砗磲采挖对珊瑚礁生态系统的破坏——以西沙北礁为例

Damages of coral reef ecosystem by the giant clam excavation—— a case study on North Reef of Xisha Islands

以西沙群岛北礁为例,通过对比采挖砗磲前后的数据,来说明该活动对珊瑚礁生态系统的破坏.2012~2014年间北礁礁坪上的造礁石珊瑚种类数量变动较大,减少了29种;优势种由之前的鹿角珊瑚（Acropora sp.）变为现在的指状蔷薇珊瑚（Montipora digitata）;礁坪的物种多样性指数也处于较低的水平.虽然当前北礁的珊瑚覆盖率为52.83%,但是相比2012年降低了大约10%,尤其是2号站位,珊瑚覆盖率降低了约20%.同时2号站位出现了珊瑚白化死亡的现象.调查结果表明,北礁的珊瑚礁生态系统,尤其是礁坪上的珊瑚礁生态系统已经受到严重的破坏,珊瑚种类减少、群落结构改变、物种多样性降低、覆盖率下降、死亡率提高.通过分析,认为砗磲采挖是造成北礁礁坪珊瑚礁生态系统破坏的一个主要因素.

The variations of coral reefs was compared before and after the excavation of giant clams on North Reef of Xisha Islands to illustrate the destructions on the coral reef ecosystem. The results showed that 29 coral species dis- appeared on the reef flat of North Reef in 2014 compared to that in 2012. Dominant species evolved from previous Acropora sp. to Montipora digitata. The diversity index of corals became low in the reef flat. Although North Reef maintained 52. 83% of mean coral coverage, around 10% reduction in coral coverage was found in 2014 compared with that in 2012. Particularly, the coral coverage was reduced as much as 20% with bleaching corals at station 2. The findings suggest that North Reef, especially the reef flat, has suffered severe damages. As results, the numbers of coral species were deceased and the community structure altered besides the deceased of species diversity and coral coverage and increased of coral mortality. It is considered that the coral reef degradation on North Reef is re- sulted from the illegal excavation of giant clams, which is an important factor destroyed and threatened the health of coral reef ecosystem in the flat.