DOI: 10.25903/bst9-w464
title: Data for: The structure and composition of macroalgal communities influence coral recruitment on an inshore reef of the Great Barrier Reef

description: <p><b>Background:</b> On inshore reefs of the Great Barrier Reef, coral communities are increasingly exposed to frequent disturbances that reduce coral cover and facilitate the proliferation of macroalgae. These shifts in benthic composition can persist for extended periods, potentially altering key ecological processes such as coral recruitment. While macroalgae are generally considered to inhibit coral recruitment, most studies treat macroalgae as a single functional group, despite substantial variation in their morphology, ecology, and spatial structure. Understanding how different macroalgal assemblages influence coral recovery is therefore critical for predicting reef resilience under changing disturbance regimes.</p>

<p><b>Methods:</b> This study was conducted on the shallow reef crest (~3 m depth) of Florence Bay, Magnetic Island, an inshore reef in the central Great Barrier Reef characterized by high macroalgal cover and moderate coral cover. Forty 1 m² plots were established and randomly assigned to one of four treatments: (1) cleared of macroalgae, (2) canopy-forming macroalgae only, (3) understorey macroalgae only, or (4) mixed macroalgal assemblage (unaltered). PVC settlement tiles were deployed in each plot one month prior to predicted coral spawning to quantify recruitment, and were retrieved and processed in February 2023. Benthic composition and macroalgal canopy structure (height and density) were recorded for each plot and around the tiles. Turf height and grazing intensity were also visually assessed. Coral recruits on tiles were counted under a dissecting microscope by a single observer blind to treatment. To assess natural patterns of coral size distribution, repeated benthic surveys were conducted across reef flat, crest, and slope habitats from September 2022 to August 2023, with coral sizes measured and categorized into three classes. Macroalgal cover, canopy height, and density were monitored at each time point.</p>

</p><b>This data record includes:</b></p>
<p>
<ul>
<li>CH3-metadata.xlsx: metadata on treatment assigned to each tile</li>
<li>Maggie-Quads-8.xlsx: dataset containing coral class sizes in Florence Bay</li>
<li>CH3-recruits-count.xlsx: number of recruits on tiles and grazing level</li>
<li>CH3-Algal-community-time-0.xlsx: macroalgal community (quadrat and perimeter) at the beginning of the experiment</li>
<li>CH3-tile-benthos.xlsx: CCA and turf cover on tiles</li>
<li>CH3-Algal-community-time-1.xlsx: macroalgal community (quadrat and perimeter) at the end of the experiment</li>
<li>canopy_data.csv: canopy data</li>
<li>Maggie-Quads-5.xlsx: macroalgal cover in February/March in Florence Bay</li>
<li>Maggie-Quads-4.xlsx: macroalgal cover in January in Florence Bay</li>
<li>Maggie-Quads-3.xlsx: macroalgal cover in November/December in Florence Bay</li>
</ul>
</p>
<p>Software/equipment used to create/collect the data: Visual surveys, settlement tiles, microscope</p>
<p>Software/equipment used to manipulate/analyse the data: Microsoft excel, R Studio</p>