Posts Tagged 'laboratory'

The fate of macroalgal carbon under microbial anaerobic respiration: a critical factor in macroalgae cultivation for climate change mitigation

Published 8 July 2026 Science Leave a Comment
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Highlights

  • Anoxic remineralization rates were not consistently lower than oxic rates.
  • Macroalgal degradation modulates the DIC pool, crucial for carbon sequestration.
  • Alkalinity generated by anaerobic respiration stabilizes the DIC pool.

Abstract

Macroalgae play a significant role in global carbon sequestration. Substantial macroalgal organic carbon inputs and subsequent degradation can cause deoxygenation; however, the impact of oxygen deficiency on carbon fate remains understudied, which is critical for assessing the climate mitigation role of macroalgae. Here, we investigated changes in the carbon pool and non-CO2 greenhouse gases (N2O and CH4) to assess the influence of oxygen levels on the carbon sink capacity of macroalgae. The microbial remineralization rate of macroalgal organic matter was not consistently slower under anoxic conditions (AK) compared to oxic conditions (OK). Total organic carbon (TOC) concentrations in the water column were 530 ± 94 (OK) and 282 ± 38 (AK) μmol kg−1. For dissolved inorganic carbon (DIC), concentrations on day 30 were 4585 ± 197 (OK) and 5200 ± 492 (AK) μmol kg−1, while those for total alkalinity (TA) were 2684 ± 18 (OK) and 4523 ± 671 (AK) μmol kg−1. Following a 30-day sealed incubation, the bags were opened to reach atmospheric equilibrium. Subsequently, DIC dropped to 1837 ± 79 (OK) and 3744 ± 354 (AK) μmol kg−1, and TA fell to 2059 ± 14 (OK) and 4431 ± 657 (AK) μmol kg−1. Ultimately, relative to the control group (seawater only, OS) under air-sea equilibrium, the ΔDIC values were −22 ± 76 and 1885 ± 351 μmol kg−1 in the OK and AK treatments, respectively, while ΔTA values were −57 ± 11 and 2315 ± 655 μmol kg−1. The emissions of N2O and CH4 did not substantially offset the climate effect of carbon sequestration. These results suggest that, beyond the traditional focus on organic carbon preservation, anaerobic respiration under anoxic conditions may also contribute to macroalgal carbon sequestration by generating alkalinity that enhances the retention and stabilization of DIC.

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Interactive effects of triclosan, microplastic vectors, and ocean warming–acidification on sea urchin embryo development

Published 6 July 2026 Science Leave a Comment
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Highlights

  • Microplastics modulate triclosan toxicity in a concentration-dependent manner.
  • Microplastic loads reverse triclosan attenuation affecting larval development.
  • Acidification amplifies triclosan–microplastic toxicity in sea urchin embryos.
  • Ocean Warming modulates toxicity; degree-day normalization reveals hidden stress.

Abstract

Understanding how emerging contaminants interact with climate-driven stressors is essential for accurate ecological risk assessment in coastal ecosystems. This study evaluates the individual and combined effects of triclosan (TC), polyethylene microplastics (MP), ocean warming (OW), and ocean acidification (OA) on the early development of Paracentrotus lividus embryos. A tiered experimental design was implemented to: (i) characterize TC dose–response curves alone and in combination with increasing concentrations of MP (300–3000 particles mL−1), and (ii) assess how OW (24 °C) and OA (pH 7.6) modulate contaminant toxicity. TC showed concentration-dependent growth inhibition, while MP exhibited a biphasic interaction with TC: at moderate concentrations, MP increased EC10 values and steepened dose–response slopes, consistent with contaminant sorption reducing freely dissolved TC. At 3000 particles mL−1, this trend reversed, lowering EC50 values and enhancing toxicity. Morphometric analyses revealed that co-exposure to TC alone and with MP loads impaired arm elongation, increased body-width ratios, and reduced stomach volume, indicating compromised feeding and skeletal development. Climate stressors significantly altered toxicological outcomes. OA strongly amplified the combined toxicity of TC + MP, reducing larval growth to near-zero levels, whereas OW alone did not exacerbate toxicity and partially mitigated OA-driven effects in MP-TC treated groups. Degree-day normalization demonstrated that warming accelerates development but reduces growth efficiency across treatments. Overall, these results reveal threshold-dependent MP–TC interactions and highlight acidification as a critical amplifier of contaminant effects. Incorporating realistic MP–pollutant interactions and climate variables is crucial for improving hazard assessments under future ocean scenarios.

