Monitoring of ichthyoplanktonic community at the Doce River mouth and adjacent marine region in Southeast Brazil after Fundão dam collapse

Abstract

In November 2015, the Fundão dam located in southeast Brazil collapsed, releasing approximately 50 million cubic meters of slurry contaminated with metals into the Doce River, reaching the marine coastal area. The main objective of this study was to analyze the effect of contaminated mud plume after the collapse on the abundance, composition, and diversity of marine ichthyoplankton during the monitoring period of one year. We also aimed to verify the impact of the Doce River discharge, meteoceanographic events, and environmental factors on the abundance of fish eggs and larvae.Samplings were conducted at 32 stations in November 2018, January, April, and July 2019. Water temperature, salinity, dissolved oxygen, nutrients and metals were assessed from samples obtained at the water's surface. Ichthyoplankton were collected at the surface and along the water column using a Neuston and a Bongo nets, respectively. Most of the eggs collected at the surface were non-viable in most sampling periods and areas. A total of 65 families were recorded along the study area, and Engraulidae, Clupeidae, Gobiidae, Carangidae, Labridae, Haemulidae, and Sciaenidae dominated. Average diversity and equitability were higher in samples collected along the water column. The influence of tailings was evidenced by the negative correlation of fish eggs and larvae abundances with some metals, and by the association of non-viable fish eggs with cobalt. In addition, periods of greater flow from the Doce River were related to lower mean ichthyoplankton abundances. Further studies are needed to monitor the continuity of the effects of the toxic mud and the possible changes it causes in the ichthyoplanktonic assemblages.