Abundant microplastics pollution in oceans is likely to have been greatly underestimated, as per research suggesting that the number of particles present there could be at least double than what was thought previously.
The waters off coasts of the UK and US, when trawled by the scientists using nets with a fine mesh size, usually used to filter microplastics, they found many more particles compared to when they used coarser ones that are typically used to filter microplastics.
With the addition of these smaller particles to global estimates of surface microplastics, the range increases from within 5tn and 50tn particles to 12tn-125tn particles, the scientists say.
Plastic pollution is known to be hazardous for the fertility, growth, and survival of marine life. As the smaller particles are the same size as the food, they are eaten by zooplankton, which underpins the marine food chain and plays a vital role in the regulation of the global climate. The new data suggests that microplastic particles may outnumber zooplankton present in some waters.
“The estimate of marine microplastic concentration could currently be vastly underestimated,” said Prof Pennie Lindeque, of the Plymouth Marine Laboratory in the UK, who led the research.
She said the numbers “could be even larger again” as there could be even smaller particles compared to those caught by the fine mesh nets.
There is another new study that shows how microplastics have entered the food chain in rivers. The birds found to be consuming hundreds of particles daily through the aquatic insects on which they feed.
Microplastic pollution is almost everywhere around us, from Arctic snow and mountain soils to many rivers and the deepest oceans. People also consumed and inhaled microplastics, the health impacts of which are yet to be known.
As per the research published last month, microplastics are present in greater quantities than ever before on the seabed that suggested that hundreds of thousands of tonnes of microplastics could be blowing ashore on the ocean breeze every year.
Lindeque’s team, the research published in the journal Environmental Pollution, used nets having mesh sizes of 100 microns (0.1mm), 333 microns, and 500 microns. The particles found in the finest net is 2.5 times more than in the 333-micron net, the kind which is usually used to filter microplastics and 10 times more than in the 500-micron net.
The similar results obtained from the trawl of surface off the coast of Plymouth and the coast of Maine in the UK and the US, suggesting they belong to waters near populated land. The particles were mostly fibers from textiles like ropes, nets, and clothing.
“Using an extrapolation, we suggest microplastic concentrations could exceed 3,700 particles per cubic meter – that’s far more than the number of zooplankton you would find,” Lindeque said. These tiny animals are among the planet’s most plentiful species.
Dr Ceri Lewis, a marine biologist at Exeter University, who was part of the team, said: “Understanding more about the smaller microplastics is important as it is these smaller particles that are more likely to be ingested by the zooplankton that form the basis of marine food webs.”
In a study on microplastics in rivers published in the journal Global Change Biology, the scientists found startling results when they analyzed the droppings and regurgitated pellets of white-throated dippers at 15 river sites in south Wales.
They found the birds that feed on river insects were eating around 200 pieces of plastic per day. These were mostly fibers, and 1/4th of them were of a size larger than 500 microns.
The team also found dippers feeding thousands of plastic fibers to their nest-bound chicks during their development. Previous research by the scientists had disclosed that 50% of the river insects contain microplastic fragments.
Prof Steve Ormerod, of Cardiff University, who led the work, said: “In almost 40 years of researching rivers and dippers, I never imagined that one day our work would reveal these spectacular birds to be at risk from the ingestion of plastics. It is a measure of how this pollution problem has crept upon us.
“Dippers are the world’s only songbirds able to dive and feed on river insects, but that wonderful adaptation also means they have no escape from this pollution.”
However, the impact on the health of the birds is not yet understood. “It is imperative we understand whether microplastics add to the other pollution problems that affect dippers and other river organisms, and we use that knowledge to guide remedial action,” Ormerod said.