12 February: Crown of Thorns thriving as ocean temperatures rise

Scientists from the Australian Institute of Marine Science (AIMS)* have revealed in a study published in Scientific Reports today that rising sea surface temperatures are contributing to the survival rate of the coral-eating seastar, Acanthaster planci – better known as the Crown of Thorns (COTS).

Much of the research was carried out in the National Sea Simulator at AIMS, a high-tech marine laboratory near Townsville in Queensland.

“Warmer sea temperatures were found in this study to enhance COTS survival along with other, cumulative pressures on the reef,” said report author and AIMS scientist, Dr Sven Uthicke.

Uthicke explained that a 2° C increase in sea temperature can increase the probability of survival of COTS by 240% under certain conditions. These conditions include the availability of nutrients for COTS larvae to feed on.

“Recognising the role of synergistic effects of increased nutrient flows and sea surface temperatures on COTS survival better enables scientists to understand the science behind outbreaks,” said Uthicke.

COTS outbreaks are a significant stress on the survival of corals on the Great Barrier Reef (GBR). A range of scientific research indicates that COTS outbreaks are a major contributor to the estimated 50% decline in coral cover during the period of 1985 and 2012.

“Given that the most moderate climate change scenarios predict a 1-2° C increase in average sea temperatures, the present study further demonstrates the value of taking a holistic, multi-variable approach to understand better how cumulative factors affect the survival of species such as COTS,” Dr Uthicke concluded.

*Two of the researchers involved in this study are working at the University of Sydney and the University of Otago.

**The Australian Institute of Marine Science's National Sea Simulator (SeaSim) is a world-class marine research aquarium facility for tropical marine organisms in which scientists can conduct cutting-edge research. Using SeaSim, Australian and international scientists can research the impact of complex environmental changes with large, long-term, experiments in which they can manipulate key environmental factors.