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The rejected brines from desalination plants contain significant amounts of heavy metals. In this study, we evaluated the effectiveness of Phallusia nigra Savigny, 1816 (P. nigra) in removing vanadium from the rejected brines of desalination plants through the bioaccumulation process. Initial assessments revealed a remarkably high accumulation rate of vanadium in P. nigra with a bioaccumulation factor exceeding 4.7 × 10 4 in the tunic and 5.1 × 10 5 in the mantle body. Acclimation experiments demonstrated that P. nigra could survive salinities up to 56 practical salinity units (psu), temperatures of ≤32 °C, and pH of 6.5-8.5. We employed the L-16 Taguchi approach in experimental design to optimize environmental conditions for vanadium removal by P.nigra. Our results indicated that temperature has the most significant effect on increasing vanadium bioaccumulation in P. nigra, followed by salinity and pH. Under optimal conditions, the vanadium concentration reached 1892.30 ppm in the entire body of P. nigra compared to 350 ppm in natural conditions. Considering that, a high concentration of vanadium is toxic to the environment and the conventional methods of its removal from brine are costly and include the use of chemicals that pollute the environment, therefore, vanadium removal from brine using P. nigra can be considered a cost-effective and environmentally friendly method in the future, as opposed to some chemical methods., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Metal concentrations (Cu, Zn, Cr, Fe, As, Pb, Ni, V, and Co) in surface sediments were determined in the southern Caspian Sea. Sediment pollution was investigated using geochemical index such as Enrichment Factor (EF) and ecological risk indices like modified Hazard Quotient (mHQ) and Toxic Risk Index (TRI). The highest calculated geochemical index was observed in sediments near the cities of Chalus and Ramsar, which are highly polluted due to human activities. The ecological potential indices indicated that Ni contents in all the studied stations would impose harmful effects on aquatic organisms, while other metals had a low risk. Principal component and cluster analyses suggested that As and Pb emanated from anthropogenic sources, and other metals probably originated from lithogenic sources., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The Caspian Sea, the world's largest enclosed water body, experiences significant transformations in its physico-chemical properties and a decline in bioresources due to extensive anthropogenic activities. These activities include the discharge of diverse pollutants and bio-physical alterations such as over-fishing, hunting, and physical alterations to rivers. While acute manifestations such as a fall in the Caspian water levels and wetland desiccation are more overt, the pervasive impact of human activities contributes to a likely irreversible decline in environmental quality that we aim to spotlight in this discussion in order to facilitate its restoration., Competing Interests: Declaration of competing interest The authors declare no competing interests., (Copyright © 2024. Published by Elsevier Ltd.)

The present document is intended to fill the knowledge gap on spatiotemporal variation of suspended particulate matter (SPM) concentration and composition by collecting samples from 26 stations during two contrasting seasons of summer and winter. The horizontal distribution of surface SPM is characterized by hotspots (up to 4.0 mg/l) along the river estuaries which sharply declined to <1 mg/l in the offshore region. The average SPM concentration for surface, 25 m, and near-bottom decreased from summer to winter by a factor of 1.1, 1.3, and 1.7, respectively. In the offshore region, the particle composition was dominated by particulate organic matter which accounted for 66 % of bulk SPM. The concentration of opaline silica increased from summer to winter presumably from the bloom of diatoms. The concentration of particulate trace elements in winter decreased in the order of Fe ≫ Ba > Mn ≈ Zn > Ni ≈ Cr ≫ Pb > Cd. The non-crustal portion is the predominant fraction for most trace metals and shows enrichment relative to the upper continental crust, local soil background, and deposited dust that is highest for Cd and lowest for Mn., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Hamid Ershadifar reports administrative support was provided by Iran National Environment Fund. Hamid Ershadifar reports administrative support was provided by Iran National Science Foundation. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

This study aimed to geochemically investigate the sediments of the south Caspian Sea at different depths in summer and winter 2020. Sampling was conducted in 5 transects along the south coastline of the Caspian Sea and sediment grain size, hydrogen sulfide, Oxidation-reduction potential (Eh), total nitrogen, nitrite, nitrate, ammonium, total phosphorus, organic and inorganic phosphorous were measured. Eh values showed significant differences between seasons and between different transects (p < 0.05). Hydrogen sulfide ranged from 1.87 to 307.00 ppm. No significant difference was observed in hydrogen sulfide between seasons and among depths (p > 0.05). Total, inorganic and organic phosphorus contents were 782.96-1335.79 ppm, 639.66-1183.60 ppm, and 42.58-205.46 ppm, respectively. Total nitrogen revealed significant differences among transects (p < 0.05). Based on sediment quality guidelines, most sampling sites had alerting conditions for organic matter, and phosphorous contamination was detected at all stations. Anoxic condition was seen at most sites according to sedimentary Eh., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

The concentrations of heavy metals (Cr, Cd, Ni, and Pb) were investigated in sediment and cyprinid fish (Capoeta razii) from Telar River, Iran in spring, summer, and autumn. Mean concentration of metals in fish and sediment over the seasonal sampling was as follows: Cr > Ni > Pb > Cd. Metal deposition in sediment was higher than their bioaccumulation in fish tissue. Unlike sedimentary metals, the tissue-content of Pb and Cr varied seasonally. Enrichment Factor (EF) values of Cr and Ni showed partial enrichment, implicating the role of anthropogenic inputs, while Pb was derived from natural weathering. When considering Pollution Load Index (PLI), an uneven temporal and spatial distribution of contamination was observed in sediment with moderate contamination level in spring and summer and no pollution in autumn. Tissue-contents of Pb, Cr, and Cd were below permissible limits while a higher risk level of Ni was noted for human consumption., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier Ltd.)

