First plastiglomerate reported from the Indian subcontinent

A research team has found a piece of ‘plastiglomerate’ during a marine litter survey in the Andaman and Nicobar Islands¹. The piece ― a molten mixture of sediments and other natural debris held together by plastic ― indicates widespread plastic pollution in these pristine and deserted beaches, the researchers say.

Beach campfires or trash-fires generate plastiglomerates, as molten plastic, sand grains, coral fragments, shells and wood debris lump together. Since their first documentation in 2014 on Kamilo Beach, Hawaii, plastiglomerates have been found on the beaches of the United States of America, Indonesia, Portugal, Canada and Peru.

This plastigomerate recovered from Aves Island, is the first reported from and Indian subcontinent beach, said environmental chemist and team leader Punyasloke Bhadury at the Indian Institute of Science Education and Research Kolkata in West Bengal.

Bhadury and his colleague Prasun Goswami studied the plastiglomerate’s structural and chemical composition using sophisticated imaging techniques. They found that it had gas bubble apertures and vesicles filled with other substances. The plastiglomerate contained a green plastic material polyethylene, frequently used in the packaging industry, and a black plastic piece that resembled polyvinyl chloride, used in electrical insulation.

The flame-resistant polyvinyl chloride piece retained its shape on the plastiglomerate while the polyethylene melted. “On the less-frequented beach of Aves Island, weathering and waves can release microplastics from such plastiglomerates which may be washed into the sea and end up in humans via marine animals, primarily edible fish,” Bhadury said.

Geologist Patricia Corcoran from the University of Western Ontario in Canada, who coined the term plastiglomerate, said loose microplastics pose more risk to organisms than those embedded inside a plastiglomerate. This is because the particles in a plastiglomerate fragment are "cemented" to one another in the molten matrix, which means it can’t weather easily.

However, large plastiglomerate pieces and slabs could cover and hamper beach ecosystems. “This cover may block sunlight and therefore change habitat temperature for small organisms living beneath the surface,” Corcoran explained.

Despite being hard, weather-resistant objects, plastiglomerates are a threat to marine animals. Prosun Bhattacharya, who studies groundwater pollution at the KTH Royal Institute of Technology in Sweden, says plastiglomerates can release small plastic particles and block the digestive system of marine animals.

Recent research has detected the presence of microplastics in the gastrointestinal tract of the long-distance migratory seabird common tern (Sterna hirundo) and its prey during the non-breeding season². “In addition to releasing microplastics, plastiglomerates may trap sea creatures and birds, harming and killing them,” Bhattacharya said.