Introduction

The Arabian Gulf, which extends along the coast of Dammam and Qatif, Saudi Arabia, is exposed to various sources of marine pollution and is affected by human activities, development of urban infrastructure, along the east-coast, and the several industrial complexes was established during the past 30 years. Industries such as fisheries, maritime cultivation, transport, and tourism, together with deficient of waste water treatment units, are a threat to marine life (Böhlmark, 2003; Naser, 2011; 2013). Physical and chemical alterations due to dredging and reclamation may reduce biodiversity, richness, abundance and biomass of marine organisms (Smith and Rule, 2001). Additionally, elevated levels of heavy metals are mobilized during dredging and reclamation activities (Guerra et al., 2009; Hedge et al., 2009). These contaminants may enter into important food web components including fish and shellfish, and ultimately pose threats to human health.

The effluent from these activities discharged into the shallow semi-closed water body of the Gulf has caused major disturbance to the coastal environment (Sheppard et al., 2010; Khan and Al-Homaid, 2003; Sadiq and Alam, 1989). Pollution of the water has increased alarmingly. There is a huge amount of waste water from these activities discharged into the water body of the Gulf; leads to disturbance in the coastal environment. The increasing of heavy metals concentrations in natural waters is a serious problem, toxic metals which are some of the most dangerous pollutants can move from aquatic ecosystems by various processes and through biological chain then it is accumulated by human beings. The concentration of heavy metals in marine organisms may exceed the recommended threshold limits and pose a risk to humans and ecosystems (Pourang and Amini, 2001; Szefer, 2002; Rainbow, 2002; El-Gendy, 2003). Metal contamination can have adverse effects on marine organisms only after uptake and accumulation (Cajaraville et al., 2000; Funes et al., 2006)

There are important scientific and economic reasons to quantify the different forms of nitrogen and phosphorus (N and P) inputs and transformation in marine environment. Excessive nutrient loading of seawater and consequently results in eutrophication (Nutrient enrichment) and sometimes may cause red tide phenomenon are important regional problems with potentially large economic impacts in terms of lost resources. Further consequences of human activities leads to: the decrease of water quality, aesthetic flow and navigation water problems and extinction in some water bodies of some oxygen depending organisms or animals.

Coastal waters are generally considered healthy when the pH range is 7.5–8.5. pH responds to changes in dissolved carbon dioxide concentrations, alkalinity, and to a lesser extent, temperature. pH values are driven to more frequent and greater extremes under eutrophic conditions, which allow algal species with tolerance to extreme pH to grow and dominate communities, and to potential form algal blooms (Hinga, 2002). Changes in pH can also have indirect impacts on aquatic organisms. For example, changes in pH can alter the biological availability of metals and the toxicities of ammonium, aluminum, and cyanide. Increases in pH can also cause the electrostatic forces that bind viruses to particles to be overcome, thus facilitating their release to the water column (Miller, 2001). pH is important in calcium carbonate solubility, which may be important for some shell-forming organisms. 

The concentrations of dissolved oxygen (DO) reflect the equilibrium between oxygen-producing processes (e.g. photosynthesis) and oxygen-consuming processes (e.g. aerobic respiration, nitrification, chemical oxidation), as well as the rates at which DO is added to and removed from the system by atmospheric exchange and hydrodynamic processes. The solubility of oxygen in marine waters varies inversely with salinity, water temperature, and atmospheric and hydrostatic pressures. 

In the marine environment, the abundance of phytoplankton is highly associated with nutrient availability, monitoring of chlorophyll-a (chl-a), together with the dissolved nutrients, provides a basis for detecting the possible occurrence of eutrophication events (i.e. hyper-nitrification or over-enrichment as a result of excessive anthropogenic nutrient inputs) in the coastal waters.  Eutrophication is the enrichment of an ecosystem with mineral nutrients, especially phosphorus and nitrogen, leading to enhanced algal and higher plant biomasses (Sutcliffe and Jones, 1992).

