Archive Page 51

Satellite-derived ocean color data for monitoring pCO2 dynamics in the North Indian Ocean

Published 27 January 2025 Science Closed
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Highlights

  • A Multiparametric Linear Regression (MLR) model was developed using in-situ and satellite observations to accurately estimate pCO2 in the NIO region.
  • Validation of the MLR model showed significant low errors (MRE = 0.08, MNB = 0.013, RMSE = 7.26 μatm) and a high correlation coefficient (R2 = 0.96), demonstrating superior performance.
  • The interannual (2012-2022) variability of pCO2 in the NIO region shows an increasing trend.
  • The study reveals seasonal variability in pCO2 in the NIO, peaking pre and post-monsoon, influencing marine ecosystems.

Abstract

The partial pressure of carbon dioxide (pCO2) in the North Indian Ocean (NIO) undergoes significant variations due to factors such as biological activity, ocean circulation patterns, and atmospheric influences. Understanding these variations is crucial for assessing the ocean role in the global carbon cycle and their impact on climate change. Estimating pCO2 through in-situ platforms is challenging due to the time-consuming, expensive, and complex nature of water sample collection, particularly under rough oceanic conditions. Conversely, remote sensing technology offers high spatiotemporal resolution data over extensive synoptic scales, making it a valuable tool for pCO2 estimation. Current models for estimating pCO2 in the NIO region are limited due to the improper selection of model parameters and the scarcity of in-situ measurements, highlighting the need for a more accurate approach. This study develops a Multiparametric Linear Regression (MLR) method, integrating satellite and in-situ observations of sea surface temperature (SST), sea surface salinity (SSS), and chlorophyll-a (Chla) concentration. To develop and validate this model, in-situ data were sourced from the Global Ocean Data Analysis Project (GLODAP). Validation results showed that the proposed MLR approach outperformed existing global models, achieving low mean relative error (MRE = 0.08), mean normalized bias (MNB = 0.013), and root mean square error (RMSE = 7.26 μatm), with a high correlation coefficient (R2 = 0.96). This study has the potential to improve understanding of carbon dynamics in the NIO region and its contribution to the global carbon cycle. The pCO2 maps generated in this study improve climate modeling and monitoring, supporting predictions and mitigation efforts. This accurate model also aids policy-making, environmental management, and ecological assessments.

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Ocean climate change and ocean acidification indicators for Ireland’s marine strategy framework directive

Published 27 January 2025 Newsletters and reports Closed
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Oceanographic physical and chemical processes underpin the functioning of marine ecosystems; changes to these marine environmental conditions due to human activity could significantly impact marine life. Monitoring and assessing these processes, and their interplay with biological systems provide insights into the current impacts of climate change and allow us to parameterise models which can help us understand what could happen to marine ecosystems under different climate scenarios. Currently, the monitoring and assessment of ocean climate change is not mandated under any EU legislation. Recent guidance from the European Commission has made recommendations on how Member States could consider climate change within the Marine Strategy Framework Directive (MSFD) and paves the way for its potential inclusion in this Directive. This report explores how Ireland could integrate climate change into MSFD assessments through linking potential new and existing MSFD indicators with associated Essential Ocean Variables.

Systematic measurements of essential ocean variables underpin our understanding of ocean climate change and ocean acidification. Ireland monitors a number of essential ocean variables through fixed moorings, annual surveys, and sentinel sites. Data collected through these monitoring programmes are included in national, regional, and international assessments and reports, including the Global Carbon Budget. Ireland included thirty-four indicators in their Article 8 assessment in 2024 and current essential ocean variable monitoring data is used to assess some of these indicators. This provides an initial link between MSFD reporting and essential ocean variables and presents a starting point of how climate change could be integrated more in MSFD assessments.

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IAEA’s Ocean Acidification International Coordination Centre trains scientists to evaluate impacts of ocean changes on marine organisms

Published 27 January 2025 Web sites and blogs Closed

IAEA scientist Francois Oberhaensli showcases aquabenches, which can recreate various aquatic environments, at the IAEA Marine Environment Laboratories. (Photo: L. Hansson/IAEA)

In November of last year, the second Winter School on Ocean Acidification and Multiple Stressors held at the IAEA Marine Environment Laboratories in Monaco provided early-career scientists with new tools and knowledge to address challenges to sustainable ocean health. By equipping a new generation of researchers with these skills, the Winter School is paving the way for more effective management and preservation of marine ecosystems in the face of global challenges, impacting communities worldwide that depend on marine resources.

