Posts Tagged 'morphology'

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The impact of ocean acidification on gastropod shell dissolution and microstructure

Published 11 April 2025 Science Closed
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Highlights

  • Ocean acidification causes gastropod shell dissolution and microstructural change.
  • Shell growth is inhibited below pH 7.5, with dissolution pits in the inner surface.
  • At pH 7.1, shell surface erosion intensifies, with extensive periostracum peeling.
  • Shell dissolution negatively correlates with pH, offering a new bio-proxy.
  • Shell structural changes can assess past ocean acidification events.

Abstract

Global seawater pH is projected to decrease by 0.3–0.5 units on average by the end of this century, which is considered detrimental to the shells of marine calcareous organisms. However, there is limited understanding of how ocean acidification affects the morphology and structure of these shells, as well as the underlying mechanisms. This study examines the shell growth, surface erosion, and microstructural changes of the marine gastropod Lunella coronata granulata after 85 days of exposure to varying pH (8.1–7.1). The results reveal that at pH ≤ 7.5, shell growth is notably inhibited, with pronounced dissolution hole formation on the inner surface. At pH 7.1, shell surface erosion becomes more pronounced, accompanied by extensive peeling of the shell periostracum. These changes—dissolution hole formation and periostracum peeling—are critical indicators of gastropod shell response to ocean acidification and can serve as biological indicators reflecting current and past ocean acidification. Additionally, our study shows a clear negative correlation between shell dissolution and pH, providing new bio-proxy for indicating the pH changes.

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Skeletal morphometrics suggests high fitness of hybrid coral recruits under ocean warming and acidification

Published 10 April 2025 Science Closed
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Anthropogenic greenhouse gas emissions increase sea surface temperature and acidification, inhibiting calcification of reef-building corals. While ocean acidification is known to hinder skeletal development of newly settled coral recruits, little is known of its effects on older purebred or interspecific hybrid recruits, or its combined effects with temperature. Using 3D X-ray microscopy, we found that predicted mid-century ocean warming and acidification conditions (28 °C, 685 ppm pCO2) negatively affected the skeletal development of 7-month-old Acropora purebreds and hybrids in one direction (Acropora cf. kenti mother x Acropora loripes father). Conversely, the skeletal parameters of reciprocal hybrids (A. loripes mother x A. cf. kenti father) remained unaffected. Skeletal measurements taken from 3D data revealed patterns overlooked by previous 2D measurements, leading support to the likelihood of hybrid vigour in hybrids of A. loripes (mother) and A. cf. kenti (father) and the potential of interspecific hybridization as a reef restoration tool to enhance coral resilience.

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Initiation of bivalve shell calcification under ocean acidification: integrating insights from shell to cell

Published 9 April 2025 Science Closed
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The formation of initial bivalve shell is sensitive to ocean acidification, encoding the basis of shell formation and environmental information. Here, we demonstrated how the initial shell building processes were affected under various acidified conditions. With decreasing pH, larvae showed smaller shells and higher incidences of deformity. Shell elemental and isotopic profiles suggested that larvae almost exclusively used seawater dissolved inorganic carbon to calcify and exhibited diminished ability to maintain the calcifying fluid homeostasis. Compared to those reared at pHNBS 8.1, larvae exposed at pHNBS 7.7 downregulated the expression of genes related to transport of calcification substrates and regulation of carbonate chemistry, all of which were subsequently upregulated at pHNBS 7.4. This integrated finding advances the application of sclerochronology by providing insights into the initial shell formation, a crucial phase that is overlooked in sclerochronological studies, particularly in how environmental stressors affect the interpretation of geochemical proxies in adult shells.

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Metabolomic and physiological analyses of two picochlorophytes from distinct oceanic latitudes under future ocean acidification and warming

Published 28 March 2025 Science Closed
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Highlights

  • Ocean acidification and warming impacted picochlorophytes’ metabolome and physiology
  • High CO2 significantly altered Chlorella‘s metabolome, with fewer changes in Parachlorella.
  • High temperature enhanced Chlorella photosynthesis, while high CO2 benefited Parachlorella.

