Neustonic microplastic pollution in the Persian Gulf

Disparities in Methods Used to Determine Microplastics in the Aquatic Environment: A Review of Legislation, Sampling Process and Instrumental Analysis

Plastic particles smaller than 5 mm, i.e., microplastics, have been detected in a number of environments. The number of studies on microplastics in marine environments, fresh water, wastewater, the atmosphere, and the human body are increasing along with a rise in the amounts of plastic materials introduced into the environment every year, all contributing to a range of health and environmental issues. Although the use of primary microplastics has been gradually reduced by recent legislation in many countries, new knowledge and data on these problems are needed to understand the overall lifecycle of secondary microplastics in particular. The aim of this review is to provide unified information on the pathways of microplastics into the environment, their degradation, and related legislation, with a special focus on the methods of their sampling, determination, and instrumental analysis. To deal with the health and environmental issues associated with the abundance of microplastics in the environment, researchers should focus on agreeing on a uniform methodology to determine the gravity of the problem through obtaining comparable data, thus leading to new and stricter legislation enforcing more sustainable plastic production and recycling, and hopefully contributing to reversing the trend of high amounts of microplastics worldwide.

Source and risk assessment of heavy metals and microplastics in bivalves and coastal sediments of the Northern Persian Gulf, Hormogzan Province

The objectives of the current study are to investigate the concentration, biological risks, chemical speciation, and mobility of of heavy metals and also the determination of their distribution, physicochemical characteristics, and abundance of microplastics in coastal sediments and edible bivalves in the Persian Gulf, the coastal area of Hormozgan Province. Sampling points were selected considering the location of industrial, urban and Hara forest protected areas. In November 2017, a total of 18 sediment samples from coastal sediments (top 0-10 cm) and the most consumed bivalve species in the region were collected from two stations, Lengeh and Bandar Abbas Ports. The average concentration of heavy metals (except for Ni and Cd) in the sediments were lower than their average shale and the upper continental crust. Enrichment factors revealed significant enrichment of Ni, Mn, Cr, Cd and As. The fractionation of heavy metals using the Community Bureau of Reference (BCR) sequential extraction scheme indicated the high bioavailability of Zn, As, Mn, and Co. In general, the highest concentration of Mo, Cd, Pb, Zn, Cr, Cu, Mn, Hg, and Sb was detected in areas with frequent human activities including Shahid Rajaee Port, Shahid Bahonar Port, and Tavanir station. Shahid Rajaee and Shahid Bahonar Ports are the most important ports on the coast of Hormozgan province. The Risk Assessment Code calculated for the study elements indicates that As, Co, Zn, and Cu pose a moderate environmental risk a threat to the aquatic biota. Health risks of most heavy metals arising from bivalves consumption were safe, except for As which is associated with the high target cancer risk values. With reference to the type of microplastics found, they were mainly fibeours with lengths ranging between 100 and 250 μm in sediments and bivalves. Most of the microfibers found in the sediments were made of polyethylene terephthalate (PET) and polypropylene (PP), and the fibers found in the bivalves were made of PP.

Microplastics decrease the toxicity of triphenyl phosphate (TPhP) in the marine medaka (Oryzias melastigma) larvae

