Zooplankton
The Greek term plankton literally means ‘drifter’. It is used as a collective term for various organisms that float freely in the water and are too small to move independently of the currents. While drifting single-celled plants are called phytoplankton, the term zooplankton includes animals from various taxonomic groups, from Protozoa to Vertebrata. For many marine mammals, such as baleen whales, zooplankton is the main food source. Euphausiids, a group of crustaceans also known as krill, are among the most important. Many people know what an indispensable part of the marine food web they are. However, a recent WWF report by a researcher from Imperial College London shows what an important contribution these small creatures also make to our global climate—from their phytoplankton diet, they absorb carbon. When they excrete their feces or moult their exoskeletons, these sink to the seabed and the carbon is stored there. Dr Emma Cavan analyzed that in this process about 23 million tonnes of carbon are sequestrated by Antarctic Krill every year. According to this estimate, the sequestration service of these tiny but numerous crustaceans is worth USD 15.2 billion annually.
Sources: Hewitt, Roger P. and Jessica D. Lipsky, “Krill and other Plankton”, Encyclopedia of Marine Mammals, eds. Bernd Würsig, J. G. M. Thewissen, and Kit M. Kovacs, 2018.
Cavan, Emma et al., Antarctic Krill: Powerhouse of the Southern Ocean, edited by WWF-Australia, Sydney, 2022.