As human activities intensify, coastal and marine ecosystems face mounting pressures, from overfishing and pollution to climate change and ocean acidification. The combined effects of these “stressors” often far exceed their individual impacts, threatening biodiversity and livelihoods worldwide. Yet, research on how these drivers combine to affect marine life is complex, and remains limited, with many studies often lacking robust design or misusing key concepts. Understanding how these stressors interact is crucial for predicting their impacts on marine ecosystems and developing strategies to mitigate these effects, particularly in regions heavily dependent on marine resources.

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Perspectives from developers and users of the GOA-ON in a box kit: a model for capacity sharing in ocean sciences

Published 24 January 2025 Science Closed
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Providing reliable instrumentation that enables collection of high-​quality, comparable data is one of the most challenging aspects of establishing ocean acidification monitoring programs. This is especially true for under-resourced countries, where such data are mostly unavailable. In 2016, The Ocean Foundation (TOF) worked with international bodies, including the International Atomic Energy Agency’s Ocean Acidification International Coordination Centre and the Global Ocean Acidification Observing Network (GOA-ON), and subject matter experts to develop a set of equipment known as the “GOA-ON in a Box” kit (The Ocean Foundation, 2017). This comprehensive kit provides researchers with everything needed—down to specialized rubber bands—to obtain weather-quality carbonate system measurements as defined by GOA-ON (Newton et al., 2015). Data are generated from spectrophotometric measurements of pHT and manual titrations for total alkalinity from discrete samples as well as in situ sensors, the iSAMI-pH and a CTD. The kit’s modular design, composed of nearly 100 unique items, makes it much less expensive than comparable integrated systems and allows for easier troubleshooting and replacement of supplied spare components.

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Job opportunity: scientist – ocean acidification and climate change impact on marine ecosystems

Published 24 January 2025 Jobs Closed

Job description

The Marine and Freshwater Research Institute (MFRI) in Iceland is seeking to hire an accomplished and motivated scientist to enhance its expertise in ocean acidification impacts and the broader effects of climate change on marine organisms and ecosystems. The candidate is expected to develop and work on a wide range of research projects that increase understanding of ocean acidification and climate change impact through a variety of methods such as fieldwork, scientific cruises, experimentation and/or modeling. The institute has nearly completed setting up an experimental facility to investigate the impact of ocean acidification, temperature and other environmental parameters.

The candidate will have a role in developing and taking part in research using that facility and is expected to facilitate capacity building through collaboration and mentoring.

The MFRI is a governmental institute and a leader in marine research in Iceland. The position is full time and permanent and will include diverse work in line with the role of the institute such as increasing knowledge on the marine ecosystem in the region, providing advice to ensure a sustainable use of marine resources and public outreach.

The candidate will join a team of about 25 people working in the environmental division but in line with the interdisciplinary nature of the work, tasks will involve working on diverse collaboration projects with external parties and with a diverse group of scientists across the institute.

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Applications open: Training Course on Ocean Alkalinity Enhancement — Assessing the Impacts on Marine Organisms

Published 24 January 2025 Courses and training Closed

Dates: 7–11 April 2025

Location: IAEA Marine Environment Laboratories in Monaco

Deadline for receipt of application from the nominating national authority: 21 February 2025

The course is organized by the IAEA OA-ICC in partnership with the Prince Albert II of Monaco Foundation through the OACIS Initiative (Ocean Acidification and other ocean Changes – Impacts and Solutions).

Introduction

The Training Course on Ocean Alkalinity Enhancement — Assessing the Impacts on Marine Organisms is part of the capacity building program of the IAEA Ocean Acidification International Coordination Centre (OA-ICC). The program aims to support IAEA Member States to minimize and address the impacts of ocean acidification (Sustainable Development Goal 14.3) and related stressors.

