جستجوی مقالات مرتبط با کلیدواژه "qeshm island" در نشریات گروه "علوم پایه"

Chlorophyll-a, as an important indicator of algal blooms and water quality, holds significant importance in marine studies. This research aims to compare linear and nonlinear regression models based on machine learning algorithms for estimating the chlorophyll-a levels in the coastal waters of Bandar Abbas, Hormuz, and Qeshm Island. The study utilizes data from the TERRA sensor’s MODIS satellite and field measurements from various points within the study area. The examined models include linear regression, generalized linear model with Poisson distribution, random forest, and support vector machine. The performance of these models is evaluated using metrics such as root mean square error (RMSE), mean percentage error (MPE), mean absolute error (MAE), and coefficient of determination (R-squared). The results demonstrate that linear regression and generalized linear models perform poorly, while random forest and support vector machine exhibit better performance. Particularly, the random forest model shows the highest performance with an RMSE of 0.5725 and R-squared of 0.6632. This model has the capability to detect nonlinear and complex patterns and can effectively handle large datasets by employing a large number of decision trees. Overall, this research highlights the effectiveness of machine learning models, especially random forests, in accurately predicting chlorophyll-a levels as a crucial factor in managing marine ecosystems in the study area.

The present study was carried out in the fishing grounds of small pelagic fish on Qeshm Island (namely Ramcha, Souza, Messen, and Salakh) from September 2022 to June 2023. Field sampling was performed by double-boat purse seiners and conducting 57 netting. The length, height, and mesh size of purse seines were 300 m, 50 m, and 10 mm (STR). Data of date, time of setting, location, and weight of target species and bycatch were recorded for each setting net. The mean CPUE (±95% CI) of small pelagic fish was overally obtained at 991.23 ± 157.14 kg per set. This was 1300 ± 364.01 for Salakh, 1246.88 ± 295 for Ramchah, 669.23 ± 214.20 for Messen, and 587.5 ± 155.71 for Souza, which there was a significant difference between Salakh and Ramcha compared to Souza and Messen (P<0.01). Also, the mean CPUE (±95% CI) of target catch for warm and temperate seasons were 1227.42 ± 224.11 and 709.62 ± 174.20 kg per setting net, which was significantly differ (P<0.01). The maximum and minimum of occurrence percentages were attributed to anchovy (with 100%) and Trichiurus lepturus (with 1.75%). The highest and lowest of mean CPUE (±95% CI) for bycatch species/groups, were related to the Trichiurus lepturus (1.75 ± 3.51) and Dasyatidae (0.07 ± 0.10) kg per setting. Given that fishing efforts have increased in recent years in the region, the estimated values of CPUE for target catch were smaller than in previous studies. Therefore, the fisheries managers must take immediate action to optimize the ongoing fishing effort.

Qeshm Island, with an area of ​​1,486 square kilometers, is located at the southeastern end of the Zagros Belt and at the western end of the Strait of Hormuz. Since the tectonic era, it seems possible to assess the influence of neotectonics and fault dynamics on island morpho-tectonic deformation using basin tectonic indicators. In this research, five indicators are extracted and calculated using satellite images, geological maps, aerial photographs, and a digital elevation model (30 meters) using various software. The smoothness and asymmetry of waterways (AF), watershed shape index (BS), cross-topographic symmetry index (T), river meandering index (S) and their comprehensive evaluation are evaluated in model form (IAT)). It is an index to evaluate the degree of tectonic deformation in the basin, and the obtained results indicate the relative dynamics of various tectonic deformations on the island. Furthermore, based on the IAT index, 26 of the 44 subbasins belong to a very high tectonic layer, consistent with the number of faults, so more active tectonic deformation is observed in the western part of the island.

Background and Theoretical Foundations: 

The effluents of cage culture, mainly uneaten food and faecal, are released directly into the environment and result in many environmental problems such as eutrophication, and changes of benthos communities .Therefore, studies related to the effects of this type of activity on marine ecosystems seem to be very necessary. In this study, the possible effects of cages culture Asian sea bass fish (Lates calcarifer) on water quality in coastal waters of Rigo region of Qeshm Island in Hormozgan province during a period of six months during 2008 were investigated.

