Dual Stressors Research Articles

Dual Stressors and Female Pre-school Teachers' Job Satisfaction During the COVID-19: The Mediation of Work-Family Conflict.

Online education has become a vital weapon to fight against the COVID-19 epidemic in the world. In the home-based online education environment, female pre-school teachers are expected to balance the dual roles of teacher and mother at the same time, which may trigger the work-family conflict. Although previous studies analyzed individual stressors, work-family conflict and its outcomes, there is little research on pre-school teachers' work and parenting experience during major public health emergencies. The current study examined the associations among work overload, parenting stress, work-family conflict, and job satisfaction during the COVID-19. Seven hundred eighteen female pre-school teachers with children who worked online at home participated in the study. Female pre-school teachers reported that the COVID-19 has increased work overload and parenting stress. Moreover, work overload was negatively associated with job satisfaction via its positive association with work-to-family conflict. Parenting stress was negatively associated with job satisfaction via both family-to-work conflict and work-to-family conflict. The study contributes to a better understanding of the association among female pre-school teachers' work overload, parenting stress, work-family conflict, and job satisfaction. Our findings highlighted potential avenues for interventions aimed at balancing female pre-school teachers' work and family and improving their job satisfaction during the COVID-19.

Robust Nitritation of Anaerobic Digester Centrate Using Dual Stressors and Timed Alkali Additions.

Nitrogen is commonly removed from wastewater by nitrification to nitrate followed by nitrate reduction to N2. Shortcut N removal saves energy by limiting ammonia oxidation to nitrite, but nitrite accumulation can be unstable. We hypothesized that repeated short-term exposures of ammonia-oxidizing communities to free ammonia (FA) and free nitrous acid (FNA) would stabilize nitritation by selecting against nitrite-oxidizing bacteria (NOB). Accordingly, we evaluated ammonium oxidation of anaerobic digester centrate in two bench-scale sequencing batch reactors (SBRs), seeded with the same inoculum and operated identically but with differing pH-control strategies. A single stressor SBR (SS/SBR) using pH set-point control produced HNO3, while a dual stressor SBR (DS/SBR) using timed alkalinity addition (TAA) produced HNO2 (ammonium removal efficiency of 97 ± 2%; nitrite accumulation ratio of 98 ± 1%). The TAA protocol was developed during an adaptation period with continuous pH monitoring. After adaptation, automated TAA enabled stable nitritation without set-point control. In the SS/SBR, repeatedly exposing the community to FA (8-10 h/exposure, one exposure/cycle) selected for FA-tolerant ammonia-oxidizing bacteria (Nitrosomonas sp. NM107) and NOB (Nitrobacter sp.). In the DS/SBR, repeatedly exposing the community to FA (2-4 h/exposure, three exposures/cycle) and FNA (4-6 h/exposure, two exposures/cycle) selected for FA- and FNA-resistant AOB (Nitrosomonas IWT514) and against NOB, stabilizing nitritation.

Concurrent white noise and acute hypobaric hypoxia: Effect on aviation cognitive performance

Introduction: Optimal cognitive performance is the essence of effective execution of a flying mission. Effects of two commonly encountered aviation stressors, hypoxia and noise, on performance have been studied. However, studies on effects of concurrent dual effects of both these stressors on key cognitive parameters are sparse; hence, the objective was to examine these effects. Material and Methods: Cognitive performances were assessed among 30 healthy volunteers (28 males and 2 females) sequentially in four different conditions – baseline (without stressors), 85 dB(A) noise, 14,000 ft altitude, and concurrent exposure to 85 dB(A) noise at 14,000 ft altitude. White noise was simulated through software, altitude in the hypobaric chamber and cognitive performance was assessed with tests from Psychology Experiment Building Language (PEBL) test battery. Data were analyzed using descriptive statistics and repeated measures ANOVA. Results: The study revealed statistically significant direct detrimental effect of altitude and noise on implicit reaction time independently as well as concurrently. However, there was insignificant interaction effect between the dual stressors on implicit reaction time. There were no statistically significant effects of dual stressors on implicit correctness, visuospatial working memory, and selective attention. Although statistically not significant, noise enhanced the performance level in the form of increased Corsi block memory span and Corsi block total score. Conclusion: No significant effect of the dual stressors was observed on most of the cognitive parameters. However, implicit reaction time, a measure of pilot’s risk-taking behavior, was found to be significantly affected by the dual stressors. Further research with a larger sample of aircrew population who differ in age, experience, and other potentially influencing factors is recommended.