Objectives

The ocean is under pressure from warming, acidification and oxygen loss, adversely impacting marine ecosystems and the communities and societies who depend on them. But the ocean, covering 70% of Earth’s surface, can also be a vital part of the solution and our ally to mitigate and adapt to climate change. Meeting the objectives of the Paris Agreement to limit warming to well below 2º C would not only require drastic cuts in carbon dioxide (CO2) emissions, but also the active removal of carbon CO2 on the order of 100–1000 Gt CO2 over the 21st century (IPCC, 2018). Ocean alkalinity enhancement (OAE) is a marine Carbon Dioxide Removal (mCDR) approach which is receiving growing interest from scientists, policy makers and industry. It entails the addition of alkaline materials to the sea with the goal to increase the ocean’s potential to absorb CO2. There is limited scientific information to date about the impact that OAE might have on marine organisms and ecosystems. Building technical expertise to assess ecological impacts of OAE is critically needed to allow for informed policy decisions about this approach.

The aim of this course is to train scientists on how to perform laboratory experiments on the potential impacts of OAE on marine organisms. The course includes both theoretical and practical exercises with the goal to design purposeful experiments, analyze complex datasets, avoid typical pitfalls, and ensure data comparability with other studies. Lectures on the broader context and implications of OAE will also be provided (e.g., societal and governance aspects). The course will be largely based on the 2023 Guide to Best Practices for Ocean Alkalinity Enhancement Research, especially the chapters on experimental design.

Target Audience

The course is open to 10-12 trainees. Priority will be given to early-career scientists with experience in marine environmental changes who already received training on ocean acidification and seawater carbonate chemistry. At least one publication in the field of marine environmental changes is required.

Working Language

English

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Participation and Registration

Scientists wishing to participate in the event must 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 21 February 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 regard 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 must have already received training on ocean acidification and seawater carbonate chemistry or performed ocean acidification experiments.

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

  • A motivation letter with a short description of your research interests, why you would like to participate, and your plans regarding present and future research on OAE (max one A4 page)
  • CV with publication list
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Delayed ocean acidification confirmed in Gulf of Maine

Published 23 January 2025 Press releases Closed
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Recent research indicates a delayed onset of ocean acidification in the Gulf of Maine due to complex water mass interactions and temperature variations. The Gulf of Maine, significant for its ecological and economic value, particularly for fisheries, has become the focus of increasing scrutiny due to concerns about rising atmospheric CO2 levels affecting marine life。

The study reveals a surprising trend: seawater pH levels were low (~7.9) for much of the last century, but increased by +0.2 pH units over the past 40 years, contradicting the rising levels of atmospheric CO2. This unexpected increase raises questions about the factors influencing coastal water chemistry and the potential impacts on marine species.

Conducted by researchers including J.A. Stewart, B. Williams, and M. LaVigne, the study spans pH records from 1920 to 2018 CE, primarily focusing on changes noted from 1980 to 2000 CE. The researchers employed boron isotope measurements from long-lived coralline algae to create proxy records indicating seawater pH trends.

Significantly, the researchers highlight the remarkable interplay between different water masses within the Gulf of Maine. The influx of warmer, higher alkalinity waters derived from the Gulf Stream contributed to the increased pH, acting as a buffer against ocean acidification’s effects.

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Delayed onset of ocean acidification in the Gulf of Maine

Published 23 January 2025 Science Closed
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The Gulf of Maine holds significant ecological and economic value for fisheries and communities in north-eastern North America. However, there is apprehension regarding its vulnerability to the effects of increasing atmospheric CO2. Substantial recent warming and the inflow of low alkalinity waters into the Gulf of Maine have raised concerns about the impact of ocean acidification on resident marine calcifiers (e.g. oysters, clams, mussels). With limited seawater pH records, the natural variability and drivers of pH in this region remain unclear. To address this, we present coastal water pH proxy records using boron isotope (δ11B) measurements in long-lived, annually banded, crustose coralline algae (1920–2018 CE). These records indicate seawater pH was low (~ 7.9) for much of the last century. Contrary to expectation, we also find that pH has increased (+ 0.2 pH units) over the past 40 years, despite concurrent rising atmospheric CO2. This increase is attributed to an increased input of high alkalinity waters derived from the Gulf Stream. This delayed onset of ocean acidification is cause for concern. Once ocean circulation-driven buffering effects reach their limit, seawater pH decline may occur swiftly. This would profoundly harm shellfisheries and the broader Gulf of Maine ecosystem.

