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Influence of monsoon seasonality and tidal cycle on microplastics presence and distribution in the Upper Gulf of Thailand

The Science of The Total Environment 2024 28 citations ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count.
Haruka Nakano, María Belén Alfonso, Suppakarn Jandang, Nopphawit Phinchan, Suchana Chavanich, Voranop Viyakarn, Atsuhiko Isobe

Summary

Researchers surveyed microplastic pollution around Si Chang Island in the Gulf of Thailand across different monsoon seasons and found that seasonal weather patterns strongly influence microplastic abundance and distribution. Evidence suggests that UV exposure during dry seasons fragments plastic waste on land, which is then washed into the ocean by heavy rains during the wet season. The findings highlight how tropical climate cycles drive microplastic contamination in Southeast Asian coral reef areas.

Study Type Environmental

Southeast Asian countries are recognized as significant contributors to the discharge of abundant plastic waste into the ocean. In this study, we conducted neuston net surveys on Si Chang Island of the Gulf of Thailand, a coral reef conservation area, to determine the presence of microplastic (MP) pollution. The survey, conducted during the wet (southwesterly monsoon), transition, and dry seasons (northeasterly monsoon), revealed that the MP abundance was in the range of 0.02-42.46 particles m-3. The precipitation, wind, and current direction induced by monsoons influenced the abundance and distribution of MP, presenting a significant seasonality. The cluster analysis for colors and polymer types of MPs suggested that the origin of plastic particles is diverse. Based on our results, a proposal for the generation, sources, and pathways for MPs in the Gulf of Thailand is presented: 1) plastic wastes exposed to strong UV light during the dry season get fragmented around the river, and 2) heavy rains wash away the particles during the wet season. This proposal is applicable to tropical regions, including the Gulf of Thailand. Therefore, this paper concluded that ocean currents induced by monsoons and the unique climate, resulting in the generation of MPs on land, increase MP presence and distribution in the ocean surrounding Southeast Asia countries. Furthermore, coral reef ecosystems can be particularly threatened by MPs in these areas. So, an increase in MP monitoring on coral ecosystems from Thailand and the world is highly recommended.

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