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

The researchers are now trying to understand how microplastics enter and affect the host

Upendra Nongthomba, Professor in the Department of Molecular Reproduction, Development and Genetics (MRDG) at the Indian Institute of Science (IISc.), would cherish going to the backwaters of the Krishna Raja Sagar (KRS) dam and having fried fish on the bank of Cauvery river. But in recent times, he has been noticing physical deformities in some of the fish and began to wonder whether it has something to do with the quality of water.

A new study led by Prof. Nongthomba, 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,” said Abass Toba Anifowoshe, a PhD student in Prof. Nongthomba’s lab, and the first author of the study.

Prof. Nongthomba’s lab conducted a comprehensive study of pollution at the KRS dam and its potential effects on fish. 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.

In the first part of the study, 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).

Microplastics are found in several household and industrial products, and chemicals containing the cyclohexyl group, such as cyclohexyl isocyanate, are commonly used in agriculture and the pharmaceutical industry.