Archive Page 33

Impacts of acidification and warming on carbon sequestration capacity in Pacific oysters: roles of biosynthesis and biodeposition

Published 14 July 2025 Science Closed
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Highlights

  • Adjustments in carbon budget and digestion enable adaptation to OA and OW.
  • All treatments enhance somatic carbon sequestration.
  • Energy reserve inhomogeneity can be attributed to metabolic disturbances.
  • OW disrupts microbial homeostasis more than OA or OA&OW.

Abstract

Bivalve aquaculture shows promise as a carbon sink, but its sensitivity to temperature and pH fluctuations highlights the need to study the effects of ocean acidification (OA) and ocean warming (OW) on carbon sequestration. This study investigates the effects of OA and OW on physiological processes and carbon sequestration mediated by biosynthesis and biodeposition in Crassostrea gigas. OA significantly enhances carbon ingestion, reduces respiratory carbon, increases carbon allocation to growth, improves digestive efficiency, and promotes TOC accumulation in soft tissues (all p < 0.05). While OW significantly increases excreted and fecal carbon (p < 0.05), but enhanced digestion compensates for energy loss, sustaining TOC accumulation. Combined OA and OW significantly altered soft tissue carbon sequestration, with values between OA and OW alone (p < 0.05). Notably, their interaction increases biodeposit density and sinking velocity (p < 0.05), potentially enhancing carbon burial. Tissue-specific metabolic responses reveal that muscle tissue prioritizes energy production, whereas the digestive gland follows an opposite trend, resulting in uneven energy distribution. Furthermore, functional predictions based on KEGG pathway analysis and correlation patterns suggest that SCFAs production via tryptophan metabolism might be a potential mechanism through which probiotics modulate host metabolism and contribute to biosynthesis-mediated carbon sequestration. However, disruptions in microbial homeostasis due to an imbalance between probiotics and pathogens in the digestive gland may threaten the long-term sustainability of this sequestration process. These findings provide insights into the complex physiological and microbial responses of oysters under climate change, highlighting potential mechanisms for carbon sequestration in marine ecosystems.

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Ocean acidification induces changes in circadian alternative splicing profiles in a coral reef fish

Published 14 July 2025 Science Closed
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Alternative splicing is a fundamental mechanism of gene expression regulation that increases mRNA diversity and can be partially regulated by the circadian clock. Time-dependent production of transcript isoforms from the same gene facilitates coordination of biological processes with the time of day and is a crucial mechanism enabling organisms to cope with environmental changes. In this study, we determined the impact of future ocean acidification conditions on circadian splicing patterns in the brain of fish, while accounting for diel CO2 fluctuations that naturally occur on coral reefs. The temporal splicing pattern observed across a 24-hour period in fish from the control group was largely absent in those exposed to either stable or fluctuating elevated CO2 conditions. Splicing patterns were influenced not only by an overall increase in CO2 concentration but also by its stability, with 6am and 6pm emerging as key timepoints when the majority of aberrant splicing events were identified. We found that fish in fluctuating CO2 conditions exhibited increased temporal plasticity in splicing events compared to fish in stable CO2 conditions. This was especially notable for genes associated with neural functioning. Our findings suggest that natural temporal splicing patterns in fish brains are disrupted by elevated CO2 exposure, with CO2 stability also influencing molecular responses. The increased plasticity in temporal splicing activity observed in fish in fluctuating CO2 environments may provide greater flexibility in biological responses to external pH changes, potentially enabling them to better cope with future ocean acidification conditions.

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Ocean acidification: impacts on marine ecosystems

Published 11 July 2025 Science Closed
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Ocean acidification, driven primarily by increased atmospheric CO₂ absorption, is one of the most pressing environmental challenges of our time. This paper examines the chemical mechanisms underlying acidification, its historical trends, and the widespread implications for marine organisms and ecosystems. It examines physiological and ecological effects on species ranging from microscopic plankton to coral reefs and addresses broader ecosystem-level disruptions and their cascading impacts. The socioeconomic implications, particularly for coastal communities and fisheries, are evaluated alongside mitigation strategies and the importance of long-term research and monitoring. The study underscores the urgency of interdisciplinary approaches to understanding and combating ocean acidification as part of the global climate agenda.

