Measurement of heavy metals accumulation in ctendia of Anadara ehrenbergi ( Dunker , 1868 ) using energy-dispersive x-ray fluorescence ( EDXRF )

Specimens were collected from three estuarine localities of the Arabian Gulf (Saudi Arabia) namely northern Khobar, southern Khobar and Ad-Dammam estuarine beaches during January and August 2013 and June 2014. Three collections in the form of twenty specimens were samples in each month from each locality. Immediately these samples were dissected and ctendia were isolated and frozen at 20°C. Using energy dispersive X Ray fluorescence (EDXRF), accumulations of Sodium, manganese, aluminium, phosphate, sulphur, chlorine, cadmium, calcium, iron, nickel, copper, zinc and lead were measured. This trail has been investigated in triplets. Concentration of the heavy metals studied was compared with United Kingdom Quality Standards, the United States Environmental Protection Agency (USEPA), Egyptian Organization for Standardization and Saudi Arabian Standards Organization. One way analysis of variance (ANOVA) with P˂0.05 and Turkey`s multiple analysis test were applied to all the data obtained from the software. This study concluded that clams live in southern Khobar estuarine beach contain percentage of heavy metals ≥ Saudi Arabian Standards whereas the clams live the northern Khobar and Ad-dammam easuarine beaches contain percentage of heavy metals ≈ Saudi Arabian Standards.


INTRODUCTION
Biological markers allow the direct determination of pollutant impact in marine ecosystems.Most studies on marine pollution have focused on animals nearer to the lower end of the food web.Heavy metals such as mercury, lead, arsenic, cadmium, tin, chromium, zinc, and copper are among the most dangerous pollutants in the marine environment (Al-Mahroos and Al-Saleh, 2000;Al-Jedah and Robinson, 2001;Readman et al., 2002;De Forest et al., 2007).Pollution with organic and inorganic chemicals plays an important role in threatening marine *Corresponding author.E-mail: gaibrahim@uod.edu.saAuthor(s) agree that this article remain permanently open access under the terms of the Creative Commons Attribution License 4.0 International License organisms (Zyadah, 2010).Arabian Gulf is set as extremely arid region of a shallow semi-closed water basin, it receives a huge amount of waste water and other pollutants from global oil transportation, drilling oil, industrial and human activities, it leads to disturbance to the coastal environment (sadiq and Alam, 1989;Khan and Al-Homaid, 2008;Zyadah, 2011).Therefore, the heavy metal contamination in water and marine organisms were monitored to determine the rate of accumulation in tissues of marine animals.The concentration of metals in the animal organs can be reasonable guide for public health standards and for the organisms condition (Zyadah, 2011).As a result high levels of heavy metals in aquatic ecosystems can be toxic and get incorporated into the food chain.Previous studies showed that heavy metals concentrations in marine organisms may exceed the allowable limits, where it may lead to a risk to ecosystems and humans consumption (El-Gendy, 2003;Zyadah and Al-Motairy, 2012).There are few published articles on the background of heavy metals in marine organisms in Arabian Gulf, Saudi Arabia (Sadiq and Alam, 1989;Sadiq et al., 1992;Zyadah and Almoteiry, 2012).However, analysis of heavy metals bioaccumulation to identify mutations in the genes and molecular characterization proteins of Ciona intestinalis collected from three localities from the Mediterranean Sea, Alexandria, Egypt have been investigated (Saad et al., 2008(Saad et al., , 2011)).In these studies it was concluded that heavy metal pollution affects nearly all tissues and molecular structure characterization of this fouling animal.Historically, pearl oysters represent a major marine resource in the Arabian Gulf and Mediterranean Sea countries.Several studies have been conducted to detect heavy metal contamination in the pearl oyster, Pinctada radiata in the Mediterranean Sea.Selected heavy metals were determined in the tissue of this pearl oyster (Buo-Olayan and Subrahmanyam, 1997;Hedge et al., 2009;Radwan et al., 2009).These studies noted a significant increase in the levels of Cu, Pb and Zn in oysters.Molluscs have long been known to accumulate essential and nonessential elements in aquatic ecosystems (Al-Saleh and Doush, 2002;Al-Darwish et al., 2005).Mussels accumulate many chemicals due to their great filtration capacity, concentrate metals in their soft tissues, and hence serve as bioindicators of metal contamination (Naser, 2010).
The key objectives addressed in this present study is to understand the accumulation pattern of sodium, manganese, aluminium , phosphate, sulphur, chlorine, cadmium, calcium, iron, nickel , cupper, zenic and lead in ctendia in Anadara ehrengergi under chronic exposure of metals.This study could determine the pollution capacity of each study locality.A. ehrengergi has an open circulatory system, and any change in their ambient environment will be reflected in the ctendia as soon as water bathes the body.A life in water requires that ctendia and other body surfaces be designed for the efficient exchange of oxygen and other essential molecules.A. ehrengergi (Dunker, 1868) were collected from shallow water of three localities in Arabian Gulf, Saudi Arabia namely Ad-Dammam beach, northern Khobar at front of Merydien hotel and southern Khobar at the vicinity of Bahrain bridge during January and August 2013 and June 2014 (Figure 1).Three collections in the form of twenty samples were chosen in each collection from each locality.Identification of the clam was carried out according to Sahin et al. (2009), De Mora et al. (2010), Khade and Mane (2012) and Vedrana et al. (2012).Immediately these samples were stored in an insulated box containing ice cubes and transferred to deep freeze (-20°C) until the time for metal analysis.Three samples of ctendia were taken from each seasonally collections of each group from each study site and prepared for heavy metals analysis using energy dispersive X Ray fluorescence (EDXRF) without any chemical pre-treatment.These heavy metals are sodium, manganese, aluminium, phosphate, sulphur, chlorine, cadmium, calcium, iron, nickel, cupper, zenic and lead.In EDXRF spectrometers, all of the elements in the sample are excited simultaneously, and an energy dispersive detector in combination with a multi-channel analyzer is used to simultaneously collect the fluorescence radiation emitted from the sample and then separate the different energies of the characteristic radiation from each of the different sample elements.Resolution of EDXRF systems is dependent upon the detector, and typically ranges from 150 to 600 eV.The principal advantages of EDXRF systems are their simplicity, fast operation, lack of moving parts, and high source efficiency.