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The spatiotemporal distribution of dissolved inorganic carbon in the global ocean interior: reconstructed through machine learning

Published 22 January 2025 Science Closed
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The oceans mitigate climate change by absorbing approximately 25% of anthropogenic carbon emissions. Decadal variability in the ocean carbon sink, such as a weakening in the 1990s and a strengthening in the 2000s, has been suggested by pCO2-based reconstructions, but its causes remain poorly understood. This variability is also not well represented in climate models, raising concerns about our ability to accurately project future changes. To address potential biases from sparse observational data, machine learning methods have been applied to surface pCO2 and interior dissolved inorganic carbon (DIC), but global reconstructions of full-depth DIC remain lacking. We aim to determine whether ocean carbon sink variability is real and to understand the role of interior DIC inventory changes in the carbon budget. Using neural networks trained on GLODAPv2.2023 observations and predictors like atmospheric CO2, location, temperature, and salinity from EN4 analysis, we reconstruct full-depth global DIC distributions from the 1990s to the 2010s using a residual neural network (ResNet). Validation through prediction of independent datasets show an improvement over previous products. Validation with the ECCO-Darwin dataset results in an average RMSE of 15.1 µmol/kg and bias of -0.3 µmol/kg. The global average uncertainty is 16.85 µmol/kg. The global change in the DIC inventory exhibits pronounced peaks in decadal variability, especially in the early 2000s driven primarily by intermediate waters at depths of 300-1200 m, particularly in the Atlantic, Indian, and Southern Oceans, and to a lesser extent in the Pacific. The accumulation rate of DIC increases steadily from the mid-2000s.

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Single-larva RNA sequencing reveals that red sea urchin larvae are vulnerable to co-occurring ocean acidification and hypoxia

Published 22 January 2025 Science Closed
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Anthropogenic carbon dioxide emissions have been increasing rapidly in recent years, driving pH and oxygen levels to record low concentrations in the oceans. Eastern boundary upwelling systems such as the California Current System (CCS) experience exacerbated ocean acidification and hypoxia (OAH) due to the physical and chemical properties of the transported deeper waters. Research efforts have significantly increased in recent years to investigate the deleterious effects of climate change on marine species, but have not focused on the impacts of simultaneous OAH stressor exposure. Additionally, few studies have explored the physiological impacts of these environmental stressors on the earliest life stages, which are more vulnerable and represent natural population bottlenecks in organismal life cycles. The physiological response of the ecologically and commercially important red sea urchin (Mesocentrotus franciscanus) was assessed by exposing larvae to a variety of OAH conditions, mimicking the range of ecologically relevant conditions encountered currently and in the near future along the CCS. Skeleton dissolution, larval development, and gene expression show a response with clearly delineated thresholds that were related to OAH severity. Skeletal dissolution and the induction of Acid-sensing Ion Channel 1A at pH 7.94/5.70 DO mg/L provide particularly sensitive markers of OAH, with dramatic shifts in larval morphology and gene expression detected at the pH/DO transition of 7.71/3.71–7.27/2.72 mg/L. Experimental simulations that describe physiological thresholds and establish molecular markers of OAH exposure will provide fishery management with the tools to predict patterns of larval recruitment and forecast population dynamics.

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Exposure to a gradient of warming and acidification highlights physiological,molecular, and skeletal tolerance thresholds in Pocillopora acuta recruits

Published 21 January 2025 Science Closed
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Ocean warming and acidification are among the biggest threats to the persistence of coral reefs. Organismal stress tolerance thresholds are life stage specific, can vary across levels of biological organization, and also depend on natural environmental variability. Here, we exposed the early life stages of Pocillopora acuta in Kāne‘ohe Bay, Hawai‘i, USA, a common reef-building coral throughout the Pacific, to projected ocean warming and acidification scenarios. We measured ecological, physiological, biomineralization, and molecular responses across the critical transition from larvae to newly settled recruits following 6 days of exposure to diel fluctuations in temperature and pH in Control (26.8-27.9°C, 7.82-7.96 pHTotal), Mid (28.4-29.5°C, 7.65-7.79 pHTotal) and High conditions (30.2-31.5°C, 7.44-7.59 pHTotal). We found that P. acuta early life stages are capable of survival, settlement, and calcification under all scenarios. The High conditions, however, caused a significant reduction in survival and settlement capacity, with changes in the skeletal fiber deposition patterns. In contrast to a limited impact on the expression of biomineralization genes, the dominant transcriptomic response to the High conditions relative to the two other treatments included depressed metabolism, reduced ATP production and increased activity of DNA damage-repair processes. Collectively, our findings indicate that corals living in environments with large diurnal fluctuations in seawater temperature and pH, such as Kāne‘ohe Bay, can tolerate exposure to moderate projected increased temperature and reduced pH. However, under more severe environmental conditions significant negative effects on coral cellular metabolism and overall organismal survival jeopardize species fitness and recruitment.

