Coral, as a bioreactor, has to continuously interact with surrounding environment to maintain a healthy state. A multi-physics reaction engineering model has been developed to capture this interaction. The coral interior is modeled as interconnected reaction units respectively for photosynthesis, respiration, and calcification, whose reaction kinetics are influenced by environmental fluctuations. Coupling between coral and environment is realized by bi-directional mass transfer at the coral-seawater interface, with consideration of the unique flow fields induced by ciliary beating. By resorting to this comprehensive model, we discover that ciliary beating demonstrates distinctively different diurnal and nocturnal functions. During daytime, beating can help reduce photosynthetic oxygen accumulation to prevent hyperoxia-induced mortality, while enhancing carbon dioxide uptake efficiency to promote nutrient production. At night, however, beating promotes oxygen acquisition for adequate respiration, while expelling carbon dioxide to inhibit symbiotic destruction under acidic stress. The model further enables mechanistic analysis of the detrimental impact of climate change on coral health, where the influences from two key factors (i.e., temperature and CO2 level) can be decoupled. It’s interesting to find out that the elevated temperature plays a dominant role during daytime, while at night the coral is dominantly influenced by rising CO2 level.
Continue reading ‘Understanding coral health from reactor engineering perspective: multiphysics modeling of coral–environment interactions’Posts Tagged 'individualmodeling'
Understanding coral health from reactor engineering perspective: multiphysics modeling of coral–environment interactions
Published 30 January 2026 Science Leave a CommentTags: biological response, corals, individualmodeling, modeling, photosynthesis, physiology, respiration
Colony formation sustains the global competitiveness of N2-fixing Trichodesmium under ocean acidification
Published 10 November 2025 Science ClosedTags: biological response, growth, individualmodeling, modeling, nitrogen fixation, photosynthesis, primary production, prokaryotes
Anthropogenic CO2 emissions drive ocean acidification (OA). Trichodesmium, a key marine N2 fixer, displays contrasting growth responses to OA across morphotypes, with negative responses in free trichomes but neutral or positive in colonies. However, the lack of mechanistic understanding for these discrepancies has impaired our ability to predict the ecophysiological response of Trichodesmium in the changing ocean. Here, we developed ecophysiological models of Trichodesmium and underpin mechanisms behind contrasting responses to OA by distinct morphological adaptations. For free trichomes, our diurnal model corroborated previous findings that OA impairs nitrogenase efficiency and photosynthetic energy production. In colonies, however, OA alleviated copper and ammonia toxicity within the microenvironment, potentially with increased iron acquisition synergies, outweighing the minor effects of inorganic carbon limitation relief in the colony center. Projections suggest that globally, OA will reduce N2 fixation of trichomes by 16±6% but increase that of colonies by 19±24% within this century. By resolving morphotype-specific mechanisms, our study clarifies Trichodesmium’s adaptive strategies, which may enable it to sustain its competitiveness and biogeochemical impacts in the changing ocean.
Continue reading ‘Colony formation sustains the global competitiveness of N2-fixing Trichodesmium under ocean acidification’Internal hydrodynamics within the skeleton of Acropora pulchra coral
Published 11 February 2025 Science ClosedTags: biological response, corals, dissolution, individualmodeling, modeling
Highlights
- Consistent flow patterns are observed in Acropora coral CT scans-based simulations
- Implications of these patterns for coral growth are discussed in detail
- A prediction of coral skeleton dissolution under ocean acidification is presented
Summary
Many marine life forms, like Acropora coral, develop abiotic components to host and support the growth of living organisms. Using numerical models based on real coral samples reconstructed from micro-computed tomography (CT) scan images, we simulated internal flows inside the skeletons of Acropora pulchra coral under the influence of ambient ocean currents. The results showed that the coral’s skeletal structure, with specially connected pore space, leads to the flow and material transport within and through the skeleton to assist the coral growth and stability. However, under intensified ocean acidification, the skeletal internal flow may induce the dissolution of aragonite inside the skeleton and weaken the whole coral structure.
Continue reading ‘Internal hydrodynamics within the skeleton of Acropora pulchra coral’Ocean acidification may contribute to recruitment failure for Bering Sea red king crab
Published 29 January 2025 Science ClosedTags: biological response, crustaceans, fisheries, individualmodeling, modeling, North Pacific, reproduction
We used semi-parametric Bayesian regression to determine whether ocean acidification or climate warming could explain declining productivity for southeast Bering Sea red king crab (Paralithodes camtchaticus). Negative effects of acidification explained ~21% of recruitment variability over 1980-2023, and ~45% since 2000. Ocean warming had a negligible effect in our analysis. Model-estimated annual mean bottom pH in the region has fallen from ~8.03 in 1980 to ~7.89 in 2023, approaching levels that reduce juvenile survival in laboratory studies. Improved model validation and better understanding of potential threshold effects on red king crab are needed to better understand the possible population-level acidification effect that we demonstrate.
