Anthropogenic stressors, including ocean acidification (OA), ocean warming (OW), and salinity changes, are rapidly altering marine ecosystems, with Arctic regions being particularly vulnerable. This study investigates the combined effects of these stressors on the fertilization success of the green sea urchin (Strongylocentrotus droebachiensis) from Kongsfjorden, Svalbard. We exposed gametes to various levels of pH, temperature, and salinity to assess their individual and combined impacts on fertilization performance. Our results show that temperature and pH significantly influenced fertilization success, with temperature having the strongest effect, while salinity had no significant impact. A significant statistical interaction between temperature and pH indicated that warming enhanced fertilization more effectively at higher pH levels, while low pH suppressed this increase. To compare the relative influence of each stressor, we used a conceptual model based on standardized slopes, which supported temperature as the dominant driver, followed by pH. These findings highlight the importance of considering the effects of combined stressors when assessing marine organism responses to climate change, especially in polar ecosystems. Our study underscores the need for further research into the mechanisms driving these combined effects, given that Arctic ecosystems face accelerated environmental changes.
Continue reading ‘Combined effects of ocean acidification, warming, and salinity on the fertilization success in an Arctic population of sea urchins’Archive Page 4
Combined effects of ocean acidification, warming, and salinity on the fertilization success in an Arctic population of sea urchins
Published 9 January 2026 Science ClosedTags: Arctic, biological response, echinoderms, laboratory, multiple factors, reproduction, salinity, temperature
Effect of experimental seawater acidification on the prooxidant-antioxidant system of the Pacific oyster Magallana gigas (Thunberg, 1793) under normoxic and hypoxic conditions
Published 8 January 2026 Science ClosedTags: biological response, Black Sea, fisheries, laboratory, mollusks, mortality, multiple factors, oxygen, physiology
Highlights
- Lipid peroxidation in oyster gills was enhanced during exposure to acidification + hypoxia.
- SOD and GPx activities changed in gills and hepatopancreas, while CAT activity unchanged in both.
- Water acidification does not promote DNA strand breaks in hemocytes of M. gigas.
- Acidification + hypoxia more severe damaging than acidification under normoxia.
Abstract
Bivalve mollusks, particularly the Pacific oyster (Magallana gigas), are both environmentally and commercially significant species that live in coastal waters and may be affected by global climate change factors including hypoxia and acidification. In this study, we investigated the impact of acidification in combination with normoxia and hypoxia on oxidative stress markers in the gills and hepatopancreas of M. gigas oysters. Oysters were collected from a shellfish farm and subjected to acidified conditions (pH 7.3 ± 0.05) in combination with either normoxic (8.0 ± 0.3 mg/L O2) or hypoxic (2.0 ± 0.3 mg/L O2) conditions for an 8-day period. Changes of DNA damage levels, reactive oxygen species (ROS) production in hemocytes, as well as antioxidant enzyme activities (catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx)) and lipid peroxidation in the gills and hepatopancreas were evaluated. Additionally, the mortality rate in experimental groups was monitored throughout the experiment. Our results showed that lipid peroxidation in gills was enhanced during prolonged acidification in combination with hypoxia (6–8 days). We observed rapid and consistent changes in SOD and GPx activity in gills and hepatopancreas. CAT activity remained stable in both tissues. The results of the study indicate that acidification was shown to induce oxidative stress in oysters. Combination of acidic environment to hypoxia had a more severe effect on oysters compared to acidification under normal oxygen conditions, leading to their death after 8 days of exposure.
Continue reading ‘Effect of experimental seawater acidification on the prooxidant-antioxidant system of the Pacific oyster Magallana gigas (Thunberg, 1793) under normoxic and hypoxic conditions’A trend-based ecological indicator framework for spatially classifying ocean acidification risk to global coral reefs
Published 8 January 2026 Science ClosedTags: biological response, chemistry, corals, policy, review
Highlights
- Global aragonite saturation state declined at −0.0068 ± 0.00013 yr−1 from 1985 to 2023.
- Equatorial Pacific shows fastest acidification with Ωₐᵣ declines of −0.012 yr−1.
- Novel trend-based K-means clustering identifies emerging coral reef risk zones.
