Burgo, Martina, Fabricius, Katharina E., and Hoey, Andrew S. (2025) The structure and composition of macroalgal communities influence coral recruitment on an inshore reef of the Great Barrier Reef. Coral Reefs. (In Press)

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Abstract

On inshore coral reefs, coral cover declines from disturbances are often accompanied by increases in macroalgal cover. Thus, coral recovery often occurs against a backdrop of elevated macroalgae cover. While ‘macroalgae’ are generally assumed to reduce coral recruitment, their taxonomic composition and structure vary considerably. Here, we test whether different macroalgal assemblages affect coral recruitment on an inshore reef by experimentally manipulating macroalgal assemblages within forty 1 m2 plots on the shallow reef crest in Florence Bay, Magnetic Island (central inshore Great Barrier Reef). Specifically, we investigated the effect of canopy-forming macroalgae (e.g. Sargassum, Turbinaria, Sirophysalis), understorey macroalgae (e.g. Hypnea, Lobophora, Padina), mixed macroalgal assemblages (both canopy- and understorey macroalgae) and plots cleared of macroalgae on rates of coral recruitment to tiles. We also quantified coral size frequency distribution in Florence Bay to investigate its relationship with macroalgal structure and composition. The presence of canopy-forming macroalgae was the most important factor affecting coral recruitment, with coral recruitment being ~ fivefold greater in plots with no canopy-forming macroalgae compared to those with canopy-forming macroalgae. Moreover, the presence of two macroalgal taxa, Sargassum and Lobophora, within the plots was associated with lower coral recruitment to the tiles. Coral size frequency distribution in Florence Bay showed similar trends, with smaller corals (< 20 cm diameter) only present in areas with low density and height of canopy-forming macroalgae and, in particular, low abundance of Sargassum. We thus suggest that both the structure and composition of the macroalgal community drive, at some point, coral replenishment dynamics.

Item ID:	85930
Item Type:	Article (Research - C1)
ISSN:	1432-0975
Copyright Information:	This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
Funders:	ARC Centre of Excellence for Coral Reef Studies
Date Deposited:	23 Jun 2025 22:58
FoR Codes:	31 BIOLOGICAL SCIENCES > 3103 Ecology > 310305 Marine and estuarine ecology (incl. marine ichthyology) @ 100%
SEO Codes:	28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280102 Expanding knowledge in the biological sciences @ 100%
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