Physiological and morphological responses of the temperate seagrass Zostera muelleri to multiple stressors: investigating the interactive effects of light and temperature

Understanding how multiple environmental stressors interact to affect seagrass health (measured as morphological and physiological responses) is important for responding to global declines in seagrass populations. We investigated the interactive effects of temperature stress (24, 27, 30 and 32°C) and shading stress (75, 50, 25 and 0% shade treatments) on the seagrass Zostera muelleri over a 3-month period in laboratory mesocosms. Z. muelleri is widely distributed throughout the temperate and tropical waters of south and east coasts of Australia, and is regarded as a regionally significant species. Optimal growth was observed at 27°C, whereas rapid loss of living shoots and leaf mass occurred at 32°C. We found no difference in the concentration of photosynthetic pigments among temperature treatments by the end of the experiment; however, up-regulation of photoprotective pigments was observed at 30°C. Greater levels of shade resulting in high photochemical efficiencies, while elevated irradiance suppressed effective quantum yield (ΔF/FM'). Chlorophyll fluorescence fast induction curves (FIC) revealed that the J step amplitude was significantly higher in the 0% shade treatment after 8 weeks, indicating a closure of PSII reaction centres, which likely contributed to the decline in ΔF/FM' and photoinhibition under higher irradiance. Effective quantum yield of PSII (ΔF/FM') declined steadily in 32°C treatments, indicating thermal damage. Higher temperatures (30°C) resulted in reduced above-ground biomass ratio and smaller leaves, while reduced light led to a reduction in leaf and shoot density, above-ground biomass ratio, shoot biomass and an increase in leaf senescence. Surprisingly, light and temperature had few interactive effects on seagrass health, even though these two stressors had strong effects on seagrass health when tested in isolation. In summary, these results demonstrate that populations of Z. muelleri in south-eastern Australia are sensitive to small chronic temperature increases and light decreases that are predicted under future climate change scenarios.

Effects of work-related sleep restriction on acute physiological and psychological stress responses and their interactions: A review among emergency service personnel

Emergency work can expose personnel to sleep restriction. Inadequate amounts of sleep can negatively affect physiological and psychological stress responses. This review critiqued the emergency service literature (e.g., firefighting, police/law enforcement, defense forces, ambulance/paramedic personnel) that has investigated the effect of sleep restriction on hormonal, inflammatory and psychological responses. Furthermore, it investigated if a psycho-physiological approach can help contextualize the significance of such responses to assist emergency service agencies monitor the health of their personnel. The available literature suggests that sleep restriction across multiple work days can disrupt cytokine and cortisol levels, deteriorate mood and elicit simultaneous physiological and psychological responses. However, research concerning the interaction between such responses is limited and inconclusive. Therefore, it is unknown if a psycho-physiological relationship exists and as a result, it is currently not feasible for agencies to monitor sleep restriction related stress based on psycho- physiological interactions. Sleep restriction does however, appear to be a major stressor contributing to physiological and psychological responses and thus, warrants further investigation.

Towards the optimization of performance of Atlantic salmon reared at different water temperatures via the manipulation of dietary ARA/EPA ratio