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Study on the mechanical characteristics of the stress relaxation in the carbonate rock after high-temperature acidification

Published 3 July 2026 Science Leave a Comment
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To elucidate the mechanism by which acidification influences wellbore stability in deep reservoir formations, this study investigates the rheological and mechanical behaviors of the carbonate rock subjected to high-temperature acid etching. A novel experimental system was developed to characterize the stress relaxation behavior of the acid-etched carbonate rock, and the characteristics of the stress relaxation curves under various acid etching conditions and strain levels were systematically analyzed. Combined with Burgers model and the Levenberg–Marquardt algorithm, the evolution of rheological parameters of the carbonate rock under different acid etching regimes was quantitatively evaluated. The results indicate that the acid-etched carbonate rock exhibit significant rheological mechanical properties due to the presence of developed microcracks and complex pore structures. Under the identical acid etching duration and temperature, the initial stress, residual stress, and time required for stress relaxation stabilization all increase with increasing the strain level. Overall, the stress relaxation magnitude prior to the core fracture ranges from 15 to 25 MPa, and the stabilization time for the core stress relaxation falls between 5 and 7 h. The stress relaxation behavior of the acid-etched carbonate core is well described by the Burgers model. At fixed strain levels and temperatures, the instantaneous shear modulus  decreases linearly with extended acid etching time, whereas the instantaneous shear modulus  and the viscosity coefficients  and  exhibit exponential degradation. The final variation ranges of the key rheological parameters are determined as follows: instantaneous shear modulus  ranges from 5 × 103 to 2 × 104 MPa, instantaneous shear modulus  ranges from 6 × 105 to 2 × 106 MPa, viscosity coefficient  ranges from 2 × 107 to 8 × 107 MPa h, and viscosity coefficient  ranges from 1 × 105 to 1.2 × 106 MPa h. Furthermore, the evolutionary equations correlating the global model fitting parameters with the porosity of acid-etched samples are established, using acid etching time as an intermediate variable. The results of this study provide a theoretical basis for the analysis of wellbore stability after acidification and the selection of acid fracturing completion methods of deep reservoirs.

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Thermal regulation of benthic fluxes in temperate estuaries

Published 2 July 2026 Science Leave a Comment
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The effects of short-term heatwave extremes on biogeochemical cycling and fluxes in a temperate estuary of a semi-dry climate were studied using an experimental setup of temperature-controlled benthic incubations. The results demonstrated a strong thermal effect, notably under extreme warming events, for shifts in exchanges across the sediment-water interface. Extreme heatwave conditions (+5 °C of the seasonal mean) boosted acidification, hypoxia, and ammonification, due to accelerated remineralization rates, resulting in strong effluxes of NH4, Si(OH)4, and PO4 to the overlying water. These excessive nutrient loads may increase eutrophication risk via runoff or tidal action, specifically in adjacent oligotrophic coastal waters. CO2 production rates reached ~4000 µatm under extreme hypoxia and acidification, 2.3-fold higher than the ambient rate, with a maximal flux of ~27.0 mmol m-2 d-1. Hence, our experiments show that marine heatwaves amplify CO2 emissions while reducing the CO2 buffering capacity of temperate estuaries. It emphasizes temperate estuaries as highly sensitive ecosystems to climate change.

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Short-term plasticity and long-term transcriptomic rewiring under natural ocean acidification in an ecosystem-relevant sea urchin

Published 1 July 2026 Science Leave a Comment
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Highlights

  • Natural CO2 vents reveal transcriptomic responses to chronic ocean acidification.
  • Acute low-pH exposure triggers rapid but limited plastic responses in Arbacia lixula.
  • Vent-origin Arbacia lixula exhibit extensive metabolic reprogramming and antioxidant activation.
  • Low pH supresses biomineralization genes and up-regulates collagen and extracellular matrix pathways.
  • Persistence under ocean acidification is associated with energetic trade-offs and skeletal homeostasis.

