Suboptimal Temperatures Research Articles

Mitigation of cold stress in Nile tilapia (Oreochromis niloticus) through dietary lipids supplementation: a preliminary network meta-analysis.

There is a growing body of evidence suggesting that water temperature can significantly impact the dietary fatty acid requirements of Nile tilapia (Oreochromis niloticus). Therefore, this study assessed the effectiveness of different dietary lipid sources on the growth performance of Nile tilapia reared at suboptimal temperatures. A network meta-analysis was performed, including searches of PubMed and Scopus from inception to January 2022, for trials that evaluated the effects of lipid sources on cold-stressed Nile tilapia. The Bayesian hierarchical framework was used to pool and compare the effect sizes of growth parameters such as weight gain, feed intake, and feed conversion ratio (FCR). Furthermore, the surface under the cumulative ranking curve (SUCRA) was obtained to calculate the probability that each lipid source was the most effective against cold stress. All subsequent numbers refer to comparisons with diets containing only fish oil. Dietary Aurantiochytrium significantly increased weight gain (SMD = 2.00, CrI: 0.70 to 3.40). In contrast, diets containing coconut oil led to significantly lower weight gain (SMD = - 3.30, CrI: - 6.00 to - 0.63) and higher FCR (SMD = 17.0, CrI: 6.70 to 27.0). Additionally, dietary corn oil was associated with a decrease in feed intake (SMD = - 2.32, CrI: - 3.91 to - 0.80), while a combination of fish and corn oil reduced FCR (SMD = - 5.70, CrI: - 11.0 to - 0.81). In general, the analysis of SUCRA values revealed that in cold-stressed Nile tilapia, Aurantiochytrium, sunflower oil, and the combination of fish and corn oil were the most effective lipid sources for improving growth at suboptimal temperatures. The results of the current study can serve as a basis for future studies that focus on the use of dietary lipid sources to mitigate cold stress in Nile tilapia.

Copper-contaminated soil compromises thermal performance in the springtail Folsomia candida (Collembola)

The widespread agricultural and industrial emissions of copper-based chemicals have increased copper levels in soils worldwide. Copper contamination can cause a range of toxic effects on soil animals and influence thermal tolerance. However, toxic effects are commonly investigated using simple endpoints (e.g., mortality) and acute tests. Thus, how organisms respond to ecological realistic sub-lethal and chronic exposures across the entire thermal scope of an organism is not known. In this study, we investigated the effects of copper exposure on the thermal performance of a springtail (Folsomia candida), regarding its survival, individual growth, population growth, and the composition of membrane phospholipid fatty acids. Folsomia candida (Collembola) is a typical representative of soil arthropods and a model organism that has been widely used for ecotoxicological studies. In a full-factorial soil microcosm experiment, springtails were exposed to three levels of copper (ca. 17 (control), 436, and 1629 mg/kg dry soil) and ten temperatures from 0 to 30 °C. Results showed that three-week copper exposure at temperatures below 15 °C and above 26 °C negatively influenced the springtail survival. The body growth was significantly lower for the springtails in high-dose copper soils at temperatures above 24 °C. A high copper level reduced the number of juveniles by 50 %, thereby impairing population growth. Both temperature and copper exposure significantly impacted membrane properties. Our results indicated that high-dose copper exposure compromised the tolerance to suboptimal temperatures and decreased maximal performance, whereas medium copper exposure partially reduced the performance at suboptimal temperatures. Overall, copper contamination reduced the thermal tolerance of springtails at suboptimal temperatures, probably by interfering with membrane homeoviscous adaptation. Our results show that soil organisms living in copper-contaminated areas might be more sensitive to thermally stressful periods.

