Dual Stressors Research Articles

Metabolomic and microbiomic resilience of Hong Kong oysters to dual stressors: Zinc oxide nanoparticles and low salinity

Zinc oxide nanoparticles, increasingly used in industrial and consumer products, and low salinity, exacerbated by climate change-induced alterations in precipitation patterns, represent significant environmental pressures in estuarine and coastal environments. This study advances previous research on their impacts on Hong Kong oysters (Crassostrea hongkongensis) by integrating metabolomics of hepatopancreas and gills with intestinal microbiomics. Employing advanced multi-omics integration methods, our analysis reveals novel insights into metabolic resilience under combined stress conditions. This resilience is characterized by coordinated, organ-specific adjustments in energy metabolism (d-glucose 1-phosphate in hepatopancreas, cytidine in gills), antioxidant defenses (glutathione, meso-2,6-diaminoheptanedioate, pimelic acid in hepatopancreas; indole, 3-(3-hydroxyphenyl)propanoic acid in gills), immune function (l-glutamine, ergocalciferol in hepatopancreas; argininosuccinic acid in gills), and membrane stability (lanosterin in hepatopancreas, allantoin in gills). Notably, under dual stressors, we observed a previously undescribed stabilization of microbial alpha diversity and certain phyla, an absence of distinctive biomarkers, and certain metabolic activity stabilization within the intestinal microbiota. These findings suggest robust compensatory mechanisms that maintain physiological homeostasis and microbial balance under stress, contrasting with primarily negative impacts reported in previous studies. Integration of metabolomic and microbiomic data revealed coordinated responses between microbial community changes and metabolic adjustments, particularly in osmoregulation, energy metabolism and antioxidant defenses, under dual stressors. This comprehensive approach provides a more realistic model of environmental challenges, revealing sophisticated adaptive strategies in Hong Kong oysters. Our study offers critical insights for understanding bivalve resilience, informing conservation strategies, and managing marine ecosystems in the face of increasing anthropogenic pressures.

Hospital Readmissions Among Infants With Neonatal Opioid Withdrawal Syndrome

Although cases of neonatal opioid withdrawal syndrome (NOWS) increased 5-fold in recent years, no study has examined national hospital readmission rates for these infants. To examine hospital readmissions for infants with and without NOWS. This retrospective cohort study analyzed serial cross-sectional samples of US hospital discharge records from the Nationwide Readmissions Database for calendar years 2016 to 2020. Infants with NOWS were identified using International Classification of Diseases, Tenth Revision, Clinical Modification codes. The data analysis was performed between January 5, 2023, and May 6, 2024. Neonatal opioid withdrawal syndrome. Survey-weighted logistic regression was used to examine 90-day all-cause and cause-specific hospital readmissions. Multivariable models adjusted for sex, low birth weight, gestational age, multiple gestation, type of insurance, and year of birth. Of the 13 855 246 newborns identified in this weighted analysis, 89 018 (0.6%) were diagnosed with NOWS, of whom 53.8% were male and 81.1% born full-term (>36 weeks gestation). The 90-day all-cause readmission rate was 4.2% for infants with NOWS compared with 3.0% for those without NOWS (P < .001). After risk adjustment, the odds of all-cause readmission were higher among infants with NOWS (adjusted odds ratio [AOR], 1.18; 95% CI, 1.08-1.29). Infants with NOWS had significantly higher odds of readmissions for seizures (AOR, 1.58; 95% CI, 1.01-2.46), failure to thrive (AOR, 1.99; 95% CI, 1.36-2.93), traumatic brain injury (AOR, 2.95; 95% CI, 1.76-4.93), and skull fractures (AOR 3.72; 95% CI, 2.33-5.93). Infants with NOWS had higher odds of receiving a diagnosis of confirmed maltreatment (AOR, 4.26; 95% CI, 2.19-8.27), including for neglect (AOR, 14.18; 95% CI, 5.55-36.22) and physical abuse (AOR, 2.42; 95% CI, 0.93-6.29); however, the latter finding was not statistically significant. In this nationally representative cohort study, infants with NOWS were at increased risk of readmission for any cause as well as for trauma and confirmed maltreatment. These findings may in part reflect the dual stressors that mothers with opioid use disorder face in caring for a newborn with NOWS in the context of a substance use disorder and underscore the need for family-based, in-home services that focus concurrently on substance use treatment and parenting support.