Water sampling was performed to measure some of water quality parameters in three stations, including the first station in the center, the second station at the end of the cages and the third at a distance of 1000 meters from the cages (reference site). A total of 540 water samples were collected using a Nansen sampler bottle to measure nutrients (nitrate, nitrite, total ammonia and phosphate). All nutrient samples were measured based on colorimetric method by spectrophotometer. Measurements of temperature, pH, salinity, dissolved oxygen, oxygen saturation, turbidity and chlorophyll a were performed by multiparameter in the water column. To classify water quality, trophic status and risk of eutrophication in coastal waters of the study area, scale and upscale trix indices were used.

The water temperature range in this study is equal to 22.56-31.48 Co; Salinity, 36.98-37.55 ppt; Dissolved oxygen, 3.03-5.92 mg/l ; pH, 8-8.46; Turbidity, 4.3-27.4 NTU; Nitrate, 0.005-0.04 mg/l; Nitrite, 0.001-0.003 mg/l; Total ammonia, 0.003-0.04 mg/l; Phosphate was 0.002-0.043 mg/l and chlorophyll a was equal to 0.1-3.8 µg /l. The results of one-way analysis of variance test showed that there was a significant difference (P<0.05) between the studied at the location of the cages culture and the refrences site in terms of measured water quality parameters (except water temperature, pH and salinity) also the concentrations of nitrate, total ammonia, phosphate, nitrite, turbidity and chlorophyll a measured at the location of the cages were much higher than farther from the location of the cages (the references site). The mean value of Trix index, eutrophication risk index, trophic efficiency coefficient and N: P ratio in the coastal waters of the study area were 4.97, 3.98, 0.2 and 3.6, respectively. Based on the amount of Trix index, the level of trophy at the location of the cages culture was high, the water quality was moderate, and the trophy efficiency coefficient and the Eutrophication risk were high.

In general, the results of the present study showed that fish farming activities in cages could decrease water quality, increase trophic levels and the risk of eutrophication in the waters adjacent to the cages, while the effects of such activities on the coastal waters of the study area were ineffective at the time of the study.

The aim of this study was to isolate and identify a-amylase-producing bacteria present in mangrove ecosystems on Qeshm Island, Hormozgan, Iran. Samples of mangrove leaves and roots were screened for a-amylase activity using Lugol’s solution. Crude extracts were prepared of positive samples, and their a-amylase activity was determined by the Bernfeld method. The two strains with the highest activity were identified by molecular analysis of their 16S rRNA genes. a-Amylase production and activity were optimized by varying temperature and pH. 46 bacterial strains were isolated from mangrove tree leaf and root samples. Of these, 28 strains were capable of producing a-amylase. 16S rRNA gene sequence analysis of two strains with the highest enzyme production identified them as Bacillus sp. strain HR10 and Bacillus sp. strain HR11. The optimum temperature for enzyme production was 35 and 30 °C for strains HR10 and HR11, respectively, and the optimum pH was pH 8 for both strains. The highest enzyme activity was observed at 70 °C and 60 °C for the HR10 and HR11 strains, respectively, and the optimum pH was pH 8 for both strains. In conclusion, we have shown that bacteria isolated from mangrove leaf and root samples are potential source of a-amylases, tolerating a wide range of temperature and pH. Such a-amylases may be of interest for use in environmentally friendly industries.

