Ecological risk assessment of microplastics and mesoplastics in six common fishes from the Bay of Bengal Coast.

Plastic particles have emerged as a growing threat to both ecosystems and human well-being, as they are being ingested and accumulate at different trophic levels. However, microplastic and mesoplastic contamination and its risk to coastal and marine water fish have not been well studied, particularly in the northern Bay of Bengal. In this study, the presence of small-scale plastic particles (micro- and meso-sized) in the gastrointestinal tract (GIT) and muscles of six edible fish species from the northern Bay of Bengal Coast were identified and analyzed. The overall range of microplastics was 1.74 ± 0.23-3.79 ± 2.03items/g in muscle and 0.54 ± 0.22-5.96 ± 3.16 items/g in the GIT, with 16.38 ± 8.08-31.88 ± 12.09 items/individual. No mesoplastics were found in muscle tissue, but they were present in the GIT at concentrations ranging from 0.33 ± 0.27 to 0.03 ± 0.02 items/g and from 0.51 ± 0.05to 1.38 ± 1.01 items/individual. Lepturacanthus savala accumulated the most microplastics in muscle, and Harpadon nehereus had the least. In addition, the highest levels of mesoplastics were detected in the GIT of Polynemus paradiseus and the lowest was detected in the GIT of Lutjenus sanguineus. Omnivorous fish showed higher plastic concentrations than carnivorous fish, which was linked to dietary habits, feeding strategies and digestive processes. Plastic material predominantly accumulated in the GIT rather than in the muscle. The majority of ingested plastic particles were fibres (95.18 %), were violet in color (34 %), and were < 0.5 mm in size (87 %). The dominant microplastic polymers included 38 % PE, 15 % PP, 33 % PU, and 14 % CES. In contrast, the prevalent mesoplastic polymers comprised 45 % PE, 19 % PP, 13 % PS, 16 % PA, and 7 % PET. Subsequently, a hazard analysis using the polymer hazard index (PHI) revealed that plastic contamination was of distinct hazard categories for different polymer types, ranging from grade I (<1) to grade IV (100-1000). The assessment of the contamination factor (1 < CF < 3) and pollution load index (PLI > 1) indicated moderate contamination of fish by the ingestion of plastic debris. This study provides the foremost evidence for the presence of mesoplastics and microplastics in coastal and marine fish in the study region, paving the way for future investigations and policy implementation.

Heavy metals in afforested mangrove sediment from the world's largest delta: Distributional mapping, contamination status, risk assessment and source tracing.

This study aims to assess seasonal and spatial variations, contamination status, ecological risks, and metal sources (Ni, Pb, Cr, Cu, Mn, and Zn) in human-afforested mangrove sediments in a deltaic region. Five sampling locations were sampled during dry and wet seasons. Heavy metal concentrations followed the order: Mn > Zn > Ni > Cr > Cu > Pb. Metal loads, except Cu and Pb, were higher during the dry season, aligning with national and international recommendations. Sediment quality guidelines, contamination factor, geoaccumulation index, enrichment factors, and pollution load index indicated uncontaminated sediment in both seasons. Potential ecological risk assessment showed low risk conditions in all sites. However, modified hazard quotient indicated moderate pollution risk from all metals except Pb. Analysis suggests anthropogenic sources, particularly evident near shipbreaking yards in Sitakunda. While initially uncontaminated, ongoing metal influx poses a potential risk to mangrove ecosystems.

The contribution of homestead pond fish culture to household food security and dietary diversity in central coast of a developing country.