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Oceanic enrichment of ammonium and its impacts on phytoplankton community composition under a high-emissions scenario

Published 21 January 2025 Science Closed
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Ammonium (NH4+) is an important component of the ocean’s dissolved inorganic nitrogen (DIN) pool, especially in stratified marine environments where intense recycling of organic matter elevates its supply over other forms. Using a global ocean biogeochemical model with good fidelity to the sparse NH4+ data that is available, we project increases in the NH4+:DIN ratio in over 98% of the ocean by the end of the 21st century under a high-emission scenario. This relative enrichment of NH4+ is driven largely by circulation changes, and secondarily by warming-induced increases in microbial metabolism, as well as reduced nitrification rates due to pH decreases. Supplementing our model projections with geochemical measurements and phytoplankton abundance data from Tara Oceans, we demonstrate that shifts in the form of DIN to NH4+ may impact phytoplankton communities by disadvantaging nitrate-dependent taxa like diatoms while promoting taxa better adapted to NH4+. This could have cascading effects on marine food webs, carbon cycling, and fisheries productivity. Overall, the form of bioavailable nitrogen emerges as an potentially underappreciated driver of ecosystem structure and function in the changing ocean.

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Meta-analysis of larval bivalve growth in response to ocean acidification and its application to sea scallop larval dispersal in the Mid-Atlantic Bight

Published 21 January 2025 Science Closed
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Ocean acidification, caused by increasing atmospheric carbon dioxide and coastal physical, biological, and chemical processes, is an ongoing threat to carbonate-utilizing organisms living in productive coastal shelves. Bivalves exposed to acidification have shown reduced growth, reproduction, and metabolic processes, with larval stages exhibiting the greatest susceptibility. Here, we compile results from published studies on larval bivalve growth responses to acidification to estimate a relationship between larval growth and seawater aragonite saturation state. We then apply this relationship to a larval dispersal individual-based model for Atlantic sea scallops (Placopecten magellanicus), an economically vital species in the Mid-Atlantic Bight that is historically under-studied in acidification research. To date, there have been no published studies on sea scallop larval response to ocean acidification. Model simulations allowed the identification of potential impacts of acidification on scallop success in the region. Results show that larval sea scallops that are sensitive to ocean acidification had a 17% lower settlement success rate and over 50% reduction in larval passage between major Mid Atlantic Bight fisheries habitats than those that are not sensitive to acidification. Additionally, temperature and ocean acidification interact as drivers of larval success, with aragonite saturation states > 3.0 compensating for temperature-induced mortality (> 19 ˚C) in some cases. This balance between drivers influences larval settlement success across spatial and interannual scales in the Mid Atlantic Bight.

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The ITLOS advisory opinion on climate change: revisiting the relationship between the United Nations Convention on the Law of the Sea and the Paris Agreement

Published 21 January 2025 Science Closed
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The International Tribunal for the Law of the Sea (ITLOS) has issued its highly anticipated Advisory Opinion on Climate Change and International Law, following a request from the Commission of Small Island States on Climate Change and International Law (COSIS). The landmark Advisory Opinion elucidated numerous contentious issues around the interplay between the climate change and the law of the sea regimes. This article critically examines the ITLOS Advisory Opinion with respect to the relationship between the Paris Agreement and the United Nations Convention on the Law of the Sea (UNCLOS), contextualising them within the extensive academic and political discourse preceding the Opinion. In particular, the lex specialis question is brought into sharper focus. The Tribunal rejected the notion that the Paris Agreement is lex specialis with respect to climate change impacts on the ocean and clarified the nexus between adaptation measures and the overarching obligation to protect and preserve the marine environment. The analysis reveals that the Advisory Opinion conveys a generally critical view of the Paris Agreement, and may, despite its imposition of far-reaching obligations upon States to mitigate marine pollution from greenhouse gases, inadvertently undermine global efforts to combat climate change. However, by articulating concrete legal obligations for States under the UNCLOS to prevent, control and reduce marine pollution from greenhouse gas emissions, the Advisory Opinion could further strengthen the legal foundations for domestic and international climate change litigation and elevate the profile of the oceans in global climate change negotiations

