Marine debris types and their use by organisms on rocky and sandy shorelines in the Gower Peninsula

Marine debris provides artificial surfaces for organisms to colonise, but also poses significant threats to marine life through entanglement, ingestion, toxicity, and entrapment. This study investigates the settlement of organisms on litter across (i) a rocky and (ii) a sandy shoreline on the Gower Peninsula, South Wales, analysing how litter type, colour, size, and shoreline type influence the settlement of different organisms. By assessing organism-litter interactions, this research provides an insight into the ecological impact of marine litter in two differing coastal habitats.

Data collection was conducted along 100-metre transects at each site, with quadrats placed every 10 metres to assess biodiversity and, where present, record litter type, colour, size and buoyancy. Data from early September 2024 was analysed and the two sites were compared, using Chi-Squared tests, summary and descriptive statistics. These sites, both classified as‘exposed’ to the North Atlantic Ocean, were selected for their proximity to one another, andtheir distinct coastal characteristics. Shoreline type influenced the abundance of litter, with twice the number of pieces of litter being found on the sandy shoreline. However, a wider variety of litter (a mean of 5, compared to a mean of 4.3), with a larger percentage with organisms on (21.1%, compared to 12.5%), was seen on the rocky shoreline. Much larger sizes of debris were found on the sandy shoreline. Organisms found living on the litter on the sandy shoreline were not in their usual habitat, however almost all organisms found on litter on the rocky shoreline were typical of the area. On both beaches, little to no correlation was found between litter distance from the high tide and the number of organisms found on it. On the rocky shoreline, litter colour was found to have some influence on organism settlement- this was not the case on the sandy shoreline. This study contributes to a growing global understanding of how marine debris interacts with the ecosystem, highlighting differences in litter distribution and organism settlement between rocky and sandy shorelines.