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Ocean Acidification: Causes, Issues and Solutions
The catastrophic effects of increasing levels of carbon dioxide are widely known and publicized - global warming and climate change have been described as the challenges of the century. But many people have not heard about another highly concerning impact of rising CO2 levels - the acidification of the Earth's oceans.
Ocean acidification is a relatively new term, and it wasn't until the early 2000s that scientists first became aware of its threat to marine life. The effects of a more acidic ocean are extensive and we're only just beginning to see its impact.
👉 In this article we'll explore the process of ocean acidification, its causes, and what can be done to prevent further harm to our delicate marine ecosystems.
Climate change and ocean acidification
The Industrial Revolution was a period of technological and scientific development that transformed societies across Europe and North America. However, this advancement came at a cost since it relied on the use of greenhouse gas-emitting fossil fuels. The concentration of carbon dioxide in the atmosphere (ie. atmospheric carbon dioxide) has been on the rise ever since, upsetting the Earth's carbon cycle and disturbing its natural equilibrium.
The effects of this are catastrophic with global temperatures rising resulting in alarming changes to our climate, but it's also resulting in something that's not as widely publicized or talked about - something called ocean acidification.
So, what exactly is ocean acidification?
Well, in order to understand ocean acidification, you first need to understand the carbon cycle, so let's start by taking a quick look at this process in more detail.
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What is the carbon cycle?
The carbon cycle is the process by which carbon moves around the Earth's atmosphere.
It consists of various carbon-emitting processes (for example breathing which releases carbon dioxide) which are in turn balanced out by carbon sinks (carbon sinks include the Earth's oceans, forests, vegetation, and soil).
👉 The carbon cycle is a finely tuned process that has a natural balance, however, human activity has interfered with this equilibrium and now it is dangerously out of sync.
Human activity
The industrial revolution fuelled advancement, however, it also resulted in huge amounts of excess carbon being poured into the atmosphere through the burning of fossil fuels - a practice that hasn't stopped ever since.
This excess carbon has nowhere else to go except into the Earth's atmosphere, which in turn traps heat and results in global warming. However, global warming isn't the only effect of rising levels of carbon dioxide.
Carbon sinks
As we've touched on, carbon sinks are part of the carbon cycle and help to counteract the excess carbon dioxide that is released into the atmosphere.
👉 The world's oceans are the biggest carbon sinks and absorb around 30% of the carbon dioxide that is released into the atmosphere.
As we continue to release ever more carbon dioxide, the levels absorbed by the oceans also continue to rise.
Ocean chemistry
It would be great if the excess carbon dioxide was simply absorbed by the ocean without any side effects, but sadly this is not the case - the excess carbon dioxide impacts the chemical composition of the seawater.
When carbon dioxide is absorbed by the ocean water, a series of chemical reactions result which ultimately cause the concentration of hydrogen ions in the water to increase. The result of this is that the seawater becomes more acidic and levels of carbonate ions are decreased.
For context, before the Industrial Revolution, the ocean's PH level was 8.2, which means that it is actually more alkaline than acidic. However, the rising levels of carbon dioxide in the water are gradually altering this PH balance and we're seeing a shift towards more acidic water - the current average PH level of the world's oceans is 8.05 on the PH scale.
This change may sound small and insignificant, but it's having huge repercussions for the world's oceans which are a finely balanced ecosystem and highly sensitive to chemical changes. The change in PH level actually equates to an increase in acidity of 40%, and by the end of the century, the world's oceans are on track to be 150% more acidic than current levels.
👉 Human activity is quite literally changing the chemical composition of our oceans.
The effects of ocean acidification
If you're thinking that ocean acidification doesn't sound like good news - you'd be right. But up until relatively recently, scientists weren't aware of the effects.
Scientists have been tracking the ocean PH for over 30 years, however, it wasn't until the early noughties that scientists became aware of the biological impact, and the term ocean acidification was first coined. So what exactly are the repercussions of ocean acidification?
Carbonate ions
Carbonate ions are a key building block in ocean water, and falling levels can make it difficult for marine organisms such as coral and plankton to form shells and skeletons.
What's more, is that it may even cause some existing shells to dissolve. Let's take a closer look at the effects on some of the individual marine species that are the most susceptible to the changing chemical composition of the Earth's oceans.
Coral reefs
Coral reefs house coral animals and provide a habitat for a huge variety of different species. Unfortunately, they're particularly vulnerable to ocean acidification because they're formed from calcium carbonate.
Ocean acidification not only corrodes existing coral structures, it also slows the development of new skeletons and results in weaker coral structures that are more vulnerable to damage and erosion.