Continue reading ‘Ocean acidification may contribute to recruitment failure for Bering Sea red king crab’Meta-analysis of larval bivalve growth in response to ocean acidification and its application to sea scallop larval dispersal in the Mid-Atlantic Bight
Published 21 January 2025 Science ClosedTags: biological response, growth, individualmodeling, modeling, mollusks, reproduction, review
Ocean acidification, caused by increasing atmospheric carbon dioxide and coastal physical, biological, and chemical processes, is an ongoing threat to carbonate-utilizing organisms living in productive coastal shelves. Bivalves exposed to acidification have shown reduced growth, reproduction, and metabolic processes, with larval stages exhibiting the greatest susceptibility. Here, we compile results from published studies on larval bivalve growth responses to acidification to estimate a relationship between larval growth and seawater aragonite saturation state. We then apply this relationship to a larval dispersal individual-based model for Atlantic sea scallops (Placopecten magellanicus), an economically vital species in the Mid-Atlantic Bight that is historically under-studied in acidification research. To date, there have been no published studies on sea scallop larval response to ocean acidification. Model simulations allowed the identification of potential impacts of acidification on scallop success in the region. Results show that larval sea scallops that are sensitive to ocean acidification had a 17% lower settlement success rate and over 50% reduction in larval passage between major Mid Atlantic Bight fisheries habitats than those that are not sensitive to acidification. Additionally, temperature and ocean acidification interact as drivers of larval success, with aragonite saturation states > 3.0 compensating for temperature-induced mortality (> 19 ˚C) in some cases. This balance between drivers influences larval settlement success across spatial and interannual scales in the Mid Atlantic Bight.
Continue reading ‘Meta-analysis of larval bivalve growth in response to ocean acidification and its application to sea scallop larval dispersal in the Mid-Atlantic Bight’Acidification and nutrient management are projected to cause reductions in shell and tissue weights of oysters in a coastal plain estuary
Published 27 November 2024 Science ClosedTags: biological response, individualmodeling, modeling, mollusks, morphology, North Atlantic
Coastal acidification, warming, and nutrient management actions all alter water quality conditions that marine species experience, with potential impacts to their physiological processes. Decreases in calcite saturation state (ΩCa) and food availability, combined with warming water temperatures, pose a threat to calcifying organisms; however, the magnitude of future changes in estuarine systems is challenging to predict and is not well known. This study aims to determine how and where oysters will be affected by future acidification, warming, and nutrient reductions, and the relative effects of these stressors. To address these goals, an oyster bioenergetics model for Eastern oysters (Crassostrea virginica) was embedded in a 3-D coupled hydrodynamic-biogeochemistry model implemented for two tributaries in the lower Chesapeake Bay. Model simulations were forced with projected future conditions (mid-21st century atmospheric CO2, atmospheric temperature, and managed nutrient reductions) and compared with a realistic present-day reference run. Together, all three stressors are projected to reduce ΩCa and growth of oyster shell and tissue. Increased atmospheric CO2 and temperature are both projected to cause widespread reductions in ΩCa. The resulting reductions in oyster shell and tissue growth will be most severe along the tributary shoals. Future warming during peak oyster growing seasons is projected to have the strongest negative influence on tissue and shell growth, due to summer water temperatures reducing filtration rates, enhancing shell dissolution and oyster respiration rates, and increasing organic matter remineralization rates, thus reducing food availability. Nutrient reductions will exacerbate deficits in oyster food availability, contributing to further reductions in growth. Quantifying the effects of these stressors provides insight on the areas in the lower bay where oysters will be most vulnerable to mid 21st-century conditions.
Continue reading ‘Acidification and nutrient management are projected to cause reductions in shell and tissue weights of oysters in a coastal plain estuary’Projected impacts of climate change and watershed management on carbonate chemistry and oyster growth in a coastal plain estuary
Published 15 August 2024 Science ClosedTags: biological response, chemistry, individualmodeling, modeling, mollusks, morphology, North Atlantic
Coastal acidification, warming, and nutrient management actions all alter water quality conditions that marine species experience, with potential impacts to their physiological processes. Decreases in calcite saturation state (ΩCa) and food availability, combined with warming water temperatures, pose a threat to calcifying organisms; however, the magnitude of future changes in estuarine systems is challenging to predict and not well known. This study aims to determine how and where oysters will be affected by future acidification, warming, and nutrient reductions, and the relative effects of these stressors. To address these goals, an oyster bioenergetics model for Eastern oysters (Crassostrea virginica) was embedded in a 3-D coupled hydrodynamic-biogeochemistry model implemented for tributaries in the lower Chesapeake Bay. Model simulations were forced with projected future conditions (mid-21st century atmospheric CO2, atmospheric temperature, and managed nutrient reductions) and compared with a realistic present-day reference run. Together, all three stressors are projected to reduce ΩCa and growth of oyster shell and tissue. Increased atmospheric CO2 and temperature are both projected to cause widespread reductions in ΩCa. The resulting reductions in oyster shell and tissue growth will be most severe along the tributary shoals. Future warming during peak oyster growing seasons is projected to have the strongest negative influence on tissue and shell growth, due to summer water temperatures reducing filtration rates, enhancing respiration and shell dissolution rates, and increasing organic matter remineralization rates, thus reducing food availability. Nutrient reductions will exacerbate deficits in oyster food availability, contributing to further reductions in growth. Quantifying the effects of these stressors provides insight on the areas in the lower bay where oysters will be most vulnerable to mid 21stcentury conditions.