Abstract

Ocean acidification is reshaping coastal ecosystems as a consequence of anthropogenic CO2 emissions. Natural CO2 vent systems provide valuable analogues for investigating organismal responses to long-term acidified conditions under ecologically realistic scenarios. Here, we examined genome-wide transcriptomic responses of the sea urchin Arbacia lixula, an ecosystem-relevant grazer inhabiting a natural CO2 vent system in La Palma (Canary Islands, Spain). Using RNA sequencing of 24 adults (n = 8 per treatment), we compared: (i) acute experimental exposure of ambient-origin individuals to low pH, (ii) chronic exposure by comparing ambient and vent-origin populations in their native pH conditions, and (iii) a genotype-of-origin comparison under shared low pH. Acute exposure triggered a limited transcriptional response (116 differentially expressed genes, DEG), characterized by activation of ion transport, redox regulation, and NAD-associated metabolism. In contrast, chronically exposed vent-origin urchins showed a tenfold increase in transcriptional changes (1053 DEG), reflecting metabolic reprogramming involving lipid, carbohydrate and amino acid pathways, and strengthened antioxidant capacity. Chronic low-pH exposure was also associated with suppression of biomineralization and developmental genes, alongside strong upregulation of collagen and extracellular matrix–associated genes that may help maintain skeletal performance under reduced carbonate availability. Genotype-of-origin effects (131 DEGs) revealed constitutive differences in metabolic, redox, extracellular matrix, and biomineralization pathways in vent populations. Together, these findings indicate that persistence under natural acidification involves both rapid plastic responses and sustained physiological reorganization, providing mechanistic insight into how calcifying species maintain functional performance under ongoing ocean acidification.

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Impact of water quality and gear type on Eastern oyster (Crassostrea virginica) growth in Narragansett Bay, RI

Published 1 July 2026 Science Leave a Comment
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Oyster aquaculture is expanding in Rhode Island, yet key farming regions in the lower West Passage of Narragansett Bay (WPNB) lack the in-situ, high-temporal resolution monitoring needed to evaluate emerging stressors and support production. At the same time, the industry is undergoing rapid technological development aimed at improving production while reducing labor and overall costs. In recent years, a low maintenance, alternative surface gear was introduced in WPNB; however, its impact on oyster performance relative to traditional cultivation methods has not been quantified. This study established a 1.5-year continuous water quality time series in WPNB and paired these observations with physiological assessments of Crassostrea virginica grown in three cultivation methods (i.e., traditional surface, alternative surface, and bottom gear). This work aimed to better understand the impact of environmental variability and gear type on oyster health, growth, and survival. Multiparameter sondes and discrete bottle samples were used to monitor water quality and calculate carbonate saturation state (Ω) at a 4-acre oyster farm. Nine mesh bags containing early-life stage C. virginica (16 ± 0.4 mm; n = 300 per bag) were deployed in July 2025, with three replicate bags in each gear type. Subsamples (n = 15) from each gear type were collected over a 6-month period for morphometric measurements and scope for growth (SFG) determinations. Minimal differences in carbonate chemistry were observed among sampling sites and Ω remained supersaturated (Ω >1) for the majority of the study period, indicating that ocean acidification was not a major stressor for farmed oysters. Survival was highest (82 ± 4.5%) in surface gear types compared to bottom gear (27 ± 0.58%), while physical growth (shell and tissue) and SFG were largely similar among all gear types. These results suggest that the alternative surface gear may support comparable production and product quality to traditional gear types, while also reducing maintenance and labor demands. Overall, this study provides important physiological and biological context for oyster aquaculture while informing gear selection and farm management strategies.

