Journal of Oceanography
Year:2020 | Volume:11 | Issue:40|Papers Count:13

A quality index method scheme for Goldlined seabream Rhabdosargus sarba stored at refrigerator was developed and its efficiency for freshness evaluation was compared with colorimeter, microbial and physicochemical methods. The quality index method results indicated a shelf life of 9 days. Physicochemical (TVBN, pH, TBARS and FFA) microbiological (mesophilic, psychrophilic and Enterobacteriaceae) and sensory analysis were carried out at 0, 3, 6, 9 and 12 days of storage. Variations in TVBN, pH, TBARS and FFA were observed throughout the storage period. Sensory analysis attributes exhibited significant variations and correlations with time storage, which is a showing of the fish´ loss of freshness. QI showed a linear relationship to storage time (QIM= 8. 23× storage time-7. 23, R2= 0. 988), and the shelf life of Goldlined seabream could be estimated with an accuracy of ± 3 days. A regression analysis using the acceptability limit mesophilic counts (7 log cfu/g) showed that shelf life for Goldlined seabream Rhabdosargus sarba stored at refrigerator was 9 days. TVBN, pH, TBARS, microbiology, color and sensory analysis displayed very strong correlations with storage time, and they may be considered suitable indicators for evaluating of shelf life of Goldlined seabream stored at refrigerator.

The aim of this study was to investigate the histopathologic changes of spleen tissues as biomarkers for assessing the health of common Pomadasys kaakan and Lutjanus johnii. In this research, 9 pieces of Pomadasys kaakan with a mean length 35. 54 ± 4. 35 cm and a mean weight of 512. 6 ± 58. 5 grams and 9 pieces of Lutjanus johnii with an average length of 22. 5 ± 3. 41 cm and mean weight 205. 6 ± 22 grams of Ramin, Haft Tir and Konarak stations were caught using by gillnet. In order to observe the severity of tissue lesions, spleen tissue was separated and fixed in Bouin's solution. The tissue samples were prepared for histological studies according to standard histology methods, dehydration, clarification, parafinization. Then they were prepared by microtome cutting device with transverse sections of 5 microns thickness. After staining with hematoxylin-eosin, it was examined by a light microscope equipped with a digital photographic Camera. Results showed lesions in the spleen tissue such as melanomacrophage aggregations, blood vessel dilatation, vacuolation, necrosis, cell density, white pulp, plasma cells dilution. Lowest lesions in the spleen tissue of Pomadasys kaakan and Lutjanus johnii were observed at Ramin and Konarak stations. In the other hand, the highest lesions in the spleen tissue of both fish were recorded at Hatf Tir station. Which can be explained by the close vicinity of the station and the proximity of two Shahid Kalantari and Shahid Beheshti docks and high levels traffic of flotation.

The purpose of this study is to obtain the base shear force and overturning moment of the jacket at the three wave heights of 20, 23 and 28 cm. In this regard, the model of the jacket structure is constructed at a height of 4. 55 meters, 402 meters in length and 4 meters in depth of water, exposed to random waves of the sea and is subjected to the JONSWAP spectrum in the flume of Fars National Marine Laboratory (NIMALA). Based on the results obtained, in all examinations, deep water conditions prevail. Considering the effective wave, for the wave height decreases from 28 to 23 cm, 14. 17%, 23 to 20 cm, 52. 9%, 28 to 20 cm, 74. 57%, reduction of the base shear; and for the decrease of wave height reduction from 28 to 23 cm, 33. 79%, 23 to 20 cm, 17. 06%, 28 to 20 cm, and 56. 63%, overturning moment reduction were obvious.

