Heavy metal contents in growth bands of Porites corals: Record of anthropogenic and human developments from the Jordanian Gulf of Aqaba

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Marine Pollution Bulletin 54 (2007) 1912–1922 www.elsevier.com/locate/marpolbul

Heavy metal contents in growth bands of Porites corals: Record of anthropogenic and human developments from the Jordanian Gulf of Aqaba Saber A. Al-Rousan a

a,*

, Rashid N. Al-Shloul b, Fuad A. Al-Horani a, Ahmad H. Abu-Hilal

b

Marine Science Station, The University of Jordan and Yarmouk University, P.O. Box 195, Aqaba 77110, Jordan Department of Earth and Environmental Science, Faculty of Science, Yarmouk University, Irbid 21163, Jordan

b

Abstract In order to assess pollutants and impact of environmental changes in the coastal region of the Jordanian Gulf of Aqaba, concentrations of six metals were traced through variations in 5 years growth bands sections of recent Porties coral skeleton. X-radiography showed annual growth band patterns extending back to the year 1925. Baseline metal concentrations in Porites corals were established using 35 years-long metal record from late Holocene coral (deposited in pristine environment) and coral from reef that is least exposed to pollution in the marine reserve in the Gulf of Aqaba. The skeleton samples of the collected corals were acid digested and analyzed for their Cd, Cu, Fe, Mn, Pb and Zn content using Flame Atomic Absorption Spectrophotometer (FAAS). All metal profiles (except Fe and Zn) recorded the same metal signature from recent coral (1925–2005) in which low steady baseline levels were displayed in growth bands older than 1965, similar to those obtained from fossil and unpolluted corals. Most metals showed dramatic increase (ranging from 17% to 300%) in growth band sections younger than 1965 suggesting an extensive contamination of the coastal area since the mid sixties. This date represents the beginning of a period that witnessed increasing coastal activities, constructions and urbanization. This has produced a significant reduction in coral skeletal extension rates. Results from this study strongly suggest that Porites corals have a high tendency to accumulate heavy metals in their skeletons and therefore can serve as proxy tools to monitor and record environmental pollution (bioindicators) in the Gulf of Aqaba. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Heavy metals; Fossil corals; Porites; Growth bands; Gulf of Aqaba; Red Sea

1. Introduction Due to their apparent sensitivity to physical and chemical changes in the marine environment, reef-building corals have provided potentially useful proxies for interpreting past environments and chemistry of ambient seawater for several decades (e.g. Shen and Boyle, 1987; Shen et al., 1992; Delaney et al., 1993; Shen et al., 1996; Fallon et al., 2002). The internal growth bands that massive scleractinian corals accumulate (related to annual peri-

*

Corresponding author. Tel.: +962 3 2015145; fax: +962 3 2013674. E-mail address: [email protected] (S.A. Al-Rousan).

0025-326X/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpolbul.2007.08.014

odicity) can preserve changes in seawater properties, nutrient levels, and even pollution entering the marine environment during the coral lifetime (continuous time-series record) and provide time markers for the development of long chronologies (Knutson et al., 1972; Scoffin et al., 1992) which permit sub-annual dating resolution and enable accurate sampling. Corals can be exposed to high metal concentrations as a result of human activities such as harbor dredging or sewage discharges (Bastidas and Gracia, 1999; Esslomont et al., 2000; Fallon et al., 2002). These metals might occur in coral skeletons as a result of structural incorporation of metals into the aragonite (e.g. Goreau, 1977), inclusion of particulate materials in skeletal cavities (reviewed by

