Journal of Oceanography
Year:2018 | Volume:9 | Issue:35 |Papers Count:9

The Caspian Sea is sensitive to anthropogenic impacts as it is isolated from other seas. The environmental pollutions significantly increased in the last years. The impact of fish cage culture on the phytoplankton community was studied at 3 stations near the cage and 3 control stations in the southern Caspian Sea during January and April 2013. A total of 19 phytoplankton taxa belonging to diatoms (12 species), chlorophytes (2 species), cyanophytes (2 species), and dinoflagellates (3 species) were identified in the study area. The diatoms abundance was dominated (with 86% total abundance). The finding showed that the abundance of exotic species as diatoms Pseudosolenia calcar-avis and Pseudo-nitzschia seriata were dominated in the stations beside the fish cage culture comparing with the control stations. The PCA analysis confirmed significant difference between abundance of phytoplankton in the stations near the fish cage culture and the control stations. Furthermore, CCA analysis confirmed that there were strong relationship between diatoms, cyanophytes and nutrients levels (r = 0. 82). The reason for high phytoplankton abundance and exotic species in the fish cage culture stations could be related to the high nutrients concentrations due to fish nutrition and fecal. This study was performed during a short period, so the effect of fish cage culture on the Caspian Sea ecosystem should be taken into account in the future studies.

This research aimed to show different reactions of Callista umbonella in the oxidative stress caused by hydrocarbon pollution in sediments with different grain size. Regarding the differences in Porosity, Permeability and Penetrability in sandy shores, the grain size is an important factor that changes the severity of pollution caused by oxidative stress. In this research, we investigated the total length size of bivalve shell and values of antioxidant enzymes (GPx, GR, SOD and CAT) in soft tissue of C. umbonella in shores of three industrial sites (Site 1, Site 2 and site 5) and two control sites (site 3, site 4). Collected samples fixed rapidly in liquid nitrogen. The enzymes were extracted using perpendicular force and measured by spectrophotometry analysis. The values of SOD and CAT showed a positive and significant correlation (P˂ 0. 05) as well as GR and GPx during the research. With average of 47. 08 (± 4. 7) mm, Site 4 showed largest sample records in length size (± SD) but samples records on Site 1 with average length (± SD), 37. 72 (± 3. 9) mm were in minimum scale. The results showed that metabolic reaction of C. umbonella, for controlling the oxidative stress of being exposed to the pollution in sediments with higher porosity was decreasing the metabolism, while the reaction in sediment with higher permeability was vice versa. Finally, according to the results, C. umbonella showed better growth in clean sediments with the high porosity.

The shoreline situation is influenced by sea level changes, erosion and sedimentation processes. Its displacement has overshadowed human life and coastal facilities. The purpose of this study was to measure and compare the shoreline changes in the Gorganrood delta and Sefidrood delta by the Digital Shoreline Analysis System (DSAS). In this study, in order to extract the shoreline, Landsat imageries for the years 1986, 2000, and 2015 were used and shoreline changes at intervals of 50 meters were measured. The results showed that the effect of sea level changes on displacement of shoreline was not the same in both of studied areas. During this 30-year period, the total rate of changes was estimated in Gorganrood delta and Sefidrood delta as 104. 85 and-2. 1 meters/year respectively. In fact, the Gorganrood delta had shown remarkable retrogression and the Sefidrood delta had shown little changes.

In this study, the solitary wave was used to simulate shallow water wave. The Smooth Particle Hydrodynamics (SPH), that is a mesh-free Lagrangian method, has been used frequently to simulate nonlinear and free surface problem. The purpose of this study was to investigate the effect of solitary wave run-up on nonlinear beach slope in comparison with its linear state by SPH method. Also, solitary wave hydrodynamic characteristics were investigated at different time intervals. The results showed that the error of the presented SPH method in comparing with the experimental data was about 3. 5%. Therefore, the proposed SPH method had a good agreement with experimental data. The results showed that the ratio of solitary wave run-up on nonlinear slope to linear slope (Runonlinear/Rulinear) decreased nonlinearly with increasing power or slope beach. Finally, a new formulation was proposed for determining the solitary wave run-up from nonlinear slopes to linear beach slopes.

