Dr. Michael Landry, Scripps Institution of Oceanography
Single-celled eukaryotes (protists) are typically the dominant consumers of primary production in marine ecosystems, yet this major flux pathway is more often than not left off diagrammatic representations of carbon and biogeochemical cycling in marine food webs. Over the past decade, research in the California Current and adjacent ocean ecosystems (subtropical and eastern tropical Pacific) has provided new quantitative and integrative data for understanding structure, dynamics and ecological relationships in these contrasting ocean systems. Here, examples from these studies are used to illustrate protistan consumer roles in phytoplankton community structure, carbon cycling, the biological pump and trophic transfer to higher-level consumers. Advances in compound-specific isotopic techniques hold additional promise for assessing regional differences in the number of protistan trophic steps in marine food webs, which remains an outstanding problem for constraining carbon fluxes among alternate pathways.