Luidia - Copyright Richard Kirby Luidia plankton. © Richard Kirby.

By Royal Society University Research Fellow Dr. Richard Kirby
University of Plymouth

What are Plankton?

Plankton are ocean dwelling organisms. Living in the sunlit surface of the sea, they drift at the mercy of the ocean currents. There are two main types of plankton; tiny plant like cells called phytoplankton, and the animal plankton, otherwise known as zooplankton. While a number of the zooplankton live their whole life floating near the surface, others are the larval form of animals that live on the sea bed (such as crabs and mussels). Although most are invisible to the naked eye, some jellyfish can be up to 2m across.

Why are plankton important to the world’s oceans?

Without the plankton the sea would be a barren wilderness; they underpin all marine life. At the bottom of the oceanic food chain, the phytoplankton are the food source for the grazing zooplankton, which in turn are eaten by other zooplankton, fish, oceanic seabirds,  and even the arctic bowhead whale.

What makes plankton important to the rest of the world?

Using sunlight to convert carbon dioxide into the tissues of their bodies in the same way that land plants grow, phytoplankton account for half of the world’s photosynthesis, and consequently help to regulate our climate.

How are plankton important to us?

As well as underpinning the marine food chain, it was the dead remains of plankton, that after sinking to the seafloor, slowly created the world's oil and gas reserves. The carbon in these deposits was laid down over thousands of millions of years. Today, man’s burning of oil and gas is returning this carbon to the atmosphere much faster than it is being removed by the plankton.