Colony-forming scleractinian cold-water corals (CWCs) are important ecosystem engineers, forming complex 3-dimensional habitats in the deep sea, which in turn sustain high biodiversity. They are threatened by future environmental changes such as ocean acidification, warming, deoxygenation, and food limitation, but little is known about the effect of these drivers in combination or on the long-term. We conducted a year-long aquarium experiment with Lophelia pertusa (syn. Desmophyllum pertusum) under projected end-of-century conditions, investigating the combined effect of differences in pH (8.1 and 7.7), temperature (9°C and 12°C), oxygen concentration (100% and 90%) and food supply (100% and 60%) on coral survival, growth, respiration rates, skeletal dissolution and energetic reserves. Growth rates of L. pertusa decreased significantly in both multiple driver treatments, resulting in negative and more variable growth rates. However, growth rates only started to decrease after 4.5 months, clearly showing a delayed response. In addition, survival rates and energetic reserves were slightly lower in multiple driver treatments, whereas L. pertusa was not affected by reduced oxygen concentration examined as a single factor. Negative growth rates in multiple driver treatments were driven by dissolution of bare skeletal parts due to reduced seawater pH and temporary aragonite undersaturation, visualised here through micro-computed tomography images. While live CWCs may be able to cope with projected future environmental changes over the timescale of 1 year, ocean acidification will lead to dissolution of the dead skeletal framework of CWC reefs and net loss, reducing the complexity and associated biodiversity of these reefs. However, the challenge remains in closing the gap between long-term experiments and the much longer-term chronic exposure of CWCs to projected environmental changes.
Continue reading ‘Skeletal growth and loss of the cold-water coral Lophelia pertusa from multiple environmental drivers in a year-long experiment’Posts Tagged 'dissolution'
Skeletal growth and loss of the cold-water coral Lophelia pertusa from multiple environmental drivers in a year-long experiment
Published 27 March 2026 Science Leave a CommentTags: biological response, corals, dissolution, growth, laboratory, morphology, mortality, multiple factors, North Atlantic, oxygen, physiology, respiration, temperature
Effects of long-term exposure to ocean acidification on the Patagonian scallop Zygochlamys patagonica (P.P. king, 1832), a strategic fishery resource in the Southwest Atlantic ocean
Published 12 March 2026 Science ClosedTags: biological response, dissolution, fisheries, laboratory, mollusks, morphology, mortality, South Atlantic
Highlights
- Scallops were resilient to low pH within the present range of natural variability.
- Negative impacts were observed under true ocean acidification scenario, including:
- Increased mortality & decreased shell mass condition index
- Dissolution of the external shell surface modifying shell ornamentation
- Shell disarticulation leading to the lost ability to swim
- During depuration time were observed:
- A recovery of the scallops’ vital functions when the stressor (low pH) was not present
- No recovery for shell mass condition index, shell ornamentations and disarticulated scallops
- No new disarticulated scallops
Abstract
Ocean acidification (OA) is a global process leading to a decrease in seawater pH. It is a direct consequence of the increase in CO2 emissions due to human activities with documented impacts on marine species and ecosystems. Effects of a long-term OA exposure (6 months) followed by a 2 months depuration period were evaluated on the Patagonian scallop Zygochlamys patagonica, an important seafood species of the Southwest Atlantic Ocean. Scallops were exposed to three target pHs, (1) pH 7.93, the mean annual pHT at the sampling site, (2) pH 7.83, the minimum value of the natural variability recorded at the sampling site and, (3) pH 7.53, a 0.3 pH unit below the minimum pH. Mortality, shell growth, and shell mass, adductor muscle mass and gonadal mass condition indices were measured at the beginning of the experiment and after 3, 6 and 8 months of exposure. Decreased pH led to a significant increase in mortality and decrease in the shell mass condition index. Shell growth was minimal over the course of the experiment with no effect of pH. The external shell surface showed a gradual dissolution and discolouration over the 6 months exposure to low pH. Shell disarticulation due to ligament damage was also observed in 29% of the animals exposed to low pH after 6 months resulting in loss of swimming ability of scallops, whereas no disarticulated animals were recorded in the high pH treatment. These results show the vulnerability of this species to future OA conditions with implications for the ecosystem services it provides, such as a decline in scallop numbers, greater vulnerability to predation and lower quality of commercial products.
