Seasonal change in environmental DNA concentration of a submerged aquatic plant species

Environmental DNA (eDNA) methods are increasingly used to detect aquatic organisms. To optimize survey efficiency in natural environments, it is necessary to understand the seasonal change in eDNA concentrations of target species and identify the season and environmental conditions in which eDNA concentrations are highest. Recently, eDNA methods have been developed to detect aquatic plant species, but the seasonal change in the eDNA concentrations remains uninvestigated. Many aquatic plants undergo considerable changes in abundance, size, and shape throughout the year. Therefore, their eDNA concentration may change along with their phenology. We investigated the seasonal change in the eDNA concentration of an aquatic submerged species, Hydrilla verticillata, in agricultural ponds in Japan by measuring the eDNA concentration of H. verticillata from 5 ponds 5x in a year. This species has a dormant period during winter and a growth period from spring to autumn. The eDNA concentrations were higher during the growth period than during the dormant period. Management and conservation surveys that use eDNA for species detection should be done when eDNA concentrations are highest to maximize detection probabilities and therefore survey efficiency.