جستجوی مقالات مرتبط با کلیدواژه « persian gulf » در نشریات گروه « اکولوژی »

Microbial enzymes isolated from marine environments have found special applications in various industries, due to their unique properties. The Persian Gulf is a pristine place for the isolation of bacterial strains with the potential to produce new enzymes due to its rich biodiversity. Protease, lipase, and amylase are among the most widely used enzymes in various industries and due to the increasing importance and demand for microbial-marine enzymes in industry, this study aims to optimize and partial purify these enzymes from new strains isolated in port. Choubdeh (north of the Persian Gulf) was performed for the first time. Sampling was performed in November 2019 from 10 different stations (water and sediment samples). A new strain, Aeromonas taiwanensis - Persiangulf ST16 (accession number: OM189448) capable of producing protease, lipase, and amylase were identified by phylogenetic analysis of 16 SrRNA sequences. Optimal conditions for the growth of this bacterium included temperature of 30-37 ° C, pH 6, and salt concentration of 2.5%. The highest enzyme activity was observed for all three enzymes on the second day of incubation. The highest production of protease was reported at 37 ° C, pH 7, with the presence of maltose as a source of carbon and casein as a source of nitrogen, and the lowest was observed in the presence of dextrose and Beaf extract. The optimal conditions for lipase production at 37 ° C were 6-7 pH, and in the presence of olive oil and tryptone. The use of tween 20 and casein produced the lowest amount of enzyme. Optimal amylase production was observed at 35 ° C, pH 7, and the use of starch and yeast extract, but sorbitol and ammonium sulfate-induced the lowest production. During the purification steps, the specific activity of all three enzymes increased so that in the last stage of purification, protease, lipase, and amylase enzymes were purified by 16.23, 2.69, and 2.43 times respectively compared to the crude enzyme. Optimization of production of all three enzymes with significant activity by Aeromonas taiwanensis-Persiangulf ST16 showed that this bacterium could be a good candidate for further studies and use in industry.

Chlorophyll-a concentration is among the most important parameters used to investigate the primary production in marine ecosystems. Chlorophyll-a concentration is influenced by climatic/environmental factors, including Sea Surface Temperature (SST). Satellite sensors are able to provide reliable products of chlorophyll-a concentration and SST data with an adequate spatiotemporal resolution. In this study, level 3 (resolution 4 km) MODIS monthly products of chlorophyll-a concentration and SST  from year 2003 to 2018 of the Persian Gulf and the Oman Sea were used. The data were transformed into a raster format and the values of each pixel were extracted. Several gaps were observed in MODIS products of chlorophyll-a concentration. The Data INterpolating Empirical Orthogonal Functions (DINEOF) algorithm was used to reconstruct these gaps. Pearson correlation procedure was applied to analyze the correlation between chlorophyll-a concentration and SST. Results showed that during the study period, the correlation between the two parameters was negative (-0.44 to -0.67) and significant in the most part of the study area. The correlation coefficients in December were negative (-0.67 to -0.05) and significant in the Oman Sea and the most areas of the Persian Gulf, while in July those relationships were mostly positive (0.13 to 0.64) and significant.

Among the various species of small pelagic fish, Sardinella sindensis (Day ,1878) has high economic and ecological importance and is one of the most important species exploited by fishermen. In recent years, the catch rate of this species has increased, and due to the limited data available on its stock in southern waters, it is not possible to use models based on the complementary data to assess its stock. In the present study, the catch-maximum sustainable yield (CMSY) model was used to determine the stock status of Sardinella sindensis in southern waters. Catch data related to the last 23 years (1997- 2019) were collected and entered into the model to calculate fisheries reference points. The value for B/BMSY by the model was estimated to be more than 1.0 and the value of F/FMSY was less than 1.0, which indicates the healthy stock status of this species in the southern waters of Iran. The maximum sustainable yield (MSY) was estimated to be  86,000 tons. In recent years, the catch rate has been exceeded this amount and has caused the stock to move gradually towards the overfishing zone. Based on the results, it is suggested to control and manage the fishing activities regionally (specially in Hormozgan province) by taking into account the fishery potentials, monitoring the exploitation status with regard to the environmental factors affecting the stocks of this species.

The present study has made an effort to analyze the individual and the coupled effects of the sea surface temperature (SST) and the El Nino-Southern Oscillation (ENSO) on precipitation variability in the South-Central parts of Iran over the period of 1957-2019. The SST data comprise the monthly time series of this variable over eight grids located in various parts of the Red Sea (1 grid), Persian Gulf (1 grid), Oman Sea (2 grid) and the Arabian Sea (1 grid). In addition to these gridded data, the SST-precipitation relationships are also examined for differential values of these gridded datasets. Correlation coefficients are consistently found to be negative when monthly or seasonal SSTs are regressed with corresponding precipitation data in all considered stations. The strongest correlations are found when differential values of SST (The Red Sea minus eastern parts of the Persian Gulf) are regressed with precipitation data in Sirjan. Differential values have generally yield stronger correlations than if the data of a single grid are used. Fluctuation of the SSTs data over the Red Sea, western Parts of the Persian Gulf and eastern side of the Arabian Sea exhibited strongest relationships with rainfall variability over the study area. In contrast, the less significant associations are observed for the grids that are located over the Oman Sea. The SST-precipitation relationships are found to be negative during both the warm and cold phases of ENSO.