Exogenous methyl jasmonate enhanced the antioxidant capacity of Malus baccata by stimulating jasmonate signalling under suboptimal low root-zone temperature

Methyl jasmonate (MeJA) has been documented to mitigate the oxidative stress caused by abiotic triggers. In this study, we investigated the mechanism through which exogenous MeJA alleviates oxidative damage in the roots of Malus baccata under a suboptimal low root-zone temperature. A suboptimal low root-zone temperature promoted increases in the activity and transcription of allene oxide synthase (AOS) and jasmonic acid carboxyl methyltransferase (JMT), elevated the levels of endogenous jasmonic acid (JA), MeJA and jasmonate isoleucine (JA-Ile), and induced the accumulation of malondialdehyde (MDA) and reactive oxygen species (ROS). The addition of exogenous MeJA further increased the JA (1 h, 12–24 h), MeJA (1–24 h), and JA-Ile (1–6 h) contents and enhanced the activities and transcription of lipoxygenase (LOX) and JMT. The upregulated expression of JASMONATE ZIM-DOMAIN (JAZ) and MdMYC2 indicated that suboptimal low root-zone temperature could activate JA signalling in roots, and exogenous MeJA could further strengthen JA signalling under low-temperature stress. Exogenous MeJA alleviated oxidative damage to stressed roots by enhancing ascorbate–glutathione (AsA–GSH) cycle activity. In addition, pre-treatment with phenidone (an inhibitor of lipoxygenase) exerted the opposite effects to those induced by exogenous MeJA treatment. These findings indicated that exogenous MeJA enhanced antioxidant systems and detoxified ROS by regulating JA signalling and thereby protected M. baccata roots from damage caused by suboptimal low root-zone temperature stress.

Physiological response of an Antarctic cryptophyte to increasing temperature, CO2, and irradiance

AbstractThe Southern Ocean, a globally important CO2 sink, is one of the most susceptible regions in the world to climate change. Phytoplankton of the coastal shelf waters around the Western Antarctic Peninsula have been experiencing rapid warming over the past decades and current ongoing climatic changes will expose them to ocean acidification and high light intensities due to increasing stratification. We conducted a multiple‐stressor experiment to evaluate the response of the still poorly studied key Antarctic cryptophyte species Geminigera cryophila to warming in combination with ocean acidification and high irradiance. Based on the thermal growth response of G. cryophila, we grew the cryptophyte at suboptimal (2°C) and optimal (4°C) temperatures in combination with two light intensities (medium light: 100 μmol photons m−2 s−1 and high light [HL]: 500 μmol photons m−2 s−1) under ambient (400 μatm pCO2) and high pCO2 (1000 μatm pCO2) conditions. Our results reveal that G. cryophila was not susceptible to high pCO2, but was strongly affected by HL at 2°C, as both growth and carbon fixation were significantly reduced. In comparison, warming up to 4°C stimulated the growth of the cryptophyte and even alleviated the previously observed negative effects of HL at 2°C. When grown, however, at temperatures above 4°C, the cryptophyte already reached its maximal thermal limit at 8°C, pointing out its vulnerability toward even higher temperatures. Hence, our results clearly indicate that warming and high light and not pCO2 control the growth of G. cryophila.

Improved Ionic Transport Using a Novel Semiconductor Co0.6Mn0.4Fe0.4Al1.6O4 and Its Heterostructure with Zinc Oxide for Electrolyte Membrane in LT-CFCs

Improving the ionic conductivity and slow oxygen reduction electro-catalytic activity of reactions occurring at low operating temperature would do wonders for the widespread use of low-operating temperature ceramic fuel cells (LT-CFCs; 450–550 °C). In this work, we present a novel semiconductor heterostructure composite made of a spinel-like structure of Co0.6Mn0.4Fe0.4Al1.6O4 (CMFA) and ZnO, which functions as an effective electrolyte membrane for solid oxide fuel cells. For enhanced fuel cell performance at sub-optimal temperatures, the CMFA–ZnO heterostructure composite was developed. We have shown that a button-sized SOFC fueled by H2 and ambient air can provide 835 mW/cm2 of power and 2216 mA/cm2 of current at 550 °C, possibly functioning down to 450 °C. In addition, the oxygen vacancy formation energy and activation energy of the CMFA–ZnO heterostructure composite is lower than those of the individual CMFA and ZnO, facilitating ion transit. The improved ionic conduction of the CMFA–ZnO heterostructure composite was investigated using several transmission and spectroscopic measures, including X-ray diffraction, photoelectron, and UV–visible spectroscopy, and density functional theory (DFT) calculations. These findings suggest that the heterostructure approach is practical for LT-SOFCs.

