Gorgan Bay Research Articles

Demonstration of MicroPlastics Distribution Map in the Sediment and Water of Gorgan Bay, Caspian Sea

Demonstration of MicroPlastics Distribution Map in the Sediment and Water of Gorgan Bay, Caspian Sea

Source of plastic contamination of the rivers ending to the Gorgan Bay, southeast of the Caspian Sea, Iran

The widespread presence of microplastics (MPs) in freshwater systems as an emerging environmental pollutant has caused a global environmental problem. The present study investigates the distribution and abundance of source pathway and abundance of microplastics in surface sediment samples from rivers discharging into the Gorgan Bay, southeast of the Caspian Sea. A total of 57 surface sediment samples were taken from 19 stations to investigate the potential hot spots of pollution in the four rivers leading to the Gorgan Bay. The average level of microplastics was 333 ± 268 particles/kg. The highest amount is in the estuary of the Qarasu River (1080 ± 380 particles/kg) due to the accumulation of fishing, boating and tourism activities and the lowest amount in the forest area (80 ± 19 particles/kg) in the Klak River. The most common type of microplastic was fiber (68%). Microplastic pollution in the studied rivers is mostly black and gray (75.39%), and about 53% of them were sized less than 1000 μm. Spectroscopic analysis (Fourier Transform Infrared (FT-IR) of the MP showed that 37% were polyethylene, polyethylene (37%) and polypropylene (27%) were the dominating groups. The sediments’ size was significantly correlated (p>0.05) with the presence of microplastics. Sediments with a coarse grain (sand) demonstrated a great potential to store microplastics. The results of this study can be used for the management and protection policies of Gorgan Bay.

Bathymetry monitoring of shallow coastal environment using remote Sensing data

The Caspian Sea (CS), the largest lake in the world, is an exceptional water body that is well-known for its rapid sea level (SL) change. This study aims to monitor the bathymetry of southeastern CS and Gorgan Bay (GB) under rapid sea level change. For this purpose, the water depth was extracted from the visible bands (blue, green, and red) of Landsat images using the Random Forest (RF) algorithm. The bathymetry survey results were validated through hydrography (field) and altimetry data. The results of bathymetry showed that R2 and RMSE values were 0.996 and 0.106 m, respectively in 2016. Moreover, the predicted depth for the period between 1992 and 2016 was consistent with the altimetry data. Due to rapid sea level fall, shallow coastal features like GB need to be monitored continuously. Therefore, the GB water depth was predicted by the RF algorithm for 2001 and 2023. The results showed that the GB bathymetry map corresponds closely to the altimetry data. The study also emphasizes the need for remote sensing data to prepare bathymetry maps which are hardly possible through field surveys.

Spatial and temporal distribution of physicochemical parameters of water in Gorgan Bay (the southeast of the Caspian Sea - Iran): Fundamentals for the monitoring of the Caspian Sea coastal areas

Gorgan Bay as a main part of the Miankaleh (a natural biosphere reserve registered by UNESCO) is one of the richest ecological area in the West Asia and very important internationally recognized refuge for the wildlife. To date, multi physicochemical parameters have not been examined on a large scale. To fill this knowledge gap, the present study aimed to explore the seasonal and spatial variability of water quality parameters of the bay. The results showed that except for depth and transparency, there are significant variations in most parameters across the four seasons. The patterns of these changes in the bay vary, as evidenced by a comparison of the distribution maps of the various factors throughout the year. Notably, alkalinity declined from east to west, reaching its highest levels at important entry points such as the Qarasu River, Bandar-Gaz, and the pier. TDS, on the other hand, increased westward, reaching its highest concentration in the shallow western regions. Maximum depth (310 cm) and transparency (250 cm) were observed in the central bay. While the pH was higher in deeper areas, the distribution of PO4 was more uniform. With lower levels in the east (salinity = 0.40 ‰) and higher levels in the west (salinity = 28.9 ‰), the salinity showed a coherent gradient. Agricultural land use in the basin of the bay and fluxes of nutrients and sediments of the rivers entering the bay has significant contribution to the bay pollution situation. These results will serve as a guide for improving our understanding of the Gorgan Bay ecosystem. They also have implications for informed conservation and management plans adapted to the specifics of this special region within the Caspian Sea.

