High carbonate alkalinity can impose composite hydrochemical stress on bivalves by altering inorganic carbon speciation, buffering capacity and ion-exchange conditions. The Hong Kong oyster (Crassostrea hongkongensis) naturally inhabits estuarine areas where low salinity can occur together with carbonate-system disturbance, yet its physiological response to high carbonate alkalinity under a low-salinity background remains unclear. In this study, oysters were exposed at salinity 5 to a Control treatment, A10 (carbonate alkalinity 10 mmol L⁻¹) and A20 (carbonate alkalinity 20 mmol L⁻¹). Salinity was treated as a controlled background condition, whereas the alkalinity treatments represented a composite carbonate-alkalinity perturbation involving alkalinity, pH and carbonate chemistry. Survival, feeding rate, oxygen consumption, ammonia excretion and hemolymph ammonia were measured across Control, A10 and A20. Hemolymph catalase (CAT), glutathione peroxidase (GSH-Px), glucose and ATP were analyzed as A10 and A20 time-course endpoints because a parallel Control was not included for these assays. A 24-h mantle transcriptome was used to screen candidate transcripts associated with innate defense and glutathione metabolism. Oysters under A10 retained partial compensatory capacity, whereas A20 significantly reduced survival. A10 and A20 suppressed early oxygen consumption and ammonia excretion, and altered feeding allocation among microalgae. Within the A10 and A20 biochemical time-course dataset, CAT, GSH-Px, glucose and ATP showed stage-specific variation, suggesting redox and energy-metabolism adjustment under alkalinity stress. Overall, high carbonate alkalinity reduced survival and was associated with metabolic depression, feeding compensation and hemolymph redox-energy remodeling in C. hongkongensis. This study will provide a theoretical basis for water quality regulation in saline-alkaline water aquaculture and the sustainable development of aquaculture.
Continue reading ‘The effects of high carbonate alkalinity under low salinity on the survival, physiological metabolism, and redox homeostasis of Crassostrea hongkongensis’Posts Tagged 'salinity'
The effects of high carbonate alkalinity under low salinity on the survival, physiological metabolism, and redox homeostasis of Crassostrea hongkongensis
Published 28 July 2026 Science Leave a CommentTags: biological response, laboratory, mollusks, mortality, multiple factors, oxygen, performance, physiology, salinity
Climate change and aquatic ecosystems: impacts on salinity, species survival, and ecological resilience
Published 29 June 2026 Science ClosedTags: biological response, fisheries, mesocosms, mortality, phytoplankton, reproduction, review, salinity
Highlights
- Unveils Climate-Driven Disease Mechanisms Across Aquatic Systems.
- Integrates Multistressor Impacts Including Pollution, Eutrophication, and Salinity Fluctuations.
- Explores Shifts in Species Distribution, Reproduction, and Food Web Dynamics.
- Highlights Adaptive Traits and Resilience Mechanisms in Aquatic Organisms.
- Provides Science-Based Recommendations for Climate-Responsive Management.