Additive impacts of deoxygenation and acidification threaten marine biota.

Deoxygenation in coastal and open-ocean ecosystems rarely exists in isolation but occurs concomitantly with acidification. Here, we first combine meta-data of experimental assessments from across the globe to investigate the potential interactive impacts of deoxygenation and acidification on a broad range of marine taxa. We then characterize the differing degrees of deoxygenation and acidification tested in our dataset using a ratio between the partial pressure of oxygen and carbon dioxide (pO2 /pCO2 ) to assess how biological processes change under an extensive, yet diverse range of pO2 and pCO2 conditions. The dataset comprised 375 experimental comparisons and revealed predominantly additive but variable effects (91.7%, additive; 6.0%, synergistic; and 2.3%, antagonistic) of the dual stressors, yielding negative impacts across almost all responses examined. Our data indicate that the pO2 /pCO2 -ratio offers a simplified metric to characterize the extremity of the concurrent stressors and shows that more severe impacts occurred when ratios represented more extreme deoxygenation and acidification conditions. Importantly, our analysis highlights the need to assess the concurrent impacts of deoxygenation and acidification on marine taxa and that assessments considering the impact of O2 depletion alone will likely underestimate the impacts of deoxygenation events and their ecosystem-wide consequences.

Chronic Stress Exposure Suppresses Mammary Tumor Growth and Reduces Circulating Exosome TGF-β Content via β-Adrenergic Receptor Signaling in MMTV-PyMT Mice.

Preclinical models of breast cancer have established mechanistic links between psychological stress and cancer progression. However, epidemiological evidence linking stress and cancer is equivocal. We tested the impact of stress exposure in female mice expressing the mouse mammary tumor virus polyoma middle-T antigen (MMTV-PyMT), a spontaneous model of mammary adenocarcinoma that mimics metastatic hormone receptor–positive human breast cancer development. MMTV-PyMT mice were socially isolated at 6 to 7 weeks of age during premalignant hyperplasia. To increase the potency of the stressor, singly housed mice were exposed to acute restraint stress (2 hours per day for 3 consecutive days) at 8 to 9 weeks of age during early carcinoma. Exposure to this dual stressor activated both major stress pathways, the sympathetic nervous system and hypothalamic-pituitary-adrenal axis throughout malignant transformation. Stressor exposure reduced mammary tumor burden in association with increased tumor cleaved caspase-3 expression, indicative of increased cell apoptosis. Stress exposure transiently increased tumor vascular endothelial growth factor and reduced tumor interleukin-6, but no other significant alterations in immune/inflammation-associated chemokines and cytokines or changes in myeloid cell populations were detected in tumors. No stress-induced change in second-harmonic generation-emitting collagen, indicative of a switch to a metastasis-promoting tumor extracellular matrix, was detected. Systemic indicators of slowed tumor progression included reduced myeloid-derived suppressor cell (MDSC) frequency in lung and spleen, and decreased transforming growth factor β (TGF-β) content in circulating exosomes, nanometer-sized particles associated with tumor progression. Chronic β-adrenergic receptor (β-AR) blockade with nadolol abrogated stress-induced alterations in tumor burden and cleaved caspase-3 expression, lung MDSC frequency, and exosomal TGF-β content. Despite the evidence for reduced tumor growth, metastatic lesions in the lung were not altered by stress exposure. Unexpectedly, β-blockade in nonstressed mice increased lung metastatic lesions and splenic MDSC frequency, suggesting that in MMTV-PyMT mice, β-AR activation also inhibits tumor progression in the absence of stress exposure. Together, these results suggest stress exposure can act through β-AR signaling to slow primary tumor growth in MMTV-PyMT mice.

Respiratory Health Effects of Exposure to Ambient Particulate Matter and Bioaerosols.