Continue reading ‘Projected impacts of climate change and watershed management on carbonate chemistry and oyster growth in a coastal plain estuary’Modelling the multiple action pathways of projected climate change on the Pacific cod (Gadus macrocephalus) early life stages
Published 23 July 2024 Science ClosedTags: biological response, chemistry, fish, growth, individualmodeling, modeling, mortality, North Pacific
Highlights
- We used projections of oceanographic conditions and an individual-based model (IBM) to study the impacts of climate on the early life stages of Pacific cod in the eastern Bering Sea from 2021 to 2100.
- Besides temperature and prey density, we also examined the impacts of ocean acidification on some biological aspects of cod larvae.
- We found that a high CO2 emission scenario (RCP8.5) may increase starvation events and decrease cod survival, while the moderate CO2 emission scenario (RCP4.5) may not produce significant impacts.
- We identified a retention area in the southeastern Bering Sea that may provide a refuge for larval cod under future environmental conditions.
- Our IBM can be used for other gadids in the same region to study the impacts of projected climate conditions on early life stages.
Abstract
Understanding how future ocean conditions will impact early life stages and population recruitment of fishes is critical for adapting fisheries communities to climate change. In this study, we incorporated projected changes in physical and biological ecosystem dynamics from an oceanographic model into a mechanistic individual-based model for larval and juvenile stages of the Pacific cod (Gadus macrocephalus) in the eastern Bering Sea. We particularly investigated the impacts of ocean currents, temperature, prey density, and pCO2 on the hatching success, growth, survival, and spatial distribution of this species during 2021–2100. We evaluated two CO2 emission scenarios: RCP8.5 (high CO2 emissions, low mitigation efforts) and RCP4.5 (medium CO2 emissions and mitigation efforts). We found that the increase in temperature and decrease in prey density were the main drivers of faster growth rates and lower survival through increased starvation by the end of the century. Conversely, pCO2 had negligible impacts, which suggests that this species might be resilient to ocean acidification. The largest effects were observed under the high CO2 emission scenario, while the RCP4.5 projections displayed minimal impacts. We also identified an area with favourable conditions in the southeastern Bering Sea that will likely persist in future decades. This study provides relevant information on the future impacts of climate change on Pacific cod, and our results can be used to implement and inform climate-ready management for this important stock in Alaska.
Continue reading ‘Modelling the multiple action pathways of projected climate change on the Pacific cod (Gadus macrocephalus) early life stages’Potential distribution of Crassostrea sikamea (Amemiya, 1928) along coastal China under global climate change
Published 7 March 2024 Science ClosedTags: abundance, biological response, chemistry, field, individualmodeling, modeling, mollusks, North Pacific, otherprocess
Highlights
- The salinity and temperature primarily dictate the distribution of C. sikamea.
- C. sikamea exhibits a south-to-north future migration pattern due to rising sea temperatures.
- By 2100s, C. sikamea’s northern boundary is expected to surpass 33–34°N.
- C. sikamea’s habitat suitability may decline by 2050s but recover gradually by 2100s.
Abstract
Global climate change has led to ocean warming, acidification, hypoxia, and alterations in the biogeochemical circulation, thereby influencing the distribution, abundance, and population patterns of marine organisms. Particularly, oysters, which tend to attach to rocks in intertidal zones, may be more vulnerable to climate change. The Kumamoto oyster, Crassostrea sikamea (Amemiya, 1928), is renowned for its nutritional content, breeding benefits, and ecosystem restoration abilities. Previous research has demonstrated that the geographical range of C. sikamea in China has gradually shifted. In this study, the Maximum Entropy (MaxEnt) model was employed to predict the suitability for C. sikamea under different climate scenarios. We utilized first-hand data collected by our research team over the past 14 years, which consisted of 3030 C. sikamea samples from seven provinces in China. The contribution rate of the environmental variables and the jackknife test revealed that salinity (13–21PSS) and temperature (24.6–25.5 °C) are the primary factors influencing the distribution of C. sikamea. The future distribution shows a south-to-north migration pattern triggered by increased sea temperature, resulting in increased suitability at higher latitudes. The migratory effect is more dramatic under the high-emission scenario (Representative Concentration Pathways 8.5 (RCP8.5)) compared to medium-(RCP4.5/RCP6.0) and low-emission scenarios (RCP2.6) and becomes increasingly evident over time. Model predictions indicated that C. sikamea could maintain its suitability under all climate scenarios until the 2050s. However, by the 2100s, the suitability is expected to shift northward beyond the 33–34°N boundary under RCP2.6, RCP6.0, and RCP8.5, extending to the northern coast of Jiangsu. The suitability of C. sikamea within its habitat may experience a significant decline by the 2050s, followed by a gradual recovery over the next 50 years. The potential northward migration of C. sikamea presents new prospects for oyster aquaculture and artificial reefs establishment in China. However, this migration will inevitably lead to significant impacts on the invaded ecosystems and overall biodiversity.