Microplastics (MPs) have been found in marine systems more frequently. We aim to analyze the MPs abundances, distribution, and characteristics in the intertidal sediments along the Oman Sea. Samples were collected from 7 locations with three replicates. Density separation was used to extract MPs, which were then visually counted and categorized based on their size, shape, and color. MPs abundance ranged between 219.6 ± 38.3 particles.kg -1 dw and 617.3 ± 99.9 particles.kg -1 dw with a mean abundance of 315.4 ± 24.4 particles.kg -1 dw. Fragments and fibers were the dominant shapes. Red and blue colors were observed in 61.6 % of the collected MPs. In addition, 100-500 μm size range of MPs were more abundant. Micro-Raman spectroscopy analysis revealed polypropylene was the major polymer constituent. The present study revealed the widespread occurrence of MPs as anthropogenic pollutants throughout the Oman Sea and highlighted the urgent need for regulations and policies to reduce the entry of this material into marine environments., Competing Interests: Declaration of competing interest The authors confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

This study was conducted to assess microplastic (MP) pollution in some aquatic animals inhabiting planted and natural mangrove swamps in the northern Gulf of Oman. The KOH-NaI solution was used to retrieve MPs from the gastrointestinal tracts of animals. The highest MP prevalence was recorded in crabs (41.65 %) followed by fish (33.89 %) and oysters (20.8 %). The abundance of MPs in examined animals varied from zero in Sphyraena putnamae to 11 particles in a Rhinoptera javanica specimen. When polluted-only animals were considered, the mean abundance of MPs significantly varied among species and between locations. The mean density of ingested MPs was higher in the planted mangrove animals (1.79 ± 2.89 vs. 1.21 ± 2.25 n/individual; mean ± SD). Among the examined fish species, R. javanica ingested the highest number of MPs (3.83 ± 3.93 n/individual; mean ± SD). The polyethylene/ polypropylene fragments or fibers of average 1900 μm size were recorded as predominant (>50 % occurrence) MP particles., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

During the last two decades, the number of tropical cyclone (TC) events in the Arabian Sea has increased dramatically. These events have led to severe human and economic damage in Oman, Iran and Pakistan. Within this context, Gonu, Phet and Shaheen were the Arabian Sea's most destructive TCs on record, leading to a total of 6.07 billion USD in damages and 159 fatalities. Previous studies have mainly focused on atmospheric, sea surface temperature (SST) and anthropogenic impacts of TC generation and intensification. By contrast, oceanographic currents, Persian Gulf water outflow and the role of ocean-atmospheric interactions on the distribution of outflow water into the Arabian Sea and their impacts on TC intensification, are poorly understood. In order to address this issue, we use historical TC records, satellite data, atmospheric and reanalyzed oceanographic data to shed new light on the relationship between large-scale atmospheric forcing and ocean currents on TC intensification in the Arabian Sea. The results demonstrate that pre-monsoon TCs mainly occurred during co-existing La Niña, cold Indian Ocean Basin Model (IOBM) and anomalous northern hemisphere circulations over the Persian Gulf. By contrast, post-monsoon TCs were generally generated during warming acceleration period. Poleward movement of the monsoon belt provided the required humidity and energy for TC generation and increased upwelling events. Water salinity and temperature have increased in the north and northwestern parts of the Arabian Sea following rising upwelling events and a decrease in Persian Gulf outflow water depth. Rapid TC intensification has increased noticeably since 2007 and >72 % of cyclones have reached category 3 or more. We find that the rate of SST rise in the Arabian Sea is higher than the other parts of the northern Indian Ocean since 1998. SST and salinity in the Arabian Sea have been controlled by Persian Gulf outflow water and oceanographic currents. TC intensity is controlled by warm and saline (>36.6 PSU) water distribution patterns, mediated by eddy and jet currents. Rapid intensification of pre-monsoon TCs occurred by tracking to the north and northwest, with most landfalls occurring during this period. Post-monsoon TCs generally affect the center and the southwest of the Arabian Sea. The risk of intensive TCs manifests an increasing trend since 2007, therefore education programs via international platforms such as the International Ocean Institute (IOI) and UNESCO are required for the countries most at risk., Competing Interests: Declaration of competing interest We confirm that the manuscript has been read and approved by all named authors and that there are no other persons who satisfied the criteria for authorship but are not listed. We further confirm that the order of authors listed in the manuscript has been approved by all of us., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The spatial and temporal variations of mesozooplankton in relation to environmental parameters were investigated in the Persian Gulf and the Gulf of Oman. For this purpose, the physicochemical parameters were measured using a CTD probe and mesozooplankton were sampled vertically using a closing net aboard the RV Persian Gulf Explorer during two expeditions. Results showed a relationship between mesozooplankton assemblages and water mass distributions. Four mesozooplankton cluster station groups divided the sampled stations into masses, which was also confirmed by the PERMANOVA test. Overall, ninety taxa were identified that were dominated by copepods and characterized by small cyclopoids. Based on the results the mesozooplankton communities of the Persian Gulf and the Gulf of Oman are mostly shaped by the combined effect of temperature, salinity, and dissolved oxygen that significantly influences mesozooplankton occurrence during summer and spring., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

