What is Plankton?

Plankton is the term used to describe a diverse range of microscopic organisms, including bacteria, protists, and even some small invertebrates. These organisms support the aquatic food chain and form the base of virtually all aquatic ecosystems. Plankton are found in the ocean, rivers, lakes, and even soil and air. Plankton are both plant and animal life, though the vast majority of plankton consist of photosynthetic autotrophs.

What Types of Plankton Exist?

There are two major classes of plankton—Phytoplankton and Zooplankton. Phytoplankton are photosynthetic autotrophs and the main primary producers of the ocean. These microorganisms are microscopic in size, ranging from 0.2 to 50 microns (1 micron = 1 millionth of a meter). Phytoplankton consist mainly of diatoms, dinoflagellates, and cyanobacteria.

Zooplankton are the other type of plankton and act as grazers, consuming phytoplankton, bacteria, and even other zooplankton. Zooplankton obtain their energy by consuming phytoplankton and are generally found in higher concentrations in the open ocean compared to estuarine and inshore environments. Zooplankton have a wide size range and can be anything from small bacteria-feeding copepods and rotifers to large krill and jellyfish.

Why is Plankton Important?

Plankton is vital to both terrestrial and aquatic life. They play a crucial role in nutrient cycling, photosynthesis, gas exchange, and energy transfer. Plankton act as food for larger animals such as fish, mollusks, crustaceans and whales, making up from 50-90% of a marine mammal’s diet. Fish larvae and bivalves also rely on phytoplankton for sustenance, and the larvae of many commercial species of fish rely on copepods and other zooplankton for early development.

In addition, plankton are responsible for up to 50% of Earth’s total oxygen production, making them important players in the global carbon cycle. Plankton have also been found to play a role in climate regulation; they act as cloud condensation nuclei, which in turn helps to cool down the Earth’s surface. Finally, the aquatic food chain is almost entirely dependent on the presence of plankton, and without plankton, the aquatic environment would collapse.