The primary function of phytoplankton in marine ecosystems is their role as foundational producers, converting sunlight and carbon dioxide into oxygen and organic matter through photosynthesis. Serving as the base of the marine food web, they provide sustenance for a variety of marine organisms, including small fish and zooplankton. Furthermore, phytoplankton contribute significantly to the global carbon cycle, influencing climate regulation. Their health and population dynamics reflect broader changes in marine environments, making them vital indicators of ecosystem health. Supporting phytoplankton populations is crucial for maintaining the balance of marine ecosystems.