Continue reading ‘Effects of long-term exposure to ocean acidification on the Patagonian scallop Zygochlamys patagonica (P.P. king, 1832), a strategic fishery resource in the Southwest Atlantic ocean’Experimental observations on ultrastructure of scales of red seabream (Pagrosomus major) for seawater pH monitoring
Published 18 February 2026 Science ClosedTags: biological response, dissolution, fish, laboratory, morphology, North Pacific
Ocean acidification monitoring relies predominantly on field test and numerical modeling, while bioindicators are emerging as practical and economic approaches for seawater pH monitoring. Here, we report indoor dissolution experiments on the scale of red seabream (Pagrosomus major) under varied pH (from 7.1 to 7.9), showing that the mean aspect ratio of ventral ctenii and caudal/ventral lepidonts negatively correlated with pH. We propose to employ these ultrastructures of fish scale to be a novel bioindicator for marine pH reconstruction. This semiquantitative proxy would be applicable to both contemporary biomonitoring and paleo-oceanic pH reconstruction for the extensive occurrences of fish in modern oceans and fossil records.
Continue reading ‘Experimental observations on ultrastructure of scales of red seabream (Pagrosomus major) for seawater pH monitoring’Mussel periostracum protects against shell dissolution
Published 6 August 2025 Science ClosedTags: biological response, dissolution, laboratory, mollusks, morphology
Reductions to seawater pH challenge the shell integrity of marine calcifiers. Many molluscs have an external organic layer (the periostracum) that limits exposure of underlying shell to the outside environment, which could potentially help combat shell dissolution under corrosive seawater conditions. We tested this hypothesis in adult California mussels, Mytilus californianus. We quantified shell dissolution rates as a function of periostracum cover across three levels of reduced pH (7.7, 7.5, and 7.4 on the total scale). Since periostracum can also be eroded over time, we additionally conducted a first-pass examination of whether differing surface textures induced by abrasional processes might influence dissolution rates. We contextualized this set of experiments with measurements of mussel periostracum cover in multiple intertidal habitats. Our results indicate a threefold reduction in shell dissolution rate as periostracum cover increases from 10 to 85% of shell surface area. Dissolution was higher in lower-pH treatments and in treatments where periostracum removal resulted in shells with rougher surface texture, potentially due to increased microtopographic surface area of underlying shell exposed to corrosive seawater. Periostracum loss in the field was greater for mussels at higher shoreline elevations and in sunnier locations, where heat, ultraviolet radiation, and desiccation at low tide may weaken attachment of the periostracum to the shell and. These findings highlight the potential for protective structures of marine organisms to help confront increasingly acute global environmental stressors.
Continue reading ‘Mussel periostracum protects against shell dissolution’Dynamics of ocean acidity, CO2 fluxes and metabolic rates on a shallow reef of Weizhou Island: a buoy-based observational study
Published 5 August 2025 Science ClosedTags: biological response, BRcommunity, chemistry, corals, dissolution, field, North Pacific, physiology, respiration
Highlights
- Diel cycles of reef seawater pH, calcification, and production were documented through a 37-day high-frequency time series.
- Daily net ecosystem production and calcification maintain a strong linear relationship even during dark periods.
- The studied reef exhibited persistent daily net heterotrophy and net CaCO3 dissolution for over weeks.
Abstract
The metabolic processes of calcification and production serve as crucial indicators of how environmental changes impact reef health. Previous studies suggest that Net Ecosystem Production (NEP) primarily drives Net Ecosystem Calcification (NEC) in the short-term. However, the functional relationship between these two carbon metabolisms remains poorly understood. We employed a mooring buoy approach to obtain simultaneous, high-frequency data of seawater pH, aragonite saturation state, CO2 fluxes, and carbon metabolic rates over a coral reef on Weizhou Island for 37 consecutive days. Our findings revealed a strong linear correlation between NEC and NEP across both diel cycles and day-to-day timescales—this relationship held even when analyzing nighttime periods alone. This indicates an intrinsic link between carbon metabolisms that can operate independently of light. Furthermore, we observed predominantly negative daily NEC and NEP values, indicating persistent net CaCO3 dissolution and net heterotrophy across the studied reef for over weeks. Our results suggest that CaCO3 dissolution is more likely to occur in waters with heterotrophic conditions, implying that heterotrophy contributes to CaCO3 dissolution. This tight coupling could be explained by reef sediment dissolution through the Carbonate Critical Threshold (CCT) mechanism. Our study highlights the significance of ambient respiration in driving reef ecosystem-scale CaCO3 dissolution, especially in reefs with low live hard coral coverage. This process releases alkalinity into the seawater, helping to neutralize respiration-induced acidification. Additionally, we identified a higher rate of respiratory CO₂ release as the primary driver of CO2 emissions from the studied reef.