The occurrence of microplastics (MPs) in beach sediments of the southern Caspian Sea was well documented, however, there are still many unknowns about the abundances and distributions of MPs in the rivers ending to the Caspian Sea. Here, bank sediments of 26 sites in the thirteen rivers were surveyed in two seasons. However, there was not any significant difference (p > 0.05) between the concentrations of MPs during the two seasons. MPs were detected in all samples with mean concentrations of 214.08 ± 14.35 MPs/kg. The most common size, shape, color, and polymer types of MPs were L < 300 μm, fragment/film, white/transparent, and polystyrene (PS), respectively. In all rivers, positive MP gradients from upstream to downstream were observed. Maximum concentrations of MPs were found in the downstream parts of Chalus, Haraz, and Safarud rivers. Recreational-tourism and fishing activities had significant positive relationships (p < 0.05) with concentration of MPs in the rivers., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

To assess the role of near-hypoxic and hypoxic conditions on the mesozooplankton community, we studied twenty stations in the Persian Gulf and the Gulf of Oman. The physicochemical parameters were measured using a CTD probe and mesozooplankton were sampled vertically using a closing net. Results showed the hypoxic conditions of 0.52 ± 0.11, 1.40 ± 0.48, and 0.84 ± 0.08 in the lower layers in stations T11S3, T0S8B, and T9S5 in the Gulf of Oman and near-hypoxic conditions in station T6S3 (2.99 ± 0.05) in the Persian Gulf. The marginal test revealed that stratification during summer and dissolved oxygen and salinity during spring in the Persian Gulf and temperature, stratification, and dissolved oxygen during spring in the Gulf of Oman significantly explained the variation of mesozooplankton composition in the study areas (p < 0.05). The present study reveals some general patterns of mesozooplankton assemblage in near-hypoxic and hypoxic conditions, but a future detailed investigation will be essential., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022. Published by Elsevier Ltd.)

This investigation aimed to determine the contents of biogenic SiO 2 and different phosphorus forms (P) and to evaluate phosphorus ecological risk in surface sediment of Anzali wetland. According to the results, biogenic SiO 2 ranged from 0.29 to 3.04%. Also, the average biogenic SiO 2 at all studied stations was 1.36 ± 0.83%. Results indicated that total P (TP) was between 493 and 771 ppm, averaged 637.20 ± 79.41 ppm. Moreover, inorganic P (INTP) ranged from 256.63 to 376.89 ppm and composed 51.46 ± 4.68% of total P. The percentage of P-forms was in descending order: residual-P > Fe-P > Ca-P > Al-P > labile-P. Phosphorus pollution index (PPI) ranged from 0.82 to 1.29, with an average of 1.06 in the sediment of the Anzali wetland. The Sediment P saturation (SPS) values varied considerably from 40.96 to 83.57, with an average SPS value of 49.1. Based on the eutrophication risk index, all stations except one had a low eutrophication risk index., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Industrial, agricultural, and recreational activities dump several pollutants into the Caspian Sea, which is one of the main water bodies of Iran. Therefore, performing risk assessments would be required as part of the monitoring programs. Herein, non-cancer health risk assessment of the consumption of macroalgae was performed and the ecological risk assessment of metal pollution in sediments of the southern Caspian Sea was presented using sediment quality guidelines (SQGs), enrichment factors (EF), contamination factors (CF), contamination degrees (CD), pollution load indices (PLI), geo accumulation indices (I geo ), and potential ecological risk indices (RI). Next, machine-learning approaches were used to predict the stable isotope value of nitrogen in macroalgae, in which physicochemical information of water and heavy metal levels in macroalgae were used separately and together as predictor variables. Results indicated that simultaneous use of physicochemical properties of water and heavy metal levels resulted in the best prediction of isotopic nitrogen content., (Copyright © 2021. Published by Elsevier Ltd.)

The spatial and temporal variability of suspended particulate matter (SPM) in the Persian Gulf and Oman Sea coastal waters has remained challenging to understand among researchers. Here, for the first time in the region, we parametrized SPM concentration in the study area utilizing derived remote sensing reflectance (R rs ) values from Moderate-resolution Imaging Spectroradiometer (MODIS), using 555 and 667 nm wavelengths. Likewise, the findings showed that the developed optical model based on the optical ratio of R rs (667)/R rs (555) was sensitive to the concentration of Chromophoric dissolved organic matter (CDOM) in the seawater, within the visible wavelengths less than 600 nm. Comparing the new estimates of the SPM concentration with in situ measurements by Spearman's Rank correlation for validation revealed that the association between estimated and measured SPM concentration would be considered statistically significant (ρ up to 0.86, p < 0.05). This study increased the average accuracy of the estimates up to 73%., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Eutrophication and algal blooms occur frequently in coastal waters of the Makran, for which phosphorus is an important driving factor. Therefore, in this study, sequential extraction procedure was used to evaluate abundance of five phosphorus chemical species. Total phosphorus (TP) concentration ranged from 672.3 to 2031.9 μg/g in pre-monsoon and 771.7 to 2095.7 μg/g in post-monsoon. More than 87% of TP was inorganic P and contribution of organic phosphorus was low. Potential bioavailable P (PBAP) comprised of 52.1 and 35.5% of TP in the pre and post-monsoon, respectively. Average phosphorus pollution index was higher than one in all stations and seasons, implying that sediments in the study area are polluted by phosphorus and are under eutrophication risk. Thus, in the future, foregoing information will be important for assessment of phosphorus loading and pollution in the Makran., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The occurrence of microplastics (MPs) in nearshore zones of the southern Caspian coasts is well documented; however, no data are available on MP occurrence in offshore sediments. In this study, six sandy beach stations and 18 inshore-offshore stations (six transects) were surveyed. MPs were detected in all sediment samples. The mean abundances of MPs in the beach and inshore-offshore stations were 196.67 ± 11.58 and 103.15 ± 7.21 MPs/kg, respectively. Fibers constituted the most common shape of MPs. Polystyrene (PS) and polyethylene terephthalate (PET) were the major polymer types found in the beach and inshore-offshore sediments, respectively. In most transects, negative MP gradients were observed from nearshore to offshore, which showed that coastal fishing, tourism, and rivers were the main sources of MPs in this area. These results will improve our understanding on MPs pollution in the marine ecosystem. We recommend further MP studies in different parts of the Caspian Sea to develop appropriate management programs., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

