Coastal upwelling zones, shaped by global change and human impacts, naturally impose hypoxia and acidification on marine species, creating selective pressures that influence physiological responses and drive phenotypic variability. Understanding these responses is crucial for predicting marine biodiversity dynamics in heterogeneous seascapes. We explored diel cycles of pH and dissolved oxygen (DO) and their influence on the metabolic performance of the kelp crab Taliepus dentatus, a species with limited larval dispersal. Kelp crabs from two environmentally contrasting sites along an upwelling seascape in central Chile—an upwelling shadow and an active upwelling zone—were studied using field sensor data and laboratory experiments. Active upwelling disrupted the regular diel pH cycle, resulting in persistently low pH (pHT ≈ 7.5) decoupled from oxygen dynamics. Experimental simulations of diel pH–DO fluctuations revealed that nocturnal low DO/low pH conditions (DO = 1 and 5 mg l⁻¹; pH = 7.5 and 7.8 for ‘upwelling’ and ‘downwelling’ conditions, respectively) reduced metabolic rates and respiratory quotient in crabs. Individuals from the active upwelling zone exhibited elevated metabolic rates, haemolymph pH and lactate accumulation under extremely low pH/low DO conditions compared with those from the upwelling shadow, suggesting site-specific physiological adjustments. These findings underscore the importance of incorporating natural variability into experimental designs and management frameworks aimed at predicting species resilience under climate change.
Continue reading ‘Diel variability and decoupled pH-oxygen dynamics drive metabolic plasticity in kelp crabs from an upwelling seascape’Posts Tagged 'South Pacific'
Diel variability and decoupled pH-oxygen dynamics drive metabolic plasticity in kelp crabs from an upwelling seascape
Published 25 March 2026 Science Leave a CommentTags: biological response, chemistry, crustaceans, laboratory, multiple factors, oxygen, physiology, respiration, South Pacific
Long-term pH trends and spatiotemporal variability of the carbonate system in Jakarta Bay
Published 20 March 2026 Science Leave a CommentTags: biogeochemistry, chemistry, field, South Pacific
Jakarta Bay, an industrialized and densely inhabited coastal area, presents considerable environmental issues as a result of excessive organic pollution and nutrient inflow. Understanding the spatiotemporal variability of the carbonate system in such an affected bay is critical for assessing marine ecosystem health. The spatiotemporal variability of the carbonate system, pH, partial pressure of carbon dioxide (pCO2), total alkalinity (TAlk), and dissolved inorganic carbon (DIC) was investigated in Jakarta Bay during the rainy and dry seasons of 2023. pH datasets from 2011 to 2023 were also collected from the Environmental Agency of DKI Jakarta (DLH DKI Jakarta) for trend analysis. The temporal analysis shows that during the SE monsoon, the lowest pH (mean: 8.06 ± 0.43); lowest TAlk (mean: 2099 ± 340 µmol kg-1); highest pCO2 (mean: 879 ± 1177 µatm); and highest DIC (mean: 2068 ± 806 µmol kg-1) were observed. The pH distribution gradually increased from the river outlet to the outer bay; inversely, pCO2, TAlk, and DIC gradually decreased. Furthermore, from 2011 to 2023, pH in Jakarta Bay showed a slight upward tendency that was statistically insignificant, reflecting high variability and the influence of local biogeochemical processes. The carbonate system variability reflects changes in biogeochemical (Chl-a, DO and nutrients) and physical (SST and Sal) parameters. In addition, the semi-enclosed hydrodynamic properties, together with the influence of human activities, including a continuous supply of nutrients and organic materials from the mainland through the incoming rivers, further affected the balance of the carbonate system in the bay.
Continue reading ‘Long-term pH trends and spatiotemporal variability of the carbonate system in Jakarta Bay’Fatoata’s NOAA Ocean Acidification Program empowers stewardship among educators and students
Published 19 March 2026 Media coverage Leave a CommentTags: education, South Pacific
The remoteness of American Samoa is, for the most part, to our benefit when it comes to the health of our island’s ecosystems. Being in the middle of the ocean, away from everything, has its advantages. Our ocean waters are still relatively clean. Although we deal with marine debris, most of it is land-based and within our control (we just need to control it). We do not have major factories dumping toxins into our waters that kill off hundreds of species. We have even managed to stave off climate change’s evil twin, ocean acidification, and our goal is to keep it that way.
Like trees, the ocean also absorbs carbon dioxide. Carbon dioxide (CO2) is created by the burning of fossil fuels. Everyday activities that contribute to CO2 overload in the atmosphere include running your air conditioner all day and driving a car with low fuel mileage, as both require fossil fuels to operate. Increased CO2 in the ocean makes it harder for coral reefs and shell-forming organisms (like clams) to build their skeletons and shells. However, there are solutions too! One of the simplest things you can do with any environmental issue you are passionate about is to share what you know. That is exactly what Tafuna High School marine science educator, Ms. Roberta (Ertta) Laumoli, and her class did this school year.
