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Code Blue: our oceans in crisis

In Australia, our love of the ocean is truly profound – most of us live near the coast, we surf it, camp by it, we marvel at its incredible beauty from its many pristine sandy shores and we are proud of the unique and wondrous sea life that inhabits it.

Our oceans are in trouble. As our climate changes, driven by the unchecked burning of fossil fuels, our seas are transforming before our eyes. Marine heatwaves are surging, coral reefs are on the brink, ice
sheets are melting at an alarming rate, currents are slowing and seas are rising. Put simply: the climate crisis is an ocean crisis.

The ocean is the beating heart of planet Earth, and the lifeblood for all humanity. It produces over half the oxygen we breathe. Its currents regulate our climate and weather. The marine life within it provides sustenance for billions. Our cultures, economies and very identity are tied to the sea.

We have pushed this wondrous, life-giving system to the brink by burning coal, oil and gas. More than 90 percent of the heat trapped by greenhouse gas emissions has been absorbed by the ocean. Parts of the ocean could reach a near-permanent heatwave state within decades.

Our iconic Great Barrier Reef may soon face annual mass coral bleaching. Entire island nations like Tuvalu and Kiribati could become uninhabitable this century as seas rise.

The ocean is a vital carbon sink, absorbing more than 30 percent of the carbon dioxide that humans emit by burning fossil fuels and clearing land. This has changed the chemical make-up of the entire ocean,
making it more acidic.

By absorbing excess heat, and carbon, the ocean has shielded us from the worst of climate change so far. But we are now seeing the consequences of its sacrifice. The climate crisis is no longer a far-off threat. The ocean is screaming a warning that cannot be ignored.

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Changes in the macrobenthic infaunal community of the Southern California continental margin over five decades in relation to oceanographic factors

Climate change has altered the physiochemical conditions of the coastal ocean but effects on infaunal communities have not been well assessed. Here, we used multivariate ordination to examine temporal patterns in benthic community composition from 4 southern California continental shelf monitoring programs that range in duration from 30 to 50 yr. Temporal changes were compared to variations in temperature, oxygen, and acidification using single-taxon random forest models. Species richness increased over time, coupled with a decline in overall abundance. Continental shelf macrobenthic communities from the 2010s comprised a broader array of feeding guilds and life history strategies than in the 1970s. Changing water temperature was associated with northward shifts in geographic distribution and increases in species abundance, while acidification was associated with southward shifts and declines in abundance of other species. Acidification was also associated with changes in depth distribution of benthic fauna, with shelled molluscs declining in abundance at depths most associated with increasing exposure to acidification. This broad-scale community-level analysis establishes causal hypotheses that set the stage for more targeted studies investigating shifts in abundance or distribution for taxa that appear to be responding to climate change-related disturbances.

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Editorial: the changing carbonate systems in coastal, estuarine, shelf areas and marginal seas

Editorial on the Research Topic
The changing carbonate systems in coastal, estuarine, shelf areas and marginal seas

Global atmospheric CO2 concentrations have increased from 320 ppm in the 1960s to the present-day value of 420 ppm, primarily due to anthropogenic activities. This increase influences the seawater carbonate system, impacting the marine ecosystem. There are still gaps that need to be resolved for predicting how these marine systems respond to current and future CO2 levels. Any actions to mitigate the change in pH will require adaptive management of multiple stressors across several spatial scales. Combined, these perspectives yield a more comprehensive picture of events during ocean acidification (OA).

This Research Topic brings together articles from different regions, including coastal, estuarine, and shelf areas and marginal seas, all susceptible to changing atmospheric conditions, riverine inputs, air-sea CO2 exchanges, and multiple acid-base reactions that can alter carbonate chemistry. Articles on the long-term trends of CO2 system descriptors and the interactions with calcifying organisms were also sought. The present Research Topic is primarily based on original articles devoted to carbonate systems in the marginal seas, but it is a pity that some interesting papers dealing with freshwater inflows, estuaries, and related coastal areas were not accepted.