Plastics have been recognized as a serious threat to the environment. Besides their own toxicity, microplastics can interact with other environmental pollutants, acting as carriers and potentially modulating their toxicity. In this study, the toxicity of polystyrene (PS) microplastic fragments (plain PS; carboxylated PS, PS-COOH and aminated PS, PS-NH₂) and triphenyl phosphate (TPhP) (an emerging organophosphate flame retardant) at the environmentally relevant concentrations to the marine medaka (Oryzias melastigma) larvae was investigated. Larvae were exposed to 20 μg/L of microplastic fragments or 20 and 100 μg/L of TPhP or a combination of both for 7 days. The results showed that the three microplastics did not affect the larval locomotor activity. For TPhP, the larval moving duration and distance moved were significantly decreased by the TPhP exposure, with a maximum decrease of 43.5% and 59.4% respectively. Exposure to 100 μg/L TPhP respectively down-regulated the expression levels of sine oculis homeobox homologue 3 (six3) and short wavelength-sensitive type 2 (sws2) by 19.1% and 41.7%, suggesting that TPhP might disturb eye development and photoreception and consequently the low locomotor activity in the larvae. Interestingly, during the binary mixture exposure, the presence of PS, PS-COOH or PS-NH₂ reversed the low locomotor activity induced by 100 μg/L TPhP to the normal level. Relative to the larvae from the 100 μg/L TPhP group, the movement duration and distance moved were increased by approximately 60% and 100%, respectively, in the larvae from the TPhP + PS, TPhP + PS-COOH and TPhP + PS-NH₂ groups. However, the gene expression profiles were distinct among the fish from the TPhP + PS, TPhP + PS-COOH and TPhP + PS-NH₂ groups, implying different mechanisms underlying the reversal of the locomotor activity. The findings in this study challenge the general view that microplastics aggravate the toxicity of the adsorbed pollutants, and help better understand the environmental risk of microplastic pollution.

Microplastics accumulation in sediments and Periophthalmus waltoni fish, mangrove forests in southern Iran

This investigation was aimed to identify microplastics in the sediment and mudskipper fish (Periophthalmus waltoni) in mangrove forests in southern Iran. Sediments and mudskipper samples were collected at high, mid, and low tidal points of five stations. A total of 2657 plastic particles in different size, color, shape, and genera were identified from sediment samples and 15 microplastic were isolated from mudskippers. The highest and lowest abundance of isolated microplastics from sediments was observed in mangrove forests of Bidkhoun (urban area) and Bordkhon, respectively while no microplastics were found in the fish tissue in those stations. The black (60%) and white (7%) color microplastics in the mudskipper had the highest and the lowest frequency. The highest and lowest polymers in mangrove forest sediments were corresponded to polystyrene (26%) and polycarbonate (3%), respectively. Raman and Fourier transform infrared spectroscopy (FT-IR) techniques were used to identify the type of the polymer. Most of the microplastics found were made of polystyrene, polypropylene, and polyethylene terephthalate. The type of studied area and texture of sediment separately affected the frequency of microplastic and mesoplastic (P-value <0.05) in the sediment samples. The abundance of microplastics in the sediment samples of the Bidkhoun mangrove forest was higher than other studied stations due to proximity to urban and industrial areas. The findings of this study raised concerns about microplastic pollution in the mangrove forests of southern Iran, a threat to the ecosystem and public health, which requires careful actions to prevent and diminish its adverse effects.

Emerging contaminants in the water bodies of the Middle East and North Africa (MENA): A critical review

Many emerging contaminants (ECs) are not currently removed by conventional water treatment methods and consequently, often reach the aquatic environment. In the absence of proper management strategies, ECs can accumulate in water bodies, which poses potential environmental and health risks. This paper critically reviews, for the first time, the reported occurrence and treatment of ECs in the Middle Eastern and North Africa (MENA) region. The paper also provides recommendations to properly manage EC risks. In the MENA region, pharmaceuticals and personal care products (PPCPs) have been detected in surface water, seawater, groundwater, and wastewater treatment plants. A focus on surface water in the published literature suggests that studies are skewed towards worldwide trends, whereas studies on ECs in seawater are of great importance in the study region. The types of PPCPs detected in the MENA region vary, but anti-inflammatories and antibiotics dominate. In comparison, microplastics have mainly been studied in surface waters and seawater with much less focus on drinking water. The majority of microplastics in the region are secondary types resulting from the degradation of larger plastic debris; polyethylene (PE) and polypropylene (PP) fibers are the most frequently detected polymers, which are indicative of local anthropogenic sources. Research progress on ECs varies between countries, having received more attention in Iran and Tunisia. Most MENA countries have now begun monitoring water bodies for ECs; however, studies are still lacking in some countries including Sudan, Djibouti, Syria, Ethiopia, and Bahrain. Based on this review, critical knowledge gaps and research needs are identified. Countries in the MENA region require further research on a broader range of EC types. Overall, water pollution due to the use and release of ECs can be tackled by improving public awareness, public campaigns, government intervention, and advanced monitoring and treatment methods.

