What role do phytoplankton play in aquatic ecosystems?

Phytoplankton are essential components of aquatic ecosystems primarily because they serve as primary producers. Through the process of photosynthesis, phytoplankton convert sunlight and carbon dioxide into organic matter, creating energy-rich compounds that support the entire food web in aquatic environments. This foundational role enables them to produce oxygen as a byproduct, which is critical for the survival of many marine and freshwater organisms.

Their photosynthetic activity also supports higher trophic levels, making them vital for the sustainability of fish populations and other consumers within these ecosystems. Without phytoplankton, energy transfer to primary consumers (like zooplankton and some fish) would be severely disrupted, leading to a cascade of negative effects throughout the food web. Thus, their role in photosynthesis and energy production underpins the health and function of aquatic ecosystems.