Marine Litter and Microplastics in Protected Areas: A Five-Year Review

The presence of plastic marine litter (ML) and its associated negative environmental impacts have been documented in all existing parts of the marine and coastal environment, including protected areas (PAs). The aim of this study is to identify gaps in existing research related to the lack of standardization of methods and scarcity of detailed information on the characteristics of ML found. This systematic review provides current information on the methods and results of studies focused on the problem of ML and microplastic (MP) pollution on the coastlines of PAs. This study was conducted in accordance with the PRISMA 2020 statement. It is based on 28 peer-reviewed publications from four online databases and search platforms: ScienceDirect, PubMed, MDPI and Google Scholar, published between 2021 and 2025. The presence of ML was detected in all 28 studies (100%), confirming the relevance of the problem along the coastlines of PAs, even those far from industrial centers. The reported densities, however, ranged from a few fragments of litter to several thousand items. Plastic was the most common material of ML among all the peer-reviewed publications analyzed. Most of the studies showed that polyethylene (PE) fragments were the dominant type of microplastic (MP) found in coastal environments of PAs. However, despite the growing research on this topic, the problems of lack of detailed information and standardization of methods remain unresolved. This review emphasizes the importance of applying unified methods and conducting long-term monitoring experiments in future research.