This tiny aquatic creature breaks down plastic into nano-sized bits and may transfer them into food chain: Study
There is a lot we do not know about the fate of plastic waste that enters water bodies, including the oceans. Some organisms eat them. Others like a common freshwater species do something even more alarming: they appear to be digesting and breaking down microplastics into nano-sized ones, which are about a thousand times smaller than a cell. These findings are a part of a new study.
Plastic debris — micro- and nano-sized — are invisible to the naked eyes. The former is widespread in marine, freshwater, and terrestrial environments. "It is estimated that 99% of the global plastic waste entering the oceans goes ‘missing’, pointing towards gaps in knowledge regarding the microplastic fate," said researchers from the University College Cork (UCC) in Ireland.
Helping researchers fill in the missing data is the tiny Gammarus duebeni, an aquatic organism. It belongs to a group of crustaceans such as crabs, lobsters, crayfish, shrimps, prawns, krill. Alicia Mateos-Cárdenas, the lead author of the study, told MEA WordWide (MEAWW) that she began studying it to understand the negative impact of plastics on the aquatic environment. But she found "surprising" results suggesting that there was something more going on, piquing her interest.
In their lab, the researchers exposed Gammarus duebeni to microplastics in the absence of food. They then tagged the micro-sized plastics with fluorescent dyes, which allowed them to visualize the internal processes: ingestion and fragmentation. Within four days, researchers saw that the organism fragmented microplastics into nano-sized ones. They ingested them, "grinding them with their mandibles [jaws] as they eat them and pass them on to the digestive system,” Mateos-Cárdenas, told The Guardian.
For long, scientists thought UV sunlight, mechanical abrasion, wave action were involved in the breakdown of plastics. "Here, we add more information on the processes that can drive a rapid plastic fragmentation of microplastics into nanoplastics," Mateos-Cárdenas added.
While the long-term consequences of fragmentation are not known yet, researchers suspect that it could affect other organisms. "Here, we show that a very common aquatic species can rapidly produce such nanoplastics with unknown effects. These crustaceans are prey for other fish and birds. Therefore, they may be transferring these plastic fragments into food chains," she explained.
When asked if other organisms are capable of disintegrating microplastics, she added: "I would not be surprised if this is the case." Previous research has shown that krill, marine polychaetes, and sea urchins could also be doing the same. "We hope to see more of this in future studies," she added. The researches hope to understand how the organism carried out the breakdown process. "There are some hypotheses on physical grinding, enzymatic, or even microbiome digestion," she noted.
Further, they tested a widely-used plastic called polyethylene in their study. "There is a wide range of synthetic polymers currently polluting the environment. So we need to understand whether other plastics follow the same path," Mateos-Cárdenas explained, adding that we also need to look for solutions to address the pollution crisis.
The study was published in Scientific Reports.