This paper presents the assessment of effect of climate change on surface temperature of the Persian Gulf, using MIKE three-dimensional numerical model. Parameters such as air temperature, relative humidity, wind speed components, precipitation rate and the sky transparency have been utilized for hydrodynamics simulation of the region. ECMWF data in the Persian Gulf for the period of (1980-2000) and downscaled CORDEX data in RCP 8. 5 scenario for the period of (2080-2100), have been implemented to the model. The effect of the climate change on sea surface temperature was evaluated by studying the differences between the average patterns in years 1980-2000 and 2080-2100. The results demonstrate that surface temperature in future; will increase in all seasons. This increment becomes smaller towards the deeper parts of the region. Based on conducted numerical modeling results, it is predicted that the water temperature in future climate, will have the highest increment in summer with the value of 4. 6 ° C. Spring will have the lowest increment with the value of 3. 5° C. It is also predicted that the average sea surface temperature in the Persian Gulf will increase about 4. 1 ° C in autumn and 3. 8° C in winter.

Conservation and exploitation of the genetic resources of non-national maritime areas need to a legal structure that has not been foreseen at the time of the adoption of the Convention on the Law of the Sea. The Convention on Biological Diversity Considers Marine Genetic Resources in the Territory of States Parties, While the Convention on the Law of the Sea does not provide for the exploration of genetic resources of the Free Seas and the Area. This paper seeks to analyze the role of the Convention on Biological Diversity and the Convention on the Law of the Sea in shaping the future legal structure and exploiting deep sea genetic resources. The results of this research show that identification of genetic resources in the Convention on Biological Diversity from one side and identifying the common heritage of humankind beings in the Convention on the Law of the Sea, on the other hand, can be used to provide a model for the establishment and approval of a proposed biodiversity implement agreement in areas beyond national jurisdiction.

Temperature is one of the important factors influencing the growth and reproduction of aquatic animals. In this research, the effect of temperature on fertilization indices and stress response of rainbow trout was investigated. Two treatments of temperature, 14. 5 and 17. 2° C in three replications were considered. Rainbow trout eggs (average weight of 81. 30 ± 1. 91 mg) with a density of 5000 eggs were stocked per each trough and were exposed to different temperatures until hatching stage. According to the results, it was found that the duration of eyed and hatching stages was shortened with increasing the temperature, and also the percentage of hatching and active swimming decreased. The values of 32. 66% and 30% were obtained for hatching and active larvae, respectively, at 17. 2 ° C, which showed significant difference with another treatment. Responses to the stress of temperature in the early stages of the egg were not noticeable, but the effect of stress on embryos grown at various temperatures caused differences in the response of cortisol to stress at the hatchery stage, which led to an increase in the cortisol level at hatching compared to eyed-stage. When the fish are exposed to stress in the embryonic period, the delayed response of cortisol to stress does not occur immediately after hatching. Finally, the results indicate that the hypothalamus-pituitary-Inter renal (HPI) axis is activated at the hatching stage and responds to environmental stresses (as temperature).

Distribution and ecological preferences of aquatic organisms have often not been studied. Species Distribution Modeling can improve our knowledge and enhance the ecosystem management and protection. This study conducted in 2017 with the objective of predicting the potential suitable habitat for Avicennia marina and the most important environmental factors influencing its distribution. Mangroves as the world's valuable habitats with high biomass and productivity, play an important role for fauna and flora both land and sea, providing shelter, nursing and feeding grounds. In this study, 9 biochemical variables from Bio-ORACLE database were compiled. The correlation coefficient between each pair of variables was calculated to identify highly correlated variables and reduce multicollinearity. Finally, the distribution model was produced with MaxEnt. Results show that suitable habitats for mangrove distribution have placed in the Eastern part of the Persian Gulf and the Oman Sea. Moreover, Chlorophyll-a minimum range, summaximum and pH were found to be the top variables affecting the distribution. Results can be used in a decision-making framework that helps conservation outcomes deliver as a result of managers’ strategy.

