فصلنامه اقیانوس شناسی
پیاپی 36 (زمستان 1397)

This research has been conducted to simulate the wind and wave pattern due to the winter Shamal Wind. This wind is a local systematic wind with the duration of 3 to 7 days which normally occurs in cold months of December to March. COWAST modelling has been adapted to simulate wave pattern. This software is used to couple WRF and SWAN models. For model calibration buoy data located in coastal area of Bushehr, statistical wind data from ECMWF and those data from synoptic station of Bushehr has been adapted. Those results derived from the coupled model showed that maximum wave height during the winter Shamal wind was about 1.1 m higher than that before bellowing the wind. It was also observed that those results derived from the coupled model show reasonable agreement with field data. The bias for significant wave height, wave period, and wave direction were calculated as 0.1, 0.64, and 11.03 respectively.

The formation of mycotoxins in feedstuffs is a worldwide issue affecting digestive physiology of aquatic animals and resulting in lower animal performance. Total of 540 rainbow trout with an average body weight of 3±0.2 g were allotted to 9 distinct treatments including various dietary levels of aflatoxin B1 (0, 25 and 50 ppb) and zearalenone (0, 200 and 400 ppb) for 4 weeks. At the end of the trial, pyloric ceaca samples were taken for determining alkaline protease, lipase and amylase activity. Results revealed that feeding on diets contaminated with aflatoxin B1 and zearalenone for 4 weeks did not significantly affect alkaline protease activity (p<0.05), however, did significantly affect lipase and amylase activity of rainbow trout fingerlings (p<0.05). The highest lipase activity was recorded in control group (feeding on diet devoid of any mycotoxins) and treatment co-contaminated with containing 25 ppb aflatoxin B1 or 200 ppb zearalenone. However, the lowest lipase activity belonged to treatments contaminated with only 400 ppb zearalenone or 25 ppb aflatoxin B1. The highest amylase activity was assayed in group fed on diet without any mycotoxin contamination in comparison to those fed diet contaminated with any levels (25 or 50 ppb) of aflatoxin B1 (p<0.05). It can be concluded that co-contamination with both aflatoxin B1 and zearalenone reduced their negative effect on lipase activity of fish.

Marine microbiology is developing worldwide because of importance of its bioactive compound. Marine actinomycetes are potential sources of bioactive compound and rich source of secondary metabolites. One of the most promising sources of bioactive compounds is Nocardia genus, which was reported as an antibiotic producer. Aim of this study is isolation and identification of Nocardiopsis isolate from Deylam nearshore and study of its antimicrobial activity. After collecting of soil sediment samples, the treated samples were serially diluted and used starch casein agar as a culture medium. Identification of isolate was done using 16S rRNA analysis. Antimicrobial assay of the bacterial extracts was performed using standard well diffusion assay. Nocardia isolate was isolated and identified. Differential analyses results for catalase and Gram test were positive and other tests were negative. Antimicrobial assays showed that the isolate has more antifungal than antibacterial activity against tested pathogenic microbes.The results of this investigation revealed that Deylam nearshore sediments were potent source of rare actinomycetes which produced bioactive compounds.

The southern coasts of Iran are exposed to tsunami waves due to Makran subduction. Therefore, understanding the propagation and run-up of tsunami waves through numerical simulation and experimental studies is vital. In this research, by applying OpenFOAM computational fluid dynamics open source Software, propagation and run-up of tsunami waves in different conditions are estimated and the results of numerical simulations are compared with experimental data. Solitary waves are considered as the model for tsunami waves. Initially, the propagation of non-breaking and then the breaking solitary wave as two-dimensional numerical simulation has been investigated. The effect of submerged obstacle on the decreasing run-up is studied numerically and experimentally. The results show that OpenFOAM software model the propagation precisely and predicts the wave run-up with acceptable level of accuracy in numerous wave conditions. Furthermore, results shows the submerged obstacle can reduce up to 19.7 percent of the tsunami run up.

Marine animals are important sources of bioactive natural products due to their secondary metabolites. Siphonaria gastropods are marine mollusks that few studies have been performed on their biomedical properties. This study was performed to evaluate antibacterial properties of different extracts ( wet and dry ethanolic and aqueous) on Escherichia coli, Staphyloccus aureus, Saprolegnia parasitica by using well method as well as antioxidant activity by using MDA method. Results revealed that ethanolis extracts from dry tissue showed minimum lipid peroxidation( 30.54± .49) , and thus the highest autoxidation(44.45±0.74 ) activity. The results of antibacterial assay of the examined extracts showed no significant antibacterial property. This study revealed some antioxidant activities of Siphonaria carbo extracts. Detailed biochemical studies is recommended for identification of compounds causing this property.

In this study, scour pattern around submarine pipelines which were located on an erodible bed was simulated using Group Method of Data Handling (GMDH). Also, to assess the performance of hybrid models, the Monte Carlo simulations (MCs) were applied. In current study, the k-fold Cross Validation (k=6) was used for examination of the models ability. In following using the effective parameters on scour, six various GMDH model were developed. By analyzing the numerical models, the superior model was introduced. The model predicted the experimental results with reasonable accuracy. For instance, correlation coefficient, scatter index and root mean square error were calculated 0.914, 0.160 and 0.141, respectively. For superior model some relations were obtained in order to predict the scour around submarine pipelines. Additionally, using sensitivity analysis, the ratio of the distance between pipe and erodible bed to diameter pipe (e/D) is identified as the most influential parameter.

Salinity intrusion to the upstream of estuaries became a major issue in the coastal areas. This phenomenon intensifies in lack of river discharges. The result is, salinity increment in agricultural lands located near the estuaries. In this study, the tidal currents, as well as the river discharges were measured by using an Acoustic Tomography technique. Two acoustic stations were deployed on both sides of Kyu Ota Estuary and measured the variations of stream flow effected by tidal currents for 42 hours. The results of measurement showed that the river discharge was between 20 to 50 m3/s, whereas, the stream flow direction changed abruptly to the upstream at the time of passing tidal bores. The maximum stream flow was approximately 20 m3/s to the landward. Therefore, acoustic tomography technique can be introduced as an appropriate instrument to monitor the estuary stream flows.