Applications open: Sixth International Symposium on the Ocean in a High-CO2 World

Published 28 July 2026 Events Closed

The IAEA’s Ocean Acidification International Coordination Centre (OA-ICC) (https://www.iaea.org/ocean-acidification) is cooperating on the organization of this event and has limited funds at its disposal to help meet the costs of the attendance of selected participants from eligible IAEA Member States to present their work and foster international collaboration at the conference.

The deadline to apply is Friday September 4th. To apply, applicants will need to submit their application through their national authority to the IAEA – in most cases, this will be your country’s permanent mission to the IAEA.

If you have questions on the application procedure, please contact Ms Lina Hansson (L.Hansson(at)iaea.org) or Ms Carolina Galdino (C.Galdino(at)iaea.org).

Dates: 13–16 October 2026

Location: Tākina Convention & Exhibition Centre, Wellington, New Zealand

Form A and Form C

Introduction
Held every four years, the International Symposium on the Ocean in a High-CO2 World is the largest global gathering on ocean acidification. The Symposium brings together scientists, communities, policymakers, and stakeholders from sectors such as fisheries and aquaculture to share and discuss the latest research on the impacts of ocean acidification on marine life and potential solutions to counter its effects. The Sixth edition will maintain a focus on ocean acidification but will also expand to consider other ocean climate impacts, such as ocean warming and deoxygenation, particularly in a multiple-driver context. Research on marine carbon dioxide removal interventions, which have been suggested to mitigate climate change and ocean acidification, will also be a key part of the conference. More information on the seven key themes of the conference, its 22 workshops, and the detailed programme can be found on the Symposium website (https://highco2-vi.org/).

Objectives
The purpose of the event is to provide a space for scientists from the ocean acidification (OA) research community to disseminate the results of their research, discuss joint projects with peers and engage with stakeholders. The event, held every four years, is the world’s largest conference on OA and related stressors.

Target Audience
Scientists from developing IAEA Member States. Priority will be given to early-career scientists actively working on ocean acidification, multiple stressors or marine carbon dioxide removal (mCDR). Applicants should hold a university degree in marine biology, oceanography or a related scientific field. Female scientists are encouraged to apply.

Working Language
English

…

Participation and Registration
All persons wishing to participate in the event through the IAEA have to be designated by an IAEA Member State.

In order to be designated by an IAEA Member State, participants are requested to send the Participation Form (Form A) and Grant Application Form (Form C – if applicable) to their competent national authority (e.g. Ministry of Foreign Affairs, Permanent Mission to the IAEA or National Atomic Energy Authority) for onward transmission to the IAEA by 4 September.

Selected participants will be informed in due course on the procedures to be followed with regard to administrative and financial matters.

Participants are hereby informed that the personal data they submit will be processed in line with the Agency’s Personal Data and Privacy Policy and is collected solely for the purpose(s) of reviewing and assessing the application and to complete logistical arrangements where required. The IAEA may also use the contact details of Applicants to inform them of the IAEA’s scientific and technical publications, or the latest employment opportunities and current open vacancies at the IAEA. These secondary purposes are consistent with the IAEA’s mandate.

…

Additional Requirements
The participants should have a university degree in marine chemistry, biology, oceanography, or a related scientific field, and must be active researchers in the ocean acidification /mCDR field or should have already received technical training on ocean acidification / mCDR by the IAEA or through other efforts.

Selection will be based on merit and motivation. Applications must include, in addition to Form A and C, if applicable:

  •  A motivation letter with a short description of research interests, motivation to participate, and plans regarding present and future research on OA and/or mCDR (max one A4 page)
  •   CV with publication list
Continue reading ‘Applications open: Sixth International Symposium on the Ocean in a High-CO2 World’

Chapter 22 – Environmental ethics and the case of ocean acidification

Published 2 September 2026 Science Leave a Comment
Tags: ,

Ocean acidification (OA) is a paradigm case of an encroaching long-term environmental problem that is mainly caused by CO2-emissions and will have diverse and often uncertain impacts on marine organisms and ecosystems. SDG 14 (‘Life below water’) demands to halt or slow down OA. Since occurrence of OA is remote to our daily terrestrial life, it has not been in the focus of moral attention so far. This chapter emerged from the BIOACID research programme at Kiel University. It examines five sources of normativity in environmental ethics, addresses problems of uncertainty and framing, and interprets the metaphor of ‘ocean health’ with recurrence to an updated version of Aldo Leopold’s principle. The chapter argues that basic non-anthropocentric approaches, such as biocentrism, ecocentrism, and holism, face severe problems with respect to marine environments and can’t serve as solid groundings for an ocean ethics. The chapter proposes that a deep anthropocentric environmental ethics can provide an appropriate grounding for ambitious marine stewardship policies, including ocean acidification. Finally, the chapter proposes to define a critical threshold for OA which should not be passed.

22.1 Introduction

This chapter addresses ocean acidification (OA) from an environmental ethics perspective. Ocean acidification is seen as a paradigm case for post-normal science. At its core, the chapter adopts and substantiates several ethical building blocks from a discourse-pragmatic approach, as (a) common heritage of humankind, (b) strong sustainability, (c) Aldo Leopold’s principle, and (d) ecosystem services, with a special eye on cultural services. The idea to attribute inherent moral value to marine organisms and ecological systems is seen critically.

This chapter emerged from the research programme BIOACID (Biological Impacts of Ocean Acidification) being conducted at Kiel University. Within the final period of the BIOACID research programme, a work package on environmental ethics was included to address the underlying normative issues. This project resulted in a monograph: Frederike Böhm and Konrad Ott, Impacts of Ocean Acidification: An Analysis from an Environmental Ethics Perspective (Böhm & Ott, 2019).1 The following chapter presents the essential lines of reasoning of this book and adds new thoughts. It is organized as follows: Section 22.2 gives a brief overview of the scientific dimension. Section 22.3 presents a post-normal-science framing of OA. Section 22.4 deals with interrelated sources of normativity which stem from environmental ethics. Section 22.5 addresses the problem of defining a planetary boundary for OA.

…

Continue reading ‘Chapter 22 – Environmental ethics and the case of ocean acidification’

Chapter 21 – How can we curb ocean acidification in a time of multiple competing crises?

Published 2 September 2026 Science Leave a Comment
Tags: ,

Since the 1972 Stockholm Conference, many global environmental agreements have been struck for climate, biodiversity, and sustainable development goals. Still, the planets environment has continued to decline, including on the ocean. One result has been ocean acidification, caused by the uptake of 30–40 per cent of all carbon dioxide from the atmosphere. On its face, this ocean CO2 uptake sounds positive. However, with a continuous increase of CO2 in the atmosphere, this also means an increase in the ocean, which alters its chemistry in ways that may disrupt oceanic biodiversity through making waters more acidic. When coupling this with other major global crisis, we see that we have only adopted global environmental agreements that protect humans from our own nature-induced change – and not ensured that we take our ethical obligation to nature itself by protecting it from human use. This chapter looks at the risk perception literature and considers how the science–policy interface can be exploited to convey the importance of ocean acidification, and whether the anthropogenic lens is what will always be necessary to ensure action to protect something from ourselves.

