Pinto abalone (Haliotis kamtschatkana), the only abalone species native to Washington, declined by 97% in the state from 1992 to 2017. Their decline is a loss for indigenous tribes, recreational divers, and the health of subtidal rocky reefs and kelp beds. Current restoration actions are facing threats of ocean acidification and warming in the northeast Pacific. This research aims to deepen our understanding of the tolerance and physiological flexibility of early life history stages of pinto abalone and inform hatchery practices under future climate change scenarios. We conducted an experiment to test how seawater pH and temperature stress impact abalone larvae. We exposed abalone post-fertilization to elevated temperature and reduced seawater pH for ten days spanning their larval development period: (1) 7.95pH/14°C (ambient), (2) 7.60pH/14°C, (3) 7.95pH/18°C, and (4) 7.60pH/18°C. Abalone in the ambient treatment had the best survival, those in the 7.60pH/18°C treatment had the worst survival, and those in the two single-stressor treatments had survival in between. Among the surviving larvae, pH was the dominant stressor influencing settlement success, with higher settlement rates under ambient pH treatments at both temperatures. pH also had a stronger effect than temperature on shell length. The information gleaned from this study is essential for optimizing future restoration aquaculture for pinto abalone and determining their ideal habitat and potential geographic range.
Continue reading ‘Exposure of larval pinto abalone to ocean acidification and warming negatively impacts survival, settlement, and size’Archive Page 38
Exposure of larval pinto abalone to ocean acidification and warming negatively impacts survival, settlement, and size
Published 13 May 2025 Science ClosedTags: biological response, laboratory, mollusks, morphology, mortality, multiple factors, North Pacific, reproduction, temperature
A critical review on ocean acidification driven by disinfection by-products discharge from ships’ ballast water management systems: impacts on carbon chemistry
Published 12 May 2025 Science ClosedTags: chemistry, review
Highlights
- Reviewed 41 relevant chemicals from ballast water and their role in ocean acidification.
- Quantified pH and carbonate ions change in seawater by DBPs using PyCO2SYS.
- Presented the risk assessment and implications of DBPs on the marine environment.
- Presented chemical reactions of discharged DBPs contributing to OA.
- Identified regulatory gap insights and DBPs acidifying effects in the ocean.
Abstract
The world’s blue economy is closely tied to maritime trade, but ballast water from ships often carries harmful aquatic organisms and pathogens, which disrupt the marine environment. To address this, the International Maritime Organization (IMO) mandated ballast water treatment to eradicate these invasive species. However, the treatment processes inherently generate numerous Disinfection by-Products (DBPs). The discharge of these DBPs exacerbates ocean acidification through various acid- and CO2-releasing reactions. The IMO’s Ballast Water Working Group has listed 41 high-priority DBPs for risk assessment due to their toxicity and prevalence in treated ballast water. This review quantitatively evaluates changes in pH and carbonate ions in seawater using the PyCO2SYS software package. Results reveal that DBPs can reduce ocean pH by ∼0.057 units and carbonate ion concentrations by 24.06 μmol kg−1 during a single discharge of 1 m3 treated water. In addition, this review outlines the challenges and research gaps for marine ecosystems sustainability.
Continue reading ‘A critical review on ocean acidification driven by disinfection by-products discharge from ships’ ballast water management systems: impacts on carbon chemistry’Ocean acidification and its consequences upon the environment
Published 9 May 2025 Science ClosedTags: biological response, mitigation, review
Ocean acidification describes the decline in pH of marine environments as the continue to absorb carbon dioxide (CO2). Research over the past ~15 years has reported the levels of ocean acidification forecasted for the end of the century (CO2 ~800-1000 µatm; pH ~7.6-7.7) This process alters the chemical balance of seawater, leading to significant ecological impacts on marine life, particularly those species that rely on calcium carbonate for shell and skeleton formation. This paper explores the causes, mechanisms, and consequences of ocean acidification, as well as its broader implications for marine ecosystems, biodiversity, fisheries, and human societies. It also highlights potential mitigation strategies to address this pressing environmental challenge, the aim of this study is finding a good strategies to decrease the ocean acidification and decreasing the amount of CO2, also suggesting a suitable ways for protection the animals which effected by ocean acidification. Understanding these impacts is crucial to addressing one of the lesser-known but profoundly important aspects of global climate change.