However, the severity with which different coral species will be affected varies - some corals are proving to be rather resilient when it comes to ocean acidity and can produce their skeletons with bicarbonate instead of the carbonate ions, and other corals can temporarily survive without a skeleton.
👉 Over the coming decades we'll certainly see a change in the composition of coral reefs around the world. Since coral reefs form an important part of many marine ecosystems, this will also have profound effects on the many different organisms that rely on them for their survival.
Shellfish
Ocean acidification is bad news for shellfish such as mussels, clams, and sea urchins. As is the case with coral reefs, most shellfish rely on carbonate ions to form their shells.
👉 Research shows that by the end of the century, the shells of mussels and oysters will decrease by around 25% and 10% respectively. Weaker calcium carbonate shells mean that these creatures are more at risk of being crushed or eaten.
And it's not just their shells that suffer. The fibers that mussels use to attach themselves to rocks are also impacted by ocean acidification - the impact being that mussels can't attach to rocks as securely.
Oyster larvae are also affected - they need to form a shell to start feeding, but the lack of carbonate in the water is preventing them from doing so. This has already had a huge impact on oyster farms in the Northwest of the United States - some oyster farms have experienced a loss of up to three-quarters of their oyster larvae.
As is the case with coral reefs, the loss of these organisms is also problematic for the wider ecosystem, with other animals and creatures depending on them for food and habitat.
Plankton
There are many different species and subspecies of plankton that are susceptible to the changing chemical balance of our oceans. These tiny organisms are often under-appreciated for the important role they play in marine ecosystems.
Take Zooplankton for example - zooplankton is an incredibly important part of the ocean food chain - nearly all marine life either eats Zooplankton or eats larger creatures that eat zooplankton. The problem is that some subspecies of Zooplankton form shells from calcium carbonate, and in acidic conditions these shells quickly dissolve.
Phytoplankton are another important type of plankton. Not only because they provide food for Zooplankton, but also because they form a crucial part of the carbon cycle. In fact, Phytoplankton are responsible for the majority of the transfer of carbon dioxide from the atmosphere into our oceans. Phytoplankton achieve this by consuming carbon dioxide during photosynthesis - similar to the way that the leaves of a tree convert and store carbon dioxide.
👉 Research shows that different species of Phytoplankton respond differently to the increasingly acidic level of our oceans, with some species dying out, and others either migrating regions or flourishing. This has the potential to significantly disrupt delicate marine ecosystems and completely alter the composition of marine creatures that live within them.
Algae
Algae are one species of marine life that actually benefit from the increased acidic conditions of our oceans. Plants and algae make their energy from carbon dioxide and so the increased levels in the water help them to thrive - good news right? Well… not always.
You see, algae can be harmful in large quantities. Harmful algae blooms occur when algae populations grow out of control, producing high levels of toxins which can be harmful to animals, plants, and even humans.
👉 Depending on the species of algae, algae blooms can even be life-threatening, or cause respiratory and gastrointestinal illness in humans.
Fish
Although fish don't have shells, they're not unaffected by ocean acidification. The cells of fish are more alkaline in nature than that of the surrounding ocean water they swim in, this results in an acid-base regulation, which means that the cells of a fish absorb carbonic acid, resulting in a decrease (or acidification) of the PH level of the fish's blood - a condition called acidosis.
This increased PH balance can hugely affect the physiology of the fish, resulting in increased metabolic rates and behavioral changes. For example, it's been shown that in more acidic waters, clownfish are unable to flee threats efficiently and that they're unable to smell their way back home.
Food web disruption
The impact of ocean acidification extends beyond individual species and disrupts entire marine food webs. Changes in the abundance and health of key species like corals, shellfish, and plankton cascade through the ecosystem, affecting predator-prey relationships and ecosystem services. For example, declining populations of plankton can reduce food availability for higher trophic levels, impacting fish stocks and other marine animals that rely on them.
Economic Impacts
The economic consequences of ocean acidification are also significant:
- Fisheries: Fisheries are directly affected by the decline in shellfish populations and disruptions to fish stocks. This can lead to reduced catch yields and economic losses for commercial and artisanal fisheries.
- Tourism: Coral reefs are major attractions for tourism, contributing to local economies through activities like snorkeling and diving. The degradation of coral reefs due to acidification affects tourism revenue and can have broader economic repercussions for coastal communities.
- Coastal Communities: Many coastal communities rely on marine resources for their livelihoods, including fishing and tourism. As ocean acidification impacts marine ecosystems, these communities face economic challenges, including job losses and reduced income. The loss of vital marine species and ecosystem services further exacerbates these economic impacts.
What human actions are causing ocean acidification?