Scientific studies on microplastics pollution in Iran: An in-depth review of the published articles

This literature review was conducted to collect present data on microplastics pollution in Iran's ecosystems. Most of the studies performed in aquatic environment were conducted in Persian Gulf & Oman Sea (70%). The Persian Gulf, along with the beaches of Bushehr and Hormozgan Provinces, are the most studied areas. Moreover, most of the studies were conducted in aquatic environments and only four studies were conducted in terrestrial environment (4/42). One study has assessed microplastics in commercial salt and another study has reported the microplastics presence in Iranian bottled mineral water brands. The investigation of microplastics associated with biota was highlighted, customarily for fish species. Microplastics were also present in urban wastewater samples in Sari and Bandar Abbas cities. Three studies were performed in freshwater ecosystems until now (Haraz River, Anzali wetland, and Taleqan dam). The need for further studies in this field still exists, especially in terrestrial and freshwater compartments.

Microplastic's story

The problem of microplastic pollution is now the order of the day in front of everyone's eyes affecting the environment and the health of leaving creature. This work aims to retrace the history of microplastics in a critical way through a substantial bibliographic collection, defining the points still unresolved and those that can be resolved. Presence of marine litter in different environments is reviewed on a global scale, focusing in particular on micro and macro plastics definition, classification and characterization techniques.

Micro and Nano-Plastics in the Environment: Research Priorities for the Near Future

Plastic litter dispersed in the different environmental compartments represents one of the most concerning problems associated with human activities. Specifically, plastic particles in the micro and nano size scale are ubiquitous and represent a threat to human health and the environment. In the last few decades, a huge amount of research has been devoted to evaluate several aspects of micro/nano-plastic contamination: origin and emissions, presence in different compartments, environmental fate, effects on human health and the environment, transfer in the food web and the role of associated chemicals and microorganisms. Nevertheless, despite the bulk of information produced, several knowledge gaps still exist. The objective of this paper is to highlight the most important of these knowledge gaps and to provide suggestions for the main research needs required to describe and understand the most controversial points to better orient the research efforts for the near future. Some of the major issues that need further efforts to improve our knowledge on the exposure, effects and risk of micro/nano-plastics are: harmonization of sampling procedures; development of more accurate, less expensive and less time-consuming analytical methods; assessment of degradation patterns and environmental fate of fragments; evaluating the capabilities for bioaccumulation and transfer to the food web; and evaluating the fate and the impact of chemicals and microorganisms associated with micro/nano-plastics. The major gaps in all sectors of our knowledge, from exposure to potentially harmful effects, refer to small size microplastics and, particularly, to the occurrence, fate and effects of nanoplastics.

Three-dimensional numerical modelling of transport, fate and distribution of microplastics in the northwestern Arabian/Persian Gulf

Marine plastic litter has been a major concern over the past decade particularly in semi-enclosed seas such as the Arabian/Persian Gulf, which are likely to impose a relatively higher threat to ecosystem and human health. In this work, we have focused our efforts on the transport features of marine surface microplastics (MPs) in the Gulf. The assessment utilizes a 3D hydrodynamic model of the northern Gulf which was coupled with a particle tracking model. We have considered five release locations and investigated two dominant wind conditions by applying different numerical scenarios. The results revealed that the northerly winds result in high dispersion and seaward transport of MPs in the open coastal zones, while in semi-enclosed regions they result in high trapping and beaching verified by visual investigation. The study shows that further detailed field investigations are warranted to enable the models to better parameterize the fate and distributions of MPs.

Microplastics in the environment: Interactions with microbes and chemical contaminants

Microplastics (MPs) are contaminants of emerging concern that have gained considerable attention during the last few decades due to their adverse impact on living organisms and the environment. Recent studies have shown their ubiquitous presence in the environment including the atmosphere, soil, and water. Though several reviews have focused on the occurrence of microplastics in different habitats, little attention has been paid to their interaction with biological and chemical pollutants in the environment. This review therefore presents the state of knowledge on the interaction of MPs with chemicals and microbes in different environments. The distribution of MPs, the association of toxic chemicals with MPs, microbial association with MPs and the microbial-induced fate of MPs in the environment are discussed. The biodegradation and bioaccumulation of MPs by and in microbes and its potential impact on the food chain are also reviewed. The mechanisms driving these interactions and how these, in turn, affect living organisms however are not yet fully understood and require further attention.