Fransson et al. examined the effects of glacial and sea-ice meltwater on ocean acidification in the waters near the 79 North Glacier (79 NG) and the northeast Greenland shelf. The researchers investigated various ocean acidification factors and the influence of freshening, primary production, and air-sea CO2 exchange. One of the key findings was that the biological removal of CO2 through primary production played a crucial role in offsetting the negative impact of freshwater dilution on the aragonite saturation state (ΩAr), which is a measure of ocean acidification. This compensation effect was most pronounced in 2012, especially in the vicinity of the 79 NG front, where there was a significant presence of glacial meltwater and surface stratification. In 2016, a different scenario was observed, with a more homogenized water column due to sea-ice meltwater. In this case, the compensation effect of biological CO2 removal on ΩAr was weaker compared to 2012. The study also suggests that in the future, with ongoing climate and ocean chemistry changes, the increasing influence of meltwater may surpass the mitigating effects of biological CO2 removal. This could lead to unfavorable conditions for organisms that rely on calcium carbonate for their shells and skeletons. Thus, all the proposed factors need to be closely monitored as they could have significant implications for marine ecosystems and calcifying organisms in the face of ongoing environmental changes.

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Scientists say warming seas helped cause Alaska’s snow crab crash

Courtesy Of Tacho
According to a NOAA study, the most likely cause for the mass disappearance was starvation caused by a marine heatwave between 2018 and 2019.

When scientists estimated that more than 10 billion snow crab had disappeared from the Eastern Bering Sea between 2018 and 2021, industry stakeholders and fisheries scientists had several ideas about where they’d gone.

Some thought bycatch, disease, cannibalism, or crab fishing, while others believed it could be predation from other sea animals like Pacific cod.

But now, scientists say they’ve distinguished the most likely cause for the disappearance. The culprit is a marine heatwave between 2018 and 2019, according to a new study authored by a group of scientists with the National Oceanic and Atmospheric Administration.

More carbon dioxide in the atmosphere means warmer temperatures, Litzow said, which is bad news for the cold-loving snow crab. And more greenhouse gasses also mean more acidic oceans, which can also be dangerous for some crab.

Carbon dioxide that we release through fossil fuels is also taken up by the oceans and has the effect of reducing the pH of the ocean — it makes it more acidic,” Litzow explained. “Because crab use calcium carbonate in their exoskeleton, they’re vulnerable to that acidification because calcium carbonate dissolves more and more easily as pH goes down.”

The good news — at least for snow crab — is they’re not as sensitive to ocean acidification as other species.

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Communication and community: my internship contributing to a new wave of ocean acidification education

Isaac Olson wonders why there is not a single visitor in sight at an aquarium’s ocean acidification exhibit. (Image credit: Shruthika Kandukuri)

Ocean acidification (OA) is one of the most imposing, yet still misunderstood, threats to our coasts. Even within aquariums, it can be hard to find detailed information about OA. This is a huge missed opportunity, especially as aquariums serve as one of the best places to not only educate people on marine issues, but also center issues in the affected communities. Indeed, the clock is ticking: OA is already becoming increasingly devastating ecologically, economically, and culturally. Yet, there is still an opportunity to mitigate much of the worst effects … if we act now. Thus, to enable equitable and sustainable change, it is vital to connect with people through OA communication that engages and empowers people to take action, especially in the most at-risk regions.

That’s why, as a class of 2022 Hollings Scholar, I worked with NOAA’s Ocean Acidification Program, the Aquarium Conservation Partnership, and the International Alliance to Combat Ocean Acidification on a project to address that knowledge gap. We created a suite of six StoryMaps intended for use in aquariums to educate, empower, and engage guests. Each StoryMap focuses on a different region in the NOAA Coastal Acidification Network (Alaska, the California Current, the Gulf of Mexico, the Southeast, the Mid-Atlantic, and the Northeast). Users can explore OA trends, impacts, and responses in their region, and learn how they can take action at both an individual and community level. The StoryMaps themselves are also highly adaptable for use by educators, community organizations, marine learning centers, and other groups: sections can be turned into interactive displays, sent out as virtual learning resources, and even uniquely individualized to increase community relevance. 

Explore this StoryMap for OA in Alaska, or check out our full collection of StoryMaps!

