Benthic foraminifer communities of the Persian Gulf

Eighteen types of benthic foraminifer communities inhabiting depths of 0–200 m are described for the Persian Gulf including the analysis of 269 sampling sites. The species area is mostly localized by the geographical position and bathymetrical features, including the water masses advection, the upwelling, the river discharge, and the concentrations of CaCo₃ and C_org in the bottom sediments.     

Wave height forecasting in Dayyer, the Persian Gulf

Forecasting of wave parameters is necessary for many marine and coastal operations. Different forecasting methodologies have been developed using the wind and wave characteristics. In this paper, artificial neural network (ANN) as a robust data learning method is used to forecast the wave height for the next 3, 6, 12 and 24 h in the Persian Gulf. To determine the effective parameters, different models with various combinations of input parameters were considered. Parameters such as wind speed, direction and wave height of the previous 3 h, were found to be the best inputs. Furthermore, using the difference between wave and wind directions showed better performance. The results also indicated that if only the wind parameters are used as model inputs the accuracy of the forecasting increases as the time horizon increases up to 6 h. This can be due to the lower influence of previous wave heights on larger lead time forecasting and the existing lag between the wind and wave growth. It was also found that in short lead times, the forecasted wave heights primarily depend on the previous wave heights, while in larger lead times there is a greater dependence on previous wind speeds.     

Acute ecological risk associated with soot deposition: a Persian Gulf case study

Many studies have been carried out in the past to provide solutions to the threat of chemicals to the ecosystem. However, the basic scientific capability to predict the risk of adverse effects on the ecological system has not kept pace with society's increasing demand for uses of chemicals. As a scientific methodology for quantifying the risk to the environment associated with exposure to chemicals, ecological risk assessment is increasingly important in environmental problem solving. The purpose of this paper is to present a methodology for conducting ecological risk assessment using deterministic and probabilistic approaches. A systematic discussion on elements of ecological risk assessment is presented. A framework of ecological risk assessment is explained with the help of the Persian Gulf environmental problem as a case study. The study was based on the output of a long-range transport model of soot deposition in the Gulf. Results of the assessment using the deterministic and probabilistic approaches are discussed.     

Scleractinian coral communities of Hormuz Island in the Persian Gulf

The abundance and health of scleractinian coral communities of Hormuz Island were investigated. For this purpose, we employed 20 m line intercept transects—12 in the intertidal zone and 15 subtidally to evaluate coral cover and community composition. The estimated dead coral coverage was 6.21%±0.81%, while live coral coverage was 16.93%±1.81%, considered as very poor. Totally, 12 genera were recorded, of which Porites with 11.9%±1.4% live cover was the dominant, while Goniopora had the least cover (0.07%±0.08%). Based on Mann-Whitney U-test, live coral coverage, dead coral coverage, algal coverage, cover of other benthic organisms and abiotic components showed significant univariate differences between zones (p<0.05). The Spearman correlation test between the abundance of biotic and abiotic components indicated significant negative correlation of live coral and sand with zoantharian and significant positive correlation of algae and other benthic organisms with rubble. The reef health indices used for the corals indicated that, in general, the environmental conditions were not suitable, which could be attributed to both natural and anthropogenic factors, the most important of which was zoantharian’ overgrowth on the scleractinian corals in this region.     

Interannual variability and seasonal contribution of thermal expansion to sea level in the Persian Gulf

