Bioaccumulation of Some Heavy Metals on Silver-Cheeked Toadfish ( Lagocephalus sceleratus ) from Antalya Bay , Turkey

In the present study, the heavy metal concentration (Cd, Cu, Pb, Ag, Co, Cr, Fe, Mn, Ni & Zn) in skin and muscle were studied in silver-cheeked toadfish Lagocephalus sceleratus collected from Antalya Bay. The heavy metals concentration ranges in muscle tissue were Cu (0.276-0.518 μg/g); Fe (5.996-21.367 μg/g); Mn (0.601-2.633 μg/g); Zn (51.472-86.635 μg/g); Cd (0.045-0.139 μg/g); Co (0.541-0.833 μg/g); Cr (0.205-0.361 μg/g); Ni (0.108-0.765 μg/g) and Pb (1.464-2.560 μg/g). The heavy metal concentration ranges in skin were Cu (0.168-0.209 μg/g); Fe (1.738-4.467 μg/g); Mn (0.012-0.414 μg/g); Zn (3.337-6.451 μg/g); Cd (0.113-0.217 μg/g); Co (0.432-0.739 μg/g); Cr (0.101-0.148 μg/g); Ni (0.038-0.217 μg/g) and Pb (0.342-0.584 μg/g). The concentrations of Zn and Pb in the muscle tissues exceeded the acceptable levels for a food source and are not safe for human consumption. Further, this is the first report on distribution of heavy metals of Lagocephalus sceleratus from Antalya Bay, northern Levantine Sea, in the Eastern Mediterranean Sea south of Antalya Province, Turkey.


Introduction
Heavy metals are natural components and environmentally ubiquitous in the earth's crust that readily dissolved in, taken up by aquatic organisms and cannot be degraded or destroyed.They are dangerous elements due to their bioaccumulation and toxicity can threaten aquatic living organisms (Lenntech, 2004).Since the metals are actively used in agriculture, medicine and industry, they could not be ignored from daily life (Permatasari, 2006).Metals may exert beneficial or harmful effects on life, depending on their concentration.Some heavy metals like mercury, cadmium and lead have no known role in aquatic organisms while some others such as copper, zinc, iron and manganese are essential for fish metabolism.These essential metals always function in combination with organic molecules, usually proteins.But the essential metals being above the threshold bioavailable level are also toxic to aquatic organisms and humans (Küçüksezgin et al., 2006).Fish and their some tissues can also be considered as the most significant indicators in water systems for the estimation of metal pollution level (Henry et al., 2004).For these reasons, it is important to determine the concentrations of heavy metals in fish in order to evaluate the possible risks relating both aquatic environment and human health.Therefore, the commercial and edible species have been widely investigated in order to check for those hazards (Begum et al., 2005).
Heavy metals released to aquatic environments result from both natural sources, such as atmospheric deposition and erosion of the geological matrix, and anthropogenic sources, such as industrial effluents and mining wastes (Alam et al., 2002).In agricultural areas, some heavy metal concentrations such as copper and zinc were found highly in fish tissues (Rashed, 2001;Dural et al., 2007).Antalya region is an important touristic area.Hence, there has not heavily industrial activities in the Antalya Bay.However, due to suitable climate of this region, it has been carried out intensive agricultural activities in the region and has been used a lot of fertilizers and pesticides which may lead to water and fish contamination with heavy metals.
Puffers are marine fish species that are distributed in tropical and subtropical areas of the Atlantic, Indian and Pacific Ocean.Puffers include 28 genera and approximately 184 species in all over the world marine waters within the Tetraodontidae family (Matsuura, 2015;Farrag et al., 2016), among which at least ten are found in the eastern Mediterranean (Farrag, 2014).The silvercheeked toadfish Lagocephalus sceleratus (Gmelin, 1789) is a reef-associated pufferfish (Tetraodontidae) distributed in the tropical Indo-West Pacific Ocean (Smith and Heemstra, 1986), which entered the Mediterranean Sea via the Suez Canal and was reported as a confirmed record from the Gökova Bay in Turkish marine waters (Akyol et al., 2005).Subsequently, this Lessepsian invasive species has established large populations along the coasts of many countries of the eastern basin such as Israel, Lebanon, Turkey (Mediterranean and Aegean coasts), Cyprus and Greece (Aegean and Ionian coasts), while still rapidly expanding westwards along the coasts of Egypt, Libya, and along the entire Tunisian coastline (Ben-Soussi et al., 2014).
Apart from several large species used for human consumption as a delicious food in few countries, particularly in China, Korea, Japan and Taiwan (Makoto et al., 2000), most pufferfish species have not commercial value.Besides the small size of most species, the family is renowned for the occurrence of a powerful toxin in their skin and organs called tetrodotoxin (TTX).Tetrodotoxin is a very potent neurotoxin and one of the strongest marine paralytic toxins known (El-Sayed et al., 2003;Tsang et al., 2007).In this study, it was aimed to analyze the bioaccumulations of some heavy metals (Cd, Cu, Pb, Ag, Co, Cr, Fe, Mn, Ni & Zn) in muscle and skin tissues of L. sceleratus and also to discuss the allowable limit of these heavy metals via fish consumption.
To the best of our knowledge, present study is the first to investigate bioaccumulation of some heavy metals of L. sceleratus individuals caught by commercial fisheries from the Antalya Bay, Eastern Mediterranean.

