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Surveying ocean acidification on the Northwest Atlantic shelf

In August of 2022, Prof. Samantha Siedlecki and Prof. Craig Tobias, along with students Halle Berger and Alex Frenzel, went on the East Coast Ocean Acidification Cruise (ECOA-3). The cruise was led by scientists at the University of New Hampshire, joined through transdisciplinary partnerships with other universities, aboard the NOAA Ship Ronald H. Brown. The UConn Avery Point members joined the cruise to investigate the contribution of sediments to carbon chemistry and how that ultimately impacts ocean acidification.

“Core team” on the deck of NOAA Ship Ronald H. Brown with multi-core sampler. Left to right: Halle Berger, Samantha Siedlecki, Craig Tobias, Alex Frenzel

Sam, Craig, Halle and Alex were the sediment coring team. The cores go all the way down to the bottom of the ocean and collect both the upper part of the sediment and the layer of water above it. This way, it is possible to understand chemical reactions in this zone between the sediments and the water above it. “The idea here is to understand how sediments control the chemistry of bottom water. There are sediment reactions that could help buffer acidity. But it’s unclear how sediments talk to the water above it or how that communication might change in the future” says Craig. You can learn more on the Facebook page of research vessel Ronald H. Brown.

These measurements are valuable information because they are not only timestamps of what is happening at the moment of collection. Increasing the number of observations and fine-tuning the measurements of these chemical processes in bottom waters helps the research of modelers, like Sam. Models are important to test our understanding of ocean processes. We need more measurements like this to more accurately predict marine climate change. Part of Sam’s work is to use this information into regional ocean models to better constrain the role of sediments in the chemistry of the ocean.

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PhDs study pH levels that could threaten fragile ecosystem of 17 separate reefs and banks along the Texas Gulf Coast


Is ocean acidification affecting the Texas coast’s Flower Garden Banks National Marine Sanctuary? Texas A&M University scientists collected data Oct. 25­–28 in the Gulf of Mexico to help answer this question and more, as the fate of the unique and fragile Flower Garden Banks ecosystem is potentially threatened by climate change and acidification.

“Ocean acidification is a process that affects the entire ocean and is driven by the combined effects of climate change and CO2 emissions, which are believed to increase to oceanic pH levels,” said cruise chief scientist Steven DiMarco, professor in Texas A&M’s Department of Oceanography and Department of Ocean Engineering, and Geochemical and Environmental Research Group (GERG) scientist.

Funded by the Ocean Acidification Program of the National Oceanographic and Atmospheric Administration and sailing on the RV Pelican, the four-day research cruise investigated the impact of ocean acidification in the coastal ocean environmental of the northwestern Gulf of Mexico. It is the third of four planned cruises, with two completed in 2021 and one upcoming in February 2023.

“The decreased pH levels can have catastrophic effect on marine organisms, particularly calcifying organisms that build and maintain shells, skeletons, and calcium carbonate structures,” DiMarco said.

Located about 100 miles off the coasts of Texas and Louisiana, the Flower Garden Banks sanctuary spans 17 separate reefs and banks, including thriving shallow-water coral reefs, algal-sponge communities, and deeper mesophotic reefs full of black coral, octocoral and algal nodule habitats. Together, the reefs create a chain of protected habitats for ecologically and economically important species across the northwestern Gulf of Mexico.

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Here’s why the West Coast Dungeness crab season has been delayed

A crab pot with caught Dungeness crab inside, off the port of Port Orford.

Oregon’s most valuable commercial fishery, Dungeness crab, will have its season delayed from its traditional Dec. 1 start date because of low meat yields.

Testing shows the crabs in some ocean areas off the West Coast don’t have enough meat in them to satisfy the commercial market.

In some areas, testing also showed elevated levels of the naturally occurring toxin domoic acid, which can make the crabs unsafe to eat.

Carin Braby, marine resources program manager with the Oregon Department of Fish and Wildlife, said officials will continue to test for meat yield and domoic acid in the coming weeks, and the results will determine whether the season needs to be delayed beyond Dec. 16. Right now, she said, some parts of the Oregon coast still have biotoxins from a big biotoxin event this fall, and other areas have crabs with low meat fill.