Researchers have been studying the respiratory health effects of ambient air pollution for more than 70 years. While air pollution as a whole can include gaseous, solid, and liquid constituents, this article focuses only on the solid and liquid fractions, termed particulate matter (PM). Although PM may contain anthropogenic, geogenic, and/or biogenic fractions, in this article, particles that originate from microbial, fungal, animal, or plant sources are distinguished from PM as bioaerosols. Many advances have been made toward understanding which particle and exposure characteristics most influence deposition and clearance processes in the respiratory tract. These characteristics include particle size, shape, charge, and composition as well as the exposure concentration and dose rate. Exposure to particles has been directly associated with the exacerbation and, under certain circumstances, onset of respiratory disease. The circumstances of exposure leading to disease are dependent on stressors such as human activity level and changing particle composition in the environment. Historically, researchers assumed that bioaerosols were too large to be inhaled into the deep lung, and thus, not applicable for study in conjunction with PM2.5 (the 2.5-μm and below size fraction that can reach the deep lung); however, this concept is beginning to be challenged. While there is extensive research on the health effects of PM and bioaerosols independent of each other, only limited work has been performed on their coexposure. Studying these two particle types as dual stressors to the respiratory system may aid in more thoroughly understanding the etiology of respiratory injury and disease. © 2020 American Physiological Society. Compr Physiol 10:1-20, 2020.

Social adaptation and climate mitigation through agrotourism: a case study of tourism in Mastatal, Costa Rica

ABSTRACTCosta Rica has shifted from a primarily agrarian economy to a service sector driven market with a strong focus on tourism. Rural communities, which have been supported by agricultural livelihoods, face dual stressors in the form of economic pressure from falling crop prices and the increasing impacts of climate change. While a significant amount of work has tracked the growth of ecotourism in Costa Rica, little research on the potentially multifaceted benefits of agrotourism exists. The economic, social, and environmental effects of tourism were explored through experiences of stakeholders in the village of Mastatal due to its high concentration of agrotourism offerings. Analysis of socio-economic data using the framework of change indicates that agrotourism is a viable and sustainable adaptation strategy to economic and climate change stressors. Assessing the economic and climate drivers of change, community-based agrotourism has enabled agency, increased local revenue, diversified jobs, increased food security and decreased the depletion of natural resources. The practices of intergenerational and business-to-business knowledge transfer have increased social capital, expanded economic opportunities and reduced competition in the community by reinforcing the concept of mutual mission and success.

Termites mitigate the effects of drought in tropical rainforest.

Termites perform key ecological functions in tropical ecosystems, are strongly affected by variation in rainfall, and respond negatively to habitat disturbance. However, it is not known how the projected increase in frequency and severity of droughts in tropical rainforests will alter termite communities and the maintenance of ecosystem processes. Using a large-scale termite suppression experiment, we found that termite activity and abundance increased during drought in a Bornean forest. This increase resulted in accelerated litter decomposition, elevated soil moisture, greater soil nutrient heterogeneity, and higher seedling survival rates during the extreme El Niño drought of 2015-2016. Our work shows how an invertebrate group enhances ecosystem resistance to drought, providing evidence that the dual stressors of climate change and anthropogenic shifts in biotic communities will have various negative consequences for the maintenance of rainforest ecosystems.

Molecular effects of a variable environment on Sydney rock oysters, Saccostrea glomerata: Thermal and low salinity stress, and their synergistic effect

Bivalves are frequently exposed to salinity and temperature fluctuations in the estuary. This study explored the molecular effect of these fluctuations by exposing Sydney rock oysters, (Saccostrea glomerata), native to Australia, to either low salinity, elevated temperature or a combined salinity and temperature stress. Following the exposures, RNA-Seq was carried out on the collected oyster tissues.Differential transcript analysis resulted in a total of 1473, 1232 and 2571 transcripts, which were differentially expressed in S. glomerata exposed to low salinity (10 ppt), elevated temperature (30 °C) or the combined stressor (15 ppt and 30 °C), respectively, when compared to control oysters. All stress treatments had some effect on molecular processes such as innate immune response or respiration, with overall the strongest effects seen in S. glomerata exposed to the combined stressor. Additionally, most transporters putatively involved in osmoregulation were found to be suppressed in response to the combined stressor and the low salinity exposure.This study provides insight into the oyster's responses to both, single and dual stressors commonly found in an estuarine environment.

