Untreated effluent caused decreases in seawater pH from 8.1 to lower than 7.5.
Decreases in pH led to nonlinearly declined abundance of all plankton groups.
Plankton abundance recovered as pH bounced back to normal levels.
Negative impacts of decreases in pH on the marine planktons were reversible.
Abstract
An event of releasing untreated effluent caused serious decreases in surface seawater pH from 8.1 to lower than 7.5 in seven years and increased back to prior levels after 15 years. It gives us a rare natural experiment to examine the impacts of decreases in pH on the marine plankton communities (phytoplanktons, zooplanktons, shrimp larvae, crab larvae, fish eggs, and larvae) in the natural environment. Observed decreases in pH had a nonlinear effect ubiquitous on all plankton groups, leading to a reduction of approximately 50 % in their density and abundance compared to the level at pH 8.1. Non-linear responses of planktons implied the existence of specific groups more robust to decreases in pH. As pH bounced back to normal levels, the density and abundance of the plankton communities also recovered, further indicating that the negative impacts of decreases in pH on the marine plankton communities were reversible.
Shellfish are a good source of nutrition, and many people enjoy harvesting and eating them. Oysters, razor clams, and mussels have long been food sources for Washingtonians. They’re an integral part of local traditions and livelihoods. Many shellfish are also filter-feeders, which means they help keep water clean.
But these animals are in trouble. Carbon pollution from human activities is turning their home — the ocean — into a hostile environment because of ocean acidification. To help communities adapt, we created an ocean acidification indicator to visualize changing marine water conditions in Washington state. An “indicator” is a simply presented data reference tool used by scientists to communicate complex information.
…
Tracking ocean acidification
Our long-term ocean acidification monitoring program, established in 2019, tracks how carbon pollution affects marine waters. We measure water conditions monthly at 28 locations in Puget Sound and along the coast. For each location, we sample water at the surface and at 100 feet, which tells us how acidification conditions change with depth.
Our measurements let us estimate a water property called aragonite saturation state. Aragonite is a form of calcium carbonate that many marine organisms produce to build their skeletons and shells. The lower the saturation state, the more difficult it is for shellfish and salmon to build and maintain their protective skeletons and shells. This effect will worsen as ocean acidification shifts the ocean’s chemistry.
…
Making an invisible problem visible
Using over four years of monitoring data, we created the Ocean Acidification Indicator to visualize annual ocean acidification conditions and to track the long-term effects of carbon pollution in greater Puget Sound. The indicator represents the number of days in each year when water conditions are favorable for sensitive marine animals. Think of it as a window of opportunity for oysters, crabs, and young salmon to grow and thrive.
Our research helps us pinpoint two annual timeframes:
The range of days when water conditions are favorable, which is the ocean acidification indicator
The range of days when water conditions are corrosive, making it more difficult for shellfish and salmon to thrive
Ocean chemistry is shifting because of carbon emissions. Our data show seasonal changes in greater Puget Sound. Water conditions are favorable for shellfish and salmon from spring to summer, and unfavorable from fall to winter. Favorable conditions have declined since the early 1800s.
What have we learned by tracking and studying ocean acidification in Washington? Puget Sound and the coastal environment are changing rapidly because of carbon pollution.
There are seasonal changes in Puget Sound when favorable conditions for shellfish and salmon begin in spring and continue through most of the summer.
Water in deep parts of Puget Sound and the coast is more corrosive than water in shallow areas, increasing stress for organisms near the seafloor like Dungeness crabs and oysters.
Some regions of Puget Sound are more at risk because ocean acidification is worsening naturally occurring corrosive conditions.
The more we learn, the more we can share with our partners to help them adapt and adjust management practices. We’re sharing our data with Tribes, shellfish farmers, resource managers, policymakers, and scientists throughout the state and the west coast.
Shellfish farmers can use the indicator to track months when water conditions are better for growing shellfish. Resource managers and policymakers can evaluate whether they need to adjust management practices. Scientists and research partners can build on our data to develop new tools or studies to better understand ocean acidification and forecast future conditions.
We strive to support thriving shellfish communities and healthy ocean habitats by sharing this information and coordinating with our partners.