Ms. Ertta took the first step in contributing to Ocean Stewardship this past summer by participating in Fatoata’s NOAA Ocean Acidification Program (OAP) Educator’s Workshop. The workshop provided educators with tools and resources to help them incorporate ocean acidification in their classrooms. As the school year began, the educators took what they learned about ocean acidification and shared it with their students. Ms.Ertta, Claire Bacus-Deewees and Mary Cheung-Fuk worked together and independently within their classrooms to highlight ocean acidification in their lesson plans. Their students conducted outreach, and got creative, through the development of public service announcements that shared what they learned about ocean acidification. In January, educators shared their teaching experience through photos and public service announcements. Ms. Ertta’s class excelled in all aspects of ocean acidification education, and her students’ public service announcement won first place.
Continue reading ‘Fatoata’s NOAA Ocean Acidification Program empowers stewardship among educators and students’A holistic approach to evaluating climate vulnerability of French Polynesia pearl oyster farming: bridging communities and scientific knowledge
Published 13 March 2026 Science ClosedTags: fisheries, socio-economy, South Pacific
Highlights
- A holistic assessment of climate vulnerability of black pearl aquaculture social-ecological system.
- Co-definition of adaptation strategies by scientific/institutional actors and local communities of French Polynesia.
- A list of scientifically robust and locally relevant vulnerability criteria potentially transferable to other Pacific pearl-producing countries.
- Interviewees consistently identify climate change as a factor that amplifies existing weaknesses in the pearl farming sector.
- COVID-19 exposed the sector’s dependence on global markets.
Abstract
While there is wide consensus about the reliance of climate projections at global scale, there is still uncertainty about changes at finer scale and even less on the effects of such fluctuations for local economies and societies. The vulnerability of social-ecological systems (SES) to climate change is a framework that takes into account the strong link between environment and local communities that depend on ecosystem services to ensure their livelihoods. This study explores the vulnerability of pearl farming SES to climate change, combining scientific insights with local knowledge from French Polynesian communities. A preliminary list of eighty-two criteria of exposure, sensitivity and adaptive capacity, identified through a targeted scoping review, was used to develop the interview guide that informed fifty-six face-to-face interviews and workshops conducted in 2020 and 2025. Using a combination of ranking questions and open-ended responses, the results highlight differences in the perceived exposure between scientific/institutional actors and local communities, which is reflected in the degree of sensitivity of the SES to climate drivers. Expectedly, the priorities given to adaptation measures were also different. The thematic analysis of the responses, however, shows that the two parties are aware of their own limitations in understanding the effects of climate change and recognise the need to fill mutual gaps through a collaborative production of knowledge. By integrating complementary forms of knowledge, this approach may help overcome the limitations of vulnerability assessments based exclusively on scientific expertise, and support the development of climate policies that are scientifically sound and socially accepted.
Continue reading ‘A holistic approach to evaluating climate vulnerability of French Polynesia pearl oyster farming: bridging communities and scientific knowledge’Physiology and survival of intertidal calcifiers in two contrasting upwelling systems
Published 27 February 2026 Science ClosedTags: adaptation, biological response, field, laboratory, mollusks, morphology, mortality, otherprocess, physiology, South Pacific
Climate change alters the oceans’ temperature, pH, and oxygen concentration. These changes are expected to increase globally over the coming decades, affecting a wide range of marine organisms. Coastal upwelling zones, characterized by their high environmental variability, serve as ideal natural laboratories to study the potential impacts on marine organisms and ecosystems of temperature change, acidification, and ocean deoxygenation. The estimation of survival using capture‐mark‐recapture (CMR) data has been commonly applied to vertebrates, and to date, very few studies have been done on marine invertebrate organisms. In this study, we combined field CMR data and laboratory measurements to assess the physiological responses (metabolic rate and heart rate) and survival probability of individuals in two populations of intertidal mollusks, Chiton granosus and Scurria zebrina, in contrasting upwelling environments (i.e., semi‐permanent vs. seasonal). We found that (1) there are no differences between the two studied populations for heart rate in both species, (2) the S. zebrina population subjected to seasonal upwelling has a higher metabolism, (3) there are no differences in the calcification rate between the two studied populations of both species, and (4) survival is significantly higher in the semi‐permanent upwelling location for both species. Our findings highlight species‐specific responses to contrasting upwelling regimes, suggesting that phenotypic plasticity and survival differences may influence resilience under ongoing climate change.
Continue reading ‘Physiology and survival of intertidal calcifiers in two contrasting upwelling systems’Assessing sponge resilience to ocean acidification in natural reef environments
Published 28 January 2026 Science ClosedTags: biological response, BRcommunity, community composition, field, otherprocess, photosynthesis, porifera, prokaryotes, respiration, South Pacific, vents
Highlights
- Sponges are key components of coral reefs globally providing a range of important functional roles.
- We used in situ incubation chambers to measure chlorophyll concentrations, oxygen fluxes and microbial communities for two common Indo-Pacific sponge species (Melophlus sarasinorum and Neopetrosia chaliniformis) at a natural CO2 vent (pHT 7.6–7.7) and control site in Papua New Guinea.
