Posts Tagged 'North Atlantic'

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Atlantic surfclams’ response to a changing environment

Published 12 March 2025 Web sites and blogs Closed
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Atlantic surfclams support an important commercial fishery in the Northeast United States. Landings were valued at nearly $41.7 million in 2022. They also improve water quality by removing excess nutrients from the water when they filter and consume plankton. Our research aims to understand how surfclams respond to changes in their environment. 

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NOAA Milford Lab scientists built a model that projects Atlantic surfclam growth based on water temperature and the partial pressure of carbon dioxide. This is a commonly used metric of ocean acidification. This model indicates that ocean acidification will decrease surfclam growth and reproduction by the year 2100, under the Intergovernmental Panel on Climate Change’s high carbon dioxide emission scenario. 

Now we are studying surfclam populations in their natural habitat to see how well real-world observations match these model predictions. We will use data collected in the field to make our growth model for surfclams more accurate.

Research Chemist Matt Poach collecting surfclams from a clam dredge boat in Shinnecock Inlet, Long Island, New York. Behind, crewmembers of the F/V Susan H shovel clams from the dredge to a safe zone for the scientists to collect them. Credit: NOAA Fisheries/Katyanne Shoemaker

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Research Questions

  • Does temperature or carbonate chemistry of either the seawater or the water within the sediment affect the growth of surfclams?
  • Do differences between the subspecies affect the relationship between environmental conditions and growth?
  • How well do our lab-based growth models predict surfclam growth rates in the field based on the environmental conditions of their habitat?

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UK waters facing accelerated ocean acidification, new PML-led study reveals

Published 5 March 2025 Press releases Closed
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Revealing critical insights into air-sea carbon dioxide exchanges, pH trends in the North Atlantic, and detailed observations in UK shelf seas, the study also details how ocean acidification impacts marine species through both direct physiological effects from changing pH and CO2 levels and indirect effects via food web disruption.

While some organisms like certain phytoplankton and seaweeds may show positive or neutral responses to elevated CO2, many marine invertebrates and fish species experience neutral or negative effects. Species that build calcium carbonate structures, including corals, shellfish, and important plankton groups, face particularly high risk. Even more developed organisms like fish, though less susceptible to direct impacts, could suffer from the loss of key prey species. The research highlights the need for better integrated approaches that scale from experiments to biogeochemical models. It also emphasizes the urgent need for enhanced observational capacity and improved model accuracy to better understand and address ocean acidification.

Access the report here >>

Key highlights from the update:

  • Atmospheric CO2 surpassed 420 ppm in 2024, continuing to rise by approximately 2.5 ppm annually over the past decade
  • The global ocean absorbs roughly 25% of anthropogenic carbon dioxide emissions each year
  • The North Atlantic Ocean, containing the highest levels of anthropogenic CO2 among ocean basins, is experiencing ongoing surface water acidification
  • Bottom waters in some locations are acidifying faster than surface waters
  • Certain marine species already show effects from ocean acidification during short-term fluctuations, potentially serving as indicators for long-term ecosystem impacts
  • Models project that continental shelf seawater pH will continue to decline through 2050, with rates increasing in the second half of the century depending on emissions scenarios
  • Coastal pH decline is projected to be faster in areas like the Bristol Channel compared to the Celtic Sea
  • Under high-emission scenarios, bottom waters on the North-West European Shelf seas could become corrosive to aragonite as soon as 2030
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Ocean acidification around the UK and Ireland

Published 5 March 2025 Newsletters and reports Closed
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KEY FACTS
What is already happening

  • Atmospheric CO2 exceeded 420 ppm in 2024 and has continued to increase by approximately 2.5 ppm per year over the last decade. The global ocean absorbs approximately a quarter of anthropogenic carbon dioxide (CO2) emissions annually.
  • The North Atlantic Ocean contains more anthropogenic CO2 than any other ocean basin, and surface waters are experiencing an ongoing decline in pH (increasing acidity). Rates of acidification in bottom waters are occurring faster at some locations than in surface waters.
  • Some species are already showing effects from ocean acidification when exposed to short-term fluctuations and could be used as indicator species for long-term impacts on marine ecosystems.

