Coral Reefs: Their importance and restoration efforts

Delving beneath that perfect blue surface lies something insanely surreal — infinitely unique structures, the color of phosphenes, holding the mind mesmerized. Fields of corals and sponges, like the ocean's specialised garden; fish flitting like butterflies; showy ribbons flowing against the ocean’s current in alluringly smooth motions; a cacophony of sounds emanating muffledly through the murky waters.

Nowadays, bustling coral reefs are becoming increasingly scarce; once utopian gardens lie barren and sparse, dotted with the bleached skeletons of multicolored organisms. The cause of these dying coral reefs lies within human activity, specifically global warming.

There is a distinct difference between corals and coral reefs. Coral reefs are non-living structures of calcium carbonate skeletons built by the coral polyps living upon these structures. The coral polyps are invertebrate creatures made up of hundreds of thousands of minuscule creatures composed solely of a mouth and a stomach (Robin, 2024). In the image below, you can clearly identify individual coral polyps.

Save the Reef. (n.d.). [Close up of individual coral polyps] [Photograph]. Save the Reef. https://savethereef.org/about.html

Lewis, A. L. (2014, July 31). Galaxea fascicularis specimen [Photograph]. LIRRF. https://lirrf.org/meet-mighty-coral-polyps/

Lewis, A. L. (2014, July 31). Galaxea fascicularis macro [Photograph]. LIRRF. https://lirrf.org/meet-mighty-coral-polyps/

The importance of corals

Corals aren’t simply an aesthetic of nature, but an essential function in the ocean’s ecosystems. These corals not only house approximately 25% of all marine life, but also act as a wavebreaker in the face of rising sea levels. Apart from environmental contribution, these coral reefs are also directly related to human activity. Many coastal cultures regard coral reefs as a significant part of their identities, the fish thriving in coral reefs serving as a central source of food for coastal areas. Organisms in coral reefs are also being researched for their potential to cure a variety of mortal afflictions, including cancer, arthritis, and bacterial/viral infections (NOAA National Ocean Service Education: Corals Tutorial, n.d.).

Threats to Coral Reefs

Global warming has led to an onslaught of rising temperatures, sea levels, and carbon emissions. Due to the increase in temperature and decrease in pH(due to carbon dioxide dissolving in the ocean), coral bleaching has become far more prevalent and an increasingly concerning problem. The rising temperatures create an uncomfortable environment for coral polyps, whilst the acidic pH of the ocean triggers a sort of acid-base reaction between the calcium carbonate reefs and the ocean water. This reaction wears down on the reef’s structural integrity, whilst the pH negatively affects the environment-sensitive corals.

A prime example of such an event is the mass coral bleaching of the Great Barrier Reef, off the coast of Australia. To clarify, coral bleaching doesn’t signify coral death, but rather coral stress. Corals receive their coloration from a symbiotic relationship with the algae zooxanthellae, which provide oxygen to the corals through photosynthesis. When these corals are under immense stress, they expel the algae, obtaining a transparent-whitish coloration. In the 2024 bleaching of the Great Barrier Reef off of Australia, a research team kept track of 462 coral colonies, 80% of which were undergoing the bleaching process, with a 44% mortality rate in afflicted corals. (Cycle of Coral Bleaching on the Great Barrier Reef Now at “catastrophic” Levels, 2025)

Hudson, T. H., & Torda, G. T. (2016). Healthy Table Coral & Bleached Table Coral [Imagery of the Great Barrier Reef’s mass bleaching, Photograph].FT Magazine. https://www.ft.com/content/7954eaaa-c184-11e6-9bca-2b93a6856354

In the midst of underwater destruction, many solutions have been developed to rebuild the ocean’s reef systems. A proposed and widely practiced solution is coral restoration and gardening. However, this solution is only effective when practiced concurrently with efforts to make the ocean more habitable. This is because cultivated corals aren’t likely to survive in a predominantly harmful environment. (Mandy, 2024)

Another more recent solution is to deceive coral larvae into settling down in select areas. Published in March 2024, a study has proven that playing the audio of a healthy reef will coax coral larvae to settle down at higher rates, averaging 1.7 times more frequently, with 7 times being the peak (Aoki et al., 2024). It sounds rather odd that coral reefs produce sounds, and it is, because reefs don’t produce sounds. Rather, the marine organisms settling in coral reefs produce these sounds. Fish produce croaks, grunts and pops to communicate with other fish, pistol shrimp snapping, whilst crustaceans may scrape against corals or rocks whilst moving. These sounds encapsulate a healthy coral reef. The idea behind this solution is that healthy reef sounds attract coral larvae to settle, thus rebuilding the reef to thrive and flourish.

Despite the grim nature of the current state of coral reefs, there is still hope that these reefs will endure. I hope that I can continue to delve beneath the surface of perfect blue — to float, breathless, in the presence of mesmerizingly multicolored structures — and not to be met by a graveyard of chalky-white skeletons.

References:

Aoki, N., Weiss, B., Jézéquel, Y., Zhang, W. G., Apprill, A., & Mooney, T. A. (2024). Soundscape enrichment increases larval settlement rates for the brooding coral Porites astreoides. Royal Society Open Science, 11(3). https://doi.org/10.1098/rsos.231514

Coral bleaching events. (2025, April 16). AIMS. https://www.aims.gov.au/research-topics/environmental-issues/coral-bleaching/coral-bleaching-events#:~:text=Aerial%20survey%20results%20show%2073,of%20the%20Great%20Barrier%20Reef.

Cycle of coral bleaching on the Great Barrier Reef now at “catastrophic” levels. (2025, January 21). The University of Sydney. https://www.sydney.edu.au/news-opinion/news/2025/01/21/coral-bleaching-2024-great-barrier-reef-one-tree-island.html#:~:text=The%20results%20revealed%20that%2066,staggering%2095%20percent%20mortality%20rate.

Mandy. (2024, May 29). What is Coral Restoration, and Can it Save Coral Reefs? Coral Reef Alliance. https://coral.org/en/blog/what-is-coral-restoration-and-can-it-save-coral-reefs/

NOAA National Ocean Service Education: Corals Tutorial. (n.d.). https://oceanservice.noaa.gov/education/tutorial_corals/coral07_importance.html

Save the Reef. (n.d.-b). https://savethereef.org/about.html

Shannon, D. (2021, July 21). Meet some mighty coral polyps. Lizard Island Reef Research Foundation. https://lirrf.org/meet-mighty-coral-polyps/

Smyth, J. (2016, December 16). Paradise lost: the crisis on the Great Barrier Reef. Financial Times. https://www.ft.com/content/7954eaaa-c184-11e6-9bca-2b93a6856354