Antarctica and the Southern Ocean are key elements in the physical and biological Earth system. Human-induced climate change, and other human activities in the region, are leading to several potential interacting tipping points with major and irreversible consequences. Here, we examine eight potential physical, biological, chemical, and social Antarctic tipping points. These include ice sheets, ocean acidification, ocean circulation, species redistribution, invasive species, permafrost melting, local pollution, and the Antarctic Treaty System. We discuss the nature of each potential tipping point, its control variables, thresholds, timescales, and impacts, and focus on the potential for cumulative and cascading effects as a result of their interactions. The analysis provides substantial evidence of the need for more concerted and rapid action to limit climate change and to minimise the impacts of local human activities to avoid these cascading tipping points.
Continue reading ‘Cascading tipping points of Antarctica and the Southern Ocean’Archive Page 56
Cascading tipping points of Antarctica and the Southern Ocean
Published 19 December 2024 Science ClosedTags: Antarctic, review
Impact of ocean acidification on marker enzymes in Asian seabass Lates calcarifer
Published 19 December 2024 Science ClosedTags: biological response, fish, laboratory, physiology
Backgrounds: The influence of ocean acidification (OA) is particularly significant on calcifying organisms in marine environment. A possible explanation for acidification-induced changes in fish behaviour is that acidification interferes with marker enzymes in the liver, muscle and brain. Under a range of severe environmental circumstances, marine organisms can be susceptible to oxidative stress and results in the changes in the biochemical components which can be assessed to know the health status of organisms.
Aim of the Works: The aim of this study is to observe the impact of ocean acidification in Asian seabass Lates calcarifer and to employ a large number of biomarker to discover distinct and unique patterns. For this the fingerlings of L. calcarifer were exposed to OA, in order to understand the changes in marker enzymes in liver, muscle and brain of L. calcarifer.
Methodology: Fish fingerlings were exposed to OA condition with two different pH (7.8 and 7.5) for a period of 9 weeks in order to assess changes in biomarker. Acid phosphatase (ACP) and alkaline phosphatase (ALP), alanine transaminase (ALT), and aspartate transaminase activity (AST) were examined in the liver, brain and muscles of fish.
Results: The Liver has considerably higher in ACP and ALP enzymes after 3 weeks of OA exposure. AST and ALT marker enzymes were induced in the brain at greater levels and in most cases, the entire marker enzymes in the liver, muscle and brain were concentration dependent and also the exposure period. The observed changes in marker enzymes which detected in the brain and liver tissues of L. calcarifer were statistically significant.
Conclusions: The present study showed a significant association between the entire biomarkers tested in fish exposed to OA. Overall, the results indicate that brain and liver is the most vulnerable component to OA exposure when compared to muscles and brain it may be employed as a bioindicator of OA exposure.
Continue reading ‘Impact of ocean acidification on marker enzymes in Asian seabass Lates calcarifer’Advanced deep learning technique for estimating global surface ocean calcium carbonate saturation (Ωcal)
Published 18 December 2024 Science ClosedTags: chemistry, globalmodeling, methods, modeling
Highlights
- The study employed FFNN, RF, and TabNet ML models to estimate Ωcal using in-situ measurements and satellite-derived data.
- The TabNet model outperformed with significantly low errors (RMSE=0.39, MNB=0.0058, MRE=0.019) and high accuracy (R2=0.96).
- SST strongly correlated with Ωcal (r=0.98), SSS moderately (r=0.49), and Chla showed a weak negative correlation (r=-0.27).
- The study observed seasonal Ωcal variability, with higher values in summer months, notably in temperate and polar regions.
- Emphasized a declining trend of Ωcal from 2012 to 2022, likely influenced by changing oceanic and atmospheric conditions.
Abstract
The accurate estimation of surface ocean calcium carbonate saturation (Ωcal) is crucial for understanding the impacts of ocean acidification (OA) on marine ecosystems, particularly for calcifying organisms. This study investigates the estimation of global surface ocean Ωcal using machine learning (ML) models and satellite-derived data. Three ML models such as feed-forward neural networks (FFNN), random forests (RF), and Tabularnet (TabNet) were employed to estimate Ωcal, utilizing in-situ and satellite measurements of sea surface temperature (SST), sea surface salinity (SSS), and Chlorophyll-a concentration (Chla). Among these, the TabNet model exhibited superior performance, with a root-mean-square error (RMSE) of 0.39, mean relative error (MRE) of 0.019, mean normalized bias (MNB) of 0.0058 and coefficient of determination (R2) of 0.96. SST showed a strong positive correlation with Ωcal (r = 0.95), while SSS and Chla exhibited moderate positive (r = 0.49) and weak negative (r = −0.27) correlations, respectively. The study revealed significant spatiotemporal variability in Ωcal, driven by seasonal changes and ocean circulation patterns. Sensitivity analysis highlighted the robustness of the TabNet model, maintaining high predictive capability despite variations in SST, SSS, and Chla. The TabNet model high accuracy provides a valuable tool for monitoring and forecasting changes in ocean chemistry, informing conservation efforts and policy-making. This study emphasizes the importance of advanced ML models in marine science and their potential for enhancing our understanding of global oceanic processes.