Ecophysiological, transcriptomic and metabolomic analyses shed light on the response mechanism of Bruguiera gymnorhiza to upwelling stress

Mangroves, due to their unique habitats, endure dual stressors from land to ocean and ocean to land directions. While extensive researches have been conducted on land-ocean stressors, studies on ocean-land stressors like upwelling are considerably scarce. In this study, ecophysiological, transcriptome, and metabolome analyses were conducted to determine the responses of mangrove plant (Bruguiera gymnorhiza, B. gymnorhiza) to upwelling stress. The results suggested that upwelling stress in B. gymnorhiza induces oxidative stress and membrane damage, which are mitigated by the synergistic actions of antioxidant enzymes and osmoprotectants. Transcriptomic and metabolomic analyses revealed that upregulated genes related to oxidation-reduction and carbohydrate metabolism, along with accumulated metabolites such as amino acids, lipids, phenols, and organic acids, contribute to enhancing antioxidant capacity and maintaining osmotic balance. Further analysis identified key KEGG pathways involved in the response to upwelling stress, including amino acid metabolism, carbohydrate and energy metabolism, flavonoid biosynthesis, and plant hormone signal transduction. These findings provide vital information into the multi-level response mechanisms of mangrove plants to upwelling stress.

How to Reduce the Influence of COVID-19 Epidemic on Employees’ Anxiety of Continuous Work in China? Empirical Analysis Based on Industrial Enterprises

ABSTRACT The COVID-19 epidemic not only impacted China’s economy but also induced periodic anxiety among employees, especially during its peak. Even as governmental controls relaxed, enterprises seemed unaffected externally. However, beneath the surface, the lingering effects on employee mental health persisted. Many faced dual stressors concerning their job and personal well-being due to the epidemic, heightening work-related anxieties. This research, a year after China resumed work, delves into the psychological stress influencing this sustained anxiety. A survey of 516 employees helped test the hypothesis using a multiple regression model. Findings indicated heightened continuous work anxiety due to the epidemic, particularly in hard-hit areas. However, individual resilience, organizational, and social support were found to mitigate these effects. The study underscores the sustained psychological aftermath of the epidemic on employees, urging health authorities to address it.

Functional-Molecular Mechanisms of Sympathetic-Parasympathetic Dysfunction in PVC-Induced Cardiomyopathy Revealed by Dual Stressor PVC-Exercise Challenge

BackgroundThe significance of autonomic dysfunction in premature ventricular contraction–induced cardiomyopathy (PVC-CM) remain unknown. ObjectivesUtilizing a novel “dual stressor” provocative challenge combining exercise with premature ventricular contraction (PVCs), the authors characterized the functional and molecular mechanisms of cardiac autonomic (cardiac autonomic nervous system) remodeling in a PVC-CM animal model. MethodsIn 15 canines (8 experimental, 7 sham), we implanted pacemakers and neurotelemetry devices and subjected animals to 12 weeks of bigeminal PVCs to induce PVC-CM. Sympathetic nerve activity (SNA), vagal nerve activity (VNA), and heart rate were continuously recorded before, during, and after treadmill exercise challenge with and without PVCs, at baseline and after development of PVC-CM. Western blot and enzyme-linked immunosorbent assay were used to evaluate molecular markers of neural remodeling. ResultsExercise triggered an increase in both SNA and VNA followed by late VNA withdrawal. With PVCs, the degree of exercise-induced SNA augmentation was magnified, whereas late VNA withdrawal became blunted. After PVC-CM development, SNA was increased at rest but failed to adequately augment during exercise, especially with PVCs, coupled with impaired VNA and heart rate recovery after exercise. In the remodeled cardiac autonomic nervous system, there was widespread sympathetic hyperinnervation and elevated transcardiac norepinephrine levels but unchanged parasympathetic innervation, indicating sympathetic overload. However, cardiac nerve growth factor was paradoxically downregulated, suggesting an antineurotrophic counteradaptive response to PVC-triggered sympathetic overload. ConclusionsSympathetic overload, sympathetic dysfunction, and parasympathetic dysfunction in PVC-CM are unmasked by combined exercise and PVC challenge. Reduced cardiac neurotrophic factor might underlie the mechanisms of this dysfunction. Neuromodulation therapies to restore autonomic function could constitute a novel therapeutic approach for PVC-CM.