The occurrence of rhodolith beds in the stratigraphic record from the Cretaceous to the Pleistocene was analysed from published papers. Most data refer to low-mid latitude records of rhodolith beds described in the Tethyan-Paratethyan-Mediterranean domain. The first putative rhodolith beds are from Albian (uppermost Lower Cretaceous) deposits. These rhodolith beds are made up mostly of unattached loose branching corallines as well as of nodular structures. From the Coniacian (Upper Cretaceous) to the Langhian (Middle Miocene), abundance of rhodolith beds shows a generally increasing fluctuating trend with two significant expansions in the Priabonian (late Eocene) and during the Aquitanian-Langhian (Early-Middle Miocene). After the Langhian maximum, rhodolith beds sharply declined to a minimum in the Zanclean (Early Pliocene). During the Pleistocene, they recovered to values similar to those reached in the Langhian. The general increase in rhodolith beds up the Langhian maximum correlates well with global temperature and pCO2 declines and with an ocean pH increase. The tectonic activity leading to important palaeogeographic changes in the Tethyan-Parathetyan-Mediterranean realm might account for the Serravallian-Zanclean downfall of rhodolith-dominated deposits. The Cretaceous-Pleistocene record of rhodolith beds shows that these ecosystems withstood successfully a highly changing world. The rapid acclimation of particular taxa to environmental changes and the variable reaction of taxa distributed at different water depths can be crucial to understand their success. In this regard, it would be interesting to analyse how different taxa in modern deep rhodolith beds respond to changing oceanic conditions.
Marine microalgae demonstrate a notable capacity to adapt to high CO2 and warming in the context of global change. However, the dynamics of their evolutionary processes under simultaneous high CO₂ and warming conditions remain poorly understood.
Here, we analyze the dynamics of evolution in experimental populations of a model marine diatom Phaeodactylum tricornutum. We conducted whole-genome resequencing of populations under ambient, high-CO2, warming and high CO2 + warming at 2-yr intervals over a 4-yr adaptation period.
The common genes selected between 2- and 4-yr adaptation were found to be involved in protein ubiquitination and degradation and the tricarboxylic acid (TCA) cycle, and were consistently selected regardless of the experimental conditions or adaptation duration. The unique genes selected only by 4-yr adaptation function in respiration, fatty acid, and amino acid metabolism, facilitating adaptation to prolonged high CO2 with warming conditions. Corresponding changes at the metabolomic level, with significant alterations in metabolites abundances involved in these pathways, support the genomic findings.
Our study, integrating genomic and metabolomic data, demonstrates that long-term adaptation of microalgae to high CO2 and/or warming can be characterized by a complex and dynamic genetic process and may advance our understanding of microalgae adaptation to global change.
The marine cyanobacterium Synecococcus sp. (CCMP 1334) was grown in a continuous culture system on a 12:12 h light:dark cycle at all combinations of low and high pCO2 (400 and 1000 ppmv, respectively), nutrient availability (nitrate-limited and nutrient-replete conditions), and temperatures of 21, 24, 28, 32, and 35°C. The maximum nutrient-replete growth rate was ~1.15 day−1 at 32–35°C. Median nutrient-replete growth rates were higher at 1000 ppmv than at 400 ppmv pCO2 at all temperatures. Carbon:nitrogen ratios were independent of pCO2 at a fixed relative growth rate (i.e., growth rate ÷ nutrient-replete growth rate) but decreased with increasing temperature. Carbon:chlorophyll a ratios were decreased monotonically with increasing temperature and were higher under nitrate-limited than nutrient-replete conditions. Ratios of phycoerythrin to chlorophyll a were independent of growth conditions. Productivity indices were independent of temperature and nutrient limitation but were consistently higher at 1000 ppmv than 400 ppmv pCO2. Both growth rates and dark respiration rates were positively correlated with temperature, and the associated Q10 values were 2.2 and 2.3, respectively. A model of phytoplankton growth in which cellular carbon is allocated to structure, storage, or the light or dark reactions of photosynthesis accounted for the general patterns of cell composition and growth rate. This strain of Synechococcus appears well suited to changes in environmental conditions that are expected as the climate warms in response to anthropogenic emissions of CO2.
Do marine herbivores adjust their trophic niches under climate change?.
Specialist and generalist herbivore niches and their food were tested using stable isotopes.
Food resources were dominated by turf algae and SOM under climate change.