Continue reading ‘Potential distribution of Crassostrea sikamea (Amemiya, 1928) along coastal China under global climate change’Cool-edge populations of the kelp Ecklonia radiata under global ocean change scenarios: strong sensitivity to ocean warming but little effect of ocean acidification
Published 9 February 2024 Science ClosedTags: biological response, individualmodeling, laboratory, modeling, morphology, multiple factors, phanerogams, photosynthesis, physiology, South Pacific, temperature
Kelp forests are threatened by ocean warming, yet effects of co-occurring drivers such as CO2 are rarely considered when predicting their performance in the future. In Australia, the kelp Ecklonia radiata forms extensive forests across seawater temperatures of approximately 7–26°C. Cool-edge populations are typically considered more thermally tolerant than their warm-edge counterparts but this ignores the possibility of local adaptation. Moreover, it is unknown whether elevated CO2 can mitigate negative effects of warming. To identify whether elevated CO2 could improve thermal performance of a cool-edge population of E. radiata, we constructed thermal performance curves for growth and photosynthesis, under both current and elevated CO2 (approx. 400 and 1000 µatm). We then modelled annual performance under warming scenarios to highlight thermal susceptibility. Elevated CO2 had minimal effect on growth but increased photosynthesis around the thermal optimum. Thermal optima were approximately 16°C for growth and approximately 18°C for photosynthesis, and modelled performance indicated cool-edge populations may be vulnerable in the future. Our findings demonstrate that elevated CO2 is unlikely to offset negative effects of ocean warming on the kelp E. radiata and highlight the potential susceptibility of cool-edge populations to ocean warming.
Continue reading ‘Cool-edge populations of the kelp Ecklonia radiata under global ocean change scenarios: strong sensitivity to ocean warming but little effect of ocean acidification’Modeled foraminiferal calcification and strontium partitioning in benthic foraminifera helps reconstruct calcifying fluid composition
Published 5 February 2024 Science ClosedTags: biological response, calcification, individualmodeling, modeling, physiology, protists
Foraminifera are unicellular organisms that inhabit the oceans. They play an important role in the global carbon cycle and record valuable paleoclimate information through the uptake of trace elements such as strontium into their calcitic shells. Understanding how foraminifera control their internal fluid composition to make calcite is important for predicting their response to ocean acidification and for reliably interpreting the chemical and isotopic compositions of their shells. Here, we model foraminiferal calcification and strontium partitioning in the benthic foraminifera Cibicides wuellerstorfi and Cibicidoides mundulus based on insights from inorganic calcite experiments. The numerical model reconciles inter-ocean and taxonomic differences in benthic foraminifer strontium partitioning relationships and enables us to reconstruct the composition of the calcifying fluid. We find that strontium partitioning and mineral growth rates of foraminiferal calcite are not strongly affected by changes in external seawater pH (within 7.8–8.1) and dissolved inorganic carbon (DIC, within 2100–2300 μmol/kg) due to a regulated calcite saturation state at the site of shell formation.
Continue reading ‘Modeled foraminiferal calcification and strontium partitioning in benthic foraminifera helps reconstruct calcifying fluid composition’Sometimes (often?) responses to multiple stressors can be predicted from single-stressor effects: a case study using an agent-based population model of croaker in the Gulf of Mexico
Published 18 January 2024 Science ClosedTags: abundance, biological response, BRcommunity, communitymodeling, fish, individualmodeling, modeling, morphology, mortality, multiple factors, North Atlantic, otherprocess, oxygen, performance, reproduction, temperature
Abstract
Objective
Rapid changes in the world’s oceans make assessment of fish population responses to multiple stressors, especially on scales relevant to management, increasingly important. I used an existing agent-based, spatially explicit model of Atlantic Croaker Micropogonias undulatus in the northern Gulf of Mexico to examine how temperature, hypoxia, and ocean acidification, singly and in combinations, affect long-term population dynamics.