Heavy metals are known to occur in natural waters at varying concentrations, of which the most potentially dangerous are lead (Pb), cadmium (Cd), and mercury (Hg).  It is well documented that the accumulation, even at very low (trace) amounts, of the toxic metals in different organs of marine organisms and their subsequent transfer to man through the food chain may result in deleterious effects (Hosono et al., 2011). Anthropogenically, heavy metals can be introduced to coastal and marine environments through a variety of sources, including industries, waste waters and domestic effluents (Fu and Wang, 2011). The accumulation of trace metals, however, may only begin upon exposure of the organisms to high concentrations in the surrounding medium (Rainbow and White, 1989). In Saudi Arabia, trace metal loadings to the marine environment may result from various human activities, including marine disposal of petroleum and petrochemical wastes.  Crude oil contains relatively high concentration of metals such as nickel (Ni), vanadium (V), chromium (Cr), and copper (Cu). Abouhend and  El-Moselhy (2015) found that the annual means of metal concentrations in water in Red Sea in Egypt  were 0.14 ± 0.04 - 0.42 ± 0.03, 0.39 ± 0.11 - 4.71 ± 0.87, 0.16 ± 0.04 - 2.15 ± 0.10, 0.94 ± 0.07 - 12.07 ± 2.78, 0.73 ± 0.43 - 5.84 ± 0.74, 0.10 ± 0.02 - 0.42 ± 0.01, 0.06 ± 0.04 - 0.39 ± 0.07 and 8.68 ± 0.80 - 36.53 ± 2.76 μg l-1 for Cd, Cu, Ni, Zn, Pb, Co, Mn and Fe, respectively, and these results are within the normal range. According to different standards of marine water quality guidelines, heavy metals concentrations at the most of studied.

Material and methods

This study was carried out on Coastal, drainage discharge, and inside gulf of Tarut Bay, it is located in the eastern Province of Saudi Arabia and extends from the northern coast of the city of Dammam and ends at RasTanura city in Coastal of Arabian Gulf, covering an area of 41 thousand hectares (410 k2) approximately.

Monthly field surveys have been performed from December 2014 to January 2016. 18 sites divided to three groups (10 sites as Coastal group, 5 sites as drainages group, and 3 sites inside the Gulf) were selected to represent all different environmental conditions in terms of human activities, public resort beaches and some reference sites Table 1.

Table 1 GPS points of the study locations in coastal, drainage and inside Gulf groups in Tarut Bay Arabian gulf

Water temperature, salinity, dissolved oxygen (DO) and pH were measured in situ at each sites using a pH/ISE/conductivity/RDO/DO Meter Thermo Scientific Orion Star A329 Portable.  Duplicate water samples for water quality variables were collected at 50-mts. interior from the shore line and at 0.50-m depth (below surface water), using a PVC Niskin bottle. NH₃-N concentrations were determined according to IOC (1983). NO2-N, NO₃-N, PO₄-P Total-P and SiO4-Si concentrations were determined on pre-filtered seawater samples, (Whatman GF=C) following the techniques described by IOC (1993) and Strickland and Parsons (1972). The concentration of Dissolved Inorganic Nitrogen (DIN as the sum of NH₃-N, NO₂-N, and NO₃-N) was calculated. For chlorophyll-a (Chl-a) determination, additional water samples were collected and filtered on 0.45 mm filters. Chl-a was extracted by using 90% acetone and measured spectrophotometrically according to Strickland and Parsons (1972). Heavy metals was measured by  ICP- OES; inductively coupled plasma-optical emission spectrometer, Varian Company, Model Unit Varian 720-ES by AOAC 993.14-1993 and mercury was measured by Direct mercury analyzer (DMA-80), Milestone Company, Model Unit DMA-80ICP. Atomic absorption spectrophotometer instrument (Model thermo electron corporation, S, series AA spectrometer with Gravities furnace, UK) was used to detect Mg and Ca by AOAC 974.27-1984 method and AOAC 973.53-1990 for K and Na. IDEXX Colilert-18 and Quanti-Tray Test Method was used to detection of  coliforms bacteria and Fecal Coliforms bacteria .

Statistical analysis was run using the Statistical Package for the Social Science (SPSS 20). One and two way ANOVA were employed to find the significant differences of physicochemical parameters, heavy metals and coliform and fecal bacteria of water between sites and season, also, means ± standard errors and Duncan were derived for all data.

