Assessment of anthropogenic macro-litter and its impacts on the seagrass meadows of the remote Andaman and Nicobar Islands, northern Indian Ocean.

Macro-litter, particularly plastics, poses a grave threat to marine ecosystems, yet its occurrence in seagrass meadows of the Indian Ocean remains poorly quantified. This study provides the first basin-scale evidence of macro-litter abundance, composition, and ecological risk in seagrass meadows of the Andaman and Nicobar Islands (ANIs), a data-deficient biodiversity hotspot in the northern Indian Ocean. Visual surveys using snorkelling and SCUBA recorded 4257 macro-litter items, with a mean density of 0.59 ± 0.17 items m. Plastics dominated the litter assemblage (88%), followed by glass (8%), metal (3%), and rubber (1%). Land-based activities accounted for 85% of litter, while fishing-related sources contributed 15%. Plastic fragments (38%) and bottles (10.9%) were most prevalent. Environmental quality indices revealed conditions ranging from moderately clean to heavily polluted (CEI: 8.88-39.18), with high plastic loads even at remote islands (PAI: 2.36-8.92), indicating long-range transport from the wider Indian Ocean. Hazardous litter, particularly abandoned fishing gear (HII: 0.42-2.81), posed substantial entanglement risks. Litter accumulation in the seagrass meadows poses entanglement hazards to threatened fauna such as dugongs and sea turtles. These findings underscore the urgent need for sustained monitoring and enhanced regional waste-management strategies to mitigate the impacts of marine litter on seagrass ecosystems.