A study supported by the Australian Institute of Marine Science (AIMS) has identified that non-toxic waste materials can be utilized to produce coral settlement tiles for large-scale reef restoration. The research suggests a method for developing these tiles using readily available, low-cost materials, which has the potential to support coral aquaculture and restoration efforts, particularly in developing nations.
Research Findings
The study, led by Indonesian marine scientist Dr. Widiastuti Karim from Universitas Udayana in Bali, found that coral settlement tiles can be manufactured from low-cost clay combined with common waste materials without negatively affecting the settlement of juvenile corals. Traditionally, these tiles are made from ceramics or concrete.
Coral settlement tiles are integral to a restoration technique known as ‘coral seeding’. In this method, coral larvae, cultivated in aquaculture facilities after spawning, settle onto these small tiles. The tiles, with attached young corals, are then placed on reefs to facilitate coral growth and expansion across the reef surface.
Material Composition and Mechanism
Dr. Karim's research demonstrated that incorporating non-toxic waste materials such as coconut charcoal, breadcrumbs, or grog (waste clay from brick-making and pottery) into the clay can facilitate coral settlement. During the tile firing process, these waste materials combust, creating crevices that are conducive to coral attachment. This addition also contributes to reducing the overall production cost of the tiles.
Benefits and Broader Implications
The use of these cost-effective materials could support the establishment of a sustainable local coral aquaculture industry. Compared to asexual propagation through fragmentation—a common coral restoration technique in Indonesia where fragments from a mother coral are grown—the aquaculture methods focused on sexually produced corals, as developed by AIMS, offer advantages. These include enhanced genetic diversity for coral communities and the potential for larger-scale implementation, proving more cost-effective over the long term.
Dr. Cathie Page, a senior co-author from AIMS, noted that the study not only identifies methods to lower restoration costs but also supports the advancement of coral aquaculture and restoration techniques in developing nations. This approach reduces the reliance on collecting wild corals for fragmentation, shifting focus towards the production of sexually reproduced corals in controlled aquaculture environments. Dr. Page also highlighted the significance of reef restoration and coral exports to Indonesia's economy, acknowledging that the collection of wild corals for export, combined with pressures from climate change and growing populations, can stress coral reefs.
Ongoing Work
Dr. Karim, who gained expertise in coral spawning and aquaculture during experiments at AIMS, has since initiated data collection in Bali with her students. Their work focuses on understanding the spawning window and fecundity of seven Acropora species around Bali. This information is intended to support collaboration with marine ornamental companies in the region to enhance their sustainability practices.
Funding
The research was funded by the 2023 Australia Women in Research Fellowship, awarded to Dr. Widiastuti. AIMS authors received support from the Australian Coral Reef Resilience Initiative, which is funded by AIMS and BHP.