Marine microplastic has been in the limelight recently. This study aimed to describe microplastic types ingested by 274 fish from Thailand’s eastern coast in 2020 and to compare the microplastic content among different feeding traits. The microplastics in the gastrointestinal tracts and gills were extracted, analyzed, and identified using FT-IR spectroscopy. Approximately 13.14% of the total specimen ingested microplastics, with an average of 0.14 items per individual. The detection frequency of microplastics was relatively high compared with other regions in Thailand but relatively low compared to global standards. Of the microplastic contaminated specimens, 56.41% had at least one piece of microplastic in their gastrointestinal tract. Pelagic (14.47%) species were found to have ingested more microplastics than the demersal (12.63%) group. Dominant aspects found included PET (as in polymers), fiber (as in shape), and black (as in color). However, microplastic numbers fluctuated with the size, weight, and feeding behavior of fish. This result suggested that the pelagic has a higher exposure risk and microplastic ingestion in relatively small quantities in a range of fish species. Our results indicated that the occurrence of microplastics in fish is not influenced by organism habitat or trophic level, although the characteristics of pelagic fish might significantly increase the chance of exposure to microplastics in pelagic species.

The study investigated the influence of tides (low and high) on composition and abundance of microplastic. Suspended microplastics (MP) were sampled in surface waters around the Chaophraya River mouth in Upper Gulf of Thailand using Neuston trawl (330-µm mesh) during tidal cycle at both tides in rainy season (August) of 2019. The abundance and types of microplastic had been analyzed. Overall, the concentration of MP during spring tide was significantly lower than the concentration during neap tide (p < 0.01). Suspended microplastic particle concentration ranged from 16.74 to 59.06 pieces per 100 m 3 (spring tide) and 43.26 to 126.13 pieces per 100 m 3 (neap tide). Concentration of MP found during flood tide was higher which suggested marine derived MP. Dominant samples identified under stereomicroscope were fibers and film. Using Fourier transform infrared spectrophotometry, the majority of the particles was identified as polypropylene. The effect of the tidal amplitude was an important factor determining the extent of the variations in microplastic abundance, which was stronger between the lower low tide and the higher high tide.

Microplastic pollution is a common problem in the coastal and marine environment, especially in the transferential process through trophic levels. This study analyzed the characteristics of microplastics in the seawater, sediments, and green mussels (Perna viridis) around Sri Racha Bay, Thailand, during the dry and wet season in 2020. This area is a semi-enclosed bay highly affected by extensive green mussel farms and anthropogenic activities. Qualitative and quantitative analysis of microplastics was undertaken using a stereomicroscope and micro-Fourier transform infrared spectrometer (ATR-μ-FT-IR). During the wet season (July), the average abundance of microplastics was found to be relatively higher in water (2.06 ± 1.78 particles/m3) and sediment (69.35 ± 22.29 items/Kg D.W.) than those found in the dry season (April) (0.85 ± 0.25 items/m3 in water and 48.30 ± 28.17 items/Kg D.W.). Overall, the most abundant microplastic polymers were PE, PP, and poly in water, but PE, nylon, and PP in sediments. In green mussels, microplastic counts were 0.15 ± 0.41 and 0.22 ± 0.57 items/individual in the dry and wet season, respectively, and PET, PP, and nylon were the three most abundant. Some inter-specific differences were found, but no evidence for a sampling sites or seasons was highlighted, although the tendency was higher during the wet season. The excessive riverine freshwater discharge transported terrestrial plastic debris into the estuarine system; hence, higher microplastic contamination in surface seawater and sediment was evidenced. The presence of colorants in organisms revealed an anthropogenic origin through the use of a wide array of applications. This study provides thoughtful insights for coastal area management and food-safety planning.