- We found little evidence for any physiological differences between vent and control sponges, and no differences in the overall microbial communities
- Overall, our results support the emerging evidence that heterotrophic sponges will likely be resilient to future ocean acidification.
Abstract
Sponges are key components of coral reefs globally providing a range of important functional roles. While sponges are under threat from the impacts of global climate change, there is an emerging picture of sponge tolerance to ocean acidification (OA). However, to date all physiological studies on sponge tolerance to OA have been under ex-situ experimental conditions and only for a limited number of sponge species. Instead, here we used in situ incubation chambers to measure chlorophyll concentrations and oxygen fluxes for two common Indo-Pacific sponge species (Melophlus sarasinorum and Neopetrosia chaliniformis) at a natural CO2 vent (pHT 7.6–7.7) and control site in Papua New Guinea. We also explored differences between the sponge microbial community composition between control and vent locations for N. chaliniformis. We found very low concentrations of chlorophyll in both species, compared to other sponges, suggesting these species are largely heterotrophic. We also found little evidence for any physiological differences between vent and control sponges, and no differences in the overall microbial communities, except some specific microbes. Overall, our results support the emerging evidence that heterotrophic sponges will likely be resilient to future ocean acidification.
Continue reading ‘Assessing sponge resilience to ocean acidification in natural reef environments’Core transcriptional plasticity pave the way for fish to succeed in a high-CO2 world
Published 26 January 2026 Science ClosedTags: biological response, BRcommunity, field, fish, molecular biology, performance, South Pacific, vents
Ocean acidification (OA) can alter the physiological and behavioural traits of marine fishes, raising concerns about how wild species will adapt to rising pCO2. Using natural volcanic CO2 vents at White Island, New Zealand, as analogues for future OA conditions, we quantified behaviours in situ and sequenced the brain transcriptomes of four highly site-attached fish species from two vents and a nearby control site with ambient pCO2, of which two species exhibit increased population densities at the vent. We found that two species showed changes in habitat preferences, and all four species with significant changes in gene expression related to circadian rhythm, visual perception, and energy metabolism at the vents. Strikingly, three differentially expressed genes, a heat shock protein (HS90A) and two immediate early genes (IEGs: JUN and FOS), were central regulators for transcriptional changes across all species at the vents. Within the circadian entrainment pathway, expression changes in opsins may act as a trigger, while core clock genes and IEGs function as downstream effectors, suggesting that elevated pCO2 may reset the circadian clock in these fishes. Notably, the two species with increased populations at the vents exhibited distinct transcriptional responses in genes involved in calcium signalling, reproduction, intracellular pH regulation and energy metabolism. Together with convergent evolution in a calcium signalling gene and an HS90 facilitator, these molecular features may confer their reproduction advantages and ability to cope with elevated pCO2. Our study provides novel insights into the molecular mechanisms underlying fish responses to OA and highlights key pathways that may support survival and ecological success under a naturally high-CO2 world.
Continue reading ‘Core transcriptional plasticity pave the way for fish to succeed in a high-CO2 world’Differing proteome responses to ocean acidification between two common pocilloporid corals
Published 24 December 2025 Science ClosedTags: adaptation, biological response, corals, laboratory, otherprocess, physiology, South Pacific
Ocean acidification threatens coral reef ecosystems by challenging calcification processes fundamental to reef accretion. Yet many corals continue to calcify under elevated pCO2, suggesting species-specific physiological plasticity and potential cellular compensations. Here, we use label-free quantitative proteomics to investigate proteomic responses of two common pocilloporid corals, Stylophora pistillata and Pocillopora damicornis, with known differential resistance to ocean acidification after two months at moderate (~ 940 ppm) and high (~ 2,800 ppm) pCO2 compared to the control (~ 480 ppm). S. pistillata exhibited extensive proteomic restructuring under high pCO2, marked by widespread declines of energy-generating pathways, yet selective increase of proteins involved in ion transport, cytoskeletal stability, and stress responses. This indicates a strategy of general metabolic suppression coupled with targeted investment into essential cellular functions, potentially sustaining calcification despite reduced overall metabolic capacity. In contrast, P. damicornis showed much less proteomic adjustment, primarily involving structural proteins and those potentially linked to cellular redox balance, signifying a moderate, targeted strategy for physiological stability. These divergent responses highlight contrasting modes of resistance (plasticity versus stability). Integrated with physiological data, our findings clarify cellular mechanisms controlling calcification, demonstrating the value of proteomics in coral ecophysiology and providing new insights into species-specific vulnerability under future ocean conditions.
Continue reading ‘Differing proteome responses to ocean acidification between two common pocilloporid corals’Developing scientific capacity to address ocean acidification in the Pacific Islands
Published 22 December 2025 Web sites and blogs ClosedTags: South Pacific
The Pacific Islands Ocean Acidification Centre hosted its second collective regional training on ocean acidification. The event not only enhanced the scientific skills of Pacific researchers but also strengthened a regional network dedicated to understanding and mitigating the growing impacts of ocean acidification across the Pacific.
