© by PSP Volume 24 – No 10. 2015 Fresenius Environmental Bulletin LEVELS OF TRACE METALS IN FISH (Euthynnus affinis) FROM THE GULF OF AQABA, JORDAN Tariq Al-Najjar1,*, Khalid Abu Khadra2, Omar Rawashdeh2, Maroof Khalaf1 and Mohammad Wahsha3 1 Department of Marine Biology, The University of Jordan, Aqaba Branch, Jordan 2 Department of Biological Sciences, Yarmouk University, Irbid, Jordan 3 Marine Science Station, The University of Jordan, Aqaba Branch, Jordan ABSTRACT metal bioaccumulation in Tilapia Zilli and Clarias Gariepi- nus, intestine was the tissue with the second highest metal The aim of this study is to provide knowledge and es- bioaccumulation after gills due to the mucus on the gills tablish data about the levels of some trace metals in the Eu- which was nearly impossible to reove completely and con- thynnus affinis fish. The Euthynnus affinis is an important tained high metals levels. It was found by Al-Najjar et al. commercial migratory fish consumed by the locals in the [8] that bones of Caesio varilineata and Caesio lunaris Gulf of Aqaba, Red Sea, during its seasonal period. The contain very low concentrations of Cu, Ni, Pb, Cd, Zn and levels of these heavy metals (magnesium, manganese, Fe, and a high concentration of Mg, which might be related nickel, chromium, cobalt, cadmium and copper) were de- to the significance and importance of Mg in absorbance of termined in the liver, heart, spleen, muscle, kidney, gills, Ca from blood to the bones. gonads and stomach of forty Euthynnus affinis fish col- Euthynnus affinis (common name kawakawa or lected from the Gulf of Aqaba, Red Sea. Significant differ- ences in the levels of trace metals were found among dif- mackerel tuna) belong to the superclass Osteichthyes, class ferent organs and high variations in the concentrations and Actinopterygii, Perciformes order and the family Scombri- dae. E. affinis may grow up to 1 meter in fork length and the levels of the analyzed metals were obtained. Our study reveals that the length of the samples did not affect the lev- about 13.5 Kg in weight [9]. E. affinis is considered as an els of most of the analyze metals, and for those metals that important commercial fish in Aqaba, as well as one of the favorite meals for the locals. At ecological level the im- were affected there is a negative relationships with the length. portance of E. affinis and other fish species comes from their feces that form a natural fertilizer for the producers to get nutrition from, thus signifying their rule in balancing the ecosystems. For these reasons, studying and examining KEYWORDS: trace metals, levels, concentration, E. affinis, Red Sea, Aqaba. the metals level in the organs of E. affinis and the effect of other factors such as the body size on the bioaccumulation of trace metals is very significant and important for the monitoring and assessment of the ecosystem. 1. INTRODUCTION Several studies reveal a high susceptibility of the Gulf Toxic elements, or more generally trace elements, are of Aqaba to metal pollution. These studies stated that the now considered to be among the most effective environ- Gulf of Aqaba is surrounded mostly by dry desert lands, mental contaminants. The releasing of the trace elements thus, it has a great chance to get polluted with metals car- into the environment is increasing in the last decades, ried by air currents [10]. However, the aim of this study is threatening invertebrates, fish, and humans [1]. Fish are to establish background data and knowledge about the lev- relatively situated at the top of the aquatic food chain; els of some trace metals in the organs of the E. affinis fish, therefore, they normally accumulate heavy metals from which is an important commercial migratory fish, con- food, water and sediments. Therefore, many international sumed by the locals during its seasonal period. monitoring programs have been established in order to as- sess the quality of fish for human consumption and to mon- itor the quality, and suitability as well as the health of the 2. MATERIAL AND METHODS aquatic ecosystem [2]. In the last few decades, the concen- trations of heavy metals in fish have been extensively stud- 2.1 Study Area ied in different parts of the world [3-6]. In a study [7] on The Gulf of Aqaba is located at the east fork of the Red Sea (Figure 1). Its coasts are shared by Jordan, Palestine, * Corresponding author Egypt and Saudi Arabia. The Gulf contains the only port 1 © by PSP Volume 24 – No 10. 