Multi-Tool Marine Metabarcoding Bioassessment for Baselining and Monitoring Species and Communities in Kelp Habitats.

The astonishing biological diversity found in Californian kelp forests requires efficient and robust monitoring tools to better understand ecological trends and mitigate against loss or disruption of ecosystem services due to human pressure and climate changes. With environmental DNA (eDNA) metabarcoding becoming a popular biodiversity assessment approach, we set out to evaluate a combination of powerful, rapid and sustainable eDNA solutions for characterising marine community composition in kelp-dominated habitats along the central California coast, in the newly proposed Chumash Heritage National Marine Sanctuary. We employed and compared the efficiency of several eDNA collection approaches, including 'traditional' surface water filtration, the collection of organisms encrusting cobble rocks and various deployments of an artificial passive sampler, the metaprobe (i.e., attached to divers, dangled from a boat and cast from the shore using a fishing rod). By combining the information from fish specific (Tele02 12S) and universal metazoan (COI) markers, we 'captured' 501 unique marine taxa, belonging to at least 36 phyla, over 400 of which were identified to genus/species level, and including 52 vertebrate species typical of Californian kelp forest ecosystems. Despite differences in the type of biodiversity returned by the tested sampling methods, the overall community structure of the surveyed area was highly spatially structured and strongly influenced by the biogeographic break around Point Conception (Humqaq). We discuss the benefits of integrating eDNA metabarcoding in existing monitoring programs and devising a reproducible approach to monitor faunal changes in kelp forest habitats and beyond.