21.1 Introduction

Around the end of the eighteenth century, with the design of the steam engine by James Watt, the geological age of the Anthropocene started (Crutzen 2006). This has led to unprecedented changes in the natural environment, the most serious of which is climate change. We have tried to change our paths since then though. In fact, more than 50 years have now passed since the 1972 Stockholm Conference (Rockström et al. 2021) – the United Nations Conference on the Human Environment. This was when global leaders for the first time made the environment and the triple planetary crisis of climate, nature, and pollution a focus issue. At that time, in 1972, they warned – and this still holds true today – that ‘Through ignorance or indifference we can do massive and irreversible harm to the earthly environment on which our life and well-being depend’ (United Nations 1973).

Since then, state leaders have created the United Nations Environment Programme (UNEP) entered into force both a climate and biodiversity agreement (United Nations Framework Convention on Climate Change (UNFCCC) and the Convention on Biological Diversity (CBD)) with many iterations; signed the UN 17 Sustainable Development Goals (SDGs) in 2015 with corresponding targets, as part of the realization of Agenda 2030; and in 2022 and 2023, state leaders also signed the Kunming-Montreal Global Biodiversity Framework (GBF) and the Agreement under the United Nations Convention on the Law of the Sea on the conservation and sustainable use of marine biological diversity in areas beyond national jurisdiction (BBNJ). Still, we have continued to saturate Earth’s capacity to support future generations (Intergovernmental Panel on Climate Change 2018). The planet is more polluted than earlier, there are fewer fish in the ocean, the temperature is increasing, methane levels are at their highest in 800,000 years, polar regions are melting, plastics are ubiquitous, and the ocean is more acidic than ever (Barnes & Kaiser 2009; Hönisch et al. 2012; Worm & Branch 2012; MacLeod et al. 2021; Intergovernmental Panel on Climate Change 2022).

In fact, six of nine planetary boundaries that are needed for humans to be able to develop and thrive for generations to come have been breached already (Richardson et al. 2023). Then, in 2025, the ocean acidification boundary was crossed (Findlay et al. 2025). This is a boundary that is also specifically mentioned in the SDGs, with target 3 of SDG14 Life below water specifying the need to ‘Minimize and address the impacts of ocean acidification, including through enhanced scientific cooperation at all levels’. It was in fact the only by-product of climate change and greenhouse gas emission that was singled out to be included under this goal (United Nations Department of Economic and Social Affairs 2022). Still, there is a lack of concrete knowledge of how breaching this boundary will impact either non-human populations or the corresponding human population that depends on these (Buckley et al. 2017).

In light of this, the current chapter considers ocean acidification within the planetary boundaries framework and assesses the lack of responses that led to, and may further exacerbate, the breaching of this boundary. We argue that this in part can be explained by the human-centric perspective of global environmental governance, where effective governance is linked to risk perception within a human context. In terms of ocean acidification, we argue that humans still have a low personal risk perception, coupled with a lack of knowledge (or interest) about it, which directly hinders its agenda setting and implementation of effective governance. We conclude with considering whether the increased saliency of biodiversity challenges, as brought to the surface with the signing of the GBF in 2022, can bring more attention to the role of stressors such as ocean acidification on sustainability and the consequences the breach of this planetary boundary can have on not only humans but also non-human populations.

…

Continue reading ‘Chapter 21 – How can we curb ocean acidification in a time of multiple competing crises?’

Chapter 20 – Introduction to the ocean acidification boundary

Published 2 September 2026 Science Leave a Comment
Tags: ,

The oceans mirror many of the environmental problems described in the planetary boundaries framework and reported widely in the media, such as overfishing and deep-sea mining (biosphere integrity), plastic islands or microplastics (novel entities), shipping (atmospheric aerosol loading), or dead zones lacking oxygen (biogeochemical flows). Less present in the media is the problem of ocean acidification addressed by the planetary boundary. Like the atmosphere, the oceans are sinks for CO2 produced by the burning of fossil fuels.

CO2 absorption changes the chemistry of the oceans, lowering their pH. The resulting acidification also leads to fewer of the calcium carbonate shells produced by numerous creatures sinking carbon to the ocean floor before they dissolve back into the water. The boundary’s control variable relates to this by describing the ‘carbonate ion concentration in surface seawater’ and, more specifically, the ‘average global surface ocean saturation state with respect to aragonite’ (Richardson et al. 2023). Aragonite is one of the most abundant forms of calcium carbonate. The boundary is at more than 80 per cent of the pre-industrial aragonite concentration, defined as 3.44. In 2023, the level was 81 per cent, meaning the ocean boundary was, at that time, still one of the few that had not been crossed. Thus, Pelejero et al. (2010: 332) describe ocean acidification as the ‘“evil twin” of global warming’ – it is a moot question, though, as to which is of the two is more evil. This also means that reducing greenhouse gas emissions will reduce the pressure on ocean acidification.

Acidification of the oceans and declining concentrations of calcium carbonate are becoming a problem for marine life. Many creatures depend on the presence of these calcium compounds in the water to build their shells or skeletons. Lower pH not only erodes the existing structures of these creatures, but they also find less calcium to rebuild them. These include plankton, corals, crustaceans, and molluscs, which are vital to marine biodiversity, marine food chains, and, ultimately, human food security (Rockström et al. 2009). So, the control variable of the ocean boundary is the global average saturation state of calcium carbonate in surface water. The framework sets the preindustrial Holocene base value at 3.44 and the boundary value at 2.75. Since 2009, the actual values have fluctuated between 2.8 and 2.9 (Richardson et al. 2023). In 2025, the ocean acidification boundary was first recognized as having been crossed (Findlay et al. 2025).

Both chapters on ocean acidification take the problem structure of the ocean acidification boundary as the starting point of their ethical reflections. Konrad Ott describes it as post-normal, that is, a situation when problem-solving has to cope with uncertain facts, disputed values, high-stakes, and urgent decisions (Funtowicz & Ravetz 1993). Ott explores the issue of ocean acidification from an environmental ethics perspective. He discusses different ways of justifying why ocean acidification is an ethical problem and what follows from this. In doing so, he aims to show how well the most common environmental ethical approaches can address the issue. They mostly differ in their scope of the moral community, that is, to whom we have direct moral obligations: to humans only, or also to individual animals, species, or ecosystems? Depending on the answer one gives, the reasons for protecting oceans will change. Ultimately, Ott intends to specify the normative building blocks of deep anthropocentrism as his preferred approach to the issue.

