Environmental characteristics of the United Arab Emirates waters along the Arabian Gulf : Hydrographical survey and nutrient salts

Abstract

<span style="font-size:14.0pt;line-height: 115%;font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" color:black;mso-ansi-language:en-in;mso-fareast-language:en-in;mso-bidi-language:="" hi"="" lang="EN-IN">Surface and bottom seawater samples were collected monthly from October 1993 to September 1994 at twenty-four stations. The levels of different parameters were in the range of : temperature (16.90-34.60°C), salinity (35.2-44.0×10^-3 ),transparency (0.5- 13.0 m), <i>p</i>H (7.91-8.60), dissolved oxygen (3.63-9.02 mg/l), biological oxygen demand (0.05-6.11mg/l), ammonia (ND- 15.32μg-at N/l), nitrite (ND-5.18μg-at N/l), nitrate (0.07-14.32μg-at N/l), phosphate (0.01- 10.2 μg-at P/l), and silicate (0.4-26.5μg-at Si/l). The patterns of distribution indicated insignificant differences between surface and bottom layers due to the shallowness of the area, turbulence of the water column, and effects of sewage wastewaters. Water temperatures exhibited their lowest average value in the winter season and the highest in the summer season. The lowest averages of salinity, transparency, <i>p</i>H, and dissolved oxygen were measured in the summer season. Whereas, the highest averages for these parameters were observed in the winter season. Except for nitrate and phosphate, insignificant differences between average values of other nutrient salts in the summer and winter seasons were observed. Nitrate and phosphate showed lower average values in the summer season compared to the winter season due to the increase in the rate of uptake by phytoplankton which was more abundant in the summer season. Horizontal patterns of distributions for hydrographic parameters revealed only an increase for transparency and a decrease for biological oxygen demand in a seaward direction. Except for Sharjah creek, no distinct horizontal patterns of distributions for nutrient salts were observed. At Sharjah, most of the nutrient salts decreased in a seaward direction due to the presence of effective sewage pollution sources inside the creek. The atomic ratio of the elements N: P: Si were similar in Abu-Dhabi, Umm al-Quwain, and Ras al-Khaimah areas, but with lower values in Sharjah. It is concluded that the discharge of sewage and industrial wastes has affected the quality of seawater inside some semi-enclosed areas, especially Sharjah creek, as indicated by the increase in the levels of biological oxygen demand and the elevation in the concentrations of the nutrient salts.</span>