Revealing functional-molecular parasympathetic dysfunction in PVC-induced cardiomyopathy via dual stressor PVC and exercise

Abstract Background Exercise intolerance is a common presentation of premature ventricular contractions-induced cardiomyopathy (PVC-CM). In a canine PVC-CM model, previous studies have shown cardiac autonomic nervous system remodeling, resulting in persistent sympathetic excess. Nevertheless, the molecular mechanisms and functional implications of this neural remodeling, as well as parasympathetic alterations, remain unclear. Purpose We aim to evaluate the functional-molecular mechanisms of parasympathetic remodeling and its potential contribution to exercise intolerance in an animal model of PVC-CM. Methods We studied 15 canines (8 experimental vs 7 sham controls) chronically instrumented with pacemakers and telemetry devices to deliver 12-weeks of bigeminal PVCs (200ms coupling) to induce PVC-CM and to record sympathetic (SNA), vagal nerve activity (VNA) and heart rate (HR) over this period. Exercise challenge was conducted in sinus rhythm (SR) and in the presence of bigeminal PVCs ("dual stressor") at baseline and after development of PVC-CM. Sympatho-vagal neural and HR responses were assessed during and after exercise at baseline and after PVC-CM development, with and without PVCs, thus comparing baseline SR, baseline with PVCs, CM SR and CM with PVCs. Western Blot was performed on intrinsic and extrinsic cardiac neural tissues to evaluate molecular mechanisms of neural remodeling. Results Compared to baseline, SNA was significantly higher in PVC-CM in all phases of exercise (rest, exercise, recovery, p=0.03). In contrast, VNA was significantly lower in PVC-CM than baseline during exercise recovery (P=0.014). After exercise, HR recovery (HRR) was impaired (p=0.001), VNA lower (p=0.014) and SNA (p=0.03) higher in PVC-CM compared with baseline. Tyrosine hydroxylase (TH) immunoreactivity in the left ventricle (LV, p=0.001) and stellate ganglia (SG, p=0.03) and trans-cardiac plasma NE levels (p=0.03) were higher in PVC-CM compared with sham. Choline Acetyltransferase (CHAT) was not significantly different in either vagus (p=0.33) or LV (p=0.8) between PVC-CM vs sham. Cardiac (LV) Nerve Growth Factor (NGF), Growth Associated Protein (GAP-43) and beta 1-adrenoreceptor levels were lower (p=0.042, p=0.003, p=0.002 respectively) whereas beta 2-adreno- and muscarinic M2-cholinergic receptors were higher (p=0.02, p&amp;lt;0.01 respectively) in PVC-CM compared with sham. Conclusion Neural remodeling in PVC-CM results in an imbalanced sympathetic excess and sympathetic-parasympathetic dysfunction characterized by a loss of sympathetic functional reserve during exercise and impaired parasympathetic activity and HRR after exercise. Adaptive downregulation of NGF might explain this imbalance and dysfunction. These data open the intriguing possibility of neural-targeted therapies to reverse remodeling and restore autonomic function disrupted by chronic PVCs.GraphsMolecular

Complex environmental control of growth in a dominant Mediterranean‐alpine shrub species

Abstract Mediterranean‐alpine plants are exposed to harsh conditions, forcing them to perform with well‐adapted physiological strategies to withstand the dual stressors that arise from winter cold and summer drought. Such growth strategies are not yet fully understood, although they gain importance with regard to the resilience of species in the face of ongoing climate variability. Here, we aimed at understanding shrub growth in a widespread Mediterranean‐alpine species, Cytisus galianoi Talavera &amp; Gibbs. Using long‐term time series of stem diameter change obtained from dendrometer measurements across the species´ range, we were able to characterise its spatiotemporal growth plasticity. Furthermore, separating water‐related fluctuations in stem diameter from irreversible stem increment allowed us to disentangle the species´ seasonal growth patterns. Using fine‐scale measurements of on‐site environmental conditions, we were then able to identify micro‐ecological drivers controlling the species´ growth processes by applying correlation analysis and partial least squares regressions. We show the species´ adaptation to the spatial heterogeneity across its range for the first time. Our findings highlight that the combination of bimodality and overall high growth plasticity likely allows the species to cover a wide geographical range across alpine areas and over a wide range of weather conditions. We show the environmental control of bimodal growth in C. galianoi, and the importance of pre‐growth environmental control, leading to pronounced carry‐over effects. These lead to a major advantage in resisting adverse growth conditions and adapting to changing conditions. Synthesis: Overall, our findings improve the understanding of the species´ ecological niche and show that preceding photosynthetic activity helps C. galianoi to perform even under unfavourable conditions in winter and during the active growth phase, challenging the general assumption on the coupling of growth to specific seasons and suggesting that the species is capable of adapting to future climate variability.