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Iron and phosphorus limitations modulate the effects of carbon dioxide enrichment on a unicellular nitrogen-fixing cyanobacterium

Published 21 January 2025 Science Closed
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Iron (Fe) and phosphorus (P) availability constrain the growth and N2 fixation of diazotrophic cyanobacteria in the global ocean. However, how Fe and P limitation may modulate the effects of ocean acidification on the unicellular diazotrophic cyanobacterium Crocosphaera remains largely unknown. Here, we examined the physiological responses of Crocosphaera watsonii WH8501 to CO2 enrichment under both nutrient-replete and steadily Fe- or P-limited conditions. Increased CO2 (750 μatm vs. 400 μatm) reduced the growth and N2 fixation rates of Crocosphaera, with Fe limitation intensifying the negative effect, whereas CO2 enrichment had a minimal impact under P limitation. Mechanistically, the high CO2 treatment may have led to a reallocation of limited Fe to nitrogenase synthesis to compensate for the reduction in nitrogenase efficiency caused by low pH; consequently, other Fe-requiring metabolic pathways, such as respiration and photosynthesis, were impaired, which in turn amplified the negative effects of acidification. Conversely, under P limitation, CO2 enrichment had little or no effect on cellular P allocation among major P-containing molecules (polyphosphate, phospholipids, DNA, and RNA). Cell volumes were significantly reduced in P-limited and high CO2 cultures, which increased the surface : volume ratio and could facilitate nutrient uptake, thereby alleviating some of the negative effect of acidification on N2 fixation. These findings highlight the distinct responses of Crocosphaera to high CO2 under different nutrient conditions, improving a predictive understanding of global N2 fixation in future acidified oceans.

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Physiochemical responses of an asterinid starfish (Echinodermata: Asteroidea) to global ocean change

Published 20 January 2025 Science Closed
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The continuous increase in greenhouse gas (GHG) emissions, especially carbon dioxide (CO2), since the beginning of global industrialization has resulted in significant alterations in seawater physicochemical properties, particularly elevated seawater temperatures (ocean warming, OW) and ocean acidification (OA). These changes have wide-ranging consequences for marine organisms, affecting their biological functions and ecological roles. The combined effects of OW and OA may amplify adverse outcomes compared to individual stressors due to the complex reorganization of cellular mechanisms and molecular pathways, which subsequently appear in behavioral modifications. However, organismal reactions and thresholds to these stressors are variable, which might differ within organism ontogeny or among taxa, making predictions challenging. Therefore, increasing research has been performed to better understand the potential mechanisms underlying the ability of marine organisms to alleviate the effects of environmental change, mainly due to OW and OA. Thus, employing multiple bioindicators, specifically keystone species such as starfish, to evaluate the impacts of OW and OA offers a comprehensive approach to examining their effects not simply on the organism concerned but also on the broader ecosystem.

The presented studies in this thesis aim to contribute to the understanding the role of physiochemistry and trade-offs on marine ectotherms, particularly asterinid starfish, in coping with environmental stress. For this purpose, mineralogic, metabolic, behavioral, lipidomics, and enzymatic activity approaches are used. The research summarized in this thesis provides the first investigation of the effects of global ocean change on biomineralization and physiological traits through long-term experiments using asterinid starfish species, Aquilonastra yairi, distributed in tropical to subtropical regions (across the Mediterranean Sea, Red Sea, and Gulf of Suez). The starfish were exposed to two temperature levels (27 °C and 32 °C) crossed with three pCO2 regimes (455 µatm, 1052 µatm, and 2066 µatm), representing factorial combinations of ambient conditions and future levels of CO2 and temperature change according to the IPCC-Representative Concentration Pathways (RCPs) 8.5 greenhouse gas emission scenario for the year 2100.

