Studies on the impact of ocean acidification on marine organisms involve exposing organisms to future acidification scenarios as projected for open ocean, which has limited relevance for coastal calcifiers. Characterization of reaction norms across a range of pH and identification of tipping points beyond which detrimental effects are observed has been limited and focus on only a few macro-physiological traits. Here we filled this knowledge gap by developing a framework to analyze the broad macro-physiological and molecular responses over a wide pH range of juvenile Pacific oyster, a model species for which the tolerance threshold to acidification remains unknown. We identify low tipping points for physiological traits at pH 7.3-6.9 that coincide with a major reshuffling in membrane lipids and transcriptome. In contrast, shell parameters exhibit effects with pH drop well before tipping points, likely impacting animal fitness. These findings were made possible by the development of an innovative methodology to synthesize and identify the main patterns of variations in large -omic datasets, fit them to pH and identify molecular tipping-points. We propose the application of our framework broadly to the assessment of effects of global change on other organisms.
Continue reading ‘Revisiting tolerance to ocean acidification: insights from a new framework combining physiological and molecular tipping points of Pacific oyster’Posts Tagged 'methods'
Revisiting tolerance to ocean acidification: insights from a new framework combining physiological and molecular tipping points of Pacific oyster
Published 28 September 2021 Science ClosedTags: biological response, calcification, growth, laboratory, methods, molecular biology, mollusks, morphology, North Pacific, physiology
Contrasting controls of acidification metrics across environmental gradients in the North Pacific and the adjunct Arctic Ocean: insight from a transregional study
Published 27 September 2021 Science ClosedTags: Arctic, chemistry, field, methods, North Pacific
Abstract
The spatiotemporal variabilities and drivers of ocean acidification (OA) metrics, [H+], pH, and aragonite saturation state (Ωarag) across environmental gradients remain poorly constrained. We use a novel high-precision measurement of underway pH to investigate the hemispheric-scale distributions of OA metrics from East Asia to the Arctic Ocean. While temperature and its induced air-sea gas exchange fundamentally control the OA metrics distributions, we show that biological activity exerts the most prominent but different modifications on pH and Ωarag patterns. Strong photosynthesis counteracts the temperature-driven pH pattern but reinforces that of Ωarag. Ice melt-induced dilution in the Arctic Ocean additionally strengthens the Ωarag-temperature relationship but insignificantly affects [H+] and pH. This study provides the first coherent assessment of comprehensive processes on OA metrics across large spatial regions, and highlights the potential of sea-ice melt in changing Ωarag distribution, which should be included by Earth system models projecting future climate change.
Plain Language Summary
The ocean uptake of anthropogenic carbon dioxide (CO2) is causing increase in hydrogen ion concentration ([H+]) and reductions in pH and carbonate mineral aragonite saturation state (Ωarag), together of which are commonly referred to as ocean acidification (OA). The coupled behavior of these affected OA metrics responding to physical and biogeochemical processes across environmental gradients has barely been examined in a comparative manner. To address this issue, we conduct a survey measuring high-precision underway pH from East Asia to the Arctic Ocean. We find that, besides the temperature effects which ultimately control the distributions of OA metrics, biological activity induces the strongest interruptions. Photosynthesis weakens the temperature-driven pH pattern but reinforces that of Ωarag. In addition, ice melt-induced dilution in the polar region strengthens Ωarag-temperature relationship but makes less difference to [H+] and pH. These findings are important as they are based on the first large-scale direct measurements of underway pH, and have implications for future studies on ocean acidification in the context of climate change.
Continue reading ‘Contrasting controls of acidification metrics across environmental gradients in the North Pacific and the adjunct Arctic Ocean: insight from a transregional study’Integrating environmental variability to broaden the research on coral responses to future ocean conditions
Published 13 September 2021 Science ClosedTags: chemistry, corals, field, methods, North Atlantic, South Pacific
Our understanding of the response of reef-building corals to changes in their physical environment is largely based on laboratory experiments, analysis of long-term field data, and model projections. Experimental data provide unique insights into how organisms respond to variation of environmental drivers. However, an assessment of how well experimental conditions cover the breadth of environmental conditions and variability where corals live successfully is missing. Here, we compiled and analyzed a globally distributed dataset of in-situ seasonal and diurnal variability of key environmental drivers (temperature, pCO2, and O2) critical for the growth and livelihood of reef-building corals. Using a meta-analysis approach, we compared the variability of environmental conditions assayed in coral experimental studies to current and projected conditions in their natural habitats. We found that annual temperature profiles projected for the end of the 21st century were characterized by distributional shifts in temperatures with warmer winters and longer warm periods in the summer, not just peak temperatures. Furthermore, short-term hourly fluctuations of temperature and pCO2 may regularly expose corals to conditions beyond the projected average increases for the end of the 21st century. Coral reef sites varied in the degree of coupling between temperature, pCO2, and dissolved O2, which warrants site-specific, differentiated experimental approaches depending on the local hydrography and influence of biological processes on the carbonate system and O2 availability. Our analysis highlights that a large portion of the natural environmental variability at short and long timescales is underexplored in experimental designs, which may provide a path to extend our understanding on the response of corals to global climate change.
