Ocean Acidification

On a clear day at Plymouth marina you can see across the harbour out past Drake’s Island – named after the city’s most famous son, Francis Drake – to the Channel. It’s quite often possible to see an abundance of marine vessels, from navy ships and passenger ferries to small fishing boats and yachts. What you might not spot from this distance is a large yellow buoy bobbing up and down in the water about six miles off the coast.

This data buoy – L4 – is one of a number belonging to Plymouth Marine Laboratory (PML), a research centre in Devon dedicated to marine science. On a pleasantly calm May morning, Prof James Fishwick, PML’s head of marine technology and autonomy, is on top of the buoy checking it for weather and other damage. “This particular buoy is one of the most sophisticated in the world,” he says as he climbs the ladder to the top. “It’s decked out with instruments and sensors able to measure everything from temperature, to salinity, dissolved oxygen, light and acidity levels.”

It’s the hourly recordings of this last measurement, the pH of the water, that are adding to a picture locally and globally that is increasingly concerning scientists.

The results show that ocean acidification is rising – and it is doing so at an alarming rate. Ocean acidification, often called the “evil twin” of the climate crisis, is caused when carbon dioxide is rapidly absorbed into the ocean, where it then reacts with water molecules leading to a fall in the pH of the seawater.

Six high school students at the Alabama School of Math and Science are taking science to the sea. They are students from all over the state of Alabama doing college-level research projects that deal with our coastal ecosystems.

Students and instructors at working on research projects in one of the ASMS labs

All of these projects deal with ocean acidification, which occurs when excess carbon dioxide in the atmosphere reacts with water and creates carbonic acid. Lillian Abernathy, a student researcher at ASMS, explains, “Carbonic acid takes away the necessary nutrients that oysters need to grow their shells.”

Here are the six projects these students are researching:

• Calcium-binding proteins in Crassostrea virginica as indicators of in situ pH stress (Lillian Abernathy, a senior from Geneva County).
• Evaluating the impact of phytochemicals on reducing pathogenicity in Crassostrea virginica under ocean acidification (Naria Khristoforova, a senior from Shelby County).
• Effect of ocean acidification, Perkinsus marinus, submerged aquatic vegetation on apoptosis of hemocytes in Crassostrea virginica (BoKyeong Kim, a junior from Autauga County).
• Ocean acidification’s impact on the susceptibility of Perkinsus marinus in Crassostrea virginica (Hyerin Park, a junior from Autauga County)
• Effects of ocean acidification on Pif gene expression in Crassostrea virginica (Kayty Phan, a junior from Mobile County).
• Lower pH levels decrease the productivity of the nitrogen cycle in Crassostrea virginica pallial fluid (Emma Kate South, a junior from Baldwin County)

“I’m looking at gene expression and what’s called the extra pallial fluid cavity in the eastern oyster,” said Emma Kate South, another student researcher.

Ocean acidification can also affect the oyster’s immune system. Hyerin Park notes that this makes oysters more susceptible to Parkinsus marinas, which eats away at the oyster’s tissue. “It’s a really common pathogen down here and it really affects a lot of the oysters,” Park said.

Protecting oysters is very important for conserving our local habitats and preserving a way of life for many along the Gulf Coast. Abernathy stated, “Maintaining those populations is something I’m really passionate about because people need to make money.”

The Alabama School of Math and Science is able to provide these students with these research opportunities thanks to university level labs. This research helps students decide their future.

“Funding from NOAA from the education grant gives us the ability to do this class…and a skillset that is transferable from high school on to college,” said Dr. Rebecca Domangue.

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The Alpena High School Underwater Research Robotics (UR2) team collaborated last summer with researchers at the National Oceanic and Atmospheric Administration’s Thunder Bay National Marine Sanctuary to address the issue of increased acidification in the Great Lakes.

The team discovered that the surge in acidity is caused by the absorption of carbon dioxide (CO2) from activities such as fossil fuel combustion, leading to a decrease in lake and ocean waters’ potential hydrogen (pH) levels.

The Great Lakes Environmental Research Lab and TBNMS requested that UR2 leverage their marine technology expertise to create a sampler that can fit a remotely-operated vehicle (ROV).

“Our initial approach involved using a Niskin bottle to take water samples attached to the ROV,” a summary of the project, called WARP (Water Acidification Research Project), explains. “Once the ROV reached the designated depth and location, the Niskin bottle was released using the ROV’s grabber. Although this method worked reasonably well, the research protocol stipulated that the water sample had to be sealed at depth and shielded from exposure to surface air.”