Rachel Haug Fossbakk, too, addresses the issue of decision-making relating to uncertainty and risk perception. She argues that the human response to ocean acidification is inadequate. This is despite the fact that there is already enough knowledge to act. Her hypothesis is that action requires an adequate perception of risk, which many people do not have when it comes to ocean acidification. She concludes by asking who has a responsibility to act, and on what ethical basis. Rachel Haug Fossbakk then advocates an ecocentric perspective by which she understands a situation ‘where humans are part of nature and need to live sustainably as part of it on the same term as other species’.

Continue reading ‘Chapter 20 – Introduction to the ocean acidification boundary’

The Ocean Acidification News Stream turns 20!

Published 1 September 2026 Science Leave a Comment

Time flies – the Ocean Acidification News Stream celebrated its 20th anniversary this summer! The very first post on this news stream goes back to 5 July 2006.

Some stats for the past 20 years:

  • Close to 20,000 posts
  • More than 1,9 million views
  • Close to 630,000 visitors
  • Country affiliation of top 10 visitors: US, France, China, Australia, UK, Canada, Germany, India, New Zealand, Spain

A word from the founder, Jean-Pierre Gattuso, CNRS-Sorbonne Université Laboratoire d’Océanographie:

I could not have imagined, back in 2006, that the blog I started would still exist 20 years later! At the time, ocean acidification was not a prominent topic on the research agenda. It gained momentum with the European Project on Ocean Acidification, followed by many other projects, both small and large. I am deeply grateful to the IAEA Ocean Acidification International Coordination Centre and everyone who has maintained the news stream over the years, beginning with Lina Hansson and continuing with the current caretaker, Carolina Galdino.

Current and past contributors:

  • Carolina Galdino
  • Courtney Witkowski
  • Lina Hansson
  • Sarah Flickinger
  • Olga Anghelici
  • Frank Graba
  • Nicholas Theux Lowen
  • Ashley Bantelman
  • Trevor Eakes
  • Einat Adam
  • Tanmay Misra
  • Hasti Dessa
  • Anne-Marin Nisumaa
  • Jean-Pierre-Gattuso

Thank you to all followers, and, as always, don’t hesitate to contact the team to suggest improvements or send us information that you would like to share!

Continue reading ‘The Ocean Acidification News Stream turns 20!’

The Global Ocean Data Analysis Project version 3 (GLODAPv3) – an internally consistent biogeochemical data product for the world ocean

Published 1 September 2026 Science Leave a Comment
Tags: ,

The Global Ocean Data Analysis Project (GLODAP) is a synthesis effort providing surface-to-bottom ocean biogeochemical observations determined through chemical analysis of discrete bottle samples, with an emphasis on seawater inorganic carbon chemistry and related variables. Version 3 of GLODAP comprises data from 1181 cruises, spanning more than 50 years of observations (1972–2023). It includes all data from the previous GLODAPv2.2023 (Lauvset et al., 2024) together with newly added data from 57 cruises. For all cruises, 13 core variables (temperature, salinity, oxygen, nitrate, silicate, phosphate, dissolved inorganic carbon, total alkalinity, CFC-11, CFC-12, CFC-113, CCl₄, and SF6) have undergone extensive quality control with particular focus on the identification and removal of systematic differences between cruises. The data are available in two formats: (i) as submitted by the data originators, converted to World Ocean Circulation Experiment (WOCE) exchange format, and (ii) as a merged data product in which adjustments have been applied. These adjustments were determined using crossover analyses in combination with a newly developed global inversion method, the furthest-first routine. The applied adjustments are intended to remove systematic differences arising from differences in measurement methods, calibration, and/or data-handling practices, while preserving known or likely temporal trends and natural variability. The consistency of the adjusted data product is estimated to be 0.0013 for salinity, 0.7 % for oxygen, 0.4 % for nitrate, 0.5 % for silicate, 0.5 % for phosphate, 1.2 µmol kg⁻¹ for dissolved inorganic carbon, and 1.4 µmol kg⁻¹ for total alkalinity. Consistency estimates could not be derived for transient tracers, but they are believed to be consistent to better than 5 % (10 % for SF₆). The enhanced consistency enables different datasets to be used together with greater confidence. Newly introduced cruise-specific uncertainty estimates for all core variables provide more granular quantifications of remaining cruise-to-cruise inconsistencies. Additional variables, including pH, discrete CO₂ fugacity (fCO₂), isotopic tracers, and others, were not subjected to secondary quality control but are included in the data product.

The original data, their documentation (metadata), and DOIs are available through the Ocean Carbon and Acidification Data System (OCADS) of NOAA’s National Centers for Environmental Information (NCEI), which also hosts the merged data product. All secondary quality control decisions and supporting information can be found in the online adjustment table (https://glodapv3.geomar.de, last accesses 26.06.2026). The product is distributed as a single global file and as four regional subsets (Arctic, Atlantic, Indian, and Pacific Oceans) under https://doi.org/10.25921/m6tp-mj50 (Lange et al., 2026). These adjusted files also include ancillary and approximated data obtained through interpolation or calculation from measured data.

Continue reading ‘The Global Ocean Data Analysis Project version 3 (GLODAPv3) – an internally consistent biogeochemical data product for the world ocean’

Climatic factors effects on gastropods (Phylum: Mollusca): a review of the biodiversity of freshwater, marine, and terrestrial snails

Published 1 September 2026 Science Leave a Comment
Tags: , ,

Climate change is altering ecosystems worldwide through rising temperatures, changing precipitation patterns, and more frequent extreme weather events, including heatwaves. Gastropods in freshwater, marine, and terrestrial environments are affected through changes in habitat characteristics, geographic distribution, abundance, physiology, and behavior. In freshwater systems, warming and drought can reduce dissolved oxygen and shrink suitable habitats. In marine environments, ocean acidification can impair shell formation and, under severe conditions, dissolve calcium-carbonate shells. In terrestrial habitats, increasing temperature and declining soil moisture can force snails into prolonged inactivity and increase desiccation risk. Effective climate information, predictive models, and early-warning systems are therefore essential for climate resilience, biodiversity conservation, and disease-risk management. Further comparative research is needed to clarify how phylogenetic history and adaptive variation influence heat tolerance and resilience among gastropod taxa.

Continue reading ‘Climatic factors effects on gastropods (Phylum: Mollusca): a review of the biodiversity of freshwater, marine, and terrestrial snails’

Seasonal forecasts of pH and aragonite saturation for the Bering Sea Shelf

Published 1 September 2026 Press releases Leave a Comment

Similar to weather forecasts for the atmosphere, numerical models can also be used to forecast ocean conditions. Since the ocean changes more slowly, particularly below the surface, forecasts of ocean conditions can be made for multiple months out. These forecasts can be helpful for marine resource managers by providing early warning of anomalous events, such as marine heatwaves or more acidic ocean conditions.

