فهرست مطالب

  • Volume:7 Issue:24, 2017
  • تاریخ انتشار: 1396/05/14
  • تعداد عناوین: 6
|
  • Hamid Rezai*, Seid Ali Mohtarami, Hammed Dehghani, Parviz Tavakoli, Hamid Reza Bargahi, Keivan Kabiri Pages 1-8

    Field studies were conducted in a number of intertidal and offshore islands in the Persian Gulf between 2006 to 2013. SCUBA and skin diving surveys were conducted around Larak, Hormuz, Qeshm, Hengam, Farur, Kish, Lavan, Khark and Farsi islands in the northern region of the Persian Gulf. Marine invertebrates including nudibranchs were photographed up to 32 m. Several species of nudibranchs are reported from the northern region of the Persian Gulf, over the Iranian side. In total, 32 genera of nudibranchs are recorded, which include Fryeria rüeppelii, Haminoea sp., Chromodoris annulata, Gymnodoris rubropapulosa, Cuthona yamasui, Hypselodoris maridadilus, Glossodoris pallida, Glossodoris sp., Asteronotus cespitosus, Marioniopsis viridescens, Stylocheilus striatus, Jorunna funebris and Elysia sp. were recorded from several Iranian Island in the Persian Gulf. The most common species was Chromodoris annulata throughout most of the surveyed islands, but Haminoea sp. was highly abundant and conspicuous species only in Farsi Island. Except for G. pallida, Glossodoris sp. and C. annulata, all the above species are considered new records for the northern region of the Persian Gulf, but Bursatella leachii, M. viridescens, Phestilla lugubris, Discodoris lilacina and Haminoea sp. are new records from the Persian Gulf proper. An increase in several new records to the Iranian fauna and new records of rare species, in relatively few years results mainly from sampling effort and contributions by specialists on samples of poorly known sampled areas. Prospects for finding new and more species are promising given more diving operations are carried out.

    Keywords: Nudibranchs, SCUBA, Underwater photography, Islands, Diversity, Persian Gulf
  • Maziar Khosravi*, Vahid Chegini, Seyed Mostafa Siadat Mosavi, Ross Vennell Pages 9-18

    Thirteen repetitions of a cross-channel transect in the Khuran Channel within the Strait of Hormuz allowed the description of the mean flow and semidiurnal tidal properties of a northsouth transect. Water velocity profiles were obtained with a 614.4 kHz TRDI Work Horse Broadband ADCP along this 3.3 km long transect on 10 October 2014, the third day of secondary spring tide. The M2, M4 and M6 frequencies were separated from the observed current using sinusoidal least squares regression analysis. The semidiurnal tidal currents along this transect exhibited typical amplitudes of 160-170cm/s, decreasing toward coastal waters. The mean flow which confirmed the occurrence of asymmetry between ebb and flood phase of tidal current in Khuran Channel were ebb dominant in the deeper part of the channel and southern slopes and flood dominant over the shallower areas, with greatest magnitudes (10 cm/s) near the surface mainly in the deeper parts of the northern side of the channel. The tidal current amplitudes decreased and for the most with depth and followed the bathymetry particularly in the middle of channel, which reveals the dominants of frictional forces. The large overtide amplitude is as a result of nonlinearities that were produced by increased frictional effects that lead to the asymmetry between ebb and flood phase of tidal current in this channel.

    Keywords: Khuran Channel, Strait of Hormuz, Tidal Currents, Persian Gulf
  • Mohammad Akbarinasab* Pages 19-28

    In this study, measured hydrophysical data collected by the University of Miami researchers from the southern part of the Strait of Hormuz during the period December 1996 to March 1998 and climate data from the Qeshm island meteorological station were used to simulate water column turbulence south of the Qeshm Island, via General Ocean Turbulence Model (GOTM). The model does not use slip and fluxes as a bottom boundary condition. Therefore, the model's vertical domain was chosen so that the bottom does not influence the upper boundary layer simulation. The vertical domain considered for simulation is from z = 0 m, at the surface, to z = -110 m, in an equally spaced Cartesian grid of 1 meter. The time laps were three hours. The simulation results showed different seasonal turbulent kinetic energy (TKE) and thus, different penetration depths. In the cold season, TKE extends from the surface to bottom, but is restricted to the upper depths of thermocline layer. In addition, results show that the TKE is similar to the buoyancy frequency (N).