Continue reading ‘Dynamics of ocean acidity, CO2 fluxes and metabolic rates on a shallow reef of Weizhou Island: a buoy-based observational study’Mangrove-driven acidification and shell dissolution on intertidal oyster reefs in a subtropical estuary
Published 4 August 2025 Science ClosedTags: biological response, BRcommunity, chemistry, dissolution, field, mollusks, morphology, North Atlantic, phanerogams
Tropicalization, resulting from warmer minimum temperatures, has allowed mangroves to expand poleward and increase in abundance in historical ranges. Since 1984, mangrove abundance on intertidal oyster reefs in Mosquito Lagoon, Florida, USA, has increased by 198% due to tropicalization. Oysters provide abundant ecosystem services including engineering reef habitat and water filtration, but shells are prone to dissolution in acidic conditions. Mangroves are associated with soil acidification and therefore may alter the pH of oyster reef sediment. The goal of this research was to determine if mangroves acidify oyster reef porewater (i.e. water within the sediment) and determine if mangrove-correlated acidification caused oyster shell dissolution as indicated by shell mass loss. Porewater, up to 10 cm depth, was collected monthly for 2 yr, and the pH was compared between 4 habitats: mudflats, oyster-dominated reefs (oyster reefs), transitioning reefs (oyster reefs with mangroves), and mangrove-dominated sites (mangrove islands). Porewater was more acidic with mangroves present. Transitioning reefs had a mean pH of 7.13 compared to oyster-dominated reefs (mean pH: 7.52). To measure shell dissolution, bags containing 10 pre-weighed oyster shells were deployed and re-weighed after 6, 12, and 24 mo. After 24 mo, mangrove-dominated sites lost more shell mass (8% loss) compared to oyster-dominated sites (1% loss). Transitioning reefs had intermediate shell mass loss. Combined, these data suggest that mangrove expansion on intertidal oyster reefs can negatively impact oysters. With oyster reef habitats in global decline, understanding new sources of degradation, including mangrove-driven acidification, is crucial to supporting conservation and restoration efforts.
Continue reading ‘Mangrove-driven acidification and shell dissolution on intertidal oyster reefs in a subtropical estuary’Shell dissolution rates differ fourfold between mussel species
Published 1 August 2025 Science ClosedTags: biological response, dissolution, laboratory, mollusks, North Pacific
Ocean acidification poses a critical threat to marine calcifiers globally and is particularly severe in the California Current System, where ecologically and economically important bivalves experience reduced calcification under climate change. Marine mussels display differential habitat preferences, with species like Mytilus californianus favouring fully saline environments and M. trossulus inhabiting sites with greater freshwater input. Determining abiotic dissolution rates of these species under ocean acidification is essential for predicting future consequences of climate change for coastal populations. We examined shell dissolution rates of mussel congeners under a range of pH (6.5–9.3) and aragonite saturation states (0.1–9.0). We also experimentally quantified the relative importance of dissolution from interior versus exterior shell surfaces. M. trossulus exhibited fourfold higher shell dissolution rates than M. californianus. When the shell interior was sealed against seawater exposure, dissolution rates decreased significantly in both species, indicating high abiotic dissolution on the shell interior. Results demonstrate that dissolution rates can vary between congeners inhabiting the same biogeographic region. Our finding that freshwater-tolerant M. trossulus has higher abiotic dissolution under ocean acidification is important because low salinity may further retard calcification, altering future intertidal population structure along freshwater-influenced coastlines.