Monaco is once again at the forefront of marine conservation, hosting the second IAEA Winter School on Ocean Acidification and Multiple Stressors this past November. Over two weeks, a group of early-career scientists from around the world got hands-on experience and expert guidance on how to protect our oceans from rising threats like climate change, pollution, and acidification.

The world’s oceans are under pressure like never before, with human activities causing ripple effects that threaten marine life and coastal communities. Overfishing, pollution, and shifting ocean chemistry don’t just act alone—their combined effects can be far worse than expected, making it even harder to predict and prevent damage. That’s where this program steps in, training the next generation of marine scientists to understand these complex interactions and find solutions to protect ocean ecosystems.

Bringing together 12 young researchers from 11 countries, the Winter School mixed cutting-edge science with real-world applications. Participants learned to distinguish between different types of ocean stressors and conducted lab experiments on coral health, investigating how acidification, warming waters, and pollutants like lithium impact marine life. Their findings will contribute to a global research effort aimed at better predicting and mitigating these effects.

Host Dave Schlom is joined by two researchers who have connections to UC Davis’s Bodega Marine Laboratory on the Northern California coast.

Emily Longman, now a marine biologist at the University of Vermont, was a leader in a detective story with roots in UC in the days leading up to World War II.

Two young undergrads did a study of mussel colonies at Bodega in 1941. Their unpublished paper was found recently and Longman led a team to see how the mussel colony had changed in the course of 80 years.

Astonishingly, they found that while mussels are struggling on parts of the California coast, they are thriving at the original study site!

Then, UC Berkeley Professor Rachel Carlson visits with Dave to discuss her work on mapping ocean acidification along the Pacific coast and its implications for marine life as our climate changes.

Climate change is causing serious problems for our oceans, and it’s crucial that lawmakers, scientists, and leaders act quickly. Two major issues are ocean acidification and rising sea levels, which are affecting millions of people, marine life, and coastal areas. These changes are forcing us to rethink how we manage and protect our oceans.

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Ocean acidification is another major problem caused by climate change. The ocean absorbs carbon dioxide, making it more acidic. Since the Industrial Revolution, ocean acidity has increased by 30%. This harms marine life, especially creatures like corals and shellfish, which need calcium carbonate to form their shells. As these species struggle to survive, it affects entire ecosystems, including fisheries, coastal protection, and biodiversity. Disappearing coral reefs are also hurting the marine life that depends on them.

Aquaculture and fishing industries are also impacted. Many communities rely on shellfish and other marine species for jobs and food, but their numbers are shrinking due to acidification. This leads to economic problems, especially in developing countries. International cooperation is needed to help these areas find new ways to improve their economies. Even though scientists are still learning about ocean acidification, global efforts to share data and find solutions are essential.

Since the oceans connect the entire world, all countries need to work together to solve these problems. Rising sea levels and acidification cannot be fixed by one country alone. Before climate change became a major issue, maritime laws like the United Nations Convention on the Law of the Sea were created. These laws must be updated to address modern problems like ocean acidification, rising sea levels, and the rights of countries affected by climate change. The Paris Agreement recognizes the importance of oceans in fighting climate change, but more action is needed. For example, using ecosystems like mangroves to absorb carbon dioxide can help both coastal communities and the environment.

Small and developing countries often lack the resources to deal with climate change. Supporting them in adapting to rising sea levels and ocean acidification should be a top priority for international organizations like the Green Climate Fund. Regional cooperation is also important. Organizations like the Arctic Council and the Pacific Islands Forum help countries address local issues, and strengthening these groups can lead to better solutions.

Ocean acidification is a very real environmental threat. But what’s the science behind how it works?

Oysters have been farmed in the US Pacific Northwest of the United States for thousands of years. A source of local pride, and a tenet of regional folklore, their history has made them a source of regional pride. Native American mythology, for instance, tells of man being born from an oyster, and European settlers understood them to be a gift from God. This reverence has survived, and to this day the creatures exist regionally as cultural and economic touchstones.

However, in 2007, oyster farmers in Washington State and Oregon began to notice large numbers of their stocks mysteriously disappearing, and oyster seeds dying at an unprecedented rate. Seed production in the Northwest dropped by 80% between 2005 and 2009, a shift that devastated local economies and livelihoods. The culprit was a newly discovered phenomenon – often dubbed as ‘climate change’s evil twin’ – called ocean acidification.