S.A. Al-Rousan et al. / Marine Pollution Bulletin 54 (2007) 1912–1922

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Howard and Brown, 1984), surface adsorption onto exposed skeleton (St. John, 1974; Brown et al., 1991), and chelation with the organic matrix of the skeleton (Mitterer, 1978). These metals will remain embedded forever in the coral skeleton since the new growth will cover old carbonate surfaces (St. John, 1974). The Sr/Ca, Mg/Ca, U/Ca, B/Ca and isotopic d18O in coral skeleton have been used to reconstruct sea surface temperatures (e.g. Cole and Fairbanks, 1990; Beck et al., 1992; Gagan et al., 1994; Fallon et al., 1999; Suzuki et al., 2001), whereas, Cd/Ca, Mn/Ca and Ba/Ca values were used to reconstruct rainfall, upwelling and river discharge events (e.g. Lea et al., 1989; Shen et al., 1992). On the other hand, the abundance of heavy metals, such as Hg, Pb, Cd, Mn, Cu, Zn and others, in coral skeletons reflects the anthropogenic and/or terrestrial influences on marine environments such as industrial and sewage pollution (Schneider and Smith, 1982; Dodge et al., 1984; Shen et al., 1987; Shen and Boyle, 1988; Guzman and Jimenez, 1992; Ramos et al., 2004; Al-Ouran, 2005), nuclear testing (Knutson et al., 1972) and anthropogenic CO2 increase (Nozaki et al., 1978; Aharon, 1991). Furthermore, some short coral chronologies have detected environmental changes through time scales (e.g. Dodge and Gilbert, 1984; Shen et al., 1987; Shen and Boyle, 1987; Guzman and Jarvis, 1996; David, 2003; Inoue et al., 2004; Al-Ouran, 2005). In this study, 80 years-long heavy metal record (1925– 2005) from the annually banded Porites coral is presented in order to investigate contamination resulting from natural and anthropogenic activities and to assess the suitability of this corals as environmental proxies from the Jordanian coast of the Gulf of Aqaba. In addition, 35 years-long heavy metal record from the same species and site was obtained from well preserved Holocene coral to serve as background metal concentration in corals.

The study site is located within the Jordanian coast of the Gulf of Aqaba (Fig. 1). Well preserved fossil coral (late-Holocene) samples of massive Porites sp. from the submerged reef terraces were collected near the Royal Jordanian Navy (RJN) site. Living corals of the same species were collected at a depth of about 5 m from the same area that hosts different developmental and human activities. To investigate the potential long term variations of heavy metal concentrations in Porites species, two relatively long cores (6.5 cm in diameter) were obtained from the recent and fossil massive Porites sp. coral (using diamond hand drill corer, CARDI, MOD. TALPA 1850 EL-A1, 1850 W). The core from the recent coral was 80 cm long while the one from the fossil coral was about 40 cm. The two cores were sectioned with a lubricated diamond saw along the coral’s maximum growth axis to obtain slices of about 5–6 mm thick. The slices were carefully cleaned with distilled water and dried in oven at 60 °C for 24 h. Tips of the living corals (Porites sp.) were collected at a depth of 5 m from the Marine Science Station (MSS) reef; a reserve and unpolluted site (Fig. 1). Portions less than 3 cm were sampled to represent recent skeleton growth. None of the coral samples showed any sign of bioeroders that may affect the results as found by Bastidas and Gracia (1999).

2. Gulf of Aqaba

3.2. X-ray diffraction

The Jordanian coastline of the Gulf of Aqaba (about 27 km length) supports a relatively small coral reef area, composed entirely of narrow and steep fringing reefs which represents the northern limit (29°32 0 N) for reef corals in the western Indo-Pacific region (Schuhmacher et al., 1995). The Gulf of Aqaba is situated between the Sinai desert and the western Arabian Desert. The area is extremely arid with high evaporation (400 cm yr1) and negligible precipitation (2.2 cm yr1) and runoff (Reiss and Hottinger, 1984). However, flash floods through major wadis in winter transport terrestrial material into the Gulf, resulting in large deltas and incision of submarine canyons. The mean sea surface temperatures are 23.5 °C and mean salinity values in the upper waters are 40.4–40.6& (Manasrah et al., 2004). The Gulf of Aqaba is the only marine access of Jordan. This relatively limited coastline has to serve all conflicting uses of the coastal area. Therefore, the Jordanian portion

