Combination Of Elevated Temperature Research Articles

Impacts of elevated temperature, decreased salinity and microfibers on the bioenergetics and oxidative stress in eastern oyster, Crassostrea virginica

Projected increases in temperature and decreases in salinity associated with global climate change will likely have detrimental impacts on eastern oyster, Crassostrea virginica, as these variables can influence physiological processes in these keystone species. We set out to determine how the interactive effects of temperature (20 °C or 27 °C) and/or salinity (27‰ or 17‰) impacted the energetic reserves, aerobic and anaerobic metabolism, and changes to oxidative stress or total antioxidant potential as a consequence of an altered environment over a 21-day exposure. Gill and adductor muscle were used to quantify changes in total glycogen and lipid content, Electron Transport System and Citrate Synthase activities, Malate Dehydrogenase activity, Protein Carbonyl formation, lipid peroxidation, and total antioxidant potential. A second exposure was performed to determine if these environmental factors influenced the ingestion of microfibers, which are now one of the leading forms of marine debris. Elevated temperature and the combination of elevated temperature and decreased salinity led to an overall decline in oyster mass, which was exacerbated by the presence of microfibers. Changes in metabolism and oxidative stress were largely influenced by time, but exposure to elevated temperature, decreased salinity, the combination of these stressors or exposure to microfibers had small impacts on oyster physiology and survival. Overall these studies demonstrate that oyster are fairly resilient to changes in salinity in short-term exposures, and elevations in temperature or temperature combined with salinity result in changes to the oyster energetic response, which can be further impacted by the presence of microfibers.

High-Temperature Hydrothermal Extraction of Phenolic Compounds from Brewer's Spent Grain and Malt Dust Biomass Using Natural Deep Eutectic Solvents.

Aligned with the EU Sustainable Development Goals 2030 (EU SDG2030), extensive research is dedicated to enhancing the sustainable use of biomass waste for the extraction of pharmaceutical and nutritional compounds, such as (poly-)phenolic compounds (PC). This study proposes an innovative one-step hydrothermal extraction (HTE) at a high temperature (120 °C), utilizing environmentally friendly acidic natural deep eutectic solvents (NADESs) to replace conventional harmful pre-treatment chemicals and organic solvents. Brewer's spent grain (BSG) and novel malt dust (MD) biomass sources, both obtained from beer production, were characterized and studied for their potential as PC sources. HTE, paired with mild acidic malic acid/choline chloride (MA) NADES, was compared against conventional (heated and stirred maceration) and modern (microwave-assisted extraction; MAE) state-of-the-art extraction methods. The quantification of key PC in BSG and MD using liquid chromatography (HPLC) indicated that the combination of elevated temperatures and acidic NADES could provide significant improvements in PC extraction yields ranging from 251% (MD-MAC-MA: 29.3 µg/g; MD-HTE-MA: 103 µg/g) to 381% (BSG-MAC-MA: 78 µg/g; BSG-HTE-MA: 375 µg/g). The superior extraction capacity of MA NADES over non-acidic NADES (glycerol/choline chloride) and a traditional organic solvent mixture (acetone/H2O) could be attributed to in situ acid-catalysed pre-treatment facilitating the release of bound PC from lignin-hemicellulose structures. Qualitative 13C-NMR and pyro-GC-MS analysis was used to verify lignin-hemicellulose breakdown during extraction and the impact of high-temperature MA NADES extraction on the lignin-hemicellulose structure. This in situ acid NADES-catalysed high-temperature pre-treatment during PC extraction offers a potential green pre-treatment for use in cascade valorisation strategies (e.g., lignin valorisation), enabling more intensive usage of available biomass waste stream resources.