Specimens of
Thin samples of ctendia were polished by abrasion on diamond discs and finally mirror polished with a nonaqueous 1 μm diamond suspension (ESCIL, PS-1MIC).The polished-thin samples were surrounded with a conductive silver paint to make contact on the surface, carbon-coated in a Balzers BAF-400 rotary evaporator, and then maintained in desiccators to prevent air-contact before analysis.Elemental energy-dispersive X-ray microanalysis were rapidly performed within two days of preparation in an environmental scanning electron microscope (FEI XL30 ESEM-FEG), operating at 15 to 20 kV and a working distance of 10 mm.A total of 9 polished thin slices for each season taken from 45 samples were imaged by back-scattered electrons (BSE) and analysed for the elemental composition of the minerals present.Elemental analyses have been carried out on the surface of 2μm size mineral concretions.EDX microanalyses with an acquisition time of 60 s have been obtained for the frozen samples in order to determine whether any mineral transformation took place through chemical reactions during sample preparation.The elemental quantitative analysis used an automatic background subtraction and a ZAF correction matrix to calculate the elemental composition in weight percent and atomic percent.For quantitative analysis of the mineral concretions, the contributions of the C-coating and the embedding resin containing C, O and trace of Cl were subtracted from the quantitative data of each spectrum.The contribution of Ccoating was evaluated to 25 At % of C from a pure mineral sample (hydroapatite) C-coated in the same conditions.The remaining C was attributed to the resin and an amount of O (At %) was subtracted in the same proportion, deduced from reference spectra of pure resin (C/O ratio 8:1).More details about the techniques applied is given in Injuk et al. (2006), Corbari et al. (2008), Pete (2010) and Nicholas et al. (2012).
The XRFAES software system has been applied for all calibrations.It consists of three procedures.The evaluation of the spectra, the calculation of concentrations and the post-processing unit (Rindby, 1989;Perring and Blanc, 2008).