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Hindsight informs foresight: revisiting millennial forecasts of impacts and status of rocky shores in 2025

Published 11 July 2025 Science Closed
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Highlights

  • Rocky shores face multiple threats from land, sea and global environmental changes.
  • We revisited 25-year predictions made in 2002 about impacts to rocky shores.
  • Some predictions were accurate (oil spills, invasives) while others missed (acidification).
  • We use hindsight to forecast rocky shore ecosystems’ next 25 years through 2050.

Abstract

Rocky shorelines are characterised by vulnerability to both land- and sea-derived impacts. They face acute impacts such as pollution from shipping accidents, chronic pollution from point sources, run-off and catchments plus disturbances by food gathering, recreation and sediment deposition in sheltered areas. Coastal urbanisation can both impact natural shores and create impoverished artificial rocky shores. Superimposed upon local and regional scale impacts are global environmental changes including warming, sea-level rise, increasing storm frequency, ocean acidification and non-native invasive species. Rocky shores are, however, amenable to long-term ecological monitoring and ecological experimentation. Thompson, Crowe and Hawkins (2002) reviewed anthropogenic impacts on rocky intertidal habitats and forecasted their status for the next 25 years. The paper was critiqued by invited experts (Branch, Castilla) at a subsequent conference in 2003 (Environmental Future of Aquatic Ecosystems, Zurich, 23-27 March 2003), culminating in a consensus chapter in Aquatic Ecosystems: Trends and Global Prospects (Branch et al., 2008). Nearly 25 years later, we revisit and evaluate their predictions to explore implications for the next 25 years as new potential impacts emerge in parallel with societal attempts to transition to net zero carbon outputs. An update is provided on what was largely correct (oil-spills, food harvest, invasive species, sedimentation/run-off, organotins, global-change, artificial habitats, recreation/research/education) and what was partially/completely wrong (eutrophication, aquaculture/GMOs, renewable energy, UV radiation) or omitted (coastal mining, ocean acidification, plastic, light, noise pollution). We also consider the challenges and uncertainties inherent in predicting impacts of environmental changes by using hindsight to inform foresight.

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Impact of ocean acidification on fish health and marine ecosystem dynamics

Published 11 July 2025 Science Closed
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Ocean acidification (OA) causes an increase in carbon dioxide (CO2) and a reduction in the pH of ocean waters. This chapter reviews the current literature to investigate the adverse effects of OA on fish health and marine ecosystem dynamics. OA poses serious threats to marine biodiversity and ecosystem dynamics. Fish experience severe physiological problems such as impaired growth, development, tissue damage, Impaired behavioral changes, sensory and brain functions, and disruption in predator-prey interactions due to acidification with a 74% decline in survival rates of egg and larval stages. Besides affecting fish, OA also affects marine ecosystem dynamics: reducing calcification rates in calcifying species, increasing seagrass production, causing effects on habitat-forming species, and disrupting the food web. Vulnerable species, such as coral reef fish, show high sensitivity, risking the stability of their habitats. The United Nations recognized the OA as a threat to marine biodiversity through the Convention on Biodiversity. The future research needs to focus on understanding fish and marine animals’ adaptive mechanisms to OA, its interaction with other stressors, and global collaboration to address the underlying causes of OA.

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Differential performance of diploid, mated triploid, and induced triploid Pacific oysters under varied environmental conditions: insights into impacts of temperature, dissolved oxygen, and pCO2

Published 11 July 2025 Science Closed
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Highlights

  • In the lab we explore environmental stress impacts on diploid and triploid oysters.
  • At mid pCO2 (1450–1700 μatm) mated triploids had lower survival than other groups.
  • Differences between mated and induced triploids may impact performance.
  • Consider the environment when selecting which ploidy for shellfish aquaculture.