Co-occurring elevated temperature and drought stress inhibit cotton pollen fertility by disturbing anther carbohydrate and energy metabolism

The effects of individually applied heat or drought stress on cotton’s pollen fertility, and consequently on yield formation, have been extensively studied. In contrast, the effects of their compound stress have received minimal attention. To address this, a pond experiment was conducted using a cotton cultivar, Yuzaomian 9110 and the treatments consisted of control (CK), drought stress (DS), elevated temperature (ET), and the combination of elevated temperature and drought stress (ET+DS). Results revealed that ET+DS resulted in larger decreases in cottonseed number per boll and boll weight than DS or ET, which were attributed to the lower pollen fertility under the combined stress compared to either single stress. The decreases in pollen fertility under all stress conditions were further associated with disturbances in anther carbohydrate and energy metabolism. Pollen viability was negatively correlated with sucrose content, but was positively correlated with starch and ATP contents under different conditions. Specifically, DS increased anther sucrose content by increasing sucrose phosphate synthetase (SPS) activity to enhance sucrose synthesis, and by decreasing sucrose synthetase (SuSy) and acid/alkaline INV activities to restrict sucrose hydrolysis to fructose and glucose. Similar to DS, ET+DS increased anther sucrose content, which was attributed to the restricted sucrose hydrolysis, due to the reduced activities of SuSy and acid/alkaline INV, and acid INV activity even was lower under ET+DS than DS. However, ET enhanced acid invertase (INV) activity to promote sucrose hydrolysis, and down-regulated the expression of GhSUT3A/D (sucrose transporter gene), GhSUT4 (sucrose transporter gene) and GhSWEET55 (encoding Sugars Will Eventually Be Exported Transporters proteins) to inhibit sucrose transport into anthers, so the anther sucrose content was decreased. Furthermore, ET, DS and ET+DS treatments significantly decreased starch synthesis by down-regulating the expression of GhAGP, GhGBSS and GhSSS; however, the ET+DS treatment had a lower GhSSS expression than any single stress, which further inhibited amylopectin synthesis and resulted in lower anther starch content compared to CK and either of the individual stresses. In addition, significant reductions were observed in anther pyruvate content under all stress conditions, which inhibited the ATP production in the tricarboxylic acid cycle. Nevertheless, different pathways were involved in the response of energy metabolism to single and combined stresses. In particular, single ET or DS down-regulated GhHK1 and GhPK to decrease pyruvate formation, while the downregulation of GhHK1 and GhPGK were responsible for the decreased pyruvate content under combined stress. Additionally, either single stress resulted in the upregulation and downregulation of GhATP α subunit and GhATP β subunit of ATP synthase, respectively, the opposite was observed under the condition of combined stress, indicating that differential response mechanisms of ATP synthase are activated between the combined stress and any individual stresses. All these confirmed that elevated temperature combined with drought stress have a unique effect on carbohydrate and energy metabolism of anthers, resulting in larger decreases in pollen fertility, cottonseed number per boll and boll weight than either of the stresses alone.

The limits of stress-tolerance for zooplankton resting stages in freshwater ponds.

In seasonal environments, many organisms evolve strategies such as diapause to survive stressful periods. Understanding the link between habitat stability and diapause strategy can help predict a population's survival in a changing world. Indeed, resting stages may be an important way freshwater organisms can survive periods of drought or freezing, and as the frequency and extent of drought or freezing vary strongly among habitats and are predicted to change with climate change, it raises questions about how organisms cope with, and survive, environmental stress. Using Daphnia magna as a model system, we tested the ability of resting stages from different populations to cope with stress during diapause. The combination of elevated temperatures and wet conditions during diapause shows to prevent hatching altogether. In contrast, hatching is relatively higher after a dry and warm diapause, but declines with rising temperatures, while time to hatch increases. Resting stages produced by populations from summer-dry habitats perform slightly, but consistently, better at higher temperatures and dryness, supporting the local adaptation hypothesis. A higher trehalose content in resting eggs from summer-dry habitat might explain such pattern. Considering that temperatures and summer droughts are projected to increase in upcoming years, it is fundamental to know how resting stages resist stressful conditions so as to predict and protect the ecological functioning of freshwater ecosystems.