The aim of this study is to determine the most important geomorphometric indices and structural features affecting Submarine Groundwater Discharge (SGD) into the Persian Gulf coastlines. For this purpose, firstly, the maps of lithology, density of lineament, zoning rainfall and temperature, vegetation (NDVI), drainage density, slope, elevation classes, abundance and distribution of springs, profile, length, cross section, general, plate, tangent, total curvatures, and surface ratio, topographic roughness, Vector Ruggedness Measure, Topographic Position, and Topographic Wetness, was prepared on three radii of 10 (buffer 1), 20 (buffer 2) and 30 (buffer 3) km from the coast to the land, using ENVI 5.3, Arc GIS10.3.1, and SAGA GIS 2.1.0 software. Then, the most important factors and the contribution of them in presence the SGD areas were determined using multivariate regression analysis. The results showed that the plate and profile curvatures are the most important curvatures with opposite scores and values. Indicators affecting the presence of SGD areas for the cold season are: springs abundance on buffers 2 and 3, topographic wetness on buffer 3, drainage density on buffer 1 and 3, fault density on buffer 2 and aquifer surface on buffer 1, and for the warm season are: springs abundance on buffer 2 and 3, topographic wetness on buffer 1, cross section curve on buffer 2, total curvature on buffer 2, temperature index on Buffer 3, fault density on Buffer 3, and aquifer surface on buffer 1. In overall, the SGD mapping can be create by

Submarine Groundwater Discharge (SGD) is defined as any water subsurface flow from the land into the sea. Recognizing the area having this flow is very important for hydrologic and ecologic studies. For determination of Submarine Groundwater Discharge Probable Areas into the Persian Gulf on Coastlines of Bushehr Province, at first, required corrections (atmospheric, radiometric, and geometric) were made on the obtained thermal band 10 data of Landsat 8 during 2015 and 2016 across the study area using ENVI® 5.3 software. Then, by mapping sea surface temperature (SST) and standard temperature anomaly (STA) and thus determining the minimum shared area of thermal anomalies during 2015 and 2016 by GIS10.3.1 software, SGD probable areas into the Persian Gulf on Bushehr Province coastlines was recognized and mapped. The results show that there are SGD probable areas on Bandar Mogham to Kangan, Kangan to Mond River, Mond River to Shif Island, Bandargah to Ganaveh, and Bandar Rig to Hendijan coastlines with, respectively, 2823, 4165, 6159, 4725, and 4445 hectares. This area on coastlines of Bushehr Province is 22317 hectares discharging into the Persian Gulf that may suppose an Impressive flow. Therefore, surveying more details and quantifying is essential for estimating the precise rate.

Estuaries are one of the most productive aquatic ecosystems that both ecologically and economically are important. The study purposed to investigate the distribution and abundance of phytoplankton from Helleh river estuary (Boushehr- Persian Gulf). Samples were taken in mid-season from summer 2011 to spring 2012 for one year period. Results showed that the dissolved oxygen، temperature، salinity، pH and the visible depth of Secchi disk were varied in the range of 6. 45-12. 25 mg/l، 13-34. 4 oC، 9-45 ppt، 8. 04-8. 23 and 40-55 cm، respectively. The phytoplankton community comprised of Ochrophyta (3 classes، 17 families، and 22 genera)، Myzozoa (1 class، 6 families، and 8 genera)، Cyanophyta (1 class، 2 families، and 2 genera)، Chlorophyta (2 classes، 2 families، and 2 genera) and Haptophyta (1 class، 1 family، and 1 geneus). All samples were dominated by Ochrophyta، especially Bacillariophyceae class. The range of phytoplankton abundance were obtained 2266. 7-13533. 3، 4933. 3-11866. 7، 2066. 7-9266. 7 and 1333. 3-28666. 7 cells/L in summer، autumn، winter and spring، respectively. In addition، there were significant correlation between phytoplankton abundance with pH (r= 0. 57، P<0. 01) and salinity (r= 0. 52، P<0. 05). This study showed that Bacillariophyceae (diatoms) was the important class of phytoplankton in Helleh estuary and also the pH and salinity were the most important environmental parameters for phytoplankton distribution and abundance.

In this study, the concentrations of some heavy metals in surface sediments of Naibandmarine national Park (the first marine national park of Iran) have been evaluated.Surface sediment sampling was done from July 2010 to March2011. Sediment sampleswere collected from the tidal zone of Mangrove ecosystem in 5 different stations. At each station, sampling was repeated three times, and the sediments were digested by acid after drying. Concentration of Cd, Ni, Pb and Cu was measured by atomic absorption spectrophotometer, Varian 200 Perkin Elmer. Results showed that Cd, Ni, Pb and Cu concentration in the sediments were 0.2(0.4-0.07), 40.1(94.03-14.6), 52.23 (64.6-40.2) and 5.2 (8.01-2.8) mg/kg respectively. All metals concentrations ofdry season werehigher than the metals concentration of the rainy season. Data were analyzed using SPSS16 software. Muller geochemical indicators (Igeo) and (Ipoll)indices were used as pollution index to classifying of sediments quality. Based on these indicess, sediments were moderately polluted by Pband unpollutedfor the other metals. Alsocompare of the metals concentrations to Sediment Quality Guidelines (SQG) showedno metal pollution for Cd and Cu and moderate level of pollutionfor Ni and Pb.