among different reservoirs. The Cryptophyceae class stood out for its dominance in different environments, indicating the importance of turbidity as a selective factor, restricting the development of other groups. Diversity analysis highlighted the importance of beta diversity on smaller scales, showing high heterogeneity among different regions of the same reservoir. Seasonality was identified as the main factor influencing phytoplankton diversity in the Doce river, surpassing spatial factors such as reservoir location and distance from the dam breach site. Additionally, the study emphasized that the Aimorés Plant, with a distinct management system, exhibited intra-reservoir differences, highlighting the impact of reduced flow on phytoplankton in this context. The study found that seasonality plays a fundamental role in phytoplankton dynamics and that the effects vary according to the environment and management system of each reservoir, providing valuable information to guide conservation and environmental recovery measures in the region.