Coastal waters are impacted by a range of natural and anthropogenic factors, which superimpose on effects of increasing atmospheric CO2, resulting in dynamically changing seawater carbonate chemistry. Research on the influences of dynamic pH/pCO2 on marine ecosystems is still in its infancy, although effects of ocean acidification have been extensively studied. In the present study, we manipulated the culturing pH to investigate physiological performance and fatty acid (FA) composition of two coastal diatoms, Skeletonema costatum and Thalassiosira weissflogii, in both steady and fluctuating pH regimes. Generally, seawater acidification and pH variability showed neutral or positive effects on the specific growth rate, chlorophyll a, and biogenic silica contents of the two species. Decreased pH inhibited the net photosynthetic rate by 27 % and enhanced the mitochondrial respiration rate of S. costatum by 36 % in the steady pH regime, while these rates were unaltered by decreased pH in the fluctuating regime. Acidification conditions led to lower saturated FA and higher polyunsaturated FA proportions in both species, regardless of steady or fluctuating regimes. Our results indicate that coastal acidification could affect primary production in a different way from ocean acidification. Together with the altered nutritional quality of prey for higher trophic levels, coastal acidification might have far-reaching consequences for marine ecosystem functioning.
Continue reading ‘Effects of pH/pCO2 fluctuations on photosynthesis and fatty acid composition of two marine diatoms, with reference to consequences of coastal acidification (update)’Archive Page 47
Effects of pH/pCO2 fluctuations on photosynthesis and fatty acid composition of two marine diatoms, with reference to consequences of coastal acidification (update)
Published 10 March 2025 Science ClosedTags: biological response, growth, laboratory, North Pacific, photosynthesis, physiology, phytoplankton
Biomarkers responses in the amphipod Tiburonella viscana exposed to the biocide DCOIT and CO2-induced ocean acidification
Published 10 March 2025 Science ClosedTags: biological response, crustaceans, laboratory, multiple factors, physiology, South Atlantic, toxicants, zooplankton
Highlights
- Biomarkers responses in amphipods assessed in sediment testing with the biocide DCOIT;
- Environmentally relevant concentrations of DCOIT produced biomarker responses;
- Enzymatic activities of GST and AChe were reported, including LPO and DNA damage;
- Biomarkers responses were observed in CO2-induced acidification conditions.
Abstract
Anthropogenic carbon dioxide emissions (CO2) have led to climate change and marine acidification, with an estimated decrease in ocean surface pH of 0.3-0.4 units by the end of the current century. Chemical pollution also contributes to biodiversity loss in marine environments. This issue is particularly critical in areas under pressure from shipping activities, where the introduction of new antifouling system formulations poses a major threat to non-target species. The biocide DCOIT is the most widely used alternative to organotin compounds due to its rapid degradation in seawater. The toxicity of waterborne DCOIT to marine organisms has been documented, but sediment-bound effects are limited to apical responses and pH scenarios corresponding to current levels. In this study, we determine in a combined way, the toxicity of DCOIT under marine acidification scenarios assessing biomarker responses in the burrowing amphipod Tiburonella viscana as a parameter of sublethal effects in solid phase exposures. Environmental relevant concentrations of DCOIT caused inhibition of the enzyme glutathione S-transferases (GST), changed acetylcholinesterase-like activity (AChE), and increased DNA damage at pHs of 7.7 and 7.4. For lipid peroxidation (LPO), increased levels caused by DCOIT were found for both control (8.1) and intermediate (7.7) conditions of pH. Our data provides evidence of oxidative and genotoxic effects induced by DCOIT, with activation of detoxification and defense mechanisms in T. viscana. These results are important for ecological risk assessment and managing of antifouling paint biocides in multiple stressors scenarios.
Continue reading ‘Biomarkers responses in the amphipod Tiburonella viscana exposed to the biocide DCOIT and CO2-induced ocean acidification’Influences of global warming and upwelling on the acidification in the Beaufort Sea
Published 7 March 2025 Science ClosedTags: Arctic, chemistry, modeling, regionalmodeling
Over the past three decades, increasing atmospheric CO2 (AtmCO2) has led to climate warming, sea ice reduction and ocean acidification in the Beaufort Sea (BS). Additionally, the effects of upwelling on the carbon cycle and acidification in the BS are still unknown. The Regional Arctic System Model (RASM) adequately reflects the observed long-term trends and interannual variations in summer sea ice concentration (SIC), temperature, partial pressure of CO2 (pCO2) and pH from 1990 to 2020. Multiple linear regression results from a control case show that surface (0–20 m) pH decline is significantly driven by AtmCO2 and SIC, while AtmCO2 dominates in subsurface (20–50 m) and deep layers (50–120 m). Regression results from a sensitivity case show that even if the AtmCO2 concentration remained at 1990 levels, the pH would still exhibit a long-term decline trend, being significantly driven by SIC only in the surface layers and by SIC and net primary production (NPP) in the subsurface layers. In contrast to the nearly linearly increasing AtmCO2 over the last three decades, the ocean pH shows more interannual variations that are significantly affected by SIC and mixed layer depth (MLD) in the surface, NPP and Ekman pumping velocity (EPV) in the subsurface and EPV only in the deep layer. The comparison of results from high and low SIC years reveals that areas with notable pH differences are overlapping regions with the largest differences in both SIC and MLD, and both cause a statistically significant increase in pCO2 and decrease in pH. Comparison of results from high and low EPV years reveals that although stronger upwelling can lift up more nutrient-rich seawater in the subsurface and deep layers and lead to higher NPP and pH, this effect is more than offset by the higher DIC lifted up from deep water, leading to generally lower pH in most regions.