What could happen in the future

  • Models project that the average continental shelf seawater pH will continue to decline to year 2050 at similar rates to the present day, with rates then increasing in the second half of the century, depending on the emissions scenario.
  • The rate of pH decline in coastal areas is projected to be faster in some areas (e.g. Bristol Channel) than others, such as the Celtic Sea.
  • Under high-emission scenarios, it is projected that bottom waters on the North-West European Shelf seas will become corrosive to moresoluble forms of calcium carbonate (aragonite). Episodic undersaturation events are projected to begin by 2030.
  • By 2100, up to 90% of the north-west European shelf seas may experience undersaturation for at least one month of each year.
  • High levels of nearshore variability in carbonate chemistry may mean that some coastal species have a higher adaptative capacity than others. However, all species are at increased risk from extreme exposure episodes.
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Statistical prediction of in situ coral reef carbonate dynamics using endmember chemistry, hydrodynamic models, and benthic composition

Published 3 March 2025 Science Closed
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In the face of rapidly compounding climate change impacts, including ocean acidification (OA), it is critical to understand present-day stress exposure and to anticipate the biogeochemical conditions experienced by vulnerable ecosystems like coral reefs. To meaningfully predict nearshore carbonate chemistry, we must account for the complexity of the local benthic community, as well as connectivity between habitats and relevant endmember carbonate chemistry. Here, we adopt a system-scale approach to predict site-scale effects of benthic metabolism on the carbonate system of the Florida Reef Tract (FRT). We utilize bimonthly carbonate chemistry data from ten cross-shelf transects spanning 250 km of the FRT to model changes in dissolved inorganic carbon (DIC) and total alkalinity (TA). Benthic habitat maps were used to broadly classify communities known to impact carbonate chemistry. A SLIM 2D hydrodynamic model with mesh resolution reaching 100 m over reefs and along the coastline was used to determine the relevant water mass histories and identify the upstream benthic communities shaping local carbonate chemistry. These historical metabolic footprints, or “flowsheds”, were used to build predictive models of the change in DIC and TA at each station. The best predictive models included the chemical impacts of benthic ecosystem metabolism, as defined by water mass trajectories, weighted endmember chemistry, volume, time, and other environmental parameters (light, temperature, salinity, chlorophyll-a, and nitrate). Considering water mass for 5 days prior to sample collection yielded the highest model skill.

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Quantifying coral-algal interactions in an acidified ocean: Sargassum spp. exposure mitigates low pH effects on Acropora cervicornis health

Published 3 March 2025 Science Closed
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Increasingly frequent large-scale pelagic Sargassum algae blooms in the Atlantic have become a problem for coastal ecosystems. The mass decay of these blooms reduces water quality for coastal flora and fauna. However, the effects of living Sargassum blooms on seawater quality and consequently coral reef ecosystems that rely on delicately balanced carbonate chemistry are more ambiguous. Future oceans are predicted to be more acidic as additional anthropogenic CO2 emissions are absorbed, potentially tipping the balance in favor of algal blooms at the cost of coral survival. This study aimed to simulate the indirect interaction between pelagic Sargassum spp. and Acropora cervicornis coral fragments from the Florida Reef in current-day and future ocean pH conditions over the course of 70 days in a mesocosm experimental system. Measurements of coral growth and health via buoyant weight and Pulse Amplitude Modulated (PAM) fluorescence measurements reveal an unexpected coral-algal interaction. After 1 month, coral growth was significantly reduced under ocean acidification conditions and exposure to Sargassum; at the same time quantum yield and maximum electron transport rate of photosynthesis were increased relative to control counterparts in ambient and future pH scenarios by up to 14% and 18% respectively. These improvements in photosynthetic efficiency did not translate to significant differences in growth by the final measurement time point. In addition, the presence of Sargassum spp. did not raise seawater pH in the system, raising questions about how it benefited photosynthetic efficiency in exposed corals. Heterotrophy of detrital algal matter is suspected to compensate for impaired photosynthesis of pH stressed corals. Therefore, despite their current negative reputation, Sargassum blooms could provide short term localized benefits to corals in present and future ocean conditions.

