Environmental DNA metabarcoding uncovers environmental correlates of
fish communities in spatially heterogeneous freshwater habitats
Biomonitoring of complex heterogeneous environments is highly
challenging. Fish in deep water bodies occupy different habitats,
therefore a combination of survey methods has traditionally been used.
Environmental DNA (eDNA) metabarcoding is a novel monitoring tool that
can overcome spatial heterogeneity in a highly sensitive and entirely
non-invasive manner. However, taxon detection probability is dependent
on real-time environmental variables. In this study, three reservoirs
were sampled in two seasons using a spatiotemporally distributed
sampling design covering major environmental gradients. In all sampling
campaigns, 31 fish taxa were detected which exceeded expectations. Data
reliability was confirmed by a tight positive correlation between
individual taxon scores derived from gillnet sampling and eDNA site
occupancy. Analyses confirmed anticipated trends, such as the highest
number of taxa were observed in the largest water body, and more taxa
were detected in inflows and littoral regions compared to open water.
The most important factors for fish distribution were temperature, age
and trophic status (expressed as total Chlorophyll a concentration) of
water bodies. Taxon detection reflected ecological niches of individual
species, e.g. warm water wels catfish (Silurus glanis) and cold water
salmonids. This study provides further evidence that eDNA metabarcoding
is suitable for ecological study in heterogeneous environments and may
substitute conventional fish sampling techniques.