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The appendicularian Oikopleura dioica can enhance carbon export in a high CO2 ocean

Gelatinous zooplankton are increasingly recognized to play a key role in the ocean’s biological carbon pump. Appendicularians, a class of pelagic tunicates, are among the most abundant gelatinous plankton in the ocean, but it is an open question how their contribution to carbon export might change in the future. Here, we conducted an experiment with large volume in situ mesocosms (~55–60 m3 and 21 m depth) to investigate how ocean acidification (OA) extreme events affect food web structure and carbon export in a natural plankton community, particularly focusing on the keystone species Oikopleura dioica, a globally abundant appendicularian. We found a profound influence of O. dioica on vertical carbon fluxes, particularly during a short but intense bloom period in the high CO2 treatment, during which carbon export was 42%–64% higher than under ambient conditions. This elevated flux was mostly driven by an almost twofold increase in O. dioica biomass under high CO2. This rapid population increase was linked to enhanced fecundity (+20%) that likely resulted from physiological benefits of low pH conditions. The resulting competitive advantage of O. dioica resulted in enhanced grazing on phytoplankton and transfer of this consumed biomass into sinking particles. Using a simple carbon flux model for O. dioica, we estimate that high CO2 doubled the carbon flux of discarded mucous houses and fecal pellets, accounting for up to 39% of total carbon export from the ecosystem during the bloom. Considering the wide geographic distribution of O. dioica, our findings suggest that appendicularians may become an increasingly important vector of carbon export with ongoing OA.

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French coastal network for carbonate system monitoring: the CocoriCO2 dataset

Since the beginning of the industrial revolution, atmospheric carbon dioxide (CO2) concentrations have risen steadily and have induced a decrease of the averaged surface ocean pH by 0.1 units, corresponding to an increase in ocean acidity of about 30 %. In addition to ocean warming, ocean acidification poses a tremendous challenge to some marine organisms, especially calcifiers. The need for long-term oceanic observations of pH and temperature is a key element to assess the vulnerability of marine communities and ecosystems to these pressures. Nearshore productive environments, where a large majority of shellfish farming activities are conducted, are known to present pH levels as well as amplitudes of daily and seasonal variations that are much larger than those observed in the open ocean. Yet, to date, there are very few coastal observation sites where these parameters are measured simultaneously and at high frequency.

To bridge this gap, an observation network was initiated in 2021 in the framework of the CocoriCO2 project. Six sites were selected along the French Atlantic and Mediterranean coastlines based on their importance in terms of shellfish production and the presence of high- and low-frequency monitoring activities. At each site, autonomous pH sensors were deployed both inside and outside shellfish production areas, next to high-frequency CTD (conductivity- temperature-depth) probes operated through two operating monitoring networks. pH sensors were set to an acquisition rate of 15 min and discrete seawater samples were collected biweekly in order to control the quality of pH data (laboratory spectrophotometric measurements) as well as to measure total alkalinity and dissolved inorganic carbon concentrations for full characterization of the carbonate system. While this network has been up and running for more than two years, the acquired dataset has already revealed important differences in terms of pH variations between monitored sites related to the influence of diverse processes (freshwater inputs, tides, temperature, biological processes). Data are available at (Petton et al., 2023a).

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Photographic characterisation of acidification-induced larval malformations in the European lobster Homarus gammarus (Linnaeus, 1758) (Decapoda: Astacidea: Nephropidae)

Occurrence of developmental malformations is of interest since they potentially influence organismal performance and fitness. We report an increased incidence (⁓ 46 fold) of physical malformations in the larvae of the American lobster Homarus Gammarus (Linnaeus, 1758) in response to seawater acidification (–0.58 pH units relative to nominal pH 8.0). We observed three malformations under the influence of seawater acidification previously undescribed in lobster larvae: a flared carapace, twisted tail, and cross claw. Larvae reared under seawater acidification exhibit significantly lower survivorship (by ⁓14%) and the occurrence of a malformation decreases survivorship (12.7%). Larvae with four types of malformations did not progress through development to reach post-larval stages. Namely, these malformations were a flared carapace, curled carapace, twisted tail, and cross claw. Results from this study provide photographic documentation of various lobster larval malformations that ultimately affect individual success and can be applied for quality-control in hatcheries.