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Skeletal porosity of a cold-water coral increases with decreasing aragonite saturation state along a depth gradient in the Mediterranean Sea

Published 29 June 2026 Science Leave a Comment
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Background

Cold-water corals (CWCs) are key ecosystem engineers that create complex three-dimensional habitats much like tropical reefs, but in deep, cold seas. However, like other reef-building systems, they are increasingly threatened by climate change and ocean acidification. CWC communities in the Mediterranean Sea may be especially vulnerable because these waters absorb more atmospheric CO2 than the global ocean, making it a mesocosm that mirrors broader global trends affecting marine life. Since calcification is energetically costly and likely becomes even more demanding as pH and carbonate ion availability decline, understanding how the decrease in aragonite saturation state (Ωarag) affects biomineralization is essential for predicting the future of these corals.

Results

Here, we investigated skeletal structural and compositional changes of the scleractinian CWC Desmophyllum dianthus along an Ωarag gradient in the Mediterranean Sea using specimens collected between 400 and 1200 m depth. Our findings indicate that skeletal porosity increases at the macro-scale with decreasing Ωarag, while micro- and nano-scale structural and compositional features remained unaffected.

Conclusions

The persistence of micro- and nano-scale skeletal features across an 800 m depth gradient suggests that D. dianthus maintains tight biological control over mineralization at these scales, even as Ωarag declines. This control does not extend to the macro-scale, where increasing porosity alters the skeleton’s overall architecture under lower Ωarag. D. dianthus thus appears to preserve the fundamental “building blocks” of its skeleton while changing its larger-scale structure, a decoupling that may make macro-scale porosity an early marker of acidification stress in CWCs.

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Acute low pH associated with coastal acidification is detrimental to larval development of the Cape urchin Parechinus angulosus

Published 26 June 2026 Science Leave a Comment
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Acidification in coastal habitats is increasing in duration and amplitude under the continued influence of ocean acidification and contributing coastal processes. The impacts of low pH conditions on calcifying organisms, especially echinoderms, is well established, with the early developmental stages being especially vulnerable. This is the first study to assess the impact of locally relevant coastal acidification scenarios on the early development of the Cape urchin Parechinus angulosus. Our findings suggest that the early larval stages of this species are unlikely to survive when exposed to low pH conditions, specifically during the onset of skeletogenesis. In our laboratory experiments, larvae that were exposed to the low pH treatment (pH 7.32) showed significantly reduced growth (GLMM, Time × Treatment interaction: β = −0.361 ± 0.019, z = −19.06, p < 0.001) and developmental regression compared with those from the control treatment (pH 7.95). Substantially slower growth rates were observed in the low pH treatment (length = 72.3 hpf0.18) compared with in the control treatment (length = 24.24 hpf0.54). There was also evidence of abnormal and delayed development and potential dissolution of skeletal structures under the low pH condition. However, fertilisation success and larval survival did not differ significantly between the experimental treatments, suggesting that developmental impacts of low pH over short durations, even though substantial, may be sublethal. The developmental impacts are likely to impair the transition of larvae to the adult stages, which may ultimately affect populations of this ecologically important species under future coastal acidification scenarios.

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Lithium isotopes reveal impaired ion transport in tropical corals exposed to high pCO2

Published 26 June 2026 Science Leave a Comment
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Ocean acidification, driven by rising atmospheric CO₂, threatens the ability of corals to build their skeletons by reducing their capacity to maintain an elevated pH at the calcification site (pHcf), a process essential for calcium carbonate precipitation. Boron isotopes have commonly been used to show that the response of pHcf to ocean acidification is highly species-specific. However, the physiological mechanisms underlying this variability remain poorly understood. Recently, lithium (Li) isotopes have been used to trace the activity of ionic transport involved in cellular pH regulation and calcification (e.g. H+, Na+ and Ca2+), and may therefore help resolve these mechanisms. Here, we investigate multiple coral species from Tutum Bay (Papua New Guinea), a natural CO₂ seep system creating pH gradients (mean pHT = 7.66 at seeps vs. 8.01 at control sites) analogous to future ocean acidification scenarios. Our results show a relationship between seawater pH, calcifying fluid chemistry, and lithium isotopic composition. Corals exposed to low seawater pH exhibit significantly altered δ⁷Li values relative to colonies from the control site, with some species becoming enriched in ⁷Li (up to 2‰) as pHcf declines. This isotopic shift is consistent with reduced efficiency of Na⁺/H⁺ exchangers (NHEs), active transporters that preferentially incorporate the lighter ⁶Li isotope under optimal conditions but may become less effective under elevated proton concentrations. By linking Li isotopes to calcifying-fluid chemistry, these results provide geochemical evidence that ocean acidification may disrupt ionic regulation in corals and that Li isotopes can help to resolve biogeochemical controls of carbonate-systems.  