Abstract

Phytoplankton are cosmopolitan marine photosynthetic organisms that are vital to biogeochemical cycles and marine ecosystems. The current rise in atmospheric CO2 and surface ocean temperatures are poised to disrupt the ecological niches of phytoplankton. Picochlorophytes, a broad taxon of small green eukaryotic phytoplankton, have been shown to perform well under future rising oceanic CO2 and temperature scenarios. This study investigates the acclimation responses of cosmopolitan picochlorophytes from the Chlorella-lineage under high CO2 (1000 p.p.m.) and a rise of 4˚C (8˚C – polar picochlorophyte; 32 ˚C, tropical picochlorophyte). In order to determine how the future ocean warming and acidification might affect picochlorophytes, a polar strain of Chlorella and a tropical Parachlorella were selected, and their physiology and GCMS-based metabolomics were investigated. Growth rate and cellular dimensions (diameter, volume, and surface area) of Chlorella significantly increased in all environmental future scenarios compared to Parachlorella. Photosynthetic parameters of the picochlorophytes studied showed acclimation, with high temperature and high CO2 triggering the adaptation of Fv/Fm , NPQmax, and Ek of Chlorella and Parachlorella, respectively. High CO2 induced the most changes in the Chlorella metabolome, altering the levels of metabolites related to amino acids and their derivatives, glutathione production, carbohydrates, and photochemical quenching. Combined high CO2/temperature altered Parachlorella’s metabolome, though with a small number of biomarkers detected. This study provided evidence to support the hypothesis that picochlorophytes could thrive in a more acidified and warmer ocean.

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Combined effects of ocean acidification and copper exposure on the polyps of moon jellyfish Aurelia coerulea

Published 24 March 2025 Science Closed
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Ocean acidification (OA) can interact with Copper (Cu) pollutants and threaten marine organisms and ecosystems. In this study, we assessed the effects of OA and Cu2+, alone and in combination, on the polyps of Aurelia coerulea, a common jellyfish renowned for its complex life cycle and frequent global blooms. The results revealed that ocean acidification and Cu2+ exposure significantly inhibited the activities of catalase, Ca2+-ATPase, acid phosphatase, and alkaline phosphatase in polyps, resulting in antioxidative stress effects and a significant increase in respiratory metabolism. In addition, the combination of ocean acidification and Cu2+ exposure caused severe tissue damage to polyps, thereby impeding their predation behavior and reducing their asexual reproduction rates. These two environmental stressors showed synergistic effects on the Ca2+-ATPase activity, predation rate, reproduction rate, and injury index of polyps. Therefore, reduced seawater pH and copper contamination adversely affect the physiology, growth, and development of A. coerulea polyps, which may affect the survival and population dynamics of wild populations.

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Resilient mantle, vulnerable shell: ocean acidification’s impact on juvenile pen shell Atrina maura

Published 24 February 2025 Science Closed
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Highlights

  • OA does not affect the mantle tissue structure.
  • OA influences shell growth but does not impact the shell index.
  • OA produces malformation and dissolution of the calcite prismatic and nacre layers of juvenile A. maura.

Abstract

Ocean acidification results from the accumulation of CO2 in seawater. Predictions indicate a pH decrease of 0.3–0.5 units by the year 2100 and 0.7 units by the year 2300. The effects of OA vary among species, exposure time, physiological limits, and short-term adaptability. This phenomenon can be exacerbated in many coastal marine habitats due to nutrient inputs, upwelling events, and terrestrial sources of acidity. This study analyzed the effects of pH reduction on the shell and mantle tissue structure of the juvenile pen shell (Atrina maura) living in coastal bay where the natural pH is 7.8. These organisms were exposed to a reduction of pH (7.5) for 40 days. Scanning electron microscopy (SEM) analysis of the shells revealed signs of malformation and dissolution of the calcite prismatic layer and the nacre layer at acidic pH (7.5 ± 0.2) compared to controls (7.8 ± 0.1) throughout the experiment. However, shell growth increased 13.95 % after CO2 injection after 40 days of exposure, while the shell index and the mantle tissue remained unaffected any of the times evaluated. The results suggest that A. maura, a species naturally exposed to acidic environments, may experience effects from pH reductions primarily in their shell microstructure, while mantle morphology remains unaffected. The results obtained here prove that resilience of marine species, such as A. maura, can be compromised by ocean acidification (OA), highlighting the importance of continued exploration in this field to better understand the broader implications of OA on marine ecosystems.

