Archive Page 32

Long-term pH trends across depth in coastal areas of the southeastern Bay of Biscay

Published 1 August 2025 Science Closed
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Highlights

  • We examined pH trends over time across depth in the Basque coast upon 21733 observations during 2002-2022.
  • Significant pH decreases over time (0.022 to 0.041 units decade-1) across 0-100m likely driven by the global increase of atmospheric CO2.
  • Marked seasonality and higher ocean acidification rates in deeper relative to surface layers tied to environmental factors and the biological activity.
  • Importance of pH monitoring in coastal areas to warn on the effect of ocean acidification on marine ecosystems.

Abstract

Increased CO2 concentrations in the atmosphere have triggered ocean acidification over the past decades in the global ocean. However, regional efforts of pH monitoring across the southern Bay of Biscay´s Basque coast remain elusive, with only a few short-term studies limited to the ocean’s surface. Here we examine pH trends over time across the Basque coast using 21733 observations of long-term data collected during 2002-2022 with quarterly CTD casts from surface down to 100 m at three coastal sites. Results revealed significant pH decreases over time in all depth layers (0.5-100 m) at the three coastal sites (0.022 to 0.041 units decade-1), presumably driven by the global increase of atmospheric CO2. Across depth, the pH trends observed also showed significantly higher ocean acidification rates with depth. Seasonally, observed changes ranged from wintertime highs of 8.18 ± 0.07 to summertime lows of 8.14 ± 0.05, with a mean seasonal amplitude of about ∼0.04 pH units. The observed pH seasonality and vertical patterns appeared to be tied to the combined effect of environmental factors alongside the development of the thermocline as well as to differences in the biological activity across the water column. Taken together, these findings highlight the importance of pH monitoring in coastal areas to warn on the effect of ocean acidification on marine ecosystems and the services they provide to society.

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These microscopic ocean animals may hold the secret to climate survival

Published 1 August 2025 Press releases Closed

In a surprising twist for marine science, researchers have discovered that copepods—tiny but crucial creatures at the base of the ocean food chain—use not one but two molecular toolkits to survive in a warming, acidifying ocean.

The discovery reveals a two-pronged strategy: one genetic, the other epigenetic, that helps these animals rapidly adjust and evolve across generations.

The findings, published July 15 in Proceedings of the National Academy of Sciences, offer a rare dose of optimism in climate research. Led by Melissa Pespeni at the University of Vermont, the study tracked 25 generations of marine copepods under simulated future ocean conditions. The result? Clear evidence that these organisms are not just adapting genetically over time, but also deploying rapid, reversible changes through epigenetic modifications—chemical tags on DNA that influence which genes get expressed.

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The team raised populations of Acartia tonsa—a globally abundant copepod species—in lab conditions mimicking ocean warming, acidification, and their combination. Over one year and 25 generations, researchers measured everything from egg production to genome-level changes. Using cutting-edge sequencing, they tracked:

  • Genetic adaptation (DNA sequence changes)
  • Epigenetic variation (DNA methylation)
  • Gene expression patterns (which genes were turned on or off)

What they found was startling: genetic and epigenetic changes occurred in different regions of the genome and seemed to operate independently. Yet both mechanisms contributed to the copepods’ ability to tolerate stressful environments.

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Complementary genetic and epigenetic changes facilitate rapid adaptation to multiple global change stressors

Published 1 August 2025 Science Closed
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Significance

Organisms must adapt or acclimate to survive global change, but how these processes interact and the role of epigenetic variation is unknown. We experimentally evolved the marine copepod Acartia tonsa for 25 generations in global change conditions and measured their genomic, epigenomic, and gene expression responses. We found that both genetic and epigenetic changes contributed to resilience and were inversely related, acting in different regions of the genome. Epigenetic changes were functionally linked to the regulation of stress and transposable elements and correlated with shifts in gene expression. These findings paint a surprising picture of the complementary contributions of both genetic and epigenetic mechanisms to population resilience in global change conditions.

