Synergistic Effects Of Temperature Research Articles

A low-complexity metabolic network model for the respiratory and fermentative metabolism of Escherichia coli.

Over the last decades, predictive microbiology has made significant advances in the mathematical description of microbial spoiler and pathogen dynamics in or on food products. Recently, the focus of predictive microbiology has shifted from a (semi-)empirical population-level approach towards mechanistic models including information about the intracellular metabolism in order to increase model accuracy and genericness. However, incorporation of this subpopulation-level information increases model complexity and, consequently, the required run time to simulate microbial cell and population dynamics. In this paper, results of metabolic flux balance analyses (FBA) with a genome-scale model are used to calibrate a low-complexity linear model describing the microbial growth and metabolite secretion rates of Escherichia coli as a function of the nutrient and oxygen uptake rate. Hence, the required information about the cellular metabolism (i.e., biomass growth and secretion of cell products) is selected and included in the linear model without incorporating the complete intracellular reaction network. However, the applied FBAs are only representative for microbial dynamics under specific extracellular conditions, viz., a neutral medium without weak acids at a temperature of 37℃. Deviations from these reference conditions lead to metabolic shifts and adjustments of the cellular nutrient uptake or maintenance requirements. This metabolic dependency on extracellular conditions has been taken into account in our low-complex metabolic model. In this way, a novel approach is developed to take the synergistic effects of temperature, pH, and undissociated acids on the cell metabolism into account. Consequently, the developed model is deployable as a tool to describe, predict and control E. coli dynamics in and on food products under various combinations of environmental conditions. To emphasize this point,three specific scenarios are elaborated: (i) aerobic respiration without production of weak acid extracellular metabolites, (ii) anaerobic fermentation with secretion of mixed acid fermentation products into the food environment, and (iii) respiro-fermentative metabolic regimes in between the behaviors at aerobic and anaerobic conditions.

Formation and dynamics of Au nanoparticles in a silica-glass: synergistic effects of temperature and fluences of ion irradiations

To investigate formation and dynamics of Au nanoparticles in a silica-glass, Au2+ ions are implanted in silica matrix at elevated temperatures up to 600 °C. Optical absorption, Raman spectroscopy and electron microscopy results confirm athermal growth of the Au nanoparticles. Growth dynamics has strong dependence on ion fluences and target temperatures. For example, with the highest ion fluences and at the maximum target temperature, Au nanoparticles have coalesced to form nanorods of Au. Rutherford backscattering spectrometry reveals surprising results about narrowing of implanted profiles of Au atoms with increase of the ion fluences and target temperatures. Observed phenomena are explained in the light of radiation-enhanced diffusion of Au atoms in the ion-implanted silica-glass samples.

Interactive effects of temperature and copper toxicity on photosynthetic efficiency and metabolic plasticity in Scenedesmus quadricauda (Chlorophyceae)

Warming and copper (Cu) toxicity are two key abiotic stressors that strongly affect cell growth, photosynthetic rate, and metabolism in microalgae. In this study, a freshwater chlorophyte, Scenedesmus quadricauda, was exposed to various concentrations of copper sulfate (300, 600, and 1000 μM nominal concentrations of CuSO4·5H2O) at 25 and 35 °C. The changes in cell density, photosynthetic parameters, in vivo absorption spectra, reactive oxygen species (ROS) levels, and metabolic profile were analyzed. The effects of copper toxicity on the physiology and biochemistry of microalgae were highly dependent on water temperature. The interactive effects of both stressors induced significant impact on the photosynthetic parameters such as maximum quantum yield (Fv/Fm), saturation irradiance (Ek), and non-photochemical quenching (NPQ). Temperature induced significant impact on cell density, Ek and NPQ, while the Cu toxicity significantly affected the Fv/Fm and NPQ. Changes in the in vivo absorption spectra and high levels of reactive oxygen species (ROS) were observed across different treatments. Overall, S. quadricauda adapted to the two abiotic stresses via NPQ and metabolic restructuring. Key metabolites including glycine, proline, hexadecanoic acid, propanoic acid, octadecanoic acid, galactose, lactose, and sucrose were involved in the microalgal response. The synergistic effects of temperature and Cu stresses on microalgae might affect community tolerance and species distribution in the long run.

