Zooplankton   Copepod 5by5  Calanus Finmarchicus  Oithona _photo Corycaeus

Zooplankton is the term given to the small animals that live in the sea and include protozoans, small crustaceans and at certain times of the year, the larvae of other marine organisms (meroplankton).
Most zooplankton also live in photic zone of the sea, although some are known to migrate to the surface waters on a daily basis from the deeper areas of the sea. This is believed to be a predatory avoidance mechanism. Zooplankton graze on the phytoplankton making them the primary consumers of the sea. They are then food for fish, corals, jellyfish and basking sharks etc. Changes seen in the plankton community have been show to have a 'knock on' effect throughout the marine food chain.


The zooplankton community is dominated by the crustacean group copepods. Copepods are small (typically 1mm- 10mm in length) crustaceans with long antennae and a muscular, segmented body. They are capable of limited locomotive power and use their antennae and legs to propel themselves through the water column. This results in a darting or flicking movement and is likely to be a predator avoidance strategy, but also helps them maintain their position in the water column.

Copepods graze on phytoplankton by either filtering them from the water or handling them manually with their appendages/ mouthparts. Filter feeding copepods produce a stream of water past their bodies by flapping their appendages (antennae, mandibles and maxillpeds (legs), moving the phytoplankton cell into a position where they can grasp it and eat it. Other copepods simply seize their prey with their appendages and eat it.

   Copepod Morphology Copepod morphology           Classification Of Copepods _2  Classification of Copepods              Other zooplankton