Continue reading ‘Shell dissolution rates differ fourfold between mussel species’Vulnerability to ocean acidification of marine calcifying organisms cannot be predicted from the mineral type in their shells
Published 31 July 2025 Science ClosedTags: biological response, dissolution, review
Scientific Significance Statement
Anthropogenic CO2 is acidifying the surface ocean water, a process called ocean acidification (OA). This process can result in conditions that are corrosive for seashells with more “delicate” calcium carbonate shells. An important debate in OA research centers on the degree of vulnerability of the calcium carbonate shell forming groups. It is widely believed that the vulnerability can be simply inferred from the particular mineral type forming the shells (related to the mineral’s solubility). This idea is widespread and has found its way into policy reports. We argue that the idea is over-simplified and can lead to wrong assessments of vulnerability to OA. Shell dissolution kinetics is not only a function of the mineral type but also of microstructure and organic content. This means that vulnerability assessments in, for example, some models and policy reports have to be revised.
Continue reading ‘Vulnerability to ocean acidification of marine calcifying organisms cannot be predicted from the mineral type in their shells’Species-specific mechanisms of benthic foraminifera in response to shell dissolution
Published 31 July 2025 Science ClosedTags: biological response, dissolution, laboratory, light, mortality, multiple factors, North Atlantic, performance, photosynthesis, protists, respiration
Highlights
- Living specimens and empty tests of two benthic foraminifera species were cultured in different pH and light conditions.
- In acidic conditions, greater dissolution of empty tests compared to living specimens was observed.
- No differences in the degrees of dissolution between the two species were observed.
- Living foraminifera have active mechanism(s) to tolerate acidification.
Abstract
Ammonia confertitesta and Haynesina germanica are two common estuarine benthic foraminifera subject to sediment acidification. Nevertheless, mechanisms involved in their response to acidification are still poorly understood. Since H. germanica is kleptoplastic and photosynthetically active, unlike A. confertitesta, these species were cultured in controlled experiments to determine whether these mechanisms could mitigate acidification-induced shell dissolution. Both living and dead specimens were incubated at two pH (8.0 and 6.8) and two light conditions (0 and 24 μmol photon m-2.s-1) for 18 days. For each species, respiration and photosynthesis rates were calculated based on oxygen measurements. At the end of incubation, foraminiferal viability was assessed with CellTracker Green™ biomarker, and each test was categorised according to a dissolution scale (DS) using SEM. For both species, in acidic conditions, the tests of dead specimens were significantly more dissolved than the tests of living specimens, suggesting active mechanisms providing tolerance to acidification. For the living specimens, no significant difference in the DS distribution was observed between the two species at both conditions, suggesting that kleptoplast photosynthetic activity in H. germanica does not provide additional resistance to acidification. Until at least day 12, respiration data revealed a different biological activity for the two species, and we observed distinct behaviours (e.g., encystment and pseudopod emission). These suggest each species exhibits species-specific responses to cope with acidification. On day 18, respiration rates and binocular observations showed low biological activity, suggesting dormancy or death. Further investigation is required to identify the cellular mechanisms involved to counter acidification stress.
Continue reading ‘Species-specific mechanisms of benthic foraminifera in response to shell dissolution’Morphological responses of a temperate intertidal foraminifer, Haynesina sp., to coastal acidification
Published 17 July 2025 Science ClosedTags: biological response, dissolution, laboratory, morphology, North Atlantic, protists
Coastal acidification could have widespread impact on marine organisms, affecting the ability of calcifying organisms to build shells and skeletons through calcium carbonate precipitation. As an abundant group of calcifying organisms, some protists within the phylum Foraminifera demonstrate potential success under elevated partial pressure of carbon dioxide (pCO2) due to their ability to modulate intracellular pH. However, little is known about their responses under more extreme acidification conditions that are already seen in certain coastal environments. Here we exposed specimens of Haynesina sp., which belongs to a genus that is prevalent in temperate intertidal salt marshes, to moderate (pCO2 = 2386.05+/−97.14 μatm) and high acidification (pCO2 = 4797.64+/−157.82 μatm) conditions through the duration of 28 days. We demonstrate that although this species is capable of withstanding moderate levels of coastal acidification with little impact on overall test thickness, it can experience precipitation deficiency and even dissolution of the calcareous test under highly elevated pCO2. Interestingly, such a deficit was primarily seen among live foraminifera, as compared to dead specimens, throughout the four-week experiment. This study suggests that a combination of environmental stress and the physiological process of test formation (i.e., calcite precipitation) could induce thinning of the test surface. Therefore, with the acceleration of coastal acidification due to anthropogenic production of CO2, benthic foraminifera and other calcifying organisms among coastal ecosystems could reach a tipping point that leads to thinning and dissolution of their calcareous tests, which in turn, will impair their ecological function as a carbon sink.