Continue reading ‘Integrating environmental variability to broaden the research on coral responses to future ocean conditions’Cyanobacteria net community production in the Baltic Sea as inferred from profiling pCO2 measurements
Published 10 September 2021 Science ClosedTags: Baltic, biogeochemistry, chemistry, field, laboratory, methods, modeling, phytoplankton, prokaryotes, regionalmodeling
Organic matter production by cyanobacteria blooms is a major environmental concern for the Baltic Sea, as it promotes the spread of anoxic zones. Partial pressure of carbon dioxide (pCO2) measurements carried out on Ships of Opportunity (SOOP) since 2003 have proven to be a powerful tool to resolve the carbon dynamics of the blooms in space and time. However, SOOP measurements lack the possibility to directly constrain depth-integrated net community production (NCP) in moles of carbon per surface area due to their restriction to the sea surface. This study tackles the knowledge gap through (1) providing an NCP best guess for an individual cyanobacteria bloom based on repeated profiling measurements of pCO2 and (2) establishing an algorithm to accurately reconstruct depth-integrated NCP from surface pCO2 observations in combination with modelled temperature profiles.
Goal (1) was achieved by deploying state-of-the-art sensor technology from a small-scale sailing vessel. The low-cost and flexible platform enabled observations covering an entire bloom event that occurred in July–August 2018 in the Eastern Gotland Sea. For the biogeochemical interpretation, recorded pCO2 profiles were converted to C∗T, which is the dissolved inorganic carbon concentration normalised to alkalinity. We found that the investigated bloom event was dominated by Nodularia and had many biogeochemical characteristics in common with blooms in previous years. In particular, it lasted for about 3 weeks, caused a C∗T drawdown of 90 µmol kg−1, and was accompanied by a sea surface temperature increase of 10 ∘C. The novel finding of this study is the vertical extension of the C∗T drawdown up to the compensation depth located at around 12 m. Integration of the C∗T drawdown across this depth and correction for vertical fluxes leads to an NCP best guess of ∼1.2 mol m−2 over the productive period.
Addressing goal (2), we combined modelled hydrographical profiles with surface pCO2 observations recorded by SOOP Finnmaid within the study area. Introducing the temperature penetration depth (TPD) as a new parameter to integrate SOOP observations across depth, we achieve an NCP reconstruction that agrees to the best guess within 10 %, which is considerably better than the reconstruction based on a classical mixed-layer depth constraint.
Applying the TPD approach to almost 2 decades of surface pCO2 observations available for the Baltic Sea bears the potential to provide new insights into the control and long-term trends of cyanobacteria NCP. This understanding is key for an effective design and monitoring of conservation measures aiming at a Good Environmental Status of the Baltic Sea.
Continue reading ‘Cyanobacteria net community production in the Baltic Sea as inferred from profiling pCO2 measurements’Reconstruction of global surface ocean pCO2 using region-specific predicators based on a stepwise FFNN regression algorithm
Published 8 September 2021 Science ClosedTags: chemistry, globalmodeling, methods, modeling
Various machine learning methods were attempted in the global mapping of surface ocean partial pressure of CO2 (pCO2) to reduce the uncertainty of global ocean CO2 sink estimate due to undersampling of pCO2. In previous researches the predicators of pCO2 were usually selected empirically based on theoretic drivers of surface ocean pCO2 and same combination of predictors were applied in all areas unless lack of coverage. However, the differences between the drivers of surface ocean pCO2 in different regions were not considered. In this work, we combined the stepwise regression algorithm and a Feed Forward Neural Network (FFNN) to selected predicators of pCO2 based on mean absolute error in each of the 11 biogeochemical provinces defined by Self-Organizing Map (SOM) method. Based on the predicators selected, a monthly global 1° × 1° surface ocean pCO2 product from January 1992 to August 2019 was constructed. Validation of different combination of predicators based on the SOCAT dataset version 2020 and independent observations from time series stations was carried out. The prediction of pCO2 based on region-specific predicators selected by the stepwise FFNN algorithm were more precise than that based on predicators from previous researches. Appling of a FFNN size improving algorithm in each province decreased the mean absolute error (MAE) of global estimate to 11.32 μatm and the root mean square error (RMSE) to 17.99 μatm. The script file of the stepwise FFNN algorithm and pCO2 product are distributed through the Institute of Oceanology of the Chinese Academy of Sciences Marine Science Data Center (IOCAS; http://dx.doi.org/10.12157/iocas.2021.0022, Zhong et al., 2021).