Abstract

Pacific oysters (Crassostrea gigas) are an important aquaculture species due to their fast growth, high market demand, and adaptability. Triploid oysters, have an additional set of chromosomes relative to diploids, grow faster and are functionally sterile. Thus, triploids comprise a large proportion of oysters grown worldwide. Triploid oysters are reported to experience higher mortality than diploids. Growers must make decisions that balance the risks and rewards of growing triploids. Understanding how stressors affect oysters is essential to understanding the drivers of triploid mortality and to prepare for the impacts of climate change on individuals in aquaculture. Here, we examined impacts of temperature, dissolved oxygen (DO), and pCO2 on genetically related juvenile diploid, chemically induced triploid, and mated triploid Pacific oysters. Diploid and induced triploid groups were full siblings, mated triploids were half-siblings. We measured whole organism physiological responses—growth, mortality and respiration — after a 4-week exposure to different environmental conditions. Survival was high in all groups across a broad range of temperature and DO levels. Survival of mated triploids was negatively impacted at lower (but higher than ambient) pCO2 levels. Diploids and induced triploids had similar respiration across temperature and pCO2 experiments. Diploids respired more across all dissolved oxygen treatments. Differing performance of mated triploids suggests that production method or genetic background may contribute to their resilience or susceptibility to stress. Considering the stressors that will be placed on individuals in commercial aquaculture when making ploidy selections is essential to ensure the resilience of aquaculture as the climate changes.

Continue reading ‘Differential performance of diploid, mated triploid, and induced triploid Pacific oysters under varied environmental conditions: insights into impacts of temperature, dissolved oxygen, and pCO2’

Warming enhances the effects of acidification on aquatic biota: a global meta-analysis

Published 11 July 2025 Science Closed
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Aim: Global elevated atmosphere CO2 concentration-induced acidification poses a great threat to aquatic organisms worldwide. However, a comprehensive understanding of the response variability to acidification is still lacking, especially in the context of concurrent global warming. Addressing the response patterns of aquatic biota to acidification under the context of warming can facilitate the identification and prediction of probable consequences of global climate change.

Location: Global.

Time Period: 1996–2024.

Major Taxa Studied: Aquatic biota.

Methods: We performed a meta-analysis by synthesising 221 studies containing 3669 observations to summarise the effects of CO2 on multiple aquatic biota, including primary producers, consumers, and decomposers. We further examined the effects of different ecosystems, experimental venue, CO2 concentration, and ambient experimental temperature on the response magnitude.

Results: Acidification had significant positive effect on primary producers and decomposers, yet significant negative effect on consumers. We found that invertebrates were the most negatively affected of all organisms, and the marine ecosystems are suffering more severity of acidification than freshwater ecosystems. We further found that the response magnitude showed a significant dose effect, indicating that reducing greenhouse gas emissions would minimise the impact of acidification. In addition, we found that higher temperatures enhanced the sensitivity of primary producers to acidification, suggesting that global climate warming may interact with acidification in a synergistic way.

Main Conclusions: Our results showed that distinct trophic levels showed significant differences in the response direction and magnitude. Specifically, the consumer is generally the most sensitive trophic level that is negatively affected by acidification. We emphasise that the simultaneous exposure of primary producers to anthropogenic stressors associated with acidification and warming is expected to produce interactions that may potentially reinforce the negative consequences, which is key to predicting and mitigating the acidification effect under future climate change scenarios

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Groundwater discharge found to alter coral reef ecosystems

Published 11 July 2025 Press releases Closed
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Groundwater directly affects water chemistry in coral reefs and triggers a cascade of changes in the coastal ecosystem, according to a new study led by University of Hawaiʻi at Mānoa oceanographers. The researchers describe the effect as a “Goldilocks scenario”—too much groundwater has a negative impact, and when the input is “just right,” the reef benefits.

Freshwater from land that flows into the ocean beneath the sea surface, termed submarine groundwater discharge, was found to increase nutrient availability, change acidity of the seawater, and impact the process by which corals build their skeletons. This research, published recently in Ecological Monographs, provides critical insights into the complex interactions between the land and ocean. 

“Submarine groundwater discharge is a widespread and underappreciated land–sea connection that delivers terrestrial nutrients and carbon to coastal ecosystems,” said Nyssa Silbiger, lead author of the study, associate director of the Uehiro Center for the Advancement of Oceanography, and associate professor in the Department of Oceanography at the UH Mānoa School of Ocean and Earth Science and Technology. “This profoundly influences coral reef health by triggering a cascade of chemical and biological changes that alter the cycling of carbon in these ecosystems.” 

The fundamental connection between land and sea through the flow of freshwater is a universal principle recognized as important for coastal health across all cultures. Porous volcanic islands throughout the tropics deliver much of this water through rivers and streams, but a major fraction emerges unseen directly into the coral reefs that ring these islands. This submarine groundwater discharge has long been recognized by Pacific peoples as important, with seeps frequently named and associated with specific communities of algae and fish relevant to subsistence. The new research has helped define the complex interplay of chemistry and biology that makes these inputs so important to the ecology of coral reefs. 