Continue reading ‘Morphological responses of a temperate intertidal foraminifer, Haynesina sp., to coastal acidification’Infaunal bivalves exhibit resilience to ocean acidification but remain sensitive to food supply
Published 26 June 2025 Science ClosedTags: biological response, chemistry, dissolution, laboratory, mesocosms, mollusks, morphology, multiple factors, physiology, South Pacific
Soft-sediment habitats are crucial for marine coastal ecosystems, supporting diverse biodiversity both above and below the sediment. Ocean acidification, driven by rising CO2 and nutrient influx, enhances heterotrophic metabolism, raising CO2 levels and lowering pH. These alterations complicate the dynamics of tidal flat, emphasizing the need for further research into their impact on biodiversity. Within these ecosystems, deposit- and suspension-feeding bivalves play crucial roles. Tagelus dombeii, a bivalve mollusc found in soft sediments, exhibits burrowing behavior linked to food supply and is of significant commercial value in southern Chile. This study assessed the response capacity of T. dombeii to key stressors associated with global ocean change, such as ocean acidification and food availability. Our results revealed significant differences in pH levels between the water column and pore water from the sediment in experimental mesocosms. T. dombeii was affected by ocean acidification and food availability in terms of its morphological traits (i.e. length, width, height and growth rate), while oxygen consumption was influenced only by the interaction between acidification and food supply. Notably, heart rate remained constant but increased when food supply was low. Our study suggests that T. dombeii exhibits partial tolerance to variations in seawater pH and carbonate chemistry, possibly due to its natural exposure to acidic pore water, but it is sensitive to food availability. These plastic physiological responses suggest that T. dombeii may be less vulnerable to future global change scenarios, demonstrating potential resilience and ecological success in its natural habitat.
Continue reading ‘Infaunal bivalves exhibit resilience to ocean acidification but remain sensitive to food supply’Pteropods as early-warning indicators of ocean acidification
Published 6 May 2025 Science ClosedTags: Antarctic, biological response, BRcommunity, chemistry, community composition, dissolution, field, mollusks, morphology, otherprocess, zooplankton
Aragonite undersaturation (Ωar < 1) events are projected to rapidly increase in frequency and duration in the Antarctic Weddell Sea by 2050. Thecosome pteropods (pelagic snails) are bioindicators of ocean acidification (OA) because their aragonite shell dissolves easily at low Ωar saturation states. Here, we describe the shell dissolution state of the pteropod Limacina helicina antarctica in relation to the water column Ωar in the southern Weddell Sea during austral summer 2018 as benchmark for future monitoring of ongoing OA. Ωar depth profiles at the sampling sites were consistently close to or in the range of threshold levels (Ωar ~ 1.1–1.3) for pteropod shell dissolution. Pteropods contributed up to 69% of total mesozooplankton biomass, and their distribution correlated positively with Ωar and chlorophyll a concentration. When analyzed with scanning electron microscopy, 78% of the investigated shells exhibited dissolution, and 50–69% showed the more severe Type II dissolution exceeding current projections of pteropod shell dissolution for the Southern Ocean. But importantly, in our study, only two specimens had the most severe Type III dissolution. Dissolution often co-occurred with and occurred in scratch marks of unclear origin supporting notions that an intact periostracum protects the shell from dissolution. Where dissolution occurred in the absence of scratches or absence of evidence of periostracum breaches, microscale/nanoscale breaches may have been an important pathway for dissolution commencement supporting recent findings of a reduction of the organic shell content caused by low Ωar/low pH. The dissolution benchmark we provide here allows future application of pteropods as early-warning indicators of presumably progressing OA in the Weddell Sea.
Continue reading ‘Pteropods as early-warning indicators of ocean acidification’Calcification of planktonic foraminifer Neogloboquadrina dutertrei and its indicative significance for ocean acidification
Published 16 April 2025 Science ClosedTags: biological response, dissolution, field, morphology, paleo, protists
Planktonic foraminifera are widespread calcifying protozoa and represent a primary source of marine biogenic calcium carbonate. Elucidating the mechanisms underlying the calcification processes of planktonic foraminifera holds significant importance for understanding the marine biological pump and carbon cycling.
