Ocean acidification is expected to negatively affect many ecologically important organisms. Here we explored the response of Caribbean benthic foraminiferal assemblages to naturally discharging low-pH waters similar to expected future projections for the end of the 21st century. At low pH (~7.7 pH units) and low calcite saturation, agglutinated and symbiont-bearing species were relatively more abundant, indicating higher resistance to potential carbonate chemistry changes. Diversity and other taxonomical metrics declined steeply with decreasing pH, despite exposure of this ecosystem for millennia to low pH conditions, suggesting that tropical foraminifera communities will be negatively impacted under acidification scenarios SSP3-7.0 and SSP5-8.5. The species Archaias angulatus, a major contributor to sediment production in the Caribbean, was able to calcify at conditions more extreme than those projected for the late 21st century (7.1 pH units), but the calcified tests were of lower density than those exposed to higher-pH ambient conditions (7.96 pH units), indicating that reef foraminiferal carbonate budget might decrease. Smaller foraminifera were highly sensitive to decreasing pH and our results demonstrate their potential as indicators to monitor increasing OA conditions.
Continue reading ‘Foraminiferal assemblages and test characteristics associated with natural low pH waters at Puerto Morelos reef lagoon springs, QR Mexico’Archive for the 'Science' Category
Foraminiferal assemblages and test characteristics associated with natural low pH waters at Puerto Morelos reef lagoon springs, QR Mexico
Published 26 May 2023 Science Leave a CommentTags: abundance, biological response, BRcommunity, community composition, dissolution, laboratory, morphology, North Pacific, otherprocess, protists, sediment
New Zealand’s media and the crisis in the ocean: news norms and scientific urgency
Published 26 May 2023 Science Leave a CommentTags: review, socio-economy
1. To date, no studies have analysed New Zealand’s media coverage of ocean-related threats, potential harms, or sources used for their coverage. This is concerning given that marine media coverage is linked to public support, awareness of conservation issues, and policymaking.
2. This research helps fill this gap, examining all ocean-related articles 2 weeks before and after the 2019 Intergovernmental Panel on Climate Change (IPCC) report’s release on the oceans and cryosphere.
3. It first analyses the media’s reporting of threats, potential harms arising from the threats, and the sources on whom journalists relied and gave voice, then it tests a report of global significance for influence on reportage.
4. Second, it examines whether the threats covered by media align with scientists’ main concerns (from the IPCC report and a survey of New Zealand scientists).
5. In contrast to previous studies on media sources for environmental conservation, this study found that journalists in New Zealand relied considerably on scientists as key sources. However, it found that coverage of ocean-related threats did not match scientists’ main concerns.
6. Finally, the research found that the IPCC report appeared to influence coverage in two areas: reporting on threats to island nations, and multiple potential harms. Otherwise, New Zealand’s media covered the IPCC report as any other news item, reporting on it and then shifting to other matters.
7. The lack of coverage on primary scientific concerns and that a globally significant momentous report did not dramatically impact the marine media landscape is problematic for conservation of ocean habitats, species, and broader environmental and societal outcomes owing to poor understandings by policymakers and the public, which can lead to inaction and policy failures.
8. The potential reasons and solutions to advance communication of marine conservation issues for a more educated and mobilized public are explored.
Continue reading ‘New Zealand’s media and the crisis in the ocean: news norms and scientific urgency’Acidification and hypoxia drive physiological trade-offs in oysters and partial loss of nutrient cycling capacity in oyster holobiont
Published 26 May 2023 Science Leave a CommentTags: biological response, BRcommunity, community composition, laboratory, molecular biology, mollusks, mortality, multiple factors, North Pacific, otherprocess, oxygen, physiology, prokaryotes
Introduction:
Reef building oysters provide vast ecological benefits and ecosystem services. A large part of their role in driving ecological processes is mediated by the microbial communities that are associated with the oysters; together forming the oyster holobiont. While changing environmental conditions are known to alter the physiological performance of oysters, it is unclear how multiple stressors may alter the ability of the oyster holobiont to maintain its functional role.