Continue reading ‘Reconstruction of global surface ocean pCO2 using region-specific predicators based on a stepwise FFNN regression algorithm’Rapid, but limited, zooplankton adaptation to simultaneous warming and acidification
Published 1 September 2021 Science ClosedTags: biological response, crustaceans, laboratory, methods, molecular biology, morphology, mortality, multiple factors, North Atlantic, reproduction, temperature
Predicting the response of marine animals to climate change is hampered by a lack of multigenerational studies on evolutionary adaptation, particularly to combined ocean warming and acidification (OWA). We provide evidence for rapid adaptation to OWA in the foundational copepod species, Acartia tonsa, by assessing changes in population fitness on the basis of a comprehensive suite of life-history traits, using an orthogonal experimental design of nominal temperature (18 °C, 22 °C) and pCO2pCO2 (400, 2,000 µatm) for 25 generations (~1 year). Egg production and hatching success initially decreased under OWA, resulting in a 56% reduction in fitness. However, both traits recovered by the third generation, and average fitness was reduced thereafter by only 9%. Antagonistic interactions between warming and acidification in later generations decreased survival, thereby limiting full fitness recovery. Our results suggest that such interactions constrain evolutionary rescue and add complexity to predictions of the responses of animal populations to climate change.
Continue reading ‘Rapid, but limited, zooplankton adaptation to simultaneous warming and acidification’A proteomic analysis of the effect of ocean acidification on the haemocyte proteome of the South African abalone Haliotis midae
Published 17 August 2021 Science ClosedTags: biological response, laboratory, methods, mollusks, physiology, socio-economy, South Atlantic
Highlights
- 227 proteins were differentially expressed in response to ocean acidification conditions.
- Under OA conditions, H. midae underwent a metabolic shift to generate ATP via energy-efficient mechanisms.
- Haemocyte stabilisation and homeostasis in response to OA was reflected by up-regulation of oxidative stress and cytoskeletal proteins.
- An interplay between the stress and immune response was observed through up-regulation of proteins involved in protein synthesis and turnover, as well as intracellular signalling and transport.
Abstract
As a result of increasing CO2 emissions and the prevalence of global climate change, ocean acidification (OA) is becoming more pervasive, affecting many trophic levels, particularly those that rely on succinctly balanced ocean chemistry. This ultimately threatens community structures, as well as the future sustainability of the fishing/aquaculture industry. Understanding the molecular stress response of key organisms will aid in predicting their future survivability under changing environmental conditions. This study sought to elucidate the molecular stress response of the South African abalone, Haliotis midae, an understudied organism with high economic value, utilising a high throughput iTRAQ-based proteomics methodology. Adult abalone were exposed to control (pH 7.9) and experimental (pH 7.5) conditions for 12, 72 and 168 h, following which protein was isolated from sampled haemocytes and subsequently processed. iTRAQ-labelled peptides were analysed using mass spectrometry, while an array of bioinformatics tools was utilised for analysing the proteomic data. COG analysis identified “Cytoskeleton”, “Translation, ribosomal structure and biogenesis”, “Post-translational modification, protein turnover, chaperones”, and “Intracellular trafficking, secretion and vesicular transport” to be the most enriched functional classes, while statistical analysis identified a total of 33 up-regulated and 23 down-regulated effectors of OA stress in abalone. Several of the up-regulated proteins that were identified function in central metabolism (ENO1, PGK, DUOX1, GPD2), the stress/immune response (CAMKI, HSPA5/GRP78, MAPKI), and cytoskeleton, protein sorting and signal transduction (IQGAP1, MYO9B, TLN1, RDX, TCP-1/CCT, SNX6, CHMP1a, VPS13a). Protein-protein interactions were predicted using STRING DB, Cytoscape and Ingenuity Pathway Analysis, providing a model of the effects of OA on the H. midae haemocyte proteome. The data indicated that H. midae underwent a metabolic shift under OA conditions to utilize more energy-efficient mechanisms of ATP generation, while attempts at restoring haemocyte stabilisation and homeostasis were reflected by up-regulation of oxidative stress and cytoskeletal proteins. Our results support other molluscan studies that report a complex array of overlapping functions of both the stress and immune response systems. This interplay of the mounted stress and immune response is maintained and observed through the up-regulation of proteins involved in protein synthesis and turnover, as well as intracellular signalling and transport. The data presented in this study highlight the value of employing sensitive and robust -omics technologies for assessing the effects of changing environmental conditions on marine organisms.
