Differential Impact of Monsoon and Large Amplitude Internal Waves on Coral Reef Development in the Andaman Sea

The Andaman Sea and other macrotidal semi-enclosed tropical seas feature large amplitude internal waves (LAIW). Although LAIW induce strong fluctuations i.e. of temperature, pH, and nutrients, their influence on reef development is so far unknown. A better-known source of disturbance is the monsoon affecting corals due to turbulent mixing and sedimentation. Because in the Andaman Sea both, LAIW and monsoon, act from the same westerly direction their relative contribution to reef development is difficult to discern. Here, we explore the framework development in a number of offshore island locations subjected to differential LAIW- and SW-monsoon impact to address this open question. Cumulative negative temperature anomalies – a proxy for LAIW impact – explained a higher percentage of the variability in coral reef framework height, than sedimentation rates which resulted mainly from the monsoon. Temperature anomalies and sediment grain size provided the best correlation with framework height suggesting that so far neglected subsurface processes (LAIW) play a significant role in shaping coral reefs.

安达曼海（Andaman Sea）及其他大潮差半封闭热带海域广泛发育大振幅内波（large amplitude internal waves, LAIW）。尽管大振幅内波会引发温度、pH值及营养盐等要素的剧烈波动，但目前学界对其对珊瑚礁发育的影响仍知之甚少。另一个更为学界熟知的珊瑚扰动源为季风：季风通过湍流混合与沉积作用对珊瑚产生影响。由于在安达曼海，大振幅内波与季风均源自同一西风方向，因此二者对珊瑚礁发育的相对贡献难以区分。为此，本研究选取了一批受不同强度大振幅内波与西南季风影响的离岸岛礁区域，探究其珊瑚礁格架的发育情况，以解答这一悬而未决的科学问题。以负温度距平累积值作为大振幅内波影响的代用指标，其对珊瑚礁格架高度变异的解释度高于主要由季风引发的沉积速率。温度距平与沉积物粒径与格架高度的相关性最优，这表明此前被学界忽视的次表层过程（大振幅内波）在塑造珊瑚礁形态的过程中发挥着重要作用。