Continue reading ‘Ocean acidification and its consequences upon the environment’Examining behavioral alterations in zebrafish (Danio rerio) larvae in the context of anthropogenic climate change
Published 9 May 2025 Science ClosedTags: biological response, fish, laboratory, multiple factors, performance, reproduction, temperature
Behavioral responses induced by climate change in fish have received increased attention in recent years. Near future projected CO₂ levels (420 µatm to 1000 µatm) and increased temperature (~4 °C) expected in ocean and freshwater basins by 2100 have been shown to impair various behaviors such as locomotor activity and learning in early life stage fish. Despite widespread characterization, we know little about why these disruptions occur and how compounded effects of climate change might disrupt behavioral paradigms. Using the biomedical research model, the zebrafish (Danio rerio), a species with a well-documented behavioral repertoire and broadly utilized for mapping neural activity linked to behavior, this study aimed to assess how elevated CO₂ and temperature may affect behavior during early development. Larvae 6-7 days post fertilization were acclimated to either control (420 µatm CO₂; 28 °C) or 1,000 µatm pCO₂ and temperatures of 32 °C combined or singly before being subjected to various behavioral assays, consisting of acoustic- and visual stimuli to examine startle responses and their habituation. The results suggest that temperature more than CO₂ significantly altered the startle response, and to some extent, the habituation of this response. Both acoustic- and visual startle response were negatively affected by climate change relevant heat-exposure, while aquatic acidification had no significant effect on the acoustic startle response singly. Conversely, habituation appears to have increased under elevated temperature treatment in isolation compared to ambient levels. This experiment may help highlight zebrafish’s potential as a model organism for further climate- behavioral and physiological investigations, supported by their advanced gene editing and transgenic tools, optical transparency, and compatibility with high-throughput screening approaches.
Continue reading ‘Examining behavioral alterations in zebrafish (Danio rerio) larvae in the context of anthropogenic climate change’Increasing acidification does not affect sexual reproduction of a solitary zooxanthellate coral transplanted at a carbon dioxide vent
Published 8 May 2025 Science ClosedTags: biological response, corals, field, Mediterranean, morphology, reproduction, vents
The absorption of atmospheric carbon dioxide is causing significant changes to the carbonate chemistry of the ocean, in a phenomenon called ocean acidification. The latter makes it potentially more difficult for marine calcifiers like corals, to build their calcium carbonate structures, thus affecting their ability to survive and reproduce. Research on how ocean acidification impacts coral sexual reproduction has focused on tropical species investigated under controlled conditions in aquaria, lacking insights into the intricate natural environment. Here we show that the sexual reproduction of the zooxanthellate solitary scleractinian Balanophyllia europaea transplanted at a CO2 vent off the Island of Panarea (Tyrrhenian Sea, Italy) for up to 5 months is unaffected by decreasing pH (pH range 8.1–7.4). These findings reinforce earlier evidence, suggesting that zooxanthellate corals may exhibit a certain degree of short-term resilience to ocean acidification. However, the interplay between ocean acidification and additional environmental stressors, including warming, will ultimately define the boundaries that distinguish winners and losers amid swift climatic changes.
Continue reading ‘Increasing acidification does not affect sexual reproduction of a solitary zooxanthellate coral transplanted at a carbon dioxide vent’Sea-Bird Scientific reintroduces stable, long-term pH instruments
Published 8 May 2025 Media coverage ClosedTags: methods
Sea-Bird Scientific has announced that the company has restarted production and service of their cutting-edge Shallow SeaFET™ and Shallow SeapHOx™. After rigorous qualification, testing, and field deployments, the company is now accepting requests for quotes and service.