Statistical analysis
Analysis of variance (ANOVA) is a broad group of techniques for identifying and measuring different sources of variation within the data set.It consists of a set of procedures by which a variance of the random variable is broken down by certain sources of variation of its value.With the components of variance, depending on the sources, one can conclude if there is a significant difference between the values of dependent variable for different levels of the observed factor variables.In the present study, a one-way analysis of variance is used to compare the three groups of ctendia which have different levels of one variable.If the above-mentioned assumptions for ANOVA are not met, the Turkey`s Multiple Comparison Test is used for determining whether three or more independent samples originate give a clear cut differences.When this test leads to significant results, at least one sample differs from the others.A principal component analysis is a standard tool in modern data analysis.It is a simple, nonparametric method for extracting relevant information out of confusing data sets.Principal component analysis is concerned with the interpretation of the variance and covariance structure of the original set of variables through a small number of their linear combinations.The general objectives of principal component analysis are data reduction and interpretation in order to reduce the number of variables (Dijana et al., 2012).
However, results of the different heavy metals analyzed in this study are shown in Tables 1 to 9 in original form from the software.However, concentration of all metals in ctendia will be summarized as follows: (1) Sodium concentrations in mixed tissues of ctendia ranged from 2.1 to 3.6 mg/Kg dry weight in samples of  Ad-Dammam, 3.2 to 3.7 mg/Kg dry weight in samples of northern Khobar whereas 7.9 to 8.2 mg/Kg dry weight in samples of southern Khobar.Histogram (1) clarifies that sodium contamination in ctendia is Ad-Dammam ˂ northern Khobar ˂ southern Khobar (Tables 1 to 10) (Figure 2).The means significant difference (P < 0.05) is obvious and Tukey's multiple comparison test with either P < 0.05 or P > 0.05 is denoted Table 11.
(2) Manganese concentrations in mixed tissues of ctendia ranged from 0.5 to 1.5 mg/Kg dry weight in samples of Ad-Dammam, 0.7 to 1.4 mg/Kg dry weight in samples of northern Khobar whereas 1.5 to 2.8 mg/Kg dry weight in samples of southern Khobar.Histogram 2 clarifies that Manganese contamination in ctendia is Ad-Dammam ≈ northern Khobar ˂ southern Khobar (Tables 1 to 10).The means significant difference (P < 0.05) is obvious and Tukey's multiple comparison test with either P < 0.05 or P > 0.05 is denoted in Table 12.
(3) Aluminium concentrations in mixed tissues of ctendia ranged from 2.1 to 2.5 mg/Kg dry weight in samples of Ad-Dammam, 1.8 to 2.6 mg/Kg dry weight in samples of northern Khobar whereas 2.7 to 7.9 mg/Kg dry weight in   1 to 10).The means significant difference (P < 0.05) is obvious and Tukey's multiple comparison test with either P < 0.05 or P > 0.05 is denoted in Table 14.
(5) Sulphur concentrations in mixed tissues of ctendia ranged from 5.7 to 6.0 mg/Kg dry weight in samples of Ad-Dammam, 7.1 to 12.6 mg/Kg dry weight in samples of northern Khobar whereas 4.6 to 30.4 mg/Kg dry weight in samples of southern Khobar.Histogram 5 clarifies that sulphur contamination in ctendia is Ad-Dammam ˂ northern Khobar ˂ southern Khobar (Tables 1 to 10).The means significant difference (P < 0.05) is obvious and       1 to 10).The means significant difference (P < 0.05) is not not obvious and Tukey's multiple comparison test with either P < 0.05 or P > 0.05 showed no difference.
(11) Nickel concentrations in mixed tissues of ctendia ranged from 0.4 to 0.5 mg/Kg dry weight in samples of  1 to 10).The means significant difference (P < 0.05) is not obvious and Tukey's multiple comparison test with either P < 0.05 or P > 0.05 is denoted in Table 19. (12) Copper concentrations in mixed tissues of ctendia ranged from 4.1 to 3.4 mg/Kg dry weight in samples of Ad-Dammam, 0.1 to 3.7 mg/Kg dry weight in samples of northern Khobar whereas 0.9 to 3.7 mg/Kg dry weight in samples of southern Khobar.Histogram 10 clarifies that copper contamination in ctendia is Ad-Dammam > northern Khobar < southern Khobar (Tables 1 to 10).The means significant difference (P < 0.05) is not obvious and Tukey's means significant difference with either P < 0.05 or P > 0.05 is denoted in Table 20.(13) Zinc concentrations in mixed tissues of ctendia ranged from 1.7 to 2.5 mg/Kg dry weight in samples of Ad-Dammam, 0.8 to 1.0 mg/Kg dry weight in samples of northern Khobar whereas 1.0 to 2.5 mg/Kg dry weight in  1 to 10).( 15) Lead concentrations in mixed tissues of ctendia ranged from 0.4 to 0.7 mg/Kg dry weight in samples of Ad-Dammam, 0.2 to 9.0 mg/Kg dry weight in samples of northern Khobar whereas 1.3 to 3.7 mg/Kg dry weight in samples of southern Khobar.It can be concluded that  1 to 10).
Histogram 12 clarifies that lead contamination in ctendia is Ad-Dammam < northern Khobar < southern Khobar (Tables 1 to 10).The means significant difference (P < 0.05) is not obvious and Tukey's multiple comparison test with either P < 0.05 or P > 0.05 is denoted in Table 22.
The most dramatic results came with the analysis of the samples of the southern Khobar estuarine beach in the three collections time.The data gathered showed very high concentration of total sodium, aluminium, phosphate, sulphur, chlorine, cadmium, nickel, zinc, mercury and lead excluding iron that can cause significant adverse effects on bivalve species if concentrations continue to accumulate and bio-magnify in the food chain.Clams live in southern Khobar estuarine beach contain percentage of heavy metals ≥ Saudi Arabian Standards whereas the clams live the northern Khobar and Ad-dammam easuarine beaches contain percentage of heavy metals ≈ Saudi Arabian Standards.The accumulation of multiple metals and pollutants can have a synergistic effect that can increase the threat level