Fish farming in homestead ponds help alleviate poverty, provide animal source food, micronutrients, and indirect income and various jobs in developing nations. This study investigated the impact of homestead pond fish farming on dietary diversity (HDDS and MDD-W), food security (HFIAS and ELCSA), income, and women's engagement. A total of 185 households were selected randomly for data collection through well-structured questionnaire interviews in the central coast of Bangladesh. HDDS revealed significant dietary diversity (73.3%) among beneficiary farmers, surpassing controls and nearly doubling that of non-aquaculture farmers (41.1%). Additionally, this study found that 86.7% and 74.3% of women in beneficiary and homestead pond farmers exhibited high dietary diversity (MDD-W ≥ 5), whereas 48.6% of women in non-aquaculture farmers' households had low dietary diversity (MDD-W ≥ 5). Based on both ELCSA and HFIAS, higher prevalence of food security was observed among the beneficiary farmers that was about 60% and 63.3%, respectively compared with the control farmers. Most non-aquaculture farmers (62.9%) indicated their family consumed fish for one week before the research. More than half of the homestead pond culture (55.7%) and more than 90% of the beneficiary farmers, aquaculture farmers and non-aquaculture farmers had gross income (<$ 500). Pertaining to women's participation in homestead pond was positively correlated to productivity while male dominated tasks was negatively correlated with productivity. The results offer insights into how homestead pond fish farming can enhance food security by supplying direct animal protein, addressing protein and micronutrient deficiencies, and boosting income. The study emphasizes the urgent necessity for training and promoting homestead pond culture, increasing female participation, and advocating comprehensive support from governmental organizations (GOs) and non-governmental organizations (NGOs) to optimize production, improve micronutrient adequacy, and guarantee household food security. Keywords: Fish farming, food security, dietary diversity, women's participation.

Migratory history of the threespine stickleback Gasterosteus aculeatus in western Ireland.

Microchemical analysis of trace elements in otoliths and bio-mineralised earstones of teleost fishes is an emerging approach to analysing the environmental migratoryand life histories of fish species. The migration history of the three-spine stickleback (Gasterosteus aculeatus) collected in western Ireland was examined using calcium (Ca) and strontium (Sr) concentrations in otoliths. The otolith Sr:Ca values fluctuated with the habitat. The habitat use and migration history of G. aculeatus can be categorised into two types, as determined by the mean value and life history transect of the otolith Sr:Ca; that is, freshwater and estuarine residents, whereas there were no anadromous sticklebacks which is believed to be a typical migration pattern in the species. The otolith Sr:Ca profiles of the freshwater resident fishes exhibited constantly low Sr:Ca values, averaging 0.41-0.58 × 10-3 from the core towards the edge. However, the otolith Sr:Ca profiles of the estuarine resident fishes exhibited constantly high Sr:Ca values from the core towards the edge without a clear transition point from low to high Sr:Ca values, as found in the anadromous fish, averaging 1.82-4.26 × 10-3. The present study is the first published confirmation that 100 % of sticklebacks living in coastal habitats in Ireland > have an estuarine resident migratory pattern, constantly residing in marine environments or brackish water throughout their lifespan and not in freshwater environments in Ireland.

Risk Assessment and Sources Apportionment of Toxic Metals in Two Commonly Consumed Fishes from a Subtropical Estuarine Wetland System.

The widespread occurrence of heavy metals in aquatic environments, resulting in their bioaccumulation within aquatic organisms like fish, presents potential hazards to human health. This study investigates the concentrations of five toxic heavy metals (Pb, Hg, Zn, Cu, and Cr) and their potential health implications in two economically important fish species (Otolithoides pama and Labeo bata) from a subtropical estuarine wetland system (Feni estuary, Bangladesh). Muscle and gill samples from 36 individual fish were analyzed using energy dispersive X-ray fluorescence (EDXRF). The results revealed that the average quantities of heavy metals in both fishes' muscle followed the declining order of Zn (109.41-119.93 mg/kg) > Cu (45.52-65.43 mg/kg) > Hg (1.25-1.39 mg/kg) > Pb (0.68-1.12 mg/kg) > Cr (0.31-5.82 mg/kg). Furthermore, Zn was found to be present in the highest concentration within the gills of both species. While the levels of Cu, Zn, and Cr in the fish muscle were deemed acceptable for human consumption, the concentrations of Pb and Hg exceeded the permissible limits (>0.5 mg/kg) for human consumption. Different risk indices, including estimated daily intake (EDI), target hazard quotient (THQ), hazard index (HI), and carcinogenic or target risk (TR), revealed mixed and varying degrees of potential threat to human health. According to the EDI values, individuals consuming these fish may face health risks as the levels of Zn, Cu, and Cr in the muscle are either very close to or exceed the maximum tolerable daily intake (MTDI) threshold. Nevertheless, the THQ and HI values suggested that both species remained suitable for human consumption, as indicated by THQ (<1) and HI (<1) values. Carcinogenic risk values for Pb, Cr, and Zn all remained within permissible limits, with TR values falling below the range of (10-6 to 10-4), except for Zn, which exceeded it (>10-4). The correlation matrix and multivariate principal component analysis (PCA) findings revealed that Pb and Cr primarily stemmed from natural geological backgrounds, whereas Zn, Cu, and Hg were attributed to human-induced sources such as agricultural chemicals, silver nanoparticles, antimicrobial substances, and metallic plating. Given the significance of fish as a crucial and nutritious element of a balanced diet, it is essential to maintain consistent monitoring and regulation of the levels and origins of heavy metals found within it.