Prediction of the optimal vulcanization of a fiber‐reinforced elastomeric isolator made of natural rubber‐ethylene propylene diene monomer blend

AbstractTo seismically isolate a structure, it is possible to interpose a rubber device between the foundation and superstructure that increases the period of the superstructure, a feature that allows the structure to be “transparent” to the seismic excitation. A package of several rubber pads typically constitutes a seismic isolator; they are 10–20 mm thick vertically interspersed with either steel laminas or fiber‐reinforced polymer dry textiles suitably treated. So, the rubber has a primary role and must be vulcanized correctly to create the polymer cross‐linking properly. All rubber mechanical properties are strongly affected by curing temperature and curing time. Under vulcanization is a typical production error that suppliers make in large‐scale productions, especially when the size of the devices is considerable. It is common to deal with elastomeric isolators where rubber pads have been treated at a largely suboptimal temperature. This article proposes a numerical model for predicting the cross‐linking degree of rubber pads used in seismic isolation and made by a natural rubber‐ethylene propylene diene monomer rubber compound. The aim is to correctly define the optimal curing temperature and exposition time for producing a rubber quadruple shear test specimen and a fiber reinforced elastomeric isolator (FREI). The model is a kinetic one and takes into consideration the induction time. An experimental investigation has been conducted to validate the model with visible inspections and hardness measurements taken on the rubber pads (quadruple shear specimens) and the rubber devices. The results have shown the reliability of the new numerical model proposed, with a homogeneous mechanical properties distribution obtained within the rubber pads and the FREI.

Mismatches between phenotype and environment shape fitness at hyperlocal scales.

In the era of human-driven climate change, understanding whether behavioural buffering of temperature change is linked with organismal fitness is essential. According to the 'cost-benefit' model of thermoregulation, animals that live in environments with high frequencies of favourable thermal microclimates should incur lower thermoregulatory costs, thermoregulate more efficiently and shunt the associated savings in time and energy towards other vital tasks such as feeding, territory defence and mate acquisition, increasing fitness. Here, we explore how thermal landscapes at the scale of individual territories, physiological performance and behaviour interact and shape fitness in the southern rock agama lizard (Agama atra). We integrated laboratory assays of whole organism performance with behavioural observations in the field, fine-scale estimates of environmental temperature, and paternity assignment of offspring to test whether fitness is predicted by territory thermal quality (i.e. the number of hours that operative temperatures in a territory fall within an individual's performance breadth). Male lizards that occupied territories of low thermal quality spent more time behaviourally compensating for sub-optimal temperatures and displayed less. Further, display rate was positively associated with lizard fitness, suggesting that there is an opportunity cost to engaging in thermoregulatory behaviour that will change as climate change progresses.

Increased Ammonium Enhances Suboptimal-Temperature Tolerance in Cucumber Seedlings.