A new study, focused on the Bering Sea, tested an ocean model to see if it was capable of forecasting acidified bottom water conditions several months in advance. The cold and carbon rich waters of the Bering Sea make the region vulnerable to ocean acidification (OA) due to the naturally low carbonate saturation states. Scientists assessed the ocean model by running a suite of reforecasts (retroactively forecasting previous years) and comparing to the conditions that did occur. 

They found that the ocean forecasting model was skilled at predicting anomalies in bottom water pH on lead times up to nine months owing primarily to strong persistence. However, predictive skill for finer scale spatial anomalies was more limited and variable. They found that the model can be an effective tool to notify marine resource managers several months in advance of the expected development of relatively more acidic water conditions. This early warning can enable managers to make tactical decisions regarding upcoming fisheries quotas and assist rebuilding plans following fishery closures, such as the red king crab fishery that has faced recent closures and is threatened by OA.

Learn how NOAA Pacific Marine Environmental Laboratory studies the ecosystems of the North Pacific Ocean, Bering Sea and U.S. Arctic to improve understanding of ecosystem dynamics and applies that understanding to the management of living marine resources by clicking here.

Continue reading ‘Seasonal forecasts of pH and aragonite saturation for the Bering Sea Shelf’

SDG14 assessment of progress against sustaining life below water: a case study from Torres Strait

Published 31 August 2026 Science Leave a Comment
Tags: , , ,

The United Nations Sustainable Development Goals (SDGs) represent a global call for action to sustain humans, the planet and prosperity. SDG14 (Sustaining Life below water) focuses on oceans, their conservation and sustainable use. Since committing to the 2030 Agenda for Sustainable Development, there have been several calls to take stock of progress and encourage decisive action to build a sustainable future. Here we evaluate progress against achieving each of the SDG14 goals using as an example Australia’s Torres Strait tropical rock lobster (TRL) Panulirus ornatus fishery because of the very strong dependence of Indigenous fishers and local communities on this resource. Our evaluation draws on 40 years of research, highlighting how changes have improved alignment or are on-track to meet the 2030 targets. We assessed that all targets were achieved to 2025 due to the small fishery ecological footprint, sound sustainable fishery and ecosystem management, science-based management plans, economic benefits derived though sustainable management, growth in research capacity as well as access for small-scale artisanal fishers to marine resources and markets. Our case-study therefore complements best practices examples in achieving SDG14 for a regionally important fishery. To meet 2030 aspirational goals, progress was assessed as on-track to address impacts of ocean acidification, enhanced transfer of marine technology and need to work with global partners to encourage market access for sustainable fisheries that are vital in supporting Indigenous and regional livelihoods. Overall, we calculated a conservative score of 3.5 reflecting very high achievement (~ 88%) towards future aspirational SDG targets.

Continue reading ‘SDG14 assessment of progress against sustaining life below water: a case study from Torres Strait’

What can a lobster fishery teach us about SDG 14?

Published 31 August 2026 Web sites and blogs Leave a Comment

As the deadline for the United Nations Sustainable Development Goals approaches, there is increasing interest in understanding where progress is being made and what practical examples can offer useful lessons. A new, open access article in Reviews in Fish Biology and Fisheries takes this perspective to the ocean, using the Torres Strait tropical rock lobster fishery in northern Australia as a case study to assess progress toward SDG 14, the goal focused on conserving and sustainably using marine resources.

The fishery is unusual in several respects. Tropical rock lobster (Panulirus ornatus) is a high-value species that supports livelihoods in Torres Strait communities, where Indigenous peoples have managed and depended on marine resources for generations. The fishery is also jointly connected to Australia and Papua New Guinea through the species’ migratory life cycle and shared management arrangements. 

Drawing on four decades of scientific monitoring, the authors evaluated progress across all ten SDG 14 targets. Their assessment highlights a combination of factors behind positive outcomes, including long-term ecological surveys, science-based stock assessment, precautionary fisheries management and strong participation from Indigenous fishers and communities. According to the study, the fishery currently meets the SDG 14 targets that can be assessed against present-day conditions and shows substantial progress toward the longer-term aspirational goals for 2030. 

Ecological footprint
One aspect of the case study that stands out is the fishery’s relatively small ecological footprint. Lobsters are collected by hand rather than through trap-based methods, reducing impacts on habitats and limiting the amount of fishing gear deployed in the environment. The article also describes how monitoring programs have evolved over time, incorporating new technologies and extensive fishery-independent surveys while maintaining continuity in the data needed for management decisions.

The authors are careful not to present the fishery as a finished success story. Some targets remain works in progress, particularly those related to the impacts of ocean acidification, technology transfer and broader international cooperation that can help support sustainable fisheries and market access. The study also notes that external pressures, including marine pollution transported from outside the region and environmental variability affecting lobster recruitment, continue to require attention.

While the findings are specific to Torres Strait, the paper offers a useful example of how sustainability goals can be evaluated using long-term evidence rather than broad assumptions. For researchers working on fisheries, marine conservation, resource management or sustainability policy, it provides a detailed look at how local practices, community engagement and sustained scientific investment can be brought together to track progress toward global environmental objectives. 

Continue reading ‘What can a lobster fishery teach us about SDG 14?’

Coral reef community structure and photophysiology differ between upwelling and non-upwelling locations on the Pacific Coast of Costa Rica

Published 28 August 2026 Science Leave a Comment
Tags: , , , , , , , ,

Reef-building corals and coralline algae form the calcium carbonate frameworks that underpin tropical coral reefs, yet in some locations, coral cover has declined by ~50% in recent decades due to marine heatwaves and other stressors. Identifying refugia environments, such as upwelling systems, that may buffer stress, promote recovery, and could enhance resilience by promoting physiological plasticity that supports thermotolerance is therefore critical. Here, we compared benthic community composition, coral percent cover, and photophysiology between an upwelling location in the Gulf of Papagayo and a non-upwelling location in Sámara on the Pacific coast of Costa Rica. Waters in Papagayo were cooler, more acidic, and had higher chlorophyll-a concentrations. Reefs at this location exhibited higher crustose coralline algae, higher sea urchin abundance, and lower macroalgae cover, compared to Sámara. Papagayo also showed higher stony coral cover, driven by Pocillopora spp., while Sámara was dominated by massive, heat-tolerant Porites spp. Photophysiological parameters were significantly different between locations. Specifically, photosynthetic efficiency (Fv′/Fm′) was 10–45% higher, and maximum photosynthetic rate (Pmax) was 20–40% lower in corals from Papagayo than in those from Sámara. These results reveal that two locations differing in environmental regime within a relatively small geographic area also differ in coral community composition and photophysiological features. Although further research is needed to resolve whether these environmental contrasts shape the observed biological differences, the observed patterns are consistent with the hypothesis that such regimes may support reef persistence or refugia, providing a basis for future work to test this hypothesis directly.

