Ocean acidification and warming could have substantial negative impacts on marine organisms, particularly shell-building species. These environmental drivers may operate independently or interactively, amplifying or mitigating their impacts. Previous results have primarily come from lab studies, yet these climate drivers co-occur within naturally dynamic systems with high abiotic and biotic variability. Within intertidal habitats, the impacts of these drivers in situ remain poorly understood. We conducted a 6-month field manipulation to determine the effects of ocean acidification and warming on a habitat-forming shellfish, the Pacific blue mussel (Mytilus trossulus), in a dynamic intertidal system. Fourteen tide pools containing mussels were manipulated, including ambient (unmanipulated control), CO2 added, warmed, and combined CO2 added and warmed treatments. We measured mussel shell thickness, strength, and corrosion at 0, 3, and 6 months of exposure to treatment conditions. CO2 addition led to decreases in shell thickness and strength and increases in shell corrosion. However, we also detected increases in shell strength compared to controls for mussels exposed to both CO2 addition and warming. These findings indicate that ocean acidification negatively impacted shellfish overall, and the effects of acidification on shell strength might be mitigated under concurrent exposure to moderate warming, leading to an interactive effect of acidification and warming on this critical habitat-forming shellfish.
Continue reading ‘Factorial field manipulation reveals CO2 and temperature effects on a critical habitat-forming shellfish’Posts Tagged 'morphology'
Factorial field manipulation reveals CO2 and temperature effects on a critical habitat-forming shellfish
Published 14 August 2025 Science ClosedTags: biological response, laboratory, mollusks, morphology, multiple factors, North Pacific, temperature
When time reveals the cost: effects of long-term exposure to low pH on a predatory gastropod
Published 13 August 2025 Science ClosedTags: biological response, calcification, growth, laboratory, Mediterranean, mollusks, morphology
Ocean acidification, a direct consequence of anthropogenic carbon dioxide emissions, is among the major challenges for marine organisms. While an increased body of evidence is documenting the negative effects of ocean acidification, most of these studies are still based on short-term exposure. Long-term experiments, studying multiple traits simultaneously, and accounting for short-term local pH variability in the species’ habitat are needed. This study investigated the impact of a 310-day exposure to low pH on the banded-dye murex, Hexaplex trunculus (Linnaeus, 1758), a predatory Mediterranean gastropod. Temperature strongly influences the behavior and activity of the banded-dye murex, so we allowed it to vary naturally in this experiment. Our results showed that the net calcification rate was negatively affected by low pH throughout the duration of the experiment. While the banded-dye murexes were able to maintain their total body weight at the beginning of the experiment, it decreased under chronic exposure to low pH. Soft tissue body weight remained unaffected for more than 200days, followed by a pronounced decrease when exposed to lower pH. No sex-specific differences in response to low pH were observed, but females generally exhibited higher rates of calcification and growth during the winter period, likely due to energy allocation strategies associated with the reproductive cycle. These results suggest that while the banded-dye murex can temporarily reallocate energy to maintain essential physiological functions under low pH, this capacity diminishes over time, revealing physiological limits to long-term stress tolerance. This finding highlights the importance of incorporating long-term, multi-trait experiments in ocean acidification research to better predict species vulnerability, ecosystem-level impacts, and the resilience of coastal marine communities under future climate change scenarios.
