Coral structures show a healthy range of colors

Coral Resilience in Our Ecosystem

Ocean Literacy

Tropical Tragedies and Reef Resilience

Picture yourself, snorkeling underneath crystal blue waters with tropical fish off the coast of a tropical island. Above you, the sun is shining with a slight breeze, and below you, is a beautiful ecosystem with every color of the rainbow. Besides being beautiful, coral is endangered. The top threat to coral reefs currently is climate change and global warming. In the evolutionary sense, it is unknown to what extent coral can adapt to the warming oceans (Császár et al., 2010). Unfortunately, the toll the Anthropocene has left is a concern for coral reefs due to their environmental sensitivity resulting in coral bleaching (Torda et al., 2017). Coral bleaching will occur if the temperatures rise only 1.5 degrees Celsius (Tropical corals , n.d.). Tropical coral reefs make up one percent of the ocean but help to support a quarter of the ocean making it a vital ecosystem (Tropical corals , n.d.).

The three major types of coral are fringing reefs, barrier reefs, and atolls. Fringing reefs grow in shallow waters and border a coast closely or can be separated by a narrow stretch of water (Goreau et al., 1979). As their name suggests, barrier reefs are on a coast but they tend to be parallel to a coast and farther away, perhaps the most famous one is Australia’s Great Barrier Reef. Finally, atolls are chains or rings of coral islands that are encompassing a lagoon, which many can be round on volcanic cones (Goreau et al., 1979).

The Anatomy of Coral and Coral Proteins

Corals are well-known for their bright coloration caused by fluorescent proteins which are found in four color types which include green, red, cyan, and a blue/purple non-fluorescent chromoprotein (Palmer et al., 2009). Fluorescent proteins are plentiful within anthozoans, which includes sea anemones, sea fans, corals, and sea pens (Palmer et al., 2009). Their proteins live in their calcium carbonate skeleton with an algae they used to create food called zooxanthellae which also helps to give them color (Palmer et al., 2009). Most coral live in a symbiotic relationship with zooxanthellae, as the algae is dependent on coral for a habitat and coral uses the algae for photosynthesis (US Department of Commerce, N. O. and A. A., n.d.). Zooxanthellae creates dissolved oxygen under normal conditions, but once there is any stress like thermal stress (like climate change), an increase of oxidative stress can be created in the host or the symbiont, resulting in coral expelling zooxanthellae, or coral bleaching (Palmer et al., 2009).

Is Coral Really Affected That Much?

The short answer is YES!

 

Coral Adaptations

Climate change has increased in the past 20 years, usually during El Nino Southern Oscillation which happens every two to seven years (Coles & Brown, 2003). During El Nino, the water warms and the normal conditions of cold, nutrient dense water that usually upwell stop or weaken resulting in fewer phytoplankton off the coast, resulting in more tropical species (US Department of Commerce, N. O.A. A. ,n.d.). La Nina or “a cold event”, pushes colder waters north into the Pacific Ocean, resulting in the southern United States being drier and flooding or heavy rains in Canada or the Pacific Northwest (US Department of Commerce, N. O.A. A.,n.d.). Since coral is very sensitive to temperature changes and once the seawater temperatures rise, coral bleaching can occur during El Nino’s warmer temperatures (Coral & Brown, 2003). Coral reefs prefer to live between 73° and 84° Fahrenheit though some can tolerate temperatures as low as 68° F and as high as 90° F (Coral Reef Alliance, n.d.) Unfortunately, while reporting ongoing temperature analysis, NASA’s Goddard Institute for Space Studies (GISS) stated the average global temperature has increased by at least 1.1 degree Celsius or 1.9 degree Fahrenheit since 1880 (NASA, 2020). Since 1975, it has occurred at approximately 0.15 to 0.20 °C (NASA. 2020).

Some corals have adapted to stressful conditions. For example, Acropora has experienced a rapid evolution of proteins that are responsible for interaction with the environment that appears to promote adaptive processes (Gittens et al., 2015). Acropora Hyacinthus is associated with protective proteins that have heat resistant and heat-shock proteins and antioxidant enzymes that are beneficial to them as well (Gittens et al., 2015). In response to the elevated levels, anthozoans (corals) have antioxidant enzymes, for example, superoxide dismutase that assist in catalyzing changing superoxide anion to water and hydrogen peroxide (Palmer et al., 2009). Corals need light for photosynthesis with zooxanthellae; however, there are some coral species that do not have zooxanthellae, for example Lopoholelia, a colonial branching coral, that lives in the deep, cold waters in Norway’s fjords that can tolerate lower salinities, lower temperatures, and great depths (Goreau et al., 1979).

