Posts Tagged 'growth'

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Salinity-dependent effects of seawater acidification on growth, photosynthetic physiology and biochemistry of the invasive macroalga Codium fragile

Published 25 March 2025 Science Closed
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Highlights

  • Decreased and increased salinity adversely affect the growth and photosynthetic physiology of Codium fragile under ambient pCO2 conditions.
  • Ocean acidification could help Codium fragile to encounter moderate salinity stress by up-regulating photosynthetic ability.
  • The deleterious effect of progressively decreased salinity on growth of Codium fragile was magnified when pCO2 increased.

Abstract

Ocean acidification (OA) and seawater salinity are two major environmental factors that influence the growth and distribution of macroalgae in coastal ecosystems. To investigate the effects of OA and salinity on the invasive macroalga Codium fragile, the growth, Chlorophyll a fluorescence, and biochemical compositions (pigment and soluble carbohydrate contents, the superoxide dismutase (SOD) activity, and malondialdehyde (MDA) contents) were studied after exposure to two pCO2 levels (400 ppmv, LC; and 1000 ppmv, HC) and four salinity regimes (high salinity, 40 psu; control salinity, 30 psu; medium salinity, 20 psu; low salinity, 10 psu). The results showed that, except for SOD activity at 20 psu, the growth, maximum and effective quantum yield of PSII, and maximum relative electron transport, pigment and soluble carbohydrate contents, SOD activity, and the MDA content were adversely impacted by both hypo- and hypersaline under LC conditions. Similarly, under HC conditions, the growth, photosynthetic physiology and biochemistry were negatively impacted by low salinity, while high salinity enhanced pigment contents and chlorophyll fluorescence parameters but inhibited SOD activity and MDA contents. Furthermore, higher pCO2 significantly promoted growth, pigment contents, and photosynthetic performance at 20 and 40 psu, while it amplified the depression in growth at 10 psu. These findings suggest that OA may enhance the potential invasive ability and salinity tolerance of C. fragile under medium hyposaline and hypersaline conditions by alleviating the negative effects of salinity stress on growth, photosynthesis, and pigments synthesis. However, it may also synergistically reduce algal growth at further reduced salinity. These data collected herein are valuable for understanding C. fragile cultivation and predicting its future distribution in response to changing ocean conditions.

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Food availability, but not tidal emersion, influences the combined effects of ocean acidification and warming on oyster physiological performance

Published 25 March 2025 Science Closed
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Highlights

  • Effects of pH/temperature conditions, tidal treatments, and food levels are studied.
  • Ocean acidification and warming enhance the physiological performance of oysters.
  • Food level impacts responses to future conditions and disease susceptibility.
  • Intertidal oysters increase food intake to compensate for limits during emersion.

Abstract

Many studies on the effects of ocean acidification and warming (OAW) in intertidal mollusks overlook critical factors like tidal emersion and food availability, both of which can shape organisms’ responses. Experiments on intertidal bivalves often use constant immersion and abundant food, which likely underestimate global change impacts and underscore the need for more realistic experiments mimicking natural ecosystems. This study investigated the physiological responses of juvenile Pacific oyster Crassostrea gigas exposed for 81 days to current and OAW conditions (+3 °C, −0.3 pH units) under two tidal treatments (0 vs. 30 % emersion) and two food levels (ad libitum vs. limited). We measured growth, reproduction, food ingestion, respiration, and biochemical traits like energy reserves and membrane fatty acids. At the experiment’s end, oysters were challenged with a viral disease to assess the physiological cost of acclimation and potential trade-offs. Results showed improved oyster physiological performance under OAW with high food level. Nevertheless, food availability emerged as the predominant factor in oyster performance, limiting growth, reproduction, and energy reserves, while increasing oxygen consumption and disease susceptibility. Food deprivation attenuated the beneficial effects of OAW through antagonistic interaction, suggesting physiologically weakened oysters may struggle to adapt to environmental hazards. Finally, tidal treatment had no significant effect, implying that oysters possess physiological compensatory mechanisms, particularly in food acquisition, enabling them to meet nutritional needs during immersion periods. This study provides valuable insights for designing global climate change experiments that align with ecological realism and improves our understanding of the acclimation potential in bivalves facing rapid ocean changes.

