Phytoplankton Size Class

Phytoplankton size classification is a fundamental framework for organizing plankton communities and understanding their ecological roles and biogeochemical impacts. Developed by Sieburth, Smetacek, and Lenz in 1978, size classes (pico-, nano-, micro-, macro-phytoplankton) define distinct functional groups with different nutritional requirements, growth rates, grazing vulnerabilities, and sinking rates. Size-based classification enables rapid assessment of plankton community structure and prediction of ecosystem responses to environmental change.