Nitrate nitrogen (NO3--N) is widely used in the cultivation of the cucumber (Cucumis sativus L.). In fact, in mixed nitrogen forms, partially substituting NO3--N with NH4+-N can promote the absorption and utilization of nitrogen. However, is this still the case when the cucumber seedling is vulnerable to the suboptimal-temperature stress? It remains unclear as to how the uptake and metabolism of ammonium affect the suboptimal-temperature tolerance in cucumber seedlings. In this study, cucumber seedlings were grown under suboptimal temperatures at five ammonium ratios (0NH4+, 25%NH4+, 50%NH4+, 75%NH4+, 100%NH4+) for 14 days. Firstly, increasing ammonium to 50% promoted the growth and root activity and increased protein and proline contents but decreased MDA content in cucumber seedlings. This indicated that increasing ammonium to 50% enhanced the suboptimal-temperature tolerance of cucumber seedlings. Furthermore, increasing ammonium to 50% up-regulated the expression of the nitrogen uptake-transport genes CsNRT1.3, CsNRT1.5 and CsAMT1.1, which promoted the uptake and transport of nitrogen, as well as the up-regulation of the expression of the glutamate cycle genes CsGOGAT-1-2, CsGOGAT-2-1, CsGOGAT-2-2, CsGS-2 and CsGS-3, which promoted the metabolism of nitrogen. Meanwhile, increased ammonium up-regulated the expression of the PM H+-ATP genes CSHA2 and CSHA3 in roots, which maintained nitrogen transport and membranes at a suboptimal temperature. In addition, 13 of 16 genes detected in the study were preferentially expressed in the roots in the increasing ammonium treatments under suboptimal temperatures, which, thus, promoted nitrogen assimilation in roots to the enhance the suboptimal-temperature tolerance of cucumber seedlings.

The effects of inbreeding on stress resistance of the Pacific oyster Crassostrea gigas at different temperatures and salinities

ABSTRACT The Pacific oyster (Crassostrea gigas) is a commercially important shellfish widely cultured worldwide. Understanding the effect of inbreeding on C. gigas is critical to the long-term feasibility of breeding programmes, especially when selected lines are developed in hatcheries with limited effective population sizes. The effect of inbreeding on stress resistance in C. gigas remains to be explored. The present study evaluated the physiological and immune responses to different temperatures (16–36°C) and salinities (20–40 psu) in an inbreeding line and a wild population of C. gigas. Two physiological parameters, including ammonia-N excretion rate (AER) and oxygen consumption rate (OCR), and three enzyme activities including superoxide dismutase activity (SOD), catalase activity (CAT), and contents of malondialdehyde (MDA) were measured on day 14 of the temperature and salinity exposure. Compared with the wild population, the physiological parameters (AER and OCR) were significantly lower, and the enzyme activities (SOD, CAT, and MDA) were significantly higher in the inbreeding line at suboptimal temperatures or salinities. These results showed that inbreeding has negative effects on stress resistance in C. gigas. In addition, multiple groups with different inbreeding levels would be needed to quantify the effects of inbreeding on stress resistance in C. gigas.

Ethanol as a carotenoid production stimulator in Dunaliella salina CCAP 19/18.

Dunaliella salina is a rich source of carotenoids. Carotenoid production is induced under specific conditions, i.e., high light intensity, high salt concentration, nutrient limitation, and suboptimal temperatures in this microalga. The control of environmental factors is vital for high productivity of carotenoids. In this paper, the effect of different ethanol concentrations in combination with nitrogen deficiency was investigated to induce carotenoid production in D. salina CCAP 19/18. Also, some biochemical and molecular parameters were investigated in response to ethanol in the cells. It was shown that ethanol at 0.5% concentration increased cell number but, at 5% concentration, reduced cell viability compared to the control. The highest carotenoid production was achieved at 3% ethanol concentration, which was 1.46 fold higher than the nitrogen deficiency condition. Investigation of the 3 carotenoid biosynthesis genes revealed that their expression levels increased at 3% ethanol concentration, and the phytoene synthase gene was the most upregulated one. Lipid peroxidation increased at both 3% and 5% ethanol concentrations. At 3% concentration, the activity of catalase and superoxide dismutase increased, but no significant changes were seen at 5% ethanol concentration. Peroxidase activity reduced at both 3% and 5% concentrations. Moreover, proline and reducing sugar content increased at 3% concentration while decreased at 5% ethanol concertation. The results showed that at 3% ethanol concentration, higher carotenoid productivity was associated with an increase in other intracellular responses (molecular and biochemical). Ethanol as a controllable element may be beneficial to increase carotenoid production even under inappropriate environmental conditions in D. salina.

