Ecological indices from environmental DNA to contrast coastal reefs
under different anthropogenic pressures
Abstract
Human activities can degrade the quality of coral reefs, cause a decline
in fish species richness and functional diversity and an erosion of the
ecosystem services provided. Environmental DNA metabarcoding (eDNA) has
been proposed as an alternative to Underwater Visual Census (UVC) to
offer more rapid assessment of marine biodiversity to meet management
demands for ecosystem health indices. Taxonomic information derived from
sequenced eDNA can be combined with functional traits and phylogenetic
positions to generate a variety of ecological indices describing
ecosystem functioning. Here, we inventoried reef fish assemblages of two
contrasted coastal areas of Curaçao, (i) in close proximity to the
island’s capital city and (ii) in a more remote area under more limited
anthropogenic pressure. We sampled eDNA by filtering large volumes of
sea water (2 x 30L) along 2km boat transects, which we coupled with
species ecological properties related to habitat use, trophic level and
body size to investigate the difference in fish taxonomic composition,
functional and phylogenetic indices recovered from eDNA metabarcoding
between these two distinct coastal areas. Despite no marked difference
in species richness, we found a higher phylogenetic diversity in
proximity to the city, but a higher functional diversity on the more
isolated reef. Composition differences between coastal areas were
associated with different frequencies of reef fish families. Because of
a partial reference database, eDNA only partly matched those detected
with UVC, but eDNA surveys nevertheless provided rapid and robust
species occupancy responses to contrasted environments. eDNA
metabarcoding coupled with functional and phylogenetic diversity
assessment can serve the management of coastal habitats under increasing
threat from global changes.