Effects Of Acclimation Research Articles

The Effect of Post-Exercise Warm Water Immersion on Anaerobic Power Performance in College Students

Background/Objectives: The purpose of this study was to investigate the effect of a short-term passive post-exercise heat acclimation (HA) protocol on anaerobic performance in college students. Methods: In total, 28 participants (age 22.3 ± 2.1 years, height 168 ± 9.1 cm, mass 71.5 ± 16.6 kg) volunteered and were randomly divided into either an intervention (INT) or control (CON) group. Both groups followed a consecutive two-day protocol, consisting of a 25 min submaximal cycle @ 50–60% heart rate reserve (HRR), followed by a 25 min hot water immersion (INT) or nothing (CON). All participants performed a 30 s Wingate Anaerobic Test (WAnT) on four separate occasions—familiarization, pre-intervention, acutely post-intervention, and 24 h post intervention. The WAnT measured their peak power (W), relative peak power (W/kg), mean power (W), fatigue index (%), and total work (kJ). Results: From the results of the Factorial ANOVA, it was found that there were no significant differences, with no main effect for group (INT vs. CON) or time (Trials 1–4) and no significant interaction across all measured variables (p > 0.05). Conclusions: A two-day post-exercise passive HA protocol utilizing hot water immersion had no significant effect on the measurement of anaerobic performance in college students.

Acclimation during Embryogenesis Remodulates Telomerase Activity and Gene Expression in Baikal Whitefish Larvae, Mitigating the Effects of Acute Temperature Stress.

Acclimation through the hormesis effect increases the plasticity of organisms, which has been shown for many ectothermic animals, including fish. We investigated the effect of temperature acclimation in Baikal whitefish Coregonus baicalensis (Dybowski, 1874). Telomere length, telomerase activity, and the expression of genes, whose products are involved in the regulation of telomere length and defense against reactive oxygen species, were selected to assess the state of the larvae. Acclimation and acute temperature stress (+12 °C) had no effect on telomere length, but altered telomerase activity (acclimation decreased it; stress increased it) and the levels of genes expression. Under stress, the expression of superoxide dismutase genes was increased in acclimated larvae and that of glutathione peroxidases in non-acclimated larvae, which may indicate lower reactive oxygen species formation and slower antioxidant responses in acclimated fish. The expression of some telomere-related genes was reduced under temperature stress, but the expression of the tzap and smg genes, whose products improve the control of telomere length by preventing them from lengthening or shortening, was increased in acclimated individuals. The data obtained indicate a positive effect of acclimation on the state of the Baikal whitefish larvae by remodulation of their telomerase activity and the transcriptional profile.

The effect of seasonal heat acclimatization on cool-seeking behaviour during passive heat stress in young adults.

Seasonal heat acclimatization is known to enhance autonomic thermoeffector responses, whereas the behavioural response following seasonal heat acclimatization remains unknown. We investigated whether seasonal heat acclimatization would alter autonomic and behavioural thermoregulatory responses. Sixteen healthy participants (eight males and eight females) underwent two trials involving 50 min of lower-leg passive heating (lower-leg submersion in 42°C water) with (Fan trial) and without (No fan trial) the voluntary use of a fan in a moderate thermal environment (27°C, 50% relative humidity) across winter and summer months. In Fan trials, participants were allowed to use a fan to maintain thermal comfort, but this was not allowed in the No fan trials. Cool-seeking behaviour was initiated at a lower change in rectal temperature [mean (SD): 0.21 (0.18)°C vs. 0.11 (0.13)°C, P=0.0327] and change in mean skin temperature [2.34 (0.56)°C vs. 1.81 (0.32)°C, P<0.0001], and cooling time was longer [16.46 (5.62) vs. 20.40 (4.87) min, P=0.0224] in summer compared with winter. However, thermal perception was not modified by season during lower-leg passive heating (all P>0.0864). Furthermore, rectal temperature was higher in summer (P=0.0433), whereas mean body temperature and skin temperature were not different (all P>0.0631) between the two seasons in Fan trials. In conclusion, seasonal heat acclimatization enhanced the cool-seeking behaviour from winter to summer.

