High stream flows dilute environmental DNA (eDNA) concentrations and reduce detectability

Abstract

Aim Environmental DNA (eDNA) is a rapidly emerging methodology with important applications to environmental management and conservation. However, the effects of stream flow or discharge on eDNA have been minimally investigated in lotic (stream and river) environments. In this study, we examined the role of stream flow on eDNA concentrations and detectability of an invasive clam (Corbicula fluminea), while also accounting for other abiotic and biotic variables. Location Illinois, United States of America. Methods We used a longitudinal study over a year in two streams, as well as a seasonal study (summer, autumn) in eight streams, to investigate the effects of variable stream flow on eDNA concentrations and detectability. We used linear mixed‐effects models to assess the influence of various factors on eDNA concentration and occupancy models to make predictions on how seasonality can influence eDNA detection. Results We found higher stream flows decreased eDNA concentrations, and floods produced false negatives or non‐detections at locations where C. fluminea was relatively common. In addition, we found concentrations and detectability of C. fluminea eDNA to be higher in summer than in autumn. Main conclusions We found that stream flow dilutes eDNA concentrations, which may have serious implications for the detection of low abundance organisms. Managers and practitioners applying eDNA for rare species should seek to sample at low or base stream flows when feasible, and future studies should investigate whether our findings here are consistent for other taxa and lotic ecosystems.

eDNA Detection of Native and Invasive Crayfish Species Allows for Year-Round Monitoring and Large-Scale Screening of Lotic Systems

“…However, LMM analysis indicated that there is a difference in eDNA detectability between winter and summer samples both with regard to detection rate and eDNA concentration (Figures 2, 3). This result is in line with previous studies, showing that eDNA detectability can be affected by season, depending on the biology of the target species (e.g., reproduction period, activity) (Buxton et al, 2018;Curtis et al, 2020). For crayfish, reduced detection rates in winter were an anticipated effect, since all European crayfish species show reduced activity and metabolism during winter (Bubb et al, 2002), which likely results in reduced eDNA shedding rates.…”

“…Finally, water volume, e.g. during flood conditions, has been found to influence eDNA detectability (Curtis et al, 2020). This might imply an influence of stream size on crayfish eDNA detectability, which, however, has not been investigated yet.…”

“…For instance, eDNA transport distances in lotic systems, that are often taxon-specific (Deiner and Altermatt, 2014;Wacker et al, 2019), are unknown for freshwater crayfish, although persistence of eDNA was assessed in laboratory and mesocosm experiments (Dunn et al, 2017;Harper et al, 2018). Moreover, unlike in other taxa (Buxton et al, 2018;Wacker et al, 2019;Curtis et al, 2020), seasonal variation of crayfish eDNA detectability has never been consistently assessed; existing studies either sampled only during one season or included preliminary field experiments (Ikeda et al, 2016;Harper et al, 2018;Rusch et al, 2020). Finally, water volume, e.g.…”

Detection of Endangered Aquatic Plants in Rapid Streams Using Environmental DNA

“…This method can be applied to detect other species of Podostemaceae in Japan. Although it was raining at the time of the 2019 survey, which can dilute eDNA concentrations and lead to false negatives for target species (Curtis et al, 2020;Sales et al, 2021), Podostemaceae eDNA was detectable in all samples near known habitats. Therefore, the method employed in this study seems to be effective under various weather conditions.…”

Recent advances in environmental DNA‐based biodiversity assessment and conservation

“…Curtis et al. (2021) investigated the role of water flow on eDNA concentrations and subsequent effects on the detectability of an invasive freshwater clam ( Corbicula fluminea ) in streams across seasons. Their results indicated that higher stream flows decreased eDNA concentrations and that stream floods increased the rate of false negatives (i.e.…”