Continue reading ‘A proteomic analysis of the effect of ocean acidification on the haemocyte proteome of the South African abalone Haliotis midae’Climate change negates positive CO2 effects on marine species biomass and productivity by altering the strength and direction of trophic interactions
Published 13 August 2021 Science ClosedTags: fish, mesocosms, methods, performance, primary production
Highlights
- We need more insight into how future food webs might be altered under climate change
- We used empirical data of species interactions from multi-species mesocosms to model trophic interaction strengths within the food web
- We separate direct from indirect species interactions, something which is seldom considered in climate studies
- We show that warming is an overwhelming climate stressor that alters trophic interactions in both negative and positive ways
- Ocean acidification boosted primary productivity which enabled energy to flow upward to higher trophic levels
- We further show that the direct effects of warming are more severe than its indirect effects
Abstract
One of the biggest challenges in more accurately forecasting the effects of climate change on future food web dynamics relates to how climate change affects multi-trophic species interactions, particularly when multiple interacting stressors are considered. Using a dynamic food web model, we investigate the individual and combined effect of ocean warming and acidification on changes in trophic interaction strengths (both direct and indirect) and the consequent effects on biomass structure of food web functional groups. To do this, we mimicked a species-rich multi-trophic-level temperate shallow-water rocky reef food web and integrated empirical data from mesocosm experiments on altered species interactions under warming and acidification, into food-web models. We show that a low number of strong temperature-driven changes in direct trophic interactions (feeding and competition) will largely determine the magnitude of biomass change (either increase or decrease) of high-order consumers, with increasing consumer biomass suppressing that of prey species. Ocean acidification, in contrast, alters a large number of weak indirect interactions (e.g. cascading effects of increased or decreased abundances of other groups), enabling a large increase in consumer and prey biomass. The positive effects of ocean acidification are driven by boosted primary productivity, with energy flowing up to higher trophic levels. We show that warming is a much stronger driver of positive as well as negative modifications of species biomass compared to ocean acidification. Warming affects a much smaller number of existing trophic interactions, though, with direct consumer-resource effects being more important than indirect effects. We conclude that the functional role of consumers in future food webs will be largely regulated by alterations in the strength of direct trophic interactions under ocean warming, with ensuing effects on the biomass structure of marine food webs.
Continue reading ‘Climate change negates positive CO2 effects on marine species biomass and productivity by altering the strength and direction of trophic interactions’Consider the following: a pilot study of the effects of an educational television program on viewer perceptions of anthropogenic climate change and ocean acidification
Published 11 August 2021 Science ClosedTags: education, methods
Climate change portends significant harms to humans and biodiversity but public knowledge of relevant scientific information remains limited. As societal changes and investment are essential to addressing anthropogenic climate change, efforts to better promote both civic science literacy and public awareness of climate change impacts are urgently required. Popular scientific television programming provides one avenue for broad climate change communication efforts.
Our pilot study seeks to evaluate the effects viewing a popular scientific television program, “Bill Nye Saves the World: The Earth is a hot mess” on both fact recall and personal perceptions. We surveyed undergraduate students enrolled in non-majors courses at two institutions of higher education, one large selective private university, and one community college with open enrollment before and after viewing this program. The survey contained both open-response questions and Likert-like ordinal responses intended to evaluate both fact recall and beliefs related to climate change.
After viewing the program, student awareness of climate change impacts was improved, especially for topics emphasized by the program such as sea level rise. Student awareness of ocean acidification was extremely low prior to viewing the program, and improved dramatically, with most respondents aware that ocean acidification is already impacting marine life after viewing. Our pilot study suggests that scientific television programs may successfully promote awareness of climate change impacts and increase perceived personal relevance of climate change, but additional data from a larger and demographically broad population is required to test whether this result is more broadly applicable.