DISCUSSION
The goal of this study was to determine the presence of heavy metals in ctendia of Anadara ehrenbergi collected from three estuarine beaches of Arabian Gulf (Saudi Arabia).A determination of metal concentrations in organisms should be a part of any assessment and monitoring program in the coastal zone.In the present study, Tables 1 to 10 showed that A. ehrenbergi concentrated heavy metals in its ctendia; however, little is known about the potential of the other species to do the same in the same study sites.It has been shown above that the samples collected from western estuarine beach in Khobar have anomalous heavy metal values.The most dangerous heavy metals measured in this study are aluminum, phosphate, calcium, nickel, potassium, mercury, iron, copper, chromium and zinc.metals that accumulate in ctendia of A. ehrenbergi pose a threat to the survivorship of individual species as well as the ecosystem.Several authors in the available literature interested to investigate the problem of heavy metals bioaccumulation in marine invertebrates and fishes (Khan et al., 2001;Bu-Olayan and Thomas, 2001;Islam and Tanaka, 2004;Naithani et al., 2010;Freije, 2014;Radwan et al., 2014) (1994).This study reported elevated levels of Pb and Cd that exceeded the recommended standards of the World Health Organization (WHO).Similarly, elevated levels of heavy metals were reported in P. radiata collected from areas that were subject to dredging and shipping activities along the Qatari coastline (Al-Madfa et al., 1998).This study reported high mean concentrations for V exceeded the international standards.De Mora et al. ( 2004) also found very high concentrations of Zn in pearl oysters near the oil refinery in Bahrain.Al-Sayed and Dairi (2006) measured selected heavy metals in the marine snail Turbo coronatus collected from nearshore sites around Bahrain.This study found that the levels of Cu and Pb were higher than the WHO acceptable limits for marine organisms.Selected heavy metals were measured in the edible clam Meretrix meretrix collected from stations along the coastline of Saudi Arabia (Alyahya et al., 2011).Elevated levels of Pb that exceeded the maximum permissible level recommended by the European Union standards.Nonetheless, this study concluded that the clam from the sampling region was within the safe limits for human consumption.Al-Farraj et al. (2011) determined the levels of selected heavy metals in the cuttlefish Sepia pharaonis collected from different fish markets at Al-Khober City in the Arabian Gulf.This study concluded that the levels of the investigated heavy metals in the cuttlefish were generally low and/or well within the maximum permitted concentrations imposed by different organizations and authorities, and consequently within the safe limits for human consumption.The study agrees with the finding of Al- Farraj et al. (2011), Sepia pharaonis is not a filter feeder as clams.Heavy metal accumulation in the gill tissue of fishes from Arabian Gulf were reported (Islam andTanaka, 2004).Mercury and other metals, such as lead and cadmium have been shown to accumulate in living organisms living in marine ecosystems (Al-Hashimi and Al-Zorba, 1991).Metal accumulation by the clam Meretrix meretrix as lead, titanium, zinc, nickel, vanadium and copper were measured in Arabian Gulf (Sadiq, et al., 2002).In the present study, tissues of ctendia of A. ehrenbergi showed higher concentrations for most heavy elements than other body parts, except in the case of calcium.The concentrations of Cu, Zn, Fe and Pb are much more variable.Thus, it appears that a non-selective sampling strategy for different parts of the ctendia would be sufficient.The ratio of the metals Fe, Zn, Cu, and Pb remains approximately respectable of study site.This pattern may be changed in systems where predominantly one element is discharged.Further work is required to establish whether it is possible to use this ratio predictively.The EDXRF technique is well suited for multi-element determinations in environmental samples.Cadmium (Cd) is one of the most toxic heavy metals for humans; the main source of non-occupational exposure