Ocean acidification is the reduction in the pH (and therefore ‘acidification’) of the oceans due their absorption of carbon dioxide (CO₂) from the atmosphere. This is largely the product of human activity. Since the industrial revolution, human action, such as burning fossil fuels and using land have released 2.3 trillion tonnes of CO₂  into the atmosphere. Our oceans are bearing the brunt of this, absorbing one third of all anthropogenic carbon emissions, the equivalent of over 500 billion Volkswagen Beetles dumped into the sea. This uptake has raised the ocean’s acidity by 30%, changing the pH from 8.2 to 8.1; a shift that has carried extreme consequences for marine life. 

So, how are these changes manifesting? The most impactful effect has been the reduction of carbonate minerals (minerals containing carbonate ions e.g. aragonite) in the oceans. Without these ions, sea creatures are unable to effectively construct their shells, rendering them brittle and stunting their growth. The effect of this is concentric. Responsible for filtering and cleaning the surrounding water, and providing other organisms with habitat and food, the effect of their mortality is not contained, and has a knock-on effect on marine eco-systems more broadly. Other ocean habitats are endangered by the acidification too. Coral reefs, for instance, struggle with skeleton growth, and stop growing altogether at a pH of below 7.8. 

The effect, then, extends beyond the oyster. As oceans continue to acidify worldwide, fishing industries will continue to collapse, creating a loss of income and dietary protein that will be felt around the globe; the United Nations estimates that the industry supports the livelihoods of 10-12% of the world.

Coupled with temperature increase and oxygen loss, the oceans are facing what The Guardian calls a “triple threat” which is devastating marine ecosystems. As it acidifies, the ocean loses its efficacy as a carbon sink, meaning that it can no longer absorb the gases that contribute to the greenhouse effect and global heating. The effect is one of accumulation.

Frighteningly, this effect is reaching a tipping point. A recent report by the Potsdam Institute for Climate Impact Research revealed that we are nearing an irreversible  threshold for ocean acidification, which, if broached, would be the seventh of the nine climate thresholds that are required for Earth to support life. It’s sobering news, to say the least.

However, not all hope is lost. While the effects of ocean acidification are most likely irreversible, the rate of change could be slowed down. Scientists believe that cutting down on fossil fuels emissions could go a long way in preserving a rapidly diminishing marine ecosystem. According to the IPCC  (Intergovernmental Panel on Climate Change), a serious reduction in emissions could spare up to 30% of coral reefs from extinction. 

And while the biggest emitters may be major fossil fuel companies, we as individuals can still make a difference. By cutting down our individual carbon emissions (reducing meat consumption, for instance, can reduce our carbon footprint by up to 30%) we can partake in the conservation of what is a fast dying, yet incredibly important, aspect of our ecosystem. Research suggests that we have five years to make a change. The time to act is now. 

Ocean acidification is an urgent environmental challenge caused by rising atmospheric carbon dioxide (CO2) levels, mainly due to human activities. It involves a continuous decrease in the pH of ocean water, with profound implications for marine ecosystems and the communities that rely on them. When CO2 is absorbed by seawater, it reacts to form carbonic acid, resulting in lower pH levels and increased acidity in the oceans.

Since the Industrial Revolution – a period of major technological and economic change that transformed society from an agrarian economy to one based on industry and manufacturing – ocean pH has dropped from about 8.19 to approximately 8.05, representing a 30 per cent increase in acidity. Although this change may seem minor, it can significantly affect marine life. 

The primary concern regarding ocean acidification lies in its effects on marine organisms, especially those that depend on calcium carbonate to form their shells and skeletons. They include corals, molluscs and certain plankton species. Ocean acidity decreases the availability of carbonate ions, which is crucial for these organisms, making it increasingly difficult for them to construct and maintain their structures. This physiological stress from lower pH levels can disrupt marine species’ growth, reproduction and overall health.

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Ocean acidification has been referred to as “climate change’s evil twin” because it intensifies many of the same issues associated with global warming and presents unique challenges. While climate change leads to rising ocean temperatures and altered weather patterns, ocean acidification directly threatens marine chemistry and biology.

The pace of acidification is alarming, estimated to be about 100 times faster than any natural changes over the past 650,000 years, indicating that human activities are dramatically altering ocean ecosystems at an unprecedented speed. These changes threaten individual species and entire food webs. 