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Marine invertebrates and fishes exhibit inconsistent body size responses to ocean acidification

Published 18 June 2026 Science Closed
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Body size is a fundamental characteristic of all living organisms that determines physiological functions and life-history traits. Ecological theory predicts that ocean acidification can cause body size reductions, confirmed by several studies reporting miniaturization in ectotherms. Based on this prediction, we would expect a broad suite of species to show similar plastic body-size responses to elevated CO2. Using four natural climate change analogues of ocean acidification across the northern and southern hemispheres, we quantified body size alterations across 18 marine invertebrate and fish taxa to test for climate-driven miniaturization. Only three species consistently showed body-size reductions under ocean acidification: one urchin and two fish species. In contrast, 15 other species, ranging from highly calcified to non-calcified, displayed unchanged or increased body sizes or inconsistent miniaturization. If body-size miniaturization responses were consistently reproducible across taxa we would have observed it more frequently, suggesting that species responses to ocean acidification are more variable than previously thought and likely vary depending on a species’ physiology and life history. Thus, rather than entire communities undergoing miniaturization, species are likely to display a spectrum of responses, with some exhibiting size reductions, others demonstrating physiological resistance to elevated CO2, and others potentially benefiting from the indirect effects of ocean acidification.

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Pteropod vulnerability to ocean acidification in the eastern Arabian Sea

Published 18 June 2026 Science Closed
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Highlights

  • First study on pteropod response to ocean acidification in the eastern Arabian Sea.
  • High pteropod abundance during fall inter monsoon season due to food availability.
  • pH in the Arabian Sea was low during south west monsoon with pHT upto 7.75
  • Pteropod shell dissolution was observed under acidified conditions
  • Protrusions through the pteropod shell were observed under acidified conditions

Abstract

The rapid rise in atmospheric CO2 and its subsequent uptake by the oceans has led to ocean acidification and other associated changes in the marine ecosystem. The recent reports of the shoaling of the aragonite saturation horizon in the northern Indian Ocean are particularly alarming, as they pose a serious threat to the survival of calcareous organisms. Pteropods, also known as sea-butterflies, are believed to be highly susceptible to ocean acidification due to their thin aragonite shell. In our study in the eastern Arabian Sea, we found low pH conditions with surface pHT as low as 7.751 during late South-west monsoon (SWM). The pteropod abundance is high during the fall inter-monsoon (FIM), suggesting that the system continues to sustain productivity even after the cessation of peak monsoon activity. This also implies that the food availability regulates pteropod abundance in the eastern Arabian Sea. As pteropods are key components of food sources for many marine species, such as fish, any changes in their abundance can have cascading effects on the marine food web. To show how pteropods will be affected in futuristic elevated CO2 conditions, a CO2 manipulation experiment was conducted in the eastern Arabian Sea during December 2024. Pteropods belonging to Creseis acicula from the eastern Arabian Sea were subjected to pHT = 7.470, and pCO2 = 1734 μatm under controlled conditions. Our findings suggest that acidification led to the dissolution of pteropod shells. Acidification also led to protrusion through the shells, and these protrusions varied in length up to 88 μm. These structural alterations represent an acute response of pteropod shells to reduced pH, highlighting their rapid vulnerability to acidification stress. These observed protrusions need to be assessed further to determine if they provide any competitive advantage in combating or minimizing the impact of ocean acidification.

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Shifts of tentacles-associated prokaryotes of Anemonia viridis along a natural pH gradient

Published 18 June 2026 Science Closed
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Highlights

  • A. viridis tentacle microbiomes were studied under changing natural pH conditions.
  • Notable shifts in the abundance of specific taxa emerged in the acidified sites.
  • Differences in seawater emphasized the host’s unique microbial signature.
  • Rickettsiales predominance suggested a specialized ecological role in symbiosis.
  • Further research is needed to discern the role of microbes for host resilience.