Methods
I performed a factorial simulation experiment with each stressor at three levels and analyzed various treatment combinations to assess the additivity and multiplicity of interactions. The response variables were long-term equilibrium (final year) values of spawning stock biomass (SSB), recruitment, weight at age, and two measures of stock productivity (recruits per SSB and maximum recruitment) derived from the spawner–recruit relationship fitted to model output. I used the single-stressor effects from the experiment to predict how the response variables would change when all three stressors were changed. Single-stressor effects were combined as the sum of the fractional changes (additive scale) and the product of ratios of changes (multiplicative scale) and compared to the responses in simulations with all stressors imposed.
Result
Analyzing the factorial design for two-way and three-way interactions showed that there were many interactions on the additive scale but very few on the multiplicative scale. Thus, the responses to multiple stressors were well predicted from single stressor effects when combined as multiplicative effects.
Conclusion
I discuss how the lack of strong interactions could be due to model assumptions, the structure of the model, or oversimplified representation of stressor effects. Alternatively, the model and analysis may be sufficiently realistic and weak interactions on the multiplicative scale may be common. This would reduce a complicated multi-factor situation to a series of more tractable single-factor effects. A critical next step is to determine how we can a priori identify situations of low interactions (i.e., predictable from single-stressor effects) without having to already know the multi-stressor response.
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Continue reading ‘Sometimes (often?) responses to multiple stressors can be predicted from single-stressor effects: a case study using an agent-based population model of croaker in the Gulf of Mexico’Using meta-analysis to explore the roles of global upwelling exposure and experimental design in bivalve responses to low pH
Published 16 August 2023 Science ClosedTags: biological response, individualmodeling, modeling, mollusks, physiology, respiration, review
Highlights
- Meta-analysis was used to assess bivalve responses to low pH.
- Strong upwelling regions may yield bivalves that are less sensitive to low pH.
- Upwelling explains up to 49 % variability of bivalve metabolic responses to low pH.
- Larger carbonate chemistry deltas in experiments yield stronger responses.
Abstract
Low pH conditions, associated with ocean acidification, represent threats to many commercially and ecologically important organisms, including bivalves. However, there are knowledge gaps regarding factors explaining observed differences in biological responses to low pH in laboratory experiments. Specific sources of local adaptation such as upwelling exposure and the role of experimental design, such as carbonate chemistry parameter changes, should be considered. Linking upwelling exposure, as an individual oceanographic phenomenon, to responses measured in laboratory experiments may further our understanding of local adaptation to global change. Here, meta-analysis is used to test the hypotheses that upwelling exposure and experimental design affect outcomes of individual, laboratory-based studies that assess bivalve metabolic (clearance and respiration rate) responses to low pH. Results show that while bivalves generally decrease metabolic activity in response to low pH, upwelling exposure and experimental design can significantly impact outcomes. Bivalves from downwelling or weak upwelling areas decrease metabolic activity in response to low pH, but bivalves from strong upwelling areas increase or do not change metabolic activity in response to low pH. Furthermore, experimental temperature, exposure time and magnitude of the change in carbonate chemistry parameters all significantly affect outcomes. These results suggest that bivalves from strong upwelling areas may be less sensitive to low pH. This furthers our understanding of local adaptation to global change by demonstrating that upwelling alone can explain up to 49 % of the variability associated with bivalve metabolic responses to low pH. Furthermore, when interpreting outcomes of individual, laboratory experiments, scientists should be aware that higher temperatures, shorter exposure times and larger changes in carbonate chemistry parameters may increase the chance of suppressed metabolic activity.
Continue reading ‘Using meta-analysis to explore the roles of global upwelling exposure and experimental design in bivalve responses to low pH’Model development to assess carbon fluxes during shell formation in blue mussels
Published 28 July 2023 Newsletters and reports , Science ClosedTags: biogeochemistry, biological response, calcification, individualmodeling, modeling, morphology
In order to quantify the amount of carbonate, precipitated as calcium-carbonate in the shells of blue mussel (Mytilus edulis) in a temperate climate, an existing Dynamic Energy Budget (DEB) model for the blue mussel was adapted by separating shell growth from soft tissue growth. Hereby, two parameters were added to the original DEB-model, a calcification cost [J/mgCaCO3] and an energy allocation fraction [-], which resulted in the energy allocated for structural growth being divided between shell and meat growth. As values for these new parameters were lacking, they were calibrated by fitting the model to field data. Calibration results showed that an Energy allocation fraction of 0.5 and a calcification cost of 0.9 J/mgCaCO3, resulted in the best fit when fitted on 2017 and 2018 field data separately. These values however, show the best fit for data obtained within the first couple of years of the shellfish life, and do not take later years into account. Also it could be discussed that some parameters vary throughout the lifespan of the species. The results were compared to a regular DEB model, where the shell output was calculated through a simple allometric relationship. It is sometimes assumed that the carbon storage in shell material as calcium carbonate could be regarded as a form of carbon sequestration, with a positive impact on the atmospheric CO2 concentrations. However, studies on the physical-chemical processes related to shell formation have shown that from an oceanographic perspective, shell formation should be regarded as a source of atmospheric CO2 rather than a sink. The removal of carbonates, through the biocalcification process, reduces the buffer capacity (alkalinity) of the water to store CO2. As a result CO2 is released from the water to the atmosphere when shell material is formed. The actual amount of CO2 that escapes from the water to the atmosphere as a result of biocalcification depends strongly on local water characteristics. In this study, the effect of calcification by mussels on the CO2 flux to the atmosphere is studied using an adapted DEB model where energy costs of calcification are modelled explicitly. The model was subsequently run under two future climate scenarios, (RCP 4.5 and RCP 8.3) with elevated temperature and decreased pH, and the total released CO2 as a result of shell formation was calculated with the SeaCarb model. This showed growth of mussels, under future climate conditions to be slower, and with that the cumulative shell mass and carbonate precipitated to CaCO3 to decrease. Yet the amount of CO2 released, due to biocalcification, increased. This is due to the fact that the amount of CO2 released/gr of CaCO3 precipitated will be higher, as a result of the decreased buffering capacity of seawater under future climatic environmental conditions.