Continue reading ‘Advanced deep learning technique for estimating global surface ocean calcium carbonate saturation (Ωcal)’Sensitivity of pteropod calcification to multi stressor variability in coastal habitats
Published 18 December 2024 Science , Uncategorized ClosedTags: biological response, field, modeling, mollusks, morphology, multiple factors, North Pacific, regionalmodeling, temperature, zooplankton
Highlights
- Pteropod calcification under coastal multiple stressors was investigated.
- Shell morphometrics and high-resolution model outputs was combined.
- Saturation state, temperature and food are drivers of calcification.
- Different calcification modes are dependent on the type of environment.
- Stable vs dynamic conditions induce different calcification strategy.
Abstract
Comprehensive understanding of environmental multiple stressors on calcification in marine calcifiers remains an important topic of study, especially under ocean global change associated with multiple stressors. We explore the impact of multiple stressor variability on pteropod calcification in the southern Salish Sea (Washington, U.S.), a coastal estuarine system that exhibits a high degree of spatial and temporal variability in multiple environmental parameters across sampling locations. We hypothesized that such variability is associated with differences in pteropod calcification. Shell thickness and shell density across pteropod life history stages was compared with high-resolution outputs from a realistic model of regional circulation and biogeochemistry to explore how the mean and variability of multiple stressors (aragonite saturation state (Ωar), temperature, food availability) influence calcification. We found that both the mean and variability in multiple stressors play a major role in calcification in pteropods, with a generalized linear model explaining more than 60% of the variance in calcification. We suggest two different modes of shell building: stable conditions of lower mean Ωar trigger the loss of shell thickness and density. In the more variable habitats, i.e., where the variability occurs over diel and seasonal scales, shell thickness increases at higher Ωar variability and greater food availability, which might partially compensate for the loss of shell density. This plastic response appears to be consistent across life stages and could represent a response mechanism that allows some compensatory calcification under less favourable conditions. However, compensation is very limited, as evident by lower shell growth resulting in lower shell sizes comparable to early life stages. These results substantially improve the understanding of the variability in multiple stressors on the calcification process under multiple stressors and provide a foundation for the development of two new proxies for calcification monitoring, and with implications for marine carbon dioxide removal strategies.
Continue reading ‘Sensitivity of pteropod calcification to multi stressor variability in coastal habitats’Buffer properties in the Guadalquivir Estuary (SW Iberian Peninsula)
Published 18 December 2024 Science ClosedTags: chemistry, field, North Atlantic
Highlights
- The inorganic carbon system is mainly regulated by river flow and tidal conditions.
- The estuary is well buffered, being more sensitive in the innermost area.
- The estuary exports inorganic carbon to the coastal zone.
Abstract
The Guadalquivir Estuary (main source of continental waters to the Gulf of Cadiz) has a carbonate basin, which enables the transport of inorganic carbon to adjacent coastal areas. Therefore, in order to study the dynamic of the carbonate system and its buffer capacity, a total of 12 samplings were carried out from 2017 to 2022. Samplings included longitudinal transects and tidal cycles in different seasonal and tidal conditions. Total alkalinity (TA) and dissolved inorganic carbon (DIC) showed increased values upstream, while calcium (Ca2+) presented the highest values in most of the marine samples. The ranges values obtained for these three variables were of 2180–5140 μmol kg−1, 430–3950 μmol kg−1 and 1295–10,855 μmol kg−1 for TA, DIC and Ca2+, respectively. Two buffer factors (βDIC and βH) were also calculated to study the variability of the buffer capacity of the Guadalquivir Estuary. These indicate that the estuary is well buffered for salinities above 10, while the inner part is more vulnerable to acidification effects. Using a non-linear 1D hydrodynamic model, net inorganic carbon system transports were calculated, showing that the Guadalquivir Estuary is exporting TA, DIC and Ca2+ to the Gulf of Cadiz.