Abstract
Climate change is rapidly transforming aquatic ecosystems, posing complex environmental challenges with far-reaching ecological and socio-economic implications. Rising temperatures, sea-level rise, altered precipitation patterns, shifting hydrological regimes, and sea-ice loss are intensifying pressures on coastal, estuarine, freshwater, and polar systems. These stressors contribute to habitat degradation, increased frequency of hypoxic events, and altered species distributions. Crucially, while some dual stressors, such as warming and acidification, can paradoxically increase primary producer biomass, our findings reveal that this resultant biomass often accumulates as detritus rather than being efficiently transferred to higher trophic levels. This observation directly challenges the simplistic assumption that “more growth” is invariably beneficial, highlighting complex indirect effects on food web dynamics and ecosystem function. Ecological perturbations propagate through trophic networks, resulting in biodiversity loss, reduced ecosystem resilience, and declining fisheries productivity, thereby threatening food security and coastal livelihoods. Marine and freshwater organisms are increasingly exposed to multiple, interacting stressors, including warming, acidification, salinity fluctuations (requiring distinct osmoregulatory strategies, e.g., heterosmotic regulation in teleosts vs. isosmotic intracellular regulation in crustaceans), pollution, and overexploitation. These cumulative pressures can exacerbate disease outbreaks, modify host–pathogen dynamics, and facilitate the emergence and spread of aquatic pathogens, with consequences for ecosystem stability and human health. In aquaculture systems, climate-driven stress often acts synergistically with anthropogenic disturbances, amplifying production risks and economic vulnerability. Furthermore, anthropogenic infrastructure like reservoirs can act as unintended hubs facilitating species dispersal following extreme events like floods, altering community structures. At the biogeochemical scale, climate-induced alterations in nutrient cycling, primary productivity, and carbon sequestration are reshaping ecosystem functioning, particularly in high-latitude and freshwater environments where adaptive capacity is comparatively constrained. Changes in food web architecture and energy transfer efficiency further compromise ecosystem services. This review specifically centers on the biological and ecological mechanisms underlying these climate-driven changes, including organism-level stress responses, shifts in species interactions, and alterations in pathogen dynamics. Recognizing the societal implications and public discourse surrounding climate change underscores the urgency of examining its tangible impacts on sensitive environments, such as estuarine ecosystems, which serve as critical interfaces between terrestrial and marine realms and are thus highly susceptible to both climatic shifts and human influence.
Continue reading ‘Climate change and aquatic ecosystems: impacts on salinity, species survival, and ecological resilience’Long term variability of temperature and pH in the Bay of Bengal: an investigation on acoustic perspective
Published 28 May 2026 Science ClosedTags: field, Indian, modeling, regionalmodeling, salinity
This study comprehensively assesses the long-term variability of temperature, ocean acidity changes, and their implications on sound absorption and acoustic propagation in the Bay of Bengal. The analysis reveals a persistent warming trend in the Indian Ocean over the past 50 years, with a significant increase in temperature observed during the Sagar Maitri cruise in 2019. Thermal structure analysis using HadleySST EN4 data indicates warming in the upper 50m but a cooling trend in the 100-200m depth range. Oceanic Heat Content analysis highlights an increasing tendency of heat storage in the upper 50m, indicative of global warming.
In the context of surface ducted propagation, Sonic Layer Depth (SLD) and gradients in the Sound Speed Profile (SSP) were crucial factors influencing acoustic energy behavior. The study revealed a decreasing trend in in-layer gradient (Gr_SL) since 1990, intensifying after that period. The below-layer gradient (Gr_BL) also exhibited a decreasing trend, implying complex dynamics in the sonic layer with potential implications for sound propagation in the surface duct.
The investigation into pH changes spanning 65 years demonstrates a declining trend, particularly since the 1990s, attributed to increased atmospheric CO2 dissolution. The study linked this decrease to anthropogenic activities, aligning with global trends. The analysis of sound absorption illustrated a nonlinear relationship between absorption, frequency, and pH, emphasizing a significant impact of ocean acidification on sound absorption in the Bay of Bengal. The acoustic propagation modeling further highlighted a decrease in transmission loss with reducing pH, leading to increased sound travel and potentially noisier oceans. Salinity variations play a more significant role than temperature in influencing sound absorption.
Continue reading ‘Long term variability of temperature and pH in the Bay of Bengal: an investigation on acoustic perspective’Changes in salinity impact nitrogen removal and carbon preservation in coastal wetlands sediment
Published 18 May 2026 Science ClosedTags: biological response, chemistry, laboratory, multiple factors, North Pacific, salinity, sediment
Highlights
- Coastal freshening suppressed N removal via denitrification while accelerating net organic carbon mineralization.
- Salinity shaped N removal vs. N retention and carbonate vs. alkalinity balance through sulfate availability.
- Salinity changes had concurrent implications for coastal eutrophication and ocean acidification.