Dietary potassium and cold acclimation additively increase cold tolerance in Drosophila melanogaster

In the cold, chill susceptible insects lose the ability to regulate ionic and osmotic gradients. This leads to hemolymph hyperkalemia that drives a debilitating loss of cell membrane polarization, triggering cell death pathways and causing organismal injury. Biotic and abiotic factors can modulate insect cold tolerance by impacting the ability to mitigate or prevent this cascade of events. In the present study, we test the combined and isolated effects of dietary manipulations and thermal acclimation on cold tolerance in fruit flies. Specifically, we acclimated adult Drosophila melanogaster to 15 or 25 °C and fed them either a K+-loaded diet or a control diet. We then tested the ability of these flies to recover from and survive a cold exposure, as well as their capacity to protect transmembrane K+ gradients, and intracellular Na+ concentration. As predicted, cold-exposed flies experienced hemolymph hyperkalemia and cold-acclimated flies had improved cold tolerance due to an improved maintenance of the hemolymph K+ concentration at low temperature. Feeding on a high-K+ diet improved cold tolerance additively, but paradoxically reduced the ability to maintain extracellular K+ concentrations. Cold-acclimation and K+-feeding additively increased the intracellular K+ concentration, aiding in maintenance of the transmembrane K+ gradient during cold exposure despite cold-induced hemolymph hyperkalemia. There was no effect of acclimation or diet on intracellular Na+ concentration. These findings suggest intracellular K+ loading and reduced muscle membrane K+ sensitivity as mechanisms through which cold-acclimated and K+-fed flies are able to tolerate hemolymph hyperkalemia.

Dynamic effects of thermal acclimation on chytridiomycosis infection intensity and transmission potential in Xenopus laevis.

The pandemic amphibian pathogen Batrachochytrium dendrobatidis (Bd) can cause more severe infections with variable temperatures owing to delays in host thermal acclimation following temperature shifts. However, little is known about the timing of these acclimation effects or their consequences for Bd transmission. We measured how thermal acclimation affects Bd infection in Xenopus laevis, using a timing-of-exposure treatment to investigate acclimation effect persistence following a temperature shift. Consistent with a delay in host acclimation, warm-acclimated frogs exposed to Bd immediately following a temperature decrease (day 0) developed higher infection intensities than frogs already acclimated to the cool temperature. This acclimation effect was surprisingly persistent (five weeks). Acclimation did not affect infection intensity when Bd exposure occurred one week after the temperature shift, indicating that frogs fully acclimated to new temperatures within 7 days. This suggests that acclimation effect persistence beyond one week post-exposure was caused by carry-over from initially high infection loads, rather than an extended delay in host acclimation. In a second experiment, we replicated the persistent thermal acclimation effects on Bd infection but found no acclimation effects on zoospore production. This suggests that variable temperatures consistently exacerbate individual Bd infection but may not necessarily increase Bd transmission.

Hypoxia-acclimation adjusts skeletal muscle anaerobic metabolism and burst swim performance in a marine fish

Red drum, Sciaenops ocellatus, are a marine teleost native to the Gulf of Mexico that routinely experiences periods of low oxygen (hypoxia). Recent work has demonstrated this species has the capacity to improve aerobic performance in hypoxia through respiratory acclimation. However, it remains unknown how hypoxia acclimation impacts anaerobic metabolism in red drum, and the consequences of exhaustive exercise and recovery. Juvenile fish were acclimated to normoxia (n = 15, DO 90.4 ± 6.42 %) or hypoxia (n = 15, DO 33.6 ± 7.2 %) for 8 days then sampled at three time points: at rest, after exercise, and after a 3 h recovery period. The resting time point was used to characterize the acclimated phenotype, while the remaining time points demonstrate how this phenotype responds to exhaustive exercise. Whole blood, red muscle, white muscle, and heart tissues were sampled for metabolites and enzyme activity. The resting phenotype was characterized by lower pHe and changes to skeletal muscle ATP. Exhaustive exercise increased muscle lactate, and decreased phosphocreatine and ATP with no effect of acclimation. Interestingly, hypoxia-acclimated fish had higher pHe and pHi than control in all exercise time points. Red muscle ATP was lower in hypoxia-acclimated fish versus control at each sample period. Moreover, acclimated fish increased lactate dehydrogenase activity in the red muscle. Hypoxia acclimation increased white muscle ATP and hexokinase activity, a glycolytic enzyme. In a gait-transition swim test, hypoxia-acclimated fish recruited anaerobic-powered burst swimming at lower speeds in normoxia compared to control fish. These data suggest that acclimation increases reliance on anaerobic metabolism, and does not benefit recovery from exhaustive exercise.

