Microplastics in Cauvery river may be harming fish: IISc. study

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Microplastics in Cauvery river may be harming fish: IISc. study

  • A new study published in the journal Ecotoxicology and Environmental Safety, reveals that pollutants like microplastics may be causing growth defects in fish, including skeletal deformities, in the Cauvery river.
  • Water is essential for everyone, including animals and plants. When it is polluted, it is capable of causing diseases, including cancer.
  • A lab conducted a comprehensive study of pollution at the Krishna Raja Sagara dam and its potential effects on fish.

What are microplastics?

  • Microplastics are defined as synthetic solid particles sized ranging 1 micrometre (μm) to 5 millimetre (mm).
  • These are insoluble in water.
  • Microplastics are recognised as a major source of marine pollution.

The major sources of microplastics are

  • untreated sewage from many cities along the river’s course
  • Industrial waste
  • Religious offerings wrapped in non-degradable plastics
  • The plastic products and waste materials released or dumped in the river are eventually broken down into micro particles.

The Study

  • They collected water samples from three different locations with varying speeds of water flow – fast-flowing, slow-flowing, and stagnant – since water speed is known to affect the concentration of pollutants.
  • The team analysed the physical and chemical parameters of the water samples.
  • All but one parameter were within the prescribed limits. The exception was dissolved oxygen (DO), whose levels were much lower than they needed to be in samples collected from the slow-flowing and stagnant sites.
  • Water from these sites also had microbes such as Cyclops, Daphnia, Spirogyra, Spirochaeta and E. coli, well-known bio-indicators of water contamination.
  • Using a technique called Raman spectroscopy, the team detected microplastics – minute pieces of plastic often invisible to the naked eye – and toxic chemicals containing the cyclohexyl functional group (atoms in a compound that determine its chemical properties).

The Raman Spectroscopy

  • Raman spectroscopy is an analytical technique where scattered light is used to measure the vibrational energy modes of a sample.
  • In 1928, Raman discovered that when a stream of light passes through a liquid, a fraction of the light scattered by the liquid is of a different colour.


  • Second part of the study, they investigated whether pollutants in water could account for the developmental abnormalities seen in wild fish.
  • They treated embryos of the well-known model organism Zebrafish with water samples collected from the three sites, and found that those exposed to water from the slow-flowing and stagnant sites experienced skeletal deformities, DNA damage, early cell death, heart damage, and increased mortality.
  • The researchers also found unstable molecules called ROS (Reactive Oxygen Species) in the cells of the fish that developed abnormally.
  • ROS build-up is known to damage DNA and affect animals in ways similar to what was seen in fish treated with water from the slow-flowing and stagnant sites.
  • As millions of people are dependent on Cauvery river water and a recent study from the Netherlands has shown that microplastics can enter the bloodstream of humans

What are the measures needed?

  • Swachh Bharat must mean not merely keeping waste out of sight, achieved through costly dumping contracts.
  • It instead means sharply reduced waste generation, full segregation and recycling.
  • Plastic waste around the world is threatening the food web.
  • The crisis thus demands a new global treaty modelled on the Montreal Protocol and the Paris Agreement.
  • India needs to demonstrate that it is serious about a clean-up at the domestic level. Improving plastic waste management and the subsequent reduction in microplastic pollution should be the priority.
  • Various stakeholders, including industry, the government and civil society organisations, need to join hands.

Exam Track

Prelims Take Away

  • Microplastics
  • Raman Spectroscopy