Dual stressors of infection and warming can destabilize host microbiomes.

Climate change is causing extreme heating events and intensifying infectious disease outbreaks. Animals harbour microbial communities, which are vital for their survival and fitness under stressful conditions. Understanding how microbiome structures change in response to infection and warming may be important for forecasting host performance under global change. Here, we evaluated alterations in the microbiomes of several wild Caenorhabditis elegans isolates spanning a range of latitudes, upon warming temperatures and infection by the parasite Leucobacter musarum. Using 16S rRNA sequencing, we found that microbiome diversity decreased, and dispersion increased over time, with the former being more prominent in uninfected adults and the latter aggravated by infection. Infection reduced dominance of specific microbial taxa, and increased microbiome dispersion, indicating destabilizing effects on host microbial communities. Exposing infected hosts to warming did not have an additive destabilizing effect on their microbiomes. Moreover, warming during pre-adult development alleviated the destabilizing effects of infection on host microbiomes. These results revealed an opposing interaction between biotic and abiotic factors on microbiome structure. Lastly, we showed that increased microbiome dispersion might be associated with decreased variability in microbial species interaction strength. Overall, these findings improve our understanding of animal microbiome dynamics amidst concurrent climate change and epidemics. This article is part of the theme issue 'Sculpting the microbiome: how host factors determine and respond to microbial colonization'.

Enhanced capacity of a leaf beetle to combat dual stress from entomopathogens and herbicides mediated by associated microbiota.

Herbicides have demonstrated their impact on insect fitness by affecting their associated microbiota or altering the virulence of entomopathogenic fungi toward insects. However, limited research has explored the implications of herbicide stress on the intricate tripartite interaction among insects, associated bacterial communities, and entomopathogens. In this study, we initially demonstrated that associated bacteria confer a leaf beetle, Plagiodera versicolora, with the capability to resist the entomopathogenic fungus Aspergillus nomius infection, a capability sustained even under herbicide glyphosate stress. Further analysis of the associated microbiota revealed a significant alteration in abundance and composition due to glyphosate treatment. The dominant bacterium, post A. nomius infection or following a combination of glyphosate treatments, exhibited strong suppressive effects on fungal growth. Additionally, glyphosate markedly inhibited the pathogenic associated bacterium Pseudomonas though it inhibited P. versicolora's immunity, ultimately enhancing the beetle's tolerance to A. nomius. In summary, our findings suggest that the leaf beetle's associated microbiota bestow an augmented resilience against the dual stressors of both the entomopathogen and glyphosate. These results provide insight into the effects of herbicide residues on interactions among insects, associated bacteria, and entomopathogenic fungi, holding significant implications for pest control and ecosystem assessment.

Do Organochlorine Contaminants Modulate the Parasitic Infection Degree in Mediterranean Trout (Salmo trutta)?

We investigated the occurrence of organochlorine pollutants (OCs) in the muscle of brown trout and evaluated their potential modulation of parasite infection. The toxicological risk for consumer health was assessed, too. Trout were collected from the Sila National Park (Calabria region, South of Italy). The highest concentrations emerged for the sum of the 6 non-dioxin-like (ndl) indicator polychlorinated biphenyls (Σ6ndl-PCBs), followed by the 1,1,1-trichloro-2,2-di(4-chlorophenyl)-ethane (DDT), dioxin-like PCBs, hexachlorobenzene (HCB), and dieldrin. Measured on lipid weight (LW), the mean value of Σ6ndl-PCBs amounted to 201.9 ng g-1, that of ΣDDTs (the sum of DDT-related compounds) to 100.2 ng g-1, with the major contribution of the DDT-metabolite p,p'-DDE which was detected in all sample units (97.6 ng g-1 on average). Among dioxin-like congeners, PCB 118 showed the highest mean concentration (21.96 ng g-1 LW) and was detected in all sample units. Regression analysis of intestinal parasites on OC concentration was performed, controlling for two potential confounding factors, namely sex and sexual stage. The results evidenced the existence of interactions between the dual stressors in the host-parasite system in the wild. A negative and statistically significant correlation was estimated, suggesting that OCs may decrease parasite infection degree. Regarding the toxicological risk evaluation, OC concentrations were consistently below the current European Maximum Residue Limits.

