The Mediterranean Sea has one of the highest concentrations of marine plastic debris. As it is a semi-closed sea, dispersion of plastics is limited due to water circulation and tidal flow. Through mechanical degradation of wave action and abrasion by sand, this plastic debris is broken down in to microplastics (<5mm). Additional processes that enhance the breakdown of plastics are UV radiation and microbial activity. Microplastics are ubiquitous in the aquatic environment. The seafloor, however, is the ultimate sink for most of these particles. Here they become available to benthic species such as mussels, barnacles, sea worms, and holothurians. Many studies have shown that microplastics are ingested. Additional concerns of microplastics are that they are being transported through the food web and can act as a vector for persistent organic pollutants.

One of the current projects of the Microplastic Team of Archipelagos is to quantify and identify the microplastics in the shallow marine sediments starting at Psili Amos, a beach located in the southeast of Samos Island. This is a touristic beach and has a large quantity of macro plastics (> 5 mm), making it likely that microplastics are also abundant here. The Archipelagos Microplastic Team aims to better understand the spatial distribution of microplastics in shallow marine sediments. For this reason, three transects of 100 m, perpendicular to the shoreline were conducted using a sediment core. The top 15 cm of the shallow marine sediment were sampled. In the laboratory the organic matter is removed from the microplastics and sediment. Consequently, a density seperation method is used to separate the microplastics from sediment. Finally, the supernatant is removed and filtered. The microplastics are identified through a 10x and 40x magnification lens and classified according to colour and fragment type: rounded, sub rounded, angular, and sub angular.

By quantifying the amount of microplastics and understanding where they accumulate, this study will provide insight on the impact of microplastic on the marine ecosystem.

Vera de Ruijter, University of Utrecht, The Netherlands