Yield and Seed Chemical Composition under Elevated CO<sub>2</sub> and Temperature Based on the RCP 4.5 Scenario of Important Thai Rice

This research aimed to examine the effects of combining increased temperature and carbon dioxide (CO₂) under RCP 4.5 scenarios on yield and seed chemical composition of Thai rice cultivars; Chinat1, Phathumthani1, and Phitsanulok2. The field warming experiment was conducted at Phitsanulok from 2018 to 2020. Sixteen field-open top chambers (OTCs) were applied to simulate the expected future climate situation under RCP 4.5 (the elevated temperature at 2℃ and CO₂ up to 800 ppm, respectively). The results revealed that the single factor of elevated temperature at 2℃ led to statistically significant grain size reductions of 2 rice cultivars; Chinat1 and Phitsanulok2. We also found that the combination of elevated temperature and CO₂ induced a significant grain yield loss (ton.ha-1) by 68% in Phitsanulok2 but an increase of 38% appeared in Chainat1. Considering results in seed chemicals, the statistically significant decrease trends in Amylose and Brix values were shown in 3 cultivars. These results suggest that elevated temperature and CO₂ caused the imbalance in seed nutrient contents and an increase in yield loss in some Thai rice cultivars.

Ecology of Methanonatronarchaeia.

Methanonatronarchaeia represents a deep-branching phylogenetic lineage of extremely halo(alkali)philic and moderately thermophilic methyl-reducing methanogens belonging to the phylum Halobacteriota. It includes two genera, the alkaliphilic Methanonatronarchaeum and the neutrophilic Ca. Methanohalarchaeum. The former is represented by multiple closely related pure culture isolates from hypersaline soda lakes, while the knowledge about the latter is limited to a few mixed cultures with anaerobic haloarchaea. To get more insight into the distribution and ecophysiology of this enigmatic group of extremophilic methanogens, potential activity tests and enrichment cultivation with different substrates and at different conditions were performed with anaerobic sediment slurries from various hypersaline lakes in Russia. Methanonatronarchaeum proliferated exclusively in hypersaline soda lake samples mostly at elevated temperature, while at mesophilic conditions it coexisted with the extremely salt-tolerant methylotroph Methanosalsum natronophilum. Methanonatronarchaeum was also able to serve as a methylotrophic or hydrogenotrophic partner in several thermophilic enrichment cultures with fermentative bacteria. Ca. Methanohalarchaeum did not proliferate at mesophilic conditions and at thermophilic conditions it competed with extremely halophilic and moderately thermophilic methylotroph Methanohalobium, which it outcompeted at a combination of elevated temperature and methyl-reducing conditions. Overall, the results demonstrated that Methanonatronarchaeia are specialized extremophiles specifically proliferating in conditions of elevated temperature coupled with extreme salinity and simultaneous availability of a wide range of C1 -methylated compounds and H2 /formate.

Effect of elevated CO2 and temperature on maize resistance against the Asian corn borer

AbstractThe increasing atmospheric CO2 concentration and temperature has altered the plant‐insect interactions. However, little is known about the intrinsic mechanisms between plant resistance and insect survival strategies under the combined conditions of elevated CO2 and temperature. This study investigated the effects of elevated temperature alone and in combination with CO2 enrichment on the nutrition and resistance of maize (Zea mays L.) to the Asian corn borer (ACB) (Ostrinia furnacalis [Guenée]) and feeding, survival, and physiological response of ACB over 2‐year growing seasons. The maize plants were grown in free‐air CO2 enrichment connected by infrared heating system with the ambient (control), ~4.0°C increase in air temperature (ET) and ET together with ~700 ppm concentration of atmospheric CO2 (ETEC). Elevated CO2 alleviated the effect of ET on total non‐structural carbohydrates (TNC)/N in maize, and thus ETEC did not change this parameter. ETEC enhanced the defensive enzyme activities in maize. Elevated CO2 enhanced the ET effect on increased total phenolics content in maize. ET and ETEC increased the expression levels of the jasmonic acid (JA) defence‐related genes and JA content in maize. Above insect resistance‐related secondary metabolism in maize was enhanced by ACB damage. Except for amylase, ET and ETEC had no effect on the digestive enzyme activities and food intake of ACB, but enhanced its protective enzyme activities. ET and ETEC decreased the survival rate, overwintering larval body weight and fecundity, increased supercooling point of ACB fed on maize. These findings demonstrate that the combination of elevated temperature and CO2 did not influence the nutritional metabolism, but enhanced insect resistance‐related secondary metabolism of maize, which could alleviate the occurrence and damage of ACB in maize under the context of future climate change scenarios.

