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Toxic Bacteria Found on Microplastics Retrieved From Tropical Waters

When these tiny pieces of plastics are ingested by marine organisms, they may accumulate and be transferred up the food chain.

There are currently more than 150 million tons of plastics in the ocean. Pieces of plastic smaller than 5 millimetres in size, called microplastics pose an evident problem as many marine organisms, such as shrimps, mussels and fish, often mistake these tiny plastics for food. This leads to the accumulation and subsequent transfer of marine pathogens in the food chain.

Microplastics take a long time to degrade due to the presence of salt and a lower temperature in the ocean. As a result, they present a habitable environment for marine biota to colonise. Yet, despite their prevalence, the distribution of microplastics along the coasts of tropical regions is not well studied.

To better help manage plastic pollution on a national and global scale, the distribution of microplastics and organisms attached to it must first be studied.

Marine scientists from the National University of Singapore (NUS) have uncovered toxic bacteria living on the surfaces of microplastics collected from the coastal areas of Singapore. These bacteria are capable of causing coral bleaching, and triggering wound infections in humans.

They also discovered a diversity of bacteria, including useful organisms – such as those that can degrade marine pollutants like hydrocarbons – in the plastic waste.

This six-month study is the first to examine the bacterial community on microplastics found in tropical coastal regions. The results were published in Science of the Total Environment.

Using high-throughput sequencing techniques, the team discovered more than 400 different types of bacteria across all the microplastics collected. Some bacteria identified were Erythrobacter – which is capable of degrading plastic, Pseudomonas veronii – which have been used to clean up oil spills, Photobacterium rosenbergii, often associated with coral bleaching and disease, Vibrio – major cause of wound infections in humans, as well as Arcobacter – known to cause gastroenteritis in humans.

This study demonstrates that microplastics are a rich habitat that is home to many types of bacteria, including toxic ones. The NUS research team will conduct further studies to examine the origin of the bacteria species transported by the microplastics. This will allow the identification of non-native species that threaten the existing biodiversity, and provide insights on managing the urgent issue of marine plastic pollution. [APBN]