棘冠海星暴发及其对珊瑚礁的生态影响研究进展

A review of research on crown-of-thorns starfish and their ecological effects on coral reefs

棘冠海星的反复暴发是导致印度—太平洋区域珊瑚礁生态系统退化的最主要原因之一。然而,我国对棘冠海星的研究非常有限。本文综述了国内外关于棘冠海星及其暴发的生态影响和应对策略的研究进展,得出以下主要结论:1)雌性棘冠海星个体每年产卵数量高达50万—2亿个,环境因素变化只要导致幼虫和幼体存活率的轻微提高,成体就将得到大量补充;2)棘冠海星暴发的阈值为1000—1500个/km^(2),暴发周期为10—27 a,每次暴发持续1—10 a,最终可能以“种群集体感染疾病而崩溃”结束;3)棘冠海星暴发对印度洋及太平洋东部和北部珊瑚礁的破坏性非常小,却直接导致太平洋的西部和南部珊瑚礁90%以上的珊瑚死亡,并通过改变珊瑚群落组成、减少珊瑚和鱼类多样性而对珊瑚礁产生间接影响;4)关于棘冠海星暴发原因的假说中“陆地营养物质输入假说”和“捕食者过度捕捞假说”得到了最普遍的认可,但都不能解释所有的暴发事件;5)应对棘冠海星暴发的主要策略有改善水质、设立保护区、投放天敌和人工清理等,其中人工清理是最直接有效的策略,但迄今并没有发现可长期抑制棘冠海星暴发的方法。因此,急需加强对棘冠海星的深入研究,探查其暴发的根本原因和对策。

Crown-of-thorns starfish(CoTs)outbreaks remain a major cause of coral mortality in the Indo-Pacific,contributing to widespread and accelerating degradation of coral reef environments.Coral reefs in the South China Sea also outbreak CoTs,but research on CoTs in our country is limited.In this study,we reviewed the advances in research on CoTs physiology and ecology,the ecological effects of CoTs outbreaks,and the measures used to manage such outbreaks.The main conclusions are as follows:1)Each CoTs female produces approximately half a million to two-hundred million eggs per year,indicating a high reproductive potential.Consequently,if an environmental change leads to a marginal increase in the survival rate during the growing period of CoTs,a substantial number of adults will recruit,and thus lead to a CoTs outbreak.2)The CoTs outbreak threshold is defined as 1000—1500 starfish/km^(2)in areas with more than 20%coral cover.Outbreaks usually persisted for 1—10 years,and the time gap between the start of two outbreaks ranged from 10 to 27 years.Outbreaks were most likely to end with population precipitous decline caused by the rapid transmission of disease.3)Incidences of large-scale destruction(>90%coral mortality)of scleractinian corals by CoTs outbreaks occurred primarily within the southern and western Pacific,but not in the Indian Ocean or in the northern and eastern parts of the Pacific Ocean,which may be explained by the relative dominance of Acropora in the southern and western Pacific.Outbreaks also indirectly destroy coral reefs by changing the benthic composition of the reefs,increasing the abundance of soft coral and macroalgae,and reducing the fish and coral diversity.4)Whereas the terrestrial run-off hypothesis and predator removal hypothesis are the most biologically probable among numerous hypothesized outbreak causes,so far no single hypothesis could account for all the outbreaks.5)Measures to manage outbreaks of CoTs include improving the water quality in marine environment,increasing the extent of no-take marine protected areas,releasing the predators of CoTs larvae to coral reefs,and directly removing CoTs from coral reefs.Among these,removing CoTs is the most direct and effective measure.However,irrespective of the improvements in the efficiency of direct control of CoTs populations,these measures will possibly only provide temporary or short-term solutions for minimizing the effects of CoTs outbreaks on coral reefs.Therefore,further research will be required to understand the ultimate cause(s)of CoTs outbreaks,which will provide long-term or permanent solutions.