Archive Page 37

Impact of subtropical mode water formation variability on surface layer CO2 chemistry in the western North Pacific

Published 5 June 2025 Science Closed
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Abstract

Deep understanding of contemporary trends, variability and their controlling mechanisms of ocean CO2 chemistry are crucial in projecting the ocean CO2 uptake and acidification. In surface layers of the 137°E high-frequency repeat hydrographic section in the Kuroshio recirculation (KR) region of the western North Pacific, salinity-normalized total dissolved inorganic carbon (nDIC) in summer exhibited a significant interannual to decadal variability ranging ±15 μmol kg−1 for the years 1994–2018. It was positively correlated with the thickness of the underlying subtropical mode water (STMW) (±160 m) due to the shallowing/deepening of the upper STMW and negatively with the Pacific Decadal Oscillation (PDO) index when a 3-year lag was applied. The nDIC variability caused large variability in the aragonite saturation index (±0.2), but the impact of nDIC variability on CO2 partial pressure (pCO2sea) and pH were smaller than that of temperature variability that concurrently acted in the opposite direction. In contrast, the variability of nDIC in the winter mixed layer was primarily controlled by the deepening of mixed layer but was also affected by the thickness of the STMW due to the entrainment of upper STMW in which nDIC was lower/higher when the STMW was thicker/thinner. These observations indicate that the changes in the wind forcing in the central North Pacific remotely influence the CO2 chemistry in surface layers of the KR region through the changes in the formation and advection of the STMW and have different impacts between summer when surface layer is stratified and winter when mixed layer deepens.

Key Points

  • Surface layer CO2 chemistry in the Kuroshio recirculation region in summer showed decadal variability over the past 25 years
  • The variability was correlated with subtropical mode water formation and also remotely connected with the Pacific Decadal Oscillation
  • In winter, the variability was influenced partially by subtropical mode water formation and dominantly by vertical convection

Plain Language Summary

To project future increases in ocean CO2 levels and the resulting ocean acidification in response to rising human industrial CO2 emissions and their mitigation, it is crucial to understand the natural processes that control variability in ocean CO2 content. In the subtropics of the western North Pacific, to the south of Kuroshio, we found that the dissolved inorganic carbon (DIC) in the surface layer varies with the thickness of the subtropical mode water (STMW). This water mass, which forms to the south of the Kuroshio Extension in winter, is distributed below the surface layer in the studied region. Its volume changes on a decadal scale in association with the Pacific Decadal Oscillation, exhibiting impacts on surface layer DIC in different manners between summer and winter. In summer, the DIC content increased when the STMW was thicker due to the increased supply of DIC from the subsurface layer to the surface. In winter, the DIC content in the surface layer increased as the winter mixed layer developed deeper while it was also partially influenced by STMW thickness.

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Regionally distinct drivers of the carbonate system dynamics in the Drake Passage and northern Antarctic Peninsula

Published 4 June 2025 Science Closed
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Highlights

  • AT and CT in the DP and NAP were influenced by salinity, terrestrial inputs, and coastal upwelling.
  • Oceanic regions of the DP were significantly influenced by phosphate levels and high eddy kinetic energy.
  • AT and CT in the DP and NAP exhibited both conservative (coastal regions) and non-conservative (oceanic regions) behaviors.
  • The highest risk for carbonate undersaturation was observed in the NAP.

Abstract

The Drake Passage (DP) and the adjacent northern Antarctic Peninsula (NAP) are highly dynamic regions within the Southern Ocean where physical and biogeochemical processes simultaneously influence the CO2 system. Ocean total alkalinity (AT) and total dissolved inorganic carbon (CT) serve as valuable early indicators of calcium carbonate undersaturation and help evaluate the buffering capacity of the ocean. However, significant uncertainty remains in predicting carbonate system dynamics in the DP and NAP due to a lack of seasonal representation and the spatial variability. To address this uncertainty, we identified factors affecting the carbonate system at a regional level using unprecedented surface data from two consecutive austral summer and early fall periods (February–April 2003 and 2004). The data revealed that the dynamics of AT and CT in the DP and NAP exhibited both conservative and non-conservative behaviors influenced by the position of the Polar Front (PF), and the proximity to land. In coastal regions, salinity and terrestrial influence were major determinants, while in oceanic regions, nutrients and phytoplankton productivity played a more prominent role. The position of the PF creates a latitudinal edge in nutrient ratios, establishing a new hierarchy of carbonate chemistry drivers where silicate gains prevalence toward the southern DP and NAP. The results highlight significant regional variability in the carbonate system, with increasing AT and CT from north to south, making NAP the most vulnerable region due to accelerated acidification and ice melt-growth. Susceptibility to ocean acidification and seasonal fluctuations in the carbonate system indicate a higher risk to calcareous structures in the southernmost region.

