4.1 Influence of sampling time on species richness and community
composition
Our results indicated that differences in species richness were caused
by seasonality but not sample replicates, which matched our
expectations. High similarity among sampling positions likely occurred
due to the complete mixing of eDNA in the water body, with smaller
compositional differences occurring by replication, the three water
samples taken within the sampling site, and not by systematic
differences between positions (Macher et al., 2021). The stream sampled
in our study had a water depth <1 m and sampling positions
were less then 10 m apart with a mostly turbulent flow, all of which can
reduce community heterogeneity (see Shogren et al., 2017; Fremier et
al., 2019 for further discussions).
Temporal beta-diversity shifted in a seasonally cyclical and gradual
pattern, which was primarily driven by turnover, with turnover and
nestedness both returning to the same level after one year. The
potential of eDNA in detecting seasonal shifts in community composition
has been already shown for marine environments (Jensen et al., 2022; Liu
et al., 2022) but not for freshwater.