Microplastics are minute plastic particles that are becoming a growing source of worry due to their extensive prevalence in the oceans and their possible physical and toxicological concerns to aquatic species. Plastic fragments have been detected in organisms ranging in size from minute crustaceans to huge mammals. Microplastic pollution in the world's oceans is a rising issue and most us focus on the land based sources like abandoned plastic bags or water bottles. But we have forgotten the link between the microplastics and the fishing activity. Now few researchers have identified that the fishing activity is also a potential source of microplastics in Ocean.
Fishing gear a source of microplastics.
Nets, ropes and pots used in fishing are all potential sources of microplastics in the water. The microscopic particles could be worn away from fishing gear during usage, or they could appear if the gear is lost or thrown into the ocean. According to new research, the pulling of rope on maritime vessels could result in billions of microplastic particles entering the water every year. The research, conducted by the International Marine Litter Research Unit at the University of Plymouth, look into the possibility of rope being a source of microplastic pollution in the ocean and they are the first to research microplastics in maritime rope.
Maritime rope and its contribution to Microplastics
In order to assess the contribution of microplastics by the maritime rope it was assessed based on the quantity and characteristics of microplastics formed while they were in use. The researchers have compared the variety of synthetic ropes routinely used in the marine industry with differing in age, wear surface, and substance. The researchers have imitated the rope hauling activity both in lab and field as that conducted on board maritime vessels such as fishing boats. The findings revealed that every metre tugged, new and one year old ropes might release roughly 20 microplastic bits into the water. However, the aged rope, can release a greater number of fragments. Ropes that are two years old shed roughly 720 fragments per metre on average, whereas ropes that are ten years old discharge more than 760 fragments per metre.
According to researchers, depending on the type of vessel, the rope length released during each haul during fishing activities might be up to 220m deep. The researchers have predicted that for each time hauling of new rope from a boat, it could discharge between 700 and 2000 microplastic fragments, it is based on a computation of 50m rope being hauled from a boat in field experiments. While using an old age rope for same length and hauling it could release of about 40,000 fragments.
Fishing Vessels in UK and its contribution to microplastics
There are more than 4,500 operational fishing vessels in the UK and the researchers have estimated that the UK fleet alone might release around 326 million to 17 billion microplastic fragments into the ocean every year. Dr. Imogen Napper the lead researchers of this research said that the estimate was based on the hauling of 2.5kg weight. But most fishing vessels would be hauling much bigger loads, which will cause more friction and more fragmentation of maritime rope.
The fragmentation of Polypropylene Rope, Polyethylene Rope and nylon rope was studied by Welden and Cowie in 2016. Based on their result about 47,616 tons of microplastic would be created annually by the degradation of abandoned, lost, and discarded fishing gear.
The reason for shedding of more amount of microplastics by the old age rope is due to the environmental degradation which occurs due to the exposure of maritime rope to UV and sea water. The use of hydraulic net haulers or net drums on most industrial fishing vessels can cause significant abrasion of maritime rope which results in direct discharge of microplastic into the marine environment.
The University of Plymouth was given the Queen's Anniversary Prize for Higher and Further Education in 2019 for being the first to recognize the global problem of marine microplastics caused by maritime rope.
The commercial fishing vessels are the major source of microplastic pollution but surprisingly, many of the fragmented particles settles in deep sediments on the ocean floor and it is tedious to estimate the amount of microplastic pollution. The bottom dwellers such as Molluscs, oysters and scallops swallows these microplastics and in turn they reach the human food chain.
Currently there are no strict guidelines or rules for renewal or replacement of ropes and lines in fishing vessels. But at present we can follow some best practices to reduce the effects of environmental degradation of rope by storing the rope away from direct heat and sunlight, or placing it in a separate compartment in the fishing vessel which is dry, properly ventilated, free from chemicals, detergents and other source of potentially damaging agents. Before usage the maritime rope has to be inspected internally and externally for deterioration, excessive wear, or damage. The wear of the rope can be reduced by applying coatings of resins. In order to reduce the abrasion and to avoid pinching when hauling of the rope, the diameter of the pulley groove should be placed 10% greater than the diameter of the pulley. The best practices can be followed to a limit but there is an urgent need for imposing of standards in the maritime industry for rope maintenance, replacement, and recycling. There is also an urgent research needed to address and asses the problem of microplastic pollution due to maritime rope, to develop a maritime rope to reduce microplastic emissions or to develop a biodegradable fishing gear that can be utilised by both small and large boats in the sector.