- Strong pCO₂-Ωₐᵣ correlations (ρ < −0.9) in tropical upwelling regions monthly.
- Framework supports SDG 14.3 and Global Biodiversity Framework implementation.
Abstract
Ocean acidification driven by anthropogenic CO₂ uptake poses a critical threat to coral reef ecosystems. Using global surface ocean carbonate data from 1985 to 2023, we provide a high-resolution, observation-based assessment of long-term trends in pCO₂, pH, and aragonite saturation state (Ωₐᵣ). Our results show a robust global decline in Ωₐᵣ (−0.0068 ± 0.00013 yr−1), with the most pronounced losses in the equatorial Pacific and Southern Hemisphere. Monthly correlations reveal strong inverse pCO₂–Ωₐᵣ relationships (ρ < −0.9) and positive pH–Ωₐᵣ correlations (ρ > 0.9) in tropical upwelling zones, highlighting spatially persistent acidification stress. A key innovation of this study is the use of a trend-based K-means clustering framework that classifies ocean regions into high, moderate, and low impact categories based on Ωₐᵣ decline rates. Unlike conventional assessments relying on absolute Ωₐᵣ thresholds, this approach identifies regions that remain suitable today but are deteriorating rapidly, thus at risk of crossing biological thresholds in the near future. High-impact zones, including the Coral Triangle and eastern tropical Pacific, show Ωₐᵣ declines of −0.010 to −0.012 yr−1 and have already reached levels near 2.4–3.0, suggesting growing stress on reef calcification. By leveraging high-resolution observational data rather than model projections, this approach reduces uncertainty and offers a scalable tool for anticipating ecological vulnerability under ongoing acidification. The findings underscore the urgent need for conservation in tropical high-impact zones and for sustained monitoring in lower-risk regions. This work provides a science-based framework to support spatially targeted reef management and informs global policy priorities including SDG 14.3 and the Global Biodiversity Framework.
Continue reading ‘A trend-based ecological indicator framework for spatially classifying ocean acidification risk to global coral reefs’Ocean acidification in Massachusetts bay and Boston harbor: insights from a 1-D modeling approach
Published 8 January 2026 Science ClosedTags: biogeochemistry, chemistry, modeling, North Atlantic, regionalmodeling
Highlights
- NeBEM, an ERSEM-based biogeochemical and ecosystem model, is established for the U.S. Northeast.
- NeBEM provides process-based insights into carbonate system variability beyond the capability of empirical data-fitting methods.
- Biological processes strongly influence TA and DIC variability in outer Massachusetts Bay.
Abstract
Massachusetts Bay (MB)/Boston Harbor (BH) in the northeastern United States has reduced buffering capability, making it highly vulnerable to ocean acidification (OA). We applied the U.S. Northeast Biogeochemistry and Ecosystem Model (NeBEM), integrating the unstructured grid, Finite Volume Community Ocean Model with a modified European Regional Seas Ecosystem Model (ERSEM), to investigate seasonal and interannual OA variability through one-dimensional (1-D) experiments. Objectives were to (a) evaluate model skill in reproducing observed seasonal cycles of OA-related variables, particularly pCO2 and pH, in shallow and deep regions, and (b) assess sensitivity to parameterizations and algorithms for calculating dissolved inorganic carbon (DIC), total alkalinity (TA), pCO2, and pH. The 1-D NeBEM reproduced variability of nutrients, dissolved oxygen, chlorophyll-a, pCO2, and pH at the deep outer bay site, where air-sea interactions dominate, but failed at the shallow inner bay site due to the absence of river discharge-driven advection. Of TA algorithms tested, the semi-diagnostic method best captured observed seasonal pCO2 variation, achieving the highest correlation and lowest root mean square error, although all methods performed similarly for pH. Comparisons with multi-linear regression methods showed that empirical models are highly sensitive to calibration set. Mechanistic analysis indicated that TA variability is mainly regulated by nitrification and net community production (NCP), while DIC variability is driven primarily by NCP. Atmospheric CO₂ loading was the first-order contributor to DIC change in magnitude. However, it has decreased in MB over the past two decades, in contrast to regional and global trends. Therefore, it is not a major driver of OA progression in this system.