Continue reading ‘Quantifying coral-algal interactions in an acidified ocean: Sargassum spp. exposure mitigates low pH effects on Acropora cervicornis health’

Carbonate and nutrient dynamics in a Mississippi River influenced eutrophic estuary

Published 25 February 2025 Science Closed
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There is limited information on how the nutrient and freshwater input affects water column carbonate chemistry in the estuaries along the northern Gulf of Mexico. In this study, we assess the seasonal and spatial variability in carbonate chemistry in the Barataria Basin, a eutrophic estuary adjacent to the mouth of the Mississippi River. Eleven stations were sampled along a salinity gradient during the winter (January), spring (April), summer (July), and fall (October) of 2021. Surface and bottom water samples were collected for the analyses of dissolved inorganic carbon (DIC); total alkalinity (TA); and nitrite plus nitrate (NO2 + NO3), phosphate (PO4), and dissolved silica (SiO4). Dissolved CO2 (pCO2) was measured in the surface water. Seasonal surface DIC and TA values ranged from 1553 to 2582 μmol kg−1 and 1217 to 2217 μmol kg−1, respectively. DIC and TA varied seasonally and showed an increasing trend from fresh stations to saline stations. The highest DIC and TA values were observed during the fall season, likely due to the increased contribution of DIC and TA from adjacent marshes as a result of enhanced porewater exchange. In contrast to DIC and TA, pCO2 decreased with the increase of salinity. The seasonal and spatial patterns in carbonate chemistry could not be explained solely by physical mixing and reflected complex interactions between biogeochemical processes driven by nutrient supply and temperature as well as tidal flushing and material exchanges with adjacent marshes.

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Metabolomic and phenotypic effects of ocean acidification on cuttlefish differ across early life stages

Published 24 February 2025 Science Closed
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Highlights

  • Low pH conditions delay the timing of hatching and reduce hatching success of cuttlefish
  • Low pH conditions impact cuttlefish egg swelling but not hatchling size
  • The maximum rate of O2 consumption is not altered in response to low pH exposure
  • Metabolome suggests a metabolic depression in embryos exposed to seawater pH below 7.54
  • Metabolic stress due to hatching event exceeds pH effect on metabolite profile

Abstract

Ocean acidification (OA) affects the physiology and behaviour of some marine organisms, impacting their development and metabolism during vulnerable early-life stages. Among them, the embryo of the cuttlefish develops for about two months in encapsulated eggs with harsh perivitelline conditions of hypoxia and hypercapnia, potentially worsened by OA. In this study, common cuttlefish Sepia officinalis embryos and juveniles, were exposed to five pH conditions (pHT 8.08 to 7.43). Growth, development and metabolite profiles were explored during the embryonic development period up to 10 days-post-hatching. Our results show delayed embryonic development and decreased hatching success at pH 7.43, but no effect on juvenile weight upon hatching. The 1H Nuclear Magnetic Resonance (NMR) spectroscopy revealed that decreasing pH affected metabolites profiles in embryos until a metabolic suppression was observed at pH 7.43. The O2 consumption in 10d-old juveniles did not change with pH whereas metabolites indicated a switch to anaerobic metabolism under low pH. Overall, our results suggest that the transition from the encapsulated embryonic stage to the free juvenile life shapes a metabolomic reprogramming more drastically than ocean acidification.

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High-resolution temporal assessment of physicochemical variability and water quality in tropical semi-enclosed bays and coral reefs

Published 24 February 2025 Science Closed
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Highlights

  • Mangrove, seagrass, and coral habitats are at risk from global and local stressors
  • We assessed >20 (a)biotic parameters and pollution at high temporal resolution
  • Strong diel and seasonal variability was recorded in semi-enclosed bays
  • The bays showed higher nutrient levels and ecotoxicological risks than nearby reefs
  • A water quality monitoring framework for reef-associated habitats is provided