Continue reading ‘When time reveals the cost: effects of long-term exposure to low pH on a predatory gastropod’Interactive effects of ocean acidification and warming disrupt calcification and microbiome composition in bryozoans
Published 12 August 2025 Science ClosedTags: abundance, adaptation, biological response, BRcommunity, bryozoa, community composition, communitymodeling, field, Mediterranean, modeling, molecular biology, morphology, mortality, otherprocess, prokaryotes, vents
Marine habitat-forming species provide crucial ecosystem functions and services worldwide. Still, the individual and combined long-term effects of ocean acidification and warming on bryozoan populations, structures, and microbiomes remain unexplored. Here, we investigate the skeletal properties, microbiome shifts, and population trends of two bryozoan species living inside and outside a volcanic CO2 vent, a natural analog to future ocean acidification conditions. We show that bryozoans can acclimatize to acidification by adjusting skeletal properties and maintaining stable microbiomes. However, we document a decrease in microbial genera playing essential functions under acidified conditions. Moreover, we show that ocean acidification exacerbates bryozoan cover loss and mortality caused by ocean warming. The observed shifts in the microbiome and cover suggest that, despite their morphological plasticity, bryozoan species will be heavily impacted by future ocean conditions, posing a threat to many benthic ecosystems in which they play a pivotal role.
Continue reading ‘Interactive effects of ocean acidification and warming disrupt calcification and microbiome composition in bryozoans’Short-term and long-term ocean acidification effects on seagrass performance: evidence from shallow CO2 vents
Published 8 August 2025 Science ClosedTags: biological response, field, Mediterranean, morphology, phanerogams, physiology, vents
Highlights
- Cymodocea nodosa performance under in-situ ocean acidification has been evaluated.
- Morphology of long-term acidified plants does not differ from that of control plants.
- Higher performance was found in short-term acidified plants.
- The response of apical shoots was particularly enhanced.
Abstract
Future ocean acidification conditions have the potential to affect seagrasses, although predicting the outcomes remains challenging due to the complexity of ecological interactions. This study aimed at evaluating the effects of ocean acidification on the morphology and physiology of the seagrass Cymodocea nodosa. A field manipulative experiment was conducted (Aeolian Islands, Italy) at a natural low pH site, where shallow submarine CO2 seeps occur, and other control pH sites. The effects of long-term acidification (by comparing untouched plants from control pH to the low pH sites) and a short-term acidification (by comparing transplanted plants from control pH sites to low pH site with translocated control pH plants) were evaluated. The evidence provided suggest that the seagrass may be considered a low pH tolerant seagrass, as the long-term acidification only determined an increase in photopigment concentrations, while the short-term acidification led to the increase in morphology, biomass and pigments, counteracting the negative effects due to cutting manipulation. These enhancements were more pronounced in apical shoots, suggesting a high clonal specialization. Our study provides evidence of morphological and physiological acclimation of C. nodosa in response to acidified conditions, suggesting that future ocean acidification scenarios could also favour this autochthonous seagrass species.
Continue reading ‘Short-term and long-term ocean acidification effects on seagrass performance: evidence from shallow CO2 vents’Skeleton-forming responses of reef-building corals under ocean acidification
Published 7 August 2025 Science ClosedTags: biological response, corals, laboratory, molecular biology, morphology, North Pacific
Ocean acidification is becoming more prevalent and may contribute to coral reef degradation, yet our understanding of its role in global reef decline remains limited. Therefore, there is an urgent need to study the impact of reduced pH levels on the growth patterns of major reef-building corals. Here, we studied the skeleton-forming strategies of 4 widely distributed coral species in a simulated acidified habitat with a pH of 7.6 to 7.8. We reconstructed and visualized the skeleton-forming process, quantified elemental calcium loss, and determined gene expression changes. The results suggest that different reef-building corals have diverse growing strategies in lower pH conditions. A unique “cavity-like” forming process starts from the inside of the skeletons of Acropora muricata, which sacrifices skeletal density to protect its polyp–canal system. The forming patterns in Pocillopora damicornis, Montipora capricornis, and Montipora foliosa were characterized by “osteoporosis”, exhibiting disordered skeletal structures, insufficient synthesis of adhesion proteins, and low bone mass, correspondingly. In addition, we found that damage from acidification particularly affects pre-existing skeletal structures in the colony. These results enhance our understanding of skeleton-forming strategies in major coral species under lower pH conditions, providing a foundation for coral reef protection and restoration amidst increasing ocean acidification.