Abstract

Marine hydrothermal vents are extreme environments that naturally select for organisms with strong resistance and the ability to cope with special conditions of acidification. Sea anemones are an interesting example that are able to buffer intracellular pH conditions. In this study, the influence of a natural pH gradient on microbial communities associated with Anemonia viridis (Cnidaria, Anthozoa) tentacles was investigated. We hypothesized that exposure to a natural pH gradient would be associated with changes in the structure and activity of A. viridis-associated microbial communities, potentially contributing to the host’s resilience in hydrothermal environments. Microbial enzymatic activities within anemones’ tentacles were investigated by incubation with fluorogenic compounds. The leucine amino peptidase activity was highest in the tentacles of specimens living in more acidified sites. A microbial biodiversity loss was observed in bacterial symbionts from less acidified to more acidified sites, with a reduction of relative abundance in certain groups (i.e., Planctomycetota, Firmicutes, and Desulfobacterota). Results obtained by a metabarcoding approach provided interesting insights into the taxonomic shifts of the A. viridis holobiont system in naturally acidified environments.

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Response of HAB-forming microalgae competition to ocean acidification, warming, and changing light fields

Published 17 June 2026 Science Closed
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In recent years, the East China Sea (ECS) has experienced frequent harmful algal blooms (HABs), driven by the complex interplay of climate change—specifically ocean warming and acidification—and eutrophication-induced light attenuation. Despite their ecological significance, the interactive effects of these environmental stressors on the competitive dynamics between bloom-forming microalgae remain poorly understood. This study aimed to elucidate how warming, reduced light, and elevated CO2 influence the competition between two dominant diatoms. We conducted controlled monoculture and mixed-culture experiments using two key species: Skeletonema costatum and Chaetoceros curvisetus. The experimental design incorporated varying levels of CO2, temperature, and light intensity to simulate future coastal scenarios. Growth rates, peak cell densities, and successional patterns were monitored to assess competitive outcomes under multiple stressors. Monoculture results indicated that high temperature and low light intensity promoted the growth of both species. However, in mixed cultures, these conditions significantly accelerated the time to reach peak density and induced a definitive successional shift from S. costatum to C. curvisetus. Notably, while the general successional pattern was consistent, elevated CO2 further enhanced the competitive advantage of C. curvisetus, particularly when combined with high-temperature and low-light scenarios. These findings suggest that the synergy of future warming, declining light availability, and intensified ocean acidification in the ECS will likely favor C. curvisetus over S. costatum. This shift may increase the frequency of HAB events dominated by C. curvisetus, driving significant climate-related restructuring of phytoplankton communities in coastal ecosystems.

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Geographic variation in proteomic responses to ocean acidification in a cold-water coral (Balanophyllia elegans)

Published 16 June 2026 Science Closed
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In the face of a rapidly changing climate, assessing organismal responses to future stressors in the context of current, natural exposure to stress could provide key insights to understanding marine ecosystem resilience. I used Balanophyllia elegans, a cold-water, solitary, azooxanthellate coral as a model to better understand how varying oceanographic conditions across its geographic range have shaped its ability to tolerate and potentially adapt to current and future ocean acidification conditions. I collected B. elegans individuals from four sites across 2,500km of their range and subjected them to two pH treatments to investigate site-specific protein expression in response to low pH. Using proteomic analysis, I found that corals from each site responded differentially to low pH, mainly through changes in regulation of metabolism, calcification, and homeostasis-related proteins. Additionally, health condition varied significantly between sites after exposure to low pH, providing further evidence of site-specific responses. These results demonstrate site-specific variation in responses and tolerance to low pH, a pattern that could inform future investigations into environmental-driven adaptive expression. Such site-specific responses highlight the importance of multi-source studies for predicting a species’ ability to navigate future climate changes.

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Short communication: skin melatonin and cortisol responses to water acidification and basification within the optimal pH range in three-spined sticklebacks

Published 15 June 2026 Science Closed
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Highlights

  • Cutaneous Mel, unlike cortisol, shows high sensitivity to slight shifts in water pH.
  • Water pH was regulated by a custom-designed system controlling dissolved CO2 levels.
  • High skin Mel levels and distinct pH-dependent responses indicate local Mel synthesis.

