The Structure and Diversity of Prokaryotic and Eukaryotic Plankton Communities Within the Southern California Bight (2014-2018)

We explore spatial variations in prokaryotic and eukaryotic plankton communities in the Southern California Bight, as well as how these variations are structured by the physical environment. We leverage a unique data set from the NOAA CalCOFI Genomics Time Series (NCOG), which is comprised of more than 800 samples from a five-year period (2014-2018) collected from the southern sector of the California Current Ecosystem (CCE) for high-throughput amplicon sequencing. Using a machine-learning approach known as self-organizing maps, we find that both the prokaryotic and eukaryotic datasets cluster into contrasting, but internally consistent nearshore and offshore communities. The distribution of these contrasting communities is most closely tied to patterns in sea-surface temperature variability, rather than mean conditions, across the Southern California Bight. For eukaryotes, gradients in diversity, evenness, and species richness orient along the nearshore to offshore gradient, with the highest levels of all three ecological variables occurring offshore. Prokaryotic communities, however, show no significant horizonal distribution for the same three ecological parameters. Instead, prokaryotic communities in the deep chlorophyll maximum appear to be more diverse, even, and species rich than communities at the surface.