Abstract

To persist under unprecedented rates of global change, populations can adapt or acclimate. However, how these resilience mechanisms interact, particularly the role of epigenetic variation in long-term adaptation, is unknown. To address this gap, we experimentally evolved the foundational marine copepod Acartia tonsa for 25 generations under ocean acidification, warming, and their combination and then measured epigenomic, genomic, and transcriptomic responses. We observed clear and consistent epigenomic and genomic divergence between treatments, with epigenomic divergence concentrated in genes related to stress response and the regulation of transposable elements. However, epigenetic and genetic changes were inversely related and occurred in different regions of the genome; levels of genetic differentiation (FST) were up to 2.5× higher in regions where methylation did not differ between treatments compared to regions with significant methylation changes. This negative relationship between epigenetic and genetic divergence could be driven by local inhibition of one another or distinct functional targets of selection. Finally, epigenetic divergence was positively, though weakly, associated with gene expression divergence, suggesting that epigenetic changes may facilitate phenotypic change. Taken together, these results suggest that unique, complementary genetic and epigenetic mechanisms promote resilience to global change.

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Shell dissolution rates differ fourfold between mussel species

Published 1 August 2025 Science Closed
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Ocean acidification poses a critical threat to marine calcifiers globally and is particularly severe in the California Current System, where ecologically and economically important bivalves experience reduced calcification under climate change. Marine mussels display differential habitat preferences, with species like Mytilus californianus favouring fully saline environments and M. trossulus inhabiting sites with greater freshwater input. Determining abiotic dissolution rates of these species under ocean acidification is essential for predicting future consequences of climate change for coastal populations. We examined shell dissolution rates of mussel congeners under a range of pH (6.5–9.3) and aragonite saturation states (0.1–9.0). We also experimentally quantified the relative importance of dissolution from interior versus exterior shell surfaces. M. trossulus exhibited fourfold higher shell dissolution rates than M. californianus. When the shell interior was sealed against seawater exposure, dissolution rates decreased significantly in both species, indicating high abiotic dissolution on the shell interior. Results demonstrate that dissolution rates can vary between congeners inhabiting the same biogeographic region. Our finding that freshwater-tolerant M. trossulus has higher abiotic dissolution under ocean acidification is important because low salinity may further retard calcification, altering future intertidal population structure along freshwater-influenced coastlines.

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The vulnerability of marine shells to ocean acidification does not depend solely on their mineral composition

Published 31 July 2025 Press releases Closed

The resistance or vulnerability of marine organisms’ shells to ocean acidification does not depend only on the type of mineral they are made of, as previously thought, but also on factors such as their microstructure and organic content. This is the main conclusion of a study by the ICTA-UAB, which calls for a reassessment of current scientific models.

Ocean acidification — driven by increasing atmospheric CO₂ — has become a critical threat to marine life, particularly for organisms that build calcium carbonate shells. For years, it has been widely assumed that organisms with aragonitic shells (a more soluble form of Calcium carbonate CaCO₃) are more vulnerable than those with shells made of calcite (a less soluble form). However, this assumption was based on the behaviour of synthetic monocrystals produced in inorganic precipitation experiments. Calcium carbonate shells, by contrast, are highly complex structures containing organic material as well as minerals. A new study reveals a far more complex reality challenging oversimplified assumptions based synthetic monocrystals

The research shows that the vulnerability of these organisms cannot be predicted based solely on the mineralogy of their shells. Instead, other factors — such as the shell’s microstructure and organic content — are also critical for understanding how these structures respond to undersaturated and corrosive conditions.

“We have a generalized idea about the impact of ocean acidification on marine shells, but it’s not enough to know whether they’re made of aragonite or calcite. It also matters how they’re built,” explains Gerald Langer, ICTA-UAB researcher and lead author of the study. The way organisms build their shells — including internal structure and organic matter — varies between species and can significantly influence their resistance to more acidic seawater.

The experimental evidence analyzed by the team includes cases where structures made of the same mineral exhibit very different dissolution behaviours, depending on their internal design or the presence of organic coatings. A paradigmatic example is that of coccolithophores, where the same species shows variable shell resistance depending on its life cycle stage, even though all phases use the same type of calcium carbonate.

This finding has important implications for conservation policies and for scientific models predicting the impacts of climate change on marine biodiversity. Many of these models use mineralogy as a direct proxy for vulnerability — a practice that, according to this new research, needs to be fundamentally re-evaluated.

“This study challenges one of the foundations of relevant scientific assessments used by international bodies, by showing that mineralogy alone does not predict the resilience of calcifying species in acidifying oceans,” says Patrizia Ziveri, ICTA-UAB research professor and co-author of the study. ““As oceans continue acidifying, improving our understanding of which species are most at risk is essential for designing effective protection strategies,” Ziveri adds.

