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Plankton – an overview

Plankton – an overview

PLANKTONS

  • 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.

Phytoplanktons

  • 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

Sunlight:

  • 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.

Nutrients:

  • 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.

Temperature:

  • 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.

Salinity:

  • 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.

Distribution:

  • 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

  • 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.

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Environment & Biodiversity

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