Niche breath of generalists narrowed under climate stress but widened in specialists.
Generalists and specialists appear to converge their trophic niches under climate change.
Abstract
When humans drive rapid environmental change, is it favourable to be a generalist or specialist? To address this question, we compare how specialist and generalist marine herbivores adjust their isotopic niches (used as proxy for trophic niche) in response to predicted resource alterations under the simulated effects of ocean warming and acidification (based on a 6-month mesocosm experiment). Here, we show that when exposed to multiple climate stressors, food resources homogenized towards dominance of turf algae and suspended organic matter, with generalists and specialists adjusting their trophic niches in opposing ways. Whilst the niche breath of most generalists narrowed under climate stressors, those of specialists generally broadened, causing increasing overlap between their niches. The magnitude of this change was such that some generalists turned into specialists, and vice versa. Under ocean acidification, there was a greater probability of generalists increasing and specialists maintaining their biomass, respectively, but under warming the biomass of both specialists and generalists had a greater probability of collapse. For specialists, this collapse occurred even though they had adequate thermal tolerance and the capacity to expand their trophic niche. Climate change constrains or liberates resources, but where they are homogenized, generalists and specialists are likely to converge their trophic niches so they can exploit transforming environments for their survival or adaptive advantage.
A predicted consequence of ocean acidification is its negative effect on the pools of Particulate Inorganic Carbon (PIC) that are essential for ‘ballasting’ the sinking of organic carbon, potentially leading to decreased subsurface oxygen. To explore such possible feedbacks, we investigated the relationships between PIC, coccolithophores, carbonate chemistry, and dissolved oxygen in the Southeast Pacific open ocean oxygen minimum zone, which naturally exhibits extremely low dissolved oxygen, low pH, and high pCO2 levels. Measurements of PIC and coccolithophore counts during late-spring 2015 and mid-summer 2018 revealed that coccolithophores, particularly Gephyrocapsa (Emiliania) huxleyi, significantly contributed to PIC through the shedding of coccoliths in the upper waters. On average, about a half of the PIC was attributed to countable coccoliths, with significantly diminished quotas observed below the euphotic depth. Temperature, oxygen, and pH were identified as key variables influencing PIC variation. PIC quotas were similar to those reported in other upwelling zones. However, PIC:POC ratios were substantially lower than what has been reported both in other open ocean and coastal margin areas, an effect that was more pronounced within the vertically defined oxygen minimum zone core. This study contributes to understanding the role of coccolithophores in PIC pools and suggests that the presence of low O2/low pH subsurface waters does not inhibit coccolithophore PIC quotas but may decrease the role of PIC in ballasting the export of organic carbon.
Monitoring the surface partial pressure of carbon dioxide (pCO2) in the oceans is fundamental for understanding both the health of the oceans and the general state of the climate across the planet. In this context, the measurement of this variable in areas where the scarcity of data is more marked is increasingly important: Giovanni Soldini’s navigation using the Maserati Multi70 Trimaran, properly equipped for the measurement of this quantity, fits precisely into filling this gap. The comparison of the post-processed experimental data with the model data provided by the Copernicus platform, although based on some necessary method approximations, is encouraging, showing relative differences below 5%.
The marine shellfish aquaculture industry across the U.S. Pacific region faces escalating ocean acidification and its associated challenges. This study examines industry participant perceptions and experiences regarding ocean acidification, additional threats, and future research needs, finding a notable decrease in perceived concern regarding ocean acidification over the past decade. Through structured interviews, broad industry perspectives are explored regarding current practices and two specific ocean acidification adaptation strategies under development: parental priming and native species portfolio expansion. While parental priming garnered cautious support contingent on scientific validation, perceptions of native species expansion were polarized, driven by skepticism about regulatory barriers, economic viability, and scalability. Enhanced environmental monitoring emerged as the most widely supported adaptation measure, underscoring its importance in addressing multiple stressors in addition to ocean acidification. By considering industry and operation characteristics while examining potential decision-making biases, this study provides unique insights for co-producing relevant adaptation strategies. Additionally, the critical role of collaboration between stakeholders, researchers, and policymakers in fostering resilience is emphasized.
This unique program will host up to 40 Early Career Researchers, PhD students, and motivated MSc students passionate about advancing their knowledge and research in ocean acidification and deoxygenation.