Hugh Link, the outgoing director of the Oregon Dungeness Crab Commission, said it’s better for everyone involved in the industry if the meat yield is high before fishing begins.

“We like to wait until they’re ready with the best possible meat fill before we open up the season,” he said. “It’s a win-win-win for everybody, the fishermen, the processors and the consumer.”

Braby said phytoplankton blooms happen every year, but now they are often accompanied by harmful algal blooms that produce the domoic acid toxin.

“The research that’s been done on those suggests that we will see that more and more with climate change,” she said. “The warmer conditions and the acidified water will promote the harmful algal bloom species and the toxin production. It’s going to get incrementally worse.

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Role of government in ocean acidification

The oceans are more acidic now than they have been for at least 300m years, due to carbon dioxide emissions from burning fossil fuels, and a mass extinction of key species may already be almost inevitable as a result, leading marine scientists warning the general public and government to take action. An international audit of the health of the oceans has found that overfishing and pollution are also contributing to the crisis. In the warning yet of the threat to ocean health, the International Programme on the State of the Ocean (IPSO) said: “This [acidification] is unprecedented in the Earth’s known history. We are entering an unknown territory of marine ecosystem change, and exposing organisms to intolerable evolutionary pressure. The next mass extinction may have already begun.” 

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Coral reefs near Texas may not escape greater damage from climate change

Lobed star coral, a threatened species at Flower Garden Banks National Marine Sanctuary. National Ocean Service (NOS)

Coral reefs in the Flower Garden Banks National Marine Sanctuary 100 miles off the Texas coast have remained healthier than many of their counterparts around the world in the face of climate change. But warming waters in the Gulf of Mexico could change that, warn scientists at Rice University, the University of Colorado Boulder and Louisiana State University in a recent paper in the Journal of Geophysical Research (JGR) Biosciences.

The researchers used models maintained by the National Center for Atmospheric Research to simulate climate warming from 2015 to 2100 under two scenarios. The first was “business as usual,” with very high emissions, and the second involved reduction of emissions to high levels. An analysis of regional warming patterns in each suggested the Gulf of Mexico could see critically warm temperatures as early as 2050. The key determinant of coral mortality in each scenario is the number of months corals are exposed to prolonged temperatures hotter than the hottest average months projected for 2015-2034.

One of the clear findings is that it matters which scenario prevails, according to Sylvia Dee, a climate modeling expert at Rice University and one of the authors, who spoke with Texas Climate News. The research indicates that curbing emissions during the next 10 to 20 years could make a big difference for these reefs.

Reef-building hard corals host photosynthetic algae that help feed the coral organisms. Corals also rely on carbonate minerals in seawater to construct their hard skeletons. Climate-change-related warming temperatures and increased acidification in the ocean threaten these processes. Prolonged, abnormally warm temperatures, for example, can cause corals to expel their algae, a phenomenon known as bleaching. If water temperatures drop, corals take back the algae and recover. If temperatures remain high enough, corals eventually starve.

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Océanos: La fórmula perfecta de la acidificación (in spanish)


La acidificación en los océanos se da por un conjunto de reacciones químicas entre el agua y el CO2, que al estar ambos en contacto provoca la liberación de iones de hidrógeno, lo que lleva a un incremento de la acidez del agua, afectando no sólo a los océanos sino también a los estuarios costeros y canales. La acidificación del océano disminuye la concentración de iones carbonatos, que son indispensables para algunos organismos (esponjas, corales de aguas profundas y superficiales, pepinos de mar) que forman sus conchas o esqueletos de carbonato del calcio, haciendo que sea más difícil para ellos mantener o crear estas estructuras. De esta manera, altera la diversidad funcional del ecosistema, incluidos los hábitats biogénicos costeros, lo que resulta en la homogeneización y simplificación del ecosistema. 

Entre más CO2 encontremos, habrá más acidificación en los océanos. Tengamos en cuenta que los niveles de este gas han aumentado desde la Revolución Industrial a causa de la quema de combustibles fósiles, dando lugar a una disminución en el pH del agua superficial del 0.1 que representa un aumento del 30% en la acidez de los océanos en comparación con los niveles pre-industriales. Es importante disminuir el CO2 al menos a 350 ppm (partes por millón), ya que en la actualidad hemos llegado a las 400 ppm.

