Journal of Oceanography
Year:2018 | Volume:9 | Issue:34 |Papers Count:8

In this study, the laboratory observations were accomplished for 36 random and irregular waves initiated according to the JONSWAP spectrum to study the impotance of energy transition to low and high frequency harmonics due to wave breaking in the outer surf-zone. The wave transformation was investigated using two trinary groups of pressure sensors at the beginning and end of ramp with the slope of 1: 16. The maximum observed transferred energy due to wave breaking was about 22% of dissipated energy which was equal to 9% of total energy of the primary wave. In this manner, the prediced significant broken wave height was 8% underestimated using phased avraged wave models. The observations indicated the fraction of dissipated energy, which was transferred to low and high frequencies growth with increment of primary wave Ursell parameter at the initial depth.

In this study, the status of coral coverage and coral reef health were investigated in Kharg and Kharko islands. The line Intercept Transect (LIT) method was used to estimate the coral coverage. The coral health status was assessed by condition and development index. The human activities, including fishing and coastal construction, were also studied. The result showed that the coral coverage in Kharg Island (64%-77%) was better than Kharko (48%-62%) and also coral health index in Kharg Island were better than Kharko Island, but more human activities were recorded. Also, the dominance of resistant species in Kharg Island showed that in this Island, coral reefs were exposed to more human threats which can destroy corals.

The purpose of this study was to investigate the effect of effective factors on port's performance. Survey method, field study and interview with managers and active experts in the port area were used to collect data. In order to conduct the research, first, the factors affecting the performance of ports were identified and then, by examining the correlation between these variables, the main components for entering the data into the regression model were determined. The results showed that the variables; type and number of input vessels, average hours (presence, waiting and service), investment and port facilities had the greatest impact on port performance. Therefore, port officials need to focus on these variables, so that they can improve the performance of ports.

The present study was to evaluate the effect of soybean lecithin on some immunological parameters (Lysozyme, ACH50 and Total antibody), hematological and serological parameters, and liver antioxidant enzymes activity of Salmo trutta caspius. For this purpose, 90 fish (350g ± 10) were randomly divided into three treatments with three respective replicates. The first group (control) was fed only with commercial feed, while the second group was fed with diet supplemented with 12% soybean oil, and the third one received feed supplemented with 6% soybean oil and 6% soybean lecithin for 90 days. In treatments 2 and 3, immunological, glutathione S transferase and superoxide dismutase activities and some biochemical parameters (LDL, HDL and Cholesterol), except VLDL and triglyceride, were significantly higher than in the control treatment (P<0. 05). VLDL of treatment 1 was significantly higher than that of treatments 2 and 3 (those fish received soybean oil and/or lecithin). Hematological indices of treatment 2 including RBC, Hb and Hct, and Hct and WBC of treatment 3 were significantly different from treatment 1 (P<0. 05). In conclusion, addition of 6% soybean lecithin as a supplementary feed to the diet of Caspian Sea salmon (Salmo trutt caspius) is suggested due to its ameliorative effects on physiological indices.

Extreme rainfalls of 13 synoptic stations located in the southern coast of the Caspian Sea were investigated using two approaches of Extreme Value Analysis Theory, including Generalized Extreme Value Distribution (GEVD) and Generalized Pareto Distribution (GPD) during the period of 1957-2016. The distribution parameters were calculated using maximum likelihood and generalized maximum likelihood estimation. Return level of extreme precipitation were calculated in each station at 95% confidence level based on the return periods of 2, 5, 10, 20 and 100 years. The stationarity of the extreme values at each station was examined using the Mann-Kendall trend test before estimating the return levels. Results of the trend test showed that extreme rainfall of Anzali synoptic station according to the Block Maxima approach, as well as Ramsar and Maraveh-Tappeh stations based on the Peak over threshold approach, were considered to be non-stationary with P-values of 0. 04, 0. 03 and 0. 03 respectively. The models comparison performed using graphical methods as well as the Akaike information criterion (AIC). It was found that the block maxima approach based on the maximum likelihood estimation was more suitable for most of the stations in the region. Rasht, Anzali, Astara, Noshahr, Ramsar and Gorgan stations provided better results with a longer time series, especially based on graphical tests. Results showed that, despite the uncertainty, the extreme rainfalls at the stations of Anzali, Ramsar and Babolsar would increase at a higher rate than other stations in the region. This trend in Rasht, Sari and Manjil stations would likely increase in the future, although at a slower rate.

The purpose of this study was to design and develop a three-dimensional numerical model using primitive equations in spherical coordinates of the Earth with the Sigma pressure vertical array to simulate currents in the Caspian Sea. In this study, the finite difference method was used for numerical solution and discretization of equations using the two step Lax-Wendroff scheme for advection terms and DuFort-Frankel scheme for diffusion terms. The results of the study showed that the clockwise eddy in the middle and the counterclockwise alongshore current near the western coast of the southern Caspian Sea continued throughout the year. Furthermore, due to the steeper slope of the bed in this basin, it is more stable than the currents pattern in the North and Middle basins of the Caspian Sea. Also, the divergence of the current in the surface Ekman layer is balanced by the convergence of current in the bottom Ekman layer in the middle and southern basins of the Caspian Sea, which indicates that the bed topography beside the wind plays a key role in the production and steering of the currents in the Caspian Sea.

Dinoflagellates are one of the main groups of phytoplankton and have two forms of autotrophic and heterotrophic in marine ecosystem. In this paper, the sediment samples were collected using Ekman Grab 225 cm2. The cyst samples were identified and counted by invert microscope. Diversity and abundance of dinoflagellates cysts in recent sediments of the southern coast of Iran in winter and spring 2014 were studied. Totally, 25 species of dinoflagellate belonging to the 9 genera were identified. Protoperidinium (51. 53%) and Scrippsiella (15. 16%) had the highest abundance and Zygabikodinium (0. 67%) had the lowest abundance. ANOVA results showed that dinoflagellate cysts abundance were significantly different among stations (P>0. 05) and showed no significant difference between the two seasons (P<0. 05). Physical and chemical characteristics of the sediment and water column were also measured. The result showed that the type of sediments and organic matters had a positive correlation. But other environmental factors such as temperature, salinity, pH and depth showed negative correlation. The Gwatar station with the smallest grain size (clay) and highest total of organic matter (5. 24) had the highest frequency of the 510 cyst. 10g. Also, values of diversity and richness of Gowater stations were 4. 32 and 2. 47 that were higher than other stations. In total, the results of this study showed that the diversity and abundance of dinoflagellate cysts were affected by the sediment type and the amount of organic matter.