The impact of ocean acidification on the balance of ocean ecosystems
The Intergovernmental Panel on Climate Change (IPCC) has said several times that ocean acidification is one of the most serious but often overlooked effects of growing levels of carbon dioxide (CO₂) in the air.
The IPCC’s Sixth Assessment Report (AR6) says that the ocean has absorbed over 30% of human-caused CO₂ emissions and more than 90% of the extra heat from global warming. Now, a new report from the Planetary Boundaries Science Lab reveals that seven out of nine planetary boundaries have been breached, with ocean acidification officially entering the danger zone.
The combined effects of warming and acidification are very harmful to marine species and to societies that depend on healthy ocean ecosystems. This is especially true in Small Island Developing States (SIDS) like those in the Pacific. Coral reefs that are deteriorating are harmful to fisheries and coastal protection, and the loss of marine biodiversity could jeopardise the tourist economy.
Understanding, monitoring, and responding to these changes is therefore not just a scientific need; it is a matter of survival for many island communities.
Continue reading ‘Developing scientific capacity to address ocean acidification in the Pacific Islands’Morphological adjustments enable sea urchins to sustain calcified structure function under ocean acidification
Published 10 December 2025 Science ClosedTags: biological response, echinoderms, field, morphology, South Pacific, vents
Ocean acidification can reduce the size of calcified structures produced by marine calcifiers, raising questions about their competitiveness and persistence in future oceans. Yet, size reduction in calcified structures may represent a plastic response to ocean acidification if these structures remain functional. To test this hypothesis and examine whether morphological plasticity can influence the functionality of calcified structures, we assessed the effects of ocean acidification on the morphological, mechanical and chemical properties of the calcified structures of a sea urchin species prevailing at natural CO2 vents. We found that the rigid shells covering sea urchins’ bodies (‘tests’) were thinner and that they had smaller teeth and lower spine density at vents, but the mechanical performance of these calcified structures (mechanical resilience, wear resistance and bending strength) was maintained, possibly mediated by the capacity of sea urchins to sustain acid-base balance for calcification (i.e. increased Na/Ca). Our findings suggest that such morphological shifts in calcified structures may enable sea urchins to maintain structural performance under ocean acidification. Since ocean acidification is a slow process relative to the life cycle of sea urchins, some sea urchin species may acclimate, or even adapt, to ocean acidification so that their populations and ecological functions can persist in a future high-CO2 world.
Continue reading ‘Morphological adjustments enable sea urchins to sustain calcified structure function under ocean acidification’Volcanic bubbles in Papua New Guinea a window into coral’s future
Published 9 December 2025 Press releases ClosedTags: corals, South Pacific, vents
By the end of this century, coral reefs in Australia and around the world could be slower to recover, structurally simpler, and increasingly dominated by fleshy algae as rising carbon dioxide reshapes ocean chemistry.
These are the predictions that new international research – published this week in Communications Biology – is warning against, as scientists present a volley of stark new findings about the current and long-term impact of a process known as ocean acidification.
As the oceans absorb more carbon dioxide from the atmosphere, they are becoming increasingly acidic – eroding the very calcium carbonate skeletons that build coral reefs. Yet despite decades of laboratory studies and ecosystem models, scientists have lacked real-world systems that reflect how entire reef communities respond to these long-term chemical shifts.
Researchers from the Australian Institute of Marine Science (AIMS) have now filled that gap by studying shallow-water reefs naturally bathed in volcanic CO₂. These reefs, located near remote submarine vents in Papua New Guinea’s Milne Bay Province, experience chronic exposure to elevated carbon dioxide, offering scientists a rare preview of the seascapes expected under future emissions scenarios.
Continue reading ‘Volcanic bubbles in Papua New Guinea a window into coral’s future’Impact of seawater acidification on the growth, nutritional composition, sensory profile, and antioxidant activity of Caulerpa racemosa in laboratory culture
Published 20 November 2025 Science ClosedTags: algae, biological response, growth, laboratory, morphology, physiology, South Pacific
Fluctuations in coastal water pH, driven by ocean acidification, can strongly influence photosynthetic marine species, including seaweeds. This study investigated the effects of seawater acidification on the growth, nutritional composition, sensory profile, and antioxidant activity of the green alga Caulerpa racemosa. Cultured under varying pH levels (8.25, 8.00, 7.75, and 7.50) adjusted using HCl, C. racemosa exhibited significant morphological and biochemical changes. Lower pH conditions caused bleaching and textural brittleness, with pH levels between 7.50 and 7.75 showing the most pronounced impacts. Conversely, pH 8.25 supported optimal growth, with superior morphometric performance (absolute growth of 138.30 ± 3.70 g; specific growth rate of 3.08 ± 0.04% day⁻1). Acidification decreased chlorophyll content but enhanced carotenoids, indicating reduced photosynthetic efficiency. Protein content declined under acidic conditions, while lipid and carbohydrate levels increased. Notably, antioxidant activity peaked under pH 7.50 (15.09 ± 0.04%; IC50 275.04 ± 0.85 ppm), suggesting an adaptive physiological response. Sensory evaluation revealed that C. racemosa cultured at pH 8.25 achieved the highest overall acceptability, supporting its potential for culinary and nutritional use. These findings highlight the capacity of C. racemosa to acclimate to acidified environments, providing insights into its adaptive mechanisms and applications in food, pharmaceuticals, and sustainable aquaculture.
