The Effect of Climate on the Chemical Composition of the Coral Reefs around Kubbar Island—Kuwait ()
1. Introduction
The southern section of Kuwaiti waters includes three islands; Kubbar, Qaruh and Umm Al-Maradim. Large number of coral reef colonies is flourishing in the subtidal zones of the three islands but most pronounce around Qaruh Island. Kubbar Island is relatively small with an area of 0.9 km2 and a maximum elevation above sea level that equals to 4.5 m. The distance between Kubbar and Failaka Island is 36 km; it is located at approximately 34 km perpendicularly east from Al-Fahaihil area (Figure 1). It is considered a natural heaven for many species of different plants, great number of seagulls, birds, and the best nesting grounds for different types of sea turtles. Natural vegetation and coral reef colonies are considered the principal features of Kubbar Island (Figure 2). It is undeveloped except for the presence of landing field for helicopter, guarding tower and a jetty.
The intertidal zone has a width ranging between 5 to 11 m. The island beaches are relatively tranquil and covered by coarse to medium-grained calcareous sands (Figure 2(C)). The carbonate constituents are mainly represented by shell fragments and coral reef debris, and to a lesser extent, some oolitic grains and quartz sand grains. The supratidal and inland zones form a raised platform of about 4.8 m above sea level, and is characterized by moderately to steep banks with a dipping angle ranging from 40˚ to 75˚. Fieldwork observation indicated the occurrence of large number of bullet shells, as well as, empty cans is seen at the supratidal and inland zones, which resulted from the shooting of sea birds by many island visitors and the dumping of their garbage. Many pebbles of various sizes are found scattered among the surface sediment, which consists mainly of quartz and igneous rock fragments and sedimentary rock fragments. The majority of the sedimentary pebbles were mainly produced by the reworking action of waves on the beach rocks, whereas the quartz and igneous pebbles were extracted from the constructing materials used along the beaches. The island is characterized by a strategic and touristic importance, and considered significant fisheries. The diverse types of fish and the abundance of marine life made the island site for diving and fishing, as well as harmful human activities on the mainland of the island. Therefore, safeguarding the coral reefs of the island
(A) (B) Figure 1. Showing, (A) Map of Kuwait and the location of Kubbar Island; (B) Sample location and the different zones around Kubbar Island.
Figure 2. Field photomicrographs from Kubbar Island showing, (A) Carbonate beaches, inclined beach rocks at the southern tip of the island, and the coral reef around the island; (B) Underwater photographs for corals from the coral reef around the island; (C) Carbonate beach sediments; (D) Inclined beach rocks.
should be the main priority, because these corals are the main reason for the existence of many types of fauna and flora species in the waters around it. Moreover, the aquatic biota as well as land dwelling animals and bird species are greatly influenced by toxic materials in their host sediments, which are the result of human activities. All of these activities are greatly noticed and they are affecting the well-being and the existence of the coral reefs around the island, as well as the existence of many types of bird communities and other land and marine fauna and flora.
Ref. [1] elucidated the effect of weather variations such as prevailing wind direction and temperature, and water salinity on the coral colonies and the nature of the accumulated sediments along the shores of the southern islands. Moreover, [1] indicated that the petrographic study on intertidal sediments from all the southern islands specify variation in grain size, micritization and boring extent of the carbonate constituents between the seasons. The present study revealed that the presence of halite and gypsum crystals as cements and detached crystals is higher during June and October. The results also indicate differences in grain size along the shores of the islands, which is dependent on the prevailing wind direction and wave action [1-3].
The corals of Kuwait are living in a stressed environment, which is subject to high and temperatures and also oil pollution. Ref. [4] concluded that the major problems facing these corals at present are anchor damage to corals, over fishing and litter. Refs. [5,6] indicated that Anchors have destroyed large tracts of the reefs at all sites, and over-fishing has reduced populations of large predators, such that few fish greater than 20 cm are seen. They also postulated that oil pollution has not caused massive mortalities to reefs, even though most were in the path of the massive oil spill during the Gulf War. Ref. [6] postulated that, the reefs of Kuwait are exposed to a very heavy load of particles due to the shallow water environment and input from the Shatt Al-Arab. The interest of studying the affect of weather parameters on corals arises from the importance of coral reefs for the support of marine life, hence the productivity of the marine environment and the availability of marine food resources.
The purpose of this research is to investigate the variations in chemical composition of the corals according to the changes in climate, especially temperature, wind pattern and water temperature, salinity and the pollution degree these corals are affected with.