Continue reading ‘Photographic characterisation of acidification-induced larval malformations in the European lobster Homarus gammarus (Linnaeus, 1758) (Decapoda: Astacidea: Nephropidae)’

Poetry of science: “dissolving depths” (text & video)

This poem is inspired by recent research, which has found that ocean acidification in the Mediterranean is already affecting the calcification of marine plankton. The increasing levels of carbon dioxide emissions from human activities, such as the burning of fossil fuels, are not only warming our planet but are also causing a significant change in our oceans, known as ocean acidification. This process begins when the excess carbon dioxide in the atmosphere dissolves into seawater, forming carbonic acid. This acid then lowers the ocean’s pH, making the water more acidic. This shift in pH can have harmful effects on marine life, particularly on species that rely on calcium carbonate to build their shells and skeletons. The long-term consequences of ocean acidification, especially over decades to centuries, are complex and not fully understood, making it a critical area of environmental research. To better understand these impacts, the researchers studied three sediment cores from the Mediterranean Sea, which contain records spanning several centuries. They specifically looked at the weight, chemical composition, and other aspects of the shells of planktic foraminifera. The findings were concerning – as the levels of human-made carbon dioxide increased, these creatures’ shells became lighter, indicating weaker calcification. This is likely due to the increasing acidity of the ocean and the presence of carbon from fossil fuels. The study suggests that if carbon dioxide levels continue to rise, these tiny but vital sea creatures in the Mediterranean Sea will face increasing difficulties in building their shells, which could have broader implications for the marine ecosystem.
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COP28 Virtual Ocean Pavilion

We are excited to share the launch of the COP28 Virtual Ocean Pavilion, a free to access online platform dedicated to raising the visibility of the ocean and showcasing why the ocean matters in climate negotiations and to all life on our planet. You can access live and on–demand ocean and climate events, including high level speakers, explore exhibition booths, watch on-location COP28 reporting and interviews with delegates, take educational quizzes, earn certifications of attendance, access valuable networking opportunities and discover the treasure trove to learn more about the ocean and climate connection.
The pavilion aims to democratize the ocean at COPs and promote unity and inclusivity, whilst increasing knowledge, commitment, and action for the ocean-climate nexus at key events during the UN Climate Conference (COP28) in Dubai, UAE, 30 November-12 December 2023. It is also a key tool in increasing transparency and equitable access to climate discussions and information. To aid this process you can find an overview of the ocean events taking place at the COP28 itself with livestreaming links where available.  

The COP28 Virtual Ocean Pavilion is in its third year running and co-organized by the Global Ocean Forum and Plymouth Marine Laboratory with further collaborating partners from across the globe. The diversity of organizers and collaborating partners ensures a wide range of perspectives on ocean and climate issues and provides opportunities for forging cross-sectoral cooperation and collaboration on ocean-climate action at the national, regional, and global levels.

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Microbial associates of an endemic Mediterranean seagrass enhance the access of the host and the surrounding seawater to inorganic nitrogen under ocean acidification

Seagrasses are important primary producers in oceans worldwide. They live in shallow coastal waters that are experiencing carbon dioxide enrichment and ocean acidification. Posidonia oceanica, an endemic seagrass species that dominates the Mediterranean Sea, achieves high abundances in seawater with relatively low concentrations of dissolved inorganic nitrogen. Here we tested whether microbial metabolisms associated with P. oceanica and surrounding seawater enhance seagrass access to nitrogen. Using stable isotope enrichments of intact seagrass with amino acids, we showed that ammonification by free-living and seagrass-associated microbes produce ammonium that is likely used by seagrass and surrounding particulate organic matter. Metagenomic analysis of the epiphytic biofilm on the blades and rhizomes support the ubiquity of microbial ammonification genes in this system. Further, we leveraged the presence of natural carbon dioxide vents and show that the presence of P. oceanica enhanced the uptake of nitrogen by water column particulate organic matter, increasing carbon fixation by a factor of 8.6–17.4 with the greatest effect at CO2 vent sites. However, microbial ammonification was reduced at lower pH, suggesting that future ocean climate change will compromise this microbial process. Thus, the seagrass holobiont enhances water column productivity, even in the context of ocean acidification.

