Journal of Tropical Oceanography ›› 2019, Vol. 38 ›› Issue (6): 74-79.doi: 10.11978/2019006CSTR: 32234.14.2019006

Special Issue: 南海专题

• Marine Biology • Previous Articles     Next Articles

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

ZHAO Kuan1,2, ZHANG Ting1,2, CHEN Tianran1()   

  1. 1. CAS Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Guangzhou 510301, China
    2. University of Chinese Academy of Sciences, Beijing 100049, China
  • Received:2019-01-09 Revised:2019-02-26 Online:2019-11-20 Published:2019-11-26
  • Contact: Tianran CHEN E-mail:chentianran@scsio.ac.cn
  • Supported by:
    National Science Foundation of China(41476038);National Science Foundation of China(41676049);Youth Innovation Promotion Association CAS(2015284);Natural Science Foundation of Guangdong Province(2018A030313142)

Abstract:

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.

Key words: bioerosion, microorganism, coral reef, northern South China Sea, scanning electron microscope