Continue reading ‘Buffer properties in the Guadalquivir Estuary (SW Iberian Peninsula)’Projections of coral reef carbonate production from a global climate coral reef coupled model
Published 17 December 2024 Science ClosedTags: biological response, BRcommunity, calcification, communitymodeling, corals, modeling, multiple factors, temperature
Coral reefs are under threat due to climate change and ocean acidification. However, large uncertainties remain concerning future carbon dioxide emissions, climate change and the associated impacts on coral reefs. While most previous studies have used climate model outputs to compute future coral reef carbonate production, we use a coral reef carbonate production module embedded in a global carbon-climate model. This enables the simulation of the response of coral reefs to projected changes in physical and chemical conditions at finer temporal resolution. The use of a fast-intermediate complexity model also permits the simulation of a large range of possible futures by considering different greenhouse gas concentration scenarios (Shared Socioeconomic Pathways (SSPs)), different climate sensitivities (hence different levels of warming for a given level of acidification), as well as the possibility of corals adapting their thermal bleaching thresholds. We show that without thermal adaptation, global coral reef carbonate production decreases to less than 25% of historical values in most scenarios over the twenty-first century, with limited further declines between 2100 and 2300 irrespective of the climate sensitivity. With thermal adaptation, there is far greater scenario variability in projections of reef carbonate production. Under high-emission scenarios the rate of twenty-first century declines is attenuated, with some global carbonate production declines delayed until the twenty-second century. Under high-mitigation scenarios, however, global coral reef carbonate production can recover in the twenty-first and twenty-second century, and thereafter persists at 50-90% of historical values, provided that the climate sensitivity is moderate.
Continue reading ‘Projections of coral reef carbonate production from a global climate coral reef coupled model’Science update: ocean and coastal acidification: building community resilience to our changing ocean
Published 17 December 2024 Events ClosedJoin us on Thursday, March 13, 2025, from 7:00 PM to 8:00 PM ET, to learn about ocean acidification.
The ocean acts like a sponge, absorbing carbon dioxide from the atmosphere. Increased absorption by the ocean causes changes to our ocean’s chemistry from pole to pole. This is known as ocean acidification. Ocean acidification has regional and local impacts on marine life, ecosystems, and the people who depend on them. Additional processes and stressors near our coasts like nutrient pollution and algae blooms cause coastal acidification, introducing additional impacts. We’ve advanced our science enough to be able to assess regional vulnerability and identify and build adaptive strategies to help people prepare for and mitigate these challenges.
In this web seminar, the presenters will talk about NOAA’s efforts to assess resilience and vulnerability to ocean and coastal acidification and provide resources and solutions supporting coastal and inland communities. The presenters will also share the latest research in the emerging field of marine carbon dioxide removal to mitigate ocean acidification.
All individuals receive a certificate of participation and 100 NSTA activity points for attending the live seminar and completing the end-of-program survey. A certificate of participation is not awarded for watching the recorded version of the program.
We invite you to register for upcoming web seminars at NSTA.
Register today to participate in this web seminar. Upon registering you will receive an e-mail confirmation including information about the program and suggested links to visit in preparation of the event. Additional information about the web seminar will be e-mailed to you days before the program.
New Users: Log in 15 minutes prior to the start time for an introduction to NSTA web seminars.
Each web seminar is a unique, stand-alone, program. Archives of the web seminars and the presenters’ PowerPoint presentations will be available through the links on this web page. Read answers to frequently asked questions from participants.
For more information contact: webseminars@nsta.org
Continue reading ‘Science update: ocean and coastal acidification: building community resilience to our changing ocean’Long-term warming and acidification interaction drives plastic acclimation in the diatom Pseudo-nitzschia multiseries
Published 17 December 2024 Science ClosedTags: adaptation, biological response, growth, laboratory, molecular biology, multiple factors, otherprocess, physiology, phytoplankton, temperature
Highlights
- Temperature shows stronger effects than CO2 on P. multiseries growth and stress reponses.
- Multi-omics analysis reveals phenotypic plasticity and molecular adaptations under long-term warming and acidification.
- Short-term experiments effectively predict long-term P. multiseries responses to combined temperature and CO2 changes.
Abstract
Ocean warming (OW) and acidification (OA) are expected to interactively impact key phytoplankton groups such as diatoms, but the underlying mechanisms, particularly under long-term acclimation, remain poorly understood. In this study, we investigated the responses of the toxic diatom Pseudo-nitzschia multiseries to combined changes in temperature (20 °C and 30 °C) and CO2 concentration (pCO2 400 μatm and 1000 μatm) using a multi-omics approach over an acclimation period of at least 251 generations. Physiological data suggest that elevated temperature, either alone or in combination with CO2, reduced the net photosynthesis and nitrate uptake rate, thus inhibiting P. multiseries growth. Conversely, elevated CO2 alone stimulated P. multiseries growth. Comparative genome analysis revealed the phenotypic plasticity in response to temperature and pCO2 variations, even after more than 251 generations acclimation period. Temperature was identified as the dominant environmental factor, showing stronger effects than CO2. Transcriptomic profiles indicated that genes involved in stress- and intracellular homeostasis such as Hsps, ubiquitination process and antioxidant defense were mostly down-regulated under long-term warming acclimation. This study demonstrates that P.multiseries responds similarly to both short-term and long-term experimental selection, suggesting that short-term experiments can be used to predict long-term responses.
