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Roskilde University (RUC) 2015

Spatial Distribution and Characteristics of Surface Sampled Plastic Debris in the Southwest Mediterranean Sea

Fares John Biginagwa, Bahati Sostenes Mayoma

Titre : Spatial Distribution and Characteristics of Surface Sampled Plastic Debris in the Southwest Mediterranean Sea

Coordinateur : Fares John Biginagwa, Bahati Sostenes Mayoma

Université de soutenance : Roskilde University (RUC)

Grade : BSU Students’ Master Thesis 2015

Résumé
The Mediterranean Sea is considered one of the world marine systems with high levels of plastic pollution emanating from both land- and sea-based activities. As one of the most common and persistent pollutants in water bodies, plastics have serious ecological impacts influenced by their physico-chemical characteristics. This study presents the physical and chemical characteristics of surface plastic items sampled in the southwest (SW) Mediterranean Sea at seven transects during a 10 day expedition from Sicily (Italy) to Malaga (Spain) in September 2014, using a 330 μM mesh manta trawl. Furthermore, we evaluate the presence and implementation challenges of several regional and international bodies such as the Water Framework Directive, The Marine Strategy Framework Directive, the Barcelona- and MARPOL-conventions, aimed at protecting the Mediterranean Sea from pollution. Plastics mean abundance recorded here was 11466 particles/Km2 but generally, there was a decrease in abundance from transect one (east) to transect seven (west) with the highest value being recorded at transect 3 (76395 particles/Km2) in the Algerian gyres. The general trend and/or spatial distribution of plastics observed from transect one to seven is partly signifying the influence of the hydrodynamics in the basin. Abundance with respect to size appeared to decrease with increase in the size of plastic particles. The majority of the plastic items obtained were fragments although other types such as thin films, lines, pellets and foams were observed in quantities which fluctuated widely across transects. Based on colour, transparent and white particles comprised the majority of the total plastics collected with 58% and 33% respectively. Despite their small number, plastics of >5mm weighed more than particles of 1-<5mm and 0.355-<1mm sizes. According to the FT-IR analysis results, the most prominent polymer type was polyethylene (59%) followed by polyethylene (40%) and 1% of co-polymers which occurred at transect one only. Despite the presence of several multilateral bodies which aim at reducing wastes as well as rising awareness among member states, there have been a number of unsolved challenges with regard to their implementations including ; variations in scientific understanding regarding marine plastic pollution, existing knowledge gap for freshwater systems, inadequate involvement of local community in environmental planning and waste disposal process particularly in the Southern region, economic inequality and cultural diversity among members, political instability in some member states and lack of willingness for some riparian states to ratify the cooperation. This study, apart from being the first to document the chemical composition of plastic items floating in the SW Mediterranean Sea, it shows the current plastic contamination level as well as giving an overview of the regulatory development regarding plastics pollution in the whole basin.

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Page publiée le 26 mars 2020