A large scale temporal and spatial environmental DNA biodiversity survey of marine vertebrates in Brazil following the Fundão tailings dam failure

Seawater contains a wealth of genetic information, representing the
biodiversity of numerous species residing within a particular marine
habitat. Environmental DNA (eDNA) metabarcoding offers a cost effective,
non-destructive method for large scale monitoring of environments, as
diverse taxonomic groups are detected using metabarcoding assays. A
large-scale eDNA monitoring program of marine vertebrates was conducted
across three sampling seasons (Spring 2018, Autumn 2019 and Spring 2019)
in coastal waters of Brazil. The program was designed to investigate eDNA
as a testing method for long term monitoring of marine vertebrates
following the Fundão tailings dam failure in November 2015. While no
baseline samples were available prior to the dam failure there is still
value in profiling the taxa that use the impacted area and the trajectory
of recovery. A total of 40 sites were sampled around the mouths of eight
river systems, covering approximately 500km of coastline. Metabarcoding
assays targeting the mitochondrial genes 16S rRNA and COI were used to
detect fish, marine mammals and elasmobranchs. We detected temporal
differences between seasons and spatial differences between
rivers/estuaries sampled. Overall, the largest eDNA survey in Brazil to
date, revealed 69 families from Class Actinopterygii (fish), 15 species
from Class Chondrichthyes (sharks and rays), 4 species of marine and
estuarine mammals and 23 species of conservation significance including 2
species of endangered dolphin. Our large-scale study reinforces the value
eDNA metabarcoding can bring when monitoring the biodiversity of coastal
environments and demonstrates the importance of collection of time-stamped
environmental samples to better understand the impacts of anthropogenic
activities.