Exploring the spatial distribution, composition, and depth-related patterns of marine litter in the Mediterranean Sea : insights from the MEDITS survey data

Abstract

Marine litter is one of the most serious anthropogenic challenges to the global marine ecosystem. Public awareness is often limited to the visible litter that washes up on beaches or floats on the ocean surface. Less attention is paid to marine litter that is deposited and accumulates on the seafloor. The Mediterranean Bottom Trawl Survey (MEDITS) aims to provide insight into the state of seabed litter by collecting marine litter from the seabed. This study analyses the MEDITS 2020/2021 marine litter dataset in terms of spatial, temporal and depth distribution in the Geographical Subarea (GSA) 15, i.e. off the coast of Malta. The composition of the litter and potential major sources were determined. For these analyses, the two-sided independent t-test was applied using SPSS. Visualisation was done by creating maps and bar charts using MATLAB and QGIS. Results reveal tourism and household items as primary contributors to marine litter, with plastics comprising the majority. Surprisingly, the COVID-19 pandemic appears correlated with a significant reduction in seafloor litter accumulation. Spatial distribution dynamics suggest that subsurface currents influence the transport of light litter like plastic, while heavy litter, such as metals, tends to remain localised. Compared to other Mediterranean regions, the seabed off Malta demonstrates a relatively clean status. This study not only contributes valuable insights into the local marine environment but also underscores the need for global strategies to address marine litter. The findings prompt considerations for future environmental management practices and highlight potential areas for further research in the broader context of marine ecology and pollution.