What term describes unicellular algae found on the surface of water bodies?

The term that describes unicellular algae found on the surface of water bodies is plankton. Plankton refers to a diverse collection of organisms that live in large bodies of freshwater and saltwater, suspended in the water column. This group includes both phytoplankton, which are photosynthetic organisms such as algae, and zooplankton, which are small animals that feed on phytoplankton. Phytoplankton typically float near the surface where there is adequate sunlight for photosynthesis, making them crucial to the aquatic food web and global oxygen production.

Euglenas and dinoflagellates are specific types of phytoplankton, but they are part of the broader category that plankton covers. By calling these unicellular algae plankton, it encapsulates all those forms of life that share the characteristic of floating in the water and being transported by currents. Thus, plankton serves as the most accurate term for these unicellular algae found on the surface of water bodies.