Reduced salinity of seawater wreaks havoc on coral chemistry

New research suggests massive plumes of fresh water from the recent North Queensland floods could put Great Barrier Reef corals under extreme stress, as marine heatwaves have done. Drastic changes in ocean salinity from, for example, severe freshwater flooding, provoke a similar response in corals as extreme heating, resulting in “freshwater bleaching” and if unabated, coral death.

Researchers from the ARC Centre of Excellence for Coral Reef Studies at James Cook University  (Coral CoE) and University of Technology Sydney (UTS) report that extreme and sudden changes in salinity, or the ocean salt concentration, cause a biochemical response in corals that is similar to marine heatwaves, but in some ways, more damaging to their cells ability to function.

“Corals are sensitive organisms, known to only tolerate slight changes in their environment. Thriving in clear, sunlit waters – the majority of reef-building corals are found in tropical and subtropical waters with a salinity between 32 to 42 parts per thousand,” said senior author Prof David Miller of Coral CoE.