Integrating temperature-dependent production of environmental DNA into its relationship with organism abundance

Despite a consensus on the correlative relationship between eDNA concentration andorganism abundance, precise and reliable abundance estimation using eDNA analysis is in its infancy, especially in nature. Although previous studies suggested that water temperature could drive not only eDNA degradation but also eDNA production, it remains unclarified how the eDNA-abundance relationship is influenced by water temperatures. To address the knowledge gap, this study conducted a numerical simulation considering temperature-dependent eDNA production and degradation. A previous dataset estimating fish eDNA production and decay rates at different water temperatures was re-analyzed to obtain the parameters of the temperature-dependent eDNA production and degradation. Then, using the parameters, population-level eDNA concentrations depending on a given temperature, the number of individuals, and their mass distribution were generated. The strength (R2 value) of the eDNA-abundance relationship was generally improved by warmer temperaturesregardless of eDNA production scenarios. In contrast, the sensitivity (regression slope) of the relationship was enhanced by warmer temperatures when temperature-dependent eDNA production was considered, but it rather decreased unless it was considered. Although further efforts have to be required to integrate organism physiology into eDNA production, the present study demonstrated the importance of linking the production mechanism of eDNA particles to organism physiology, offering a groundwork for theorizing the eDNA-abundance relationship depending on environmental conditions, including temperatures, for making eDNA signals more quantitative and reliable.