Key environmental pressures
No severe climate-related pressures affected the inshore Reef over the 2020-21 summer. No major cyclone made landfall, and rainfall and river discharge were close to (just above) the long-term average.
Sea-surface temperatures over the 2020-21 summer were slightly above long-term averages but remained below the threshold likely to lead to significant bleaching.
How did inshore corals respond?
- Inshore coral reef findings:
- Inshore corals remain in an overall ‘poor’ condition, primarily due to the legacy of past storms and above average sea-temperatures in summer 2019-20. Some signs of recovery were observed, with both macroalgal cover declining and juvenile density increasing at some locations.
- In the Wet Tropics, there was marked difference between the sub-regions. Coral community conditions remained ‘good’ in the Herbert-Tully sub-region, with coral cover recovering well since severe Tropical cyclone Yasi, in 2011. Recovery was observed in the Johnston-Russell-Mulgrave sub-region, which has suffered ongoing outbreaks of crown-of-thorns starfish. However, coral community condition in the Barron-Daintree sub-region remained ‘moderate’, mostly driven by low densities of juvenile corals and very high cover of macroalgae in some reef sites.
- In the Burdekin, thermal stress in the summer of 2019-20 caused severe bleaching at most reefs. A slight decrease in the coral condition in 2021 was attributed to the legacy of this stress event.
- Coral community condition remained ‘poor’ in the Mackay-Whitsundays region. However, signs of recovery since the impacts of Tropical cyclone Debbie in 2017 have been detected, such as a decrease in macroalgal cover and an increase in the density of juvenile corals.
- Similar to the coral communities in the Burdekin region, corals in the Fitzroy region were severely bleached in 2020. The observed decline and ‘poor’ condition are a result of the long-term effect of this thermal stress event. Macroalgal cover remains high across all sites.
What is monitored and where?
Condition and trend of inshore coral communities are surveyed at two and five meters at reef sites located in the Wet Tropics, Burdekin, Mackay-Whitsundays, and Fitzroy regions.
- At these sites, coral monitoring assesses the following indicators:
- coral cover
- proportion of macroalgae
- juvenile coral density
- rate at which coral cover changed
- coral community composition (genus level)
- Additionally, signs of bleaching, disease, physical scars, and any other damage are recorded.
- Detailed information on the sites surveyed can be found here.