Journal of Earth Science & Climatic Change
Open Access

Globally, the marine ocean is responsible for the uptake of nearly 50% of all atmospheric carbon dioxide, establishing itself as the largest carbon storing substance, or carbon sink. This trait makes it one of the most productive naturally occurring biological buffers for the drastic increase in anthropogenic CO2 emissions from fossil fuels, cement production, deforestation and other forms of combustion from human daily life [1]. Ocean acidification is a process directly connected to climate change that occurs across global oceans as a result of increased anthropogenic carbon dioxide (CO2), where the carbon dioxide gas reacts rapidly with the seawater, resulting in carbonic acid [2].

Now although this research paper will not dive into the specifics of ocean chemistry or the multiple climate change factors that feed into ocean acidification, it will be important to note some common terminology and concepts that drive the impacts of ocean acidification we are seeing around the world today. While the previously mentioned carbon dioxide storage ability the ocean has can slow down the drastic impacts from increased CO2 emissions, there is already another source of carbon dioxide that circulates the ocean. This event, termed “upwelling”, brings deep, cold, nutrient-rich waters to the surface, often containing large amounts of CO2 as a result of cold water’s increased ability to dissolve carbon dioxide gas [4, 5, 6]. Upwelling is important to identify, as this biological process illustrates the vulnerability of colder waters in absorbing more toxic gasses, and the dangerous position this places on the ocean when it's under future anthropogenic stress.

The carbonic acid mentioned earlier also has important significance, as this acid has been revealed to have an effect on the structure of calcium within the shells of many species of benthic organisms like crabs, lobster, shrimp etc., weakening their shells and decreasing their ability to thrive in the wild, proposing similar issues within the skeletal makeup of coral reefs, which use a method called “calcification” to turn calcium into strong, solid tissue to form the tall, branch-like towers we see in images today [2, 8]. Another term popular to scientists studying ocean acidification is aragonite saturation state (Ωarag) which measures carbonate ion concentration in water, a substance that aids coral in building their strong structures, along with the shellfish mentioned previously. This is important to note since an increase in CO2 has caused there to be a lower saturation state, placing stress on the structures of these organisms [9].

Potential hydrogen, better known as pH, is a measuring scale that determines how many positively charged protons (H+) are within a liquid. Substances that measure between 1-6 on the scale are acidic, with higher amounts of protons present than those substances that measure between 8-14 that are basic, or otherwise known as alkaline. Anything that measures 7 is neutral [10]. In terms of the ocean, increased CO2 has been discovered to lower the pH from a pre-industrial level of an 8.2 alkaline state to a 7.8 slightly more acidic state (or about a 30% increase) by the end of this century [4, 6, 9, 10]. When the atmospheric CO2 is transformed into carbonic acid, it in turn releases hydrogen ions into the water, lowering the pH [11].

Significance of ocean acidification

A lower pH due to increased carbon dioxide in seawater is detrimental to many parts about the ocean that our communities thrive on. The effects of this sector of climate change have proposed catastrophic ecological and economical effects. Again, while the ocean does a great job at balancing oceanic to atmospheric CO2 levels, there has been an alarming amount of research that has shown that the ocean won’t be able to take much more of it, as an increase in atmospheric amounts of CO2 will force the ocean to pressurized absorbance of CO2, forever changing the natural processes the ocean has when it comes to mediating carbon intake [5]. An increase in CO2 emissions has also caused scientists to see future projections alternating many of the oceans’ pH sensitive physiological processes and organisms, from photosynthesis and food webs, to enzyme activity and protein functions in aquatic life [10, 4].

The global coral reef ecosystem’s fragility to a change in the carbon chemistry of the ocean has resulted in research projecting a 55% decrease in coral's ability to produce strong, resilient skeletons (Shaw et al., 2011) [9]. To give an example of how important coral reefs are, 120 million people living within the Coral Triangle region (Indonesia, Malaysia, Philippines, Papua New Guinea) rely on reefs for security and income including tourism, along with essential nutritional protein intake from a variety of the fish, molluscs and crustaceans that live around these reefs and are consequently also affected by ocean acidification [12].

