Researchers trawled waters off the UK and US coast using nets with a finer mesh size that that usually used to filter microplastics. The results from using the finer nets, which can catch smaller plastic particles, increased the global estimate of surface microplastics from 5tn-50tn particles to 12tn-125tn.
“The estimate of marine microplastic concentration could currently be vastly underestimated,” said Pennie Lindeque, of Plymouth Marine Laboratory, who led the research, adding that there may still be smaller plastic particles that were able to slip through the finer nets.
Microplastics are typically filtered using nets with mesh sizes of 333 microns. By contrast, Lindeque's team used 100-micron nets, which found more than 2.5 times more particles than the 333-micron nets that her team also used.
The particles collected by the research were dominated by fibres from ropes, nets and clothing, with the results from both the UK and US showing similar concentrations of microplastics – suggestive that the concentrations gathered are representative of waters near populated land.
Microplastics have a deleterious effect on food chains, particularly when small enough to be eaten by zooplankton, the category of species which underpin the marine food chain. As such, Lindeque's findings as to the underestimation of the scale of ocean plastic pollution is desperate news.
“Using an extrapolation," Lindeque notes, “we suggest microplastic concentrations could exceed 3,700 particles per cubic meter – that’s far more than the number of zooplankton you would find.”