Continue reading ‘Consider the following: a pilot study of the effects of an educational television program on viewer perceptions of anthropogenic climate change and ocean acidification’Consistency and stability of purified meta-cresol purple for spectrophotometric pH measurements in seawater
Published 9 August 2021 Science ClosedTags: chemistry, methods, North Pacific
Highlights
- Consistent pH (±0.0012) can be obtained when impurities are properly removed.
- Robust QA/QC protocols are required to prevent pH-dependent errors.
- HPLC is an effective approach to identify the presence of impurities.
- Impurities alone cannot explain different pH-dependent behavior in recent cruises.
- Dye solutions are stable to ±0.001 for 2 years when stored properly.
Abstract
Analysis of a global hydrographic data product showed a clear pH-dependent discrepancy between pH on the total scale measured spectrophotometrically (pHspec) using purified meta-cresol purple (mCP) and pH calculated from total alkalinity and dissolved inorganic carbon. However, this was based mainly on US cruises, and three recent Japanese cruises do not show this pH-dependent discrepancy. One potential explanation is that purified mCP batches obtained from different institutions lead to significantly different pHspec. Here, we tested this hypothesis by comparing the performance of purified mCP obtained from four different institutions. We demonstrate that consistent pH of ±0.0012 (95% C.I.) can be achieved regardless of the institution when impurities are properly removed. However, there was at least one batch from three of the four institutions that had significant pH-dependent errors that were as large as −0.008. The presence of impurities that led to pH-dependent errors was identified using HPLC and, for 8 out of the 9 cases, by spectrophotometry (although issues still remain for the latter). We conclude that pH-dependent errors due to impurities that remain after the purification process are, by themselves, too small to account for the differences observed between the recent set of cruises. Identifying the source of this difference should be a top priority. This study also highlights the importance of establishing robust quality assurance and quality control protocols to ensure consistent behavior with previously published equations to compute pH. We recommend a centralized system where one or a handful of institutions distribute purified mCP for the community, as this distribution approach will lead to lower prices and simplify quality assurance.
Continue reading ‘Consistency and stability of purified meta-cresol purple for spectrophotometric pH measurements in seawater’Sustainable management of the coastal water pH of Pulau Tuba using the Inverse Distance Weighted (IDW) method
Published 5 August 2021 Science ClosedTags: chemistry, field, Indian, methods, modeling, policy, regionalmodeling, socio-economy
Ocean acidification can be managed and monitored effectively through the application of spatial interpolation methods. The purpose of this study is to evaluate the precision of the Inverse Distance Weighted (IDW) interpolation method to estimate and map the coastal water pH for the sustainability of Pulau Tuba, Langkawi, Kedah. About 30 sampling points have been set up during two sampling activities in November 2018. The pH meter has been calibrated and lowered to 1 meter below the water surface to measure the reading of pH. The development of the spatial model was developed using the spatial analyst tool available in ArcGIS Software. Several types of statistical analyses were carried out to compare the observed and predicted value of pH. such as correlation analysis, regression analysis, and error analysis. Accuracy assessment was conducted later after the transformation of a spatial model into a surface map. The study found that the IDW interpolation method successfully interpolated the pH readings. The result showed that there is a strong positive correlation between the observed and predicted values. For error analysis, Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) were recorded at 0.033 and 0.044, respectively. After the transformation of the spatial model to the surface map, the accuracy of the map is recorded at 81.25%. The study also outlines the sustainable mechanisms and opportunities for the government to implement in combatting the ocean acidification processes. The map produced can be used for social and economic development and the protection of biodiversity for the coastal water of Pulau Tuba.