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Vulnerability to ocean acidification of marine calcifying organisms cannot be predicted from the mineral type in their shells

Published 31 July 2025 Science Closed
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Scientific Significance Statement

Anthropogenic CO2 is acidifying the surface ocean water, a process called ocean acidification (OA). This process can result in conditions that are corrosive for seashells with more “delicate” calcium carbonate shells. An important debate in OA research centers on the degree of vulnerability of the calcium carbonate shell forming groups. It is widely believed that the vulnerability can be simply inferred from the particular mineral type forming the shells (related to the mineral’s solubility). This idea is widespread and has found its way into policy reports. We argue that the idea is over-simplified and can lead to wrong assessments of vulnerability to OA. Shell dissolution kinetics is not only a function of the mineral type but also of microstructure and organic content. This means that vulnerability assessments in, for example, some models and policy reports have to be revised.

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Species-specific mechanisms of benthic foraminifera in response to shell dissolution

Published 31 July 2025 Science Closed
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Highlights

  • Living specimens and empty tests of two benthic foraminifera species were cultured in different pH and light conditions.
  • In acidic conditions, greater dissolution of empty tests compared to living specimens was observed.
  • No differences in the degrees of dissolution between the two species were observed.
  • Living foraminifera have active mechanism(s) to tolerate acidification.

Abstract

Ammonia confertitesta and Haynesina germanica are two common estuarine benthic foraminifera subject to sediment acidification. Nevertheless, mechanisms involved in their response to acidification are still poorly understood. Since H. germanica is kleptoplastic and photosynthetically active, unlike A. confertitesta, these species were cultured in controlled experiments to determine whether these mechanisms could mitigate acidification-induced shell dissolution. Both living and dead specimens were incubated at two pH (8.0 and 6.8) and two light conditions (0 and 24 μmol photon m-2.s-1) for 18 days. For each species, respiration and photosynthesis rates were calculated based on oxygen measurements. At the end of incubation, foraminiferal viability was assessed with CellTracker Green™ biomarker, and each test was categorised according to a dissolution scale (DS) using SEM. For both species, in acidic conditions, the tests of dead specimens were significantly more dissolved than the tests of living specimens, suggesting active mechanisms providing tolerance to acidification. For the living specimens, no significant difference in the DS distribution was observed between the two species at both conditions, suggesting that kleptoplast photosynthetic activity in H. germanica does not provide additional resistance to acidification. Until at least day 12, respiration data revealed a different biological activity for the two species, and we observed distinct behaviours (e.g., encystment and pseudopod emission). These suggest each species exhibits species-specific responses to cope with acidification. On day 18, respiration rates and binocular observations showed low biological activity, suggesting dormancy or death. Further investigation is required to identify the cellular mechanisms involved to counter acidification stress.

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Embedding a multichannel ion-sensitive field-effect transistor-pH sensor array in marine sediments: a new approach for continuous in situ pH monitoring

Published 31 July 2025 Science Closed
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Human activities have significantly increased carbon dioxide emissions, leading to global warming and ocean acidification, which threaten marine ecosystems, including coral reefs with high biodiversity. Coral reef maintenance relies on a balance between calcium carbonate formation and dissolution. Among the processes, sandy sediments, covering vast areas and highly sensitive to ocean acidification, require urgent investigations to elucidate their dissolution mechanisms. However, conventional glass electrodes have limitations in continuous monitoring of the spatiotemporal distribution of pH within sediment. To address this, we developed a multichannel ion-sensitive field-effect transistor (ISFET)-pH sensor array with a tantalum oxide sensing membrane, which was embedded in the sediment to enable high-resolution and continuous pH monitoring. A 24-h pH monitoring experiment was conducted in coral reef sediments to validate the method. The performance of the sensor was evaluated through both laboratory and field observations, and a comparison with a conventional glass electrode confirmed that the ISFET-pH sensor provided stable pH measurements within the uncertainty range of the glass electrode. The developed sensor array is a low-cost and durable automatic measurement system, offering an alternative to conventional glass electrodes, which are expensive and fragile. However, optimizing sputtering conditions, annealing processes, and data processing techniques is necessary to reduce environmental influences and enhance measurement accuracy. The proposed array-based observation method enables the acquisition of high-resolution vertical pH profiles and is expected to contribute to the quantitative evaluation of the chemical role of sandy sediments and the elucidation of carbon cycling in coral reef ecosystems.

