A land survey by a team of marine scientists from the National University of Singapore (NUS) has uncovered toxic bacteria living on the surfaces of microplastics, which are plastic pieces less than 5 millimeters in size, assembled from the coastal areas of Singapore. These bacteria can cause coral bleaching and trigger wound infections in humans.
The NIS team also discovered a variety of bacteria, including useful organisms – like those that can break down marine pollutants like hydrocarbons – into the plastic waste.
Dr Sandric Leong, research director and senior researcher at the NUS Tropical Marine Science Institute (TMSI), said: "Microplasty is a major part of plastic pollution in marine environments. Marine organisms can unintentionally consume bit of microplasty, which can lead to accumulation and subsequent transfer of marine pathogens in the food chain, therefore, the understanding of the distribution of microplasty and the identification of the organisms associated with them is crucial steps in the management of plastic pollution at national and global level. "
This study is the first to investigate the bacterial community of microplastics found in tropical coastal areas. The results were first published in the journal Total environmental science November 17, 2018.
Small plastic, big problem
There are currently more than 150 million tons of plastic in the sea. Microplasty is especially a problem that many marine organisms, such as shrimp, mussels and fish, often commit to these small plastics.
Compared to terrestrial microplasty, microplasty in aquatic ecosystems takes much longer to break down due to the presence of salt and a lower sea temperature. As a result, they present a habitable environment for marine biota to colonize. However, despite their spread, the distribution of microplastics along the coast in tropical areas has not been well studied.
Dr. Leong and Emily Curren, PhD students from TMSI and the Department of Biological Sciences at the NUS faculty, began a six-month study to study the bacterial communities on microplastics collected from the coastal areas of Singapore.
Different bacterial communities living on microplastics
From April to July 2018, the research team collected and examined 275 microplastics from three beaches along Singapore's coastline, Lazarus Island, Sembawang Beach and Changi Beach. Using high-throughput sequencing techniques, the team discovered more than 400 different types of bacteria across all collected microplastics.
The nature of the bacteria Erythrobacterwhich are capable of degrading plastic and bacterial species Pseudomonas veroniiused to clean up oil spills was found. "In view of the expected increase in pollution of plastic waste in oceans, the discovery of such bacteria provides important natural-friendly alternatives to limiting plastic pollution and toxic pollutants such as hydrocarbons," says Ms. Curren.
In contrast, the bacteria are Photobacterium rosenbergiiwhich is often associated with coral bleaching and disease was also identified. The proliferation and accumulation of this bacterium can be detrimental to the coral reefs in Singapore, as the southern stretch is characterized by several large-scale biodiversity-preserved coral finds.
The research team also uncovered species of marine Vibrio, a major cause of wound infections in humans and species of Arcobacter known to cause gastroenteritis in humans. "Since the microplastics we studied were assembled from sites that were easily accessible to the public and in areas widely used for recreation, the identification of potentially pathogenic bacteria would be important to prevent the spread of disease," Ms Curren explains. .
Future studies to identify bacterial sources
This study shows that microplasty is a rich habitat that is home to many types of bacteria, including toxic ones. The NUS research team will carry out further studies to investigate the origin of the bacterial species transported by microplasty. This will allow the identification of non-native species that threaten existing biodiversity and provide insight into dealing with the acute marine pollution issue.