to Cd includes contaminated sea foods (Khan and Price, 2002).The World Health Organization (WHO, 1993) estimates that 80% of the world population presently uses herbal medicine.Several articles have reported of adverse effects of these herbal preparations due to the presence of high level of heavy metals such as Cd, lead, chromium, nickel, etc. (Naithani et al., 2010).The results revealed that the concentrations of some heavy metals, including Cd, were far greater than the permissible limits proposed by the International Regulatory Authorities for herbal drugs.Acute or chronic exposure of Cd causes respiratory distress, lung, breast and endometrial cancers, cardiovascular disorders and endocrine dysfunction (Nagata et al., 2005;Nadim, et al., 2008Chang et al., 2009;Khamdan and Al Madany, 2009;Naithani et al., 2010;de Mora et al., 2010;Al Farraj, et al., 2011).In addition, Cd is a common inorganic contaminant of coastal sediments and waters due to anthropogenic pollution and natural sources (Fowler et al., 2007).It can be accumulated in aquatic animals (crabs, shrimps, oysters, clams and mussels) after entering through different way such as respiratory tract, digestive tract, surface penetration etc. (Sokolova, 2004;Sokolova et al., 2004;USFDA, 2006;Juma and Al-Madany, 2008;Juma and Al-Madany, 2008;Khamdan and Al Madany, 2009;Naser, 2012).It is seriously harmful to the growth of aquatic life and survival, resulting in decline of their populations.At the same time, as aquatic food products, these animals exposed to Cd might threaten human health.
Several elemental, environmental, and organismal factors influence the absorption of these metals including: What the metal is bonded to chemically, if the ion is small, neutrally charged, and/or lipophilic, water hardness, pH, and temperature, concentration of compound, and route of exposure (gill, contaminated food, non-food particles, oral intake of water, and dermal absorption).After exposure it is transported by the blood, usually bonding to a protein at some point, and will then be distributed to and accumulates in a tissue which it has a high affinity for.Over 80% of marine pollution comes from land-based activities (Al-Jamali et al., 2005;Al-Busaidi et al., 2011;Daoji and Dag, 2004;Sheavly and Register, 2007).From plastic bags to pesticides-most of the waste we produce on land eventually reaches the marine ecosystem, either through deliberate dumping or from run-off through drains and rivers.This includes oil, fertilizers, plastic garbage, sewage disposal and toxic chemicals.The prevalence of these metals accumulating in the ctendia of A. ehrenbergi might be an indicator of a disastrous future for the Arabian Gulf ecosystem.
A high prevalence of certain heavy metals and elements could cause what is known as a dead zone that will yield catastrophic effects to the ecosystem.A dead zone is an area on an aquatic ecosystem that is unable to support life due to lack of dissolved oxygen.When excess phosphate is in the watershed combined with excess nitrogen the populations of algae and phytoplankton drastically increase.When the large populations die they sink and begin to be broken down by bacteria.Bacteria that break down this large layer of biomass use dissolved oxygen and release carbon dioxide, which significantly depletes the aquatic environment of dissolved oxygen.The depletion of dissolved oxygen renders the area unable to support life dependent on aerobic respiration, thus getting the name dead zone (SASO, 1997).
The results of this study showed serious heavy metals accumulation problems in the Arabian Gulf ecosystem.Heavy metals are accumulating and bio-magnifying and have a very real potential to increase the toxicity present throughout the Arabian Gulf ecosystem.
This study illustrated the use of the EDXRF technique in rapid assessment of metal contamination in biological material.The distribution of heavy metals in different parts of ctendia of A. ehrenbergi has been analyzed, and the results obtained agree well with those of other authors on other species collected from Arabian Gulf, especially Zyadah and Al-Motairy (2012) and Freije (2014).