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Applications open: basic training course on ocean acidification

Published 4 June 2025 Events Closed

Dates: 11-15 August 2025

Location: Kingston, Jamaica

Deadline for receipt of application from the nominating national authority: 25 June 2025

Form A and Form C

The course is a cooperative effort organized by the International Atomic Energy Agency’s Ocean Acidification International Coordination Centre (OA-ICC) and hosted by the Government of Jamaica through the University of the West Indies (UWI) as the local organizer.

Introduction

The IAEA’s Ocean Acidification International Coordination Centre (OA-ICC) supports IAEA Member States to minimize and adapt to OA and report towards SDG 14.3 and the GBF, with a strong focus on building capacity to study ocean acidification and related stressors and promoting international collaboration and coordination.

Caribbean Small Island Developing States (SIDS) are particularly vulnerable to ocean acidification due to their reliance on the ocean for food, income, and recreation. This Basic Training Course on Ocean Acidification will provide scientists from Caribbean SIDS with foundational knowledge on conducting ocean acidification monitoring and designing purposeful experiments to understand the impacts of ocean acidification on key marine organisms in the Caribbean region. By the end of the course, participants will have a better understanding of the challenges and complexities presented by ocean acidification and the critical role we all play in addressing this issue and developing solutions.

Objectives

The course aims to empower Caribbean SIDS to monitor ocean acidification and its effects on key marine species, informing both SDG 14.3 and Target 8 of the Global Biodiversity Framework, and to explore local solutions to increase the resilience to ocean acidification in the region.
It will cover various topics, including theoretical aspects and best practices for the measurement of seawater carbonate chemistry, how to evaluate the impacts of ocean acidification on marine species and ecosystems, and potential solutions for minimizing its effects, including possible local adaptation measures. Guidance on how to report towards Sustainable Development Goal 14.3 and its indicator 14.3.1 on ocean acidification will be provided.

The course will be taught by experts in the field of ocean acidification, who will provide lectures, interactive discussions, and hands-on activities to ensure that participants gain a comprehensive understanding of the topic. The course will also provide opportunities for participants to network with peers and engage with the broader ocean acidification community. Local aquaculture managers will be invited to a special session to discuss potential local adaptation measures to counter the effects of ocean acidification in the Caribbean.

Target Audience

The course is intended for scientists from the Caribbean who are entering the ocean acidification field. It is open to 10 to 12 trainees from the following countries: Antigua and Barbuda, Bahamas, Barbados, Belize, Cuba, Dominica, Dominican Republic, Grenada, Guyana, Haiti, Jamaica, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines, Suriname and Trinidad and Tobago.

Priority will be given to early-career scientists with experience in marine sciences. Scientific publications in related fields will be valued.

Working Language: English

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Participation and Registration

All persons wishing to participate in the event have to be designated by an IAEA Member State or should be members of organizations that have been invited to attend.

In order to be designated by an IAEA Member State, participants are requested to send the Participation Form (Form A) to their competent national authority (e.g. Ministry of Foreign Affairs, Permanent Mission to the IAEA or National Atomic Energy Authority) for onward transmission to the IAEA by 25 June 2025. Participants who are members of an organization invited to attend are requested to send the Participation Form (Form A) through their organization to the IAEA by the above deadline.

Selected participants will be informed in due course on the procedures to be followed with regards to administrative and financial matters.

Participants are hereby informed that the personal data they submit will be processed in line with the Agency’s Personal Data and Privacy Policy and is collected solely for the purpose(s) of reviewing and assessing the application and to complete logistical arrangements where required. The IAEA may also use the contact details of Applicants to inform them of the IAEA’s scientific and technical publications, or the latest employment opportunities and current open vacancies at the IAEA. These secondary purposes are consistent with the IAEA’s mandate.

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Additional Requirements

The participants should have a university degree in marine chemistry, biology, oceanography or a related scientific field, and should be currently involved in or planning to study ocean acidification. Scientific publications in related fields will be valued.