Responses of zinc recovery to temperature and mineral composition during sphalerite bioleaching process

Temperature and energy resources (e.g., iron, sulfur and organic matter) usually undergo dynamic changes, and play important roles during industrial bioleaching process. Thus, it is essential to investigate their synergistic effects and the changes of their independent effects with simultaneous actions of multi-factors. In this study, we explored the synergistic effects of temperature and original mineral compositions (OMCs, energy resources) on the sphalerite bioleaching process. The microbial community structure was monitored by 16S rRNA gene sequencing technology and showed clear segregation along temperature gradients and Shannon diversity decreased at high temperature. On the contrary, the physicochemical parameters (pH and [Fe3+]) in the leachate were significantly affected by the OMCs. Interestingly, the influence of temperature on zinc recovery was greater at relatively simpler OMCs level, whereas the influence of OMCs was stronger at lower temperature. In addition, using [Fe3+], pH, relative abundances of dominant OTUs of microbial community and temperature as variable parameters, several models were constructed to predict zinc leaching efficiency, providing a possibility to predict the metal recovery efficiency under temperature change and variable energy resources.

Synergistic effects of temperature, oxidation, and stress level on fatigue hysteresis behavior of cross-ply ceramic-matrix composites at room and elevated temperatures under cyclic loading

In this paper, the synergistic effects of temperature, oxidation, and stress level on the fatigue hysteresis behavior of cross-ply SiC/CAS ceramic-matrix composites (CMCs) at room temperature and 700 and 850 °C in air atmosphere has been investigated. The relationships between the fatigue hysteresis loops, fatigue hysteresis-dissipated energy, fatigue hysteresis modulus, and the fiber/matrix interface shear stress have been established using the hysteresis loop models considering different matrix cracking modes. The fatigue damage evolution process of SiC/CAS composite under tension–tension fatigue loading has been analyzed using the hysteresis loops. By comparing the experimental fatigue hysteresis-dissipated energy with theoretical computational values, the interface shear stress of SiC/CAS composite were obtained for different cycle numbers and fatigue peak stress. It was found that at elevated temperature in air, the interface shear stress degradation rate is much more affected by the fatigue peak stress than that at room temperature due to interface oxidation. The comparisons of interface shear stress evolution between unidirectional SiC/MAS and SiC/CAS, 2D SiC/SiC, and cross-ply SiC/CAS composites have been analyzed.

Synergistic effects of temperature and humidity on the symptoms of COPD patients

This panel study investigates how temperature, humidity, and their interaction affect chronic obstructive pulmonary disease (COPD) patients' self-reported symptoms. One hundred and six COPD patients from Shanghai, China, were enrolled, and age, smoking status, St. George Respiratory Questionnaire (SGRQ) score, and lung function index were recorded at baseline. The participants were asked to record their indoor temperature, humidity, and symptoms on diary cards between January 2011 and June 2012. Altogether, 82 patients finished the study. There was a significant interactive effect between temperature and humidity (p<0.0001) on COPD patients. When the indoor humidity was low, moderate, and high, the indoor temperature ORs were 0.969 (95% CI 0.922 to 1.017), 0.977 (0.962 to 0.999), and 0.920 (95% CI 0.908 to 0.933), respectively. Low temperature was a risk factor for COPD patients, and high humidity enhanced its risk on COPD. The indoor temperature should be kept at least on average at 18.2°C, while the humidity should be less than 70%. This study demonstrates that temperature and humidity were associated with COPD patients' symptoms, and high humidity would enhance the risk of COPD due to low temperature.

Synergistic effects of temperature, oxidation, loading frequency and stress-rupture on damage evolution of cross-ply ceramic-matrix composites under cyclic fatigue loading at elevated temperatures in oxidizing atmosphere

In this paper, the synergistic effects of temperature, oxidation, loading frequency and stress-rupture on damage evolution of cross-ply ceramic-matrix composites (CMCs) under cyclic fatigue loading at elevated temperatures in oxidizing atmosphere have been investigated. The Budiansky-Hutchinson-Evans shear-lag model was used to describe the micro stress field of the damaged composite considering interface wear and interface oxidation. The damage parameters of fatigue hysteresis dissipated energy, fatigue hysteresis modulus, and fatigue peak strain have been used to monitor the damage evolution inside of CMCs. The relationships between damage parameters and internal damage of matrix cracking, interface debonding and slipping have been established. The experimental fatigue hysteresis, interface slip lengths and peak strain of cross-ply SiC/MAS composite under cyclic fatigue loading at different testing temperatures, loading frequency and stress-rupture time in air condition have been predicted.