Why Join? The summer school is part of the Global Ocean Oxygen Decade (GOOD) and Ocean Acidification Research for Sustainability(OARS) programs under the UN Ocean Decade. Participants will receive cutting-edge training from world-class experts in a collaborative environment designed to inspire discussion and innovation.
📍 Location: CEMACS, Penang, Malaysia 📅 Dates: 4–11 November 2025
This study examined the carbon cycling dynamics in the tropical Atlantic Ocean from 1985 to 2023, focusing on factors influencing the surface partial pressure of CO2 (pCO2), freshwater input, total alkalinity (ALK), total dissolved carbon (TCO2), and pH levels. The time series data revealed significant trends, with average pCO2 concentrations rising from approximately 350 μatm in the early 1990s to over 400 μatm by 2023. The TCO2 levels increased from about 2000 μmol/kg to 2200 μmol/kg, while ALK rose from approximately 2300 μmol/kg to 2500 μmol/kg. This increase highlights the ocean’s role as a carbon sink, particularly in areas with high biological productivity and upwelling where TCO2 also rose. This study employed Empirical Orthogonal Functions (EOFs) to identify variability modes and understand spatial patterns of pCO2. Freshwater dynamics significantly affect TCO2 concentrations, particularly in coastal regions, where pH can shift from 8.2 to 7.9, exacerbating acidification. Rising sea surface temperatures have been linked to elevated pCO2 values. These findings support the need for ongoing monitoring and effective management strategies to mitigate the impacts of climate change and ensure the sustainability of marine resources. This study documented the long-term trends in tropical Atlantic CO2 parameters linked to the North Atlantic Oscillation (NAO) and Atlantic Multidecadal Oscillation (AMO).
Coccolithophores are pivotal players in ocean biogeochemistry, yet the impact of changing pH on the physiology of different species remains unclear as there has been a dominant focus on Gephyrocapsa huxleyi. Meta-analyses of existing experimental data are challenging due to the differences in multidimensional culture conditions. This study investigated the response of three species—Gephyrocapsa huxleyi, Coccolithus braarudii, and Chrysotila carterae—under varying CO2 conditions (via pH). The sensitivity to pH differed between species, but all species showed reduced growth rates under the highest CO2 (lowest pH) treatment possibly due to high [H+]-related inhibition. Low pH impacted cellular physiology and elemental stoichiometry, while the impact of high pH was less adverse. The changes in elemental production induced by low pH could exert a negative influence on the contribution of coccolithophores to nutrient and carbon export, especially for biogeochemically relevant open-ocean species. pH also affected coccolith formation, especially in C. braarudii, through CO2 limitation at high pH and low calcite saturation state at low pH. Contrasting species-specific pH sensitivities highlighted the potential for species like G. huxleyi to further outperform others like C. braarudii in an acidic ocean. Literature synthesis showed that coccolithophores show a broad CO2 optimum, although growth rates and particulate inorganic carbon to particulate organic carbon ratios consistently declined with increasing CO2. Strain-specific CO2 optima partly contributed to the variability within responses of individual species, giving the misleading perception of a broad species-level CO2 optimum. Strain-specific optima exist possibly due to their adaptation to carbonate chemistry conditions at the place of origin.
One of the main issues emerging from environmental change with significant ramifications for marine life is Ocean acidification. It alludes to the cycle by which the sea turns out to be more acidic because of expansion in the concentration of carbon dioxide in the environment. As carbon dioxide levels ascend in climate a critical part is consumed by the sea which prompts a progression of redox responses that decline the pH of ocean water. This peculiarity has broad ramifications for marine life, especially for coral reefs, which are among the most miscellaneous and monetarily significant biological ecosystems in the world. The purpose of this review is to address and assess the impact of ocean acidification on coral reefs and marine life in order to conserve and sustain marine life below water thus fulfilling Sustainable Development Goal 14 (Life below water).
Ocean acidification represents a significant and growing threat to some species of marine plankton, with wide-ranging implications for marine ecosystems and the services they provide. The alterations in plankton physiology, behavior, and community structure under acidified conditions exemplify the profound impact of anthropogenic CO₂ emissions on the ocean’s smallest, yet most essential inhabitants.
