Types of Plankton
Plankton are free-floating organisms that are at the mercy of the water due to their limited ability of locomotion. The word plankton actually comes from the Greek word planktos which means "drifter" or "wander". They can be plant, animal, bacteria, or even a virus. Plankton plays a vital role in the health and survival of life in the world's oceans. In fact, they are responsible for the largest production of photosynthesis in the ocean. Plankton absorbs most of the sun's energy and then transfers it to many of the communities found in the ocean. On land there can be no life without trees, shrubs, and other plant life that emit gasses which are vital for most living creatures to survive. The plankton works the same way for life in the ocean.
Plankton can be classified into one of seven sizes. The largest plankton in the ocean is megaplankton measuring more than 20 centimeters (cm). The next largest plankton is macroplankton organisms that can be between 2 to 20 centimeters in size. Mesoplankton measures between 0.2 to 20 milimeters (mm) in size. These size groups can be seen with the naked eye. They are also considered net plankton because they are able to be captured in nets.
Microplankton measures between 20 to 200 micrometers (µ). Nanoplankton is even smaller with measurements of 2 to 20 micrometers. Picoplankton is only 0.2 to 2 micrometers. They are primarily bacteroplankton. The smallest is femtoplankton. Femtoplankton measures less than 0.2 micrometer (µ). Viroplankton fall into this category.
Phytoplanton are considered autotrophs. In this case, phytoplanton uses photosynthesis to produce energy. They float along currents in the ocean and create the base of the food web for many ocean communities. Phytoplanton are too small to be seen without the aid of a microscope and are classified as nanoplankton. However, if there is a high concentration of phytoplankton in the water, the water may have a green tint to it. This is due to the chlorophyll in the cells of the plankton.
Zooplankton are free-floating animal plankton. Zooplankton feed from phytoplankton, bacteroplankton, and even other zooplankton. Zooplankton has their vital role in the food web of the ocean. They are a great nutrient supply for several fish species as well as baleen whales.Their size can vary from microplankton all the way to the net plankton sizes.
Zooplankton can be further classified as holoplankton or meroplankton. Holoplankton spend their entire life cycle as plankton. Meroplankton only spend a part of their life, usually as larvae, as plankton. Many adult meroplankton will either spend their lives on the ocean floor or become nekton. Neckton are animals of the open ocean capable of moving at will against the flow of water unlike plankton which has limited means of travel except where the water takes them.
Many bacterioplankton are saprotrophic meaning they obtain their energy by consuming dead or decaying materials produced by other organisms. Other bacterioplankton are autotrophic and process energy via photosynthesis or chemosynthesis. They fall into the picoplankton size classification. Although small, they play a huge role in the ecological structure of the ocean. They contribute to nitrogen fixation, dentrification, remineralisation, nitrification, and methanogenesis.
Viroplankton, sometimes spelled virioplankton, is the smallest of plankton and is classified as a femoplankton .Viruses are known to thrive in an aquatic environment. In fact, scientists believe viroplankton out number bacterioplankton. However, there is still much to learn about viroplankton. Research has shown that viroplankton communities are made of bacteriophage and eukaryotic algal viruses. It is theorized that viroplankton plays their own vital role in aquatic microbial communities because the impact it has on bacteria and unicellular algae populations.
Plankton used to be classified into only two groups: phytoplankton and zooplankton. Thanks to the hard work and break through research, oceanographers and marine biologist are able to further classify different types of plankton. Although there is still much to learn about these organisms, scientists have made amazing strides to discover how plankton function as well as their crucial role in the communities of the ocean.
© 2014 L Sarhan