Continue reading ‘Impact of seawater acidification on the growth, nutritional composition, sensory profile, and antioxidant activity of Caulerpa racemosa in laboratory culture’Environmental stressors interplay with top-down and bottom-up effects upon shell structure and function of an intertidal marine snail
Published 17 November 2025 Science ClosedTags: biological response, calcification, growth, laboratory, mesocosms, mollusks, morphology, multiple factors, physiology, predation, South Pacific, temperature
Highlights
- Environmental stressors affect shell properties varied across the trophic network.
- OA, OW and predator cues, reduced snail’s shell growth and calcification.
- OA and OW influenced shell structure and resistance more than predator risk.
- Food quality modulates periostracum organic content under OA and OW conditions.
- Biopolymer plasticity aids shell resistance, reducing climate stress vulnerability.
Abstract
Mollusc gastropods have evolved complex shells to protect their soft tissues from biotic and abiotic stress, but the impact of biological and environmental interactions on shell properties is not well understood. This study assessed how the individual and combined effects of increased temperature and pCO2 affect the structural and functional properties in shells of the intertidal snail Tegula atra, considering predator risk from the crab Homalaspis plana and changes in the nutritional quality of its food source, the brown kelp Lessonia spicata. Ocean acidification (OA) and ocean warming (OW) significantly affected growth rate and calcification of snails, with greater impacts under predator risk (top-down) than food quality (bottom-up) influences. FTIR-ATR analyses of the organic composition of shell periostracum indicated that OA conditions increased total organic matter, while polysaccharides, and carbonate content signals showed complex interactive effects under OA and OW conditions, with minor predator cue effects, while the nutritional value of the food source alters polysaccharides and lipids signals. Functional properties (resistance) of the shell material were affected by OA, OW, and predator cues but not by food quality source. These findings provides a novel understanding of how interacting climate stressors and trophic dynamics shape the structural (biomineralization) and functional (biomechanical) resilience of intertidal gastropods.
Continue reading ‘Environmental stressors interplay with top-down and bottom-up effects upon shell structure and function of an intertidal marine snail’Pacific Islands lead global push on ocean acidification
Published 14 November 2025 Media coverage ClosedTags: South Pacific
A Pacific Island researcher collects ocean samples from a coral reef to monitor changes in seawater chemistry — a scene from “Changing Waters: Time for Action on Ocean Acidification.” Image courtesy of the International Alliance to Combat Ocean Acidification (OA Alliance).
Pacific Island regional scientists and policy makers are featured in the upcoming short film, “Changing Waters: Time for Action on Ocean Acidification,” highlighting regional leadership on climate-ocean science and solutions.
Pacific Island nations are taking centre stage at the United Nations Framework Convention on Climate Change Meeting COP30 with the premiere of “Changing Waters: Time for Action on Ocean Acidification,” a short film that showcases how Fiji and the broader Pacific Island region are leading global efforts to address one of climate change’s invisible threats.
The short film “Changing Waters: Time for Action on Ocean Acidification,” produced by the International Alliance to Combat Ocean Acidification (OA Alliance) and LUMA Studio, will premiere at the Moana Blue Pacific Pavilion on November 17 at 5 pm, with a virtual screening available through the Virtual Ocean Pavilion on November 19 at 12 pm (Belém time).
Ocean acidification – caused by the ocean absorbing carbon dioxide from the atmosphere – may affect Pacific coral reefs, shellfish, fisheries, and the livelihoods of those who depend on healthy ocean ecosystems for food security, storm protection, and income.
Yet, as the film reveals, Pacific Island communities are not just witnessing these changes; they are pioneering solutions that combine local science with local practice.
Filmed in Fiji, Colombia, and Washington State, “Changing Waters: A Time for Action on Ocean Acidification” uses personal storytelling and on-the-ground projects to highlight ocean acidification science and policy leadership around the world.
The Fiji segment showcases how island nations are advancing local monitoring, ecosystem restoration, and policy advocacy — demonstrating how applied ocean acidification science can be integrated across broader climate policy.
“We in the Pacific contribute very little to carbon emissions, yet we are at the forefront of the impacts of climate change. Monitoring and research allow us to make informed decisions, now and for generations to come,” said Katy Soapi, Coordinator of Partnership and Engagement at the Pacific Community.
From traditional ecological knowledge to ocean monitoring networks, Pacific Island nations have become a model for integrating local expertise with scientific research and domestic policies.
Ocean acidification is a consequence of carbon emissions, and addressing it is central to global climate action, marine governance, and equity. Yet many regions around the world still lack scientific, policy, and financing support in responding to acidification at the local level.