These high-tech pH ocean sensors are equipped with advanced Ion-Sensitive Field Effect Transistor (ISFET) technology and are ideal for all coastal applications up to 50 meters deep.
The Shallow SeaFET V2 uses the ISFET technology for stable, long-term pH measurements in salt water and has been used extensively around the globe for ocean acidification research, coral reef research, coastal marine biology, and environmental monitoring. The Shallow SeaFET V2 can be autonomous with internal power, sample scheduling, and data logging capabilities.
The Shallow SeapHOx V2 combines the Shallow SeaFET V2 with the SBE 37-SMP-ODO MicroCAT CTD+DO sensor. This integration enables comprehensive data collection of pH alongside critical oceanographic and biological measurements of temperature, salinity, and oxygen. The Shallow SeapHOx V2 benefits from the SBE 37SMP-ODO’s pumped flow path and anti-fouling technology, extending deployment durations in some cases.
Continue reading ‘Sea-Bird Scientific reintroduces stable, long-term pH instruments’Open science for the ocean. Recommendations from the perspective of marine carbon observations in Germany, Brazil, and beyond
Published 8 May 2025 Science ClosedTags: policy
The ocean plays an essential role in regulating the global climate, absorbing around 25 % of global CO2 emissions. Scientific knowledge of the ocean’s capacity as a carbon sink is therefore essential for policy-making at the national and international level. However, the capacity of the existing marine science system to deliver this information at sufficiently high quality, without geographical and temporal gaps, and with equitable contributions by and access for less affluent national science systems, is far from assured. This contribution applies the six guiding principles of Open Science as a yardstick for science in the service of society to assess the current state of marine (carbon) science, pointing out strengths and shortcomings, and deriving specific recommendations for science policy. This contribution results from a three-year interdisciplinary research project with researchers from Brazil and Germany and was discussed within the UN Ocean Decade Program Ocean Acidification Research for Sustainability (OARS) to validate the applicability of insights and recommendations beyond these particular contexts.
Continue reading ‘Open science for the ocean. Recommendations from the perspective of marine carbon observations in Germany, Brazil, and beyond’New study shows how ‘marine revolution’ shaped ocean life
Published 7 May 2025 Press releases ClosedTags: paleo
A scanning electron micrograph of Globorotalia tumida, a calcareous planktic foraminifera. This specimen was collected from IODP Site U1559 in the South Atlantic Ocean. Credit: Chris Lowery.
Between 252 and 66 million years ago, the ocean underwent a revolution.
That’s when plankton with calcium carbonate skeletons colonized the open ocean. When they died, their remains fell like snow over large parts of the seafloor. The abundance of their skeletons over time changed the marine landscape, leading to unique rock formations and vast deposits of carbonate rock.
This buildup of carbonate minerals was an important part of the Mesozoic Marine Revolution, or MMR — a period of transformation in Earth’s oceans that helped set the stage for today’s modern marine ecosystem.
According to a new study led by researchers at The University of Texas at Austin and published in the Proceedings of the Royal Society B: Biological Sciences, the change in calcium carbonate dynamics in the ocean appears to have influenced the evolutionary trajectory of tiny but mighty sea creatures: foraminifera.
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Forams can make their skeletons out of different materials, including sediments and organic matter. The researchers found that after the MMR, calcareous forams — which build their shells by secreting calcium carbonate — flourished, going on to become the dominant type of foram living today.
The study’s lead author Katherine Faulkner, who conducted the research when she was an undergraduate student at UT, said that in addition to shedding light on foram diversity through time, the findings could help researchers learn about how other forms of marine life responded to swings in ocean chemistry over geologic time.