Abstract
Coastal wetlands naturally remediate nitrogen (N) pollution through microbial pathways that either remove reactive N via denitrification and anammox, or retain it via dissimilatory nitrate reduction to ammonium (DNRA). The balance among three processes is closely linked to the carbon (C) cycle, as both heterotrophic denitrification and DNRA consume organic C and release alkalinity. While salinity fluctuations can disrupt these processes through direct ionic stress or sulfur (S) cycling, their net impact on N removal and C preservation services remains unclear. Here, we deployed microcosm experiments using mangrove sediments under a large salinity gradient (0-30 psu). We quantified N transformation rates using 15N isotope tracing technique, combined with geochemical analysis, and functional genes quantification. Freshening from ambient 30 psu to 10 psμ decreased N removal efficiency by ∼20%. This decline was caused by reduced denitrification, whereas anammox and DNRA were unaffected. Meanwhile, lower salinity appears to have stimulated C decomposition via reduced ionic stress. The reduced sulfate input diminished total alkalinity (TA) generation relative to dissolved inorganic carbon (DIC). The stoichiometric shift of TA:DIC ratio could further contribute to acidification in adjacent coastal waters. Additionally, the S-mediated regulation of N partitioning appears to be nitrate-dependent: under nitrate limitation, higher sulfate favored N retention; conversely, with enriched nitrate, it potentially favored N removal. Integrating the coupling effect of salinity on interaction between N, C and S cycles, our study demonstrates that coastal water freshening may weaken wetlands’ ability to remove N and preserve C.
Continue reading ‘Changes in salinity impact nitrogen removal and carbon preservation in coastal wetlands sediment’Projected future of African marine ecosystems under climate change and stratospheric aerosol injection
Published 8 May 2026 Science ClosedTags: biological response, modeling, multiple factors, North Atlantic, phytoplankton, regionalmodeling, salinity, temperature
Stratospheric Aerosol Injection (SAI) has been proposed as a potential strategy to cool the planet. The ARISE-SAI-1.5 approach, which employes a moderate emission scenario, is simulated to limit future global warming to 1.5°C by injecting aerosols into the stratosphere in the year 2035. However, the climate response to this SAI scenario, particularly along the African coast, remains unclear. In this study, we investigate the potential impacts of climate change under the SSP2-4.5 scenario and ARISE-SAI-1.5 on regional African marine ecosystems through key biological (chlorophyll), physical (salinity, temperature), and chemical (nitrate, acidification, and dissolved oxygen) parameters. Our results indicate that climate change may reduce productivity in African coastal ecosystems, with chlorophyll concentrations decreasing between 10% and 62%. Sea surface temperatures are projected to rise by 1.5°C along the entire coast by 2069, while surface salinity increases up to 0.3 g/kg, except for a slight decrease of up to 0.1 g/kg along the Congolese-Angolan coast. This salinity dipole in the Gulf of Guinea results from enhanced precipitation and river discharge, reinforced by stratification that traps freshwater at the surface. Additionally, climate change drives ocean acidification and may expand the oxygen minimum zone in the Gulf of Guinea, with oxygen levels decreasing by 10%–30% at depths of 100–200 m. Although ARISE-SAI-1.5 may help reduce surface oxygen depletion, it may not significantly mitigate subsurface oxygen loss or continued acidification. Nevertheless, it may reduce some negative climate change impacts on marine ecosystems by stabilizing chlorophyll levels, sea surface temperatures, and salinity.
Plain Language Summary
Stratospheric Aerosol Injection is being explored as a way to cool the planet and limit future global warming, for instance, to 1.5°C in the scenario we explore here (ARISE-SAI-1.5). However, its effects on the ocean, especially along the African coast, are not fully understood. This study examines key factors such as chlorophyll, water temperature, salinity, and oxygen levels to assess changes in marine ecosystems. Our findings show that climate change could reduce productivity, with chlorophyll levels dropping by 10%–62%. Sea surface temperatures are expected to rise by 1.5°C by 2069, and salinity will increase along most coastal areas. The low-oxygen zone in the Gulf of Guinea may expand, making deep waters less habitable for marine life. While the SAI we study here helps slow oxygen loss near the surface, it does not prevent deeper waters from losing oxygen or the ocean from becoming more acidic. However, it can still reduce some harmful effects of climate change by stabilizing chlorophyll levels, temperatures, and salinity.
