The word “plankton” refers to the floating marine organisms that live on the surface of oceans. These organisms can be plants or animals. The plant forms are microscopic algae whose photosynthesis reactions provide the Earth‘s atmosphere with the majority of its oxygen. The other type of plankton, composed of tiny animals, is called zooplankton.
Zooplankton is made up of hundreds of thousands of different species of animals. Some are baby or larval forms of the animals while others spend their whole life as free-floating organisms. The entire scope of species of zooplankton is enough for scientists to have identified whole communities of these organisms. These communities are very dynamic in that they change their structure and populations on a seasonal basis.
- Many members of a zooplankton community begin their lives in estuaries where crabs, fishes, and a whole host of various invertebrates come to breed.
- In many species of zooplankton, the larval forms look nothing like the adults they will become. A remarkable example is the flounder fish.
- As a bottom-dwelling adult it becomes a flat fish with eyes on the upper surface of its body. Then it is ready to produce more planktonic larvae.
- Many members of the zooplankton community feed on other members of the population, and in turn become the meals of other larger predators.
- In the polar regions, a small component of the zooplankton community called krill is the basic diet of the many summer-feeding whales.
- One of the benefits of becoming a pelagic, or open ocean-dwelling, organism for a specific population is that the drifting currents move the offspring from one place to another. This ensures species distribution, which is critical to the survival of many species. It keeps genetic diversity high and populations healthy.
- The waterborne distribution of zooplankton helps its population survive harsh environmental conditions such as freezing, high heat, large storms, and other severe natural phenomena.
- For many planktonic forms, their lifestyle as organisms suspended on the ocean surface, means that they can avoid unfavorable conditions in the deeper regions of the water column.
- One of the concerns raised by the increasing depletion of the ozone layer is how the increased influx of ultraviolet radiation that it causes will affect zooplankton.
- As in all food web chains, the zooplankton provide a foundation for so many other and larger food species that some forms of higher predators may be seriously impacted.
- Until the increasing ozone loss is curbed, the protection of estuaries, deltas, and other coastal planktonic breeding grounds is crucial for the continued production of zooplankton.