Continue reading ‘New study shows how ‘marine revolution’ shaped ocean life’High heterotrophic capacity favors Mediterranean coral success and resilience in the face of ocean acidification
Published 7 May 2025 Science ClosedTags: biological response, corals, field, Mediterranean, physiology, vents
Coral ecosystems support a diverse array of marine life and healthy ecological functioning, yet they are vulnerable to decreases in ocean pH caused by anthropogenic carbon dioxide emissions. In temperate rocky reefs of the Mediterranean, the corals Cladocora caespitosa and Astroides calycularis live at sites with ambient seawater pH and at adjacent submarine volcanic CO2 vent sites with low seawater pH where it is more energetically demanding to grow. We collected corals from distinct ambient pH (average pHT 8.05) and lower pH CO2 vent sites (average pHT 7.74–7.90) and quantified their physiological health and heterotrophic capacity (i.e., feeding capacity). Both species at CO2 vent sites had higher heterotrophic capacity than their ambient site counterparts, enabling them to maintain energy reserves. Our results indicate that high heterotrophic capacity underlies the success of these two temperate corals at CO2 vent sites. Therefore, conservation of CO2 vent coral could be strategically important to maintaining rocky reef ecosystem function and ecological resilience in the Mediterranean.
Continue reading ‘High heterotrophic capacity favors Mediterranean coral success and resilience in the face of ocean acidification’A widely distributed clam, Chama macerophylla, exhibits mixed responses to single and combined warming and acidification stress
Published 7 May 2025 Science ClosedTags: biological response, laboratory, mollusks, morphology, multiple factors, North Atlantic, physiology, temperature
Bivalves enhance microhabitat complexity and improve water clarity in coastal ecosystems. Ocean warming (OW) and acidification (OA), pose a significant threat to bivalves in shallow continental shelf environments where stressors can be amplified and uncoupled. This study investigated global change effects on Chama macerophylla, a widespread clam in the Gulf of Mexico. Laboratory experiments assessed physiology and shell mineralogy of C. macerophylla exposed to different levels of OW, OA, and combined stressors (OWA). Temperature and carbonate chemistry from collection sites confirm ambient (control) treatments used in experiments were commonly observed in the field. Clam oxygen consumption increased with OW and, initially, with OA. After 30 days, clams within moderate and extreme OA lowered consumption. In contrast, clam oxygen consumption declined in OWA treatments. Net calcification was only affected by OA with higher calcification in the extreme treatment than in moderate. Meat weight relative to shell weight (condition) was negatively affected by OW in the extreme treatment. Shell accretion, clearance rates, and mineralogy were unaffected by OW, OA, and OWA. This is the first report of a bimineralic shell for this species. Results highlight resilience of clam survivorship to stressors. OW appears to increase metabolism and drive declines in clam condition (meat: shell weight). OWA may have a greater impact on C. macerophylla than single stressors, particularly if reduced oxygen consumption is sustained. This research underscores the need to understand long-term stress on bivalves. Future research should examine both size-age relationships with global stressors and the role of acclimation to prolonged stress.
Continue reading ‘A widely distributed clam, Chama macerophylla, exhibits mixed responses to single and combined warming and acidification stress’Deciphering seawater acidification in the Muping Marine Ranch in summer: pH vs. aragonite saturation state
Published 6 May 2025 Science ClosedTags: chemistry, field, fisheries, North Pacific
Highlights
- Seawater pH was regulated by a combination of temperature and biological effects.
- Changes in seawater Ωarag were primarily driven by biological processes.
- CO2 flux and water mixing exerted little influence on seawater pH and Ωarag.
- Seawater Ωarag serves as a more suitable indicator for assessing acidification.