Methods:
Here, we exposed oysters to acidification and hypoxia to examine their physiological responses (molecular defense and immune response), changes in community structure of their associated microbial community, and changes in water nutrient concentrations to evaluate how acidification and hypoxia will alter the oyster holobiont’s ecological role.
Results:
We found clear physiological stress in oysters exposed to acidification, hypoxia, and their combination but low mortality. However, there were different physiological trade-offs in oysters exposed to acidification or hypoxia, and the combination of stressors incited greater physiological costs (i.e., >600% increase in protein damage and drastic decrease in haemocyte counts). The microbial communities differed depending on the environment, with microbial community structure partly readjusted based on the environmental conditions. Microbes also seemed to have lost some capacity in nutrient cycling under hypoxia and multi-stressor conditions (~50% less nitrification) but not acidification.
Discussion:
We show that the microbiota associated to the oyster can be enriched differently under climate change depending on the type of environmental change that the oyster holobiont is exposed to. In addition, it may be the primary impacts to oyster physiology which then drives changes to the associated microbial community. Therefore, we suggest the oyster holobiont may lose some of its nutrient cycling properties under hypoxia and multi-stressor conditions although the oysters can regulate their physiological processes to maintain homeostasis on the short-term.
Continue reading ‘Acidification and hypoxia drive physiological trade-offs in oysters and partial loss of nutrient cycling capacity in oyster holobiont’Exposure to extremes in multiple global change drivers: characterizing pH, dissolved oxygen, and temperature variability in a dynamic, upwelling dominated ecosystem
Published 25 May 2023 Science Leave a CommentTags: chemistry, field, modeling, regionalmodeling
In upwelling systems, fluctuations in seawater pH, dissolved oxygen (DO), and temperature can expose species to extremes that differ greatly from the mean conditions. Understanding the nature of this exposure to extremes, including how exposure to low pH, low DO concentrations, and temperature varies spatiotemporally and in the context of other drivers, is critical for informing global change biology. Here, we use a 4-yr time series of coupled pH, DO, and temperature observations at six nearshore kelp forest sites spanning the coast of California to characterize the variability and covariance among these drivers. We further compare observed properties to those derived from a high-resolution coupled physical-biogeochemical simulation for the central California current system. We find the intensity, duration, and severity of exposure to extreme conditions beyond heuristic, biologically relevant pHT (< 7.7), and DO (< 4.6 mg L−1) values were greatest at sites with strong upwelling. In contrast, sites with relatively weaker upwelling had little exposure to pH or DO conditions below these heuristic values but had higher and more variable temperature. The covariance between pH, DO, and temperature was highest in sites with strong upwelling and weakest in sites with limited upwelling. These relationships among pH, DO, and temperature at the observation locations were mirrored in the model, and model output highlighted geographic differences in exposure regimes across the California marine protected area network. Together, these results provide important insight into the conditions marine ecosystems are exposed to relevant to studies of global change biology.
Continue reading ‘Exposure to extremes in multiple global change drivers: characterizing pH, dissolved oxygen, and temperature variability in a dynamic, upwelling dominated ecosystem’A shift in the mechanism of CO2 uptake in the Southern Ocean under high emission-scenario
Published 25 May 2023 Science Leave a CommentTags: Antarctic, biogeochemistry, modeling, regionalmodeling
The Southern Ocean is a major region of ocean carbon uptake, but its future changes remain uncertain under climate warming. Here we show the projected shift in the Southern Ocean CO2 sink using a suite of Earth System Models, revealing changes in the mechanism, position and seasonality of the carbon uptake. Dominant CO2 uptake shifts from the Subtropical to the Antarctic region under the high-emission scenario by the end of the 21st century. The warming-driven sea-ice melt, increased ocean stratification, mixed layer shoaling, and a weaker vertical carbon gradient will together reduce the winter outgassing in the future, which will trigger the switch from mixing-driven outgassing to solubility-driven uptake in the Antarctic region during the winter season. The future Southern Ocean carbon sink will be poleward-shifted, operating in a hybrid mode between biologically-driven summertime and solubility-driven wintertime uptake with further amplification of biological uptake by the increasing Revelle Factor.