The present study investigated the controlling mechanisms of calcification in modern planktonic foraminifer Neogloboquadrina dutertrei by analyzing the foraminiferal shell weight data from 92 sets of surface sediments from different ocean areas, including the eastern tropical Indian, the western tropical Pacific, the eastern tropical Pacific, and the western tropical Atlantic. First, this study reveals that deep-ocean carbonate dissolution, which is related to deep-ocean carbonate ion saturation state (Δ[CO32-]), is the dominant factor influencing the shell weight of N. dutertrei in surface sediments. Then, by correcting the dissolution effect on the shell weight of N. dutertrei, we estimated the initial shell weight from which to assess secular changes in the degree of calcification of N. dutertrei. The initial shell weight results suggest that the calcification of N.dutertrei is mainly controlled by seawater carbonate system parameters such as pH, carbonate ion concentration ([CO32-]), and carbon dioxide concentration (pCO2). Calcification of N. dutertrei would decrease with ocean acidification.
Furthermore, we reconstructed initial shell weight of N.dutertrei at sites KX97322-4 and U1490 in the western tropical Pacific to evaluate the response of N. dutertrei calcification to climate changes over glacial-interglacial time scales. Calcification of N. dutertrei in the western tropical Pacific has increased during glacial periods in response to lower atmospheric pCO2 since 800 ka, confirming the dominant influence of ocean acidification on N. dutertrei calcification. We suggest that the shell weight of specific planktonic foraminiferal species may serve as a potential proxy for past seawater carbonate system reconstructions.
Continue reading ‘Calcification of planktonic foraminifer Neogloboquadrina dutertrei and its indicative significance for ocean acidification’The impact of ocean acidification on gastropod shell dissolution and microstructure
Published 11 April 2025 Science ClosedTags: biological response, dissolution, growth, laboratory, mollusks, morphology, North Pacific
Highlights
- Ocean acidification causes gastropod shell dissolution and microstructural change.
- Shell growth is inhibited below pH 7.5, with dissolution pits in the inner surface.
- At pH 7.1, shell surface erosion intensifies, with extensive periostracum peeling.
- Shell dissolution negatively correlates with pH, offering a new bio-proxy.
- Shell structural changes can assess past ocean acidification events.
Abstract
Global seawater pH is projected to decrease by 0.3–0.5 units on average by the end of this century, which is considered detrimental to the shells of marine calcareous organisms. However, there is limited understanding of how ocean acidification affects the morphology and structure of these shells, as well as the underlying mechanisms. This study examines the shell growth, surface erosion, and microstructural changes of the marine gastropod Lunella coronata granulata after 85 days of exposure to varying pH (8.1–7.1). The results reveal that at pH ≤ 7.5, shell growth is notably inhibited, with pronounced dissolution hole formation on the inner surface. At pH 7.1, shell surface erosion becomes more pronounced, accompanied by extensive peeling of the shell periostracum. These changes—dissolution hole formation and periostracum peeling—are critical indicators of gastropod shell response to ocean acidification and can serve as biological indicators reflecting current and past ocean acidification. Additionally, our study shows a clear negative correlation between shell dissolution and pH, providing new bio-proxy for indicating the pH changes.
Continue reading ‘The impact of ocean acidification on gastropod shell dissolution and microstructure’The effect of carbonate mineral additions on biogeochemical conditions in surface sediments and benthic–pelagic exchange fluxes (update)
Published 11 February 2025 Science ClosedTags: biogeochemistry, chemistry, dissolution, mitigation, modeling, regionalmodeling, sediment
Coastal sediments are hotspots of biogeochemical processes that are impacting subsurface and overlying water conditions. Fluid composition in sediments is altered through the mineralization of organic matter which, under oxic conditions, further lowers both pH and the carbonate saturation state. As a potential mitigation strategy for this sediment acidification, we explored the effects of mineral additions to coastal sediments. We experimentally quantified carbonate mineral dissolution kinetics of carbonate shells suitable for field application and then integrated these data into a reactive transport model that represents early diagenetic cycling of C, O, N, S, and Fe and traces total alkalinity, pH, and saturation state of CaCO3. Model simulations were carried out to delineate the impact of mineral type and amount added, porewater mixing, and organic matter mineralization rates on sediment alkalinity and its flux to the overlying water. Model results showed that the added minerals undergo initial rapid dissolution and generate saturated conditions demonstrating the potential of alkalinity enhancement in mitigating surface sediment acidification. Aragonite dissolution led to higher total alkalinity concentrations than calcite. Simulations of carbonate mineral additions to sediment environments with low rates of organic matter mineralization exhibited a substantial increase in mineral saturation state compared to sediments with high CO2 production rates, highlighting the environment-specific extent of the effect of mineral addition. Our work indicates that carbonate additions have the potential to effectively buffer surficial sediments over multiple years, yielding biogeochemical conditions that counteract the detrimental effect of low-pH sediment conditions on larval recruitment and potentially increase benthic alkalinity fluxes to support marine carbon dioxide removal (mCDR) in the overlying water.