In this study, heavy metal levels in sediments, human hair, and fish muscle tissue as well as organic matter (OM%) content in surface sediments of Chabahar Bay were determined to assess their ecological risks and sources. Totally, 96 samples were collected from 16 stations (Tiss, Konarak, desalination plant, entrance of Chabahar Bay, Posm, Ramin, and reference stations) and were analyzed using inductively coupled plasma mass spectrometry (ICP-MS). Abundances of elements were of the following order: Ca>Al>Fe>Mg>Na>K>S>P>Ti>Mn>Sr>Ba>Cr>Ni>V>Li>Zn>Cu>Co>Pb>As>Cd>Ag>Se>Sb>Be>Mo>Bi. Element levels in sediments were within the range of low pollution areas, except for Cr, As, Ni, and Cd. Dominant sources of elements were natural, except for Cd, which was anthropogenic. All geo-accumulation index (I geo ) values were less than zero, except for Ag, Cd, and Sr from heavily to moderately contaminated areas. E r values indicated low ecological risk, except for Cd which showed a high ecological risk. The As levels limit the consumption of fish meal per month.i values indicated low ecological risk, except for Cd which showed a high ecological risk. The As levels limit the consumption of fish meal per month., (Copyright © 2021. Published by Elsevier Ltd.)

In this article dissolved oxygen results of research cruises through the Persian Gulf during 2018-2019 are discussed. The results showed that summer to autumn hypoxia occurred mainly at depths ≥ 50 m to the bottom. This seasonal hypoxia started in late summer reaching its greatest severity in mid-autumn with an area of 50,000 km 2 in the Persian Gulf. The minimum oxygen measured at the near-bottom layer of the western basin in autumn (25.8 μmol/kg) was lower than any previous measurement in the open waters of the Persian Gulf. In the Strait of Hormuz, the seasonal hypoxia appeared in summer in the near bottom of the most eastern part at the Iranian side. pH T values recorded in hypoxic waters were as low as what is predicted for surface ocean under ocean acidification in 2100. Considering the results, we suggest evaluating the effects of hypoxia and acidification on the Persian Gulf ecosystems., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

In this study, selected PCB congeners (IUPAC numbers 28, 52, 101, 138, 153, and 180) were quantified in 34 stations of Chabahr bay and around it in the Makran region of Iran. The sum of total PCB concentrations varied from below the detection limit to 485 ng kg -1 dry weight of sediment. Based on the Canadian Sediment Quality Guidelines, the effect of detected PCBs was negligible for aquatic organisms. According to the dominance of PCB 28 and 52 with average range of 62 to 100% of total PCBs, maritime transportation and atmospheric deposition appear to be the important source of PCBs in this region. Further, the presence of components of commercial products such as ClophenA50 appears to be one of the probable sources., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

In this investigation, δ 13 C and δ 15 N isotope ratios and heavy metal levels were assessed in macroalgae, sediment samples, and benthic species from northern parts of the Persian Gulf and the Gulf of Oman. The highest δ 15 N values in algal samples (11±0.42), indicative of anthropogenic organic N inputs, were detected in the Sadaf region, whereas the lowest values (3.17 ± 0.12), indicative of anthropogenic inorganic inputs, were detected in the Parvaz region. In addition to sediment quality guidelines (SQGs), contamination factors (CF), enrichment factors (EF), contamination degree (CD), pollution load index (PLI), geo accumulation index (Igeo), and potential ecological risk index (RI) were employed to assess the anthropogenic influence on sediment quality and to describe the sensitivity of the biota to toxic heavy metals. The obtained results demonstrate that the analyzed elements (Mn, Cr, Ni, Pb, Zn, Cu, Co, and V) had no ecological risk in the sampling area., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

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., Competing Interests: Declaration of competing interest The authors confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

This research characterizes the temporal and spatial variability of the seawater carbonate chemistry on the near-shore waters of the northern Persian Gulf and Makran Sea. In general, normalized total alkalinity (nA T ) showed a westward decrease along the coasts of Makran Sea and the Persian Gulf. Intertidal seawater was always supersaturated in terms of calcium carbonate minerals during the daytime. Rocky shore waters in the Persian Gulf were sinks for CO 2 in the winter during the daytime. The nA T decreased from Larak to Khargu Island by 81 μmol/kg. As expected, the two hypothetical drivers of bio-calcification, i.e., Ω and the [HCO 3 - ]/[H + ] ratio, were significantly related at a narrow range of ambient temperature. However, as data were pooled over seasons and study sites, in contrast to Ω Ar , the [HCO 3 - ]/[H + ] ratio showed a slight dependence on temperature, suggesting that the ratio should be investigated as a more reliable factor in future biocalcification researches., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Currently, microplastics are a major challenge threatening marine environment. Given little information on their prevalence in the Persian Gulf, the present study as the first comprehensive study was conducted to evaluate microplastics abundance in surface waters. Neustonic samples were collected from 15 stations along the Persian Gulf. Visually separated microplastics were categorized according to their size, shape, and color. ATR-FTIR method was used to identify the composition of polymers. Microplastics were found in all sampling stations and their density varied from 1.5 × 10 3 to 4.6 × 10 4 particle.km -2 with a mean density of 1.8 × 10 4 particle.km -2 . Fibers were the most dominant shape of microplastics (44.1%). Approximately 76% of the analyzed microplastics were polyethylene and polypropylene and the predominant colors of the microplastics were white and blue. Results of the study confirmed prevalence of microplastics in the Persian Gulf, and findings suggested a pressing need to investigate their effects on marine life and human health., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