Post little ice age drying of eastern Australia conflates understanding of early settlement impacts

Understanding the relative influences of climate and people in driving environmental change is a fundamental aspect of Quaternary research. In Australia, numerous studies have investigated the effect of European settlement on the landscape, yet few have explicitly explored the role that natural climate variability played in modulating those impacts. Using a combination of new and existing proxy data, we demonstrate that European settlement of eastern Australia coincided with a marked decline in available moisture which occurred towards the end of the nineteenth century, c. 1850–1900 CE. This marked decline in rainfall would have increased ecosystem vulnerability to a number of human-induced stressors. By contrast, this aridification is likely to have masked some impacts of European occupation, in particular increased catchment runoff resulting from land clearance. We propose that the eastern Australian landscape has therefore suffered dual stressors of agricultural expansion and climate drying, with implications for both establishing environmental baselines and natural resource management.

High-performance work systems, dual stressors and ‘new generation’ employee in China

Received human resource management (HRM) studies have paid much attention to the relationship between high-performance work systems (HPWS) and employees’ attitudes and behaviours, but they lack deep understanding on how such HRM systems work for ‘new generation’ employees and accommodate ‘new generation’ preferences and characteristics. Embracing ‘new generation’ workforce characteristics, we collected two waves of data from 561 employees who were based in 23 Chinese firms. Our findings reveal that, first, HPWS is positively related to ‘new generation’ employees’ engagement; second, hindrance-related stressors partially mediate the relationship between HPWS and ‘new generation’ employee engagement, but the mediation role of challenge-related stressors is not evident; third, procedural justice negatively affects the relationship between HPWS and hindrance-related stressors; finally, HPWS and procedural justice jointly affect ‘new generation’ employee engagement partly through hindrance-related stressors. We conclude that the study not only contributes to the link between HPWS and employee engagement in a ‘new generation’ workforce context, but also argues for the importance of having occupational stress- management for a ‘new generation’ employee workforce.

Erratum to: Pre-exposure to simultaneous, but not individual, climate-change stressors limits acclimation capacity of Irukandji jellyfish polyps to predicted climate scenarios

Researchers have investigated the immediate effects of end-of-century climate change scenarios on many marine species, yet it remains unclear whether we can reliably predict how marine species may respond to future conditions because biota may become either more or less resistant over time. Here, we examined the role of pre-exposure to elevated temperature and reduced pH in mitigating the potential negative effects of future ocean conditions on polyps of a dangerous Irukandji jellyfish Alatina alata. We pre-exposed polyps to elevated temperature (28 °C) and reduced pH (7.6), in a full factorial experiment that ran for 14 d. We secondarily exposed original polyps and their daughter polyps to either current (pH 8.0, 25 °C) or future conditions (pH 7.6, 28 °C) for a further 34 d to assess potential phenotypic plastic responses and whether asexual offspring could benefit from parental pre-exposure. Polyp fitness was characterised as asexual reproduction, respiration, feeding, and protein concentrations. Pre-exposure to elevated temperature alone partially mitigated the negative effects of future conditions on polyp fitness, while pre-exposure to reduced pH in isolation completely mitigated the negative effects of future conditions on polyp fitness. Pre-exposure to the dual stressors, however, reduced fitness under future conditions relative to those in the control treatment. Under future conditions, polyps had higher respiration rates regardless of the conditions they were pre-exposed to, suggesting that metabolic rates will be higher under future conditions. Parent and daughter polyps responded similarly to the various treatments tested, demonstrating that parental pre-exposure did not confer any benefit to asexual offspring under future conditions. Importantly, we demonstrate that while pre-exposure to the stressors individually may allow Irukandji polyps to acclimate over short timescales, the stressors are unlikely to occur in isolation in the long term, and thus, warming and acidification in parallel may prevent polyp populations from acclimating to future ocean conditions.

