Marine litter in mangrove soils of Roatán, Western Caribbean: Abundance, sources, and ingestion by an American crocodile (Crocodylus acutus)

Mangrove forests in insular regions are increasingly exposed to marine litter, even within designated protected areas. These ecosystems provide key ecological services but remain vulnerable to pollution via solid waste accumulation. Caribbean mangroves, in particular, are underrepresented in global assessments. This study provides the first baseline of macrolitter accumulation in mangroves on Roatán Island, within the Bay Islands National Marine Park, Honduras.

We assessed: (1) the abundance and composition of macrolitter (≥5 cm) across four mangrove sites; (2) potential sources of macroplastics through brand and country-of-origin analysis of labeled items; and (3) the composition of litter ingested by an American crocodile (Crocodylus acutus) found near one site.

A total of 3417 litter items were collected across 20 quadrats, with an average concentration of 6.83 items m⁻². Plastics dominated the litter, making up 98.7 % of all items. Only 2.4 % items had legible labels, most originating from Honduras and Guatemala. Among the subset of bottles with visible dates, the average age was 7 years, suggesting long-term retention within the mangrove environment. The deceased C. acutus found near one of the sites had ingested 62 litter items. A Principal Component Analysis revealed that the composition of ingested materials closely matched the litter profile of the nearby sampling site, indicating likely local exposure.

These findings confirm that mangroves act as long-term sinks for plastic and highlight risks to mangrove fauna. The presence of banned and foreign-sourced litter underscores poor enforcement and transboundary pollution. Coordinated regional policies, improved waste management, and targeted cleanup in protected ecosystems are urgently needed.