What term is used to describe free-floating organisms in aquatic ecosystems?

The term that describes free-floating organisms in aquatic ecosystems is "plankton." Plankton are a diverse group of organisms that drift with the currents in oceans and other water bodies. They are not strong swimmers and cannot control their movements against the water currents. This group includes both microscopic organisms, such as tiny algae and bacteria, as well as larger forms that might be visible to the naked eye.

Within plankton, there are different categories, such as zooplankton and phytoplankton. Phytoplankton, which is a subset of plankton, consists of photosynthetic organisms that are crucial for producing oxygen and serving as the foundation of the aquatic food web. Zooplankton, on the other hand, refers specifically to small, often microscopic animals that feed on phytoplankton and other small organisms.

The term "nekton" refers to free-swimming aquatic animals capable of moving independently of the currents, such as fish and whales, which differentiates them from the non-swimming or drifting nature of plankton. Therefore, referring to free-floating organisms collectively means using the broader term "plankton," which encompasses both phytoplankton and zooplankton.