To investigate the diagenesis status in fossil coral, about 1 cm3 (cube) samples were taken from different sections of the fossil coral species for X-ray diffraction (XRD). In addition, several samples were taken from recent coral sections for comparison purposes. The 1 cm3 (cube) samples were ground under ethanol and approximately 100– 200 mg of coralline powder from each sample were smeared onto glass slide. The slides were analyzed on a Sietronic Diffractometer with the Cobalt X-ray tube on 90% loading (30 mA, 50 Mv) and scanned from 2U of 10–70°. The aragonite and calcite contents (%) on each sample were recorded automatically by the instrument. Samples with less than 98% aragonite were neglected.

of the Gulf of Aqaba has witnessed major development during the past four decades with respect to industrial, tourism and constructions of new ports and resorts accompanied by intensive shipping and terrestrial transportation which increased pressure on the marine ecosystem of the Gulf. 3. Materials and methods 3.1. Coral samples

3.3. Growth bands and sub-sampling procedure Coral slices of the two long Porites cores (recent and fossil) were X-rayed following Buddemeier et al. (1974) and

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Hudson (1981) to reveal the annual growth bands using local hospital facility in Aqaba. The X-radiograph negatives were printed onto photographic paper giving a positive image (Fig. 2). The positive images of the X-radiographs were used to mark separate annual growth bands along the cores. The annual extension rates (cm yr1) from both corals were directly measured along the major growth axes from the positive prints. Each couple of high-/low density bands represent an annual growth increment. The upper growth band of the recent coral was assigned to the date of collection (2005), however, it was not possible to assign a fixed date for the Holocene fossil coral top. The years count for both corals followed the annual growth bands chronology (Fig. 2), and the annual bands were grouped into fiveyears sections. Each section was cut with a micro drill (PROXXON, NG5/E, FBs 12/E). The number of coral sections obtained were 16 and 7 resulting in a total of 80 (1925–2005) and 35 years for recent and Holocene corals, respectively. After cutting, the skeletal material was cleaned and crushed (using an agate mortar and pestle) following the procedure of Esslemont (1999).

3.4. Heavy metal measurements Fig. 2. X-radiograph positive prints of recent (right) and fossil (left) coral slabs showing the skeletal density bands. Each annual growth band consists of a dark and a white adjacent band. Five years bulk samples were taken from both corals.

From each section, 2 g (dry weight) of the ashed skeletal material samples were analyzed for heavy metals content using the standard procedure of the American Environmental Protection Agency (EPA) for soil and biota (EPA

S.A. Al-Rousan et al. / Marine Pollution Bulletin 54 (2007) 1912–1922

uous record from the time of collection 2005 back to the year 1925, whereas the fossil coral core provides 35 years continuous record from late Holocene time window. Analysis for the annual linear extension rates from recent coral revealed that there is a significant (p < 0.05) decrease of extension rate between sections older than 1965 (average 1.00 ± 0.23 cm yr1) and sections younger than 1965 (average 0.88 ± 0.14 cm yr1). The extension rate in the 35 years-long fossil coral record (average 0.98 ± 0.16 cm yr1) was similar to extension rates in recent coral older than 1965 (Fig. 3).

#3050). Cd, Cu, Fe, Mn, Zn, and Pb have been measured in each section. All samples were analyzed using Flame Atomic Absorption Spectrophotometry (FAAS) by the use of the Analytical Jena novAA 300 atomic absorption spectrophotometer. Duplicate measurements were made for each sample, by direct aspiration into air acetylene flame of the instrument. The instrument was instructed to give the mean value and standard deviations of three readings as the final reading of each sample. The precision of the whole procedure was assessed by 10 replicates for a sample and the results agreed to within 4%. Duplicate blanks were used for each patch of digested samples. The blanks were read with their related patch of samples. The mean value of the blank, if any, was subtracted from the reading of the samples to give the final readings. Blank values ranged from 2% to 25% of the total uncorrected sample values.