Continue reading ‘Coral reef community structure and photophysiology differ between upwelling and non-upwelling locations on the Pacific Coast of Costa Rica’

New tool could predict ocean acidity in Bering Sea

Published 28 August 2026 Press releases Leave a Comment

Listen

Disaster declarations have been declared for both the Bering Sea snow crab and Bristol Bay red king crab fisheries in recent years. Corey Arnold/Alaska Bering Sea Crabbers

Crab populations in the Bering Sea are struggling. And researchers say climate change is a big cause. A new tool described in a study published Aug. 3 in the Journal of Geophysical Research Oceans will help researchers predict one of climate change’s biggest threats to crabs: ocean acidity. The study’s authors hope their work can help crabbers and fishery managers.

“I’m excited with this new model and study,” said Jamie Goen, the executive director of the nonprofit trade association Alaska Bering Sea Crabbers. “It will help us better understand what could be happening and how that might impact fisheries.”

Darren Pilcher, the study’s lead author and an oceanographer at the University of Washington, said he started the study because of requests from fisheries stakeholders.

The ocean absorbs a quarter of our carbon emissions, which make the water more acidic when the two mix. Acidic conditions are harmful for many different animals. This is especially true for shellfish, like crabs.

“They can eat more, and that helps a little bit, only to a certain point,” Pilcher said. “In fact, in some of the previous experiments with red king crab, if you lower the pH to a value of 7.5, the crab just die.”

Scientists have pointed to factors from climate change, like ocean acidification, as the reason the number of Bristol Bay red king crabs has plummeted in recent years. Goen said that other species, like snow crab, have also tanked.

“When I started this job eight years ago, we had 60 vessels in the fleet,” she said. “But obviously with the collapse of snow crab and the closure of red king crab, we’re down to 40 active vessels right now.”

Pilcher and his team wanted to help the fishery by creating a tool that could forecast acidity in the Bering Sea. Ocean acidity doesn’t exist in a vacuum, so the first step was to make a computer model of the entire Bering Sea, recreating the water conditions at any given time. They put a lot of existing data into their model on ocean conditions over time, measuring things like temperature, currents, and distribution of phytoplankton.

Then they added in ocean acidity data collected from the region, and tested their new tool by having it forecast the acidity of the Bering Sea over a roughly 40 year period. They compared that forecast to what actually happened each year.

Pilcher said they also compared their new tool to a simple baseline model, which predicts that conditions at the beginning of the year will stay the same throughout the year.

“It’s actually a really good forecast for the ocean because the ocean doesn’t really change that quickly,” he said.

They tested both models for both the bottom and surface of the ocean. Pilcher found that they were both equally good at predicting acidity at the bottom of the ocean. But he said their new model did a lot better at predicting surface temperatures than the baseline model.

“It kind of makes sense because the bottom waters, especially during the summer, are more cut off from the atmosphere,” he said. “Whereas of course the surface is still very connected to the atmosphere and is responding to it on a quicker time frame.”

Pilcher hopes the information from their experiment, and his new model, can inform future management.

“We could say, ‘Hey, this is what we’re predicting for the upcoming summer,’ so that we can give everybody a little bit advance notice if there are, say, worse acidification conditions,” he said.

He said they’ve also discussed partnering with a new king crab mariculture project happening on St. Paul Island. The plan is to raise larval Bristol Bay red king crabs in a lab, and release them back into Bristol Bay when they reach a certain size. But because juvenile crabs are more vulnerable to ocean acidity than adults, Goen said Pilcher’s model could provide important data.

“Where I could see an immediate benefit is knowing if those waters are going to be unusually acidic or higher in temperature in a given year,” she said. “Then maybe that’s not the best year to put some brood stock back into Bristol Bay.”

Goen said she hopes for more research on the changing ocean chemistry in the Bering Sea, so fishermen can make informed decisions. But for now, she said Pilcher’s results are very promising.

Continue reading ‘New tool could predict ocean acidity in Bering Sea’

Seasonal forecasts of pH and aragonite saturation for the Bering Sea shelf

Published 28 August 2026 Science Leave a Comment
Tags: , , , ,

The number of numerical model forecasts of ocean environmental conditions has greatly expanded in recent years, including biogeochemical variables. Forecasts can provide marine resource managers with advance warning of extreme events such as heatwaves and hypoxia, though forecast products are scarcer in high-latitude environments. The Bering Sea shelf is a large marine ecosystem that supports critical commercial, cultural, and subsistence ecosystem services that are vulnerable to extreme events and anthropogenic stressors such as ocean acidification (OA). Here, we use a regional oceanographic model of the Bering Sea to assess model forecast skill in predicting bottom water pH and aragonite saturation state (Ωarag) on lead times from 1 to 9 months. We simulate 28 years (1982–2010) of 3-member ensemble retrospective forecasts, initialized both in April and May following the retreat of winter sea ice and several months in advance of early fall when the most acidic bottom water conditions occur. The results suggest that the model is skillful (anomaly correlation coefficients > 0.5) in forecasting shelf-wide anomalies in bottom water pH and Ωarag, on lead times up to 9 months owing primarily to strong persistence. However, predictive skill for finer scale spatial anomalies is more limited and variable. Model forecast skill is also strong in Bristol Bay, home to the red king crab fishery that has faced recent closures and is threatened by OA. The model forecasts presented here can provide several months advanced notice for acidified water conditions and bolster a suite of products used to support evidence-based fisheries management.

Plain Language Summary

Similar to weather forecasts for the atmosphere, numerical models can also be used to forecast ocean conditions. The skill of these forecasts can be high up to several months in advance because the ocean has a relatively long memory and changes occur more slowly, particularly below the surface. The Bering Sea sustains substantial marine fisheries, which are threatened by changing ocean conditions such as increasing water acidity. Here we used an ocean model to test how well the model can forecast acidified bottom water conditions several months in advance. We did this by running a suite of reforecasts (i.e., we retroactively forecast years that have already occurred) and comparing to the model simulation of the conditions that did occur. Our results suggest that the model can generate skillful forecasts with lead times of up to 9 months, mainly because the conditions that occur at the start of our forecast tend to persist through the summer and into the fall. These forecasts can provide Bering Sea resource managers with advance warnings of water conditions that are harmful to marine species, such as Bristol Bay red king crab.