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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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Transcriptome‐to‐phenome response of larval Eastern oysters under multiple drivers of aragonite undersaturation

Published 19 February 2025 Science Closed
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Understanding how interactive environmental challenges affect marine species is critical to long‐term ecological and economic stability under global change. Marine calcifiers are thought to be vulnerable to ocean acidification (OA; elevated pCO2); active dissolution of aragonite (Ωar) is associated with disrupted development, survivorship, and gene expression in bivalve larvae, resulting in an early life‐stage bottleneck. Dynamic carbonate chemistry in coastal systems emphasizes the importance of multiple stressors, e.g., warming and low salinity events may change organismal responses relative to OA alone. We exposed Eastern oyster larvae ( Crassostrea virginica ) to a full‐factorial experimental design using two temperatures (23°C and 27°C), salinities (17 and 27), and pCO2 levels (~700 μatm and 1850 μatm pCO2), resulting in Ωar conditions 0.3–1.7. Ωar reduced by low salinity, elevated pCO2, and low temperature, each slowed early development and reduced survival. Low salinity × elevated pCO2 was linked to severe Ωar undersaturation (< 0.5) that suppressed expression of bicarbonate transport, biomineralization and augmented expression for ciliary locomotion, proteostasis, and histone modifiers. In isolation and under moderate Ωar intensity (0.5 < Ωar < 1), larvae increased transcription for osmoregulatory activity and endocytosis under low salinity, and suppressed transcription for iron metabolism under elevated pCO2. Although shell growth and survival were affected by Ωar undersaturation, gene expression patterns of D‐stage oyster larvae and oyster juveniles suggests tolerance to dynamic estuarine environments. Genes and expression patterns that confer survival of postmetamorphosed oysters can improve our understanding of environmental‐organismal interactions and improve breeding programs enabling sustainable production.

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What controls planktic foraminiferal calcification?

Published 17 February 2025 Science Closed
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Planktic foraminifera are key producers of pelagic carbonate, and their shell weight is suggested to have been influenced by the environment in which they calcify. However, there is debate about the use of size-normalised weight (SNW) as a proxy, as some authors invoke a carbonate system control on calcification (and by extension SNW as a pCO2 proxy), while others suggest that species optimum conditions, nutrient concentration, or temperature drive shell weight. To better understand this proxy, we investigate what drives SNW and whether discrepancies in the proposed control on weight are due to differing data collection methodologies and/or regionally different drivers. We integrate new and published SNW data with environmental hindcast data from the CMIP6 modelling suite. Using Bayesian regression modelling, we find that the environment alone does not explain the variability in SNW across species. Although physiology likely modulates the response to the environment, we find little evidence of a unifying driver at the ecogroup level. Instead, we identify species-specific responses associated with drivers including (but not limited to) the carbonate system, which are likely different between ocean basins. We hypothesise that this is partly influenced by cryptic species and regional phenotypic plasticity in changes to shell weight that are not well understood, such as the thickness of calcite deposited during some species’ reproductive phases. Consequently, which species to use as a pCO2 proxy or whether multiple species should be used in parallel to reduce uncertainty should be carefully considered. We strongly encourage the regional testing and calibration of pCO2–SNW relationships.

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Ocean acidification and the future of clam- Paphia undulata- a study on characterization, composition and property

Published 14 February 2025 Science Closed
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This study delves into the multifaceted impacts of ocean acidification on Paphia undulata shells, elucidating the interconnected consequences of increased carbon dioxide (CO2) emissions. As a major driver of climate change, CO2 is absorbed by the ocean, inducing a chemical transformation termed ocean acidification. The altered seawater chemistry affects the alkalinity of the ocean and leads to a decline in the concentration of calcium carbonate in Paphia undulata shell powder, impacting the calcination process in bivalves. SEM analysis reveals a reduction in the size of Paphia undulata shell powder. GCMS analysis identifies pharmacologically important compounds, such as thymol-TMS and demelcolcine, in the shell biomineral. XRD analysis demonstrates changes in crystallinity due to ocean acidification. Additionally, the biomedical properties of powdered Paphia undulata shells offer valuable insights for developing alternative antiviral drugs. The comprehensive findings underscore the far-reaching consequences of ocean acidification on the thickness, strength and integrity of economically and ecologically vital Paphia undulata shells, emphasizing the urgency of addressing this environmental challenge. Embracing sustainable practices, adopting circular economy models and minimizing carbon emissions are emphasized as crucial steps in averting further ocean acidification and preserving marine environments.

