Microplastic pollution: a review of techniques to identify microplastics and their threats to the aquatic ecosystem.

Microplastics (MPs), small synthetic particles, have emerged as perilous chemical pollutants in aquatic habitats, causing grave concerns about their disruptive effects on ecosystems. The fauna and flora inhabiting these specific environments consume these MPs, unwittingly introducing them into the intricate web of the food chain. In this comprehensive evaluation, the current methods of identifying MPs are amalgamated and their profound impacts on marine and freshwater ecosystems are discussed. There are many potential risks associated with MPs, including the dangers of ingestion and entanglement, as well as internal injuries and digestive obstructions, both marine and freshwater organisms. In this review, the merits and limitations of diverse identification techniques are discussed, including spanning chemical analysis, thermal identification, and spectroscopic imaging such as Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and fluorescent microscopy. Additionally, it discusses the prevalence of MPs, the factors that affect their release into aquatic ecosystems, as well as their plausible impact on various aquatic ecosystems. Considering these disconcerting findings, it is imperative that appropriate measures should be taken to assess the potential risks of MP pollution, protect aquatic life and human health, and foster sustainable development.

Sinisalibacter aestuarii sp. nov., isolated from estuarine sediment of the Arakawa River.

A Gram-stain-negative, rod-shaped, non-motile and strictly aerobic bacterium, which showed biofilm-forming ability on polystyrene, designated as strain B-399T, was isolated from the estuarine sediment of the Arakawa River near Tokyo Bay. It grew at pH 6.0-8.5, at 15-35 °C and in the presence of 0-7.5 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain B-399T was clustered in the genus Sinisalibacter and has 96.94 % sequence similarity to Sinisalibacter lacisalsi X12M-4T, which was the only validly described species in this genus. On the basis of our genome sequencing analyses, the average nucleotide identity and digital DNA-DNA hybridization values between strains B-399T and S. lacisalsi X12M-4T were 79.54 and 22.30 %, respectively, which confirms that strain B-399T represents a novel species of the genus Sinisalibacter. The draft genome size and the DNA G+C content of strain B-399T were 4.12 Mb and 65.2 mol%, respectively. The major fatty acids (>10 %) of strain B-399T were C16 : 0, summed feature 8 (C18 : 1 ω6c and/or C18 : 1 ω7c) and C19 : 0 cyclo ω8c. The polar lipids were phosphatidylcholine, phosphatidylglycerol, an unidentified phospholipid, an unidentified aminolipid and unidentified lipids. The respiratory quinone was Q-10. These chemotaxonomic features were almost coincident with those of the genus Sinisalibacter. Therefore, strain B-399T should be classified as representing a new species of the genus Sinisalibacter, for which the name Sinisalibacter aestuarii sp. nov. is proposed. The type strain is B-399T (=NBRC 115629T=DSM 114148T).

Microplastic pollution in the gastrointestinal tract of giant river catfish Sperata seenghala (Sykes, 1839) from the Meghna River, Bangladesh.

Freshwater rivers are considered the major route for microplastics (MPs), yet limited studies have been reported on MPs in freshwater river fish, especially in Bangladesh. This research reveals the intake of MPs by the giant river catfish Sperata seenghala, collected from the Meghna River, which is the only outlet of the Ganges-Brahmaputra River. Three locations, namely, Chandpur Sadar, Bhola Sadar, and Char Fasson, along the Meghna River, were selected in order to investigate the gastrointestinal tracts (GIT) of the fish. Ninety percent (n=27) of fish (n=30) were contaminated, with fragment-shaped MPs (65%) as the most abundant among the four types. A total of 179 MP particles were detected using micro-Fourier transformed infrared spectroscopy (µ-FTIR), with an average of 5.96 ± 1.32 MP particles per fish. Among the four size groups, the highest proportion of MPs (54%) occurred in the 45-100 µm group; the dominant color among the seven color groups was white (30%). The highest quantity of MPs was found in the relatively densely populated Chandpur Sadar region. Polypropylene-polyethylene copolymer (PP-PE, 23%) was proportionally dominant among the 15 types. No significant relationship was found between the total number of observed MPs and the GIT weight. This study will help us to understand MP pollution in S. seenghala that may transmit to the human body through the food chain.