El problema del aumento de los GEI está afectando gravemente a nuestros océanos, dando paso a una bomba de tiempo que acabará no sólo con éstos, sino también con los seres humanos, pues no debemos olvidar que al aumentar la temperatura también es posible liberar el metano que ha quedado atrapado por tanto tiempo en el fondo marino y en el permafrost (suelo permanentemente congelado), lo que ayudaría a un ascenso de temperatura más rápido y sin retorno, algo parecido a lo que ocurrió hace 56 millones de años en el llamado Máximo Térmico Paleoceno-Eoceno.

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U.S. announcements on ocean-climate action at COP27

Ocean-based climate solutions have a key role in keeping the goal to limit temperature rise to 1.5 degrees Celsius within reach and improving global climate resilience.  On the occasion of the “Oceans and Coastal Zones” thematic day at COP27, the United States highlights the following ocean-climate action.

Developing a National Ocean Acidification Action Plan: The United States announced the commencement of a process to create/develop the United States’ Ocean Acidification Action Plan (OA-AP), with a goal of finalizing it by COP28.  The OA-AP aims to 1) identify U.S. actions that address the root causes of ocean acidification, 2) highlight U.S. leadership and priorities on ocean acidification, 3) illustrate the coordinated approach to OA across U.S. federal, state, and local agencies, 4) identify gaps and opportunities for further action, and 5) serve as a mechanism to promote greater international collaboration among members of the OA Alliance.  The OA-AP will be closely tied to the United States’ Ocean Climate Action Plan, which will guide significant ocean-based climate mitigation and adaptation actions, including on green shipping, ocean-based renewable energy, ocean acidification, and other ocean-related solutions.  Drafting and releasing the U.S. national action plan will provide a model for other members seeking to integrate OA research, monitoring, and adaptation efforts across their governments.

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Greenhouse gas concentrations higher than in all of human civilisation

The latest data from the Copernicus Climate Change Service shows that Europe just had the warmest October on record, with temperatures almost two degrees above the 1991-2020 average.

The warming that we are seeing here on land would be even more rapid if it wasn’t for the oceans. It’s calculated that they are absorbing up to 90% of the excess heat in the atmosphere trapped by greenhouse gases. And they are suffering.

The Mediterranean has suffered repeated heatwaves over the past couple of years and Jean-Pierre Gattuso, the CNRS Research Director, at the Laboratoire D’océanographie De Villefranche-Sur-Mer describes what impact that is having.

“The main effect of marine heat waves is massive mortality of invertebrates and plants, mollusks, sponges, and corals. Between the surface and 50 metres in depth, there are many invertebrates and plants that are affected negatively and die.”

Marine life in the Mediterranean under threat from successive heatwaves

But do the decisions that are taken at COP27, make any difference and are they really going to change things like acidification and heatwaves? Jean-Pierre Gattuso again. 

“The negotiations that are taking place at COP 27 are obviously extremely important. The scenarios that are being projected by the IPCC (The Intergovernmental Panel on Climate Change) show that if the Paris agreement is implemented quickly and fully, we can stabilize temperatures and ocean acidification. This does not mean that we will return to the situation as it was before. It means we can stop the warming and stop the increase in acidity.”

The atmosphere at COP27 is business-like because everybody knows that the window is closing to reach the goals of the Paris Agreement and limit global warming to well below two degrees Celsius.

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Ocean acidification: COP27 event highlights IAEA capacity building to help African communities at risk

Scene from the IAEA side event on Ocean Acidification Adaptation and Resilience in Africa, held at its #Atoms4Climate pavilion at COP27. (Photo: A.Evrensel/IAEA)

The ocean plays a major role in the carbon cycle and absorbs about 30 per cent of all human-made CO2 emitted into the atmosphere each year. Over the last few decades, the amount of CO2 released due to human activities, such as the burning of fossil fuels and deforestation, has drastically increased. As a result, the chemistry of the ocean is changing, which can have lasting effects on the health of marine organisms and ecosystems, and subsequently for populations who depend on these for their livelihoods. 