Sedimentation rate challenge in the Gorgan Bay (southeastern of the Caspian Sea) and suggested management strategies

Sedimentation rate challenge in the Gorgan Bay (southeastern of the Caspian Sea) and suggested management strategies

Calculation and modeling of 232Th distribution in Gorgan Bay in the Caspian Sea

The aim of this study was to obtain a relationship that can estimate the emission pattern of 232Th in calm and low pressure aquatic environments such as Gorgan Bay. The 232Th emission pattern in sediments near the outlets of Gaz and Qarasu rivers using experimental data measured by gamma radiation spectrometry using high purity germanium (HPGe) detector and quasi-experimental model recommended by IAEA 2001 as well as the concentric circular diffusion model proposed by authors was investigated. The mean specific activity of 232Th in sediment samples for Gaz Block and Qarasu Block is 30.46 Bqkg−1 and 28.80 Bqkg−1 for, respectively.In Gaz Block, for model1: the average of CsModel1 was 29.03 Bqkg−1 and the mean relative error is 10.76%. For model2: the average of CsModel2 was 30.34 Bqkg−1 and the mean relative error is 7.58%.In Qarasu Block, for model1: the average of CsModel1 was 27.48 Bqkg−1 and the mean relative error is 12.08%. For model2: the average of CsModel2 was 34.17 Bqkg−1 and the mean relative error is 38.99%.The results of this research show that diffusion models 1 and 2 in the calm environment of Gorgan Bay can accurately predict 232Th diffusion. But as increase the amount of turbulence and interference effects in the environment, the accuracy of these two models decreases. These two models can be used in similar calm aquatic environments in other parts of the world.

Spatiotemporal dynamics of chlorophyll-a in the Gorgan Bay and Miankaleh Peninsula biosphere reserve: Call for action

Gorgan Bay (GB) and Miankaleh Peninsula biosphere reserve has faced an endangering condition because of a significant water loss and quality degradation due to intensive eutrophication. However, a synoptic view of the spatiotemporal dynamic of eutrophication is missing. In this study, we first used MODIS data to trace the long-term trend of eutrophication in GB between 2003 and 2021. To investigate the intra-annual variability of Chl-a in GB at a much higher spatial resolution, we developed an Artificial Neural Network (ANN) algorithm that uses Sentinel-2 imagery to map monthly Chl-a in the water year 2020–2021. Finally, we explored the major physical controls on eutrophication in GB. Long-term status of trophic index in GB revealed that 4%, 18%, 15%, 24%, and 39% of the months between 2003 and 2021 were under the oligotrophic, intense oligotrophic, mesotrophic, eutrophic, and intense eutrophic condition, respectively. The results also showed a very good agreement between the observed Chl-a concentration and that estimated from ANN, as evidenced by R2 = 0.88 and RMSE = 1.51 mg/m3. We found that in eight months of the water year 2020–2021, there was a region of high Chl-a concentration in the southeast of GB near the outlet of the Qarasu River. We also observed that nutrient entrance to GB from the Qarasu River imposes a greater impact on Chl-a concentration in GB than that from the Gorganrud River. Our findings suggest that under the current GB's water circulation, the critical eutrophication status in GB has a slight impact on the pollution of the Caspian Sea, except along the southeastern shoreline.

Emission Pattern of NORMs and 137Cs in the Sediments of the Gaz River and the Gorgan Bay, North Iran

Information on the distribution and emission patterns of natural and artificial radionuclides and their radiation level in the environment is very important for assessing the health effects of people living in a given region. In this study, the specific activity of radionuclides was measured using high purity germanium detector and a map of their distribution was drawn. The samples were collected from the Gaz River sediment in northern Iran, in the mountains of Golestan Province, and sediments on the middle and southern side of Gorgan Bay. The average of specific activities of 226Ra, 232Th, 40K, and 137Cs was 17.61, 35.91, 398.65, and 4.01 Bq/kg, respectively, which for natural radioactive nuclei are lower than the global average. The highest concentration of 40K was obtained in the sediments of the Gaz River estuary due to the use of potassium fertilizers for agriculture in this region. The highest concentration of 137Cs was obtained in the sediments of Gorgan Bay because 137Cs is injected both directly through the atmosphere and transfer by river water from upstream points to the Gorgan Bay. The diffusion pattern of 137Cs in the Gorgan Bay was exactly the opposite of 232Th and showed the tendency of 137Cs to precipitate in calm areas in the middle of the Bay.

