Taxon-specific community structure partitions marine particle size spectra into stable and dynamic components

Abstract

Oceanic particle size distributions (PSDs) link plankton community structure to biogeochemical cycling. Although the influence of community composition on size spectra is well recognized in theoretical approaches, long-term empirical evidence connecting taxon-specific variability to bulk PSD structure remains limited. Here, we use 9 yr of taxon-resolved PSDs spanning ~ 7–100 μm in the surface waters of the oligotrophic North Pacific to show that deviations from canonical scaling are structured, repeatable, and attributable to variability in specific taxa. We show that bulk PSDs reflect the superposition of a persistent baseline assemblage dominated by small spherical particles, dinoflagellates, and haptophytes, and a dynamic component driven by diatoms, colonial cyanobacteria, and detritus that restructure the size spectrum across seasons. By quantifying how taxon-specific variability propagates into bulk size metrics, this study provides new empirical constraints for interpreting PSD variability in oligotrophic systems and for linking community composition to particle size structure in modeling contexts.