We've been hearing a lot lately about how disintegrated waterborne trash is one of the main sources of ocean microplastics pollution. A new study, however, suggests that aging maritime rope could also be making a significant contribution.
Ocean microplastics are tiny particles or fibers of plastic that are suspended in the water, where they get consumed by fish. When those fish are eaten by humans or other animals, the microplastics get passed along into their bodies, potentially causing health problems.
Previous studies have determined that a great deal of microplastics come from plastic packaging and other garbage, which gradually deteriorates after being dumped in or washed into the sea. Other sources include synthetic textile fibers that enter the wastewater stream from washing machines, and even particles of automobile tire rubber that get washed off the roads and down into storm sewers.
All of that being said, scientists from Britain's University of Plymouth wondered if the polymer ropes used for hauling in fishing nets might also be to blame.
In both lab-based simulations and field experiments, it was initially determined that one-year-old ropes release about 20 microplastic fragments into the ocean for every meter (3.3 ft) hauled. That figure rose to 720 fragments per meter for two-year-old ropes, and over 760 for 10-year-old ropes.
With those figures in mind, it was estimated that a 50-m (164-ft) length of new rope likely releases between 700 and 2,000 microplastic fragments each time it's hauled in. For older ropes, the number could be as high as 40,000 fragments. It was further estimated that the UK fishing fleet – which includes over 4,500 vessels – may be releasing anywhere from 326 million to 17 billion rope microplastic fragments annually.
"These estimates were calculated after hauling a 2.5-kg [5.5-lb] weight," says the lead scientist, Dr. Imogen Napper. "However, most maritime activities would be hauling much heavier loads, creating more friction and potentially more fragments. It highlights the pressing need for standards on rope maintenance, replacement and recycling in the maritime industry. However, it also shows the importance of continued innovation in synthetic rope design with the specific aim to reduce microplastic emissions."
The research is described in a paper that was recently published in the journal Science of the Total Environment.
Source: University of Plymouth
