26-05-2025
Tar balls from oil spills resurface during monsoon and accumulate toxic metals and bacteria along indian west coast
Kochi: Remains from oil spills in oceans and seas do not disappear from waters but resurface as tar balls, accumulating heavy toxic metals and bacteria as they float into coastal regions during monsoon.
These are the findings of a joint study carried out by researchers from Cochin university, the Centre for Marine Living Resources and Ecology and Atal Centre for Ocean Science and Technology for Islands. Samples were collected from Arabian Sea coast from Kanyakumari to Mumbai.
The tar ball survey was conducted by visual observation during cruises onboard FORV Sagar Sampada and ORV Sagar Kanya. Tar balls were collected from the surface using a bucket as well as by towing a bongo net (Hydrobios) available onboard the two Indian Ocean research vessels.
"We observed the surface-floating tar balls, both small and large, and monitored them through two monsoon seasons to understand their behaviour and contents," said Cusat chemical oceanography department assistant professor Shaju S S. The paper is under review for publication.
Shaju said these tar balls, formed from large oil molecules, attract bacteria and goose barnacles, have toxic heavy metals, and may contain human pathogens like Vibrio species.
Winds transport them along the coast, posing ongoing environmental and health risks.
He mentioned that they were around 0.1-4 cm. "We found 11 types of hydrocarbons and harmful heavy metals, including lead, chromium and cadmium, which can bioaccumulate and enter the food chain."
The analysis of tar ball samples showed significant concentrations of heavy metals, with the highest levels of lead and cadmium found in samples from off the Mumbai water surface (75m depth). The concentrations were 1,396.34ppm for lead and 1,354.03ppm for cadmium while the lowest concentrations were 32.71ppm for lead from off the Goa surface station (50m) and 15.55ppm for cadmium from off the Mumbai surface station (75m depth).
The study stated that temperature plays an important role in maintaining the stickiness of the tar balls. As the temperature increases, the stickiness of the tar balls also increases, which can harm marine mammals, birds, and fish.