Minerals and fatty acid profile of small indigenous fish species from homestead ponds within a Sub-tropical coastal region.

Malnutrition has emerged as a noticeable obstruction to the socio-economic advancement of rural areas along the coastal regions of Bangladesh. Small indigenous fish species (SIS) have the potential to alleviate the malnutrition issue because of having higher nutritional compositions. However, prior research has overlooked the detailed nutritional value of SIS originating from coastal regions. Consequently, the current investigation sought to analyze the mineral and fatty acid composition of twelve SIS obtained from coastal homestead ponds. The findings indicated that the mineral composition in SIS exhibited the following descending order: calcium (Ca) > phosphorus (P) > potassium (K) > magnesium (Mg) > iron (Fe) > zinc (Zn). Furthermore, when considering the overall mineral content in SIS, it ranked in the following decreasing order: A. testudineus, M. tengara, C. punctatus, N. nandus, P. sophore, C. fasciatus, A. mola, C. batrachus, H. fossilis, P. sarana, M. aculeatus, and O. pabda. The analysis of the fatty acid profile further revealed that SIS is a rich source of palmitic acid, linoleic acid, oleic acid, stearic acid, myristic acid, palmitoleic acid, and linolenic acid. The saturated fatty acid content of the SIS varied between 42.66 % and 63.37 %, and the highest content was found in A. mola whereas the lowest was in A. testudineus. On the other hand, the total monounsaturated fatty acid content of the SIS ranged from 26.49 % (A. mola) to 46.12 % (P. sarana), and the total PUFAs contents among the fish species ranged from 5.7 % (A. mola) to 16.54 % (H. fossilis). Therefore, SIS could be a key source of minerals and essential fatty acids for human well-being. This can help fulfill nutrient requirements and reduce malnutrition among coastal populations. It can be said that, if these fishes are introduced in the culture systems, it will be used for consumption as well as support the livelihood of coastal people.

Microplastic Quantification in Aquatic Birds: Biomonitoring the Environmental Health of the Panjkora River Freshwater Ecosystem in Pakistan.

Microplastic pollution has become a global concern, with potential negative impacts on various ecosystems and wildlife species. Among these species, ducks (Anas platyrhynchos) are particularly vulnerable due to their feeding habits and proximity to aquatic environments contaminated with microplastics. The current study was designed to monitor microplastic (MP) pollutants in the freshwater ecosystem of the Panjkora River, Lower Dir, Pakistan. A total of twenty (20) duck samples were brought up for four months and 13 days on the banks of the river, with no food intake outside the river. When they reached an average weight of 2.41 ± 0.53 kg, all samples were sacrificed, dissected, and transported in an ice box to the laboratory for further analysis. After sample preparation, such as digestion with 10% potassium hydroxide (KOH), density separation, filtration, and identification, the MP content was counted. A total of 2033 MP particles were recovered from 20 ducks with a mean value of 44.6 ± 15.8 MPs/crop and 57.05 ± 18.7 MPs/gizzard. MPs detected in surface water were 31.2 ± 15.5 MPs/L. The major shape types of MPs recovered were fragments in crop (67%) and gizzard (58%) samples and fibers in surface water (56%). Other types of particles recovered were fibers, sheets, and foams. The majority of these detected MP particles were in the size range of 300-500 µm (63%) in crops, and 50-150 µm (55%) in gizzards, while in water samples the most detected particles were in the range of 150-300 µm (61%). Chemical characterization by FTIR found six types of polymers. Low-density polyethylene (LDPE) had the greatest polymer detection rate (39.2%), followed by polyvinyl chloride (PVC) (28.3%), high-density polyethylene (HDPE) (22.7%), polystyrene (6.6%), co-polymerized polypropylene (2.5%), and polypropylene homopolymer (0.7%). This study investigated the presence of microplastics in the crops and gizzards of ducks, as well as in river surface water. The results revealed the significant and pervasive occurrence of microplastics in both the avian digestive systems and the surrounding water environment. These findings highlight the potential threat of microplastic pollution to wildlife and ecosystems, emphasizing the need for further research and effective mitigation strategies to address this pressing environmental concern.

