Ice cover and seasonal variation shape eDNA detection in a southern high-latitude river

Abstract

Environmental DNA (eDNA) based analysis has emerged as a valuable tool for monitoring fish biodiversity, especially in remote and difficult-to-access environments. However, significant knowledge gaps remain regarding the influence of extremely low temperatures and ice cover on eDNA detection in freshwater systems. This study aimed to evaluate the influence of biological and environmental factors on fish detection probability using a species-specific eDNA-based approach in a high-latitude river system. A field experiment was conducted to assess detection of an exotic and a native fish species at two biomass levels and multiple distances from the source acrosscontrasting seasons. Results showed that detection probability was generally higher in summer than in winter. Notably, ice cover had a significant and species-specific impact, drastically reducing detection probability, emphasising the critical role of ice in modulating eDNA persistence and detectability in cold-region freshwater systems. Despite observing an intermittent eDNA signal with no specific spatial pattern over distance, both species were detected at distances up to 640 m from the source, regardless of the biomass and season. These findings underscore the importance of accounting for seasonality when designing eDNA-based protocols and provide guidance for biodiversity monitoring in cold-region freshwater ecosystems facing extreme winters and icecover.