PO-455617-6 FUNCTIONAL CONSEQUENCES OF SYMPATHETIC NEURAL REMODELING IN PREMATURE VENTRICULAR CONTRACTION-INDUCED CARDIOMYOPATHY REVEALED BY DUAL STRESSOR PVC AND EXERCISE CHALLENGE

A common presentation of PVC-induced cardiomyopathy (PVC-CM) is exertional fatigue and dyspnea without overt heart failure. The sympathetic nervous system is an adaptive mechanism that augments the cardiac response to an external stressor such as PVCs. We hypothesize that one mechanism of exercise intolerance in PVC-CM is due to the inability of the remodeled sympathetic nervous system maximally recruited from chronic frequent PVC exposure to further augment in response to exercise challenge. To assess the sympathetic neural response to exercise in the presence or absence of PVCs, during baseline state and after development of PVC-CM. In 8 canines, we implanted pacemakers to administer bigeminal PVCs at 200ms coupling for 12-weeks to induce PVC-CM and radio-telemetry device to record ambulatory ECG and nerve activity from the left stellate ganglion nerve (SNA). In order to assess the sympathetic nerve response to exercise (exercise - rest SNA), we subjected animals to the “dual stressor” of a 9-minute exercise tolerance test (ETT, 1.1-3.3mph) in SR and in the presence of bigeminal PVCs (200ms coupling), at baseline (before 12-week PVC exposure) and after development of PVC-CM (after 12-week PVC exposure). SNA (Figure 1A) was significantly increased during exercise compared with rest in all groups except when exercise was performed in presence of PVCs in PVC-CM (CMPVC). The absolute increase in SNA with exercise (exercise-rest SNA) (Figure 1B) was significantly greater in the presence of PVCs compared with SR at baseline but this was reversed in PVC-CM, i.e., significantly less in the presence of PVCs compared with SR. In PVC-CM, the % increase in SNA with exercise (Figure 1C) was less than at baseline, particularly in the presence of PVCs. In PVC-CM, there is generalized sympathetic upregulation but also a failure to further augment the sympathetic response response to exercise, most likely because of maximally recruited nerve endings from chronic frequent PVC perturbation. This data could explain exercise intolerance observed in patients with PVC-CM and suggest that exercise testing could be a useful tool in the clinical assesment of patients with PVC-CM.

Exposure to copper increases hypoxia sensitivity and decreases upper thermal tolerance of giant salmonfly nymphs (Pteronarcys californica)

Many aquatic insects are exposed to the dual stressors of heavy metal pollution and rising water temperatures from global warming. These stresses may interact and have stronger impacts on aquatic organisms if heavy metals interfere with the ability of these organisms to handle high temperatures. Here we focus on the effect of copper on upper thermal limits of giant salmonfly nymphs (Order: Plecoptera, Pteronarcys californica), a stonefly species which is common in parts of western North America. Experimental exposure to copper reduced upper thermal limits by ∼ 10 °C in some cases and depressed the hypoxia tolerance (Pcrit) of nymphs by ∼ 0.5 mg L−1 DO. These results suggest that copper inhibits the delivery of oxygen, which may explain, in part, the strong reductions in CTMAX that we report. Fluorescence microscopy of Cu-exposed individuals indicated high levels of copper in chloride cells but no clear evidence of damage to or high levels of copper on the gills themselves. Our study indicates that populations of aquatic insects from copper-polluted environments may be further at risk to future warming than those from uncontaminated environments.

