Surface scars on massive corals as evidence of previous crown-of-thorns starfish (Acanthaster planci) outbreaks on the Great Barrier Reef

In April 1985, massive corals on 5 mid-shelf reefs (Green Island, Feather Reef, John Brewer Reef, Rib Reef and Wheeler Reef) and 1 outer-shelf reef (Potter Reef) were surveyed for feeding scars caused by the crown-of thorns starfish (Acanthaster planci). Each reef, with the exception of Wheeler Reef, had experienced crown-of-thorns starfish outbreaks between 1962 and 1985.The survey involved 2 divers using SCUBA equipment swimming along randomly placed 200 m (approximately) sections of the reef perimeter. These swims were carried out in a slow meandering pattern covering as much of the reef slope as possible to a depth of approximately 12m. Various size classes of Diploastrea heliopora and a number of species of Porites were surveyed. Each individual colony encountered was recorded in 1 of 4 diameter categories and 1 of 4 proportional damage categories. The height difference between the scarred surface and the living surface was measured using a specially built PVC height gauge.Shallow cores (to 20 cm) were taken in the dead surfaces of some Porites colonies for the purpose of dating the dead surface. For each colony, measurements were made of total height, maximum diameter, the diameter perpendicular to the maximum diameter, and 5 independent measurements of the heights between adjacent 'steps', where a 'step' is the distance between adjacent dead or living and dead surfaces normal to the lower surface. The cores were bleached, sun dried and logged. The dead surfaces were then dated using a fluorescent banding technique. This study set out to examine the feasibility of eliciting reliable data on previous crown-of-thorns (Acanthaster planci) aggregations by dating surface scars on massive corals. The objectives of the surveys were to assess the level of damage caused by the most recent Acanthaster planci outbreaks on various size classes of Porites and Diploastrea, and to locate suitable specimens for detailed measurement and dating of scars. This research was a component of 'The Crown-of thorns Study', which was supported by the Commonwealth Community Employment Program'

1985年4月，研究人员对5个中陆架珊瑚礁（绿岛、羽毛礁、约翰·布鲁尔礁、里布礁和惠勒礁）及1个外陆架珊瑚礁（波特礁）上的大型珊瑚开展调查，旨在识别棘冠海星（Acanthaster planci）造成的摄食疤痕。除惠勒礁外，其余珊瑚礁在1962-1985年间均发生过棘冠海星暴发事件。调查由2名潜水员使用水肺（SCUBA）设备完成，他们沿随机布设的珊瑚礁周长段（约200米）缓慢蜿蜒游动，尽可能覆盖深度达12米的珊瑚礁斜坡区域。研究涵盖不同尺寸等级的太阳蕈珊瑚（Diploastrea heliopora）与多种孔珊瑚属（Porites）物种：遇到的每个珊瑚群体需记录其直径类别（共4类）及比例损伤类别（共4类）；采用特制聚氯乙烯（PVC）高度测量仪测定疤痕表面与活体表面的高度差；在部分孔珊瑚属群体的死亡表面采集浅层岩芯（深度达20厘米）用于年代测定。针对每个群体，测量指标包括总高度、最大直径、垂直于最大直径的直径，以及相邻“台阶”间高度的5次独立测量——“台阶”指相邻死亡表面或活体与死亡表面间垂直于下表面的距离。岩芯经漂白、晒干及记录后，通过荧光条带技术完成死亡表面定年。

本研究旨在验证通过大型珊瑚表面疤痕定年获取棘冠海星（Acanthaster planci）既往聚集可靠数据的可行性，具体目标为：评估近期棘冠海星暴发对不同尺寸等级孔珊瑚属与太阳蕈珊瑚的损伤程度，以及筛选适合疤痕详细测量与定年的样本。

本研究是“棘冠海星研究”的组成部分，该项目获英联邦社区就业计划（Commonwealth Community Employment Program）资助。