Creative eDNA capture strategies for measuring marine biodiversity

The ocean is the largest habitat on our planet and it remains the least explored, with 75% of the seafloor unmapped and an estimated 90% of marine species left undiscovered. Already from the fraction of marine species and ecosystems that we do know about, it is overwhelmingly clear that ocean life is interconnected to all life on Earth and provides vital services to society. Despite an inherent link between ocean life and the well-being of people, many of our measurements of biodiversity are occasional, focus on single species, can be invasive and counter-intuitive to conservation efforts, and are not feasible for marine managers to routinely implement. Now more than ever before, a rapid, broadly applicable, non-invasive, low-cost technology exists to generate multi-species observations of marine life, which are critical for their management and conservation. Environmental DNA (eDNA) metabarcoding should make marine biodiversity discovery and monitoring an easy feat, but a major challenge that slows its widespread uptake is the cumbersome and limiting processes required to capture and concentrate eDNA from vast marine habitats. This thesis examines mechanisms for overcoming those challenges by investigating two new and creative strategies for capturing eDNA: i) by leveraging the filtration capacity of marine sponges as natural eDNA sampling accumulators; ii) by deployment of simple, quasi-passive eDNA samplers in association with SCUBA diving activities; and explores how these strategies could extend the reach of current marine biodiversity monitoring efforts. Two chapters are dedicated to each eDNA capture technique, where the first displays a proof-of-concept for the method while the second provides a fine-tuned and targeted application of the approach. The thesis highlights how working in partnership, particularly to share resources already existing in the worlds’ biological collections and to include non-professional scientists and communities in the research process, significantly enhances scientific discovery. Life below water exists over vast ocean habitats that can be difficult to measure but we now have technologies that spark optimism. Creativity and resourcefulness are necessary ingredients that will help us overcome any remaining challenges and make effective stewardship possible everywhere.