Climate refugia could disappear from Australia’s marine protected areas by 2040
Published 3 November 2025 Science ClosedTags: chemistry, modeling, policy, regionalmodeling, South Pacific
Abstract
Climate change manifests in the ocean as chronic stressors, including warming, acidification and deoxygenation, and as acute stressors such as marine heatwaves. While marine protected areas (MPAs) are often designed to mitigate local stressors such as fishing and mining, their design seldom considers climate change. Using the Australian marine estate as a case study, we use projections from 11 CMIP6 Earth System Models to assess the climate exposure of Australian waters, and implications for the MPA network. We find that, under scenarios that exceed 1.8°C of global surface warming this century, ocean climate is projected to surpass recent variability (1995–2014) from mid-century. This results in the disappearance of climate analogs—where future ocean conditions remain within recent variability—and of climate refugia—regions with slowest rates of environmental change, most likely to retain biodiversity—by 2040. Australian MPAs and unprotected areas exhibit similar patterns of exposure to warming, acidification, deoxygenation, and marine heatwaves, suggesting that MPA placement with respect to future climate is no better than random. Despite potential re-emergence of climate refugia after 2060 under lower-emissions scenarios, continued emissions under current Nationally Determined Contributions (SSP2–4.5) risk ecosystem collapse from chronic and acute thermal stress across protected and unprotected waters. While cutting emissions can partially cap or delay climate impacts, even under lower-emissions scenarios, effective conservation requires adaptive strategies that protect biodiversity in place and on the move.
Plain Language Summary
Marine protected areas (MPAs) are designed to safeguard ocean biodiversity from threats like fishing, but their design rarely considers climate change impacts. We assessed the future exposure of Australia’s MPAs to climate change using projections of ocean climate. Our findings reveal that if global surface warming exceeds 1.8°C this century, Australian marine ecosystems will face entirely novel ocean conditions beyond recent historical variability (1995–2014) by mid-century. This results in the Australia-wide disappearance of regions with slowest rates of climate change—climate refugia—representing a substantial threat to marine biodiversity. Our results suggest that MPAs are no better off than unprotected areas, facing the same risks from warming, acidification, deoxygenation, and marine heatwaves as unprotected waters. We found that reducing emissions could facilitate the reappearance of some climate refugia after 2060, but continuing along current emissions trends risks ecosystem collapse from warming throughout Australia’s protected and unprotected waters. Effective marine conservation requires both emissions reductions and adaptive strategies to protect biodiversity as species respond to a changing ocean climate.
Key Points
- Ocean climate in Australia will reach a climate horizon by mid-century, representing novel conditions beyond recent variability (1995–2014)
- Under global warming scenarios exceeding 1.8°C this century, climate refugia are projected to disappear from Australian waters by 2040
- Existing MPAs and unprotected areas exhibit equivalent patterns of exposure to multiple ocean climate metrics, suggesting a lack of climate-smart design
Job: senior programme assistant – early career ocean professionals (ECOP) & ocean acidification monitoring (PIOAC)
Published 27 October 2025 Jobs ClosedTags: South Pacific
Description
The Pacific Community (SPC) is the principal scientific and technical organisation in the Pacific region, supporting development since 1947. We are an international development organisation owned and governed by our 27 country and territory members. In pursuit of sustainable development to benefit Pacific people, our organisation works across more than 25 sectors. We are known for our knowledge and innovation in such areas as fisheries science, public health surveillance, geoscience, and conservation of plant genetic resources for food and agriculture.
The In commemorating the SPC’s 70th anniversary, the 10th Pacific Community Conference agreed to establish the Pacific Community Centre for Ocean Science (PCCOS) to be hosted at SPC and become a true flagship for scientific excellence and a dedicated regional science information and knowledge hub. PCCOS leads the design of the SPC Ocean Flagship through consultation with SPC divisions and regional partners, as well as coordinating cross-divisional projects, implemented across SPC divisions (FAME, GEM, CCES). PCCOS is also implementing seed-projects/programmes such as the Pacific Islands Ocean Acidification Centre (PIOAC), the Pacific Early Career Ocean Professionals (ECOP) Network and Placement Programme, the Pacific Islands Decade Coordination Centre (PI-DCC), and the Regional Alliance of the Global Ocean Observing System for the Pacific Islands (PIGOOS), that all have regional coordination mandates.
The role – Senior Programme Assistant – Early Career Ocean Professionals (ECOP) & Ocean Acidification Monitoring (PIOAC) will be responsible to support the PCCOS work on Pacific Early Career Ocean Professionals (ECOP), assisting with work of the Pacific Early Career Ocean Professionals (ECOP) Network and Placement Programme. The position will also assist with the coordination of ocean acidification monitoring and capacity-building activities within PCCOS and GEM division in close collaboration with existing activities in other divisions.