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Impacts of multiple coastal stressors across life-history stages in the eastern oyster

Published 31 July 2025 Science Closed
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Urbanized estuaries are characterized as a complex of biotic and abiotic stressors, which currently challenge marine life and are expected to intensify and become increasingly unpredictable under the ongoing impacts of climate change. The persistence of coastal species that inhabit these stressful environments will ultimately depend on their ability to adapt. Many of these species have complex life cycles, featuring distinct morphological and physiological developmental stages that can exhibit unique responses to environmental pressures. However, since all stages share the same genome, selective pressures acting on one stage can have cascading effects throughout the life cycle. The larval stage, being particularly sensitive to environmental stressors and often the only free-moving stage, plays a crucial role in gene flow across populations. Consequently, selection during this stage can set the trajectory for the entire life cycle and significantly influence the adaptive structure of populations. This dissertation explores the impacts of multiple environmental stressors across the life-history stages of the eastern oyster (Crassostrea virginica). In Chapter 1, we integrated genomic information about larval stressor response into a seascape genomics framework, using adult oysters sampled from various localities with differing environmental profiles in Narragansett Bay, Rhode Island. We identified environmentally driven signatures of local adaptation corresponding to different genomic regions, even amidst high gene flow. In loci putatively under selection in larvae exposed to coastal stressors, we found stressor-specific associations with environmental conditions that aligned with adult candidate loci, highlighting the critical role of the larval stage in shaping population adaptive divergence. In Chapter 2, we exposed genetically diverse pools of larval oysters to diurnal fluctuating acidification and hypoxia for most of their development. Genomic analysis of samples taken before and after exposure revealed substantial shifts in allele frequencies at loci putatively under selection, suggesting a potential for rapid adaptation to future environmental conditions. Chapter 3 extended this work by exposing oysters to these stressors from the pediveliger stage, through settlement, and into early juvenile development. Genomic analysis from the larval and settlement exposure periods revealed both unique and shared signatures of selection across the early developmental stages. While the juvenile stage was more tolerant to the stressor conditions, we found that stressor exposure through the pediveliger larval and settlement stages had short-term carryover effects on juvenile performance. These findings demonstrate the complex connection of evolutionary responses across the full life cycle. While early developmental stages are sensitive to coastal stressors, our analysis reveals adaptive responses that highlight the resilience of this species. Specifically, these early life-stage responses can influence later developmental stages, shaping the species’ overall adaptive capacity and impacting population structure dynamics. Consequently, understanding these dynamics is crucial for predicting how population structure and adaptive divergence will evolve in response to intensifying coastal stressors.

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Ocean acidification will be so bad that we need a new indicator for it

Published 30 July 2025 Press releases Closed

“The signs of the ocean in distress are all around us”, said Peter Thomson, Special Envoy of the Secretary-General of the United Nations for the Ocean, at the conference in Nice, France last week. “The time of debating with the denialists is over”. This statement of intent backed a slew of agreements that aim to remedy the damage already done to our oceans and prevent further harm. Overfishing, deep-sea mining, pollution with a focus on plastic, with acidification and other threats associated with climate change were on the agenda of global problems to eliminate. We all knew these problems were bad and getting worse, but a new report reveals that we continue to race past critical tipping points without even realizing it.

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When carbon dioxide is released into the atmosphere about 25% of it will end up in the oceans where it dissolves, and makes the water more acidic. This change in pH is as drastic a change in the environment as temperature or any other abiotic factor. This new aquatic chemistry isn’t something to which organisms can adapt, and they’re correspondingly suffering. Comparing certain species of shellfish with their pre-Industrial Revolution conspecifics (members of the same species) collected in 1875 by the crew of the HMS Challenger, we see that they’re up to 76% thinner than their ancestors. This was observed with a 40% increase in acidity. By 2100 the oceans will be 150% more acidic than at present.

This “Evil Twin” of Climate Change has been underestimated. We’re realizing that we’ve crossed a significant tipping point five years ago. Ocean Acidification is so dramatic that shellfish larvae can’t form their shells. We now understand that the acidity interferes with the creation of calcium carbonate that’s need to form the shells of these organisms. Oyster farmers from the Pacific Northwest have observed this since at the early 2000s. Coral, Crabs, and Krill are some of the organisms that have been specifically studied and seen to be struggling. It would be sad in and of itself if we couldn’t enjoy delicious crabs and mussels anymore, but this is worse when we consider that it signals a pending, global ecological catastrophe.