Ecological environment monitoring for sustainable development goals in Gomishan international wetland, Gorgan Bay, Caspian Sea.

Monitoring of coastal ecosystems is of particular importance for sustainable development and environmental management. Remote sensing, using satellite imagery, can play an important role in these studies. In this study, changes of qualitative parameters in Gomishan wetland and Gorgan Bay located in the southeast of the Caspian Sea were investigated using Landsat images. Based on the results of the range of chlorophyll-a and water temperature changes in both ecosystems, there was an increasing trend. Evaluating of Secchi disk (transparency) ranges showed a decreasing trend until 2018. Also, among the studied years, 2009 has the lowest fluctuations. Overall, the findings of this study showed that changes in water quality parameters of Gorgan Bay and Gomishan wetland had been affected by ecological conditions and human activities such as industrial-domestic and agricultural effluents. Also, satellite data in such coastal ecosystems at different time intervals have valuable results and can be given special attention for the study of similar ecosystems.

Hydrodynamic and Sediment Transport Studies of Gorgan Bay (Case Study: Khozeini Channel and Investigation of Jetty’s Role in Reducing Active Sedimentation After Channel Dredging)

Hydrodynamic and Sediment Transport Studies of Gorgan Bay (Case Study: Khozeini Channel and Investigation of Jetty’s Role in Reducing Active Sedimentation After Channel Dredging)

Health risk assessment of some heavy metals detected in edible fishes of Gorgan Bay, Caspian Sea (Iran), for human.

Just recently, heavy metals have been dramatically detected in aquatic animals, especially in fishes; hence, documented method to assess their health risks for humans who eat these contaminated fishes could be helpful. For the sake of this aim, the health risk assessment of four heavy metals including arsenic, cadmium, lead, and copper in three main edible fishes caught from Gorgan bay was studied. Mullet, roach, and common carp have been caught randomly in winter and spring of 2021 from three different fishing sites of Gorgan bay, including Miankaleh wetland, estuary of Qaresu River, and mouth of Chapaghli canal. Heavy metal measurement has been done with MOOPAM method, and risk assessment of fish consumption was assessed by estimated daily (EDI) and weekly intakes (EWI), target hazard quotient (THQ), hazard index (HI), and target cancer risk (TCR) indices. In this study, estimated daily intake (EDI) was much lower than the tolerable daily intake. Although TCR of cadmium within all fishes and arsenic in two fishes were more than acceptable value, THQ and HI values were less than one, and TCR of lead as well as copper was lower than the critical values, which suggests heavy metals of the Gorgan bay have no serious risks to consumer health.

Tracking of sea level impact on Caspian Ramsar sites and potential restoration of the Gorgan Bay on the southeast Caspian coast.

The situation of Ramsar sites along the Caspian Sea coast has deteriorated over the past decades, and this is more noticeable in the narrow coastal strip of the south Caspian Sea. In this study we investigate how the Caspian Sea level changes affect the coastal Ramsar sites. Particularly, we focus on the Gorgan Bay in the southeast corner of the Caspian Sea, which is experiencing extensive water level decline, even desiccation. We used satellite images from three periods corresponding to periods of two sea level falls and one sea level rise, in order to decipher spatio-temporal changes of the wetlands. We conducted field campaign in the Gorgan Bay for sampling and measurement of physical, chemical and biological parameters. We simulated water circulation for the past, current and future conditions of the Gorgan Bay, which is essential to sustain better water exchange between the Bay and the Caspian Sea. We applied dust simulation in the case of a total desiccation of the Gorgan Bay. The result shows that the total area of the Caspian coastal Ramsar sites during the two periods of the sea level fall is almost the same; however, the aerial changes in the southern wetlands are more visible. Nutrient and plankton analysis of the Gorgan Bay display mainly mesotrophic conditions, in some areas close to eutrophic ones. The average current velocity in the main inlet is 2.5 cms-1. Dust simulation indicates that in case of the Gorgan Bay desiccation, it will become a dust source for the surrounding area up to 60 km. Simulation of the water circulation with dredging of inlets (future scenario), indicates that the water exchange velocity doubles compared to the current scenario. A recommended inlet maintenance would accelerate water circulation and reduce residence time, which will lead to better trophy and prevent bay desiccation.