Continue reading ‘Skeleton-forming responses of reef-building corals under ocean acidification’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’Epigenetic insights into physiological resilience: multigenerational readouts of CO2-induced seawater acidification effects on fish embryos
Published 5 August 2025 Science ClosedTags: adaptation, biological response, fish, laboratory, molecular biology, morphology, otherprocess, physiology, reproduction
Highlights
- Ocean acidification causes generation-specific developmental and metabolic changes.
- F2 embryos show enhanced resilience through transcriptional recovery mechanisms.
- Hypomethylation of ion transport genes drives adaptive acid-base regulation.
- Epigenetic inheritance facilitates multigenerational acclimation to acidification.
Summary
Anthropogenic CO2 emissions are acidifying oceans, threatening marine organisms during early development. We investigated multigenerational effects of projected 2100 acidification (pH 7.6) on marine medaka (Oryzias melastigma) embryos across three generations using integrated phenotypic, physiological, transcriptomic, and epigenetic analyses. Prolonged acidification altered developmental trajectories, with F2 embryos showing size reductions. Metabolic responses were generation-specific: F0 embryos displayed decreased ammonium excretion, while F1 and F2 maintained stable profiles. Transcriptomic analysis revealed generational changes in neurotransmission, ion regulation, and epigenetic pathways. F2 embryos exhibited attenuated transcriptional perturbations and partial restoration of acid-base homeostasis, suggesting enhanced adaptability. Adaptive gene expression correlated with hypomethylation recovery of ion transport genes AE1a and NHE2 in F2 embryos. Increased hypomethylated AE1a promoter CpG sites in F1 and F2 generations aligned with elevated transcription, indicating epigenetically-driven enhancement. These results demonstrate epigenetic control’s crucial role in multigenerational plasticity and adaptive responses to ocean acidification.
Continue reading ‘Epigenetic insights into physiological resilience: multigenerational readouts of CO2-induced seawater acidification effects on fish embryos’Abalone and seaweed co-culture: growth and shell biomineralization of an iconic California gastropod
Published 5 August 2025 Science ClosedTags: algae, biological response, chemistry, fisheries, laboratory, mitigation, mollusks, morphology, physiology, reproduction
Climate change threatens shellfish aquaculture worldwide, with ocean acidification (OA) accelerating shell dissolution and reducing calcification, hindering growth. This study addressed the negative impacts of OA on juvenile red abalone (Haliotis rufescens), a life stage that is particularly susceptible to climate stressors, and the ability of the red seaweed, dulse (Devaleraea mollis), to mitigate these effects. I tested the hypothesis that Integrated Multi-Trophic Aquaculture (IMTA), with abalone and seaweed grown in co-culture, can raise seawater pH through photosynthesis to yield more favorable conditions for abalone growth and shell construction. A 5-month experiment was conducted to determine the benefits of IMTA on abalone growth, shell composition, and morphology under simulated ocean acidification conditions. In each tank, 620 abalone were raised in either High (8.1 ± 0.3), Ambient (7.9 ± 0.2), Medium (7.8 ± 0.3), or Low pH (7.6 ± 0.2). Abalone raised in High and Ambient pH treatments exhibited greater shell length, weight, area, and condition compared to those raised in medium and low pH treatments. Shell analyses indicated that these growth differences translate into differences in physical and chemical properties, with shells from the high and ambient pH treatments containing higher levels of Mg2+ and being more resistant to fracturing. These findings indicate that IMTA could shepherd abalone through the susceptible juvenile stage, increasing resilience of abalone aquaculture even within the context of future climate change.