Continue reading ‘Projected future of African marine ecosystems under climate change and stratospheric aerosol injection’Triple threat: ocean acidification, warming, and hyposalinity synergistically weaken shell integrity in a Mediterranean calcifying mollusk
Published 30 January 2026 Science ClosedTags: biological response, fisheries, laboratory, Mediterranean, mollusks, morphology, mortality, multiple factors, salinity, temperature
Highlights
- OA, OW, and hyposalinity drive skeletal and mineralogical responses in a Mediterranean clam.
- Combined stress makes shells less dense, more porous, and more fracture-prone.
- Microstructural changes reveal early calcification impairments under triple stress.
- Triple-stressor synergy compromises shell integrity and threatens fishery species resilience.
Abstract
Anthropogenic climate change is rapidly altering marine environments primarily through ocean warming, acidification, and hyposalinity, posing significant challenges for marine calcifying organisms. This study investigated the short-term effects of these stressors on the Mediterranean bivalve Chamelea gallina, a key fishery species in the Adriatic Sea, by integrating skeletal, mechanical, and mineralogical responses. Adult clams of commercial size were exposed for 21 days to eight experimental treatments manipulating two levels of temperature (18 °C vs. 22 °C), pH (8.0 vs. 7.9), and salinity (35 vs. 32), chosen to reproduce near-future climate projections and the freshwater-driven variability typical of the Adriatic Sea. Despite the short exposure duration, the combined exposure to low pH, high temperature, and reduced salinity weakens the shell of Chamelea gallina at multiple levels, compromising shell integrity, by making shells less dense, more porous, more fragile, and more susceptible to fracture, and increasing mortality. Microstructural analysis revealed smaller aragonite crystallites and lower calcium content, indicative of early impairments in the calcification process. The study highlights the occurrence of synergistic effects among stressors and reveals the vulnerability of Chamelea gallina to near-future ocean conditions, with potential cascading consequences for ecosystem functioning and fishery sustainability, given the species’ key ecological role and commercial relevance in the Adriatic Sea.
Continue reading ‘Triple threat: ocean acidification, warming, and hyposalinity synergistically weaken shell integrity in a Mediterranean calcifying mollusk’Combined effects of ocean acidification, warming, and salinity on the fertilization success in an Arctic population of sea urchins
Published 9 January 2026 Science ClosedTags: Arctic, biological response, echinoderms, laboratory, multiple factors, reproduction, salinity, temperature
Anthropogenic stressors, including ocean acidification (OA), ocean warming (OW), and salinity changes, are rapidly altering marine ecosystems, with Arctic regions being particularly vulnerable. This study investigates the combined effects of these stressors on the fertilization success of the green sea urchin (Strongylocentrotus droebachiensis) from Kongsfjorden, Svalbard. We exposed gametes to various levels of pH, temperature, and salinity to assess their individual and combined impacts on fertilization performance. Our results show that temperature and pH significantly influenced fertilization success, with temperature having the strongest effect, while salinity had no significant impact. A significant statistical interaction between temperature and pH indicated that warming enhanced fertilization more effectively at higher pH levels, while low pH suppressed this increase. To compare the relative influence of each stressor, we used a conceptual model based on standardized slopes, which supported temperature as the dominant driver, followed by pH. These findings highlight the importance of considering the effects of combined stressors when assessing marine organism responses to climate change, especially in polar ecosystems. Our study underscores the need for further research into the mechanisms driving these combined effects, given that Arctic ecosystems face accelerated environmental changes.
Continue reading ‘Combined effects of ocean acidification, warming, and salinity on the fertilization success in an Arctic population of sea urchins’Impact of climate change driven freshening, warming, and ocean acidification on the cellular metabolism of Atlantic cod (Gadus morhua)
Published 27 October 2025 Science ClosedTags: biological response, fish, laboratory, multiple factors, North Atlantic, physiology, salinity, temperature
Climate change is causing increasing sea surface temperature, ocean acidification and, in near shore waters, freshening. We investigated the metabolic effects of all three and their combination in Atlantic cod from the Skagerrak (eastern North Sea) by measuring concentration changes of a wide range of metabolites involved in energy production in the liver and muscles. Liver metabolism was more strongly affected than muscle, reflecting its central regulatory role. Most amino acid concentrations declined in both tissues across all treatments, and metabolomic pathway analysis revealed significant enrichment in ten metabolic pathways. This suggests enhanced amino acid metabolism in a climate change future. Warming and ocean acidification induced increased liver concentrations of lactate, glucose and fructose 1,6-bisphosphate indicating that gluconeogenesis will increase to meet increased production of enzymes to counter future stress. The molar contribution of glutamine to the total change in liver amino acids constituted 49%, 16% and 29% under warming, ocean acidification and their combination accentuating its importance in energy production also under future climate change. We observed contrasting responses in AMP, ADP, and NAD+ concentrations between warming and acidification suggesting possible antagonistic effects. Our findings demonstrate significant and complex metabolic responses to future climate stress in Atlantic cod in northern European waters.