Coral reefs are vital marine ecosystems that harbor a significant proportion of the ocean’s biodiversity. However, these ecosystems are increasingly threatened by anthropogenic activities, particularly the emission of greenhouse gases leading to climate change and ocean acidification. Ocean acidification refers to the reduction in pH of marine waters due to the absorption of CO₂ from the atmosphere, forming carbonic acid (H₂CO₃), which dissociates into bicarbonate (HCO₃−) and hydrogen ions (H+), thus lowering pH. This sequence of reactions leads to an increase in hydrogen ion concentration, causing a decrease in pH. The reduction in carbonate ions (CO₃2−) is particularly detrimental to marine calcifiers, including corals, which rely on carbonate for the formation of their calcium carbonate (CaCO₃) skeletons. Coral reefs are constructed by the deposition of CaCO₃ by coral polyps. Zooxanthellae, symbiotic algae living within coral tissues, provide essential nutrients through photosynthesis, facilitating calcification. Acidification disrupts this symbiotic relationship by impairing photosynthetic efficiency and reducing the availability of carbonate ions necessary for skeletal growth. As ocean acidification progresses, the concentration of carbonate ions diminishes, making it energetically more challenging for corals to secrete their skeletons, thereby slowing growth rates and compromising structural integrity. Coral bleaching occurs when corals, under stress, expel their zooxanthellae, leading to a loss of pigmentation and a decline in energy reserves. Stressors include elevated sea temperatures, pollution, and acidification. The loss of zooxanthellae not only deprives corals of their primary food source but also disrupts calcification processes. Thermal stress is a predominant factor in coral bleaching. Elevated sea temperatures can destabilize the photosynthetic machinery of zooxanthellae, producing reactive oxygen species (ROS) that damage both the algae and coral tissues. Prolonged exposure to high temperatures exacerbates acidification effects, intensifying bleaching events. The decline in coral health due to bleaching and acidification has profound ecological impacts, including the loss of habitat for numerous marine species, reduced biodiversity, and compromised fisheries. Socioeconomically, coral reef degradation affects tourism, coastal protection, and the livelihoods of communities dependent on reef resources. Reduction of CO₂ emissions through global policy agreements and renewable energy adoption. Local conservation efforts, such as marine protected areas (MPAs) have the potentials to enhance reef resilience. Conservation efforts may be complemented by research into coral species and strains with higher tolerance to acidification and thermal stress, potentially involving selective breeding and genetic modification. Marine water acidification and coral bleaching are intricately linked phenomena driven by anthropogenic climate change. The decline of coral reefs signals a broader environmental crisis that necessitates urgent scientific, policy, and community responses to mitigate adverse effects and foster adaptive resilience in marine ecosystems.
Dual stress of OA and SMX may harm survival and reproduction in T. niloticus.
OA increased immune and antioxidant responses in T. niloticus.
SMX exposure boosted antioxidant responses and oxygen consumption.
Exposure to OA combined with SMX impaired cellular energy allocation in T. niloticus.
Abstract
Ocean acidification, a major consequence of climate change, poses significant threats to marine organisms, particularly when combined with other environmental stressors such as chemical pollution. This study investigated the physiological responses of Trochus niloticus to a 28-day exposure of ocean acidification and/or sulfamethoxazole, a commonly detected antibiotic in the South China Sea. Exposure to either acidification or sulfamethoxazole individually triggered adaptive responses through immune activation, antioxidant reactions, and metabolic adjustments. However, concurrent exposure resulted in significant adverse effects, including compromised immunity, oxidative damage, and disrupted energy budget. These findings provide new insights into how ocean acidification interacts with antibiotic pollution to synergistically impact marine gastropods, suggesting that multiple stressors may pose greater threats to T. niloticus populations than single stressors alone.