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Impact of simulated pH conditions on phenotypic expression in shrimp pathogenic and non-pathogenic Vibrio campbellii strains

Published 13 March 2025 Science Closed
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Environmental pH fluctuation in oceanic and marine ecosystems can significantly impact the distribution and behavior of pathogenic Vibrio species, including their interactions with marine invertebrates such as crustaceans. This study focused on Vibrio campbellii, a common shrimp pathogen, and its phenotypic responses to varying pH conditions. Both pathogenic strain HY01 and non-pathogenic strain ATCC BAA-1116 were cultured in 30 pL/L Luria-Bertani Sea Salt under 3 pH conditions, including pH 6 (slightly acidic), pH 8 (representing the oceanic pH), and pH 9 (alkaline). Growth patterns and phenotypic traits were evaluated. Results revealed no significant growth difference between the 2 strains under the different pH conditions, although the non-pathogenic strain showed a slight growth reduction at pH 9 during the exponential phase. Both strains were able to buffer environmental pH shifts, adjusting to near-oceanic pH levels (around pH 8). At pH 9, a stressor level for V. campbellii, delays were observed in bioluminescence, biofilm formation, exopolysaccharide production, shrimp surface colonization, motility, and caseinase production, affecting both strains. In contrast, mildly acidic conditions (pH 6) induced the highest expression of several phenotype traits. Statistical analyses indicated significant interactions between strain type and pH levels in influencing phenotypic expression. In conclusion, the pathogenic V. campbellii strain HY01 exhibited greater adaptability and virulence across various pH conditions compared to the non-pathogenic ATCC BAA-1116, emphasizing pH as a critical environmental factor in shaping the growth and pathogenic potential of V. campbellii. Our studies provide valuable insights into managing pH conditions in aquaculture environments to optimize proper shrimp cultivation and prevent cross-contamination of V. campbellii from seawater habitats to farms. These findings provide a physiological profile of Vibrio under pH stress, which can support the development of predictive outbreak models to assess the risk of luminous vibriosis, especially in to seasonal changes and ocean acidification.

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Effects of pH/pCO2 fluctuations on photosynthesis and fatty acid composition of two marine diatoms, with reference to consequences of coastal acidification (update)

Published 10 March 2025 Science Closed
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Coastal waters are impacted by a range of natural and anthropogenic factors, which superimpose on effects of increasing atmospheric CO2, resulting in dynamically changing seawater carbonate chemistry. Research on the influences of dynamic pH/pCO2 on marine ecosystems is still in its infancy, although effects of ocean acidification have been extensively studied. In the present study, we manipulated the culturing pH to investigate physiological performance and fatty acid (FA) composition of two coastal diatoms, Skeletonema costatum and Thalassiosira weissflogii, in both steady and fluctuating pH regimes. Generally, seawater acidification and pH variability showed neutral or positive effects on the specific growth rate, chlorophyll a, and biogenic silica contents of the two species. Decreased pH inhibited the net photosynthetic rate by 27 % and enhanced the mitochondrial respiration rate of S. costatum by 36 % in the steady pH regime, while these rates were unaltered by decreased pH in the fluctuating regime. Acidification conditions led to lower saturated FA and higher polyunsaturated FA proportions in both species, regardless of steady or fluctuating regimes. Our results indicate that coastal acidification could affect primary production in a different way from ocean acidification. Together with the altered nutritional quality of prey for higher trophic levels, coastal acidification might have far-reaching consequences for marine ecosystem functioning.

Continue reading ‘Effects of pH/pCO2 fluctuations on photosynthesis and fatty acid composition of two marine diatoms, with reference to consequences of coastal acidification (update)’

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

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

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

Interactive effects of elevated atmospheric CO2 and UV-B radiation: a multi-level study on marine diatom Skeletonema pseudocostatum

Published 24 February 2025 Science Closed
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Highlights

  • Combined effects of UVB radiation and increased atmospheric CO2 was assessed on Skeletonema pseudocostatum.
  • Additive, synergistic and antagonistic effects were characterized based on modified independent action (IA) model.
  • The combined effects on S. pseudocostatum were dose-dependent and target-specific.
  • Additivity was most common, synergy occurred in ROS and growth, while carotenoids content reduced antagonistically.
  • An effect pathway was developed to characterize the propagation of combined effects across t biological levels.