2. Material and Methods
2.1. Sample Collection
The intertidal sediment samples were gathered from the eight geographic quadrants: North, South, East, West, Northeast, Northwest, Southeast, and Southwest. Normally two sediment samples were gathered at each location, one from the highest tidemark and one from the low-tide mark within the intertidal zone of Kubbar Island, odd numbers referred to high-tide locations and even numbers for low-tide locations (Figure 1(B)). The total number of gathered sediment samples is 48 and is from three different seasons. The abbreviations used in tables K, KO, KJA and KJ are referred to Kubbar, October coral samples, January coral samples and June coral samples, respectively. Sampling was carried out after drawing a square with sides equal to 30 cm (30 cm ´ 30 cm), and the depth of sediment samples collected from this square should not exceed 2 cm.
2.2. Chemical Investigations
This study is based on chemically analyzing all coral fragments of the size portion 0.5 mm (controlling factor) from high-tide and low-tide points from all the eight geographic directions. Some sediment samples lack coral sizes of 0.5 mm, therefore the researcher separated corals from the 2 mm and 1 mm size portions (Table 1). A total of 48 coral samples were analyzed by two different methods to measure the total Ca and Mg, trace elements (Na, Fe, Sr, Al, K), and heavy metals (Cu, Pb, Zn, Co and Cr) concentrations. The major elements and the trace elements were analyzed by using Inductive Coupled Plasma-optical emission spectrometric method (ICP). Few bulk sediment samples were analyzed by X-Ray diffraction method to determine the mineral constituent. BDL in tables is referred to below detection limits.
3. Meteorology and Oceanography
The Arabian Gulf is a 1000 km long and 200 - 300 km wide open shelf in an arid subtropical area [7,8]. Refs. [7,8] also mentioned that the sea floor of the Arabian Gulf slopes gently northwards on the west, with an average overall depth of about 35 m. Maximum depth at 100 m occurs along the Iranian coast [7,8]. Normally the beaches along the Arabian Gulf coasts are exposed to the strong northwesterly winds and the 2 m spring tides, and are composed of coarse sand with aeolian quartz, ooids, shell debris, and intraclasts [9]. In very arid regions wind
Table 1. Separated coral fragments from all locations around Kubbar Islands used in chemical analysis.
plays a significant role in redistributing sediments.
Kuwait is situated on the northwestern shore of the Arabian Gulf, and Kubbar Island lies at the southern sea area of Kuwait at 29˚ North (Figure 1). Kuwait is mainly characterized by hot and dry climate, and affected by two main wind directions through out the seasons. These are the “Shamal” wind (blowing from the northwest direction) and the “Kose” wind (blowing from the southeast direction). The mean temperature reaches 45˚C in July and August, and 12˚C in winter [10]. Ref. [11] pointed out that the mean annual temperature of Kuwait’s surface water is 23.8˚C, with maximum temperature in July and August (30.5˚C - 36˚C) and minimum temperature in January and February (10˚C - 14˚C).
The weather changes throughout the year and the corals around Kubbar Island are affected by different weather patterns. It is noted that during the months following October (November, December and January), temperature will subside and humidity increase, where the lowest mean temperature = 1.41˚, mean highest temperature = 26.16˚, mean humidity = 89.71% [12]. This weather pattern will results in the lack of oxygen and nutrients that corals require, hence the death of the coral polyps. The mean rain-fall precipitation from November to January equals to 112.09 mm [12]. There is another weather pattern prevailing in Kuwait after January. During February and March temperature will be moderate that boosts the growth of algae (mean low temperature = 1.09˚ and mean highest temperature = 25.96˚) [12]. Then, during April and May there will be the monsoon season (“Sarrayat”) that is known for its high wind activitywave action and thunder rainstorms. The mean rainfall precipitation from February to April equals to 112.09 mm [12].
In addition to extreme temperatures, seawater salinity around the island also fluctuates, but is generally high (average high = 43.43%, average low = 39.06%). Ref. [13] revealed that mean annual salinity of Kuwait’s water is 41.6 psu, however, it could reach up to 45 psu. Ref. [14] attributed abnormal salinities throughout the Arabian Gulf to the excessive evaporation and partial isolation from the Indian Ocean. Ref. [10] studied the near shore wave characteristics and tidal currents around the islands. They concluded that the high wave energy and low wave energy were found in the western and eastern areas of the islands. Generally, the prevailing winds (the “Shamal”) blow from the Northwest and provide the dominant energy input with wave-effectiveness limits at about 20 - 30 m, primarily controlling facies patterns [9].
4. Petrography
The petrographic study was an excellent tool to determine the nature of the sediments, composition, and environment of deposition, behavior of deposition and differences and similarities between the depositional sights along the shores of the island. It indicated that the intertidal sediments from all locations share the same bioclastic components and these are divided into major and minor components, and indicative of reef to back-reef depositional environment.