2015 Fresenius Environmental Bulletin for Jordan, Aqaba port, which the Gulf is named after. The muffle furnace at 450 °C for 8 hours. The ash was digested Gulf biodiversity is unique, and some species are endemic using wet digestion method. Wet digestion method was to the area. It gained a high and unique biodiversity due to carried out using 10 ml diluted Hydrochloric acid (2X pre- its semi enclosed nature, which also makes it more suscep- pared from stock of 12X HCl), the Teflon beakers contain- tible to pollution with these metals. After the year 2000, ing the samples were heated on a hot plate under the fume Aqaba was declared as a special economic zone. The hood until the solution started to boil. Samples solutions chance for a pollution to occur has increased in the Jorda- were filtered using Whatman No. 2 filter paper. Teflon nian sector of the Gulf of Aqaba, especially the chance for beakers were then washed with small amounts of distilled a metal pollution due to the developments that were made water and the washed water was collected and filtered us- along the coastline of the Gulf, represented by the projects ing the same filter paper and then added to the samples. that were carried out in different activities such as industry This process was repeated until the total volume of the and tourism [3, 5]. samples reached 25 ml. Finally filtered solution were trans- ferred to plastic bottles and stored at room temperature to be analyzed for metals concentrations. Blanks were pre- pared for each metal using the same method but without a sample (only heated the 10 ml HCl on the hot plate until it starts to boil, then filtered using the same method). The fi- nal concentration of trace metals in each sample was meas- ured using Analytikjena Flame Atomic Absorption Spec- trophotometer novAA 400, available at the Marine Science Station. 2.3 Statistical analysis All statistical analysis was carried out using Minitab (developed by researchers from the Pennsylvania State University). The concentrations of trace metals among dif- ferent organs were compared with weights. Analysis of Variance (ANOVA) was performed to compare the means between different organs. Regression test was used to ver- ify if a relationship between the weight and the Metals lev- els in the organs exist. FIGURE 1 - Gulf of Aqaba, with its semi-enclosed nature. 3. RESULTS 2.2 Samples collection and preparations 3.1 Metal concentrations among the different organs Forty fish sample were collected for this study. Fresh Figure 2 shows mean concentrations of magnesium in samples were bought from the local fishermen at the mini- all sampled organs ± standard deviations. The clear differ- port in Aqaba. The collected fish were placed in clean plas- ences shown by Figure 2 were found to be significant (P tic bags and transferred to the laboratory at the Marine Sci- Value = 0.000, R-Sq = 79.33%). Gills were found to be the ence Station for further study and analysis were performed major site of magnesium bioaccumulation, with mean of according to the procedures recommended by Abu Hilal 1.8366 g/Kg, Tukey’s pairwise comparison test showed and Ismail [3]. Each fish was washed by distilled water, to that the liver is the second bioaccumulation site for magne- get rid of any remnants of trace metals on the outer surface sium, with mean concentration of 1.2989 g/Kg, followed of the fish. For each fish sample, morphometric data in- by gonads, muscle, stomach and the spleen, with means cluding weight and length were recorded, the fork length concentrations of 1.1107, 1.0569, 1.0484 and 1.0484 g/Kg ranges from 66.5 to 45 cm wear as the weight ranges from respectively, and no significant differences between them, 3907 to 943 g. Then samples were dissected using a stain- and both the kidney (0.8483 g/Kg) and the heart (0.7747 g/ less steel knife. Samples of each of the following organs Kg) had the least concentrations of magnesium per dry were taken: liver, heart, spleen, muscle, kidney, gills, gon- weight. ads and stomach. The organs were placed in glass Petri The variation of nickel levels that was resulted from o dishes, before they were placed into an oven at 85 C for the tissue type (different organ) was found to be weak (R- 24 hours to obtain dry samples. Dry samples were grinded Sq = 6.01%), however it is statistically significant (P value using a mechanical homogenizer, and stored in plastic bags = 0.015). Tukey’s test could not detect any significant dif- for storage at room temperature until further use. ferences between the organs. Because ANOVA rejected About 0.1 mg of dry weight of each sampled organ was the H0, it is safe to use fisher test to do the pairwise com- placed in a crucible and dry ashed ????? using Carbolite parison. Fisher test showed that nickel had three major sites 2 © by PSP Volume 24 – No 10. 2015 Fresenius Environmental Bulletin FIGURE 2 - Magnesium concentrations in E.