Continue reading ‘Abalone and seaweed co-culture: growth and shell biomineralization of an iconic California gastropod’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’Mid-Miocene warmth pushed fossil coral calcification to physiological limits in high-latitude reefs
Published 28 July 2025 Science ClosedTags: biological response, calcification, corals, field, growth, morphology, paleo
The history of resilience of organisms over geologic timescales serves as a reference for predicting their response to future conditions. Here we use fossil Porites coral records of skeletal growth and environmental variability from the subtropical Central Paratethys Sea to assess coral resilience to past ocean warming and acidification. These records offer a unique perspective on the calcification performance and environmental tolerances of a major present-day reef builder during the globally warm mid-Miocene CO2 maximum and subsequent climate transition (16 to 13 Ma). We found evidence for up-regulation of the pH and saturation state of the corals’ calcifying fluid as a mechanism underlying past resilience. However, this physiological control on the internal carbonate chemistry was insufficient to counteract the sub-optimal environment, resulting in an extremely low calcification rate that likely affected reef framework accretion. Our findings emphasize the influence of latitudinal seasonality on the sensitivity of coral calcification to climate change.
Continue reading ‘Mid-Miocene warmth pushed fossil coral calcification to physiological limits in high-latitude reefs’Adaptive responses of large yellow croaker Larimichthys crocea to ocean acidification: integrative analysis of gill and kidney transcriptomics and antioxidant enzyme activities
Published 21 July 2025 Science ClosedTags: adaptation, biological response, fish, laboratory, molecular biology, morphology, North Pacific, otherprocess, physiology
Anthropogenic acidification is a long-term challenge to marine ecosystems. Though coastal acidification is intensifying, the large yellow croaker (Larimichthys crocea) exhibits good adaptability to pH fluctuations, the underlying mechanisms of which remain poorly understood. This study investigated the morphology, antioxidant enzyme activity, and gene expression of L. crocea under varying acidification conditions (pH 8.1 (H group), 7.8 (M group), and 7.4 (L group)). Water pH fluctuations were also monitored to explore the physiological responses and potential adaptive molecular mechanisms of L. crocea under various acidified environments. The results indicated that the water pH decreased in the H group, significantly increased in the L group (p < 0.05), and remained stable in the M group during the experiment. The lowest MDA content and the highest antioxidant enzyme activities (CAT, SOD, GSH-Px) were observed in L. crocea at pH 7.8, suggesting pH 7.8 was optimal for L. crocea. Transcriptomic analysis revealed distinct gene expression patterns between the gills and kidneys under acidification stress. Differentially expressed genes (DEGs) in the gills were primarily observed between the M and L groups (62.3%), whereas in the kidneys, the majority of DEGs were observed between the M and H groups (43.2%). These findings suggested that the gills play a critical role in adapting to low pH in L. crocea, while the kidneys were more responsive to high pH. Enrichment analysis identified critical pathways, including vasopressin-regulated water reabsorption, mineral reabsorption, and aldosterone-regulated sodium reabsorption, which are associated with water and ion metabolism. These pathways play a pivotal role in the acid–base homeostasis and metabolism of L. crocea. These results provide insights into the adaptive mechanisms of L. crocea to acidified environments, with implications for aquaculture management and future ocean acidification adaptation.
Continue reading ‘Adaptive responses of large yellow croaker Larimichthys crocea to ocean acidification: integrative analysis of gill and kidney transcriptomics and antioxidant enzyme activities’Adaptation strategy of the planula strobilation in moon jelly, Aurelia coerulea to acidic environments in terms of statolith formation
Published 21 July 2025 Science ClosedTags: adaptation, biological response, cnidaria, laboratory, morphology, North Pacific, otherprocess
Simple Summary
Ocean acidification poses a significant threat to marine invertebrates with calcium-based structures. This study investigated the effects of low pH on two types of strobilation in Aurelia coerulea: polyp-strobilation (conventional asexual reproduction from polyps) and planula-strobilation (direct development from planulae). Experiments were conducted under pH 6.8, 7.8, and 8.1 conditions to observe morphological changes and statolith formation in ephyrae. Under the pH 6.8 condition, polyp-strobilation failed to produce normal ephyrae, while planula-strobilation succeeded in releasing morphologically normal ephyrae, albeit without statoliths. Under the pH 7.8 condition, both strobilation types produced ephyrae with altered statolith morphology. These statoliths were smaller in size but more numerous than those formed at pH 8.1 as normal pH, suggesting a compensatory mechanism that maintains total statolith mass and potentially preserves function. Planula-strobilated ephyrae had fewer but larger, needle-shaped statoliths, suggesting rapid statolith development. These findings suggest that planula-strobilation functions as a stress-adaptive reproductive strategy, producing the minimum necessary morphology and internal structures to ensure survival in a changing environment. The ability of Aurelia coerulea to adjust reproductive strategy and developmental traits under acidified conditions may contribute to its ecological success and persistence under future climate change scenarios.
