18S & COI mesozooplankton metabarcoding - Eastern North Pacific 0-1000m

We characterized zooplankton diversity and community composition in the upper 1000m of the northeast Pacific Ocean using DNA metabarcoding of two markers (18S-V4 and mtCOI). We tested whether the North Pacific Transition Zone is a biogeographic boundary region for mesopelagic zooplankton. We also tested whether zooplankton taxa occupying different vertical habitats and bearing different ecological traits differed in the ranges of temperature, Chl-a, and dissolved oxygen conditions inhabited. We found the depth of the maximum taxonomic richness deepens with increasing latitude in the North Pacific. We found increased community similarity in the mesopelagic zone in comparison with the epipelagic zone, and no evidence for a biogeographic boundary between previously delineated mesopelagic biogeochemical provinces. Epipelagic zooplankton exhibited larger temperature and Chl-a ranges than mesopelagic taxa. Within the epipelagic, taxa with larger temperature and Chl-a ranges also had broader distributional ranges. However, mesopelagic taxa were distributed across wider dissolved oxygen ranges, and within the mesopelagic only oxygen ranges covaried with distributional ranges. Environmental and distributional ranges also varied among traits both for epipelagic taxa and mesopelagic taxa. The strongest differences in both environmental and distributional ranges were observed for taxa with or without Diel Vertical Migration behavior. Our results suggest that zooplankton species traits can influence the differential effects of physical dispersal and environmental selection in shaping biogeographic distributions.