Mapping mangrove sustainability in the face of sea level rise and land use: A case study on Leizhou Peninsula, China

Habitat loss and degradation of mangrove forests can be caused by both sea level rise (SLR) and unsustainable land practices. Current long-term change projections are often based on changes to mangrove extent; however, this may overlook fragmentation and the associated habitat resilience decline and therefore fail to adequately reveal the risks to mangrove habitats. A mangrove sustainability index (MSI) was proposed in this study to assess the impact of SLR and land use on mangrove habitats. The index consists of four components: habitat area change, habitat quality, landscape pattern, and protection ratio. Ecological models and landscape models were combined to calculate the MSI. Considering the SLR under RCP4.5 and RCP8.5 and land use strategies, four scenarios were set with prediction periods of base year (2020) to 2050 and 2100. The Leizhou Peninsula, China was used as the case study. The results showed that dual stressors would reduce the extent of mangroves by 16.6%–56.2%. Habitat quality was sensitive to land use change but was not affected by SLR. Landscape pattern and protection ratio were influenced by SLR but less effected by land use. In all scenarios, mangroves tended to migrate out of the protected areas, with protection ratio decreasing from 37% to 16.9%–29.9%. Newly expanding habitats may suffer from patch fragmentation and low connectivity. Unsustainable mangrove distribution sites on Leizhou Peninsula were identified as hotspots for management. Projections under different scenarios showed that some unsustainable sites could be reversed to sustainable sites through improvements in land use policies. The proposed approach could provide essential tools for the formulation of mangrove conservation and restoration strategies adapted to climate change.

Nitrogen and sulfur deposition reductions projected to partially restore forest soil conditions in the US Northeast, while understory composition continues to shift with future climate change.

Human activities have dramatically increased nitrogen (N) and sulfur (S) deposition, altering forest ecosystem function and structure. Anticipating how changes in deposition and climate impact forests can inform decisions regarding these environmental stressors. Here, we used a dynamic soil-vegetation model (ForSAFE-Veg) to simulate responses to future scenarios of atmospheric deposition and climate change across 23 Northeastern hardwood stands. Specifically, we simulated soil percent base saturation, acid neutralizing capacity (ANC), nitrate (NO3 -) leaching, and understory composition under 13 interacting deposition and climate change scenarios to the year 2100, including anticipated deposition reductions under the Clean Air Act (CAA) and Intergovernmental Panel on Climate Change-projected climate futures. Overall, deposition affected soil responses more than climate did. Soils recovered to historic conditions only when future deposition returned to pre-industrial levels, although anticipated CAA deposition reductions led to a partial recovery of percent base saturation (60 to 72%) and ANC (65 to 71%) compared to historic values. CAA reductions also limited NO3 - leaching to 30 to 66% above historic levels, while current levels of deposition resulted in NO3 - leaching 150 to 207% above historic values. In contrast to soils, understory vegetation was affected strongly by both deposition and climate. Vegetation shifted away from historic and current assemblages with increasing deposition and climate change. Anticipated CAA reductions could maintain current assemblages under current climate conditions or slow community shifts under increased future changes in temperature and precipitation. Overall, our results can inform decision makers on how these dual stressors interact to affect forest health, and the efficacy of deposition reductions under a changing climate.

Clinico-pathological findings and expression of inflammatory cytokines, apoptosis, and oxidative stress-related genes draw mechanistic insights in Nile tilapia reared under ammonia-N exposure and Aeromonas hydrophila challenge

