Floating marine litter in the two main marine protected areas of the Canary Islands

Abstract

Plastic pollution in high-biodiversity oceanic islands is a global environmental issue. While studies on microplastics have increased in the last decades, research on large floating marine debris and its relationship with meso- and microplastics remains limited. The Canary Islands (Northeast Atlantic), a natural barrier within the Canary Current and the North Atlantic Subtropical Gyre, are no exception; despite growing concerns about marine pollution in this archipelago, systematic data on large floating debris is still lacking. The main objective of this study was to estimate the density and distribution of floating marine litter in two marine protected areas (MPAs) of the Canary Islands: “Franja Marina de Teno-Rasca” (Tenerife) and “Franja Marina de Mogán” (Gran Canaria). The study also examines the relationship between the density of large floating debris (macrolitter > 5 cm) and small floating debris (including microlitter 200µm-5mm and mesolitter 0.5cm-2.5 cm) and discuss the distribution of floating debris in the context of regional oceanographic dynamics. Field sampling in both MPAs was carried out between July 2022 and February 2023, and combined large floating debris collection with a macro net and small floating debris sampling with a manta net, both applied simultaneously along the same transects to ensure comparability. The concentration of macrolitter (> 5 cm) ranged from 0 to 13,433 items/km² while the concentrations of micro-mesolitter (200 µm – 2.5 cm) varied between 0 and 106,667 items/km². Our results confirm the widespread presence of marine debris in both protected areas, which correspond to leeward zones prone to debris accumulation, particularly during calmer periods (September–October). Although their density can vary drastically among years and seasons, both MPAs emerged as hotspots for floating debris, highlighting the need for mitigation measures and sustained monitoring to safeguard marine biodiversity in these Marine Protected Areas.