Material and Methods
One species of marine puffer fishes from Tetraodontidae family namely silver-cheeked toadfish, Lagocephalus sceleratus (Fig. 1) were collected from Antalya Bay (latitude 36°50'04"; longitude 30°37'74''), in the Eastern Mediterranean Sea south of Antalya Province, Turkey during the period of spring (Fig. 2).In total, 10 specimens of species were collected and the samples were transported to the laboratory within 5-6 h in ice packed condition in a storage box.The specimen was thawed to room temperature for morphometric study and weight was examined for all the collected specimen.All the specimen were measured to the nearest mm, whereas weights were recorded with the use of electronic balance to the nearest 0.01 g and stored in −20°C for further heavy metal analysis.Species identification were carried out according to Golani et al. (2006).After catch, fish samples were made the species identification (Golani et al., 2006), refrigerated and transported to Iskenderun Technical University Marine Sciences and Technology Faculty's laboratory where they were instantly frozen (-18ᴼC) for later analyze procedure.Weight for skates and disc width (DW) and weight estimations for rays were made to the closest 0.1 cm, and gram, individually (Table 1).Throughout the study, all acids and chemicals used were analytical grade.For acid digestion, various parts namely, skin and muscle tissue of fish samples were dissected using sterile stainless knife and scissor.The segments of the skin and muscle tissues from the examples were evacuated, homogenized and around 1.0± 0.2 g was taken for investigation.10 ml of nitric acid is added to the sample and kept overnight at room temperature.Afterwards the examples were processed, utilizing a water bath at 60ᴼC for 3 days.Then, the samples were cooled to room temperature, filtered and was completed to 50 ml (UNEP, 1984).
After dilution, metal contents of tissue measured on a inductively coupled plasma atomic emission spectrometry (ICP-AES) (Varian model, Liberty Series II; Palo Alto, USA) and metal concentration in the tissue was presented as μg/g.For calibration ICP-AES was used as a High Purity Multi Standard.All digested samples were analyzed three times for the each metals.Blank samples were prepared in the same manner as the samples and the same acid matrix was used in the standard solution.

Results and Discussion
Puffer fishes are bottom living, carnivorous, slow swimmer and non-target fish species.Nowadays, consumption of puffer fishes as an alternative food to meet out the increasing food demand due to growing population and day-by-day collapse of natural resources.The main reasons for the consumption of puffer fishes are due to easily available nature and low marker price.The concentrations of heavy metals Cu, Fe, Mn, Zn, Cd, Co and Cr in skin and muscle tissues of puffer fishes were showed in Table 2.
Pb is a nonessential element for living organism and also it possess various adverse effects such as neuro and nephro toxicity, rapid behavioral malfunction, and decreases the growth, metabolism, and survival rate, alteration of social behavior in some mammals (Malik et al., 2010).Rashed (2001) found that elevated Pb level in fishes obtained from fresh water ecosystem affected by extended agriculture, poultry forms, textile, industrial and other activities.So the sediments could be the major sources of Pb contamination and the bottom feeders may directly affects with this deposited element in consequence to their feeding habitat (Garcia et al., 2010).Zn is the essential element for both human and aquatic organisms and they showed productive activity against Cd and Pb toxicity in biological organisms (Sarkar et al., 2016).
The high accumulation of heavy metals in puffer fishes is due to its carnivorous feeding nature and bottom habitat.Even though the puffer fishes are non-target species, peoples are started to consume because of their huge quantity or extended by-catch, low market price and high nutrient value.The present study concluded that the long term consumption of these fishes may leads to potential risk to humans in future.So regular monitoring of marine resources is essential to improve the quality of sea-food against contaminants.
Compared with other studies, the results in the present study were lower than the previously reported values of Cu, Cd in fish species from different and also same area (Table 3) (Kaleshkumar et al., 2017;Mat-Piah, 2011;Nurjanah et al., 2015;Kumagai & Saeki, 1983;Uysal & Emre, 2011;Tepe et al., 2008;Türkmen et al., 2008;Türkmen et al., 2009;Tepe, 2009;Yipel & Yarsan, 2014;Aktan & Tekin-Özan, 2012;Gökkuş & Türkmen, 2016;Duysak & Uğurlu, 2017;Tekin-Özan, 2014;Kayhan et al., 2010).When the Zn values were compared, the values in the study of Mat-Piah (2011) were found to be higher than those in our study.The same situation is seen in the value of Pb in the study of Kaleshkumar et al. (2017).Compared with the studies given in Table 3, Co (except Duysak and Uğurlu, 2017), Mn (except Mat-Piah, 2011) and Ni (except Tepe et al., 2008;Türkmen et al., 2008 and2009 in Antalya Bay) values are generally higher in our study.However, these comparisons should be used with caution due to differences in fish species and habitats between the studies.Although the skin is a consumed part of the fish, it has not been studied in previous works in this area.This study indicated that concentrations of heavy metals were lower in all of the skin samples than in the muscle samples.
This study showed that Lagocephalus sceleratus contain high level of Zn and Pb accumulation in muscle tissues organs when compare to the skin.The high accumulation of heavy metals in puffer fishes is due to its carnivorous feeding nature and bottom habitat.Even though the puffer fishes are non-target species, peoples are started to consume because of their huge quantity or extended by-catch, low market price and high nutrient value.The present study concluded that the long term consumption of these fishes may leads to potential risk to humans in future.So regular monitoring of marine resources is essential to improve the quality of sea-food against contaminants.This is first report of heavy metal analysis on recently silver-cheeked toadfish Lagocephalus sceleratus on Antalya Bay region and this finding may lead new insight for further research.

Table 2 .
Mean (±SD) concentrations of heavy metals (μg/g wet weight) in some organs of Lagocephalus sceleratus collected from Antalya Bay.

Table 3 .
Heavy metal levels in fish muscles from different locations worldwide