فهرست مطالب hamid ershadifar

The Persian Gulf hosts a variety of marine ecosystems, including mangrove forests, seagrass beds, and coral reefs, which have adapted to the challenging environmental conditions of the region to some extent. These ecosystems are increasingly influenced by rapid population growth, economic development in the countries surrounding the Persian Gulf, as well as, the impact of climate change in the region. They are facing mounting pressure from human activities. The influx of nutrients, coupled with the warming of the Persian Gulf, can result in a reduction in the dissolved oxygen concentration in the water. Consequently, the simultaneous occurrence of warming, reduced oxygen, and acidification in the Persian Gulf has become a significant challenge for its valuable ecosystems. According to studies, hypoxic areas in the Persian Gulf in mid-autumn can extend to more than 50,000 square kilometers. The occurrence of hypoxia in the Persian Gulf during late summer is confined to two primary areas in the western and central regions. In the eastern Strait of Hormuz, hypoxic conditions are observed in the near-bottom layer from early summer to mid-winter in areas distant from the Gulf's outflow. The reconstruction of dissolved oxygen concentrations in recent decades also indicates a declining trend accompanied by an increase in the extent and duration of hypoxia in the Persian Gulf. The degradation of water quality in the Persian Gulf, in addition to its adverse effects on its valuable ecosystems and consequently on fisheries and aquaculture in the Gulf, can significantly impact the Gulf of Oman and even the Arabian Sea in various ways, exacerbating the conditions of Oxygen Minimum Zones (OMZ) in these expansive seas. The Gulf of Oman and the Arabian Sea naturally and permanently host the widest and thickest OMZ in the world ocean. Depths exceeding 400 meters in the Gulf of Oman exhibit suboxic conditions (oxygen concentration less than 6 µmol/kg) during both summer and winter. The OMZ in the Arabian Sea and the Gulf of Oman has intensified over the past few decades. Oxygen levels recorded in 1960 in the core of the OMZ in the Arabian Sea and the Gulf of Oman ranged from 6 to 12 µmol/kg but have now dropped to levels below 6 µmol/kg (suboxic). This intensification of the OMZ in the Arabian Sea and the Gulf of Oman has adverse effects on the ecosystems of this region and the livelihoods of dependent populations. Marine organisms residing in the near-bottom layer or surface sediments are most affected by the expansion and intensification of hypoxic and suboxic conditions. Oxygen deficiency leads to a decline in the biodiversity of benthic communities, promoting resilient species such as polychaeta in surface sediments. The reduction in oxygen levels in the Arabian Sea has significantly influenced the composition of phytoplankton communities, the vertical migration of zooplankton, and myctophidae in the water column. The expansion and intensification of the OMZ, with its adverse impacts on fishing and aquaculture, also carry socio-economic implications for residents of the coastal areas of the Indian Ocean, the Gulf of Oman, and the Arabian Sea. Considering the prevalence of seasonal hypoxic conditions in the Persian Gulf and permanent suboxic conditions in the Gulf of Oman, addressing this trend and mitigating its environmental and economic impacts in the region is crucial. Management and policy strategies to halt or reduce the effects of oxygen depletion in the Persian Gulf and the Gulf of Oman can be classified into three main categories: a) ecosystem-based mitigation measures for environmental restoration and protection, b) adaptation-based measures to restore and protect marine organisms and fisheries, c) implementation and maintenance of monitoring programs and analysis of the information obtained. In essence, efforts to integrate research, management, and policy actions in oceans and seas across all biological, geochemical, and physical disciplines, addressing all climate change-related issues such as warming, acidification, and oxygen reduction, and involving all academic, industrial, governmental, and regulatory sectors, constitute the most effective roadmap recommended for combating the impacts of climate change on marine resources.