Selection will be based on merit and interest. Applications should include:

  • A motivation letter with a short description of the candidate’s research interests and how the course would benefit the applicant’s current or future research (max one A4 page).
  • CV with publication list.
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Ocean acidification and elevated temperatures alter the behavior of a sub-Antarctic fish

Published 3 June 2025 Science Closed
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Highlights

  • Climate change stressors impair the behavoir of subantarctic fish.
  • Activity levels of E. mclovinus increased with higher temperatures.
  • Future pCO2 levels increased fish’s boldness.
  • Implications of behavioral changes on the species’ fitness remain unknown.

Abstract

The interaction of multiple climate change stressors can affect the behavior of marine fish. While these effects have been reported in tropical and temperate species, much less is known for fish inhabiting high latitudes. We analyzed the combined effects of ocean acidification and the highest and lowest seasonal temperatures on the activity level and boldness of Eleginops maclovinus, an ecologically and commercially important notothenioid fish from the subantarctic area. Juveniles were acclimated for one month to two temperatures (T = 4 and 10 °C) and two pCO2 levels (∼500 and ∼1800 μatm) in a full factorial design. In an open field test, the time spent active was significantly affected by temperature, with fish at 10 °C 1.63 times more active than those at 4 °C, but not by pCO2 or the interaction (T × pCO2). No differences were observed in the average swimming velocity measured when active, nor in the time spent in the inner zone of the tank. A refuge emergence test indicated increased boldness under near-future pCO2 levels with fish emerging 2.06 (4 °C) and 1.23 (10 °C) times faster than those acclimated to present-day pCO2 levels. The disruptions of these fundamental behaviors by these climate-driven stressors could have consequences for foraging and predator-prey interactions, with likely detrimental effects on the interactions among sympatric subantarctic fishes under projected climate change scenarios.

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Diel variability affects the inorganic marine carbon system in the sea-surface microlayer of a Mediterranean coastal area (Šibenik, Croatia)

Published 2 June 2025 Science Closed
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The ocean plays a crucial role in the global carbon cycle by absorbing and storing substantial amounts of atmospheric carbon dioxide (CO2). It is estimated that the ocean has sequestered approximately 26% of CO2 emissions over the last decade, resulting in significant changes in the marine carbon system and impacting the marine environment. The sea-surface microlayer (SML) plays a crucial role in these processes, facilitating the transfer of materials and energy between the ocean and the atmosphere. However, most studies on the carbon cycle in the SML have primarily addressed daily variability and overlooked nocturnal processes, which may lead to inaccurate global carbon estimates. We analysed temperature, salinity, pHT25, and pCO2 using data collected over three complete diel cycles during an oceanographic campaign along the Croatian coast near Šibenik in the Middle Adriatic. Our analysis revealed statistically significant differences (p < 0.05) between daytime and nighttime measurements of temperature, salinity, and pHT25. These differences may be related to the occurrence of buoyancy fluxes, which are typically more pronounced during the day and could enhance CO2 fluxes, as observed with values of 1.98 ± 2.52 mmol cm⁻² h⁻¹ during the day, while at night, they dropped to 0.01 ± 0.02 mmol cm⁻² h⁻¹. These findings emphasise the importance of considering complete diurnal cycles to accurately capture the variability in thermohaline features and carbon exchange processes, thereby improving our understanding of the role of the ocean in climate change.

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Ocean acidification events at 2025 UN Ocean Conference

Published 30 May 2025 Events Closed

If you will be at the 2025 UN Ocean Conference in Nice, France, please join the following events:

Science to action on SDG 14.3

  • 9 June 2025, 14:00 – 17:00 (including reception and social hour)
  • Le Negresco, 37 Prom. des Anglais, Nice
  • RSVP through this link
  • Organized by the OA Alliance, Ocean Acidification Research for Sustainability (OARS), the Global Ocean Acidification Observing Network (GOA-ON), and the Intergovernmental Oceanographic Commission (IOC) of UNESCO
  • See flyer for more information

Ocean-based solutions: from blue carbon to ocean alkalinity enhancement

  • 9 June 2025, 18:30 – 21:30 (reception to follow panel discussion)
  • Institut de la Mer de Villefranche
  • By invitation only: email L.Hansson@iaea.org if interested in attending.
  • Organized by Ocean Acidification and other ocean Changes – Impacts and Solutions (OACIS) with the participation of the Global Ocean Decade Programme for Blue Carbon (GO-BC) and Ocean Negative Carbon Emissions (ONCE)
  • See flyer for more information

