Dr Susanna Theroux1, Dr Ryan Guillemette2, Jayde Zimmerman1, Dr Kylie Langlois1, Dr Nastassia Patin1,3,4, Dr Joshua Steele1, Dr John Griffith1
1SCCWRP, Costa Mesa, USA, 2University of Southern California, Los Angeles, USA, 3NOAA CalCOFI, La Jolla, USA, 4Scripps Institution of Oceanography, La Jolla, USA
Biography:
Susanna Theroux is a principal scientist at the Southern California Coastal Water Research Project (SCCWRP). She specializes in the development of environmental DNA (eDNA) methods for biomonitoring and bioassessment. Dr. Theroux leads the California Water Quality Monitoring Council’s Molecular Methods Workgroup and serves on the Marine Technology Society eDNA Technology Committee.
Abstract:
The use of environmental DNA (eDNA) for biological monitoring has revolutionized our ability to monitor and assess marine organisms. However, our ability to interpret eDNA signals hinges on an improved understanding of the fate, transport, and decay of eDNA molecules in the environment. This study explored the role of bacterial communities in marine eDNA decay rates, focusing on how eDNA decay is modulated by microbial community composition, temperature, and eDNA state. We performed a series of mesocosm experiments to measure eDNA decay rates over two weeks, at five temperatures, using three spike-in treatments: fish cell line (intracellular eDNA), purified fish DNA (dissolved, extracellular eDNA), and fish aquarium water (mixed). Samples were collected for quantitative analysis (digital droplet PCR), bacterial metabarcode sequencing, and microscopy. As anticipated, our study observed faster eDNA decay at warmer temperatures. However, we observed unexpected trends in the impact of eDNA state on decay rate, including slower eDNA decay rates in the first 24 hours in the extracellular spike-in treatment in comparison to intracellular eDNA. We will also present our recent advances in methodologies for the capture of dissolved eDNA state, resulting in the recovery of greater than 90% of the starting material. In all, this study provides a thorough investigation into the role of bacterial community composition and activity on marine eDNA decay and will help to inform future efforts to model eDNA decay rates for ocean monitoring.