Identification and characterization of micro-plastics in the marine environment: A mini review

Micro-plastics (MPs) are an environmental threat that has been gaining importance lately with an increasing number of studies demonstrating that they are a larger threat than previously thought. Scientists around the world have used a wide number of methods in their studies and they have adapted changes in response to the specific nature of the research undertaken. This article provides an account of the historical development of the MP menace, development of methods and tools used in MP research and also describes the challenges that are faced to further advancement to take place. The article is categorized into various sections that include history, sources, isolation, extraction, and characterization of MPs. Among the thermal characterization techniques, direct pyrolysis mass spectrometry and secondary ion mass spectrometry, which are widely used to characterize the plastics, but not utilised so far in this field are also highlighted for future direction.

Spatio-temporal evaluation of macro, meso and microplastics in surface waters, bottom and beach sediments of two embayments in Niterói, RJ, Brazil

This study evaluated in the dry and rainy periods, the anthropogenic influence and the hydrodynamics in the distribution of plastic items in surface waters and bottom and beach sediments of the Jurujuba (Guanabara Bay, low and medium hydrodynamic) and Itaipu (oceanic region, high hydrodynamics) embayments; places of cultivation and extraction of mussels. Microplastics were 83% of the wastes collected, with a higher average concentration (138.41 items.kg^-1) in beach sediments. High density polyethylene (HDPE) (38%), polypropylene (21%), and styrene (10%) were the most frequent polymers. There was no difference between the water and bottom sediment samples in the different embayments, in the studied periods, different from that observed in the beach sediment samples, with higher concentrations in the rainy season in Jurujuba. The results suggest that beach sediments are the best compartment to understand the dynamics of the distribution of plastic waste over time.

Microplastic pollution as a grand challenge in marine research: A closer look at their adverse impacts on the immune and reproductive systems

Microplastic (MP) pollution of the marine environment is now a growing global concern posing a threat to a variety of species through the ingestion and transfer within food webs. This is considered a potential toxicological threat to marine species due to the chemical additives used to make many plastic products, or the persistent organic pollutants that may accumulate on them while residing in the environment. While the presence of MPs in the marine environment is widely documented, there are no other review articles providing a summary of published effect studies of MPs on the immune and reproductive systems of marine species. This manuscript reviews reproductive and immune-system changes in response to MPs in 7 and 9 species, respectively. Some species such as Mytilus galloprovincialis and oyster Crassostrea gigas were investigated in multiple papers. Most studies have been conducted on invertebrates, and only 3 studies have been performed on vertebrates, with exposure times ranging between 30 min and 60 days. A review of the literature revealed that the most common MPs types studied in relation to adverse impacts on immune system and reproductive success in marine species were polystyrene (PS) and polyethylene (PE). The immune system's responses to MPs exposure varied depending on the species, with altered organismal defense mechanisms and neutrophil function observed in fish and changes in lysosomal membrane stability and apoptotic-like nuclear alterations in phagocytes reported in invertebrate species. Reproductive responses to MPs exposure, varied depending on species, but included significant reduction in gamete and oocyte quality, fecundity, sperm swimming speed, and quality of offspring. The lack of published data means that developing a clear understanding of the impact across taxonomic groups with different feeding and behavioral traits is often difficult. Further work is required to better understand the risk MPs pose to the immune and reproductive systems of marine species in order to fully evaluate the impact these ubiquitous pollutants are having on marine ecosystems and the associated goods and services they provide.

