28. Effects of ocean acidification and warming on early benthic juveniles of Crown of Thorns Starfish, Acanthaster planci indicate enhanced development at near future acidification

Pamela Kamya (1)*, Symon A. Dworjanyn (1), Maria Byrne (2)

1 National Marine Science Centre, Southern Cross University, Coffs Harbour, New South Wales, Australia
2 Schools of Medical and Biological Sciences, The University of Sydney, Sydney, New South Wales, Australia

Background
To assess the effects of ocean acidification and warming, an understanding of which species will benefit or be disadvantaged at different life history stages is important to determine population success in a changing ocean, especially for ecologically important species such as the coralivorous Crown of thorns starfish, Acanthaster planci.

Methods
We assessed the effects of near-future acidification and warming on the sensitive early juveniles stages of A. planci that initially feed as juveniles on crustose coralline algae (CCA). The responses of growth, calcification and feeding rates of juveniles were assessed at three pH (8.1, 7.8, 7.6) and three temperature (26°C, 28°C, 30°C) treatments in a fully factorial experimental design.

Findings
There was no affect of temperature on growth and feeding rates of juveniles, but they grew faster and had greater feeding rates at pH 7.6. Production of spines, as a proxy for calcification, was not affected by acidification and warming. Levels of warming used in our study did not breach thermal tolerance levels for A. planci juveniles.

Conclusions
Future ocean acidification conditions promoted growth in A. planci at a highly sensitive juvenile stage. The increase in growth of juveniles was supported by elevated feeding rates on its CCA prey. At moderate levels of warming early juveniles of A. planci are highly thermotolerant. The positive effects of ocean acidification on development of the early juveniles of A. planci may have population spill over effects on coral eating adults.