The major bioclastic composition include; various types of corals, coralline algae, molluscs as bivalves and gastropods, and different types of echinoderm spines. The intragranular porosity of some bioclasts are either cemented by acicular aragonite crystals or filled by micrite, the bioclasts are affected by micritization and burrowing. The most important finding is the rosette-shaped high-Mg calcite cement and the longitudinal aragonite crystals seen by the Scanning Electron Microscope, [3].
The minor bioclastic components are foraminifera, brachiopods and ostracode tests. The SEM study indicated that the pore spaces of bioclasts are filled by finer organisms such as radiolarians, foraminifera, bryozoans, and Coccolithis (Figure 3). The non-bioclastic components consist mainly of intraclasts of various types and sizes, in addition to some minor oolitic grains and pellets. The most dominant nonclastic constituent within the sediment samples is quartz.
The study by polarizing microscope indicated that the origin of quartz grains is mainly igneous and metamorphic, and they are mainly rounded to well rounded grains, although some angular quartz grains do exist. The majority of quartz grains are of aeolian origin, especially the grains that are of fine sand to silt sizes which are windblown from northern Kuwait. Other nonclastic components include heavy minerals, metallic particles, rusty iron particles, and feldspars. Rusty iron particles tend to be the dominant grins among these three constituents.
The sediments gathered in October and June show very high amount of cubic and prismatic crystals especially in the sediment portions of 0.063 and 0.032 mm namely halite, calcite and some gypsum. The existence of such crystals is an indication of high temperatures and salinity. The majority of crystals are found free, not attached to the grains composing the sediment samples.
5. Geochemistry
Two major elements (Ca and Mg), five trace elements (Na, Sr, Al, Fe, and K), and five heavy metals (Pb, Zn, Cu, Co, and Cr) were analysed for all the collected coral samples during all seasons. The purpose of chemical analysis of the corals is to identify any chemical variations in corals composition and effect of pollution on them.
5.1. Major Carbonate Elements (Ca and Mg)
CaCO3 concentration in all coral samples gathered from
Figure 3. Backscattered images from the SEM showing different organisms: (A) Gastropods; (B) Diatoms and coccoliths; (C) Diatoms; (D) Coccoliths; (E) Diatoms; (F) Bryozoans.
high-tide mark range between 94.759 - 98.35 Mole% with an average mean equals to 96.691 ± 1.0 (Table 2). Coral Samples gathered during October from high tide mark include CaCO3 concentrations that range from 94.759 - 98.10 Mole% with an average mean value equals to 96.652 ±1.16 Mole% (Table 3). Coral samples gathered during June from high-tide mark include CaCO3 concentrations that range from 94.963 - 98.35 Mole% with an average mean value equals to 96.756 ± 1.39 Mole% (Table 3). Coral samples gathered during January from high-tide mark include CaCO3 concentrations that range from 95.087 - 97.90 Mole% with an average mean value equals to 96.665 ± 0.80 Mole% (Table 3).
Table 2 and Figure 4, shows that although the hightide corals are slightly Mg-rich, they show nearly the same relationship during all the seasons. Figure 4(A) show that there is CaCO3 enrichment at the following locations: NE, SE, and NW, while corals from all the other locations are enriched in Mg.
The concentration of CaCO3 corals gathered from low-tide range between 97.644 - 99.02 Mole% with an average mean equals to 98.458 ± 1.0 (Table 4). Coral samples gathered during October from low-tide mark include CaCO3 concentrations that range from 98.013 - 98.729 Mole% with an average mean value equals to 98.4 ± 0.25 Mole% (Table 3). Coral samples gathered during June from low-tide mark include CaCO3 concentrations that range from 97.644 - 98.422 Mole% with an average mean value equals to 98.213 ± 0.26 Mole% (Table 3). Coral samples gathered during January from low-tide mark include CaCO3 concentrations that range from 98.388-99.02 Mole% with an average mean value equals to 98.762 ± 0.21 Mole% (Table 3). Corals gathered from the low-tide during October and January share the same relationship, while corals gathered during June show an antipathetic relationship to corals gathered from the high-tide (Figure 4(B)).
Figure 5 show the distribution of CaCO3 in corals according to the different seasons. Figure 5(A) indicate that all the corals gathered from the NE, SW, NW during October contain the highest CaCO3 concentrations, while all other locations are enriched in Mg. Figure 5(B) indicate that although low-tide sediments has nearly the same Ca concentration, the corals gathered from the high-tide has variable CaCO3 concentration and show an antipathetic relationship with low-tide corals. Figure 5(C) show that corals gathered during October has the same relationship with corals gathered during January.