Environmental parameters and their short and long-term variations are widely studied to monitor the changes in coastal water quality. Dynamic changes in parameters such as temperature, pH, DO, and nutrients are closely related to primary production by autotrophic species and their population structure. The availability of nutrients and their ratio is considered the key factors regulating the biomass of phytoplankton (Roelke, Eldridge, & Cifuentes, 1999). The growth and metabolism of these organisms are strongly influenced by nitrogen, phosphorus, and silicon as nutrients. The biological response to environmental changes is closely related to the periodicity of fluctuations in these parameters. While the variation in seasonal scale is influenced by the seasonal pattern of currents and meteorological parameters, on a diurnal scale, they are influenced by the processes of photosynthesis and decomposition of organic matter. These fluctuations in hydrochemical parameters can shape the population structure of phytoplankton, the outbreaks of harmful species, and the expansion of low-oxygen regions in the upper layers of the water column in the post-bloom phase. Therefore, the trophic status is evaluated in various ways, including the concentration of nutrients or chlorophyll-a (Carlson & Simpson, 1996).In the northern regions of the Gulf of Oman, meteorological conditions and water column characteristics are mostly governed by the summer (June-August) and winter (December-March) monsoons. Most of the summer monsoon's impact on hydrochemistry and function of biological life is through local wind-driven or eddy-induced upwelling in coastal areas, during which, colder nutrient-rich waters rise to the surface from depths (Harrison, Piontkovski, & Al-Hashmi, 2017). During the winter monsoon, cool convective mixing increases the mixing layer depth and helped nutrients to reach the surface (Harrison et al., 2017).The frequent occurrence of harmful algal blooms and the establishment of hypoxic conditions as a result of the increase in the concentration of nutrients have affected the coastal waters of Chabahar in recent years (Ershadifar et al., 2020; Kor, Ghazilou, Ershadifar, & Koochaknejad, 2020). On the other hand, Gulf of Oman, as a part of the northwest of the Arabian Sea, has the potential to be considered globally as a sensitive indicator of global climate change at the oceanic scale (Fauzi et al., 1993). The region is host to various biogeochemical phenomena such as the upwelling of nutrient-rich waters, nitrogen fixation, and nitrogen deficiency, as well as deoxygenation in both coastal and offshore areas.

In the present study, the short-term fluctuations (diurnal) as well as seasonal variations in hydrochemical parameters including salinity, temperature, pH, dissolved oxygen, and nutrients (nitrate, silicate, and phosphate) were investigated in Chabahar coastal waters. Sampling was done from a single station (depth of 30 m) on October 9 of 2018, November 19 of 2018, January 07 of 2019, and March 10 of 2019. The samples were collected in time intervals of 3 h and from three depth levels of 0, 10, and 30 m using a Niskin bottle each in three replicates. Environmental parameters including temperature, salinity, DO and pH were recorded by using portable devices at the sampling site. The samples were stored in a freezer at -20°C and analyzed for a short period of time. In the laboratory, nutrients concentration were measured according to the instructions for the analysis of nutrients in marine environments (Hansen & Koroleff, 1999). The double beam Rayleigh UV-920 spectrophotometer with 2 cm pathlength was used for colorimetric determination. Measurement of total phosphorus and nitrogen in unfiltered samples was also done by wet oxidation method in the presence of persulfate as an oxidizing agent at high-temperature conditions followed by the spectrophotometric determination of nitrate and phosphate (Grasshoff, Kremling, & Ehrhardt, 1999). To measure chlorophyll-a, the samples were extracted in 90% acetone and measured by the spectrophotometric method according to ESS Method 150.1 (EPA, 1991). The Ocean Data View (odv 5.1.7) software was used to depict the temporal-vertical fluctuations (Schlitzer, R., 2020, Ocean Data View, http://odv. awi.de). The General Linear Model (GLM) followed by Tukey's posthoc tests (Minitab V17 software) was used to evaluate the seasonal changes in the investigated parameters.

Continuous monitoring of coastal water quality is required for the sustainable development of cage culture projects, marine ecotourism, and desalination plants, and also to protect the sensitive ecosystems of the region, including coral reefs. The diurnal and vertical variations in the distribution of hydrochemical parameters in the coastal waters of Chabahar are affected by the changes in the water column structure varied from strong stratification in the fall intermonsoon monsoon to mixed column in the winter monsoon. As the temperature declined, the seasonal thermocline established in October completely faded in January, and the vertical gradients in hydrochemical parameters weakened or completely faded. Dissolved oxygen and pH, which have experienced low values in the inter-monsoon period, more profoundly in the near bottom layer, were affected by the processes of aerobic remineralization of organic matter. They were increased in the winter monsoon and there was no significant difference between the surface and near bottom values. Surface nutrients, with low concentrations during the stratification period, showed an increase toward winter monsoon. However, the average values of silicate, nitrate, and nitrogen over the water column showed a general decreasing trend from October to March. As a result of the increase in water column mixing, Chl-a also shows its maximum in March. The ratio of nitrate to phosphate is less than 10 in 90% of samples. The average value of the nitrate: phosphate ratio was 5.0, which was much lower than the theoretical value of 16 suggested by Redfield for offshore open ocean waters. This could imply a higher probability of nitrogen limitation rather than phosphorus limitation. In 45% of the samples, the silicate concentration was less than 2.0 µM, including the surface samples in October and November and almost all samples from March, which showed the active removal by diatoms. The diurnal fluctuations of the parameters, especially during the stratification period of the water column, are influenced by tidal and non-tidal currents so that the maximum and minimum values in a diurnal cycle could appear in both low and high-tide situations.