Microplastic contamination in the sediments of Qarasu estuary in Gorgan Bay, south-east of Caspian Sea, Iran.

Given the important ecological role of estuaries and implications of microplastics (MPs) in ecosystems, we assessed the occurrence, abundance, size, and polymer types of MPs present in the sediments of the Qarasu estuary in 2019. MPs were extracted from sediments by density separation, after which they were detected under a stereomicroscope and considered according to shape, size and color. Identification was implemented using Fourier-Transform Infrared Spectroscopy (FT-IR). The abundance and size of MPs in the samples ranged between 40 and 460 particles/kg and 200-5000 μm, respectively. The dominant shape of MPs was fiber (72%), followed by fragment (26%) and film (2%). Black and white were the most abundant colors with 48% and 29%, respectively. In total, 4 MPs polymers including polypropylene (33%), polyethylene (24%), polyamide (21%), and polystyrene (14%) were identified. Results from PCA showed that stations with a high abundance of microplastics had a significant correlation with the amount of clay.

Radiological impact assessment and dose distribution pattern in gorgan bay, Northern Iran

Radiological impact assessment and dose distribution pattern in gorgan bay, Northern Iran

Distinction of driver contributions to wetland decline and their associated basin hydrology around Iran

Study regionSix wetland sites around Iran (Gavkhoni and Hur al-Azim wetlands, Gorgan Bay, and Namak, Urmia, and Maharloo & Bakhtegan lakes) and their associated hydrological basins. Study focusThe aim was to distinguish the contributions of climatic and non-climatic changes (including land-use/land-cover, LULC) to areal decline in six Iranian wetlands. This was done using data-driven quantification methodology that combined comparative change correlation and Budyko-based analyses of evapotranspiration (ETb), and runoff (Rb) changes in the hydrological basin of each wetland, extended to consider explicitly climate-driven change in evaporation rate (Ew) from the wetland area and the shift from previous Ew to ETb caused by the wetland decline itself. New hydrological insights for the regionComparative correlation analysis revealed an overall stronger correlation of wetland decline with LULC changes (mainly cropland, urban land) than with changes in temperature (T) or precipitation (P) across all wetland sites. The extended Budyko-based analysis revealed that the predominant cause of wetland decline across all sites was increased ETb, with related decrease in Rb from basin to wetland, whereas changes in Ew and in wetland decline shifting Ew to ETb had only a weak influence. In line with the correlation analysis results, non-climatic drivers were revealed as causing ETb increases and Rb decreases, leading to wetland decline to a greater degree than climate change (T, P).

Bioaccumulation of Some Hazardous Heavy Metals in Three Edible Fishes Caught from Gorgan Bay, Caspian Sea.

A survey was conducted to evaluate heavy metal accumulation in edible fishes caught from Gorgan Bay, as a part of the Caspian Sea ecosystem. Fish samples including mullet, roach, and common carp were just randomly prepared from fishing locations in three different areas of Gorgan Bay including estuary, channel, and Miankale wetland twice the fishing seasons. A total of 135 samples were measured using an atomic absorption spectrometer to 4 heavy metals of arsenic (As), lead (Pb), cadmium (Cd), and copper (Cu) (a total of 540 metal samples). The highest accumulation of As was related to the mullet of estuary, and the lowest contamination was related to the mouth of the channel. In relation to Cd, the highest pollution in all three species related to the fishes caught from the estuary and the lowest accumulation related to the Miankaleh wetland. In the case of metal Pb, results showed the most contamination related to the Mullet caught from Miankaleh wetland and the lowest accumulation related to the roach of the mouth of the channel. In all three fish species, the highest contamination of Cu was in the estuary and the lowest was in the fish caught from Miankaleh wetland. In general, the highest accumulation belonged to all three species located in estuaries. The probable reason can be pouring river pollution to the bay more than wetlands and channel. Due to the enclosure of the Caspian Sea and consequently the Gulf of Gorgan, limiting the fishing times and points to the periods of least incoming pollutants is very helpful for public health, especially food hygiene and fishing from this ecologically sensitive and vulnerable basin.

