Poster Australian Marine Sciences Association 2022

Age and available coral species modulate transition probability from herbivory to corallivory in juvenile Acanthaster cf. solaris (Crown-of-Thorns Seastar) (#466)

Rachel Neil 1 2 3 , Maria Gomez Cabrera 2 , Sven Uthicke 2
  1. College of Science and Engineering, James Cook University, Douglas, QLD, Australia
  2. Australian Institute of Marine Science, Cape Cleveland, QLD, Australia
  3. AIMS@JCU, Townsville, QLD, Australia

Outbreaks of Acanthaster spp., Crown-of-Thorns Seastars (COTS), are a major threat to coral reefs in the Indo-Pacific region. Although COTS are important coral predators, juveniles consume crustose coralline algae for several months after settlement. The transition from herbivory to corallivory in juvenile COTS is an important yet unresolved knowledge gap in the biology and ecology of these seastars. To help address this gap, two experiments were conducted across two distinct cohorts of Acanthaster cf. solaris, to test the age and size that COTS transition to feeding on corals, and to investigate the effect of available coral species on the timing of the switch. COTS were found to begin transitioning to coral at 7.5 -8.5 mm in diameter, with first transitions observed 136 – 145 days post-settlement and 50% of cohorts transitioning to feed on Acropora tenuis between 175 – 191 d. At 175 d, significantly more COTS had transitioned to feeding on A. tenuis (51%) compared to A. millepora (38%) and Stylophora pistillata (7%). These data provide important information for population modelling, COTS control and understanding the cause of outbreaks, as well as evidence for an undescribed feedback mechanism between predator and prey that can delay COTS transition to coral.