    Keywords: Turbulent kinetic energy, Model GOTM, Strait of Hormuz, Buoyancy frequency
  • Leila Samadi*, Nasim Zanguee, Seyed Mohammad Mousavi, Mohammad Zakeri Pages 29-42

    In this study, Effects of garlic (Allium sativum) extract on growth indices and hemolymph parameters of Litopenaeus vannamei with mean weight 18.21±0.29 g were studied for a period of 56 days. This study was conducted inside 300-liter polyethylene containers as four treatments each with four replicates and each replicate testing 5 shrimps. A basic diet supplemented by 0 (control), 40, 80 and 100 ppm of garlic extract was provided for shrimps. Shrimp biometry was performed at the end of experiment and hemolymph was collected by 2ml syringe. The results showed that garlic extract positively affected daily feed intake, feed conversion efficiency, protein efficiency ratio, molting rate (P<0.05), but no significant change in weight gain rate, specific growth rate, condition factor and hepatosomatic index (P>0.05). Also, treated showed significant changes in body protein (increased levels), fat and ash composition (decreased levels) compared with control group (P<0.05). Total hemocytes count was not affected but differential hemocytes count and total plasma protein was significantly changed treated shrimps compared with control shrimps (P<0.05). Based on the results obtained from this study, garlic extract may be applied as a food supplementation in shrimp aquaculture.

    Keywords: Garlic extract, hemolymph, Growth, Litopenaeus vannamei
  • Omid Reza Safiyari, Babak Banijamali, Mahmood Reza Akbarpour * Pages 43-66

    Investigation of the waves generated by underwater disturbances gives precious insight into the effect of man-made underwater explosions as well as natural phenomena, such as underwater volcanoes or oceanic meteor impact. On the other hand, prediction of the effects of such waves on the coastal installations and structures is required for preparation worthwhile criteria for coastal engineers to prepare a reliable design. This study aimed to investigate the interactional effects of water waves generated by underwater disturbances on sea walls through numerical modeling using the Smoothed Particle Hydrodynamics (SPH) method. The simulation was performed using the Dual-SPHysics numerical code. Comparison of the numerical results with the experimental data extracted from case studies demonstrated the good capability of the SPH algorithm used in the numerical code in the simulation of initial wave generation by the underwater disturbance and its propagation over the body of water. To examine the wave force exerted on the walls, the results of laboratory experiences on the effect of tsunami waves on coastal structures were used to verify the numerical model. The study found that the phenomena with such nonlinear behavior can be very well simulated with a calibrated SPH model. We also explored the effects of this type of wave and temporal changes of its resultant force on the wall. In this article, the explosion-generated water wave produced much stronger fluctuations in the vicinity of the wall than did the solitary wave, thus naturally, it can be more destructive.

    Keywords: Wave generation, Seawall, Numerical modeling, Wave force, Underwaterexplosion, Smoothed Particle Hydrodynamics (SPH), Graphics Processing Unit (GPU)
  • Elaheh Owlad*, Parvin Ghafarian, Hasan Khaleghi, Parviz Irannejad Pages 67-84

    Currently, continuous measurements of wind speed and direction in the Persian Gulf Basin are limited to the locations of few fixed buoys. The main reason for doing this research was the lack of sufficient observations of surface wind data over the Persian Gulf Basin .Surface wind data are essential in maintenance of coastal structures, oil industry, transportation and fishery in the region. In this study, two sources of offshore wind speeds and directions including ERA-Interim reanalysis data with three resolutions (0.75, 0.25 and 0.125) and satellite data collected from National Climatic Data Center-Blended Sea Winds (NCDC-BSW) are compared against the corresponding verifying buoys observations. If gaps exist in buoys dataset, the nearest synoptic station data are used instead to generate relevant wind roses and distributions. Observed buoys data are obtained from three buoys located in different parts of the Persian Gulf‘s Northern Coast. Examining the observed buoys data show that the wind circulates from Northwest in Bushehr synoptic station to West in Asaluyeh and finally, to Southwest in Qeshm. This circulation that is also confirmed by sea level pressure and streamline maps could be associated to the effect of intense Shamal winds which blow most of the times during the year in the region. The results of comparison of the reanalyzed and satellite wind data against the corresponding buoys data showed that if the wind speeds in the reanalyzed and satellite wind data are in the range of 3.6-6.6 m/s, then lower RMSEs and also better correlations are calculated both for satellite and reanalyzed datasets. Generally, as the wind speeds deviate from their respective mean values then, the errors in both datasets will increase. Overall results for wind directions are much better. NCDC-BSW showed acceptable
    correlation and fine P values with observations collected by buoys, nevertheless, the results for reanalyzed datasets were not as satisfactory, and attempting different resolutions of this dataset did not improve the results significantly, as the main resolution of this data set is 0.75 and other resolutions are just retrieved by the interpolation of the original data.

    Keywords: sea surface wind, ERA Interim, NCDC-BSW, observation, buoy, Persian Gulf