In summary the conclusions of the project were:
- Biocalcification (shell formation) of marine organisms, such as bivalves, cannot be regarded as a process resulting in negative CO2 emission to the atmosphere;
- The actual amount of CO2 that, due to biocalcification, is released from the water to the atmosphere depends on the physicochemical characteristics of the water, which are influenced by (future) climate conditions;
- Our first model calculations suggest that at future climate conditions mussel’s grow rate will be somewhat reduced. While the amount of CO2 that due to biocalcification, escapes to the atmosphere during its life-time will slightly increase. Making the ratio of g CO2 release/g CaCO3 precipitated slightly higher;
- Our model calculations should be considered an exercise rather than a definite prediction of how mussels will respond to future climate scenarios. Additional information/experimentation is strongly needed to validate the model settings, and to test the validity of the above mentioned outcome of the model.
The roles of carbonate, borate, and bicarbonate ions in affecting zooplankton hatching success under ocean acidification
Published 27 June 2023 Science ClosedTags: biogeochemistry, biological response, individualmodeling, modeling, multiple factors, physiology, reproduction, respiration, review, temperature, zooplankton
Two ocean acidification studies about egg hatching success (HS) in geographically important marine copepods, Calanus finmarchicus and C. helgolandicus, were reanalyzed with improved statistical procedures. The new results at low and moderate levels of seawater acidification showed no HS inhibition at normal habitat temperatures but statistically significant inhibition at warmer and colder temperatures. These HS results were compared with seawater carbonate system and borate concentrations from precise seawater measurements. The temperature dependent differences in HS could not be directly explained by changes in the seawater concentrations of either H+, bicarbonate (HCO3−), or CO2* (CO2* being the sum of unhydrated CO2 and H2CO3). In contrast, HS differences did match trends in seawater carbonate (CO32−) concentrations. A numerical model was developed which evaluates the concentrations of O2 or CO2*, HCO3−, and CO32− at the cellular level across an egg and embryo by considering both gas diffusion with the seawater and respiration by the embryo. Again, temperature-dependent trends in HS could not be explained changes in intracellular CO2* or HCO3− concentrations, but HS did trend with the changes in intracellular CO32− concentrations. Carbonate ions form strong coordination complexes with metals, so acidification-driven decreases in external seawater carbonate concentrations, which are amplified at warmer temperatures, could release injurious metals, thus driving the HS inhibition at warmer temperatures. Increases in cytoplasmic carbonate concentrations at warmer temperatures caused by seawater acidification could complex with biochemically-needed nutrient-type metals within the cells, also causing the increased HS inhibition at warmer temperatures. Furthermore, boron is essential in chemically signaling within and between cells. Seawater borate concentrations were closely correlated with HS inhibition via Michaelis-Menton equations, suggesting that acidification-driven decreases in seawater borate concentrations may also inhibit HS. Finally, the acidification-driven increases in CO2 diffusion into cells dramatically increased intracellular bicarbonate concentrations. At mild levels of seawater acidification, an organism might compensate by exporting bicarbonate from the cells to the haemolymph and then to the seawater. Although the energetic cost, as percentage of ATP production, might be high, increased respiration rates at warmer temperatures might better allow the organism to survive. However, as temperature is lowered, the cellular respiration rate declines more rapidly with respect to temperature than does the gas diffusion coefficient. Consequently, bicarbonate accumulation driven by inward CO2 diffusion might overwhelm the egg’s bicarbonate export capacity at colder temperatures, explaining the colder temperature HS inhibition.