In an attempt to understand the causes of the sea-level seasonal cycle in the Persian Gulf, we investigated the relationships of sea-level data from 11 stations with atmospheric pressure and thermosteric level. Sea level is significantly correlated among all stations. The mean trend in sea level for the Persian Gulf is about 2.34 mm/year. The thermosteric sea-level variability is estimated from temperature profiles at one-degree grid points. Contour maps of thermosteric level show that the height due to thermal expansion is high in summer and autumn, and low during winter and spring. The monthly mean thermostric height ranges from +2.2 cm in July to −2.1 cm in February. The major change in sea level due to the thermosteric level seems to be associated with the large change of the thermohaline circulation in the Persian Gulf. The maximum expansion occurs in summer, and the maximum contraction occurs in winter.Results of the regression analysis demonstrate that from 62% to 90.2% of the variance in the seasonal cycle is due to atmospheric pressure. The inclusion of the thermosteric sea level as a secondary forcing in the regression model improves the variance explained to 78.1–90.7%. The remaining change should be due to the halosteric effect and upwelling. Tide-gauge stations located at the Gulf's head show high correlation with Ekman vertical velocity. There are two distinct tide gauge stations in the Persian Gulf. One is found in the first cyclonic gyre and the other in the second gyre. The inclusion of Ekman upwelling to the model, improves significantly the variations explained as well, from 82.3% to 91.9%.     

Assessment of coral health in the coastal areas of the Persian Gulf

In this study, Zooxanthellae density, chlorophyll a concentration, and mitotic index (MI) were measured in the coral Porites compressa obtained from coastal areas of the Persian Gulf in early February to September 2008. During the summer, zooxanthellae density declined by approximately 30% compared to the winter peak (3,607,849 ± 229,894, n = 15) and reached a minimum of 2,536,732 ± 169,776, n = 15. The highest value of chlorophyll a (0.828 ± 0.043 μg/cm²) was recorded in the south while the lowest (0.604 ± 0.048 μg/cm²) was measured in the north sampling site at the cold season. There was a higher level of MI in the warm season followed by cold > and temperate seasons. The MI were significantly higher (p < 0.05) in the warm and cold seasons in comparison with the temperate season. Differences in response may be attributed to the drastic seasonal temperature changes. However, the significant decline found in the north sampling site indicates that anthropogenic stressors may adversely affect coral P. compressa. These results imply that there were negative impacts on coral P. compressa in our study site.     

Variation in the size structure of corals is related to environmental extremes in the Persian Gulf

The size structure of coral populations is the culmination of key demographic events, including recruitment, mortality and growth, thereby providing important insights to recent ecological dynamics. Importantly, the size structure of corals reflects both intrinsic (inherent life-history characteristics) and extrinsic (enhanced mortality due to chronic or acute disturbances) forcing on local populations, enabling post-hoc assessment of spatial and taxonomic differences in susceptibility to disturbance. This study examined the size structure of four locally abundant corals (Acropora downingi, Favia pallida, Platygyra daedalea, and massive Porites spp.) in two regions of the Persian Gulf: the southern Gulf (Dubai and Abu Dhabi) and eastern Gulf (western Musandam). Significant and consistent differences were apparent in mean colony sizes and size-distributions between regions. All corals in the southern Gulf were significantly smaller, and their size structure positively skewed and relatively more leptokurtic (i.e., peaky) compared to corals in the eastern Gulf. Sea surface temperatures, salinity, and the recent frequency of mass bleaching are all higher, in the southern Gulf, suggesting higher mortality rates and/or slower growth in these populations. Differences in size structure between locations were more pronounced than differences between species at each location, suggesting that extreme differences in environmental conditions and disturbance events have a greater influence on population dynamics in the Gulf than inherent differences in their life-history characteristics.     

Combining echo sounding,sediment and biological data to map benthic habitats in a coastal area of the Persian Gulf

