Marine litter in the south-east of the Bay of Biscay: A review of current methods, standards, databases and challenges

Abstract

Marine litter represents a significant global environmental challenge, in which plastics are considered the most concerning components. The widespread use of plastics, which exceeded 410 million tons in 2023, has led to a significant plastic litter accumulation in the oceans. The Bay of Biscay, characterized by its unique physical oceanography and intense human activities has been identified as a marine litter accumulation zone with litter densities in the same range of enclosed seas as the Mediterranean Sea. The purpose of this study is to provide a unique contribution to the south-east of the Bay of Biscay by collecting relevant information about marine macro litter, synthesizing the scientific outcomes for beaches, seafloor, and floating marine litter. In this region, beach litter density varies greatly depending on the beach and the time of year, with densities reaching 494 items/100 m. Litter density is influenced by factors such as wind, river flows, precipitation, or distance to ports or cities. In terms of floating marine litter, the Bay of Biscay is considered an accumulation zone influenced by wind patterns, with litter densities ranging from 0,16 to 3,13 items/km². The seafloor is similarly impacted, with submarine canyons acting as sinks for marine litter and Arcachon Canyon (located in the studied area) as the second most polluted canyon of the entire Bay of Biscay with a record of 9,5 items per 100 images.