Continue reading ‘Sustainable management of the coastal water pH of Pulau Tuba using the Inverse Distance Weighted (IDW) method’Understanding and advancing natural resource management in the context of changing ocean conditions
Published 3 August 2021 Science ClosedTags: education, methods, North Atlantic, policy, socio-economy
Changing ocean conditions, such as ocean acidification, hypoxia, and ocean warming, are impacting marine ecosystems and posing a variety of immediate and future challenges for natural resource managers and affiliated industries. In order to successfully facilitate adaptation and mitigation responses to changing ocean conditions, research efforts and synthesis products should be developed in collaboration with resource managers and decision makers. Using interviews and surveys, we sought to advance collaborative science approaches by identifying the most pressing concerns, barriers, and research and monitoring needs of natural resource managers in Washington State, USA, where marine waters are particularly vulnerable to changing ocean conditions. Survey participants indicated that they are most concerned by ocean acidification, followed by water temperature and hypoxia. Our findings reveal a desire to prioritize laboratory and in situ studies to identify survival thresholds of ecologically or commercially important organisms, specifically zooplankton, fish, Dungeness crab, and conditions that promote harmful algal blooms. Scientific literature and in-person workshops and meetings were the preferred way for survey participants to learn about new science and affiliated results. Our findings highlight a need for continued and expanded monitoring and research efforts, the development of interpretive science products for resource managers, and enhanced communication between entities before information on changing ocean conditions can be effectively incorporated into resource management and policy decisions.
Continue reading ‘Understanding and advancing natural resource management in the context of changing ocean conditions’Community science for coastal acidification monitoring and research
Published 2 August 2021 Science ClosedTags: chemistry, education, field, methods, North Pacific
Ocean and coastal acidification (OCA) present a unique set of sustainability challenges at the human-ecological interface. Extensive biogeochemical monitoring that can assess local acidification conditions, distinguish multiple drivers of changing carbonate chemistry, and ultimately inform local and regional response strategies is necessary for successful adaptation to OCA. However, the sampling frequency and cost-prohibitive scientific equipment needed to monitor OCA are barriers to implementing the widespread monitoring of dynamic coastal conditions. Here, we demonstrate through a case study that existing community-based water monitoring initiatives can help address these challenges and contribute to OCA science. We document how iterative, sequential outreach, workshop-based training, and coordinated monitoring activities through the Northeast Coastal Acidification Network (a) assessed the capacity of northeastern United States community science programs and (b) engaged community science programs productively with OCA monitoring efforts. Our results (along with the companion manuscript) indicate that community science programs are capable of collecting robust scientific information pertinent to OCA and are positioned to monitor in locations that would critically expand the coverage of current OCA research. Furthermore, engaging community stakeholders in OCA science and outreach enabled a platform for dialogue about OCA among other interrelated environmental concerns and fostered a series of co-benefits relating to public participation in resource and risk management. Activities in support of community science monitoring have an impact not only by increasing local understanding of OCA but also by promoting public education and community participation in potential adaptation measures.
Continue reading ‘Community science for coastal acidification monitoring and research’Econometric modelling of carbon dioxide emissions and concentrations, ambient temperatures and ocean deoxygenation
Published 29 July 2021 Science ClosedTags: methods, review, socio-economy
This paper analysed several longitudinal data sets for investigating the dynamic inter-relationships between CO2 emissions and atmospheric concentrations, ambient temperatures and ocean acidification and deoxygenation. The methodological framework addressed issues such as the use of temperature ‘anomalies’, diffusion of CO2 to atmospheric stations, distributional misspecification and non-stationarity of errors affecting empirical models, and use of spline functions for modelling trends in temperatures. Longitudinal data on CO2 emissions for 163 countries and atmospheric CO2 concentrations at 10 stations, ambient temperatures from over 8,500 weather stations and seawater composition from over 380,000 oceanographic stations were analysed for 1985–2018 by estimating dynamic random effects models using maximum likelihood methods. The main findings were that CO2 emissions exhibited rapid upward trends at the country level, while minimum and maximum temperatures showed cyclical patterns; economic activity and population levels were associated with higher CO2 emissions. Second, there were gradual upward trends in annual and seasonal temperatures compiled at weather stations, and atmospheric CO2 concentrations were significantly associated with higher temperatures in the hemispheres. Third, there was a steady decline in dissolved oxygen levels, and the interactive effects of water temperatures and pH levels were significant. Overall, the results underscore the benefits of reducing CO2 emissions for ambient temperatures and for ocean deoxygenation. Synergies between CO2 emissions, ambient temperatures and ocean acidification are likely to exacerbate the melting of polar ice.
