Coral reseeding

Fig. 1: Harrison et al. (2021). Larval mesh enclosure with the frame attached onto the reef. CC BY 4.0 DEED.

Coral reseeding, coral restoration or coral gardening is a conservation technique aimed at restoring and regenerating damaged or degraded coral reefs by collecting coral eggs and sperm from healthy sections of the reef, supporting their development into larvae and then reintroducing them to the degraded segments of the reef, where they settle and mature into new coral colonies (Hein et al., 2020). Coastal regions across Oceania that have experienced coral reef degradation due to factors such as coral bleaching, pollution, overfishing, and habitat destruction can benefit from coral reseeding. 

Name of NbS

Coral reseeding

Type of NbS

Ecosystem restoration

Location

Coral reseeding can work along coastal regions across Oceania including urban/peri-urban/rural coastlines, tourist resorts or marine protected areas (MPAs). 

Relationship to Indigenous knowledge:

Indigenous cultures in the Pacific Islands have deep-rooted connections to the moana (ocean in Māori). Coral reefs play a critical role in this connection as they support the marine biodiversity upon which many Pacific Islanders depend. Indigenous knowledge encompasses an understanding of local coral species, their ecological roles, and the historical changes observed in the reef ecosystems over generations. The sea is often central to their way of life, with fishing and navigation being vital aspects of their culture. 

Climate change benefits

Biomass cover loss; Increased temperatures; Coastal erosion; Coastal inundation; Loss of ecosystem services; Sea level rise; Storm surges; and Ocean acidification.

Healthy coral reefs act as natural barriers that provide protection to coastal communities against storm surges and extreme weather events (Ferrario et al., 2014). Reseeded reefs exhibit increased resilience to climate stressors such as rising sea temperatures and ocean acidification (Bowden-Kerby, 2023). Restored reefs contribute to the overall health of coastal ecosystems, providing benefits such as shoreline stabilisation, erosion control, and the protection of critical habitats (Ferrario et al., 2014). Coral reseeding also helps maintain ecological connectivity between reefs, which is important for the exchange of genetic material and the movement of marine species (Ortiz & Tissot, 2012).  

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Societal / socio-cultural benefits

Biodiversity health and conservation; Climate change adaptation; Disaster risk reduction; Economic and social development.

Coral reseeding helps preserve cultural heritage and traditional knowledge. Coral reseeding projects often involve local communities, providing opportunities for engagement, education, and capacity building. By restoring coral reefs, reseeding projects can increase tourism, leading to economic benefits and improved livelihoods (Spalding et al., 2017). Restored reefs can enhance fish populations, supporting local fisheries and ensuring an indirect benefit as providing a sustainable source of food for coastal communities (Albert et al., 2015).  

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Ecological and biodiversity benefits

Aesthetic value / artistic inspiration; Climate regulation; Disturbance prevention; Species maintenance; Purification (of water, soil, air); Education and knowledge; Genetic resources; Habitat provision; Nutrient cycling; Recreation and Tourism.

Reseeding coral reefs can have several significant ecological and biodiversity benefits, contributing to the health and sustainability of coral reef ecosystems. One of the primary ecological benefits of reseeding is the restoration of coral cover on degraded reefs. As coral cover increases, so does the diversity of associated marine life (Fisher et al., 2015). Reestablishing coral cover can enhance the availability of food and shelter for juvenile fish, which can have positive effects on fish populations. Coral reefs play a role in nutrient cycling within the marine environment, helping maintain water quality and supporting the growth of algae and seagrasses, which are also important components of the ecosystem (Fisher et al., 2015).  

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Technical requirements

 Coral nurseries are established in either field-based (in-situ) or land-based (ex-situ). Carefully collected healthy coral fragments from donor colonies are propagated either through asexual fragmentation or sexual reproduction for planting in the nursery. Further, the coral fragments are transplanted on the reef substrate once the coral fragments are large enough to have a good survival rate (Boström-Einarsson et al., 2020).

Issues and Barriers

Oceania is home to some of the world’s most biodiverse coral reefs, but it’s also vulnerable to the impacts of climate change, pollution, overfishing, and other stressors. Many restoration projects require significant financial resources for research, materials, and ongoing maintenance, and securing adequate funding for long-term projects could be challenging. Maintaining and monitoring reseeded corals could also be logistically complex, requiring consistent resources, personnel, and equipment.