Continue reading ‘Ocean acidification in Massachusetts bay and Boston harbor: insights from a 1-D modeling approach’An updated version of the OA-ICC bibliographic database is available online.
The database currently contains 9,682 references and includes citations, abstracts and assigned keywords. Updates are made every month.
The database is available as a group on Zotero. Subscribe online or, for a better user experience, download the Zotero desktop application and sync with the group OA-ICC in Zotero. Please see the “User instructions” for further details.
Continue reading ‘OA-ICC bibliographic database updated’Modeling the spatiotemporal effects of ocean acidification and warming on Atlantic sea scallop growth to guide adaptive fisheries management
Published 7 January 2026 Science ClosedTags: biological response, communitymodeling, fisheries, modeling, mollusks, morphology, multiple factors, North Atlantic, temperature
Highlights
- We spatially couple a scallop bioenergetic model to a regional oceanographic model.
- Our model reproduces observed growth patterns using temperature, food, and pCO2.
- Mid-century warming enhances scallop growth except in the south.
- By 2100, scallops grow faster but reach smaller sizes under warming and acidification.
- This tool can inform adaptive fisheries management under climate change.
Abstract
Climate-ready fisheries management requires reliable predictions of species responses to changing conditions across large-scale environmental gradients. Bioenergetic frameworks, such as Dynamic Energy Budget (DEB) models, relate physiological processes to environmental conditions, enabling predictions of organismal growth under projected climate change conditions. Here, we provide the first large-scale coupling of a DEB model to downscaled regional oceanographic simulations to resolve spatiotemporal changes and reveal how climate stressors emerge at relevant biogeographic, economic, and oceanographic scales. We calibrated our DEB model for the Atlantic sea scallop (Placopecten magellanicus) with forcing from a realistic oceanographic and biogeochemical model for the Northeast U.S. continental shelf to predict the effects of ocean acidification (OA) and warming on individual growth historically and over the next century. Our model reproduced observed historical patterns in scallop age at harvest size and maximum size. At mid-century (2035–2050), scallop growth was projected to increase in most areas except the southern Mid-Atlantic, and OA effects were limited to the deep Gulf of Maine. By the end of the century (2080–2095) under a high emissions scenario, scallops were predicted to grow faster but attain smaller maximum sizes. Our results highlight that warming stress is more acute than previously accounted for, particularly in the southern Mid-Atlantic. While warming stress emerges in the south first, OA stress emerges before warming in the north. Together, these emerging stressors compress the spatial range for optimal growth. Altogether, our findings demonstrate the utility of the spatially coupled DEB model as a tool to inform adaptive fisheries management.
Continue reading ‘Modeling the spatiotemporal effects of ocean acidification and warming on Atlantic sea scallop growth to guide adaptive fisheries management’Navigating uncertainty: an assessment of climate change risks to the marine and coastal environment of Sri Lanka
Published 7 January 2026 Science ClosedTags: biological response, fisheries, Indian, policy, review
Sri Lanka is highly vulnerable to the impacts of marine climate change due to the low coastal profile, which is densely populated with many rural areas dedicated to fishing and aquaculture. Motivated by this, this study aimed to compile and analyse the available evidence and identify steps to improve climate adaptation by undertaking an assessment of marine climate change risks for Sri Lanka. The stepwise approach consisted of a comprehensive literature review and synthesis of risks, followed by appraisal, validation and scoring by expert stakeholders. Here we present a summary of key findings regarding marine climate variables (temperature, sea-level rise, ocean circulation, salinity, ocean acidification, dissolved oxygen, storminess, precipitation and wind), and risks to marine biodiversity and ecosystem services. The most important biodiversity risks identified include decreasing plankton productivity; threats to sea turtles; changes in fish communities; increasing threats to coral reefs; changes to mangrove and seagrass habitats; shoreline erosion; and increasing risk of bio-invasions. Key risks to ecosystem services include declining fisheries; damage and disruption to critical infrastructure and services; threats to tourism; and loss of protective coastal habitats. We also identified important knowledge gaps and uncertainties involving lack of climate data and evidence of impacts. Finally, we provide recommendations regarding marine monitoring and research, and options to strengthen climate policies and climate adaptation in Sri Lanka.
