The Effects of Ocean Acidification on the Great Barrier Reef



Ocean acidification (OA) has become a growing area of concern among scientists and environmentalists over the past few decades. Existing research explores the causes of ocean acidification, its possible impacts on marine ecosystems and how it is likely to progress during the 21st century. Of the completed studies, the majority emphasize coral reefs as these ecosystems are both biological and geological structures (Hoegh-Guldberg, Pendleton & Kaup 5). More recently, OA shifted from being purely a scientific topic to an area of public interest. This move was powered by the realization of how severe and irreversible OA is not only for us but also future generations. All the studies have linked the subject in question to the recent human activities such as the burning of fossil fuels. These fuels emit carbon to the atmosphere some of which dissolve into the oceans (National Research Council 6). Prolonged absorption of carbon dioxide into earth’s waterbodies caused changes in the chemistry of the oceans thus making them acidic.

Ocean Acidification as a result of CO2 emissions into the atmosphere has caused irreversible damage not only to the structures within coral reefs but also organisms living within them such as jelly fish, hydroids and sea anemones. Furthermore, the effects of OA extend to the communities that benefit from these reefs such as fishermen as there is currently a decline in fish stock and quality. The Great Barrier Reef (GBR) of Australia is one such reef that is greatly impacted by Ocean Acidification. If humans continue to emit carbon di oxide to the earth’s atmosphere, organisms and structures in the GBR will be gradually exposed in the coming decades as a consequence of acidification of the seawaters. However, all is not lost, with proper recommendations and action, much can be done to protect coral reefs around the globe so that they are not lost to us forever.

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Although the period following industrial evolution contributed to the growth of the world’s economy, it also led to grave environmental degradation. Greenhouse gas content has rapidly changed over the past century and a half and now the concentrations levels of carbon dioxide and methane have also risen. These changes have contributed significantly to the overall rise in the temperatures of the earth’s atmosphere as well as the upper layer of the ocean (Lluch-Cota 149). The ocean waters are now 70C warmer than they were a century ago (Attenborough, 2010). Attenborough (2010) also noted that the increased atmospheric CO2 has also influenced the drop of the ocean water pH by 0.1 since pH levels are logarithmic, the acidity of the ocean has increased 10 times! Increased acidity suggests removal of 30–40 μmol kg-1 carbonate ions from the world’s oceans which commonly have 250–300 μmol kg-1 of the same properties (Albright et al. 364). The change in the highlighted conditions has significantly impacted all coral reefs in the world. The increased sea temperatures have pushed corals beyond their thermal tolerance resulting in events of mass coral bleaching. These episodes of bleaching were first reported in 1979, but their intensity and frequency have increased drastically ever since. The most basic understanding of coral bleaching is the breakdown of a coral and its symbiotic dinoflagellate. The process of coral bleaching begins when the warm temperatures of the water causes the corals to expel zooxanthellae that live within them (Hoegh-Guldberg & Hoegh-Guldberg 9). This release turns the corals completely white. Studies established that mass mortalities of corals were the following step in most cases that reported coral bleaching. The survey also determined that after a year of the first report of these episodes, about 16% of the world’s corals had been lost by bleaching alone (Hoegh-Guldberg 27). Although recent documentaries on the National Geographic channel note that the reefs have begun to recover after the 1998 bleaching episode, the recovery process has been prolonged, and the present corals have a minimal resemblance to what was first witnessed within these reef systems (Harrould-Kolieb et al. 32). Although previous research tried to separate the effect of acidification from the warmer ocean, future ocean conditions will incorporate both of these elements. Therefore, it may be difficult to explain how warm oceans alone impacts the coral reef system (Hoegh-Guldberg & Hoegh-Guldberg 21).  