The present work revealed that asterinid starfish demonstrate high stressor tolerance and resilience to increased temperature and pCO2 through adaptive adjustments in physiological functions or behavioral activities, suggesting high homeostatic capacities and the ability to regulate physiochemical response to maintain survival, fitness, and metabolic biosynthesis under chronic conditions. The temperature was the predominant factor, exerting a significant effect on the magnitude and frequency of the affected physiological-related processes; however, concurrent exposure to OA and OW stress produced synergistic effects on some of the starfish physiology-related responses tested. While decreased pH negatively affects starfish calcification performance, the increased temperature potentially mitigates these effects. However, increased temperature might also lead to more magnesium (Mg2+) incorporation into the calcite lattice, potentially compromising the starfish skeleton. Furthermore, it was revealed that starfish can preserve lipid-associated biochemistry (FAs) under elevated temperature and pCO2, which potentially provides molecular instruments to cope with future OA and OW scenarios. However, combined OA and OW significantly affected Ca-ATPase and Mg-ATPase enzyme activities, which are recognized to play an important role in the biomineralization pathway, raising concerns about potential susceptibilities in skeletal development and preservation.

Investigating the complex impacts of global ocean change on marine organisms requires a comprehensive research approach that encompasses diverse biological, chemical, and physical traits. Understanding the physiological and chemical responses of bioindicator species, e.g., asterinid starfish, to combined stressors OW and OA is important to comprehend the relationships and interactions between biological processes and abiotic environmental conditions, which in turn essential for accurately predicting their resilience, ecological implication, and broader ecosystem dynamics. At the ecosystem scale, this study significantly contributes to the ongoing knowledge for future studies of the impact of climate change on coral reef-associated invertebrates. Specifically, this finding is beneficial for the conservation of coral reef ecosystems under future ocean conditions.

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Carbon cycling and ocean acidification studies in Baffin Bay and Nares Strait

Published 20 January 2025 Science Closed
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The marine carbon cycle in Canadian Arctic waters, particularly in Nares Strait and Baffin Bay, is undergoing rapid change due to a shifting climate. Despite this, there’s been a paucity of research into the carbonate chemistry and biogeochemical processes in these regions. This thesis addresses this gap by investigating the complex carbon dynamics in these waters, critical for understanding their role in the global carbon cycle. The first research chapter evaluates the strength of the biological carbon pump during the spring ice-edge bloom in Baffin Bay. We found stark differences in springtime net community production (NCP) between Arctic and Atlantic water domains, in western and eastern Baffin Bay, respectively. Arctic outflow waters exhibited low spring NCP (< 1 mol C m-2) due to persistent sea-ice cover and strong stratification of the upper water column, whereas the Atlantic water domain displayed high NCP rates (up to 5.7 mol C m-2). The first comprehensive examination of the marine carbon dynamics in Nares Strait is also presented. Using a multi-tracer linear mixing model, we distinguished the role of physical and biological processes on the distribution of dissolved inorganic carbon in Nares Strait. We identified water mass mixing as the dominant control on marine carbon dynamics, with primary production also playing an important role in decreasing surface pCO2. Importantly, this investigation also provided the first documented evidence of Siberian river waters arriving in Nares Strait. The final research chapter of this thesis investigates the biogeochemical processes affecting aragonite saturation states (ΩAr), and the state of ocean acidification in Baffin Bay, with a focus on the west Greenland continental shelf region, which has remained under-studied in terms of its marine biogeochemistry. We identify two main depth-dependent processes shaping the ΩAr distribution throughout Baffin Bay; within the upper 200 metres, lower ΩAr coincides with increasing fractions of Arctic-outflow waters, while below 200 metres organic matter respiration is responsible for decreasing ΩAr. Surprisingly, substantial Arctic-outflow waters were identified on the west Greenland shelf, challenging what is currently known of circulation patterns in the bay, and underscoring the need for further research.

