Novel Use of Environmental DNA Metabarcoding to Assess the Impacts of a Large-Scale Seismic Survey on Tropical Fish Communities

Abstract

Although environmental DNA (eDNA) metabarcoding has become a widespread tool used by ecologists to monitor wildlife diversity, there have been few applications of the approach for impact assessments. Here we use eDNA collected in a before–after, control-impact (BACI) experimental design to determine if the noise produced by a large-scale seismic survey modified the fish community on a tropical shelf. We compared abundance estimates of fishes calculated using metrics that included eDNA counts and an eDNA index of relative abundance (a proportional metric) with estimates sampled using baited remote underwater video stations (BRUVS). In total, we detected 102 different genera of fishes using the BRUVS and eDNA datasets combined, although there were more genera observed using BRUVS (n = 71) than with eDNA metabarcoding (n = 57). There was a weak positive relationship between the estimates of relative abundance sampled using BRUVS and eDNA counts when data from common genera were combined, although relationships at the genera level were inconsistent. We found no evidence of major change in the community structure of fishes at the high impact zone of the seismic survey compared to control zones. This result was confirmed using metrics across fish taxa within the BACI framework, suggesting no material impacts to species richness or abundance due to the seismic survey. The power to detect change in the fish community structure and abundance was high (99% probability) for detecting an 80% change in all metrics tested; however, it was considerably lower for detecting smaller changes. Our study highlights the utility and applicability of eDNA metabarcoding to assess point-source impacts on fish communities, particularly when used in parallel with other techniques such as BRUVS.