Continue reading ‘Long-term warming and acidification interaction drives plastic acclimation in the diatom Pseudo-nitzschia multiseries’Decreases in pH from effluent had a devastating but reversible impact on the coastal plankton communities
Published 16 December 2024 Science ClosedTags: biological response, chemistry, community composition, field, North Pacific, otherprocess, phytoplankton, zooplankton
Highlights
- 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.
Continue reading ‘Decreases in pH from effluent had a devastating but reversible impact on the coastal plankton communities’New indicator tracks & visualizes ocean acidification in Washington
Published 16 December 2024 Web sites and blogs ClosedShellfish 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.
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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.
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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.
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Continue reading ‘New indicator tracks & visualizes ocean acidification in Washington’Rhodolith beds in a shifting world: a palaeontological perspective
Published 16 December 2024 Science ClosedTags: algae, biological response, paleo, review
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.
Continue reading ‘Rhodolith beds in a shifting world: a palaeontological perspective’The dynamics of adaptive evolution in microalgae in a high-CO2 ocean
Published 13 December 2024 Science ClosedTags: adaptation, biological response, laboratory, molecular biology, multiple factors, otherprocess, phytoplankton, temperature
Summary
- 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.
Interactive effects of CO2, temperature, and nitrate limitation on the growth and physiology of strain CCMP 1334 of the marine cyanobacterium Synechococcus (Cyanophyceae)
Published 13 December 2024 Science ClosedTags: biological response, growth, laboratory, multiple factors, nutrients, photosynthesis, physiology, phytoplankton, respiration, temperature
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.
Continue reading ‘Interactive effects of CO2, temperature, and nitrate limitation on the growth and physiology of strain CCMP 1334 of the marine cyanobacterium Synechococcus (Cyanophyceae)’Resource homogenisation drives niche convergence between generalists and specialists in a future ocean
Published 13 December 2024 Science ClosedTags: algae, biological response, community composition, laboratory, mesocosms, multiple factors, otherprocess, prokaryotes, temperature
Highlights
- 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.
Continue reading ‘Resource homogenisation drives niche convergence between generalists and specialists in a future ocean’Particulate inorganic carbon quotas by coccolithophores in low oxygen/low pH waters off the Southeast Pacific margin
Published 12 December 2024 Science ClosedTags: biogeochemistry, biological response, chemistry, community composition, field, otherprocess, phytoplankton, South Pacific
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.
Continue reading ‘Particulate inorganic carbon quotas by coccolithophores in low oxygen/low pH waters off the Southeast Pacific margin’Surface partial pressure of CO2 in seawater: a preliminary comparison between in-situ measurement and model data, along a round-the-world route
Published 12 December 2024 Science ClosedTags: chemistry, field
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%.
Continue reading ‘Surface partial pressure of CO2 in seawater: a preliminary comparison between in-situ measurement and model data, along a round-the-world route’Navigating ocean acidification in shellfish aquaculture: stakeholder perspectives of developing strategies in the U.S. Pacific region
Published 12 December 2024 Science ClosedTags: fisheries, mitigation, North Pacific, socio-economy
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.
Continue reading ‘Navigating ocean acidification in shellfish aquaculture: stakeholder perspectives of developing strategies in the U.S. Pacific region’Apply to join the 2025 GOOD-OARS summer school to be held in Malaysia in November 2025
Published 11 December 2024 Events Closed
Apply to join the 2025 GOOD-OARS summer school to be held in Malaysia in November 2025.
Applications are now open for the 2025 GOOD-OARS Summer School on Ocean Acidification and Deoxygenation, taking place 4–11 November 2025 at the Centre for Marine and Coastal Studies of Universiti Sains Malaysia (CEMACS) in Penang, Malaysia.
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
Important Deadlines:
Application Deadline: 10 January 2025
Selected Applicants Announced: 7 February 2025
For inquiries, please contact:
📩 go2ne-secretariat@unesco.org
📩 ssgo2025@gmail.com
Interannual and seasonal variability of CO2 parameters in the tropical Atlantic Ocean
Published 11 December 2024 Science ClosedTags: chemistry, field, South Atlantic
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).
Continue reading ‘Interannual and seasonal variability of CO2 parameters in the tropical Atlantic Ocean’Differential impacts of pH on growth, physiology, and elemental stoichiometry across three coccolithophore species
Published 10 December 2024 Science ClosedTags: biological response, growth, morphology, photosynthesis, physiology, phytoplankton
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.
Continue reading ‘Differential impacts of pH on growth, physiology, and elemental stoichiometry across three coccolithophore species’