Microplastics in Different Tissues of a Commonly Consumed Fish, Scomberomorus guttatus, from a Large Subtropical Estuary: Accumulation, Characterization, and Contamination Assessment.

Microplastics (MPs) ingestion by fish signifies a worldwide threat to human health but limited research has examined their existence within the consumable portions (muscle) of fish. Thus, this study was undertaken to unveil the prevalence, characterization, and contamination extent of MPs across various body tissues, including the muscle of the king mackerel (S. guttatus) from the lower Meghna estuary in Bangladesh-a pioneering investigation in this region. In our analysis, we identified a total of 487 MPs, with an average abundance of 48.7 ± 20.3 MPs/individual. These MPs were distributed across different tissues, with respective concentrations of 0.84 ± 0.45 items/g in the digestive tract, 2.56 ± 0.73 items/g in the gills, and 0.3 ± 1.72 items/g in the muscle tissue. The observed variations among these tissue types were statistically significant (p < 0.05). Moreover, a significant positive correlation indicated that fish with higher weight had higher MPs in their gills and DT (digestive tract). The majority were <0.5 mm in size (97.74%) and exhibited a fiber-like shape (97.74%), with a notable prevalence of transparent (25.87%) and a pink coloration (27.92%). Remarkably, the majority of MPs were discovered within the size range of <0.5-1 mm (100%), particularly in the muscle tissue, signifying a substantial transfer of MPs into the human diet. Besides, we discovered only three polymer types of microplastics which could be attributed to the extensive use of food packaging, plastic containers, wrapping plastics, residential garbage, and plastic pipes that end up in the aquatic environment via river discharges. The contamination factor (CF) values of fish muscle (5.75) and the digestive tract (5.50) indicated that these fish organs were considerably contaminated (3 < CF < 6) with MPs. The pollution index of MPs (PLI > 1) indicated a high contamination level for MPs pollution of S. guttatus in the lower Meghna River estuary.

Trace metals in transboundary (India-Myanmar-Bangladesh) anadromous fish Tenualosa ilisha and its consequences on human health.

Hilsa shad (Tenualosa ilisha, Hamilton, 1822), the highly coveted table fish within the Indian subcontinent, is Bangladesh's most significant single-species fishery. To assess the risk that toxic metals pose to human health, certain health risk indices-estimated daily intake (EDI), target hazard quotient (THQ), total target hazard quotient (TTHQ), and target cancer risk (TR)-were calculated. The hierarchy of toxic metals (µg/g-ww) in Hilsa shad of the bay showed as Zn (13.64 ± 2.18) > Fe (9.25 ± 1.47) > Mn (2.98 ± 0.75) > Cu (0.57 ± 0.18) > Cr (0.23 ± 0.06) > Pb (0.22 ± 0.04) > As (0.08 ± 0.02) > Ni (0.06 ± 0.02) > Co (0.04 ± 0.01) > Cd (0.01 ± 0.003) in the wet season and Zn (11.45 ± 1.97) > Fe (10.51 ± 1.38) > Mn (3.80 ± 0.75) > Cu (0.73 ± 0.17) > Pb (0.30 ± 0.03) > Cr (0.20 ± 0.05) > As (0.09 ± 0.01) > Ni (0.08 ± 0.02) > Co (0.07 ± 0.02) > Cd (0.02 ± 0.004) in the dry season. The EDI of all the examined trace metals indicated no risk to human health from consuming Hilsa fish. The estimation of THQ and TTHQ suggested that the ingestion of both individual and combined trace metals through Hilsa shad consumption was safe from the perspective of human health. Also, there was no evidence of carcinogenic risk for consumers based on the evaluation of the TR value of metals (As, Pb, Cd, and Ni) due to Hilsa shad consumption.