Aside from the damage being done to marine life and ecosystems, there are two large economical industries in ocean acidification's threatening path: fisheries and tourism. Global fisheries across areas of New England, the Pacific Northwest, and the Gulf of Mexico have a massive $1 billion dollar shellfish industry that has been studied by NOAA, highlighting its vulnerable position to ocean acidification, along with Alaska, a state that accounts for approximately 60% of the United States commercial fish production, and maintains over 100,000 jobs (NOAA). On a global scale, over 2.6 billion people rely on fish for a minimum of 20% of their protein intake [2], illustrating that this issue not only affects those in the fishery business, but also seafood consumers.

There are a multitude of direct and indirect forces that are a result of climate change, ocean acidification being among one of the worst we will see in this century. To this date, the ocean has absorbed approximately 620 billion tons of anthropogenic forms of carbon dioxide emissions within the last two-and-a-half centuries, connected to the burning of fossil fuels on land [13]. This number demonstrates the effects that are going to come from ocean acidification that will ultimately have high impact rates on the future of coastal communities, stemming from a decrease in tourism rates, fishery production, marine reproduction, and coral reef ecosystem efficiency.

Effects on coral reef ecosystems

Within the beginning of the 21st century, there has been an overwhelming accumulation of evidence that points towards rises in ocean acidification rates having a direct effect on coral reef species, causing great damage for the future of these ecosystems [14]. The change in oceanic chemistry and carbon content within these large bodies of water negatively influence the functions coral reefs have for calculating the perfect calcification characteristics needed to build a structure that will provide for the organisms that depend on them for habitat and food sources [15]. Decreased skeletal growth is the foundation of the issues we see surrounding decreased ecosystem life, as coral are often the engineers for a functioning amount of the marine life surrounding them, as well as providing conditions that break apart intense storm surge, preventing forceful hits to the shorelines and promoting growth for mangroves and seagrass beds [15]. Take away this vital ecosystem, and you risk losing the species that depend solely on coral reef support to sustain life.

The uptake of CO2 within the oceans carbon sink is responsible for weakening coral polyps at their vulnerable growth stage, lowering the calcite and aragonite saturation states in the upper ocean [4]. Because of this, the carbonate ions that hold together these structures become stressed with an increase in carbonic acid presence, lowering saturation states and weakening their ability to rebuild as strong as they used to. A fragile ecosystem demonstrates what scientists are predicting for future coral reef ecosystems, and as the atmospheric to oceanic CO2 concentrations begin to increase at similar levels, the ability for the ocean to store as much carbon as it used to, is being pushed to its boundaries [9].

A research study conducted by [7]. Examined coral reefs under high carbon stress both near-shore and offshore. Their data suggests that the standard level of aragonite saturation state at 3, will reduce to a 1 by the end of the century, with fluctuations between high and low stressors through different seasonal elements and water temperature. This extreme variability will cause a more chaotic ocean ecosystem that will have an effect on the species that usually thrive around this ecosystems’ moderate and stable environment.

Similarly another research study conducted by [9]. Collected data on extreme daily variability in a surface water reef along Australia's Great Barrier Reef. The results showed catastrophically high aragonite saturation states between 1.1 and 6.5, exceeding the range that is projected for the end of this century through NOAA. To accompany this data, they also found that changes in ocean carbon chemistry are amplified around low tide and less of a threat to species at times of high tide. These fluctuations shown present clear evidence that each coral reef species is going to respond uniquely to the changes they’re experiencing due to ocean acidification, demonstrating that coral’s net community (level of activity in a singular reef community) is largely dependent on the active energy at the cite of calcification in the skeleton, and that corals are slightly less affected by other climate change issues like temperature and nutrient composition.

Synthesizing the collected data, coral reefs have begun to show signs of deterioration within their strength, and consequently, a domino effect of concerns arise, including increased storm surge threats, loss of community life, and a rapid decline in tourism, fisheries and marine reproduction–the other effects analyzed in this paper.