GIS, geo-statistics and autocorrelation analysis were employed to reveal spatial structure of sedimentary ∑16PAHs. Global Moran's I index outlined significant ∑ 16 PAHs clusters for the entire region (Moran's I index =0.62, Z-score = 25.6). Anselin Moran's I index specified locations of the significant low/high spatial clusters. The levels of random and structural variance of ∑ 16 PAHs were about 0.083 and 0.154, respectively. Nugget to sill ratio confirmed that ∑ 16 PAHs has a moderate level of spatial structure and the major part of PAHs variability is not random. Prediction and standard error maps of ∑ 16 PAHs, produced by ordinary kriging, highlighted that more samples should be taken from high cluster region for next studies. Fuzzy logic functions (OR and AND) were used to develop eco-risk maps. It revealed that the potential hazards of PAHs are considerable at the vicinity of petrochemical facilities., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Current study aimed to evaluate the microplastics abundance in the surface waters of Chabahar Bay for the first time. 21 neuston net water samples were collected from 7 stations. Microplastics were visually counted by stereomicroscope, sorted into 4 size categories, 4 shape categories, and identified by ATR-FTIR spectroscopy. Density of microplastics varied from 0.07 ± 0.03 to 1.14 ± 0.27 with an average density of 0.49 ± 0.43 particle·m -3 . Microplastics were mostly found in the shape of fibers. 69% of analyzed particles were polyethylene and polypropylene. Main colors of the collected microplastics were white, blue and red. The results showed that the largest number of microplastics was found at station near populated area. Therefore, it can be concluded that, there is a pressing-need to investigate the distribution of microplastics in sediments and biota of this Bay as well as their effects on marine life and human health., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

In this study, polycyclic aromatic hydrocarbon contents in zooplanktons of coastal waters of Bushehr Province at the north of the Persian Gulf were evaluated. Zooplankton samples were collected from 18 stations in both summer and winter (2017), and their polycyclic aromatic hydrocarbon contents were measured by gas chromatography-mass spectrometry after ultrasound-assisted extraction. Results revealed that among 16 compounds that were analyzed, only 7 compounds were recognizable at both seasons. Pyrene was the most common individual compound of polycyclic aromatic hydrocarbons, whereas acenaphthene was the least individual compound found at both seasons. Additionally, the highest content of the measured compounds in both summer and winter was 16.4-75.9 ng/g and 17.3-93.7 ng/g, respectively. On the basis of the obtained results, the total concentration of polycyclic aromatic hydrocarbons was significantly higher in winter than in summer (P < 0.05)., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Surface sediments (n = 35) and a core sample around Pars Special Economic Energy Zone were analyzed to address spatiotemporal variations of heavy metals. Enrichment factors classified the elements as: (1) poorly enriched, geogenic elements (Co, Cr, Fe, Li, Mn, Mo, Ni, Ti, and V), (2) minimal enriched elements (Zn and Mg), (3) moderately enriched elements (Ag, Cd, Pb, Se, and Sr), and (4) significantly enriched element (As and Hg). The core profile showed that As, Hg, Ag, and Cd had considerable anthropogenic inventories. Arsenic levels were continuously increasing toward the top of the core and sedimentary cycling was not an effective factor on its enrichment. Pollution load index classified the area as a severely affected region and Risk Index values suggested that 57% of the sediments had a moderate potential risks. The mapping techniques proposed a polluted and hazardous patch at the entrance and center part of the Nayband Bay., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

This work is the first study on the spatial and temporal distribution of metals in zooplankton collected along the Persian Gulf. The rank order distribution of metals in terms of their overall average concentration in the zooplankton was observed to be Fe > Zn > Cu > Cd > Ni > Cr > Pb > Co > V. No clear pattern and no statistical differences were detected among the areas and the sampling stations. The highest concentrations of Cu, Zn, and Pb were observed in summer while the highest concentration levels of Fe and Ni were observed in winter. The highest mean zooplankton metal concentration level was found to be Fe with 10.42 μg/g (in winter) and the lowest levels were for V (in spring and summer) and Co (in winter), both of which had a level of 0.01 μg/g. The results can be used to establish base-line data for the trace metal content of zooplankton in the northern region of the Persian Gulf., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