Continue reading ‘The effect of carbonate mineral additions on biogeochemical conditions in surface sediments and benthic–pelagic exchange fluxes (update)’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’Single-larva RNA sequencing reveals that red sea urchin larvae are vulnerable to co-occurring ocean acidification and hypoxia
Published 22 January 2025 Science ClosedTags: biological response, dissolution, echinoderms, fisheries, molecular biology, multiple factors, North Pacific, oxygen, physiology, reproduction
Anthropogenic carbon dioxide emissions have been increasing rapidly in recent years, driving pH and oxygen levels to record low concentrations in the oceans. Eastern boundary upwelling systems such as the California Current System (CCS) experience exacerbated ocean acidification and hypoxia (OAH) due to the physical and chemical properties of the transported deeper waters. Research efforts have significantly increased in recent years to investigate the deleterious effects of climate change on marine species, but have not focused on the impacts of simultaneous OAH stressor exposure. Additionally, few studies have explored the physiological impacts of these environmental stressors on the earliest life stages, which are more vulnerable and represent natural population bottlenecks in organismal life cycles. The physiological response of the ecologically and commercially important red sea urchin (Mesocentrotus franciscanus) was assessed by exposing larvae to a variety of OAH conditions, mimicking the range of ecologically relevant conditions encountered currently and in the near future along the CCS. Skeleton dissolution, larval development, and gene expression show a response with clearly delineated thresholds that were related to OAH severity. Skeletal dissolution and the induction of Acid-sensing Ion Channel 1A at pH 7.94/5.70 DO mg/L provide particularly sensitive markers of OAH, with dramatic shifts in larval morphology and gene expression detected at the pH/DO transition of 7.71/3.71–7.27/2.72 mg/L. Experimental simulations that describe physiological thresholds and establish molecular markers of OAH exposure will provide fishery management with the tools to predict patterns of larval recruitment and forecast population dynamics.
Continue reading ‘Single-larva RNA sequencing reveals that red sea urchin larvae are vulnerable to co-occurring ocean acidification and hypoxia’The role of rolling corals and free-living calcifying coralline algae in the management of greenhouse gas CO2 in the Colombian Caribbean
Published 25 November 2024 Science ClosedTags: algae, biological response, BRcommunity, calcification, corals, dissolution, field, laboratory, mitigation, North Atlantic, photosynthesis, primary production, respiration
The ongoing increase in anthropogenic CO₂ emissions since the industrial revolution has accelerated ocean acidification (OA) by introducing CO₂ into seawater, forming carbonic acid and reducing pH levels. This acidification threatens marine calcifiers by weakening their capacity to build calcium carbonate structures and promoting the dissolution of existing skeletons. Nonetheless, calcifying organisms may contribute to mitigating OA effects. This study explores the roles of corals (rolling Siderastrea radians, a seagrass dweller) and free-living calcifying coralline algae (back reef) in CO₂ mitigation in seawater. Field experiments were conducted on Isla Grande (Corales del Rosario and San Bernardo National Natural Park, Colombian Caribbean), to observe the diel variations in photosynthesis and calcification of these uncommon reef builders across different times of the day. Results demonstrate diel shifts influenced by photosynthesis/respiration and calcification/dissolution, with free-living coralline algae exhibiting higher productivity and calcification rates than corals during the day. Notably, free-living coralline algae displayed pronounced hysteresis, reflecting high sensitivity to light. These findings underscore the significant role of free-living coralline algae in marine carbon cycling, suggesting a more substantial impact on CO₂ mitigation than previously recognized. Conserving free-living coralline algae and their habitats is thus critical for supporting marine ecosystem health and resilience amidst global change, warranting further research into their metabolic responses to inform conservation strategies.