Abstract

Tropical coastlines featuring mangrove, seagrass, and coral habitats are of immense ecological and socio-economic importance, supporting biodiversity, carbon storage, coastal protection, fisheries, and tourism. However, climate change, coastal development, and low water quality increasingly threaten these interconnected coastal ecosystems, particularly in semi-enclosed bays where the impacts of these stressors are often amplified. Yet, physicochemical conditions are rarely assessed at sufficient temporal resolution (i.e., diel and seasonal variation) and time-integrated pollution monitoring is rarely performed. Here, we used a multi-disciplinary approach to assess >20 abiotic parameters characterizing two mangrove- and seagrass-dominated inland bays and two nearby coral reefs in Curaçao (southern Caribbean) during the cool, dry season and warm, wet season. This was combined with time-integrated pollution monitoring using bioindicators to assess nutrients and trace metal pollution (inland bays only), and passive samplers and bioassays to assess organic chemical pollution (all four sites) during the wet season. This approach revealed a previously undocumented extent of strong diel and seasonal environmental variability in Curaçao’s inland bays, with temperature, pH, and dissolved oxygen frequently reaching values predicted under moderate-to-severe future climate scenarios as outlined by the IPCC (2021). In addition, the inland bays had greater nutrient concentrations (especially ammonium) and potential ecotoxicological risks than the nearby reefs during the wet season due to run-off and anthropogenic activities. These findings emphasize the importance of high-resolution monitoring to understand risks across appropriate temporal scales and establish an environmental baseline against which future monitoring can be benchmarked. Moreover, our study provides a robust water quality assessment framework that can be used by natural resource managers to monitor reef-associated habitats and conserve their high ecological and socio-economic value. Overall, our work highlights the urgent need to improve monitoring, water quality, and protection of these valuable reef-associated habitats.

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Excess alkalinity and its impacts on pCO2 estimation in coastal and estuarine waters of the Yellow Sea

Published 17 February 2025 Science Closed
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Highlights

  • Excess alkalinity (TAEX) in western Korea coastal waters reached up to 50 μmol kg−1.
  • Higher TAEX was observed in lower salinity waters, emphasizing riverine contributions.
  • Seasonal TAEX peaks aligned with lower DIC and AOU, suggesting biological production.
  • Quantifying TAEX in coastal areas is crucial to reduce carbon parameter calculation errors.
  • TAEX estimates in low-salinity water must account for calculated TA uncertainty.

Abstract

Excess alkalinity (TAEX) represents an uncharacterized component of total alkalinity (TA), which can introduce significant uncertainty in the estimation of other carbonate parameters. This effect is particularly pronounced in productive coastal regions, where the use of measured TA as an input parameter may lead to inaccurate assessment. In this study, we evaluated the seasonal variability of TAEX along the western coast of South Korea by applying an overdetermination method, which allows for the quantification of discrepancies (i.e., TAEX) between measured TA and values calculated from pH and dissolved inorganic carbon (DIC). Samples with salinity below 20 were excluded due to difficulties in accurately quantifying uncertainties in TAEX calculations, which increase significantly below this threshold. Elevated TAEX concentrations were found in waters with salinity below 25, with some instances exhibiting TAEX values reaching up to 50 μmol kg−1, suggesting riverine influence. Additionally, elevated TAEX values (> 20 μmol kg−1) were also observed in locations markedly undersaturated with respect to atmospheric CO2, indicating contributions from in-situ biological production. The high TAEX values associated with increased water transparency during autumn and winter months suggested that light penetration may significantly enhance biological activity, subsequently increasing TAEX levels. These findings highlight the importance of riverine inputs and biological processes in shaping the spatial and temporal distribution of TAEX. In the study area, TAEX should be accounted for in seawater partial pressure of CO2 (pCO2) calculations using the DIC–TA pair, as TAEX significantly influences these calculations compared to the pH–TA and pH–DIC pair.

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Long-term biogeochemical variations in the southern South China Sea and adjacent seas: A model data analysis

Published 17 February 2025 Science Closed
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Highlights

  • Sea surface temperature in the southern South China Sea is rising by 0.2°C per decade, highlighting climate change’s impact on the region.
  • Significant declines in Dissolved Oxygen and pH levels highlight broader impacts on ocean health in the southern SCS.
  • SST anomalies strongly influence biogeochemical changes, highlighting biogeochemistry’s sensitivity to climate variability.