We investigated the bioavailability, mobility, and origin of heavy metals present in sediments from the Anzali Wetland. Chemical speciation of the metals was performed according to the Tessier method. Results indicated that Cd and As showed the highest level of bioavailability, whereas Cr showed the lowest level. Cr, Co, and V were shown to have a terrestrial origin. The metal As was mostly found in the reducible fraction (F3), whereas other metals were highest in the residual phase. The levels of Co present in the oxidizable fraction (F4); Pb and Cd present in the carbonate fraction (F2); and the other metals present in the exchangeable fraction (F1) were found to be the lowest. On the basis of the Risk Assessment Code of metals, Cd at most stations, As and Ni at some stations, and Zn at one station revealed to have a moderate risk. Co and Pb were found to have a low risk at all stations. Considering Pollution Load Index, stations 2 and 3 were classified as moderately polluted and the remaining stations were unpolluted. As suggested by enrichment factor analysis, As was moderately enriched and other metals had a deficiency to minimal enrichment at all the stations., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

High spatial resolution WorldView-2 (WV2) satellite imagery coupled with field observations have been utilized for mapping the coral reefs around Hendorabi Island in the northern Persian Gulf. In doing so, three standard multispectral bands (red, green, and blue) were selected to produce a classified map for benthic habitats. The in-situ observations were included photo-transects taken by snorkeling in water surface and manta tow technique. The satellite image has been classified using support vector machine (SVM) classifier by considering the information obtained from field measurements as both training and control points data. The results obtained from manta tow demonstrated that the mean total live hard coral coverage was 29.04% ± 2.44% around the island. Massive corals poritiids (20.70%) and branching corals acroporiids (20.33%) showed higher live coral coverage compared to other corals. Moreover, the map produced from satellite image illustrated the distribution of habitats with 78.1% of overall accuracy., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The surface sediments (0-4cm, n=6) from Chabahar Bay were analyzed to assess the concentrations, composition, and potential eco-hazards of associated PAHs. The range of ∑16 PAHs' concentration was 25.75-312.38ngg -1 dw, with mean and median levels of 126.7 and 55.12ngg -1 dw, respectively. The bay was classified as a region with low to moderate PAH pollution. The sources of PAHs varied, and 2-3-ring compounds were dominant (37-90%). There was no significant correlation between TOC/grain size and levels of PAHs. Total carcinogenic PAHs ranged from 0.21 to 79.68ngg -1 dw, and benzo(a)pyrene was the main constituent of calculated toxic equivalencies. The bay sediments were rarely hazardous and could not address narcotic hazards for the benthic community. Biota-sediment accumulation was not predicted for the examined coral Acropora valida. In equilibrium conditions, release of ∑16PAHs from the bay sediments was estimated to be 0.536μgL -1 at its maximum., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

In this work, the results of hydrochemical studies aboard the R/V Iran Behshahr in southern Caspian Sea in late-winter 2014 were presented. Salinity, temperature, dissolved oxygen, pH, total dissolved inorganic carbon, total alkalinity, nitrate, phosphate and silicate concentrations in water column of Neka-Amir Kabir oil platform section in the southern Caspian Sea were measured to study the status of hydrochemistry of this area. Results showed that the hypoxia continues to intensify in the deep-water basin of the South Caspian Sea. Near-zero concentration of dissolved oxygen and accumulation of phosphate, silicate and total dissolved inorganic carbon in near-bottom layers in the study area showed that vertical winter mixing of water column did not reach the near-bottom layers at the time of this survey. Nitrate showed its maximum concentration at the intermediate maximum depth of 300m., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The purpose of this study was to quantify phosphorus bioavailability and various forms of this element in surface sediments of the southern Caspian Sea. To do, sediment samples were collected from different depths in autumn 2015 using a Van Veen Grab. Phosphorus forms were recognized by a sequential extraction procedure (SEDEX). Results revealed that the range of total phosphorus (TP) was between 431ppm and 594ppm with a mean value of 535.25±45.05ppm. Organic phosphorus (OP) ranged from 62 to 99ppm and contributed 14.85±2.21% of total phosphorus in average. The contents of loosely phosphorus, iron-bound phosphorus, authigenic phosphorus and detrital phosphorus varied 35-55ppm, 50-94ppm, 125-189ppm and 152-217ppm, respectively. Generally, inorganic phosphorus (IP) was between 365 and 522ppm which comprised 81.9-88.53% of total phosphorus. Findings showed levels of different phosphorus forms in a descending order: detrital P>Authigenic P>Organic P>Fe-P>Loosely P. Bioavailable phosphorus concentration was between 153ppm and 240ppm and consisted 37.21±3% of total phosphorus. Based on molar ratio of TOC/OP, organic matter obtained from the studied stations suggested a terrestrial origin., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Mand River is one of four permanent rivers flowing into the Persian Gulf. Intense industrial activities have significantly impacted its watershed and estuary. In order to evaluate metal contamination and their provenance nine sediment samples were taken from the Mand Delta. Enrichment factors were employed to detect anthropogenic contributions to levels of metal pollution. We also calculated weathering indices in order to identify the source of the metals, related to geological units. Pollution levels were assessed using the modified degree of contamination. Geological units, oil combustion, aerosols and industrial activities are the main factors controlling the abundance of Cr, As, Ni and Pb. Wave action, coastal currents, grain-size parameters, mineralogy, bio-accommodation and organic matter are the factors affecting the distribution and concentration of metals in the study area. More studies are needed to evaluate the impact of metal pollution on the fisheries industry and public health., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

This research was conducted to examine variations of antioxidant enzyme activity in Phragmites australis as a biomarker for metals such as As, Pb, Cu, and Cd. Samples of sediment and plants were collected from 7 stations located in Anzali wetland. Biochemical parameters including Catalase, Peroxidase and Ascorbate Peroxidase activity were analyzed in the roots, stems and leaves of P. australis. The obtained results indicated that there were significant differences among activities of antioxidant enzymes in three organs (p<0.05). Antioxidant enzyme activities in the organs for all studied stations were as the following order: stem

