zooplankton

Zooplankton are a diverse group of tiny drifting creatures found in water, especially in the ocean but also in lakes and rivers. The name comes from the Greek words "zoon" (animal) and "planktos" (wanderer or drifter), which fits the way they move with currents. Unlike phytoplankton, which make their own energy through photosynthesis, zooplankton feed on other organisms, mainly phytoplankton and even smaller drifting life. This makes them a key link in the food web, passing energy from very small life forms to larger animals such as fish, whales, and seabirds.

They are not just tiny versions of larger animals. This group includes many kinds of life, such as copepods, krill, jellyfish larvae, the young stages of many fish, and some other very small drifting organisms. Some are so small that you need a microscope to see them, while others are large enough to be seen with the naked eye.

Their size varies a lot, but they share one main trait: they drift with the water instead of traveling strongly against it, although many can move up and down in the water. They matter not only because they feed larger animals, but also because they help move carbon through the ocean.

Scientists study zooplankton to learn how healthy oceans and other waters are, and how they are changing as the climate changes. If the number or location of these drifters changes, the effects can spread through the whole ecosystem. So when you picture the ocean, it is worth remembering these tiny wanderers, quietly supporting life all around them.