Perturbations to common gardens of anaerobic co-digesters reveal relationships between functional resilience and microbial community composition.

We report the relationship between enrichment of adapted populations and enhancement of community functional resilience in methanogenic bioreactors. Although previous studies have shown the positive effects of acclimation, this work directly investigated the relationships between microbiome dynamics and performance of anaerobic co-digesting reactors in response to different levels of an environmental perturbation (loading of grease interceptor waste [GIW]). Using the methanogenic microbiome from a full-scale digester, we developed eight sets of microbial communities in triplicate using different feed sources. These substrate-specific microbiomes were then exposed to three independent disturbance events of low-, mid- and high-GIW loading rates. This approach allowed us to directly attribute differences in community responses to differences in community composition. Despite identical inocula, environment (digester operation, substrate loading rate, and feeding patterns) and general whole-community function (methane production and effluent quality) during the cultivation period, different substrates led to different microbial community assemblies. Lipid pre-acclimation led to enrichment of a pool of specialized populations, along with thriving of sub-dominant communities. The enrichment of these populations improved functional resilience and process performance when exposed to a low level of lipid-rich perturbation compared with less-acclimated communities. At higher levels of perturbation, the communities were not able to recover methanogenesis, indicating a loading limit to the resilience response. This study extends our current understanding of environmental perturbations, feed-specific adaptation, and functional resilience in methanogenic bioreactors.IMPORTANCEThis study demonstrates, for the first time for GIW co-digestion, how applying similar perturbations to different microbial communities was used to directly identify the causal relationships between microbial community, function, and environment in triplicate anaerobic microbiomes. We evaluated the impact of feed-specific adaptation on methanogenic microbiomes and demonstrated how microbiomes can be influenced to improve their functional (methanogenic) resilience to GIW inhibition. These findings demonstrate how an ecological framework can help improve a biological engineering application, and more specifically, increase the potential of anaerobic co-digestion for converting wastes to energy.

Lung function parameters are associated with acute mountain sickness and are improved at high and extreme altitude

At altitude, factors such as decreased barometric pressure, low temperatures, and acclimatization might affect lung function.The effects of exposure and acclimatization to high-altitude on lung function were assessed in 39 subjects by repetitive spirometry up to 6022 m during a high-altitude expedition. Subjects were classified depending on the occurrence of acute mountain sickness (AMS) and summit success to evaluate whether lung function relates to successful climb and risk of developing AMS.Peak expiratory flow (PEF), forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) increased with progressive altitude (max. +20.2 %pred, +9.3 %pred, and +6.7 %pred, all p<0.05). Only PEF improved with acclimatization (BC1 vs. BC2, +7.2 %pred, p=0.044). At altitude FEV1 (p=0.008) and PEF (p<0.001) were lower in the AMS group.The risk of developing AMS was associated with lower baseline PEF (p<0.001) and longitudinal changes in PEF (p=0.008) and FEV1 (p<0.001). Lung function was not related to summit success (7126 m). Improvement in PEF after acclimatization might indicate respiratory muscle adaptation.

Effects of slow temperature acclimation of photosynthesis on gross primary production estimation