Acute exposure to perfluorooctane sulfonate exacerbates heat-induced oxidative stress in a tropical coral species.

Perfluorooctane sulfonate (PFOS) is among the most commonly per- and poly-fluoroalkyl substances (PFAS) found in environmental samples. Nevertheless, the effect of this legacy persistent organic contaminant has never been investigated on corals to date. Corals are the keystone organisms of coral reef ecosystems and sensitive to rising ocean temperatures, but it is not understood how the combination of elevated temperature and PFOS exposure will affect them. Therefore, the aims of the present study were (1) to evaluate the time-dependent bioconcentration and depuration of PFOS in the scleractinian coral Stylophora pistillata using a range of PFOS exposure concentrations, and (2) to assess the individual and combined effects of PFOS exposure and elevated seawater temperature on key physiological parameters of the corals.Our results show that the coral S. pistillata rapidly bioconcentrates PFOS from the seawater and eliminates it 14 days after ceasing the exposure. We also observed an antagonistic effect between elevated temperature and PFOS exposure. Indeed, a significantly reduced PFOS bioconcentration was observed at high temperature, likely due to a loss of symbionts and a higher removal of mucus compared to ambient temperature. Finally, concentrations of PFOS consistent with ranges observed in surface waters were non-lethal to corals, in the absence of other stressors. However, PFOS increased lipid peroxidation in coral tissue, which is an indicator of oxidative stress and enhanced the thermal stress-induced impairment of coral physiology. This study provides valuable insights into the combined effects of PFOS exposure and ocean warming for coral's physiology. PFOS is usually the most prevalent but not the only PFAS defected in reef waters, and thus it will be also important to monitor PFAS mixture concentrations in the oceans and to study their combined effects on aquatic wildlife.

Structural Stability of the SUPER304H Steel Used in Energetics.

This paper describes the influence of technological treatments (i.e., bending or welding) on the structural stability of SUPER304H austenitic steel used in reheaters and superheaters in fossil fuel power plants. Although the worldwide trend is transitioning to green power sources, the lifetime of existing power plants has to be prolonged until the transition is complete. Experimental material was tested in as-received state (straight tubes), bends, and homogeneous weld joints. Part of the specimens was solution-annealed after the technological operation. Afterwards, all the samples were thermally aged in furnace (650, 675 and 700 °C) for 7560–20,000 h. For comparison, bent specimens were placed at experimental sites on an operating powerplant for 10,000+ h. The long-term aging causes the formation of Cr-based carbides on the grain boundaries along with the Fe-Cr sigma phase. Combination of elevated temperature and residual stress accelerates formation of the sigma phase. This can be prevented by solution-annealing after bending. Mechanical properties were evaluated by Vickers hardness and tensile tests. The microstructure was observed using light optical microscopy (LOM) and scanning electron microscopy (SEM) with the energy-dispersive X-ray detector (EDXS). Electron backscatter diffraction (EBSD) and X-ray powder diffraction (XRPD) were used to characterize the brittle phases.

Interactive effects of light, CO2 and temperature on growth and resource partitioning by the mixotrophic dinoflagellate, Karlodinium veneficum.

