Context: Recently, a team of scientists from the Indian National Centre for Ocean Information Services (INCOIS) have discovered a way to measure the quantity of chlorophyll-a that indicates abundance of phytoplanktons in the Bay of Bengal in real-time.
About the study

• The scientists closely tracked the long-term trends of chlorophyll-a in the northwestern Bay of Bengal.
• It was based on in-situ and satellite data spanning over the last 16 years, from January 2003 to December 2018.
• National Aeronautics and Space Administration (NASA)’s MODIS (Moderate Resolution Imaging Spectroradiometer), NASA’s VIIRS (Visible Infrared Imaging Radiometer Suite) sensor and Indian Space Research Organisation (ISRO)’s OCM-2 (Ocean Colour Monitor-2) were used for satellite data.
• As per findings there were two peaks of chlorophyll: the primary peak occurred during the pre-southwest monsoon due to the recurrent phytoplankton bloom in the coastal water and the secondary peak occurred during the end of the southwest monsoon, spreading to far offshore areas.
• Reasons: Along with increase in phytoplanktons, other reasons for peak in chlorophyll-a may be physical forces such as upwelling, wind-induced vertical mixing, convective overturn and chemicals from various sources including river runoff.

Conclusions

• Increased Nutrients and More Phytoplanktons: It reveals that the study area experienced maximum spatial variability during pre-southwest monsoon with salinity, and nutrients, the major controlling factors for the abundance and distribution of phytoplankton.
• Chances of Eutrophication: Increase in nutrients could tell an overall improved health status of the ecosystems as a whole; at the same time excessive phytoplanktons could be detrimental to ocean health because of eutrophication.
• Eutrophication: When a water body becomes overly enriched with minerals and nutrients which induce excessive growth of algae or algal bloom.
• This process also results in oxygen depletion of the water body affecting other aquatic animals.

About Phytoplanktons  

• Phytoplanktons are plants while zooplanktons are animals, this is the main difference between them. Other Crustaceans, krills are examples of zooplanktons; algae and diatoms are examples of phytoplanktons. 
• These two types of planktons float on water surfaces. Both are economically important and are similar in size.  
• While phytoplanktons are a source of primary producers in the aquatic food chains, zooplanktons are consumers, it eats phytoplanktons.  
• Phytoplanktons either produce food through chemosynthesis or photosynthesis. They are known to liberate large amounts of oxygen through photosynthesis and are deemed as good indicators of ocean health. 

Significance of Phytoplanktons

• They contribute more than half of the oxygen in the environment.
• They reduce global warming by absorbing human-induced carbon dioxide.
• They also serve as the base of the ocean food chain.
• They are important bioindicators regulating life in oceans. Their abundance determines the overall health of the ocean ecosystem.

Chlorophyll

• Chlorophyll is the major pigment used by plants for photosynthesis, the process by which light energy is converted to chemical energy through the synthesis of organic compounds.
• The word chlorophyll comes from two Greek words; Chloros which means green and phyllon which means leaf.

Four types of chlorophyll

• Chlorophyll a, found in all higher plants, algae and cyanobacteria.
• Chlorophyll b, found in higher plants and green algae.
• Chlorophyll c, found in diatoms, dinoflagellates and brown algae; and
• Chlorophyll d, found only in red algae.