By: Melina Farahmand

Founder of Past Present Future Co.

Executive Director: Guardians of Our Democracy

Author of: From Dust to Breath and When the Stars Collide

* The following article was written for a college writing course. *

Abstract:

This literature review will examine the most up-to-date research on coral reef bleaching, ocean acidification, and methods for addressing dying reefs as a result of climate change and rising sea temperatures. As the global temperature continues to increase, ecosystems are drastically changing in ways that are detrimental to the planet's systems as well as its species. Scientists and marine conservationists know why corals are dying off rapidly. The next step in the research is finding sustainable, long-term solutions to help preserve coral reef systems and help create new ones under the challenging conditions of a planet facing grave consequences driven by climate change's impacts. Additional research is still necessary to determine the efficacy and best practices for coral nurseries. Furthermore, science needs to tackle the issue of whether these newly planted corals are able to adapt to a changing climate and stressful environment.

Introduction:

Under the cover of the blue waves, a vibrant sun, and green algae resides one of the planet’s most paramount ecosystems: coral reefs. This dynamic and diverse underwater ecosystem serves as a home for thousands of oceanic organisms with a wide range of shapes and sizes. Some refer to these vibrant ecosystems as “the rainforest of the sea” (Floral Garden Banks National Marine Sanctuary, Coral bleaching 2019) because of their diversity and the variety of habitats they help create. But what makes coral reefs so important, and why should people have more concern over their current state? Millions of people rely on the reefs for necessities such as food, income for the local economy, and modern medicine also utilizes coral reefs. According to National Oceanic and Atmospheric Administration data, “the net economic value of the world’s coral reefs is estimated to be nearly tens of billions of U.S. dollars per year.” Additionally, coral reef systems are able to help coastal cities with storm protection, as reefs absorb some of the impacts of waves.

What is currently happening worldwide to our reef systems is devastating as it is concerning. Corals will begin to decay and can die when the ocean environment is too stressful. As ocean acidification, bad fishing practices, and pollution collide together, a poor environment for ocean life is born. Stress forces coral polyps to “expel their symbiotic algae” (Floral Garden Banks National Marine Sanctuary, Coral bleaching 2019), resulting in coral bleaching, turning the coral white. This algae resides in a coral’s tissue, and they form a symbiotic relationship with both providing nutrients to the other. Additionally, when water surface temperatures rise to certain levels, it creates a process known as coral bleaching, also known as “when corals expel their colorful endosymbiotic algae, leaving the still living, but white, coral skeleton behind” (Forbes). Corals can recover over time from the bleaching process; however, due to current circumstances such as climate change, overfishing, pollution, high temperatures, and additional factors, it is most likely that the recovery process will take years, or the coral reefs will continue to decay and die. While a systemic change is necessary to address the overall issue of ocean conservation policies on a domestic and global level, governments need to properly address the human impact on global warming, which is exacerbating the poor conditions of reef systems.

Diagram source: https://www.noaa.gov/education/resource-collections/ ocean-coasts-education-resources/ocean-acidification

Background:

There is a plethora of information provided by various trusted organizations such as the Environmental Protection Agency, the National Oceanic and Atmospheric Administration (who made up a large bulk of the research read for this review), and numerous non-governmental organizations and universities around the world. All sources used peer-reviewed, science-based research to guide their restoration programs. We are fortunate that this information is available to the public to learn and share the best methods and practices for preserving coral reefs while protecting the larger oceanic ecosystem. In light of a large percentage of coral reefs dying worldwide, scientists, organizations, and government agencies have come up with a viable way to save these reefs: coral reef nurseries, which focuses on planting new corals in areas that have undergone significant bleaching to try and help revive them.

Case Study #1 — Great Barrier Reef:

Home to over 9,000 known species, the Great Barrier Reef located in Australia is the most extensive reef system on the planet. Located off the coast of Queensland mainland, Australia, the Great Barrier Reef comprises 2,900 reefs and is over 131,600 miles. This coral reef system is known for its beauty and is a hot spot for snorkeling and scuba diving. Marine biologists and ocean lovers revere this stretch of land. Sadly ”a 2018 study showed that about one-third of the Great Barrier Reef had experienced substantial damage from bleaching" (National Geographic). While the reef has a history of resilience against marine heatwaves, coral bleaching, and more, it appears that the many hits to its system have made it more challenging to recover. Recent research and data updates indicated that “a future where hotter water temperatures will likely cause bleaching every year, along with ongoing threats of cyclones and coral-eating starfish. Recovery requires reprieve – and those opportunities will diminish as climate change progresses” (Emslie, 2023). While some may claim this is doomsday talk, the research shows what we already can guess, if the issues are not adequately addressed, significant problems will arise for the Great Barrier Reef. The goal is also to avoid mass bleaching events which seem to be occurring annually.

