Vulnerability of mangrove ecosystems to anthropogenic marine litter along the southeast coast of India.

Human-caused marine pollution poses a constant threat to marine ecosystems, particularly tropical mangrove forests, which are vulnerable to litter from both inland and marine sources due to inadequate waste management. Despite well-documented effects of marine litter on various maritime habitats, its impact on mangrove forests remains underexplored. This study investigates the abundance, composition, sources, and impacts of human-caused marine litter on mangroves along the Thoothukudi coast in the Gulf of Mannar, southeast India. The study recorded an average litter abundance of 6.7 ± 1.2 items/m on the mangrove ground and 8.6 ± 0.3 items/tree, with plastic litter comprising over 81 % of all collected litter. Single-use plastic items were the most common across all sites. Several indices, including the General Index, Clean Coast Index, Pollution Load Index (PLI), and Hazardous Items Index (HII), were used to evaluate mangrove floor cleanliness, all indicating poor conditions. The PLI revealed "Hazard Level I" plastic debris concerns, with litter levels varying significantly by location. Areas with high population density and poor solid waste management had significantly more stranded litter. Litter sources were identified as both local (land-based) and external (marine fishing). Trapped plastic was found to impair mangrove pneumatophores and branches. To mitigate the negative impacts on mangrove ecosystems and ensure their conservation, the study emphasizes the need for strict law enforcement, a unified solid waste management strategy, and a widespread behavioural shift among citizens.