Abstract
Ocean acidification, caused by increased atmospheric CO2, threatens marine organisms that depend on calcium-based structures such as jellyfish statoliths. This study investigated the effects of low pH on the morphology and statolith formation of ephyrae in Aurelia coerulea, comparing two developmental pathways to form ephyra: polyp-strobilation and planula-strobilation. Under the pH 6.8 condition, polyps failed to produce viable ephyrae, whereas planula-strobilation succeeded in releasing ephyrae with normal morphology, though statoliths were absent. Under the pH 7.8 condition, both strobilation types produced normal-shaped ephyrae with reduced statolith size but increased statolith number compared with the control (pH 8.1), suggesting a compensatory response to acidification. Statolith morphology differed between pathways: planula-strobilated ephyrae had needle-shaped statoliths with high aspect ratios, indicating a rapid, early-stage crystallization process. Despite their minimal body size and statolith development, planula-strobilated ephyrae maintained the functional mass of statoliths necessary for survival. This rapid, morphologically minimized development suggests that planula-strobilation is an adaptive reproductive strategy in response to environmental stress. Our findings suggest that A. coerulea possesses a flexible life history strategy that may facilitate its resilience to ongoing ocean acidification scenarios.
Continue reading ‘Adaptation strategy of the planula strobilation in moon jelly, Aurelia coerulea to acidic environments in terms of statolith formation’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’Physiological and growth responses of Black Sea salmon (Salmo labrax) to long-term salinity and high carbon dioxide stress
Published 16 July 2025 Science ClosedTags: biological response, Black Sea, fish, fisheries, growth, laboratory, molecular biology, morphology, multiple factors, physiology, salinity
Black Sea salmon (Salmo labrax), an anadromous salmonid species of regional importance, is increasingly considered for aquaculture in the Black Sea. This study investigates the physiological and growth responses of Black Sea salmon to seawater transfer, with a particular focus on carbon dioxide (CO₂) stress. The experiment began on 5 July 2022 with 720 fish (76.68±15.34 g) reared under semi-controlled conditions using a freshwater recirculating aquaculture system (RAS). On 12 October 2022, a group of fish was transferred to Black Sea water (18 ppt), and a subgroup was exposed to elevated CO₂ (1000 µatm pCO₂) until the end of the trial on 7 March 2023. Exposure to carbon dioxide showed negligible or minimal effects on seawater adaptation and growth. In contrast, physiological markers such as gill Na⁺/K⁺-ATPase (NKA) activity and the expression of nkaα1a, nkaα1b, and nkcc1a genes, along with growth metrics—including specific growth rate (SGR), condition factor (K value), and liver gene expression of igf-I, igfbp1b, ghr1, and ctsl—indicated that the fish were not physiologically prepared for seawater transfer in autumn. These findings suggest that the commonly practiced autumn sea transfer in the region may lead to suppressed growth and suboptimal performance. The results emphasize the importance of aligning seawater transfer with the smoltification window to support fish health and optimize aquaculture outcomes in Black Sea salmon farming.
