The effect of large amplitude internal wave (LAIW) and monsoon exposure on growth and skeletal density of Porites lutea

kristina.beck [ at ]


The Similan Islands, a chain of islands in the Andaman Sea, are subject to large amplitude internal waves (LAIW, or solitons) and the southwest monsoon. The ocean facing west side of this archipelago near the Thai continental shelf break is exposed to LAIW and monsoon, whereas the eastern side is sheltered from both. LAIW mainly influence greater depth and are known to change environmental factors that affect coral growth. The monsoon however, causes higher wave action and increased sedimentation and therefore primarily influences shallow reef areas. In the present study, the impact of LAIW and monsoon on linear extension rate, skeletal bulk density and calcification rate of the scleractinian coral Porites lutea are investigated. Coral skeletons have been collected at two depths (7 and 20 m) at the west and east sides of the central Similan island Ko Miang. X-radiography and fluorescence analysis are used to examine the linear extension rate due to the annual banding in the coral skeletons. Measurements of skeletal bulk density, micro-density and porosity are based on the buoyant weighing technique, calculation of the total enclosed volume and measurement of matrix volume by Archimedean methods. Higher skeletal bulk densities were found at the west side of the island Ko Miang with highest values at W 7 m. As no correlation of the skeletal bulk density with the intensity of LAIW was found, higher density values could be attributed to the impact of the monsoon. For the linear extension and calcification rates, no significant differences between side and depth were observed. In addition, no correlation with the intensity of internal waves was discovered, which indicates that other environmental factors than internal waves primarily affect growth and calcification of P. lutea.

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Beck, K. K. (2015): The effect of large amplitude internal wave (LAIW) and monsoon exposure on growth and skeletal density of Porites lutea , Bachelor thesis, Bremen University.

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