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Why is this happening?

We’ve been abundantly releasing carbon since the Industrial Revolution. Even with man-made global warming being hypothesized in the late 1800s, it’s taken a long time for us to feel its effects. Part of this is because significant amounts of carbon dioxide get absorbed into the oceans, from atmosphere to ocean surface, removing its warming potential. The oceans are so vast that as of 2010 they were storing about 16 times as much of carbon as makes up all living plants and animals on earth. This quantity is 60 times the amount that was in the atmosphere before the Industrial Revolution.

The oceans will have a saturation point at which they can’t absorb more carbon. That can be a concern eventually but don’t worry, that won’t happen until about a pH of 7.5. The majority of marine life will be dead by then. How serious of a problem is this? How likely are we to reach levels where even our biggest carbon reserve can’t take it anymore? If not likely any time soon, it’s a real enough of a question that scientists are proposing a new indicator to quantify ocean acidification.

Gamma Subscript CO2

In this paper published in May of this year, scientists propose a new variable (γCO2) to represent the absorption potential of the oceans. This is needed because as stated, we have pumped so much carbon into the atmosphere, which in turn absorbs into the oceans, that we need new math to do future calculations. Without modifying our current trajectory, we could reach a pH of 7.8 by 2100, which would be comparable to 14-17 million years ago when our planet was in the midst of an extinction event.

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A new indicator can assess absorption capacity for carbon dioxide and ocean acidification

Published 30 July 2025 Science Closed
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The ocean has absorbed 25% of anthropogenic carbon dioxide emissions over the past 40 years, effectively slowing atmospheric carbon dioxide growth but causing ocean acidification. As acidification intensifies, the seawater absorption capacity for carbon dioxide will decline. While the Revelle factor has been used to assess carbon dioxide absorption, it becomes inapplicable at pH < 7.5. Here, we propose a new factor, γCO2, to better measure the absorption capacity for carbon dioxide and acidification. γCO2 decreases with increased partial pressure of carbon dioxide and decreased pH, indicating reduced absorption capacity and intensified acidification. In 2020, global surface ocean γCO2 was 15.50 ± 0.21, a 13% decline since 1992. Projections under SSP5-8.5 anticipate an average γCO2 of 4.72 by 2100, with 61.5% of global ocean regions below the critical threshold of γCO2 = 3.0, potentially harming aragonite-based organisms.

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Unraveling natural carbonate variability in Narragansett Bay, RI using multiple high temporal resolution pH time series

Published 30 July 2025 Science Closed
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The increase in atmospheric carbon dioxide (CO2) over the last 200 years has largely been mitigated by the ocean’s function as a carbon sink. However, this continuous absorption of CO2 by seawater triggers ocean acidification (OA), a process in which water becomes more acidic and more depleted in carbonate ions that are essential for calcifiers. OA is well-studied in open ocean environments; however, understanding the unique manifestation of OA in coastal ecosystems presents myriad challenges due to considerable natural variability resulting from concurrent and sometimes opposing coastal processes—e.g. eutrophication, changing hydrological conditions, heterogeneous biological activity, and complex water mass mixing. Developing a mechanistic understanding of carbonate chemistry variability and its drivers across different time scales is a critical first step in identifying the anthropogenic OA signal against background variability and predicting future OA in coastal systems. This study analyzed high temporal resolution pH data collected during 2022 and 2023 from Narragansett Bay, RI—a mid-sized, urban estuary that since 2005 has undergone a 50% reduction in nitrogen loading—with weekly, discrete bottle samples to verify sensor data. Over a year’s worth of data revealed a distinct diurnal cycle of pH, with pH increasing during the day and decreasing during the night, with an average daily range between 0.05 and 0.1 pH units. Further, we observed a strong seasonal cycles with higher mean pH in winter (8.07 ± 0.15) and lower mean pH in summer (7.72 ± 0.07). By separating the drivers of pH variability into effects from temperature, salinity, water mass mixing, biological activity, and air-sea gas flux, we determined that biological production has the most significant influence on pH from daily to annual timescales and in episodic pH changes. To a lesser extent, the seasonal air-sea CO2 exchange and temperature cycle further modified pH on monthly to seasonal timescales. The dominant influence of biological activity in modulating pH has allowed Narragansett Bay’s nutrient reductions, which have been successful in increasing bottom water DO and pH conditions, to modestly reduce summertime surface pH through reduced primary production. This study offers an in-depth understanding of Narragansett Bay’s natural carbonate variability and highlights the sensitivity of an estuary to water management policy. These findings will benefit future OA prediction and will ultimately assist in making environmental management decisions in coastal estuaries with implications for multiple coastal stakeholders.