Case Study #2 — Florida Reef Systems & Rising Temperatures:

When researching coral reef acidification, one of the first things that appears on the news is Florida's recent struggle with high ocean temperatures reaching 100 degrees Fahrenheit and local scientists' attempt to stop the decaying of reefs. Ultimately, the Coral Restoration Foundation found on July 20th that corals had reached 100% mortality, meaning these reefs would not survive without intervention. It's important to note that this topic ties in with recent reports that the Gulf Stream current could collapse with the dramatic temperature changes the world is experiencing. In simple terms, when the water temperatures have too much variation from their baseline temperatures, it could cause the bulb stream to collapse and for even more issues for the reef systems as well. As with all things in nature, everything connects somewhere. For places like Florida, which have an expansive coral reef system, the site of coral tissue disease is concerning and has, according to the team at the Florida Fish and Wildlife Conservation Commission, caused millions of these colonies to die. The state is under a bleaching alert.

Coral Nurseries & Replanting Efforts:

An estimated 25% of the coral reefs have already disappeared. With the help of various organizations, labs, and government agencies have documented successes in coral nurseries and restoration programs. This suggests that the replanting method is something to consider implementing in all places near an ocean with reef systems in a fragile state. Based on the research from Mote Marine Laboratory and Aquarium, their efforts to restore coral reefs have been incredibly successful. In fact, “since 2008, Mote scientists have planted more than 216,000 corals of multiple native species and more than 325 genotypes to restore depleted reefs” (Rutger, 2020). Different organizations have slightly different methods in their nursery process. At the core of it, the focus is on the reproduction of corals and having nurseries set up two different ways: field-based, which is typically located off-site from existing reefs, or land-based, which, according to the Reef Resilience organization, is more so for coral gardening. Both methods have benefits and downsides, but overall, high success rates for these coral nurseries. One advantage of land-based nurseries is that the growing coral is protected from bleaching events, which is one of the significant concerns about the success rates of these nurseries. The effort can quickly go to waste if newly planted corals die or face issues because of coral bleaching. The goal is “optimal coral survivorship and growth year-round” (Coral Resilience Network, 2023). This type of nursery is more expensive.

Conversely, field-based nurseries are the norm and are located off-site from reefs. Fortunately, this is a lower cost than a land-based nursery. One exciting aspect of this type of nursery is that anyone with fewer skills can maintain these coral nurseries and help plant them. A few years ago, there was a news article about retired veterans helping conduct dives to maintain these nurseries. This could be a great way to get more environmental activists involved in the

Floating PVC tree used for growing and rearing staghorn corals. Tavernier, Florida. Photo © Coral Restoration Foundation.

effort if it takes little to no training to accomplish. Two key structure types for field-based nurseries are fixed or floating. See the image on the left side below for an example of a floating nursery. The image below on the right is an example of a field-based nursery. Ultimately, it comes down to funding, location, and local climate to determine which type of nursery is the best fit. Either method works well and has high success rates.

The Nature Conservancy USVI Programs land based coral nursery facility in St Croix USVI. Photo © MJS Vision.

Conclusion & Further Research:

An overwhelming amount of the sources used in this literature review highlight the importance of using science-based research to address the issue of coral bleaching to try and save these reefs in a code blue state. The science is unmistakable on climate change, which is ultimately the biggest culprit that needs a global initiative to tackle. To save our oceans and reefs, we need systemic change to fishing practices, a massive global emissions reduction target, and we need to make the shift towards renewables. Regarding replanting programs, some may need to consider methods of making corals more resilient, which could be through genetically modified coral. Researchers would need to do a more formal study on this idea and run field trials to see how these modified corals adapt and work. We still have much to learn about these limestone-composed structures deposited by coral polyps. Coral reefs are worth protecting, and I look forward to seeing developments in studies and new ideas on addressing this issue of coral bleaching and ocean acidification.

As an environmental science student, I suggest we continue testing which species of coral withstand high temperatures the best, try planting more of those, and see how well they do during a marine heatwave. Witnessing the recovery time is another crucial factor here. In conclusion, while more work is left, the efforts we are seeing are encouraging.