Investigating the Limits of Detection of Environmental DNA From Loggerhead and Hawksbill Turtles

Understanding the movement and distribution of marine species at a variety of spatial and temporal scales is a foundation to their protection. Traditionally, most techniques used to identify the presence or build knowledge of their biology and distribution required the capture of an animal and techniques such as mark-recapture. Recently, molecular approaches such as eDNA analysis have been used as a non-invasive technique to identify the presence of a species in a habitat by identifying trace DNA material in the environment. One of the key gaps in the use of eDNA approaches is a paucity of information on the shedding and degradation rate of DNA within the water body. Controlled experiments were set up using loggerhead turtles (Caretta caretta) as a model species to quantify shedding and degradation. We also developed a new eDNA assay targeting hawksbill turtles (Eretmochelys imbricata). Five individual loggerhead turtles were placed in experimental aquaria for a period of 6 h, with eDNA samples being collected at set intervals over a six-hour period to determine shedding rates. After the experimental period, turtles were removed from experimental aquaria, and eDNA samples were collected at set intervals for 10 days to determine degradation rate. In controlled experiments, loggerhead turtle eDNA was shed with a 17% increase each hour of turtle presence. The decay constant was determined to be 0.018, with a DNA half-life of approximately 39 h, and residual eDNA degraded below detection limits within 5 days after the removal of turtles from aquaria. A hawksbill turtle (E. imbricata) eDNA assay successfully differentiated between the commonly co-occurring sea turtle species and identified E. imbricata presence in aquaria samples. Understanding the factors influencing eDNA detection rates is crucial for designing robust eDNA sampling protocols, as well as interpreting results of eDNA studies.

Aquatic Conservation: Marine and Freshwater Ecosystems

Aquatic Conservation: marine and freshwater ecosystems

35

1099-0755

N/A

8

10