Continue reading ‘Navigating uncertainty: an assessment of climate change risks to the marine and coastal environment of Sri Lanka’Thu, Jan 8, 2026 6:00 PM – 7:30 PM CET
Join Us for the Ocean Acidification Day of Action Webinar
The Coastal Acidification Networks (CANs) of the Mid-Atlantic, Gulf of America, Southeast, and Caribbean are pleased to host a webinar in recognition of Ocean Acidification Day of Action on January 8.
What is Ocean Acidification Day of Action? Ocean Acidification Day of Action was established by the NOAA Ocean Acidification Program (OAP) to raise awareness about ocean acidification and the significance of the global average seawater pH of 8.1. While seawater remains alkaline, the decline from approximately 8.2 over the past 250 years reflects a 26% increase in acidity, driven largely by increased atmospheric carbon dioxide. Now recognized as an international event, Ocean Acidification Day of Action highlights ongoing efforts to understand, mitigate, and adapt to the impacts of ocean acidification on marine ecosystems, coastal communities, and economies. For more information, visit the NOAA OAP webpage: https://oceanacidification.noaa.gov/2025-ocean-acidification-day-or-action/
Guest Speakers
Dr. Aurea Rodríguez Santiago, Founder and Director, Taller Ecológico de Puerto Rico
Dr. De’Marcus Robinson, Postdoctoral Fellow, Florida A&M University
Each speaker, alongside CAN coordinators, will deliver a 15-minute presentation highlighting their work and the actions they are taking to better understand and address the impacts of ocean acidification. The webinar will conclude with a public panel discussion and Q&A, creating space for dialogue on research, community engagement, and collaborative actions to advance ocean acidification awareness and solutions.
This webinar is open to researchers, managers, educators, students, and community members interested in learning more about ocean acidification and pathways for action.
Continue reading ‘Webinar: ocean acidification day of action’Ocean acidification enhances microplastic uptake and alters physiological responses in Manila clams
Published 6 January 2026 Science ClosedTags: biological response, laboratory, mollusks, multiple factors, North Pacific, physiology, plastics, respiration
Highlights
- Ocean acidification (OA) impairs particle selection, increasing microplastic ingestion.
- Microplastic retention in clams is higher under acidified conditions.
- Stress-related suppression of filtration and respiration is diminished under OA.
- OA and microplastics interact, highlighting multi-stressor ecological risks.
Abstract
Microplastic (MP) pollution and ocean acidification (OA) are co-occurring stressors in coastal ecosystems, yet their combined effects on bivalves remain unclear. We investigated how OA influences MP ingestion, excretion, and physiological performance in the Manila clam Ruditapes philippinarum. Clams were exposed to two pH levels (8.1 and 7.6) for 10 days and three MP concentrations (0, 10, and 1000 items/L) during the final three days. MP accumulation in gills/labial palps and digestive tracts, MP content in excreted material, and filtration and respiration rates were measured. Acidified conditions impaired particle selection, leading to greater MP accumulation in the digestive tract, whereas MP excretion was unaffected. Filtration and respiration were maintained at higher levels under OA, suggesting suppressed stress responses. These results demonstrate that OA enhances MP retention and modulates physiological stress reactions, highlighting synergistic effects that may influence energy balance and ecosystem functioning under future ocean conditions.
Continue reading ‘Ocean acidification enhances microplastic uptake and alters physiological responses in Manila clams’From sea to shore: the impact of ocean acidification on child health
Published 5 January 2026 Science ClosedTags: fisheries, socio-economy
Since the Industrial Revolution, ocean water acidity has risen by 26% due to anthropogenic emissions—a process known as ocean acidification—posing a risk for marine life and the communities depending on it. This paper examines the consequences of ocean acidification for child health, using data from coastal regions in 36 low- and middle-income countries from 1972 to 2018, encompassing 41% of the world’s coastal population. Leveraging short-term exogenous shifts in ocean acidity near human settlements for identification, we find that prenatal exposure to higher water acidity significantly raises the risk of death in the first months of life and impacts early childhood development. We show evidence consistent with these effects being associated with maternal malnutrition, as increased acidity reduces catches for small-scale fisheries, increasing seafood prices and reducing consumption of crucial nutrients. Our findings indicate limited adaptation to these impacts. We estimate that, absent intervention, ocean acidification could contribute to as many as 77 million neonatal deaths in this region by 2100—a consequence that should not be ignored in the projected cost of climate change.