Addressing and minimizing ocean acidification: success stories, opportunities, and new commitments

  • 10 June 2025, 14:00 – 15:00
  • Ocean Literacy Pavilion, Green Zone/La Baleine
  • Register for access to La Baleine
  • Organized by Plymouth Marine Laboratory, the International Atomic Energy Agency (IAEA), the Intergovernmental Oceanographic Commission (IOC) of UNESCO, the University of Washington, Ocean Acidification Research for Sustainability (OARS), the Global Ocean Acidification Observing Network (GOA-ON), the International Coral Reef Society (ICRS), the International Cryosphere Climate Initiative (ICCI), the OSPAR Commission, Convention on Biological Diversity Secretariat, Velux Foundation, The Economist, and BNP Paribas

Beyond tipping points: safeguarding biodiversity in a changing ocean

  • 11 June 2025, 13:15 – 14:45 (lunch included)
  • Mama Shelter, Nice, France
  • RSVP by 4 June to L.Hansson@iaea.org
  • Organized by Ocean Acidification and other ocean Changes – Impacts and Solutions (OACIS)
  • See flyer for more information

Policy action to implement SDG 14.3

  • 11 June 2025, 14:45 – 15:30
  • Manta Room, Green Zone/La Baleine
  • RSVP to jturner@unfoundation.org
  • Organized by the OA Alliance
  • See flyer for more information
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Species-specific proton and oxygen flux in Hawaiian corals under ocean acidification—a microsensor analysis of the concentration boundary layer

Published 30 May 2025 Uncategorized Closed
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Coral reefs are essential for the foundation of marine ecosystems. However, ocean acidification (OA) driven by rising atmospheric carbon dioxide (CO₂) threatens coral growth and biological homeostasis. In this study, we examined the microenvironmental fluxes of two Hawaiian coral species—Montipora capitata and Pocillopora acuta to elevated pCO₂, focusing on proton (H⁺) and oxygen (O₂) flux within the concentration boundary layer (CBL) at the zone of primary calcification (ZPC). Utilizing pH and O2 microsensors under controlled light and dark conditions, we characterized species-specific CBL traits and quantified material fluxes. Our results revealed that while both species maintained a positive net proton flux, P. acuta showed a pronounced reduction in dark proton efflux (-188%) and a significant increase in light O₂ flux (+ 175%), suggesting impaired metabolic and calcification dynamics. In contrast, M. capitata showed minimal changes in both flux parameters under similar OA conditions. Statistical analyses using linear models showed several significant interactions between species, treatment, and light conditions, identifying physical, chemical, and biological drivers for species responses to OA. We also present a conceptual model correlating external measures with internal physiologies to explain our findings. We indicate that OA exacerbates microchemical gradients in the CBL and potentially acts to reduce calcification in vulnerable species like P. acuta while highlighting the resistance of M. capitata. This study advances our understanding of how species-specific microenvironmental processes could influence coral responses to changing ocean chemistry.

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Effects of acidification and habitat loss on coastal nitrogen cycling dynamics

Published 29 May 2025 Science Closed
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Excess nitrogen (N) in urbanized coastal waterways from wastewater or agricultural inputs causes widespread habitat decline due to harmful algal blooms, poor water quality, and changes to seawater chemistry. For example, during an algal bloom, nocturnal respiration and seasonal decomposition of algal biomass release carbon dioxide (CO2) into the water column, which lowers seawater pH in a process known as coastal acidification. Additionally, high N loading leads to the death of salt marsh vegetation communities, in turn leading to salt marsh erosion and loss, with implications for coastal stability. Estuarine habitats such as seagrass beds and salt marshes are known as hotspots of microbially-mediated nutrient cycling, but it has been unclear how stressors caused by N loading (i.e., coastal acidification, macroalgal blooms, and salt marsh erosion/loss) impact vital biogeochemical processes in these habitats. This dissertation explored the effects of acidification on nutrient cycling in eelgrass beds and salt marshes (in Shinnecock Bay, Long Island and Jamaica Bay, New York City, respectively), as well as the impacts of salt marsh loss on N dynamics in eutrophic urban estuaries. Results show that lower seawater pH shifted sediments in eelgrass beds from net sources of reactive N to net N sinks, with implications for water quality mitigation. In salt marshes, acidification appeared to have no effect on nutrient cycles. Instead, N cycling in salt marshes is likely to respond to erosion and increasing inundation. De-vegetated marsh sediments showed net N release compared to still-intact vegetated marsh areas, suggesting that losses in salt marsh habitat may contribute to water quality decline and algal bloom conditions, as well as perpetuate further habitat loss. This body of research addressed critical gaps in understanding the processes that underpin coastal habitat function under various N loading-related stressors, such as acidification-induced impacts on nitrification and denitrification in eelgrass beds and changes to sediment N cycling as marshes erode. The former finding may suggest that N loading may be at least partially mitigated during a coastal acidification event, while the latter finding suggests that marsh restoration may prevent loss of N removal services. The applications of this research are likely to become increasingly critical, as these habitats serve as vital natural infrastructure against sea level rise, storm surges, and coastal change.

