The critical role of phytoplankton in marine ecosystems cannot be overstated, as they are primary producers that perform photosynthesis. These microscopic organisms convert sunlight, carbon dioxide, and nutrients into organic matter, forming the base of the marine food web. Phytoplankton not only provide food for a variety of marine organisms, including zooplankton and fish but also produce a significant portion of the world's oxygen. Their health directly impacts marine biodiversity and helps to regulate the global carbon cycle and climate.