A thriving coral reef ecosystem in Tobacco Caye, Belize

Coral Survival
Coral is in desperate need of assistance and there are multiple options available.

Marine biologists and divers can take part in fragmentation of coral reefs to assist in growing the reefs. The three different types of coral restoration are coral gardening, larval seeding, and reef balls. Coral gardening is fragmentation to assist corals in growing asexually, growing a coral clone. The colonies will continue to be fragmented for further growth and cloned multiple times in underwater nurseries and transported to a reef ( Meesters et al., 2015).

Larval seeding is the process when large amounts of coral eggs and sperm are collected in the field with sexual fertilization or reproduction in the lab, resulting in coral growing a certain size before being transported to a reef (Meesters et al., 2015). Finally, reef balls are concrete structures that provide a design for protection for fish as well as a possible attachment for organisms like coral (Meesters et al., 2015).
In 2023, there was an unprecedented coral bleaching event in Florida which assisted NOAA in learning more about how to assist corals (NOAA confirms 4th global coral bleaching event | National Oceanic and Atmospheric Administration, 2024).

NOAA moved some of the corals to deeper waters and moved sunshades over some of the coral nurseries (NOAA confirms 4th global coral bleaching event | National Oceanic and Atmospheric Administration, 2024). Coral research is definitely necessary in order for coral survival. Some scientists are considering building coral reef resilience through scientific assisted evolution (Torda et al., 2017). In Australia, the Great Barrier Reef Foundation is growing cross-bred heat resistant corals as well as cryopreservation technologies to help save coral reefs (Restoring coral reefs,2024).

Some scientists are considering building coral reef resilience through scientific assisted evolution (Torda et al., 2017). In Australia, the Great Barrier Reef Foundation is growing cross-bred heat resistant corals as well as cryopreservation technologies to help save coral reefs (Restoring coral reefs,2024).

Why Should We Care? How Can We Help?


There are many benefits coral reefs provide protection and food for thousands of species of fish, but are also important for humans for tourism, livelihood, food, and protection (US Department of Commerce, N. O. and A. A, n.d.). Coral reefs are essential to the ecosystem but are being destroyed by multiple threats to them including climate change, ocean acidification, pollution, physical damage, overfishing, or coral harvesting (US EPA, 2017). While some coral species have been able to adapt in small ways there is still a lot that can be done, and ways that we can help, even if we are not near an ocean. For example, a way we can slow down climate change in the rising ocean temperatures is by reducing chemical fertilizers, properly disposing of trash, recycling, saving energy at home by using energy efficient devices, and being cautious when diving or snorkeling (US EPA, 2017).
There are many dive programs, education events, internships, or citizen science programs that are specifically related to coral, like the Coral Restoration Foundation (Coral restoration foundation | United States, n.d.).

Reef safe sunscreen guide | save the reef. (n.d.)

But How Do I Know What Sunscreen To Pick?

At this time, it has become pretty common to hear the term “reef-safe sunscreen” or “mineral-based” sunscreen. But what does it really mean? There are no strict definitions or guidelines and when further researched, interesting results were undercovered. Hawaii and the Florida Keys have issued legislative bans on oxybenzone and octinoxate-containing sunscreen. However, the National Oceanic and Atmospheric Administration (or NOAA) would like stricter enforcement, noting that eight chemicals are toxic to coral but used in sunscreen.

When deciding which sunscreen to choose, you want to make sure it is healthy for coral reefs. Even if a sunscreen says “reef-friendly” there are still some ingredients to be aware of. Since legislation has not been passed in any of the United States for all of the chemicals, you may have to research a bit to find that perfect match! There are some organizations like Save The Reef and the Coral Restoration Foundation (Coral restoration foundation | united states. (n.d.) that have up to date information and examples of sunscreens that are reef safe. While it may be hard to remember the list of chemicals that pose a threat, the easiest way to remember is that you want to stay away from it is a small way we can help coral, even if we are landlocked.

Coral is in desperate need of assistance and even with adapting it still may not be able to survive the rising temperatures. Coral reefs are animals that are silently dying and without a voice, they need our help and assistance to be saved. It is our fault that they are being bleached, and in order to accelerate protection marine biologists are creating efforts to protect the oceans and help them to adapt to climate change. The detrimental effects of the anthropocene can be witnessed by the bleaching white corals or felt in the hot summer days that are no longer sustainable for coral reefs. Coral reefs have adapted slowly, but without assistance, it may be a rush against time to restore coral reefs in rising temperatures. So why should we care about coral reefs? The truth is that they are a beautiful animal in our oceans but that is not all. Coral contributes to biodiversity, tourism, coastal protection, food, and medicine to name a few. Now is the time to step forward and not only be in awe of them but help to insure the vital ecosystem thrives.