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Ocean acidification alters the transcriptomic response in the nervous system of Aplysia californica during reflex behaviour

Ocean acidification (OA) has numerous impacts on marine organisms including behaviour. While behaviours are controlled in the neuro system, its complexity makes linking behavioural impairments to environmental change difficult. Here we use a neurological model Aplysia californica with well-studied simple neuro system and behaviours. By exposing Aplysia to current day (~500 micro atm) or near-future CO2 conditions (~1100 micro atm), we test the effect of OA on their tail withdrawal reflex (TWR) and the underlying neuromolecular response of the pleural-pedal ganglia, responsible for the behaviour. Under OA, Aplysia relax tails faster due to increased sensorin-A expression, an inhibitor of mechanosensory neurons. We further investigate how OA affects habituation, which produced a ‘sensitization-like’ behaviour and affected vesicle transport and stress response, revealing an influence of OA on neuronal and behavioural outputs associated with learning. Finally, we test whether GABA-mediated neurotransmission is involved in impaired TWR, but exposure to gabazine did not restore normal behaviour and provoked little molecular response, rejecting the involvement in TWR impairment. Instead, vesicular transport and cellular signalling link other neurotransmitter processes directly with TWR impairment. Our study shows effects of OA on neurological tissue parts that control for behaviour revealing the neurological mechanisms when faced with OA.

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Warming, acidification, and calcification feedback during the first hyperthermal of the Cenozoic—The Latest Danian Event

The Latest Danian Event (LDE; ca. 62.15 Ma) is a major double-spiked eccentricity-driven transient warming event and carbon cycle perturbation (hyperthermal) in the early Paleocene, which has received significantly less attention compared to the larger events of the late Paleocene−early Eocene. A better understanding of the nature of the LDE may broaden our understanding of hyperthermals more generally and improve our knowledge of Earth system responses to extreme climate states. We present planktic and benthic foraminiferal Mg/Ca and B/Ca records that shed new light on changes in South Atlantic temperature and carbonate chemistry during the LDE. Our planktic Mg/Ca record reveals a pulsed increase in sea-surface temperature of at least ∼1.5 °C during the older carbon isotope excursion, and ∼0.5 °C during the younger isotope excursion. We observe drops in planktic and benthic B/Ca, synchronous with pronounced negative excursions in benthic δ13C, which suggest a shift in the carbonate system toward more acidic, dissolved inorganic carbon−rich conditions, in both the surface and deep ocean. Conditions remained more acidic following the LDE, which we suggest may be linked to an enhanced ocean alkalinity sink due to changes in the makeup of planktic calcifiers, hinting at a novel feedback between calcifier ecology and ocean-atmosphere CO2.

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SOARCE webinar series: Ocean Protector, an online ocean acidification game (text & video)


Ocean Protector is a new online game-based learning program to teach middle school students about the impacts of ocean acidification (OA) and positive actions to help. Thanks to funding from the NOAA OAP Education mini-grant, the game was developed collaboratively with educators to deliver a digital program that is engaging, easy to use, and integrates NOAA data into a framework that aligns with Next Generation Science Standards. Students begin the game by learning about OA and selecting a character role, such as marine park manager, fishing boat captain, or ocean tour guide. Students then evaluate and select decisions for how to reduce OA impacts on their character and marine life. After each decision the game updates dynamically and students analyze how their actions influenced OA impacts using data and their learned knowledge. Ultimately, this decision-driven process helps foster student-centered learning and ocean literacy, including with students from inland communities. Ocean Protector and associated lesson-plans are released freely online at…. The presentation will detail the design structure, game details/usability, and educator resources along with lessons learned from the entire development process.

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Ocean acidification: time for action

The role of action plans in tackling a mounting ocean crisis


The world is waking up to the threat that ocean acidification (OA)—a rise in the acidity of seawater caused by excess carbon dioxide entering it from the atmosphere—poses to marine ecosystems and to the coastal economies that depend on them. Since OA’s damaging effects on shellfish were first documented 15 years ago, research organisations have mobilised to collect, on an ongoing basis, huge volumes of OA-related data from the world’s oceans. Based on those data, as well as data gathered in coastal areas, scientists have published a wealth of studies examining the causes and effects of OA.