Heavy metals in wild and cultured shrimp, supplied feeds, and their habitats: Assessing public health risk.

The contamination and risk assessment of heavy metals (HMs) in highly priced tiger shrimp and its associated ecosystems and farming conditions (hatcheries and commercial grow-out ponds) were scarcely investigated in South Asian countries. In this study, we determined the five HMs (Cu, Zn, Pb, Cd, and Cr) concentrations in PL14 (fourteen days of Post-Larva) of Penaeus monodon, commercial diets, surface water, and sediments from hatcheries, farms, rivers using ICP-MS for two years. The results revealed that surface sediments of rivers and hatcheries had the highest amounts of Cr (65.85 ± 0.82 and 72.50 ± 0.42 mg/kg), Cu (18.82 ± 3.96 and 19.26 ± 4.61 mg/kg), and Zn (63.74 ± 11.14 and 87.42 ± 17.96 mg/kg), whereas commercial farms had the greatest levels of Cd (0.09 ± 0.05 mg/kg). Pb was significantly higher in sediment of hatcheries and farms than in other sites. Except for Zn in surface waters, all metals were found above the recommended limit. In case of supplied feed, all values were in the safe limit excepting Cr (3.39 ± 1.45 to 108.92 ± 3.49 mg/kg). On the other hand, among the metals, only Cr (VI) ranging from 1.75 ± 1.39 mg/kg in P. monodon samples exceeded the suggested international guidelines. The Igeo values of all the metals were Igeo <0, indicating that the study areas were practically unpolluted. PLI values in every station were found to be below 1 which indicates the perfection of the sediment. The Potential Risk Index (PERI) values were less than 150 suggesting low risk of metals in sediments. The public health risk assessment estimated through the calculated daily intake (EDI), target hazard quotient (THQ) and hazard index (HI) has shown that the shrimp was safe for consumers except for Cd and Cr. The THQ for Cd and Cr were higher than the threshold (>1) indicating potential health hazards. The low CR values for Cd, Cr Pb were 3.1 × 10-4, 3.7 × 10-4 and 1.6 × 10-4, respectively indicates no cancer risks upon consuming P. monodon.

Mitochondrial cytochrome c oxidase subunit I gene analysis of the yellowfin snapper, Lutjanus xanthopinnis in the Indo-Pacific region and a note on Lutjanus lutjanus population structure.

The yellowfin snapper, Lutjanus xanthopinnis, was recorded as a newly described species in the Indo-Pacific region in 2015. However, the knowledge of its biology, biogeography and ecology is scarcely understood, and, hence, its current conservation status is categorized as Data Deficient. The mitochondrial cytochrome c oxidase subunit I (COI) gene was examined to confirm species identification. We also examined the COI gene haplotypes of L. xanthopinnis in Brunei Darussalam and Malaysia together with other waters, i.e., Bangladesh, Indonesia, Japan, Singapore, Sri Lanka and Taiwan. Our molecular analyses found that Brunei Darussalam and eastern Peninsular Malaysia samples were genetically similar. However, the former showed higher genetic diversity than the latter. The samples from these two sites also showed signatures of population expansion. Furthermore, identical haplotypes could be found in different locations, suggesting the absence of spatial genetic structure. On the other hand, Lutjanus lutjanus showed a population structure associated with geographical locations, i.e., western Pacific Ocean, Indian Ocean and Maluku in Indonesia.

Potential Toxic Elements and Their Carcinogenic and Non-Carcinogenic Risk Assessment in Some Commercially Important Fish Species from a Ramsar Site.