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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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Molecular and physiological responses of black rockfish (Sebastes schlegelii) to short- and medium-term ocean acidification

Published 5 February 2025 Science Closed
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Ocean acidification (OA) is one of the greatest threats to marine species, with widespread impacts on their physiological functions. However, the adaptive capacities of many marine species to OA and the underlying mechanisms remain unclear. In this study, we investigated the effects of short-term (4 days) and medium-term (30 days) CO2 exposure (pH 8.0, 7.6, and 7.3) on black rockfish (Sebastes schlegelii), focusing on histopathological changes in gill tissues, ion transport biomarkers, oxidative stress indicators, and transcriptomic responses. The results showed that both short-term and medium-term OA induced significant morphological changes in gill tissues, including epithelial lifting, hyperplasia, hypertrophy, and lamellar clubbing, which are likely adaptive mechanisms for maintaining homeostasis. Both Na+/K+-ATPase and carbonic anhydrase (CA) activities increased significantly in both short- and medium-term exposure, while Ca2+-ATPase activity was elevated only in the short-term, suggesting differential enzyme regulation over time to sustain ionic balance. Additionally, oxidative stress indicators (superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA), reduced glutathione (GSH) and glutathione peroxidase (GPx)) were significantly elevated after both exposure durations, indicating that the antioxidant defense system was activated. Moreover, the integrated biomarker response (IBR) index further indicated that the stress response was more pronounced during short-term exposure. Transcriptomic analysis reveals significant alterations in pathways related to calcium signaling, cytoskeletal structure, energy metabolism, and oxidative stress following short-term exposure. In contrast, medium-term exposure leads to significant enrichment of pathways associated with cell-environment interactions, highlighting the molecular adaptations of S. schlegelii to OA-induced stress. These findings provide valuable insights into the mechanisms of OA tolerance in S. schlegelii and contribute to understanding the adaptability of marine species in future ocean environments.

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

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

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Effects of sediment acidification on germinability of Scrippsiella acuminata cysts in hypoxic zones

Published 16 January 2025 Science Closed
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We investigated the calcareous cysts of Scrippsiella acuminata, with a focus on morphological changes from spiny to naked types in the surface sediments of hypoxic zones. The cyst-type abundance and bottom environmental conditions at two stations, representing hypoxic and normoxic conditions, were compared. Germination tests simulating in situ pH conditions were conducted to elucidate differences in germinability between spiny and naked cysts. The pH values at the hypoxic station reached a minimum of 7.2 in September, coinciding with high bottom-water temperatures and low dissolved oxygen levels. Significant differences in cyst abundance were observed; naked and intermediate cysts dominated the hypoxic station, whereas spiny cysts were more abundant at the normoxic station. Both cyst types exhibited a similar negative effect of germinability decrease (62 to 25% for spiny cysts and 75 to 32% for naked cysts) in acidic conditions (7.2) compared to normal pH conditions (7.7). Morphological changes in ungerminated cysts, such as cytoplasmic degradation and wall thickening, occurred under acidified conditions.

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Future climate change scenarios of increased CO2 and temperature strongly affect a coral reef meiobenthic harpacticoid (Crustacea) community

Published 15 January 2025 Science Closed
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Small metazoans, especially harpacticoid copepods, are an important component in the benthic food webs of benthic environments. However, studies on the effects of elevated CO2 and temperature on these animals are scarce and those that do exist focus mainly on the individual species level. A laboratory experiment was conducted to evaluate the impact of different climate change scenarios on a community of harpacticoid copepods from a coral reef environment. Samples were collected from the coral reef subtidal zone of Serrambi beach (Ipojuca, Pernambuco, Brazil), using colonized artificial substrate units. The units were exposed to control treatments and to three climate change scenarios and were collected after 14 and 29 days. A highly diverse community of harpacticoids was analyzed [H′(log2) = 4.37]. Changes in the community structure were observed, and the response of the copepod community structure to the different scenarios varied according to the sampling period. The maintenance of a highly diverse community enabled a complex pattern of responses to be observed at a species level with three different response patterns to the changing seawater conditions: sensitive species represented by Tisbe sp., Stenhelia sp. and Ameira sp.; mildly sensitive represented by Cyclopoida and Dactylopusia sp.; resistant or opportunist represented by Ectinosoma sp.1, Ectinosoma sp.2 and Mesochra sp. The increase in malformed adult animals in the most severe scenario indicated that species that do not suffer mortality are not exempt from sublethal symptoms. Harpacticoid organisms are shown as reliable tools to assess climate change in coral reef environments.