The slow temperature acclimation of photosynthesis has been confirmed through early field experiments and studies. However, this effect is difficult to characterize and quantify with some simple and easily accessible indicators. As a result, the impact of slow temperature acclimation of photosynthesis on gross primary production (GPP) estimation has often been overlooked or not integrated into most GPP models. In this study, we used a theorical variable-state of acclimation (S), to characterize the slow temperature acclimation. This variable represents the temperature to which the photosynthetic machinery adapts and is defined as a function of air temperature (Ta) and time constant (τ) required for vegetation to respond to temperature, to discuss its impact on GPP simulation. We used FLUXNET2015 dataset to calculate S and established a GPP model using S and shortwave radiation (SW) based on random forest algorithm (S model). As a comparison, we directly used Ta and SW to build the other GPP model (Ta model). Moreover, the divergent temperature acclimation capacities of plants are crucial to predict and make preparations for likely temperature stress in the future. Therefore, the spatial distribution of τ values was also mapped using satellite sun induced chlorophyll fluorescence (SIF) and Ta datasets. The results indicated that: (1) taking into account the slow temperature acclimation of photosynthesis led to a more precise estimation of GPP which mainly reflected in reduction of excessive fluctuations in GPP predictions; (2) considering the slow temperature acclimation of photosynthesis can reduce the sensitivity of vegetation to temperature; (3) the improvement of S model in GPP estimations was different in different vegetation growth stages which was more significant in the springtime recovery stage; (4) τ values had significant spatial distribution which was strongly affected by the determinants of vegetation growth and seasonal variations in temperature.

Heat-stress memory enhances the acclimation of a migratory insect pest to global warming.

In the face of rising global temperatures, the mechanisms behind an organism's ability to acclimate to heat stress remain enigmatic. The rice leaf folder, Cnaphalocrocis medinalis, traditionally viewed as temperature-sensitive, paradoxically exhibits robust larval acclimation to heat stress. This study used the heat-acclimated strain HA39, developed through multigenerational exposure to 39°C during the larval stage, and the unacclimated strain HA27 reared at 27°C to unravel the transgenerational effects of heat acclimation and its regulatory mechanisms. Heat acclimation for larvae incurred a fitness cost in pupae when exposed to high temperature, yet a significant transgenerational effect surfaced, revealing heightened fitness benefit in pupae from HA39, even without additional heat exposure during larval recovery at 27°C. This transgenerational effect exhibited a short-term memory, diminishing after two recovery generations. Moreover, the effect correlated with increased superoxide dismutase (SOD) enzyme activity and expression levels of oxidoreductase genes, representing physiological and molecular foundations of heat acclimation. Heat-acclimated larvae displayed elevated DNA methylation levels, while pupae from HA39, in recovery generations, exhibited decreased methylation indicated by the upregulation of a demethylase gene and downregulation of two methyltransferase genes at high temperatures. In summary, heat acclimation induces DNA methylation, orchestrating heat-stress memory and influencing the expression levels of oxidoreductase genes and SOD activity. Heat-stress memory enhances the acclimation of the migratory insect pest to global warming.

Evidence for transient deleterious thermal acclimation in field recapture rates of an invasive tropical species, Bactrocera dorsalis (Diptera: Tephritidae).

Knowing how environmental conditions affect performance traits in pest insects is important to improve pest management strategies. It can be informative for monitoring, but also for control programs where insects are mass-reared, and field-released. Here, we investigated how adult thermal acclimation in sterile Bactrocera dorsalis affects dispersal and recapture rates in the field using a mark-release-recapture method. We also considered how current abiotic factors may affect recapture rates and interact with thermal history. We found that acclimation at 20 or 30 °C for 4 d prior to release reduced the number of recaptures in comparison with the 25 °C control group, but with no differences between groups in the willingness to disperse upon release. However, the deleterious effects of acclimation were only detectable in the first week following release, whereafter only the recent abiotic conditions explained recapture rates. In addition, we found that recent field conditions contributed more than thermal history to explain patterns of recaptures. The two most important variables affecting the number of recaptures were the maximum temperature and the average relative humidity experienced in the 24 h preceding trapping. Our results add to the handful of studies that have considered the effect of thermal acclimation on insect field performance, but notably lend support to the deleterious acclimation hypothesis among the various hypotheses that have been proposed. Finally, this study shows that there are specific abiotic conditions (cold/hot and dry) in which recaptures will be reduced, which may therefore bias estimates of wild population size.

Effect of drought acclimation on sugar metabolism in millet.