Climate and productivity shape fish and invertebrate community structure in subarctic lakes

Summary Climate change and land‐use intensification are increasing productivity in subarctic lakes. Simultaneously, fish and invertebrate species adapted to temperate conditions are expanding their range northwards into subarctic habitats. Community level studies are required to predict long‐term effects of these dual stressors on subarctic freshwater ecosystems. We conducted a space‐for‐time study examining the fish, benthic invertebrate and pelagic zooplankton communities in littoral, profundal and pelagic habitats in 19 subarctic lakes situated on a temperature, land‐use and productivity gradient in northern Europe. Fish density (ranging between 0.5 and 150.5 fish per net series h−1) and biomass (range between 92 and 5,147 g per net series h−1) increased significantly with increasing lake temperature and productivity. This was associated with significantly decreasing body size (26 to 12 cm total length; 174 to 19 g body mass) and a shift in fish community structure from salmonid (Arctic charr Salvelinus alpinus, whitefish Coregonus lavaretus), to percid (ruffe Gymnocephalus cernua, perch Perca fluviatilis) and ultimately cyprinid (roach Rutilus rutilus, bleak Alburnus alburnus) dominance. Changes in fish community composition were most apparent in littoral and pelagic zones. Benthic macroinvertebrate density peaked in mesotrophic lakes, zooplankton density was highest at either end of the gradient, indicating habitat specific differences in predation pressure and top‐down control. Body size of zooplankton and benthic macroinvertebrates was negatively related to temperature and productivity. These results suggest that climate change and intensification of land‐use practices are gradually turning subarctic lakes into warmer, less transparent and more productive systems harbouring abundant, small‐sized and warmer adapted communities.

The dual synchronizing influences of precipitation and land use on stream properties in a rapidly urbanizing watershed

AbstractConversion of natural ecosystems to urbanized land cover dominated by impervious surfaces can alter hydrologic delivery of terrestrially derived materials to aquatic ecosystems. By changing hydrologic regimes, urbanization has important ramifications for water quality, particularly when considering how land use change might interact with other potential environmental stressors. Here, we analyzed a suite of physical, chemical, and biological time series (2007–2008) in 11 streams in a rapidly urbanizing watershed to determine how spatiotemporal synchrony is structured in urban vs. rural stream ecosystems. We further assessed how a doubling of seasonal precipitation influenced the landscape‐level stream synchrony patterns between years via changes to the local hydrologic regime. Consistent with existing theory and observations, physical variables (i.e., water temperature, flow rate) regulated by external climate features operating at broad spatial scales were more synchronous than the variables associated with fluxes of dissolved solutes (i.e., conductivity, salinity, dissolved nutrients), which are typically controlled by local and internal ecosystem processes. Both urbanization and increased precipitation modified synchrony patterns by increasing the temporal coherence of water flow and the concentration of certain dissolved solutes (i.e., conductivity, salinity). Urban streams exposed to more precipitation exhibited the greatest similarity in physicochemical conditions, suggesting an interaction among the dual stressors of precipitation and urbanization to instill ecosystem synchrony. These results suggest that taking a spatially explicit perspective in understanding urbanization and its interactions with a changing climate is critical for the future management of aquatic resources in highly developed landscapes.

Net effects of multiple stressors in freshwater ecosystems: a meta-analysis.

The accelerating rate of global change has focused attention on the cumulative impacts of novel and extreme environmental changes (i.e. stressors), especially in marine ecosystems. As integrators of local catchment and regional processes, freshwater ecosystems are also ranked highly sensitive to the net effects of multiple stressors, yet there has not been a large-scale quantitative synthesis. We analysed data from 88 papers including 286 responses of freshwater ecosystems to paired stressors and discovered that overall, their cumulative mean effect size was less than the sum of their single effects (i.e. an antagonistic interaction). Net effects of dual stressors on diversity and functional performance response metrics were additive and antagonistic, respectively. Across individual studies, a simple vote-counting method revealed that the net effects of stressor pairs were frequently more antagonistic (41%) than synergistic (28%), additive (16%) or reversed (15%). Here, we define a reversal as occurring when the net impact of two stressors is in the opposite direction (negative or positive) from that of the sum of their single effects. While warming paired with nutrification resulted in additive net effects, the overall mean net effect of warming combined with a second stressor was antagonistic. Most importantly, the mean net effects across all stressor pairs and response metrics were consistently antagonistic or additive, contrasting the greater prevalence of reported synergies in marine systems. Here, a possible explanation for more antagonistic responses by freshwater biota to stressors is that the inherent greater environmental variability of smaller aquatic ecosystems fosters greater potential for acclimation and co-adaptation to multiple stressors.