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Impact of natural CO2 leaks on marine ecosystems

Published 30 July 2025 Web sites and blogs Closed
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Panarea Island, in the Aeolian Archipelago, served as a unique environmental setting for a pilot study on the impact of CO2 on calcifying phytoplankton and zooplankton, in an area characterized by the presence of natural CO2 seeps on the seafloor. 

Patrizia Ziveri a Panarea, les illes Eòlies

This research allowed scientists from ICTA-UAB and the National Institute of Oceanography and Experimental Geophysics (OGS) of Italy to directly address the impact of these CO₂ leaks and ocean acidification on the ecosystems, as well as the species-specific physiological responses, including the calcification processes. 

Oceans absorb a large amount of atmospheric carbon dioxide, which helps mitigate climate change. In certain areas, such as volcanic zones near Sicily, natural CO₂ emissions from the seafloor can be observed. These leaks alter the water chemistry and may have consequences for marine life. 

The study of biodiversity changes resulting from these leaks will deepen the understanding of the role of calcifying plankton in ocean carbon sequestration and will provide valuable insights into their influence on the biogeochemical carbon cycle. This first pilot study greatly benefited from the existing OGS marine laboratory facilities at Panarea.

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Potential for regional resilience to ocean warming and acidification extremes: projected vulnerability under contrasting pathways and thresholds

Published 30 July 2025 Science Closed
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We analyze the frequency and amplitude of projected warming and ocean acidification extremes under high CO2 and strongly mitigating scenarios. We find interpretational differences in projections arising from methodological choices associated with specification of stressor thresholds. Use of absolute versus distribution-based thresholds, and, in the distribution-based case, the inclusion or exclusion of seasonal variability, can lead to very different regional patterns in projected stress. The choice of fixed versus adaptive baseline, for example, determines whether future stress frequency in the low-CO2 scenario most closely resembles that in the high-emissions scenario or historical period. We find that mitigation through emissions reductions, in combination with representation of rates of adaptation that are realistic for some marine organisms, has the potential to dampen end of century threshold exceedance to frequencies of occurrence closer to the recent historical period than to the high-emissions scenario.

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Effect of temperature on predation in a warming ocean

Published 29 July 2025 Science Closed
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Temperature is one of the most critical abiotic factors, influencing biological processes at every level, from cells to individuals, communities, and ecosystems. For ectotherms, which have limited control over their body temperature, environmental temperature can directly affect physiological activity, behavior, and ecological interactions. Predation is a key factor in determining the abundance and distribution of species and is crucial in structuring natural communities. Since most organisms in the ocean are ectotherms, temperature regulates predation across marine habitats. As the ocean warms at an unprecedented rate, understanding the impact of temperature on marine habitats has become one of the most urgent scientific questions. The Galápagos Archipelago holds significant ecological, economic, and cultural value. It has high endemicity, supports large fisheries, and has played a fundamental role in our understanding of natural history. Its unique oceanographic conditions create a dynamic system with substantial variations in water temperature. As a result, the Galápagos serves as an ideal natural laboratory for studying the role of temperature in regulating ecological interactions. This dissertation employs multiple approaches to better understand the relationship between temperature and predation within marine communities by integrating a systematic review and meta-analysis, physiological assays, and laboratory and field experiments. In Chapter 1, I reviewed the effects of ocean warming and acidification on predation and herbivory in marine organisms. In Chapter 2, I measure asymmetries in thermal performance across intertidal predators and their prey. Chapter 3 explores the effects of temperature across traits and predation in the lab and the field, using a whelk and its primary prey, a barnacle, as a model system. In Chapter 4, I investigate how starvation influences thermal performance. Finally, in Chapter 5, I measure fish predation on reefs across a temporal and spatial temperature gradient. This research highlights how temperature influence predation in intertidal and subtidal habitats in the Galápagos. Furthermore, it underscores the vital role of temperature in shaping ecological interactions, which are fundamental to structure of marine communities and determine ecosystem functioning. Understanding these temperature-driven dynamics is essential for predicting the future of marine community structure and ecosystem functioning in a changing climate.

