PHYSICAL PROPERTIES AND EXCHANGE SYSTEM OF SEAWATER IN AYLA LAGOONS IN THE NORTHERN GULF OF AQABA, RED SEA

摘要

Spatial and temporal variation of temperature, salinity, sigma-t, dissolved oxygen (DO) and residence time in the artificial Ayla lagoons in the northern Gulf of Aqaba were studied during the period June 2012-May 2013 to achieve, for the first time, a detailed description of water properties. That’s for obtaining scientific bases for management and sustainable use. Monthly base measurements were carried for the temperature, salinity, sigma-t, DO at 25 sites in the three lagoons and for water flow at 7 sites in the tidal lagoon. The statistical tests of all parameters revealed significant differences among months. There were no significant differences among sites and lagoons except for salinity among sites and lagoons and for sigma-t among lagoons. The seasonal trend of temperature, sigma-t and DO were observed but no distinct pattern was observed for salinity. The results showed that temperature played a major role in thermohaline structure and DO, where salinity had minor role. The annual range of seawater temperature, salinity, sigma-t and DO, for all sites in the Ayla lagoons, were 16.24-27.76 °C, 39.95-41.2, 27.03-30.42 kgm-3 and 6.21-8.23 mg/l, respectively. Besides, temporal variation of all parameters was in general comparable with open sea. The results of current measurements revealed an excellent condition with expected secure environment. The average residence time of seawater in the lagoons during period June 2012-May 2013 was 2.58 ± 0.66 days. This period is assumed to be better than the proper needed time for ensuring a complete flushing in the lagoons. In general, it is needed to increase water pumping in wintertime because tidal current is weaker compared to summer, particularly for the Tidal lagoon (TL) because it is connected directly with the open sea.