Continue reading ‘The role of rolling corals and free-living calcifying coralline algae in the management of greenhouse gas CO2 in the Colombian Caribbean’Effects of ocean acidification on the interaction between calcifying oysters (Ostrea chilensis) and bioeroding sponges (Cliona sp.)
Published 18 November 2024 Science ClosedTags: biological response, BRcommunity, calcification, community composition, dissolution, laboratory, mollusks, otherprocess, porifera, respiration
Ocean acidification can negatively affect a broad range of physiological processes in marine shelled molluscs. Marine bioeroding organisms could, in contrast, benefit from ocean acidification due to reduced energetic costs of bioerosion. Ocean acidification could thus exacerbate negative effects (e.g. reduced growth) of ocean acidification and shell borers on oysters. The aim of this study was to assess the impact of ocean acidification on the oyster Ostrea chilensis, the boring sponge Cliona sp., and their host-parasite relationship. We exposed three sets of organisms 1) O. chilensis, 2) Cliona sp., and 3) O. chilensis infested with Cliona sp. to pHT 8.03, 7.83, and 7.63. Reduced pH had no significant effect on calcification, respiration and clearance rate of uninfested O. chilensis. Low pH significantly reduced calcification leading to net dissolution of oyster shells at pHT 7.63 in sponge infested oysters. Net dissolution was likely caused by increased bioerosion by Cliona sp. at pHT 7.63. Additionally, declining pH and sponge infestation had a significant negative antagonistic effect (less negative than predicted additively) on clearance rate. This interaction suggests that sponge infested oysters increase clearance rates to cope with higher energy demand of increased shell repair resulting from higher boring activity of Cliona sp. at low seawater pH. O. chilensis body condition was unaffected by sponge infestation, pH, and the interaction of the two. The reduction in calcification rate suggests sponge infestation and ocean acidification together would exacerbate direct (reduced growth) and indirect (e.g., increased predation) negative effects on oyster health and survival. Our results indicate that ocean acidification by the end of the century could have severe consequences for marine molluscs with boring organisms.
Continue reading ‘Effects of ocean acidification on the interaction between calcifying oysters (Ostrea chilensis) and bioeroding sponges (Cliona sp.)’Long-term study of the combined effects of ocean acidification and warming on the mottled brittle star Ophionereis fasciata
Published 27 September 2024 Science ClosedTags: biological response, BRcommunity, calcification, dissolution, echinoderms, growth, mesocosms, mortality, multiple factors, physiology, respiration, temperature
The global ocean is rapidly changing, posing a substantial threat to the viability of marine populations due to the co-occurrence of multiple drivers, such as ocean warming (OW) and ocean acidification (OA). To persist, marine species must undergo some combination of acclimation and adaptation in response to these changes. Understanding such responses is essential to measure and project the magnitude and direction of current and future vulnerabilities in marine ecosystems. Echinoderms have been recognised as a model in studying of OW-OA effects on marine biota. However, despite their global diversity, vulnerability, and ecological importance in most marine habitats, brittle stars (ophiuroids) are poorly studied. A long-term mesocosm experiment was conducted on adult mottled brittle star (Ophionereis fasciata) as a case study to investigate the physiological response and trade-offs of marine organisms to ocean acidification, ocean warming and the combined effect of both drivers. Long-term exposure of O. fasciata to high temperature and low pH affected survival, respiration and regeneration rates, growth rate, calcification/dissolution, and righting response. Higher temperatures increased stress and respiration and decreased regeneration and growth rates as well as survival. Conversely, changes in pH had more subtle or no effect affecting only respiration and calcification. Our results indicate that exposure to a combination of high temperature and low pH produces complex responses for respiration, righting response and calcification. We address the knowledge gap of the impact of a changing ocean on ophiuroids in the context of echinoderm studies, proposing this class as an ideal alternative echinoderm for future research.
Continue reading ‘Long-term study of the combined effects of ocean acidification and warming on the mottled brittle star Ophionereis fasciata’