The aim of the current study was to assess the agreement of the religious halal norm with difference in histamine, urea, and methanol levels as well of selected aquatic animal species. Samples of Arius maculatus, Atule mate, Cynoglossus bilineatus, Planiliza macrolepis, Portunus pelagicus, Rhinoptera javanica, Saccostrea cuccullata, and Sphyraena putnamae were obtained from the Chabahar Bay. The concentrations of total protein, histamine, and urea were estimated in dorsal muscle of fish, claw muscle of Portunus pelagicus, and soft tissue of the Sccostrea cuccullata samples, using the ELIZA method. Colorimetric kits were used for methanol determination. Comparison of the mean urea concentrations amongst examined species indicated significantly higher levels of urea in haram species (W= 167.5, p= 0.013). Mean histamine levels on the other hand, were not significantly different between halal and haram food (F= 2.61, p= 0.11). Yet, histamine content in R. javanica fried flesh was more elevated compared to halal food. Also Protein levels were considerably decreased in cooked R. javanica meat. Methanol concentration was lower than the detection limit in all samples. We speculated that the cooked food should be considered for assessing the agreement level between halal norm with food quality. Colorimetric kit was used to detect methanol in samples.

This study was performed to investigate the chemical composition of the caudal spine in Hemitrygon bennettii (Muller and Henle, 1841) as a source for hydroxyapatite (HA) extraction. Therefore, the chemical structure of caudal spines of fish sampled from the mangrove swamps at Chabahar Bay was determined at calcined (baked at high temperature) and uncalcined conditions. The Raman spectroscopy and ICP-OES were used for structural and elemental analyses, respectively. The sharpest peaks in the Raman were observed at 962cm-1 which was probably due to the symmetric stretching vibrations of apatite phosphates. The adsorbed OH ions also indicated peaks at 3400-3500cm-1 of both calcined and uncalcined samples. The presence of organic residue in uncalcined samples was highlighted by several peaks at 2700-3050 and 1300-1500cm-1 which may be due to both stretching and bending vibrations of CH, CH2 and CH3 groups. Some peaks at 1200-1800cm-1 may also be related to amine residues of proteins. In terms of ion concentrations, high amounts of sodium and magnesium contents in the spine structure (compared to other natural resources of HA extraction) may improve the biocompatibility of extracted HA.

Chabahar Bay is a semi-closed environment in the southeastern coast of Iran, with two important ports of Konarak and Chabahar in its margins. The connection of this Bay to the Indian Ocean through the Oman Sea causes this region to be affected by the Monsoon phenomenon, especially the southwest Monsoon, in the late spring to late summer. On the other hand, with the expansion of various industries and increasing marginal population, it is expected that aquatic environment and, as a result, sensitive ecosystems such as coral habitats and mangroves, as well as water desalination plants affected by human activities. In this research, the effects of the Monsoon phenomenon on physicochemical parameters, nutrient concentration and Chl a will be studied. Also, the possibility of the effect of loading nutrients through the ports of Konarak and Tiss will be examined by comparing the results from these ports with the adjacent stations in the Bay.

Sampling from 4 stations in the Bay in two depths (0.5 m beneath the surface and 1 m above the bottom) was performed using five liters Niskin bottle in three replicates. Physicochemical parameters were measured by relevant portable probes at the sampling site. In the laboratory, the reagents were prepared for colorimetric detection according to the instructions (MOOPAM, 1999), and the amount of nutrients were measured by spectrophotometer in a quartz cell with a path length of 2 cm. Statistical analysis were performed using PRIMER 6 and STATISTICA 10 software.

