A team of researchers from several French and Spanish institutions demonstrated that the actual amount of plastic floating around in oceans is much lower than previously believed, according to a study published in Science (1). It’s not all good news, however. The team also found that these plastics can remain in the water much longer than predicted, further increasing the damaging effects of plastic pollution on aquatic systems.
Plastics are a major environmental problem, particularly affecting our marine and freshwater locations. Due to poor management on land, it’s estimated that millions of tonnes of plastic end up in rivers, oceans and other water sources. However, these estimates are often much higher than the amount of plastic actually found floating around in the sea. Is it a case that the calculations are incorrect? Or is there a missing plastic sink, a place where plastic goes to hide somewhere?
Now, a French and Spanish team believe they have found an answer to solve this “plastic sink” mystery. It turned out previous assessments overestimated the amount of plastic by at least two to three orders of magnitude. The researchers spotted that earlier evaluations not only overestimated the size and weight of microplastic particles found in rivers and oceans but also combined data from different databases collected using different sampling techniques.
“The in situ data that we now have for microplastics in rivers, compared to early empirical modelling studies, allowed us to assemble a robust database which we were then able to analyse to obtain a more reliable estimate for the quantity of microplastics being discharged from rivers into the sea”, said Dr Lisa Weiss from the University of Perpignan. “This process revealed several significant methodological errors in previous flux estimates. When we then corrected these mistakes, we found that the global river flux estimates are two to three orders of magnitude less than previously thought”.
This may seem like good news at first, but we should not dismiss the problem that plastics continue to pose just yet. In fact, the team found that most plastics stay at the surface for years rather than just days, as previously estimated. This means that, even if we were to stop discharging microplastics today, these tiny particles would continue to damage marine ecosystems for at least several years.
This is a relatively new field of research. We are now just now starting to understand the life cycle of plastic in the water. In the future, more research is needed to ensure we have a chance at winning the battle against plastic pollution. It’s essential that the scientific community gets together, correct past mistakes and follow standard protocols to deliver the best possible advice needed to protect our water.
(1) Weiss L, Ludwig W, Heussner S, Canals M, Ghiglione J, Estournel C, Constant M, Kerhervé P (2021) The missing ocean plastic sink: Gone with the rivers. Science 373, 107-111 DOI: 10.1126/science.abe0290