Sustainable Coral Reef Restoration: Innovative Use of Waste Materials

A new study supported by the Australian Institute of Marine Science (AIMS) has found that non-toxic waste materials can be used to create a crucial tool in large-scale coral reef restoration. The study, led by Indonesian marine scientist Dr Widiastuti Karim, found that coral settlement tiles can be made from low-cost clay and other common waste materials without impacting the successful settlement of baby corals. The tiles are usually made from ceramics or concrete and are used as part of a reef restoration method called ‘coral seeding’, where, following spawning in aquaculture facilities, the resulting coral larvae settle onto small tiles. In this process, the tiles are then placed onto reefs where the young corals can grow and spread onto the reef surface. Widiastuti, hailing from the Universitas Udayana in Bali, spent two months at AIMS conducting the experiment and building both skills and capacity in coral spawning and aquaculture. “We found that adding non-toxic waste materials like coconut charcoal, breadcrumbs, or a material known as grog – waste clay from brick-making and pottery – to the clay may help corals settle successfully,” she said. “The waste materials combust during tile firing, creating crevices that some coral like to settle in. “Adding these materials makes the tiles cheaper, and this may also assist with the development of a sustainable local coral aquaculture industry.” Widiastuti said the most common technique employed in Indonesia to help corals is to detach smaller fragments from a mother coral collected from a reef, grow the fragments in facilities or in special in-water ‘farms’, and outplant them into coral reefs. This is known as asexual propagation through fragmentation. According to Widiastuti, the coral aquaculture method that AIMS is developing offers benefits in terms of genetic diversity for coral communities and is cheaper to implement in the long term when compared to other practices. “At AIMS I learnt it was essential to understand the spawning window and reproductive potential of the targeted coral species in order to apply this technique,” she said. “Once I returned to Indonesia, my students and I began collecting data on the spawning window and fecundity of seven Acropora species at reefs around Bali, and we are now ready to share this information and collaborate with marine ornamental companies in our region to increase their sustainability.” AIMS’ Dr Cathie Page acted as senior co-author for the paper publishing these findings. “Reef restoration and coral exports form an important part of the economy in Indonesia. But the collection of wild corals by exporting industries may be adding to the increasing pressures on coral reefs in these regions from climate change and growing populations. “We were pleased to work closely with Dr Widiastuti on this project and support the capacity building of scientists in neighbouring Indonesia.” Funding for the research was provided by the 2023 Australia Women in Research Fellowship awarded to Dr Widiastuti. AIMS authors were supported by the Australian Coral Reef Resilience Initiative funded by AIMS and BHP. Related stories: From rubble to resource: Federal boost for university concrete recycling tech