Results and Discussion

Water temperature, salinity, TDS, EC, pH and dissolved oxygen (DO) values reported in the present study are shown in Table 2 and seasonal average values are illustrated in (Fig.1) 

Figure 1 The Seasonal variation of parameters ; Chlorophyll ”a” , NH3, NO3, NO2, Total p, PO4, EC, and salinity in marine water in three investigation groups ; Costal groups, drainage groups and inside gulf groups

Table 2 The annual means ± standard error of physico-chemical parameters, macro elements, heavy metals and coliform and fecal bacteria in water of coastal, drainages and inside Gulf (the Tarout Bay) Arabian Gulf Saudi Arabia

Distribution of water temperature was accompanied with their geographic and temporal variations i.e. they followed seasonal changes in atmospheric at different regions of the present study. Temperature varied in winter  ranged (14.0℃ - 26.10℃), (17.70℃ – 28.50℃) and (15.85℃ – 27.30℃) in three groups of  investigation; Costal, drainages and inside gulf respectively and also the average means ± slandered error were (19.76℃ ± 0.53 ℃),( 25.42℃ ± 0.64℃) and (22.59℃ ± 0.58℃) , but it was increased trend in spring to summer and fall where the range recorded (21.0℃- 28.40℃), (22.1℃ - 31.80℃) and (10.50℃ - 30.10℃) in spring and (23.9℃ -32.40℃), (24.10℃ -32.70℃) and (24.00℃ - 32.55℃) in summer and average means were (25.15℃ a ± 0.43℃), ( 26.19℃ a ± 1.94℃) and (25.67 a ± 1.189℃) in spring and in summer recoded that (29.11℃ ± 0.53),(29.62℃± 0.81℃) and (29.37℃ ± 0.67℃), and in fall ranged recorded (22.6℃ - 33.60℃), (25.70℃ - 35.30℃) and (24.15℃ - 34.45℃) and average means were (28.71 a℃ ± 0.53), (29.62 a℃ ± 1.03) and (29.16 a ℃ ± 0.78).In all times of investigation period recoded no significant difference between the three groups and the annual average means were (25.31℃ ± 0.43), (27.39℃ ± 0.65) and (26.35℃ ± 0.54) in three groups Costal , drainages and inside gulf respectively. A slight increase in water temperature was observed from spring season to summer and fall and decrease in winter they followed seasonal changes in atmospheric temperature. Water temperature in these areas changes naturally, as a part of daily and seasonal cycles, with the variations in atmospheric temperature, currents, and local hydrodynamics. Discharges of thermal waters from cooling systems of power plants as well as from municipal or industrial effluent are the sources of thermal pollution in the coastal zone. Any abnormal changes in water temperature may disrupt natural ecosystem processes, either directly through physiological effects on organisms or indirectly as a result of habitat loss. Photosynthesis and aerobic respiration, and the growth, reproduction, metabolism and the mobility of organisms may also be adversely affected by changes in water temperature. If temperature goes too above or below the tolerance range for a given taxon (e.g. fish, zooplankton, phytoplankton, and microbes), its ability to survive may be compromised. Any unnatural changes in water temperature may also impact indirectly upon biota through loss of supporting habitats, such as coral reefs (Hoegh-Guldberg,1999) , by changing the solubility of oxygen and calcium carbonate in water, or by influencing the extent to which metal contaminants and other toxicants are assimilated by physiological processes (Luoma, 1983).

The general distribution of dissolved oxygen (DO) indicated high values and the presence of well oxygenated waters. Patterns, in terms of punctual the average values of all groups; Costal, drainages and inside gulf  respectively and the means were (11.281±0.396 mgl^-1),(7.421±0.879 mgl^-1) and (9.351±0.638 mgl^-1) and ranged (6.930-18.860 mgl^-1), (2.460-16.210 mgl^-1) and (4.695-17.535 mgl^-1) equivalent to DO % means ( 123.24±4.95%),(84.44±10.60%) and (103.84±7.77%) in winter and decreased the values by increased the temperature. Do recoded the average means in different seasons as (9.950±0.593 mgl^-1), (7.065±1.147 mgl^-1) and (6.828±0.302 mgl^-1) in Spring, (6.542±0.519 mgl^-1), (5.571±0.571 mgl^-1) and (5.949±0.334 mgl^-1)  in summer and (5.669±0.378 mgl^-1), (5.518±0.511 mgl^-1) and (7.942±0.088 mgl^-1) in Fall; the results recorded more significant differences in costal groups than the drainages group and inside group ; with an annual mean (8.499 b ±0.315 mgl^-1), ( 6.537 a ±0.445 mgl^-1) and (6.913 a ±0.182 mgl^-1), equivalent to (101.56 b ±3.63%), (81.86 a ±5.39%)( 85.06 a ±2.16%) in three groups; Costal, drainages and inside gulf respectively.

