Cross-shore Changes in Vertical Habitats of Mesozooplankton: A Paired Metabarcoding and Morphological Approach

The California Current Ecosystem (CCE) comprises a range of physical environments, inhabited by zooplankton communities ranging from nearshore upwelling driven, high biomass blooms to stratified, offshore oligotrophic assemblages with lower biomass and higher diversity. We tested the hypothesis that the vertical habitat of selected species shifts in the cross-shore direction, as populations respond to variability in food availability, mixed layer depth, light conditions, and predation pressure. The cross-shore connectivity of zooplankton communities is dependent upon both offshore transport, and on the ability of the animals that inhabit the upper ocean to survive transport and mixing. Understanding the community composition, structure, and dynamics of the region requires consideration both of the ecological interactions between species (often correlated with traits such as size) and life history and species specific environmental constraints. Complementary metabarcoding and digital Zooscan methods were used to address both levels of specificity, with a focus on change in community structure over space. Four distinct environmental subregions of the CCE were sampled by vertically stratified MOCNESS. Paired morphological and genetic analyses were used to assess variability in distributions of individual OTUs, assessed at the mitochondrial COI and nuclear 18S regions, as well as biomass and abundance patterns of broader taxonomic groups. We present results examining vertical shifts in zooplankton community patterns in the context of a ‘space-for-time’ exchange, permitting prediction of future community patterns. We also test the depth dependence of population connectivity at depths extending from the surface to the upper mesopelagic (400m).