4.2. Fossil coral mineralogy Textural and mineralogical investigations on the skeletons of the fossil coral samples using optical microscopy (thin sections) and X-ray diffraction was conducted to define the state of preservation and the degree of diagenetic alteration. Results of this method showed that fossil specimens used in this study composed of 100% aragonite and no mineralogical alteration (low-magnesium calcite) have occurred (Fig. 4). Petrographic thin sections made for fossil corals were also used for differentiation of the major carbonate minerals. The deep red to black color of the sample indicated that sample is composed mainly of aragonite mineral.

4. Results 4.1. Age model and extension rate of corals

Coral extension rate (cm.yr-1)

The sclerochronology of both recent and fossil Porites corals were determined from X-ray images of the coral growth bands (Fig. 2). The consistent pattern of annual density band pairs (high and low) was used to count annual layers in the coral. The recent coral core provides a contin-

a

1.5 1.3

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Sections >1965 (0.88± 0.14 cm.yr-1)

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Year Fig. 3. Variations of five-years average skeletal extension rates (cm yr1) for: (a) recent Porites coral over the period (1925–2005), and (b) fossil Holocene Porites coral (35 years-long). Average and standard deviation values are shown.

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1965 (Table 1). The values averaged 4.19 ± 0.51, 3.8 ± 0.22, 14.49 ± 2.42, 0.35 ± 0.0, and 38.17 ± 3.24 lg g1 for Cd, Cu, Fe, Mn, and Pb, respectively (Table 1).

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5. Discussion 5.1. Coral extension rates

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2Theta Fig. 4. Examples of X-ray diffraction patterns for the fossil coral (Porites sp.), where: (a) represents well preserved aragonite skeleton and (b) diagenetic calcite skeleton.

4.3. Heavy metal profiles Fig. 5 shows time series record of coral metal concentration (Cd, Cu, Fe, Mn, Pb and Zn) for the recent coral between 1925 and 2005. The concentration of heavy metals differs significantly among skeletal sections older than 1965 and that younger than 1965. Cadmium, manganese, copper, and lead concentrations in recent coral record, showed relatively flat profiles before the year 1965 and a steep (Cd, Mn) and gradual (Cu, Pb) increase over the last 40 years (Fig. 5). The average values were 2.35 ± 0.38, 4.70 ± 0.47, 2.46 ± 0.27, and 41.51 ± 3.43 lg g1 in sections older than the year 1965 and began to increase dramatically up to 5.15 ± 0.26, 5.36 ± 0.36, 8.22 ± 0.26, and 42.91 ± 1.94 lg g1 in sections younger than 1965. By comparison, the 35 years-long fossil coral (Porites sp.) record showed consistent values around 3.6 ± 0.60, 3.83 ± 0.35, 2.89 ± 0.34, and 43.14 ± 3.37 lg g1, for Cd, Cu, Mn, and Pb, respectively (Fig. 5). Iron and zinc concentrations from recent coral record (1925–2005) display fluctuated patterns with average values of 30.29 ± 17.93 and 5.46 ± 1.54 lg g1, respectively (Fig. 5). However, the fossil coral record showed consistent and lower values around 17.06 ± 3.47 and 5.06 ± 0.97 lg g1 for Fe and Zn, respectively (Fig. 5). High values were observed in the outermost layer of the coral. Heavy metal concentrations in recent coral collected from the MSS showed lower values of all metals (except Zn) compared to recent sections younger than the year