We already know that human activity is the driving force behind the disruption to the carbon cycle, and therefore is also the reason that our oceans are becoming increasingly acidic in nature. But what human activities contribute the most to this?
Fossil fuel consumption
The burning of fossils is the primary driving force of carbon emissions. We use fossil fuels such as coal, gas, and petroleum for a variety of purposes - from the running of our cars to the heating of our homes, to the fuelling of industrial operations - fossil fuels are ingrained into modern society.
💡 Fossil fuels supply around 82% of the world's energy and account for as much as 90% of global carbon dioxide emissions.
Deforestation
Another contributing factor is deforestation. Forests and vegetation are the Earth's other main carbon sink. Trees and plants absorb carbon dioxide for photosynthesis and store the carbon in their organic tissue.
👉 Deforestation means that this carbon is released back into the atmosphere when the trees are cut down and either decay or are burnt. This results in an increased amount of carbon dioxide in the atmosphere which places additional strain on the Earth's oceans.
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How bad is the situation?
We're now starting to see the real-life effects of ocean acidification on marine life around the world. However, ocean acidification does not impact all regions equally. The rate and severity of acidification can vary significantly based on geographic and environmental factors. Understanding these regional variations is crucial for developing targeted mitigation and adaptation strategies.
Arctic Ocean
The Arctic Ocean is experiencing some of the most rapid rates of acidification due to its unique conditions. Several factors contribute to this phenomenon:
- Cold water absorption: Cold water holds more carbon dioxide than warmer water, leading to higher concentrations of CO2 and increased acidification in the Arctic. This exacerbates the already challenging conditions for marine life in this region.
- Melting ice: The melting of sea ice reduces the amount of sunlight reflected back into space, increasing the absorption of heat by the ocean. This not only accelerates warming but also affects the chemical balance of the ocean, compounding acidification effects.
- Freshwater input: The influx of freshwater from melting glaciers and rivers dilutes seawater, altering its chemistry and potentially enhancing acidification. Freshwater inputs also affect the buffering capacity of the ocean, making it more susceptible to pH changes.
The rapid acidification in the Arctic poses significant risks to local marine species, such as shellfish and plankton, which are crucial to the Arctic food web. Additionally, changes in the Arctic can have broader implications for global climate patterns and marine ecosystems.
Coral Triangle
In contrast, the Coral Triangle - a region encompassing parts of Indonesia, Malaysia, the Philippines, and Papua New Guinea - faces its own set of challenges. Although the Coral Triangle is a biodiversity hotspot with high levels of marine life, it is also highly vulnerable to ocean acidification for several reasons:
- High coral diversity: The region's rich coral diversity means that different species respond differently to acidification. Some corals may be more resilient, while others may be severely impacted, leading to shifts in reef composition and function.
- Local stressors: The Coral Triangle is subjected to additional stressors such as overfishing, pollution, and coastal development. These combined pressures can amplify the effects of acidification and hinder the ability of marine ecosystems to adapt.
Mid-Latitude Oceans
Mid-latitude oceans, such as those off the coast of Europe and North America, also experience acidification but at a different rate and intensity. In these regions:
- Variability in pH: The rate of acidification varies depending on local ocean currents, water temperature, and other environmental factors. Some areas may experience more significant pH declines, while others may see slower changes.
- Economic and ecological impacts: These regions often have significant commercial fisheries and tourism industries, making them particularly sensitive to the impacts of acidification. Changes in shellfish populations, fish stocks, and marine ecosystems can have substantial economic and ecological consequences. In the Northwest region of North America for example, oyster farms are already being severely impacted. This has knock-on effects on food supply chains and the livelihoods of those who depend on the Earth's oceans for their income.
Tropical Oceans
Tropical oceans, including regions such as the Caribbean and Pacific Islands, also face acidification challenges:
- Coral reefs: Coral reefs in tropical waters are highly sensitive to acidification, which can affect coral growth and health. Since these reefs support diverse marine life and are vital to local economies, their decline can have severe implications.
- Ocean circulation patterns: Tropical oceans are influenced by complex circulation patterns that can affect the distribution and impact of acidification. Variations in these patterns can lead to regional differences in how acidification manifests.
Worryingly, the issue will only get worse as carbon dioxide levels in the Earth's atmosphere continue to rise.
The extent of future ocean acidification is directly linked to future increases in carbon dioxide in our atmosphere. If we continue on the current trajectory, seawater PH could decrease by as much as 0.4 units by the end of the century, which could prove catastrophic for many species of marine life, and hugely destabilizing for ocean ecosystems. This is why urgent action is needed to prevent any further acidification of the Earth's oceans.