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Japanese Arctic projects’ contributions to the Central Arctic Ocean Fisheries Agreement

Published 28 May 2025 Science Closed
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One of the project goals of the Arctic Challenge for Sustainability II (ArCS II) is the social implementation of research results to assess risks and to develop policies that allow effective management. The Central Arctic Ocean Fisheries Agreement (CAOFA) set an example for such social implementation with a collaboration of social and natural scientists from the ArCS II. Here, we examine the contributions of the ArCS II and earlier Japanese Arctic studies to the CAOFA based on the implementation plan of the CAOFA’s Joint Program for Scientific Research and Monitoring. Japan’s research results were useful for prioritizing research areas and assessing the marine environment and ecosystem mainly in lower trophic levels on the Pacific side of the Arctic Ocean. Future contributions to the CAOFA are expected through the scientific surveys to be conducted by a Japanese new icebreaker.

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Alleviation of competitive constraints through long-term adaptation to high CO2 in mixed cultures of two diatom species

Published 27 May 2025 Science Closed
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Highlights

  • The resources competition of two diatoms reduced most performance parameters.
  • High CO₂ adaptation partially alleviates the detrimental effects of competition.
  • Resource competition changes phytoplankton’s adaptation strategy to high CO2.

Abstract

Diatoms play a pivotal role in marine ecosystems, contributing significantly to global primary production and carbon cycling. Understanding their responses to high CO₂ is critical for predicting oceanic changes under future climate scenarios. This study investigates the long-term adaptation of two diatom species, Thalassiosira weissflogii and Phaeodactylum tricornutum, to high CO₂ (1000 µatm) over 3.5–4 years and the consequences of their interactions in mixed cultures. Mono- and mixed-species cultures were maintained under both ambient (400 µatm) and high CO₂ conditions to assess various physiological performances. Our results revealed that most measured parameters (growth rate, photosynthesis and respiration rate, chlorophyll fluorescence parameters, and pigment concentration) were significantly reduced in mixed cultures compared to mono-cultures under both CO₂ conditions, underscoring the detrimental effects of interspecific competition. However, long-term adaptation to high CO₂ partially alleviated these reductions, particularly in photosynthesis, respiration, and chlorophyll-a content. These findings highlight the complex interplay between physiological adaptation and interspecific competition in shaping diatom responses to high CO₂. This study advances our understanding of the ecological and evolutionary implications of ocean acidification and underscores the importance of long-term experimental approaches for assessing the impacts of climate change on marine phytoplankton.

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Surface seawater chlorophyll-a variability in the South China Sea: influence of pCO2 and co-varying environmental factors

Published 26 May 2025 Science Closed
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Highlights

  • Surface seawater Chl-a shows a generally stable trend with slight decline over 20 years.
  • Limited CO2-driven Chl-a response detected over two decades.
  • Light–nutrient–temperature co-limitation dominates phytoplankton growth in the SCS.