The purpose of this study is to investigate interpolation methods for estimating and rehabilitating climate data. Due to the fact that two factors of rainfall and temperature are known as the most effective parameters in many applied decisions and in many studies of land physics, agriculture, hydrology, etc., climatic data are used. But climatic data are not always available at all intervals, or researchers need weather data to predict climatic conditions. In these cases, different interpolation methods are used. Therefore, in this research, existing methods for interpolation of climatic data in Ramsar, Babolsar and Bandar Anzali synoptic stations in period of 1951-2017 were evaluated. The results of the research indicated that the Neville and Spline interpolations provided a more accurate approximation for all studied stations. Other findings of the study were that temperature interpolation for the months of the summer season was less than the winter. There was also no significant difference between interpolations for different stations.

In the present study, the Aden Gulf water masses have been detected using a concentration passive tracer with the MITgcm model. The modeling domain is in the range 0. 5° N-30° N, 44° E-77° E. The initial data (Temperature, salinity, wind, net heat flux, evaporation and precipitation) is appropriate to the model and modeling has been run for 20 years. Comparing the results of the model with the measured data shows a good agreement. The results of modeling indicate that there are three water masses up to 900 meters deep (modeled depth) in the Gulf of Aden. The Aden Gulf surface water mass is to the depth of 100-200 meters with a maximum salinity of 37 psu and density of 1023-1024 kg/m3. The water mass of the Aden Gulf's intermediate layers with the salinity of 35. 9 to 36. 9 psu and density of 1024-1026 kg/m3 at a depth of 100-600 m and deep water mass with salinity of 35. 9-36. 9 psu and density 1026-1027. 5 kg/m3 located at depths of 400-900 meters and below. The horizontal density gradient due to salinity changes between the deep salty water and the low salty water of the Gulf of Aden leads to the creation of baroclinic instability. The calculation of the density ratio represents the establishment of a thermohaline convective regime between the Gulf of Aden water masses. The results of the release of passive tracer with a concentration of 100% in the Gulf of Aden from surface to depth also confirm the existence of three water masses. The surface plume spread to the length of the 46° E after 270 days under the influence surface currents of the Gulf of Aden. The output of plume at depths of 200 and 400 meters in two northern and southern channels extended to 47° E after 270 days in the Gulf of Aden. The critical width of the deep water flow for separation from the coastal boundary was calculated, by calculating the radius of Rossby deformation, as 30. 25 km in the winter and 50. 4 km in the summer.

The objective of the present work was to investigate the removal of cadmium by red algae Gracilaria as biomass. The effect of independent variables on biosorption of cadmium ion by the red algae Gracilaria as biomass was evaluated. The experimental data were analyzed via two custom isotherm models, i. e., Langmuir and Freundlich. The experimental design was developed for evaluating the interactions of pH, contact time, temperature, biomass dosage and initial metal concentration. The Box-Behnken model in response surface modeling was used for the optimization of the experimental data in Minitab 18 software. The five parameters were fitted into second order polynomial equation and a mathematical function was developed. Statistical significance of coefficients in the second order polynomial equation was evaluated by t-test and p-value. The optimum conditions were determined at pH of 8, initial cadmium concentration of 50 mg/L, temperature of 30 ℃ , the biomass dosage of 5 mg, and of contact time of 40 minutes. In these conditions, the calculated value (68. 878 mg/g) was matched very well to the experimental value (68. 256 mg/g). The modified equation can be used for the prediction of biosorption in any conditions.

The present study aimed to investigate the histological structure of testis as an important organ of the reproductionon and survival in the male blue swimming crab Portunus segnis in the Persian Gulf. In this regard, 20 male blue swimming crabs with average weight of 229. 09± 15. 17 gr caught from the coasts of Hendijan in Khuzestan Province from September to June, 2016. After anesthesia and morphological examination, samples were stained with Hematoxylin and Eosin method. Based on the results, testis was surrounded by connective tissue. The connective tissue lamellae divide testicular parenchyma into a number of specific lobules. Testis lobules have a Germinal Zone and a Transformation Zone. Vas deferens has anterior, medial and posterior portions. The three portions of vas deferens are surrounded externally by connective tissue and internally by cuboidal and culomnar epithelium. Spermatophores with circular to oval shapes of various sizes were observed in all three portions of vas deferens. Averages diameter of spermatophores were measured 167. 64± 26. 38 µ m.