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Regional school LAOCA 2025: unraveling the impact of deoxygenation and coastal acidification in the Latin American region: from physical and chemical perspectives to evolutionary implications

Published 29 July 2025 Events Closed

Language: Spanish
Location: Universidad del Mar, Puerto Ángel, Oaxaca, Mexico
Course date: 10-14 November 2025

Application deadline: 25 August 2025

Scope: The Regional School “Unravelling the Impact of Deoxygenation and Coastal Acidification in the Latin American Region: From Physical and Chemical Perspectives to Evolutionary Implications” is designed to address existing knowledge and capacity gaps by fostering scientific collaboration and strengthening research capabilities across the region. Organized by the Latin American Ocean Acidification Network (LAOCA), in collaboration with the Coastal Social-Ecological Millennium Institute (SECOS) and the Millennium Institute of Oceanography (IMO), and sponsored by international partners including The Ocean Foundation (TOF) and the Scientific Committee on Oceanic Research (SCOR), and Chilean (UdeC) and Mexican universities (UABC, UMAR), this school offers an interdisciplinary platform to train approximately 18 Latin American scientists in cutting-edge methodologies and concepts related to ocean deoxygenation and acidification.

This initiative will also emphasize the socioeconomic dimensions of these environmental challenges, with a focus on empowering coastal communities to build resilience through sustainable practices and informed policy interventions. Including researchers from underrepresented regions will ensure a diversity of perspectives and promote equity in scientific capacity building. By creating a network of trained scientists equipped to study and address these critical issues, the Regional School will contribute to the long-term goal of mitigating the impacts of deoxygenation and coastal acidification in Latin America. Additionally, it will strengthen collaboration among local, regional, and global initiatives, including the Global Ocean Acidification Observing Network (GOA-ON) and Global Ocean Oxygen Network (GO2NE). With representation from at least 4 to 5 Latin American countries involved in LAOCA, as well as other developing nations, the workshop will convene nine renowned Latin American scientists from Mexico and Chile, along with 16 to 18 selected participants

How to apply? Interested participants must complete the online application form available at the following link:
https://docs.google.com/forms/d/e/1FAIpQLSeUaBYFXM7TYBh-PIGHKubpt2CrI2rYJFcSXLd1QelTLYrGmQ/viewform?usp=header

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Apply to join Pier2Peer

Published 29 July 2025 Courses and training Closed

Pier2Peer is currently accepting applications for mentees and mentors! Apply by 14 September 2025 to be considered for the 2025-2026 P2P cohort. Before applying, please review eligibility requirements and terms of reference on the Pier2Peer webpage.

Pier2Peer is an international mentorship program that pairs mentees who are new to ocean acidification work with experienced mentors in the field. The program aims to foster community among OA professionals, build long-term capacity to measure and address OA globally, and provide training opportunities to support careers in OA-related fields. Pier2Peer now accepts new cohorts of mentees on an annual basis. 

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A day in the life of an ocean acidification scientist

Published 29 July 2025 Resources Closed
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This is the third video in the ProBleu Water Chemistry Science Story. Join Amy Kenworthy from the Plymouth Marine Laboratory as she joins PhD student Lily Anna Stokes in the field and the lab, where she takes samples that will help her uncover how ocean acidification is affecting coastal environments.

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Climate change in the “vulnerable” Eastern Mediterranean and adjacent areas: a literature review of ecological impacts and threats

Published 29 July 2025 Science Closed
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The Mediterranean Sea (MS) represents a complex system that acts as a convergence zone for various biogeographical influences stemming from both temperate and tropical oceanic bodies. Its intricate topography has promoted speciation and adaptation, leading to the development of distinctive and varied marine sites. The MS has a greater total alkalinity than the open ocean, which allows it to absorb a larger amount of human-induced CO2 per unit of surface area, suggesting an increased threat of acidification. The Eastern Mediterranean (EM) region has been identified as a critical climate change (CC) hotspot; by the end of the 21st century, it is anticipated that heatwaves in the EM will occur more than seven times as often and last more than three times as long. Here, we provide an extensive literature review on the CC-induced impacts and threats on biota throughout EM and adjacent areas, supporting potential mitigation actions.

