Ebbs and Flows of Marine Biodiversity: Navigating Spatio-Temporal Patterns of Environmental DNA in a Coastal Tidal Ecosystem

This experiment aimed to explore fine-scale spatio-temporal patterns of eDNA-derived marine eukaryotic diversity and non-indigenous species (NIS) diversity in a tidal coastal ecosystem. The research addressed several key questions:1. Temporal Patterns: Investigated whether temporal patterns or shifts in localized biodiversity emerged throughout a tidal period, specifically within a 12-hour window.2. Spatial Variability: Examined significant shifts in detected biodiversity between sheltered and stable environments (e.g., marina) compared to more transient locations characterized by high and rapid water turnover (e.g., channel), across a small spatial scale.3. Contribution to NIS Detection: Explored how spatio-temporal patterns in eDNA signals contributed to the detection of marine NIS.Sampling was conducted in the Bay of Islands Marina, Opua, Aotearoa New Zealand, chosen for its unique geography and known hotspot for non-indigenous marine species. Hourly samples were collected using vertical plankton net tows within the upper 2 m water layer, with triplicate samples taken at each time point over a 12-hour sampling window (07:30 to 19:30) to encompass the tidal period.Concentrated water samples were filtered through a 5 micron pore size cellulose acetate filter, and metabarcoding analysis was performed using two primer sets: the mitochondrial Cytochrome c Oxidase subunit I (COI) gene for metazoans and the V3-V4 region of the nuclear small-subunit ribosomal RNA (18S rRNA) gene for general eukaryotes. The broader eukaryotic community was screened for marine NIS using an online metabarcoding data screening app (exPAT).The results of this study may contribute to the development of optimized sampling protocols and improve the efficiency of metabarcoding as an initial screening method for marine NIS, thereby enhancing our understanding of marine ecosystem dynamics and biodiversity conservation efforts.