Fish diseases have a “stress-related” nature, whereas fish exposure to stressors will increase their susceptibility to infections. It was also noted that fish exposure to biotic and abiotic stressors would exaggerate the disease signs, elicit high mortalities, and cause severe economic losses. Motile aeromonad septicemia (MAS) is a major bacterial disease affecting a variety of finfish species throughout the globe and is caused by Aeromonas hydrophila. Herein, we have evaluated the impacts of ammonia-N stress and/or Nile tilapia challenge with pathogenic A. hydrophila on the clinical picture of MAS disease. Clinical signs, postmortem lesions, histoarchitectural changes, and gene transcription analysis were studied. Fish experimentally infected with A. hydrophila were exophthalmic and showed darkened skin. Moreover, opercular hyperemia, petechial hemorrhages, and gill congestion alongside dermal ulcerations were noticed in ammonia-exposed fish. On the other side, fish exposed to both stressors exhibited exophthalmia, corneal opacity, severe dropsy, and hemorrhagic dermal ulcerations. At the tissue levels, the histopathological lesions were exaggerated in the fish group exposed to ammonia stress and challenged with A. hydrophila than fish group exposed to each one alone. At the molecular levels, the mRNA expression analysis reveals significant upregulation of inflammatory cytokines such as interleukin-1 beta, CXC chemokine, and tumor necrosis factor-alpha in the kidney tissues of Nile tilapia exposed to ammonia and/or challenged with A. hydrophila. In a similar trend, the mRNA expression values of heat shock protein 70 (HSP70), oxidative stress related genes (SOD and CAT) and apoptosis-related genes (caspase 3, BAX, and cytochrome P450) were also increased in the hepatic tissues of fish exposed to singular or dual stressors. Interestingly, the highest expression levels of the above-mentioned genes were found in the fish group exposed to both stressors. Taken together, these findings indicate the occurrence of severe inflammatory and apoptotic changes in fish exposed to ammonia and infected with A. hydrophila more than each one alone. In contrast, there was a significant decrease in the expression values of the antioxidant enzyme glutathione-S-transferase (GST) in stressed fish, suggesting the occurrence of oxidative stress. This study will be helpful to draw mechanistic insights into the exposure of fish to ammonia stress and infection with A. hydrophila.

Woody plant secondary chemicals increase in response to abundant deer and arrival of invasive plants in suburban forests.

Plants in suburban forests of eastern North America face the dual stressors of high white‐tailed deer density and invasion by nonindigenous plants. Chronic deer herbivory combined with strong competition from invasive plants could alter a plant's stress‐ and defense‐related secondary chemistry, especially for long‐lived juvenile trees in the understory, but this has not been studied. We measured foliar total antioxidants, phenolics, and flavonoids in juveniles of two native trees, Fraxinus pennsylvanica (green ash) and Fagus grandifolia (American beech), growing in six forests in the suburban landscape of central New Jersey, USA. The trees grew in experimental plots subjected for 2.5 years to factorial treatments of deer access/exclosure × addition/no addition of the nonindigenous invasive grass Microstegium vimineum (Japanese stiltgrass). As other hypothesized drivers of plant secondary chemistry, we also measured nonstiltgrass herb layer cover, light levels, and water availability. Univariate mixed model analysis of the deer and stiltgrass effects and multivariate structural equation modeling (SEM) of all variables showed that both greater stiltgrass cover and greater deer pressure induced antioxidants, phenolics, and flavonoids, with some variation between species. Deer were generally the stronger factor, and stiltgrass effects were most apparent at high stiltgrass density. SEM also revealed that soil dryness directly increased the chemicals; deer had additional positive, but indirect, effects via influence on the soil; in beech photosynthetically active radiation (PAR) positively affected flavonoids; and herb layer cover had no effect. Juvenile trees’ chemical defense/stress responses to deer and invasive plants can be protective, but also could have a physiological cost, with negative consequences for recruitment to the canopy. Ecological implications for species and their communities will depend on costs and benefits of stress/defense chemistry in the specific environmental context, particularly with respect to invasive plant competitiveness, extent of invasion, local deer density, and deer browse preferences.

Not all smokers are alike: the hidden cost of sustained attention during nicotine abstinence

Nicotine Withdrawal Syndrome (NWS)-associated cognitive deficits are notably heterogeneous, suggesting underlying endophenotypic variance. However, parsing this variance in smokers has remained challenging. In this study, we identified smoker subgroups based on response accuracy during a Parametric Flanker Task (PFT) and then characterized distinct neuroimaging endophenotypes using a nicotine state manipulation. Smokers completed the PFT in two fMRI sessions (nicotine sated, abstinent). Based on response accuracy in the stressful, high cognitive demand PFT condition, smokers split into high (HTP, n = 21) and low task performer (LTP, n = 24) subgroups. Behaviorally, HTPs showed greater response accuracy (88.68% ± 5.19 SD) vs. LTPs (51.04% ± 4.72 SD), independent of nicotine state, and greater vulnerability to abstinence-induced errors of omission (EOm, p = 0.01). Neurobiologically, HTPs showed greater BOLD responses in attentional control brain regions, including bilateral insula, dorsal ACC, and frontoparietal Cx for the [correct responses (–) errors of commission] PFT contrast in both states. A whole-brain functional connectivity (FC) analysis with these subgroup-derived regions as seeds identified two circuits: Precentral Cx↔Insula and Insula↔Occipital Cx, with abstinence-induced FC strength increases seen only in HTPs. Finally, abstinence-induced FC and behavior (EOm) differences were positively correlated for HTPs in a Precentral Cx↔Orbitofrontal cortical circuit. In sum, only the HTP subgroup demonstrated sustained attention deficits following 48-hr nicotine abstinence, a stressor in dependent smokers. Unpacking underlying smoker heterogeneity with this ‘dual (task and abstinence) stressor’ approach revealed discrete smoker subgroups with differential attentional deficits to withdrawal that could be novel pharmacological/behavioral targets for therapeutic interventions to improve cessation outcomes.