Drought stress triggers sugar accumulation in plants, providing energy and aiding in protection against oxidative damage. Plant hardening under mild stress conditions has been shown to enhance plant resistance to severe stress conditions. While sugar accumulation and metabolism under drought stress have been well-documented in crop plants, the effect of drought acclimation treatment on sugar accumulation and metabolism has not yet been explored. In this study, we investigated the impact of drought stress acclimation on sugar accumulation and metabolism in the leaves and root tissues of two commonly cultivated foxtail millet (Setaria italica L.) genotypes, 'PI 689680' and 'PI 662292'. Quantification of total sugars (soluble sugar, fructose, glucose, and sucrose), their related enzymes (SPS, SuSy, NI, and AI), and the regulation of their related transcripts (SiSPS1, SiSuSy1, SiSWEET6, SiA-INV, and SiC-INV) revealed that drought-acclimated (DA) plants exhibited levels of these indicators comparable to those of control plants. However, under subsequent drought stress conditions, both the leaves and roots of non-acclimated plants accumulated higher levels of total sugars, displayed increased activity of sugar metabolism enzymes, and showed elevated expression of sugar metabolism-related transcripts compared to drought-acclimated plants. Thus, acclimation-induced restriction of sugar accumulation, transport, and metabolism could be one of the metabolic processes contributing to enhanced drought tolerance in millet. This study advocates for the use of acclimation as an effective strategy to mitigate the negative impacts of drought-induced metabolic disturbances in millet, thereby enhancing global food security and promoting sustainable agricultural systems.

Interactive effects of temperature, cadmium, and hypoxia on rainbow trout (Oncorhynchus mykiss) liver mitochondrial bioenergetics.

Fish in their natural environments possess elaborate mechanisms that regulate physiological function to mitigate the adverse effects of multiple environmental stressors such as temperature, metals, and hypoxia. We investigated how warm acclimation affects mitochondrial responses to Cd, hypoxia, and acute temperature shifts (heat shock and cold snap) in rainbow trout. We observed that state 3 respiration driven by complex I (CI) was resistant to the stressors while warm acclimation and Cd reduced complex I +II (CI + II) driven state 3 respiration. In contrast, state 4 (leak) respirations for both CI and CI + II were consistently stimulated by warm acclimation resulting in reduced mitochondrial coupling efficiency (respiratory control ratio, RCR). Warm acclimation and Cd exacerbated their individual effect on leak respiration to further reduce the RCR. Moreover, the effect of warm acclimation on mitochondrial bioenergetics aligned with its inhibitory effect on activities of citrate synthase and both CI and CII. Unlike the Cd and warm acclimation combined exposure, hypoxia alone and in combination with warm acclimation and/or Cd abolished the stimulation of CI and CI + II powered leak respirations resulting in partial recovery of RCR. The response to acute temperature shifts indicated that while state 3 respiration returned to pre-acclimation level, the leak respiration did not. Overall, our findings suggest a complex in vivo interaction of multiple stressors on mitochondrial function that are not adequately predicted by their individual effects.

Mitochondrial Fission Is Involved in Heat Resistance in Zebrafish.

Global warming and extreme weather events pose a significant threat to global biodiversity, with rising water temperatures exerting a profound influence on fish conservation and fishery development. In this study, we used zebrafish as a model organism to explore the impact of a heat acclimation period on their survival rates. The results demonstrated that a 2-month heat acclimation period almost completely mitigated heat stress-induced mortality in zebrafish. Subsequent analysis of the surviving zebrafish revealed a predominance of hepatic mitochondria in a fission state. Remarkably, a short-term fasting regimen, which induced hepatic mitochondrial fission, mirrored the outcomes of the protective effect of heat acclimation and augmented animal survival under heat stress. Conversely, treatment with a mitochondrial fission inhibitor within the fasting group attenuated the elevated survival rate. Furthermore, zebrafish embryos subjected to brief heat acclimation also exhibited increased heat resistance, a trait diminished by a chemical intervention inhibiting mitochondrial fission. This suggests a shared mechanism for heat resistance between embryos and adult zebrafish. These findings underscore the potential use of inducing mitochondrial fission to enhance heat resistance in zebrafish, offering promise for fish biodiversity conservation in the face of global warming.

Effects of acute hypoxia exposure and acclimation on the thermal tolerance of an imperiled Canadian minnow.