Abstract
Coastal seasonal acidification has severely impacted marine aquaculture, particularly shellfish farming. However, factors controlling seawater acidification vary in different aquaculture conditions. This study conducted summer cruises of a typical shellfish farming in China, from June to July 2022 to analyze the spatiotemporal distributions of seawater pH and aragonite saturation state (Ωarag), and their response to temperature, sea-air CO2 exchange, mixing, CaCO3 formation/dissolution, and biological effects. The pH and Ωarag of bottom seawater were both lower than surface seawater, with the pH of surface and bottom seawater ranging from 8.02 to 8.09 and 7.87 to 8.02, while the Ωarag ranging from 2.80 to 3.80 and 2.21 to 2.43, respectively. The bottom seawater pH and Ωarag both show a decreasing trend, with Ωarag at certain stations close to or below 2. Biological (surface seawater: 51 % ± 4 %; bottom seawater: −39 % ± 8 %) and temperature (surface seawater: −28 % ± 6 %; bottom seawater: −41 % ± 8 %) effects were crucial on regulation of seawater pH. Biological effects were the dominant factor in the variation of Ωarag in both the surface (64 % ± 7 %) and bottom (−48 % ± 9 %) seawater. Additionally, the dissolution of calcium carbonate in bottom seawater contributed to an increase in Ωarag to some extent (15 % ± 27 %). Ωarag better reflects the influence of non-temperature processes (e.g., CaCO3 formation/dissolution and biological effects). This study advocates for Ωarag as a more suitable indicator of seawater acidification in coastal aquaculture areas.
Continue reading ‘Deciphering seawater acidification in the Muping Marine Ranch in summer: pH vs. aragonite saturation state’Surface and subsurface compound marine heatwave and biogeochemical extremes under climate change
Published 6 May 2025 Science ClosedTags: chemistry, field, globalmodeling, modeling
Marine species are increasingly threatened by extreme and compound events, as warming, deoxygenation, and acidification unfold. Yet, the surface and especially the subsurface distribution and evolution of such compound events remain poorly understood. We present the current and projected distributions of compound marine heatwave (MHW), low oxygen (LOX), and high acidity (OAX) events throughout the water column, using observation‐based data from 2004 to 2019 and large ensemble Earth system model simulations from 1890 to 2100. Our findings reveal that compound MHW‐OAX and OAX‐LOX events are prevalent in the low to mid latitudes at the ocean surface. At 200 and 600 m, MHW‐OAX and MHW‐LOX events are frequent in the high latitudes and parts of the tropics, while OAX‐LOX events occur globally. Subsurface compound events are often associated with vertical displacements of water masses, with the climatological vertical gradients of ecosystem stressors typically explaining their occurrence patterns. Projections show a strong rise in compound event frequency over the historical period and under continued global warming, primarily driven by shifts in mean oceanic conditions. The portion of the top 2,000 m affected by extreme or compound events rises from 20% % to 98% % under 2°C of global warming in a high emissions scenario using a preindustrial baseline, and to 30% % using a shifting‐mean baseline. However, physical and biogeochemical changes may also lead to regional decreases in subsurface events, highlighting complexities in how warming, deoxygenation, and acidification unfold in the ocean interior. Increasing compound event frequency poses a major threat to marine ecosystems, potentially disrupting food webs and biodiversity.
Continue reading ‘Surface and subsurface compound marine heatwave and biogeochemical extremes under climate change’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’Compound marine heatwaves and acidity extremes in the Southern Ocean
Published 5 May 2025 Science ClosedTags: Antarctic, chemistry, modeling, regionalmodeling
Compound extremes of temperature and acidity that extend over substantial fractions of the water column can be particularly damaging to marine organisms, as they experience not only additional stress by the potentially synergistic effects of these two stressors, but also a reduction in habitable vertical space. Here, we detect and analyse such column-compound extremes (CCX) in the Southern Ocean between 1980 and 2019, and characterise their duration, intensity, and spatial extent. To this end, we use daily output from a hindcast simulation of the Regional Ocean Modeling System (ROMS), coupled with the Biological Elemental Cycling (BEC) model. We first detect extremes in temperature and acidity ([H+]) within the top 300m using a relative threshold of 95% and then identify CCX where conditions are extreme for both stressors for at least 50m of the water column. When analysed on a fixed baseline, positive trends in ocean warming and acidification caused CCX to last longer, intensify, and expand throughout the Southern Ocean. In the Antarctic zone, CCX expanded between 1980 and 2020 by more than 10 times in volume, lasted up to 120 days longer, and doubled in anomaly. Some of the largest and longest events occurred in Antarctic Marine Protected Areas (MPAs), covering more than 200 000 km2 and persisting for over 500 days. CCX in the Subantarctic and Northern zones quadrupled in volume and increased by more than 30% in anomaly. Across the Southern Ocean, the increasing occurrence of CCX exacerbates the risks to marine ecosystems from warming and acidification.