Abstract

Fish skin functions not only as a passive protective barrier but also as an active site of key physiological processes, including a local stress response system. In fish, this system involves the hormones cortisol and melatonin (Mel), which contribute to counteracting environmental stressors and maintaining homeostasis. In this study, we examined the sensitivity of both components of the cutaneous stress response system (CSRS) in three-spined sticklebacks (Gasterosteus aculeatus) exposed to acidic (pH = 6.54) and basic (pH = 8.70) water conditions, representing the boundary values of the species’ optimal pH range, under either rapid or gradual pH change regimes. Water pH in the aquaria was precisely controlled using a custom-designed gas-exchange system regulating dissolved CO2 levels. Mel concentrations were measured in the skin, brain and eyeball, while cortisol was determined in the skin. Samples were collected during the day. Skin Mel levels were significantly higher under acidification than under basification (P = 0.036; rapid change regime), whereas cortisol remained stable across all conditions. Ocular Mel levels were not affected by treatments. Brain Mel concentrations were generally very low but tended to be slightly higher under basification than under acidification in both regimes (P = 0.05, borderline significance). The marked differences in skin Mel levels between acidic and basic pH water conditions, accompanied by stable cortisol concentrations, indicates that cutaneous Mel, but not cortisol, is highly sensitive to subtle water pH fluctuations even within the species’ optimal range.

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High-resolution reconstruction of the pH-upregulation and its seasonal drivers in the temperate coral Cladocora caespitosa

Published 12 June 2026 Science Closed
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Ocean acidification (OA) and associated changes in seawater carbonate chemistry, combined with thermal stress, hampers coral calcification. By upregulating pH and dissolved inorganic carbon, corals can optimize their calcification, giving them some resilience to OA. Little is known about the seasonal- and interannual‑scale impacts of thermal stress and OA on pH upregulation and calcification in the temperate coral Cladocora caespitosa, despite it being the only zooxanthellate reef builder in the Mediterranean Sea. δ¹¹B and B/Ca were determined seasonally in C. caespitosa skeletons from two NW Mediterranean sites to reconstruct the effect of seawater temperature and pH on the carbonate chemistry of the coral calcifying fluid (CF), at a bimonthly resolution from June 2013 to August 2017 (Columbretes Islands, Spain), and June 2016 to February 2022 (Villefranche-sur-Mer, France). Cladocora caespitosa displayed a similar pH upregulation strategy to most tropical corals, albeit with an apparently lower sensitivity to seasonal environmental change. Temperature was the main driver of seasonal variability in the CF composition and coral calcification, with seawater pH having a comparatively lower seasonal variability, and acting on longer timescales. While longer coral records and investigations into inter-population variability would still be beneficial in order to fully understand the response of C. caespitosa to environmental change, our records constitute an important first step in understanding the biomineralization strategy of this ecologically important coral species.

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Response mechanism of Sepia esculenta larvae under global warming, ocean acidification and salinity fluctuation: Integrated biochemical and transcriptome profiling

Published 12 June 2026 Science Closed
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Highlights

  • Analysis based on global warming, ocean acidification and salinity fluctuation.
  • Multi-angle analysis of Sepia esculenta under temperature, pH and salinity stress.
  • Different stress enhanced the immune defense and antioxidant defense of S.esculenta.
  • The hub genes closely related to stress resistance were identified and screened out.

Abstract

The Sepia esculenta occupies a significant economic proportion in the squid family, and it is also the squid with the largest economic value in the northern sea area of China. With the occurrence of global warming, ocean acidification and ocean salinity fluctuations, it has caused serious negative effects on the development of the S. esculenta artificial breeding industry. Therefore, in the research, we employed weighted gene co-expression network analysis (WGCNA) to investigate the effects of three environmental factors, including salinity, temperature and pH, on the molecular mechanism of S. esculenta larvae, and proved the reliability of transcriptome results through physiological indicators. Enrichment analysis of each module indicated that environmental exposure markedly influenced immune function, oxidative stress responses, and other physiological processes in S. esculenta larvae. Our research elucidates the comprehensive response mechanism of S. esculenta under different environmental stresses, clarifies the significant molecular pathways essential for its growth and development.

