Date of Award

2004

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Science

First Advisor

Dr. Waleed Hamza

Second Advisor

Dr. Andrea Lami

Third Advisor

Dr. Sofian Alian

Abstract

Al Wathba Lake was created in 1982 by accidental discharge of over-capacity treated sewage water from Al Mafraq Waste Water Treatment Plant (WWT). The lake lies on the north side of the Abu Dhabi - Al Ain truck road, approximately 40 km Southeast of Abu Dhabi Island. In 1998, the lake and its surroundings were designated as protected area, the Al Wathba Wetland Reserve, and placed under the management of the Environmental Research and Wildlife Development Agency (ERWDA). The reserve covers an area of approximately 5 km2, and the lake system covers an area of 1.5 km2. The continued inputs of water and high evaporation rates have resulted in fluctuating water salinity of the lake from fresh to hyper-saline. The reserve attracts large numbers of migrating waterfowl and waders including the greater flamingos (Phoenicopterus ruber) which is the only known currently breeding colony in the Arabian Peninsula. Brine shrimp (Artemia sp.), the only crustaceans inhabiting the lake, are the main food source for the flamingos. Brine shrimp can tolerate a wide range of water quality conditions, particularly water salinity variations. However, little information is available on the effects of water quality on Artemia populations inhabiting Al Wathba Lake. Considering the potential importance of brine shrimp as a food source for the flamingos population, and the government interest to conserve the established population, the present study was carried out to examine the dynamics of brine shrimp population in relation to the surrounding environment. The second goal of the study has also aimed to develop a management plan for the lake environment, in order to guarantee continuous reproduction of Artemia population and consequently the conservation of the established flamingos population.

In the framework of the present study, a total of 14 sampling sites were investigated on a monthly basis form April 2002 to January 2003. At each site, water samples were collected from both surface and near-bottom levels and in case of sampling sites that are less than 50cm in depth, only surface sample was collected. Water temperature, salinity and pH were measured in situ using a multi meter hydrolab device. The collected water samples were analysed in the laboratory to determine the surface and near-bottom concentrations of nitrite, nitrate, phosphate, ammonia, magnesium and calcium for each sampling site. Moreover, the density of Artemia organisms and their cysts numbers were counted for each site.

In order to evaluate the tolerance of Artemia organisms to the variations in the lake environment, Artemia specimens were collected from Al Wathba Lake and tested for the following variables: a- water temperature (150, 250, 300, 40oC), b- water pH (7.5, 8, 9.5, 10), c- water salinity (75, 100, 150, 200 ppt) and d- food types (Duluniella, Chiarella, Tetraselimus sp., yeast). These tests were run for three weeks until the last individual died, and the optimum survival rates were detected. In addition, Artemia specimens were sent to the Laboratory of Aquaculture and Artemia Reference Centre in Belgium for taxonomic identification. From the preliminary investigation, the centre has identified the given specimens as Artemia franciscana.

Results from the collected field data revealed that the Artemia population inhabiting Al Wathba Lake is mostly affected by water temperature and water salinity. Artemia was absent during the summer months due to the high water temperature (maximum= 34.5 °C) and salinity (maximum= 237.5 ppt). In winter, Artemia was abundant in the lake when water temperature was 18.6 °C and water salinity was dropped off to 70.4 ppt. The statistical analysis of the studied parameters showed that the chemical composition of the lake water had no significant effect on the presence or absence of Artemia in the lake.

The laboratory experiment showed that Artemia sp. was greatly influenced by water salinity and water pH. It was found that Artemia population inhabiting Al Wathba Lake maintains better performance at salinity of 75 ppt and a pH of 8, and the survival was longer than the other combinations. In addition, it was found that the optimum temperature at which the best performance and longest survival were recorded of all between 25-30 °C.

According to the preliminary identification of the Artemia species, and in light of the field and laboratory results, it seems that the existing Artemia species at Al Wathba Lake may match the A. franciscana behavior. However, the response to other environmental parameters did not match that of A. franciscana features. Therefore, further genome analysis is suggested in order to identify the specific taxonomic rank of the Artemia population in Al Wathba Lake.

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