Continue reading ‘The roles of carbonate, borate, and bicarbonate ions in affecting zooplankton hatching success under ocean acidification’Ocean afforestation’s effect on deep-sea biogeochemistry
Published 8 June 2023 Science ClosedTags: biogeochemistry, chemistry, individualmodeling, mitigation, modeling
If climate change is left unchecked it will lead to unprecedented deterioration of human health, economy and ecology. According to the IPCC, in order to avoid severe consequences, global warming will need to be limited to 1.5°C. However, the 1.5°C warming will be exceeded if current trends continue, which is why the need for Carbon Dioxide Removal (CDR) has become increasingly apparent. Ocean afforestation is currently one of the most promising CDR approaches, with the least competition for space, high carbon sequestration potential and high technical feasibility. Ocean afforestation approaches attempt to sequester carbon by sinking seaweed to deep-sea areas. This research looks at the consequences of the seaweed input to deep-seafloor. An early diagenetic model called RADI is used to predict the fate of the carbon and the effect on biogeochemistry. The model was adapted to include new sources of sedimentary organic matter, such as seaweed (Sargassum, Saccharina, Macrocystis) and Sugarcane bagasse, which are currently considered potential candidates for ocean afforestation purposes. Sargassum, an invasive free-floating species, has a large sequestration potential and is readily available. Sinking Sargassum in pulse, large amounts over short times, leads to high carbon retention in the sediment (up to 25% after two years) but leads to hypoxic conditions in the sediment for at least two years after addition. Continuous Sargassum sinking also leads to carbon sequestration but with a much less invasive impact on the seafloor. The carbon from continuous sinking does not remain in the sediment but is remineralized and flows out to the bottom water as inorganic carbon. Saccharina, an edible coastal species, could be used to grow on free floating organic buoy. Having the additional sequestration benefit from the carbon fixed in the organics. Carbon retention is highest for the pulse addition of this seaweed (33% after two years), compared to a continuous approach (30%) in which the seaweed is added over longer timescales in small amounts. Since this pulse input also leads to hypoxic conditions in the sediment, the continuous approach is more favourable for this approach. Macrocystis, the giant kelp known for forming ecosystems, is a fast-growing coastal species. This species requires harvesting and baling for use in carbon sequestration. Carbon retention is much higher for pulse addition (30%). Sugar cane bagasse is an agricultural residue with high carbon content. Sinking this residue to anoxic basins, has been proven to retain more carbon than in oxygenated bottom waters. This can be confirmed with the results which showed a carbon retention of up to 50% after two years. The effect on the benthic biome is also less intense since the low oxygen conditions already necessitate a specialized microbiome. Sugarcane bagasse is furthermore the only addition capable of increasing bottom water pH. Whereas all seaweed approaches had higher dissolved inorganic carbon than alkalinity flow to the bottom water, resulting in net acidification. This research provides a first look into the effects of ocean afforestation on deep sea biogeochemistry, and illustrates the importance of the composition, quantity and input duration of the seaweed used.
Continue reading ‘Ocean afforestation’s effect on deep-sea biogeochemistry’Reduction in size of the calcifying phytoplankton Calcidiscus leptoporus to environmental changes between the Holocene and modern Subantarctic Southern Ocean
Published 5 June 2023 Science ClosedTags: Antarctic, biological response, individualmodeling, modeling, morphology, paleo, phytoplankton, regionalmodeling, sediment
The Subantarctic Zone of the Southern Ocean plays a disproportionally large role on the Earth system. Model projections predict rapid environmental change in the coming decades, including ocean acidification, warming, and changes in nutrient supply which pose a serious risk for marine ecosystems. Yet despite the importance of the Subantarctic Zone, annual and inter-annual time series are extremely rare, leading to important uncertainties about the current state of its ecosystems and hindering predictions of future response to climate change. Moreover, as the longest observational time series available are only a few decades long, it remains unknown whether marine pelagic ecosystems have already responded to ongoing environmental change during the industrial era. Here, we take advantage of multiple sampling efforts – monitoring of surface layer water properties together with sediment trap, seafloor surface sediment and sediment core sampling – to reconstruct the modern and pre-industrial state of the keystone calcifying phytoplankton Calcidiscus leptoporus, central to the global marine carbonate cycle. Morphometric measurements reveal that modern C. leptoporus coccoliths are 15% lighter and 25% smaller than those preserved in the underlying Holocene-aged sediments. The cumulative effect of multiple environmental drivers appears responsible for the coccolith size variations since the Last Deglaciation, with warming and ocean acidification most likely playing a predominant role during the industrial era. Notably, extrapolation of our results suggests a future reduction in cell and coccolith size which will have a negative impact on the efficiency of the biological pump in the Southern Ocean through a reduction of carbonate ballasting. Lastly, our results tentatively suggest that C. leptoporus coccolith size could be used as a palaeo-proxy for growth rate. Future culture experiments will be needed to test this hypothesis.