According to the acquired results, the concentration of phosphate, nitrite and nitrate, as well as chlorophyll a, are higher in the post-monsoon period and are in the order of post-monosoon > pre-monsoon> monsooon. In the case of silicates, this trend is different and is as pre-monsoon> monsoon≈post-monsoon. Comparison of inter-annual results shows that the phosphate, nitrate and nitrite values in year 2017 were more than the corresponding values in 2013-2014. Chlorophyll a indicates a positive correlation with the nutrient concentration, which indicates that the primary production is controledl by the nutrients availablity. The pH and DO values have a positive correlation and both are generally less in the pre-monsoon than the post-monsoon in both sampling periods of 2013-2014 and 2017.

Comparison of the results between 2013-2014 and 2017 shows that there is a difference in nutrients and physicochemical parameters due to differences in the intensity and duration of the monsoon in different years. High concentrations of nitrate, phosphate and nitrite in the post-monsoon season are due to the monsoon-induced upwelling and the emergence of nutrient-rich waters. Lower silicates in the post-monsoon season than the pre-monsoon and post-monsoon seasons seems to be the result of the silicate depletion by diatoms that blooms during this period, as the Chl a in the post-monsoon is greater than the preceding seasons. Finally, the comparison of nutrients in two marginal seaports with adjacent stations in the Bay shows that the amounts are significantly higher. However, they are still not at the stage to intensely elevate the nutrients levels in the Bay.

This study aimed to assess the temporal variation in fish assemblage in Chabahar Bay mangrove habitat. Baited Remote Underwater Video (BRUV) sampling method was applied to record the fish presence. Fishes were sampled monthly from June 2017 to April 2018 at daylight time (9:00 to 14:00) during high tide. Water temperature, turbidity, and salinity were recorded at the time of sampling. During the study, a total of 17 species belonging to 12 families were identified. Ambassis gymnocephalus was found as the dominant fish throughout the year except in November and December. The most abundant fish fauna in numbers was characterized by the following five species: Ambassis gymnocephalus (53.38%), Sardinella sp. (17.13%), Terapon jarbua (4.79%), Rhabdosargus sarba (3.25%) and Acanthopagrus berda (2.9%). ANOSIM showed that significant differences in the assemblage structure occurred among months (R=0.613, P< 0.001), and the CLUSTER analysis, together with the SIMPROF test showed that December is significantly different in term of fish assemblage. Canonical Correspondence Analysis (CCA) on species-environment correlations revealed that temperature and turbidity were the main parameters influencing fish occurrence in the mangrove habitat of Chabahar Bay. The overall diversity (Shannon–Wiener, Simpson’s Index of Diversity, and Pielou’s evenness), as well as functional diversity indexes (FRic and FDis), was higher in autumn and spring pointing out that the diversity is higher when the temperature had the closest value to averaged value

In recent years, the incidence of many cases of algal blooms have been reported in the southeastern coasts of Iran, which led to the loss of mass mortality of marine fish in this area. The aim of this study was to use regression trees to investigate the effects of physicochemical parameters and nutrient concentration on algal blooms. During the one-year study period, sampling was done in 6 stations along 2 transects in the coastal waters of Pasabandar and Beris. The trend of changes in pH, salinity, temperature, dissolved oxygen, nitrate concentration, nitrite, phosphate, and silicate with the community of dominant phytoplankton genera was recorded. Overall, 40 phytoplankton genera were identified and more than 95% of the total number of observed cells belonged to 14 genera of phytoplankton. Results showed that increase in the pH, temperature, salinity, phosphate, nitrate and silicate were the effective parameters to bloom of Gonyaulax, Leptocylindrus, Mesodinium, Chaetocerus, Prorocentrum, Rhizosolenia and Nitzschia, respectively.

Observations from an eight-year ocean station at Chabahar showed that both salinity and electrical conductivity (EC) have increased over the past nine years. Meanwhile, pH remained at steady state levels and there was no significant trend in mean annual temperatures. The best repeating pattern of monthly oscillations was depicted in temperature data with the highest and the lowest temperatures occurring at 4th/ 5th and 10th/ 11th months, respectively. Changes in salinity/EC and temperature were moderately correlated. The mean monthly pH levels rarely fell below 8.00. There were no signs of hypoxia during the study period.

Hypersaline ecosystems provide excellent conditions for ecological studies of aquatic ecosystems. Lipar Lagoon is an understudied hypersaline lagoon located in southeasternmost Iran (northern Gulf of Oman). Knowledge about the biotic and abiotic characteristics of this hypersaline water system is limited. This research thus investigated the plankton community composition and abundance, and also its variability under variable environmental conditions over one year.