Nuclear and isotopic techniques can help assess the impacts of ocean acidification on the livelihoods of coastal African populations, participants heard at an IAEA event on the sidelines of the 27th Annual UN Climate Change Conference, COP27, today.

Coastal areas that already face issues such as overfishing, pollution and habitat destruction are at high risk of being affected by ocean acidification. In Africa, fisheries and aquaculture currently contribute around USD $24 billion to the economy, employing more than 12 million people and providing sustenance to millions of people around the continent. Additionally, demand for fish and ocean products has increased significantly and is expected to further increase 30 per cent by 2030. The combination of already delicate ocean health and ocean acidification puts communities that are heavily reliant on fisheries and ocean products – mostly rural coastal African populations – at significant risk.

“Isotopic techniques are very powerful methods to assess ocean acidification risk to marine organisms and ecosystems,” said Jana Friedrich, Head of the Radioecology Laboratory at the IAEA Marine Environment Laboratories. “Accurate data allows us to better equip regional communities with the means necessary to address the impacts of ocean acidification, for example on local seafood species and their habitats.”

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Climate change: West Africa’s oceans at risk because of a lack of monitoring

The West African coastline is a source of livelihood for millions. Wikimedia Commons/Paul Walter

The West African Canary Current extends along the north-west African coast, from the northern Atlantic coast of Morocco to Guinea-Bissau. It’s a hotspot for changes in the oceans driven by climate change. These include rising temperatures, ocean acidification and ocean deoxygenation. All affect marine life on multiple levels.

The current is one of the world’s most productive ocean ecosystems, a consequence of the upwelling of cold and nutrient-rich waters. Ecosystems like this provide around 20% of global fish catches and support livelihoods in coastal communities.

From 2016 -2019, we worked with an international team to draw attention to the impacts of climate change on the West African Canary Current. In a recent publication, we described the limited economic and institutional capacity to monitor and respond to climate variability and change in the countries bordering the West African Canary Current and the urgent need to build scientific capacity in the region in order address this shortcoming.

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PML scientist leads ocean acidification update of new marine climate change review

Image: Cold-water coral habitat off the west coast of Scotland taken during the JC073 Changing Oceans research cruise in 2012.

Dr Helen Findlay, Biological Oceanographer at PML, led a team of internationally recognised scientists to bring together the Marine Climate Change Impacts Partnership (MCCIP) Topic Review Update on Ocean Acidification.

Published during the 1st week of COP27 at the Marine Alliance for Science and Technology for Scotland Annual Science Meeting, these MCCIP Topic Review Updates are a comprehensive exploration of the current science on the topics of aquaculture, coastal flooding and stratification as well as ocean acidification.

The MCCIP Ocean Acidification Topic Review Update summary:

  • Atmospheric carbon dioxide (CO2) exceeded 414 ppm in 2021 and has continued to increase by approximately 2.4 ppm per year over the last decade. The global ocean absorbs approximately a quarter of this anthropogenic CO2 emissions annually.
  • The North Atlantic Ocean contains more anthropogenic CO2 than any other ocean basin and surface waters are experiencing a decline in pH (increased acidity).
  • Some species are already showing effects from ocean acidification when exposed to short-term fluctuations and could be used as indicator species for long-term impacts on marine ecosystems.
  • Models project that the pH of the average continental shelf seawater will continue to decline at similar rates as today until 2050, when rates will then increase in the second half of the century, depending on the emissions scenario used in the model run.
  • The rate of pH decline in coastal areas is projected to be faster in some areas (e.g. Bristol Channel) than others (e.g. Celtic Seas).
  • Under high-emission scenarios, it is projected that waters at the bottom of the north-west European shelf seas will become corrosive to more-soluble forms of calcium carbonate (aragonite), which organisms such as cold-water corals and molluscs use to build their skeletons and shells, and this is projected to begin by 2030.
  • By 2100, up to 90% of the north-west European shelf seas may become corrosive to some species for at least one month of each year.
  • High variability in coastal carbonate chemistry may mean that some species have a higher adaptative capacity than others. However, all species will be at an increased risk from extreme exposure episodes.