Distribution and characteristics of microplastics in urban waters of seven cities in the Tuojiang River basin, China

Microplastics pollution presents an increasing concern worldwide due to the large amount and potential risks. However, data on microplastics in the freshwater environment are still limited, especially in southwest China. This study investigated the microplastics distribution, characteristics and risks in urban water of different cities in the Tuojiang River basin in southwest China. Microplastics were found in all seven cities of the Tuojiang River basin and the concentrations varied from 911.57 ± 199.73 to 3395.27 ± 707.22 items/m³, among which Ziyang urban water had the highest microplastics concentration. Fiber (34.88-65.85%) was a typical and abundant microplastic type. The small size (0.5-1 mm) (27.27-66.67%) was predominant, and white (23.30-54.29%) was the dominant color among all samples. Polypropylene was identified as the main polymer type by Fourier transform infrared spectroscopy. The morphological analysis by scanning electron microscopy indicated that the surfaces of the microplastics had many cracks and a multitude of particles were adsorbed onto it. According to correlation analysis, there was a significant positive correlation between gross domestic product(P=0.015<0.05) and gross domestic product of the secondary industries(P=0.014<0.05) of cities in the Tuojiang River basin and microplastics concentrations, demonstrating impacts of the secondary industries on the microplastics pollution. In addition, water bodies with lower oxidation-reduction potential tended to have higher microplastics abundance. In the Tuojiang River basin, microplastics pollution was more serious in location where water quality was poor. The polymer risk index (H) was calculated to assess the environmental risk of microplastics in different cities, and the results showed that Fushun sites had the highest risk in regard to microplastics. This study provides a valuable reference for a better understanding of the microplastics level and source identification in southwest China.

Estimation of plastic waste inputs from land into the Persian Gulf and the Gulf of Oman: An environmental disaster, scientific and social concerns

It has been reported that, the huge amount of plastic waste is present in marine environments. This study evaluated solid waste generation, management, disposal approaches, and the amount of plastic waste entered into the Persian Gulf and the Gulf of Oman in 2016. The findings showed that waste in the Persian Gulf and the Gulf of Oman regions has been mismanaged by 65% and 81%, respectively. According to our estimates, about 1634.9 k-tons (Kt) and 204.6 Kt of plastic waste have been, respectively, generated by the Persian Gulf and the Gulf of Oman littoral states in 2016. Most likely, the mass of plastic waste entering the Persian Gulf and the Gulf of Oman in 2016 was ranged from 155 to 413.4 Kt and 29.2-77.9 Kt, respectively. Without implementation of effective waste management strategies, it is estimated that by 2030, the mass of plastic waste entering the Persian Gulf will increase to 199.4-531.6 Kt, while in the Gulf of Oman it would be about 40.4-107.7 Kt. The entry of plastic waste into the Persian Gulf and the Gulf of Oman has been expected to increase by 29% and 38% in 2030, respectively. As a result, the related cumulative environmental and health effects can be more intensive. It can be emphasized that all countries located in the coastal areas of the Persian Gulf and the Gulf of Oman need to modify their solid waste management, plastic waste in particular, policies to conserve sensitive marine ecosystems.

Sustainable energy from waste organic matters via efficient microbial processes

This review emphasizes utilization of waste organic matters from water bodies and soil sources for sustainable energy development. These organic waste matters (including microplastics) from a variety of environmental sources have created a big challenge to utilize them for energy development for human needs, maintaining a cleaner environment and thereby, producing useful bioproducts (sustainable bioenergy or other primary metabolites). Anaerobic digestions as well as other effective wastewater treatment approaches are discussed. From the water bodies, waste organic matter reduction can be achieved by a reduction of chemical oxygen demand and biological oxygen demand after the waste treatment. Other forms of organic waste matter are available in the form of agro wastes or residues (stalk of wheat or rice, maize, corn etc.) due to crop cultivation, which are generally burnt into ashes. Such wastes can be utilized for bioenergy energy production, which would help for the reduction of climate changes or other toxic gases. Hydrogen, bioelectricity, ethanol, butanol, methane and algal diesel or other types of fuel sources would help to provide sustainable source of bioenergy that can be produced from these wastes via degradation by the biological processes. This review will discuss in depths about the sustainable nature of organic matters to produce clean energy via application of efficient biological methods to maintain a clean environment, thereby providing alternative options to fossil energy fuels.