The skeletal extension rate measurement using the Xradiography was found to reveal identical results to measurements from the d18O isotopic curve (Al-Rousan et al., 2003). Results from recent coral record display a significant difference between the skeletal extension rates before and after the year 1965. The values in skeletal sections older than 1965 were higher than those in skeletal sections younger than 1965 and did not differ from that for fossil coral (35 years-long record). These results are similar to those reported by Runnalls and Coleman (2003) who found a decrease in skeletal extension rate of Montastraea annularis coral consistent with an increase in Pb and Zn at polluted site from Barbados. The increased metals concentration in the study area was not sufficient to kill the corals since Porites corals (used in this study) is known to be robust and survive under harsh conditions (e.g., high sedimentation) and are able to slough off sediments compared with other coral species (Fallon et al., 2002). Thus, the annual cyclicity of growth banding in Porites corals is not only a measure of time, but rather a useful indicator for pollution, which can inhibit coral growth (Barnes and Lough, 1996, 1999). 5.2. Fossil coral mineralogy For corals, diagenesis refers to the precipitation of secondary aragonite or calcite in skeletal voids or the replacement of skeletal aragonite usually with calcite (Bathrust, 1975). During this transformation, isotopes and trace elements are exchanged and removed, thus changing the geochemistry of the coralline matrix that may affect coral proxy records (Guilderson et al., 1994; Tudhope et al., 2001; McGregor and Gagan, 2003). According to XRD test, the fossil coral used in the present study appears to contain more than 98% aragonite. In thin sections of the fossil coral, all skeletal features were seen with almost complete absence of void filling or cement formation by calcite or secondary aragonite. These findings indicate that the fossil corals used in the present work are equivalent in mineralogy to modern corals and the possibility of diagenetic alteration of pristine geochemical signatures in the fossil coral is minimal and can generally be neglected. 5.3. Heavy metal profiles from the fossil coral The 35 years-long fossil coral record displays consistent values for all metals comparable (on average) to those obtained from the recent coral from the MSS (Fig. 6). However, the record exhibited higher values in the outer-

S.A. Al-Rousan et al. / Marine Pollution Bulletin 54 (2007) 1912–1922 8

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Fig. 5. Time series record of heavy metal (Cd, Cu, Fe, Mn, Pb, Zn) concentrations (lg g1) measured in recent (1925–2005) and fossil (35 years long) Porites coral sp. collected from the northern Gulf of Aqaba. Analytical error bars are shown.

most growth interval (Fig. 5). This could be due in part to metal associated with tissue that remains in the organic rind of the corals and/or due to incorporation of detrital particles within the aragonite skeleton due to high porosity of this layer as suggested by David (2003). In support to this, El-Wahab and El-Sorogy (2003) found highest metal concentrations in skeletons with loose crystal backing and high intergranular porosity compared with tight crystal packing and lower reactive surface area and intercrystalline porosity skeletons. Fossil corals were deposited in a pristine environment unaffected by human activities, for

that average values were used in this study as baseline metal concentrations. 5.4. Heavy metal profiles from the recent coral Different conditions at which the corals were growing could be reflected in the metal profiles of the coral skeleton. These metals were incorporated into corals as a result of dissolved metal incorporation, included particulate material absorbed by coral tissue, or coral feeding (Barnard et al., 1974; St. John, 1974; Brown, 1987; Hanna and Muir,

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Table 1 Average heavy metal concentrations (lg g1) in Porites corals from recent coral profiles (before and after 1965), fossil coral profiles and from the control site (Marine Science Station, MSS) Coral section

Average metal concentration (lg g1) ± SD Cd

Cu

Fe

Mn

Pb

Zn

Older than 1965 Younger than 1965 Fossil coral Recent (MSS)

