Sydney, Oct 19 (Agency) Researchers from the University of Sydney have found that predatory sea stars can remain resilient to heatwave conditions, sparking concerns for the survival of corals amid climate change-driven ocean warming. In their study published Wednesday in the Global Change Biology journal, marine biologists tested the thermal tolerance of the crown-of-thorns sea stars, a keystone coral predator. Results showed that the juvenile starfish displayed a remarkably high heat tolerance, compared to their adult counterparts, and withstood conditions that cause coral bleaching and mortality. In acute temperature experiments, the upper thermal limit of the juveniles was proven to be in the range of 34–36 degrees Celsius. “We found juvenile crown of thorns starfish can tolerate almost three times the heat intensity that causes coral bleaching, using a model that measures temperature over time,” said Maria Byrne, lead author of the study and professor of marine biology. “Juveniles might well benefit from warming waters.
The increase in the amount of their rubble habitat, generated by coral bleaching and mortality, allows their numbers to build over time,” Byrne noted. According to Byrne, the juveniles can survive and wait for at least six years for the reef to recover from the previous coral bleaching event before they can grow into coral-eating predators and start the cycle again. Featuring venomous and needle-sharp spines, the crown-of-thorns starfish is marked by the Australian Institute of Marine Science as a species native to the Great Barrier Reef whose outbreaks have been a major source of coral loss since 1962. With a fourth outbreak currently underway in the world-heritage area, the research agency noted that the starfish can kill up to 90 percent of corals on the affected reefs. “Loss of natural predators due to overfishing and the buildup of nutrients in the water have been suspected to contribute to outbreaks of crown-of-thorns starfish,” said Matt Clements, co-author of the study and PhD student. “Now we have evidence that bleaching-induced coral mortality could aid the seafloor-dwelling juveniles, leading to subsequent large waves of adults in reefs that exacerbate the ravages of climate change,” he added.