Continue reading ‘From sea to shore: the impact of ocean acidification on child health’Acidification and plastic pollution threaten Bangladesh’s blue economy
Published 2 January 2026 Media coverage ClosedTags: fisheries, Indian, socio-economy
The Bay of Bengal has long been the engine of Bangladesh’s blue economy—a vast, resource-rich frontier that sustains millions of people and generates vital export earnings.
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Bangladesh’s total marine fish harvest fell to 628,622 tonnes in FY 2023–24, the lowest in nine years (Department of Fisheries – Annual Report 2024). Deep-sea trawler catches declined by 21% year-on-year (FAO), while catch per artisanal boat has dropped nearly 70% over the past two decades—from 13 tonnes in 2000 to barely 4 tonnes in 2020 (World Bank Fisheries and Aquaculture Review).
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Overfishing and IUU (Illegal, Unreported, and Unregulated) fishing are well-known problems. But two largely untold reasons lie behind this steady deterioration: acidification and plastic pollution—silent yet powerful forces that destabilise the marine ecosystem.
Acidification: An invisible enemy beneath the waves
The ocean has long served as Earth’s greatest climate regulator, absorbing nearly one-third of all carbon dioxide (CO₂) emitted by human activities (IPCC, 2023). While this process helps slow global warming on land, it comes at a devastating cost beneath the surface.
When CO₂ dissolves in seawater, it forms carbonic acid, lowering the ocean’s pH and disrupting marine chemistry.
In the early 1980s, Bay of Bengal surface waters averaged a pH of 8.3 (Indian Ocean Research Consortium). Today, coastal and estuarine zones measure between 7.9 and 8.0, with some readings as low as 7.73 (UNEP South Asia Marine Assessment). This 0.2–0.3 drop in pH represents nearly a 30% increase in ocean acidity over five decades (NOAA; IPCC).
Continue reading ‘Acidification and plastic pollution threaten Bangladesh’s blue economy’Reproduction of the viviparous marine isopod Cirolana harfordi held in seawater with raised temperature and lowered pH
Published 2 January 2026 Science ClosedTags: biological response, crustaceans, growth, laboratory, mortality, multiple factors, reproduction, temperature, zooplankton
Cirolanid isopods play important ecological roles as predators and scavengers, but when populations increase, they can form swarms that attack fish and humans. Understanding how the reproduction of cirolanid isopods will be affected by future warmer and more acidic oceans is therefore important. Samples of the viviparous species Cirolana harfordi were held in 4 combinations of 2 temperatures (18 and 24°C) and 2 pH levels (7.7 and 8.1), and the development of embryos and mancas was investigated by microscopic examination of each pregnant female through the transparent ventral cuticle of their thorax. Higher temperature increased the rate of development, thereby reducing pregnancy duration and accelerating the growth of mancas postpartum. By contrast, increased acidity had no significant effect on these parameters and had no deleterious effects on the development of the mancas. Higher temperature did not have a significant effect on the number of postpartum mancas after the 22 weeks that the adults spent in treatments. Increased temperature and/or lowered pH had no effect on the adult survival or growth. These data are in keeping with the hypothesis that C. harfordi may be able to withstand future warmer and more acidic oceans. Longer-term studies are needed to determine whether decreasing pregnancy durations in higher temperatures increases the number of times females can become pregnant over their lifetime, potentially leading to greater population numbers.
Continue reading ‘Reproduction of the viviparous marine isopod Cirolana harfordi held in seawater with raised temperature and lowered pH’How rising ocean acidity is changing India’s coasts and fisheries
Published 1 January 2026 Press releases ClosedTags: Indian
The ocean has always seemed immeasurably vast and unchanging, a realm so deep and ancient that human activity could hardly make a dent in its rhythms. Scientists now warn that this assumption is outdated. While it might be calming to stand on a beach and watch the waves roll in, little do we realise that a quiet change is taking place within the familiar-looking ocean. The water is slowly turning more acidic, almost like a few extra drops of lemon in a glass of water. We cannot see it, but marine life feels it every day. For a country like India, where millions depend on the sea for food and income, this invisible change carries real consequences.
