Determining the Seasonality of Oceanic eDNA Source Waters

With offshore wind development planned for US coastal waters, there are potential impacts construction and operations may have on traditional surveys used to assess the marine species within the turbine farm areas. Environmental DNA (eDNA) offers a uniquely efficient method of monitoring marine communities since species do not have to be actively caught with a traditional trawl survey. It is important to quantify the past trajectory of the sampled water to properly interpret the representative space of the processed eDNA. To better understand the range and movement of the ocean water containing the eDNA samples backwards drift models were utilized to identify the origin of the sample and the dependence of sample range on location and season. Using a 10-year HF Radar surface current data set from 2007 to 2016, the reverse drift of particles were simulated off the coast of southern New Jersey. This was accomplished using the OpenDrift model that was seeded with 100 virtual particles and advected backwards in time for five days, encompassing the likely detection threshold of eDNA in the water. This analysis tested particle movement distances by varying location from the shore, as well release date within each season of the year. These findings suggest that eDNA has the potential to travel farther in the fall compared to the other seasons. A more practical result of the analysis is that around the 24-hour mark, particles originated within 10 km of sampling location regardless of season or location. This is an important time scale to observe because an estimate of the half-life of eDNA is around 24 hours. Variability in travel distance was only seen in time periods beyond 24 hours.