Chronic trace metals effects of mine tailings on estuarine assemblages revealed by environmental DNA

Abstract

Mine tailing disasters have occurred worldwide and contemporary release of tailings of large proportions raise concerns of the chronic impacts that trace metals may have on the aquatic biodiversity. Environmental metabarcoding (eDNA) offers an as yet poorly explored opportunity for biological monitoring of impacted aquatic ecosystems from mine tailings and contaminated sediments. eDNA has been increasingly recognized to be an effective method to detect previously unrecognized small-sized Metazoan taxa, but their ecological responses to environmental pollution has not been assessed by metabarcoding. Here, we evaluated chronic effects of trace metal contamination from sediment eDNA of the Rio Doce estuary, 1.7 years after the Samarco mine tailing disaster, which released over 40 million m3 of iron tailings in the Rio Doce river basin. We identified 123 new sequence variants environmental taxonomic units (eOTUs) of benthic taxa and an assemblage composition dominated by Nematoda, Crustacea and Platyhelminthes; typical of other estuarine ecosystems. We detected environmental filtering on the meiofaunal assemblages and multivariate analysis revealed strong influence of Fe contamination, supporting chronic impacts from mine tailing deposition in the estuary. This was in contrast to environmental filtering of meiofaunal assemblages of non-polluted estuaries. Here, we suggest that the eDNA metabarcoding technique provides an opportunity to fill up biodiversity gaps in coastal marine ecology and may become a valid method for long term monitoring studies in mine tailing disasters and estuarine ecosystems with high trace metals content.

Metal contamination and oxidative stress biomarkers in estuarine fish following a mine tailing disaster

“…This is a key advantage of the use of these biomarkers, as most contaminated areas lack baseline studies as in the studied estuary. Thus, the observed biomarker responses are an additional support for the indication of chronic trace metal contamination effects in this ecosystem (Gusso-Choueri et al, 2018;Bernardino et al 2019).…”

“…The nature of the disaster made the establishment of control sampling sites impossible as the entire estuary was impacted. However, multiple evidence is available concerning the increase in sediment contamination and its impacts on benthic assemblages and effects on fish ecology due to the impact event (Gomes et al, 2017;Bernardino et al, 2019;Andrades et al, 2020). Qualitative fish sampling was conducted in the estuary in August, 2017 with the aid of a gillnet (5 cm internodes).…”

“…The location of samples are part of a long-term (4-year) monitoring of the estuary that include preimpact and post-impact monitoring (Gomes et al, 2017;Bernardino et al, 2019); which provides a temporal evidence for the increased contamination of estuarine sediments associated with the tailings deposited after the disaster in 2015. Surface water physicochemical parameters, namely salinity, temperature, pH and total dissolved solids (TDS) were measured in situ using a HANNA HI9829 multi-parameter probe (Table 1).…”

“…The arrival of tailings in the Rio Doce estuary caused immediate impacts to biodiversity and a rapid (<2 days) accumulation of Fe and associated trace metals (Cr, Pb, Mn, and Al) in estuarine sediments (Gomes et al, 2017;Queiroz et al, 2018;Andrades et al, 2020). Nearly two years (2017) after the initial impact, there is evidence for continued chronic effects from trace metal contamination on benthic assemblages (Bernardino et al, 2019), but the extent of the metal contamination and sublethal effects to fisheries in the estuary remain to be determined.…”

Gypsum Amendment Induced Rapid Pyritization in Fe-Rich Mine Tailings from Doce River Estuary after the Fundão Dam Collapse

“…Since 2015, when the Fundão tailings dam in Brazil collapsed (the largest dam failure of the world, known as "Mariana disaster"), metal contamination has been identified as one of the most concerning phenomena along the Brazilian Coast [13][14][15][16][17]. After the Mariana disaster, a huge amount of Fe-rich mining tailings entered the Doce River estuary increasing the trace metal content in the soil [14].…”