There is little information on the impacts of climate change on resource partitioning for mixotrophic phytoplankton. Here, we investigated the hypothesis that light interacts with temperature and CO2 to affect changes in growth and cellular carbon and nitrogen content of the mixotrophic dinoflagellate, Karlodinium veneficum, with increasing cellular carbon and nitrogen content under low light conditions and increased growth under high light conditions. Using a multifactorial design, the interactive effects of light, temperature and CO2 were investigated on K. veneficum at ambient temperature and CO2 levels (25°C, 375 ppm), high temperature (30°C, 375 ppm CO2), high CO2 (30°C, 750 ppm CO2), or a combination of both high temperature and CO2 (30°C, 750 ppm CO2) at low light intensities (LL: 70 μmol photons m-2 s-2) and light-saturated conditions (HL: 140 μmol photons m-2 s-2). Results revealed significant interactions between light and temperature for all parameters. Growth rates were not significantly different among LL treatments, but increased significantly with temperature or a combination of elevated temperature and CO2 under HL compared to ambient conditions. Particulate carbon and nitrogen content increased in response to temperature or a combination of elevated temperature and CO2 under LL conditions, but significantly decreased in HL cultures exposed to elevated temperature and/or CO2 compared to ambient conditions at HL. Significant increases in C:N ratios were observed only in the combined treatment under LL, suggesting a synergistic effect of temperature and CO2 on carbon assimilation, while increases in C:N under HL were driven only by an increase in CO2. Results indicate light-driven variations in growth and nutrient acquisition strategies for K. veneficum that may benefit this species under anticipated climate change conditions (elevated light, temperature and pCO2) while also affecting trophic transfer efficiency during blooms of this species.

Vegetative Reproduction Is More Advantageous Than Sexual Reproduction in a Canopy-Forming Clonal Macroalga under Ocean Warming Accompanied by Oligotrophication and Intensive Herbivory.

Ocean warming and the associated changes in fish herbivory have caused polarward distributional shifts in the majority of canopy-forming macroalgae that are dominant in temperate Japan, but have little effect on the alga Sargassum fusiforme. The regeneration ability of new shoots from holdfasts in this species may be advantageous in highly grazed environments. However, little is known about the factors regulating this in Sargassum species. Moreover, holdfast tolerance to high-temperature and nutrient-poor conditions during summer has rarely been evaluated. In the present study, S. fusiforme holdfast responses to the combined effects of temperature and nutrient availability were compared to those of sexually reproduced propagules. The combined effects of holdfast fragmentation and irradiance on regeneration were also evaluated. Propagule growth rate values changed from positive to negative under the combination of elevated temperature (20 °C–30 °C) and reduced nutrient availability, whereas holdfasts exhibited a positive growth rate even at 32 °C in nutrient-poor conditions. The regeneration rate increased with holdfast fragmentation (1 mm segments), but was unaffected by decreased irradiance. These results suggest that S. fusiforme holdfasts have a higher tolerance to high-temperature and nutrient-poor conditions during summer than propagules, and regenerate new shoots even if 1-mm segments remain in shaded refuges for fish herbivory avoidance.

Elevated temperature and CO2 interactively modulate sexual competition and ecophysiological responses of dioecious Populus cathayana

It remains unclear how global climate change affects dioecious plants that may be especially vulnerable to climate drivers, because they often exhibit skewed sex ratios and eco-physiological specialization in certain microhabitats. In this study, female and male saplings of Populus cathayana were employed to explore sex-specific responses and the effects of sexual competition under elevated temperature (ET), elevated CO2 (EC) and combination of elevated temperature and CO2 (ETC). The results demonstrated that elevated temperature and CO2 interactively modulated sexual competition and responses of P. cathayana. Moreover, competition patterns affected the eco-physiological responses of P. cathayana to climate change treatments. Under both intra- and inter-sexual competition, biomass components, photosynthetic parameters and carbon-related metabolites of females were most strongly affected by ET, while males exhibited a higher photosynthesis and resource use efficiency, and a better biomass accumulation and carbon balance mechanism when compared to females when experiencing intra-sexual competition under EC. The competitive pressure of females on males in inter-sexual competition was intensified by ET, while it was alleviated by ETC. We conclude that climate change drivers and competition patterns differently regulate the sex-specific responses and competitive intensity of males and females, which may have a crucial effect on sex ratios, spatial sexual segregation, biomass production and carbon sequestration in dioecious species in the future.