Continue reading ‘Physiological and growth responses of Black Sea salmon (Salmo labrax) to long-term salinity and high carbon dioxide stress’Acidification, warming, and nutrient management are projected to cause reductions in shell and tissue weights of oysters in a coastal plain estuary
Published 16 July 2025 Science ClosedTags: biological response, communitymodeling, fisheries, modeling, mollusks, morphology, multiple factors, North Atlantic, nutrients, respiration, temperature
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 growth 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 and atmospheric temperature under Representative Concentration Pathway (RCP) 8.5, as well as 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 is 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, warming, and nutrient management are projected to cause reductions in shell and tissue weights of oysters in a coastal plain estuary’Impact of ocean acidification on skeletal structures in gilthead sea bream (Sparus aurata): in vitro and in vivo studies
Published 15 July 2025 Science ClosedTags: biological response, fish, growth, laboratory, Mediterranean, molecular biology, morphology, physiology
Highlights
- Ocean acidification affects bone mineralization.
- Ocean acidification modifies otolith size.
- Low extracellular pH increases the viability and mineralization of osteoblasts.
- Changes in cell culture pH modify the gene expression of osteoblasts.
Abstract
Ocean acidification is considered a significant risk to aquaculture, as it may adversely affect the growth and development of aquatic organisms. The effect of ocean acidification has been shown to impair the growth and survival of fish and to increase otoliths calcification in certain species; however, its effects on bone mineralization remain not well studied. The objective of the present study was to examine the effects of seawater acidification on the skeletal mineralization of gilthead sea bream juveniles, and to assess the direct impact of distinct pH levels on bone-derived cells development. After 68 days of exposure to low pH, fish exhibited a significantly reduced specific growth rate and elevated plasma pH levels, which influenced electrolyte concentrations such as potassium. Moreover, fish exposed to low pH showed increased otoliths size but no differences in shape. In bone, a higher vertebral length/height ratio was also observed, accompanied by significantly reduced opacity and increased expression of the osteoblast and osteoclast markers, alkaline phosphatase (alp) and matrix metalloproteinase 9 (mmp9), respectively, suggesting an elevated rate of bone turnover although reduced mineralization. In vitro, osteoblasts exposed to a low extracellular pH for 30 days exhibited increased viability and mineralization compared to cells maintained at a plasma pH or an alkaline pH. Additionally, the pH level significantly influenced the expression of several extracellular matrix components and osteoblast markers supporting those observations. Overall, these findings underscore the threat that ocean acidification poses to aquaculture, particularly through its impact on skeletal mineralization in gilthead sea bream, and highlight the importance of identifying approaches to farming resilient fish.
Continue reading ‘Impact of ocean acidification on skeletal structures in gilthead sea bream (Sparus aurata): in vitro and in vivo studies’Differential performance of diploid, mated triploid, and induced triploid Pacific oysters under varied environmental conditions: insights into impacts of temperature, dissolved oxygen, and pCO2
Published 11 July 2025 Science ClosedTags: biological response, fisheries, laboratory, mollusks, morphology, mortality, multiple factors, North Pacific, respiration, temperature
Highlights
- In the lab we explore environmental stress impacts on diploid and triploid oysters.
- At mid pCO2 (1450–1700 μatm) mated triploids had lower survival than other groups.
- Differences between mated and induced triploids may impact performance.
- Consider the environment when selecting which ploidy for shellfish aquaculture.