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Terrestrial nutrient inputs restructure coral reef dissolved carbon fluxes via direct and indirect effects

Published 11 July 2025 Science Closed
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The addition of terrestrial inputs to the ocean can have cascading impacts on coastal biogeochemistry by directly altering the water chemistry and indirectly changing ecosystem metabolism, which also influences water chemistry. Here, we use submarine groundwater discharge (SGD) as a model system to examine the direct geochemical and indirect biologically mediated effects of terrestrial nutrient subsidies on a fringing coral reef. We hypothesize that the addition of new solutes from SGD alters ecosystem metabolic processes including net ecosystem production and calcification, thereby changing the patterns of uptake and release of carbon by benthic organisms. SGD is a common land–sea connection that delivers terrestrially sourced nutrients, carbon dioxide, and organic matter to coastal ecosystems. Our research was conducted at two distinct coral reefs in Moʻorea, French Polynesia, characterized by contrasting flow regimes and SGD biogeochemistry. Using a Bayesian structural equation model, our research elucidates the direct geochemical and indirect biologically mediated effects of SGD on both dissolved organic and inorganic carbon pools. We reveal that SGD-derived nutrients enhance both net ecosystem production and respiration. Furthermore, the study demonstrates that SGD-induced alterations in net ecosystem production significantly influence pH dynamics, ultimately impacting net ecosystem calcification. Notably, the study underscores the context-dependent nature of these cascading direct and indirect effects resulting from SGD, with flow conditions and the composition of the terrestrial inputs playing pivotal roles. Our research provides valuable insights into the interplay between terrestrial inputs and coral reef ecosystems, advancing our understanding of coastal carbon cycling and the broader implications of allochthonous inputs on ecosystem functioning.

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Responses of the natural phytoplankton assemblage to Patagonian dust input and anthropogenic changes in the Southern Ocean

Published 10 July 2025 Science Closed
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Abstract

The cumulative effects of multi‐faceted changes on the phytoplankton community of the Southern Ocean (SO) are not yet known, which is a major limitation to predicting the future direction of the biological carbon pump. Thus, our study aimed to estimate the effects of intensified Patagonian dust inputs, warming and acidification on the growth, composition and production of phytoplankton assemblages in the Polar Frontal Zone (PFZ) and the High‐Nutrient Low‐Chlorophyll (HNLC) region of the Indian sector of the SO during the austral summer 2022. Natural phytoplankton communities were incubated for 5‐day under 4 scenarios (present and future conditions, and 2 intermediate scenarios). In the PFZ, +3°C and acidification stimulated the growth of phytoplankton, mainly cyanobacteria, while intensified dust inputs alone did not have notable impact. Conversely, in HNLC waters, the addition of Fe‐dust alone increased the total chlorophyll a of diatoms (mainly F. kerguelensis), whereas the negative effect of acidification and +3°C counteracted the positive impact of dust input on the diatoms. In these waters, future conditions benefited smaller species (haptophytes and cyanobacteria). The net particulate organic carbon production (POC) was also unaltered by future conditions, suggesting that primary production may not change in the future SO. However the increase in the length and number of long‐chain diatoms under future HNLC conditions may indicate that POC export could intensify in the future.

Plain Language Summary

Phytoplankton in the Southern Ocean (SO) play a critical role in absorbing atmospheric carbon dioxide and supporting marine ecosystems, however their response to future environmental changes remains unclear. This study examined how increased dust inputs, warming, and acidification affect the phytoplankton community in two contrasted biogeochemical domains of the SO, the Polar Frontal Zone (PFZ) and the High‐Nutrient Low‐Chlorophyll (HNLC) region. In the PFZ, warming and acidification favored the smaller phytoplankton species, while in the HNLC region, iron‐rich dust stimulated diatom species, though this effect was attenuated by warming and acidification. While overall the production of organic carbon by phytoplankton remained unchanged, diatoms may enhance carbon export to deeper waters under future conditions due to increased number and length of chain‐forming species. These findings highlighted the complexity of phytoplankton responses, which vary across regions and are influenced by interactive environmental factors. Understanding the impact of these environmental factors on phytoplankton is critical to predicting how future changes will shape the role of the SO in the global carbon cycle.

