Center for Marine Biodiversity and Conservation

There is a growing need to understand sea turtle biology and distribution as changingoceanographic conditions may cause dramatic shifts over time. However, conservation efforts for highly migratory and elusive species such as green and leatherback sea turtles remains achallenge, especially in the marine environment, limiting research to nesting females while the remainder of their life cycle is largely hidden. (1) Green turtles forage in bays and estuaries in Southern California and have been found to originate from tropical nesting beaches in Mexico. (1) On top of logistical challenges, traditional genetic studies on these species often rely on tissuesamples, which can be invasive and stressful for turtles, costly, and labor-intensive (3).Environmental DNA (eDNA) eDNA offers a non-invasive alternative, potentially revolutionizing the field. This method involves collecting samples of water, sand, air, etc. and essentially extracting DNA straight from the environment rather than the species of interest. (4) Previous studies have shown that eDNA can be extracted and identified from water samplescollected directly next to green turtles (5). The next challenge is to be able to quantify this eDNA to reliably determine presence or absence of the species, and to estimate relative abundance. Droplet Digital PCR is a system used to precisely quantify the amount of target DNA in a sample, and has not yet been used for eDNA studies of sea turtles. Without the need to capture or even see the organism itself, eDNA techniques could be vital for the detection and analysis of rare and elusive species. However, there is a need to systematically evaluate the reliability andefficacy of eDNA methodologies for sea turtle research, addressing issues related to sampleidentification, quantification, and temporal dynamics.