71. A novel combined psychosocial stress paradigm alters tumor VEGF and circulating exosomes in a spontaneous, metastatic model of breast cancer

Metastatic breast cancer carries significant risk of morbidity and mortality with limited treatment options. Psychosocial stress exposure has been linked to tumor growth and metastasis; therefore understanding the underlying neurohormonal mechanisms may yield new therapeutic options and lead to the development of more effective disease interventions. Here we investigated the impact of social isolation combined with acute restraint stress on spontaneous tumor development in MMTV-PyMT mice. Mammary tumor progression in this mouse model of metastatic breast cancer mimics that of invasive ductal carcinoma in humans. Female MMTV-PyMT mice were singly housed at 8 weeks of age during the hyperplastic stage of tumor development. Restraint stress was initiated after 2 weeks of isolation. Control mice remained in their home cages throughout the experiment. Twenty-four hours after the final restraint exposure, stressed mice exhibited elevated circulating corticosterone and splenic normetanephrine (a norepinephrine metabolite), which correlated with increased tumor VEGF and decreased splenic neutrophils. There was no difference in total tumor burden at this early carcinoma stage. Circulating CD63+ exosomes, extracellular vesicles that drive cancer pathogenesis, were decreased. These results demonstrate the dual stressor elicited potent hypothalamic pituitary axis (HPA) and sympathetic nervous system (SNS) activation in conjunction with alterations in the premetastatic tumor that may facilitate progression.

Nutrition affects survival in African honeybees exposed to interacting stressors

Summary Nutrition plays an important role in physiological stress resistance and by adjusting their intake of key nutrients, such as protein and carbohydrate, many animals can better resist stress. Poor nutrition may contribute to the widespread and on‐going declines of honeybee populations by increasing their vulnerability to abiotic (e.g. pesticides) and biotic (e.g. diseases) stressors. However, we do not know how nutrition affects stress resistance in social insects such as honeybees. Here, we examined how exposure to the toxic secondary metabolite nicotine, a neurotoxin that shares structural similarities with the neonicotinoid pesticides, and low temperatures affected nutrient regulation in honeybees using the Geometric Framework of nutrition. Groups of queenless, newly emerged worker bees were given diets containing specific ratios of protein and carbohydrate to determine, first, how toxin exposure and ambient temperature affected their nutrient intake and, secondly, how nutrition affected survival under stress. We find that low temperatures and nicotine interacted to reduce survival in African honeybees that ate low protein, high carbohydrate diets. However, bees fed a high protein diet were better able to survive insult with these interacting stressors. Although protein conferred a survival benefit in honeybees exposed to these dual stressors, when allowed to self‐select their diet, caged workers did not shift their intake towards a higher protein food to improve their survival under these stressful conditions. We discuss the possible constraints on nutrient regulation in honeybees and the role that diet could play in their decline.

Studies on combined effect of Aeromonas hydrophila and cadmium on lipid peroxidation and antioxidant status in selected tissues of Indian freshwater major carp, Catla catla: role of silver nanoparticles

. The present study was aimed to evaluate the effect of dual stressors cadmium (Cd) and Aeromonas hydrophila (AH) on pro-and antioxidant status in gills, kidneys and liver tissues of fishes, Catla catla treated with or without silver nano-particles. Significant elevation in the lipid peroxidation levels with a significant decrease in the activity levels of superoxide dismutase, catalase, glutathione-S-transferase in were observed in gills, kidneys and liver tissues of fishes exposed to individual and/or in combination with Cd and AH over controls. However, significant elevation in the activity levels of xanthine oxidase was observed in the selected tissues of fishes treated with Cd, AH and Cd+AH over controls. On the other hand, AgNPs showed a reversal effect on Cd-, AHand Cd+AH-induced alterations in lipid peroxidation levels and antioxidant enzymes in gills, kidneys and liver tissues of fishes over their respective controls. No significant changes were observed in lipid peroxidation levels and antioxidant enzymes in selected tissues of fishes exposed to AgNPs alone as compared to untreated fishes. From the findings it is clear that AgNPs protects gills, kidneys and liver against Cd and AH induced oxidative stress. Further studies in this direction might definitely augment the use of nano-based compounds as therapeutic candidates in fisheries. KEY WORDSA. hydrophila, Catla catla, lipid peroxidation, antioxidant enzymes, silver nanoparticles