 

The author, Drew Vickers

About the Author

Drew Vickers is a current graduate student with Project Dragonfly at Miami University in Oxford, Ohio studying conservation biology. Her current studies focus on engaging others about endangered species.

 

 References Cited

  • Alieva NO, Konzen KA, Field SF, Meleshkevitch EA, Hunt ME, Beltran-Ramirez V, et al. (2008) Diversity and Evolution of Coral Fluorescent Proteins. PLoS ONE 3(7): e2680. https://doi.org/10.1371/journal.pone.0002680
  • Ben-Zvi, O., Wangpraseurt, D., Bronstein, O., Eyal, G., & Loya, Y. (2021). Photosynthesis and bio-optical properties of fluorescent mesophotic corals. Frontiers in Marine Science, 8, 651601. https://doi.org/10.3389/fmars.2021.651601
  • Coles, S. L., & Brown, B. E. (2003). Coral bleaching—Capacity for acclimatization and adaptation. In Advances in Marine Biology (Vol. 46, pp. 183–223). Academic Press. https://doi.org/10.1016/S0065-2881(03)46004-5
  • Coral Reef Alliance. (n.d.). Coral Reef Alliance. What do corals reefs need to survive? Retrieved December 1, 2024, from https://coral.org/en/coral-reefs-101/what-do-corals-reefs-need-to-survive/
  • Coral restoration foundation | united states. (n.d.). CRF. Retrieved December 1, 2024, from https://www.coralrestoration.org
  • Császár NBM, Ralph PJ, Frankham R, Berkelmans R, van Oppen MJH (2010). Estimating the Potential for Adaptation of Corals to Climate Warming. PLoS ONE 5(3): e9751. https://doi.org/10.1371/journal.pone.0009751
  • Gittins, J. R., D’Angelo, C., Oswald, F., Edwards, R. J., & Wiedenmann, J. (2015). Fluorescent protein‐mediated colour polymorphism in reef corals: Multicopy genes extend the adaptation/acclimatization potential to variable light environments. Molecular Ecology, 24(2), 453–465. https://doi.org/10.1111/mec.13041
  • Goreau, T. F., Goreau, N. I., & Goreau, T. J. (1979). Corals and Coral Reefs. Scientific American, 241(2), 124–137. http://www.jstor.org/stable/24965267
  • Hochberg, E.J., Atkinson, M.J., Apprill, A. et al. Spectral reflectance of coral. Coral Reefs 23, 84–95 (2004). https://doi-org.proxy.lib.miamioh.edu/10.1007/s00338-003-0350-1
  • Meesters, H. W. G., Smith, S. R., & Becking, L. E. (2015). A review of coral reef restoration techniques. https://edepot.wur.nl/333153
  • NASA. (2020, January 29). NASA. World of change: Global temperatures.https://earthobservatory.nasa.gov/world-of-change/global-temperatures
  • NOAA confirms 4th global coral bleaching event | National Oceanic and Atmospheric Administration. (2024, April 15). https://www.noaa.gov/news-release/noaa-confirms-4th-global-coral-bleaching-event
  • Palmer, C. V., Modi, C. K., & Mydlarz, L. D. (2009). Coral fluorescent proteins as antioxidants. PLOS ONE, 4(10), e7298. https://doi.org/10.1371/journal.pone.0007298</li>
  • Reef safe sunscreen guide | save the reef. (n.d.). Retrieved March 7, 2025, from https://savethereef.org/about-reef-save-sunscreen.html
  • Restoring coral reefs. (2024, November 22). Great Barrier Reef Foundation. https://www.barrierreef.org/what-we-do/restoring-coral-reefs
  • Torda, G., Donelson, J., Aranda, M. et al. Rapid adaptive responses to climate change in corals. Nature Clim Change 7, 627–636 (2017). https://doi.org/10.1038/nclimate3374
  • Tropical corals – bioacid: Biological impacts of ocean acidification. (n.d.). Retrieved December 1, 2024, from https://www.bioacid.de/tropical-corals/?lang=en
  • US Department of Commerce, N. O. and A. A. (n.d.). Coastal pollution tutorial: Noaa’s national ocean service education. Retrieved October 14, 2024, from https://oceanservice.noaa.gov/education/tutorial_corals/coral01_intro.html
  • US Department of Commerce, N. O.A. A. (n.d.). What are el nino and la nina? Retrieved December 2, 2024, from https://oceanservice.noaa.gov/facts/ninonina.html
  • US EPA, O. (2017, January 30). Threats to coral reefs [Overviews and Factsheets]. https://www.epa.gov/coral-reefs/threats-coral-reefs