New study implicates ropes in microplastic pollution
27th September 2021
The hauling of rope on fishing and other 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 characteristics 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 onboard vessels such as fishing boats, an example of which you can see below…
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, the researchers say that in fishing, the rope length deployed during each haul could be up to 220m, depending on the type of vessel and the depth involved.
However, based on a modest 50m of rope being hauled, they estimate that each time new rope is hauled it could release between 700 and 2,000 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 326m to 17bn microplastic pieces entering the ocean annually from the UK fleet alone.
Research fellow Dr Imogen Napper, who led the study, said: “These estimates were calculated after hauling a 2.5kg weight. 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 University of Plymouth was the first to highlight the global problem of marine microplastics. Previous research, in conjunction with the Fishing for Litter initiative, has shown that commercial fishers are acutely aware of the potential for marine litter to cause lasting damage to their catches and the wider industry.
The university is also part of an ongoing project working to develop biodegradable fishing gear.
This study was funded by DEFRA as part of a wider project examining the impact of tyres and textiles on the marine environment.
Professor Richard Thompson OBE FRS, head of the International Marine Litter Research Unit, said: “For centuries, most everyday items including rope and netting used in the maritime industry were produced using natural resources. However, the large- scale increase in plastic production since the 1950s has resulted in plastics progressively replacing their natural counterparts. The durability of plastic has, however, resulted in a major environmental challenge once items reach the end of their lifetime or, as in this study, when they shed microplastics.
“Greater appreciation of the issues within wider society are starting to make a difference. However, this study emphasises a previously unquantified yet substantive source of microplastics and reinforces the level of collaboration required to achieve lasting and positive change.”
The study – ‘Potential microplastic release from the maritime industry: abrasion of rope’ – can be read here.
This story was taken from the latest issue of Fishing News. For more up-to-date and in-depth reports on the UK and Irish commercial fishing sector, subscribe to Fishing News here or buy the latest single issue for just £3.30 here. (Main image credit: University of Plymouth)
