Epilithic algal composition and the functioning of Anthropocene coral reefs

Epilithic algae dominate cover on coral reefs globally, forming a critical ecological interface between the benthos and reef organisms. Yet, the drivers of epilithic algal composition, and how composition relates to the distribution of key taxa, remain unclear. We develop a novel metric, the Epilith...

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Bibliographic Details
Published in:Marine pollution bulletin 2025-01, Vol.210, p.117322, Article 117322
Main Authors: Tebbett, Sterling B., Emslie, Michael J., Jonker, Michelle J., Ling, Scott D., Pratchett, Morgan S., Siqueira, Alexandre C., Thompson, Angus A., Yan, Helen F., Bellwood, David R.
Format: Article
Language:English
Subjects:
Algal turfs
Animals
Anthozoa
Coral recruitment
Coral Reefs
Crustose coralline algae
Environmental Monitoring
Fishes
Herbivorous fishes
Herbivory
Hydrodynamics
Turbidity
Water Quality
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Summary:Epilithic algae dominate cover on coral reefs globally, forming a critical ecological interface between the benthos and reef organisms. Yet, the drivers of epilithic algal composition, and how composition relates to the distribution of key taxa, remain unclear. We develop a novel metric, the Epilithic Algal Ratio, based on turf cover relative to total epilithic algae cover, and use this metric to assess cross-scale patterns. We reveal water quality and hydrodynamics as the key environmental drivers of the Epilithic Algal Ratio across the Great Barrier Reef (GBR), and reefs globally. On the GBR, the abundance of herbivorous fishes and juvenile corals were also related to the Epilithic Algal Ratio, suggesting that reefs with long-dense turfs support fewer herbivores and corals. Ultimately, epilithic algae represent the interface through which the effects of declining water quality, which impacts a third of reefs globally, can reverberate up through coral reefs, compromising their functioning. •A high Epilithic Algal Ratio indicates algae are typified by long dense turfs.•Water quality and hydrodynamics were linked to the Epilithic Algal Ratio.•Herbivore abundance decreased at a high Epilithic Algal Ratio on coral reefs.•Juvenile coral density decreased as Epilithic Algal Ratio increased.•Altered composition of epilithic algae could compromise coral reef functioning.
ISSN:0025-326X
1879-3363
1879-3363
DOI:10.1016/j.marpolbul.2024.117322