In the present study, the concentrations of metals in sediments along the coastline of the southern Caspian Sea were investigated. For this purpose, sediments were collected from 13 sampling sites in the southern Caspian Sea. The samples were then analyzed by inductively coupled plasma-optical emission spectrometry. Results showed that compound oxides may be responsible for the distribution of metals in the sediments of the southern Caspian Sea. According to mean effects range-median quotient, 61.5% of the studied sites from the southern Caspian Sea had a 21% probability of metal toxicity. On the basis of the enrichment factor, all metals were in the category of deficiency to minimal enrichment. Pollution load index showed that the other sampling sites had no pollution., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

In the present study, the concentrations and distribution of 16 polycyclic aromatic hydrocarbons (PAHs) in the water and surface sediments from the Chabahar Bay, Oman Sea, were investigated in May (premonsoon) and December (postmonsoon) 2012. The concentrations of PAHs in the surface water samples ranged from 1.7 to 2.8ngl -1 and from 0.04 to 59.6ngl -1 in pre- and postmonsoon, respectively. In general, the PAH levels of the water samples from Chabahar Bay were higher in postmonsoon than in premonsoon (p<0.05). The concentrations of PAHs in the sediment samples varied from undetectable levels to 92.8ngg -1 d.w. in both seasons. The seasonal comparison of the results in sediment samples showed that the overall concentration of PAH compounds was higher in the postmonsoon season (p<0.05)., (Copyright © 2016. Published by Elsevier Ltd.)

Geochemical speciation of As, Cd, Co, Cr, Cu, Ni, Pb, V and Zn were determined in the surface sediments of the southern Caspian Sea. A five-step sequential extraction technique was used to determine the chemical forms of metals. Mean concentrations (ppm) of heavy metals were (mean±S.D.) As: 9.94±1.71, Cd: 0.87±0.23, Co: 14.85±2.80, Cr: 72.29±19.48, Cu: 18.91±4.48, Ni: 32.87±5.25, Pb: 12.48±3.22, V: 86.07±20.71 and Zn: 66.85±10.11. Among the metals, Cu, As, Pb and Zn exhibited relatively higher mobility, while Cd, Co, Cr, Ni and V were found mainly in the residual fractions. Cu and As showed the highest percentages in the exchangeable phase while Co and Cr had the lowest percentages in the phase. The Risk Assessment Code (RAC) values indicated that As, Cu and V had medium risk at some sampling sites. According to pollution load index (PLI), sediments from some sampling sites were polluted., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Surface sediments (n=17) were collected from 6 sites located in the coasts of the Bushehr Peninsula. ∑ 16 PAH concentrations were in the range of 285.9-1288ngg -1 dw and the sediments were moderately polluted. Py, Ph, B(a)A and Flu showed >70% of the detected values in order of the mentioned rank. 4-ring PAHs were the dominant compounds and the molecular ratios presented the dominant pyrolytic source. The toxicity of PAHs for sediment dwelling life was averagely equivalent to occurrence of 0.08ngg -1 of Dioxin in dw of the examined sediments. The evaluated narcotic potential (confidence level of 99%) was 0.027-3.04 and upper part of the Bushehr Peninsula, where the human population is more concentrated, showed more narcotic potential. ∑n-alkane concentrations (n-C 15 -n-C 32 ) were in the range of 3.10-35.6μgg -1 dw. The dominant distribution of even carbon number n-alkanes was traced back to a possibly autochthonous source., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

In this study, the accumulation of metals, including Al, Fe, Zn, V, Ni, Cu, Cr, Cd, Co, As, and Pb, in sediments of Anzali wetland in the southwest region of the Caspian Sea was investigated. For this purpose, the sediments were collected from 17 sampling sites in Anzali wetland, Caspian Sea. The samples were then analyzed using inductively coupled plasma-optical emission spectrometry (ICP-OES). Pearson correlation coefficient showed significant and positive correlation between concentration of all metals (except As and Cd). Furthermore, the results implied that Al and Fe are probably responsible for the transportation of heavy metals into the sediments of Anzali wetland. According to mean effects range-median quotient (mean ERM quotient), the sediments from Anzali wetland had a 21% probability of toxicity., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The concentrations of polybrominated diphenyl ethers (PBDEs) were determined in the surficial sediments of Bushehr coasts, the Persian Gulf. Eighteen samples were collected from 6 sites at distances of 500, 1000 and 1500m from the coast. PBDEs were detected in all the samples, indicating their widespread occurrence in marine sediments of the studied area. BDE-209 and ∑ 7 PBDEs were in the range of n.d. (not detected) to 6.29ngg -1 and n.d. to 0.62ngg -1 dw, respectively. The studied area can be classified as the region with the minimal contamination values reported globally as yet. The concentrations of PBDEs were lower than the Canadian benchmarks, and risk quotient assessments demonstrated low ecological risk. BDE-183 and then BDE-153 were the congeners with the highest detection frequencies in the stations, confirming extensive occurrence of Octa-mix in the studied area., (Copyright © 2016. Published by Elsevier Ltd.)

