Biological quality elements have
been developed worldwide to assess
whether a water body is in a good status or not. However, current
studies mainly focus on a single taxonomic group or a small set of
species, often limited by methods of morphological identification,
and lack further aspects of biodiversity (e.g., across taxa and multiple
attributes) and ecosystem functions. Here, we advance a framework
for assessing the river’s ecological status based on complete
biodiversity data measured by environmental DNA (eDNA) metabarcoding
and measurements of ecosystem functions in addition to physicochemical
elements across a large riverine system in China. We identified 40
indicators of biodiversity and ecosystem functions, covering five
taxonomic groups from bacteria to invertebrates, and associated with
multiple attributes of biodiversity and ecosystem functions. Our data
show that human impact on ecosystems could be accurately predicted
by these eDNA-based indicators and ecosystem functions, using cross-validation
with a known stressor gradient. Moreover, indices based on these indicators
of biodiversity and ecosystem functions not only distinguish the physicochemical
characteristics of the sites but also improve the assessment accuracy
of 20–30% for the river’s ecological status. Overall,
by incorporating eDNA-based biodiversity with physicochemical and
ecosystem functional elements, the multidimensional perspectives of
ecosystem states provide additional information to protect and maintain
a good ecological status of rivers.
Dam construction and nutrient enrichment are two pervasive
stressors
in rivers worldwide, which trigger a sharp decline in biodiversity
and ecosystem services. However, the interactive effects of both stressors
on multitrophic taxonomic groups remain largely unclear. Here, we
used the multitrophic datasets captured by the environmental DNA (eDNA)
approach to reveal the interactions between dams and nutrient enrichment
on aquatic communities from the aspects of taxonomic α diversity,
β diversity, and food webs. First, our data showed that dams
and nutrient enrichment jointly shaped a unique spatial pattern of
aquatic communities across the four river systems, and the dissimilarity
of community structure significantly declined (i.e., structural homogenization)
under both stressors. Second, dams and nutrients together explained
40–50% of the variations in aquatic communities, and dams had
a stronger impact on fish, aquatic insects, and bacteria, yet nutrients
had a stronger power to drive protozoa, fungi, and eukaryotic algae.
Finally, we found that additive, synergistic, and antagonistic interactions
of dams and nutrient enrichment were common and coexisted in river
systems and led to significantly simplified aquatic food webs, with
decreases in modularity (synergistic) and robustness (additive) and
an increase in coherence (synergistic). Overall, our study highlights
that eDNA-based datasets can provide multitrophic perspectives for
fostering the understanding of the interactive effects of multiple
stressors on rivers.
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