Dr Helen Findlay commented: “The science around the chemistry of ocean acidification is very well established and we have a high level of confidence that atmospheric CO2 is increasing the acidity of the ocean.”

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Research in a multiple-stressor world: ten early-career scientists trained on experimental design in Monaco

Ten early-career scientists from as many countries (Argentina, Chile, China, Cuba, Iceland, Italy, Latvia, Peru, Portugal and Qatar) gathered at the Marine Environment Laboratories of the International Atomic Energy Agency in Monaco from 24 October to 4 November for a 2-week training course on ocean acidification in a multiple-stressor context.

The course included both lectures and practical exercises and was organized by the IAEA’s Ocean Acidification international Coordination Centre (Ocean Acidification International Coordination Centre (OA-ICC) | IAEA) in partnership with the Prince Albert II of Monaco Foundation. The OA-ICC and the Prince Albert II of Monaco Foundation teamed up with scientists of the Institut de la mer de Villefranche-sur-Mer (Imev) in the framework of the OACIS initiative to offer this training opportunity for a broad range of countries.

After lectures on key theoretical concepts on how to design multi-stressor experiments, the students had the opportunity to go to the Imev laboratories in Villefranche-sur-mer for training on lab and field sampling techniques in the bay of Villefranche, and lectures on the software R, used to calculate carbonate chemistry in the ocean.

The students then set up a 5-day long laboratory experiment at the IAEA labs, involving three stressors: ocean acidification, temperature rise, and lithium pollution, and the impacts of these stressors on sea urchin growth. While the three stressors had a negative effect on the sea urchins, the results showed that temperature was the most important stressor and that it interacted in a complex way with lithium pollution. Students are now finalizing the analyses with the goal to publish the results in a scientific journal. Students also had the opportunity to present their research and get tailored advice and guidance on specific questions and challenges they encountered in their work.  Prof Jean-Pierre Gattuso, President of the OACIS initiative, closed the event with a lecture on potential ocean-based measures to mitigate and adapt to climate change and ocean acidification.

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How carbon emissions acidify our ocean and how IAEA helps in understanding its effects

(Graphic: A. Vargas Terrones /IAEA)

Ocean acidification is a consequence of increasing carbon dioxide (CO2) emissions, a greenhouse gas driving climate change. The ocean absorbs around one third of all human induced CO2, causing a change in seawater chemistry called ocean acidification. It presents a serious threat to marine life, ecosystem health and people whose livelihoods depend on the ocean.

When CO2 dissolves in seawater, it forms carbonic acid (H2CO3), releasing hydrogen ions (H+) and increasing ocean acidity. Acidity plays a key role in many biological mechanisms, including calcification.

Calcium carbonate (CaCO3) is crucial for organisms which need calcium to develop, build and maintain their shells and skeletons, such as certain types of plankton, oysters, crabs, sea urchins, shrimps and lobsters.

Ocean acidification makes it harder for them to maintain these calcified structures. This can cause disruptions within food chains.

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Ten years of the Ocean Acidification International Coordination Centre (video)

2022 marks the tenth anniversary of the IAEA’s Ocean Acidification International Coordination Centre, which uses nuclear research to combat the damage that climate change is causing to our marine ecosystems. Ambassador Holgate visited the OA-ICC labs in Monaco to celebrate this important milestone.

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A caustic shift is coming for the Arctic Ocean


Imagine, for a moment, that you are standing on a pier by the sea, grasping, somewhat inexplicably, a bowling ball. Suddenly you lose your grip and it tumbles down into the waves below with a decisive plonk. Now imagine that the bowling ball is made of gas—carbon dioxide, to be specific, compressed down into that familiar size and weight. That’s approximately your share, on a rough per capita basis, of the human-caused carbon emissions that are absorbed by the sea every day: Your bowling ball’s worth of extra CO2, plus the 8 billion or so from everyone else. Since the Industrial Revolution, the oceans have sucked up 30 percent of that extra gas.