Abstract

Climate change as a result of increases in greenhouse gas emissions, such as CO2, is causing significant alteration in global environmental conditions, including ocean acidification (OA). Although the depletion of the ozone layer has reduced, the penetration of ultraviolet-B (UVB) radiation into the oceans still remains an environmental factor that may potentially enhance the effects of OA on biota. Improved understanding of the complex interactions between multiple stressors, such as UV-B radiation and increased CO2 levels, is thus important for safeguarding ecosystems and developing effective conservation and management strategies. A 72 h experiment was carried out to investigate the combined effects of UVB irradiance (0.5 W m−2) and varying CO2 levels (350, 500, 1000 ppm) on the diatom Skeletonema pseudocostatum. The study aimed to characterize the potential combined effects at different levels of biological organization, including ROS formation, lipid peroxidation (LPO), photosynthesis, pigments, oxidative phosphorylation (OXPHOS) and growth. The findings indicate that exposure to elevated CO2 (500 ppm) alone resulted in increased total carotenoid content and growth of S. pseudocostatum, but did not significantly impact photosystem efficiency, oxidative stress, and OXPHOS. Sole UVB exposure induced oxidative stress, inhibited photosynthesis and OXPHOS processes, and suppressed growth in S. pseudocostatum. However, when co-exposed with CO2, synergistic impacts were observed for reactive oxygen species (ROS), lipid peroxidation (LPO), and growth, while carotenoids were reduced in an antagonistic manner. A putative impact pathway was proposed as an initial effort to characterize the combined effects of these stressors under proposed future marine OA scenarios involving elevated CO2.

Continue reading ‘Interactive effects of elevated atmospheric CO2 and UV-B radiation: a multi-level study on marine diatom Skeletonema pseudocostatum’

Contrasting species-specific stress response to environmental pH determines the fate of coccolithophores in future oceans

Published 14 February 2025 Science Closed
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Highlights

  • Molecular mechanisms dictating sensitivity of coccolithophores to pH remain elusive.
  • Coastal species was resilient to pH changes, but ancient open-ocean species was not.
  • Bloom-forming species showed unique molecular changes under stress.
  • Cellular carbon fixation will be higher under future acidification.

Abstract

Molecular mechanisms driving species-specific environmental sensitivity in coccolithophores are unclear but crucial in understanding species selection and adaptation to environmental change. This study examined proteomic and physiological changes in three species under varying pH conditions. We showed that changing pH drives intracellular oxidative stress and changes membrane potential. Upregulation in antioxidant, DNA repair and cell cycle-related protein-groups indicated oxidative damage across high (pH 8.8) and low pH (pH 7.6) compared to control pH (pH 8.2), and correlated with reduced growth rates. Upregulation of mitochondrial proteins suggested higher metabolite demand for restoring cellular homeostasis under pH-induced stress. Photosynthetic rates generally correlated with CO2 availability, driving higher net carbon fixation rates at low pH. The intracellular pH-buffering capacity of the coastal Chrysotila carterae and high metabolic adaptability in the bloom-forming Gephyrocapsa huxleyi will likely facilitate their adaptation to ocean acidification or artificial ocean alkalinisation. However, the pH sensitivity of the ancient open-ocean Coccolithus braarudii will possibly result in reduced growth and shrinking of its ecological niche.

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Thalassia hemprichii may benefit from ocean acidification and slightly increased salinity in the future

Published 13 February 2025 Science Closed
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Highlights

  • Thalassia hemprichii highly adapted to acidified environments.
  • The effect of elevated salinity on the physiology and growth of Thalassia hemprichii is not linearly.
  • Ocean acidification could further enhance the resilience of Thalassia hemprichii to high salinity.
  • Both acidification and slight salinity increased the photosynthetic activity of Thalassia hemprichii.

Abstract

Since the industrial revolution, the direct impacts of elevated CO2 concentrations, such as ocean acidification, and indirect impacts, such as extreme drought events, have synergistically influenced coastal ecosystems, including seagrass meadow. Consequently, investigating the individual and combined effects of ocean acidification and extreme drought-induced increased salinity on seagrasses is crucial for enhancing the management and monitoring of these ecosystems. This study used a two-factor crossover indoor simulation experiment to thoroughly examine the effects of seawater acidification at pH 7.7 and elevated salinity levels at 43‰ and 51‰ on the physiological responses and growth status of the dominant tropical seagrass species Thalassia hemprichii. The results indicated that seawater acidification at pH 7.7 significantly enhanced the growth rate and photosynthetic activity of T. hemprichii across all salinity levels. A salinity of 43‰ activated certain antioxidant enzymes without inducing severe osmotic stress in T. hemprichii and positively influenced leaf photosynthetic activity, with a 15.6% increase in growth rate compared to the CK group. The extreme salinity of 51‰ imposed osmotic stress, leading to increase in reactive oxygen species and decreased photosynthetic activity and a 52% decrease in growth rate compared to seagrasses in the CK group. Under future scenarios of ocean acidification and frequent extreme droughts, T. hemprichii inhabiting enclosed marine environments may exhibit greater adaptability and secure an ecologically competitive edge. Our findings underscore the importance of conserving declining meadows, forecasting the ecological trajectory of these ecosystems, and managing salinity in lagoons for the well-being of seagrass ecosystems.