Environmental advocacy groups championing ocean health, charitable foundations and intergovernmental organisations have built on this work to raise global awareness of OA, fund wider research into it and prod governments around the world to take concrete actions to combat it.

Pacific pioneers: Setting the global standard for OA

National action plans are highly desirable, but it is state governments on the US Pacific coast that have set the standard of OA action for the rest of the world to follow.

Governments, however, have been slow to rise to this challenge. Although many have voiced concerns about OA and expressed an intention to fight it through international mechanisms, at the time of writing less than a dozen have published dedicated action plans. These document specific measures governments will take—or are taking—to advance understanding and the domestic response to OA.

The experts we interviewed for this report are strong advocates for OA action plans. Measures to address OA have a vital place in wider climate change and other marine management initiatives, but a dedicated OA plan stands a better chance of cementing the ambition and commitment of a country, region or locality to actively address localised manifestations of OA and turn back the tide. And while some non-government organisations (NGOs) and science institutions have issued OA action plans of their own, none will carry as much weight as those led by governments.

National action plans are highly desirable, but it is state governments on the US Pacific coast that have set the standard of OA action for the rest of the world to follow. It is here that scientists first registered the deadly impacts of OA on marine life and the threat to coastal economies and jobs. That emergency and follow-on research findings led governments in the region to commit unequivocally to combat OA with the help of dedicated, detailed and well-resourced action plans.

In examining governments’ and other entities’ progress on mobilising against OA, this report finds that existing North American action plans offer useful examples and insights for other jurisdictions. Far from all governments will be able to base their plans on the same depth of research or call on the same resources to draft them. But by including in their plans elements such as a vision of success, timelines, assignment of ownership, and a mandate for periodic review and updating, governments can call upon more resources and put their OA action plans on a firm footing.


Ocean acidification is a growing threat to many forms of marine life and to the communities that rely on them for food, jobs and economic wellbeing. OA is a direct result of the growing carbon dioxide (CO2) emissions generated by human activity. Up to 30% of carbon released into the atmosphere each year is absorbed by the ocean, which helps to mitigate global warming. But the ocean’s ability to sequester carbon cannot keep pace with rising emission volumes.1 The result is a decline in the pH level of seawater and a rise in its acidity.

Report citation: Turner J., Braby C., Findlay H., Widdicombe S., Kobayashi M. & Fujii M., 2023. Ocean acidification: time for action. The role of action plans in tackling a mounting ocean crisis. Back to Blue, Economist Impact, The Nippon Foundation. Report.

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Ocean acidification: exploring the “silent” impact of climate change


In this episode of the How to Protect the Ocean podcast, host Andrew Lewin discusses the often overlooked consequence of climate change: ocean acidification. He explains what ocean acidification is, its impact on the oceans, and explores potential solutions. This important issue is rarely discussed in the media, making it crucial for listeners to be informed and take action.

Link to article:

In this episode, the host discusses the significance of utilizing alternative modes of transportation, such as walking, cycling, or public transport, to decrease carbon emissions from cars. The host emphasizes that these alternative transportation methods not only benefit the environment but also promote personal health.

While the host acknowledges that electric vehicles (EVs) are a viable option for transportation since they don’t consume fossil fuels and therefore don’t contribute to carbon emissions, they also encourage the use of walking, cycling, or public transport. These options are not only environmentally friendly but also promote physical activity and overall well-being.

Furthermore, the host highlights the concept of reducing food miles as a means to minimize transportation-related carbon emissions. They suggest consuming locally grown foods and eating locally, as most meals in the US travel over 1,500 miles to reach consumers. By purchasing and consuming local and seasonal food, individuals can reduce the energy and CO2 emissions associated with food transportation.

Overall, the episode emphasizes the importance of utilizing alternative modes of transportation, such as walking, cycling, or public transport, to reduce carbon emissions from cars. It also promotes the idea of eating locally and consuming locally grown foods to minimize transportation-related carbon emissions.

