Water, be it salt water, fresh or even seasonal bodies of water, wherever you find it you will find plankton. Plankton is not one type of organism but is a rich, living soup of two groups of ingredients, zooplankton and phytoplankton, the meat and vegetables if you please.
The one celled algae that make up the phytoplankton, using only sun, water and some trace minerals, like any good vegetable, manages to produce proteins, amino acids and some basic carbohydrates. The waste product of this process is ninety percent of the oxygen we all enjoy so much. The concentration of this waste allowed our oxygen dependant animal friends the zooplankton, to develop and thrive while keeping the phytoplankton from poisoning or over populating itself.
Zooplankton are not one type of organism either. What will class an animal in the all inclusive family of zooplankton is more a matter of being between the size of a bacteria and a tiny fish that you can see with the naked eye.
The basic ingredient in this blend is a 70 percent mix of crustacean species representing all of the possible variations in size. Add to this generous amounts of rotifers and protozoa plus every egg and larval stage of every fish and shellfish on the planet, and spice with a dash of krill according to taste. To give the concoction some body we must not forget to add the gelatinous zooplankton, including jellyfish, medusae, salps, and comb jellies, collectively called gelata.
The larval stage of both fish and shellfish depend upon plankton for food, being both diner and dinner. There are some species that continue to feed on plankton into the juvenile adult stage and beyond, these being important food for larger fish. This forms a link between primary producers, phytoplankton, with larger or higher trophic organisms from barnacles, fish and seals to such giants as squid, whales and eventually the large percentage of people that eat seafood.
Active creatures that they are, zooplankton are not really “drifting animals” as the name implies. Recent research shows that zooplankton perform a vertical migration on a daily cycle as well as a monthly migration that coincides with lunar cycles even though it is not dependant on actual moonlight.
These cyclic motions play a role in both the transport of nutrients and the cycling of dissolved organic matter. As a result of this they are useful in the measurement of nutrient over-enrichment as well as maintaining the health of a very dynamic ecology.
If keeping the earths oxygen engine healthy and running smoothly, building and feeding the entire water born food pyramid from bacteria to whale and helping to turn the oceanic compost pile of organic debris and nutrients is not enough for such small creatures, zooplankton may be aiding the fight against global warming. Current research has shown the rapidly reproducing and short lived salp can absorb the large amounts of carbon stored in the phytoplankton it feeds on, carrying it to the ocean bottom when it dies. Further investigation will reveal how effective this carbon sequestration is on a global scale.