Abstract

The southern portion of the South China Sea (SCS), which constitutes the largest semi-enclosed marginal sea in Southeast Asia, is currently undergoing unusual surface warming, which may significantly impact its marine ecosystems. This study examines the long-term variations of biogeochemistry in the southern SCS and its adjacent seas from 1993 to 2020, using data from the Copernicus Marine Environment Monitoring Service (CMEMS) model to better understand the implications of these warming trends on nutrient dynamics and overall marine health. Analysis of interannual variations highlights a strong relationship between sea surface temperature (SST) anomalies and the occurrence of El Niño-Southern Oscillation and Indian Ocean Dipole events, leading to significant alterations in biogeochemistry in the southern SCS. These findings emphasize the sensitivity of biogeochemistry to climatic variability. Over the study period, a region-wide increasing SST trend (0.2 °C per decade) indicates the influence of climate change, while surface Chlorophyll concentration and Phytoplankton biomass show decreasing trends, suggesting potential shifts in primary productivity. Additionally, surface Dissolved Oxygen and pH levels have significantly declined, pointing to broader impacts on ocean health. These observed declining trends in biogeochemical variables are particularly pronounced in the southeastern Vietnam, East Coast of Peninsular Malaysia, and Java Sea regions, which are primarily driven by significant changes in SST and related wind patterns. The weakening of summer southwesterly winds and winter northeasterly winds, evidenced by linear trends in wind stress, has reduced nutrient supply through upwelling and decreased ocean heat loss, respectively. This disruption exacerbates surface ocean warming and limits the replenishment of essential nutrients, leading to diminished primary productivity and altering marine ecosystem dynamics. This study provides valuable insights into present biogeochemical trends under climate change, forming a crucial basis for future projection studies in this region.

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Dynamics in brood chamber pH of the European flat oyster (Ostrea edulis) in response to ocean acidification

Published 13 February 2025 Science Closed
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Ocean acidification is posing a threat to marine bivalve species who struggle to deposit calcium carbonate in order to grow their shell. Some oyster species have developed a brooding reproductive strategy which might help them cope with this acidification stress. Brooding oysters have shown to be more resilient against ocean acidification than broadcast spawning oyster species. It is suspected that because the brood chamber is on top of the maternal gills, the mothers add carbon dioxide into the chamber from her respiration. This suggests larvae evolved to develop in a more acidic environment than the surrounding water column. Through exaptation the larvae may have coopted traits needed for development in the brood chamber which now enable them to be more resilient to ocean acidification. In this study, we measured the pH inside the brood chamber of Ostrea edulis under current and future predicted ocean conditions (i.e., elevated temperature and decreased seawater pH) to get a better understanding of the ambient-maternal relationship on brood chamber pH fluctuations under ocean acidification scenarios. The results suggested that maternal respiration indeed makes the brood chamber always a more acidified environment then the surrounding water. Elevated temperatures in the surrounding water slightly lower the pH as a result of increased maternal metabolism. Yet lowering the ambient pH causes a much larger and significant reduction of internal pH levels since the oyster is constantly filtering the overlaying water while the valves open. Additionally, there seems to be a positive relationship between shell gape and internal pH changes suggesting that the mothers behaviour may also influence how fast and to which level pH values can drop inside the brood chamber. These results give an indication of what conditions brooding oysters larvae will have to face in the future and helps determine possible winners and beneficial strategies in an acidified ocean.

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The effects of combined stress from pH and microplastic-derived odours on the European green crab Carcinus maenas’s olfactory behaviour

Published 12 February 2025 Science Closed
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Simple Summary

The European shore crab, Carcinus maenas, also known as the European green crab, uses its sense of smell to detect prey, predators, and mating partners. Here, we examined how such crabs behave in environmental conditions that simulate the changes predicted by climate change. Crabs were exposed to female sexual odours, food smells, and various types of plastic leach outs. A decreased pH altered the crab’s behaviour towards food (Glutathione) and sex odour, reducing the animal’s response levels and increasing reaction times. Most interestingly, the crabs were more attracted to polyethylene (PE) odour in future ocean conditions, whilst males’ responses to female sex cues were especially reduced significantly. Response-level changes vary between the sexes, highlighting that understanding the effects of climate conditions on animal behaviour and choices is complicated and difficult to predict. That crabs become more attracted to plastic raises the question of what the bioactive chemicals are in PE that induce such a response, and this could demonstrate how climate change potentially increases the risks associated with plastic pollution in future oceans.

