News

July 18, 2018

Great Barrier Reef coral recovery slows significantly over 18-year period

News Source: ABC News

Author(s): Nick Kilvert

Over the last three decades the Great Barrier Reef has been hit by a series of intense cyclones, bleaching, crown of thorn starfish outbreaks and flood events that have caused well-documented, but reparable damage.

Scientists have hoped that an extended period of benign conditions would allow the natural processes of reef restoration to flourish, and many of the hardest-hit regions to return to a healthier, more colourful and biodiverse state.

But a new study of coral-recovery rates based on 18 years of data and published in Science Advances today, found the ability of many corals to bounce back after disturbance has significantly slowed down.

Although recovery rates were variable between different reef patches and coral types, the researchers found the overall recovery rate of corals across the Great Barrier Reef declined by an average of 84 per cent between 1992 and 2010.

Following acute disturbance events like cyclones, coral recovery was hindered by poor water quality and high temperature, according to lead author Juan-Carlos Ortiz from the University of Queensland.

The study, supported by the Australian Institute of Marine Science (AIMS) and the Nature Conservancy, looked at data from more than 90 primarily mid-shelf and offshore reefs, comparing the rate of recovery following disturbance events.

"We noticed for the first time a very large decline in the ability of the reef to recover from disturbances over those 18 years," he said.

The research team classified corals into six groups based on their growth forms. Although all groups showed an overall decline in recovery rate, two groups — the Montipora and branching Acropora both "went into negative".

What that means is they continued to decline even after the disturbance had ceased.

While increased disturbance events are expected as the impacts of climate change ramp up, the slowed recovery time is a concerning compounding factor.