In this episode, the host emphasizes the significance of eating locally grown foods as a way to reduce the transportation of food and the associated carbon emissions. The host explains that most meals in the US travel over 1,500 miles to reach our plates, and this transportation by road, rail, or air consumes energy and releases CO2, with air freight being the most polluting. By choosing to eat locally, such as shopping at farmer’s markets or local groceries, individuals can significantly reduce the distance that food needs to travel.

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Anthropogenic CO2, air-sea CO2 fluxes and acidification in the Southern Ocean: results from a time-series analysis at station OISO-KERFIX (51°S-68°E)

The temporal variation of the carbonate system, air-sea CO2 fluxes and pH is analyzed in the Southern Indian Ocean, south of the Polar Front, based on in-situ data obtained from 1985 to 2021 at a fixed station (50°40’S–68°25’E) and results from a neural network model that reconstructs the fugacity of CO2 (fCO2) and fluxes at monthly scale. Anthropogenic CO2 (Cant) was estimated in the water column and detected down to the bottom (1600 m) in 1985 resulting in an aragonite saturation horizon at 600 m that migrated up to 400 m in 2021 due to the accumulation of Cant. In subsurface, the trend of Cant is estimated at +0.53 (±0.01) µ with a detectable increase in recent years. At the surface during austral winter the oceanic fCO2 increased at a rate close or slightly lower than in the atmosphere. To the contrary, in summer, we observed contrasting fCOand dissolved inorganic carbon (CT) trends depending on the decade and emphasizing the role of biological drivers on air-sea CO2 fluxes and pH inter-annual variability. The region moved from an annual source of 0.8 molC.m-2.yr-1 in 1985 to a sink of -0.5 molC.m-2.yr-1 in 2020. In 1985–2020, the annual pH trend in surface of -0.0165 (± 0.0040).decade-1 was mainly controlled by anthropogenic CO2 but the trend was modulated by natural processes. Using historical data from November 1962 we estimated the long-term trend for fCO2, CT and pH confirming that the progressive acidification was driven by atmospheric CO2 increase. In 59 years this leads to a diminution of 11 % for both aragonite and calcite saturation state. As atmospheric CO2 will desperately continue rising in the future, the pH and carbonate saturation state will decrease at a faster rate than observed in recent years. A projection of future CT concentrations for a high emission scenario (SSP5-8.5) indicates that the surface pH in 2100 would decrease to 7.32 in winter. This is up to -0.86 lower than pre-industrial pH and -0.71 lower than pH observed in 2020. The aragonite under-saturation in surface waters would be reached as soon as 2050 (scenario SSP5-8.5) and 20 years later for a stabilization scenario (SSP2-4.5) with potential impacts on phytoplankton species and higher trophic levels in the rich ecosystems of the Kerguelen Island area.

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Can seasonal forecasts of ocean conditions aid fishery managers? Experiences from 10 Years of J-SCOPE

Multiple stressors co-occurring in coastal waters are of increasing concern to local fisheries. Many economically, culturally, or ecologically important species (e.g., oysters, crabs, pteropods) in the Pacific Northwest are already directly affected by ocean acidification (OA), warming, and hypoxia. Additional indirect economic impacts on the finfish industry are possible due to losses of prey species. Because of strong seasonal and interannual variations in ocean conditions, capability for predicting degrees of acidification and hypoxia, as well as relevant indices of impact for species of interest, could be of considerable benefit to managers. Over the past 10 years, we have developed a seasonal ocean prediction system, JISAO’s Seasonal Coastal Ocean Prediction of the Ecosystem (J-SCOPE), for the coastal waters of the Pacific Northwest. The goal has been to provide seasonal (six-month) predictions of ocean conditions that are testable and relevant to management decisions regarding fisheries, protected species, and ecosystem health. The results of this work include publicly available seasonal forecasts of OA variables, hypoxia, temperature, and ecological indicators that are tailored for decision-makers involved in federal, international, state, and tribal fisheries. We co-​designed J-SCOPE model products with state and tribal managers, and now federal managers at the Pacific Fishery Management Council receive J-SCOPE forecasts of OA and hypoxia within their annual Ecosystem Status Reports. US and Canadian managers of Pacific hake (Merluccius productus) are now briefed on J-SCOPE-driven forecasts of hake distribution. Most recently, new ocean acidification indices specific to Dungeness crab (Metacarcinus magister) have been co-produced with state and tribal managers. In each of these cases, the team has also investigated the sources of skill in forecasting ocean conditions to assess applicability of the forecasts to the variables, depths, and seasons relevant to these high-value fisheries. Observations from NOAA’s Pacific Marine Environmental Laboratory and other regional partners have provided critical validation of model performance throughout the model development process. We offer a retrospective look at the first 10 years of forecasting to provide perspective on its successes and limitations, and the potential global applicability of seasonal forecasting to inform flexible management responses to rapidly changing climate and ocean conditions.