Elevated water temperatures and low dissolved oxygen (hypoxia) are pervasive stressors in aquatic systems that can be exacerbated by climate change and anthropogenic activities, and there is growing interest in their interactive effects. To explore this interaction, we quantified the effects of acute and long-term hypoxia exposure on the critical thermal maximum (CTmax) of Redside Dace (Clinostomus elongatus), a small-bodied freshwater minnow with sparse populations in the Great Lakes Basin of Canada and designated as Endangered under Canada's Species at Risk Act. Fish were held at 18°C and acclimated to four levels of dissolved oxygen (>90%, 60%, 40%, and 20% air saturation). CTmax was measured after 2 and 10 weeks of acclimation and after 3.5 weeks of reoxygenation, and agitation behavior was quantified during CTmax trials. Aquatic surface respiration behavior was also quantified at 14 weeks of acclimation to oxygen treatments. Acute hypoxia exposure decreased CTmax in fish acclimated to normoxia (>90% air saturation), but acclimation to hypoxia reduced this effect. There was no effect of acclimation oxygen level on CTmax when measured in normoxia, and there was no effect of exposure time to hypoxia on CTmax. Residual effects of hypoxia acclimation on CTmax were not seen after reoxygenation. Agitation behavior varied greatly among individuals and was not affected by oxygen conditions. Fish performed aquatic surface respiration with low frequency, but performed it earlier when acclimated to higher levels of oxygen. Overall, this work sheds light on the vulnerability of fish experiencing acute hypoxia and heat waves concurrently.

Context-dependent effects of thermal acclimation on physiological correlates of animal personality in Asiatic toads.

Persistent individual variation in behaviour, or 'personality', is a widespread phenomenon in animals, and understanding the evolution of animal personality is a key task of current biology. Natural selection has been proposed to promote the integration of personality with animal 'intrinsic states', such as metabolic or endocrine traits, and this integration varies with ecological conditions. However, these external ecological modulatory effects have rarely been examined. Here, we investigate the effects of thermal acclimation on between-individual covariations between physiology and behaviour in Asiatic toads (Bufo gargarizans) along an altitudinal gradient. Our results reveal that the thermal modulatory effects on the covariations depend on the altitudinal population. Specifically, at low altitudes, between-individual covariations are highly plastic, with risk-taking behaviour covarying with baseline glucocorticoids (GCs) under warm acclimation, but risk-taking and exploration behaviour covarying with resting metabolic rate (RMR) under cold acclimation. In contrast, between-individual covariations are relatively fixed at high altitudes, with risk-taking behaviour consistently covarying with baseline GCs. Furthermore, at low altitudes, changes in covariations between RMR and personality are associated with adjustment of energy management models. Evidently, animal physiological states that determine or covary with personality can adapt according to the seasonal thermal environment and the thermal evolutionary background of populations. Our findings highlight the importance of a multi-system physiological approach to understand the evolution of animal personality.

Cold hardiness-informed budbreak reveals role of freezing temperatures and daily fluctuation in a chill accumulation model.

Fundamental questions in bud dormancy remain, including what temperatures fulfill dormancy requirements (i.e. chill accumulation). Recent studies demonstrate freezing temperatures promote chill accumulation and cold hardiness influences time to budbreak-the phenotype used for dormancy evaluations. Here we evaluated bud cold hardiness and budbreak responses of grapevines (Vitis hybrids) throughout chill accumulation under three treatments: constant (5 °C), fluctuating (-3.5 to 6.5 °C daily), and field conditions (Madison, WI, USA). Chill treatments experiencing lower temperatures promoted greater gains in cold hardiness (field>fluctuating>constant). All treatments decreased observed time to budbreak with increased chill accumulation. However, perceived treatment effectiveness changed when time to budbreak was adjusted to remove cold acclimation effects. Among three classic chill models (North Carolina, Utah, and Dynamic), none was able to correctly describe adjusted time to budbreak responses to chill accumulation. Thus, a new model is proposed that expands the range of chill accumulation temperatures to include freezing temperatures and enhances chill accumulation under fluctuating temperature conditions. Most importantly, our analysis demonstrates that adjustments for uneven acclimation change the perceived effectiveness of chill treatments. Therefore, future work in bud dormancy would benefit from simultaneously evaluating cold hardiness.

