Ocean Acidification and the Great Barrier Reef: Effects to Solutions
Author: Siena Inaba
Abstract: The Great Barrier Reef is a world icon that is being impacted by ocean acidification. Here the effects of ocean acidification on shallow-water corals are examined. Solutions to mitigate ocean acidification like chemical- and phyto- remediation are explored. Coral restoration practices like coral nurseries and assisted evolution are examined with regard to restoring decimated sections of the reef. The protections and policies already enacted by the Queensland and Australian governments, like the Reef 2050 Plan, are explained. Finally, it is concluded that the best way to protect the Great Barrier Reef is to use a combination of government policies, restoration practices, and public involvement.
Introduction
A common attribute of tropical seas are coral reefs. These structures are composed of live corals growing on the skeletal remains of dead corals (Ford and Kench, 2012). Corals and zooxanthellae, the algae that give corals their unique color, rely on each other to survive. This relationship is called symbiosis. Coral ecosystems are home to thousands of different fish and animal species. It is for this reason, and the fact that they generally contain low nutrients, that coral reefs are called the “rainforest of the sea”. This bond has resulted in unique and diverse ecosystems that are elemental to coastal communities.
Coral reefs are integral parts of coastal communities and ecosystems. They contain 25% of the ocean’s biodiversity (Hoegh-Guldberg, 2019). They offer coastal protection by diminishing wave sizes by up to 97% (Allemand and Osborn, 2019). Fisheries depend on the biodiversity of the reef to sustain the local population and the economy. Coral reefs also attract tourists which boosts local and national economies. In some places like the Queensland coast, they are the main attraction for overseas visitors. As shown in Fig. 1, coral reefs are being negatively impacted by increased CO2 and poor management practices which in turn affects fisheries, shoreline protection, and livelihoods (Pendelton et al., 2016).
Fig 1. This is a systems map of how coral reefs and the industries that depend on them are impacted by global threats. Adapted by (Hoegh-Guldberg et al., 2019). Originally from (Pendleton et al., 2016).
Corals are aragonite forming organisms. Aragonite is a crystallized form of calcium carbonate. It is less soluble compared to the other form of crystallized calcium carbonate, calcite. With less available carbonate available, corals are growing slower and forming weaker skeletons (Howlett, 2021). This combined with other stressors, like increased intensity in storms and coral bleaching events, has made it difficult for several coral species, particularly shallow-water species to survive (Pendelton et al., 2016). Shallow-water coral live between 0-100 meters from the surface. The largest shallow-water coral reef is called the Great Barrier Reef.
The Great Barrier Reef (GBR) is a defining monument to Australia. The reef, bordering the Queensland coast, spans 344,000 km2 (GBRIA, 2009). The Aboriginals or the first Australians, have been connected to the reef and the marine ecosystem for longer than 60,000 years (GBRMPA, 2017). The reef has since become a symbol of home to Aboriginals and other Australians. It provides a sense of identity and is a source of national pride. As of 2016, the reef added 6.4 billion Australian dollars to the Australian economy and provided 64,000 jobs (Deloitte, 2017). A total breakdown of how the reef is shown in table 1. It is the largest reef of its kind and is home to hundreds of unique ecosystems. The GBR is so unique that in 1981 it was admitted as a World Heritage Site (GBRIA, 2009). In 2012, however, the reef was reclassified as a World Heritage Site in Danger after multiple coral bleaching events and increased damage from ocean acidification (Foxwell-Norton and Konkes, 2019). Most coral mortality has occurred in the northern sections of the reef, by Point York, where the water is warmer (GBRMPA, 2017). The southern portion of the reef is being impacted by tourism, pollution, and overfishing (Reef 2050 Plan, 2015). It is expected, as water temperatures and carbon emissions increase, that coral mortality will increase throughout the entire GBR (GBRMPA, 2017).