Understanding the process of ocean acidification is essential in detailed explanation of the effects that it has on coral reefs, specifically the Great Barrier Reef. However, before exploring the essentials of this process, one must fully comprehend the details of the carbon cycle. Carbon circulates in both organic and inorganic forms from different sources such as the atmosphere, plants, animals, soil respiration, decomposition and volcanic eruptions.  (Kleypas & Yates 121). The acidification process involves three primary elements including carbon dioxide, water, and bicarbonate ions. When CO2 is released from several human activities such as the burning of fossil fuels, the excess is absorbed by the oceans thus forming carbonic acid (H2CO3). This process has taken the course for over 250 years thus explaining the increased levels of acidity in the oceans today. The resulting carbonic acid further dissociates into bicarbonate ions (HCO3) and hydrogen ions (H+). Therefore, increased levels of hydrogen ions are what reduces the water pH, consequently acidifying the oceans (Hoegh-Guldberg & Hoegh-Guldberg 33). From a chemical perspective, although the acidification process has taken place, ocean water remains with a pH that is greater than 7. Scientists have recorded that the average pH of water within the ocean surface today is at 8.1 translating to at least 0.1 pH units of what was estimated before the industrial revolution over two hundred years ago (Lluch-Cota 151). Appendix I of this document is a diagrammatic summary representing the ocean acidification process.

Great Barrier Reef

Geographic Setting

The GBR began as a national park was in 1975 but later became World Heritage Area in 1981. Presently, it is the largest continuous coral reefs ecosystems in the world covering approximately 334,000km2 and lining almost 2,300km of the Australian coastline. It is also the most famous marine park in the world and home to various marine organisms including different species of mollusks, corals, fish, marine mammals, turtles and seabirds (Hoegh-Guldberg, Pendleton & Kaup 35)

Value of Coral Reefs

The Great Barrier Reef is valuable to humans, as it comprises a variety of ecosystem services including fisheries and tourism services. Most people interested in protecting the coastlines or those who seek carbonated sands visit Australia specifically for the reefs. Furthermore, the services provided by the reef support the industries and communities concerned with this kind of ecosystems (Kleypas & Yates 110). The reefs are also beneficial in the protection of the coastline against storms. People also use calcium carbonate deposits recovered from these ecosystems to make jewelry and trade them in the market. Therefore, in a way coral reefs provide the livelihood for the Australian people through trade and eco-tourism services (GBRMP 10).

Recognized Threats to Sustainability of the Great Barrier Reef

Assessment reports by scientists established that both local and global stressors are a threat to the long-term sustainability of GBR and other coral reefs (Kleypas and Kimberly 115). Examples of domestic threats include coastal degradation, quality of the sea waters, fishing pressures among others while global factors include climate change, ocean acidification among others (Hoegh-Guldberg and Hoegh-Guldberg 58). Experts note that these two categories have already had significant impacts on some of the world’s renowned coral reefs including the GBR. While local issues have affected a considerable part of these ecosystems, most scientists perceive that the main threat to their long-term sustainability is the water quality of the oceans that result from the several agricultural activities (Harrould-Kolieb et al. 34). Agriculture has significantly increased the number of nutrients and sediments which have contributed significantly to the loss of the GBR. The evidence of this impact is demonstrated substantially through comparisons of pictures of the reefs taken a half a century ago with those made in the present day. Most of the comparisons reveal that coral communities were common along the Australian coastline while today they are rare (Lluch-Cota 148). Appendix II of this document provides a picture that compares the organisms in the coral reefs of 1980 and those of 2011.

Effects of Ocean Acidification on GBR’s

Existing evidence suggests that the Great Barrier Reef has lost almost 50% of its coral cover within the previous three decades. The literature attributes the majority of this loss to ocean acidity, storms and increased sea temperature particularly during the summer.  Humans are continuously releasing carbon dioxide from the industries and vehicles to the atmosphere while the oceans are absorbing some of the excess CO2 (Lluch-Cota 151). What remains certain from all the previous text is that ocean warming and acidification are the most significant factors that contribute to the immediate decrease in coral reefs and the further decline predicted in the future (Hoegh-Guldberg & Hoegh-Guldberg 11). In 2016, AIMS, a natural laboratory that specializes in marine ecosystems, led research that focused on the GBR involving thirty-five researchers from 20 separate institutions in nine countries all over the globe (Harrould-Kolieb et al. 38). The study established that the increasing levels of acidification of the ocean waters in Australia had several effects on three major components of the Great Barrier Reef including organisms, structures and coral communities of Australia’s main coral reef- the GBR. 