Data-driven robust model predictive control for greenhouse temperature control and energy utilisation assessment

The greenhouse microclimate, especially temperature, is highly complex, and controlling it requires significant resources due to the greenhouses' inefficient design. The application of model predictive control is a promising strategy for temperature control and efficient greenhouse management. However, it does not account for the inaccuracies and uncertainties existing in the system, leading to sub-optimal temperatures. Therefore, this study proposes a comprehensive data-driven robust model predictive control framework for greenhouse temperature control and its energy utilisation assessment in the presence of uncertainties. First, an analytical model based on mass and energy balance and a data-driven model based on an artificial neural network is developed, and their prediction performance is compared. The artificial neural network demonstrates a higher prediction accuracy and is used as the system model in the proposed control framework. A robust model predictive control strategy, based on the minimax objective function and particle swarm optimisation algorithm, is developed to handle the uncertainties in the system. Results illustrate that in the presence of uncertainties, the robust model predictive control strategy outperforms the existing greenhouse climate management system and basic model predictive control with an RMSE of 0.32 °C and 0.60 °C for a two-day simulation period in winter and summer, respectively. Furthermore, the robust model predictive control strategy leads to an energy reduction of 9.67% and 23.61% in winter and summer. The proposed framework is flexible and general and can be applied to other greenhouses with different configurations and cultivated crops by fine-tuning it on the new data set.

Non-photochemical quenching in natural accessions of Arabidopsis thaliana during cold acclimation

Cold acclimation, initiated by non-freezing low temperatures and light, is a natural strategy for increasing plant survival even at sub-zero temperatures. However, it remains unclear how the non-photochemical quenching processes, which are crucial for excessive light energy dissipation, are modulated during cold acclimation. We compared the effects of two weeks of acclimation to sub-optimal temperatures, at 10 °C (AC10) and 4 °C (AC4), with non-acclimated (NAC) Arabidopsis thaliana natural accessions grown at 21 °C, on their growth (rosette area), biochemistry (chlorophylls and epidermal flavonols), and physiology (CO2 assimilation rate, and quantum yields of photochemical and non-photochemical quenching processes). AC10 reduced rosette area in all (six) accessions, while chlorophylls and CO2 assimilation rate (Asat) decreased only in three accessions and it had no effect on maximum quantum yield (Fv/Fm). However, AC4 significantly decreased rosette area, chlorophylls, and Fv/Fm, in all accessions. Both AC10 and AC4 treatments increased the accumulation of epidermal flavonols in all accessions. In AC4 accessions, we found an increase in additional non-regulatory NPQ, Φf,d, and a decrease in the fraction of excitation energy used by PSII photochemistry, ΦPSII. A similar irradiance resulted in a marginal difference in regulatory NPQ, Φnpq, among NAC and AC10 or AC4 plants; however, AC10 plants have more energy-dependent fastest NPQ, ΦqE, whereas AC4 predominates state transition quenching, ΦqT. These variations in dissipation of absorbed light energy, when combined with reduced chlorophylls and accumulated flavonols, help to reduce the risk of photoinhibition in plants during cold periods. These findings provide new insights into how suboptimal temperature acclimation affects the regulation of NPQ molecular mechanisms in Arabidopsis thaliana natural accessions.

Solid feeding and co-culture strategies for an efficient enzymatic hydrolysis and ethanol production from sugarcane bagasse