Continue reading ‘Compound marine heatwaves and acidity extremes in the Southern Ocean’The database currently contains 9349 references and includes citations, abstracts and assigned keywords. Updates are made every month.
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Continue reading ‘OA-ICC bibliographic database updated’Comparative transcriptomic analysis reveals a differential acid response mechanism between estuarine oyster (Crassostrea ariakensis) and Pacific oyster (Crassostrea gigas)
Published 2 May 2025 Science ClosedTags: biological response, laboratory, molecular biology, mollusks, mortality, North Pacific, physiology, respiration
Highlights
- Mechanisms underlying resilience of estuarine oysters to low pH were analyzed.
- Estuarine oysters have evolved enhanced acid-tolerance responding to low pH levels.
- Frontloaded genes contributing to the enhanced acid-tolerance of estuarine oysters.
- Ion transporters and translation are crucial in mitigates low pH effects in estuarine oysters.
- Acid adaptation of estuarine oysters offers new insights into the adaptive potential of mollusks.
Abstract
Ocean and coastal acidification (OCA) poses a significant and rapidly emerging threat to mollusks. The physiological resilience of mollusks to OCA varies considerably; however, the underlying molecular mechanisms remain poorly understood. Seawater in estuaries, being more susceptible to acidification than that in open coastal zones, may enhance the tolerance of resident mollusks to low pH levels. Here, we conducted a comparative analysis between estuarine oysters (Crassostrea ariakensis) and Pacific oysters (Crassostrea gigas) using physiological phenotype and transcriptomic analyses to reveal differential acid-tolerance mechanisms in response to constant pH of 7.8. Our findings indicated that survival and respiration rates of C. ariakensis, which inhabits estuaries with fluctuating pH levels, were higher than those of C. gigas, which inhabits open coastal zones with relative stable pH conditions. Acid-responsive genes identified in C. gigas, including molecular chaperones and immune-related genes, exhibited higher constitutive expression in C. ariakensis under control conditions. Co-expression analyses revealed that C. ariakensis mitigated the effects of low pH by expressing genes involved in ion transporter activity and translation control. C. gigas activated genes associated with glycolipid metabolism while inhibiting cell division during acid stress. These findings suggested that C. ariakensis has evolved into a more energy-efficient regulatory network than C. gigas, incorporating both front-loading and responsive mechanisms to maintain acid-base homeostasis. This study is the first to investigate acid-tolerance differences between mollusks inhabiting estuarine and open coastal environments and provides critical insights into the resilience of mollusks in increasingly acidified oceans.
Continue reading ‘Comparative transcriptomic analysis reveals a differential acid response mechanism between estuarine oyster (Crassostrea ariakensis) and Pacific oyster (Crassostrea gigas)’Increase in marginal sea alkalinity may impact air–sea carbon dioxide exchange and buffer acidification
Published 1 May 2025 Science ClosedTags: Baltic, chemistry, review
Total alkalinity (TA) has increased in the Baltic Sea, with implications for atmospheric CO2-induced acidification and CO2 uptake. We compiled extensive data of TA in surface waters of the Baltic Sea, aiming to (i) identify new tendencies in the relationship between TA and salinity (TA–S relationship), (ii) update the TA trend analysis, (iii) investigate spatial–temporal patterns, and (iv) discuss potential drivers and implications. We observed a progressive decrease in the slopes and increase in the intercepts of the TA–S overtime due to the persistent process of TA enhancement. A weak seasonal pattern was identified, with warmer months presenting lower salinity and TA. Lower rates of TA increase were observed in high salinities (Skagerrak–Kattegat; +1.00 to +2.20 μmol kg−1 yr−1), intermediate trends in low salinities (Gulf of Bothnia; +3.28 to +3.57 μmol kg−1 yr−1), and maximal trends in the Central Baltic Sea (+3.70 to +4.57 μmol kg−1 yr−1) and Bornholm Basin (+4.82 to +5.32 μmol kg−1 yr−1). The increase in the intercept of the TA–S in the Gulf of Bothnia suggests a progressive increase in the external supply of TA, although lower than previously thought. The maximum trend in the Bornholm Basin suggests an increase in external supply from the Southern catchment and/or the accumulation of internal production. The positive TA–phosphorus correlations underscore a significant internal source. The TA increase amplifies the CO2 uptake by 1.8–7.8% during spring/summer and reduces the CO2 outgassing by 3.4–7.7% in autumn/winter. The TA enhancement has the potential to buffer CO2-induced acidification by 39–60% by 2050.