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CO2 fertilisation counteracts the negative effect of poor water quality on the growth and photosynthesis of a Great Barrier Reef coralline alga

Published 10 February 2025 Science Closed
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The global problem of ocean acidification and localised decline in water quality are major threats to coral reefs worldwide. This study examined the individual and interactive impacts of global and local stressors by investigating the effects of increased seawater pCO2, elevated nutrient concentrations and reduced light levels on linear growth and metabolic rates of the common branching crustose coralline alga Lithophyllum cf. pygmaeum. We found complex interactions between factors on algal growth and photosynthetic rates, but overall, growth was significantly enhanced by pCO2 enrichment under all light and nutrient combinations. This is the first study to report a positive growth response in coralline algae to elevated pCO2 using linear extension methods. In contrast, the combination of reduced light levels and high nutrient concentrations simulating poor water quality conditions reduced algal growth rates by up to 67% (compared to individuals exposed to high light, low nutrients and elevated pCO2). Decreased light levels reduced linear growth, Pgross and Pnet rates by 33%, 18% and 24%, respectively, highlighting the critical role of light in coralline algal physiology. We suggest that poor water quality may counteract any CO2 fertilisation effect under ocean acidification conditions on the growth of coralline algae, and this has implications for coral reef conservation as it emphasises the importance of improving water quality to maintaining coral reef functions. These results further highlight the need for multifactorial experiments to better understand the interplay between global and local processes on coralline algae growth.

Continue reading ‘CO2 fertilisation counteracts the negative effect of poor water quality on the growth and photosynthesis of a Great Barrier Reef coralline alga’

Proteomics analysis reveals the antagonistic interaction between high CO2 and warming in the adaptation of the marine diatom Thalassiosira weissflogii in future oceans

Published 6 February 2025 Science Closed
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Highlights

  • Central carbon and fatty acid metabolism up-regulated after warming adaptation.
  • High CO2 acted antagonistically with warming to slow down these pathways.
  • Amino acid synthesis accelerated after high CO2 and warming adaptation.

Abstract

While it is known that warming and rising CO2 level might interactively affect the long-term adaptation of marine diatoms, the molecular and physiological mechanisms underlying these interactions in the marine diatom Thalassiosira weissflogii on an evolutionary scale remain largely unexplored. In this study, we investigated the changes in metabolic pathways and physiological responses of T. weissflogii under long-term ocean acidification and/or warming conditions (∼3.5 years), integrating proteomics analyses and physiological measurements. Our findings reveal that proteins involved in central carbon metabolisms (e.g., tricarboxylic acid cycle and glycolysis) and fatty acid metabolism were significantly up-regulated in the long-term warming-adapted populations. However, the long-term adaptation to high CO2 acted antagonistically with warming, slowing down the central carbon metabolism and fatty acid metabolism by down-regulating protein expressions in the key metabolic pathways of the glycolysis and tricarboxylic acid cycle. Additionally, amino acid synthesis was accelerated in the long-term warming and its combination with high CO2-adapted populations. Physiological measurements further supported these findings, showing altered growth rates and metabolic activity under the combined warming and high CO2 conditions. Our results provide new insights into the molecular mechanisms underpinning the antagonistic interaction between high CO2 and warming on marine phytoplankton in the context of global change.