Continue reading ‘Seasonal forecasts of pH and aragonite saturation for the Bering Sea shelf’

Climate change drivers of harmful algal blooms in marine and coastal ecosystems

Published 27 August 2026 Science Leave a Comment
Tags: ,

Climate change is widely recognized to contribute to marine warming, acidification, and deoxygenation, while the frequency of harmful algal blooms (HABs) is increasing, causing severe ecological disruptions. Eutrophic regions are increasingly exposed to thermal extremes, hypoxic conditions, and low pH levels and may therefore serve as sensitive indicators of ecosystem responses to climate forcing. HAB occurrence reflects interactions among nutrient availability, temperature variability, and hydrodynamic conditions. Future work should aim to quantify the relative contributions of interacting environmental drivers to improve the robustness of predictive models of HAB dynamics under future climate scenarios. Climate change is likely to amplify HAB intensity and spatial distribution, although regional outcomes depend on interacting environmental drivers. These findings have implications for fisheries management, aquaculture sustainability, public health issues and long-term monitoring. Monitoring strategies should ideally prioritize ecosystem functional responses and early-warning indicators of climatic variability.

Continue reading ‘Climate change drivers of harmful algal blooms in marine and coastal ecosystems’

Aragonite saturation horizon variability along North Pacific seamounts and implications for deep-sea coral reefs

Published 27 August 2026 Science Leave a Comment
Tags: , , ,

The 2014 discovery of living deep-sea coral reefs along the Northwest Hawaiian Islands (NWHI) and lower Emperor Seamount Chain (ESC), despite the North Pacific’s shallow aragonite saturation horizon (ASH) and high CaCO3 dissolution rates, underscores the need to understand the local seawater chemistry where these reefs persist. We investigated seawater carbonate chemistry using discrete samples along NWHI and ESC from two cruises ∼1 year apart (08/26/21–09/26/21, 09/09/22–10/24/22). Across the two cruises, ASH depth difference ranged from 15 to 77 m. Since the Pacific ASH shoals by 1–2 m yr−1, this long-term trend cannot explain the magnitude of ASH change observed. Potential contributions from anthropogenic CO2 and examining intermediate water mass changes from temperature-salinity plots did not provide an explanation for the observed changes. Instead, ASH depth variability was primarily governed by localized biogeochemical processes, namely changes in intermediate water respiration and CaCO3 dissolution. Indicators for dissolution (TA*) and respiration (AOU) suggest changes in ASH depth were driven by changes in dissolution at the northern- and southern-most sites, whereas respiration exerted stronger control at central sites. Combining 2021 and 2022 data with data from 2014 to 2019 revealed high interannual ASH variability, by as much as >200 m. Deep-sea coral reefs across the NWHI and ESC currently reside close to the ASH depth and likely experience interannual shifts between under- and supersaturation. As ocean acidification induced shoaling occurs alongside these interannual fluctuations, the frequency of undersaturation will be an important consideration for deep-sea coral reef longevity.

Plain Language Summary

In 2014, thriving deep-sea coral reefs were found in the Pacific near Hawaii and the Emperor Seamounts, where conditions were thought too acidic for reef development. To understand how these reefs persist, we studied the carbonate chemistry of this region during two research cruises (2021 and 2022). We found that the depth at which seawater becomes corrosive for coral skeletons (aragonite saturation horizon, ASH) changed far more from year to year than the gradual Pacific trend of 1–2 m yr−1. Human sourced carbon dioxide and natural shifts in ocean water masses do not explain the observed large changes. Instead, local biological and chemical processes, respiration and the dissolution of calcium carbonate, played a major role. When comparing seawater chemistry from 2014 to 2022, the ASH fluctuated even more dramatically than the predicted trend of 1–2 m yr−1. While climate change continues to drive corrosive deep waters closer to the surface, processes that occur on shorter timescales, local respiration and dissolution, can similarly expose deep sea coral reefs to corrosive conditions that can impact their longevity. Therefore, short term and local scale processes can affect long term acidification trends, making gradual shoaling harder to observe in short term data.

Continue reading ‘Aragonite saturation horizon variability along North Pacific seamounts and implications for deep-sea coral reefs’

Early detection of coral reef acidification micro-hotspots driven by offshore energy development

Published 26 August 2026 Science Leave a Comment
Tags: , , ,

Offshore energy development is a key measure to safeguard global energy security. At present, offshore oil and gas, wind power, tidal power and other offshore energy industries are expanding rapidly worldwide. However, large-scale energy activities have become a non-negligible driver of coastal ocean acidification. Carbon emissions generated throughout the full lifecycle of energy facilities locally alter seawater chemistry. This triggers ocean acidification of varying degrees and accelerates the corrosion and degradation of surrounding coral reefs.1,2,3 If population-averaged datasets are adopted to conduct environmental assessments of ocean acidification impacts, it will inevitably fail to identify fine-scale ecological risks to coral reefs induced by energy-related activities.4,5 Undoubtedly, this will become one of the critical bottlenecks restricting the green and sustainable development of offshore energy.

This study targets corals from the South China Sea. We adopt large-view macro-lens infrared thermal imaging. The technique reveals inherent microscale heterogeneity in coral skeletal corrosion susceptibility. The findings provide new technical references for ecological impact assessment, layout optimization and environmental risk control of offshore energy facilities. It also helps promote coordinated development between offshore energy exploitation and marine ecological conservation.

HIGH-PURITY PRIMARY ARAGONITE SKELETON OF GONIOPORA FROM THE SOUTH CHINA SEA

The coral sample used in this study was collected from Wuzhizhou Island, Sanya, South China Sea (Figure 1A). Whole-rock X-ray diffraction (XRD) analysis shows that aragonite is the dominant mineral phase, with a content of 88.5%. This matches the typical mineral composition of pristine coral skeletons. Minor impurities including halite (2.3%), clay minerals (2.3%), dolomite (1.9%), quartz (1.2%), K-feldspar (1.1%), calcite (1.1%), plagioclase (0.9%), and gypsum (0.7%) are also detected in the sample (Figure 1B). Plane-polarized and cross-polarized light micrographs show that the images display regular skeletal frameworks and unevenly distributed pore networks, which lay a structural basis for the spatial differentiation of lattice defects (Figure 1C & D).

Figure 1.  Early detection of coral reef acidification micro-hotspots driven by offshore energy development.(A) Photograph of the intact coral sample collected from the South China Sea; (B) X-ray diffraction pattern, showing dominant primary aragonite with a content of 88.5%, and some minor impurities; (C, D) Plane-polarized and cross-polarized light micrographs; (E) Large-view macro-lens infrared thermal image, with a measured temperature range of 23.60~25.60 °C. The color changes from red for high EBT to purple for low EBT. Dark green areas correspond to the coral pore system, including large corallite cavities, dendritic connected pores and scattered micro-pores. Orange areas represent skeletal matrix with high EBT, which features weak corrosion susceptibility. Bright yellow and light green areas represent matrix with low EBT, acting as acidification micro-hotspots with strong corrosion susceptibility. Sporadic blue spots are residual bubbles formed during thin section preparation, not native skeletal structures.