The feasibility of second-generation (2G) processes still highly depends on improvements in the hydrolysis and fermentation steps, ensuring the whole use of biomass sugars in an integrated approach. The main bottlenecks are the differences between the optimal conditions for both steps, limitations for high solid load (HSL) hydrolysis, and hexoses and pentose co-fermentation. To overcome these problems, the present work explored a feeding strategy to improve HSL enzymatic hydrolysis of hydrothermally pretreated sugarcane bagasse (PSB), at optimal and suboptimal temperatures, further integrated with a non-recombinant yeast co-culture (Saccharomyces cerevisiae and Kluyveromyces marxianus) for sugar co-fermentation. The entire PSB fraction was used without conditioning. Efficient enzymatic hydrolysis was achieved using a feeding strategy in a helical stirred bioreactor (64 and 75% cellulose conversion with 22.5% of solids, 72 h at 35 and 50 °C, respectively), obtaining hydrolysates with high glucose and xylose concentrations (100 g/L). Simultaneous saccharification and co-fermentation (SSCF) provided high glucose (98%) and xylose (52%) conversion in 24 deep-well plates, with ethanol yield of 0.23 getOH/gS, but faced problems of cell viability loss in the bioreactor. Sequential SCF (SqSCF) co-culture stood out as a promising strategy for the use of biomass sugars. The results of this study provide significant contribution to the intensification and feasibility of 2G production, in addition to highlighting the difficulties faced for process integration aiming at the full conversion of sugars coming from high solid load enzymatic hydrolysis.

Effect of edible coating and perforated packaging on the quality and storability of mango (cv. Cat Chu) at suboptimal storage temperature

Mango fruit (Mangifera indica cv. Cat Chu) is generally susceptible to chilling injury (CI), and postharvest deterioration induces limits in its commercial potential. This study aimed to find the effects of edible coating and perforated packaging on the quality and storability of mango fruit stored at a suboptimal temperature of 8 oC for 35 days and ripening for five days at 20 oC of each seven days of storage. The edible coatings (chitosan (0.5 %) combined with lemongrass essential oil (0.025 %) (chitosan) and carnauba wax (0.5 %) (carnauba)), perforated packaging (Low-density polyethylene (25 µM) needle-perforated ten holes (0.5 mm diameter) (LDPE); LDPE perforated eight holes (0.4 cm diameter) (control)), and combination between the coating and perforated packaging (Chitosan and LDPE (needle-perforated) (Chi-LDPE); carnauba wax and LDPE (needle-perforated) (Car-LDPE)) investigated in this study. The results showed mango cv. Cat Chu in needle-perforated packaging and combination with coating had the lowest weight loss, followed by control, chitosan, and carnauba wax with the highest weight loss. The CI symptom was white-corky in the pulp of ripened mango, which appeared in all treatments except chitosan coating for 35 days at 8 oC and ripening fruit at 20 oC. The chitosan coating inhibited the respiration rate and electrolyte leakage and decreased the disease index in mango fruit during storage. The quality of ripening mango fruit was highly maintained during the extended duration of cold storage. This result revealed that the chitosan coating improved chilling tolerance and prolonged the shelf life of mango at the suboptimal temperature of 8 oC for 35 days. This application might be a green means of fruit preservation, but further enhancement of disease control is needed.

The influence of ammonium to nitrate ratio on the thermal responses of early life stages of the giant kelp Macrocystis pyrifera

The distribution and productivity of seaweeds, including kelps, are strongly influenced by changes in temperature and inorganic nitrogen (Ni) availability. However, their tolerances, sensitivities, and capacity to adjust to these changes can vary across their complex life cycle (microscopic and macroscopic stages). For the early life stages of Macrocystis, this study investigated the effect of the nitrate: ammonium ratio on physiological traits and gametophyte development at a range of temperatures (6.5 to 26.5 °C). Thermal performance curves (TPCs) were utilized to determine and predict the effect of temperature on meiospore germination success (%), gametophyte size (μm2), sex ratio and physiological traits (photosynthetic efficiency and nitrate and ammonium uptake rates). We found that the presence of NH4+ led to negative NO3− uptake rates in Macrocystis pyrifera gametophytes and reduced growth rates, and results suggest that thermal tolerance windows might vary between developmental stages and physiological traits. Our findings indicate that reduced meiospore germination and gametophyte size induced by suboptimal temperatures and increased NH4+concentrations can lead to lower physiological performance that might subsequently affect adult individuals and populations. Knowledge of the Ni uptake kinetics and source preferences across different life cycle phases can be crucial for conservation and aquaculture purposes as it might increase species productivity and persistence in a changing ocean.

Aggregation in an heterospecific population of blowfly larvae: social behaviour is impacted by species-specific thermal requirements and settlement order.