Ocean acidification is a result of increased anthropogenic carbon emissions. The carbon dioxide reacts with water to form carbonic acid. Carbonic acid then dissociates into a hydrogen ion and a bicarbonate ion. The bicarbonate ion can then further dissociate into another hydrogen ion and carbonate. This is a normal reaction that yields an important biological component, carbonate, and helps maintain a relatively constant amount of carbon dioxide. The ocean has absorbed roughly 30% of the excess anthropogenically produced carbon dioxide and allowed the Earth’s climate to remain relatively stable (Allemand and Osborn, 2019). It wasn’t until recently that the effects of this excess carbon dioxide were realized to have an acidifying effect in the ocean (Roberts, 2011). The increased carbon dioxide has forced the carbonic acid equation to the right, therefore producing more hydrogen ions and less carbonate. The equation is displayed below. This effect has since been named ocean acidification.
Organisms are being affected by ocean acidification. Carbonate is a crucial compound for organisms that use calcium carbonate for their skeletons, including minute coccolithophores to massive corals. Without available carbonate, the growth of the organism is slowed, reproduction is impeded, and the behavior of the organism might change (Allemand and Osborn, 2019). This is a relatively new area of study and the total extent of the effects are not yet known. Corals and, more specifically, shallow coral reefs are areas of particular concern.
The following case study will examine possible ways to preserve the GBR from the
effects of ocean acidification. The solution proposed will be a combination of science, policy, and public involvement.
Table 1. This table breaks down the amount of money the GBR contributes to each aspect of the Australian economy and the “full-time equivalent”(FTE) or the number of full-time jobs provided (Deloitte, 2017).
Solutions:
The “Bridging the Gap between Ocean Acidification and Economic Valuation” proposed dividing coral reef protection into four categories (mitigation, protection, adaptation, and repair) so local governments have a framework when restoring or protecting their reef (Gattuso et al., 2015). From these categories, different goals are established as shown in Fig 2. Table 2 provides a general breakdown of the solutions proposed in this paper.
Fig. 2 This is a flowchart depicting four areas where action is required to protect the GBR according to the “Bridging the Gap between Ocean Acidification and Economic Valuation'' workshop. From (Gattuso et al., 2016)
Table 2 Provides the cost, readiness, and challenges of proposed solutions discussed later in the paper (Abright and Cooley, 2019).
Protect
Coral nurseries are a relatively new idea that utilizes the “gardening concept” for coral restoration (Shafir et al., 2006). Coral nurseries are a way to grow coral populations for in-danger reefs. They all follow the same general principle of using asexual coral buds, harvested from nearby reefs, and growing the buds until they are small colonies (Pillay et al., 2011). The colonies are then attached to the threatened reef, where they continue to grow and revitalize the reef. There are several types of nurseries: secured, free-floating, and on land. Each of these nurseries will be examined as potential options for restoring the Great Barrier Reef.
A large characteristic of coral nurseries is examining the “return-on-effort” (RRE) of coral fragments(Howlett, 2021). The studies examined for this paper determined RRE based on the amount of growth and/or survivability of the corals with regards to the effort and money required to grow them. There is no universal scale for RRE’s when it comes to corals and should be used on a case-by-case basis (Howlett, 2021). Each RRE needs to be curated for the goals of each specific site, which leads to the next point of establishing “high-value” sites. These reef sites are the most important for diversity or financial gain. Due to the fact that large portions of the northern Australian coast are unpopulated, these sites are located more in the south (Reef 2050 Plan, 2015). These “high-value” sites are going to be the areas that require the most protection and action.
The secured nursery method is the oldest method for coral nurseries. It consists of a metal frame being secured to the bottom of the ocean near/on the reef or in a suitable area (Shafir et al., 2006). Coral buds are then fixed to the structure where they are supervised until they reach a suitable size when they can be transplanted. This approach, while effective, has some drawbacks. For one, the sedimentation from the ocean’s floor coats the juvenile corals and impedes their growth (Shafir et al., 2006). This method can also damage the existing reef if the cage is anchored to the original substrate (Shafir et al., 2006). Coral survivability after being outplanted from the secured-frame nursery is 80-100%, the limiting factor is the number of viable coral fragments produced by the reef, which will later be placed in the safety of the nursery (Howlett, 2021). This method has worked for a long time, but new methods have arisen that streamline the process and are more efficient.