Potentially toxic elements (PTEs) such as Hg, As, and Pb have become concentrated in the aquatic ecosystem as a result of increased human activities. However, these substances frequently have synergistic or antagonistic effects on the human body or other animals. As a result, there are concerns world-wide that commercially available food products, especially fish, may be contaminated with hazardous elements. In this study, samples of four selected fishes, Gutum (Lepidocephalichthys guntea), Baim (Macrognathus pancalus), Baila (Glossogobius giuris), Meni (Nandus nandus) were analyzed from one of the largest freshwater wetlands (designed as a Ramsar Site) in South Asia to evaluate PTEs contamination status and human health risk assessment. The result demonstrated that the degree of contamination for six PTEs decreased in the following sequences for fish: Fe > Zn > Cu > Pb > As > Hg. The edible part of G. giuris had the maximum value for Hg (0.42 µg/g dw), while N. nandus predominantly accumulated As (<0.41 µg/g dw). The estimated daily intake (EDI) values ranged from 0.003 to 1.75, which was much lower than the recommended values. The hazard index (HI), THQ, total target hazard quotient (TTHQ) scores through consuming fish followed the decreasing order of Fe > Hg > Cu > Zn > Pb. The values for each index were less than 1, indicating that there were no substantial health risks for the consumers. The carcinogenic risks (CR) derived from the intake of Pb ranged from 4.92 × 10-8 to 4.14 × 10-8 for males and 5.45 × 10-8 to 4.59 × 10-8 for females, which also did not exceed the standard limit (1.00 × 10-6). This study demonstrated that, under the existing consumption rate, there was no potential health harm to consumers from consuming the studied fishes. This study offers a chance to regularly check PTEs in this environment, reducing the contamination of heavy metals.

First Report on Microplastics Quantification in Poultry Chicken and Potential Human Health Risks in Pakistan.

Microplastics (MPs) are an emerging environmental health concern due to their widespread occurrence in food sources such as fish, meat, chicken, honey, sugar, salt, tea and drinking water, thereby posing possible risks to human health. This study aimed to observe the existence of MPs in the crop and gizzard of the farm chicken, a significant food source in Pakistan. Twenty-four chicken samples were taken from eight poultry farms across Punjab, Pakistan. A total of 1227 MP particles were found from 24 samples (crop and gizzards) originating from the 8 poultry farms. In all, 429 MP particles were found in 24 chicken crops, with a mean of 17.8 ± 12.1 MPs/crop. In contrast, 798 MP particles were found in 24 chicken gizzards, with a mean of 33.25 ± 17.8 MPs/gizzard. Comparatively larger particles, ranging between 300-500 µm, were more abundant (63%) than other considered sizes (300-150 µm [21%] and 150-50 µm [16%]). Additionally, fragments were the dominant type of shape in both sample types (crop [64%] and gizzard [53%]). The predominant colours of particles extracted from gizzards and crops were yellow (32%) and red (32%), respectively. Chemical characterisation of these particles detected four types of polymers: polyvinyl chloride (PVC) at 51.2%, followed by low-density polyethylene (LDPE) at 30.7%, polystyrene (PS) at 13.6% and polypropylene homopolymer (PPH) at 4.5%. In conclusion, we provide evidence for MPs in the gizzards and crops of farmed chickens which may originate from contaminated poultry feed. Only a few studies have been reported globally to assess MPs ingestion in chickens. The current study is the first report from Pakistan. It could be a valuable addition to support MPs literature to establish a relationship between MPs contamination and intake through the food chain.

Seasonal variation, contamination and ecological risk assessment of heavy metals in sediments of coastal wetlands along the Bay of Bengal.

Functioning of coastal wetland habitats is essential for the ecosystem integrity and sustainability of coastal development that enables human progress along transitional waterways. However, these habitats are continuously being affected by a variety of pollutants including metallic elements. In this study, seasonal variation, pollution status and ecological risks of heavy metals (Cr, Mn, Co, Ni, As, Cu, Zn and Pb) in surface sediment of the several types of coastal wetlands (estuaries, mudflats, sandy beaches, mangroves, and saltmarshes) were detected by using X-ray fluorescence (EDXRF) spectrometry. The results showed that the mean concentration level of metals in the surficial sediment samples followed the order of Cu (84.06 ± 8.60 µg/g) > Zn (51.00 ± 8.97 µg/g) > Mn (38.25 ± 11.34 µg/g) > Cr (3.52 ± 0.91 µg/g) > Pb (0.27 ± 0.13 µg/g) > Co (0.24 ± 0.13 µg/g) > As (0.21 ± 0.12 µg/g) > Ni (0.16 ± 0.08 µg/g). In comparison to the pre-monsoon period, the post-monsoon season had higher concentrations of heavy metals while the overall accumulation level of metals in the wetlands exhibited a pattern of estuarine wetland (28.47 ± 31.35 µg/g) > mangrove (22.23 ± 30.79 µg/g) > mudflat (21.79 ± 29.71 µg/g) > sandy beach (21.47 ± 28.15 µg/g) > saltmarsh (21.28 ± 30.02 µg/g). Although, the pollution assessment indices e.g., contamination factor (CF), degree of contamination (CD), geoaccumulation index (Igeo) and pollution load index (PLI) showed minimal levels of contamination in the studied sites, enrichment factor (EF) suggested greater enrichment of the metals in the pre-monsoon season but with the lowest ecological risk (RI < 40) in both seasons. Cluster analysis, principal component analysis (PCA), and Pearson's correlation were performed to determine the sources of heavy metals in collected samples which specified that Pb, As, Co and Ni predominantly came from natural sources whereas Cu, Mn, Zn and Cr emerged from anthropogenic sources such as industrial effluents, domestic wastewater, fertilizer or pesticide consumption on farmland along the riverbank, vessel emissions, and the confluence of tributary rivers.