Continue reading ‘Influences of global warming and upwelling on the acidification in the Beaufort Sea’Multiple-stressor effects of ocean warming, acidification and hypoxia on the locomotor behavior of sea cucumber Apostichopus japonicus
Published 6 March 2025 Science ClosedTags: biological response, echinoderms, laboratory, multiple factors, North Pacific, oxygen, performance, temperature
Highlights
- Ocean warming, acidification, and hypoxia simultaneously affect marine organisms.
- The combined stress significantly affects the locomotor behavior of A. japonicus.
- The movement intensity of A. japonicus was increased under combined stressors.
- The erratic movement patterns indicates a stress-induced escape response.
Abstract
Driven by human activities, global climate change is causing unprecedented changes in marine ecosystems, such as ocean warming, ocean acidification and hypoxia. These stressors, which often occur simultaneously and interact with each other, have significant negative impacts on marine organisms and ecosystems, and are referred to as the “deadly trio”. Understanding how these environmental stressors affect marine organisms is critical, particularly concerning their behavior and survival. Locomotion behavior, an essential aspect of an organism’s ability to find food, evade predators, and reproduce, can be significantly disrupted by environmental changes. The sea cucumber (Apostichopus japonicus), an IUCN-listed endangered species further threatened by climate change, serves as a crucial model organism for studying these effects. This study investigates the impact of combined stressors—ocean warming, acidification and hypoxia on the locomotion behavior of A. japonicus under future ocean scenarios. Cumulative movement distance, cumulative movement time, mean velocity, and maximum velocity of sea cucumbers were measured. The results show that the synergetic interaction of environmental stressors alters locomotor behavior of A. japonicus, increasing movement activity with more erratic patterns. Specifically, compared to the control group (NC), the combined stress group (WAH) showed an increase in cumulative movement time from 79.06 % to 93.40 % (P < 0.05), an increase in cumulative movement distance from 2722.11 cm to 5700.09 cm (P < 0.01), and an increase in mean velocity from 4.63 cm/s to 9.50 cm/s (P < 0.05). These findings indicate that combined stressors significantly affect the locomotion behavior of A. japonicus, providing new insights into its behavioral phenotypic adjustments or responses to environmental stress. This study emphasizes the importance of understanding the impacts of multiple-factor stressors on marine organisms to better predict and mitigate the effects of global climate change.
Continue reading ‘Multiple-stressor effects of ocean warming, acidification and hypoxia on the locomotor behavior of sea cucumber Apostichopus japonicus’UK waters facing accelerated ocean acidification, new PML-led study reveals
Published 5 March 2025 Press releases ClosedTags: North Atlantic
Revealing critical insights into air-sea carbon dioxide exchanges, pH trends in the North Atlantic, and detailed observations in UK shelf seas, the study also details how ocean acidification impacts marine species through both direct physiological effects from changing pH and CO2 levels and indirect effects via food web disruption.
While some organisms like certain phytoplankton and seaweeds may show positive or neutral responses to elevated CO2, many marine invertebrates and fish species experience neutral or negative effects. Species that build calcium carbonate structures, including corals, shellfish, and important plankton groups, face particularly high risk. Even more developed organisms like fish, though less susceptible to direct impacts, could suffer from the loss of key prey species. The research highlights the need for better integrated approaches that scale from experiments to biogeochemical models. It also emphasizes the urgent need for enhanced observational capacity and improved model accuracy to better understand and address ocean acidification.
