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.
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