From the Bottom Up: Phytoplankton’s Major Groups

Phytoplankton are the cornerstone of marine ecosystems, driving the marine food web by producing organic matter through photosynthesis. These tiny organisms are essential for oxygen production, carbon cycling, and nutrient transformation, making them vital to ocean health. Major groups such as diatoms, dinoflagellates, coccolithophores, cyanobacteria, and green algae each play unique roles, from supporting the silicon cycle to aiding carbon sequestration and nitrogen fixation. This overview sets the stage for exploring harmful blooms and mixotrophic capabilities in phytoplankton in the following chapters.