Madrid, 4 (European Press)
A model tracking the paths and fate of terrestrial plastic waste in the Mediterranean reveals that about 3,760 tons are currently floating in its waters.
Developed by researchers at the Hellenic Center for Marine Research in Greece, the model tracks the paths and final destination of plastic waste in the Mediterranean. She ran simulations from 2010 to 2017, tracking plastics from land-based sources such as rivers and coastal cities, taking into account important dispersal processes such as subsidence, vertical/horizontal mixing, winds, and currents. It also identified the potential accumulation patterns of microplastics and macroplastics in the surface layer, water column, sea floor and shorelines.
17,600 tons per year, of which 84% ends up on beaches
This revealed that the total annual load of plastic entering the Mediterranean is about 17,600 tons, of which 3,760 tons are currently floating in the Mediterranean. Of the total, 84% ends up on beaches and the remaining 16% ends up in the water column or the sea floor.
“Simulations of the distribution of plastic in marine environments are currently characterized by a high degree of uncertainty. Experimental data regarding the various processes that influence the fate of plastics, such as sinking, ingestion of marine organisms, and fragmentation into smaller pieces, are still very limited,” said lead author Dr. Kostas. Tsiaras.
“Our model demonstrated a reasonable ability to reproduce the observed distributions of plastics in the marine environment, and thus can be used to assess the current situation of plastic pollution in the Mediterranean and to assess the impact of future clean-up actions and management plans.”
The model, presented in Frontiers in Marine Science, also described biofouling as a potential mechanism for removing microplastics from the seawater surface. Biofouling occurs when microorganisms such as algae accumulate on floating and submerged objects, including plastic debris.
“Microplastics are less abundant at the sea surface because they sink faster due to adhesion to heavier marine organisms (biofouls) and accumulate deeper in the water column and sea floor. On the other hand, bulky plastics, such as plastic bags and Styrofoam, can “float for longer periods of time.” It travels long distances from its sources.
Sources of microplastics (such as wastewater treatment plants) are found primarily near urban cities and densely populated areas along the coasts of France, Spain, and Italy. Larger microplastics are found in areas with a high level of raw sewage, such as the coasts of Greece and Turkey.
Macroplastics were abundant in areas with important riverine contributions such as the Algerian, Albanian and Turkish coasts, and near major cities and densely populated coasts (Spain, France and Italy).
“The model results can be used to identify ecologically important (bird and cetacean habitats) or commercial (aquaculture, fisheries) areas that are likely to be threatened by plastic pollution. This is important for planning and design. Ecosystem-based management policies mitigate plastic pollution, which is often A transboundary environmental problem, as floating plastic can travel long distances from its sources,” according to Tsiaras.