Abstract
Pacific oysters (Crassostrea gigas) are an important aquaculture species due to their fast growth, high market demand, and adaptability. Triploid oysters, have an additional set of chromosomes relative to diploids, grow faster and are functionally sterile. Thus, triploids comprise a large proportion of oysters grown worldwide. Triploid oysters are reported to experience higher mortality than diploids. Growers must make decisions that balance the risks and rewards of growing triploids. Understanding how stressors affect oysters is essential to understanding the drivers of triploid mortality and to prepare for the impacts of climate change on individuals in aquaculture. Here, we examined impacts of temperature, dissolved oxygen (DO), and pCO2 on genetically related juvenile diploid, chemically induced triploid, and mated triploid Pacific oysters. Diploid and induced triploid groups were full siblings, mated triploids were half-siblings. We measured whole organism physiological responses—growth, mortality and respiration — after a 4-week exposure to different environmental conditions. Survival was high in all groups across a broad range of temperature and DO levels. Survival of mated triploids was negatively impacted at lower (but higher than ambient) pCO2 levels. Diploids and induced triploids had similar respiration across temperature and pCO2 experiments. Diploids respired more across all dissolved oxygen treatments. Differing performance of mated triploids suggests that production method or genetic background may contribute to their resilience or susceptibility to stress. Considering the stressors that will be placed on individuals in commercial aquaculture when making ploidy selections is essential to ensure the resilience of aquaculture as the climate changes.
Continue reading ‘Differential performance of diploid, mated triploid, and induced triploid Pacific oysters under varied environmental conditions: insights into impacts of temperature, dissolved oxygen, and pCO2’Responses of the natural phytoplankton assemblage to Patagonian dust input and anthropogenic changes in the Southern Ocean
Published 10 July 2025 Science ClosedTags: Antarctic, biological response, community composition, growth, laboratory, morphology, multiple factors, nutrients, otherprocess, physiology, phytoplankton, temperature
Abstract
The cumulative effects of multi‐faceted changes on the phytoplankton community of the Southern Ocean (SO) are not yet known, which is a major limitation to predicting the future direction of the biological carbon pump. Thus, our study aimed to estimate the effects of intensified Patagonian dust inputs, warming and acidification on the growth, composition and production of phytoplankton assemblages in the Polar Frontal Zone (PFZ) and the High‐Nutrient Low‐Chlorophyll (HNLC) region of the Indian sector of the SO during the austral summer 2022. Natural phytoplankton communities were incubated for 5‐day under 4 scenarios (present and future conditions, and 2 intermediate scenarios). In the PFZ, +3°C and acidification stimulated the growth of phytoplankton, mainly cyanobacteria, while intensified dust inputs alone did not have notable impact. Conversely, in HNLC waters, the addition of Fe‐dust alone increased the total chlorophyll a of diatoms (mainly F. kerguelensis), whereas the negative effect of acidification and +3°C counteracted the positive impact of dust input on the diatoms. In these waters, future conditions benefited smaller species (haptophytes and cyanobacteria). The net particulate organic carbon production (POC) was also unaltered by future conditions, suggesting that primary production may not change in the future SO. However the increase in the length and number of long‐chain diatoms under future HNLC conditions may indicate that POC export could intensify in the future.
Plain Language Summary
Phytoplankton in the Southern Ocean (SO) play a critical role in absorbing atmospheric carbon dioxide and supporting marine ecosystems, however their response to future environmental changes remains unclear. This study examined how increased dust inputs, warming, and acidification affect the phytoplankton community in two contrasted biogeochemical domains of the SO, the Polar Frontal Zone (PFZ) and the High‐Nutrient Low‐Chlorophyll (HNLC) region. In the PFZ, warming and acidification favored the smaller phytoplankton species, while in the HNLC region, iron‐rich dust stimulated diatom species, though this effect was attenuated by warming and acidification. While overall the production of organic carbon by phytoplankton remained unchanged, diatoms may enhance carbon export to deeper waters under future conditions due to increased number and length of chain‐forming species. These findings highlighted the complexity of phytoplankton responses, which vary across regions and are influenced by interactive environmental factors. Understanding the impact of these environmental factors on phytoplankton is critical to predicting how future changes will shape the role of the SO in the global carbon cycle.
