The Role of Plankton

The word plankton comes from the Greek word planktos, meaning “wanderers.” The name describes the ability of plankton to move on ocean currents. This motion is how plankton get from place to place where it can be used as a food source by a variety of marine creatures. Plankton are at the bottom of the food chain, which makes them a fundamental building block in the ecology of marine environments. Their role as the foundation of the marine food chain makes their health a critical factor in determining the health of the ocean.

What Are Plankton?

Plankton are generally microscopic plants and animals that live in both salt water and fresh water. Some species of plankton grow to a large size, such as those categorized as jellyfish. Their growth depends on many factors, such as the nutrient concentration in the water, the number and types of plankton in the water and the condition of the water itself. 

The Role of Plankton in Marine Ecology

Think of plankton as the basic food source of marine environments. A wide variety of creatures feed on plankton, so that when plankton health is threatened, the problem affects the entire food chain. Coral, clams, and whale sharks feed directly on plankton, but thousands of other species feed on the larva, eggs and adult forms of other creatures that need plankton to survive. Larger forms in turn eat these smaller creatures, so that the entire ecology can be endangered by disruptions in the supply of plankton.

Types of Plankton

Plankton can be classified into two basic types, phytoplankton and zooplankton. Phytoplankton are microscopic plants that grow abundantly to provide a food source for many different life forms. They are generally found near the surface of water, because they require sunlight for photosynthesis like other plants. They do not have a means of locomotion, but must drift with the water itself.  Zooplankton is the animal form of plankton, that may be protozoa, jellyfish, worms and small crustaceans. Zooplankton feed on the phytoplankton, and like them, they depend on the water’s currents, tides and winds for locomotion. Zooplankton are heavier than phytoplankton, however, and generally have spikes on their bodies to distribute the weight more evenly in the water.

Threats to Plankton Health

Because the plankton are so important to the life forms in any body of water, disruptions in their number can have quick and significant effects. Human activities like oil spills and pollution from chlorofluorocarbon materials from computer chips, aerosol products and air-conditioning units can have damaging effects on the bodies of water in which plankton live, grow and reproduce, causing a thinning of the ozone layer and changes in the amount of sunlight available for proper photosynthesis.  Climate change can affect the temperatures of oceans, causing a change in the amount of plankton growth. Acidification of ocean water from excess carbon dioxide in the atmosphere can also impact plankton populations. Even introduction of foreign species into marine environments can have a damaging effect on the number and growth of plankton in the bodies of water. Scientists routinely study the health of plankton to ensure that they continue to be available for the many life forms that depend upon them in our oceans, rivers, lakes and seas.