Spatial and temporal distribution of microplastics in the Belawan Estuary, Indonesia

• Microplastics were found in all water samples from various lunar phases and tidal cycle. • Higher microplastics abundance closer to the coastline during high tide and full moon phase. • Microplastic abundance is more pronounced in high tides, with the spring tide phase overshadowing the neap tide phase. • Significant influences of currents and tidal cycles on the distribution of microplastic. This study aimed to analyse the spatial and temporal patterns of microplastic pollution and their correlation with tidal cycles in the Belawan Estuary. Microplastics were found in water samples collected during various lunar phases and tidal cycles, averaging 0.071 ± 0.041 particles m −3 . This level of microplastic abundance is relatively low globally. The predominant microplastic type identified was fibres sized <1000 µm. Spatially, higher microplastic concentrations were detected closer to the coastline, particularly during the high tide and full moon phases. These findings indicate that various physical and environmental factors influence the occurrence and accumulation of microplastics in the Belawan Estuary. Further investigation is necessary to examine the primary and secondary sources of microplastic pollution and to understand the effects of natural elements, such as water currents, wind, and river transport. Understanding these patterns is crucial for developing effective strategies to tackle microplastic contamination at national, regional, and global levels. This includes integrating waste management across all stakeholders, from national policymakers to local implementers, and encouraging individual responsibility to reduce the use of single-use plastics while promoting sustainable alternatives. Such efforts can help minimise the potential harm to marine ecosystems and human health.