A diversity of bacteria have been discovered living on microplastics collected from Singapore’s beaches and coastal regions, including some that are pathogenic to humans, according to a team of marine researchers. The scientists, who are with the National University of Singapore (NUS), determined that the pathogenic bacteria can cause a variety of damages, ranging from coral bleaching to infecting open wounds. But along with these harmful microbes, the researchers also discovered some potentially useful bacteria, including a few that apparently can biodegrade oil and plastic.

“Microplastics form a large proportion of plastic pollution in marine environments,” said marine scientist Sandric Leong, a Senior Research Fellow at the NUS Tropical Marine Science Institute (TMSI), who was the senior author of the newly-published study (ref).

Microplastics — tiny pieces of plastic that range in size from the size of a grain of sand up to a small pebble — are prevalent aquatic pollutants in freshwater and marine waterways, both those that are polluted and those that appear pristine (i.e.; ref & ref).

As a new type of habitat, microplastics are indeed special: there are currently more than 150 million tons of plastics in the ocean, making them exceptionally common. Plastics make great little habitats because they are buoyant and nearly immortal, taking tens of thousands of years to degrade — and even longer in the cooler temperatures of aquatic environments, which slow the rate of degradation from that for terrestrial plastic pollution.

There is so much that is still not known about marine plastic pollution. For example, scientists only recently discovered that marine plastics often smell like food (ref), and this may trick a wide variety of marine species into actively seeking them out and eating them.

“Marine organisms may consume bits of microplastics unintentionally, and this could lead to the accumulation and subsequent transfer of marine pathogens in the food chain,” Dr. Leong said.

Plastics have been found inside the bodies of the smallest zooplankton to the largest whales, where they wreak all sorts of havoc, from concentrating organic pollutants and hormones that are absorbed by plastics, to starvation, or death from intestinal blockage or choking.

Plastic pollutants are everywhere, but we still don’t know much about them

Despite the ubiquity of microplastics, the sorts of microbes that dwell on their surfaces have never been studied before, particularly on plastic fragments retrieved from tropical waters.