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Morphological responses of a temperate salt marsh foraminifer, Haynesina sp., to coastal acidification

Published 15 January 2025 Science Closed
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Coastal acidification leads to widespread impacts on calcifying organisms across the world’s oceans, which could result in decreased calcium carbonate deposition and the dissolution of calcium carbonate. As an abundant group of calcifying organisms, some protists within the phylum Foraminifera demonstrate potential success under elevated partial pressure of carbon dioxide (pCO2) due to their ability to modulate intracellular pH. However, little is known about their responses under more extreme acidification conditions that are already seen in certain coastal environments. Here we exposed Haynesina, a foraminiferal genus that is prevalent in temperate coastal salt marshes, to moderate (pCO2 = 2386.05+/-97.14 μatm) and high acidification (pCO2 = 4797.64+/-157.82 μatm) conditions through the duration of 28 days. We demonstrate that although this species is capable of withstanding moderate levels of coastal acidification with little impact on their overall test thickness, they could experience deposition deficiency and even dissolution of the calcareous test under highly elevated pCO2. Interestingly, such a deficit was primarily seen among live foraminifera, as compared to dead specimens, throughout the four-week experiment. We propose that a combination of environmental stress and the physiological process of test formation (i.e., calcite precipitation) could induce thinning of the test surface. Therefore, with the acceleration of coastal acidification due to anthropogenic production of CO2, benthic foraminifera amongst coastal ecosystems could reach a tipping point that leads to thinning and dissolution of their calcareous tests, which in turn, will impair their ecological function as a carbon sink.

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Molecular response to CO2-driven ocean acidification in the larvae of the sea urchin Hemicentrotus pulcherrimus: evidence from comparative transcriptome analyses

Published 13 January 2025 Science Closed
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Highlights

  • Ocean acidification affects morphology of Hemicentrotus pulcherrimus larvae.
  • Comparative transcriptome analyses were performed.
  • Six key potential biomarkers correlated with low pH tolerance were identified.

Abstract

In order to explore the impact of CO2-driven ocean acidification (OA) on gene expression of sea urchins, gametes of Hemicentrotus pulcherrimus were fertilized and developed to the four-armed larvae in either seawater at current pH levels (pHNBS = 7.98) or in three laboratory-controlled OA conditions (ΔpHNBS = −0.3, −0.4, −0.5 units) based on the projections of the Intergovernmental Panel on Climate Change (IPCC) for 2100. Four-armed larval specimens were collected, and comparative transcriptome analysis was then performed. The results showed that 58 differentially expressed genes (DEGs) were identified in OA-treated groups as compared to the control. Moreover, more transition and transversion SNPs were observed in OA-treated groups than those in the control indicating a potential occurrence of adaption to OA in H. pulcherrimus larvae. Six candidate DEGs shared among OA-treated groups were identified as potential biomarkers correlated with low pH tolerance, mainly enriched in nine pathways associated with Notch signaling, dorso-ventral axis formation, oxidative phosphorylation, lysine degradation, valine, leucine and isoleucine degradation, lysosome, cell adhesion molecules, glutathione metabolism and PPAR signaling pathway. These results will not only enrich our knowledge of the impacts of OA on sea urchin larvae from the aspect of gene expression, provide a better understanding on larval forms coping with OA, but also offer more clues and biomarkers for developing protection or management strategies for sea urchins under near-future OA conditions.

Continue reading ‘Molecular response to CO2-driven ocean acidification in the larvae of the sea urchin Hemicentrotus pulcherrimus: evidence from comparative transcriptome analyses’

Ocean acidification and global warming may favor blue carbon service in a Cymodocea nodosa community by modifying carbon metabolism and dissolved organic carbon fluxes

Published 9 January 2025 Science Closed
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Highlights

  • 45-days mesocosm experiment with whole-benthic community to mimic nature conditions
  • Global warming (GW) and ocean acidification (OA) modify C dynamics on seagrasses.
  • OA enhances GPP and NCP and synergistic effects when combined with GW.
  • DOC production decreased with OA and GW separately, but increased when combined.
  • Climate change potentially increases the blue carbon service of C. nodosa populations.