In recent years, aquaculture has been facing a series of new issues, including the necessary replacement of fish oil and fish meal because of their limited supply and sub-optimal water temperature conditions. Higher water temperatures are increasingly encountered as the result of climate change related phenomena and/or the practice of farming of species in areas with environmental characteristics outside their optimal physiological range, such as the case of Atlantic salmon (. Salmo salar) farming in Australia during the summer season. Previous studies in teleost fish have shown that when fish are exposed at higher environmental temperatures, fish had a preferential increased dietary intake for arachidonic acid (20:4n - 6, ARA). This observation suggests that, given the several metabolic roles of ARA, its dietary provision may play an important role in fish for adapting at sub-optimal high water temperatures. The objective of this study was therefore to evaluate the effects of different dietary ARA/EPA ratios in juvenile Atlantic salmon as affected by time of exposition to the diet and water temperatures, with particular focus to fish performance and possible resulting modifications of tissue fatty acid composition. The study showed that independently from dietary treatments, fish held at the higher temperatures had an increased ARA accumulation, primarily in the liver and this ARA accumulation increased over time. It was also shown that the combined dietary inclusion of ARA and EPA significantly improved fish performance, compared with diets either richer in ARA or EPA. A general trend toward higher content of n - 3 LC-PUFA at lower temperatures was also quite clear, especially in the liver. Therefore, and assuming that the trends in tissue fatty acid composition could be taken as a clue of the optimal fatty acid requirements of fish, the n - 6 requirement (and in particular ARA) clearly appears to be greater for Atlantic salmon raised at high water temperatures. Protein accumulation was higher in the diet with the combined dietary inclusion of ARA and EPA for fish held at high water temperature (20. °C), with a concomitant lipid reduction. This study shows the importance of dietary ARA for maximal growth in Atlantic salmon, particularly during the period of the year when high water temperatures are often encountered. Further studies specifically looking at optimal dietary ARA/EPA ratio and roles of ARA on myogenesis, stress physiology and immune status of cultured fish are warranted. Statement of relevance: Given the current high level of fish oil replacement in aquafeed, and the often encountered sub-optimal environmental temperatures, we believe that this study could be considered as timely and highly pertinent for the aquaculture industry and associated R&D sector.

Cover, not caging, influences chronic physiological stress in a ground-nesting bird

Predator exclosures ('nest cages') around nests are increasingly used to enhance hatching success of declining ground-nesting birds. However, such exclosures are contentious and have been suggested to have detrimental effects on the species which they aim to protect. This study examines whether exclosures increase physiological stress of incubating birds, a hitherto unrecognised and untested potential drawback of exclosures. Red-capped plover Charadrius ruficapillus hatching success was radically altered and significantly higher for nests with exclosures (96.2%) compared with those without (6.8%). Chronic physiological stress in parents (as measured by the heterophil/lymphocyte [H/L] ratio in blood) did not vary between nests with and without exclosures, or between the sexes. However the absence of vegetative cover at the nest site was associated with a 62.7% elevation in H/L ratio, indicating that incubating birds which place their nests in the open are subject to increased levels of chronic stress. The results from this study demonstrate the fundamental importance of predation for the nesting success of this species and confirm that chronic stress levels are not a detrimental side effect of exclosure use.

Enhanced physiological tremor deteriorates plantar flexor torque steadiness after bed rest

This study evaluated the effectiveness of resistance training to preserve submaximal plantar flexor (PF) torque steadiness following 60 days of bed rest (BR). Twenty-two healthy male subjects underwent either BR only (CTR, n=8), or BR plus resistance training (RT, n=14). The magnitude of torque fluctuations during steady submaximal isometric PF contractions (20%, 40%, 60% and 80% of maximum) were assessed before and after BR. Across contraction intensities, torque fluctuations (coefficient of variation, CV) increased more (P<0.05) after BR for CTR (from 0.31±0.10 to 0.92±0.63; P<0.001), than for RT (from 0.30±0.09 to 0.54±0.27; P<0.01). A shift in the spectral content of torque fluctuations towards increased rhythmic activity between 6.5 and 20Hz was observed in CTR only (P<0.05). H-reflex amplitude (H(max)/M(max) ratio) declined across groups from 0.57±0.18 before BR to 0.44±0.14 following BR (P<0.01) without correlation to CV. The present study showed that increased torque fluctuation after BR resulted from enhanced physiological tremor. Resistance training prevented the spectral shift in isometric PF torque fluctuation and offset ∼50% of the decline in performance associated with long-term BR.