Continue reading ‘Econometric modelling of carbon dioxide emissions and concentrations, ambient temperatures and ocean deoxygenation’Ocean liming: a LES analisys of feasibility and effects of discharging slaked lime in the wake of a ship
Published 28 July 2021 Science ClosedTags: methods, mitigation
Climate change is one of the biggest challenges for humans in the modern world. Specifically, global warming due to greenhouse gases emissions constitutes a big part of it. Objective of The Paris Agreement, signed in 2016, is to maintain the global average temperature rise well below 2◦C above pre-industrial levels. However, global warming is strictly linked to another problem related to climate change: ocean acidification. Although various strategies that aim at counteracting global warming have been recently proposed and discussed, few are the technological solutions that prevent simultaneously global warming and ocean acidification. Among these, Ocean Liming technique is based on the idea of sequestering atmospheric carbon dioxide adding alkalinity to seawater, obtained by dissolution of slaked lime. The aim of this thesis work is to investigate the feasibility of Ocean Liming with the assessment of the calcium hydroxide concentration and seawater pH in the wake of a ship, conducted with a three dimensional reactive CFD modelling, in order to incorporate dynamic chemical parameters. The simulations have been conducted with a parallel Finite Differences – Large Eddy Simulation solver, wrote in Fortran 90. The work is divided in two main parts. The first one is focused on the code validation process, with the analysis of a laminar Poiseuille channel flow and a turbulent round jet. The second one consists in the simulation of slaked lime discharge in the near wake of a ship. In particular, the proposed configurations differ in slaked lime mass flow rate, type of injection (single or double) and the operational regime of the ship propeller (modelled with R-BET physical model). To complete the study, a preliminary analysis of the hull ship (modelled with a bluff body) effect on slaked lime dissolution is presented. The results are proposed with a study of space and time evolution of slaked lime concentration levels and pH variation across the computational domain. The solver could be used for future developments on this field of research, with the study of different slaked lime discharge configurations.
Continue reading ‘Ocean liming: a LES analisys of feasibility and effects of discharging slaked lime in the wake of a ship’Total dissolved inorganic carbon sensor based on amperometric CO2 microsensor and local acidification
Published 26 July 2021 Science ClosedTags: laboratory, methods, resource, sensor
We present a dipping probe total dissolved inorganic carbon (DIC) microsensor based on a localized acidic microenvironment in front of an amperometric CO2 microsensor. The acidic milieu facilitates conversion of bicarbonate and carbonate to CO2, which in turn is reduced at a silver cathode. Interfering oxygen is removed by an acidic CrCl2 oxygen trap. Theoretical simulations of microsensor functioning were performed to find a suitable compromise between response time and near-complete conversion of bicarbonate to CO2. The sensor exhibited a linear response over a wide range of 0–8 mM DIC, with a calculated LOD of 5 μM and a 90% response time of 150 s. The sensor was successfully tested in measuring DIC in bottled mineral water and seawater. This DIC microsensor holds the potential to become an important tool in environmental sensing and beyond for measurements of DIC at high spatial and temporal resolution.
Continue reading ‘Total dissolved inorganic carbon sensor based on amperometric CO2 microsensor and local acidification’Impact of anthropogenic pH perturbation on dimethyl sulfide cycling: a peek into the microbial black box
Published 21 July 2021 Science ClosedTags: abundance, biological response, laboratory, mesocosms, methods, North Atlantic, otherprocess, photosynthesis, phytoplankton, primary production
The objective of this study was to assess experimentally the potential impact of anthropogenic pH perturbation (ApHP) on concentrations of dimethyl sulfide (DMS) and dimethylsulfoniopropionate (DMSP), as well as processes governing the microbial cycling of sulfur compounds. A summer planktonic community from surface waters of the Lower St. Lawrence Estuary was monitored in microcosms over 12 days under three pCO2 targets: 1 × pCO2 (775 µatm), 2 × pCO2 (1,850 µatm), and 3 × pCO2 (2,700 µatm). A mixed phytoplankton bloom comprised of diatoms and unidentified flagellates developed over the course of the experiment. The magnitude and timing of biomass buildup, measured by chlorophyll a concentration, changed in the 3 × pCO2 treatment, reaching about half the peak chlorophyll a concentration measured in the 1 × pCO2 treatment, with a 2-day lag. Doubling and tripling the pCO2 resulted in a 15% and 40% decline in average concentrations of DMS compared to the control. Results from 35S-DMSPd uptake assays indicated that neither concentrations nor microbial scavenging efficiency of dissolved DMSP was affected by increased pCO2. However, our results show a reduction of the mean microbial yield of DMS by 34% and 61% in the 2 × pCO2 and 3 × pCO2 treatments, respectively. DMS concentrations correlated positively with microbial yields of DMS (Spearman’s ρ = 0.65; P < 0.001), suggesting that the impact of ApHP on concentrations of DMS in diatom-dominated systems may be strongly linked with alterations of the microbial breakdown of dissolved DMSP. Findings from this study provide further empirical evidence of the sensitivity of the microbial DMSP switch under ApHP. Because even small modifications in microbial regulatory mechanisms of DMSP can elicit changes in atmospheric chemistry via dampened efflux of DMS, results from this study may contribute to a better comprehension of Earth’s future climate.