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Chemical and biological oceanographic conditions in the Labrador Sea from 2019 to 2023

Published 10 July 2025 Newsletters and reports Closed
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The Atlantic Zone Off-Shelf Monitoring Program samples the AR7W line annually. This report summarises trends from 2019-2023 for three regions: AR7W-W (Labrador shelf and slope), AR7W-C (central Labrador Sea), and AR7W-E (Greenland shelf and slope). Samples revealed a continued increase in dissolved inorganic carbon and a decrease in pH from 2019 to 2023. Mean concentration of CFC-12 decreased in 2020, and SF6 continued its steady increase. Mean temperature from 0-100 m in the Labrador Sea was above normal in 2019, below normal on the next mission (2022), and near or above normal in 2023. Surface (0-100 m) nutrients were mainly below normal from 2019-2023, which could be attributed to mission timing. However, below-average deep nutrients (>100 m, less impacted by sampling timing) suggests a profound change in the biogeochemistry of the Labrador Sea. Integrated (0-100 m) chlorophyll-a was below normal in 2019 and in AR7W-E in 2022-2023, but above normal elsewhere, with a record high value in AR7W-C in 2022 caused by an unusually large bloom of Phaeocystis spp.. Satellite data revealed high variability in the timing of the spring and fall blooms and surface average chlorophyll-a concentration. Mesozooplankton abundances showed high interannual variability since 2019.

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Larval Arctic cod (Boreogadus saida) exhibit stronger developmental and physiological responses to temperature than to elevated pCO2

Published 10 July 2025 Science Closed
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High-latitude ecosystems are simultaneously warming and acidifying under ongoing climate change. Arctic cod (Boreogadus saida) are a key species in the Arctic Ocean and have demonstrated sensitivity to ocean warming and acidification as adults and embryos, but their larval sensitivity to the combined stressors is unknown. In a laboratory multistressor experiment, larval Arctic cod were exposed to a combination of three temperatures (1.8, 5 and 7.3°C) and two carbon dioxide (pCO2) levels (ambient: 330 μatm, high: 1470 μatm) from hatching to 6-weeks of growth. Mortality rates were highest at 7.3°C (5% day°1); however, both growth and morphometric-based condition were also highest at this temperature. When these metrics were assessed via a mortality: growth (M:G) ratio, 5°C appeared to be an optimal temperature for net population biomass, as faster growth at 7.3°C did not fully compensate for higher mortality. In contrast, although morphometric-based condition was lowest at 1.8°C, lipid-based condition was highest, which may reflect prioritization of lipid storage at cold temperatures. The capacity of larval Arctic cod to acclimate to a range of temperatures was exhibited by two lipid-based indicators of membrane fluidity, including a ratio of unsaturated to saturated fatty acids and a ratio of polar lipids to sterols. The effects of elevated pCO2 were subtle, as well as temperature- and metric dependent. When exposed to elevated pCO2 levels, Arctic cod at 1.8°C exhibited signs of lipid dysregulation, suggesting potential interference with membrane acclimation; larvae at 5°C were in lower morphometric-based condition; and larvae at 7.3°C had higher activity eicosanoid substrates, indicating possible physiological stress. Overall, Arctic cod physiological response to temperature variation was more pronounced than their response to elevated pCO2. Future projections of pCO2 effects on Arctic cod health in a warming ecosystem will need to consider the complexity of temperature-dependence and the specificity of multiple physiological responses.

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Ocean acidification decreases molting but not survival of Antarctic amphipods Djerboa furcipes, Gondogeneia antarctica, and Prostebbingia gracilis