Continue reading ‘Impact of climate change driven freshening, warming, and ocean acidification on the cellular metabolism of Atlantic cod (Gadus morhua)’Ocean acidification interacts with low salinity and phosphorus limitation to modulate growth, photosynthesis, and physiology of mass-cultivated Gracilariopsis lemaneiformis
Published 4 August 2025 Science ClosedTags: algae, biological response, fisheries, growth, laboratory, multiple factors, nutrients, photosynthesis, physiology, salinity
Due to the effective removal of phosphorus during eutrophication control and intensive macroalgal cultivation, phosphorus limitation in coastal waters is normalized. As an economic macroalga cultivated on a large scale in production, Gracilariopsis lemaneiformis is also inevitably influenced by the combination of phosphorus limitation, ocean acidification caused by the increase of dissolved CO2 concentration and salinity decrease as a consequence of rainfall. In this study, G. lemaneiformis was cultured for 15 days under two pCO2 levels (LC: 400 μatm, HC: 1000 μatm), two salinities (LS: 22, HS: 30) and two phosphorus concentrations (LP: 0.1 μmol L−1, HP: 10.1 μmol L−1) to study the growth and photophysiology responses of this macroalga to the coupling of phosphorus limitation, ocean acidification and low salinity. Lower phosphorus (LP) treatment substantially reduced multiple parameters compared to higher phosphorus (HP) condition, including relative growth rate (RGR), photosynthetic rate, chlorophyll fluorescence parameters, and the contents of pigments, soluble protein, and soluble carbohydrate. Elevated CO₂ (HC) exposure induced a significant reduction in algal RGR under LP condition, while demonstrating no statistically significant impact on RGR under HP condition. Furthermore, HC treatment significantly inhibited carotenoid biosynthesis under LP condition. Notably, lower salinity (LS) stimulation significantly enhanced RGR in the ambient CO₂ (LC) group, but this promotive effect was completely negated under HC condition. These findings demonstrated that phosphorus limitation had an adverse outcome on algal growth, and phosphorus limitation exacerbated the adverse effect of ocean acidification on its growth. Moreover, the promotion effect of low salinity on algal growth could be neutralized by ocean acidification. This study provided important information about the influence of environmental changes on the photophysiological characteristics of G. lemaneiformis and new breeding directions for large-scale cultivation of coastal economic macroalgae.
Continue reading ‘Ocean acidification interacts with low salinity and phosphorus limitation to modulate growth, photosynthesis, and physiology of mass-cultivated Gracilariopsis lemaneiformis’Physiological and growth responses of Black Sea salmon (Salmo labrax) to long-term salinity and high carbon dioxide stress
Published 16 July 2025 Science ClosedTags: biological response, Black Sea, fish, fisheries, growth, laboratory, molecular biology, morphology, multiple factors, physiology, salinity
Black Sea salmon (Salmo labrax), an anadromous salmonid species of regional importance, is increasingly considered for aquaculture in the Black Sea. This study investigates the physiological and growth responses of Black Sea salmon to seawater transfer, with a particular focus on carbon dioxide (CO₂) stress. The experiment began on 5 July 2022 with 720 fish (76.68±15.34 g) reared under semi-controlled conditions using a freshwater recirculating aquaculture system (RAS). On 12 October 2022, a group of fish was transferred to Black Sea water (18 ppt), and a subgroup was exposed to elevated CO₂ (1000 µatm pCO₂) until the end of the trial on 7 March 2023. Exposure to carbon dioxide showed negligible or minimal effects on seawater adaptation and growth. In contrast, physiological markers such as gill Na⁺/K⁺-ATPase (NKA) activity and the expression of nkaα1a, nkaα1b, and nkcc1a genes, along with growth metrics—including specific growth rate (SGR), condition factor (K value), and liver gene expression of igf-I, igfbp1b, ghr1, and ctsl—indicated that the fish were not physiologically prepared for seawater transfer in autumn. These findings suggest that the commonly practiced autumn sea transfer in the region may lead to suppressed growth and suboptimal performance. The results emphasize the importance of aligning seawater transfer with the smoltification window to support fish health and optimize aquaculture outcomes in Black Sea salmon farming.