Larvae of several blowfly species grow on carcasses and actively aggregate together. They face harsh developmental conditions resulting in a strong pressure to reduce development time: this is achieved either through thermoregulation or aggregation. We investigate how these two developmental strategies are modulated within heterospecific groups. In a first experiment, larvae of two species with different thermal requirements were deposited simultaneously on a thermal gradient. This resulted in the formation of two monospecific groups, each located at the species-specific thermal preferendum. However, when Calliphora vomitoria (Linnaeus) larvae were placed first, the later arriving Lucilia sericata (Meigen) larvae attracted the whole group to its own thermal preferendum. In the reverse experiment, half of the replicates resulted in single dense heterospecific groups observed at temperatures ranging from C. vomitoria to L. sericata preferendum. The other half of the replicates resulted in loose groups spread out on the thermal gradient. These results highlight the emergence of collective decisions ranging from thermal optimization to heterospecific aggregation at suboptimal temperatures. They demonstrate that species settlement order strongly affects self-organization processes and mixed-species group formation. We conclude that thermal optimization and heterospecific niche construction are two developmental strategies of carrion fly larvae. This article is part of the theme issue 'Mixed-species groups and aggregations: shaping ecological and behavioural patterns and processes'.

Impact of temperature and dietary replacement of fishmeal on cardiovascular remodelling and growth performance of adult Atlantic salmon (Salmo salar L.)

The development of pathophysiological cardiac alterations in farmed salmonids is a recurrent and widespread welfare issue. Although the aetiology of such cardiac alterations is still unclear, several factors, including rearing temperature, selective breeding programs, and feeding strategies, could induce a morpho-physiological remodelling of cardiac structure. This maladaptive cardiac remodelling could impair cardiac function and health of farmed salmonids leading to premature mortality and production losses. In this study, we aimed to better understand the impact of suboptimal elevated temperature, resembling a typical summer temperature in Tasmania, and different feed formulations with low inclusion of fishmeal on cardiovascular remodelling and growth performance of adult Tasmanian Atlantic salmon. Fish were reared in a seawater recirculating aquaculture system and fed one of three diets with different fishmeal contents (6, 12, and 18%), while exposed to a temperature profile characterised by an incremental increase (1 °C per day) from 15 to 19.5 °C, 84 days at 19.5 °C (elevated temperature), and finally 34 days at 15 °C (optimal temperature). In terms of cardiac morphometric parameters, ventricular roundness (measured as height:width ratio) was not affected by temperature or dietary treatment. Conversely, the angle between the bulbus arteriosus and the ventricle significantly increased after the elevated temperature phase, along with relative ventricular mass, showing signs of maladaptive remodelling compared to initial conditions. However, these cardiac parameters were not different between the elevated and optimal temperature phase, which was associated with no changes in transcript abundance of molecular markers of pathological hypertrophy and remodelling, such as, atrial natriuretic peptide (anp) and b-type natriuretic peptide (bnp). Collectively, standard growth rate (SGR) and temperature growth coefficient (TGC), along with feed conversion ratio (FCR), were significantly elevated following exposure to suboptimum elevated temperature relative to optimal temperature. However, no differences in growth rate were observed in fish fed distinct dietary treatments at both elevated and optimal temperatures. These results imply that feeds with low levels of fishmeal can be used under challenging Tasmanian summer conditions without detrimental effect on salmon growth performance. Furthermore, our findings suggest that suboptimal elevated temperatures may induce remodelling of cardiac structure in adult Atlantic salmon, thereby potentially compromising cardiac function and overall health. Future efforts to manage Atlantic salmon susceptibility to climate change will require further research on the effect of challenging environmental conditions on cardiac physiology and performance in an attempt to prevent cardiac pathology, thereby improving health and welfare of farmed salmonids.