Drainage of wastes these are rich in organic carbon, such as from sewage treatment plants and other industries, can substantially reduce DO concentrations. Most aquatic organisms require oxygen at certain concentration ranges for respiration and efficient metabolism, and DO concentration changes above or below this normal range can have adverse physiological effects.  In fact, even short-lived anoxic and hypoxic events can cause major mortalities of marine organisms, such as the so-called fish kills. In addition, the toxicity of many toxicants, such as lead, zinc, copper, cyanide, ammonia, and hydrogen sulfide, can double when DO is reduced from 10 to 5 mg/L. The death of Sedentary organisms and the avoidance of low-oxygen conditions by mobile organisms can also cause changes in the structure and diversity of aquatic communities.

This study indicates that the study area have a good DO regime, most notably during winter as a result turbulent mixing caused by prevailing strong winds. The DO in waters tend to have lower concentrations  by increase the temperature during summer, although the observed range remains higher than the guideline values prescribed by ANZECC (2000), PME (2006), APCEL,(1995) and ME-Japan (1993)

The results  for pH water indicated that decrease significant in drainages group than coastal and inside gulf groups; the average Annual means were (8.17 b ±0.05), (7.96 a ±0.04) and (8.09 a ±0.01) but no significant variation between the three groups in different seasons; winter spring summer and fall and ranged around 8 value in (Fig. 1)

Waters are generally considered healthy when the pH range is 7.5–8.5. pH responds to changes in dissolved carbon dioxide concentrations, alkalinity, and to a lesser extent, temperature. The magnitude of the change varies with salinity because various ions are involved in acid-base reactions, and because the concentration of salt influences various equilibrium constants. In natural waters, pH increases with salinity until calcium carbonate (CaCO3) saturation is reached. When CaCO₃ precipitates, the carbonate-alkalinity of the water decreases and this causes a reduction in the buffering capacity of the water and a decrease in pH. When the pH level is sub-optimal to fish, physical damage to the gills, skin, and eyes may occur.  Skin damage in fish increases their susceptibility to fungal infections, such as red spot disease. pH values are driven to more frequent and greater extremes under eutrophic conditions, which allow algal species with tolerance to extreme pH to grow and dominate communities, and to potential form algal blooms (Hinga, 2002).

Changes in pH can also have indirect impacts on aquatic organisms.  For example, changes in pH can alter the biological availability of metals and the toxicities of ammonium, aluminum, and cyanide.  Increases in pH can also cause the electrostatic forces that bind viruses to particles to be overcome, thus facilitating their release to the water column (Miller, 2001). pH is important in calcium carbonate solubility, which may be important for some shell-forming organisms. In the present study, pH exhibited spatiotemporal variation within acceptable ranges falls in the desired range of 6.5–9.5. The growth of fish will be good in the range of 7-8. It is a tolerable range for most fish as a guideline values prescribed by ANZECC (2000), PME (2006), APCEL(1995), and ME-Japan(1993).

Salinity fluctuated from lowest value in drainages group to highest value inside the water gulf group where   an annual means were  (41.23 b ±0.77), (18.83 a ±2.06) and (44.60 c ±0.21) coastal , drainages and inside group respectively the data in Table 2 and (Fig. 1) was  appeared that significant differences between the groups in all season and  between investigated groups . And also the same trend in salinity was in conductivity (EC) and the total dissolved salt (TDS) values in all groups; Significant decrease in drainages group and highly significant inside the water gulf for salinity, conductivity and total dissolved salt., this may be the drainage water salinity  which discharge after secondary and tertiary  treatment was low salinity and the amount of water drainage was more and decrease effects the salinity and TDS and EC; the gulf is semi-closed system and the area are in high temperature so the evaporation is more. Salinity is a dynamic indicator of the nature of exchange system in the marine environment. This parameter is an important determinant of the mixing regime in a water body because of the density variation associated with salinity variation. The occurrence of salinity stratification tends to inhibit vertical water mixing which is a crucial process in remobilizing organic matter from the seabed to the water column. Salinity is a vital ecological parameter due to its role in certain chemical processes in the marine environment. Most aquatic organisms function optimally within a narrow range of salinity and when salinity changes outside this range, an organism may lose the ability to regulate its internal ion concentration. Consequently, osmoregulation may become so energetically expensive that the organism may succumb to biotic pressures such as predation, competition, disease, or parasitism. In coastal waters, any drastic changes in salinity can also alter the distributions of macro-benthos, sessile organisms, as well as rooted vegetation (e.g. seagrasses) (Boesch, 1977). And in generally the values were acceptable according to national and international standard for marine water criteria ANZECC (2000), PME 2006

