Exploring marine litter abundance and composition on a rural sandy beach in Portugal

Abstract

Marine litter in coastal areas represents a significant environmental issue that severely impacts biodiversity, ecosystems, human well-being and economic activities. This study investigates the abundance and composition of marine litter on a rural sandy beach in northwestern mainland Portugal, following the guideline of the Oslo – Paris Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR). Eight seasonal field surveys were conducted from October 2022 to July 2024. A total of 6213 litter items were collected, corresponding to an average litter density of 777 items per 100 m of coastline. Plastic accounted for 83.6 % of the total debris. The top three most frequently occurring types of marine litter were plastic fragments in the 0–2.5 cm and 2.5–50 cm size ranges, along with string and cord from fishing activities. Single-use plastics, including food containers, beverage bottles, cutlery and straws, represented only 12.9 % of the total litter items. The high prevalence of plastic fragments relative to single-use plastics and the signs of weathering observed on most items highlighted the beach's role as a receptor for marine debris. A notable deposition of expanded clay pebbles was recorded throughout the study period, most likely originating from cargo handling at nearby port facilities. Additional research is required to assess their potential impacts on marine ecosystems, and corrective measures must be implemented to prevent their release into coastal waters. Furthermore, the high abundance of litter recorded on this scarcely visited beach underscores the considerable efforts still needed in waste management and public awareness to improve the quality of marine and coastal environments in the northeastern Atlantic region.