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

Abstract

Marine litter is one of the most serious anthropogenic challenges to the integrity of global marine ecosystems. 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, due to operational constraints. The Mediterranean Bottom Trawl Survey (MEDITS) can provide insights into the state of seabed litter distribution and composition collaterally with the primary fish shock assessment. This study analyses the MEDITS 2020/2021 marine litter dataset in terms of a spatial, temporal and depth distribution in the Geographical Subarea (GSA) 15, i.e. off the coast of Malta. The composition of the litter and its potential major sources were determined. For these analyses, a two-sided independent t-test was applied using SPSS. Visualization was done by creating maps and bar charts using QGIS and MATLAB. Results revealed tourism and household items as primary contributors to marine litter, with plastics comprising the majority. Surprisingly, the onset of 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 items like plastic, while heavy litter, such as metals, tends to remain localised. Compared to other Mediterranean regions, the seabed off Malta shows a relatively clean status. This study not only provides valuable insights into the local marine environment but also underscores the need for novel global strategies to address the marine litter issue. These findings prompt considerations for future environmental management practices and highlight potential areas for further research in the broader context of marine environmental monitoring.