Impacts of exposure to mine tailings on zooplankton hatching from a resting egg bank.

Abstract

In the last five years, two colossal envi- ronmental disasters involving iron-enriched mine

tailings have occurred in Brazil, affecting many

aquatic ecosystems over the short, medium and long- terms. This study investigated whether these iron- enriched mine tailings affect the main biotic strategy

to restore zooplankton populations affected by severe stress, i.e., hatching of dormant stages. A 30 day hatching experiment was conducted, using a resting

egg bank from a natural lake, exposed to 3 concen- trations of mine tailings: control (0 g), T25 (25 g) and

T50 (50 g). A total of 22, 15 and 16 species hatched in the control, T25 and T50, respectively. Conochilussp., Filinia terminalis, Hexartha mira, Bosmina longirostris and Ceriodaphnia silvestrii hatched only in the control, which suggests that these species are sensitive to any concentration of mine tailings. A gradual decrease in richness and hatchling abundance was recorded, from the control (8.0 ± 1.0 SE species and 1597 ± 73.9 hatchlings) to T25 (4.6 ± 1.2 species and 1279 ± 136.5 hatchlings) and then to T50 (2.3 ± 1.2 species and 603.3 ± 61.9 hatchlings). Our results suggest that exposure of zooplankton resting eggs to iron-enriched mine tailings may negatively impact these egg banks in natural ecosys- tems, with potential impacts on the restoration of zooplankton communities after even short-term exposures.