Continue reading ‘Proteomics analysis reveals the antagonistic interaction between high CO2 and warming in the adaptation of the marine diatom Thalassiosira weissflogii in future oceans’

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

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

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

Meta-analysis of larval bivalve growth in response to ocean acidification and its application to sea scallop larval dispersal in the Mid-Atlantic Bight

Published 21 January 2025 Science Closed
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Ocean acidification, caused by increasing atmospheric carbon dioxide and coastal physical, biological, and chemical processes, is an ongoing threat to carbonate-utilizing organisms living in productive coastal shelves. Bivalves exposed to acidification have shown reduced growth, reproduction, and metabolic processes, with larval stages exhibiting the greatest susceptibility. Here, we compile results from published studies on larval bivalve growth responses to acidification to estimate a relationship between larval growth and seawater aragonite saturation state. We then apply this relationship to a larval dispersal individual-based model for Atlantic sea scallops (Placopecten magellanicus), an economically vital species in the Mid-Atlantic Bight that is historically under-studied in acidification research. To date, there have been no published studies on sea scallop larval response to ocean acidification. Model simulations allowed the identification of potential impacts of acidification on scallop success in the region. Results show that larval sea scallops that are sensitive to ocean acidification had a 17% lower settlement success rate and over 50% reduction in larval passage between major Mid Atlantic Bight fisheries habitats than those that are not sensitive to acidification. Additionally, temperature and ocean acidification interact as drivers of larval success, with aragonite saturation states > 3.0 compensating for temperature-induced mortality (> 19 ˚C) in some cases. This balance between drivers influences larval settlement success across spatial and interannual scales in the Mid Atlantic Bight.

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Iron and phosphorus limitations modulate the effects of carbon dioxide enrichment on a unicellular nitrogen-fixing cyanobacterium

Published 21 January 2025 Science Closed
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Iron (Fe) and phosphorus (P) availability constrain the growth and N2 fixation of diazotrophic cyanobacteria in the global ocean. However, how Fe and P limitation may modulate the effects of ocean acidification on the unicellular diazotrophic cyanobacterium Crocosphaera remains largely unknown. Here, we examined the physiological responses of Crocosphaera watsonii WH8501 to CO2 enrichment under both nutrient-replete and steadily Fe- or P-limited conditions. Increased CO2 (750 μatm vs. 400 μatm) reduced the growth and N2 fixation rates of Crocosphaera, with Fe limitation intensifying the negative effect, whereas CO2 enrichment had a minimal impact under P limitation. Mechanistically, the high CO2 treatment may have led to a reallocation of limited Fe to nitrogenase synthesis to compensate for the reduction in nitrogenase efficiency caused by low pH; consequently, other Fe-requiring metabolic pathways, such as respiration and photosynthesis, were impaired, which in turn amplified the negative effects of acidification. Conversely, under P limitation, CO2 enrichment had little or no effect on cellular P allocation among major P-containing molecules (polyphosphate, phospholipids, DNA, and RNA). Cell volumes were significantly reduced in P-limited and high CO2 cultures, which increased the surface : volume ratio and could facilitate nutrient uptake, thereby alleviating some of the negative effect of acidification on N2 fixation. These findings highlight the distinct responses of Crocosphaera to high CO2 under different nutrient conditions, improving a predictive understanding of global N2 fixation in future acidified oceans.

Continue reading ‘Iron and phosphorus limitations modulate the effects of carbon dioxide enrichment on a unicellular nitrogen-fixing cyanobacterium’

Effect of CO2 driven seawater acidification on survival, growth, amino acid and fatty acid levels in the edible shrimp Litopenaeus vannamei

Published 13 January 2025 Science Closed
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Highlights

  • Survival and growth of L. vannamei were declined in OA exposures
  • Essential and nonessential amino acids were decreased in shrimps under OA
  • Vital unsaturated fatty acids were improved in shrimps under OA conditions

Abstract

Acidification in the ocean environment is considered a worldwide problem that drives serious consequences for organisms. The current investigation was focused to study the effect of CO2 induced ocean acidification (OA) on the survival, growth, and composition of amino acids and fatty acids in the shrimp Litopenaeus vannamei. A seven weeks OA experiment was conducted on the shrimp groups with different pH such as 8.2 (control), 7.8, 7.6, 7.4, 7.2, and 7.0. A considerable decline in survival, growth, essential and nonessential amino acids, and saturated fatty acids in shrimps under OA exposures (pH 7.8 to 7.0). In this context, a notable improvement in amino acids (histidine, alanine, and cysteine) and fatty acids (palmitoleic acid, linoleic acid, linolenic acid, eicosapentaenoic acid, and docosahexaenoic acid) in L. vannamei reared under acidified seawater environments suggests that the high demand for these amino acids and fatty acids to tolerate the acidic stress.