Impact of nanopesticide CuO-NPs and nanofertilizer CeO2-NPs on wheat Triticum aestivum under global warming scenarios

Concurrent effect of nanomaterials (NMs) and warming on plant performance remains largely unexplored. In this study, the effects of nanopesticide CuO and nanofertilizer CeO2 on wheat (Triticum aestivum) under optimal (22 °C) and suboptimal (30 °C) temperatures were evaluated. CuO-NPs exerted a stronger negative effect on plant root systems than CeO2-NPs at tested exposure levels. The toxicity of both NMs could be attributed to altered nutrient uptake, induced membrane damage, and raised disturbance of antioxidative related biological pathways. Warming significantly inhibited root growth, which was mainly linked to the disturbance of energy metabolism relevant biological pathways. The toxicity of NMs was enhanced upon warming, with a stronger inhibition of root growth and Fe and Mn uptake. Increasing temperature increased the accumulation of Ce upon CeO2-NP exposure, while the accumulation of Cu was not affected. The relative contribution of NMs and warming to their combined effects was evaluated by comparing disturbed biological pathways under single and multiple stressors. CuO-NPs was the dominant factor inducing toxic effects, while both CeO2-NPs and warming contributed to the mixed effect. Our study revealed the importance of carefully considering global warming as a factor in risk assessment of agricultural applications of NMs.

Comparative Effect of Melatonin and 1-Methylcyclopropene Postharvest Applications for Extending ‘Hayward’ Kiwifruit Storage Life

Kiwifruit, like many other fruits, is susceptible to dehydration, leading to texture changes and a loss of flavour during storage. Exposing kiwifruit to suboptimal temperatures can control these changes but can cause internal browning. Postharvest treatments with substances such as 1-methylcyclopropene (1-MCP) are some of the most successful commercial technologies in the conservation of fruits and vegetables. In recent years, there has been a growing interest among researchers in alternative technologies based in postharvest treatments with plant growth regulators. In this sense, melatonin (MT) has been shown to improve fruit quality, extending shelf life. The aim of this study was to compare these two different technologies applied at postharvest to evaluate the impact on kiwifruit quality. Optimal 1-MCP fumigations and MT solutions were assayed on ‘Hayward’ kiwifruit under similar conditions. Quality parameters were evaluated at 14-day intervals during 84 days of cold storage plus 5 days at 20 °C. The results showed that both treatments were similarly effective in maintaining quality parameters such as weight loss, respiration, firmness, and acidity. Although 1-MCP treatments delayed the evolution of kiwifruit colour and chlorophyll degradation as compared to MT, MT treatments controlled chilling injury better than 1-MCP. This effect was not related to a greater cell membrane integrity since fruit batches treated with 1-MCP were the ones that showed the lowest electrolyte leakage level. In conclusion, both treatments maintained fruit quality and delayed ripening in a similar way. In this sense, the results suggest that MT immersion treatments could act as efficient delaying senescence as fumigations with 1-MCP maintaining kiwifruit quality during refrigerated storage.

Exploring the effects of ventilation and air-conditioned environments, on droplet and airborne transmission of SARS-COV-2

To assess the implications of air conditioning and ventilation on droplet and airborne transmission of SARS-COV-2, several scientific research databases were searched and cross-referenced. Then, an analysis was conducted on the findings pertinent to interaction between several environmental variables affected by HVAC systems and their effect on Virus transmission. The results suggest that airflow velocity may interfere with the trajectories of large respiratory droplets and aerosols. Lower relative humidity provided suitable conditions for virus survival whereas higher temperatures increased aerosol formation, but were detrimental to virus survival. Suboptimal temperatures and humidity can compromise pathogen filtration functions in the nose, while proper use of HVAC functions can help preserve them. Transmission of SARS-COV-2 is not affected solely by the virus’s internal properties. Ambient conditions, whether natural or modified by HVAC systems can have a significant effect on the transmissibility and virulence of both the virus and virus-related sickness. The current infection prevention measures, such as social distancing, need to be revised in certain scenarios where natural ventilation or HVAC systems are involved. This will offer, hopefully, higher protection from infections with SARS-COV-2 and similar pathogens.