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PML Science urges accelerated action on ocean acidification at UN high-level ocean retreat

Published 17 January 2025 Web sites and blogs Closed
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Plymouth Marine Laboratory (PML) Director of Science, Professor Steve Widdicombe, is participating in the United Nations’ High-Level Retreat on ‘Investing in Ocean Solutions’, taking place this week (January 14 – 15) in Incheon, Republic of Korea. The retreat serves as a crucial preparatory meeting for the third United Nations Ocean Conference (UNOC3) in Nice, France, later this year and is focused on accelerating progress toward sustainable ocean management and conservation. 

As Co-Chair of the Global Ocean Acidification Observing Network (GOA-ON) and focal point for ocean acidification under the UN’s Sustainable Development Goal 14: Life Under Water, Professor Widdicombe is discussing progress on voluntary commitments related to ocean acidification.   

The reduction in the pH of the Ocean, which occurs when seawater absorbs increasing amounts of carbon dioxide from the atmosphere, poses a significant threat to marine ecosystems and the communities that depend on them. Target 14.3 of the Sustainable Development Goals specifically calls for minimising and addressing the impacts of ocean acidification through enhanced scientific cooperation at all levels. 

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OAP funds 7 ocean acidification education projects across the nation

Published 17 January 2025 Web sites and blogs Closed
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The NOAA Ocean Acidification Program (OAP) is pleased to announce the FY24 Education Mini-grant Program awards. The seven projects selected for this competitive grant opportunity will deliver ocean and coastal acidification education tools and programs in underserved and/or Indigenous communities or Tribes. The awarded projects are led by Tribal members, nonprofit organizations, academic institutions, and public organizations. The work will occur across the nation in American Samoa, the U.S. West Coast, Alabama, and North Carolina, filling some gaps in ocean acidification education and outreach and reaching new communities.

Ocean and coastal acidification are emerging issues that have far reaching impacts on ocean health and long-term sustainability of ecosystems and people. It is critical that educators have access to the latest science and tools on these topics and are able to effectively share the science of ocean and coastal acidification, potential impacts and positive actions to diverse audiences in accessible ways. 

Each project will address at least one of three goals laid out in the NOAA Ocean Acidification Education Implementation Plan. The proposed work will engage students, particularly from underserved and/or Indigenous communities or Tribes. This funding aims to increase ocean acidification awareness and action, and foster interest in career pathways in NOAA mission disciplines. 

Continue reading ‘OAP funds 7 ocean acidification education projects across the nation’

Effects of ocean acidification and warming on apoptosis and immune response in the mussel Mytilus coruscus

Published 17 January 2025 Science Closed
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Highlights

  • Global warming and ocean acidification induce changes in hemocyte immune indicators in mussels.
  • Most immune responses are severely impaired due to the combined stress of high temperature and acidification.
  • Temperature and pH have interactive effects on all immune parameters of hemocyte.
  • Warming and acidification affect both intrinsic and extrinsic pathways of cell apoptosis.

Abstract

Ocean acidification and warming are significant stressors impacting marine ecosystems, exerting profound effects on the physiological ecology of marine organisms. We investigated the impact of ocean acidification and warming on the immune system of mussels, focusing on the regulatory mechanisms of intrinsic and extrinsic apoptosis. The study explored the effects on the immune response ability of mussels (Mytilus coruscus) after 14 and 21 days under combined conditions of different temperatures (20 °C and 30 °C) and pH (8.1 and 7.7), as expected for the year 2100. The experimental results indicated that ocean acidification and warming have significant interactive effects on various immune parameters of M. coruscus. Specifically, ocean acidification and warming lead to an increase in ROS (Reactive Oxygen Species), apoptosis, TNF-α (Tumor Necrosis Factor-alpha), TGF-β (Transforming Growth Factor-beta), Caspase-8, and a decrease in IL-17 (Interleukin 17). These findings suggest that ocean acidification and warming trigger an immune inflammatory response in mussels. Regulating immune functions through apoptosis pathways may be a crucial coping mechanism in response to environmental variations, but its long-term impact on population health and sustainability remains uncertain. Our findings offer important insights into the complex interactions between bivalve immune responses and environmental stressors. This also underscores the need for further research into the adaptive capabilities of marine organisms facing the compounded challenges of ocean acidification and warming.

Continue reading ‘Effects of ocean acidification and warming on apoptosis and immune response in the mussel Mytilus coruscus’

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