Ocean Acidification

Professor Pablo Sánchez Jerez is part of the international team that has produced the  World Ocean Assessment

The University of Alicante is participating in the largest scientific assessment driven to date by the United Nations to analyse the health of the world’s oceans. This international project brings together hundreds of specialists from across the globe and currently serves as the primary global benchmark for guiding marine conservation policies internationally.

The Alicante institution’s involvement is delivered through the work of Professor Pablo Sánchez Jerez, from the Department of Marine Sciences and Applied Biology. He is part of the international team of authors for the third edition of the World Ocean Assessment, the most ambitious report compiled so far on the current state of seas and oceans, coordinated by the United Nations.

According to Sánchez Jerez, the ocean sustains processes fundamental to life on Earth, and we need to understand how its ecosystems are changing with the utmost scientific rigour in order to make effective decisions. Participating in this assessment means contributing directly to the global knowledge required to protect one of the most vital systems for the future of humanity.

The oceans constitute Earth’s primary life-support system. Covering more than 70% of the planet’s surface, they produce approximately half of the oxygen we breathe thanks to phytoplankton activity, regulate the global climate by transporting heat between continents, absorb around a third of the carbon dioxide generated by human activities, and host an extraordinary biodiversity that sustains complex ecological networks and numerous economic activities.

The health of these ecosystems is closely linked to human well-being. Activities such as fishing, aquaculture, coastal tourism, maritime transport, and numerous industrial sectors depend directly on the good condition of marine ecosystems. However, these natural systems currently face unprecedented challenges stemming from climate change, pollution, habitat loss, the overexploitation of resources, and growing human pressure on coastal areas. 

Against this backdrop, the international scientific community agrees that the conservation and restoration of marine ecosystems is one of the major environmental priorities of the 21st century. Among the most effective tools are marine reserves and marine protected areas (MPAs)—spaces capable of recovering exploited species populations, conserving habitats of high ecological value, and increasing ecosystem resilience against global disturbances such as planetary warming. 

Numerous scientific studies have shown that these protected areas function as genuine havens for biodiversity. They generate benefits that transcend their own boundaries by exporting larvae, juveniles, and adults to adjacent zones, thereby supporting both conservation and the sustainability of fisheries. It is precisely this need for robust scientific information to guide marine management and conservation that has driven the production of this third edition of the World Ocean Assessment. This global evaluation provides a comprehensive overview of the changes oceans are undergoing, the risks they face, and the potential solutions needed to guarantee their future sustainability.

The assessment is conclusive: the oceans are under increasing pressure from climate change, pollution, resource overexploitation, and the progressive degradation of marine ecosystems. Among the most worrying conclusions are the accelerated warming of ocean waters, marine acidification, rising sea levels, the expansion of oxygen-depleted zones, and the widespread accumulation of plastic and microplastic waste in practically every oceanic ecosystem on the planet.

The report further warns that the loss of marine biodiversity represents a direct threat to ecological stability and to numerous essential ecosystem services that sustain society. In this context, expanding and improving the management of marine protected areas emerges as one of the main international recommendations to strengthen ocean resilience against global change.

Acuicultura marina 

Within this international assessment, Professor Pablo Sánchez Jerez has specifically participated as an author of the chapter dedicated to medium- and large-scale marine aquaculture. This is a strategic sector called upon to play a decisive role in sustainable food production within a context marked by global population growth, an increased demand for marine protein, and the need to reduce pressure on wild fish stocks. “The future of global food security will largely depend on developing increasingly sustainable marine production systems. Aquaculture must grow, but it must do so by relying on technological innovation, environmental sustainability, and a balanced coexistence with natural ecosystems,” the researcher notes.

The chapter analyses the evolution of marine aquaculture on a global scale and addresses strategic aspects such as technological innovation, the digitalisation of production systems, the environmental sustainability of farms, the social acceptance of the activity, and the sector’s adaptation to the effects of climate change. Furthermore, it identifies significant knowledge gaps and establishes research priorities necessary to advance towards more sustainable production models compatible with marine conservation.