Continue reading ‘Responses of the natural phytoplankton assemblage to Patagonian dust input and anthropogenic changes in the Southern Ocean’Larval Arctic cod (Boreogadus saida) exhibit stronger developmental and physiological responses to temperature than to elevated pCO2
Published 10 July 2025 Science ClosedTags: Arctic, biological response, fish, growth, laboratory, morphology, mortality, multiple factors, physiology, reproduction, temperature
High-latitude ecosystems are simultaneously warming and acidifying under ongoing climate change. Arctic cod (Boreogadus saida) are a key species in the Arctic Ocean and have demonstrated sensitivity to ocean warming and acidification as adults and embryos, but their larval sensitivity to the combined stressors is unknown. In a laboratory multistressor experiment, larval Arctic cod were exposed to a combination of three temperatures (1.8, 5 and 7.3°C) and two carbon dioxide (pCO2) levels (ambient: 330 μatm, high: 1470 μatm) from hatching to 6-weeks of growth. Mortality rates were highest at 7.3°C (5% day°1); however, both growth and morphometric-based condition were also highest at this temperature. When these metrics were assessed via a mortality: growth (M:G) ratio, 5°C appeared to be an optimal temperature for net population biomass, as faster growth at 7.3°C did not fully compensate for higher mortality. In contrast, although morphometric-based condition was lowest at 1.8°C, lipid-based condition was highest, which may reflect prioritization of lipid storage at cold temperatures. The capacity of larval Arctic cod to acclimate to a range of temperatures was exhibited by two lipid-based indicators of membrane fluidity, including a ratio of unsaturated to saturated fatty acids and a ratio of polar lipids to sterols. The effects of elevated pCO2 were subtle, as well as temperature- and metric dependent. When exposed to elevated pCO2 levels, Arctic cod at 1.8°C exhibited signs of lipid dysregulation, suggesting potential interference with membrane acclimation; larvae at 5°C were in lower morphometric-based condition; and larvae at 7.3°C had higher activity eicosanoid substrates, indicating possible physiological stress. Overall, Arctic cod physiological response to temperature variation was more pronounced than their response to elevated pCO2. Future projections of pCO2 effects on Arctic cod health in a warming ecosystem will need to consider the complexity of temperature-dependence and the specificity of multiple physiological responses.
Continue reading ‘Larval Arctic cod (Boreogadus saida) exhibit stronger developmental and physiological responses to temperature than to elevated pCO2’Ocean acidification decreases molting but not survival of Antarctic amphipods Djerboa furcipes, Gondogeneia antarctica, and Prostebbingia gracilis
Published 10 July 2025 Science ClosedTags: Antarctic, biological response, crustaceans, laboratory, morphology, mortality, physiology, zooplankton
Ocean acidification refers to a decrease in the pH of the world’s oceans from the oceanic uptake of human-derived atmospheric CO2. Low pH is known to decrease the calcification and survival of many calcifying invertebrates. Shallow, hard bottom communities along the Western Antarctic Peninsula often have incredibly large numbers of invertebrate mesograzers that shelter on and are mutualists with the dominant brown macroalgae. The common amphipod species Djerboa furcipes, Gondogeneia antarctica, and Prostebbingia gracilis were collected from the immediate vicinity of Palmer Station, Antarctica (64°46′S, 64°03′W) in January–February 2023 and maintained under three different pH treatments simulating ambient conditions (approximately pH 8.0), near-future conditions for 2100 (pH 7.7), and distant future conditions (pH 7.3) for 8 weeks. Molt number and mortality were monitored throughout the course of the experiment. After the 8 week exposure, amphipods were analyzed for their biochemical compositions including the Mg/Ca ratio of their exoskeletons. There was no significant difference in biochemical composition or survival among the pH treatments for any of the amphipod species. All three species, however, had significantly fewer total numbers of molts in the pH 7.3 treatment than in the ambient treatment. These results suggest that amphipods may be able to maintain their survival in decreased pH by reallocating energy into compensatory behaviors, such as acid–base regulation, and away from energy expensive processes like molting.
Continue reading ‘Ocean acidification decreases molting but not survival of Antarctic amphipods Djerboa furcipes, Gondogeneia antarctica, and Prostebbingia gracilis’
