فهرست مطالب abolfazl naji

Seas and coasts are the most interesting field of geopolitical competition in recent decades. The coastal areas of the Caspian Sea are one of the most important ecosystems in Iran. As the largest lake in the world, this sea has important and special features in terms of sedimentology and geochemistry. Sedimentary and geochemical evaluations are important for studying the evolution of sedimentation environments and the location of basins. Investigating the mineralogical and geochemical characteristics of Caspian Sea deposits can provide valuable information regarding the origin of sediments, hydrodynamic characteristics of the region, and sediment transport conditions. Therefore, the purpose of this research is to study the texture, mineralogy and geochemistry of deposits off the coast of the Caspian sea in Babolsar city. in order to investigate the sedimentary and mineralogical characteristics, petrography and geochemistry of Deposits off the Coast of the Caspian Sea in Babolsar City, it was started by using geological maps, topography of the area and choosing the appropriate navigation route to collect sediment samples. Then, in order to sample the sediments far from the coast, 41 samples were taken from the inside of the boat to sample the soft sediments on the sea surface from a small Van Veen Grab sampler belonging to the German Hydrobius Company. Granulation analysis, microscopic inspections, XRD and XRF were carried out on the collected samples. The findings indicated that silt and clay make up the majority of the particle size of this deposit. Examining the trend of changes in particle size also showed that at the entrances of Babelroud and Shazdehroud rivers to the Caspian Sea, the size of the particles is in the range of sand, and with the distance from the coast, the amount of sand decreases and the amount of silt and clay increases. These deposits often have a silty texture with some gravel and mixed sand. These deposits along the shore, where the energy is stronger, have superior textural properties than the deposits inland, where the energy is lower.  Most of the studied sediments are debris near the coast. Deposits off the Coast is more abundant with chemical and biochemical particles and intraclast allochems, bivalve fossils, and benthic forms.This deposit's primary mineral phases include quartz, calcite, feldspar, and occasionally Illite and Dolomite. The geochemical results also show the superiority of SiO2 oxide, which is generally associated with quartz minerals. Oxides of SiO2, Al2O3, Na2O, and K2O are deficient in these deposits, whereas Fe2O3, CaO, P2O5, MnO, and TiO2 oxides are abundant. In total, the results of this research indicated a direct relationship between the deposits off the coast of the Caspian sea and the mineralogical composition of the incoming deposits from the rivers leading to this coast. The conditions of the sedimentary environment of these deposits have also been involved in the formation of the geochemical and sedimentary characteristics of these deposits.

Microplastics enter the food chain of aquatic animals; they cause damage to the digestive system, disruption of the reproductive cycle, and finally their death. The present study was conducted to investigate the microplastic pollution in the digestive system of Vanami shrimps cultivated in some shrimp farms in Bushehr, Khuzestan, and Hormozgan provinces.

Sampling was done from two shrimp farms in each port including Bandar Rig in Bushehr province, Bandar Choebdeh in Khuzestan province, and South Tiab located in Hormozgan province. 90 shrimp samples were randomly collected from each breeding farm from June to October 2019. The identification method of microplastics was done by FT-IR spectrophotometer.

The highest frequency of microplastics related to farmed shrimps was 41.11% in the fields of Khuzestan province, and a lower amount of microplastic pollution was observed in Hormozgan and Bushehr provinces with 28.88% and 17.70%, respectively. According to one-way ANOVA, the mean of microplastics in the digestive tract of shrimp had a significant difference in the studied stations (p<0.05). The most type and colors of microplastics in the digestive system of shrimps in the farms of all provinces belonged to fiber and black color. Polypropylene and polystyrene were detected in microplastics found in the digestive system of shrimps.

Microplastics were observed in some of digestive tracts of the shrimps of the breeding farms examined in this research in all three provinces of Bushehr, Khuzestan, and Hormozgan. The highest frequency of microplastics in the digestive tract of shrimps is related to the breeding farms of Khuzestan province, and Hormozgan and Bushehr respectively have a lower amount.