…

Minister of Water, Environment and Climate Change, Hon. Matthew Samuda, provides details about the outcomes of the 11th Our Ocean Conference held in Mombasa, Kenya, during a Post-Cabinet Press Briefing at Jamaica House on Wednesday (June 24). Photo: Adrian Walker.

Jamaica signed on to four key international environmental partnerships during the 11th Our Ocean Conference in Mombasa, Kenya, held from June 16 to 18.

The agreements are the Caribbean Ocean Coordination Mechanism, the Ocean Acidification Alliance, the Action in Blue Regional Network, and the Mangrove Breakthrough.

Minister of Water, Environment and Climate Change, Hon. Matthew Samuda, provided the details during Wednesday’s (June 24) Post-Cabinet Press Briefing at Jamaica House.

He explained that the Caribbean Ocean Coordination Mechanism is a platform that “shares the burden of environmental management of our shared Caribbean Sea”.

Anchored by the United Nations Environment Programme (UNEP), the mechanism places Jamaica in a leadership position to manage many of the issues that face Caribbean nations, he pointed out.

As it relates to Ocean Acidification Alliance, he explained that it is a network of scientists who are “specifically focused on the issue of ocean acidification, which is critical to the health of our coral reefs, fisheries and, indeed, to tourism”.

The nation also joined the Action in Blue Regional Network, which is focused on coordinating the protection of 30 per cent of the Caribbean Sea.

“That is something that Jamaica would have lobbied for from as far back as 2015, when Jamaica joined what is called the High Ambition Coalition for Nature, which led the way in calling for 30 per cent protection of our marine environment,” the Minister stated.

Meanwhile, through the Mangrove Breakthrough, which is managed by an alliance chaired by Colombia and Jamaica, the country will be working with partner nations and institutions to strengthen efforts on mangrove protection and restoration.

The Minister noted that Jamaica needs support in protecting its mangroves, especially along the south coast “where we are exposed to heavy storm surge in times of storms and have low coastal defences”.

Meanwhile, the Minister noted that while in Kenya, he had a bilateral meeting with the Green Climate Fund, which is also currently in Jamaica for a technical mission.

“While there, it was announced that Jamaica was approved for an additional US$2.1-million grant being managed by the CCCCC (Caribbean Community Climate Change Centre), which is the CARICOM unit that manages climate change, to assist Jamaica with getting projects ready for submission for significant grant funding,” Mr. Samuda shared.

The grant is titled ‘Catalysing Climate Action by building Jamaica’s NDA Capacity & Country Investment Platform’.

CARICOM has indicated that it will help Jamaica access international climate financing and develop a pipeline of projects needed to protect its people, economy and environment.

Ocean protection is too often treated as a moral issue, yet this conceals a harder truth: our oceans are vital economic systems under mounting pressure. In fact, if they knew what was good for them, every mercenary across the planet would want to protect our great blue expanse.

In many ways, the ocean operates like the world’s largest bank. Storing capital by preserving marine biodiversity, upholding food systems, and generating returns through fisheries, eco-tourism and coastal protection. Perhaps most importantly, it absorbs 30% of carbon dioxide (CO₂) emissions annually, protecting us and the global economy, at least in part, from our own polluting activities.

As the ocean’s investors, however, we are not making smart financial decisions. 

Overfishing, bottom trawling, and pollution reflect a familiar pattern: prioritising short-term extraction over long-term economic resilience. We are running down natural capital while congratulating ourselves on marginal gains. Yet the greatest financial threat to the ocean economy is still widely misunderstood and dangerously undervalued.

That threat is ocean acidification. 

The short-term, short-sighted mindset

For years, we have hugely overstated the capacity of blue carbon habitats such as seagrasses, mangroves and saltmarshes, to solve our emissions problem. These ecosystems are rightly celebrated for their ability to lock away carbon and support biodiversity, but they are too often framed as quick wins – assets that can be restored or offset on short timelines.