Continue reading ‘Effect of CO2 driven seawater acidification on survival, growth, amino acid and fatty acid levels in the edible shrimp Litopenaeus vannamei’

Response of the photosynthetic physiology of Ulva lactuca to Cu toxicity under ocean acidification

Published 8 January 2025 Science Closed
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Highlights

  • Low Cu concentrations promote the growth of Ulva lactuca.
  • The growth of Ulva lactuca was decreased with Cu increase under low CO2 condition.
  • Ocean acidification can exacerbate the adverse effects of Cu on Ulva lactuca.

Abstract

Ocean acidification can significantly affect the physiological performance of macroalgae. While copper (Cu) is an essential element for macroalgae and has been extensively studied, the interactive effects of ocean acidification and Cu on these organisms remain less understood. In this study, we measured the photosynthetic characteristics of Ulva lactuca exposed to varying Cu concentrations at two CO2 levels (415 ppmv, low concentration; 1000 ppmv, high concentration). The results indicated that during chronic toxicity testing, the growth of juvenile U. lactuca significantly increased at Cu concentrations of 0.001 μM, 0.01 μM, and 0.1 μM regardless of low CO2 concentrations or high CO2 concentrations condition. In acute toxicity tests, elevated Cu concentrations negatively impacted the growth rate, yield, and photosynthetic rate of U. lactuca under low CO2 concentrations. Conversely, high CO2 concentrations enhanced the photosynthetic capacity of U. lactuca with increased Cu concentrations, while the growth rate significantly decreased at Cu concentration of 1.5 μM. Additionally, the activities of peroxidase (POD) and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) increased, with an enhancement of malondialdehyde (MDA) content at 1.5 μM Cu under high CO2 conditions. However, the structure of the chloroplast thylakoid was disrupted by elevated Cu concentrations. These findings suggest that low Cu concentrations promote the growth of U. lactuca, whereas high Cu concentrations inhibit algal growth, and ocean acidification may exacerbate the adverse effects of Cu on U. lactuca in acute toxicity tests.

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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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Adaptation to warming and high CO2 influences diatom response norms and multi-trait variations across CO2 gradients 

Published 6 January 2025 Science Closed
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Understanding how phytoplankton response to elevated CO2 and/or warming through long-term genotypic adaptation is critical for predicting future phytoplankton distribution and community structure. In this study, we conducted a 4.5-year experimental evolution with the model marine diatom Phaeodactylum tricornutum Bohlin under four environmental regimes: ambient conditions, high CO2, warming, and combined high CO2 + warming. Following this long-term adaptation, we exposed the populations to a broad CO2 gradient in a short-term (7-day) experiment, assessing their multi-trait responses. Our results demonstrate that P. tricornutum Bohlin populations adapted to different regimes exhibit significant multi-trait variation across CO2 gradients. Notably, the variability driven by long-term adaptation exceeded that induced by short-term CO2 changes. Furthermore, both long-term adaptation and short-term CO2 exposure altered trait co-variations, highlighting the complex interplay between environmental history and immediate conditions. This study emphasizes the importance to assess long-term genetic changes in marine phytoplankton under global change, as short-term experiments alone may underestimate their capacity for adaptation and the broader implications for marine ecosystems under future climate scenarios.

Continue reading ‘Adaptation to warming and high CO2 influences diatom response norms and multi-trait variations across CO2 gradients ‘

Characterization of coral communities in the shallow hydrothermal vents of Mabini, Batangas, Philippines

Published 31 December 2024 Science Closed
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The existence of shallow hydrothermal vents in Mabini, Batangas, Philippines, has been recognized to contribute to CO2-rich submarine groundwater discharges. However, little is known about the existing coral community structure in the area which provides valuable ecosystem goods and ecological services. We characterized the reef community in this unique microenvironment falls within the predicted future reef condition with low pH and aragonite saturation using coral recruitment tiles, examined coral life-history strategies and size frequency distribution, and measured calcification of transplanted fragments from the genus Goniopora sp., Pectinia sp., and Porites sp. The availability of larval supply has proven that corals can still settle (45–73 recruits m−2) due to the presence of hard substrate and settlement cues such as the crustose coralline algae. The existing coral colonies were mostly dominated by stress-tolerant groups and sizes ranging from 5 to 20 cm. Deployed coral fragments showed growth via extension, and calcification was negatively affected by local conditions, such as Porites sp. fragments. Higher nutrient input may have promoted coral growth, but combined with low carbonate chemistry, it likely made the corals more susceptible to physical damage, as seen on the fragments. This study highlights the importance of naturally occurring extreme environments to determine climate-resilient corals that can adapt to changing conditions and recover from disturbances over time.

