Abstract:
That transport and fate of passive particles in large, stratified waterbodies is critical to ecosystem functioning, water quality for humans and nature, and tracing the source of small particles back to their source, such as in the case of finding invasive species through their shed DNA. Natural environmental DNA (eDNA) is a powerful tool for aquatic ecosystem monitoring. However, its transport in large lakes remains poorly understood due to both its intrinsic instability, scarcity, and heterogeneity, as well as the complex hydrodynamics of lakes. We developed synthetic biodegradable synthetic DNA (sDNA) particles that encapsulate DNA fragments with unique sequences to serve as quantitative tracers for investigating passive particle transport. Three uniquely DNA-tagged tracers were deployed at three distinct spatial locations within 15 minutes of each other during a windy period (wind speeds > 10 m/s) in Cayuga Lake (NY, USA; 172 km2 surface area). The particle dispersion was monitored through 278 depth-integrated surface 2-m samples over 33 h and ~11 km² from a boat. The samples and additional control blanks were analyzed by quantitative PCR (qPCR) for particle concentration. Despite 1-2 g release quantities at concentrations of ~1013 particles/mL, sDNA particles were detected over 7 km from the source after 33 h (when the experiment was stopped), at concentrations as low as ~3 and as high as 1047 particles/mL demonstrating the high sensitivity and dynamic range of the tracer method. A 3-D free surface hydrodynamic model (Si3D) 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 demonstrated that probabilistic particle original locations can be predicted. The coupled field observational-numerical simulation results revealed the critical importance of vertical transport processes in the horizontal transport and fate of passive particles.
Bio:
Dr. Todd Cowen is the Director of the DeFrees Hydraulics Laboratory and past Faculty Director for Energy at the Atkinson Center for Sustainability, where he continues to be a Faculty Fellow. Cowen's research interests are in environmental fluid mechanics, coastal resiliency, renewable energy, sustainability, and quantitative imaging-based measurement techniques in fluid mechanics. He pairs laboratory-based research with full-scale observational field campaigns to study natural and anthropogenic flows. Current projects include: infrared/visible light based remotely sensing of surface water flows for flow rate, bathymetry, wave celerity and gas transfer monitoring; wavy and unidirectional flows through mangrove canopies; fate, transport and residence time in lakes, and enhancing the direct air capture of CO2 across the air-water interface for carbon capture and reuse or sequestration.