Low-light-adapted Prochlorococcus ecotypes have stronger low-iron adaptation capacity
Fe limitation in Prochlorococcus is enhanced under both low growth-limiting light and high photo-inhibitory light
High CO2 promotes the growth of low-light-adapted Prochlorococcus ecotypes due to a reduction in cellular oxidation stress
Abstract
Ocean acidification caused by the ongoing increase in atmospheric carbon dioxide (CO2) is expected to impact the growth of marine phytoplankton. Additionally, CO2-driven climate change influences light intensity and iron (Fe) availability in surface seawaters, two critical factors for marine phytoplankton carbon fixation and growth due to their central role in regulating photosynthesis. The cyanobacterium Prochlorococcus often dominates marine productivity in oligotrophic oceans with low but variable Fe concentrations and light intensities. However, the combined effects of light intensity, Fe availability and CO2 concentration on the growth and photosynthesis of Prochlorococcus remain unclear. In this study, we found that the high-light-adapted Prochlorococcus strain MED4, isolated from shallower depths, required much higher Fe concentrations and light intensities to grow than the low-light-adapted strain NATL1A, isolated from deeper depths. Increased CO2 had no effect on the growth of strain MED4 under any light or Fe conditions. In contrast, increased CO2 caused a 29% increase in the growth of strain NATL1A under low Fe coupled with high photo-inhibitory light condition, owing to a reduction in cellular oxidative stress. The varying antioxidant stress capacities of different Prochlorococcus strains appeared to influence their responses to increased CO2. These results indicate complex interactions among light intensity, Fe limitation, and CO2 concentration, which may affect the species distributions and productivities of marine phytoplankton, including Prochlorococcus, in a future high-CO2 ocean.
Time-series measurements in the North Atlantic Ocean at the Hydrostation S site (32°10′N, 64°30′W), started in 1954. At that time, it was not yet possible to measure all the properties of the oceanic carbon cycle. However temperature and salinity were measured. We use these important hydrographic data with the knowledge acquired from more recent measurements (since 1989) of the CO2/carbonate properties at the near-by Bermuda Atlantic Time Series Study (BATS; 31°40′N, 64°10′W), to reconstruct, using two different approaches based upon multi-linear-regressions, the pH at this hydrostation S since its beginning. The results provide good estimates of the ocean acidification in the ocean surface of the area of stations S and BATS since the mid 1950’s, an unprecedented near 70-year trend of ocean acidification, as well as a simple way to forecast to 2100 its variations according to the various scenarios of atmospheric CO2 fugacity increase. The simplest approach shown here, further provides an easy way to estimate surface ocean acidification from satellite sea surface temperature measurements.
Coral reefs suffer from climate change, including long-term ocean acidification (OA) and warming and short-term bleaching, tropical storms, and pollution events, all of which are increasing in frequency and severity. It is urgent yet unclear how to intervene to save coral reefs. Reversal of the ocean pH to preindustrial levels could restore coral reefs to their preindustrial growth rates; however, strategies to reverse OA on environmentally relevant scales have not been established. Anecdotally, electrolysis seems to help coral reefs recover from acidification and short-term events, but few uncontrolled studies support such claims. Here, using two independent continuum simulation approaches (COMSOL and CrunchFlow), we show the effect of electrolysis on seawater chemistry relevant to coral reef survival and growth. We conclude that near the negative electrodes, the cathodes, seawater pH, supersaturation, and carbonate concentration all increase significantly. Electrolysis of seawater, therefore, can be used to restore preindustrial ocean conditions locally to save coral reefs, an approach termed eCoral here. We anticipate these simulation results to be the starting point for controlled experiments to test whether seawater electrolysis promotes coral reef growth and restoration, as these simulations predict.
Mactra veneriformis is highly susceptible to ocean acidification (OA) due to its low shell hardness during its rapid growth period. In this study, oxygen consumption rate, ammonia excretion rate, and transcriptome sequencing of mantle tissue analyses were conducted in white and purple shell-color populations of M. veneriformis under OA stress (pH = 7.6). The findings indicated a significant rise in oxygen consumption rates and ammonia excretion rates following acidification in both the two shell colors, while the clams with purple color showed comparatively lower basal metabolic levels. Transcriptomic analyses demonstrated the expression of key genes related to fatty acid synthesis were significantly inhibited, whereas genes involved in calcification, osmoregulation, and immune response were upregulated under OA exposure in the two shell-color groups. However, some genes such as CA and HSP showed a population-specific response between the two shell-color populations. KEGG enrichment analysis revealed that the MAPK signaling pathway and protein processing in the endoplasmic reticulum were significantly enriched in the two acidification groups. This study provides valuable insights into the response of M. veneriformis to OA stress and also helps to predict the future breeding of valuable strains of M. veneriformis.