Sea surface wind speed and direction data with high spatial and temporal resolution is essential to having realistic perception and being able to forecast Air-Sea interaction. Lack of enough field measurements over the Persian Gulf has been always a serious issue in meteorological studies over this area. The object of this study is to determine the mean wind field over the Persian Gulf and find out the trend of the wind in this area. To do so, three data sets including: buoy and synoptic observed data, ERA-Interim reanalysis data and blending satellite retrieved data (from NCDC-BSW) are used for long-term analysis of surface wind field over the Persian Gulf. After a comparison of in-situ observation data with estimations performed by the reanalysis model and satellite data and verification of these datasets, wind fields were extracted using satellite and reanalysis data and the long-term wind trend was retrieved from 1988 to 2010 for 23 years. Results illustrate a relative increase in the wind speed estimated from reanalysis data and a relative decrease in the wind speed estimated from satellite data. Considering everything, it could be concluded that the satellite data has had better performance in estimating wind speed. So that, long-term investigation of the increase-decrease trend in wind speed at divergent stations indicate an effect of summer and winter Shamal on the maximum and minimum wind speed and regime, that were estimated in the Persian Gulf region. Considering this effect, the highest winds in winter occur near Bushehr area while the maximum winds in summer are seen in lower latitudes and near the center of the Persian Gulf.

Hydrodynamic models are widely used for simulating water level and oceanic current; however due to uncertainties involved in this process such as accuracy of input data or realization of the governing equations, there are some errors in the simulation results. Data assimilation is one of the effective solutions to avoid and to limit some of these errors. This manuscript evaluates how Ensemble Kalman filter, one of the most advance assimilation techniques, can enhance water elevation predictions in the Persian Gulf. The open source Delft3D FM was used as a hydrodynamic model and open source code of Open DA was employed to apply Kalman Filter. The Open DA was coupled inside the code of hydrodynamic model to improve its performance. We have setup several experiments to estimate the best number of groups, error parameter of observations, error parameter of open boundary, and the most effective station for assimilation. The results show that the data assimilation can effectively improve the hydrodynamic model results and can be used for real applications.

The purpose of this study is to survey the ecological health of mangrove forest in Nayband bay by Shannon diversity index and determine the environmental factors effective in distribution of macrobenthic. 6 transects along coasts of Nayband bay were sampled for macrobenthos identification and enumeration. In each transect 3 stations were selected in perpendicular line to the beach. Physicochemical parameters such as Temperature, Salinity, Turbidity, Phosphate, Nitrate, Chlorophyll etc. were measured in addition to sediment grain size and TOM. Totally 60 macrobenthos species identified. Gastropods and Bivalves in Mollusca phylum were the dominant group with the contribution 48% of total macrobenthos population. Pirenella cingulata and Protapes gallus were the dominant species in Gastropods and Bivalves respectively. Maximum average total numbers of benthos were 5361. 56 and 5584. 78 individual/m2 in winter and summer respectively and minimum average number was 1957. 56 individual/m2 in spring. Parametric statistical tests showed significant difference between number and frequency of species in different seasons and station (p<0. 05). CCA analysis showed that salinity, turbidity and TOM are an effective factors in distribution of crustacean and bivalves. Phosphate, silt & clay and chlorophyll a have positive impact and sand present and temperature have negative impact on distribution of Gastropods. Temperature is important factor on density of polychaetes. Shannon diversity index showed that the studied area is moderate in terms of biological health.

Determination of total amount of sediment metals can be used as a measure of pollution in the area, but it alone cannot show the mobility potential, toxicity, and availability of various metal compounds in the sediment. In this research, a five-stage sequential extraction process was used to extract various compounds of iron, copper and lead from sediments. Eighteen samples were collected from different stations in Musa estuary, Persian Gulf, including Majidiyeh, Ghazaleh, Ja'fari, Musa, Merimous, and Ghanam. After drying and homogenization, 1. 0 g of each sediment was extracted with the help of selective reagents within a given temperature and time. After each extraction, the specimen was exposed to subsequent extractions to complete all five steps. The amount of metals ions in separated solutions were measured by an atomic absorption instrument. The results showed that most of the metals were in the reducible oxides and residual sections. The highest amount of copper compounds in the exchangeable portion was related to Majidiyeh (5. 3%), and for the lead was related to Ja'fari (19. 6%). Therefore, it can be said that the mobility potential of copper and lead ions in Majidiyeh and Ja'fari stations, which are under the influence of industrial and urban activities, is higher than the rest. Comparison of the average distribution of copper and lead compounds in the sediments of Musa estuary with the rest of the world showed that although the distribution pattern of metal compounds is quite similar, the amount of these compounds in sediments is significantly less than the other compared regions.