Synergistic Effects of Temperature, Oxidation and Multicracking Modes on Damage Evolution and Life Prediction of 2D Woven Ceramic-Matrix Composites under Tension-Tension Fatigue Loading

In this paper, the synergistic effects of temperature, oxidation and multicracking modes on damage evolution and life prediction in 2D woven ceramic-matrix composites (CMCs) have been investigated. The damage parameter of fatigue hysteresis dissipated energy and the interface shear stress were used to monitor the damage evolution inside of CMCs. Under cyclic fatigue loading, the fibers broken fraction was determined by combining the interface/fiber oxidation model, interface wear model and fibers statistical failure model at elevated temperature, based on the assumption that the fiber strength is subjected to two-parameter Weibull distribution and the load carried by broken and intact fibers satisfy the Global Load Sharing (GLS) criterion. When the broken fibers fraction approaches to the critical value, the composite fatigue fractures. The evolution of fatigue hysteresis dissipated energy, the interface shear stress and broken fibers fraction versus cycle number, and the fatigue life S–N curves of SiC/SiC at 1000, 1200 and 1300 °C in air and steam condition have been predicted. The synergistic effects of temperature, oxidation, fatigue peak stress, and multicracking modes on the evolution of interface shear stress and fatigue hysteresis dissipated energy versus cycle numbers curves have been analyzed.

Synergistic Effects of Temperature and Oxidation on Matrix Cracking in Fiber-Reinforced Ceramic-Matrix Composites

In this paper, the synergistic effects of temperatrue and oxidation on matrix cracking in fiber-reinforced ceramic-matrix composites (CMCs) has been investigated using energy balance approach. The shear-lag model cooperated with damage models, i.e., the interface oxidation model, interface debonding model, fiber strength degradation model and fiber failure model, has been adopted to analyze microstress field in the composite. The relationships between matrix cracking stress, interface debonding and slipping, fiber fracture, oxidation temperatures and time have been established. The effects of fiber volume fraction, interface properties, fiber strength and oxidation temperatures on the evolution of matrix cracking stress versus oxidation time have been analyzed. The matrix cracking stresses of C/SiC composite with strong and weak interface bonding after unstressed oxidation at an elevated temperature of 700 °C in air condition have been predicted for different oxidation time.

Relationship of RNA/DNA ratio to somatic growth of Nile tilapia juveniles (Oreochromis niloticus) under joint effects of temperature and salinity

Tilapia juveniles are a very important life stage, and reliably assessing their growth performance is of prime importance in aquaculture production. The suitability of the RNA/DNA as a bioindicator for growth evaluation in tilapia has not yet been reported. In this study, we examined suitability of RNA/DNA ratio for assessing growth of tilapia juveniles and variation in the ratio under the concurrent influences of temperature and salinity using the central composite design and response surface methodology. Results showed that under our experimental conditions, the synergistic effects of temperature and salinity on the RNA/DNA ratio were highly significant (P < 0.01), and the ratio varied with the two factors in a nonlinear fashion; the temperature × salinity interaction was detected at 1% significance level, and had a negative effect on the RNA/DNA ratio particularly at higher temperatures. Temperature was found to have a greater influence on RNA/DNA ratios than salinity. A model of the relation between RNA/DNA, temperature and salinity was developed, with an R2 greater than 98%. The linear relationships of absolute growth, cumulative growth and specific growth of tilapia juveniles to RNA/DNA ratio all showed an R2 of greater than 95%. Our results indicate that the RNA/DNA ratio was a responsive and accurate bioindicator for evaluating the growth performance of juvenile tilapia. These ratio-based models are neither temperature- nor salinity-dependent, and could be readily applicable to freshwater or brackish water aquaculture within temperature–salinity combinations ranging from 16 to 36°C and 0–16 ppt.

Temperature and population density: interactional effects of environmental factors on phenotypic plasticity, immune defenses, and disease resistance in an insect pest.