The fear of being infected and fired: Examining the dual job stressors of hospitality employees during COVID-19.

As the COVID-19 pandemic has posed grave threats to the financial and physical health of hospitality employees, this research unveils details of the dilemma experienced by hospitality employees during the pandemic, namely, their fear of becoming infected and fired. The research data were derived from a sample of 622 hospitality employees in the U.S. and analyzed using PLS-SEM as a new model of COVID-19 stressors are proposed and tested. The findings show that hospitality employees perceive the pandemic as a traumatic event that elevates their perceived job insecurity and infectious risk. It was also found that both job insecurity and infectious risk lead to increased job stress and turnover intentions, while job insecurity alone is a stronger predictor of turnover intentions. This study is among the first to examine the antecedents and consequences of the dual stressors encountered by public-facing occupations, including hospitality, during the pandemic.

Divergent trajectories of ocean warming and acidification

The ocean provides a major sink for anthropogenic heat and carbon. This sink results in ocean changes through the dual stressors of warming and acidification which can negatively impact the health of the marine ecosystem. Projecting the ocean’s future uptake is essential to understand and adapt to further climate change and its impact on the ocean. Historical ocean uptake of heat and CO2 are tightly correlated, but here we show the trajectories diverge over the 21st century. This divergence occurs regionally, increasing over time, resulting from the unique combination of physical and chemical drivers. We explored this relationship using a high-resolution ocean model and a ‘business as usual’ CO2 emission pathway, and demonstrate that the regional variability in the carbon-to-heat uptake ratios is more pronounced than for the subsequent carbon-to-heat storage (change in inventory) ratios, with a range of a factor of 30 (6) in heat-to-carbon uptake (storage) ratios among the defined regions. The regional differences in heat and carbon trajectories result in coherent regional patterns for sea surface warming and acidification by the end of this century. Relative to the mean global change (MGC) at the sea surface of 2.55 °C warming and a decrease of 0.32 in pH, the North Pacific will exceed the MGC for both warming and acidification, the Southern Ocean for acidification only, and the tropics and midlatitude northern hemisphere will exceed MGC only for warming. Regionally, mapping the ocean warming and acidification informs where the marine environment will experience larger changes in one or both. Globally, the projected ocean uptake of anthropogenic heat and carbon informs the degree to which the ocean can continue to serve as a sink for both into the future.

Biodiversity of coral reef cryptobiota shuffles but does not decline under the combined stressors of ocean warming and acidification

Ocean-warming and acidification are predicted to reduce coral reef biodiversity, but the combined effects of these stressors on overall biodiversity are largely unmeasured. Here, we examined the individual and combined effects of elevated temperature (+2 °C) and reduced pH (-0.2 units) on the biodiversity of coral reef communities that developed on standardized sampling units over a 2-y mesocosm experiment. Biodiversity and species composition were measured using amplicon sequencing libraries targeting the cytochrome oxidase I (COI) barcoding gene. Ocean-warming significantly increased species richness relative to present-day control conditions, whereas acidification significantly reduced richness. Contrary to expectations, species richness in the combined future ocean treatment with both warming and acidification was not significantly different from the present-day control treatment. Rather than the predicted collapse of biodiversity under the dual stressors, we find significant changes in the relative abundance but not in the occurrence of species, resulting in a shuffling of coral reef community structure among the highly species-rich cryptobenthic community. The ultimate outcome of altered community structure for coral reef ecosystems will depend on species-specific ecological functions and community interactions. Given that most species on coral reefs are members of the understudied cryptobenthos, holistic research on reef communities is needed to accurately predict diversity-function relationships and ecosystem responses to future climate conditions.