For this purpose, the station in the region of Laft, which gasoline smuggling in the intertidal area ,and at the same time, selected three similar stations in the Tabl area as a blank station, and were sampled seasonally from Autumn 2015  to Summer 2016. The total abundance of macrobenthos in Laft station (457/ m2) and Tabl stations (727 /m2) was concluded, and the maximum and minimum relative frequencies of macrobenthos in Laft estuary are Spiroloculina sp. (11.4%) and Tellina vernalis (3.8%), respectively, and in the tabl(blank station), this ratio is related to Cossura longocirrata (21%). and Spiroloculina sp. (9.8%).The results of the t-test showed that there were significant differences between the Laft and the Tabl stations(95% ), based on the tree chart derived from the cluster test , the studied regions in two regions can be divided into the first and second groups in terms of time.In addition, due to the correlation coefficients (Canonical Correlation) for each group, in particular at the Tabl station, the functions formed have a high separability to the resulting functions belonging to the Laft station, which can indicate the stability and more sustainability in the Tabl station macrobenthose communities than the Laft station, or, in other words, the ecological potential of the bottom of sea at Laft station is influenced by the gasoline smuggling less efficient than the Tabl station. The results of biodiversity indices changes showed in the two stations, showed that there are differences between the Marguerite, Shannon-Wiener and Simpson indices and Hill number between macrobenthose communities of the two stations(P<0.05). The maximum and minimum richness  Margalf indices were concluded in Tabl station ((3.28 (±0.12)) and Laft estuary station (1.9 (0.13)), respectively.

Length-weight relationship (LWR) was estimated for 86 caught black pomfret by trawl net in Qeshm Island located in the Persian Gulf in in March 2017. The total length and total weight of the fish ranged from 15.8 to 56.2 cm and 69 to 3128 g, respectively. The mean total length and total weight were 25.08 ± 0.76 cm and 358.93 ± 52.22 g, respectively. LWR for black pomfret was W = 0.0267L2.875 (R2 = 0.975). The results obtained can be valuable for improvement of the technical performances related to fisheries management in the future.

The present study was carried out to investigate the diversity and distribution of the Polychaeta species in the Qeshm Island and the effect of desalination plants on their communities. The desalination plants provide a large portion of Qeshm Island drinking water. So, their waste waters could effect on environment especially benthic animals near the coastline. Substrate sampling was carried out in summer and winter 2014 from 9 stations. Station 1 was situated near (desalination site) with the highest temperature and salinity in both summer and winter season, which shows the effects of drainage waste water on environment condition. The substrates of the most stations were silt-clay. At the stations 4 and 5, which sediments included more silt and clay, organic matters were higher than other stations. In this study 49 genera and species were identified. There was a significant negative correlation between the polychaetes abundances and sediment content of silt and clay observed. The higher abundances of polychaetes were found in the stations with lower content of organic matters and greater grain size sediments. The genera Cossura sp. and Scoloplos simplex which related to Cossuridae and Orbiniidae families respectively were dominant specimens. The lowest level of diversity was estimated in station 1. Diversity and dominance indices at stations near the wastewater outlet showed significant differ in both seasons (P<0.05). Finally, it seems that desalination plant may affects adversely on species diversity by increasing of temperature and salinity in short distances.

Since the wind pattern on various activities in islands as well as its effect on other meteorological parameters is important long – term temporal and spatial variations of the wind field are studied. Here, the warmest month (July) and the coldest month (January) 2015, are selected in order to test the sensitivity of low-level wind simulations of the Weather Research and Forecasting (WRF) model to the parameterizations of the boundary layer (PBL), the surface layer (SL) and the land surface (LSM) over Qeshm Island. As this work was focused on the simulation of near-surface and vertical wind profiles, the physical options related to the parameterizations of boundary layer processes (SL, PBL and LSM) that have significance influence for this purpose are validated. Although more physical options are available in the model (for cumulus convection, short and long wave radiation, microphysics and etc.), it is not feasible or necessary to include all the model configuration options in the sensitivity analysis to obtain an efficient model configuration optimization. The model grid comprised of four nested domains at horizontal resolutions of 45, 15, 5 and 1 km respectively. The innermost domain (D4) with 1 km spatial resolution covered the chosen area to simulate PBL wind field over Qeshm island region. The results of the simulations under five different configurations are validated with the observational wind speed data of Qeshm Airport and Marine Qeshm Stations. The results demonstrate that in both episodes, the ACM2 boundary layer scheme has presented the best performance in combination with the Pleim - Xio surface layer and the Noah land surface schemes because it considers vertical mixing both local and non-local in simulation of planetary boundary layer wind structure. The simulations of WRF are sensitive to warm and cold seasons as well as selected parameterizations. After selecting the appropriate configuration, the simulation of the wind field for one year was carried out to investigate the low level wind field, the vertical structure of the boundary layer wind and the impact of the land mask distribution on and around the Qeshm Island. These simulations indicate higher wind speed in spring and summer and the roughness of the island causes a low level wind convergence, then turn to the left on the Strait of Hormuz with decreasing wind speed. Monthly average of the wind direction during the daytime of reference month of each season are generally simulated to be southwesterly (January, April, July, October) and during the nights of January and July it is southerly to southeast and in April and October it is simulated southwesterly. The direction of the wind has significant variations at sunrise and sunset due to changes in regional scale forcing and baroclinicity behavior between the sea and the coast. Surface roughness in coastal areas, strait narrowing and sea breeze, enhance the low-level jet during summer and spring middays at altitudes of about 180 to 200 meters. In other words, we can say these low-level jet (Shamal winds) during summer and spring occurs as a result of the interaction of two pressure systems; the heat low pressure cell (low level cyclone) over Iran and a semi-permanent high over northwestern Saudi Arabia and it acquires some convergence because of the these factors.