Polycyclic aromatic hydrocarbons (PAHs) were determined in the surface sediments and in the sea cucumbers (Holothuria leucospilota and Stichopus hermanni) from around six Islands in the northern parts of Persian Gulf. The ranges of the average concentrations of PAHs in surface sediments, H. leucospilota and S. hermanni were 10.33-186.16ngg(-1) dw, 12.49-505.44ngg(-1) dw and 8.08-389.39ngg(-1) dw, respectively. The spatial distribution of PAHs reveals that pollutant concentration is relatively higher at the western parts of Persian Gulf. International sedimentary quality guidelines (TEL-PEL) indicated a low probability of harmful effects to benthic organisms. PAH source identification showed that the PAHs in the sediments come from pyrogenic and mixed origin., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The present study aimed to geochemical speciation of metals in the surface sediments of the northern Persian Gulf. Metal contents in the sediment were observed in the order: Al>Fe>Cr>Ni>V>Zn>Cu>Co>As>Pb>Cd. The results of sequential extraction procedure revealed that all metals were predominantly associated with the residual fraction. Among the metals, Cu and As exhibited higher bioavailability. The risk assessment code (RAC) indicated that Cu, As and Cd had medium environmental risk at some sampling sites. Based on enrichment factor (EF), Cd and As had moderate to significant enrichment., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

In this study, concentrations of Aluminum (Al), Iron (Fe), Chromium (Cr), Copper (Cu), Nickel (Ni), Vanadium (V), Zinc (Zn), Arsenic (As), Cobalt (Co) and lead (Pb) in the surface sediments from Chabahar Bay were studied to assess the degree of heavy metal pollution as a consequence of natural and anthropogenic sources. Metal contents in the sediments were observed in the order of: Al>Fe>Cr>V>Ni>Zn>Cu>>As>Pb>Co. According to enrichment factor (EF), Arsenic was higher than 1.5 at some sites, indicating anthropogenic inputs. Contents of Ni, As and Cr in the some sampling sites were higher than sediment quality guideline implying adverse impacts of these metals. Based on potential ecological risk (PER), the Chabahar Bay had low ecological risk., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The amounts and sources of polycyclic aromatic hydrocarbons (PAHs) and their bioaccumulation factors (BAFs) in the zooplankton community of Chabahar Bay were investigated. The highest amounts of total PAHs (tPAHs) in the water and zooplankton samples were 62.2ngL(-1) and 1478.6ngg(-1) dry weights, in near the Shahid Beheshti Port and desalination, respectively. The greatest amount of BAF (51,780) was obtained in the entry of Bay, and it was related to the phenanthrene accumulation. Using molecular ratio, the results showed that the major input source of PAH compounds in zooplankton of Chabahar Bay was pyrolytic (fuel) source., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

In the present study, antifouling paint booster biocides, Irgarol 1051 and diuron were measured in ports and marinas of Bushehr, Iran. Results showed that in seawater samples taken from ports and marinas, Irgarol was found at the range of less than LOD to 63.4ngL(-1) and diuron was found to be at the range of less than LOD to 29.1ngL(-1) (in Jalali marina). 3,4-dichloroaniline (3,4-DCA), as a degradation product of diuron, was also analyzed and its maximum concentration was 390ngL(-1). Results for analysis of Irgarol 1051 in sediments showed a maximum concentration of 35.4ngg(-1) dry weight in Bandargah marina. A comparison between the results of this study and those of other published works showed that Irgarol and diuron pollutions in ports and marinas of Bushehr located in the Persian Gulf were less than the average of reports from other parts of the world., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

The concentrations of some heavy metals (Cd, Cu, Zn andPb) were investigated in the sediments and the two species of sea cucumber (Holothuria leucospilota and Holothuria scabra) from northern part of Qeshm Island, Persian Gulf. The levels of Cu, Zn and Pb in sediment varied significantly among sampling sites (p<0.05). The highest levels of Zn and Pb in H. leucospilota were recorded in body wall whereas the highest contents of Zn and Pb in H. scabra were measured in respiratory tree organ, respectively. Cu and Cd were the most abundant elements in gonads of H. leucospilota while highest levels of Cd and Cu in H. scabra were measured in the gonad and derm, respectively. Cu and Zn concentrations were below permissible limits for human consumption while Cd and Pb were above permissible limits for human consumption., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

The concentrations of some heavy metals (Cu, Zn, Pb and Cd) were investigated in the sediments and in the mullet Liza klunzingeri from the northern part of the Persian Gulf. The levels of Cu, Zn and Pb in the sediment varied significantly among the sampling sites (P<0.05). Sediments from the northern part of the Persian Gulf had serious ecological risk when considering PER. The ranges of the average concentrations of Cu, Zn, Pb, and Cd in the tissue of L. klunzingeri were 10.00-16.66 mg/kg, 18.75-32.50 mg/kg, 3.25-14.16 mg/kg and 0.37-3.33 mg/kg, respectively. The health risk analysis of individual heavy metals in the fish tissue indicated dangerous levels of Pb and Cd for the general population at some sampling sites., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

This study aimed to evaluate major elements and heavy metal concentrations of Arsenic (As), Copper (Cu), Chromium (Cr), Cobalt (Co), Vanadium (V), Nickel (Ni), lead (Pb) and Zinc (Zn) in surface sediments of the southern Caspian Sea. Metal contents in the sediment were observed in the order of: V>Cr>Zn>Ni>Co>Cu>Pb>As. Correlations between elements showed that sediment TOM, grain size and chemical composition are the main factors that influence the distribution of heavy metals. According to the pollution load index (PLI), sediments from some sampling sites were polluted. Concentrations of Ni, As, Cr and Cu were higher than sediment quality guidelines at some sampling sites, implying potential adverse impacts of these metals., (Copyright © 2014 Elsevier Ltd. All rights reserved.)