Published 10 July 2025 Science Closed
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Ocean acidification refers to a decrease in the pH of the world’s oceans from the oceanic uptake of human-derived atmospheric CO2. Low pH is known to decrease the calcification and survival of many calcifying invertebrates. Shallow, hard bottom communities along the Western Antarctic Peninsula often have incredibly large numbers of invertebrate mesograzers that shelter on and are mutualists with the dominant brown macroalgae. The common amphipod species Djerboa furcipes, Gondogeneia antarctica, and Prostebbingia gracilis were collected from the immediate vicinity of Palmer Station, Antarctica (64°46′S, 64°03′W) in January–February 2023 and maintained under three different pH treatments simulating ambient conditions (approximately pH 8.0), near-future conditions for 2100 (pH 7.7), and distant future conditions (pH 7.3) for 8 weeks. Molt number and mortality were monitored throughout the course of the experiment. After the 8 week exposure, amphipods were analyzed for their biochemical compositions including the Mg/Ca ratio of their exoskeletons. There was no significant difference in biochemical composition or survival among the pH treatments for any of the amphipod species. All three species, however, had significantly fewer total numbers of molts in the pH 7.3 treatment than in the ambient treatment. These results suggest that amphipods may be able to maintain their survival in decreased pH by reallocating energy into compensatory behaviors, such as acid–base regulation, and away from energy expensive processes like molting.

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Ocean acidification education program expands in Southeast

Published 10 July 2025 Media coverage Closed
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An ocean acidification education program called 4-H pH is coming to Angoon and Petersburg this summer, on the heels of its success in Sitka, to teach elementary school students how to test water for its pH levels.

“In some of these communities in Southeast they are monitoring ocean acidification, and in some they might not be, so the idea is also for community awareness,” said 4-H program assistant Jasmine Shaw with the University of Alaska Fairbanks Cooperative Extension Service, who led the Sitka program with Christina Buffington of the Geophysical Institute and Natalie Monacci of the College of Fisheries and Ocean Sciences, both at the University of Alaska Fairbanks.

The idea was to create a curriculum designed for elementary school students that anyone could use, rather than just 4-H, to teach ocean acidification testing, Shaw said.

4-H pH is a specific ocean acidification education program developed for youth, particularly those in elementary school. It aims to engage young people in collecting and understanding data related to ocean acidification, its impacts and potential solutions. Ph measure acidic or alkaline levels.

The curriculum is designed to be accessible and adaptable, not just for 4-H clubs, but for anyone interested in teaching about ocean acidification.

The project, funded by the NOAA Ocean Acidification Program, is part of a citizen science program called Global Learning & Observations to Benefit the Environment Program, or GLOBE. The program is led by NASA to advance science and educate tomorrow’s workforce. The National Science Foundation, National Oceanic and Atmospheric Administration and U.S. Department of State are also part of GLOBE.

About a dozen Sitka youth participated in the program from January through May. They learned to measure pH temperature and dissolved oxygen, and measurements were uploaded to the GLOBE program’s open-source database.

During their spring break, 4-H pH students assisted the Sheet’ká Ḵwáan Tribe on its weekly ocean-monitoring trip. They learned about pH in the kitchen with a guest chef. They also created artwork as part of the program and looked at future career opportunities.

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Spatiotemporal analysis of sea-surface pH in the Pacific Ocean based on interpretable machine learning

Published 9 July 2025 Science Closed
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Increasingly severe ocean acidification (OA) disrupts the balance of marine ecosystems. Seawater pH is a key indicator of OA but remains challenging to characterize due to sparse and limited in situ observations. In this study, we propose a spatiotemporal inversion method for surface pH based on interpretable machine learning. By applying carbonate system calculations, we construct an expanded pH observational dataset and obtain spatiotemporal distributions of pH and its influencing factors across the Pacific Ocean from 2003 to 2021. The interpretability analysis reveals that physical, biological, and optical factors contribute 53.9%, 23.9%, and 22.2%, respectively, to pH variability. Sea-surface temperature is the dominant driver, contributing 15.9% of all factors by regulating CO2 solubility and biological activity. Particulate inorganic carbon (PIC) and particulate organic carbon (POC) show relative contributions of 12.6% and 9.4%, respectively, quantitatively reflecting the important roles of biogenic calcification and the biological carbon pump. Furthermore, the analysis focusing on the Niño 3.4 region reveals a potential pathway through which the ENSO disturbances may affect pH by influencing PIC and POC. Therefore, this study provides a data-driven approach to gain deeper insights into the spatiotemporal patterns of pH and its influencing factors.