Mapping surveys of coastal benthic habitat in Qeshm Island Geopark, Persian Gulf, were conducted using a combination of biological, sedimentological and echo‐sounding data. The survey area covered approximately 233 km² in a depth range of 5–25 m, and the data were acquired from a single beam echo sounder, grab, video and still photography. Sediment and macrofauna samples were collected by grab at 76 stations and subjected to classification and ordination analyses. Two acoustic classes were identified differentiating along the near/offshore axis. Sediment texture was dominated by fine grain sizes, with five distinct sub‐sediment types. In total, 214 macrobenthic taxa were identified, of which polychaetes accounted for 60%. Other dominant groups included young sponges, nematodes, malacostracan crustacean, bivalves, ostracods and ophiuroids. Underwater videos and still photos integrated the macrofaunal and sedimentary data and revealed a range of biogenic sedimentary features such as burrows and tubes. The biological data identified six main biological assemblages showing an inshore/offshore pattern. The macrobenthic abundance did not demonstrate a significant difference with depth, although polychaetes were positively correlated with depth. The highest abundance and species richness were observed at median depths. Species distribution and diversity did not show any correlation with sediment type. A preliminary habitat mapping of the south coast of the Qeshm Island Geopark has been carried out, integrating acoustic, sediment and biological data.     

Optimization of Bottom Friction Coefficient Using Inverse Modeling in the Persian Gulf

Ocean Science Journal - A practical method for the calibration of the ocean circulation model is introduced using measured water levels along the Persian Gulf coastlines. Dimensional analysis is...     

Intertidal gastropod assemblages shaped by key environmental variables across the northern Persian Gulf and the Gulf of Omanss

Variations in environmental factors can alter the species distribution pattern in intertidal rocky shores. The Persian Gulf (PG) and the Gulf of Oman (GO) vary substantially with respect to environmental and oceanographic conditions. The abundance and biodiversity of intertidal rocky gastropods in five locations across the northern PG and the GO were compared, and the environmental variables underlying the distribution pattern of these organisms were investigated. A total of 67 gastropod species were identified. The largest average density (294 ind./m²) and diversity (N = 43) for gastropods occurred in the Hotel Lipar station (LIP) located in Chabahar Bay in the GO. Clypeomorus bifasciata (107.43 ind./m²) followed by Cerithium caeruleum (94.67 ind./m²) were the most abundant species. Planaxis sulcatus and Siphonaria spp. occurred in all locations during both sampling occasions. Species richness and abundance of gastropods showed significant differences between LIP and remaining locations. A significant difference was found in assemblage structure across locations. In general, the species richness and density in the locations at GO were significantly larger than those locations in the PG, suggesting that the harsh environmental condition in the PG might be the forcing factor for this diminish. Distinct grouping was observed in both assemblage structure and species composition between locations in the PG and the GO. The spatial and temporal distribution patterns of gastropods assemblages were significantly correlated with variation in salinity and substrate rugosity.     

Determining the Gravitational Gradient Tensor Using Satellite-Altimetry Observations over the Persian Gulf

With the advent of satellite altimetry in 1973, new scientific applications became available in oceanography, climatology, and marine geosciences. Moreover, satellite altimetry provides a significant source of information facilitated in the geoid determination with a high accuracy and spatial resolution. The information from this approach is a sufficient alternate for marine gravity data in the high-frequency modeling of the marine gravity field quantities. The gravity gradient tensor, consisting of the second-order partial derivatives of the gravity potential, provides more localized information than gravity measurements. Marine gravity observations always carry a high noise level due to environmental effects. Moreover, it is not possible to model the high frequencies of the Earth's gravity field in a global scale using these observations. In this article, we introduce a novel approach for a determination of the gravity gradient tensor at sea level using satellite altimetry. Two numerical techniques are applied and compared for this purpose. In particular, we facilitate the radial basis functions (RBFs) and the harmonic splines. As a case study, the gravitational gradient tensor is determined and results presented in the Persian Gulf. Validation of results reveals that the solution of the harmonic spline approach has a better agreement with a theoretical zero-value of the trace of the Marussi gravitational gradient tensor. However, the data-adaptive technique in the RBF approach allows more efficient selection of the parameters and 3-D configuration of RBFs compared to a fixed parameterization by the harmonic splines.     

