Transboundary marine debris and its impacts on an Amazonian tourist beach

This study investigated the origin, characteristics, and dynamics of allochthonous plastic bottles accumulated on Ajuruteua Beach, northeastern Pará, Brazilian Amazon, and examined their implications for coastal management and tourism sustainability. Monthly monitoring from February 2023 to January 2024 integrated data on debris composition, plastic drift modeling (PlasticAdrift), and climatological and hydrodynamic variables. A total of 596 items were collected, of which 99% were plastic bottles, comprising 171 brands from 49 countries. African and Asian origins predominated, with Mauritania and China identified as the main sources. Most bottles were composed of PET (>90%), indicating high environmental persistence and structural durability. Expiration dates, available for 326 items, were mostly within two years of collection, a pattern that is difficult to reconcile with some estimated long-distance drift times from West Africa. These findings, together with evidence of intense maritime traffic in adjacent waters, indicate that maritime activity may have contributed to debris inputs, although the relative contribution of shipborne disposal and oceanic transport cannot be conclusively determined. Oceanographic conditions favored debris transport, exposure, and deposition along the shoreline. The results indicated that Ajuruteua Beach functions as a sink for transcontinental plastic debris, driven by interactions between hydrodynamic processes and anthropogenic activities. These findings underscore the urgent need for strengthened international cooperation, enforcement of shipborne waste regulations, and integrated coastal management policies to mitigate marine plastic pollution and promote sustainable tourism along Amazonian beaches.