|Year : 2016 | Volume
| Issue : 1 | Page : 34-38
Investigation of Cadmium and Arsenic Accumulation in Portunus pelagicus along the Asalouyeh Coast, Iran
Forouzan Fatemi, Shahrzad Khoramnejadian
Department of the Environment, Damavand Branch, Islamic Azad University, Damavand, Iran
|Date of Web Publication||4-May-2016|
Dr. Shahrzad Khoramnejadian
Department of the Environment, Damavand Branch, Islamic Azad University, Damavand
Source of Support: None, Conflict of Interest: None
Context: Accumulation of toxic metals in aquatic organisms is one of the most important problems facing the world today since these metals can enter the food chain and have a damaging impact on human health. Aims: This research determines the concentration of metals (cadmium [Cd], arsenic [As]) in the soft tissue of blue swimmer crab (Portunus pelagicus) from four different stations along the Asalouyeh coasts in Iran. Settings and Design: The West suburb of the Mond protected area in Bushehr Province was chosen as a control area. Samples were collected over a 3-month period during winter of 2014. Materials and Methods: Metal analysis was performed by atomic absorption spectrophotometer. Surface water at each sampling station was measured for selected physicochemical parameters with a multiparameter meter. Statistical Analysis Used: Analysis of variance followed by Duncan test (α = 0.05) was applied to determine the differences between the groups. Results: The results showed that the mean concentration (mg/kg dry weight) of Cd in the crab was higher than As. The concentration of both metals was higher in March. The highest concentration of Cd (1.54 ± 0.07) and As (0.35 ± 0.01) in the samples was observed for station 1 which was near to industrial zone of Asalouyeh. The mean concentrations of both metals were significantly (P = 0.000) higher in the study area than in the control area. Conclusions: Results showed that P. pelagicus is a reliable biological indicator of Cd and As contamination. The concentration of Cd in the crab samples was higher than recommended levels. Therefore, it is not suitable for consumption.
Keywords: Blue swimmer crab, Persian Gulf, physicochemical parameters, toxic metals
|How to cite this article:|
Fatemi F, Khoramnejadian S. Investigation of Cadmium and Arsenic Accumulation in Portunus pelagicus along the Asalouyeh Coast, Iran. J Earth Environ Health Sci 2016;2:34-8
|How to cite this URL:|
Fatemi F, Khoramnejadian S. Investigation of Cadmium and Arsenic Accumulation in Portunus pelagicus along the Asalouyeh Coast, Iran. J Earth Environ Health Sci [serial online] 2016 [cited 2020 Nov 29];2:34-8. Available from: https://www.ijeehs.org/text.asp?2016/2/1/34/181805
| Introduction|| |
In recent years, contamination of aquatic ecosystems by toxic metals has been considered a serious environmental concern around the world due to their toxicity and tendency to bioaccumulate.  Human activities have significantly raised the concentration of heavy metals in aquatic ecosystems.  Metal contaminants eventually settle onto the seafloor after entering the sea.  While there are some heavy metals which have beneficial effects on organisms, the excessive amounts can be very harmful and result in death.  Some physical and chemical factors such as temperature, salinity, and dissolved oxygen (DO) have a direct relationship with the concentrations and bioavailability of toxic metals in the water column. , Monitoring of physicochemical parameters of waters therefore provides important information for evaluating the potential danger of metals in the environment.
Cadmium (Cd) is a fairly toxic heavy metal that can cause cancer, gene mutation, and kidney disease in humankind. , This element is also very detrimental to marine organisms even at low doses and can have adverse influences on respiratory systems, growth rates, and molting processes.  Arsenic (As) is released into the marine environment from both natural and anthropogenic sources.  This metal poses an extreme danger to aquatic wildlife. As has the high potential to bioaccumulate in aquatic organisms at lower trophic levels.  The health effects of As rely on its chemical composition. 