A view from Point Grenville on the Quinault Indian Nation reservation where the Quinault Indian Nation has lived and harvested marine resources since time immemorial. Quinault beaches are closed to non-tribal members and require permission to access. Photo credit: Jeannette E. Waddell.

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Short-term ocean acidification decreases pulsation and growth of the widespread soft coral Xenia umbellata

Coral reefs may experience lower pH values as a result of ocean acidification (OA), which has negative consequences, particularly for calcifying organisms. Thus far, the effects of this global factor have been mainly investigated on hard corals, while the effects on soft corals remain relatively understudied. We therefore carried out a manipulative aquarium experiment for 21 days to study the response of the widespread pulsating soft coral Xenia umbellata to simulated OA conditions. We gradually decreased the pH from ambient (~8.3) to three consecutive 7-day long pH treatments of 8.0, 7.8, and 7.6, using a CO2 dosing system. Monitored response variables included pulsation rate, specific growth rate, visual coloration, survival, Symbiodiniaceae cell densities and chlorophyll a content, photosynthesis and respiration, and finally stable isotopes of carbon (C) and nitrogen (N) as well as CN content. Pulsation decreased compared to controls with each consecutive lowering of the pH, i.e., 17% at pH 8.0, 26% at pH 7.8 and 32% at pH 7.6, accompanied by an initial decrease in growth rates of ~60% at pH 8.0, not decreasing further at lower pH. An 8.3 ‰ decrease of δ13C confirmed that OA exposed colonies had a higher uptake and availability of atmospheric CO2. Coral productivity, i.e., photosynthesis, was not affected by higher dissolved inorganic C availability and none of the remaining response variables showed any significant differences. Our findings suggest that pulsation is a phenotypically plastic mechanism for Xumbellata to adjust to different pH values, resulting in reduced growth rates only, while maintaining high productivity. Consequently, pulsation may allow Xumbellata to inhabit a broad pH range with minimal effects on its overall health. This resilience may contribute to the competitive advantage that soft corals, particularly Xumbellata, have over hard corals.

Continue reading ‘Short-term ocean acidification decreases pulsation and growth of the widespread soft coral Xenia umbellata’

A closer look at ocean alkalinity enhancement (video)

This webinar is the third in a new series entitled Conversations on Ocean Carbon: A U.S. West Coast and Alaska Perspective, co-organized by the California Ocean Science Trust, California Current Acidification Network, and Alaska Ocean Acidification Network to deliver the best available information on marine carbon dioxide removal (mCDR) and to explore concepts related to coastal ocean carbon. This webinar series is intended to create a direct dialogue among industry members, tribes, natural resource managers and scientists within the California Current and Alaska Ecosystems. Through these co-designed webinars, participants will gain a better understanding of mCDR technologies, limitations, risks, and learn how to become engaged.

This webinar will provide an overview of ocean alkalinity enhancement, how it works, why it’s receiving attention as a marine carbon dioxide removal (mCDR) strategy, and potential impacts being studied.

Dr. Andrew Dickson, Scripps Institution of Oceanography;
Dr. Burke Hales, Oregon State University;
Dr. Débora Iglesias-Rodriguez, University of California Santa Barbara.
Continue reading ‘A closer look at ocean alkalinity enhancement (video)’

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