Opportunities

Coral reseeding provides a means to restore and enhance coral reef ecosystems, which are crucial for biodiversity, fisheries, and coastal protection. Healthy reefs support a wide range of marine species and provide valuable supporting (e.g., habitat provision) and provisioning (e.g., food security) ecosystem services and are significant drivers of cultural services, including tourism and recreational activities, contributing to local and national economies. Coral restoration projects could empower and engage local communities, including indigenous groups, in conservation efforts. 

Financial case

The cost-benefit of coral reseeding varies depending on several factors, including the scale of the project, the specific location, the objectives, and the funding sources. The cost expenditure could be divided into capital and operating costs, or to account for the different components of restoration (research and planning, purchasing, land acquisition, construction, financing, maintenance, monitoring, community engagement, labour and equipment repair/replacement) (Bayraktarov et al., 2016). However, the benefits of coral reseeding often extend beyond monetary value, encompassing ecological, cultural, and social dimensions. The costs can range from tens of thousands of dollars for smaller, community-led initiatives to millions for larger, more comprehensive projects in popular tourist destinations (Bayraktarov et al., 2016). 

References
  • Albert, J. A., Olds, A. D., Albert, S., Cruz-Trinidad, A., & Schwarz, A.-M. (2015). Reaping the reef: Provisioning services from coral reefs in Solomon Islands. Marine Policy62, 244–251. https://doi.org/10.1016/j.marpol.2015.09.023
  • Bayraktarov, E., Saunders, M. I., Abdullah, S., Mills, M., Beher, J., Possingham, H. P., et al. (2016). The cost and feasibility of marine coastal restoration. Ecological Applications, 26(4), 1055-1074.
  • Bowden-Kerby A (2023). Coral-Focused Climate Change Adaptation and Restoration Based on Accelerating Natural Processes: Launching the “Reefs of Hope” Paradigm. Oceans.; 4(1):13-26. https://doi.org/10.3390/oceans4010002
  • Boström-Einarsson, L., Babcock, R. C., Bayraktarov, E., Ceccarelli, D., Cook, N., Ferse, S. C. et al. (2020). Coral restoration–A systematic review of current methods, successes, failures and future directions. PloS one15(1), e0226631.
  • Ferrario, F., Beck, M. W., Storlazzi, C. D., Micheli, F., Shepard, C. C., & Airoldi, L. (2014). The effectiveness of coral reefs for coastal hazard risk reduction and adaptation. Nature Communications5, 3794. https://doi.org/10.1038/ncomms4794
  • Fisher, R., O’Leary, R. A., Low-Choy, S., Mengersen, K., Knowlton, N., Brainard, R. E., & Caley, M. J. (2015). Species richness on coral reefs and the pursuit of convergent global estimates. Current Biology25(4), 500–505. https://doi.org/10.1016/j.cub.2014.12.022
  • Harrison PL, dela Cruz DW, Cameron KA and Cabaitan PC (2021) Increased Coral Larval Supply Enhances Recruitment for Coral and Fish Habitat Restoration. Front. Mar. Sci. 8:750210. https://doi.org/10.3389/fmars.2021.750210
  • Hein MY, McLeod IM, Shaver EC, Vardi T, Pioch S, Boström-Einarsson L, Ahmed M, Grimsditch G (2020) Coral Reef Restoration as a strategy to improve ecosystem services – A guide to coral restoration methods. United Nations Environment Program, Nairobi, Kenya. https://www.icriforum.org/wp-content/uploads/2021/01/Hein-et-al.-2020_UNEP-report-1.pdf
  • Ortiz, D. M., & Tissot, B. N. (2012). Evaluating ontogenetic patterns of habitat use by reef fish in relation to the effectiveness of marine protected areas in West Hawaii. Journal of Experimental Marine Biology and Ecology432–433, 83–93. https://doi.org/10.1016/j.jembe.2012.06.005
  • Spalding, M., Burke, L., Wood, S. A., Ashpole, J., Hutchison, J., & zu Ermgassen, P. (2017). Mapping the global value and distribution of coral reef tourism. Marine Policy82, 104–113. https://doi.org/10.1016/j.marpol.2017.05.014