Year-round spawning of three tropical Cypriniformes fishes in Southeast Asia.

Present knowledge on spawning seasonality of freshwater fishes in tropical Asia and their relationship with environmental factors remains limited. Three Southeast Asian Cypriniformes fishes, Lobocheilos ovalis, Rasbora argyrotaenia and Tor Tambra, found in rainforest streams in Brunei Darussalam were studied on a monthly basis for a period of 2 years. To assess spawning characteristics, seasonality, gonadosomatic index and reproductive phases were examined from 621 L. ovalis, 507 R. argyrotaenia and 138 T. tambra. This study also examined environmental factors such as rainfall, air temperature, photoperiod and lunar illumination that may influence the timing of spawning of these species. We found that L. ovalis, R. argyrotaenia and T. tambra were reproductively active throughout the year but did not find that spawning in these species were associated with any of the investigated environmental factors. Our study showed that the non-seasonal reproductive ecology found in the tropical cypriniform species is distinctly different from that of temperate cypriniforms, which are known to follow spawning seasonality, suggesting an evolutionary adaptation to ensure their survival in an unstable environment. The reproductive strategy and ecological responses found in the tropical cypriniforms might be shifted in response to climate change scenarios in the future.

Distribution, characterization and contamination risk assessment of microplastics in the sediment from the world's top sediment-laden estuary.

Microplastics (MPs) have gained a serious attention as an emerging contaminant throughout the world because of their persistence and possible risks to aquatic ecosystems and human well-being. However, knowledge on MPs contamination from sub-tropical coastal systems is limited, and no study has been conducted on the MPs contamination in sediment from one of the highest sediment-laden estuaries, Meghna River, in the world. This is the first study to examine the quantity, morpho-chemical characteristics and contamination risk level of MPs from this large scale river. MPs were extracted from the sediment samples of 10 stations along the banks of the estuary by density separation, and then characterized using a stereomicroscope and Fourier Transform Infrared (FTIR) spectroscopy. The incidence of MPs varied from 12.5 to 55 item/kg dry sediment with an average of 28.67 ± 10.80 item/kg. The majority (78.5%) of the MPs were under 0.5 mm in size, with fibers being the most (74.1%) prevalent MPs type. Polypropylene (PP) was found to be the predominant polymer (53.4%), followed by polyethylene (PE, 20%), polystyrene (PS, 13.3%), and polyvinyl chloride (PVC, 13.3%). The highest occurrence of PP indicted the MPs in the estuary might be originated from clothing and dying industries, fishing nets, food packages, and pulp industries. The sampling stations were contaminated with MPs as shown by the contamination factor (CF) values and pollutant load index (PLI), both of which were >1. This study exposed new insights on the status of MPs in the sediments of the Meghna River, laying the groundwork for future research. The findings will contribute to estimate the global share of MPs to the marine environment.

Microplastics in surface water from a mighty subtropical estuary: First observations on occurrence, characterization, and contamination assessment.

