Potential Role of Photochemistry in Environmental DNA Degradation.

Given the severe loss of species richness across diverse ecosystems, there is an urgent need to assess and monitor biodiversity on a global scale. The analysis of environmental DNA (eDNA), referring to any DNA extracted from environmental samples and subsequently sequenced, is a promising method for performing such biodiversity related studies. However, a comprehensive understanding of the factors that drive distinct eDNA degradation rates under different environmental conditions is currently missing, which limits the spatiotemporal interpretations that are possible from the eDNA-based detection of species. Here, we explore what role photochemistry may play in the fate of eDNA in aquatic ecosystems. Since few eDNA photodegradation studies have been performed, we extrapolate measured photochemical degradation dynamics from dissolved organic matter (DOM) and cellular DNA to what is expected for eDNA. Our findings show that photochemistry may dominate eDNA degradation under certain environmental conditions (e.g., DOM-rich waters with no light-limitation) and that photochemical alteration of eDNA may impact microbial respiration rates and the quantitative polymerase chain reaction (qPCR)-based detection of eDNA. We therefore encourage future studies to analyze the impact of photochemistry on eDNA degradation and provide suggested research directions that could help improve the accuracy of spatiotemporal inferences from eDNA analyses.