A free-floating or mid-water nursery is an adaptation of the secured nursery. The concept is the coral cage is suspended in the middle of the water column using ropes. These nurseries are often removed from the area of the troubled reef so that the problems of the reef do not affect the juvenile corals (Shafir et al., 2006). The coral fragments are then fixed to the platform in the same way as a secured nursery. In this method, the sedimentation issue is eliminated and various other growth factors can be more carefully regulated. Each coral species requires different light levels, for instance. In a free-floating nursery, the height from the surface can be adjusted for each coral species (Shafir et al., 2006). These nurseries have had better circulation, as the entire cage can move in the water which increases the amount of nutrients the corals get, while also cleaning the corals of sediments and slime (Shafir et al., 2006). Another downfall of horizontal structures is the ability for algae and other organisms to collect on their surface. To combat this, new research is being done on rope nurseries, which eliminate the metal or PVC frame (Howlett et al., 2021). They are constructed similarly to midwater nurseries, as they are suspended in the middle of the water column (Frias-Torres et al., 2018). These rope nurseries can be attached directly to the reef and do not require outplanting procedures (Howlett et al., 2021). The final nursery type is the on-land nursery. These nurseries would be modeled after research stations already established on Heron Island. Water is pumped from the ocean near the location into tanks where the temperature, nutrients, UV exposure, and carbon dioxide levels can all be carefully monitored (Anthony et al., 2008; Pillay et al., 2011). These nurseries would be ideal for resorts that want to offer a coral viewing area without the worry of scuba diving-related injury to the surrounding reef. These nurseries could also be used to grow corals for the aquarium industry, to prevent wild coral harvesting (Pillay et al, 2011). Nurseries require constant maintenance and do not address the problem of ocean acidification. A slight change in temperature or water chemistry and the corals will die (Pillay et al., 2011). By having nurseries, there are corals that can be used to restore decimated reef areas. These nurseries do provide an area for assisted evolution to take place, however.
Repair
Assisted evolution is the process where stress-resilient coral traits are developed through breeding, genetic modification, or epigenetic programming (Pendelton et al., 2019). This is a relatively new process but nature has proven that it is possible to make stress-tolerant reefs. Corals found in shallow mangrove estuaries were more resistant to fluxes in temperature, available oxygen, and pH (Camp et al., 2019). After studying the corals, it was found that they contained more symbiodinaceae cells, photosynthesizing symbiont cells of corals, but these cells did not increase the net productivity (Camp et al., 2019). Assisted evolution can further be linked with coral nurseries. Developing new stress-resistant corals either through genetic modification, or continuous and controlled stress requires supervision by scientists. This process is easier to accomplish in a controlled environment like a nursery. There are research stations around GBR studying coral responses to different conditions (Anthony et al., 2008). These stations could be easily converted into or expanded to include assisted evolution coral nurseries. After the corals have been made stress-resistant they can be used to repopulate decimated areas of the reef or they can be placed on artificial reefs.
Another way to protect the GBR is to develop artificial reefs. An artificial reef is a structure, usually composed of concrete or metal that acts as a substrate for corals and other marine life to be attached. These reefs can also be constructed to provide additional coastal protection in areas where the reef is weakened (Albright and Cooley, 2019). This seems like a redundant measure when there is a naturally made reef ready to use, but it will be worth the cost to protect corals. Tourism in the GBR region alone brings in AU$2.4 to the Australian economy (Deloitte, 2017). If there is a minor abrasion to the coral’s surface the coral becomes susceptible to disease. This is especially common in highly visited sites. An artificial reef allows divers to experience the wonder of a coral reef without the risk of divers damaging the GBR. This would especially benefit “high-value” sites that depend on the GBR tourism industry. Building artificial reefs would provide relief for the GBR from tourism activity. Refuge areas also provide relief for corals from human stressors.
Additionally, refuge areas should be established for corals. A refuge area is an area with ideal conditions for coral growth (Camp et al., 2019). These areas would be used to replenish damaged reefs once conditions are favorable again. The goal of these areas is to keep the corals healthy, which translates to no scuba divers and minimal humans. These would need to be established and protected by the government. The majority of the GBR is already a marine park, as dictated by the Great Barrier Reef Marine Park Act of 1979 (Reef 2050 Plan, 2015). These sites would be considered high-value sites for their future use.
It is important to note that these solutions do not address ocean acidification. By increasing coral resilience to stress, coral reefs are more likely to survive a more acidic ocean. These corals, along with the corals in refuge areas, can later be used to repopulate decimated areas of the reef. For these efforts to be successful, ocean acidification will need to be addressed first.
