Its densely populated coastline combined with its limited connection to the Atlantic Ocean makes the Mediterranean Sea a hotspot for plastic pollution.

But how much plastic actually floats in the sea, and where does it end up? A new study published in Frontiers in marine sciences This month, a model was used to determine that there are about 3,760 metric tonnes (about 4,144.7 US tonnes) of plastic in the Mediterranean.

---

“The present study was among the first attempts, where simulated plastics distributions were compared with existing observations in the Mediterranean,” said lead author of the study, Dr Kostas Tsiaras of the Hellenic Center for Marine Research, told EcoWatch in an email. “The model developed has shown a reasonable ability to reproduce the observed distributions of plastics in the marine environment and can therefore be used to assess the current state of plastic pollution in the Mediterranean.”

A plastic hotspot

Scientists already know that plastic pollution in the Mediterranean is a major problem. In 2018, WWF warned that the body of water famous for its beaches and seafood risked becoming a “sea of ​​plastic,” which accounted for 95% of the waste polluting its waters and beaches. This has serious consequences for the marine life and human communities in the region.

“Marine organisms are known to ingest or become entangled in plastic waste, with sometimes fatal consequences,” Tsiaras said, pointing to a Study 2019 stranded toothed whales in Greece. The study examined 34 strandings and found plastic in nine of the stomachs of marine mammals, determining that it was likely fatal in three cases. Another 2018 study found that more than a third of sperm whales found dead in the eastern Mediterranean since 2001 were killed by plastic.

Another major concern is how microplastics can be ingested by smaller animals and microorganisms and then travel up the marine food web to increasingly larger animals, including humans.

“Microplastics also enter the human diet through seafood, the most likely routes being mussels, clams and small pelagic fish, which are commonly eaten without removing the digestive tract, where microplastics are concentrated. “, explained Tsiaras.

While the new study didn’t focus on the ecological impacts of plastic pollution, it can help predict and mitigate them.

“Given the paucity of observational data and the variability of ocean circulation, the distribution and fate of plastics in the marine environment can be particularly difficult to predict, as floating plastics can travel long distances from their sources. sources, ”Tsiaras said. “Thus, numerical models, simulating the movement and fate of marine litter, provide essential tools for predicting areas of plastic litter accumulation and how these areas overlap with areas ecologically (e.g. birds and cetaceans) or commercially (eg aquaculture, fisheries) important that are potentially threatened by plastic pollution.

Plastic paths

To this end, Tsiaras and his team used a model to determine where land-based plastic pollution ends up when it enters the Mediterranean Sea. (About 80 percent of all marine plastics and 98 percent of marine microplastics are estimated to come from land-based sources.) They considered plastic from river runoff, sewage discharges from coastal cities, and pollution. global plastic from human activities such as seaside tourism and aquaculture. .

They then plugged this plastic input into a particle drift model adapted from a model used to determine the spread of oil spills. The model took into account factors such as ocean currents, mixing, waves and wind.

The model estimated that about 17,600 metric tons (about 19,401 US tons) of plastics enter the sea each year. This is less than some estimates. A IUCN study last year calculated that nearly 230,000 metric tonnes (around 253,532 US tons) of plastics entered the Mediterranean Sea each year, and that number could increase to 500,000 metric tons (around 551,156 US tons) per year if nothing changes .

“Overall, the sources of plastics that end up in the marine environment are still poorly quantified and characterized by a high degree of uncertainty, both in their quantity and distribution,” Tsiaras said.

Of the total mass of plastics that enter the Mediterranean according to the model, around 84% end up on beaches. The remaining 16% or so ends up in the water column and sinks into the seabed. This is the most common fate of microplastics, which constitute a greater amount of Mediterranean plastics, but a smaller percentage of their overall mass.

An important process described by the model is biofouling. This is what happens when microplastics attach themselves to larger organisms like bacteria or algae and sink to the bottom of the sea.

This is “a poorly understood process that was explicitly described in the model, as a possible mechanism for removing microplastics from the sea surface,” Tsiaras said.

Now that the study is complete, Tsiaras hoped it would help policymakers develop strategies to manage plastic pollution with the aim of protecting vulnerable and important areas. However, he also acknowledged that the best way to deal with the plastic crisis was to prevent substances from entering waterways in the first place.

“[G]Since cleaning plastics once they are released into the marine environment can be particularly difficult, if not impossible, especially for smaller microplastics, it appears that the best way to mitigate plastic pollution is to its sources, by reducing the use of plastics and / or adopting more efficient recycling technologies, ”he told EcoWatch.

Olivia has been writing on the internet for over five years and has covered social movements for YES! Magazine and ecological themes for Real Life. For her recent MA in Art and Politics at Goldsmiths, University of London, she completed a creation memory imagine sustainable communities surviving in post-climate change London. Follow her on Twitter @orosane.