Nowadays, the demand for seawater desalination plants (SDPs) has risen worldwide. However, there is a lack of knowledge on the effects of discharging the SDPs brines into the Persian Gulf marine environment and its aquatics health. Therefore, this research was performed to examine the effects of SDPs brines discharged from this facility in the ecosystem of the Persian Gulf on survival and electrolytes in the Blue swimmer crab, Portunus segnis (Forskal,1775) under laboratory conditions.

Brines of two types of active SDPs in Hormozgan were collected; then,75 crabs of (P.segnis), with mean (±SD) carapace width of 9.71±2.18 cm and total weight of 61.22±1.04 g, were collected and transported to the laboratory from the Bandar Abbas coast. As a completely randomized design, the samples were tested in 5 treatments (with three repetitions). Mortality was recorded, and at the end of the experimental period (60 days),the level of some electrolytes of the hemolymph (sodium, calcium, magnesium, and potassium) was measured.

Crabs' survival percentage in treatments containing SDPs effluent decreased compared to control (86%), which was more evident in RO 100% and MED 100% treatments with 46.7% and 40%, respectively (p <0.01). The examined electrolyte levels in treatments containing SDPs brine increased compared to control, which were more significant for RO 100% and MED 100% treatments (p <0.01).

This study showed that the SDPs brines would have physiological consequences on aquatic organisms. In nature, the synergy of SDPs effluents with other sources of ecological stress will have severe impacts. Therefore, the necessary regulations and actions should be taken to minimize the environmental effects of SDPs.

Regarding the significant effect of temperature on biomineralization process, the study of the seasonal changes impacts on the functions and patterns of gene expression in mantle tissue as an important organ responsible for biomineralization in pearl oysters, is necessary. In this study, the gene expression patterns of 9 biomineralization genes (ASP, KRMP, SHEM5, PRISM, PEARL, CHIT, PIF, MRNP34, NACREIN) were investigated in the mantle tissue of Pinctada persica between warm and cold seasons. The cDNA was constructed using reverse transcriptase enzyme and then the expression of genes were quantified in qPCR. The results showed difference in seasonal pattern. Three genes of prismatic layer (ASP, KRMP and SHEM5) had high expression in cold season and PIF which involved in nacre layer formation, showed high level of expression in warm season. It is likely, the biomineralization rate reduce in higher temperature and the prismatic related genes play more important role in response to seasonal changes. This study has provided valuable information about mantle tissue traits of P. persica and influence of environmental factors in molecular mechanisms involved in the formation of shell and pearl.

Biofloc technology has mentioned as a new tool for sustainable aquaculture development and has overcome the problems of water scarcity and discharge of aquaculture effluents to the environment. In this system, nitrogenous wastes (Ammonia and Ammonium) are simultaneously recovered by bacteria and converted into microbial proteins that can be consumed by aquatic animals. The purpose of this study was to investigate the factors affecting the production of biofloc and evaluate it for use in aquaculture. The effect of different temperature levels (24, 28, 32 °C), salinity (0, 4, 8 g/l)  ,and C/N ratio (10:1, 15:1, 20:1) which are the main key factors to the formation and function of biofloc system was evaluated by using a response surface method designing. Moreover, the influence of those factors on total ammonia nitrogen, nitrite, nitrate, floc volume, protein, and lipid content of biofloc was investigated. The results showed that the temperature had a significant effect on floc volume and protein content of biofloc (P < 0.05), but it had no significant effect on other nitrogenous compounds and lipid content (p > 0.05). The protein, lipid and moisture of biofloc particles were decreased by increasing salinity significantly (P < 0.05). Also, TAN and nitrite concentration influenced by C/N ratio inversely. According to the factors Optimization, providing 27 °C and C/N ratio of 18:1 in brackish water and 29 °C and C/N ratio of 14:1 in fresh water resulted in high quality biofloc production and control of nitrogenous wastes in water.

