The importance of phytoplankton
Forget whales, sharks and the giant squid: it’s the smallest living organisms in the briny blue that keep life on our planet working as it should
Phytoplankton are the definition of the phrase ‘all good things come in small packages’. Simply put, most of these little ocean drifters are microscopic, single-celled plant-like organisms that photosynthesise and can be found in both marine and freshwater and are present in all of the world’s oceans. They live in the euphotic zone (the topmost layer of the ocean) where sunlight is plentiful. There are so many that if you scooped up a Coke can of seawater you’d probably have bagged yourself as many as 75–100 million individual phytoplankton.
Accompanying the phytoplankton in this heady mix of ocean soup are the zooplankton, which are tiny animals — some are the larval stages of much bigger creatures, others will remain as just tiny beasts. All plankton are unable to swim against the ocean currents and so they float at the mercy of the waves. However, there are areas where more phytoplankton occur, usually where upwelling (deep, cold water rises up to the surface) brings essential nutrient-rich water to the surface. Phytoplankton are crucial for life on Earth — it’s almost unimaginable to think of a world without them. The tiny organisms form the basis of the entire oceanic food web, photosynthesising to turn sunlight into energy and providing food for small filter-feeders and grazers, which in turn are food for larger animals, including the fish on our own plates. The phytoplankton also have a huge impact on our atmosphere as they are responsible for producing at least 50 per cent of Earth’s oxygen. They are also an important carbon sink, taking in carbon dioxide from the atmosphere that is then pulled to the bottom of the ocean when the phytoplankton dies. Over millions of years these plankton (along with other marine creatures and organic matter) build up in layers on the seabed, which, under intense pressure and heat, can form oil or natural gas.
“the tiny organisms form the basis of the entire oceanic food web”