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Coral calcification mechanisms across a natural environmental mosaic in Hawai’i

Published 9 July 2025 Science Closed
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Coral calcification is key to coral reef growth and function but may be compromised under increasing global and local stressors. Corals modify the carbonate chemistry of their calcifying fluid to facilitate calcification, but little is known about how these mechanisms vary across the substantial differences in reef seawater conditions that can occur over as little as a few kilometers. Here, we used boron-based geochemical proxies (δ11B, B/Ca) to investigate how three common Hawaiian coral species (Montipora capitata, Porites compressa, Porites lobata) regulate the carbonate chemistry of the calcifying fluid along a natural environmental mosaic of seawater carbonate chemistry and significant wave height. We found that calcification mechanisms were governed by complex species and site interactions: while all species generally differed from each other in their calcifying fluid chemistry, they also responded differently to site-specific environmental conditions. These results highlight that there are varying degrees of calcification mechanism plasticity in response to changing environmental conditions. Furthermore, species-specific patterns of pH upregulation inside the calcifying fluid were good predictors of calcification responses to ocean acidification and warming in at least two of the three species, with M. capitata being a clear winner under future ocean conditions. Our findings provide important insights into how corals calcify across a natural environmental mosaic and highlight the differential potential for an adaptive capacity in calcification mechanisms in the face of intensifying climate change.

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Climate vulnerability assessment of fish and invertebrates in the U.S. South Atlantic large marine ecosystem

Published 9 July 2025 Science Closed
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Trait-based climate vulnerability assessment (CVA) is a rapid and repeatable approach to simultaneously assess the vulnerability of a large number of species to projected regional changes in climate. We conducted the first CVA in the U.S. South Atlantic Large Marine Ecosystem for 71 ecologically, economically, and culturally important fish and invertebrate species. The CVA was conducted by a 16-member panel based on scoring 12 biological sensitivity attributes and seven climate exposure factors. About two-thirds of the species were considered highly vulnerability to future climate projected under the RCP 8.5 emissions scenario, with diadromous species, invertebrates, and deepwater reef fishes the most vulnerable functional groups. Ocean acidification, sea surface temperature, and salinity were the exposure factors with the greatest influence on climate vulnerability, while population growth rate, population status, and early life history traits were the most important biological sensitivity attributes. More than two-thirds of the species had high potential for shifts in geographic distribution, due mostly to the prevalence of broadcast spawning, extensive larval dispersal, and high adult mobility of many species, and the generalist habitat requirements of several estuary-dependent and hard-bottom reef species. Some shifts in distribution have already occurred though potential relationships to environmental conditions associated with climate are not well-understood. Uncertainty analyses confirmed the robustness of the climate vulnerability rankings, but comparison of alternative types of elicited informed judgement did not always agree, suggesting higher uncertainty in climate vulnerability for some species. In addition, several species may benefit under future climate conditions, and climate effects on some species considered to be highly vulnerable may be of relatively small magnitude. These results can be used to prioritize conservation, research, and management efforts, and identify key uncertainties related to the impacts of future climate on fishery resources in the U.S. South Atlantic region.

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Ocean acidification is erasing microscopic historians, as St. Pete scientists try to learn their secrets

Published 9 July 2025 Media coverage Closed
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Beneath the ocean floor, in layers of ancient sediment, lie microscopic storytellers, marine organisms called foraminifera, or “forams” for short. These single-celled protists, no larger than a grain of sand, hold within their calcium carbonate shells a detailed record of Earth’s climate history. But, rising carbon emissions and ocean acidification may be erasing their story before scientists can read it.

At the University of South Florida’s College of Marine Science in St. Petersburg, oceanographer Callie Crawford is at the forefront of a research effort to understand how ocean acidification, a direct result of human-caused climate change, is ultimately threatening the ocean’s ability to remember.

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Crawford, an early-career scientist with two degrees in marine science and a minor in chemistry, works in the Rafter Ocean, which is run by Patrick Rafter and Climate Lab. She and her team collaborate with other scientists and labs to study sediment cores pulled from the ocean floor, containing layers dating back tens of thousands of years; records that, when combined with research from other labs, help reconstruct Earth’s past climate.

Inside these cores, scientists find foraminifera shells that preserve the chemical conditions of the water they lived in, clues that help reconstruct ancient ocean temperatures, carbon levels, and other vital environmental data.

This field of study, called paleoceanography, is key to building climate models that help us predict the planet’s future.

