The hauling of rope on maritime vessels could result in billions of microplastic fragments entering the ocean every year, according to new research.
The study, by the University of Plymouth’s International Marine Litter Research Unit, is the first to explore the potential for rope to become a source of microplastic pollution in the marine environment.
It compared a variety of synthetic ropes commonly used in the maritime industry – but differing in age, wear surface and material – to assess the quantity and characterises of microplastics produced while they were in use.
This was achieved by simulating, in both laboratory and field experiments, the rope hauling activity which is typically performed on board maritime vessels such as fishing boats.
The results show that new and one-year old ropes can release around 20 microplastic fragments into the ocean for every metre hauled.
However, as the rope gets older it can release significantly more fragments – two-year-old ropes shed on average around 720 fragments per metre, while 10-year-old rope releases more than 760 fragments per metre.
Writing in Science of the Total Environment, researchers say that in fishing activities the rope length deployed during each haul could be up to 220m depending on the type of vessel and the depth of the ocean.
However, based on a modest 50m of rope being hauled from a boat, they estimate that each time new rope is hauled it could release between 700 and 2000 microplastic pieces. Used rope could release anywhere up to 40,000 fragments.
With more than 4,500 active fishing vessels in the UK, their estimates suggest this could result in anything between 326 million to 17 billion microplastic pieces entering the ocean annually from the UK fleet alone.