A preliminary quantitative and qualitative investigation of microplastics sampled from Maltese nearshore waters

Abstract

This study aims to characterize the microplastic pollution of the Maltese nearshore waters from an innovative perspective by targeting to shed more light on the dynamics of microplastic accumulation within the water column around the Maltese Islands over two year (2022 and 2023). This pioneering survey is in fact examining different sea layers in order to determine whether different plastic polymers accumulate with increasing water depth. We have performed an experimental sampling methodology, with the modification of our Manta trawl which has been used for the sampling of the surface water, We executed horizontal tow sampling by maintaining the Manta net at a stable depth (6 ±1m and 10 ±1m) in a parallel position, by setting up the perfect balance between the weighting of the frame of the Manta net and the speed of the tugboat to keep the net tight. The focus of our research was on the examined lower size (50-1000µm) range as the larger pieces (1000-5000µm) were typically not found in the water column samples but rather, almost exclusively in the surface samples; hence, the comparison was out of scope. Most of the particles were made of 27.9% Acrylic, 27.2% PE (Polyethylene) , 23.9% PP (polypropylene) and 11.6% PS (polystyrene). Average between the two years, 60% of the total number of plastic particles found to be distributed within the 50-350μm range. We have observed that the Microplastic pollution level of the surface waters were 0.25-7.363 particles/m3 , while in the sub-surface water column on 10 meters from the surface we found 1.090- 6.60 particles/m3.