Spatial autocorrelation of plankton community composition in a continental shelf ecosystem

The spatial autocorrelation of plankton compositional pattern is described for a productive continental shelf region for separations from 10 to 100 km. The resemblance metric (squared chord length) used to quantify community dissimilarity is a multivariate analog of the structure function used in meteorology and physical oceanography and is well suited to measuring shifts in relative dominance within a region showing very little spatial variability in species occurrence. Zooplankton biomass and zooplankton and phytoplankton community composition all show significant positive spatial autocorrelation (Mantel test). Dissimilarity correlograms for the various types of data show that the community pattern is stretched parallel to the bathymetric contours, with roughly a 3:1 ratio of alongshore: cross‐shelf correlation lengths. The zooplankton community pattern shows the most gradual loss of correlation (roughly 30‐km cross‐shelf and 100‐km alongshore). Both zooplankton biomass and phytoplankton community composition become uncorrelated at significantly smaller separations (5–25 km).