Abstract

Ocean acidification (OA) and global warming (GW) drive a variety of responses in seagrasses that may modify their carbon metabolism, including the dissolved organic carbon (DOC) fluxes and the organic carbon stocks in upper sediments. In a 45-day full-factorial mesocosm experiment simulating forecasted CO2 and temperature increase in a Cymodocea nodosa community, we found that net community production (NCP) was higher under OA conditions, particularly when combined with warming (i.e., synergistic effect). Moreover, under OA conditions, an increase in aboveground biomass and photosynthetic shoot area was recorded. Interestingly, DOC fluxes were reduced when exposed to OA; however, an increase occurred when both factors acted together (i.e., antagonistic effect), which was attributable to increased DOC release by plants. Our results suggest that C. nodosa populations in temperate latitude may favor blue carbon service in future scenarios of OA and GW by increasing the NCP, the DOC export with lower labile:recalcitrant ratio, and accumulating more organic carbon in upper sediments. These findings offer additional arguments for the urgent need to protect and conserve this valuable ecosystem.

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Combined effects of pCO2 and salinity on the silicification of estuarine diatoms

Published 8 January 2025 Science Closed
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Highlights

  • Low salinity enhanced the weakening of silicification by ocean acidification (OA).
  • OA and salinity influenced the quality of diatom frustules and cell size.
  • OA could affect estuarine diatoms’ competitiveness in future environment.

Abstract

Understanding the combined effects of seawater acidification and salinity is crucial for assessing the adaptation of estuarine organisms to climate change. This study examined the physiological and nanostructural responses of two coastal diatoms, Thalassiosira pseudonana and Thalassiosira weissflogii, under different pCO2 and salinity conditions. Our results indicated that high pCO2 and low salinity decreased the biogenic silica and chlorophyll contents in both species. The weakly condensed silicon increased alongside the decrease in biogenic silica under high pCO2 conditions, with this trend being further amplified in low salinity environments. Meanwhile, the biochemical compositions and nanostructure of the diatom frustules were significantly altered by the lower salinity, leading to reduced cell size and porosity. These changes to diatom physiology and morphology may affect the diatoms’ capacity to defend against predators and viruses. This study highlights the chemical and morphological changes occurring in diatom cell walls in future acidic estuarine waters.

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Cellular and genetic responses of Phaeodactylum tricornutum to seawater acidification and copper exposure

Published 2 January 2025 Science Closed
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Highlights

  • Seawater acidification reduced Cu uptake in marine diatom Phaeodactylum tricornutum.
  • Seawater acidification resulted in rougher surfaces, lower adhesion and modulus in the diatom.
  • Diatoms regulated Cu homeostasis via FRE1, CTR1, and ATPase 5-1B transporters.
  • The expression of CTR1 and FRE1 were significantly downregulated in response to seawater acidification.

Abstract

The ongoing decline in seawater pH, driven by the absorption of excess atmospheric CO2, represents a major environmental issue. This reduction in pH can interact with metal pollution, resulting in complex effects on marine phytoplankton. In this study, we examined the combined impacts of seawater acidification and copper (Cu) exposure on the marine diatom Phaeodactylum tricornutum. Our data indicate that elevated pCO2 had a minor effect on the growth and photochemistry and overall performance of P. tricornutum. However, seawater acidification significantly influenced cell size, surface roughness, and adhesion. Higher pCO2 levels led to increased Cu accumulation in P. tricornutum under low ambient Cu concentrations, while significantly reducing Cu accumulation. The smaller cell size and reduced negative charge on the cell surface may explain the decreased Cu accumulation and toxicity. In response to metal stress, P. tricornutum upregulated Cu efflux to mitigate the increased Cu stress in acidified seawater. The expression of the metal transporter gene CTR1 and the reductase gene FRE1 were significantly downregulated, while ATPase5-1B was upregulated in cells exposed to elevated Cu concentrations at 1200 μatm pCO2. Our study provides useful insights into the interactions between metals and diatoms in an increasingly acidified ocean.

Continue reading ‘Cellular and genetic responses of Phaeodactylum tricornutum to seawater acidification and copper exposure’

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