2.35 ± 0.38 5.15 ± 0.26 3.60 ± 0.6 4.19 ± 0.51

4.70 ± 0.47 5.36 ± 0.36 3.83 ± 0.35 3.88 ± 0.22

34.81 ± 20.04 25.76 ± 15.53 17.06 ± 3.47 14.49 ± 2.42

2.46 ± 0.27 8.22 ± 0.26 2.89 ± 0.34 0.35 ± 0.0

41.51 ± 3.43 47.91 ± 1.94 43.14 ± 3.37 38.17 ± 3.24

5.40 ± 1.42 5.52 ± 1.74 5.06 ± 0.97 7.32 ± 0.67

1990). In this study, baseline values were established from the relatively flat profiles that recent corals displayed before 1965 (except for Fe and Zn), and from consistent

values of the 35 years-long fossil coral record and recent coral from the MSS that is least exposed to contamination. No significant differences among all baseline values were

S.A. Al-Rousan et al. / Marine Pollution Bulletin 54 (2007) 1912–1922

Metal Conc. (µg.g-1)

10 8

Recent coral <1965 Fossil Holocene coral Recent coral (MSS) Recent coral >1965

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Metal Conc. (µg.g-1)

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Fe

Pb

Zn

0

Metal Fig. 6. Comparison between average heavy metals concentration in fossil coral sections, recent coral sections (<1965 and >1965) and recent coral from the MSS reef used as background values. The average and standard deviation values are shown.

found (Table 1, Fig. 6). The average values were: Cd (3.38 ± 0.93), Cu (4.14 ± 0.49), Fe (22.12 ± 11.06), Mn (1.9 ± 1.36), Pb (40.94 ± 2.53), and Zn (5.93 ± 1.21) lg g1. Unfortunately, no data on heavy metal concentrations in seawater at the MSS site are performed. However, several studies investigated the spatial distribution of heavy metals along the Jordanian coast of the Gulf of Aqaba (based on sediments and different biota; seagrass, mollusk, and corals) showed common conclusion and observe lowest metal concentrations at the MSS reserve (e.g., Al-Syaheen, 2005; Al-Ouran, 2005; Abu-Khurma, 2006). This indicates that this site could be considered as a reference area as it is designated for scientific research purposes only. The content of all metals (except Fe and Zn) in the coral skeleton sections of 5 years of growth from the recent coral (1925–2005) followed similar pattern (Fig. 5) and recorded high metal concentrations in their growth bands younger than 1965. The average metal increase from the baseline values were: 1.77 (52%), 1.16 (28%), 6.32 (333%), and 6.97 (17%) lg g1 for Cd, Cu, Mn, and Pb, respectively. This was accompanied with reduction of coral extension over the same period. These results suggest an extensive contamination of the region since mid sixties corresponding to the date of continual increasing human activities along this coastal strip. Enrichment of heavy metals (2–7

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times) in recent coral skeletons in comparison with their Pleistocene counterparts was documented by El-Wahab and El-Sorogy (2003) from the Red Sea. This was attributed to polluting human activities. Fe and Zn profiles from the recent coral showed no distinct trend (Fig. 5). The two elements fluctuated overall the record and exhibited an increase in concentration in the outermost growth interval. This could be related in part due to metal associated with tissue that remains in the organic rind of the corals which was found to concentrate 10–80 times more metals in organic phase in corals than in their exoskeletons (McConchie and Harriot, 1992). However, the organic-bound metals do not contribute significantly to total metal concentrations in samples beyond the organic-rich horizons. This could also result from detrital particles incorporation within the aragonite skeleton since this layer is characterized by its high porosity that may contribute significantly to Fe levels rather than other metals (David, 2003). The presence of Fe-bearing (and probably other elements) phases in these particles suggests a possible contribution to the total element levels observed. Bastidas and Gracia (1999) found also high Fe and Al concentrations in Porites corals as a result of high sedimentation of the suspended sediment. Due to many existing sources contributing to the continuous discharge of the metal into the sea, it is difficult to determine the metal input into the coastal water from each source. Therefore, we tried to review and survey all the potential sources and activities along the coastline that may contribute to the metal budget reaching the ecosystem. The natural and anthropogenic sources of heavy metals may include: terrigenous inputs from wadis during flash floods that transport terrestrial material into the Gulf, ground water inputs, agriculture activities, land traffic increase, sedimentation caused by filling and coastal construction and dredging, oil spills and discharges, industrial discharges (fertilizers, plastic stabilizers), ship-based sewage and solid waste, soft waste dumping (alloys, dyes, automobile tyres, anti-foulings paints and galvanizing materials), shipment of mineral products (mainly phosphate) that is considered as possible hazards increase of suspended matter. Furthermore, the development of the tourism sector in the Gulf of Aqaba is considered a pollution source through boat anchors, boat grounding, and cans and other metal littering (Pilcher and Al-Moghrabi, 2000; Abu-Hilal and Al-Najjar, 2004; Al-Horani et al., 2006).

