Marine litter on sandy littoral habitats : investigating beach macro-litter at Marfa ridge, northern Malta

Abstract

Marine litter presents a growing threat to coastal ecosystems, yet sandy littoral habitats especially dune systems remain underrepresented in monitoring frameworks such as the EU Marine Strategy Framework Directive (MSFD). This study provides the first baseline assessment of beach macro-litter (2.5–100 cm) across shoreline and dune habitats at Marfa Ridge, a key conservation area that hosts approximately half of Malta’s remaining dune systems. Two reference beaches, Ramlet il-Qortin and Ramla tat-Torri, were surveyed between 2022 and 2023 across three seasons (late summer/ autumn, spring, and winter). In addition to shoreline transects, 60 (2 × 2 m) plots were sampled within dune habitats, classified under the EU Habitats Directive. For the shoreline, spatial distribution, seasonality, and fragmentation of litter were assessed. Within dune habitats, spatial distribution was examined along the sea-to-inland gradient, together with the occurrence of vegetation cover. The results showed that the shoreline had an abundance of 1,488 litter items per 100 m, clearly exceeding international thresholds. Further inland, dune habitats acted as major long-term sinks, with a litter density seven times higher than at the shore (6.8 vs 0.98 items/m²). Moreover, a clear sea-to-inland gradient was observed, with litter density decreasing inland, particularly outside accumulation zones. Single-use plastics were pervasive across all zones and correlations between pollutants indicated shared deposition mechanisms and contrasting patterns. A weak but statistically significant correlation was found between vegetation cover and litter presence, suggesting vegetation plays a partial role in trapping pollutants. Posidonia banquettes also contributed to litter entrapment along the Driftline (EU habitat 1210), raising concerns about contamination exposure for native dune flora such as Cakile maritima. Overall, the study confirms the role of sandy littoral habitats as dual-function litter sinks, with shorelines acting as deposition zones and dunes serving as long-term retention areas. While the results align with broader Mediterranean trends, variations reflect site-specific characteristics, waste management practices, environmental factors, and seasonal changes. This highlights the importance of adopting an ecosystem-wide approach to integrated coastal management (including dune systems) that considers the ecological interplay between shoreline and dune habitats as well as the spatial and temporal variability of litter dynamics. Future research at the Marfa Ridge should expand to other litter dimensions (e.g. microplastics) and replicate this methodology across additional local and Mediterranean sandy littoral habitats to inform policy development and improve coastal conservation.