Kinetic of Aerobic Decomposition Process of Linear Alkylbenzene Sulfonate (LAS) in a Well-Shaped Bioreactor Using Commercial Inoculum

Linear alkylbenzene sulfonate (LAS) belongs to a class of surfactants claimed as an environmentally friendly detergent due to its biodegradability. However, the disposal of LAS waste into the waters without prior treatment causes a risk to the ecosystem. These experiments aimed to study the effects of commercial inoculum size EM-4 on the aerobic decomposition process of LAS in a well-shaped bioreactor. These experiments of LAS decomposition were carried out in a batch system aerated by 2.5 L/min for the low and high initial LAS concentrations. The effects of inoculum acclimation were also investigated for the high LAS concentration. The effects of inoculum size were explored at sizes ranging from 5 to 20% v/v, and samples were taken on a regular basis for residual LAS assessment. The first-order kinetic model gave the best fit to the rate of LAS decomposition, with the highest rate coefficient of 10.44 x 10-2 hour-1. This was achieved by using a 20% v/v inoculum for the initial low concentration of LAS, resulting in the highest decomposition efficiency of 89.4% after 24 hours of incubation. The decomposition rate was slower at the high LAS concentrations than at the low concentrations. The inoculum acclimation increased the decomposition rate for the high LAS concentrations. The results of this study show great potential for the bioremediation of LAS detergent waste using commercial inoculum in a well-shaped batch bioreactor.

Strong acclimation effect of temperature and humidity on heat tolerance of the Arctic collembolan Megaphorura arctica.

The Arctic is a highly variable environment in which extreme daily and seasonal temperature fluctuations can occur. With climate change, an increase in the occurrence of extreme high temperatures and drought events is expected. While the effects of cold and dehydration stress on polar arthropods are well studied in combination, little is known about how these species respond to the combined effects of heat and dehydration stress. In this paper, we investigated how the heat tolerance of the Arctic collembola Megaphorura arctica is affected by combinations of different temperature and humidity acclimation regimes under controlled laboratory conditions. The effect of acclimation temperature was complex and highly dependent on both acclimation time and temperature, and was found to have a positive, negative or no effect depending on experimental conditions. Further, we found marked effects of the interaction between temperature and humidity on heat tolerance, with lower humidity severely decreasing heat tolerance when the acclimation temperature was increased. This effect was more pronounced with increasing acclimation time. Lastly, the effect of acclimation on heat tolerance under a fluctuating temperature regime was dependent on acclimation temperature and time, as well as humidity levels. Together, these results show that thermal acclimation alone has moderate or no effect on heat tolerance, but that drought events, likely to be more frequent in the future, in combination with high temperature stress can have large negative impacts on heat tolerance of some Arctic arthropods.

Flies on the rise: acclimation effect on mitochondrial oxidation capacity at normal and high temperatures in Drosophila melanogaster.

Increased average temperatures and extreme thermal events (such as heatwaves) brought forth by climate change impose important constraints on aerobic metabolism. Notably, mitochondrial metabolism, which is affected by both long- and short-term temperature changes, has been put forward as an important determinant for thermal tolerance of organisms. This study examined the influence of phenotypic plasticity on metabolic and physiological parameters in Drosophila melanogaster and the link between mitochondrial function and their upper thermal limits. We showed that D. melanogaster acclimated to 15°C have a 0.65°C lower critical thermal maximum (CTmax) compared with those acclimated to 24°C. Drosophila melanogaster acclimated to 15°C exhibited a higher proportion of shorter saturated and monounsaturated fatty acids, concomitant with lower proportions of polyunsaturated fatty acids. No mitochondrial quantitative changes (fractional area and number) were detected between acclimation groups, but changes of mitochondrial oxidation capacities were observed. Specifically, in both 15°C- and 24°C-acclimated flies, complex I-induced respiration was increased when measured between 15 and 24°C, but drastically declined when measured at 40°C. When succinate and glycerol-3-phosphate were added, this decrease was however compensated for in flies acclimated to 24°C, suggesting an important impact of acclimation on mitochondrial function related to thermal tolerance. Our study reveals that the use of oxidative substrates at high temperatures is influenced by acclimation temperature and strongly related to upper thermal tolerance as a difference of 0.65°C in CTmax translates into significant mitochondrial changes.