In this study, proximate composition of Stichopus herrmanni divers from Hormozgan province which were caught by diving, during autumn and winter 2016 and spring and summer 2017, determined. For this, one station was selected in each province, three specimens from each three replication of different seasons sampled. In nutrition laboratory, all specimens from replication of each season of separated province, minced and analyzed proximate compositions protein, lipid, Ash and Humidity based on standard methods. Results showed that the studied sea cucumber species compromised relative high protein level (P<0.05). The highest protein content was found in Hormozgan at summer season (15±3.69) and lowest not significantly in Bushehr at autumn season (10±1.73) at spring season (10±1.8), caused by higher WT. and consequently higer chlorophyll a contents in Hormozgan water at summer season compare to samples from other studies provinces at the same seasons. Humidity percentage were the highest in the sea cucumber caught at winter (86.1±8.43) and not significantly (P>0.05), while the lowest (P<0.05) was obtained from Hormozgan samples at spring season (81.1±5.63). Lipid contents with low levels in this species showed the highest in winter season (0.29±0.08) and the lowest lipid content was obtained from sampled in Hormozgan province at Summer time (0.12±0.02) (P<0.05).

 Sea turtles are considered of the globally threatened species in the world. Mortality range of sea turtles in utero is very high due to several natural and human threats, affecting survival and regeneration of these reptiles.

Therefore, identification and control threats are vital to support habitat and survival rate. Eggs transfer to a safe place immediately after laying is a management tool for increasing the emergence success of these critically endangered species. In this study, emergence success of Eretmochelys imbricata in the coasts of Qeshm Island was studied.

 The emergence success rate was 59/92% out of 102 transferred nests (from Shib-deraz and shib- poiee beach). Results showed that no significant differences between Shib-deraz and shib- poiee beach, considering the emergence success of the transferred eggs.

According to the results, we believe that best way to protect hawks-bill turtles in this area is transferring eggs and protecting nests in a safe place to raise emerging success.

The purpose of this study is to identify suitable areas for aquaculture development and to determine the suitable locations for the establishment of marine cages for Epinephelus coioides in the waters around the Qeshm Island, with an attitude on environmental considerations and aquaculture development approach. In this regard, the ecological conditions of the studied area for the purpose of introducing the Epinephelus coioides for aquaculture in marine cages, the suitable areas for deploying marine cages through hydro biological studies, hydrography, geomorphology, geographic information system (GIS) application as a model for determining the suitable locations for deploying marine cages and prioritizing and rating the selected areas based on the (SWOT) analysis model were determined. The 16-month period of this study continued from October 2016 to January 2017 and the studied area was in Hormozgan province, the peripheral waters of Qeshm Island. Based on a series of studies on the geomorphologic features of the coastal area and the hydrography of the studied area, it was determined that the intended areas included the southern coastal area of Qeshm Island in the western part, as well as the marine range of the island are suitable and environmentally safe places that the taken measures were successful in establishing cage systems with respect to scientific management. Due to the high coefficient of confidence of the region through the PASTAKIA model and the combined matrix method, these areas had high scores. This criterion and score in the middle group are descriptive of the effect and a quantitative criterion of 50 -25 which, requires observance of the management principles in terms of decision making and action.