Continue reading ‘A shift in the mechanism of CO2 uptake in the Southern Ocean under high emission-scenario’Taphonomy and dissolution rates of the razor clam Ensis magnus shells: current status and projected acidification scenarios
Published 25 May 2023 Science Leave a CommentTags: biological response, chemistry, dissolution, field, laboratory, modeling, mollusks, morphology, multiple factors, North Atlantic, regionalmodeling, temperature
Highlights
- Natural variability of seawater (Ta, Ωaragonite and pCO2) revealed an increase of acidification though such change did not suppose abrupt detrimental effects for taphonomic characteristics of shells (length, thickness, organic content or strength).
- Temperature affected negatively shell strength and thickness, although the large correlation between the environmental variables would disturb the individual characterization of environmental parameters.
- Dissolution rates of shells subjected to projected laboratory scenarios were significantly greater for cold-acidic environment (more corrosive) as compared to warm-acidic. Mean dissolution time (DT50) for cold-acidic scenario was reduced by half (15 years) as compared to current water chemistry conditions (30 years).
- More recent shells are being secreted in a progressively less saturated carbonate environment (at an annual rate of change of −0.0127 for Ωaragonite) and accordingly, were more prone to suffer dissolution (and weakening) in projected laboratory scenarios.
- Marine shells support ecosystem services including refuge for multiple species, substrate to attach and settle of fauna that may change in future environments or may bring changes in the ecological interactions of our coastal areas affecting biodiversity and optimal functioning of the ecosystem services.
Abstract
The analysis of the natural variability of seawater (Ta, Ωaragonite and pCO2) at Rodas Beach (NW Iberian Peninsula, Spain) revealed an increase of acidification. However, such pH change was not linked to any detrimental effect of the shell taphonomic characteristics of live razor clams harvested during distinct temporal series (length, thickness, organic content or strength). Temperature affected negatively shell strength and thickness, although the large correlation between the environmental variables would limit the individual characterization. Modelled trends in pH (and Ωaragonite) showed a significant decrease in the last 20 years, despite Ω > 1. Therefore, more recent shells are being secreted in a progressively less saturated carbonate environment and, consequently, more prone to suffer dissolution (and weakening) in projected climatic scenarios. When shells of harvested razor clams were exposed to projected climatic scenarios in the laboratory, dissolution rates were significantly greater for cold-acidic scenarios (more corrosive) as compared to warm-acidic. The median dissolution time (DT50) for shells under the cold-acidic scenario was reduced by half (15 years) when compared to the values observed for shells under current water chemistry conditions (30 years).
Galician coastline, often characterised by pCO2-rich and cold waters due to upwelling system, would represent the most corrosive scenario for the shells according to the responses monitored in our survey which highlight future compromise for the ecosystem services supplied by these hard skeletons. Future climate scenarios might condition performance of bivalves but also more complex processes related to carbonate structures. Local biodiversity may be lowered which may reduce the possibility that many species find shelter and feeding grounds, diminishing the optimal substrate for other organisms as needed elements for optimal services in the ecosystems.
Continue reading ‘Taphonomy and dissolution rates of the razor clam Ensis magnus shells: current status and projected acidification scenarios’Investigating the environmental sustainability of a seabass and seabream aquaculture system in Portugal based on life cycle and nexus approaches
Published 25 May 2023 Science Leave a CommentTags: fisheries, North Atlantic, review, socio-economy
Highlights
- A Portuguese seabass and seabream aquaculture system was analysed.
- A climate change impact equal to 2.88 kg CO2-eq/kg MSF was found.
- The aquaculture system depends 59 % on non-renewable resources.
- In resource terms, 504.1 MJex are needed per kg of protein.
- Potential strategies are given to improve environmental sustainability.
