Key environmental pressures

There were no acute climatic pressures imposed on inshore reefs in 2022–23.

Sea water temperatures in early 2023 were below those likely to cause coral bleaching, and no cyclones passed through the inshore Great Barrier Reef (the Reef).

Corallivorous crown-of-thorns starfish were again present on reefs in the Johnstone Russell–Mulgrave sub-region. While their numbers have declined since a peak in 2020, in 2023 juvenile crown-of-thorns were observed at ‘outbreak’ density at Franklands East. The impact of these starfish on corals was reduced by culling undertaken by the Crown-of-thorns Starfish Control Program.

Read the latest Marine Monitoring Program Annual Inshore Coral Reef Report 2022–23.

How did inshore corals respond?

Reef-wide coral condition for inshore reefs remained in an overall ‘poor’ condition in 2023.

• In the Wet Tropics region:
• Inshore coral communities remain in a ‘moderate’ condition.
• Variation exists within the three sub-regions.
• In the Barron-Daintree, the Coral Index score continued to improve but remained within the ‘moderate’ condition range. 
• In the Johnstone Russell–Mulgrave sub-region the Coral Index score has fluctuated between ‘moderate’ and ‘good’ condition since 2016.
• In the Herbert–Tully sub-region, the Coral Index score has gradually declined since 2020 but remains ‘moderate’, partly due to legacy effects from bleaching events in early 2022.

• In the Burdekin region:
• Coral Index score remained ‘moderate’ having declined from a high point in 2020.
• Coral cover continued to increase with the regional average in 2023 higher than observed since the beginning of the program in 2005.
• However, scores for Macroalgae remained ‘poor’ or ‘very poor’ at most reefs.
• The Juvenile coral score remained ‘poor’.

• In the Mackay–Whitsunday region: 
• The Coral Index score was unimproved in 2023 and has remained ‘poor’. 
• Recovery from the severe impact of cyclone Debbie in 2017 remains slow and most indicators remained in the ‘poor’ category. 
• Signs of recovery are most evident in increasing densities of juvenile corals, but this is primarily at reefs where macroalgae is low. 
• At other reefs persistently high cover of macroalgae continues to limit coral recovery. 

• In the Fitzroy region:
• Coral condition remained ‘poor’ with no improvement in 2023.
• The state of reefs varied markedly across the region.
• Coral cover was highest at the reef furthest from the coast, Barren Island.
• The persistent cover of large, brown macroalgae continued to suppress coral community recovery at most other reefs. 

Temporal trend in regional Coral Index scores from 2005–06 to 2022–23. Values are indexed scores scaled from 0.00–1.00 and graded: ■ = very good (0.81–1.00), ■ = good (0.61–0.80), ■ = moderate (0.41–0.60), ■ = poor (0.21–0.40), ■ = very poor (0.00–0.20). Note scores are unitless. 

What is monitored?

• At these sites, coral monitoring is conducted by assessing 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 from Drupella sp. and crown-of-thorns starfish predation, and any other visible damage are recorded.

• Where is coral condition monitored?
• Wet Tropics
• Burdekin
• Mackay–Whitsunday
• Fitzroy

Additional site-level information can be found in the AIMS’ Reef dashboard.