Using repeatability to study physiological and behavioural traits: ignore time-related change at your peril

© 2015 The Association for the Study of Animal Behaviour. Broad sense repeatability, which refers to the extent to which individual differences in trait scores are maintained over time, is of increasing interest to researchers studying behavioural or physiological traits. Broad sense repeatability is most often inferred from the statistic R (the intraclass correlation, or narrow sense repeatability). However, R ignores change over time, despite the inherent longitudinal nature of the data (repeated measures over time). Here, we begin by showing that most studies ignore time-related change when estimating broad sense repeatability, and estimate R with low statistical power. Given this problem, we (1) outline how and why ignoring time-related change in scores (that occurs for whatever reason) can seriously affect estimates of the broad sense repeatability of behavioural or physiological traits, (2) discuss conditions in which various indices of R can or cannot provide reliable estimates of broad sense repeatability, and (3) provide suggestions for experimental designs for future studies. Finally, given that we already have abundant evidence that many labile traits are 'repeatable' in that broad sense (i.e. R>. 0), we suggest a shift in focus towards obtaining robust estimates of the repeatability of behavioural and physiological traits. Given how labile these traits are, this will require greater experimental (and/or statistical) control and larger sample sizes in order to detect and quantify change over time (if present).

Managing women with acute physiological deterioration: student midwives performance in a simulated setting

OBJECTIVE: Midwives' ability to manage maternal deterioration and 'failure to rescue' are of concern with questions over knowledge, clinical skills and the implications for maternal morbidity and, mortality rates. In a simulated setting our objective was to assess student midwives' ability to assess, and manage maternal deterioration using measures of knowledge, situation awareness and skill, performance. METHODS: An exploratory quantitative analysis of student performance based upon performance, ratings derived from knowledge tests and observational ratings. During 2010 thirty-five student, midwives attended a simulation laboratory completing a knowledge questionnaire and two video, recorded simulated scenarios. Patient actresses wearing a 'birthing suit' simulated deteriorating, women with post-partum and ante-partum haemorrhage (PPH and APH). Situation awareness was, measured at the end of each scenario. Applicable descriptive and inferential statistical tests were, applied to the data. FINDINGS: The mean total knowledge score was 75% (range 46-91%) with low skill performance, means for both scenarios 54% (range 39-70%). There was no difference in performance between the scenarios, however performance of key observations decreased as the women deteriorated; with significant reductions in key vital signs such as blood pressure and blood loss measurements. Situation, awareness scores were also low (54%) with awareness decreasing significantly (t(32)=2.247, p=0.032), in the second and more difficult APH scenario. CONCLUSION: Whilst knowledge levels were generally good, skills were generally poor and decreased as the women deteriorated. Such failures to apply knowledge in emergency stressful situations may be resolved by repetitive high stakes and high fidelity simulation.

Physiological status during emergency department care : relationship with inhospital death after clinical deterioration

OBJECTIVE: To examine the relationship between patient physiological status in the emergency department (ED) and inhospital mortality after rapid response team (RRT) or cardiac arrest team (CAT) activations within 72 hours of emergency admission to medical or surgical wards. DESIGN, SETTING AND PARTICIPANTS: A multisite, retrospective, cohort study of 660 randomly selected (220 patients per site) adult medical or surgical patients who were admitted from the ED during 2012 and who had had an RRT or CAT activation within 72 hours of admission, at three hospitals in Melbourne, Australia. MAIN OUTCOME MEASURE: Inhospital mortality. RESULTS: There were 825 RRT activations (for 634 patients) and 42 CAT activations (for 35 patients). The median time to the first RRT or CAT activation was 18.8 hours and was significantly shorter in patients who died in hospital (14.6 v 20.6 hours, P=0.036). Compared with survivors, patients who died were more likely to have at least one observation meeting RRT criteria during their ED stay (45.9% v 34.8%; P=0.029): tachypnoea (21.1% v 13.4%, P=0.039), hypotension (20.2% v 11.8%, P=0.018), hypoxaemia (8.3% v 3.1%, P=0.001) and altered conscious state (6.2% v 1.3%, P=0.001) were more common in patients who died. The risk-adjusted odds ratio (OR) for inhospital death was highest for patients with an altered conscious state during their ED stay (OR, 4.633; 95% CI, 1.365-15.728; P=0.014). CONCLUSIONS: In patients who needed an RRT or CAT activation within the first 72 hours of emergency admission to medical or surgical wards, there was a strong association between physiological derangement during ED care and inhospital death.