The main purpose of this paper is studying sedimentary layer in the Qeshm Island. We use aftershocks of 27 Nov. 2005 Qeshm Island (Mb=6.0), to perfume 2D tomography of Rayleigh waves.
We have analyzed surface wave data for 856 aftershocks, consist 9821 waveforms. The dispersion curves are calculated in the period range between 0.1 seconds and 10 seconds, which correspond to the shallow structures of uppermost crust including sedimentary layer. Surface wave tomography has also been performed to estimate the two-dimensional group velocity maps of Rayleigh waves in the region. The isolated surface wave fundamental modes by Herman and group velocities dispersion curves obtained by it, using Yanovskaya-Ditmar linear inversion method for estimation of 2D tomography maps. Based on the ray coverage, the area divided into cells with dimension 1 Km ×1 Km. in every cell and for distinct periods the velocities were calculated. The minimum dimension of distinct heterogeneities estimated as about 3 km.
Low-velocity anomalies in tomography maps can be related to the accumulation of salt plugs and some soft sediment in the area. In periods up to 4 sec, which related to shallower depths, a distinct lineation observed that may relate to a fault. It seems that this fault has cut off the sediments. Into the deeper sediment, this fault disappeared which means the sediments were softer and unbreakable.

High population pressure in coastal areas has led to loss in many mangrove areas. Although these areas are fish nursery grounds, but there are no accurate and up-to-date data available. In this research, the catch data in the Qeshm Island marine protected area (MPA) were investigated using 11 stake nets. Totally, 81 specimens belong to 60 genera and 63 families caught, which majority of them were discards. The commercial fish were young, andin almost all commercial fishes, the whole catches were smaller than LM50. Moreover, in case of butterfish, only 15.3% of the caught individuals were in the legal catch size. Hence, this catch composition would be a potential threat to fish stocks. The major numeric and weight based specimens were Dussumieria acuta (10.05%) and Arius maculatus (5.9%), respectively. In addition, the Clupeidae containing seven species was the most abundant family in the catch composition. Moreover, the majority of catches were occurred in the late winter to early spring and late summer to mid or late fall.

Iran's mangrove forests are considered as one of the most important regions of the world's mangroves ecosystem. Due to the special establishment in the margins of waterways with different flood conditions, establishment in low-rain and dry areas and also the low area of these forests, the establishment of mangrove forests is obviously of particular importance. For this purpose, considering the general and specific location of each habitat, the development of mangrove forests of Iran was designed and presented as special models. The present study is a case study designed and implemented in one of the habitats of Qeshm Island as a desirable development model. The research was carried out in 30 research plots. The distance from the waterways was the main factor and flood height and tidal conditions were the sub factors. In each plot the growth factors were calculated. The final results show the status of growth and development in each plot and total habitat. The forest stands were divided into four degrees from 1 to 4 based on the quantitative and qualitative condition. The 1 stands are developable stands and the 4 stands are undevelopable ones. According to the results, the desirable development models could be applied in other similar habitats in Iran and other parts of the world.

This study was conducted to identification and abundance of shell occupied by hermit crabs in 8 selected stations located in the intertidal zones of southern Qeshm Island. Sampling was conducted during the Dec. 2013. Some of samples of each station were separately fixed in 70% ethanol and were transported to the laboratory. In this study 605 samples of hermit crabs was surveyed. According to our results eight hermit crab species (Clibanarius signatus, Clibanarius virescens, Diogenes avarus, Diogenes planimanus, Dardanus tinctor, Areopaguristes perspicax, Pagurus kulkarniii and Coenobita scaevola) were identified in the intertidal zones of southern Qeshm Island. Our results showed these hermit crabs were occupied with 28, 17, 24, 10, 4, 18, 4 and 3 species of gastropods respectively for protecting their abdominal section. In general 50 gastropod shell species occupied by 8 hermit crabs species. Highest shell occupied by Clibanarius signatus with 28 gastropod shell species. Thais lacera with 13/89% occupations of all the shells was the highest frequent occupied shells. Station 5 (Mangrove forest) had the highest abundance of the hermit crabs and shell occupation.