Substrate stabilisation and small structures in coral restoration: state of knowledge, and considerations for management and implementation

Ceccarelli, Daniela M., McLeod, Ian M., Boström-Einarsson, Lisa, Bryan, Scott E., Chartrand, Kathryn M., Emslie, Michael J., Gibbs, Mark T., Gonzalez Rivero, Manuel, Hein, Margaux Y., Heyward, Andrew, Kenyon, Tania M., Lewis, Brett M., Newlands, Maxine, Mattocks, Neil, Schläppy, Marie-Lise, Suggett, David J., and Bay, Line K. (2020) Substrate stabilisation and small structures in coral restoration: state of knowledge, and considerations for management and implementation. PLoS ONE, 15 (10). e0240846.

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Abstract

Coral reef ecosystems are under increasing pressure from local and regional stressors and a changing climate. Current management focuses on reducing stressors to allow for natural recovery, but in many areas where coral reefs are damaged, natural recovery can be restricted, delayed or interrupted because of unstable, unconsolidated coral fragments, or rubble. Rubble fields are a natural component of coral reefs, but repeated or high-magnitude disturbances can prevent natural cementation and consolidation processes, so that coral recruits fail to survive. A suite of interventions have been used to target this issue globally, such as using mesh to stabilise rubble, removing the rubble to reveal hard substrate and deploying rocks or other hard substrates over the rubble to facilitate recruit survival. Small, modular structures can be used at multiple scales, with or without attached coral fragments, to create structural complexity and settlement surfaces. However, these can introduce foreign materials to the reef, and a limited understanding of natural recovery processes exists for the potential of this type of active intervention to successfully restore local coral reef structure. This review synthesises available knowledge about the ecological role of coral rubble, natural coral recolonisation and recovery rates and the potential benefits and risks associated with active interventions in this rapidly evolving field. Fundamental knowledge gaps include baseline levels of rubble, the structural complexity of reef habitats in space and time, natural rubble consolidation processes and the risks associated with each intervention method. Any restoration intervention needs to be underpinned by risk assessment, and the decision to repair rubble fields must arise from an understanding of when and where unconsolidated substrate and lack of structure impair natural reef recovery and ecological function. Monitoring is necessary to ascertain the success or failure of the intervention and impacts of potential risks, but there is a strong need to specify desired outcomes, the spatial and temporal context and indicators to be measured. With a focus on the Great Barrier Reef, we synthesise the techniques, successes and failures associated with rubble stabilisation and the use of small structures, review monitoring methods and indicators, and provide recommendations to ensure that we learn from past projects.

Item ID: 64592
Item Type: Article (Research - C1)
ISSN: 1932-6203
Keywords: coral reef ecology; unconsolidated substrate; rubble; ecological restoration; habitat complexity; regulations
Copyright Information: © 2020 Ceccarelli et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funders: Australian Institute of Marine Science, National Environmental Science Program (NESP), Reef Restoration and Adaptation Program (RRAP)
Date Deposited: 30 Oct 2020 02:30
FoR Codes: 44 HUMAN SOCIETY > 4407 Policy and administration > 440704 Environment policy @ 50%
44 HUMAN SOCIETY > 4407 Policy and administration > 440710 Research, science and technology policy @ 50%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970105 Expanding Knowledge in the Environmental Sciences @ 50%
96 ENVIRONMENT > 9607 Environmental Policy, Legislation and Standards > 960701 Coastal and Marine Management Policy @ 50%
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