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Organisms within the Reef

A significant concern about the effects of OA on GBR is that it affects various groups of the reef’s plants mainly the coral line algae and the corals as these two are considered the “ecosystem engineers” of the GBR. Loss of these two specific groups significantly affected the lives of several other organisms within the reef including coral animals such as jelly fish, hydroids and sea anemones. When the corals died within the reef’s ecosystem, the health of other sea creatures that depend on them is affected while some die. Therefore, the chain continued throughout the entire ecosystem (Harrould-Kolieb et al. 39). From a comprehensive view, OA affects biological processes essential for organisms within the coral reefs including shell building, photosynthesis enhancement, metabolism maintenance and obtaining vital nutrients and minerals (Kleypas & Kimberley 115). Some ocean creatures and algae utilize carbon ions to make their shells and skeletons. Therefore, since acidification of the oceans reduces the carbon ions in the water, such animals face difficulties while making their calcium carbonate shells (Hoegh-Guldberg & Hoegh-Guldberg 21). Additional several physiological processes operate well within a narrow pH range. Therefore, acidity slows down the biochemical reactions of the organisms thus becoming unhealthy. Some scientists have argued that some species can adjust to their surrounding conditions by establishing a balance between their external and internal environments (Lluch-Cota 139). Others have dismissed these arguments with the conclusion that such a process consumes a lot of energy which may not be a problem for the adult fish but a big issue for algae and fingerlings.

Ecologists have also attributed the decline in the fish stock and quality to loss of coral reefs within the Great Barrier Reef (Berumen et al. 739). The effect of these trends extends to the economic value of fish and the revenue earned through fisheries within these reefs. It may be correct to argue that a decline in fish within the reefs does not translate to a proportionate reduction in catch as fishermen within the GBR have not complained of a reduced catch since OA was recognized as a global phenomenon. Therefore, one may assume that although fishermen have not reported a reduction in their catch, this does not mean that the number of fish have not reduced within the GBR (Hoegh-Guldberg & Hoegh-Guldberg 32). However, from recent reports by scientists, one thing is clear, the quality of fish within the GBR fisheries has dramatically deteriorated (Kleypas & Yates 138). Existing literature records that smaller fish are being caught today while in other instances the fish from different species are being collected today. This quality has lower prices on the market value as well as nutritional value for the communities around the reef (Albright et al. 341).

OA does not entirely have a negative impact on organisms in coral reefs. Existing evidence indicates that the increased levels of CO2 in the ocean waters improve photosynthesis of plants growing in the reefs. BBC documentaries have established that several species of grass including seagrass thrives under elevated levels of carbon dioxide. These plants provide habitat for small ocean creatures within the Great Barrier Reef (Hoegh-Guldberg & Hoegh-Guldberg 44). However, studies also indicated that if these plants overgrow due to the increased levels of CO2, less robust species such as coralline algae are developed within the reef thus reducing the biodiversity of the ecosystem. Lastly, ocean acidification is not favorable for the growth of most living things within the oceans because they OA inhibit absorption of essential nutrients such as nitrogen and phosphorus. In a few cases, marine life finds it difficult to use iron particularly when this element is attached to organic compounds (Kleypas & Yates 141).