Mitigate
There are a few solutions to make the water around reefs less acidic. The first of these solutions is called chemical remediation, also referred to as liming. Through this, an alkaline chemical would be added to a small area to neutralize the water (Pendleton et al., 2019). This would need to be specialized for each segment of the reef and carefully monitored so as not to disrupt the water chemistry negatively. In a study that used an Earth System model, it was predicted that chemical remediation would be effective in neutralizing the surface dissolved CO2 and increasing the amount of available carbonate (Feng et al., 2014). It is estimated that it would cost US$51-112 billion per year to provide chemical remediation for the entire reef (Feng et al., 2014). The Australian government has pledged AU$2 billion over the next ten years (Reef 2050 Plan, 2015). This method is costly and has to be done continuously or the water will return to its normal acidity levels (Feng et al., 2014). Another thing to consider is there is very little research on how the ecosystem and the animals will react to the added mineral and changing alkalinity (Albright and Cooley, 2019). Fortunately, there is a less experimental alternative for addressing ocean acidification.
Another option is phytoremediation, which uses seagrass and other carbon-limited organisms to remove carbon dioxide from the water (Pendelton et al, 2019). Studies have shown that MPAs with seagrass beds have been able to mitigate localized ocean acidification (Albright and Cooley, 2019). The issue with this is that a new species would be added to the environment which could outcompete native species. There have been many instances of invasive species being brought to an area to solve a problem, and then the invasive species becomes a bigger problem. An example of this is an Australian seagrass, Caulerpa racemosa, invading the Mediterranean, out-competing native grasses, and choking the ecosystem (Roberts, 2012). It should also be noted that corals and seagrass require different substrates to grow (Albright and Cooley, 2019). Therefore, in order for this solution to be effective, there must be a soft substrate near the coral for phytoremediation to be possible.
Both of these solutions are only effective on a small scale and will only provide limited relief. Additional research needs to be conducted on the lasting effects of these solutions so policymakers and scientists can determine if the costs and risks are worth the outcome. The only long-term solutions to ocean acidification and protection of the reef will be dictated by the government.
Adapt
Queensland is the state the Great Barrier reef borders and as such has the most direct impact on the reef. When the reef became a World Heritage Site in 1981, Australia became responsible for the protection of the reef. In response to this, Australia established the reef as a marine park, and the 1979 Emerald Agreement was developed (GBRMPA, 2009). The Emerald Agreement established a partnership between the Queensland Government and Australian Commonwealth Government (GBRMPA, 2009). In 2009 the Emerald Agreement was replaced with the Great Barrier Reef Intergovernmental Agreement which explains clearly which government is responsible for what portions of the reef. The document reiterates policies previously enforced like the Marine Park Act 2004, which states Queensland’s responsibility to preserve its coastline and the islands off its coast. The document also explains that both the Queensland and Commonwealth governments are responsible for managing fisheries within the GBR (GBRMPA, 2009).
Additionally, the Reef 2050 Plan was enacted in 2015. The agreement was co-signed by Queensland and the Australian government, detailing set goals to preserve and improve the GBR (Reef 2050 Plan, 2015). In this act, the Australian government and Queensland government promised approximately AU$2 billion to water management, research, and the general protection of the GBR over the following 10 years (Reef 2050 Plan, 2015). The Reef 2050 Plan also works to meet the goals of the Reef Water Quality Protection Plan 2013 which is the largest water monitoring plan established (Reef 2050 Plan, 2015). This plan establishes a clear checkpoint system to ensure goals are being met and after the 2016 and 2017 bleaching events, put that system to use (Reef 2050 Plan, 2015). In 2018 a review was conducted, which further emphasized the importance of water quality and protecting the reef from the crown-of-thorns coral-eating starfish (Reef 2050 Plan, 2018). Between these three documents, it is very clear that Australia is invested in protecting the GBR.
To counter the ambitious policies, public opinion has been waning over time. A study of newspaper articles following the 1981 appointment of the GBR to a World Heritage site and then the 2012 reclassification of the reef as a World Heritage Site at Risk found that environmental messages are getting overlapped with business messages (Foxwell-Norton and Konkes, 2019). Australian media networks struggle with balancing the political, social, and business aspects of the GBR, which results in moderate enthusiasm from the community when new protection policies are enacted (Foxwell-Norton and Konkes, 2019). Despite this, Australia keeps enforcing their environmental policies and are working to ensure the health of the ecosystem. It is also made clear that the only true way to protect the reef is to curb anthropogenic carbon emissions.