Abstract

The partial pressure of CO2 (pCO2) in surface seawater continues to increase with the rising atmospheric carbon dioxide (CO2). However, whether elevated pCO2 enhances marine primary productivity and its actual impact on Chl-a shows distinct regional variability. Using chlorophyll-a (Chl-a, from Ocean Colour Climate Change Initiative satellite data), combined with high-resolution pCO2 dataset, we analyzed the spatiotemporal variations of surface seawater Chl-a and their response to pCO2 in the South China Sea (SCS) from August 2002 to December 2022. We demonstrate that Chl-a concentrations are higher in coastal regions, lower in the central basin, peak in winter, and are lowest in spring. Over the past two decades, surface seawater Chl-a has exhibited a generally stable pattern with a slight declining tendency, with a faster decrease in nearshore waters (−0.00693 mg m−3·yr−1, −0.27 %) than in central open waters (−0.00123 mg m−3·yr−1, −0.60 %). In contrast, surface seawater pCO2 has increased steadily, with a more rapid rise in central open waters (1.44 μatm yr−1) compared to nearshore areas (0.496 μatm yr−1), accompanied by a concurrent warming trend, where sea surface temperature increased at rates of 0.0346 °C·yr−1 and 0.0408 °C·yr−1 in nearshore and central open waters, respectively. Partial correlation analysis indicates that light inhibition is the main factor constraining phytoplankton growth in the SCS, while carbon availability is not a key influencing factor for phytoplankton in this region. Rising pCO2, accompanied by climate change effects such as rising sea surface temperatures and enhanced water column stratification, may contribute to a weakening of surface seawater Chl-a in the SCS. Further studies are needed to evaluate its future under climate change.

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Navigating ocean acidification in shellfish aquaculture: stakeholder perspectives of developing strategies in the U.S. Pacific region

Published 23 May 2025 Science Closed
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Highlights

  • Aquaculture ocean acidification threat perceptions declined over the last decade.
  • Shellfish industry interviews can guide adaptive strategy co-production.
  • Native species portfolio diversification met more skepticism than parental priming.
  • Enhanced environmental monitoring is a high research priority across respondents

Abstract

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.

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    Fatty acid response of calcifying benthic Antarctic species to ocean acidification and warming

    Published 22 May 2025 Science Closed
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    Highlights

    • None of the species showed changes in the immune function in response to OA or OW.
    • FA associated with cell membrane fluidity wasn’t affected in both species.
    • 20:5n-3 and 20:1n-9 FA were negatively impacted in A. eightsii under OW.
    • Both species appear capable of maintaining stable FA levels in these conditions.

    Abstract

    Ocean acidification (OA) and ocean warming (OW) are likely to alter the biochemical composition of certain organisms as a physiological response to these changing environmental conditions. Given the importance of fatty acids (FA) in energy transfer within marine food webs, this two-month laboratory study examines the response of two calcifying species from Potter Cove (Antarctica) – the bivalve Aequiyoldia eightsii and the coral Malacobelemnon daytoni – to predicted OA and OW, focusing on their FA profiles. Neither species showed significant changes compared to the control group in the composition of FA ratios associated with immune function and cell membrane fluidity in response to either OA or OW. Additionally, the FA composition related to inflammatory responses remained largely unaffected by the stressors, although the 20:5n-3 FA was negatively impacted in A. eightsii under high-temperature conditions. Overall, the FA composition in these species appears robust to near-future environmental changes.

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    Positive interactions in a warmer and more acidic ocean: crustose coralline algae holobionts enhance gorgonian larval settlement under climate change

    Published 21 May 2025 Science Closed
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    Background: The increasing frequency of marine heatwaves is leading to mass mortality of gorgonians in the Mediterranean Sea, threatening some populations with local extinction. A better understanding of the dynamics of gorgonians’ early life stages under climate change is urgent to ensure their conservation. Crustose coralline algae (CCAs) and their associated bacteria are known to induce the larval settlement of several coral species through the production of chemical cues. The larvae of the white gorgonian Eunicella singularis have been observed to preferentially settle and metamorphose on CCAs. Here, we investigated this positive interaction, and explored how it might be altered by climate change. Specifically, we tested the capacity of two Mediterranean CCA holobionts, Macroblastum dendrospermum and Lithophyllum stictiforme, to foster E. singularis larval settlement after exposure to SSP5-8.5 projected conditions for 2100 (warming and acidification), combined or not with a simulated marine heatwave event.

    Results: Our results showed a threefold increase of larval settlement in presence of the CCAs previously exposed to acidification and warming treatments. After these treatments, both CCAs hosted a consistently high abundance of bacteria belonging to the Pirellulaceae family, and exhibited a higher abundance of monosaccharides in their exudates. We hypothesize that the enhanced larval settlement was driven by the bacterial breakdown and utilization of CCA polysaccharides, in combination with their release through the CCA cell walls. This release may have been enhanced by a decalcification process induced by climate change conditions. Furthermore, we showed that CCAs act as sources of bacterial taxa that can establish and persist in adult E. singularis holobiont, independently of climate change effects.

