Do metals differentiate zooplankton communities in shallow and deep lakes affected by mining tailings? : the case of the Fundão dam failure (Brazil).

Abstract

The effects of exposure to mining tailings on water quality and biota of tropical lacustrine ecosystems remain poorly understood. We tested the hypothesis that after mining tailing spills, shallow lakes should retain higher metal concentrations in comparison with deep lakes, which might contribute to differentiating species sorting

and community structure of zooplankton in both ecosystems. Surveys were performed in 6 Brazilian lakes af- fected by the Fundão dam failure from October 2018 to September 2019. The shallow lakes showed higher values

of turbidity (19.4 ± 12.9 NTU), conductivity (846.5 ± 1727.1 μS.cm-1), total organic carbon (11.6 ± 4.6 mg.L-1),

total nitrogen (2688.7 ± 2215.6 μg.L-1), iron (2507.5 ± 726.9 μg.L-1), aluminum (419.9 ± 166.5 μg.L-1) and man- ganese (150.8 ± 146.2 μg.L-1) and lower zooplankton richness (9.2 ± 3.2) compared to the deep lakes (13.4 ±

3.0), which showed higher cyanobacteria density (84.7 103 ± 69.3 103 cel.mL-1). We recorded negative relation- ships between zooplankton richness and turbidity, conductivity, iron, zinc and vanadium, indicating that as well

as morphometric characteristics of lakes (area and depth) have an important role in zooplankton richness, the coupling between metals and limnological variables represent decisive environmental filters for species sorting

of zooplankton. The variation-partitioning analysis showed that limnological variables and metals explained zoo- plankton composition, highlighting that metals play major influence on zooplankton composition. We suggest that the shallowness of the lakes should had promoted often resuspension of mining tailings that caused in- creases in metal concentrations in water column. The results indicate that the shallow lakes presented higher vulnerability to mining tailings exposure than the deep lakes, which may have substantially contributed for differentiating zooplankton communities in both ecosystems. This study reveals the need for considering shallow lakes as priority target for conservation among freshwater ecosystems affected by mining tailings.