Continue reading ‘Impact of anthropogenic pH perturbation on dimethyl sulfide cycling: a peek into the microbial black box’Chapter six – A brief summary of what we know and what we do not know about the impacts of ocean acidification on marine animals
Published 20 July 2021 Science ClosedTags: adaptation, biological response, methods, morphology, otherprocess, performance, physiology, reproduction, review
In the past decades, the impacts of ocean acidification (OA) on marine animals have gained much attention. To date, numerous works in the literature have shown that OA can affect a variety of biological processes of marine animals, and our knowledge about its effects on marine organisms is mainly focused on the following aspects: (1) fertilization and early development; (2) biomineralization, metabolism, and growth; and (3) immunity and behaviors. However, there are still some limitations that currently exist in research on OA, which include (1) performing experiments with “constant acidification” rather than natural pH fluctuations that may not fully reflect their future true living conditions; (2) using pCO2 levels that were predicted to be reached in a hundred years in the future for experiments with relatively short exposure times, thus overlooking marine organisms’ potential for genetic adaptation or acclimation to the acidified seawater; (3) large amounts of experiments examining OA’s physiological impacts while leaving the potential affecting mechanisms largely unstudied; and (4) a lack of experiments investigating indirect effects of OA on marine organisms and the whole ecosystem. After providing a summary of the current knowledge of OA’s impacts on marine animals, this review aims to highlight potential directions for future studies.
Continue reading ‘Chapter six – A brief summary of what we know and what we do not know about the impacts of ocean acidification on marine animals’Morphological response accompanying size reduction of belemnites during an Early Jurassic hyperthermal event modulated by life history
Published 19 July 2021 Science ClosedTags: individualmodeling, methods, modeling, mollusks, morphology, paleo
One of the most common responses of marine ectotherms to rapid warming is a reduction in body size, but the underlying reasons are unclear. Body size reductions have been documented alongside rapid warming events in the fossil record, such as across the Pliensbachian-Toarcian boundary (PToB) event (~ 183 Mya). As individuals grow, parallel changes in morphology can indicate details of their ecological response to environmental crises, such as changes in resource acquisition, which may anticipate future climate impacts. Here we show that the morphological growth of a marine predator belemnite species (extinct coleoid cephalopods) changed significantly over the PToB warming event. Increasing robustness at different ontogenetic stages likely results from indirect consequences of warming, like resource scarcity or hypercalcification, pointing toward varying ecological tolerances among species. The results of this study stress the importance of taking life history into account as well as phylogeny when studying impacts of environmental stressors on marine organisms.
Continue reading ‘Morphological response accompanying size reduction of belemnites during an Early Jurassic hyperthermal event modulated by life history’Positive species interactions strengthen in a high-CO2 ocean
Published 9 July 2021 Science ClosedTags: algae, biological response, community composition, field, fish, methods, multiple factors, performance, primary production, vents
Negative interactions among species are a major force shaping natural communities and are predicted to strengthen as climate change intensifies. Similarly, positive interactions are anticipated to intensify and could buffer the consequences of climate-driven disturbances. We used in situ experiments at volcanic CO2 vents within a temperate rocky reef to show that ocean acidification can drive community reorganization through indirect and direct positive pathways. A keystone species, the algal-farming damselfish Parma alboscapularis, enhanced primary productivity through its weeding of algae whose productivity was also boosted by elevated CO2. The accelerated primary productivity was associated with increased densities of primary consumers (herbivorous invertebrates), which indirectly supported increased secondary consumers densities (predatory fish) (i.e. strengthening of bottom-up fuelling). However, this keystone species also reduced predatory fish densities through behavioural interference, releasing invertebrate prey from predation pressure and enabling a further boost in prey densities (i.e. weakening of top-down control). We uncover a novel mechanism where a keystone herbivore mediates bottom-up and top-down processes simultaneously to boost populations of a coexisting herbivore, resulting in altered food web interactions and predator populations under future ocean acidification.
Continue reading ‘Positive species interactions strengthen in a high-CO2 ocean’