Abstract

Ocean acidification (OA) associated with climate change is expected to lower the ocean’s pH by 0.5 units by 2100. Whilst associated effects such as coral bleaching and shell calcification are well documented, lesser-known impacts are the ‘invisible’ effects on animal sensory systems. Olfactory disruption impacts the behaviour towards chemical cues in many marine species, including crustaceans. We examine the effects of microplastic odour and additional stressors on the European green crab C. maenas. Using uridine diphosphate (UDP) and uridine triphosphate (UTP) as a sex pheromone bouquet, glutathione (GSH) as a food cue, and polyethylene (PE) as plastic odour, cues were mixed with carboxycellulose to create slow-release gels. Crabs were exposed to gels in seawater pH values of 8.2, 7.6, and 7.2. Crabs took longer to react to all odours in reduced pH conditions (pH 8.2 to pH 7.2, p = 0.0017). At a low pH, PE-exposed crabs exhibited attraction towards microplastic odour and changed behavioural responses by burying. The study confirms low pH as disruptive to olfaction and highlights that plastic derivatives can become more bioactive at reduced pH levels, potentially increasing the threat posed by microplastic pollution. Further research is required to determine the potential long-term impacts of the combined threat of microplastics and reduced pH in the environment.

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Behavioral and physiological effects of ocean acidification on juvenile American lobsters (Homarus americanus)

Published 12 February 2025 Science Closed
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Alteration of pH within the world’s ocean, or ocean acidification (OA), results from increased absorption of CO2 into global waters. Acidification can positively or negatively affect physiology and behavior of marine taxa, though the effects vary greatly based on species and life stage. Crustaceans are often noted as being resilient to acidification, though negative physiological and behavioral impacts have been shown. Studies on the impacts of OA on the American lobster (Homarus americanus) have primarily focused on its physiology. This thesis aims to observe the potential effects of acidification on the foraging behavior and hemolymph chemistry of juvenile American lobsters. We exposed 28 juvenile lobsters (carapace length, CL, 29mm – 52mm, average 42 +/- 1.3mm) to randomly assigned, individual pH values between 7.3 and 7.8 for 12 days to observe potential impacts of acidification. The time taken to locate blue mussels, the number of foraging trips taken, the time taken to successfully feed, and hemolymph L-lactate concentration (stress indicator) were assessed after the exposure period. Counter to our predictions, as pH decreased, lobsters successfully fed two-times quicker, maintained normal locate times of prey, and took fewer foraging trips. We found that lobsters responsed to prey cues similarly across the pH range, indicating that olfaction was likely not impaired. These results suggest that juvenile American lobsters may increase foraging activity in response to acidified conditions.

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Olfactory specialization in the Senegalese sole (Solea senegalensis): CO2 acidified water triggers nostril-specific immune processes

Published 10 February 2025 Science Closed
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Highlights

  • Exposure to high PCO2/low pH water decreases olfactory sensitivity in sole more markedly in the upper olfactory epithelium (OE).
  • Resilience of the lower OE may be linked to exposure to a different environment.
  • Regulation of genes related to neuromodulation and neuroplasticity suggests activation of compensatory mechanisms.
  • Regulation of immune processes related genes together with histological modifications will likely compromise olfactory sensitivity with behavioural consequences.
  • Ocean acidification has effects on the peripheral nervous system at various levels.