Abstract
Aquaculture plays an essential role in supplying animal-source food and protein worldwide, in this way contributing to several sustainable development goals. Notwithstanding this, the aquaculture sector’s long-term environmental sustainability is a major concern due to overall environmental impacts. To date, and to the best of the authors’ knowledge, assessments of aquaculture systems in Portugal from an environmental perspective, and the nexus between resource consumption and nutrition issues, are still lacking. This study bridges this gap by analysing an aquaculture system in Portugal in a comprehensive manner by applying and combining life cycle assessment and resources–protein nexus approaches. The overall results highlight feed as the main factor responsible for the total impact in all impact categories selected, ranging from 74 % to 98 %. Climate change impact results in 2.88 kg CO2-eq per kg of medium-size fish (functional unit). The resources–protein nexus shows that 504.1 MJex is needed to obtain 1 kg of edible protein, with a high dependency on non-renewable resources (59 %), mainly oil by-product fuels used in feed production. After identifying environmental hotspots, potential strategies to be adopted such as resource consumption reduction, eco-certification and ecosystem-based management are suggested, in this way ensuring long-term aquaculture production and environmental sustainability.
Continue reading ‘Investigating the environmental sustainability of a seabass and seabream aquaculture system in Portugal based on life cycle and nexus approaches’Effects of ocean acidification and ocean warming on the behavior and physiology of a subarctic, intertidal grazer
Published 24 May 2023 Science Leave a CommentTags: biological response, laboratory, mollusks, multiple factors, performance, physiology, temperature
The global ocean is expected to both acidify and warm concurrently; thus, multiple-stressor manipulative experimentation is an emergent area of study that ultimately aims to examine the individual and interactive effects of these factors on marine organisms. We characterized the physiological responses to acidification and warming of the intertidal grazer Lottia scutum, and examined how these ocean change variables influenced predator-prey dynamics with Evasterias troschelii, a key sea star predator. Specifically, we conducted a laboratory experiment where we exposed limpets to factorial combinations of temperature (11 and 15°C) and pH (7.6 and 8.0), and measured effects on thermal tolerance, metabolic rate, cortisol concentrations, and behavioral responses to the predator. We found that ocean warming (OW) decreased the critical thermal maxima (CTmax) and increased cortisol levels in L. scutum, whereas ocean acidification (OA) increased the mass-specific metabolic rate in this species. Additionally, we found that there was no significant effect of OA or OW on the anti-predator behavior of L. scutum when exposed to E. troschelii. These results highlight the need for future studies to integrate multidisciplinary experimental designs (i.e. behavior and physiology) that span multiple levels of biological organization to make ecologically relevant predictions for how marine organisms will respond to ocean change.
Continue reading ‘Effects of ocean acidification and ocean warming on the behavior and physiology of a subarctic, intertidal grazer’Heavy metal mobility in contaminated sediments under seawater acidification
Published 24 May 2023 Science Leave a CommentTags: chemistry, laboratory
Highlights
- Long-term effects of acidification on heavy metal mobility
- Variations in heavy metal distribution patterns in sediment–seawater systems
- CO2 enrichment acidified the pH of the system.
- Changes in effective heavy metals were obtained by diffusion gradient technique.
Abstract
The behavior of heavy metals in contaminated sediment is of ecological significance considering the change of pH caused by ocean acidification. This study investigated the mobility of Cd, Cu, Ni, Pb, Fe, and Mn under experimental conditions for seawater acidification via enrichment of CO2 gas at different reaction set-ups. The results indicated that the concerned metals behaved differently in the water compared to the sediment. The heavy metals were considerably transferred from sediment to seawater, and the resultant intensity was controlled by the degree of acidification and the chemical state of specific metals. Moreover, labile fractions of heavy metals in sediments were more susceptible to acidification than other fractions. These findings were observed and confirmed using real-time monitoring conducted via the diffusion gradient technique (DGT). Overall, the results of this study provided new insights into exploring the coupling risk of heavy metals with ocean acidification.
