Reef Remodeling: How Reef Carpets Could Change How We View Reef Restoration
Featured Image Caption: Coral reefs, renowned for their vibrant marine biodiversity, are facing significant declines in population due to the combined effects of global ocean warming and disease. (Image Source: “40 rish coral reef” by Lakshmi Sawitri, licensed under CC BY 2.0).
Reference: Horoszowski-Fridman, Y.B., Izhaki, I., Katz, S.M., Barkan, R., & Rinkevich, B. (2024). Shifting reef restoration focus from coral survivorship to biodiversity using Reef Carpets. Communications Biology. https://doi.org/10.1038/s42003-024-05831-4
People often think about corals and reefs as if they were rocks or even plants where fish and other marine animals live, but this is not the case. Coral reefs are underwater ecosystems built by corals, which are actually colonies of tiny animals called coral polyps. These coral polyps have calcium carbonate skeletons and live in perfect union with a special type of algae called Zooxanthellae, which provide the corals with energy in exchange for shelter. Yes! Corals are animals, not plants or rocks, although a type of plant that carries out photosynthesis does actually live within them.
Coral reefs support a vast array of marine life, making them one of the most diverse ecosystems on the planet. Many fish species rely on coral reefs for habitat and breeding grounds, in this way supporting fishing industries and coastal communities. Coral reefs also act as natural barriers, reducing the impact of waves and storms on coastal areas, thus helping to prevent erosion and protect shorelines. Additionally, they attract millions of tourists each year for activities such as snorkeling, diving, and eco-tourism, providing economic benefits to local communities.
However, coral reefs face numerous challenges, including climate change and the rising sea temperatures that lead to coral bleaching—which is a process in which corals expel the algae living in their tissues, causing them to turn white and potentially die if the stress persists. Increased levels of carbon dioxide in the atmosphere lead to ocean acidification, which makes it harder for corals to build their calcium carbonate skeletons. Unsustainable fishing practices, such as dynamite fishing and overfishing of herbivorous fish, can disrupt the delicate balance of coral reef ecosystems. That would definitely ruin the house these fish are living in.
Have you ever worked on a home renovation project? Remodeling a house is more than a full-time job, but it’s definitely a must in some living situations. That’s exactly why scientists are now looking into a new way to help coral reefs recover and thrive: through Reef Carpets. Restoration practices have traditionally focused on coral transplantation of singular species, where corals are grown in nurseries and then transplanted onto degraded reefs. This coral reef restoration has focused on the reproduction of a limited number of coral species that have shown to be both structurally complex, therefore serving as better habitats for fish, and resilient against disease and global ocean warming, therefore surviving more of these events in the long run. But these restoration efforts usually end up restoring sites with a single species, therefore reducing biodiversity in these restored ecosystems. That’s why Dr. Horoszowski-Fridman and their collaborators are looking to put biodiversity over survivorship in their new pilot experiment.
More than just striving for survivorship
How are they doing this exactly? Well, they selected a combination of branching corals along with the organisms that started growing on these nurseries and set up what they call Reef Carpets, hoping to overlook the higher rate of mortality and striving to impulse a greater rate of biodiversity. What they found was that all three of the Reef Carpets they assembled and transplanted in sandy areas immediately developed into vibrant reef environments. Although while moving the Reef Carpets from the nursery and onto the patch of sand, sediment moved and covered coral polyps, resulting in a higher mortality rate than traditional restoration transplantation, the corals that did survive ended up growing, thriving, and even reproducing in the following 17 months they continued to be monitored by these scientists.
So, how do we build Reef Carpets?
Dr. Horoszowski-Fridman and their collaborators used a total of 708 coral colonies, including three types of branching corals, to build their Reef Carpets. These colonies were raised in nurseries and came from adult colonies collected from natural reefs and the nursery infrastructure. The coral fragments were attached to plastic nails using super glue and grown on the Reef Carpets units for more than 8 months until they became large colonies. Each Reef Carpet unit ended up not only hosting coral colonies, but also bringing along the biota community developed during the nursery phase, including crustaceans, fishes both in adult and juvenile stages, and echinoderms. Once the coral fragments grew into large colonies, they were transferred from the nursery to the transplantation site in plastic containers filled with seawater, transported by boat. In their transplantation sites they displayed great biodiversity, ranging from large predators to tiny herbivorous fish, and including sessile animals like tunicates, sponges, and bivalves. In other words, everything and everyone wanted to be on or around these Reef Carpets. It became some very valuable real estate in a once deserted, sandy land.
Reef restoration is a must for the future of marine ecosystems as we know them. Effective reef restoration efforts play a crucial role in safeguarding the health and resilience of our coastal communities. By restoring damaged reefs, we can preserve biodiversity, support fisheries, protect coastal communities from natural disasters, and promote sustainable tourism. Moreover, coral reefs are invaluable sources of scientific knowledge. Therefore, investing in reef restoration not only benefits marine life and coastal communities but also contributes to the broader goals of conservation and sustainable development. It is innovations in these restoration practices, like those presented by Dr. Horoszowski-Fridman and their collaborators, that shine a light on the importance of biodiversity on our reefs and the benefits that they bring.