Key highlights from the update:
- Atmospheric CO2 surpassed 420 ppm in 2024, continuing to rise by approximately 2.5 ppm annually over the past decade
- The global ocean absorbs roughly 25% of anthropogenic carbon dioxide emissions each year
- The North Atlantic Ocean, containing the highest levels of anthropogenic CO2 among ocean basins, is experiencing ongoing surface water acidification
- Bottom waters in some locations are acidifying faster than surface waters
- Certain marine species already show effects from ocean acidification during short-term fluctuations, potentially serving as indicators for long-term ecosystem impacts
- Models project that continental shelf seawater pH will continue to decline through 2050, with rates increasing in the second half of the century depending on emissions scenarios
- Coastal pH decline is projected to be faster in areas like the Bristol Channel compared to the Celtic Sea
- Under high-emission scenarios, bottom waters on the North-West European Shelf seas could become corrosive to aragonite as soon as 2030
Ocean acidification around the UK and Ireland
Published 5 March 2025 Newsletters and reports ClosedTags: biological response, chemistry, field, modeling, North Atlantic, regionalmodeling, review
KEY FACTS
What is already happening
- Atmospheric CO2 exceeded 420 ppm in 2024 and has continued to increase by approximately 2.5 ppm per year over the last decade. The global ocean absorbs approximately a quarter of anthropogenic carbon dioxide (CO2) emissions annually.
- The North Atlantic Ocean contains more anthropogenic CO2 than any other ocean basin, and surface waters are experiencing an ongoing decline in pH (increasing acidity). Rates of acidification in bottom waters are occurring faster at some locations than in surface waters.
- Some species are already showing effects from ocean acidification when exposed to short-term fluctuations and could be used as indicator species for long-term impacts on marine ecosystems.
What could happen in the future
- Models project that the average continental shelf seawater pH will continue to decline to year 2050 at similar rates to the present day, with rates then increasing in the second half of the century, depending on the emissions scenario.
- The rate of pH decline in coastal areas is projected to be faster in some areas (e.g. Bristol Channel) than others, such as the Celtic Sea.
- Under high-emission scenarios, it is projected that bottom waters on the North-West European Shelf seas will become corrosive to moresoluble forms of calcium carbonate (aragonite). Episodic undersaturation events are projected to begin by 2030.
- By 2100, up to 90% of the north-west European shelf seas may experience undersaturation for at least one month of each year.
- High levels of nearshore variability in carbonate chemistry may mean that some coastal species have a higher adaptative capacity than others. However, all species are at increased risk from extreme exposure episodes.
The effects of ocean warming and elevated CO2 on the feeding behavior and physiology of two sympatric mesograzers
Published 4 March 2025 Science ClosedTags: biological response, crustaceans, laboratory, multiple factors, performance, physiology, respiration, temperature, zooplankton
Highlights
- Combining climate stressors gives better insights into climate change effects.
- Sympatric species respond differently to the same environmental stressors.
- Temperature and pH did not influence the physiology and feeding of H. niger.
- Combined effects of temperature and pH reduced feeding rate in C. filosa.
- Rates of ammonia excretion and protein catabolism increase with warming.
Abstract
Atmospheric CO2 concentrations have increased significantly since pre-industrial times, leading to ocean warming and acidification. These environmental changes affect the physiology of marine organisms as they modify metabolic processes. Despite the critical role of temperature and pH in marine biology, studies of their combined effects are limited. This study investigated the interactive effects of ocean warming and acidification on the feeding behavior and physiology of two sympatric amphipods, Hyale niger and Cymadusa filosa. Using an orthogonal experimental design with two temperatures (27 °C and 30 °C) and two pH levels (7.8 and 7.5), we assessed feeding rates, respiration rates, ammonia excretion, and O/N ratios. Results indicated that C. filosa was less tolerant to these stressors than H. niger. While H. niger showed no significant changes between treatments, C. filosa showed reduced feeding rates and altered physiological responses to elevated temperature and decreased pH. Reducing the feeding rate of C. filosa may favor macroalgal biomass and strengthen bottom-up control in phytal communities. In addition, increased ammonia excretion in C. filosa suggests increased protein catabolism to meet energy demands at higher temperatures, despite reduced oxygen consumption. This indicates a compromised metabolism and a reduction in circulating oxygen capacity for C. filosa. The study shows heterogeneous responses to climate change, highlighting the need to assess combined environmental stressors in different species to accurately understand the impacts of climate change.
Continue reading ‘The effects of ocean warming and elevated CO2 on the feeding behavior and physiology of two sympatric mesograzers’Ocean acidification: understanding the effects, exploring the solutions
Published 4 March 2025 Science ClosedTags: adaptation, biological response, mitigation, otherprocess, review
Human-induced climate change is now a proven fact, no longer in doubt in the scientific community. Heat waves, droughts and floods, storms and hurricanes of unprecedented power are current manifestations of this ongoing climate change, where exceptional events are becoming more and more frequent. The increasing combustion of fossil fuels such as coal, gas and oil, as well as deforestation for agriculture and urbanisation, are enlarging the concentration of greenhouse gases in the atmosphere, warming the planet. Of the greenhouse gases produced by this combustion, carbon dioxide (CO2) is by far the most abundant.