Table 1 .
Measurement of heavy metal contaminations in ctendia of Anadara ehrenbergi.

Table 2 .
Measurement of heavy metal contaminations in ctendia of Anadara ehrenbergi.

Table 3 .
Measurement of heavy metal contaminations in ctendia of A. ehrenbergi.

Table 4 .
Measurement of heavy metal contaminations in ctendia of A. ehrenbergi.
Samples were collected in January 2013 from eastern Khobar estuarine beach.

Table 5 .
Measurement of heavy metal contaminations in ctendia of A. ehrenbergi.
Samples were collected in August 2013 from eastern Khobar estuarine beach.

Table 6 .
Measurement of heavy metal contaminations in ctendia of A. ehrenbergi.
Samples were collected in June 2014 from eastern Khobar estuarine beach.

Table 7 .
Measurement of heavy metal contaminations in ctendia of A. ehrenbergi.
Samples were collected in January 2013 from western Khobar estuarine beach.

Table 8 .
Measurement of heavy metal contaminations in ctendia of A. ehrenbergi.
(4) Phosphate concentrations in mixed tissues of ctendia ranged from 31.8 to 36.2 mg/Kg dry weight in samples of Ad-Dammam, 35.1 to 37.5 mg/Kg dry weight in samples of northern Khobar whereas 25.9 to 53.1 mg/Kg dry weight in samples of southern Khobar.Histogram 4 clarifies that phosphate contamination in ctendia is Ad-Dammam ≈ northern Khobar ≈ southern Khobar (Tables

Table 9 .
Measurement of heavy metal contaminations in ctendia of A. ehrenbergi.
Samples were collected in June 2014 from western Khobar estuarine beach.

Table 10 .
Measurement of percentage of heavy metal contaminations in ctendia of A. ehrenbergi.Samples were collected in January and August 2013 and June 2014 from all study estuarine beaches.
0 to 11.8 mg/Kg dry weight in samples of 11.4to 22.6 mg/Kg dry weight in samples of northern Khobar whereas 3.1 to 29.7 mg/Kg dry weight in samples of southern Khobar.Histogram 6 clarifies that chlorine contamination in ctendia is Ad-Dammam ˂ northern Khobar ˂ southern Khobar (Tables1 to 10).The (7) Cadmeium concentrations in mixed tissues of ctendia ranged from 2.1 to 4.2 mg/Kg dry weight in samples of Ad-Dammam, 4.4 to 7.2 mg/Kg dry weight in samples of northern Khobar whereas 2.9 to 8.3 mg/Kg dry weight in samples of southern Khobar.Histogram 7 clarifies that cadmium contamination in ctendia is Ad-Dammam ˂

Table 11 .
One-way analysis of variance (ANOVA) and Tukey's Multiple Comparison test analyses for sodium.