Because of the increase in various forms of pollution in our natural environment, frequent monitoring of toxic metal contents in food is considered necessary.  Benthic crustaceans are able to accumulate toxic metals from contaminated sediments, water column, and food consumption.  The crab "Portunus pelagicus" with high economic value is widely distributed throughout the world.  This creature is an important part of fisheries resources in the Persian Gulf.  Crabs have vast potential as indicators of aquatic ecosystems conditions  not only because of their close contact with sediments but also because they form a key part of the population's diet.
The Persian Gulf is one of the most critical bodies of water which is located in Western Asia between Iran and Arabia. , Many natural and human sources have heavily damaged the Gulf ecosystem. Asalouyeh region in Bushehr Province is the most important energy hub of Iran, and it is known for its huge oil and gas installations. As a consequence of industrial activities in this region, levels of toxic metals, especially Cd and As, in the Persian Gulf environment have increased dramatically. P. pelagicus can be found in the Persian Gulf waters in Asalouyeh port. Previous research on evaluating levels of mercury in some marine biota species (fish, shrimp, and crab) from Khuzestan shore (Persian Gulf) demonstrated that levels of this metal in the fish and crustacean were different among the species and tissues.  Baboli and Velayatzadeh  studied heavy metals and trace elements in the muscles of marine shrimp, Fenneropenaeus merguiensis from Persian Gulf (Iran, Bandar Abbas port) and showed that mercury, Cd, lead, zinc, and copper were lower than World Health Organization, Ministry of Agriculture Forestry and Fisheries, and Food and Drug Administration standards. Rahimi and Gheysari  measured lead, Cd, As, and mercury in the fish (Scomberomorus commerson), shrimp (Fenneropenaeus indicus), and lobster (Panulirus homarus) samples from Persian Gulf (Bushehr Province) and showed that the seafoods of the Persian Gulf were contaminated with low range of these metals. However, to the best of our knowledge, very few publications are available which discuss the concentration of Cd and As in crustaceans from the Asalouyeh region. Therefore, the aims of this study are (1) to analyze the concentration of Cd and As in the crab P. pelagicus collected from Asalouyeh as a bioindicator of metal pollution, (2) to compare the results with the acceptable metal limits given by different organizations, and (3) to determine selected physicochemical parameters of water at each sampling station of the study area.
| Materials and Methods|| |
The study area was located on the Northern coast of the Persian Gulf in Asalouyeh (27°47ˊ21˝ N, 52°61ˊ46˝ E) in Southern Iran. This area is surrounded by high numbers of petrochemical, petroleum, and natural gas industries. The control area was chosen in the West suburb of the Mond protected area in Bushehr Province, located in 180 km from the contaminated area (Asalouyeh), where there was any form of human activities.
A total of 75 male crabs (five samples per station) were caught from the study area and control area between January and March 2014. Sampling was done during winter months due to our limitations on sampling and easier crab catching during this season at the study area. The study area (polluted area) size was approximately 3000 m 2 . In the study area, samples were monthly collected at four sampling stations within the same distance from each other. The criteria for selection of four study stations in the Asalouyeh region were based on locations of industrial units, Asalouyeh fishing pier, and mangrove forests of Nay band. In other words, the sampling stations were selected to reflect progression of pollution and human activities in the area. Sampling stations were geolocated using Global Positioning System receiver [Table 1]. Only male crabs were used for this study to avoid any sex-related difference in metal uptake found in previous studies. , Samples were collected based on the similarity of their size with the help of local people using traps. The crab samples were separated by the stations and transferred to the laboratory under ice boxes for analysis. On each sampling station, selected water physicochemical parameters were monitored using a multiparameter meter from Hach (model senION156).