The reason so much CO2 ends up in the oceans is because that molecule is extremely hydrophilic. It loves to react with water—much more than other atmospheric gasses, like oxygen. The first product of that reaction is a compound called carbonic acid, which soon gives up its hydrogen ion. That’s a recipe for a caustic solution. The more hydrogen ions a solution has, the more acidic it is, which is why as the CO2 in Earth’s atmosphere has increased, its water has gotten more acidic too. By the end of the century, models predict the oceans will reach a level of acidity that hasn’t been seen in millions of years. Prior periods of acidification and warming have been linked with mass die-offs of some aquatic species, and caused others to go extinct. Scientists believe this round of acidification is happening much faster.

That change is striking hardest and fastest in the planet’s northernmost waters, where the effects of acidification are already acute, says Nina Bednaršek, a researcher at Slovenia’s National Institute of Biology. She studies pteropods, tiny sea snails that are also known as “sea butterflies” due to their translucent, shimmering shells that look uncannily like wings. But scoop those snails from Arctic waters, and a close look at their exoskeletons reveals a duller reality. In more corrosive water, the once-pristine shells become flaked and pock-marked—a harbinger of an early death. Those critters are “the canary in the coal mine,” as Bednaršek puts it—a critical part of the food chain that supports bigger fish, crabs, and mammals, and a sign of coming distress for more species as the oceans become more caustic.

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Stressed out: dungeness crabs off the Pacific Northwest coast

Massive die-offs of Dungeness crab have been documented off the Pacific Northwest Coast. Once dead, the aquatic crabs often wash up on beaches, such as the ones photographed on Kalaloch Beach on June 14, 2022. Photo: Jenny Waddell/NOAA

Dungeness crab is an iconic and valuable fishery resource that is culturally and economically important to West Coast communities. Off the coast of Oregon and Washington, tribal, commercial, and recreational fishers pull up crab pots, expecting a haul of Dungeness crabs. Too often lately, what they find are pots filled with dead crabs, suffocated from a lack of oxygen near the seafloor.

Hypoxia—dangerously low oxygen levels—is killing Dungeness crabs off the Pacific Northwest Coast, predominantly during the summer and early fall. Marine animals don’t breathe air, but they still need oxygen, which they absorb from the water. If sufficient oxygen is missing from the water column, the animals may perish.

In addition, blooms of harmful algae have led to the closure of entire Dungeness crab fisheries on the West Coast in past years. Harmful algal blooms are the rapid growth of algae that can produce toxins dangerous to animals and habitats, with potential risk to humans who eat contaminated shellfish.

Multiple Stressors

Hypoxia and harmful algal blooms are considered stressors to the health of Dungeness crabs. Other stressors include ocean acidification, rising ocean temperatures, and marine heatwaves. Each of these stressors is known to harm marine species and ecosystems independently, but scientists are only beginning to unravel the ways in which environmental stressors may interact, and whether there may be unprecedented consequences.

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NOAA awards $4.2 million for multi-stressor research on Northern California Current Ecosystem

NOAA has awarded $967,505 of an anticipated four-year, $4.2 million project to support research on multi-stressor impacts on marine ecosystems under climate change. The newly funded project, led by Oregon State University and NOAA’s Pacific Marine Environmental Laboratory, will occur off the coasts of northern California, Oregon, and Washington, including NOAA’s Olympic Coast National Marine Sanctuary, and will focus on climate impacts to Dungeness crab, an iconic and valuable fishery resource that is culturally and economically important to the region’s coastal communities.

Dungeness crab outreach aboard a vessel in Washington. Credit: Olympic Coast National Marine Sanctuary.

Ocean acidification (OA), hypoxia, increasing temperatures, and harmful algal blooms (HABs) have emerged as leading environmental stressors in the northern California Current Ecosystem, impacting ecosystems, fisheries, and Indigenous and other coastal communities. Climate change is already making existing marine environmental stressors worse through changes to temperature, precipitation, seasonal cycles, and ocean chemistry. For the Dungeness crab fishery, the U.S. West Coast’s most valuable fishery, hypoxia has resulted in mass mortality of crabs in commercial pots, and HAB events have led to substantial fishing curtailment including season-scale closures. The continued intensification of this suite of multi-stressors poses substantial challenges for the management of ocean resources, ecosystems, and protected species. For marine protected areas and Tribal treaty fishing areas that have fixed boundaries, uncertainties in the expression and impacts of multi-stressors (OA, hypoxia, increasing temperatures, and HABs) threaten to undercut the ability of area-based tools to safeguard marine resources.

