October 6, 2017 — If you look very closely at a glassful of water from a bay or the ocean, you would probably be surprised by the life inside. You might see miniature crustaceans the size of the period at the end of this sentence or baby crabs and fish that spend only a short span of their lives this small. These creatures are zooplankton, aquatic animals that drift with the currents.
It’s the Little Things
These tiny animals form the basis of the food web of estuaries, coastal waters, and oceans. Zooplankton feed on microscopic plant-like organisms called phytoplankton, which get their energy from the sun. Tiny crustacean zooplankton called “copepods” are like cows of the sea, eating the phytoplankton and converting the sun’s energy into food for higher trophic levels in the food web. Copepods are some of the most abundant animals on the planet.
Fish such as anchovies cruise through the water with their mouths wide open, filtering copepods and other zooplankton from the water. Anchovies and other planktivores (plankton-eaters) are prey for bigger animals, like tuna, sharks, marine mammals, and seabirds.