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A new scientific review from researchers at Amrita Vishwa Vidyapeetham shows ocean acidification may be just as disruptive, and in some regions even more immediate, than rising temperatures or sea level rise. Its consequences could reverberate for centuries.
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Why India cannot afford to ignore ocean acidification
India has one of the longest coastlines in Asia, and millions of people depend on the sea for income. Almost seventy percent of fishing households live near or below the poverty line, making adaptation difficult.
India’s four major coral reef systems already face temperature-related bleaching. Acidification slows coral growth and weakens reef structures, affecting shore protection, fish nurseries, and tourism.
India also has a large aquaculture sector that relies on species sensitive to pH and carbonate levels. Molluscs, crustaceans, and some finfish can face growth and survival challenges in more acidic waters. Yet India’s research output on OA remains low and scattered. Most studies focus on coral bleaching or warming. There is no national OA monitoring network, and only a few long-term coastal observations exist.
The review notes that India contributes only a fraction of global OA literature and lacks coordinated national monitoring. With 67.3 percent of India’s fishing households living at or below the poverty line, disruption to marine resources could undermine livelihoods, nutrition, and coastal stability. Without long-term pH and carbonate chemistry data, policymakers lack the scientific foundation needed to anticipate risks or design adaptation measures.
Continue reading ‘How rising ocean acidity is changing India’s coasts and fisheries’Assessing the influence of ocean acidification on the deterioration of coral reefs in Sri Lanka
Published 1 January 2026 Science ClosedTags: biogeochemistry, biological response, chemistry, corals, field, Indian, review
Rising atmospheric CO2 levels have significantly increased ocean acidification (OA), endangering coral reefs, and nutrient (nitrate (NO3−), and phosphate (PO43−)) pollution also weakens the coral reef resilience. Therefore, the study evaluates the prevailing OA level over the Sri Lankan coral reef areas using the aragonite saturation state (ΩAr) and assesses the nitrate (NO3−), and phosphate (PO43−) concentrations over the coral sites. The study was conducted on coral reefs on the eastern coast (EC), southern coast (SC), northern coast (NC), and west coast (WC) of Sri Lanka from April to June 2024. A total of 63 seawater samples were collected around each coastal site for analysis. The Ω Ar were supersaturated (ΩAr> 1) and ranged from 2.98±0.04 to 4.92±0.12. Throughout the study period, the study sites had ΩAr values exceeding 2.92±0.16, indicating that the nation’s corals were resilient to deterioration, and the comparative analysis demonstrates that these sites were not vulnerable to OA. The NO3− concentrations of 2–5 µmol L− 1, from human activities, may intensify coral bleaching during heat stress. Results showed that SC (2.19±1.28 µmol L− 1) and WC (3.52±1.48 µmol L− 1) had NO3− above the permissible range, which may be due to waste discharge and high runoff. The significantly higher PO43− concentrations were reported in EC (0.35±0.07 µmol L− 1). Coral bleaching hotspot (HS) identification emphasizes how spatially distributed HS are from January to June. The OA risk assessment confirmed that climate change brought high risk to the coral reef ecosystems, which impact on the ecology and economy of Sri Lanka.
Continue reading ‘Assessing the influence of ocean acidification on the deterioration of coral reefs in Sri Lanka’Yemen fisheries and climate change
Published 31 December 2025 Newsletters and reports ClosedTags: fisheries, Red Sea, review
Yemen’s extensive coastline, encompassing the southern Red Sea, Gulf of Aden, and northwest Arabian Sea, is home to rich marine biodiversity and historically productive fisheries, crucial for the nation’s economy, food security, and livelihoods (Figure 1). However, the intersection of global climate change and a prolonged internal conflict has significantly disrupted marine ecosystems and fisheries management, exacerbating already critical challenges.