The non-standard size of the trawl fountain, especially in the bag section, increases the amount of incidental catch and non-target species caught. With the aim of standardizing the trawl springs in small floating vessels, trawl tours with 36, 40, and 44 mm fountains were used in Bushehr waters in 1396. The sampling site and sampling operations were carried out under similar conditions. And was carried out in three depth classes less than 10 meters, 10-20 meters, and 20-30 meters. At the end of the 9 trapping sequences, the species of whitefish (Metapenaeus affinis), green shrimp (Penaeus semisulcatus), shrimp (Parapenaeopsis stylifera), shrimp, or violin (Metapenaeopsis stridulans) and trachypenaeus granulosus Combined shrimp fishing. The tiger shrimp was the highest shrimp catch with 92.74%. The results also showed that depth and mean length of shrimp are significant. Also, in studying three sizes of fountains, the highest frequency of tiger shrimp was 7-10 cm. In the survey of catches, the highest catch of tiger shrimp in the 36mm fountain was found, with the highest amount of coding done on the tour. In the 36 mm range, the L50 was 5.92523 cm in the 36 mm trowel, the L50 was 6.58057 cm long and the length of 44 mm was LM50 7.233867 cm.

An experiment was conducted to evaluate the effect of biofloc system on water quality, growth performance, immunity and body composition of Nile tilapia at different stocking densities. Fry (3.2±0.05 g) stocked in 500 and 1000/m3 in biofloc and clear water system (as control) in three replicates and reared for 50 days. Results showed that the lowest TAN and highest nitrite and nitrate were observed in BFT treatments. Total suspended solid, floc volume and bacteria increased by increasing stocking density. Maximum final weight (12.9g), SGR (3.21 %/day), survival (100%) and the best FCR (0.91) were obtained in BFT (500/m3). There were no significant differences in survival among treatments (p>0.05). Lysozyme, immunoglobulin and catalase of fishes in the biofloc treatments were significantly (p<0.05) better than control. Proximate analysis revealed that protein and lipid content of fishes in BFT were slightly higher than control groups but these differences were not significant. It seems that although fishes in BFT 500/m3 statistically showed better indices than others but due to small differences in growth indices and feed conversion ratio in one hand and no difference in survival rate between 500 and 1000/m3. On the other hands, the study suggests the stocking density of 1000/m3 for larviculture of tilapia in biofloc system to use water and equipment more efficiently.

Microplastics are small pieces of plastic waste (less than 5 mm), which are found along the coast, the sea level and the bedding. The present study examines the frequency, distribution, and forms of microplastics in bivalve tissues and sediments sampled on the coast of Bandar Lengeh. Microplastic separation was performed by spectral density and spectrophotometric (FT-IR) and (SEM-ED) methods for polymer detection. The microplastics found were varied colors including black, white, transparent, red, pink and green. Using the obtained data, at the Lengeh port stations, the average total number of extracted microplasms per shell was 3.93 and the number of microplastics in Bandar-Lengeh sediments was 34.5 ± 0.17. The most commonly found polymers were polyethylene (PE), polyethylene terephthalate (PET) and nylon. The most abundant type of micro-plastics isolated from Pinctada radiata, microfibers and fragments were extracted from fiber and film sediments. The present study can provide useful information for further research as well as forensic monitoring and monitoring of this contaminant in the Persian Gulf marine environment.

Mercury (T-Hg), as the most toxic Trace metal, can have adverse effects on the environment. In this study, the concentrations of T-Hg were investigated in surface sediments of higher and lower tidal zones of Hormozgan province coasts including the stations of Shahr Jask, Ariyan International Wetland Lagoon, Khorgorsuzan Bandar Abbas, Bostono Industrial Zone, Coastal Park of Khumir, Shahrbonderlangeh, Bandarreqam, Bostaneh Harbor in summer 2017. T-Hg concentration was measured by Ftomic Atomic Aabsorption Spectrometry (FAAS, GTA120). From 16 stations in the higher and lower tidal zones, the stations of Khorgorsuzan Station and Azzin kinetic showed the lowest concentration of T-Hg. Based on accumulation index (Igeo), the geochemistry of the Igeo studied areas had a moderate to high contamination. Enrichment Factor (EF) showed a strong to extremely high enrichment. Regarding SQGS, all stations were higher than Effect Range Low (ERL) value. These findings raise awareness of the contamination status of surface sediments in coastal zone of Hormozgan Province, provide a valuable benchmark for future comparisons in the area, and are important for the design of appropriate policies and long-term management of those ecosystems by local managers and the national authorities.