RRI.CO.ID, Jakarta - A groundbreaking study has revealed that microplastic pollution in Indonesian waters is no longer confined to the surface. Research led by the National Research and Innovation Agency (BRIN) has detected synthetic particles at depths of approximately 2,450 meters along the Indonesian Throughflow (ITF), a critical maritime "conveyor belt" connecting the Pacific and Indian Oceans.

The findings, published in the international journal Marine Pollution Bulletin (2024), warn that these particles, measuring less than five millimeters, have successfully bypassed coastal boundaries to settle in the deep ocean, where they pose a direct threat to the marine food web and, ultimately, human health.

The Indonesian Throughflow, or Arlindo, serves as a strategic arterial current that transports massive volumes of water, nutrients, and salt through straits like Makassar and Lombok. Lead researcher Corry Yanti Manullang noted that while historical studies focused on physical oceanography, the vertical distribution of plastics remained a "dark zone."

“Arlindo connects two great oceans, the Pacific and Indian. In addition to carrying water mass, salt, and nutrients, this current also has the potential to carry small particles like microplastics,” Corry explained on Thursday, March 5, 2026, as quoted by BRIN's official website.

During the 2021 TRIUMPH international expedition, researchers analyzed 92 water samples across 11 stations. Using specialized "rosette samplers," they discovered that over 90 percent of the microplastics were fibers, largely originating from synthetic textiles.

“The clothes we wear can also produce microplastics. When washed, tiny fibers from synthetic fabrics can be released and eventually enter the aquatic system,” said Corry.

Further chemical analysis identified common industrial polymers such as polyester, polypropylene, and polyurethane, materials ubiquitous in modern packaging and clothing.

The most concerning aspect of the research involves the biological "entry point" for these plastics. In a parallel study published in Sains Malaysiana, the team analyzed over 6,000 copepods, tiny zooplankton that serve as the primary food source for many fish species.

The team found that these organisms are unable to distinguish between natural food and plastic debris. “Whatever passes in front of them will be caught and eaten,” Corry noted.

This consumption cycle creates a dangerous "biomagnification" effect that begins when copepods at great depths mistakenly ingest microplastics as food. In the second stage, small fish consume large quantities of these contaminated copepods, effectively concentrating the synthetic particles within their own bodies.

The process continues as larger predatory fish eat the smaller fish, further increasing the plastic load as it moves up the food chain. Finally, humans consume these large fish, completing the transfer of synthetic polymers into the human body and highlighting the direct link between deep-sea pollution and public health.

With roughly 70 percent of Indonesia’s maritime territory exceeding depths of 200 meters, this study highlights a massive, under-researched environmental crisis. The presence of plastics two kilometers below the surface suggests that the ocean floor has become a "sink" for the world's waste.

“The finding that microplastics have reached depths of more than two kilometers shows that the problem of plastic waste does not only occur on the coast. This has become a problem for the marine ecosystem as a whole,” Corry concluded.