Ranges as well as means values of different nitrogen nutrients are listed in Table 2. Their seasonally average values are illustrated in (Fig. 1) Our data indicate that dissolved inorganic nitrogen concentrations are quite low. The  annual average values of ammonia NH₃-N, ranged from ( 0.276 ± 0.036 b), ( 1.023±0.219 c) and (0.024 a ±0.002 ) mg/l in Coastal, drainages and inside groups respectively, there was a significant differences (p> 0.05) between the investigated groups in all season and between the groups; the drainages group recorded highest values in annual means and in spring season. Nitrite (NO₂- N) concentrations was significantly increases (p> 0.05) in drainage groups and no significant between (p> 0.05) groups in all season the annual average mean values were (0.022 a ±0.005), ( 0.105 b ±0.017) and (0.005 a ±0.000) mg/l in Coastal, drainages and inside groups respectively.  Nitrate (NO₃ – N) concentrations values was (0.78 a ±0.03), (0.85 ab ±0.08) and (0.68 a ±0.06) mg/l respectively with an annual average of Coastal, drainages and inside; there was no significant differences (p> 0.05) between investigated groups and all season. The levels of total dissolved nitrogen (TDN) displayed remarkable variations (1.08 b ±0.05), (1.82 c ±0.22) and (0.34 a ±0.03) with annual means of costal, drainages and inside groups respectively and was highly significant at (p> 0.05) in drainages group and more significant (p> 0.05) in trend from spring to winter to fall and summer.

Reactive phosphorus (PO₄) concentrations was observed (0.263 a ±0.031), (0.764 b ±0.080) and (0.623 b ±0.085) of annual means of costal , drainages and inside gulf groups respectively; the costal groups recorded lowest values and no significant (p> 0.05) between the drainages and inside groups. On the other  hand the total annual means of phosphorus (TP) recorded more significant(p> 0.05) in drainages group and lowest value in costal group as tabulated in Table 2 were recorded (0.390 a ± 0.032), (0.816 c ±0.079), (0.580 b ±0.076) mg/l of costal, drainages and inside group. The drainage water are contained more quantity of organic matter, nitrogen compound and phosphorus compound and degradation of this compounds, liberated and increased the N and P (these two elements).

Nitrogen naturally exists in marine waters both as inorganic and organic forms, and in dissolved and particulate forms.  Inorganic nitrogen is found both as oxidized forms, e.g. nitrate (NO₃) and nitrite (NO₂), and as reduced forms, e.g. ammonium (NH₄), ammonia (NH₃), and dinitrogen gas (N₂). In the marine environment, it is widely accepted that nitrogen is the primary nutrient limiting plant growth but recent evidence has also demonstrated the dominant role of phosphorus on certain seasons (McComb and Davis, 1993; van der Zee and Chou, 2005). The most common forms of dissolved nitrogen that are available for aquatic plant growth are the inorganic forms such as NO₂, NO₃, and NH₃, as well as the organic forms such as urea, which is breakdown product of proteins.  Among the inorganic forms, NO₃ is the most commonly available although NH₃, in its ionized form as NH₄, is the most readily assimilated by plants.

Silicate.—The silicate (SiO₄, mg/l) concentrations in the study area are shown in Table 2 not detectable in coastal water groups but founded in drainage and inside gulf groups the annual mean values recorded that (ND), (5.32±1.187), (4.245±2.122) respectively.

On the other hand, phosphate (PO₄) inputs into the coastal waters usually come from drainage discharges (point sources), although PO₄ loading from agricultural runoff and atmospheric deposition (diffuse sources) can be significant (Cole et al., 1999). Silicon in marine waters is usually associated with silicates (SiO4) in detergents, although most diffuse sources are attributed to sediment mineralization, rock weathering, and soil erosion (Cole et al., 1999). When in excessive amount in the marine environment, dissolved nitrogen, phosphorus and silicon may contribute to the stimulation of harmful algal blooms (eutrophication) which may have detrimental ecosystem and human impacts. Very high nutrient loads may also contribute to the de-oxygenation of the water column and sediment in a marine environment.