Plastic Debris in the Marine Environment: History and Future Challenges

The success of plastic as a material has shaped the development of modern society and challenged older materials in many of their established uses. However, plastic is now a major component of litter and is extensively reported within the marine environment. Impacts from plastic debris have been identified as a major global conservation issue with implications for maritime industries, tourism, marine life, and human health. Although there are many benefits of plastic, it is clear that society's relationship and reliance on plastics needs to be addressed. Conversely, alternative materials to replace plastic items, or solutions mitigating plastic release, also need to be critiqued to make sure their properties and environmental impacts are more beneficial. This review examines the history and impact of plastics in the marine environment. Current solutions that aim to mitigate plastics accumulation in the environment and the future challenges of plastic as a material are also discussed.

Microplastic pollution in the littoral sediments of the northern part of the Oman Sea

Microplastics (MPs) have been increasingly detected as environmental pollutants in the marine systems. Currently, there is no information about the microplastic pollution in the littoral sediments of the northern Oman Sea, and this problem was addressed in the present study for the first time. Sediment samples were collected at eight sampling stations. MPs were extracted by the flotation method and then, counted and categorized according to their shape, size, and color. Composition of the MPs was determined by ATR-FTIR spectroscopy. MPs were observed in all the stations and their abundance ranged from 138.3 ± 4.5 to 930.3 ± 49.1 particles·kg^-1. The major polymer constituent was Polyethylene, followed by Polypropylene, and Nylon. Fibers and fragments were dominant shapes of the MPs. Our results confirmed the prevalence of the MPs as anthropogenic pollutants in the area and highlighted the importance of management actions and education on environmental protection for reduction of the marine debris.

Evidence of microplastics (MP) in gut content of major consumed marine fish species in the State of Kuwait (of the Arabian/Persian Gulf)

Microplastics (MP), the debris that collectively refers to plastic fragments and particles of <5 mm in size within marine environments, has been the subject of interest within the past decade. Evidence of its occurrence and abundance, has been recorded in this communication after examining gastrointestinal specimens of eight commercially available fish species common to the Arabian (Persian) Gulf acquired locally from the State of Kuwait. The species studied belonged to different trophic levels, and the specimens were subjected to Micro Raman and Micro Fourier Infrared Spectroscopy (FTIR) in Attenuated Reflective Mode (ATR) to determine the presence and type of polymer of the MP. The detected MP set a president for the first time in the examined fish species within the State of Kuwait, which are of immense commercial importance. Various particles were detected, and three MP particles (fragments) were detected within the guts of Acanthopagrus latus, Eleutheronemaa tetradactylum and Lutjanus quinquelineatus. Based on the nature and behaviour of these particular fish types which prefer to stay in muddy waters and sheltered lagoons, it is suspected that common primary sources of MP (i.e. waste fragmentation) have led to passive/active intake (e.g. detritus ingestion) of these particles (fragments) by these species of fish in Kuwait.

Occurrence, trophic transfer, and health risk assessment of bisphenol analogues in seafood from the Persian Gulf

The presence of chemicals in marine organisms is an important issue for human health due to the growing rate of seafood consumption. Potential exposure to seven bisphenol analogues through seafood consumption was investigated in some popular seafood from the Persian Gulf. Bisphenols were analyzed by gas chromatography-mass spectrometry. Bisphenol A (BPA) and bisphenol B (BPB) were the first and second most common bisphenols in the studied samples, respectively. The highest levels of BPA (mean 13.58 ± 5.70 μg/kg.dw) and BPB (mean 10.30 ± 7.98 μg/kg.dw) were found in E.coioides species. Bisphenol F and bisphenol AF were detected only in P. armatus and L. klunzingeri, respectively. Trophic transfer investigation demonstrated that BPA and BPB were biomagnified in the studied organisms through their diet. The eco-toxicity and estrogenic risk assessment indicated that seafood consumption does not pose a health threat to consumers. However, routine monitoring of bisphenols in seafood seems to be necessary to ensure food safety.