Continue reading ‘Heavy metal mobility in contaminated sediments under seawater acidification’Elevated water CO2 can prevent dietary-induced osteomalacia in post-smolt Atlantic salmon (Salmo salar, L.)
Published 24 May 2023 Science Leave a CommentTags: biological response, fish, growth, laboratory, molecular biology, morphology, North Atlantic, performance, physiology
Expansion of land-based systems in fish farms elevate the content of metabolic carbon dioxide (CO2) in the water. High CO2 is suggested to increase the bone mineral content in Atlantic salmon (Salmo salar, L.). Conversely, low dietary phosphorus (P) halts bone mineralization. This study examines if high CO2 can counteract reduced bone mineralization imposed by low dietary P intake. Atlantic salmon post-seawater transfer (initial weight 207.03 g) were fed diets containing 6.3 g/kg (0.5P), 9.0 g/kg (1P), or 26.8 g/kg (3P) total P for 13 weeks. Atlantic salmon from all dietary P groups were reared in seawater which was not injected with CO2 and contained a regular CO2 level (5 mg/L) or in seawater with injected CO2 thus raising the level to 20 mg/L. Atlantic salmon were analyzed for blood chemistry, bone mineral content, vertebral centra deformities, mechanical properties, bone matrix alterations, expression of bone mineralization, and P metabolism-related genes. High CO2 and high P reduced Atlantic salmon growth and feed intake. High CO2 increased bone mineralization when dietary P was low. Atlantic salmon fed with a low P diet downregulated the fgf23 expression in bone cells indicating an increased renal phosphate reabsorption. The current results suggest that reduced dietary P could be sufficient to maintain bone mineralization under conditions of elevated CO2. This opens up a possibility for lowering the dietary P content under certain farming conditions.
Continue reading ‘Elevated water CO2 can prevent dietary-induced osteomalacia in post-smolt Atlantic salmon (Salmo salar, L.)’Ocean acidification increases inorganic carbon over organic carbon in shrimp’s exoskeleton
Published 23 May 2023 Science Leave a CommentTags: biogeochemistry, biological response, calcification, crustaceans, laboratory, morphology, respiration
Highlights
- PIC: POC ratio in shrimps’ exoskeleton may increase under future OA.
- Hyper-calcification and increased respiration are possible in shrimps under OA releasing more CO2 into the water.
- Increased PIC: POC ratio may impact the ecosystem functions as well as the carbon cycle.
Abstract
Ocean acidification (OA) may either increase or have a neutral effect on the calcification in shrimp’s exoskeleton. However, investigations on changes in the carbon composition of shrimp’s exoskeletons under OA are lacking. We exposed juvenile Pacific white shrimps to target pHs of 8.0, 7.9, and 7.6 for 100 days to evaluate changes in carapace thickness, total carbon (TC), particulate organic carbon (POC), particulate inorganic carbon (PIC), calcium, and magnesium concentrations in their exoskeletons. The PIC: POC ratio of shrimp in pH 7.6 treatment was significantly higher by 175 % as compared to pH 8.0 treatment. Thickness and Ca% in pH 7.6 treatment were significantly higher as compared to pH 8.0 treatment (90 % and 65 %, respectively). This is the first direct evidence of an increased PIC: POC ratio in shrimp exoskeletons under OA. In the future, such changes in carbon composition may affect the shrimp population, ecosystem functions, and regional carbon cycle.