Does trophic status enhance or reduce the thermal tolerance of scleractinian corals? A review, experiment and conceptual framework.

Global warming, and nutrient and sediment runoff from coastal development, both exert increasing pressures on coastal coral reefs. The objective of this study was to resolve the question of whether coastal eutrophication may protect corals from thermal stress by improving their nutritional status, or rather diminish their thermal tolerance through the synergy of dual stressors. A review of previous studies on the topic of combined trophic status and heat exposure on the thermal tolerance of corals reveals a broad range of outcomes, including synergistic, additive and antagonistic effects. We conducted a 90-day long experiment exposing corals to realistic levels of elevated nutrients and sediments, and heat stress. Colonies of two common scleractinian corals (Acropora millepora and Montipora tuberculosa) were kept in coastal seawater, or coastal seawater that was further organically and nutrient enriched (OE), and/or enriched with nitrate. Batches of OE were created daily, facilitating nutrient uptake, plankton succession and organic enrichment as observed in coastal waters. After 10 days of acclimation, 67% of the colonies had their temperature gradually increased from 27° to 31.2°C. After 3–7 weeks of heat stress, colonies of both species had significantly greater reductions in fluorescence yields and lower survival in OE than without addition of OE. Furthermore, photophysiological recovery was incomplete 31–38 days after ending the heat stress only in the OE treatments. Nitrate alone had no measurable effect on survival, bleaching and recovery in either species. Skeletal growth rates were reduced by 45% in heat-stressed A. millepora and by 24% in OE-exposed M. tuberculosa. We propose a conceptual trophic framework that resolves some of the apparently contradictory outcomes revealed by the review. Our study shows that management actions to reduce coastal eutrophication can improve the resistance and resilience of vulnerable coastal coral reefs to warming temperatures.

Disulfide stress-induced aluminium toxicity: molecular insights through genome-wide screening of Saccharomyces cerevisiae

Formation of non-native disulfide bonds within or between proteins can lead to protein misfolding and disruption to cellular metabolism. Such a process is defined as disulfide stress. A marked effect of disulfide stress in cells is the elevated accumulation of the intracellular aluminium ion (Al(3+)) accompanied by increased cytotoxicity. To gain an in-depth understanding of the underlying molecular mechanism for disulfide stress-induced aluminium toxicity, the complete set of Saccharomyces cerevisiae deletion mutants (5047) was screened in this study simultaneously with a combination of the two stressors, diamide and Al(3+). The combined treatment of a benign concentration of diamide (0.8 mM) with a sublethal concentration of aluminium sulfate (0.4 mM) revealed 494 sensitive deletion mutants, distinct from those found when either of the single stressors (0.8 mM diamide or 0.4 mM aluminium sulfate) was used. Hierarchical clustering and functional analyses of the 494 mutants sensitive to the dual stressors indicated a significant enrichment in the genes involved in cell wall homeostasis, signaling cascades, secretory transport machinery and detoxification. The results highlight the process of maintaining cell wall integrity as the central response to the combined exposure of diamide and Al(3+), which is mediated by the signaling pathways and transcription activation via Rlm1p and Swi6p for biosynthesis of the essential cell wall components such as glucan and chitin. Sensitivity of mutants associated with endoplasmic reticulum (ER), vesicle and vacuole functions demonstrates that secretory machinery is essential for surviving the stress conditions, probably due to their roles in transporting polysaccharides to the cell wall and detoxification of accumulated Al(3+). Finally, the phenotype of 100 previously uncharacterized genes against the dual stressors will contribute to their eventual functional annotation.