In reality, while their capacity to store carbon is exceptional, the rate at which they absorb it is slow. The habitats that hold the greatest carbon stocks – and provide the strongest protection – are typically ancient, intact systems that have accumulated value over centuries. In economic terms, these ecosystems function less like high-yield savings accounts and more like environmental pensions. They deliver steady, compounding returns, but only if they are safeguarded and invested in over decades. 

The lesson is clear. Even when we act in the ocean’s favour, we often do so through a short-term lens – one that favours visible, measurable gains over long-term stability.

Ocean acidification exposes the flaw in this thinking.

Ocean acidification, while not directly tied to climate change, is an issue that is becoming more problematic as the burning of fossil fuels pumps more carbon dioxide into the atmosphere. The carbon dioxide emitted into the atmosphere builds up and dissolves into the oceans, where it reacts with water to create carbonic acid.

Upwelling zones, water coming from the ocean floor to the surface, tends to be more acidic than the water in the mid to top levels of the ocean. Coastal ecosystems have adapted to tolerate the naturally low pH levels of the water. However, the addition of dissolved carbon dioxide at the surface is leading to a higher concentration of acidic water in coastal ecosystems, especially around strong upwelling zones. Ecosystems are not prepared to tolerate the speed of change and could suffer severe consequences if measures aren’t taken to reduce the amount of carbon dioxide in the atmosphere.

For more information on this study, you can find the full news release here.

The waters of Puget Sound are more susceptible to ocean acidification and sliding faster into dangerous territory for its marine wildlife than other places around the world, a new study shows.

Should the trend continue, our marine wildlife and fisheries will likely suffer greatly years or decades earlier than previously anticipated, said Alex Gagnon, a chemical oceanographer with the University of Washington.

“This sounds pretty bad,” Gagnon wrote in an email. “And it is.”

Gagnon and a team of colleagues from UW published their novel study earlier this month, outlining their findings and serving as a new warning for the potentially catastrophic risk posed by climate change. They leaned on a series of chemical analyses but also a bit of detective work, delving further into the past than those who preceded them.

Put simply, as our oceans absorb increasing amounts of carbon dioxide, a greenhouse gas produced as we burn fossil fuels, their chemistry becomes more corrosive. This acidification has accelerated since the start of the Industrial Revolution. The larger our population and emissions grew, the more carbon dioxide we pumped into the atmosphere. The ocean absorbs about a quarter of the emissions humans generate.

…

Now the world sits on a major precipice.

Not only is the accumulation of these greenhouse gases dangerously warming our atmosphere, it’s also pushing our ocean chemistry lower and lower on the pH scale. Already, the world’s oceans are about 30% more acidic than they were 200 years ago, according to a release from UW announcing the study.

Older, deeper waters tend to be more acidic, Gagnon said. This is because organic matter like dead fish and plants sink, and as they decompose or are eaten by microscopic organisms, they release carbon dioxide, turning the water more corrosive.

Already, Pacific waters up and down the North American coast are more acidic than those of most other places in the world, Gagnon said. This is due to a combination of wind patterns, undersea topography (known as bathymetry) and other factors, which churn up those deep and acidic waters and bring them closer to the surface. 

As more carbon dioxide from fossil fuel pollution enters the oceans, the water gets more acidic. Researchers in a new study note that the ocean has gotten 30 to 40% more acidic since the beginning of the industrial revolution.

Here & Now‘s Scott Tong speaks to Matt Simon, senior staff writer at Grist, about what increasing ocean acidification means for marine life and the future of the planet as a whole.

Listen here: https://player.wbur.org/hereandnow/2025/10/02/acidic-oceans

A new report released yesterday by the Department of Energy purports to provide “a critical assessment of the conventional narrative on climate change.” But nine scientists across several different disciplines told WIRED that the report mishandled citations of their work by cherry-picking data, misrepresenting findings, drawing erroneous conclusions, or leaving out relevant context.

…

The DOE says that it is opening the report up to a public comment process. In an email, Department of Energy spokesperson Andrea Woods said that the questions WIRED sent over about the use of research in specific portions of the report were too complex for the agency to answer thoroughly on a short turnaround, and encouraged scientists who spoke with WIRED to submit a public comment to the federal register.

