The importance of plankton

Without plankton there wouldn’t be polar bears on the ice.

Phytoplankton and copepods are the first two steps in the plankton food chain

In the sea, the plankton begin the marine food chain. Microscopic phytoplankton (tiny plant-like cells) use the sun's energy to combine carbon dioxide and water to create sugar and oxygen in the process known as photosynthesis. Despite being tiny (each phytoplankton cell is smaller in diameter than a strand of human hair), they are so numerous that they account for about 50% of all photosynthesis on Earth. And here, tiny creatures and big numbers start to mix, since 50% of all photosynthesis equates to about 50 billion tonnes of carbon each year, or about 125 billion tonnes of sugar!

The phytoplankton are the food of herbivorous zooplankton (animal plankton) in turn eaten by carnivorous zooplankton. Together all the plankton are the food for fish, which in turn are eaten by other sea creatures such as seabirds, sharks, and seals, in their turn eaten by larger predators like killer-whales. The plankton are also the food source of some of the largest mammals on Earth, the baleen whales. In this way the plankton food web underpins and determines the amount of life in the sea. Quite simply, without the plankton there would not be any fish in the sea for you, me or other creatures to eat, and so that is why there wouldn't be any polar bears on the ice.

The author and plankton scientist Dr Richard Kirby

Of course, as well as eating fish, we also consume many marine creatures that had a larval life in the plankton such as shrimps, crabs, and mussels etc. In some countries we also eat plankton too, such as Antarctic krill that is eaten in Japan as Okami. In fact, in Britain during the Second World War there were trials in Scottish sea lochs to determine whether large static nets could harvest sufficient plankton to supplement the national diet should food become scarce. While those early Scottish trials in the 1940s proved unsuccessful, today, a commercial copepod harvest for food for aquaculture occurs in some Norwegian Fjords by using large nets towed by trawlers.

Now, we need to pay attention to the plankton more than ever. Living at the sea surface the plankton are particularly sensitive to changes in sea surface temperature, which is influenced by the air temperature above. (We often forget that we can engineer our thermal environment unlike other life on Earth that lives where the temperature suits it best.) My research and that of other plankton scientists, is revealing that rising sea temperatures due to current climate change are altering the abundance, distribution, and seasonality of the plankton throughout the oceans with ensuing ramifications for the marine food chain, our commercial fisheries, and the wider marine ecosystem.

Unfortunately, in this short blog there wasn't time to tell you how the plankton do so much more than just support the marine food web. However, you can find out how much more by watching my short film Ocean Drifters, a secret world beneath the waves, narrated by David Attenborough:

Dr Richard Kirby is a British plankton expert, scientist, author and speaker. Follow Richard @planktonpundit on Twitter. You can see more images of plankton and learn more about them in Dr Richard Kirby’s book “Ocean Drifters, a secret world beneath the waves” available on Amazon and as an iBook.