Continue reading ‘Physiological and growth responses of Black Sea salmon (Salmo labrax) to long-term salinity and high carbon dioxide stress’Salinity-dependent effects of seawater acidification on growth, photosynthetic physiology and biochemistry of the invasive macroalga Codium fragile
Published 25 March 2025 Science ClosedTags: algae, biological response, growth, laboratory, multiple factors, North Pacific, physiology, salinity
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.
Continue reading ‘Salinity-dependent effects of seawater acidification on growth, photosynthetic physiology and biochemistry of the invasive macroalga Codium fragile’Between shells and seas: effects of ocean acidification on calcification and osmoregulation in yellow clam (Amarilladesma mactroides)
Published 14 March 2025 Science ClosedTags: biological response, laboratory, mollusks, multiple factors, physiology, salinity, South Atlantic
Highlights
- Decline in ocean pH due to increased CO2 is threatening the physiology of marine organisms.
- Yellow clams (Amarilladesma mactroides) were exposed to ocean acidification and hypersaline stress for 96 hours to assess biomarkers of calcification and osmotic balance.
- OA reduced Ca2+-ATPase activity in the mantle, damaging mineralized structures.
- Elevated salinity increases carbonic anhydrase and Na+/K+-ATPase activity in the gills.
- Increased carbonic anhydrase activity in the mantle may help maintain acid-base balance in the species.
Abstract
The decline in ocean pH due to rising CO2 levels is a critical factor impacting marine ecosystems. Ocean acidification (OA) is expected to negatively affect various organisms, particularly those with mineralized structures. While the effects of OA on the calcification of shells and exoskeletons are documented, the impact on homeostatic processes, such as osmoregulation, is less understood. Osmoregulation is vital for maintaining water and salt balance within marine organisms, crucial for their survival and physiological functions. Acidification may alter ion exchange mechanisms, affecting the regulation of ions. In this study, we evaluated the effects of intermediate OA (pH 7.6) with or without hypersaline stress (35‰) on calcification and osmotic balance biomarkers in the bivalve Amarilladesma mactroides after 96 hours of acute exposure. We found that pH did not affect hemolymph osmolality or extracellular Ca2+ concentration. However, OA impaired the bivalve’s ability to maintain its mineralized structures by decreasing Ca2+-ATPase enzyme activity in the mantle. The increase in carbonic anhydrase activity indicated a specific response to maintain acid-base balance in the tissue, i.e., compensating for the effects of acidification by neutralizing CO2 accumulation and stabilizing internal pH. In the gills, both enzymes showed increased performance under higher salinity and reduced pH. Exposure to less alkaline pH inhibited carbonic anhydrase and Na+/K+-ATPase activity, potentially affecting the regulation of essential inorganic osmolytes.
Continue reading ‘Between shells and seas: effects of ocean acidification on calcification and osmoregulation in yellow clam (Amarilladesma mactroides)’Transcriptome‐to‐phenome response of larval Eastern oysters under multiple drivers of aragonite undersaturation
Published 19 February 2025 Science ClosedTags: biological response, laboratory, molecular biology, mollusks, morphology, mortality, multiple factors, reproduction, respiration, salinity, temperature
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.
Continue reading ‘Transcriptome‐to‐phenome response of larval Eastern oysters under multiple drivers of aragonite undersaturation’Thalassia hemprichii may benefit from ocean acidification and slightly increased salinity in the future
Published 13 February 2025 Science ClosedTags: biological response, growth, laboratory, multiple factors, phanerogams, photosynthesis, physiology, salinity
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.
