Mediterranean deluged with 17,600 tonnes of plastic waste every year, study finds

Climate researchers investigating the extent of plastic pollution in the Mediterranean have found that 17,600 metric tonnes are dumped into the sea off Southern Europe every year, with 3,760 metric tonnes left to float on the surface.

Of that total, 84 per cent will ultimately be washed up on beaches while the remaining 16 per cent remains in the water or sinks to the seafloor, according to academics from the Hellenic Centre for Marine Research in Greece, who published their findings in the journal Frontiers in Marine Science.

An estimated 368m tonnes of plastic was produced globally in 2019, the total increasing year-on-year since the 1950s.

A high proportion ends up as waste in seas and oceans, with estimates suggesting there is currently 250,000 tonnes of plastic bobbing in open saltwater around the world.

The Mediterranean is particularly vulnerable to the problem because of its densely populated coastlines, bustling fishing, shipping and tourism industries and its limited outflow to the Atlantic.

Its shores are also rich in biodiversity and the plastic particles pose a threat to both the inhabitants of its delicate marine ecosystems and to the humans who risk ingesting it when they consume seafood served from its depths.

“Microplastics are less abundant in the sea surface due to their faster sinking from the attachment of heavier marine organisms (biofouling) and accumulate deeper in the water column and seafloor,” explained the report’s lead author, Dr Kostas Tsiaras.

“On the other hand, macroplastics, such as plastic bags and styrofoam may float around for longer time periods, and travel long distances from their sources.”

The study indicated that microplastics were more likely to be found in waters off the French, Spanish, Italian, Greek and Turkish coasts, while the latter was a particular issue offshore from Algeria, Albania and Turkey as well as the metropolitan cities of coastal France, Spain and Italy.

The academics developed a model to track the passage of plastics from their first use to being discarded, simulating the journey of micro- and macroplastics to the sea from land-based sources like cities and rivers, and taking into account such factors likely to disperse them as sinking, mixing, wind and currents.

“Simulations of plastic distribution in marine environments are currently characterised by a large degree of uncertainty,” said Dr Tsiaras.

“Experimental data on several processes that affect the fate of plastics, such as sinking, ingestion by marine organisms and fragmentation into smaller pieces are still quite limited.

“[But] our model showed a reasonable skill in reproducing the observed distributions of plastics in the marine environment and thus can be used to assess the current status of plastic pollution in the Mediterranean and evaluate the impact of future cleaning actions and management plans.”

Dr Tsiaras observed that it was difficult to find a unified solution to the problem because of the differing political, social and cultural issues at play among the many countries that meet the Mediterranean but said he hoped that models like his team’s would help to at least determine the ecological realities in play.

“The use of predictive models, like the one presented here, that can connect observed plastic concentrations with their sources, is critical for the designation of successful management plans,” he said.