Continue reading ‘Increase in marginal sea alkalinity may impact air–sea carbon dioxide exchange and buffer acidification’Microzooplankton community dynamics under ocean acidification: key observations and insights
Published 30 April 2025 Science ClosedTags: abundance, biological response, BRcommunity, community composition, Indian, laboratory, otherprocess, phytoplankton, prokaryotes, zooplankton
Microzooplankton (MZP) community dynamics under ocean acidification were studied through pH manipulated microcosm experiments conducted in the coastal waters of the Bay of Bengal (off Vishakhapatnam) during the months of July and October 2022 (Experiment 1 and Experiment 2). The total abundance of phytoplankton and microzooplankton (MZP) communities was varied from 3.66 × 104 to 5.27 × 105 Cells. L−1 and 0.06 × 103 to 1.53 × 103 Cells. L−1, respectively, and a significant difference in phytoplankton and MZP abundance was found between the initial and final day of the entire experimental samples (control and acidified). The initial seawater samples were dominated with centric diatom species Dactyliosolen fragilissimus (Experiment 1 and Experiment 2: 72–82%) and shifted to pennate diatoms such as Pseudo-nitzschia sp. (Experiment 1: 60–68%) and Amphora sp. (Experiment 2: 80–94%) at the end of the experiments (all acidified and control samples). The initial MZP community composition consisted of four different groups LC: loricate ciliates, ALC: aloricate ciliates (heterotrophy and mixotrophy), HDS: heterotrophic dinoflagellates and copepod nauplii, and at the end of the experiments, it was shifted entirely to the dominance of aloricate ciliates (16–73%) and heterotrophic dinoflagellates (67–100%) in all the samples (control and acidified) in Experiments 1 and 2, respectively. Statistical analysis (Spearman’s rank correlation) results showed a relative and significant inverse relation of MZP with phytoplankton biomass and abundance and heterotrophic bacterial counts in all the samples (control and acidified). Besides, the LC showed a weak correlation with Chl-a, and the HDS showed a significant correlation with LC, phytoplankton biomass and abundance, and bacterial counts (picocyanobacteria and heterotrophic bacteria). These results indicate that the MZP may graze on both picocyanobacteria and heterotrophic bacteria, and also, HDS may graze on their relative community like LC. Canonical correlation analysis (CCA) revealed that prey abundance such as phytoplankton biomass (Chl-a), picocyanobacteria, and heterotrophic bacterial communities are most influencing variables on the MZP assemblages than other environmental variables such as pH, temperature, and salinity. Thus, these findings show that the MZP community dynamics under ocean acidification may vary with different species and groups due to their food availability (indirect effect) and individual competence (direct effect) to different environmental conditions, such as pH variations.
