Rate of decomposition of crown-of-thorns starfish, Acanthaster planci, on the Great Barrier Reef

The decomposition of 67 crown-of-thorns starfish was monitored in 2 m x 2 m permanent quadrats established at John Brewer Reef in September 1985 and Little Broadhurst Reef in December 1988.Approximately 2 months prior to the commencement of each study, the starfish were kept under starvation conditions in the laboratory to simulate the general state of health that would be expected at the end of outbreaks, when food usually is limited. The starfish were transported back to the reefs and killed by immersion in fresh water for 8 hours.Four quadrats were located amongst patch reefs along the north eastern perimeter of John Brewer Reef. Two of the quadrats were located on sand at 9 m depth while the other two were amongst a mixed coral assemblage (mainly Acropora spp.) at a depth of 3 m. All 4 quadrats were within 10 m of each other and ten starfish were placed randomly in each quadrat and monitored over 9 days. Three quadrats were located on the eastern perimeter of the lagoon at Little Broadhurst Reef. The quadrats were situated next to each other on sand at 9 m depth and 9 starfish were positioned randomly in each quadrat and monitored for 7 days.Quadrats were monitored for about 1 hour each time, normally 3 times during the day and once at night. Maps of each quadrat indicated the position of starfish and their state of decomposition. Changes in the position of starfish were noted as were any instances of predation or other activities which might affect the decomposition process. The main morphological features of some predators were noted for later identification as it was not possible to obtain photographs of these animals. This preliminary taphonomic study was undertaken to determine how long the remains of the crown-of-thorns starfish (Acanthaster planci) are recognisable in the field and the factors that are important in the decomposition process.

1985年9月于约翰布鲁尔礁（John Brewer Reef）、1988年12月于小布罗德赫斯特礁（Little Broadhurst Reef）设立2m×2m的永久样方，对67只棘冠海星（crown-of-thorns starfish，学名：Acanthaster planci）的分解过程开展监测。在每项研究启动前约2个月，研究人员将海星置于实验室饥饿环境中饲养，以模拟种群暴发末期食物普遍匮乏时海星的健康状态。将海星转运至对应礁体后，通过浸没于淡水8小时将其处死。约翰布鲁尔礁东北缘的斑块礁间布设了4个样方：其中2个样方设置于9米水深的沙质区域，另外2个样方位于3米水深的混合珊瑚群落（主要为轴孔珊瑚属（Acropora spp.））中。4个样方相互间距均不超过10米，每个样方随机投放10只海星，并开展为期9天的监测。小布罗德赫斯特礁潟湖东缘布设了3个样方，所有样方相邻设置于9米水深的沙质区域，每个样方随机投放9只海星，并开展为期7天的监测。每次对样方的监测时长约1小时，通常日间进行3次监测、夜间进行1次监测。通过绘制每个样方的点位图记录海星的位置及其分解状态，同时记录海星的位置变动、所有可能影响分解过程的捕食事件或其他干扰活动。由于无法为这些捕食者拍摄照片，研究人员记录了其主要形态特征以便后续物种鉴定。本项初步埋藏学（taphonomic）研究旨在明确棘冠海星的遗体在野外可被识别的持续时长，以及影响其分解过程的关键因素。