What term describes the microscopic organisms that float near the surface of aquatic systems?

Plankton refers to the diverse group of microscopic organisms that drift or float in the water column, primarily near the surface of aquatic ecosystems. This term encompasses a wide variety of organisms, including phytoplankton (photosynthetic organisms like algae) and zooplankton (tiny animals and larval stages of larger animals). Plankton are essential components of aquatic food webs, serving as a primary food source for many larger organisms, such as fish and whales.

In contrast, nekton describes larger, typically swimming organisms that can move independently of water currents, such as fish and squid, which is not the focus of the question. Macroinvertebrates are larger organisms without a backbone, such as insects and crustaceans, often found in various habitats but not limited to the water column. Benthic organisms live on or in the seabed, far removed from the surface and the drifting nature associated with plankton. Thus, the term that accurately captures the floating, microscopic nature of these organisms in aquatic systems is plankton.