What is a characteristic feature of plankton?

Plankton are primarily characterized by their passive drift with ocean currents and waves, which distinguishes them from other marine organisms that are capable of strong swimming. This drifting nature means that plankton, which can include both the microscopic flora (phytoplankton) and fauna (zooplankton), are primarily moved by the movement of water rather than by their own propulsion.

While some planktonic organisms may have the ability to move slightly to maintain their position in the water column, they lack the robust swimming capabilities found in many fish and other aquatic organisms. As a result, the characteristic feature of plankton being carried by ocean currents and waves is fundamental to their existence and ecological role in marine environments.

The other options suggest abilities or traits that do not align with the natural behavior or classifications of plankton. For instance, not all plankton are autotrophs, as zooplankton are heterotrophic and feed on other organisms. Additionally, plankton are not confined to the ocean floor; instead, they inhabit various layers of the water column depending on factors like light and nutrient availability.