The Relative Contributions of Temperature and Moisture to Heat Stress Changes under Warming

AbstractIncreases in the severity of heat stress extremes are potentially one of the most impactful consequences of climate change, affecting human comfort, productivity, health, and mortality in many places on Earth. Heat stress results from a combination of elevated temperature and humidity, but the relative contributions of each of these to heat stress changes have yet to be quantified. Here, conditions for the baseline specific humidity are derived for when specific humidity or temperature dominates heat stress changes, as measured using the equivalent potential temperature (θE). Separate conditions are derived over ocean and over land, in addition to a condition for when relative humidity changes make a larger contribution than the Clausius–Clapeyron response at fixed relative humidity. These conditions are used to interpret the θE responses in transient warming simulations with an ensemble of models participating in phase 6 of the Climate Model Intercomparison Project. The regional pattern of θE changes is shown to be largely determined by the pattern of specific humidity changes, with the pattern of temperature changes playing a secondary role. This holds whether considering changes in seasonal-mean θE or in extreme (98th-percentile) θE events, and uncertainty in the response of specific humidity to warming is shown to be the leading source of uncertainty in the θE response at most land locations. Finally, analysis of ERA5 data demonstrates that the pattern of observed θE changes is also well explained by the pattern of specific humidity changes. These results demonstrate that understanding regional changes in specific humidity is largely sufficient for understanding regional changes in heat stress.

Surface transformation and interactions of iron oxide in glassy lubricant: An ab initio study

Density functional theory (DFT) calculation for full coverage (NaPO3)x glass on Fe2O3 (0001) surface, and ab initio molecular dynamics (AIMD) simulation for phosphate and iron/iron oxide clusters at high temperature in hot rolling of steel have been carried out to investigate the transformation of adsorbed oxide surface and the interaction of the oxide compound in the glass network. Among three main interlayer interactions, Fe-Oglass is the most dominant bond in the system with effect of weakening oxide surface topmost Fe-O bond. Osurface-P can be observed under compression conditions and Fe-P direct bonds occur in the combination of elevated temperatures, high exposure of iron and appearance of under-coordinated phosphorus. Fe atoms in Fe-P change their valence state adapting to the synergetic bonding. Na atoms from the glass network also play an important role in promoting the iron oxide deformation by generating O-terminated surfaces and reducing Fe-Osurface stability, even at normal temperatures.

Direct matter disassembly via electron beam control: electron-beam-mediated catalytic etching of graphene by nanoparticles

We report electron-beam activated motion of a catalytic nanoparticle along a graphene step edge and associated etching of the edge. The catalytic hydrogenation process was observed to be activated by a combination of elevated temperature and electron beam irradiation. Reduction of beam fluence on the particle was sufficient to stop the process, leading to the ability to switch on and off the etching. Such an approach enables the targeting of individual nanoparticles to induce motion and beam-controlled etching of matter through activated electrocatalytic processes. The applications of electron-beam control as a paradigm for molecular-scale robotics are discussed.

