Tracing Environmental DNA Transport in a Large Lake with Synthetic DNA Microparticles and Hydrodynamic Modeling

Natural environmental DNA (eDNA) offers a powerful tool for aquatic ecosystem monitoring. However, its transport in large lakes remains poorly understood due to its instability, scarcity, and heterogeneity, as well as the complex hydrodynamics of lakes. We developed biodegradable synthetic DNA particles (sDNAp) that encapsulate DNA fragments with unique sequences to serve as quantitative tracers for investigating eDNA transport. This sDNAp tracer was deployed in Cayuga Lake (NY, USA; 172 km² surface area) and its dispersion was monitored for 33 h over ∼11 km² through depth-integrated water sampling followed by quantitative PCR analysis. Despite gram-scale release quantities, sDNAp were detected over 7 km from the source after more than a day, at concentrations as low as ∼3-5 particles mL^-1, demonstrating high sensitivity and durability. A 3D hydrodynamic model incorporating wind-driven circulation and stratification reproduced key dispersion patterns observed in the field. Forward particle-tracking simulations captured both horizontal advection and vertical displacement, while backward simulations revealed that vertical position sensitivity limited the accuracy of source attribution. This approach provides one of the first lake-scale demonstrations that time-resolved, probabilistic attribution of natural eDNA sources is feasible under favorable conditions. Using sDNAp tracers, it also establishes a robust benchmark for future studies on eDNA transport in large waterbodies.