About Us  :  Online Enquiry


Plankton – an overview

Plankton – an overview


  • Planktons include both microscopic plants (like algae) and animals (like crustaceans, protozoans, etc.).
  • The term `planktons’ refers to the group of organisms which float or drift in the surface water of rivers, lakes and oceans.
  • The locomotive ability of planktons is limited.
  • Thus, their distribution is determined by the currents in an aquatic ecosystem.
  • Planktons are further classified into two types: Phytoplanktons and Zooplanktons.


  • It is the term derived from two Greek words ‘phyto’ which means ‘plant’ and ‘plankton’ which means ‘to wander’ or ‘drift’.                          Plankton – an overview
  • Phytoplanktons are microscopic in size and live in aquatic environments, freshwater as well as saltwater.
  • Like land plants, most phytoplanktons carry out photosynthesis and thus consume CO2 and release O2.
  • The total biomass of phytoplanktons is greater than that of the plants on land.

Phytoplanktons and Climate Change

  • Phytoplanktons assist in preventing climate change. Through photosynthesis, they convert CO2 into 02.
  • Moreover, the carbon stored in phytoplanktons is carried to deep seas when they die and some carbon is transferred to zooplanktons, because phytoplanktons are eaten by them.

Factors Affecting Phytoplankton Diversity


  • Phytoplanktons are limited to the upper part of oceans, where sunlight is sufficient to carry out photosynthesis.
  • The upper part of the ocean, where sunlight reaches is called euphotic zone.


  • Phytoplanktons require nutrients for their growth and reproduction, e.g., nitrogen and phosphorus. Some phytoplanktons also require silicate in significant amounts.
  • Some phytoplanktons can fix nitrogen from the atmosphere and can grow in those regions, where it is not available. Phytoplanktons also require iron in traces.
  • Low concentration of iron in ocean water hampers the growth of phytoplanktons.


  • Rate of photosynthesis increases with an increase in temperature. However, photosynthesis diminishes sharply after a point is reached.                Plankton – an overview
  • Temperature, along with illumination, influences the seasonal variations of phytoplankton production.


  • Most species of phytoplanktons reproduce actively in low saline regions.

Consumption by Zooplanktons:

  • This is one of the most important factors that determine the population of phytoplankton.


  • The highest concentration of phytoplanktons is found in temperate regions, while the tropical and subtropical regions have 10-100 times of lower concentration.

Food Web in Aquatic Ecosystems

  • Phytoplanktons are the foundation of an aquatic food web (primary producers), i.e., they produce their own food.                              Plankton – an overview
  • They are consumed by zooplanktons which are further consumed by higher animals in a marine ecosystem.
  • They can also be consumed directly by higher level organisms.
  • Phytoplanktons can also result in the death and destruction of the marine ecosystem on a large scale.
  • Certain species of phytoplanktons produce powerful biotoxins.
  • These biotoxins can kill marine life and even human beings who eat contaminated sea food.
  • Phytoplanktons can cause mortality in aquatic ecosystem in other ways as well.
  • For instance, algal blooms during eutrophication of water bodies lead to large scale destruction of aquatic life.


  • Zooplanktons are marine animals ranging from tiny flagellates to jelly fish that measures 2 m in diametre.
  • Zooplanktons, like other planktons, move due to the energy of ocean currents.


Environment & Biodiversity

Send this to a friend