…

Continue reading ‘Early detection of coral reef acidification micro-hotspots driven by offshore energy development’

Seasonal reef-scale variability in seawater CO₂ chemistry in the presence and absence of seaweed cultivation in Onna, Okinawa, Japan

Published 26 August 2026 Science Leave a Comment
Tags: , , ,

Seaweed cultivation has been proposed as an active biogeochemical intervention to elevate seawater pH and create localized refugia from ocean acidification. To date, most studies have relied on autonomous sensors to contrast seawater pH inside and outside of seaweed cultivation plots. These studies provide important temporal observations but lack information about the spatial capacity for seaweed cultivation to provide pH refugia for surrounding habitats. This study investigated the spatiotemporal variability of seawater pH and CO₂ chemistry across the Onna-son reef, Okinawa, Japan, during the fall, winter, and spring seasons, with spring surveys coinciding with the peak extent of Mozuku (Cladosiphon okamuranus) cultivation. Relative to open-ocean conditions, seawater pH was elevated during 77–100% of afternoon observations in fall (up to + 0.10), 53% in winter (up to + 0.02), and 75–92% in spring (up to + 0.13). The greatest drawdown in dissolved inorganic carbon (DIC; − 44 µmol kg⁻1) and highest spatial pH variability (0.19) were observed during spring, the period of maximum seaweed cultivation, but coincided with reduced current velocities, small wave heights, and low mean sea level, conditions conducive to enhanced biogeochemical modification. Comparable pH elevations were observed during fall under similar temperature regimes, but higher current velocities, which suggest that seaweed cultivation may not be more effective than natural macroalgal habitats in elevating local seawater pH at this site. Future assessments of seaweed aquaculture as a mitigation strategy should explicitly incorporate local hydrodynamics and natural macroalgal influences, as these will impact the variability across both space and time.

Continue reading ‘Seasonal reef-scale variability in seawater CO₂ chemistry in the presence and absence of seaweed cultivation in Onna, Okinawa, Japan’

Elucidating impact of ocean acidification on coral exoskeletons using an in-situ (S)TEM platform

Published 25 August 2026 Science Leave a Comment
Tags: , , , , , ,

Scleractinian (stony) corals can build highly ordered aragonite (CaCO3) exoskeletons, which are vital for marine ecosystems, coastal stability, and of cultural and economic importance through supporting fisheries and tourism. However, they face multiple challenges through global climate change, unsustainable human activity, and coral-specific diseases. In the latter category, Stony Coral Tissue Loss Disease (SCTLD) has recently emerged as one of the most destructive coral diseases, spreading rapidly and causing widespread tissue mortality across many marine species [1]. We have recently started exploring remnant effects of this disease on Montastraea cavernosa exoskeletons, abundant throughout the Caribbean Sea, Gulf of Mexico, and Atlantic Ocean. Indeed, through use of multi-scale electron diffraction characterization techniques, we find that their skeletogenisis is impacted by this disease from the micro- through atomic scale [2]. Notably, at the nanoscale we observe pockets of more soluble amorphous calcium carbonate (ACC) within centers of calcification (CoCs; i.e. the center of the three-dimensional fans containing arranged elongated aragonite crystals) for healthy corals, which appear absent in STCLD-afflicted corals. At the atomic level, we reveal planar defects in diseased coral, which are much lower in density in healthy corals, presumably inflicted through dysregulation processes after tissue death.

Yet, the most severe threat to global coral reefs and their exoskeletons is climate change. As oceans increase the uptake of anthropogenic CO2 primarily from burning fossil fuels, ocean acidity has increased. The reduction in pH because of this Ocean Acidification (OA) not only reduces the rate of net ecosystem calcification, but also increases net dissolution of skeletons. At current trends, most coral exoskeletons are expected to dissolve starting in 2050 [3]. Currently, it is unclear how exactly (the onset of) dissolution proceeds and affects their aragonitic framework. Given our expertise in characterization of coral skeletons, herein we discuss a developed in-situ platform to investigate OA effects at the nanoscale.

As proof of concept, we sandwiched crushed geological aragonite nanoparticles between own fabricated SiNx-based chips, compatible with a Protochips Atmosphere gas cell holder [4]. Thereafter, we introduced water vapor at 14 Torr at room temperature (∼60% relative humidity) for 10 minutes to create a hydrated environment for the particles (Fig. 1b). In a third step, we introduced gaseous CO2 at a pressure of 1 atm (Fig. 1c). The formed unstable carbonic acid produces HCO3– and H+, which increases acidity (i.e. lowers pH). Indeed, we observe rapid dissolution of aragonite particles after CO2. While we expect roughly a pH ∼4 in this system, this experimental observation matches theoretical expectations that aragonite would dissolve under these conditions (Fig 1c-f). We further observe nucleation and growth of new particles in a dendritic fashion in the vicinity of the dissolved particles (Fig 1c-f). Likely, this is crystallization of calcite, the most stable crystalline polymorph of CaCO3, induced by local dissolution of aragonite [5]. Although pCO2 in the oceans is expected to be much lower (∼400 – 500 µatm) and thus dissolution timescales are expected to shift, this illustrates our platform can capture aragonite dissolution.

To expand our platform methodology, using conventional Ga+ FIB-methods, we prepared a lamella of geological aragonite with a thinned region (∼100 nm), which was then transferred on top of a SiNx-based chip, and attached this in one of the corners between the Si support and the SiNx layer (Fig. 2a). We were able to sandwich the lamella between both chips when observing the cell in the TEM (Fig 2b,c). Next, we will target healthy and STCLD-afflicted coral sections to investigate how nanoscale dissolution proceeds at/near more soluble areas including defects due to the devastating OA process. This understanding may allow for more accurate forecasting of marine ecosystem collapse, enabling targeted mitigation strategies, protecting food supplies, and predicting climate feedback loops [6].

Fig. 1. In-situ OA platform experiment showing TEM snapshots of: a) Initial geological aragonite nanoparticles. Inset: selected area diffraction pattern indicating aragonite spots. b) Introduction of water vapor (14 Torr) after 10 min. The white arrow indicates an apparent hydration layer surrounding the large particle. c) Introduction of CO2 at 1 atm pressure after 10 s. d) 60s e) 90s and f) 150s. White arrows in c-f) mark the outer layer of the large particle dissolving in time, red arrows illustrate growth of new crystals.

Fig. 2. a) SEM image of geological aragonite lamella attached to SiNx chip. b) TEM image of lamella after cell assembly (top and bottom chip). c) In-situ selected area diffraction pattern of the lamella.