|Table 1: The mean concentration of metals in Portunus pelagicus in the sampling stations during three study months |
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In the laboratory, the crabs of each station were washed with deionized water separately and kept at a temperature of −20°C until they were prepared for chemical digestion. Frozen samples were thawed at room temperature and rinsed with deionized water to remove impurities. A dry ashing method was used for sample preparation suggested by the Institute of Standards and Industrial Research of Iran. , The soft tissues of crabs were dissected, homogenized, and placed on clean watch glasses and weighed to 5 g using an electronic weighing balance. The weighted samples were dry-ashed at 550°C for 8 h. The dried samples were milled with a mortar and pestle. The pulverized samples were digested with 10 ml concentrated nitric acid (69%) first at 40°C for 1 h and afterward at 140°C for 3 h using a Hot Block Digestion System. Deionized water was then added to bring the solution up to 50 ml. After this, digested samples were filtered through Whatman No. 1 filter paper.  Finally, liquid samples were aspirated into a graphite furnace atomic absorption spectrophotometer (Varian Spectrum AA 600 Zeeman) for metals determination. Results were expressed as dry weights.
A number of quality control methods including the use of standard operating procedures, calibration with standards, recovery of known additions and analysis of reagent blanks, and replicates were carried out to confirm accuracy of analyses. Experiments were performed in triplicate and mean values reported.
The SPSS v. 22 statistical package for Windows was used to analyze the data. The two-way analysis of variance test was applied to determine any significant differences in metal levels between the stations and also between the months. The Duncan test was used to compare the group means.
| Results|| |
[Table 1] shows the concentrations of metals in different stations and the control area. Analysis of variance revealed significant differences (P = 0.000) in Cd and As concentrations between sampling stations and also between sampling months. Duncan test revealed that there was no significant difference at the 95% confidence level in the Cd level between stations 1 and 2. The mean Cd level across the sampling stations followed the order: Station 1 = station 2 > station 3 > station 4. Results of Duncan test also showed that the mean concentrations of As in both stations 1 and 4 were significantly (P = 0.000) higher than those obtained for the stations 2 and 3.
Temperature, pH, salinity, and DO of the Persian Gulf surface water and the monthly concentrations of metals in the crab during sampling months are given in [Table 2]. This table represents that the highest levels of Cd (1.28 ± 0.09) and As (0.31 ± 0.02) were found in March and the lowest concentrations of Cd (0.45 ± 0.05) and As (0.19 ± 0.01) were in January. There were no significant variations (P = 0.000) in the concentrations of Cd and As between February and March. [Figure 1] illustrates how the concentration of metals in crab samples varies amongst the stations over a 3-month period. In this figure, the results from this study were also compared with standards established by different organizations.
|Figure 1: Comparison of metals concentration (mg/kg dry weights) in Portunus pelagicus samples|
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|Table 2: The mean and standard deviations (mean ± standard deviation) of metals in the crab and physicochemical parameters of water in the four studied stations during 3 months winter period |
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The levels of metals (Cd and As) in P. pelagicus from this study are compared with the results from several previous studies on crab species in [Table 3].
|Table 3: The concentrations of metals (cadmium, arsenic) in crab species from different parts of the world in comparison with this study |
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| Discussion|| |
Regarding [Table 1], it has been found that the highest concentrations of Cd (1.54 ± 0.07) and As (0.35 ± 0.01) were recorded in station 1. This result is due to the location of station 1 in the vicinity of industrial zone of Asalouyeh where there are huge petrochemical and gas refinery plants. Earlier studies on the Persian Gulf also reported that the increase in the concentration of heavy metals including Cd in the studied area was significantly attributable to discharges associated with petrochemical industries.  The second highest level of Cd was in station 2 (1.25 ± 0.09) which was the nearest station to Asalouyeh fishing pier. The lowest levels of Cd (0.32 ± 0.03) and As (0.16 ± 0.09) were recorded in the stations 4 and 3 (located between Asalouyeh fishing pier and Nay band forests). Station 4 had the second highest concentration of As (0.29 ± 0.03). This result could be a reflection of the crab diet preferences in this station. Diet is one of the most crucial factors which plays an important role in the bioaccumulation of metals.  Station 4 was the closest one to mangrove forest of Nay band, one of the crab's preferred habitats in the area. Thus, higher concentration of As in this location can be due to the high levels of As in Nay band algae that the crabs feed on. Previous studies have reported that algae has the ability to accumulate substantial levels of As , and approximately, the same level of As in marine organisms is found in marine algae.  It can also be seen that the mean concentrations of both metals were significantly (P = 0.000) higher in the study area than in the control area.
