Environmental DNA Particle Size Distributions: Implications for Collection and Analysis

An inherent tradeoff between filter pore size (=captured particle size) and maximum filterable water volume makes understanding the size of eDNA-bearing particles in aquatic environments essential for efficient sample collection. Nevertheless, the particle size distribution (PSD) of eDNA represents a conspicuous gap in the growing literature on eDNA surveillance. To explore the influence of biotic and abiotic environmental factors on eDNA PSD, we manipulated fish communities across nine experimental ponds. From each pond, we serially filtered water through filters of 6 pore sizes (60 - 0.2 µm) followed by eDNA precipitation, and we used qPCR to determine the proportion of Common Carp (Cyprinus carpio) or bigheaded carp (genus Hypophthalmichthys) eDNA captured within each size fraction. Using eDNA concentrations in each size fraction, we parameterized a Weibull distribution describing the eDNA PSD for each species in each pond. Likelihood ratio tests indicated that PSD did not differ between fish species, but variation did occur between ponds. Due to the influence of local biotic and abiotic conditions on eDNA PSD, future eDNA surveillance efforts should consider analysis of eDNA PSD to inform eDNA collection technique and maximize detection probability.