    Conclusions: Our results highlight that CCA-larvae interaction is critical for E. singularis recruitment success, especially under future climatic conditions, and influences the development of its microbiome. This research underscores the importance of studying positive interspecific interactions across biological levels (from microorganisms to macroorganisms) under climate change scenarios, and provides valuable insights that inform the conservation and restoration of the Mediterranean white gorgonian.

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    Exploring the land-ocean biogeochemical and microbial connectivity in the Ría de Vigo (NW Iberian Peninsula) through submarine groundwater discharge

    Published 20 May 2025 Science Closed
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    Highlights

    • SGD affects the carbonate system, methane and nitrous oxide content of the embayment
    • Solute composition of SGD largely impacted by subterranean estuary reactivity
    • Contrasting poor microbial connectivity across the different aquatic environments
    • Subterranean estuaries may act as microbial boundaries in the aquatic continuum

    Abstract

    Increasing evidence demonstrates the widespread occurrence of submarine groundwater discharge (SGD) in coastal zones, where it may influence biogeochemistry and microbial ecology. Here, we analyze the biogeochemical composition and microbial communities across diverse aquatic environments in a highly productive coastal system (Ría de Vigo, NW Iberian Peninsula), influenced by significant fresh SGD, to assess the extent of microbial and biogeochemical connectivity—i.e., mass transfer—among them. Samples were collected from surface and deep porewaters from two subterranean estuaries (STEs), surface seawater, riverine water, and continental groundwater. These samples were analyzed for a comprehensive set of microbial and biogeochemical variables, including radioisotopes used as SGD tracers. A significant correlation between SGD tracers and carbonate system parameters, N2O, and CH4 concentrations in surface seawater indicates SGD influences biogeochemistry of the embayment. However, some of these solutes do not originate from continental groundwater but are produced in the local STEs, which act as biogeochemical reactors modifying fresh SGD. The findings also reveal highly diverse microbial communities, with higher diversity in STEs due to the variety of niches present. Indicator taxa included the phyla Euryarchaeota, Chloroflexi, Omnitrophicaeota, and the family Nitrosopumilaceae in STEs; the phylum Cyanobacteria and the family Burkholderiaceae in freshwater endmembers; and the Flavobacteriaceae and Cryomorphaceae families in seawater. Most operational taxonomic units (∼87%) were unique to a single environment (river, continental groundwater, coastal water, or STE), showing STEs limit subterranean microbial transfer between groundwater and marine ecosystems. Our results highlight STEs as reservoirs of diversity and zones of intense biogeochemical reactivity.

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    A mid-decade check-in: the NOAA ocean, coastal, and Great Lakes acidification research plan 2020-2029

    Published 19 May 2025 Newsletters and reports Closed

    Starting in 2020, the National Oceanic and Atmospheric Administration (NOAA) has carried out research guided by the Ocean, Coastal, and Great Lakes Acidification Research Plan: 2020-2029 (the Research Plan). In the ensuing years, NOAA has tracked progress towards implementing the actions in the Research Plan. As we move into the second half of the decade, we would like to take this opportunity to take stock of the progress NOAA has made and reflect on the work ahead to continue to advance the research goals.

    Continue reading ‘A mid-decade check-in: the NOAA ocean, coastal, and Great Lakes acidification research plan 2020-2029’

    Share if you are attending UNOC or the One Ocean Science Congress

    Published 19 May 2025 Uncategorized Closed

    Both the One Ocean Science Congress and the third United Nations Oceans Conference (UNOC) are taking place in Nice, France in June 2025. To know who from the ocean acidification community is attending, the Global Ocean Acidification Observing Network (GOA-ON) has created a survey. Please fill out the survey if you are attending either of the events in Nice and share with ocean acidification colleagues who are coming as well.