Ocean acidification solutions
Reduce greenhouse gas emissions
The most obvious and effective way to prevent further ocean acidification is to drastically reduce carbon emissions. This means cutting down on - and ideally eliminating - our use of fossil fuels.
In order to make this a reality every sector of our global society needs to decarbonise. We need to find alternative energy sources and transition to renewable energy use, which means a collective effort by governments, companies, and individuals.
Until we make this change, carbon emissions will continue to rise which means that our oceans will continue to become more acidic.
Restoration of carbon sinks
Even if we entirely cut out the use of fossil fuels, there will still be a surplus of carbon dioxide in the atmosphere, we therefore also need to work to reduce this level by restoring and increasing the Earth's carbon sinks. This can be achieved through activities such as reforestation, afforestation, revegetation, and through sustainable forestry and agricultural practices.
Additionally, we can continue to invest in and develop technological carbon sinks to aid natural processes.
Policy and global initiatives
To effectively combat ocean acidification, global and national policies must align with the broader goals of reducing greenhouse gas emissions and protecting marine ecosystems. These policies support the necessary systemic changes and provide frameworks for collective action.
International agreements
- Paris Agreement (2015)
- The Paris Agreement represents a global commitment to limit global warming and, consequently, to mitigate ocean acidification. By targeting a reduction in greenhouse gas emissions, the agreement helps to address one of the root causes of ocean acidification. Its framework encourages countries to set and achieve emission reduction goals, which are crucial for stabilizing ocean chemistry.
- UN Decade of Ocean Science for Sustainable Development (2021-2030)
- This UN initiative focuses on enhancing our understanding of ocean processes, including acidification. It promotes international collaboration and investment in ocean science, aiming to develop innovative solutions for mitigating the effects of acidification on marine ecosystems. The Decade emphasizes the need for integrated strategies to tackle the complex challenges of ocean health.
- Convention on Biological Diversity (CBD)
- The CBD acknowledges the impacts of climate change and ocean acidification on marine biodiversity. It encourages member states to integrate ocean acidification considerations into their national strategies for biodiversity conservation, thereby supporting broader efforts to protect marine life from changing ocean conditions.
National policies:
| Country/Region | Action/Initiative | Description |
|---|---|---|
| United States | Federal Actions on Ocean Acidification | The U.S. National Oceanic and Atmospheric Administration (NOAA) actively monitors and researches ocean acidification through its Ocean Acidification Program. This program funds studies to understand the impacts on marine ecosystems and supports the development of adaptation and mitigation strategies. |
| United States | Climate Action Plan | The U.S. Climate Action Plan includes initiatives to reduce greenhouse gas emissions by promoting renewable energy and improving energy efficiency. These actions contribute to lessening the rate of ocean acidification by addressing the root cause - excessive CO2 emissions. |
| United Kingdom | UK Marine Strategy | The UK Marine Strategy aims to protect and preserve the marine environment. It includes provisions for monitoring and assessing the impacts of ocean acidification on marine life and ecosystems, and supports actions to mitigate these effects through national policies and strategies. |
| United Kingdom | Net Zero by 2050 | The UK government has committed to achieving net-zero greenhouse gas emissions by 2050. This ambitious target involves transitioning to renewable energy sources, enhancing energy efficiency, and implementing policies to reduce carbon emissions across all sectors, thereby contributing to the mitigation of ocean acidification. |
| European Union | Marine Strategy Framework Directive (2008/56/EC) | This directive provides a comprehensive approach to protecting Europe’s marine environment. It includes specific measures to address ocean acidification by monitoring its effects and developing strategies to improve marine ecosystem health. |
| European Union | European Green Deal | The European Green Deal is the EU’s overarching policy framework for achieving climate neutrality by 2050. It includes measures to reduce greenhouse gas emissions, which will help mitigate ocean acidification. The Deal promotes clean energy, sustainable industries, and other initiatives that directly contribute to reducing the causes of acidification. |
The implementation of international agreements and national policies is critical in the fight against ocean acidification. By aligning global and national efforts to reduce greenhouse gas emissions and protect marine ecosystems, these initiatives provide a structured approach to tackling the problem. Effective policy action, combined with ongoing research and public awareness, will be essential to safeguarding the health of our oceans and the myriad forms of life they support.
The bottom line
The bottom line is that even if we stop all emissions and work to increase the Earth's carbon sink capacity, ocean acidification will not end immediately.
We can expect to see a lag time before feeling the benefits of our actions. We can liken it to a car - even if you slam on the breaks, the car won't come to an immediate stop.
It's the same thing with climate change and ocean acidification - even if we eliminate emissions the climate will continue to warn and we'll continue to see the effects of ocean acidification for many years to come.
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