The study by a team at NUI Galway’s school of natural sciences found 73% of the fish they analysed had microplastic fragments in their stomachs.
The fact that the samples were from fish specimens collected from depths of 300 to 600 metres below the surface in the north-west Atlantic shows the effects are not restricted to organisms living nearer the surface.
Microplastics are the result of breakdown of larger plastic items in the ocean, or from wastewater, containing plastic clothing fibres or micro-beads from shampoos and other personal care products.
While most of these micro-plastics float near the surface of the ocean, the new research shows their occurrence was much higher than previously reported at deeper levels.
The lead author is Alina Wieczorek, a PhD student at NUI Galway’s zoology department, who conducted the research with colleagues from the university’s Ryan Institute, earth and ocean sciences, and its Marine Renewable Energy Ireland research centre.
Ms Wieczorek said that deepwater fish are likely exposed to the microplastics when they migrate to the surface at night to feed on microscopic plankton. A concern is that these fishes’ movements may aid the transport of microplastics from surface waters and adversely affect how species help transport carbon and nutrients to the deep sea.
The dead fish which they took from midwater trawls by the Marine Institute’s Celtic Explorer research vessel were from a circular current in the north-west Atlantic that is thought to accumulate micro-plastics, meaning they may have originated from a particularly polluted patch of the Atlantic Ocean.
“This would explain why we recorded one of the highest abundances of microplastics in fishes so far, and we plan to further investigate the impacts of microplastics on organisms in the open ocean,” Ms Wieczorek said.
Bills proposing a ban on micro-plastics have been introduced in recent years by the Labour and Green parties, but the Government has cited technical issues around definitions and the requirement to seek derogations from EU market rules for not legislating to date.
The heads of a bill to prohibit the use of plastic microbeads in cosmetics and detergents are being prepared by the Department of Housing, Planning and Local Government, after it got more than 3,000 submissions during a public consultation last year.
The full NUI Galway research will be published today in the Frontiers in Marine Science journal, but an online abstract article has already been viewed more than 45,000 times.
The study’s co-author, Tom Doyle of the Ryan Institute, said it shows that even seemingly remote fish thousands of kilometres from land and 600m down in the ocean are not isolated from human pollution.
“It’s worrying to think that our daily activities, such as washing our synthetic clothes in our washing machines, results in billions of microplastics entering our oceans through our waste water stream that many eventually end up in these deep sea fishes,” he said.