What role do protists such as algae play in aquatic ecosystems?

Protists, particularly algae, play a crucial role in aquatic ecosystems as they serve as the initial sources of food. In these environments, algae are primary producers that utilize photosynthesis to convert sunlight into energy, creating organic compounds that nourish themselves and form the base of the food web. This production of energy-rich organic matter is essential for supporting a diverse range of organisms, from small zooplankton to larger fish and other aquatic animals, all of which depend on algae and other primary producers for sustenance.

In addition to providing food, algae also contribute to oxygen production and are key players in the cycling of nutrients, but their primary role is as producers in the food chain. As such, they facilitate energy flow within the ecosystem, supporting various trophic levels above them.