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Ocean acidification alters hypoxia sensitivity and oxyregulation in reef-building corals

Published 9 June 2026 Science Closed
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Coastal marine ecosystems are increasingly threatened by multiple stressors such as ocean acidification and deoxygenation, but how these co-occurring stressors interact is often poorly understood. This is especially true for tropical coral reefs where deoxygenation is an emerging yet understudied threat. Using hypoxia response curves combined with rigorous pH control, we show that acidification alters hypoxia sensitivity and oxyregulation of reef-building corals in a species-specific manner: three species exhibited increased sensitivity to various degrees, while the fourth showed enhanced tolerance. Consequently, acidification pushes critical hypoxia thresholds into oxygen regimes already prevalent on reefs today, potentially driving shifts in community composition and accelerating risks to reef resilience as these stressors intensify in the future. Our findings challenge assumptions of uniform coral vulnerability under multi-faceted climate change, emphasizing the need for trait-based approaches and to account for stressor interactions in predictive models to better anticipate coral reef futures under rapid climate change.

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A screening approach for aquaculture breeders based on sperm performance under climate change-related stress

Published 4 June 2026 Science Closed
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Highlights

  • Temperature rise reduced European sea bass and Senegalese sole sperm motility.
  • Gilthead seabream sperm showed lower variation under acidification and warming.
  • Challenge tests allowed differentiation among males based on sperm performance.
  • Approach provides a screening framework for sperm performance.

Abstract

We aimed to develop a screening approach to differentiate among males of European sea bass (Dicentrarchus labrax), gilthead seabream (Sparus aurata), and Senegalese sole (Solea senegalensis) based on sperm performance under environmental acidification and temperature increase. Sperm samples were selected using a CASA system, and three challenge tests were applied. The first one consisted of sperm activation with artificial seawater (ASW) across a pH range (7.6–8.2). The second assessed activation at species-specific temperatures. The third test evaluated the combined effect of ASW pH (7.8 and 8.2) and different temperatures. Results from the third challenge test revealed differences in sperm performance under environmental variations, allowing differentiation among males. For this purpose, sperm motility values obtained for each sample under species-specific natural environmental conditions were used as references, and variations in motility were compared across challenge conditions. Different levels in the criteria (regarding the different percentages of motility variation) were applied to differentiate among males. The temperature increase affected the sperm kinetic parameters of European sea bass and Senegalese sole, while gilthead seabream sperm showed lower variation under seawater acidification and rising temperatures. The challenge test allowed differentiation among males based on sperm performance under environmental variations and represents a preliminary screening approach. However, these results are based on in vitro conditions and should be interpreted as a first proxy, requiring further validation to establish links with reproductive performance in vivo.

Continue reading ‘A screening approach for aquaculture breeders based on sperm performance under climate change-related stress’

Environmental, phylogenetic, and palaeogeographic impact on relative septal thickness in Devonian ammonoids from Morocco

Published 3 June 2026 Science Closed
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Building upon previous research, this study examines potential relationships between septal thickness in Devonian ammonoids from the Anti-Atlas of Morocco and isotopic proxy data from the literature for atmospheric CO2, sea surface temperature, oceanic pH, and weathering (δ18O, δ13C, δ11B, 87Sr/86Sr). Recent studies have demonstrated that various mollusc groups show some growth sensitive to environmental factors. Our results indicate no significant correlation between septal thickness and the examined proxies, except for significantly thinner septa in the genus Phoenixites following the environmental perturbations during the Kellwasser Event, which included anoxic conditions and possibly ocean acidification. This supports the hypothesis that a positive selection for reduced shell material occurred in response to changing seawater chemistry. Additionally, our results align with published data and may support a correlation between septal thickness and palaeolatitude. This study contributes to our understanding of the evolutionary impacts of environmental stressors such as ocean acidification on ammonoids and their adaptive strategies to changing environmental conditions.

Continue reading ‘Environmental, phylogenetic, and palaeogeographic impact on relative septal thickness in Devonian ammonoids from Morocco’

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