Simulating the Impacts of Climate Change on Sugarcane in Diverse Agro-climatic Zones of Northern India Using CANEGRO-Sugarcane Model

CANEGRO-Sugarcane model was used to assess the impact of climate change on sugarcane in different combinations of elevated temperature and CO2 concentrations. Additionally, we used dynamically downscaled bias-corrected regional climate model (RCM) data using RegCM4 under RCP4.5 scenario (2040–2060) to project the future change in sugarcane stalk fresh mass (SFM) and sucrose mass (SM). The results showed an increase in temperature, rainfall and solar radiation in the future projections at the study site. The SFM and SM were found to be vulnerable (3–25% decrease) by increasing temperature (1–4 °C), however, a higher concentration (2–14% increase) was observed for both SFM and SM under elevated CO2 levels (450–850 ppm). The combined effect of increased temperature and elevated CO2 had a beneficial effect on SFM but negative on SM (more for rainfed condition). Overall, SFM was projected to increase by 3–39% (rainfed) and 7–47% (irrigated) in 2040–2060 relative to 1971–2000 in diverse agro-climatic zones of the region. Similarly, SM was projected to decrease by 9–69% (rainfed) and 6–37% (irrigated). In general, water stress conditions combined with the projected increase in temperature adversely affected the sugarcane. The findings suggest the development of a efficient water use, heat-tolerant cane variety and improved farm management strategies in the near future to assist the sugar industry and to adapt to the changing climate in northern India. This is required in the greater perspective of decrease in sucrose mass in spite of double-fold increase in CO2.

Elevated temperature and ozone modify structural characteristics of silver birch (Betula pendula) leaves.

To study the effects of slightly elevated temperature and ozone (O3) on leaf structural characteristics of silver birch (Betula pendula Roth), saplings of four clonal genotypes of this species were exposed to elevated temperature (ambient air temperature+0.8-1.0 °C) and elevated O3 (1.3-1.4× ambient O3), alone and in combination, in an open-air exposure field over two growing seasons (2007 and 2008). So far, the impacts of moderate elevation of temperature or the combination of elevated temperature and O3 on leaf structure of silver birch have not been intensively studied, thus showing the urgent need for this type of studies. Elevated temperature significantly increased leaf size, reduced non-glandular trichome density, decreased epidermis thickness and increased plastoglobuli size in birch leaves during one or both growing seasons. During the second growing season, O3 elevation reduced leaf size, increased palisade layer thickness and decreased the number of plastoglobuli in spongy cells. Certain leaf structural changes observed under a single treatment of elevated temperature or O3, such as increase in the amount of chloroplasts or vacuole, were no longer detected at the combined treatment. Leaf structural responses to O3 and rising temperature may also depend on timing of the exposure during the plant and leaf development as indicated by the distinct changes in leaf structure along the experiment. Genotype-dependent cellular responses to the treatments were detected particularly in the palisade cells. Overall, this study showed that even a slight but realistic elevation in ambient temperature can notably modify leaf structure of silver birch saplings. Leaf structure, in turn, influences leaf function, thus potentially affecting acclimation capacity under changing climate.

Effects of elevated temperature and CO2 concentration on floral development and sex differentiation in Morus alba L.

Elevated temperature, elevated CO2 concentration, and their combination significantly promoted the number and biomass of female mulberry (Morus alba L.) flowers, but the opposite is true for males. This paper demonstrates that male mulberry trees would suffer more negative effects on floral development and differentiation under global warming. With the ongoing intensification of global warming, flower formation has attracted widespread interest because it is particularly vulnerable to the effects of environmental factors. However, current knowledge of floral development regarding gender and sex differentiation under elevated temperature, CO2 concentration, and their combination remains limited. The aims of this study were to assess how sex-related differences in the morphology, biomass, and carbon (C) and nitrogen (N) contents of flowers respond to elevated temperature and CO2 concentration. Morus alba L. saplings (monoecious plants) were subjected to two temperature conditions (ambient vs. ambient + 2 °C) and two CO2 regimes (ambient vs. ambient + 380 ppm CO2) in growth chambers for 18 months growth, and differences in flowering phase, sex ratio, floral morphology and biomass, as well as total carbon and nitrogen of male and female inflorescences were investigated. Elevated temperature, elevated CO2 concentration, and their combination significantly increased the number and biomass of female inflorescences but decreased the number and biomass of male inflorescences. Furthermore, the combination of elevated temperature and CO2 concentration significantly decreased ovary length and C/N ratio of female flowers and the fresh weight of male flowers. Additionally, C/N ratio was negatively related to morphological traits of male inflorescences but positively related to tepal length of female flowers. These findings indicate that global warming may affect floral development and sex differentiation in mulberry and that the male inflorescences of M. alba may suffer more negative effects than female inflorescences with respect to flower number, biomass, and morphological development.