An Observational and Numerical Modeling of Thermocline Development in the Persian Gulf

An observational and numerical (Princeton Ocean Model) study of the summer thermocline development in the Persian Gulf (PG) shows that as the northwesterly cold winter wind weakens and become warmer, the fresher inflow from Oman Sea penetrates much further into the PG. This is also associated with stronger solar radiation leading to the near surface thermocline development over the whole of the PG. For more realistic monthly averaged wind, the thermocline develops as is indicated by observations. This is particularly marked in the deeper central part in which it grows in depth about 0.2(m) per day. The formation of thermocline decreases the dissolved oxygen in water column due to induced stratification. Over the PG the temperature difference between surface and subsurface increases exponentially from March until May when it levels off, with similar smaller variations for salinity differences than observed.     

Tidal asymmetry in a tidal creek with mixed mainly semidiurnal tide,Bushehr Port,Persian Gulf

This study investigated the tidal asymmetry imposed by both the interaction of principal tides and the higher harmonics generated by distortions within a tidal creek network with mixed mainly semidiurnal tide in the Bushehr Port, Persian Gulf. Since velocity and water-level imposed by principal triad tides K₁-O₁-M₂ are in quadrature, duration asymmetries during a tidal period in this short, shallow inverse estuary should be manifest as skewed velocities. The principal tides produce periodic asymmetries including a strong ebb-dominance and a weak flood-dominance condition during spring and neap tides respectively. The higher harmonics induced by nonlinearities engender a flood-dominance condition where the convergence effects are higher than frictional effects, and an ebbdominance condition where intertidal storage are extended. Since the triad K₁-O₁-M₂ driven asymmetry is not overcome by higher harmonics close to the mouth, the periodic asymmetry dominates within the creek in which higher harmonics reinforce the weak flood-dominance (strong ebb-dominance) condition in the convergent channel (divergent area). Also, the maximum flood and the maximum ebb from all harmonic constituents occurred close to high water slack time during both spring and neap tides in this short creek. Since occational wetting of intertidal areas happened close to the high water (HW) time during spring tide, the water level flooded slowly close to the HW time of the spring tide.     

Holocene climate in the Persian Gulf as deduced from grain-size and pteropod distribution

Detailed coarse-fraction analyses have been made of twelve sediment cores from the Persian Gulf (40–100 m water depth) in order to detect Holocene climatic changes.The only indication of such a change was provided by the terrigenous material (i.e., the < 63 μ fraction) carried into the Gulf by rivers. All cores show characteristic variations in the quantity of terrigenous material and alternating fine- and coarse-grained layers.There was no other parameter which could point to variations in climate. This might be due to the fact that the sediments are sorted as a result of reworking by tidal currents (velocities 25–50 cm/sec): fine and light particles are removed. Any climatically-produced variations in amount or size of benthonic and planktonic organisms have probably been obliterated by tidal currents. The importance of this factor varied with time: during increased terrigenous supply, tidal currents modified the sediment surface for only short periods and a fine-grained layer was, therefore, deposited. A lesser supply of terrigenous material, on the other hand, resulted in the deposition of a coarse-grained layer.Contemporaneous sedimentation of layers with much terrigenous material (fine-grained layer) and with little terrigenous material (coarse-grained layer) is suggested. Observed petrographic variations are presumably due to large-scale changes of climate and not to local sedimentary variations (including shifts of river-mouth processes).Accordingly, the cores were correlated by examining the percentage of coarse fraction and the median diameter of the sand fraction. The assumption is that the higher the percentage of coarsegrained material, the lower the amount of terrigenous material transported into the Persian Gulf.In support of this correlation, another parameter - varying independently from grain size within one core - was examined: the species composition of pteropod shells. These quantitative changes could also be correlated, because there were different core sections with different species compositions.Correlation of the cores by grain size and by pteropod species provides the same results.Four different climatic zones could be distinguished between the lower and the upper part of the Holocene: a relatively arid period at about 9000 years B.P. was succeeded by a more humid period; this then was followed by a period of less rainfall and finally a period during the Late Holocene when rainfall increased again. This sequence is comparable to the established European climate chronology.     