Continue reading ‘Characterization of coral communities in the shallow hydrothermal vents of Mabini, Batangas, Philippines’

Divergent responses of an armored and an unarmored dinoflagellate to ocean acidification

Published 24 December 2024 Science Closed
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Highlights

  • An armored and an unarmored dinoflagellate exhibited divergent responses to OA.
  • The unarmored species presented a higher ability to withstand OA stress.
  • Cell wall structure may play essential roles in response to OA stress.
  • Unarmored dinoflagellates may have significant advantages in acidic oceans.

Abstract

Dinoflagellates, both armored and unarmored, with distinct cell wall difference, are being affected by elevated CO2-induced ocean acidification (OA). However, their specific responses to OA are not well understood. In this study, we investigated the physiological and molecular response of the armored species Prorocentrum obtusidens and the unarmored species Karenia mikimotoi to OA over a 28-day period. The results show that the two species responded differently to OA. Cell growth rate, particulate organic carbon (POC) content, and the activities of C4 pathway enzymes decreased in P. obtusidens under future acidified ocean condition (pH 7.8, 1000 μatm pCO2), but the activities of carbonic anhydrase (CA), ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO), and superoxide dismutase (SOD) increased. Whereas cell growth rate, contents of Chl a and PON, and SOD activity altered insignificantly in K. mikimotoi, but contents of POC and total carbohydrate, and the activity of RubisCO increased while the activities of CA and C4 pathway enzymes decreased. Transcriptomic analysis indicates that genes associated with antioxidative response, heat shock protein, proteasome, signal transduction, ribosome, and pH regulation were up-regulated in P. obtusidens but down-regulated in K. mikimotoi. Notably, the synthesis of soluble organic matter (i.e., spermidine and trehalose) was enhanced in K. mikimotoi, thereby regulating intracellular pH and improving stress resistance. This study highlights the divergent response of the armored and unarmored dinoflagellates to OA, with the unarmored dinoflagellate exhibiting a higher ability to withstand this stressor. Therefore, caution should be exercised when predicting the behavior and the eventual fate of dinoflagellates in the future acidified ocean.

Continue reading ‘Divergent responses of an armored and an unarmored dinoflagellate to ocean acidification’

Long-term warming and acidification interaction drives plastic acclimation in the diatom Pseudo-nitzschia multiseries

Published 17 December 2024 Science Closed
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Highlights

  • Temperature shows stronger effects than CO2 on P. multiseries growth and stress reponses.
  • Multi-omics analysis reveals phenotypic plasticity and molecular adaptations under long-term warming and acidification.
  • Short-term experiments effectively predict long-term P. multiseries responses to combined temperature and CO2 changes.

Abstract

Ocean warming (OW) and acidification (OA) are expected to interactively impact key phytoplankton groups such as diatoms, but the underlying mechanisms, particularly under long-term acclimation, remain poorly understood. In this study, we investigated the responses of the toxic diatom Pseudo-nitzschia multiseries to combined changes in temperature (20 °C and 30 °C) and CO2 concentration (pCO2 400 μatm and 1000 μatm) using a multi-omics approach over an acclimation period of at least 251 generations. Physiological data suggest that elevated temperature, either alone or in combination with CO2, reduced the net photosynthesis and nitrate uptake rate, thus inhibiting P. multiseries growth. Conversely, elevated CO2 alone stimulated P. multiseries growth. Comparative genome analysis revealed the phenotypic plasticity in response to temperature and pCO2 variations, even after more than 251 generations acclimation period. Temperature was identified as the dominant environmental factor, showing stronger effects than CO2. Transcriptomic profiles indicated that genes involved in stress- and intracellular homeostasis such as Hsps, ubiquitination process and antioxidant defense were mostly down-regulated under long-term warming acclimation. This study demonstrates that P.multiseries responds similarly to both short-term and long-term experimental selection, suggesting that short-term experiments can be used to predict long-term responses.

Continue reading ‘Long-term warming and acidification interaction drives plastic acclimation in the diatom Pseudo-nitzschia multiseries’

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