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Handling the heat: ocean acidification mitigates the effects of marine heatwaves on Posidonia oceanica seedlings 

Published 8 July 2025 Science Closed
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Ocean acidification (OA) and marine heatwaves (MHWs) are key drivers of marine ecosystem changes that can interact and influence marine organisms. Seagrasses, including the long-lived Posidonia oceanica endemic to the Mediterranean Sea, are widely distributed along coastal habitats, forming highly valuable underwater meadows. The germination and survival of the early life stages of P. oceanica are strongly affected by environmental changes. To assess the impact of warming and acidification on its future, we conducted a multifactorial experiment where P. oceanica seedlings were grown under OA conditions for six months and then exposed to a seawater warming event. Seedlings’ performance was investigated by analyzing photo-physiology, antioxidant capacity, energetic metabolism and transcriptomic profiles. The Weighted Gene Correlation Network Analysis (WGCNA) was used to integrate phenotypic plant traits with transcriptomic results to identify central genes involved in plant responses to OA and temperature exposure. Results demonstrated that prolonged OA exposure enhances P. oceanica seedling resilience to MHW. Specifically, seedlings regulated their antioxidant systems and transcriptomic machinery to better cope with thermal stress. Under current CO2 concentrations, elevated temperatures induced stress in P. oceanica seedlings, impacting photosynthesis and respiration. However, OA could mitigate the impact of warming in the future, enhancing P. oceanica‘s resilience to global stressors.

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Patterns of ocean acidification emergence in the Hawaiian Islands using dynamically downscaled projections

Published 8 July 2025 Science Closed
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Abstract

This study presents the first dynamically downscaled projections of ocean acidification (OA) for the Main Hawaiian Islands using coupled Regional Ocean Modeling System and Carbon, Ocean Biogeochemistry, and Lower Trophics models integrated with Coupled Model Intercomparison Project Phase 6 (CMIP6) outputs from the Community Earth System Model 2. We analyze three Shared Socioeconomic Pathways (SSP1-2.6, SSP2-4.5, and SSP3-7.0) and introduce a climate novelty metric to assess the extent to which future OA conditions exceed historical variability by comparing the magnitude of projected changes to past variability. Our results indicate unprecedented levels of OA within the next three decades across all scenarios, with aragonite saturation state (ΩA), pH, and substrate-to-inhibitor ratio (bicarbonate to free hydrogen ions [HCO3−]/[H+]) projected to decline significantly. By 2100, under SSP3-7.0, ΩA novelty could exceed reference variability by a factor of 12. Spatial analysis reveals heterogeneous OA impacts, with windward coastlines consistently exhibiting higher novelty levels. Importantly, we find contrasting spatial patterns of OA indices due to varying sensitivities to temperature and dissolved inorganic carbon, resulting in higher ΩA novelty in northern areas and higher pH and substrate-to-inhibitor ratio novelty in southern regions.

Key Points

  • Three climate scenarios (SSP1-2.6, SSP2-4.5, and SSP3-7.0) show distinct implications for ocean acidification in the main Hawaiian Islands
  • Aragonite saturation, pH, and substrate (bicarbonate) to inhibitor (free hydrogen) ratio lead to distinct spatial patterns
  • Future conditions under SSP3-7.0 are projected to exceed historical variability with strong spatial differences along Hawaiian coasts

Plain Language Summary

Our oceans are acidifying as they absorb carbon dioxide from the atmosphere. This change threatens coral reefs, which are vital ecosystems supporting marine life and providing coastal protection. In this study, we used advanced computer models to project how ocean chemistry around the main Hawaiian Islands might change over the 21st century under different scenarios based on how much carbon dioxide we continue to emit. Our results show that ocean acidification is expected to increase significantly across all scenarios, but the extent and timing of these changes vary. In the high-emission scenario, ocean chemistry will become dramatically different from what we have seen historically, potentially posing challenges to coral reefs and their ability to adapt. Even in the low-emission scenario, some changes are inevitable, but they are less extreme and occur more gradually. We introduced a concept called “novelty” to measure how future ocean conditions might deviate from what coral reefs have experienced in recent history, and discovered that different parts of the Hawaiian Islands may experience acidification differently. This research helps us understand the future challenges facing Hawaiian coral reefs and provides information for researchers, conservationists and policymakers for preserving these critical ecosystems for future generations.

Continue reading ‘Patterns of ocean acidification emergence in the Hawaiian Islands using dynamically downscaled projections’

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