Effects on marine reproduction

Global marine reproduction rates are another issue that has been recently researched, resulting in lower survival rates in different species of fish and crustaceans. In a reproductive research study done by [16], he and his team studied different variables of egg production, hatching success, and larval stage survival. Within this study they placed copepods, a common seawater crustacean that eats phytoplankton, under high levels of particulate CO2 (pCO2) in their diet and measured the variables listed above to compare them to normal, or controlled, conditions. The results they found were a 48% lower egg production, 87% lower hatching success, and 100% lower larval stage survival rate within high pCO2 diets. This illustrates that copepods, which are considered to be a very important keystone species for the ocean, is dramatically affected in their reproductive rates via food intake, showing that if ocean acidification continues to increase at the expected rate, a bottom of the food chain species like the copepods, could start a domino effect that ripples across the rest of the food web.

Not only are those who feed on phytoplankton or use the sun’s energy affected. An older study conducted by [17]. Examined newborn clownfish within high CO2 treatments and compared them with those in no treatment. The results showed that there was an increase in maturation of the clownfish in the high CO2 water spending more time around a predator species, with 8 day old clownfish spending 94% of their time in water near the predator specieses. Similar to this they studied damselfish larvae, which eventually started to spend 48% of their time in the predator waters. Conclusions were drawn that the higher level of CO2 (700-850 ppm) for young larvae in both clownfish and damselfish inhibited these creatures from detecting the odor of their predators and therefore avoiding them, changing that biological instinct to being attracted towards them. The results of this experiment show a newly formed risky behavior for reef marine fish (and potentially others) that puts their future species population in a vulnerable position. Therefore not only is a high pCO diet a concern, but the water concentration itself.

Understanding how carbon dioxide within water affects larval size and shape as well as altering the shells in species that have them is crucial to reproduction effects as well. This slows down the stages at which these fish mature and are able to reproduce, inhibiting process within larval stages, posing great threats to future populations [18]. Organisms are going to showcase different vulnerabilities across their lifetime, but a dangerous level of larvae are threatened by ocean acidification through the result of increased predator attraction, and impacted growth inhibitors, alternating their development and reproductive success [10].

Effects on tourism

The ocean is a popular vacation spot that is a magnet for couples, families and day to day locals visiting coastal regions. A tipping within the supply and demand of this industry with ocean acidification as a catalyst means a change in the standard tourism attractions and market [19]. For this section, I will be focusing on three areas and regions: the Florida Keys, Egypt’s Red Sea, and the general reefs within the South Pacific.

Starting with analyzing the tourism sector in the Southern Pacific [20]. found that this cluster of developing countries (Solomon Islands, Kiribati, Samoa etc) rely on tourism based on these marine environments for a huge part of their economy. From snorkeling activities to surfing, scuba diving and sailing, climate change has had a profound impact on how populus these activities are and the efficiency at what they do for the citizens living there. This threat puts these smaller, developing South Pacific countries in a precarious position if they cannot find another way to produce sufficient tourism or make adequate income.

A similar survey of tourism relative to Egypt and the Red Sea done by found that more than 90% of Egypts’ tourism industry comes from hotels and diving activities across coastal regions or in the Southern Sinaï. This natural resource dependence has been a huge part of ancient and modern Egyptian economic stability for civilization. This study also discovered that as a result of this dependence, biodiversity supports the basis of this sector of tourism for local, national and regional scales. This study moreover illustrates the dependency that Egypt has to its coastal communities, and if they were to ever lose activity because of ocean acidification (i.e. coral reef loss and decline in marine population), there would be a decline in this high exchange rate of tourism to the economy, and the local businesses that run within the circle of tourism would be at a loss indirectly because of the change in carbonate chemistry.

Lastly, research collected by surveyed the economic tourism impact of the Florida Keys. Hugging the Atlantic Ocean and stretching from Miami to the Dry Tortugas, the Florida Keys are considered the third longest coral reef ecosystem in the world and the only surviving coral reef in North America. Millions flock to this region to scuba dive, snorkel, and study the wildlife. This reef is home to more than 6,000 species of marine plants and animals, and has an estimated asset value of around $8.5 billion, combining local income and sales, along with providing 71,000 jobs (NOAA).