Climate change is not the only consequence of rising atmospheric CO2 concentrations. Anthropogenic CO2 is also partly absorbed by the oceans, where it is transformed into carbonic acid, causing “ocean acidification”. This phenomenon really emerged in the scientific literature in the early 2000s, becoming one of the most studied topics in marine science over the last twenty years. Through its effects on water chemistry, ocean acidification has multiple consequences for the marine world and its inhabitants, and consequently for the biological resources on which we depend to live. However, ocean acidification, often referred to as “the other CO2 problem” in reference to global warming, remains largely unknown to the general public. The few times the media mention this phenomenon, it is to ask whether we will still be eating oysters in 2100! While this question is relevant, as it suggests that these animals are sensitive to acidification, it deserves to be considerably broadened. In other words, the idea is to understand not only the world we live from, but also the world we live in, so that we can face the new climate regime with lucidity and pragmatism.
The aim of this book is to take a comprehensive look at ocean acidification by answering ten simple questions. It reviews the biogeochemical foundations of acidification; past, current and future trends; impacts on organisms, marine ecosystems and humans; and finally, remediation options and scientific perspectives.
The problem of ocean acidification is transdisciplinary, and finds its answers in biogeochemistry, marine biology and ecology, evolution, aquaculture and fisheries, as well as economics and sociology. May this book make accessible to as many people as possible the magnitude of this little-known phenomenon, which is nonetheless essential to understanding future changes.
Continue reading ‘Ocean acidification: understanding the effects, exploring the solutions’New study shows impact of ocean acidification on Bering Sea red king crab
Published 3 March 2025 Press releases ClosedTags: biological response, crustaceans, fisheries
A fishing tender with 65,000 pounds of Bristol Bay red king crab arrives at Peter Pan in King Cove for processing in 2011. Photo by Margaret Bauman for The Cordova Times.
Ocean acidification appears to be a driver in the decline of Bristol Bay red king crab, a highly value wild Alaska seafood that has for years been threatened by climate change.
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A new report published on Feb. 7 in the Canadian Journal of Fisheries and Aquatic Science said that negative effects of acidification explained 21% of recruitment variability of Bristol Bay red king crab between 1980 and 2023, and 45% since 2000.
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“Anthropogenic emissions of carbon dioxide into the atmosphere have generated a substantial increase in ocean carbon uptake and a shift in the marine carbonate system to a state of higher acidity and lower carbonate saturation states in a process referred to as ocean acidification,” the report said. “Carbon dioxide is more soluble in cold water, and high-latitude waters that are naturally cold and carbon-rich, such as the Bering Sea, are particularly vulnerable to acidification.”
According to Darcy Dugan, director of the Alaska Ocean Acidification Network, these findings mark a shift in messaging from the research community.
“Prior to the study researchers believed species in Alaska were likely being impacted but we didn’t have the data or analysis to back it up,” she said. “Red king crab is the first species where we can see a correlation between acidity and the decline of a wild stock.”
Continue reading ‘New study shows impact of ocean acidification on Bering Sea red king crab ‘Statistical prediction of in situ coral reef carbonate dynamics using endmember chemistry, hydrodynamic models, and benthic composition
Published 3 March 2025 Science ClosedTags: chemistry, communitymodeling, field, modeling, North Atlantic
In the face of rapidly compounding climate change impacts, including ocean acidification (OA), it is critical to understand present-day stress exposure and to anticipate the biogeochemical conditions experienced by vulnerable ecosystems like coral reefs. To meaningfully predict nearshore carbonate chemistry, we must account for the complexity of the local benthic community, as well as connectivity between habitats and relevant endmember carbonate chemistry. Here, we adopt a system-scale approach to predict site-scale effects of benthic metabolism on the carbonate system of the Florida Reef Tract (FRT). We utilize bimonthly carbonate chemistry data from ten cross-shelf transects spanning 250 km of the FRT to model changes in dissolved inorganic carbon (DIC) and total alkalinity (TA). Benthic habitat maps were used to broadly classify communities known to impact carbonate chemistry. A SLIM 2D hydrodynamic model with mesh resolution reaching 100 m over reefs and along the coastline was used to determine the relevant water mass histories and identify the upstream benthic communities shaping local carbonate chemistry. These historical metabolic footprints, or “flowsheds”, were used to build predictive models of the change in DIC and TA at each station. The best predictive models included the chemical impacts of benthic ecosystem metabolism, as defined by water mass trajectories, weighted endmember chemistry, volume, time, and other environmental parameters (light, temperature, salinity, chlorophyll-a, and nitrate). Considering water mass for 5 days prior to sample collection yielded the highest model skill.
