Occurrence, distribution and characteristics of microplastics in gastrointestinal tract and gills of commercial marine fish from Malaysia.

Microplastics are tiny plastic particles with size below 5 mm, prevalence in marine environments and the occurrence have been reported in commercial marine fish worldwide. Microplastics' abilities to absorb various marine contaminants raised considerable concern on their role as a vector to spread harmful pollutants to the alienated environment. This study focussed on the occurrence of microplastics in gastrointestinal tract (GIT) and gills of 158 fishes across 16 species from two locations in Malaysia coastal waters. Microplastics were detected approximately 86% in the GIT and 92% in the gills of examined fish. High incident of microplastics was detected in fishes from the area that is close to an urban area with average microplastics incident reaching up to 9.88 plastics items/individuals. Meanwhile, only 5.17 microplastics per individual were recorded in fishes from a less urbanised area. Isolated microplastics comprised 80.2% of fibres, 17.7% of fragments and the remaining was derived from filaments (3.1%). Infrared and Raman spectroscopy analysis of selected microplastics revealed the chemical composition of microplastics which comprised of polyethene (PE), polypropylene (PP), acrylonitrile butadiene styrene (ABS), polystyrene (PS) and polyethylene terephthalates (PET). FESEM images indicate, different surface characteristics of microplastics as a result of environmental exposure. Further, elemental analysis using EDX for green PE fragments showed the uneven distribution of chromium (Cr) and iron (Fe) on the surface, suggesting the adherence of heavy metals on the surface of microplastics. Overall findings indicate the widespread distribution of microplastics in commercial marine fishes from Malaysia waters and could potentially lead to human exposure through fish consumption.

Improving the efficiency of post-digestion method in extracting microplastics from gastrointestinal tract and gills of fish.

Post-digestion treatment is an important step during sample preparation to facilitate the removal of undigested materials for better detection of ingested microplastics. Sieving, density separation with zinc chloride solution (ZnCl2), and oil extraction protocol (OEP) have been introduced in separating microplastics from sediments. The clean-up methods are rarely highlighted in previous studies, especially in the separation of microplastics from marine biota. Thus, this study proposed and compared the suitability of three techniques, which can reduce the number of undigested particles from the digestate of GIT and gills. Our result has shown excellent removal of non-plastics materials and reduces the coloration of filter paper in all treated samples. Both sieving and density separation achieved optimum post-digestion efficiencies of >95% for both GIT and gill samples, which former showed no effect on polymer integrity. Additionally, high recovery rate was obtained for the larger size microplastics (>500 µm) with approximately 97.7% (GIT) and 95.7% (gill), respectively. Exposure to the ZnCl2 solution led to a significant loss of smaller size PET and changed the absorption spectrums of all tested polymers. Particle morphology determined by SEM revealed such exposure eroded the surface of PET fragments and elemental analysis has shown detectable peaks of zinc and chlorine appeared. Low microplastics recoveries were achieved through OPE and residue of oil was observed from the infrared spectrum of all tested polymer. The findings demonstrate sieving with size fractioning can provide exceptional removal of non-plastics materials from the digestate of GIT and gill samples.