The loss of these vital coral reefs would cause harm to those in the surrounding area, including tourists, who spend their time and money on experiences and activities around this reef. If ocean acidification continues at the rate it is heading, the loss of coral reef ecosystems and fish/shellfish production will overpower any chance for Florida, along with surrounding coastal nations and states, to continue the progressive numbers it has established based off of tourist attractions and the lives of those affected would span beyond the marine wildlife and into the homes of citizens around the world.

Effects on global fisheries

Another crucial economic sector affected by the increased ocean acidification risk is the surrounding coastal fisheries. As of now the total value of world fishery production is around $150 billion a year. Consequently, ocean acidification could impose mitigation costs around $10 billion a year [3]. The reliance for many developing countries on fish as an income has been studied over the years, showing that lower income countries that cannot afford to quickly adapt or mitigate symptoms of increased ocean acidification, will be at a standstill and loss for future expected projections.

A study done by [3]. Studied the dependency of this specific sector within Mediterranean countries. As developed countries try to push production of fish in aquaculture habitats, this exposes developing countries to ocean acidification's inescapable grip. These fishermen lack the staff and technology to keep up with the decrease in wild caught fish populations. Aside from local productions, trade barriers between countries hinder these developing countries' ability to easily import goods and fresh catch from abroad. With heavy reliance on domestic production, developing countries will be the first to lose the battle against ocean acidification.

On the opposite side, their research found that developed countries like France, Spain and and Italy showed to have increased imports of fish and other seafood from over the sea. This expands their ability for the meantime, while developing countries across the Mediterranean Sea are forced to a tight niche of where they can produce and how much they can produce. For those developed countries, it is only a matter of time before rates of ocean acidification affect the seafood populations across a global scale, inhibiting what marine protein is available for consumption in a future climate.

An experiment done by suggests that by incorporating current models and formulas, coral reef habitats are expected to decrease by a catastrophic 92% by 2100. Their conclusions found that as a byproduct of this decline, there will be an estimated annual consumer loss of around $8.3 billion in the shellfish and low-value fish market. This puts the future of fisheries in a precarious position, as losing substantial amounts of business and product could lead to more than just an economical depression, but an entire industry going out of business in the global sector.

Overall findings

Within the research I have accumulated, there is an overwhelming amount of evidence pointing towards a decline in marine habitats across the global ocean, affecting a surplus of species both plant and animal. It is essential that we understand the impacts that have been studied so far, and the processes that drive them all so that we can actively work towards inhibiting future projections of CO2 concentrations, aiming to eliminate the potential risk that now faces coastal communities in developed and developing countries worldwide. Ocean acidification is not a niche localized issue, it affects everyone. From those who enjoy vacations to Egypt’s Red Sea, snorkeling in the Florida Keys, to those who own small seafood businesses in developing countries along the Mediterranean. Unfortunately, the projected impacts have a domino effect that result in the world being affected either directly or indirectly from this issue.

In this research paper I also did not include some of the mitigation efforts that have sparked media interest. A lot of mitigation for CO2 emissions has taken place, including CO2 emission caps and limits for factories and cars across more developed countries. Unfortunately, solutions to climate change and branched issues like ocean acidification are expensive to implement and have political restraint from certain presidents, ambassadors and other heads of state.

The topic of ocean acidification is a lot more complex than I had imagined, and there is a labyrinth of information that further lies within the research I analyzed. In an effort to keep my research paper applicable and clear for everyone both in the science field and at home, my paper did not detail the formulas and compounds that are measured when studying ocean acidification. Because of this factor, my perspective was widened as to just how massive this issue is, and how it affects such a broad range of problems, which made it difficult to narrow down this paper. I would love to have an opportunity to continue studying ocean acidification, and it has once again reminded me of why I am passionate about my major, and how I desire to learn more about the chemistry composition of the ocean, using my academic studies to apply them to a real climate change issue that is happening today.

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