Describing variation in plankton community assemblages using eDNA (COI) metabarcoding in the Salish Sea

Abstract

Understanding marine plankton assemblages is crucial for assessing ecosystem health and predicting impacts of environmental change. This study uses environmental DNA (eDNA) metabarcoding methods to investigate plankton community assemblages in the Salish Sea with respect to spatial patterns, characteristic taxa, responses to environmental variables, and changing presence of harmful algal bloom (HAB) taxa. Five years of data (2017-2021) were collected from 9 sites across 5 oceanographic basins, revealing significant spatial differences in community composition among sites in the Hood Canal basin, sites in the Saratoga/Whidbey Basin, and remaining sampled basins. Additionally, temperature and phosphate represented the environmental variables significantly associated with the difference in these three distinct community assemblages. Identification of characteristic taxa from the Hood Canal basin assemblage revealed fewer and smaller diatoms compared to those identified from distinct assemblages outside of Hood Canal. The occurrence of HAB taxa likewise varied across basins over time suggesting significant implications future monitoring goals and design. Overall, this study enhances our understanding of plankton assemblage dynamics and highlights the utility of eDNA metabarcoding for long-term monitoring and conservation efforts in marine ecosystems.