Abstract

Increased carbon dioxide (CO2) in the ocean is changing seawater chemistry. Behavioural alterations in CO2 exposed fish have been linked to changes in the central nervous system (CNS). However, we hypothesise that receptor cells in direct contact with the environment are more susceptible to changes in water chemistry than the CNS. Electrophysiology, histology, and transcriptomics were used to explore the effect of exposure to CO2 acidified water on the olfactory epithelium (OE) of the Senegalese sole (Solea senegalensis). The upper and lower OE of this flatfish detect different odorants and are in contact with different environments. Acute exposure to acidified water decreased olfactory sensitivity more in the upper than in the lower OE. After chronic exposure to high CO2 there was no histological changes in the upper OE, however, in the lower OE, there was a massive infiltration of melanomacrophage (MMC) and tissue disorganization. In addition, in the upper OE, differential expressed gene transcripts (DETs) were related to inflammation and innate immune processes whereas in the lower OE, DETs were related to the adaptative immune response. Differential regulation of genes related to neurogenesis and plasticity occurred in both epithelia.

The effects of ocean acidification in sole OE depends on the nostril, however the occurrence of an exacerbated immune response, OE remodelling and reduced sensitivity indicate that ocean acidification is likely to have significant and unpredictable consequences for behaviour.

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Understanding and quantifying carbon export to coastal oceans through deltaic systems

Published 7 February 2025 Science Closed
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The ocean is the second largest carbon reservoir on Earth and a significant carbon sink to mitigate the adverse effects of climate change. However, ocean carbon sink is expected to decrease in the future with continuing seawater acidification, more stable ocean stratification, and intensified extreme weather events. Estuaries, the connection between land and the coast, undergo complex carbon reforming and pose the greatest uncertainty in global carbon budgets. Coupled physical-biogeochemical models over the Gulf of Mexico (GoM) were configured using biogeochemical boundary conditions from a global climate model (GCM), preserving the long-term climate variability and the conservation of carbon pools in the regional model (RM). Subsequently, a nested domain over the Barataria Basin was built to quantify the carbon export in the eroding estuary. Intensive model-data comparison confirmed that the RM could reliably simulate the ocean carbon system in the GoM, and added values (AVs) were achieved both at the GCM scale and the RM scale. Model results reveal that the GoM water has been experiencing a ~ 0.0016 yr-1 decrease in surface pH over the past two decades, accompanied by a ~ 1.66 µatm yr-1 increase in sea surface pCO2. The river-dominated northern GoM (NGoM) is a substantial carbon sink, and the open GoM is a carbon source during summer and a carbon sink for the rest of the year. Based on the sensitivity test for higher river discharge scenarios, the NGoM was predicted to become a stronger ocean CO2 sink in the future. Stronger fluvial influence will increase the ecosystem resilience after hurricanes’ impact but reduce its resistance at the same time. The model estimated that Barataria Basin exports approximately 52.5 ×106 kg yr-1 dissolved inorganic carbon (DIC) and 9.68 ×106 kg yr-1 total organic carbon (TOC) to the coastal water. The biggest carbon loss term of the Barataria Basin was in the form of CO2 outgassing in quantity of 98.8×106 kg yr-1.

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An observation-based method to estimate carbonate system variations in the Labrador Sea

Published 6 February 2025 Science Closed
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The ocean carbonate system consists of pH, alkalinity, inorganic carbon and the partial pressure of carbon dioxide, and during the current era of anthropogenic change, its dynamics are key for understanding changes in the ocean and its ecosystem over time. The focus of this study is to estimate the carbonate system in the Labrador Sea with time series methods, using direct observations from the ocean surface and interior, and chemical relationships between variables. Interior ocean observations are minimal for some of these variables, however, connections between the variables rooted in chemistry were used to create pseudo-observations using CO2SYS, increasing the information available. A state space model was designed that combined GLODAP and SOCAT observations along with pseudo-observations in a time series estimate of the carbonate system. The Labrador Sea between 1993 and 2016 shows increasing rates for DIC (0.57-1.16 µmol kg−1 year−1) and fCO2 (0.70-2.45 µatm year−1), as well as acidification via pH trends (0.0007-0.0018 year−1). These ranges describe the scale of rates that are occurring at various depths through the water column, though they do not change linearly with depth. Largest rates are found at the surface for DIC, 500-1500 m for fCO2, and 500-1500 m for pH. Total alkalinity also decreased and is correlated with the freshening of salinity. With the core carbonate variables estimated, other aspects of the carbonate system are calculated using CO2SYS, such as the aragonite and calcite saturation states, the Revelle factor, and the carbonate species. Our method also calculates uncertainties that vary over time and depth based on the availability of observations and their variance, which has lowered the uncertainty for pH by 71% and for fCO2 by 64% compared to time-independent methods.