…

The DOE report’s section on ocean acidification cites research by Josh Krissansen-Totton, an assistant professor at the University of Washington who specializes in planetary science and biogeochemistry, to support a claim that “the recent decline in [ocean] pH is within the range of natural variability on millennial time scales.” Research has shown that the oceans have been absorbing CO₂ from the atmosphere since the beginning of the industrial revolution, causing it to become considerably more acidic over the past two centuries.

“Ocean life is complex and much of it evolved when the oceans were acidic relative to the present,” that section of the report states. “The ancestors of modern coral first appeared about 245 million years ago. CO₂ levels for more than 200 million years afterward were many times higher than they are today.”

Krissansen-Totton told WIRED in an email that his work on ocean acidity billions of years ago has “no relevance” to the impacts of human-driven ocean acidification today, and that today calcium carbonate saturation is quickly diminishing in the ocean alongside rising acidity. Dissolved calcium carbonate is essential for many marine species, particularly those that rely on it to build their shells.

“The much more gradual changes in ocean pH we observe on geologic timescales were typically not accompanied by the rapid changes in carbonate saturation that human CO₂ emissions are causing, and so the former are not useful analogs for assessing the impact of ocean acidification on the modern marine biosphere,” he says.

Luis Acevedo-Soto, Thunder Bay National Marine Sanctuary’s Ernest F. Hollings Scholarship intern and rising senior at the University of Puerto Rico, gave updates in a lecture on Wednesday on his research at the sanctuary and the freshwater acidification project.

…

According to TBNMS, the freshwater acidification monitoring project is a response to a lack of data concerning acidification in the Great Lakes. Results from this project will inform future studies into climate-related impacts and TBNMS resources. TBNMS also states that the monitoring project will improve understanding of acidification and potential impacts on the Great Lakes ecosystem.

In his presentation at the Great Lakes Maritime Heritage Center, Acevedo-Soto explained that the freshwater acidification monitoring project is important because it tracks how pH levels in the Great Lakes can potentially affect the food web. Acidic water breaks down calcium carbonate which makes up shells of organisms in the Great Lakes.

“Calcium carbonate is the first compound of the creation of shells,” Acevedo-Soto said. “For every organism, for example, muscles or some types of plankton … these organisms are super important for the food web. If we are reducing the population of them, we are going to affect the entire food chain… that will directly affect the fish.”

Acevedo-Soto noted that if the Great Lakes continue to become more acidic, then not only will the environment be affected but so will the economy since fishing, commercial and recreational, contributes largely to Michigan’s economy.

Overall, Lake Huron has an average pH level of 8.1, according to Acevedo-Soto. He stated that this average makes Lake Huron a “base” on a pH scale, and any deviation in pH levels can impact the Great Lakes ecosystem.

“Organisms here are adapted to this environment,” he said. “Small changes in the pH can be terrible.”

Acevedo-Soto stated that he collected samples from seven TBNMS sites for his research. His conclusion from analyzing the samples is that there is a “slight decreasing trend in pH” at greater depths in Lake Huron. According to Acevedo-Soto, this may indicate ongoing acidification trends in the Great Lakes.

In addition to his findings, Acevedo-Soto noted that factors such as depth, temperature, and “biological activity” influences the chemistry of the Great Lakes. As the summer months wear on and the water gets warmer, he explained that the pH levels decrease (i.e., it becomes more acidic).

“This can be because the microbial respiration and the photosynthetic processes are improving … that also helps the CO2 to be dissolved,” Acevedo-Soto said. “So that makes the water more acidic.”

He noted that Lake Huron’s water becomes more acidic at greater depths due to less CO2 being dissolved and less mixing of water.

Globally, Acevedo-Soto explained that acidification has become a concern in both freshwater and saltwater environments. In the ocean, coral reefs are directly impacted by acidification. Acevedo-Soto said he had the opportunity to intern in the Caribbean, but recognized the lack of research on acidification in freshwater systems.

“There’s more research on acidification in the ocean … the problem is actually in the freshwater environments,” Acevedo-Soto said.

…