A plastiglomerate from a beach in Tamil Nadu. Credit: Kannan Gunasekaran

Researchers have discovered sixteen types of plastic-rock hybrids, including plastiglomerates, pyroplastics, and plasticrust, encrusted with dead marine species on Tamil Nadu's beaches in India1.

This marks the second discovery of plastiglomerates and the first identification of plasticrusts and pyroplastics in India, says lead author Kannan Gunasekaran of Chulalongkorn University in Bangkok, Thailand.

Volunteers surveyed multiple transects, 8 to 10 meters apart, along four beaches between April and July 2022, collecting the plastic-rock hybrids.

The search yielded six plastiglomerates (rocks fused with plastic), nine pyroplastics (plastic pebbles from weathering), and one plasticrust (intertidal rocks embedded with plastic). Spectroscopy confirmed their compositions as polyethylene terephthalate, polypropylene, polyvinyl chloride, polyamide, and low and high-density polyethylene.

Researchers observed vesicles (gas bubble pores) and amygdales (sand or plastic-filled vesicles) on plastiglomerate surfaces, possibly linked to illegal plastic burning or beach campfires.

Single-use plastics such as plates, cutlery, water bottles, bags, and fishing nets littering the beach exacerbate the environmental burden. Dead marine species like oyster larvae, barnacles, bryozoans, and polychaete worms cover these plastics. "These new plastic forms may harm marine organisms. It is critical to identify their distribution," says Gunasekaran.