Continue reading ‘Reduction in size of the calcifying phytoplankton Calcidiscus leptoporus to environmental changes between the Holocene and modern Subantarctic Southern Ocean’Sr/Ca in foraminiferal calcite as a proxy for calcifying fluid composition
Published 8 May 2023 Science ClosedTags: biological response, calcification, chemistry, individualmodeling, laboratory, methods, modeling, paleo, protists
Foraminifera are unicellular organisms that inhabit the oceans. They play an important role in the global carbon cycle and record valuable paleoclimate information through the uptake of trace elements such as strontium (Sr) into their calcitic (CaCO3) shells. Understanding how foraminifera control their internal fluid composition to make CaCO3 is important for predicting their response to ocean acidification and for reliably interpreting the chemical and isotopic compositions of their shells. Here, we model foraminiferal calcification and strontium partitioning in the benthic foraminifera Cibicides wuellerstorfi and Cibicidoides mundulus based on insights from inorganic calcite experiments. The model reconciles inter-ocean and taxonomic differences in benthic foraminifer Sr/Ca partitioning relationships and enables us to reconstruct the composition of the calcifying fluid. We find that Sr partitioning and mineral growth rates of foraminiferal calcite are not significantly affected by changes in external seawater pH (within 7.8–8.1) and [DIC] (within 2100–2300 µmol/kg) due to a regulated calcite saturation state at the site of shell formation. Such homeostasis of the calcifying fluid could explain why foraminifera have been resilient to changes in ocean carbonate chemistry for more than 500 million years. Nevertheless, our model indicates that past foraminiferal DSr values were lower than its modern value due to overall lower ocean pH and higher seawater temperature during the early and middle Cenozoic.
Continue reading ‘Sr/Ca in foraminiferal calcite as a proxy for calcifying fluid composition’Sensitivity of fishery resources to climate change in the warm-temperate Southwest Atlantic Ocean
Published 24 March 2023 Science ClosedTags: biological response, fish, fisheries, individualmodeling, modeling, multiple factors, oxygen, South Atlantic, temperature
Climate change impacts on fishery resources have been widely reported worldwide. Nevertheless, a knowledge gap remains for the warm-temperate Southwest Atlantic Ocean—a global warming hotspot that sustains important industrial and small-scale fisheries. By combining a trait-based framework and long-term landing records, we assessed species’ sensitivity to climate change and potential changes in the distribution of important fishery resources (n = 28; i.e., bony fishes, chondrichthyans, crustaceans, and mollusks) in Southern Brazil, Uruguay, and the northern shelf of Argentina. Most species showed moderate or high sensitivity, with mollusks (e.g., sedentary bivalves and snails) being the group with the highest sensitivity, followed by chondrichthyans. Bony fishes showed low and moderate sensitivities, while crustacean sensitivities were species-specific. The stock and/or conservation status overall contributed the most to higher sensitivity. Between 1989 and 2019, species with low and moderate sensitivity dominated regional landings, regardless of the jurisdiction analyzed. A considerable fraction of these landings consisted of species scoring high or very high on an indicator for potential to change their current distribution. These results suggest that although the bulk of past landings were from relatively climate-resilient species, future catches and even entire benthic fisheries may be jeopardized because (1) some exploited species showed high or very high sensitivities and (2) the increase in the relative representation of landings in species whose distribution may change. This paper provides novel results and insights relevant for fisheries management from a region where the effects of climate change have been overlooked, and which lacks a coordinated governance system for climate-resilient fisheries.
Continue reading ‘Sensitivity of fishery resources to climate change in the warm-temperate Southwest Atlantic Ocean’Evaluating environmental controls on the exoskeleton density of larval Dungeness crab via micro computed tomography
Published 16 March 2023 Science ClosedTags: biological response, crustaceans, field, individualmodeling, laboratory, modeling, morphology, North Pacific, reproduction
Dungeness crab (Metacarcinus magister) have significant socioeconomic value, but are threatened by ocean acidification (OA) and other environmental stressors that are driven by climate change. Despite evidence that adult harvests are sensitive to the abundance of larval populations, relatively little is known about how Dungeness megalopae will respond to these stressors. Here we evaluate the ability to use micro-computed tomography (μCT) to detect variations in megalope exoskeleton density and how these measurements reflect environmental variables and calcification mechanisms. We use a combination of field data, culture experiments, and model simulations to suggest resolvable differences in density are best explained by minimum pH at the time zoeae molt into megalopae. We suggest that this occurs because more energy must be expended on active ion pumping to reach a given degree of calcite supersaturation at lower pH. Energy availability may also be reduced due to its diversion to other coping mechanisms. Alternate models based on minimum temperature at the time of the zoea-megalope molt are nearly as strong and complicate the ability to conclusively disentangle pH and temperature influences. Despite this, our results suggest that carryover effects between life stages and short-lived extreme events may be particularly important controls on exoskeleton integrity. μCT-based estimates of exoskeleton density are a promising tool for evaluating the health of Dungeness crab populations that will likely provide more nuanced information than presence-absence observations, but future in situ field sampling and culture experiments are needed to refine and validate our results.
Continue reading ‘Evaluating environmental controls on the exoskeleton density of larval Dungeness crab via micro computed tomography’
