MARINE life in one of Scotland’s biggest estuaries has been found to be riddled with pollution caused by plastic despite attempts to cut down on the amount entering coastal waters.
The findings have been made by marine biologists who discovered that up to 80 per cent of flatfish and 60 per cent of hermit crabs in the Firth of Clyde have ingested tiny pieces of plastic.
Scientists from the Marine Biological Station on the isle of Cumbrae also found significant contamination in sandhoppers – tiny crustaceans that live in the sand below the tide line – suggesting the firth’s entire marine food chain is affected. An earlier study found 80 per cent of prawns were contaminated.
The findings, described yesterday as “deeply worrying” by environmental groups, suggest that government initiatives to cut down on plastics entering the seas around Scotland are failing. The biggest culprits are plastic shopping bags, synthetic fibres from clothes, washed in through the sewerage system, and nets used by the fishing industry.
Scientists believe most of Scotland’s firths which are surrounded by large towns and cities may have similar levels of plastic pollution as tidal eddies mean the plastics are swept round and round rather than further out to sea.
Marine biologist Dr Phillip Cowie said: “Most research until now has been on seabed organisms like prawns, which are not fussy eaters. They eat anything. But now we have found plastic in other species too, which feed differently. There were high levels of plastics in flatfish and hermit crabs, and occasionally you find hermit crabs with fragments of these cheap, blue plastic bags in their guts.
“Sandhoppers live on the strand and tend to eat degrading seaweed. They are quite discerning, which tells you these plastic filaments are mixed in with the seaweed. That probably indicates the sheer quantity of plastics in the environment is increasing.
“The fact that such a wide range of organisms can ingest plastic materials shows their pervasive nature. Many of the organisms studied are fed upon by other organisms, and these ‘persistent’ pollutants may be passed along wildlife food chains.”
Cowie said the problem was likely to be widespread. “The Firth of Clyde is a semi-enclosed basin with towns and cities lining the shore. Slicks of large and small plastics become aggregated in these areas temporarily due to the action of currents and breezes.
“It is probably not solely a Clyde issue. Many other industrialised or densely populated estuaries in the UK and internationally with high plastic input from sources related to the land and sea will have a similar issue.”
The effects of plastic contamination on small marine organisms had yet to be determined, he added. “There may be no effects, or, if they accumulate they may cause chronic effects that generally reduce the overall fitness of organisms and their ability to cope with their environment.”
Lang Banks, director of WWF Scotland, said: “It’s deeply worrying to see that the threat posed to marine wildlife by microplastics not only remains but is actually growing.
“We’ve seen good progress in recent years at cleaning up our seas, but the threat from microplastic pollution has been hidden. We must start to address this before it does any long-lasting damage to the wider marine environment.”
The Marine Conservation Society said the findings heightened the need for European countries to agree targets under the marine directive currently being debated.
Its Scottish projects officer, Anne Saunders said: “The amount of litter in the world’s oceans has been increasing year on year. Marine litter does not recognise political boundaries, and countries must work together to make our seas cleaner and safer.”
Harriet Bolt, Shetland Islands Council spokeswoman for KIMO, an alliance of European authorities working to eliminate marine litter, said: “The discovery of particles in species consumed by humans shows that, whether disposed of deliberately or not, we can’t ignore plastic pollution.”
The Scottish Government has set a target of significantly reducing marine litter by 2020. But plastics remain a major threat to the coastal economy and environment, according to the Marine Scotland agency study.
A report last year found that plastic makes up 62 per cent of the waste, up from 52 per cent in 1996. Common litter items such as plastic bags, food packaging and fishing gear have all been the subject of waste-reduction campaigns. The report said a lack of improvement in levels of sea pollution threatened Scotland’s Zero Waste Plan.