Analysis of natural and artificial radioactive emission pattern in Qarasu River catchment in Gorgan Bay, northern Iran

Knowledge of distribution and emission pattern of natural and artificial radioactive elements and their radiation level in the environment is very important to assess its effects on human health and living organisms. In this study, the specific activity of natural and artificial radioactive elements for 30 soil and sediment samples collected from upstream and the outlet of Qarasu River to Gorgan Bay as well as sediments in the eastern part of Gorgan Bay were measured using High-Purity Germanium detector and their distribution map with using SURFER and GIS software was drawn. Specific activity of 226Ra, 232Th, 40K and 137Cs was obtained from 8.80 to 31.92, from 11.16 to 43.19, from 183.77 to 562.88 and from 0.83 to 12.72 in Bq/kg respectively. Upstream of the Qarasu River, the average concentration of 226Ra, 232Th, 40K and 137Cs in the soil samples beside the Qarasu River was higher than the sediments of the river, which indicates the washing of sediments and the transport of radioactive elements by water flow and transfer of these elements to lower areas. In Qarasu estuary and Gorgan Bay, 232Th and 40K distribution patterns are almost similar and the highest concentrations of 226Ra, 232Th and 40K elements are related to Qarasu estuary sediments. The concentration of 137Cs in the mouth of Qarasu River has the lowest value and increases with its distance from the mouth to the middle parts of Gorgan Bay, which indicates a high mobility and a tendency to sediment in calmer places for 137Cs. The measured values for radiological parameters and risk indices due to nuclear radiation in this study are within the allowable range and the amount of available nuclear radiation does not threaten the health of the inhabitants of the region‎‎‎.‎

Different land uses influenced on characteristics and distribution of microplastics in Qarasu Basin Rivers, Gorgan Bay, Caspian Sea.

Concerns about the negative effects of microplastics (MPs) on human health have led to increasing attention to the occurrence of MPs in the aquatic environment. Recent studies have focus on the spatio-temporal distribution of MPs in rivers for residential and agricultural areas. Qarasu River Basin, watershed to Gorgan Bay, is the site of many permanent rivers and the levels of MP pollution in those rivers are unknown. This research was conducted in three different types of land use: forest, residential, and agricultural along 8 different rivers. A total of 9 fish species were identified and the presence of MPs in 87% of fish was confirmed. The prevalence of MP among species was Liza sp. > Carassius gibelio > Gambusia holbrooki > Rutilus rutilus > Neogobius melanostomus > Cyprinus carpio = Vimba vimba > Rutilus frisii > Barbus sp. The highest frequency of MPs was observed in Qarasu River (1880 ± 251 n/kg) and Mohammadabad River (184 ± 1340 n/kg) in agricultural land use, and the lowest frequency was related to Baghu and Ziarat Rivers with 660 ± 77 and 600 ± 91 n/kg found in forest land use respectively. The highest type, color, and size of MP sediments were fragment, black, and 1-2mm, respectively. The highest type, color, and size of MP in fishes were fiber, black, and 0.5-0.1mm respectively. Overall according to the source tracing result, agricultural land use was the main source of MP pollution of Gorgan Bay. The Bay is strongly affected by the incoming rivers, the Qarasu River Basin as the most important river supplying water.

Ecological Problems of Gorgan Bay in the Southeast Corner of the Caspian Sea (Iran) and Ways of Improvement

The article's abstract is not available.

Baseline occurrence, distribution and sources of PAHs, TPH, and OCPs in surface sediments in Gorgan Bay, Iran

Baseline polycyclic aromatic hydrocarbons (PAHs), total petroleum hydrocarbons (TPH) and organochlorine pesticides (OCPs) in surface sediments were measured in Gorgan Bay, Iran. Total PAHs, TPH, and OCPs concentrations ranged between 13.70 and 23.68 ng g−1, 2.97 to 11.51 μg g−1 dry weight, and below detection to 1.41 ng g−1, respectively. Benzo [k] fluoranthene and anthracene had the highest (BkF; 19.77 ± 0.08 ng g−1), and lowest (Ant; 4.38 ± 1.72 ng g−1) individual PAH concentrations, respectively. The most abundant OCPs were β-Endosulfan, followed by methoxychlor and endrin. PAH isomeric ratios in sediments revealed that contamination originated from mixed sources, with a strong indication of pyrogenic sources. Ecological risk assessments based on sediment quality guidelines (SQGs) suggested that individual PAHs and OCPs posed low ecological risks in Gorgan Bay.