Zooplankton is basically a group of  living animal organisms that float and drift freely with the currents of the water.  Many of these organisms are microscopic which means they are so minute that they can’t be seen with the naked eye.  Zooplankton often drifts in the top thirty metres of the sea in a ‘photic zone’ which is the layer of the sea that the sun can penetrate through. 

There are two different types of zooplankton of which one is called ‘meroplankton’.  Meroplankton is usually the larvae of fish, crabs, crustaceans and the larvae of ‘echinoderms’ which are a group of sea animals that include starfish, sea urchins and sea cucumbers and others.  Meroplankton only becomes part of zooplankton for a short while because the larvae eventually settle on the seabed to develop into adults. 

The other type of zooplankton is called ‘holoplankton’ which is group of plankton that remains as plankton through all stages of its life, like for example  ‘jellyfish’, ‘copepods’ and ‘euphausiids’.  Copepods and euphausiids are tiny crustaceans that cod like to eat.  Zooplankton plays an important role in the food chain of sea life.