Reef Structures

Reef structures are habitat to several ocean creatures and organisms. However, over the recent years, ocean acidification has contributed to the degradation of a considerable number of coral formations existing within the world’s reefs. Before evidence of OA, the structure of the Great Barrier Reef was rough and irregularly, however, today the structure is slowly becoming “flatter.”  The loss of the architectural complexity of the GBR leads to a decline of habitat diversity ultimately leading to decrease of biodiversity within the reef (Kleypas & Yates 111). Increase in acidity of the ocean made it difficult for the reef-building’ corals to keep up with the erosion rates caused by both biological and physical factors (Albright et al. 365). Therefore, the three-dimensional structure of the GBR has begun to crumble, and the process is bound to continue, and it will eventually disappear if the present CO2 levels continue to increase (Albright et al. 363). The findings of a five-year fellowship programme at Queensland focusing on the GBR established that CO2 is not the only factor that dictates the rate of the reef’s structures (Authority, Great Barrier Reef Marine Park 5). Other factors such as the intensity of the tides or storms determine whether the degradation process of the coral reef structure happens at slower or rapid rates. The study noted that the degradation process occurred rapidly in some sites of the inshore GBR sites (approximately a period of 30-50years). 

Future Projections of the GBR

Scientists have already compiled different trajectories using global climate frameworks to generate information on the future of diverse ecosystems. The data included integrates social, economic, physical and biological sequences to develop viewpoints on various aspects of the climate system including the CO2 concentrations and global temperatures (Hoegh-Guldberg & Hoegh-Guldberg 14). Recent studies indicate that organisms and structures in the Great Barrier Reef will be gradually exposed in the coming decades as a consequence of acidification of the seawaters. These findings projected that corals’ rate of calcification would reduce by 30% in the next thirty to fifty years (Kleypas & Yates 113). Scientists also expect that the calcification of algae will decrease at almost a similar rate (Harrould-Kolieb et al. 51). Environmentalists also project that the present rates of erosion and accretion will profoundly influence the growth of reefs as geological structures. Other scientists have declared that by the latter half of this century, an extension of the GBR may reverse. A recent study by Hoegh-Guldberg et al. (2017) concluded that the GBR and other carbonated coral reefs all over the world are not likely to maintain atmospheric CO2 concentrations that exceed 450ppm. Finally, recent projections note that reef-building may reverse by the half of the 21st century due to the effects of reduced accretion and increased rates of erosion (Hoegh-Guldberg & Hoegh-Guldberg 29). A summary of the past carbon dioxide levels and the future projections to the year 2100 have been presented in Appendix III of this paper.

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Global Action to Promote Sustainability of Coral Reefs

In response to the challenge of loss of coral reefs, several global environmental organizations and programmes have already taken the initiative to find a viable long-term solution. For example, the Paris Agreement is a voluntary commitment by countries to contribute to reducing greenhouse gases emission basing on what is achievable nationally. Presently, data indicates that nations who have signed the agreement falls short of 20C which translates to average global surface temperatures ranging between 3.0-3.5°C by the end of the present century (Harrould-Kolieb et al. 53). This data suggests that these conditions will cause a loss of coral reefs and other ecosystems within the oceans by the middle of 21st century. Although this data does not favor the future of ocean-based systems, if every individual nation puts more effort on the already laid down frameworks such as the earlier highlighted agreement, then there is hope for long-term sustainability of these reefs (Hoegh-Guldberg & Hoegh-Guldberg 14). Appendix IV of this article provides a summary of the pH and CO2 levels since 1955 to 2015 which will be useful in understanding the progress that the world has made on this issue over the years.


Enactment of Laws for CO2 Stabilization

The best way of protecting the world’s oceans is to enact laws or adopt policies that aim at stabilizing the levels of carbon dioxide in the earth’s atmosphere. Currently, the level of CO2 is at 390ppm (Authority, Great Barrier Reef Marine Park 40). Therefore, strategies that can reduce this concentration to 350ppm would be a significant step towards protection of oceans. Although this is a long-term solution to the current problem, it may be an effective way of stabilizing greenhouse gases concentrations. These policies should focus on industries of the world to reduce their emissions 25-40% below the levels recorded two decades ago (Kleypas & Yates 119). 

Stop Offshore Drilling

Previous studies have linked destructive practices such as offshore drilling to the destruction of life and ecosystems. These practices release carbon dioxide into the ocean waters thus making it acidic. Therefore, protection of the coral reefs requires a ban of such methods. As technology continues to advance, governments need to shift from using oil as the sources of energy to other green or alternative sources that are not dangerous to the environment (Harrould-Kolieb et al. 42).

