Plankton Inflation and Vertical Migration

• 21 Oct 2024

Source: TH

Why in News? 

Recently, researchers studied vertical migration of Pyrocystis noctiluca, a specific bioluminescent phytoplankton species which is capable of inflating its size during its migration. 

• This species can expand to six times its original size of a few hundred microns, aiding its buoyancy. 

What are Key Facts Related to Vertical Migration of Phytoplankton? 

• Vertical Migration: Many plankton travel from the cold, dark depths of the ocean to the surface, then drift back down into the darkness in a continuous cycle called vertical migration. 
  • The movement mechanism of single-celled phytoplankton, especially those without swimming appendages, remains largely unexplained. 
• Density Dynamics of Phytoplankton: Phytoplankton are generally 5%-10% denser than seawater, which poses a challenge for their ability to remain near the surface for photosynthesis. 
  • Pyrocystis noctiluca cells behave like little submarines which can control their density so they can choose where they want to reach the ocean’s surface. 
• Ballooning Mechanism: The research team utilised a “gravity machine” which can alter water pressure and density, mimicking the ocean’s depths.  
  • The team found that inflated cells were less dense than the surrounding seawater, allowing them to float toward the surface despite gravity. 
• Inflation During Cell Division: The inflation process occurs naturally during the phytoplankton’s cell cycle.  
  • When a single cell divides, an internal structure called a vacuole acts as a flexible water tank, taking in freshwater and causing the new cells to swell.  
  • This inflation allows the lighter daughter cells to float upward, reaching the nutrient-rich surface waters. 
    • The entire cell cycle of Pyrocystis noctiluca lasts approximately seven days, which aligns with the vertical pursuit of light and essential nutrients. 

What are Planktons? 

• About Planktons: Plankton are microscopic organisms that play a crucial role in marine ecosystems, serving as the foundation of the entire marine food web. 
  • An organism is classified as plankton if it is carried by tides and currents and lacks the ability to swim against these forces. 
• Types of Plankton: 
  • Phytoplankton: Plant-like organisms that perform photosynthesis, converting sunlight into energy, and are vital for producing oxygen and absorbing carbon dioxide. E.g., Cyanobacteria, Blue-green algae, diatoms, dinoflagellates. 
    • Phytoplankton depend on nutrients like phosphate, nitrate, and calcium from their environment to thrive. 
  • Zooplankton: Animal-like organisms that include microscopic animals (such as krill and sea snails) and weak swimmers like jellyfish. E.g., Radiolarians, Foraminiferans, cnidarians, crustaceans, chordates, and molluscs. 
• Size of Planktons: Plankton can vary in size, from microscopic organisms to larger species like crustaceans and jellyfish. 
• Role in the Marine Food Web: Phytoplankton form the base of the marine food web, supporting various marine life. 
  • Zooplankton primarily feed on phytoplankton and, in turn, serve as food for larger marine animals, creating a critical food chain link. 
  • E.g., Krill are a major component of the diet of humpback, right, and blue whales.  
• Migration Patterns: During the day, zooplankton drift to deeper waters to evade predators, but at night, they rise to the surface to feed on phytoplankton.  
  • This process is considered the largest migration on Earth; so many animals make this journey that it can be observed from space. 
• Habitat: Plankton inhabit both saltwater and freshwater ecosystems.   
  • Clearer waters typically indicate fewer plankton, while more turbid waters (cloudy or muddy) are often richer in plankton. 

 

 

UPSC Civil Services Examination, Previous Year Question 

Prelims

Q. Consider the following kinds of organisms:

1. Copepods
2. Cyanobacteria
3. Diatoms
4. Foraminifera

Which of the above are primary producers in the food chains of oceans? 

(a) 1 and 2  

(b) 2 and 3 

(c) 3 and 4  

(d) 1 and 4 

Ans: (b) 

Q.Which one of the following is the correct sequence of a food chain? (2014) 

(a) Diatoms-Crustaceans-Herrings 

(b) Crustaceans-Diatoms-Herrings 

(c) Diatoms-Herrings-Crustaceans 

(d) Crustaceans-Herrings-Diatomsol 

Ans: (a)