Table 12 .
One-way analysis of variance (ANOVA) and Tukey's multiple comparison test analyses for manganese.
(8)Calcium concentrations in mixed tissues of ctendia ranged from 31.6 to 33.7 mg/Kg dry weight in samples of Ad-Dammam, 11.7 to 32.0 mg/Kg dry weight in samples of northern Khobar whereas 5.9 to 23.6 mg/Kg dry weight in samples of southern Khobar.Histogram 8 clarifies that calcium contamination in ctendia is Ad-Dammam > northern Khobar > southern Khobar (Tables1 to 10).The means significant difference (P < 0.05) is not obvious and Tukey's multiple comparison test with either P < 0.05 or P > 0.05 is denoted in Table18.(9) Chromium concentrations in mixed tissues of ctendia ranged from 0.2 to 0.4 mg/Kg dry weight in samples of Ad-Dammam, zero mg/Kg dry weight in samples of northern Khobar and zero mg/Kg dry weight in samples

Table 13 .
One-way analysis of variance (ANOVA) and Tukey's multiple comparison test analyses for sodium.

Table 14 .
One-way analysis of variance (ANOVA) and Tukey's multiple comparison test analyses for phosphate.
(Tables1 to 10).The means significant difference (P < 0.05) is not not obvious and Tukey's multiple comparison test with either P < 0.05 or P > 0.05 showed no difference.(10) Iron concentrations in mixed tissues of ctendia ranged from 0.1 to 0.2 mg/Kg dry weight in samples of Ad-Dammam, 0.1 to 0.4 mg/Kg dry weight in samples of

Table 15 .
One-way analysis of variance (ANOVA) and Tukey's Multiple Comparison test analyses for sulphur.

Table 16 .
One-way analysis of variance (ANOVA) and Tukey's multiple comparison test analyses for chlorine.

Table 17 .
One-way analysis of variance (ANOVA) and Tukey's multiple comparison test analyses for

Table 18 .
One-way analysis of variance (ANOVA) and Tukey's Multiple Comparison test analyses for calcium.
(14)Mercury concentrations in mixed tissues of ctendia ranged from zero mg/Kg dry weight in samples of Ad-Dammam, zero to 0.2 mg/Kg dry weight in samples of

Table 19 .
One-way analysis of variance (ANOVA) and Tukey's multiple comparison test analyses for nickel.

Table 20 .
One-way analysis of variance (ANOVA) and Tukey's multiple comparison test analyses for copper.

Table 21 .
One-way analysis of variance (ANOVA) and Tukey's multiple comparison test analyses for zinc.

Table 22 .
One-way analysis of variance (ANOVA) and Tukey's multiple comparison test analyses for lead.
Alyahya et al. (2011)006)rk concerning heavy metals accumulations in marine animals inhabiting the Arabian Gulf isFreije (2014).In this study, the Arabian Gulf environmental status was assessed based on studies conducted in Bahrain, Kuwait, Oman, Saudi Arabia, Qatar, and United Arab Emirates (UAE) during 1983 and 2011.The present study found many more or less parallel results with that work.Moreover, other authors interested to study the problem of heavy metals in marine organisms living in the Arabian Gulf.The present study accept the finding ofAl-Sayed et al. (1994),Al-Madfa et al. (1998),De Mora et al. (2004),Al-Sayed and Dairi (2006)andAlyahya et al. (2011)and disagree with the results of(Al-Farraj et al., 2011).Levels of selected heavy metals in P. radiata collected from two oyster beds in Bahrain were determined by Al-Sayed et al.