Estuarine contamination by Microplastics (MPs) is a mater of serious concern since these areas offer the society valuable ecosystem, economic, and recreational services such as breeding and feeding ground for fish, carbon fixation, nutrients recycling and port development. The Meghna estuary, located along the Bengal delta coast, provides livelihoods for thousands of peoples in Bangladesh, and served as breeding ground for national fish, Hilsha shad. Therefore, knowledge and understanding on any kind of pollution including MPs of this estuary is essential. In this study, the abundance, characteristics and contamination assessment of MPs from the surface water of a Meghna estuary were investigated for the first time. The results demonstrated that MPs were present in all samples and the abundance ranged from 33.33 to 316.67 item/m3 with a mean value of 128.89 ± 67.94 item/m3. Morphological analyses resulted in four types of MPs such as fibers (87%), fragments (6%), foam (4%), and films (3%) with the majority of these being colored (62%) and smaller (<0.5 mm) in size (88%). On the other hand, FTIR analysis for chemical characteristics confirmed five types of polymers, including polythene (PE), polystyrene (PS), polythene terephthalate (PET), polypropylene (PP), and polyvinyl chloride (PVC). The area was determined to be moderately to severely contaminated with MPs based on contamination factor (CF) values (6.18 ± 2.08 to 2.50 ± 1.0) and the pollutant load index (PLI) value (1.94 ± 0.33) as these values were > 3-6 for CF, and >1 for PLI. These results can be utilized to develop policy for the protection of this important environment.

Vertical distribution, contamination status and ecological risk assessment of heavy metals in core sediments from a mangrove-dominated tropical river.

Understanding the vertical distribution of heavy metals aids in tracing the contamination history, however, it is limited for mangrove-dominated river. Thus, this study aimed to assess the vertical distribution of nine heavy metals and their possible ecological risk in several layers of core sediments from a mangrove-dominated river inside the Sundarban mangrove forest (World heritage and Ramsar site), Bangladesh. 45 core samples from five stations were analyzed using Flame Atomic Absorption Spectrophotometer (FAAS). The findings showed that, with the exception of Fe, Ni, and Cu, which suggested increased metal release in recent times, higher metal levels were recorded in the surface layer (0-10 cm), followed by the middle layer (10-20 cm), and inner layer (20-30 cm) of sediment cores. When compared to non-industrial forest sediment, core sediment from industrial sites contained noticeably more metals (p < 0.05). Overall, the mean metal concentration (mg/kg) followed the increasing order of Cd < As < Pb < Cu < Cr < Zn < Ni < Mn < Fe. Among the studied metals, the levels of Cd and Ni exceeded the average shale value. Contamination indices such as enrichment factor (EF), contamination factor (CF), and geo-accumulation index (Igeo) showed that the studied sediments were only contaminated by Cd. Ecological risk assessed by ecological risk factor (Eri) and risk index (RI) suggested that the analyzed heavy metals, with the exception of Cd, posed no significant ecological threats. All of the heavy metals analyzed might have originated from similar anthropogenic sources, according to the correlation matrix, cluster analysis (CA), and principal component analysis (PCA).

Spatiotemporal Variability of Trace Elements Fingerprints in Otoliths of Japanese Eel (Anguilla japonica) and Its Use in Tracing Geographic Origin.

To secure traceability along supply chains of foodstuffs, the spatiotemporal variability of trace elements' fingerprints (TEF) in fish otoliths provides a powerful tool to determine and discriminate the origin. Spatiotemporal variability of TEF was examined in a commercially important seafood, Japanese eel (Anguilla japonica), by means of laser ablation-inductively coupled plasma mass spectrometry (LA-ICPMS). Six elemental ratios (Na:Ca, Mg:Ca, P:Ca, K:Ca, Sr:Ca, and Ba:Ca) were determined in the otoliths of specimens originating from four aquaculture farms to examine the spatial variability and from one wild habitat over three years to examine the temporal variation. Significant temporal variation was found in Mg:Ca and Sr:Ca ratios; however, discriminant function analysis showed a lower temporal variation (50%) for the three years. Spatial variations were significant in Sr:Ca and Ba:Ca ratios, and discriminant function analysis showed high (80%) spatial variation among the four farms. Otolith TEF in the Japanese eel showed specific spatial variation among aquaculture farms but intangible temporal variation, suggesting the otolith TEF reflect each aquaculture environment. The present study shows that otolith TEF can be a reliable tool to discriminate the geographic origin of the Japanese eel.