Protistan diversity and distribution has yet to be comprehensively characterized in most of the world ocean despite their fundamental importance as both primary producers and consumers in almost every known microbial community. A recent study by PhD Candidate, Gerid A Ollison (advised by Dr. David Caron) examining protistan community structure from the surface to 770m (~ 600 m below the euphotic zone) across three seasons in the oligotrophic North Pacific Subtropical Gyre (station ALOHA) found that the protistan community changed markedly across two narrow ranges of increasing depths. Changes were driven by depth-specific distributions among major protistan taxa associated with the upper mixed layer, deep chlorophyll maximum, and aphotic zones in this permanently stratified water column. Compared to depth-dependent shifts in community composition, changes associated with season were insignificant at the study site with only a few photosynthetic exceptions.

The expansive pool of taxonomic and trophic diversity found in this study has implications for improved ecosystem models and accuracy in predicting community level responses to environmental change. The full study is found in Deep Sea Research Part I: Oceanographic Research Papers.