In 2015 the United Nations’ Paris Climate Agreement was signed by 196 countries. The goal of the agreement is to keep global temperature rise below 2°C by reducing carbon dioxide emissions (UNFCCC, 2015). The agreement lays out a plan to reach their goals, banking on transparency by each nation and collaborative effort to reach the joint goal (UNFCCC, 2015). According to some scientists, global temperatures need to stay below 1.5°C for coral reefs to survive. The “Bridging the Gap between Ocean Acidification and Economic Valuation'' workshop hosted by Centre Scientifique de Monaco and IAEA Environmental Laboratories is focused on protecting coral reefs by connecting scientists, economists, and politicians (Allemand and Osborn, 2019). This workshop included 22 countries and was held in 2010, 2012, and 2015, (Allemand and Osborn, 2019) but the conversations held there are still prevalent today.
Discussion
In this case study, the protection of the GBR against ocean acidification and coral bleaching was examined. If it wasn’t clear, the GBR is heavily protected by the Australian government. Some of the world’s most extensive environmental policies center around the reef. In meeting the goals assigned at the “Bridging the Gap between Ocean Acidification and Economic Valuation”, the Australian government has addressed all four categories to some extent. There has been research done on finding stress-resistant corals, and policies have been enacted to preserve the water quality of the reef. The government has also put strict guidelines for fisheries and agriculture practices within the drainage basin for the reef. There are always areas for improvement, however. As mentioned previously, the Australian people’s support has diminished for the protection of the reef. By increasing public awareness and participation, the reef will have the added protection of the Australian people. On an individual level, every citizen would be able to enforce policies locally, whether through beach clean-ups or being environmentally conscious.
The following steps are proposed to ensure the GBR survives the next century. First, a complete study of the reef must be conducted and “high-value” areas need to be established. These areas should be dictated by tourist activity and also areas of high biodiversity with minimal bleaching exposure. These areas should then be classified as refuge areas or MPAs. Secondly, local policies should be established to ensure the water quality of those areas is maintained. Thirdly, extensive research should be conducted on ways to mitigate ocean acidification, like chemical- and phyto- remediation, for small portions of the reef. While this is happening, coral restoration and research should be funded. All research should be funded by the Australian government and the UN. Stress-resistant corals should be created and propagated in coral nurseries. These stress-resistant corals should then be used to repopulate decimated sections of the reef. By following these recommendations, the GBR should be able to withstand ocean acidification through the coming century.
The problems facing the GBR are not specific to the GBR. Coral reefs are found all over the world. Most reefs experience over-exploitation, poor water quality, and issues associated with increased carbon emissions. Firstly, local governments need to establish reef protections and regulations that will preserve their reefs. Water quality from the watershed should be locally monitored. Pesticide and fertilizer use should be restricted for areas within the watershed near the reef. To accomplish this, education on reef health needs to be mandatory for local communities and taught in schools. Part of this education has to be the effects of overfishing the reef. This is an easy thing to say, but for developing countries who rely on their reefs for food and trade, it is not a simple task. These reefs are exploited by people who are trying to provide for their families, while also meeting international demands for fish and tourism. This then establishes the second point. Global regulations need to be put in place and enforced by the UN, limiting the amount of fish taken from reefs. As part of this regulation, there needs to be financial incentives by the UN for fishermen who fish sustainably. There also needs to be global action to educate the public on the importance of coral reefs.
Ocean acidification will continue to occur even if the goals of the Paris Climate Agreement are met. The ocean will continue to feel the effects of anthropogenic carbon emissions for decades to come. As such, the ocean will continue to change and adapt to a changing pH and increased temperatures. Unless action is taken and enforced immediately, the coral reefs of the world will be unable to survive this next century. The most crucial next step is increasing public awareness of the issue. People want to save things they care about and understand. It is not enough for scientists to publish studies and politicians to set policies. The only way for real change to happen is if the world rallies behind this issue and that can only happen through education.
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