The key elements contributing to the impacts and threats posed by CC in the region are: ocean warming (OW), ocean acidification (OA), and the synergistic effects of OW and OA. Additional factors encompass the combination of: i) OW and marine heatwaves (MHWs), ii) OW and non-indigenous species (NIS), iii) OW and desertification, and iv) OW and water circulation. However, the primary factor causing biodiversity decline, not just in the EM region but throughout the entire MS, seems to be the introduction of NIS, which is further worsened by OW. The primary route through the Suez Canal (SC) and its continuous expansions have sparked worry about the rising propagule pressure. There is a growing consensus that if these environmental risks are not comprehended and mitigated, a significant portion of the Mediterranean ecosystem may face severe threats to its integrity.

Ultimately, the initiative of dumping brine waste into the SC, acting as a high salinity barrier that would reduce the transfer of new species carried by the currents, is likely a practical and attractive first step towards mitigation. We suggest that this action should be embraced not only by other countries but also by international environmental organizations and agencies, through a variety of strategies, including financial support. This initiative, along with other measures aimed at alleviating the impacts of invasions on biodiversity, ecosystem services, and health, is an essential next step in the process of mitigation.

Continue reading ‘Climate change in the “vulnerable” Eastern Mediterranean and adjacent areas: a literature review of ecological impacts and threats’

Seawater carbonate chemistry along the Hawaiian‐Emperor Seamount Chain in the North Pacific

Published 28 July 2025 Science Closed
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Abstract

Below the aragonite saturation horizon (ASH), the aragonitic skeletons of deep-sea reef building corals are more susceptible to dissolution. Ocean acidification is causing the ASH to shallow worldwide, threatening the health and future of deep-sea coral reefs. Deep-sea reefs in the North Pacific already exist at or below the ASH, making them particularly vulnerable to future ocean acidification. Here we analyze multiple years (2014–2019) of seawater chemistry data from the Hawaiian-Emperor Seamount Chain (HESC), focusing particularly on intermediate depths (300–800 m) where deep-sea reefs have been found. Intermediate water masses were identified across the HESC based on characteristic temperature, salinity, and density ranges. We then characterize the corresponding carbonate chemistry of each water mass. North Pacific Intermediate Water (NPIW) dominates at intermediate depths for most of our sites. However, the influence of Pacific Subpolar Intermediate Water (PSIW) increases north of 29°N. PSIW has a shallower ASH and lower oxygen conditions than NPIW. The increasing influence of PSIW may thus play a role in restricting reef development, partially explaining why deep-sea reefs have not been found on seamounts north of Koko (34.8°N) in this region. In addition, topographic induced upwelling and temporal variability (seasonal, annual) have the potential to shift the ASH by >100 m depth. As ocean acidification progresses, chronic exposure to corrosive waters may negatively affect reef development and persistence. Characterizing the current carbonate chemistry conditions and variability is critical for informed decision making and management efforts to preserve these valuable ecosystems under future climate change.

Key Points

  • Ocean acidification is a significant threat to deep-sea coral reefs, especially in the North Pacific
  • Deep-sea coral reefs in the North Pacific may be affected by changes in seawater chemistry driven by shifts in water mass distribution
  • Seasonal and spatial variations can shift the ASH depth by over 100 m, potentially impacting reef health and persistence

Plain Language Summary

Reef-building deep-sea corals are facing new threats from climate change, including changes in ocean chemistry. These corals are especially vulnerable to increasing ocean acidity (i.e., ocean acidification). In the ocean, the aragonite saturation horizon (ASH) marks the depth below which waters become increasingly corrosive and deep-sea corals’ aragonite skeletons may dissolve. As ocean acidification progresses, the ASH is moving shallower, which can endanger the health and survival of these deep-sea reefs. Our study examines water chemistry near deep-sea coral reefs on seamounts in the Hawaiian-Emperor Seamount Chain in the North Pacific from 2014 to 2019. We observed spatial changes in water chemistry, particularly at depths where deep-sea reefs have been found, that include shallower ASH and lower oxygen levels in more northern waters, which could limit where reefs can grow. Additionally, seasonal changes may also shift the ASH depth by over 100 m, affecting local reef conditions. Understanding these chemical conditions and how they can change is crucial for managing and protecting these important deep-sea coral reef ecosystems as climate change and ocean acidification continue.

Continue reading ‘Seawater carbonate chemistry along the Hawaiian‐Emperor Seamount Chain in the North Pacific’

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