فصلنامه اقیانوس شناسی
پیاپی 33 (بهار 1397)

One of the most important issues in river and coastal engineering is the estimation of sediment transport, which is determined in delta regions by river flow, wave, and longshore currents due to the waves breaking. This study aims to evaluate the dynamics of waves, current and trend of morphology and
coastline variation of Sefidroud River Delta. In the first section, wave, flow and sediment transport characteristics were simulated using the MIKE21 model and in the second section, the rate of delta coastline changes were obtained by processing satellite images of LandSat for the last decade. results indicated that the model had the capability to generate the actual pattern of waves, currents (with nRSME factor of 12.07 to 17.02%) and sediment transport in coastal areas, as well as sediment transport trend had a good agreement with that of satellite imagery processing. Compression of the results indicated that propagation of delta’s western and eastern coastline towards the coast and the northern coastline to the landward side stems from either seawater level reduction, or sediment transport. Therefore, recognizing morphological behavior of delta coasts and seawater level variation trend can provide required measures to manage and protect Sefidroud Delta’s coasts.

The aim of this study was to investigate the orientation and shell selection behavior of hermit crab Diogenes avarus under different photoperiod situations (6L: 18D, 12L: 12D, 18L: 6D) after 48 hours. The results showed that the light affected the orientation and shell selection behavior of hermit crab Diogenes avarus. This means that the orientation of the control group were uniform (P >0.05), but their orientation in different lighting regimes compared with control, were non-uniform (P0.05). However, by increasing the time of lighting 18L: 6D, hermit crab orientation toward the target was significantly decreased (P

The present research was performed to investigate the effects of anthropogenic perturbation on spatial variations of coral reef fish distribution and abundance on a coral reef area in the northern Persian Gulf. For this purpose, wintertime and summertime coral reef fish assemblages along with some environmental parameters were assessed at three different sites along a presumed anthropogenic disturbance gradient. Results indicated that the alterations in substrate rugosity and orthophosphate concentration could be responsible for spatial variations in family composition and fish assemblage structure in winter. On the other hand, live coral cover, total zooplankton density, and TDS were identified as the most important variables regulating spatial variability of fish assemblages in summer.

The purpose of the research was to detect the oil spill phenomena via the analysis of reflectance spectra of oil obtained from sentinel-2. The oil spill event from the South Pars Platform in the Persian Gulf on February 15, 2016 was investigated as the case study. All pre-processing steps including geometric and radiometric correction were done. Then, using the reflectance spectra of oil and OIF, the optional color combinations were detected. At the end, the oil spills were accurately detected by calculating the NDWI and the related thresholds. The results showed that more OIF did not mean more proper combination. In this regard, to enhance the detection precision, it is crucial to consider the optional combination by employing reflectance spectra behavior and effective indicatory.

Container dwell time is one of the main factors for evaluating performance of the seaports. The time a container spends in a port, prior to clearance is a real cost scenario that will affect the port performance and throughput at all parts of the port. The aim of this research is to provide an analytical tool to select the best strategy to reduce the container dwell time at ports. For collecting data, historical studies, together with a technical questionare, field studies and expedrts opinions were collected. Hence. Three main strategies have been developed and the Fuzzy Analytic Hierarchy Process was used to compare and analyse these strategies.The numbers used in the fuzzy matrices for evaluating the factors have been obtained from customers and experts in the maritime transport industry of Iran. Investigations showed that three factors including Operation of Costume, Role of Cargo Owners in Clearance of Goods, and Transport Systems with sequence of relative weights of 0.44, 0.39 and 0.17 had the most effective impact on container dwell time in Iranian ports. The study evidenced that the three main strategies including Penalty for Cargo Owners, Decentralization of Ports and Development of Customs with sequential relative weights of 0.38, 0.33 and 0.29, which had been obtained according to the viewpoint of experts, were the most important factors, respectively in this process. Reduction of container dwell time is considered as productivity criteria in ports. Therefore, port managers should pay special attention to include this criterion in their decision making.

The aim of this study was to find the angle and velocity of discharge of brine sewage into the marine ambient to prevent its environmental hazards. For this purpose, in this paper, a series of tests have been conducted on inclined negative buoyant jets with angles of 30, 45 and 60 degrees and different discharge rates. The main properties of the flow are determined by processing the image obtained from the color detector in the brine sewage. The results show that increasing discharge velocity does not affect the pattern of the distribution of concentration at the highest elevation of the center line, and this profile is independent of the flow velocity, but increasing the discharge velocity increases the path length and increases the dilution. Angle variations, in spite of changes in velocity affect the concentration distribution profile pattern at the highest elevation of the center line and increase the width of the current plume and the most evolution and dilution occurs at the 60° angle.

In this research, the histophysiology of the renal apical part as a lymphoid organ and structure of blood safety in the Persian sturgeon, Acipenser persicus in two cold and hot seasons were studied. For this purpose, 10 healthy Persian sturgeons with same size were taken from pools with water temperature of 7.30 and 27.90 °C in winter and summer. 0.5 centimeter samples of head of kidney were taken and prepared with standard methods. After blood sampling, white blood cells and immunity, including lysozyme and complement, were studied. Results showed that in the differential count of white blood cells, lymphocytes had highest percentage and density in both cold and warm seasons, with a significant difference (P