Background: The presence of plastic particles in freshwater species is becoming a global concern owing to the potential impact on food security and human health. In this study, we investigated the presence microplastics (MPs) in two economically important freshwater species: the giant freshwater prawn (Macrobrachium rosenbergii) and the white leg shrimp (Litopenaeus vannamei) cultured in a polyculture pond in the central part of Thailand. Methods: The gastrointestinal tract (GT) of 300 giant freshwater prawn (160 female and 140 male) and 150 white leg shrimp specimens were investigated for the presence of MPs. Results: From the pooled samples, a total of 1,166 MP items were identified. Specifically, the GTs of female and male freshwater prawns and white leg shrimps contained an average of 33.31 ± 19.42, 33.43 ± 19.07, and 11.00 ± 4.60 MP items per individual, respectively. Further, their mean MP contents per g of gut material were 32.66 ± 5.10, 32.14 ± 4.85, and 10.28 ± 1.19 MP items, respectively. In the GT of these species, MPs with sizes in the range 500–1000 µm, were predominant, and white/transparent MPs were most prevalent (63.67%). Furthermore, regarding the morphotypes of the MPs, fibers, fragments, films, and spheres were frequently observed, with fibers shows predominance. Specifically, the proportions of fibers in the GTs of female Macrobrachium rosenbergii, male Macrobrachium rosenbergii, and Litopenaeus vannamei were 83.3, 79.91, and 46.06%, respectively. Four MP polymer types, polyethylene, polycaprolactone, polyvinyl alcohol, and acrylonitrile butadiene styrene, were also identified via FTIR spectroscopy, which further confirmed the presence of MPs in the GT of the freshwater-cultured species. Discussion: Our findings indicated that consuming shrimps and prawns without first removing the MPs from their GTs is one of the mean by which humans get exposed to MPs. Thus, MPs in freshwater species can be passed down the food chain to humans.

The distribution and diversity of aquatic insects and water quality variables were studied among three streams of the Mae Klong Watershed. In each stream, two sites were sampled. Aquatic insects and water quality variables were randomly sampled seven times in February, May, September, and December 2010 and in January, April, and May 2011. Overall, 11,153 individuals belonging to 64 families and nine orders were examined. Among the aquatic insects collected from the three streams, the order Trichoptera was most diverse in number of individuals, followed by Ephemeroptera, Hemiptera, Odonata, Coleoptera, Diptera, Plecoptera, Megaloptera, and Lepidoptera. The highest Shannon index of diversity of 2.934 and 3.2 was recorded in Huai Kayeng stream and the lowest was in Huai Pakkok stream (2.68 and 2.62). The high diversity of insect fauna in streams is an indication of larger microhabitat diversity and better water quality conditions prevailing in the streams. The evenness value was recorded as high in most sites. The high species diversity and evenness in almost all sites indicated good water quality.

Background: Microplastic (MP) contamination has been discovered in aquatic systems throughout the world. They are well known as contaminants in aquatic species, but there is a gap in understanding about pathways of MP contamination into humans (i.e., through aquatic animals). The goal of this study is to assess MP contamination in an edible aquatic insect (Pantala sp.) living in rice fields. Methods: A dragonfly larva, Pantala sp. (Odonata: Libellulidae), was tested for MPs. The study concentrated on three distinct anatomical compartments (whole body, gastrointestinal tract, and body without gastrointestinal tract), each of which was examined separately. For the physical identification and chemical analysis of MPs, a stereomicroscope and a Fourier transformed infrared spectroscope (FT-IR) were used, respectively. Results and Discussion: The microplastics content was 121 in the whole body, 95 in the gastrointestinal tract, and 66 in the body without the gastrointestinal tract, with an average of 1.34 ± 1.11, 1.06 ± 0.77, and 0.73 ± 0.51 abundance/ individual, respectively. The most common MPs discovered during this study were fragments, followed by fibers and rods. The chemical analysis by FT-IR confirmed three different polymers, including polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), and polypropylene (PP). There was no significant difference in MP abundances among the sample types (Kruskal-Wallis chi-squared = 2.774, df = 2, p = 0.250). The findings suggest that eating an edible aquatic insect (Odonata: Pantala sp.) could be one way for humans to ingest MPs.

The presence of microplastics in commercially important seafood species is a new issue of food safety concern. Although plastic debris has been found in the gastrointestinal tracts of several species, the prevalence of microplastics in edible shrimp tissues in Thailand has not yet been established. For the first time, the gastrointestinal tract (GT), heptapancreas (HEP), muscle (MU) and exoskeleton (EX) of farmed white leg shrimp (Litopenaeus vannamei) from commercial aquaculture facilities in Nakhon Pathom Province, Thailand, were analyzed for microplastics (MPs). The number of MP items per tissue was 27.36±2.28 in the GT, 17.42±0.90 in the HEP, 11.37±0.60 in the MU and 10.04±0.52 in the EX. MP concentrations were 137.78±16.48, 16.31±1.87, 1.69±0.13 and 4.37±0.27 items/gram (ww) in the GT, HEP, MU and EX, respectively. Microplastics ranged in size from < 100 to 200–250 μm, with fragment-shape (62.07%), fibers (37.31%) and blue (43.69%) was the most common. The most frequently found polymers in shrimp tissue organs and pond water were polyethylene terephthalate (PET), polyvinyl acetate (PVAc) and cellulose acetate butyrate (CAB). Shrimp consumption (excluding GT and EX) was calculated as 28.79 items/shrimp/person/day using Thailand's consumption of shrimp, MP abundance and shrimp consumption. The results of the study can be used as background data for future biomonitoring of microplastics in shrimp species that are significant from an ecological and commercial perspective. MP abundance in farmed L. vannamei may be related to feeding habits and the source of MPs could come from the aquaculture facilities operations.

Microplastics (MPs) contamination in fish species was one of the emerging environmental issues as a result of the widespread presence of plastic pollution in the environment. The presence of MPs in Thailand's freshwater was scant, and in contrast to other countries, little was known about the presence of this contaminant in freshwater fish. Hence, the purpose of this study was to examine the abundance, characteristics, and variation of MPs in various Thai commercial freshwater fish species. In order to compare the differences in MP ingestion rates across different feeding zones, 166 fish representing 24 species from various feeding zones were collected. MPs were found in the gastrointestinal tracts (GIT) of all fish samples tested, which was a substantially larger number than previously reported in other locations. Of all the fish species, Anabas testudineus, Labeo rohita, and Oreochromis mossambicus had the highest concentration of MPs (34.90 ± 21.43, 34.50 ± 7.78, 34.10 ± 11.15 items/individuals). Microscopical examinations showed that the majority of MPs were fiber-shaped and blue in color. Fourier transform infrared analysis (FTIR) showed that the polymers found in fish GIT were polyethylene, polypropylene, polyethylene terephthalate, polyvinyl acetate, poly (methyl vinyl ether), poly (methyl vinyl ether), polybutadiene, poly (ethylene-co-propylene), poly (ethylene glycol) tetrahydrofurfuryl ether, poly (methyl phenyl siloxane), poly (styrene-co-divinylbenzene), and polyvinylidene fluoride. The results of this study demonstrate that demersal fish had a higher concentration of MPs than benthopelagic and pelagic fish, indicating that plastic ingestion in fish may be related to the feeding habitat. However, it was not discovered that differences in the fish's body weight and length affected the MPs' ingestion. Our findings will help people in Thailand understand which freshwater fish and fish from which feeding zones are more contaminated with MPs for human consumption.