Continue reading ‘Thalassia hemprichii may benefit from ocean acidification and slightly increased salinity in the future’Combined effects of pCO2 and salinity on the silicification of estuarine diatoms
Published 8 January 2025 Science ClosedTags: biological response, growth, laboratory, morphology, multiple factors, North Pacific, photosynthesis, physiology, phytoplankton, salinity
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.
Continue reading ‘Combined effects of pCO2 and salinity on the silicification of estuarine diatoms’Energy budget as a tool to assess the effects of environmental stressors: a study on whiteleg shrimp (Penaeus vannamei) exposed to variations in salinity and ocean acidification
Published 10 October 2024 Science ClosedTags: biological response, crustaceans, growth, laboratory, multiple factors, oxygen, physiology, salinity, temperature
Our goal was to use the energy budget as a tool to evaluate the effects of salinity (20, 25, 30, 35 or 40‰) and ocean acidification (pH 8.0 or 7.3) in Penaeus vannamei. We assessed the energy budget a range of physiological processes (ingestion, defecation, growth, metabolism, excretion, energy substrate, hepatosomatic index, and osmoregulation). In general, salinity had an accentuated effect than pH, as it altered nearly all physiological parameters, including the energy channeled into growth (up to −56%). Reduced pH also affected the energy budget: increased energy lost in feces (25 and 40‰: +21% and 13%, respectively), excretion (25‰: +55%), and metabolism (20‰: +58%). Furthermore, acidified pH increased oxygen consumption by 60%, which may be related to higher energy expenditure. In conclusion, the energy budget can be a valuable tool for assessing the impacts of environmental stressors and the salinity has an accentuated effect than the ocean acidification predicted.
Continue reading ‘Energy budget as a tool to assess the effects of environmental stressors: a study on whiteleg shrimp (Penaeus vannamei) exposed to variations in salinity and ocean acidification’High light intensity and CO2 enrichment synergistically mitigated the stress caused by low salinity in Pyropia yezoensis
Published 7 August 2024 Science ClosedTags: algae, biological response, chemistry, growth, laboratory, light, multiple factors, North Pacific, photosynthesis, physiology, salinity
Macroalgae, playing a crucial role in coastal marine ecosystems, are subject to multiple environmental challenges due to tidal and seasonal alterations. In this work, we investigated the physiological responses of Pyropia yezoensis to ocean acidification (ambient CO2 (AC: 400 μatm) and elevated CO2 (HC: 1000 μatm)) under changing salinity (20, 30 psu) and light intensities (50, 100 μmol photons m−2 s−1) by measuring the growth, pigment content, chlorophyll fluorescence, and soluble sugar content. The key results are the following: (1) P. yezoensis exhibited better growth under normal salinity (30 psu) compared to hyposaline conditions (20 psu). (2) Intermediate light intensity increased phycoerythrin content, ultimately enhancing thalli growth without significant changes to the contents of chlorophyll a and carotenoids. (3) Ocean acidification alleviated hyposaline stress by enhancing pigment production in P. yezoensis only at a salinity of 20 psu, highlighting the complex interplay of these environmental factors. These findings indicate that higher light intensities and elevated pCO2 levels could mitigate the stress caused by low salinity.
