Cairns-Port Douglas
Reef Hub
John Edmonson
Recruitment Tile Study
In late 2023, the Cairns-Port Douglas Reef Hub led the first year of a collaborative study with local organisations to explore coral recruitment rates following coral spawning over the early summer months. This project was such a resounding success in collaborating to collect meaningful data while building skills, that it was repeated and expanded for the coral spawning in 2024, and is being continued in 2025. These are the first step in a planned long-term study of coral recruitment among and within reefs in the region delivered by a diverse community of partners.
The study aimed to help tourism operators, non-profits and the broader scientific community better understand and make decisions about local reefs.
WHAT IS CORAL RECRUITMENT?
Coral recruitment is the process by which coral larvae settle onto reef surfaces, attach, and grow into juvenile corals—a critical life cycle stage that underpins reef recovery, biodiversity, and overall ecosystem function.
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Each organisation deployed 15 limestone recruitment tiles (9 x 9 x 1.5 cm) at 3 sites per reef.
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Recruitment tiles, temporarily placed on reefs prior to and throughout the mass spawning, then taken back to the lab, help estimate coral recruitment, as new coral offspring are not visible to the naked eye until nearly 12 months old.
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Temperature loggers were also deployed at each site to track local temperature trends over time (see 2024 recruitment tile result).
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After retrieval, tiles were treated with a mild bleach solution to reveal the coral recruit skeletons on top, side and bottom surfaces.
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The tiles were analysed at JCU, where Reef Hub participants learned how to identify coral recruits and record data from the deployed tiles.
2023 & 24 Results
Data shown is the average number of recruits per recruitment tile ± SE at each site.
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Coral recruitment patterns varied within and among reefs, and from year to year. Ongoing monitoring is essential to identify long-term trends and understand how recruitment responds to environmental changes and disturbance events.
A huge thank you to all of the Hub network who deployed tiles on their reefs and who joined us in the lab to help count coral recruits on these tiles!
The Reef Hub hope to make this a long-term study contributing valuable open-source data about our region's capacity to recover through mass coral spawning events.
John Edmonson
John Edmonson