Similar results of pH and nutrient concentrations were recorded in Arabian Gulf at Qatar coast (Jedah and Robinson, 2001); in Red Sea at Rabigh and Jeddah, Saudi Arabia (Zyadah, 2011); in Medit. Sea in Turkey (Aysen et al., 1988). The increased of nutrient concentration in water may be attributed to the mixed drainage water (sewage, agricultural and industrial waste water) at these sites, where similar results were obtained in Arabian Gulf and Red Sea Coast, SA (Zyadah, 2011).

In fact, chlorophyll-a is the most widely used parameter among the marine pigments for this purpose as the abundance of phytoplankton is highly associated with nutrient availability, monitoring of chlorophyll-a (chl-a), together with the dissolved nutrients, provides a basis for detecting the possible occurrence of eutrophication events (i.e. hyper-nitrification or over-enrichment as a result of excessive anthropogenic nutrient inputs) in the coastal waters.

In this study, the concentration of chl-a was measured at all sampling sites are presented in Table 2 and (Fig. 1) where the annual means were (24.69 a ±2.49), (19.39a ± 3.66) and (17.92 a ± 2.08) µg/l for coastal, drainages and inside groups respectively and recoded no significant differences (p> 0.05) between groups and season although the costal group was recorded the highest values and winter season recorded the lower values in all groups.

Both nitrogen (N) and phosphorus (P) are essential as building blocks for plant and animal growth.  However, excessive loads of nutrients can cause the eutrophication in coastal waters.  Where eutrophication occurs, the general pattern of change in marine community structure involves a shift from large macrophytes (including seagrasses) towards fast-growing macroalgae and phytoplankton (including harmful species forming blooms) which can capture and use light more efficiently (Anderson et al., 2002; Nielson and Jernakoff, 1996; Duarte, 1995). High loadings of organic matter in the sediment promotes oxygen consumption through decomposition, and may lead to anoxic or hypoxic events.  Unfavorable DO levels and the presence of toxic algae can harm benthic invertebrates, fish, and other organisms. Nutrient enrichment can also compromise the ability of sea-grasses and salt-marshes to support fish and invertebrates even before a change in habitat occurs (Deegan, 2002).

Chlorophyll-a is a green pigment found in plants; it absorbs sunlight and converts it to sugar during photosynthesis. Chlorophyll-a concentration is an indicator of phytoplankton abundance and biomass in coastal and estuarine waters. It can be an effective measure of trophic status and an indicator of the maximum photosynthetic rate (Wellman et al., 2002), thus it is commonly used as a measure of water quality. High chl-a levels often indicate poor water quality and low levels suggest good conditions. However, elevated chl-a concentrations are not necessarily deleterious. It is the long-term persistence of elevated levels that is problematic. For this reason, annual median chl-a concentrations in a water body are used as indicator of water quality.

Total alkalinity recorded the values (156.96 b ±2.62), (184.86c±6.65), (103.44 a ±7.45) mg/l as CaCO₃ in annual means between the three groups investigation; coastal, drainages and inside group respectively; there was significant differences (p> 0.05) between the three groups and drainage groups recorded the highest values and the inside gulf recorded the lowest value but no significant (p> 0.05) between season. H2S illustrated in Table 2 appeared that annual values was no significant (p> 0.05) recorded between the three groups but significant (p> 0.05) between season (3.234 a ±0.385) (2.983 a ±0.491) (4.448 a ±0.769) µg/l.

The chemical analyses for macro elements (Ca , Mg, and K) were recorded the same significant decrease (p> 0.05)  in drainage groups than coastal and inside groups the annual values were showed in Table 2  (794.29 b ±8.83) ( 584.66 a ±81.73) ( 708.74 b ±63.31); (1551.83 b ±27.17) ( 700.59 a ±38.94) (1218.01b ±272.23) and (1048.03 b ±12.87) ( 486.58 a ±170.78) ( 831.13 b ±183.66) mg/l for Ca, Mg  and K  in three groups coastal, drainage and inside gulf respectively . In another hand the Na recorded more significant (p> 0.05) between the three groups the annual values were (12410 b ±0.65) (4930 a ±0.70) (17530 c ±0.08); the inside gulf group recorded the highest values and the drainage recorded the lowest values. These elements attributed by salinity of water and in natural the Na is the dominant cation followed by Mg, Ca, and K in descending order.

