What is the term for plant plankton in aquatic ecosystems?

Phytoplankton refers to the microscopic plant-like organisms that serve as the primary producers in aquatic ecosystems. These organisms, which are primarily composed of algae, utilize photosynthesis to convert sunlight into energy, forming the base of the food web within these environments. Phytoplankton are crucial for the health of aquatic systems because they produce oxygen and are a primary food source for various aquatic organisms, including zooplankton and small fish.

In contrast, zooplankton are primarily animal plankton that feed on phytoplankton, while the terms "thermoplankton" and "nanoplankton" refer to specific categories of plankton based on size or habitat rather than indicating plant-like organisms. Thus, phytoplankton is the correct term to describe the plant component of plankton in aquatic ecosystems.