Monthly (five replicates each month) water samplings were performed from 2017 to 2018, during pre-monsoon, monsoon, and post-monsoon seasons. Physicochemical properties of water were measured at the site using a portable multi-meter, while other parameters such as silicate, nitrate, and phosphate were analyzed by spectrophotometry. For plankton identification and density measurements, each sample was fixed by adding 3ml of acidic Lugol’s solution, and transferred to the laboratory for further analysis.

The plankton community observed during the study period included Fabrea salina, Dunaliella salina, Pseudo-nitzschia sp., and Spirulina sp. Temporal variations in plankton abundance were evident, mostly in September and November, most of which occurred due to the difference in the abundance of D. salina and F. salina. The impact of environmental parameters including salinity and the concentration of dissolved oxygen, nitrite, silicate, and phosphate on the community structure of planktons was significant.

The combination of high salinity, high evaporation rate, low freshwater input, and consequently, low nutrient levels may be the main factors behind the low biodiversity in the lagoon. Being under pronounced anthropogenic pressure due to salt extraction activities, it is evident that further hydrobiological monitoring is crucial for the long-term preservation of the lagoon

In the present study, sampling and analysis of size-fractionated suspended particulate matter (SPM) in coastal waters of Chabahar Bay have been done for the first time. Sampling has been conducted on December 25 of 2018 from 5 stations in different locations of the Bay in order to evaluate the effects of natural and human activities on SPM mass and composition. With an overall average of 2.44 and 2.37 mg/L for small size (0.4-25 μm) and large size (>25 μm) fraction, concentrations of SPM ranged from less than 1.16 mg/L in the north of the Bay to a maximum of 3.96  mg/L near the urbanized area (Konarak harbor)  in the west of the Bay, respectively. The bulk composition of SPM was mostly of lithogenic materials and particulate organic matter with low contribution from biogenic CaCO3 and even lower biogenic silica, widely varied over stations. Leaching with HCl shows that most of the particulate Fe (>60%), Mn and P (>80%) were labile, while for lithogenic elements, such as Al and Ti the acid-leachable fraction was lower than 10%.  Me/Al ratio for heavy metals of Mn, Fe, Cr, Zn, Ni, and Cu was compared with local sediment and rocks. The ratio was higher in larger size fraction except for Cu.  Enrichment factor relative to reference sediment for Mn, Fe, and Cr was usually lower than 1.0, while for the other three elements the EF values higher than 1.5 indicates a significant contribution from non-crustal sources.

Seven phytoplankton species (Alexandrium sp., Prorocentrum micans, Cochlodinium (aka Margalefidinium) polykrikoides, Mesodinium rubrum, Akashiwo sanguinea, Gonyaulax
polygramma, Ceratium sp.) were found as the main cause of Harmful algal blooms (HABs) in a three-year record of red tides in Chabahar coastal waters (North of Gulf of Oman). Autumnal blooms of Gonyaulax polygramma and Prorocentrum micans are reported for the first time in the region. The most frequent bloom events were caused by Akashiwo sanguinea (i.e. 4 times) and Mesodinium rubrum (i.e. 3 times). The highest observed density was at Oct 2017 caused by Akashiwo sanguinea (15.3*106/ litre). The recorded temperature range was from 24.4 to 31.5°C and the DO ranged widely from 3.9 to 11.2 mg/liter. In conclusion, HABs occurrences are not associated with the expansion of one particular species but with multiple taxa and there is aد suitable environmental condition for HABs in the autumn and spring in the region.

A carbon ionic liquid electrode (CILE) modified with TiO2-Fe nanoparticles was constructed by incorporating TiO2-Fe nanoparticles into the paste matrix. Under the optimized experimental conditions, using differential pulse voltammetry (DPV), the oxidation of thiocyanate and oxalate were occurred at potentials of 0.740 V and 1.010 V, respectively, at the surface of the modified electrode. Observing a high peak current along with a suitable peak separation allowed introducing the first voltammetric sensor for simultaneous determination of these anions with high sensitivity without mutual interference. A wide linear range of 1.0 × 10-5-1.8 × 10-3 M for thiocyanate with a detection limit of 6.4 × 10-6 Mand a wide linear range of 5.0 × 10-5-3.0 × 10-3 M for oxalate with a detection limit of 2.3 × 10-5 M were obtained. The modified CILE showed good reproducibility, repeatability and storage stability as well as good selectivity. The proposed sensor was successfully applied for analysis of thiocyanate and oxalate in urine samples.