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The main drivers of ocean acidification are anthropogenic CO2 emissions from burning fossil fuels, deforestation, and industrial processes. Oceans have absorbed approximately one-third of the CO2 released into the atmosphere since the Industrial Revolution. 

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Different regions of the ocean experience varying levels of acidification due to factors such as geographical location, water temperature and local environmental conditions. Coastal areas often face higher rates of acidification compared to open ocean regions because they are influenced by freshwater runoff that carries nutrients and pollutants from land. This runoff can lead to localised increases in CO2 levels and subsequent acidification.

Warmer waters hold less dissolved oxygen and can amplify the effects of acidification on marine life. Regions with high biological activity, like upwelling zones where nutrient-rich waters rise to the surface, may also experience more pronounced effects due to natural CO2 release from decomposing organic matter. These regional differences underscore the complexity of ocean acidification as a global issue. In contrast, some areas may adapt better than others. However, the overall trend is troubling for marine ecosystems worldwide.

Efforts to combat ocean acidification include mitigation strategies to reduce CO2 emissions and adaptation measures designed to help marine ecosystems cope with changing conditions. International agreements such as the Paris Agreement seek to limit global warming by curbing greenhouse gas emissions. Research initiatives are underway to understand better how different species respond to varying acidity levels and temperature changes. This knowledge can guide conservation efforts and help develop strategies for restoring affected ecosystems.

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The implications of ocean acidification extend beyond ecological concerns to pose economic threats. Due to changing ocean chemistry, coastal communities that depend on fishing and tourism face potential fish stocks and coral reef health declines. As key species become less viable or disappear altogether, food security for millions could be compromised. Cultural practices and traditions tied to these environments may also be affected as marine ecosystems shift. 

Recent studies call for immediate action before irreversible damage occurs within our oceans. The United Nations warns that without significant reductions in greenhouse gas emissions globally, we risk further accelerating this crisis with dire consequences for marine life and human communities worldwide.

L’association étudiante de La Rochelle LemonSea relève le défi de sensibiliser à l’acidification des océans. Ateliers avec les scolaires, jeu de société, podcasts, interventions publiques… Les bénévoles s’attellent à la tâche.

Les bénévoles de LemonSea ont tenu un stand de sensibilisation à l’Aquarium de La Rochelle durant la Fête de la science. LP/Amélia Blanchot

Ils étudient les sciences de la vie à La Rochelle université, en très grande majorité. Ou plutôt elles, car seulement deux garçons garnissent les rangs des 32 bénévoles que compte LemonSea. Basée à La Rochelle (Charente-Maritime), cette association étudiante a pour objectif de sensibiliser à l’acidification des océans. Dans le registre de la dégradation environnementale, « tout le monde a déjà entendu parler de la pollution plastique. Mais l’acidification des océans, le grand public connaît peu. C’est technique et assez compliqué à vulgariser », reconnaît Jeanne Dumas, bénévole.

« C’est justement ce qui est motivant ! Nous organisons des ateliers de sensibilisation et c’est gratifiant de réussir à expliquer les enjeux autour de cette thématique préjudiciable aux écosystèmes marins », affirme Louise Naudin, la présidente. Durant la Fête de la science, les étudiantes se sont mobilisées, notamment en tenant un stand à l’Aquarium de La Rochelle.

Ramassage de déchets, podcast…

Tubes à essai pour expliquer l’acidité, animaux marins en bois pour présenter les impacts sur les organismes, quiz, jeu de sept familles… Tout un attirail était de sortie pour décrypter les conséquences de la diminution progressive du PH. « Les émissions de CO2 acidifient l’océan, qui en absorbe une partie. Par exemple, les ptéropodes (type d’escargot de mer) sécrètent du calcaire pour construire leurs coquilles et s’y abriter. Avec l’acidification, ils en émettent moins. Cela peut mettre en jeu la vie de l’espèce. Tout comme le blanchiment des coraux, peut-être davantage médiatisé », décrypte Louise Naudin.

Les bénévoles de LemonSea proposent plusieurs types d’interventions à ce sujet. « Nous faisons des animations dans des classes et lors d’événements particuliers, nous organisons des ’’clean walk’’, à savoir des opérations de ramassage de déchets sur les plages. Nous avons également un podcast (Radio Seatron). À La Rochelle, la biologie marine est au cœur des préoccupations de l’université. D’ailleurs nous faisons aussi intervenir des enseignants-chercheurs pour se tenir informés », détaille la présidente.