Continue reading ‘Ocean acidification increases inorganic carbon over organic carbon in shrimp’s exoskeleton’A low-cost virtual sensor for underwater pH monitoring in coastal waters
Published 23 May 2023 Science Leave a CommentTags: chemistry, laboratory, methods
In coastal water monitoring, abrupt pH changes might indicate different pollution sources. Existing sensors for pH monitoring in coastal waters at low cost are mainly based on a glass membrane and a reference electrode. Virtual sensors are elements capable of measuring certain parameters based on data from other parameters or variables. The aim of this paper is to propose the use of a virtual pH sensor based on measuring different physical effects of H+ on the electromagnetic field generated by an inductor. Double inductors based on two solenoids of 40 and 80 spires are used as sensing elements. Samples with pH from 4 to 11 are used, and the effect of temperature is evaluated using samples from 10 to 40 °C. The induced voltage and the delay of the signal are measured for powering frequencies from 100 to 500 kHz. These data of delay, induced voltage, frequency, and temperature are included in a probabilistic neural network to classify these data according to the pH. The results indicate low accuracy for samples with a pH of 11. A second analysis, excluding these data, offered correctly classified cases of 88.9%. The system can achieve considerable high accuracy (87.5%) using data gathered at a single frequency, from 246 to 248 kHz. The predicted versus observed data is correlated with a linear model characterized by an R2 of 0.69, which is similar to the ones observed in other virtual sensors.
Continue reading ‘A low-cost virtual sensor for underwater pH monitoring in coastal waters’Ocean acidification as a hyperobject: mediating acidic milieus in the anthropocene
Published 23 May 2023 Science Leave a CommentTags: socio-economy
Through the usage of Timothy Morton’s hyperobjects (2013) as a heuristic, this essay aims to portray how Ocean Acidification can be read as a hyperobject affecting tropical seawaters and beyond. Furthermore, it illustrates how the arts and humanities, through their hermeneutical gaze, might help us grasp Ocean Acidification as a hyperobject and the wide array of other objects that act upon each other in such acidic oceanic waters. In this task, the article will close-read the Underwater Woman set of pictures by Christine Ren (2018) understanding the interpretation of art as a tool to reconnect cognition and emotion to move from the understanding of a crisis to the feeling of such crisis. Finally, it aims to shed light upon the implications arising from considering Ocean Acidification as a hyperobject. By connecting the theoretical, visual and political in the same narrative, this essay highlights the transformative potential of interpretation and thinking through hyperobjects. With this, the challenges of the Anthropocene are put at the forefront, situating specific events and problematics in a planetary scale.
Continue reading ‘Ocean acidification as a hyperobject: mediating acidic milieus in the anthropocene’Long-term physiological responses to combined ocean acidification and warming show energetic trade-offs in an asterinid starfish
Published 22 May 2023 Science Leave a CommentTags: biological response, calcification, echinoderms, laboratory, mortality, multiple factors, North Atlantic, performance, physiology, temperature
While organismal responses to climate change and ocean acidification are increasingly documented, longer-term (> a few weeks) experiments with marine organisms are still sparse. However, such experiments are crucial for assessing potential acclimatization mechanisms, as well as predicting species-specific responses to environmental change. Here, we assess the combined effects of elevated pCO2 and temperature on organismal metabolism, mortality, righting activity, and calcification of the coral reef-associated starfish Aquilonastra yairi. Specimens were incubated at two temperature levels (27 °C and 32 °C) crossed with three pCO2 regimes (455 µatm, 1052 µatm, and 2066 µatm) for 90 days. At the end of the experiment, mortality was not altered by temperature and pCO2 treatments. Elevated temperature alone increased metabolic rate, accelerated righting activity, and caused a decline in calcification rate, while high pCO2 increased metabolic rate and reduced calcification rate, but did not affect the righting activity. We document that temperature is the main stressor regulating starfish physiology. However, the combination of high temperature and high pCO2 showed nonlinear and potentially synergistic effects on organismal physiology (e.g., metabolic rate), where the elevated temperature allowed the starfish to better cope with the adverse effect of high pCO2 concentration (low pH) on calcification and reduced skeletal dissolution (antagonistic interactive effects) interpreted as a result of energetic trade-offs.
