Microplastics assessment in Arabian Sea fishes: accumulation, characterization, and method development / Avaliação de microplásticos em peixes do mar arábico: acumulação, caracterização e desenvolvimento de métodos

Around the globe, plastic has been entering the aquatic system and is ingested by organisms. Identification, optimal digestion method, and characterization of the polymers to trace sources are of growing importance. Hence, the present work investigated microplastics accumulation, digestion protocol efficiency, and characterization of polymers with FTIR analysis in the guts of five fishes (Lethrinus nebulosus, Rastrelliger kanagurta, Acanthopagrus arabicus, Otolithes ruber, and Euryglossa orientalis) from the Karachi coastal area, Arabian Sea. A total of 1154 microplastics (MPs) were ingested by 29 out of 33 fish species (87%). The highest average MP/fish was recorded in Otolithes ruber (54) and the lowest in Rastrelliger kanagurta (19.42). Microfibers were the most abundant shape with the highest numbers (35.52%) as compared to the rest of the MPs identified. Transparent microfibers were recorded as the highest in numbers followed by red, black, blue, and green. In this study, KOH with different concentrations and exposure times along with oxidizing agent hydrogen peroxide was tested (Protocols 3 and 4). Results showed these bases were highly efficient in obtaining optimal digestion of the samples. FTIR analysis confirmed that the majority of the polymers found in the fish guts were polyethylene and polypropylene. This study validated for the first time the presence of these polymers of plastic in marine fish from Pakistan.

Em todo o mundo, o plástico tem entrado no sistema aquático e tem sido ingerido por organismos. A identificação, o método de digestão ideal e a caracterização dos polímeros para rastrear fontes são de crescente importância. Portanto, o presente trabalho investigou o acúmulo de microplásticos, a eficiência do protocolo de digestão e a caracterização de polímeros com análise de FTIR nos tratos digestivos de cinco peixes (Lethrinus nebulosus, Rastrelliger kanagurta, Acanthopagrus arabicus, Otolithes ruber e Euryglossa orientalis) do litoral de Karachi, no mar Arábico. Um total de 1154 microplásticos (MP) foram ingeridos por 29 das 33 espécies de peixes (87%) estudadas. A maior média MP/peixe foi registrada no Otolithes ruber (54), e a menor no Rastrelliger kanagurta (19,42). As microfibras foram a forma mais abundante e com os maiores números (35,52%), em comparação ao restante das MPs identificadas. As microfibras transparentes foram detectadas em maior número, seguidas por vermelho, preto, azul e verde. Neste estudo, o KOH foi testado em diferentes concentrações e tempos de exposição, juntamente com o agente oxidante peróxido de hidrogênio (Protocolos 3 e 4). Os resultados mostraram que essas bases foram altamente eficientes para a obtenção de digestão ideal das amostras. A análise de FTIR confirmou que a maioria dos polímeros encontrados nos tratos digestivos dos peixes eram polietileno e polipropileno. Este estudo validou pela primeira vez a presença desses polímeros de plástico em peixes marinhos do Paquistão.

Microplastics assessment in Arabian Sea fishes: accumulation, characterization, and method development.

Around the globe, plastic has been entering the aquatic system and is ingested by organisms. Identification, optimal digestion method, and characterization of the polymers to trace sources are of growing importance. Hence, the present work investigated microplastics accumulation, digestion protocol efficiency, and characterization of polymers with FTIR analysis in the guts of five fishes (Lethrinus nebulosus, Rastrelliger kanagurta, Acanthopagrus arabicus, Otolithes ruber, and Euryglossa orientalis) from the Karachi coastal area, Arabian Sea. A total of 1154 microplastics (MPs) were ingested by 29 out of 33 fish species (87%). The highest average MP/fish was recorded in Otolithes ruber (54) and the lowest in Rastrelliger kanagurta (19.42). Microfibers were the most abundant shape with the highest numbers (35.52%) as compared to the rest of the MPs identified. Transparent microfibers were recorded as the highest in numbers followed by red, black, blue, and green. In this study, KOH with different concentrations and exposure times along with oxidizing agent hydrogen peroxide was tested (Protocols 3 and 4). Results showed these bases were highly efficient in obtaining optimal digestion of the samples. FTIR analysis confirmed that the majority of the polymers found in the fish guts were polyethylene and polypropylene. This study validated for the first time the presence of these polymers of plastic in marine fish from Pakistan.

Isolation, diversity, and biotechnological potential of rhizo- and endophytic bacteria associated with mangrove plants from Saudi Arabia.

Marine bacteria have been exceptional sources of halotolerant enzymes since decades. The aim of the present study was to isolate bacteria producing hydrolytic enzymes from seven different mangroves collected from the coastal area of Thuwal, Jeddah, Saudi Arabia, and to further screen them for other enzymatic and antifungal activities. We have isolated 46 different rhizo- and endophytic bacteria from the soil, roots, and leaves of the mangroves using different enzymatic media. These bacterial strains were capable of producing industrially important enzymes (cellulase, protease, lipase, and amylase). The bacteria were screened further for antagonistic activity against fungal pathogens. Finally, these bacterial strains were identified on the basis of the16S rDNA sequence. Taxonomic and phylogenetic analysis revealed 95.9-100% sequence identity to type strains of related species. The dominant phylum was Gammaproteobacteria (γ-Proteobacteria), which comprised 10 different genera - Erwinia, Vibrio, Psychrobacter, Aidingimonas, Marinobacter, Chromohalobacter, Halomonas, Microbulbifer, and Alteromonas. Firmicutes was the second dominant phylum, which contained only the genus Bacillus. Similarly, only Isoptericola belonged to Actinobacteria. Further these enzyme-producing bacteria were tested for the production of other enzymes. Most of the active strains showed cellulytic and lipolytic activities. Several were also active against fungal pathogens. Our results demonstrated that the mangroves represent an important source of potentially active bacteria producing enzymes and antifungal metabolites (bioactive products). These bacteria are a source of novel halophilic enzymes and antibiotics that can find industrial and medicinal use.