An assessment of the geological evidence for previous Acanthaster outbreaks

Much debate has surrounded the notion that outbreaks of the crown-of-thorns starfish (Acanthaster planci) have occurred in the geological past and hence are natural phenomena. As this debate has recently been renewed, we have reassessed statistically data presented by Frankel (1977, 1978) as evidence for the occurrence of past outbreaks. This was done using Frankel's data as well as those from extensive starfish surveys conducted prior to the commencement of his research. Our analysis of these data indicates that the occurrence of A. planci remains in recent sediments is independent of whether or not the reef from which the sample was collected had experienced a recent outbreak. Based on this premise, it is not possible to infer from Frankel's data the occurrence of past outbreaks from similar material in much older sediments. Thus while the data presented by Frankel (1977, 1978) may show that A. planci has existed within the Great Barrier Reef for at least several thousand years it does not demonstrate that outbreaks of this starfish have occurred in the geological past.