Continue reading ‘Long-term physiological responses to combined ocean acidification and warming show energetic trade-offs in an asterinid starfish’Epistemic discourses and conceptual coherence in students’ explanatory models: the case of ocean acidification and its impacts on oysters
Published 22 May 2023 Science Leave a CommentTags: education
Engaging students in epistemic and conceptual aspects of modeling practices is crucial for phenomena-based learning in science classrooms. However, many students and teachers still struggle to actualize the reformed vision of the modeling practice in their classrooms. Through a discourse analysis of 150 students’ explanatory models (as social semiotic spaces) from 14 classes, we propose a qualitative framework that investigates conceptual coherence and epistemic discourses to achieve a gapless explanation of scientific phenomena. Our framework draws attention to four critical components of students’ explanatory models: (a) key ideas based on evidence, (b) the discourse modalities of how evidence is presented, (c) scientific representations from the cultures of scientific disciplines, (d) systems thinking approaches directly and indirectly related to oceans and marine ecosystems. Our results indicate that students struggled to construct cohesive explanatory models that communicated all key ideas and the relationships among them, with the majority of student-developed models in our study categorized as ‘insufficiently’ cohesive (lacking key ideas and the relationships among them), and only a small percentage of the models considered ‘extensively’ cohesive (all key ideas attended to, as well as the relationships among them).
Continue reading ‘Epistemic discourses and conceptual coherence in students’ explanatory models: the case of ocean acidification and its impacts on oysters’Carbon dioxide mineralization by electrode separation for quick carbon reduction and sequestration in acidified seawater
Published 22 May 2023 Science Leave a CommentTags: chemistry, laboratory, methods, mitigation, North Pacific
Aiming to sequestrate the excessive carbon dioxide and convert the acidified seawater, an improved method of carbon dioxide mineralization is developed based on electrode separation mechanism and extra oxygen-supplying technique. By electrode separation the neutralizations of the anodic acidity and the cathodic alkalinity, as well as the precipitation and the dissolution of calcium carbonate (CaCO3), are prevented. In addition, the extra-supplied oxygen prevents the evolution of hydrogen, which enhances the electric conductivity of the porous cathode and the deposition of CaCO3. A series of indoor physical experiments were conducted and the results show that the acidified seawater was successfully converted to alkaline in 72h. The speed of carbon mineralizing sequestration is significantly enhanced by supplying extra oxygen. The carbon dioxide mineralization speed increases with the immerse ratio of the aerator due to the more reacted oxygen and the less hydrogen evolution, which gives more porous space in the cathode for more conductive seawater and more deposition of CaCO3. The extra-supplied oxygen increases the CaCO3 -deposition by 100-214% under excessive atmospheric- CO2 conditions and 117-200% under normal atmospheric- CO2 conditions, respectively. This method has an application potential for quick conversion of locally acidified seawater in emergent circumstances.
Continue reading ‘Carbon dioxide mineralization by electrode separation for quick carbon reduction and sequestration in acidified seawater’Evidence for an effective defence against ocean acidification in the key bioindicator pteropod Limacina helicina
Published 19 May 2023 Science Leave a CommentTags: biological response, dissolution, laboratory, mollusks, morphology, mortality, North Pacific, performance, zooplankton
The pteropod Limacina helicina has become an important bioindicator species for the negative impacts of ocean acidification (OA) on marine ecosystems. However, pteropods diversified during earlier high CO2 periods in Earth history and currently inhabit regions that are naturally corrosive to their shells, suggesting that they possess mechanisms to survive unfavourable conditions. Recent work, which is still under considerable debate, has proposed that the periostracum, a thin organic coating on the outer shell, protects pteropods from shell dissolution. Here, we provide direct evidence that shows that damage to the L. helicina periostracum results in dissolution of the underlying shell when exposed to corrosive water for ∼8 d, while an intact periostracum protects the shell from dissolution under the same conditions. This important first line of defence suggests that pteropods are more resistant to OA-induced shell dissolution than is generally accepted.
Continue reading ‘Evidence for an effective defence against ocean acidification in the key bioindicator pteropod Limacina helicina’Re-evaluation of carbonic acid dissociation constants across conditions and the implications for ocean acidification
Published 19 May 2023 Science Leave a CommentTags: chemistry, laboratory, methods
Highlights
- pHt should be measured directly rather than calculated from TA and DIC.