Continue reading ‘High light intensity and CO2 enrichment synergistically mitigated the stress caused by low salinity in Pyropia yezoensis’Physiological responses of Atlantic cod to climate change indicate that coastal ecotypes may be better adapted to tolerate ocean stressors
Published 7 June 2024 Science ClosedTags: biological response, chemistry, fish, laboratory, morphology, multiple factors, North Atlantic, performance, physiology, respiration, salinity, temperature
Healthy ecosystems and species have some degree of resilience to changing conditions, however as the frequency and severity of environmental changes increase, resilience may be diminished or lost. In Sweden, one example of a species with reduced resilience is the Atlantic cod (Gadus morhua). This species has been subjected to overfishing, and with additional pressures such as habitat degradation and changing environmental conditions there has been little to no recovery, despite more than a decade of management actions. Given the historical ecological, economical, and cultural significance of cod, it is important to understand how Atlantic cod respond to global climate change to recover and sustainably manage this species in the future. A multi-stressor experiment was conducted to evaluate physiological responses of juvenile cod exposed to warming, ocean acidification, and freshening, changes expected to occur in their nursery habitat. The response to single drivers showed variable effects related to fish biometrics and increased levels of oxidative stress dependent parameters. Importantly, two separate responses were seen within a single treatment for the multi-stressor and freshening groups. These within-treatment differences were correlated to genotype, with the offshore ecotype having a heightened stress response compared to the coastal ecotype, which may be better adapted to tolerate future changes. These results demonstrate that, while Atlantic cod have some tolerance for future changes, ecotypes respond differently, and cumulative effects of multiple stressors may lead to deleterious effects for this important species.
Continue reading ‘Physiological responses of Atlantic cod to climate change indicate that coastal ecotypes may be better adapted to tolerate ocean stressors’Ocean acidification and desalination increase the growth and photosynthesis of the diatom Skeletonema costatum isolated from the coastal water of the Yellow Sea
Published 5 April 2024 Science ClosedTags: biological response, growth, laboratory, multiple factors, North Pacific, photosynthesis, physiology, phytoplankton, salinity, temperature
Highlights
- This study aims to investigate the combined effects of pH (400 μatm and 1000 μatm), temperature (10 °C, 20 °C), and salinity (20 psu, 30 psu) on the diatom S. costatum.
- In this study, we investigated the effects of ocean acidification and seawater desalination on Skeletonema costatum in varying seasonal temperatures.
- We found that ocean acidification and seawater desalination promoted the growth of S. costatum under the simulated conditions.
Abstract
Global climate changes induce substantial alterations in the marine system, including ocean acidification (OA), desalination and warming of surface seawater. Here, we examined the combined effects of OA and reduced salinity under different temperatures on the growth and photosynthesis of the diatom Skeletonema costatum. After having been acclimated to 2 CO2 concentrations (400 μatm, 1000 μatm) and 2 salinity levels (20 psu, 30 psu) at temperature levels of 10 °C and 20 °C, the diatom showed enhanced growth rate at the lowered salinity and elevated pCO2 irrespective of the temperature. The OA treatment increased the net photosynthetic rate and biogenic silica (Bsi) contents. Increasing the temperature from 10 to 20 °C raised the net photosynthetic rate by over twofold. The elevated pCO2 increased the net and gross photosynthetic rates by 20%–40% and by 16%–32%, respectively, with the higher enhancement observed at the higher levels of salinity and temperature. Our results imply that OA and desalination along with warming to the levels tested can enhance S. costatum‘s competitiveness in coastal phytoplankton communities under influence of future climate changes.
Continue reading ‘Ocean acidification and desalination increase the growth and photosynthesis of the diatom Skeletonema costatum isolated from the coastal water of the Yellow Sea’Recent developments in ionophore-based potentiometric electrochemical sensors for oceanic carbonate detection
Published 18 March 2024 Science ClosedTags: chemistry, field, multiple factors, review, salinity, sensor, temperature
The increasing level of atmospheric carbon dioxide (CO2) driven by human activities contributes to the global concern of climate change. A consequence of these circumstances is ocean acidification, which reduces seawater pH. The increasing absorption of atmospheric CO2 into the ocean decreases the concentration of carbonate ions and causes the sea to become more acidic, severely harming marine species. This harm to marine life has created the need for in situ carbonate sensing and monitoring to understand how marine ecosystems respond to pH reduction. Over the past few decades, many sensors with different compositions and structures have been developed to detect carbonate in seawater and other aquatic environments to simulate oceanic conditions. This review summarizes the recent developments in carbonate ionophores, a key component in carbonate electrochemical sensors, and compares the reported performance of these sensors through various parameters (e.g., sensitivity, response time, lifetime, testing media, and measuring range). Current challenges within the development of carbonate ionophores and sensors and possibilities for future research are also discussed.
Continue reading ‘Recent developments in ionophore-based potentiometric electrochemical sensors for oceanic carbonate detection’