The micro elements as Hg, As, Zn, Ni, Fe, Cr, Cd, Cu and Pb were measured in water in three groups and the results indicated that Cd, Cu and Pb not detectable in water of three groups, the Fe not detectable in coastal and drainage groups but recorded the annual value in inside gulf groups (0.0004±o.0001) ppm. Hg, As and Ni were recorded no significant differences (p> 0.05)   between the three groups; the annual values were illustrated in Table 2 (0.0102a±0.0089), (0.0038a ±0.0022) and (0.0006a±0.00003); (0.0229a±0.01182), (0.0123a±0.0025) and (0.0021 a ±0.0005); and (0.0017 a ±0.0006)( 0.0017a ±0.0002)(0.0024 a ±0.0002) in three groups coastal, drainage and inside gulf groups respectively. In another hand the Zn and Cr were significant differences(p> 0.05) between groups  the inside gulf groups recorded the highest values for two elements the annual values were (0.0021a±0.0005),(0.0031a±0.0005) and (0.0038b±0.0007) and (0.0018 a ±0.0003),(0.0016a±0.0003) and (0.0176b ±0.0021) for two elements respectively in three groups; Coastal , drainage and inside gulf groups. in general the some of the  heavy metals were no detectable or recorded low values than Saudi Arabia and international standard for marine water may be attributed to the treatment of drainage water by secondary and tertiary treatment ANZECC (2000), PME (2006), APCEL(1995), and ME-Japan(1993).

The seawater samples collected for microbial indicators following a culture-based test method were analyzed for coliform and fecal coliform counts.  Results of the analysis were as the annual values (1035c± 216.11), (294.5 a ± 68.64) and (613.78b±78.5) cfu per 100 ml; and (11.33 a ± 3.18), (23 b ± 1.41) and (19.16 b ± 2.5) respectively in Coastal, drainage and inside gulf groups; the coliform bacteria recorded more significant (p> 0.05) in Coastal groups and less values in drainage groups, In general, the nearshore sites were higher in coliform counts than the sites located more offshore, but fecal coliform bacteria recorded significant increase(p> 0.05) in drainage groups than coastal and no significant (p> 0.05) between the inside groups.

The assessment of sanitary conditions in coastal waters, especially those intended for bathing and other water-contact recreation, are generally based on the examination of bacterial abundance, such as of coliforms, streptococci, and enteroviruses. Indeed, fecal coliform counts are often used as a key parameter for such assessment, but fecal coliforms normally have a limited survival in the marine waters. For instance, Hanes and Fragala (1967) noted that E. coli can only survive in marine waters for 0.8 day, while Sieracki (1989) found that E. coli degrade more rapidly with increased sunlight intensity. This tends to impose a serious methodological constraint on the assessment of bacterial abundance, thus faster alternative methods (e.g. rapid assays) for the real-time detection of microbial concentrations are required to overcome this dilemma.

The presence of fecal coliform tends to affect humans more than it does aquatic creatures. While these bacteria do not directly cause disease, high quantities of fecal coliform bacteria suggest the presence of potential disease-causing agents. Hence, the incidence of high fecal contamination is an indicator that a potential health risk exists for individuals exposed to the contaminated water.

ANZECC (2000) guideline requires that the median bacterial content in marine waters taken over the bathing season should not exceed 150 cfu/100 mL for primary contact waters. ASEAN (2005) guideline also adopts the same fecal coliform count for recreational water. The guide standard for total coliforms is 500 cfu/100 mL and 100 cfu/100 mL for fecal coliforms. These prove that the results in our study reveals well below the levels of national and international guideline.

Conclusion

The results indicated that, the drainage water discharge in Tarut Bay showed a less significant deviation from the International standards and Saudi standard values in most parameters values of marine water quality and are well below the accepted levels and no harmful level in micro flora and the fauna of Arabian gulf in the study area.

Acknowledgement

The authors are indebted to Deputy Minister for Fisheries Affairs, Ministry of Agriculture, kingdom of Saudi Arabia, for supporting this study. Many thanks for Mr. Nabil Fita Director of Fisheries research Center for his encouragement and support during the period of this study. we also thanks for all staff of Fisheries research Center, Qatif specially Mr. Ali Al Maden, Mr. El sayed yahia and Mr. Mohamed Nageeb for help us to collect the samples and analyses.     

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