- Uncertainty in the constants contributes up to 680 m of uncertainty in the aragonite saturation horizon depth.
- Calculated pHt at pCO2 between ~500–800 μatm are particularly poor, suggesting an underestimation of future ocean acidification in models.
- Evaluation of an unidentified or organic component of TA was inconclusive.
Abstract
With the increasing threat of ocean acidification and the important role of the oceans in the global carbon cycle, highly precise, accurate, and intercomparable determination of inorganic carbon system parameters is required. Thermodynamic relationships enable the system to be fully constrained using a combination of direct measurements and calculations. However, calculations are complicated by many formulations for dissociation constants (over 120 possible combinations). To address these important issues of uncertainty and comparability, we evaluated the various combinations of constants and their (dis)agreement with direct measurements over a range of temperature (−1.9–40 °C), practical salinity (15–39) and pCO2 (150–1200 μatm). The results demonstrate that differences between the calculations and measurements are significantly larger than measurement uncertainties, meaning the oft-stated paradigm that one only needs to measure two parameters and the others can be calculated does not apply for climate quality ocean acidification research. The uncertainties in calculated pHt prevent climate quality pHt from being calculated from total alkalinity (TA) and dissolved inorganic carbon (DIC) and should be directly measured instead. However, climate quality TA and DIC can often be calculated using measured pH and DIC or TA respectively. Calculations are notably biased at medium-to-high pCO2 values (~500–800 μatm) implying models underestimate future ocean acidification. Uncertainty in the dissociation constants leads to significant uncertainty in the depth of the aragonite saturation horizon (>500 m in the Southern Ocean) and must be considered when studying calcium carbonate cycling. Significant improvements in the precision of the thermodynamic constants are required to improve pHt calculations.
Continue reading ‘Re-evaluation of carbonic acid dissociation constants across conditions and the implications for ocean acidification’Short-term variation of pH in seawaters around coastal areas of Japan: characteristics and forcings
Published 18 May 2023 Science Leave a CommentTags: chemistry, field, North Pacific
The pH of coastal seawater varies based on several local forcings, such as water circulation, terrestrial inputs, and biological processes, and these forcings can change along with global climate change. Understanding the mechanism of pH variation in each coastal area is thus important for a realistic future projection that considers changes in these forcings. From 2020 to 2021, we performed parallel year-round observations of pH and related ocean parameters at five stations around the Japanese coast (Miyako Bay, Shizugawa Bay, Kashiwazaki Coast, Hinase Archipelago, and Ohno Strait) to understand the characteristics of short-term pH variations and their forcings. Annual variability (~1 standard deviation) of pH and aragonite saturation state (Ωara) were 0.05–0.09 and 0.25–0.29, respectively, for three areas with low anthropogenic loadings (Miyako Bay, Kashiwazaki Coast, and Shizugawa Bay), while it increased to 0.16–0.21 and 0.52–0.58, respectively, in two areas with medium anthropogenic loadings (Hinase Archipelago and Ohno Strait in Seto Inland Sea). Statistical assessment of temporal variability at various timescales revealed that most of the annual variabilities in both pH and Ωara were derived by short-term variation at a timescale of < 10 days, rather than seasonal-scale variation. Our analyses further illustrated that most of the short-term pH variation was caused by biological processes, while both thermodynamic and biological processes equally contributed to the temporal variation in Ωara. The observed results showed that short-term acidification with Ωara < 1.5 occurred occasionally in Miyako and Shizugawa Bays, while it occurred frequently in the Hinase Archipelago and Ohno Strait. Most of such short-term acidified events were related to short-term low-salinity events. Our analyses showed that the amplitude of short-term pH variation was linearly correlated with that of short-term salinity variation, and its regression coefficient at the time of high freshwater input was positively correlated with the nutrient concentration of the main river that flows into the coastal area.
Continue reading ‘Short-term variation of pH in seawaters around coastal areas of Japan: characteristics and forcings’