Continue reading ‘Statistical prediction of in situ coral reef carbonate dynamics using endmember chemistry, hydrodynamic models, and benthic composition’Quantifying coral-algal interactions in an acidified ocean: Sargassum spp. exposure mitigates low pH effects on Acropora cervicornis health
Published 3 March 2025 Science ClosedTags: algae, biological response, BRcommunity, corals, growth, laboratory, mesocosms, North Atlantic, physiology
Increasingly frequent large-scale pelagic Sargassum algae blooms in the Atlantic have become a problem for coastal ecosystems. The mass decay of these blooms reduces water quality for coastal flora and fauna. However, the effects of living Sargassum blooms on seawater quality and consequently coral reef ecosystems that rely on delicately balanced carbonate chemistry are more ambiguous. Future oceans are predicted to be more acidic as additional anthropogenic CO2 emissions are absorbed, potentially tipping the balance in favor of algal blooms at the cost of coral survival. This study aimed to simulate the indirect interaction between pelagic Sargassum spp. and Acropora cervicornis coral fragments from the Florida Reef in current-day and future ocean pH conditions over the course of 70 days in a mesocosm experimental system. Measurements of coral growth and health via buoyant weight and Pulse Amplitude Modulated (PAM) fluorescence measurements reveal an unexpected coral-algal interaction. After 1 month, coral growth was significantly reduced under ocean acidification conditions and exposure to Sargassum; at the same time quantum yield and maximum electron transport rate of photosynthesis were increased relative to control counterparts in ambient and future pH scenarios by up to 14% and 18% respectively. These improvements in photosynthetic efficiency did not translate to significant differences in growth by the final measurement time point. In addition, the presence of Sargassum spp. did not raise seawater pH in the system, raising questions about how it benefited photosynthetic efficiency in exposed corals. Heterotrophy of detrital algal matter is suspected to compensate for impaired photosynthesis of pH stressed corals. Therefore, despite their current negative reputation, Sargassum blooms could provide short term localized benefits to corals in present and future ocean conditions.
Continue reading ‘Quantifying coral-algal interactions in an acidified ocean: Sargassum spp. exposure mitigates low pH effects on Acropora cervicornis health’Impacts of ocean acidification on global seafood & solutions required for a sustainable future
Published 28 February 2025 Web sites and blogs ClosedThe negative impacts of ocean acidification have become a severe threat to our global seafood supply and aquatic ecosystems more than ever. Increasing carbon emissions are causing our oceans to become record-breaking acidic, significantly disrupting their natural chemical balance and harming wildlife habitats.
From contaminated marine species to decreasing seafood supply and worldwide environmental hazards, more must be done to combat the consequences of ocean acidification before the damage becomes irreversible if left unaddressed.
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Decreased Global Seafood Supply From Contaminated Marine Species
One of the most critical effects of ocean acidification is the threat to our global seafood supply. In addition to over-absorbing rising CO2 levels from burning fossil fuels, our oceans absorb pollutants from these related human actions. As a result, it contaminates the marine species we consume, like lobsters, shrimp, and minerals.
If sustainable alternatives to fossil fuels aren’t implemented to combat these negative ocean acidification effects, our seafood supply will decrease worldwide.
Additionally, this limited availability of seafood will increase consumer prices due to production and harvest challenges from this contamination.
Ocean Acidification Monitoring & Water Filtration System Investments
Commercial fisheries and aquaculture farms must invest in marine monitoring and water filtration technologies to combat the effects of ocean acidification.
Continuously monitoring oceans measures their acidification levels and allows staff to modify seawater intake based on the real-time pH accurately. It also verifies when the water quality is safe enough to farm fish and aquatic species.
Water filtration systems help land-based seafood production facilities reduce the carbon levels in their water tanks to ensure ethical animal welfare and food safety standards. These technological investments are crucial to improving the implementation and management of sustainable commercial seafood practices.
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Nearshore Aquaculture Farm Relocations to Land-Based & Offshore Sites
Relocating nearshore aquaculture farms offshore or to land-based operations reduces ocean acidification pressures. Because nearshore and coastline areas have minimal water flow and lower seafloor depth, aquaculture by-products like fish waste, uneaten fish feed, and water treatment chemicals can easily accumulate and release CO2. It can also trigger toxic algal blooms, which are among the effects of ocean acidification.
While it’s not easy or cheap to move nearshore aquaculture farms, especially large-scale facilities, they can save on costs by relocating to existing land-based infrastructures. Additionally, aquaculture farms can apply for government-funded grants and low-interest loans for financial assistance.