This report addresses these pressing issues through two interconnected analyses. The first examines recent climate-driven changes in marine ecosystem health indicators, providing insights into seasonal variability, long-term trends, and impacts from extreme climate events such as Cyclone Tej in 2023. The second analysis investigates the status of Yemen’s fisheries, highlighting historical trends, the impacts of conflict, and gaps in current monitoring and management practices.
Leveraging innovative methodologies, satellite remote sensing, computer vision, and collaborative in situ data collection, the report aims to present a cohesive framework for revitalizing Yemen’s marine research and fisheries management. Ultimately, the findings underscore the urgency of implementing targeted, adaptive, and evidence-based policies to sustain Yemen’s coastal ecosystems and the livelihoods dependent upon them.
The report is structured as follows: Section 1 presents analysis of seasonal variability, climate shocks and extreme events along with longer-term temporal trends on temperature, oceanic biomass and productivity, salinity and ocean acidification in Yemen’s coastal waters; Section 2 presents analysis of the fisheries sector, notably identifying the existing data gaps and the absence of reliable monitoring as a result of the ongoing unrest; based on these analyses, Section 3 proposes a framework for the creation of a dynamic fisheries monitoring and management model; and Section 4 concludes with policy recommendations.
While this study does not include formal projections, observed decadal trends across Yemen’s marine regions allow for indicative interpretation of the likely direction of change in key ecosystem indicators. The table below summarizes historical trajectories (2004 – 2024) of these variables, which may inform expectations of future biological productivity if current drivers persist.
Continue reading ‘Yemen fisheries and climate change’The role of heterotrophy in the response of Oculina arbuscula to ocean acidification
Published 31 December 2025 Science ClosedTags: biological response, BRcommunity, calcification, corals, laboratory, multiple factors, North Atlantic, physiology, phytoplankton
On both tropical and temperate reefs, the calcium carbonate skeletons produced by scleractinian corals provide habitat that supports a high biodiversity of fishes and invertebrates. Ocean acidification (OA), driven by excess anthropogenic CO2 uptake, causes declines in seawater pH and carbonate ion concentration and can compromise coral calcification by causing increased energetic demands. Deciphering how corals meet this increased energetic demand is critical to predicting their future persistence. Oculina arbuscula is a facultatively symbiotic temperate coral common on subtropical reefs of the South Atlantic Bight. This coral has demonstrated calcification resilience to reduced pH conditions in both symbiotic and aposymbiotic forms, despite aposymbiotic colonies lacking access to photosynthetically-derived energy. I hypothesized that energy acquired through heterotrophy is a mechanism by which O. arbuscula obtains the resources necessary to overcome the heightened energy demand created by ocean acidification. To investigate the role of heterotrophy, a 90-day laboratory experiment was conducted exposing aposymbiotic O. arbuscula fragments to a pH of either 7.7 or 8.0 under three different feeding levels of Artemia spp. nauplii. Although fragments with greater food consumption showed significantly higher calcification rates, this effect was independent of pH. Similarly, biochemical analyses indicated that total protein and total carbohydrate stores increased with higher food consumption but were unaffected by pH exposure. In contrast, total lipid stores decreased during the experiment, regardless of pH exposure or food level, suggesting the heterotrophic contribution to lipid stores was deficient. Together, these results indicate that while heterotrophically-derived energy may not be a primary mechanism underlying the ability of O. arbuscula to sustain calcification rates under OA stress, this coral species should continue to thrive in an increasingly acidifying ocean as long as heterotrophic food resources are in abundance.
