Abstract
Environmental DNA (eDNA) analysis is a technique for detecting organisms
based on genetic material in environments such as air, water, or soil.
Observed eDNA concentrations vary in space and time due to biological
and environmental processes. Here we investigate variability in eDNA
production and loss by sampling water adjacent to a managed population
of non-native cetaceans on a near-hourly timescale for 48 hours. We used
diverse sampling approaches and modeling methods to describe time
variability in observed eDNA concentrations and then compare the
magnitude of production and loss mechanisms. We parsed production and
loss in a Bayesian process model, and compared biological and physical
loss rates using a decay experiment and a physical
transport-and-diffusion tracer model. We then evaluated eDNA
concentrations along a transect away from the animal enclosure in light
of model parameter estimates. We conclude that eDNA production is best
conceptualized using a time-varying mixed-state model and biological
losses are small relative to physical losses in the marine environment.
Because physical loss is unsteady and nonlinear, tracer models are
especially helpful tools to estimate it accurately.