Semi-quantitative and qualitative assessment of inert waste lying on the seabed within Malta’s spoil ground

Abstract

Marine litter has been identified as a growing threat towards the marine environment. Although there exists a substantial body of research on marine litter at the sea surface or on coastal areas, there is limited data on that on the seafloor, despite it being the main accumulation site of debris. Locally, the spoil ground outside of Malta’s Grand Harbour is designated as a legal dumping site for litter and debris, particularly that from the construction and demolition industry, however, the available data pertaining to seafloor debris within this area is conspicuously scarce, with the first and last published research dating back to 2008. Using ROV footage collected in 2022, this study analyses the seabed beneath Malta’s spoil ground, particularly any litter and debris present, as well as habitats. This analysis was compared and contrasted with the observations made in 2008. A key finding from this study was that plastic was the most prevalent type of litter, followed by vehicle rubber tyres, which had also been identified previously in 2008. Aside from litter, most of the waste present at the spoil ground was observed to be of an inert nature, originating from the construction and demolition industry, particularly from projects such as MIDI plc, this included limestone masonry blocks, as identified also in 2008. The seabed lying under the spoil ground is characterized by circalittoral sediment bottoms, constituting of mainly muds or sands, with biocoenoses of a coralligenous type. The findings made on seabed properties and biological communities are comparable to those made in the earlier survey in 2008. Overall, based on the observations, the seabed at the spoil site appears to have remained fairly consistent over the previous 15 years, notably in terms of litter kinds, habitat, and seabed features.