Monitoring hawksbill turtle nesting sites in some protected areas from the Persian Gulf

Iranian nesting populations of the critically endangered hawksbill turtle(Eretmochelys imbricate) are some of the most important in the Indian Ocean. In this study, four of the most important hawksbill nesting grounds in the Persian Gulf, situated within three Iranian marine protected areas, were surveyed during nesting season,including Nakhiloo, Ommolgorm and Kharko Islands and the mainland beaches of the Naiband Marine-Coastal National Park(NMCNP). We present GIS maps of these key nesting grounds and describe sand texture of key nesting zones, along with conservation recommendations. About 9.2(28.3%) out of 32.5 km of all shores surveyed in this study were used by nesting hawksbill turtles follows: Nakhiloo: 1.4 km(52% of potential nesting area);Ommolgorm: 1.94 km(40%); Kharko: 3.4 km(28%), and NMCNP: 2.46 km(18.9%). The average nesting density was calculated as 131 nests/km at Nakhiloo, 76 nests/km at Ommolgorm, 7 nests/km at Kharko, and 15 nests per km at NMCNP. Highest nesting density was observed in Nakhiloo and Ommolgorm. It is thought that high hawksbill nesting density in these islands seems likely a result of limiting adequate nesting shores rather than the size of population, and also low density in Kharko and NMCNP more related to past and current pressures and low population density. With the exception of Ommolgorm Island, sands at the nesting grounds were well sorted.Grain size indicated that female hawksbill turtles in the Iranian Persian Gulf nest in sands that are generally mixed, with mean grain size ranging from coarse sands(0.4Φ;～0.5–1 mm) to fine sands(2Φ;～0.25 mm). We provide and discuss conservation recommendations and suggestions for future.     

Preliminary studies on the primary production of north-west Persian Gulf during post-monsoon period

Primary productivity, chlorophyll-a and the euphotic zone depth were determined averagely as 161 mg C (m³ day)^–1, 3.48 mg m^–3 and 6.2 m, respectively, in the north-west Persian Gulf during the post monsoon period in 1975 and 1976.     

Post-Cyclic Behavior of Carbonate Sand of the Northern Coast of the Persian Gulf

The post-cyclic behavior of biogenic carbonate sand was evaluated using cyclic triaxial testing through a stress control method under different confining pressures between 50 to 600 kPa. The testing program included a series of isotropically and anisotropically consolidated, undrained triaxial compression and extension tests on samples of remolded calcareous Bushehr sand. Grading analyses (before and after each test) were used to examine the influence of particle breakage on post-cyclic behavior of Bushehr sand. The particle breakage commonly occurred in these soils even in lower values of confining pressure, yet there was not a clear correlation between the post-cyclic responses and particle breakage. Based on the present study, a concept is suggested for post-cyclic behavior of carbonate sand. It was observed that post-cyclic strength has a good correlation with cyclic stress ratio, type of consolidation, and value of residual cyclic strain. For all specimens, it is clear that the post-cyclic strength is greater than monotonic strength, irrespective of confining pressure and relative density.     

Analysis of symbiotic Symbiodinium in scleractinian corals off Northwestern Kish Island,Persian Gulf

The genus Symbiodinium plays an essential role in the resistance and survival of reef‐building corals during temperature anomalies. Coral colonies inhabiting the Persian Gulf (PG) experience extended periods of different stresses. Kish Island is located in the harsh environment of the Northern PG with previously reported bleaching episodes. Samples of six coral species from Northwestern Kish Island were analysed by internal transcribed spacer 2 of ribosomal DNA to identify in hospite Symbiodinium populations. The results showed that lineage D of Symbiodinium was the most prevalent clade among different coral colonies, while clade C was only detected in symbiosis with a single coral species. However, the detected Symbiodinium subclades belonged to two host generalists. The predominance of the stress tolerant Symbiodinium trenchii and subclade C3 could suggest an acclimatization strategy to cope with the hostile environment of the PG.