The role of phytoplankton in ocean ecosystems is vital as they form the foundation of the marine food web. These microscopic organisms perform photosynthesis, converting sunlight into energy and producing oxygen as a byproduct. They serve as the primary food source for a diverse range of marine life, including fish, zooplankton, and larger animals. Furthermore, phytoplankton are essential in regulating carbon dioxide levels in the atmosphere, thereby influencing global climate. Monitoring phytoplankton populations helps scientists assess ecosystem health and environmental changes in oceans.