Continue reading ‘Elucidating impact of ocean acidification on coral exoskeletons using an in-situ (S)TEM platform’

Comparing ocean acidification communication strategies and effectiveness in marine education centers

Published 25 August 2026 Science Leave a Comment
Tags:

Ocean acidification (OA), one of the most impactful aspects of our changing oceans, significantly threatens ecosystems, industries, and communities reliant on at-risk species, such as corals and shellfish. Washington state, with its notable reliance on such species for both its economy and culture and its naturally acidified waters, is especially vulnerable. However, OA remains an under-discussed and misunderstood phenomenon, especially among the public. While many informal marine education centers such as aquariums, science centers, and marine reserves do provide communication on OA, the prevalence, type, and quality of this communication varies drastically, meaning that the public’s ability to receive effective OA education varies as well. Thus, I conducted staff interviews to catalogue the prevalence of OA communication efforts at marine education centers and address barriers to effective OA outreach. I found that while 88% of participating marine education centers discuss OA in some capacity, 81% feel restricted in their ability to talk about OA or ocean change, citing issues such as audience interest and politics. I also conducted visitor surveys at Point Defiance Zoo & Aquarium to determine how attendees’ preconceived knowledge of OA’s causes, impacts, and mitigation strategies changed based on provided communication and what gaps remain. While visitor knowledge of OA increased by a statistically significant amount (from 63% of visitors knowing essentially nothing about OA before the visit to 44% after; p < 0.001), only 49% of visitors correctly identified fossil fuel emissions as a primary cause of OA. Despite this, 97% of visitors indicated willingness to take action against OA, and nearly equivalent amounts of visitors supported individual-level vs societal-level action. Together, this research lays the groundwork for improving OA communication to the public by highlighting the importance of uplifting meaningful action, intentionally connecting with visitors through community-level and place-based impacts, and addressing staff hesitancy to discuss ocean change issues. Going forward, these recommendations will be critical in driving tangible action to address OA and protect at-risk communities and ecosystems.

Continue reading ‘Comparing ocean acidification communication strategies and effectiveness in marine education centers’

Why marine heat waves and acidification strike together

Published 25 August 2026 Press releases Leave a Comment

A chemistry tug-of-war between ocean acidity and carbon in warming oceans determines when and where these damaging events strike.

This data visualization shows an intense marine heat wave in the Atlantic Ocean and Mediterranean Sea on 13 August 2026. New research examines the relationship between marine heat waves and ocean acidification. Credit: European Union, Copernicus Marine Service Data

Marine heat waves and extreme ocean acidification events are each damaging on their own. But when both stressors hit simultaneously, their individual effects can be exacerbated.

That threat may be best exemplified by “the Blob” of 2013–2015, during which both a marine heat wave and an ocean acidification extreme event hit the northeastern Pacific. Fisheries were closed, marine mammals were stranded, seabirds died, and sea creatures either changed their distribution or perished.

But our understanding of these compound heat-acidity ocean extreme events is limited, with more research focused on the marine heat wave component than on the acidification aspect.

Gregor and Gruber used 43 years of monthly data (1982–2024) on surface ocean temperatures and acidity to determine when, where, and why compound heat-acidity extreme events have occurred. They defined extreme events as those situations when detrended acidity and temperature exceed their 95th percentiles.

Compound ocean heat-acidity events happen more often than would be expected by chance, the authors found. In the low to midlatitudes, they occur roughly 4 times more often than compared to chance, mostly in places with permanent stratification. In these places, heat waves drive waters to be more acidic. The compound events were least common in the eastern equatorial Pacific and around the poles, where deep waters upwell to the surface. When marine heat waves strike in these upwelling regions, a warm lens (top layer of water) prevents the surfacing of the deep acidic waters, leading to unusually low acidity for the region.

A majority (73%) of compound heat-acidity extreme events in the study period were smaller than 500,000 square kilometers (193,000 square miles, roughly the size of Spain) and lasted for about a month. But a few events, like the Blob in 2015, lasted for more than a year, sometimes with long-lasting consequences.

El Niño and La Niña events are important drivers of these compound events, but the events seldom happen at the weather events’ epicenter in the equatorial Pacific. During El Niño, warmer waters create a lens that prevents upwelling, thus reducing the typical acidity of the region. And during La Niña, cold, deep waters with higher acidity upwell, resulting in only an acidification extreme. However, it is in the neighboring regions where the knock-on effect of this warming or acidity causes compound extremes to occur.

The new findings are in line with several key facets of earlier work and offer more insights into temporal patterns and drivers. (AGU Advances, https://doi.org/10.1029/2025AV002112, 2026)

Continue reading ‘Why marine heat waves and acidification strike together’

Recent history of surface ocean acidification extremes that compound marine heatwaves

Published 25 August 2026 Science Leave a Comment
Tags: , ,

Compound extremes are of concern for ocean health, such as when ocean acidification extremes (OAX) and marine heatwaves (MHW) co-occur. These compound events (OAX∩MHW) may amplify stress beyond the impact of each driver alone, yet their historical distribution remains poorly quantified. We used an observation-based product (OceanSODA-ETHZ) to investigate surface ocean OAX∩MHW from 1982 to 2024. OAX and MHW are defined when detrended surface hydrogen ion concentration and sea surface temperature exceed their 95th percentiles. Events show distinct spatial and temporal patterns: they occur roughly four times more often than by chance in the low- to mid-latitudes, but are rare in the eastern tropical Pacific and the high latitudes. They occur primarily in summer and show strong variability associated with the El Niño-Southern Oscillation. Most events are small ( <1⁢06 km2) and brief (1 month), but several are exceptional, including: the Blob (2015) in the northeastern Pacific (12.6 ×1⁢06 km2), the North Atlantic marine heatwave lasting nearly a year (2023–2024), and the most intense event off the Western Australian coast (2011). Mechanistically, OAX∩MHW occur when warming-induced increases in [H+] are not offset by a reduction in dissolved inorganic carbon that typically accompanies MHW. This is typical of the permanently stratified low-to-mid latitude oceans, where the seasonal cycle of [H+] is controlled by temperature. By characterizing past compound extremes and improving our understanding of individual events, we highlight conditions that may lead to future ecosystems being at risk.

Plain Language Summary

This study examines the recent history of “compound extremes” in the ocean, where marine heatwaves and ocean acidification extremes occur simultaneously. Using observational data from 1982 to 2024, we find that these compound events are happening more frequently than would be expected by chance, particularly in the low- to mid-latitudes. Conversely, they are rare in the eastern equatorial Pacific and polar regions. These compound events are most prevalent during summer and are influenced primarily by the El Niño/Southern Oscillation. While most of these events are relatively small and short-lived, there have been a few exceptionally large, long, and intense occurrences. Some of the most notable events include: “The Blob,” in the northeastern Pacific in 2015; the longest-lasting event that occurred in the Atlantic Ocean from 2023 to 2024; and the most intense event that occurred off Western Australia in 2011. These compound extremes happen in areas where the warming from a marine heatwave also leads to an increase in ocean acidity. This phenomenon is most common in regions of the ocean that are permanently stratified, meaning they have distinct layers of water that do not mix well.

Continue reading ‘Recent history of surface ocean acidification extremes that compound marine heatwaves’

Subscribe

Search

  • Reset

OA-ICC Highlights

Resources