According to [Table 2], there was a gradual increase in water temperature (from 20.2°C to 26.2°C) and salinity (37.1-37.8 ppt) from January to March. Dadolahi et al.  indicated that the mean value of temperature and salinity in the Persian Gulf waters (Bushehr province) during winter were 14.8°C and 28 ppt, respectively. In contrast, DO decreased from 7.1-6.4 mg/L during winter months. The reason for this fact is because the solubility of oxygen is dependent on temperature. DO decreased as water temperature increased.  The maximum pH value was recorded in February (8.30). This value was similar to those observed by Jahanpanah and Savari.  The results from concentrations of metals in the three sampling months further support the idea around the impact of physicochemical parameters such as temperature and salinity on the removal of toxic metals from the body of aquatic organisms.  As the temperature increased during winter, the rate of metabolism also increased which resulted in a higher uptake of these metals in the crabs in March. According to the obtained results, the salinity of water increased as the temperature increased. This finding supports Hong et al.'s  finding which showed that concentration of As increased in water, sediments and organisms by increasing salinity. The concentrations of metals in three sampling months in the study area were higher than that in the control area.
A strong relationship between the uptake of nonessential metals by organisms and the bio-availability of these metals has been reported in the literature. ,, With respect to [Figure 1], we can see from the data that substantially more concentrations of Cd than As were accumulated in crab samples in the stations during the months studied except for stations 3 and 4 in January. This finding suggests that the available proportion of Cd to P. pelagicus from the medium was more than the available extent of As. It has been proved that factors such as organic matter content, age, and contaminant properties can cause change in the bioavailability of metals. 
As can be seen from [Figure 1], metals levels in all stations in the polluted area were higher than that in the control area during the study. It is also observed from this figure that the Cd concentrations in the stations 1, 2, and 3 (except for in January) were above the maximum levels (MLs) of Cd in food set by the European Union (EU) (0.5 mg/kg)  and Codex (0.5 mg/kg)  standards. Further, Cd levels in February and March were above the recommended levels of both EU and Codex standards. By contrast, As concentrations in all stations and various months were below the MLs set by Food Standards Australia New Zealand (2 mg/kg)  and UK (1 mg/kg)  standards. Concentrations of both metals in the control area were lower than the standards. While it is true that Cd can be found naturally in the earth's crust, it cannot be denied that industrial activities, large volumes of chemical discharges, and lack of control on industrial wastewaters are the main causes of dramatic increase in the levels of this metal in the Asalouyeh area. However, a recent study on red king crab (Paralithodes camtschaticus) from Norway has reported the levels of metals including Cd and As were low in comparison with European regulations. 
Referring to [Table 3], the results indicate that the Cd levels in P. pelagicus from this study were almost higher than other studies while the As levels showed lower concentrations than previous studies. It is clear that the difference between the results from several studies is a consequence of various factors that affect metal uptake by marine organisms. These include geographical position, age of marine organisms, different types of industries around the study area, principle of industrial wastewater treatment, and laboratory conditions.
| Conclusions|| |
The results of the present study demonstrate that P. pelagicus is a reliable biological indicator of metal contamination owing to the ability of accumulating different levels of metals and their high abundance in the study area. The concentration of Cd in the crab samples was higher than recommended levels. Therefore, it is not suitable for consumption. There is limited information about metal accumulation in the crustaceans from the Asalouyeh area. Further research needs to therefore be conducted to investigate the levels of these metals in this area. Continued research on comparing Cd and As concentrations in different food sources of these crabs is also desirable.
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Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]