Spatial patterns of marine litter on the Arabian Gulf’s major offshore sea turtle nesting islands

Abstract Marine litter poses growing risks to the Arabian Gulf’s major turtle nesting islands, yet its composition and fine-scale distribution have never been quantified. We combined two complementary surveys on Jana and Karan Islands—the region’s largest hawksbill (Eretmochelys imbricata) and green turtle (Chelonia mydas) rookeries. First, 988.3 m2 of 0.75 m × 0.75 m photo-quadrats (June 2017) recorded litter cover and item counts across 587 grid nodes; second, 4050 m2 of 5 m × 5 m ground quadrats (October 2020) measured marine litter count and mass across beach, vegetation-line and vegetation-within zones at 18 shoreline stations. Photo quadrats showed that plastics, styrofoam, and wood dominated stranded items. A total of 32 litter groups were observed with highest contribution by debris count from plastic drinking bottles (63.6% at Jana; 42.9% at Karan) and by litter mass from processed wood (69.5% at Jana; 68.8% at Karan). Fishing-related litter comprised 8.5% by mass and 10.4% by count at Jana Island, and 16.2% by mass and 11% by count at Karan Island. Jana Island had a higher number of plastic bottles than Karan Island. Vegetation-line plots retained roughly twice the debris density and mass of both open-beach and interior plots (p < 0.001). These patterns indicate that macroplastic accumulation already overlaps with core nesting habitat at the external fringe of the vegetation line and is likely to generate additional pressures such as microplastic deposition in nests and ingestion by adults and hatchlings. Continued monitoring, together with seasonal clean-ups and studies on interacting stressors, would guide adaptive management of the Gulf’s primary turtle rookeries.