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Continue reading ‘Impacts of ocean acidification on global seafood & solutions required for a sustainable future’Pacific-Arctic ocean acidification: decadal trends and drivers
Published 28 February 2025 Science ClosedTags: Arctic, chemistry, field, review
This study presents the first regional-scale analysis to quantify decadal trends and drivers of surface ocean acidification (OA) across the highly sensitive Pacific-Arctic Region (PAR) using a consistent trend methodology. From 1993 to 2021, the Southern PAR acidified at rates comparable to the global average, with pHT declining by 0.018 units dec−1 and aragonite saturation state (ΩAr) decreasing by 0.063 units dec−1, primarily driven by anthropogenic CO2 uptake. In contrast, the Bering Strait exhibited slower acidification, with pHT declining by 0.011 units dec−1 and ΩAr decreasing by 0.020 units dec−1 — substantially lower than previously reported — likely due to increased primary productivity. The Northern PAR experienced the most rapid acidification: pHT decreased by 0.028 units dec−1 and ΩAr by 0.078 units dec−1, with the Beaufort Gyre acidifying 2–4 times faster than the global mean. This rapid change was driven by rising atmospheric CO2 and significant freshening linked to sea ice melt and increased riverine input, which reduced the ocean’s buffering capacity. Continued warming will likely exacerbate acidification in regions transitioning from multi-year to seasonal ice. While local processes such as primary productivity can temporarily counteract OA, whether they can offset rising anthropogenic CO2 levels remains unclear. This underscores the importance of biogeochemical models that integrate climatic and biological feedbacks, enabling accurate forecasts of OA changes and their impacts on marine ecosystems. These findings highlight the urgent need for sustained monitoring in the PAR, where accelerating changes threaten critical ecosystems.
Continue reading ‘Pacific-Arctic ocean acidification: decadal trends and drivers’A global upward trend in ocean-atmosphere carbon dioxide fugacity
Published 28 February 2025 Science ClosedTags: chemistry, field, globalmodeling, modeling, review
The carbon dioxide fugacity in the global oceans has shown a slow upward trend, over the past 20 years, the carbon dioxide fugacity in global oceans has increased by 6.7%.This conclusion is based on over 160,000 quality-controlled measurements of surface ocean carbon dioxide fugacity from 2000 to 2020, and employing machine learning methods, a satellite-based assessment model for sea-air carbon dioxide fugacity (fCO2) has been developed, aiming to reveal global changes in fCO2 over the past 20 years. This study investigates the factors influencing sea-air carbon dioxide fugacity (fCO₂) by integrating a comprehensive dataset, including satellite data coordinates, fundamental seawater parameters (e.g., salinity and temperature), wind speed, seawater acidity and alkalinity, seawater velocity, geostrophic seawater velocity, surface partial pressure of carbon dioxide in seawater, downward mass flux of carbon dioxide expressed as carbon, concentrations of dissolved inorganic carbon, phosphate, nitrate, silicate, chlorophyll, and dissolved oxygen. A comparative analysis was conducted among various machine learning methods, such as XGBoost, Random Forest, Light Gradient Booster, Feedforward Neural Network, Convolutional Neural Network, and Backpropagation Neural Network. Based on the best performance, the XGBoost algorithm was selected for model construction. The results of independent field validation demonstrate that the model has a low root mean square error (RMSE = 18.08 μatm), mean absolute percentage error (MAPE = 1.1%), and a high coefficient of determination (R² = 0.91). Ultimately, the global distribution of sea-air carbon dioxide fugacity at a resolution of 0.25° × 0.25° from 2000 to 2020 was reconstructed.
Continue reading ‘A global upward trend in ocean-atmosphere carbon dioxide fugacity’Using taxonomy to strengthen aquaculture for climate change, ocean acidification and invasive species
Published 28 February 2025 Science ClosedTags: fisheries, mitigation
The Government aimed to quintuple aquaculture production within 16 years, targeting a NZD 3 billion industry. However, challenges—such as Climate Change, Ocean Acidification and threats from pests—pose hurdles that cannot be overcome by the aquaculture sector alone. Robust collaboration between scientists and the industry is imperative to address these threats and ensure success. Climate Change and Ocean Acidification disrupt the reproduction and settlement of crops, hindering shell growth and increasing the risks of pest attacks. The projected annual cost of mitigating pest species will exceed NZD 150 million. While this figure has been economically evaluated, it does not account for the additional intensification from Ocean Acidification and Climate Change. Each of these factors, alone and in combination, poses a risk of collapse for farms. Collaboration between the industry and scientists is essential for developing solutions and advancing aquaculture practices. Establishing a balanced partnership is crucial for advancing New Zealand’s aquaculture sector, ensuring sustainability and resilience against challenges. Although this perspective is based on taxonomy, developmental biology and shellfish aquaculture, the challenges and insights are applicable across various sectors. Therefore, the obstacles and solutions described are relevant to the tasks and hurdles faced by scientists in other fields.
Continue reading ‘Using taxonomy to strengthen aquaculture for climate change, ocean acidification and invasive species’Groundwater carbon biogeochemistry of coastal confined aquifers and its implications after discharge
Published 28 February 2025 Science ClosedTags: biogeochemistry, chemistry, field, North Pacific
Highlights
- Carbonate weathering and methanogenesis affect DIC production in deep groundwater.
- Deep groundwater discharge serves as a buffer against ocean acidification.