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Dynamics and drivers of the carbonate system: response to terrestrial runoff and upwelling along the northeastern Colombian Caribbean coast

Published 6 February 2025 Science Closed
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Introduction: This study investigated the variability and main drivers of the carbonate system in Gayraca Bay and Chengue Bay, located on the northeastern Caribbean coast of Colombia, through monthly measurements of partial pressure of CO2 (pCO2), pH, total alkalinity (TA), and dissolved inorganic carbon (DIC) from 2017 to 2022. Statistical analyses and Taylor series decomposition were employed to determine the seasonal and interannual contributions of sea surface temperature, salinity, TA, and DIC to changes in pCO2, pH, and calcium carbonate saturation state (Ω).

Results: The results showed significant seasonal variability influenced by annual changes in coastal upwelling, rainfall, and river runoff. Low/high pH and Ω values were associated with high/low DIC and TA values during the dry and wet seasons, respectively, while pCO2 exhibited an opposite pattern. During El Niño, negative anomalies in coastal upwelling produced negative anomalies in pCO2 and positive anomalies in Ω, DIC, and TA. Conversely, during La Niña, alternating periods of positive rainfall and upwelling anomalies were observed. Higher rainfall corresponded to negative anomalies in pCO2, DIC, and TA and positive anomalies in Ω, whereas stronger upwelling led to opposite trends. In early 2022, undersaturated levels of Ωcalc and Ωarag (<1) were observed, which could affect coral calcification and pose risks in future climate change scenarios. Taylor series decomposition analysis identified TA and DIC as primary drivers of carbonate system variability, modulated by seasonal and interannual changes in rainfall and river runoff, which are influenced by ENSO events. The observed trends in pH and pCO2 were driven by a decrease in DIC and TA, attributed to increased river runoff, contrasting with typical ocean acidification trends driven by rising atmospheric CO2 levels.

Discussion: This highlights the region’s unique dynamics and underscores the importance of local studies. This study provides a novel 6-year time-series dataset for the carbonate system in the Colombian Caribbean, offering a valuable baseline for assessing the impacts of global warming and ocean acidification in the region.

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Warming, but not acidification, increases metabolism and reduces growth of redfish (Sebastes fasciatus) in the Gulf of St. Lawrence

Published 6 February 2025 Science Closed
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Understanding the effects of global change, including temperature, pH, and oxygen availability, on commercially important species is crucial for anticipating consequences for these resources and their ecosystems. In the Gulf of St. Lawrence (GSL), redfish (Sebastes spp.) have been under moratorium from 1995 to 2024, with a massive recruitment observed in 2011–2013. However, little is known about their metabolic and thermal physiology, making predictions of their response to changing GSL conditions challenging. To address this, we quantified the effects of four acclimatation temperatures (2.5, 5.0, 7.5, and 10.0 ℃) and two pH levels (7.35 and 7.75) on standard and maximum metabolic rates (SMR and MMR), aerobic scope (AS), hypoxia tolerance (O2crit), food consumption, and growth in redfish. SMR, MMR, and AS increased with temperature, but growth decreased at the highest temperature, likely due to increased metabolic demand, with food consumption similar across 5.0 to 10.0 °C treatments. O2crit was lower for fish acclimated to 2.5 and 5.0 ℃, making redfish less hypoxia-tolerant at higher temperatures. Except from SMR, no significant effect of pH was observed. These results suggest that future changes in the GSL will challenge redfish, with potential long-term effects on their growth due to increased energy requirements.

Continue reading ‘Warming, but not acidification, increases metabolism and reduces growth of redfish (Sebastes fasciatus) in the Gulf of St. Lawrence’

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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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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