Effects of increasing temperature and acidification on the growth and competitive success of Alexandrium catenella from the Gulf of Maine

Climate driven increases in ocean temperature and pCO2 have the potential to alter the growth and prevalence of future Harmful Algal Blooms (HABs), but systematic studies on how climate drivers influence toxic algal species relative to non-toxic phytoplankton are lacking. In particular, little is known about how future climate scenarios will affect the growth of the toxic dinoflagellate Alexandrium catenella, which is responsible for the paralytic shellfish poisoning (PSP) events that threaten the health and economy of coastal communities in the Gulf of Maine and elsewhere. The growth responses of A. catenella and two other naturally co-occurring dinoflagellates in the Gulf of Maine—Scrippsiella sp., and Amphidinium carterae—were studied in mono and mixed species cultures. Experimental treatments tested the effects of elevated temperature (20 °C), lower pH (7.8), and the combination of elevated temperature and lower pH on growth rates relative to those in near-current conditions (15 °C; pH 8.1). Growth rates of A. catenella decreased under elevated temperature and lower pH conditions, a response that was largely attributable to the effect of temperature. In contrast, growth rates of Scrippsiella sp. and A. carterae increased under elevated temperature and lower pH conditions, with temperature also being the primary driver of the response. These trends did not change substantially when these species were grown in mixed cultures (A. catenella + Scrippsiella sp., and A. catenella + A. carterae), indicating that allelopathic or competitive interactions did not affect the experimental outcome under the conditions tested. These findings suggest that A. catenella blooms may become less prevalent in the southern regions of the Gulf of Maine, but potentially more prevalent in the northeastern regions of the Gulf of Maine with continued climate change.

Waterborne copper is more toxic to the killifish Poecilia vivipara in elevated temperatures: Linking oxidative stress in the liver with reduced organismal thermal performance

In this study, we measured the interactive effect of temperature (22 °C and 28 °C) and waterborne copper (Cu) contamination (9 μg/L and 20 μg/L) on the killifish Poecilia vivipara. Endpoints analyzed included parameters involved in Cu-accumulation, antioxidant capacity (antioxidant capacity against peroxyl radicals [ACAP] and total antioxidant capacity [TAC]), oxidative damage (lipid peroxidation [LPO]) and upper thermal tolerance (critical thermal maximum [CTMax]). Results show that Cu hepatic accumulation was elevated in 28 °C in comparison to 22 °C in both exposure groups. For gills, this was true only in 20 μg/L. Moreover, hepatic and brachial accumulation were concentration-dependent in both acclimation temperatures. Additionally, Hepatic ACAP and TAC were elevated in animals acclimated to 28 °C and only the animals kept at this temperature had reduced ACAP and TAC levels facing metal exposure (9 and 20 μg/L). Similarly, the combination of elevated temperature and Cu exposure raised hepatic LPO levels. Finally, animals acclimated to 28 °C had higher CTMax levels in comparison to fish acclimated to 22 °C both in control and exposed animals, however, CTMax of contaminated fish were only reduced in comparison to control in animals kept at 28 °C. Concluding, we show that the physiological mechanism besides the potentiating effect of elevated temperature in Cu toxicity is related to higher hepatic and branchial metal accumulation and elevated oxidative stress in the liver, outlined by reduced antioxidant capacity and elevated oxidative damage. We also show that these outcomes lead to compromised organismal performance, characterized by reduced CTMax. Finally, it is concluded that Cu exposure in warmer periods of the year or within global warming predictions may be more hazardous to fish populations.