Continue reading ‘Job: senior programme assistant – early career ocean professionals (ECOP) & ocean acidification monitoring (PIOAC)’On the measurement of ocean acidity with ambient sound
Published 22 October 2025 Science ClosedTags: chemistry, field, methods, North Pacific, South Pacific
Abstract
The volume-integrated pH of seawater can be determined from the frequency and depth dependence of wind-generated ambient noise in the ocean. Over the 1–10 kHz frequency band, three main processes contribute to the acoustic attenuation in seawater: the chemical relaxation of boric acid and magnesium carbonate (<3 kHz, related to pH) and of magnesium sulfate (>3 kHz, unrelated to pH). When local winds are strong (>10 m/s), the ambient noise is dominated by locally generated surface noise, which exhibits a depth-independent directionality and weak frequency and depth-dependent intensity. By measuring the depth dependence of the spectral slope, the pH may be estimated from a comparison of the experimental data with an analytical model of ambient noise. Wideband (5 Hz–30 kHz) vertical ambient sound profiles were recorded using two- and four-channel free-falling acoustic profilers at depths ranging from 500 m to 10 km during nine deployments in the Philippine Sea, Mariana Trench, and Tonga Trench from 2009 to 2021. Two analytical models of the depth dependence of ambient noise were developed: a simplified linear model valid at depths <1,500 m and a full nonlinear model valid for the deep ocean. Estimates of pH were found by minimizing the mean absolute percent error between the measurements and the models. This method of passive acoustic absorption spectroscopy demonstrates the potential and sources of uncertainty in determining the depth-averaged value of pH. The method could be suitable for the long-term passive acoustic monitoring of ocean acidity.
Plain Language Summary
In this work, we demonstrate that ambient sound in the ocean can be used to measure local, depth-averaged ocean pH. This is possible because the absorption of sound in seawater depends on chemical processes, including the relaxation of boric acid and magnesium carbonate, and has a frequency-dependent sensitivity to the pH. By analyzing the depth dependence of ambient sound over the wind-driven noise-dominated band (1–10 kHz), we can estimate pH through a comparison of measured power spectral slopes with an analytical model. Using measurements from the Philippine Sea, Mariana Trench, and Tonga Trench, carried out from 2009 to 2021 with a free-falling autonomous instrument platform, Deep Sound, we estimated the depth-averaged pH in each location. This technique can be used for long-term passive acoustic monitoring of ocean acidity.
Key Points
- The depth dependence of the spectral slope of wind-generated noise provides a measurement of the differential acoustic attenuation between 1 and 10 kHz
- The differential attenuation is used to estimate the depth-integrated pH
- The proposed method enables long-term volumetric (order of km3) monitoring of ocean acidity
From small-scale variability to mesoscale stability in surface ocean pH: implications for air–sea CO2 equilibration
Published 10 October 2025 Science ClosedTags: chemistry, field, methods, North Atlantic, South Pacific
One important aspect of understanding ocean acidification is the nature and drivers of pH variability in surface waters on smaller spatial (i.e. areas up to 100 km2) and temporal (i.e. days) scales. However, there has been a lack of high-quality pH data at sufficiently high resolution. Here, we describe a simple optical system for continuous high-resolution surface seawater pH measurements. The system includes a PyroScience pH optode placed in a flow-through cell directly connected to the underway supply of a ship through which near-surface seawater is constantly pumped. Seawater pH is measured at a rate of 2 to 4 measurements min−1 and is cross-calibrated using discrete carbonate system observations (total alkalinity, dissolved inorganic carbon, and nutrients). This setup was used during two research cruises in different oceanographic conditions: the North Atlantic Ocean (December 2020–January 2021) and the South Pacific Ocean (February–April 2022). By leveraging this novel high-frequency measurement approach, our findings reveal fine-scale fluctuations in surface seawater pH across the North Atlantic and South Pacific oceans. While temperature is a significant abiotic factor driving these variations, it does not account for all observed changes. Instead, our results highlight the interplay between temperature, biological activity, and waters with distinct temperature–salinity properties and their impact on pH. Notably, the variability differed between the two regions, suggesting differences in the dominant factors influencing pH. In the South Pacific, biological processes appeared to be mostly responsible for pH variability, while in the North Atlantic, additional abiotic and biotic factors complicated the correlation between expected and observed pH changes. While our findings indicate that broader ocean-basin-scale analyses based on lower-resolution datasets can effectively capture surface ocean CO2 variability at a global scale, they also highlight the necessity of fine-scale observations for resolving regional processes and their drivers, which is essential for improving predictive models of ocean acidification and air–sea CO2 exchange.