Microplastic particles in the Persian/Arabian Gulf - A review on sampling and identification

Microplastics are ubiquitous, persistent pollutants that are reported in abundance within the marine environment. Their presence in seawater and marine sediments poses a legitimate environmental and ecological concern for toxicity and food chain transfer via marine organisms. Their capability for sorption of other hydrophobic contaminants and the inability of the wastewater treatment plants to completely remove them pose additional risks. This review highlights the methodologies for sampling, sample preparation, and identification used in the Persian/Arabian Gulf region, which is possibly one of the least studied marginal seas with only sixteen papers published on microplastics. The review highlights the several orders of magnitude variations in microplastic concentrations among different studies; e.g. in seawater, only 12 microplastic particles were reported from 40 transects of one km length in Kuwait to 0.71 microplastics m^-3 in Qatar. Concentrations in beach sediments also show the significant difference between the northern and southern Gulf coasts, with 13 particles in 24 samples reported in Qatar, and 15 particles within 44 samples across Kuwait, to 3252 ± 2766 particles m^-2 from Bandar Abbas, Iran. The biota samples also show similar variances, with only three particles identified from 87 gut samples in Kuwait to 828 particles in 58 samples that include 46 fish and 12 shrimps from Iran. Some extremely high concentrations in biota are also reported from Iran, with concentrations as high as 0.251 particles g^-1 of muscle and 0.931 particles g^-1 in gills. It is evident that there is no consensus in the Gulf region on the sampling techniques (mesh size of plankton nets and sieves), use of fluidization solutions and very different units used in data reporting such as particles m^-3 and particles m^-2 in water samples. In sediments units like particles g^-1 and particles m^-2 have been used, and for biota it is the number of particles present in the sample, while others have quantified data as particles g^-1 of tissue. Considering the higher densities of PET, PVC, nylon and polyester than seawater, they are likely to migrate downwards into marine sediments, a transfer process that has not been studied in detail. Thus the review underscores the need to adopt harmonized protocols for microplastic studies in the region, and identifies certain aspects of microplastics that require further study.

Seasonal variation of micro- and meso-plastics in the seawater of Jiaozhou Bay, the Yellow Sea

The seasonal change in the concentrations and characteristics of micro- and meso-plastics in the surface seawater of Jiaozhou Bay were studied. The concentrations of micro- and meso-plastics were 0.063, 0.174, 0.094, and 0.050 pieces/m³ in February, May, August and November, respectively, with an annual average concentration of 0.095 pieces/m³. The size of the micro- and meso-plastics ranged from 346 to 155,200 μm, with an average of 5093 ± 43 μm. The overall percentages of fibers, fragments and plastic foams were 29%, 55% and 16%, respectively. The dominant chemical composition was polypropylene (PP), accounting for 51.04% of polymers, followed by polyethylene (PE), accounting for 26.04% of polymers. Strong rainfall resulted in an increase in the plastic concentration in May, and winds and eddies affected the spatial distribution of plastics in Jiaozhou Bay.

Microplastics in fishes of commercial and ecological importance from the Western Arabian Gulf

Microplastic particles (MPs) in the gastrointestinal tracts of nine fish species of commercial importance from different habitats (coastal, pelagic, and reef-associated) in the Saudi EEZ of the Arabian Gulf were quantified and classified. A total of eight MPs were retrieved from a total of 140 individual fish examined, with an average of 0.057 ± 0.019 microplastic items per fish (excluding possible plastic fibers). On average, 5.71%, of the fish dissected contained MPs, ranging from 5 to 15% of individual fish examined containing MPs among species (Siganus canaliculatus and Rastrelliger kanagurta, respectively). Ingested plastic consisted primarily of fishing threads (1.04 ± 0.06 mm), followed by fragments (1.16 ± 0.11 mm). It is likely that the fibers, originated from the fisheries, recreational boating, laundry, domestic wastewater, and other human activities, which is also widespread and abundant (found in 58.58% of the fish studied). Polyethylene (PE) and polypropylene (PP) were identified as the most abundant polymers ingested by the fishes. There was no significant difference (p < 0.05) between the presence of microplastic in fish depending on their habitat. The prevalence of MPs is relatively low compared to those in other regions, despite the massive industrialization of the Saudi Arabian Gulf.