Unveiling the Levant Basin as a Unique Sink for Plastic Bags and Packaging Through Comprehensive Multi-Marker Analysis

Abstract

Plastic litter is ubiquitously distributed across the seafloor, with its composition and distribution influenced by source proximity, bio-ecological drivers, hydrodynamics and bathymetry. seabed litter was collected using bottom trawls at depths of 80–1300 m in the southeastern Mediterranean, employing a novel approach that integrated plastics physical characteristics, chemical composition, and biological attachments. Our findings reveal one of the highest global densities of deep-sea plastics (3321 ± 12 items/km2), with plastic bags and packaging (PBPs) comprising 91.7 ± 0.7% of the total litter. Near-shore PBPs exhibited a significantly lower density of 194 ± 49 items/km2 (76.6 ± 8.2% of the total litter). The PBPs displayed heterogeneous distributions between the continental shelf and deep basin in the composition, shape, polymer type, and surface attachment. Calcium carbonate additives, identified as ballast to the polyethylene bags, were concentrated on the continental shelf but nearly absent in the bathyal. Although 86.5% of the PBPs exhibited relatively low levels of surface attachment (<3 µg/mm2), both organic and inorganic adhesion appeared play a pivotal role in settlement and distribution. Moreover, the minimum biofilm concentration for additional inorganic adhesion increased with depth. This comprehensive analysis provides insights into factors influencing PBPs accumulation in typical oligotrophic water body.

Keywords: Plastic bags and packaging, Southeastern Mediterranean, Seafloor, Adhesion, Sinking