The goal of the proposed work is to help resource managers and tribes of the northern California Current Ecosystem prepare for the anticipated impacts of climate change, by increasing their understanding of how multiple stressors are likely to impact these ecosystems in the future. Also, this work will help determine the biological sensitivity of Dungeness crabs (Metacarcinus magister) and krill (Euphausia pacifica) to OA, hypoxia, HABs, and increasing temperatures.

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Increasing temperatures and ocean pH may spur ecosystem-altering changes

Credit: Pixabay/CC0 Public Domain

The Pacific blue mussel (Mytilus trossulus) is a foundational and beneficial species in the intertidal environments of the northern Pacific Ocean. Comparative physiologists have recently studied how two aspects of climate change—warming temperatures and increasingly acidic waters—may affect this ecologically important species. The scientists present their findings this week at the American Physiological Society (APS) Intersociety Meeting in Comparative Physiology: From Organism to Omics in an Uncertain World conference in San Diego.

As a foundational species, Pacific blue mussels create habitat and maintain ecosystem function, much as corals do in a coral reef. They are also of growing economic value in Alaska, with about 8 million mussels cultivated each year on aquatic farms.

For marine life that relies on calcium for their outer shells—such as mussels—climate change is a double whammy. It means not only warming temperatures but also changes in the pH of their habitat. That change in pH can make calcium more scarce.

As carbon increases in the atmosphere, an increasing amount of carbon is absorbed by seawater, setting off a chemical reaction that makes the ocean more acidic. This is called ocean acidification. According to the National Oceanic and Atmospheric Administration, surface ocean waters have already become approximately 30% more acidic. Mussels, like other calcifying shellfish, rely on calcium carbonate to make their shells. But calcium carbonate dissolves in acidic environments. In fact, it is even used in common antacids, such as Tums.

For this study, the research team used tide pools in Sitka, Alaska, to simulate different aspects of climate change. Some tide pools were artificially warmed, some artificially acidified, and others were both warmed and acidified. They monitored the mussels for six months, testing shell strength and thickness at three time intervals.

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Discovered in the deep: the ‘mermaid’s wineglass’ made up of one giant cell

Acetabularia jalakanyakae, also known as the mermaid’s wineglass, is a species of algae found around the Andaman and Nicobar Islands. Photograph: Courtesy of Felix Bast.

Growing between the tides around the Andaman and Nicobar Islands, in the tropical waters of the Indian Ocean, are clusters of what look like tiny, green mushrooms. In fact, this is a type of seaweed, or algae – each one made from a single, gigantic cell.

In 2021, scientists named them Acetabularia jalakanyakae, also known as the “mermaid’s wineglass”, because of its umbrella-shaped cap.

Mermaid’s wineglass algae might grow in the relatively unpolluted waters of the Andaman and Nicobar Islands, but they face a global threat. The ocean is absorbing more anthropogenic carbon from the atmosphere and consequently becoming more acidic, which puts species like the mermaid’s wineglass algae at risk. As Bast explains, more than half of the dry weight of this algae is calcium carbonate, which melts in acidified seawater.

“Any organism, be it animal or a plant, with calcium carbonate is highly prone to ocean acidification,” says Bast. “So, that will be having a tremendous impact on species like Acetabularia because the calcium carbonate will simply dissolve into the acid.”

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Highlighting ocean acidification on the sustainability tour with Manel Bustelo and Alana Alvarez Vernice (audio)

In this podcast Melanie Boylan chats with Manuel Bustelo and Alana Alvarez Vernice about their ongoing mission to highlight ocean acidification. Listen in to find out how you can help to make everyday changes to improve our planets oceans.

The Sustainable Tour is DAN EU’s project to raise awareness of the need to drastically reduce our CO2 emissions if we want to maintain a healthy ocean. Manu and Alana are touring Europe and its surroundings (UK and Ireland in 2022) in an electric vehicle – recharging it only with renewable energy – visiting dive centres and other interested parties to give lectures on ocean acidification.

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