Microplastics have been detected thousands of metres beneath the surface of the Indian Ocean, highlighting how plastic pollution can reach some of the most remote and least explored environments on Earth.

In an exclusive CNA feature on the OceanX and NUS expedition, SCELSE-NUS Research Fellow Dr Yvonne Hii shared insights into the microbial communities associated with plastics in the deep ocean and what their presence could mean for marine ecosystems.

As part of the expedition aboard the OceanXplorer, Dr Hii investigated deep-sea microbial communities and their potential for plastic degradation, including microorganisms that colonise plastic surfaces. These communities, collectively known as the “plastisphere”, can form complex microbial ecosystems on marine plastic debris.

The expedition detected microplastics throughout the water column, including at depths approaching 5,000 metres. Larger pieces of plastic were also found on the deep-sea floor, far from the nearest coast. The microplastics detected were predominantly polypropylene, with polystyrene and other plastic types also identified.

Microorganisms can colonise plastic surfaces and form biofilms. As these biofilms develop, they can increase the weight of plastic particles, potentially contributing to their movement through the water column and eventual deposition on the seafloor.

While the concentrations of microplastics detected were broadly comparable to those reported in other studies, the presence of larger plastic pieces on the deep-sea floor was unexpected. Researchers are now investigating the microbial communities living on these plastics, including whether they may influence processes such as nutrient cycling in the deep sea.

Dr Hii emphasised that there is still much to understand about the potential effects of deep-sea microplastics on marine organisms and ecosystems:

“At this point, I will not say that it is affecting the humans or the animals because we do not have enough studies to give a conclusive answer. However, due to information and research gap in this area, there is something more we should do.”
— Dr Yvonne Hii, SCELSE-NUS Research Fellow

Her comments highlight an important research gap: while microplastics have been detected even in remote deep-sea environments, the ecological significance of their presence remains unclear. The expedition therefore provides an opportunity to investigate how plastics interact with microbial communities and deep-sea ecosystems.

At SCELSE, research spanning microbial ecology, environmental science and biotechnology seeks to understand microbial communities and explore their potential for addressing environmental challenges through sustainable solutions.

The OceanX and NUS expedition provides researchers with valuable baseline data on the deep Indian Ocean and its ecosystems, while opening new avenues for research into the interactions between human-generated pollution and marine microbial life.

Watch the CNA interview.