Continue reading ‘From small-scale variability to mesoscale stability in surface ocean pH: implications for air–sea CO2 equilibration’Effects of climate change on marine ecosystems in the southeastern Pacific: multiple ocean stressors assessed through climate velocities
Published 3 October 2025 Science ClosedTags: chemistry, modeling, regionalmodeling, South Pacific
Anthropogenic climate change (CC) has triggered a cascade of impacts on marine ecosystems, often referred to as the ‘deadly trio’: warming, acidification, and deoxygenation. While these stressors will globally lead to the compression of marine habitats, their regional effects vary significantly and remain understudied. This is particularly true for the southeastern Pacific (SEP), which supports rich pelagic and benthic ecosystems closely linked to a complex seafloor featuring archipelagos and extensive seamount chains. Using model simulations from Phase 6 of the Coupled Model Intercomparison Project, this study examines future regional-scale environmental changes in the SEP. Our analysis builds on the observation that the South Pacific Ocean Gyre is among the regions experiencing the least warming globally and that the epipelagic zone within the oxygen minimum zone (OMZ) may oxygenate in the future. These conditions may promote habitat expansion, which we assess using the climate velocities for temperature, oxygen, and pH. Estimates of climate velocities from the ensemble model mean under a pessimistic near future (2015-2050) yield values ranging from –730 to 449 km/year, exhibiting greater absolute climate velocities for oxygen than pH. Over the longer-term horizon (2015–2100), the area of zones where absolute climate velocity exceeded the 75th percentile increased by 65%, 72%, and 215% for temperature, oxygen, and pH, respectively. The strongest velocities (absolute value) occur in the equatorial sector and in the Humboldt system. While all regions mostly show a climate-driven habitat loss due to surface-to-200 m pH decline, two broad areas benefit from conservation below the surface: a region in the tropics extending from 10°S–100°W to the east of Rapa Nui and the coastal region of Peru and Chile, extending up to the Desventuradas and Juan Fernández archipelagos. While the former is due to the slow warming rates (<2.9 km yr−1), the latter results from both slow deoxygenation and oxygenation climate velocities (between −2.9 and 2.9 km yr−1) along the coast of those countries, a zone that overlaps with the lowest changes in pH in the SEP, giving them a unique conservation value. We demonstrate that epipelagic ecosystems within the OMZ may be less impacted by CC than those outside of it. These findings highlight key areas for conservation under future ocean warming, deoxygenation and pH changes.
Continue reading ‘Effects of climate change on marine ecosystems in the southeastern Pacific: multiple ocean stressors assessed through climate velocities’Using boron isotopes to examine calcification fluid pH changes in marine calcifiers under environmental change
Published 23 September 2025 Science ClosedTags: biological response, calcification, laboratory, light, mollusks, multiple factors, physiology, South Pacific, temperature
CO₂-driven ocean acidification (OA) decreases seawater pH and carbonate ion concentrations, which can impact the calcification and physiology of marine calcifiers. These organisms form calcium carbonate skeletons and shells from a specialized calcification fluid that is, to varying degrees, isolated from surrounding seawater. The carbonate structures serve as archives, preserving the chemical signature of the calcification fluid, which can be analyzed using geochemical proxies. In the following thesis, I examine how different taxa respond to future ocean changes by exposing them to predicted future acidification scenarios. Additionally, I aim to understand if an organism’s resilience to the impacts of ocean acidification is linked to their ability to regulate their calcification fluid chemistry using geochemical proxies.
In Chapter 1, I investigate the geochemistry of three reservoirs important for biomineralization – seawater, the extrapallial calcification fluid (EPF), and the shell – of two commercially important bivalve species: Crassostrea virginica and Arctica islandica to understand if the boron isotope proxy is probing calcification fluid pH. Additionally, I examined the effects of three ocean acidification conditions (ambient: 500 ppm, moderate: 900 ppm, and high: 2800 ppm CO2) on the calcification and chemistry of the calcification fluid of the same three reservoirs for C. virginica. Comparisons of seawater and extrapallial fluid geochemistry indicated that the EPF has a distinct composition that differs from seawater. Additionally, our OA experiments show that EPF chemistry is significantly affected by ocean acidification, demonstrating that the biological pathways regulating or storing these ions are impacted by ocean acidification. I also found that shell δ11B does not faithfully record seawater pH, but rather was correlated with EPF pH, despite an offset from in situ microelectrode pH measurements. However, the δ11B-calculated pH values were consistently higher than microelectrode pH measurements, indicating that the shell δ11B may reflect pH at a more localized site of calcification, rather than pH of the bulk EPF.
In Chapter 2, I investigate the effects of four different seawater pH levels (8.03, 7.93, 7.83, and 7.63) on seven complexes of temperate coralline algae collected from New Zealand. I examined the photophysiology, calcification, and geochemical proxies to probe the internal carbonate chemistry of seven different species of coralline algae under simulated end-of-century ocean acidification scenarios. Under ambient conditions we found clear physiological differences between branching and encrusting species. We found that OA treatments only had a significant effect on calcification of three of the seven species, Corallina berteroi, Corallina spp., and Jania “bottlebrush.” Additionally, OA only affected the calcification fluid pH (pHCF) of two species, decreasing pHCF for both Corallina beteroi and Jania “feather.” Nonetheless, for all species pHCF was constantly upregulated compared to seawater pH, indicating a strong control over calcifying fluid chemistry. My results underscore the high resilience of coralline algae calcification under the different end-of-century ocean acidification scenarios. This tolerance to OA is related to the species’ ability to maintain a stable carbonate chemistry to support calcification as seawater pH declined.
Continue reading ‘Using boron isotopes to examine calcification fluid pH changes in marine calcifiers under environmental change’