Utilization of Offshore Wind Energy

Wind is a clean source of energy which can be harvested offshore and utilized by industries, companies and for domestic use. The level of gases from fossil fuels would be drastically reduced if governments decide to promote utilization of this energy form. Federal governments can encourage the purpose of this energy through extending the tax credits for investments made into wind technology. Furthermore, nations can use policy mechanisms that support the demand of and the supply of renewable sources of energy. Finally, the transport sector should also utilize these clean sources and establish develop new infrastructure so that the electric trains can be used (Kleypas & Yates 122). 

Building Resilience of Marine Ecosystems.

Emission of greenhouse gases and their absorption into the ocean is not the only factor that influences ocean acidification. Other human activities in the seas that do not involve the burning of fossil fuels reduce the ability of the sea to cope up with the increased levels of acidity. It is evident from the discussion in this paper that ecosystems existing in the oceans have a better chance of enduring the pressures caused by OA if they are not struggling to cope up with other human threats such as overfishing (Albright et al. 366). 

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Public Education Programs

The public should be educated on the effects that their polluting lifestyles have on the seawaters and the environment at large. Environmentalists should also spearhead advocacy campaigns that will not only persuade the public to engage in environmental-friendly practices but also influence the legislators and decision makers to adopt policies that protect the environment from human activities that are destructive to the environment (Sidsel & Burgess 553). Different communication strategies should be employed in these advocacy campaigns. Even though media consumption continues to undergo many challenges, communication through conventional mass media methods remains a very cost-effective method of relaying consistent messages to large audiences. The grassroots are also an essential method of influencing legislators (Kleypas & Yates 132). Therefore, the first step in involving people at the grassroots is through engaging supporters in the identification of ways of protecting the oceans. Secondly, demonstrating leadership through sharing expertise, knowledge and strategic thinking while also relinquishing some control will help in gaining the support of people in the grassroots level.

Possible Obstacles to the Recommendations

Although modification of the existing laws on stabilization of carbon di oxide levels may seem straightforward, some obstacles may work against these efforts. These factors may cause either delay or create a complete block on some of the proposed modifications. First, the vote requirements have the potential to become an obstacle if the policies to be enacted requires a majority vote to be passed (Kleypas & Yates 128). Secondly, the proposed changes may not be popular with the public and some of the policymakers as it may be adding a provision that either of these parties does not like (Sidsel & Burgess 553). An example of such a group that is likely to be affected by CO2 stabilization are corporations and large industries. Corporations have no sense of corporate responsibility and will unlikely support laws that limit their working conditions.


From the discussions made in this paper, it is clear that ocean acidification is a global problem that requires the collective responsibility of the society as a whole. This phenomenon is threatening all forms of marine life and needs to be resolved immediately. It is also evident that although the scale of ocean acidification is predictable, its effects on coral reefs all over the planet is less likely foreseeable. Therefore, the global community should maximize their efforts in walking towards a sustainable future. A sustainable world can best be achieved by adopting the concept behind deep ecology. This idea primarily directs human thoughts about the environment and the world around us (Kleypas & Yates 131). It will help every individual within the coral communities to recognize their responsibility in environmental conservation and work towards reducing the levels of carbon dioxide in the planet’s atmosphere. The devastating effects of ocean acidification, call for a solution using every possible means. One of the methods to be used is cleaner transportation options and adopting cleaner fuels such as biofuels and electric cars. Proper car maintenance methods should be embraced and ensuring regular check-ups.  Scientists and analysts have come up with a plan known as ‘Half the Oil’ that is designed to cut the use of Oil in America (Hoegh-Guldberg & Hoegh-Guldberg 17). Whenever possible, citizens should walk or bike over shorter distances. Using public means of transport is also a way of ensuring that pollution is reduced at a considerable rate. Although this paper has covered significant effects of OA on the GBR, there is still a gap in understanding how social and economic systems related to the GBR will respond to ocean acidification and climate change. Therefore, research needs to be conducted to understand this area better.

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