Continue reading ‘The role of heterotrophy in the response of Oculina arbuscula to ocean acidification’Assessing the impact of riverine water on the Northwest Pacific using normalized total alkalinity
Published 30 December 2025 Science ClosedTags: chemistry, field, North Pacific
The impact of riverine water was assessed using salinity-normalized Total Alkalinity observations of the Northwest Pacific, including the coastal areas of Japan (20–50° N, 120–160° E). The observational data included surface carbonate parameters obtained from decades of surveys conducted by volunteer cargo ships and research vessels in this area. This study uses data and statistical methods (e.g., re-gridding and Fourier regression) like those in a previous study that analysed air-sea CO2 flux but focuses instead on the diffusion of normalized Total Alkalinity from land. First, the seawater area affected by riverine water was identified using an Empirical Orthogonal Function analysis of normalized Total Alkalinity. The differences in normalized Total Alkalinity and Dissolved Inorganic Carbon from the surrounding area were then analysed to evaluate the potential drivers, such as riverine water supply, advection effects, and biological activities. In addition, the impact of riverine water on oceanic CO2 uptake and acidification in the study area was assessed. The analysis showed that riverine water was the main cause of the higher total Alkalinity compared to the surrounding area, whereas its contribution to the increase in Dissolved Inorganic Carbon was relatively minor. The supply of riverine water had little effect on oceanic CO2 uptake throughout the year. The supply of riverine water had a minor effect on pH but contributed to coastal acidification, as indicated by a decrease in the calcification index (Ωarg, the aragonite saturation state) by 0.09±0.01 over the past 20 years, even after accounting for the buffering effect of riverine Total Alkalinity, which reduced the overall decrease by approximately 71 %. The results of this study are expected to be further improved by enhancing observations, such as the vertical profiles of carbonate parameters, and are expected to expand to other sea areas and be applied to global budgets.
Continue reading ‘Assessing the impact of riverine water on the Northwest Pacific using normalized total alkalinity’Shell proteome plasticity assists oyster larval biomineralization in adverse carbonate chemistry
Published 30 December 2025 Science ClosedTags: biological response, laboratory, mollusks, morphology, mortality, physiology, reproduction
Bivalve planktonic development is a critical phase during which larvae must secrete the first calcium carbonate shell, the prodissoconch I (PD I). As PD I formation is in close contact with seawater, this process can be negatively affected by adverse seawater carbonate chemistry. It is hypothesized that bivalves can regulate shell formation under environmental stress through biologically controlled biomineralization involving a complex extracellular shell proteome. However, the plasticity of this regulatory mechanism during PD I development is unknown. We assessed the PD I shell proteome of the Hong Kong oyster (Magallana hongkongensis) in carbonate chemistry that was adverse or favorable for biomineralization to understand the regulatory capacity of larval shell formation. While survival rates were not affected in adverse carbonate chemistry, there were significant changes, including the upregulation of several calcium-binding proteins and downregulation of proton-generating processes and putative calcification inhibitors. With 198 sequences, the oyster larval shell proteome was twice to over six times larger than those reported for other bivalve species at the same developmental stage. However, in adverse carbonate chemistry, the oyster larval shells were thinner and smaller, and protein diversity decreased to 131 sequences, with overall lower functional redundancy and reduced expression of structural proteins, indicating potential trade-offs. The proteomic and shell structural data also suggest that direct cellular control and biologically induced mechanisms, which will require further investigation, may be involved in PD I formation.
Continue reading ‘Shell proteome plasticity assists oyster larval biomineralization in adverse carbonate chemistry’Ventilation and buffering capacity effects on ocean acidification in low oxygen environments
Published 30 December 2025 Science ClosedTags: chemistry, methods
Ocean acidification results from oceanic uptake of anthropogenic CO2 (ΔCant). Weak carbonate buffering capacity (high Revelle factor, RF) amplifies acidification, but its role in persistently low-oxygen, poorly ventilated regions is unclear. Here we compare preindustrial to present changes in partial pressure of CO2 (pCO2), hydrogen ion concentration ([H+]), pH, aragonite saturation state (Ωara), and RF within permanent oxygen minimum zones (OMZs) versus well-ventilated regions. We find that acidification is negligible in the least-ventilated, poorly buffered lower OMZs, but detectable in moderately ventilated upper OMZs. In upper OMZs, pCO2 and [H+] increase faster while Ωara, pH, and RF change more slowly than in adjacent well-ventilated regions. Our analysis reveals that limited ΔCant delivery by ventilation ultimately constrain acidification in low-oxygen regions. Accordingly, low-oxygen regions with poor ventilation will experience less acidification than well-ventilated regions, and different metrics (notably [H+] versus Ωara) respond distinctly due to their different definitions and sensitivities.
Continue reading ‘Ventilation and buffering capacity effects on ocean acidification in low oxygen environments’
