南海北部滨珊瑚骨骼微生物侵蚀

Micro-bioerosion in Porites corals in the northern South China Sea

微生物对珊瑚骨骼的侵蚀作用相对肉眼可见的大型生物侵蚀更加隐蔽,研究也相对稀少,国内更是空白。本文对采自涠洲岛、大亚湾以及西沙琛航岛的滨珊瑚骨骼切片在扫描电镜下开展微生物侵蚀研究。在涠洲岛和大亚湾的滨珊瑚骨骼切片中存在微生物侵蚀形成的“橘色条带”,可能与当地水体富营养化有关,而琛航岛的样品中则没有类似的条带。扫描电镜观察发现,这些“橘色条带”为内生藻Ostreobium quekettii,是一种热带珊瑚礁区常见的侵蚀微生物。O.quekettii侵蚀的珊瑚骨骼结构被破坏,其厚度减小,孔隙率提高了1.54%至6.76%、抗压强度下降了27.1%至51.2%,使得珊瑚骨骼变得更加“疏松”,且在整个骨骼次表面形成了一层“骨质疏松层”。该种侵蚀微生物扮演了“先行者”的角色,使珊瑚更容易被大型生物侵蚀,而大型生物侵蚀又会进一步促进微生物侵蚀,该“正反馈效应”正好解释了在富营养化的南海北部发现的珊瑚骨骼内侵蚀加剧的现象。

The effect of microorganisms on coral skeletons is more concealed than that by macro-bioerosion,which is visible to the naked eye.The study of micro-bioerosion is rare,and there is no such research in China.In this study,micro-bioerosion research was carried out under scanning electron microscopy on the coral skeletons of the Porites samples collected from Weizhou Island,Daya Bay and Chenhang Island.The“Orange Bands”were formed by microorganisms in the coral skeletons of Weizhou Island and Daya Bay,while there were no similar bands in the samples of Chenhang Island.This phenomenon may be related to the eutrophication of local sea water.Scanning electron microscopy of these"Orange Bands"revealed that this was caused by an endolithic algae—Ostreobium quekettii,a common eroding microorganism in the tropical coral reef area.The structure of Porites skeleton eroded by Ostreobium quekettii is destroyed,the thickness is reduced,the porosity is increased from 1.54%to 6.76%,and the compressive strength is reduced from 27.1%to 51.2%.The microorganism makes the coral skeleton more"loose"and form a layer of"osteoporosis"on the entire surface of the coral.This microorganism acts as a“forerunner,”making corals more susceptible to macro-bioerosion,which in turn promote micro-bioerosion.The“positive feedback effect”explains the increased bioerosion of the coral skeleton in the eutrophic northern South China Sea.