- Neglecting deep groundwater overestimates the effect of TSGD on ocean acidification.
Abstract
Shallow groundwater discharge from unconfined aquifers is known to affect ocean carbon budget and ocean acidification. However, the role of deeper groundwater discharge from confined aquifers in ocean carbonate chemistry was previously overlooked. Here, we characterized dissolved inorganic carbon (DIC) and total alkalinity (TA) concentrations and estimated DIC and TA fluxes from confined aquifers (50 ∼ 520 m depth) in the northern Yangtze River Delta. The results show that deep groundwater generally exhibits high DIC concentrations, primarily influenced by carbonate weathering and methanogenesis. The DIC concentrations in the deep groundwater (50 ∼ 520 m depth) are about 14 % lower than the TA concentrations, indicating that the deep groundwater discharge mitigates ocean acidification. However, the DIC concentrations in shallow groundwater (< 30 m depth) are much higher than the TA concentrations, indicating the strengthening of ocean acidification after discharging to the sea. The mean [TA-DIC] flux from the deep groundwater accounts for approximately 8 % of that from the shallow groundwater, but overlooking the deep groundwater will considerably overestimate the effect of terrestrial groundwater on ocean acidification.
Continue reading ‘Groundwater carbon biogeochemistry of coastal confined aquifers and its implications after discharge’Drivers and variability of ocean carbonate chemistry near Hawai‘i
Published 27 February 2025 Science ClosedTags: biogeochemistry, chemistry, field, North Pacific
Ocean carbon uptake, cycling and sequestration are variable on all time scales, and modulated by an interplay of complex physical and biogeochemical drivers, including anthropogenic CO2 increase and associated ocean acidification. This dissertation disentangles the contributions of and feedbacks between these drivers to assess past changes and potential future shifts in biological production, carbon sequestration and the interplay between ocean physics and carbon speciation. The variability of the CO2-carbonate system is investigated from seasonal to interannual time scales at two different locations in the North Pacific that represent crucial environments to study in the face of global change. The first two studies investigate dynamics in the oligotrophic North Pacific Subtropical Gyre near Hawai‘i, which is the largest ecosystem on earth, and a significant sink for anthropogenic carbon from the atmosphere. A seasonal mixed layer carbon budget stresses the importance of the (relatively steady) carbon supply from horizontal transport balanced by the (spring to summer) biological drawdown over a year. Long-term changes over 35 years are then explored in the mixed layer, as well as subsurface water masses, at the same location. A substantial enhancement of ocean acidification is detected in several subsurface layers, driven by multiple combinations of source water changes from atmospheric forcing (with a focus on freshwater forcing), and/or biological produc1vity, as well as increasing ingrowth of respired carbon and alkalinity during subduction. The influence of salinity changes in addition to biological and temperature changes on modulation of ocean acidification is then further examined in a coastal coral reef environment on the shores of O‘ahu, Hawai‘i, where an increase in seawater carbon dioxide has not led to a measurable decline in calcium carbonate saturation state. Here, global temperature and regional salinity changes exert opposing influences on coastal acidification. This is additionally exacerbated by local high respiration, but also buffered by dissolution of calcium carbonate in sediments and/or the water column. Insights from all three chapters shed a light on the complex interplay of physical, geochemical, and biological drivers of marine CO2-carbonate chemistry in these locations, and on the implications for global carbon cycling and the fate of anthropogenic CO2.
Continue reading ‘Drivers and variability of ocean carbonate chemistry near Hawai‘i’Impacts of ocean acidification on the palatability of two Antarctic macroalgae and the consumption of a grazer
Published 27 February 2025 Science ClosedTags: algae, Antarctic, biological response, BRcommunity, crustaceans, laboratory, performance
Increases in atmospheric CO2 have led to more CO2 entering the world’s oceans, decreasing the pH in a process called ’ocean acidification’. Low pH has been linked to impacts on macroalgal growth and stress, which can alter palatability to herbivores. Two common and ecologically important macroalgal species from the western Antarctic Peninsula, the unpalatable Desmarestia menziesii and the palatable Palmaria decipiens, were maintained under three pH treatments: ambient (pH 8.1), near future (7.7) and distant future (7.3) for 52 days and 18 days, respectively. Discs of P. decipiens or artificial foods containing extracts of D. menziesii from each treatment were presented to the amphipod Gondogeneia antarctica in feeding choice experiments. Additionally, G. antarctica exposed to the different treatments for 55 days were used in a feeding assay with untreated P. decipiens. For D. menziesii, extracts from the ambient treatment were eaten significantly more by weight than the other treatments. Similarly, P. decipiens discs from the ambient and pH 7.7 treatments were eaten more than those from the pH 7.3 treatment. There was no significant difference in the consumption by treated G. antarctica. These results suggest that ocean acidification may decrease the palatability of these macroalgae to consumers but not alter consumption by G. antarctica.
