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Document Type |
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Thesis |
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Document Title |
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Physiological and Ecological Studies of Two Reef Building Corals Species Seriatopora hystrix and Lobophyllia corymbosa in the Red Sea دراسات فسيولوجية وبيئية لنوعين من بانيات الشعاب المرجانية سرياتوبورا هيستريكس واللوبوفيليا كرومبوسا في البحر الأحمر |
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Subject |
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biological sciences department |
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Document Language |
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Arabic |
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Abstract |
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Some aspects of the physiology and ecology of the corals Seriatopora hystrix and Lobophyllia corymbosa from the Red Sea are described in this thesis. These two species were selected on the basis of their different growth form and nutritional strategies. The lowest mean seawater temperature was 27.42°C and 27.17°C at 5m and 10m depths respectively in March (2010). However, the maximum mean seawater temperature was observed in August (2009) and was about 32.67°C and 31.17°C in 5m and 10m depths respectively. Salinity varied only between 39.5‰ (in winter) and 41‰ (in summer). The daylight duration was 12.75 hours in summer with an integrated daily irradiance of 11.26 µE m-2 d-1 at 5m depth, whilst in winter the day length was 11.75 hours and the integrated daily irradiance was 7.32 µE m-2 d-1 at the same depth. The light transmission was observed decreasing with increasing depth. The two species showed some variations in skeleton and biomass characteristics. Skeletal densities of both species (S. hystrix and L. corymbosa) were 2.5 g.cm-3 and 2.75 g.cm-3 respectively. In summer the S. hystrix had the lower biomass of tissue per surface area percentage (14.83% and 30.13%) at 5m and 10m depths respectively than the L. corymbosa. Similarly in winter also the lowest biomass of tissue per surface was observed in the S. hystrix (49.26% and 71.31%) than the L. corymbosa. Regarding the zooxanthellae density, both species showed similar annual cycle, i.e., higher in winter than the summer. In context, S. hystrix had 6.5% and 6.2% lower density of zooxanthellae in summer than the winter at 5m and 10m depths respectively. It was also lower in L. corymbosa (13.6% and 12.23%) in summer than the winter at 5m and 10m depths. There was only a little variation in the respiration rates of the zooxanthellae between the two species, and declined gradually for both species according to the depth variation and season. Photosynthesis versus irradiance (P v I) curves was obtained and lines fitted to the data using the hyperbolic tangent function. The lower Pgmax values were observed in S. hystrix in winter than summer, hence sensitive to the temperature variations. Conversely, the Pgmax of L. corymbosa was higher in summer than winter, suggesting the possibility of compensatory process of either the lower light-levels or lower water temperature during winter. The growth rate of the two species was lower in the winter than in summer. In S. hystrix, the protein content was higher in summer both at 5m and 10m depths similar to L. corymbosa. On the contrary, carbohydrate content was higher in winter in both the species at 5m depth but lower in winter at 10m depth. At 5m depth, lipid content was 4.5 times higher in winter in S. hystrix whereas in L. corymbosa it was approximately twice as high in summer compared to winter. Whereas the quantity of lipid was higher in winter but it was not significantly high at 10m depth. In winter, there was little variation in the chlorophyll "a" in S. hystrix, while in summer there was distinct increase at the 5 m and 10 m depth while in L. corymbosa the pattern was slightly different at 5 m and 10 m depths, the amount of chlorophyll increased with depth and the same pattern followed in summer too. Chlorophyll "b" concentration of S. hystrix was lower at 5 m depth in the summer and was increased at 10 m depth. The amount of chlorophyll increased with depth in both seasons at 5 m depth. At 10 m depth the Chlorophyll "b" concentration of S. hystrix was lower than the L. corymbosa at 5 m and 10 m in both seasons. All these finding indicated that S. hystrix was predominantly depending on autotrophic feeding while L. corymbosa relies mainly on heterotrophic feeding. The sexual reproduction of these corals revealed that, S. hystrix is a hermaphrodite brooder with internal fertilization and developing the larvae within their polyps whereas the L. corymbosa is a hermaphrodite broadcaster with external larval developing and hence embryos of the species are not observed in the histological examinations. |
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Supervisor |
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Prof. Dr. Talal A. Zari |
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Thesis Type |
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Doctorate Thesis |
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Publishing Year |
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1433 AH
2012 AD |
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Co-Supervisor |
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Dr. Abdulmohsin A. Al-Sofyani |
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Added Date |
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Sunday, March 11, 2012 |
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Researchers
| يحي أحمد فلوس | Floos, Yahya Ahmed | Researcher | Doctorate | |
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