5.5. Heavy metals in seawater from the Gulf of Aqaba Among the very little data available on the concentration of heavy metals in Aqaba’s seawater, the data published by Shridah et al. (2004) represent the most recent investigation (Table 2). The results were based on samples taken during February 1999 in the framework of the scientific program of METEOR cruise 44.

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Table 2 Range and average values (±SD) of heavy metal concentrations (lg l1) in the Gulf of Aqaba (after Shridah et al., 2004) Value

Heavy metal concentrations (lg l1) Fe

Zn

Mn

Cu

Cd

Pb

Range Mean ± SD

1.38–4.44 3.05 ± 1.18

0.21–0.48 0.36 ± 0.08

0.09–0.19 0.16 ± 0.03

0.10–0.29 0.19 ± 0.07

0.51–0.59 0.55 ± 0.02

0.20–0.41 0.32 ± 0.06

Results from this study indicated higher concentrations of Fe, Cd and Pb compared to other metals. However, all the concentrations observed are much lower than those compiled by most workers in the Mediterranean sea and are typical of open ocean water (e.g., Hamza and Amierh, 1992; Leal et al., 1997). 5.6. Comparison with other studies The overall mean values of heavy metal concentrations in Porites coral skeletons used in the present study were comparable to the published data from different areas throughout the world (reviewed by Reichelt-Brushett and McOrist, 2003). The mean average values noted in the present study were within the ranges reported by Hanna and Muir (1990) and El-Wahab and El-Sorogy (2003) from the Red Sea and Al-Ouran (2005) from the Gulf of Aqaba. In the Gulf of Aqaba, Al-Ouran (2005) reconstructed the metal pollution history at the industrial zone in Aqaba during the last 20 years (1980–2000). All heavy metals investigated showed fluctuating concentrations with general increasing trends where the lowest concentrations found at the bottom of the core (1980–1985) and topmost having the peak values indicating an increase of coastal activities during the last two centuries. The concentrations of Cd, Pb, Cu and Zn in core (A) from the industrial site rises from 1.11, 3.71, 3.54, and 0.78 in 1980 to about 2.60, 7.26, 16.63 and 7.5 in the year 2000 with an average increase of about 134%, 95%, 369% and 859%, respectively. Worldwide, many other investigators have reported similar historical events in coral records. For example, David (2003) traced the historical input of mine tailings in the coastal region of Marinduque Island, Philippines through variations of heavy metal concentrations in Porites coral growth bands. Bastidas and Gracia (1999) studied ten metals in 35 years skeletal sections of the coral Porites astreoides from Nacional Morrocoy in Venezuela to determine the influence of river inputs on the metal content of this coral species. Inoue et al. (2004) presented 40 years-long skeletal chronologies of tin (Sn) and copper (Cu) from an annually banded coral (Porites sp.) collected from Pohnpei Island, Micronesia. High values of extra-skeletal Cu/Ca and Sn/Ca atomic ratios were found between late 1960s and late 1980s during a period of active use of tributyltin (TBT) based antifouling paints worldwide. Considering Porites corals as good indicator of metal concentration in its environment, it can be concluded that the Jordanian coast of the Gulf of Aqaba has been exposed to relatively high metal concentrations since the mid sixties

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