Population, behavioural and physiological responses of an urban population of black swans to an intense annual noise event

Wild animals in urban environments are exposed to a broad range of human activities that have the potential to disturb their life history and behaviour. Wildlife responses to disturbance can range from emigration to modified behaviour, or elevated stress, but these responses are rarely evaluated in concert. We simultaneously examined population, behavioural and hormonal responses of an urban population of black swans Cygnus atratus before, during and after an annual disturbance event involving large crowds and intense noise, the Australian Formula One Grand Prix. Black swan population numbers were lowest one week before the event and rose gradually over the course of the study, peaking after the event, suggesting that the disturbance does not trigger mass emigration. We also found no difference in the proportion of time spent on key behaviours such as locomotion, foraging, resting or self-maintenance over the course of the study. However, basal and capture stress-induced corticosterone levels showed significant variation, consistent with a modest physiological response. Basal plasma corticosterone levels were highest before the event and decreased over the course of the study. Capture-induced stress levels peaked during the Grand Prix and then also declined over the remainder of the study. Our results suggest that even intensely noisy and apparently disruptive events may have relatively low measurable short-term impact on population numbers, behaviour or physiology in urban populations with apparently high tolerance to anthropogenic disturbance. Nevertheless, the potential long-term impact of such disturbance on reproductive success, individual fitness and population health will need to be carefully evaluated.

Predicting physiological capacity of human load carriage - a review

This review article aims to evaluate a proposed maximum acceptable work duration model for load carriage tasks. It is contended that this concept has particular relevance to physically demanding occupations such as military and firefighting. Personnel in these occupations are often required to perform very physically demanding tasks, over varying time periods, often involving load carriage. Previous research has investigated concepts related to physiological workload limits in occupational settings (e.g. industrial). Evidence suggests however, that existing (unloaded) workload guidelines are not appropriate for load carriage tasks. The utility of this model warrants further work to enable prediction of load carriage durations across a range of functional workloads for physically demanding occupations. If the maximum duration for which personnel can physiologically sustain a load carriage task could be accurately predicted, commanders and supervisors could better plan for and manage tasks to ensure operational imperatives were met whilst minimising health risks for their workers.

The acute physiological stress response to an emergency alarm and mobilization during the day and at night

The purpose of this study was to investigate the acute physiological stress response to an emergency alarm and mobilization during the day and at night. Sixteen healthy males aged 25 ± 4 years (mean ± SD) spent four consecutive days and nights in a sleep laboratory. This research used a within-participants design with repeated measures for time, alarm condition (alarm or control), and trial (day or night). When an alarm sounded, participants were required to mobilize immediately. Saliva samples for cortisol analysis were collected 0 min, 15 min, 30 min, 45 min, 60 min, 90 min, and 120 min after mobilization, and at corresponding times in control conditions. Heart rate was measured continuously throughout the study. Heart rate was higher in the day (F20,442 = 9.140, P < 0.001) and night (F23,459 = 8.356, P < 0.001) alarm conditions compared to the respective control conditions. There was no difference in saliva cortisol between day alarm and day control conditions. Cortisol was higher (F6,183 = 2.450, P < 0.001) following the night alarm and mobilization compared to the night control condition. The magnitude of difference in cortisol between night control and night alarm conditions was greater (F6,174 = 4.071, P < 0.001) than the magnitude of difference between the day control and day alarm conditions. The augmented heart rate response to the day and night alarms supports previous observations in field settings. Variations in the cortisol responses between conditions across the day and night may relate to differences in participants' ability to interpret the alarm when sleeping versus when awake.