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    Hydrothermal vents as observatories for future ocean acidification (OA) scenarios: an in-situ study to unravel the involvement of ATP binding cassette transporters in the adaptation of marine polychaetes Platynereis spp. to OA

    Published 16 May 2025 Science Closed
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    The marine annelid Platynereis dumerilii, is a key model in genetics, evolution, neurobiology, ecology, and ecotoxicology. Along with its sibling species, P. cfr massiliensis, it thrives in both normal and naturally acidified environments. This makes these species ideal candidates for studying mechanisms of tolerance to acidified conditions, resembling future ocean acidification (OA) scenarios. The ATP-binding cassette (ABC) transport proteins help mitigating the adverse impacts of drugs, xenobiotics and physical stressors. There is growing evidence for their involvement to mediate tolerance towards acid-stress in bacteria and tumor cell lines. Such a function may be relevant for the ability of marine species to cope with OA and may be important to consider when predicting future OA scenarios for marine fauna. Here we addressed the question if ABC transporters of Platynereis spp. are involved in compensating adverse effects of low pH by studying ABC transporter transcript levels in marine animals exposed to various pH levels. We firstly examined P. dumerilii whole genome data (version EMBL_pdum_1.0, Genbank assembly: GCA_026936325.1) for the presence of ABC transporter genes, by homology searches, and, using the single-cell atlas database with P. dumerilii gene expression data, we then determined the presence of a potentially relevant subset of ABC transporters from the ABCB, C and G subfamilies in different organs/tissues. Finally, to assess how seawater pH affects ABC transporter expression, we conducted an in-situ reciprocal transplant experiment involving individuals of P. dumerilii/P. cfr massiliensis. Adult specimens were collected inside and outside the CO2 vents off Castello Aragonese (Ischia Island, Italy). Individuals collected from normal pH areas (8.18 ± 0.005) were transplanted to acidified conditions (7.33 ± 0.312), and vice versa, while others were placed in their original areas. We found 81 orthologs from ABC transporter subfamilies A-G, expressed in different organs/tissues including midgut, neurons, body epidermis and ectodermal cells, and somatic and visceral muscle. Following the 30 days transplant experiment, qPCR analyses were performed to examine the expression levels of seven selected genes from the ABCB, ABCC, and ABCG subfamilies (abcb_1, abcb_2, abcb_3, abcc_1, abcc_2, abcc_3, and abcg). Three of these genes were differentially expressed in specimens transplanted from normal pH to low pH areas (abcb_1 and abcg up-regulated while abcb_3 down-regulated). Based on the homology with human ABCB1 and ABCG2, which are crucial in tumor cell adaptation to acidified environments, it seems reasonable to hypothesize that abcb_1, abcb_3 and abcg play a similar role in Platynereis spp. helping in maintaining cellular homeostasis and surviving acid stress.

    Continue reading ‘Hydrothermal vents as observatories for future ocean acidification (OA) scenarios: an in-situ study to unravel the involvement of ATP binding cassette transporters in the adaptation of marine polychaetes Platynereis spp. to OA’

    Ocean Sciences Meeting town hall and session proposal brainstorming

    Published 15 May 2025 Meetings Closed

    The deadline for session and town hall proposal submissions to the 2026 Ocean Sciences Meeting is fast approaching on May 28th, and the GOA-ON secretariat has created a spreadsheet to track ideas for submissions within the OA community. 

    Have an idea for a session or town hall? Add it ASAP to the brainstorming spreadsheet and see what others are planning. Reach out to a previous submitter if you’re interested in learning more about their idea or potentially collaborating on their session. 

    You’re welcome to add an idea for an OA-relevant session even if you’re not a GOA-ON member. Questions or interested in joining GOA-ON? Email secretariat@goa-on.org. 

    Continue reading ‘Ocean Sciences Meeting town hall and session proposal brainstorming’

    Climate change and its impact on marine biodiversity: a study of ocean acidification and coral reef health

    Published 14 May 2025 Science Closed
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    The ongoing changes in climate have led to a significant increase in atmospheric CO₂ levels, resulting in ocean acidification, a process that is having profound effects on marine biodiversity, particularly on coral reef ecosystems. Coral reefs, one of the most diverse ecosystems on the planet, are increasingly vulnerable to rising ocean temperatures and the decrease in ocean pH caused by increased carbon dioxide absorption. This paper explores the interconnectedness between ocean acidification, climate change, and the health of coral reef ecosystems, focusing on the impact of reduced pH levels on marine species’ survival, reproduction, and overall biodiversity. We also examine the potential long-term consequences for human communities that depend on these ecosystems for food, tourism, and coastal protection. Through a synthesis of recent studies, this paper aims to provide a comprehensive understanding of the mechanisms by which climate change is reshaping marine life and the urgent need for mitigation and adaptation strategies to safeguard marine biodiversity.

    Continue reading ‘Climate change and its impact on marine biodiversity: a study of ocean acidification and coral reef health’

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