فصلنامه اقیانوس شناسی
پیاپی 37 (بهار 1398)

This study has been carried out in order to identify the phytoplankton cysts from sediment of Lipar zone (southeast coast of Iran) based on morphology and phylogeny of germinated cell. The sediment samples were collected from three sations by Ekman grab with 225 cm2 collecting area in 2015. Unknown cysts with different morphology were cultured in the petridishei containing the F2 medium and kept in phycolab and Germinator undere a proper condition 12:12 L/D in 25 ºC±1. The germinated cell was similar to the Chattonella subsalsa based on intitial morphological assessment. To confirm the identification, DNA of germinated cell was extracted and PCR and gene sequence of partial LSU-rDNA region were done. Phylogenetic analysis showed that germinated cell with 98% boot strap support was resembeled to the C. subsalsa. The assessment of cyst/theca relationship in the phytoplankton lifecycle can be a useful tool in the identification of the phytoplankton cells.

Magnetic susceptibility is one of the most important tools for monitoring the sediment composition during environmental studies. In this research, in order to reconstruct the Caspian Sea level changes, magnetic susceptibility variations were used during the studies of 5 sedimentary cores (K1, K3, K5, K7, N1), collected from bottom sediments of Gorgan Bay. Samples were analyzed for grain size, total organic matter, carbonate content and magnetic susceptibility (MS). The results showed a close relationship between particle size distribution and MS magnitude due to variation in terrestrial influx, which was caused by sea-level fluctuations in different times. This process increases with rising particle size and magnitude of MS simultaneously with sea level fall and decreases during sea-level rise. Moreover, no relationship between magnitude of MS and carbonate content was observed. It could be concluded that using magnetic susceptibility curves with other data, such as geological and historical data, could be suitable for the reconstruction of marine environments, especially in the near shore coastal area.

In this study, the Scallop bivalves were used for biofiltration of wastewater in shrimp farms during spring 2018 from Guowater Bay. Sedimentation, biological and aeration ponds were prepared for biofiltration around the main pool, then, oyster bivalves were collected from natural environment (sea) and were placed in these pools. Concentration of quality parameters were investigated in four sampling stations including station 1 (sea water), station 2 (inlet water), station 3 (outlet waste) from main pond, and station 4 (water sampled before entering the sea). The results showed that the concentration of parameters were significantly higher in the outlet waste of main pond (station 3) than the other stations (P<0.05). The results of the correlation test showed there was significant negative correlation between biofiltration ratio and quality parameters, so that concentrations of parameters were decreased with increasing in filtration rate. The concentration of nitrate, phosphate, turbidity, EC, TDS and dissolved oxygen were 0.67, 1.52, 22.36, 39.78, 20.21 and 9.49 mg/l in main pond, and 0.56, 0.79, 16.81, 38.68, 16.45 and 12 mg/l after biofiltration, respectively. The results showed that there were significant differences between parameters before and after biofiltration. There were significant differences in the biofiltration rate between the different time intervals (P<0.05), so that the highest and lowest filtration rates were observed in the fifth and first day, respectively. The rate of 20, 48, 27, 22 and 2.5 % of nitrate, phosphate, turbidity, TDS and EC were removed from wastewater during biofiltration process. Therefore, the Scallop bivalve has a high ability for biofiltration of wastewater in shrimp farms that can be used as a good indicator for biofiltration of fish and shrimp farms.

In this study, the compound and overtide constituents resulted from nonlinear triad interactions were evaluated using Bispectral method at the eastern Iranian coasts of Makran. It was found that the most significant compound constituents at the studies area were KO2, KP2, MS4 and MN4. Also, the overtides of M4 and S4 were detectable by means of implemented method. The superiority of Bispectral method comparing with least square method (harmonic analysis) is in recognizing some of compound tides such as KO2, which is never identifiable using least square method.
The corresponding Fourier harmonic frequencies to main tidal constituents were identified by comparing the results of the least square method and the Fourier analysis. Finally, the analysis was performed with d.o.f.s of 16, 32 and 64. The repeated significant bicoherence values in all three d.o.f.s and in the main tidal constituent frequencies range were regarded as the intensive and effective interactions.

The aim of this article is to measure the impact of main factors affecting the reduction of discharge and loading performance compared to dry bulk discharge and loading in terminal of Imam Khomeini Port. For this purpose, the actual data presented in Imam Khomeini Port for discharging and loading statistics and library documented data were used. In order to answer the research questions, multiple regression method was used applying STATA14 software. According to the first model results, variables such as displacement of labour equipment, technical defect of ship equipment and delay in the separation had significant effect on loading rate via an indirect Chanel. Also, based on the second model results, independent variables such as displacement of labor equipment, technical defect of ship equipment and quarantine, had a significant effect on discharging rate variable and this effect found to be indirect. Moreover, almost all of the variables were significant in both regressing models.

In the paper, the atmospheric conditions in the Persian Gulf region and southwest of Iran were studied by analyzing several case studies in cold and warm seasons. For this purpose, three case studies were selected from the dust events occurred between September and March and have been studied using meteorological stations data, satellite imagery, ECMWF global data, and HYSPLIT and DREAM outputs models. The results showed that one of the main dust transport factors into the southwestern Iran was the northwesterly winds over western neighboring countries. This study showed that atmospheric mean layer patterns (500 hPa), did not play a fundamental role in the transport of dust, and, in all circumstances, duststorms occured in the northern flow of Earth's surface. However, a trough of low contours in 500 hPa was effective in enhancing convection and storm intensification. The ranging 0.2 to 0.6 Pa/s of downward vertical component of wind speed at a level of 925 hPa is suitable to control dust concentration near the surface of the Earth.The effect of the friction force on the Earth's surface, which causes the dust, doesn’t move completely along the North-South direction and expand in the region horizontally. Northwest winds (Shamal wind) more than 25 kt at 925 hPa results in continued dust transportation to Iran. With the formation of a low level jet stream, the strengthening and development of duststorms is more likely. The output of the HYSPLIT model was as good as predicting the path of the particle in the direction of the northwest winds, and the output of the DREAM model showed a sharp decrease in horizontal visibility. By comparing horizontal visibility in Ahwaz and Abadan, as well as studying the output of the HYSPLIT model, it can be seen that local dwarfs are also formed in Ahwaz, which, in addition to the source of dust, can also be considered domestic sources.

Polycyclic aromatic hydrocarbons (PAHs) are classified as an important category of semi-volatile and persistent organic pollutants. They cause environmental problems due to their toxicity and accumulation in sediments. In this research, offshore sediments of 19 stations in 8 transects of the Persian Gulf in Bushehr province were studied to assess the sources of PAHs. The extraction and clean up method were based on pressurized liquid extraction (PLE) with the cleanup by packed silica gel-based column. The compounds were analyzed by GC-MS. Recovery of the compounds was over 70%. The range of total 15 PAHs in sediment was from 6.5 to 35.5 ng g-1 sediment dry weight. The results showed that the levels of PAHs in the sediments were in the category of low pollution sediments. The highest concentrations of PAHs have been recorded in the station number 4 and 15 near the Kharg Island (Abouzar oil field) and Golshan oilfield, respectively. The cross plots of the diagnostic ratios of PAHs have come into common use as a tool for identifying and assessing pollution emission sources. Three cross-plots for the diagnostic ratios were applied in this study. They showed that the PAHs in the area had mixed sources of pyrogenic and pyrolytic. A progressive increase in the levels of PAHs was observed compared to the ROPME Cruise in 2006 that reflected more impact of anthropogenic activities on the sediments in recent years.