Water quality boosts reef recovery

Coral reefs exposed to poor water quality recover slowly from disturbances and are more susceptible to coral disease, reports a paper published online this week in Nature Ecology & Evolution. The study finds that improving local water quality may help some reefs better withstand the bleaching impacts of climate change, but these efforts are insufficient to save the most iconic reefs.

Climate change and other pressures are already damaging broad sections of the Great Barrier Reef. The future resilience of this reef will be determined by its ability to resist disturbances and recover from coral loss.

Aaron MacNeil and colleagues used data on coral cover collected from 46 locations in the Great Barrier Reef between 1995-2017 to assess how damage inflicted by tropical cyclones, disease outbreaks and coral bleaching have affected the reef. They also examined how well the reef recovered from various types of damage.

The authors found that poor water quality, resulting from river run-off, was the biggest impediment to coral recovery. They found that corals in areas with poor water quality were in fact somewhat more resistant to coral bleaching, due to the low level of light penetrating the turbid water. However, these corals recovered from bleaching more slowly and were more susceptible to disease outbreaks.

The authors suggest that a 6-17% improvement in water quality may buffer the predicted increases in coral bleaching at some inshore locations. This level of improvement is within the scope of local government improvement plans, although the targets are unlikely to be met. However, the authors caution that improvements in water quality alone will not protect the heat-sensitive corals typical of outer-shelf reefs.