Continue reading ‘Impacts of ocean acidification on the palatability of two Antarctic macroalgae and the consumption of a grazer’Spatiotemporal variability of seawater carbonate chemistry in diverse coral reef environments in South East Asia and Australia
Published 26 February 2025 Science ClosedTags: biogeochemistry, chemistry, field, modeling, regionalmodeling, South Pacific
Coral reefs are under threat from global environmental perturbations including ocean warming, acidification, and deoxygenation. The degree to which these perturbations will affect coral reefs is dependent on a range of factors including the local hydrodynamics and biogeochemical processes, both which vary widely across space and time. Consequently, not all coral reefs will be affected equally due to differences in local properties and processes. To develop predictive capacity for how coral reefs will be affected by ocean acidification (OA) it is necessary to first understand the current seawater CO2 chemistry variability and drivers. In this dissertation, autonomous sensors and discrete seawater samples were used to characterize the natural spatial and temporal variability of seawater CO2 chemistry across different reef scales and habitats in Australia and South East Asia (i.e., Heron Island, Great Barrier Reef; Dongsha Atoll and Taiping Island, South China Sea; and Onna-son Reef, Okinawa). In Heron Island, the largest spatial and temporal variability in seawater chemistry was associated with the most shallow, western region of the platform that also had the longest residence time. Interactions between reef geomorphology and timing of the tidal cycle greatly influenced chemical gradients and variability leading to some unexpected trends and patterns. On Dongsha, elevated pH and aragonite saturation state (ΩAr) were observed inside a semi-enclosed lagoon during both day and night. Future projections showed that this environment will not cross, detrimental aragonite thresholds (e.g., ΩAr < 2.92) as frequently as patch reefs and the large-scale lagoon of Dongsha. However, concurrent high water temperature and hypoxia indicated that this environment will not offer respite to taxa sensitive to OA. In Onna-son, the influence of seaweed cultivation on seawater chemistry during spring was compared to times of no cultivation during fall and winter. pH elevation was observed during both spring (+0.13 units) and fall (+0.10 units), but it was not possible to separate the role of cultivated seaweed from natural taxa. This dissertation demonstrates current coral reef seawater CO2 chemistry conditions and biochemical function, information that will be critical for making rigorous projections for the future.
Continue reading ‘Spatiotemporal variability of seawater carbonate chemistry in diverse coral reef environments in South East Asia and Australia’Climate-driven shifts in Southern Ocean primary producers and biogeochemistry in CMIP6 models
Published 26 February 2025 Science ClosedTags: Antarctic, biogeochemistry, biological response, BRcommunity, chemistry, community composition, modeling, otherprocess, phytoplankton, regionalmodeling
As a net source of nutrients fuelling global primary production, changes in Southern Ocean productivity are expected to influence biological carbon storage across the global ocean. Following a high-emission, low-mitigation pathway (SSP5-8.5), we show that primary productivity in the Antarctic zone of the Southern Ocean is predicted to increase by up to 30 % over the 21st century. The ecophysiological response of marine phytoplankton experiencing climate change will be a key determinant in understanding the impact of Southern Ocean productivity shifts on the carbon cycle. Yet, phytoplankton ecophysiology is poorly represented in Coupled Model Intercomparison Project phase 6 (CMIP6) climate models, leading to substantial uncertainty in the representation of its role in carbon sequestration. Here we synthesise the existing spatial and temporal projections of Southern Ocean productivity from CMIP6 models, separated by phytoplankton functional type, and identify key processes where greater observational data coverage can help to improve future model performance. We find substantial variability between models in projections of light concentration (>15 000 (µE m−2 s−1)2) across much of the iron- and light-limited Antarctic zone. Projections of iron and light limitation of phytoplankton vary by up to 10 % across latitudinal zones, while the greatest increases in productivity occurs close to the coast. Temperature, pH and nutrients are less spatially variable – projections for 2090–2100 under SSP5-8.5 show zonally averaged changes of +1.6 °C and −0.45 pH units and Si* ([Si(OH)4]–[NO3–]) decreases by 8.5 µmol L−1. Diatoms and picophytoplankton and/or miscellaneous phytoplankton are equally responsible for driving productivity increases across the subantarctic and transitional zones, but picophytoplankton and miscellaneous phytoplankton increase at a greater rate than diatoms in the Antarctic zone. Despite the variability in productivity with different phytoplankton types, we show that the most complex models disagree on the ecological mechanisms behind these productivity changes. We propose that a sampling approach targeting the regions with the greatest rates of climate-driven change in ocean biogeochemistry and community assemblages would help to resolve the empirical principles underlying the phytoplankton community structure in the Southern Ocean.
Continue reading ‘Climate-driven shifts in Southern Ocean primary producers and biogeochemistry in CMIP6 models’