Continue reading ‘Microzooplankton community dynamics under ocean acidification: key observations and insights’Low-pH conditions drive transient changes in shell calcification and the microbiome in a pH-resistant strain of the the Pacific oyster Magallana gigas
Published 29 April 2025 Science ClosedTags: biological response, BRcommunity, community composition, laboratory, molecular biology, mollusks, morphology, North Pacific, otherprocess, prokaryotes
The study explores the effects of elevated pCO2 on shell calcification, microbiome composition, and gene expression in a strain of Pacific oyster (Magallana gigas) selectively bred for low-pH resistance. Juvenile oysters reared under low-pH conditions exhibited increased shell mass compared to the control population by 51 days post-fertilization, despite high variance in shell size at earlier stages. Microbiome analyses revealed significant shifts in community composition under low-pH conditions, particularly in bacterial taxa involved in CO2 production and biogeochemical cycling, which could influence carbonate chemistry within oyster tissues. Gene expression profiling demonstrates differential regulation of genes related to biomineralization, immunity, and microbial interactions under low-pH conditions. For example, multiple carbonic anhydrases exhibited treatment-specific expression patterns, suggesting a role in adapting to low-pH environments. Observed changes in immune-related genes imply a relaxation of immune responses, potentially reflecting resource reallocation toward calcification processes. These results collectively support the “dysbiosis hypothesis,” where oysters adapt to environmental stress by modulating their microbiomes and gene expression. Future studies should investigate whether these responses are consistent across oyster strains and environmental conditions, providing insights into the resilience of aquaculture species to ocean acidification.
Continue reading ‘Low-pH conditions drive transient changes in shell calcification and the microbiome in a pH-resistant strain of the the Pacific oyster Magallana gigas’Disentangling the effects of global and regional drivers on diverse long‐term pH trends in coastal waters
Published 29 April 2025 Science ClosedTags: chemistry, modeling, North Pacific, regionalmodeling
Abstract
Unlike declines of pH in the open ocean on the total scale (pHT), coastal systems have shown complex long‐term trends in pHT due to a multitude of global and regional drivers. These drivers include changes in nutrient loading, human‐accelerated chemical weathering of watersheds, acid‐rain and land‐use changes, and ocean acidification due to atmospheric CO2 increase. We lack understanding of how these co‐occurring processes have influenced long‐term pHT changes in coastal waters. To address this knowledge gap, a coupled hydrodynamic‐biogeochemical‐carbonate chemistry model was used to conduct a hindcast simulation and scenario analyses of carbonate chemistry in the Chesapeake Bay between 1951 and 2010. Trend analysis reveals increasing pHT in the upper Bay due to river alkalinization but decreasing pHT in the bottom waters of the mid‐and lower Bay due to ocean acidification. No trend is detected in the surface waters of the mid‐ and lower Bay due to competition between the two drivers. The effect of river alkalinization on the acidic volume in the estuary is twice that of ocean acidification. Our findings show that river alkalinization provides an important buffer against acidification while eutrophication plays a secondary role. Our results also suggest ocean alkalinity enhancement could be effective in mitigating acidification in coastal waters.
Plain Language Summary
Ocean acidification due to uptake of atmospheric CO2 is a concern in the open ocean. In contrast, pH in coastal systems has shown both decreasing and increasing long‐term trends. A number of global and regional processes drive these diverse trends, including changes in nutrient loading, human‐accelerated chemical weathering in watersheds, changes in acid‐rain and land‐use, as well as atmospheric CO2 increases. Using the Chesapeake Bay as a model coastal system, we conducted a 60‐year model simulation and scenario analysis of carbonate chemistry between 1951 and 2010. We found pH increased in the upper Bay, decreased in the bottom waters of the mid‐and lower Bay, and displayed no trend in the surface waters of the mid‐ and lower Bay. River alkalinization drove the pH increase in the upper Bay, whereas ocean acidification drove the pH decline in the lower Bay. The two drivers canceled each other in the surface waters of the mid‐ and lower Bay and resulted in no long‐term trends in pH there. As ocean alkalinity enhancement (OAE) is being considered as an approach for marine carbon dioxide removal, results of this analysis strongly suggest that OAE could be an effective way to mitigate ocean acidification in coastal waters.
Continue reading ‘Disentangling the effects of global and regional drivers on diverse long‐term pH trends in coastal waters’