Temperature and crowding are key environmental factors mediating the transmission and epizooty of infectious disease in ectotherm animals. The host physiology may be altered in a temperature‐dependent manner and thus affects the pathogen development and course of diseases within an individual and host population, or the transmission rates (or infectivity) of pathogens shift linearly with the host population density. To our understanding, the knowledge of interactive and synergistic effects of temperature and population density on the host–pathogen system is limited. Here, we tested the interactional effects of these environmental factors on phenotypic plasticity, immune defenses, and disease resistance in the velvetbean caterpillar Anticarsia gemmatalis. Upon egg hatching, caterpillars were reared in thermostat‐controlled chambers in a 2 × 4 factorial design: density (1 or 8 caterpillars/pot) and temperature (20, 24, 28, or 32°C). Of the immune defenses assessed, encapsulation response was directly affected by none of the environmental factors; capsule melanization increased with temperature in both lone‐ and group‐reared caterpillars, although the lone‐reared ones presented the most evident response, and hemocyte numbers decreased with temperature regardless of the population density. Temperature, but not population density, affected considerably the time from inoculation to death of velvetbean caterpillar. Thus, velvetbean caterpillars succumbed to Anticarsia gemmatalis multiple nucleopolyhedrovirus (AgMNPV) more quickly at higher temperatures than at lower temperatures. As hypothesized, temperature likely affected caterpillars' movement rates, and thus the contact between conspecifics, which in turn affected the phenotypic expression of group‐reared caterpillars. Our results suggest that environmental factors, mainly temperature, strongly affect both the course of disease in velvetbean caterpillar population and its defenses against pathogens. As a soybean pest, velvetbean caterpillar may increase its damage on soybean fields under a scenario of global warming as caterpillars may reach the developmental resistance faster, and thus decrease their susceptibility to biological control by AgMNPV.

The biogeography of fertilization mode in the sea

AbstractAimKnowledge of the biogeography of life histories is central to understanding and predicting the impacts of global change on key functional traits that shape species distributions and transcend taxonomic boundaries. Whether species are internal or external fertilizers is a fundamental aspect of reproductive diversity in the sea, and has profound ecological and evolutionary consequences. However, geographic variation in this trait and the factors that potentially drive it (e.g. transitions in associated life‐history traits, ecological conditions that favour one mode over the other or the evolutionary history of species) remain poorly characterized.LocationOceans world‐wide.MethodsWe collated life‐history data (modes of fertilization and development), geographic data and biophysical data (sea‐surface temperatures and food availability) for 1532 marine species spanning 17 invertebrate phyla. We used standard and phylogenetic logistic regressions to evaluate latitudinal gradients in fertilization mode, plus their interactions with development (transitions from planktonic to aplanktonic development, or from feeding to non‐feeding larvae) and taxonomy. We also explored the dependence of fertilization mode on biophysical variables to understand how ecology potentially contributes to geographic variation in this trait.ResultsFertilization mode often varies predictably with latitude, but the exact nature of this relationship depends on developmental mode and the phylum under consideration. Some commonalities were evident, however, with the likelihood of internal fertilization declining at higher latitudes for Annelida and Echinodermata with aplanktonic development, but increasing at higher latitudes for Cnidaria and Porifera with non‐feeding, planktonic larvae. Synergistic effects of temperature and food availability may potentially shape some of these patterns.Main conclusionsThere are latitudinal gradients in fertilization mode in the sea. The variation among phyla and developmental modes, however, is a complexity that is unexplained by existing theory. Combined effects of recent adaptation and deeper phylogenetic history have probably shaped this systematic variation in the reproductive ecology of marine organisms.

Isolated and synergistic effects of PM10 and average temperature on cardiovascular and respiratory mortality.

OBJECTIVETo analyze the effect of air pollution and temperature on mortality due to cardiovascular and respiratory diseases.METHODSWe evaluated the isolated and synergistic effects of temperature and particulate matter with aerodynamic diameter < 10 µm (PM10) on the mortality of individuals > 40 years old due to cardiovascular disease and that of individuals > 60 years old due to respiratory diseases in Sao Paulo, SP, Southeastern Brazil, between 1998 and 2008. Three methodologies were used to evaluate the isolated association: time-series analysis using Poisson regression model, bidirectional case-crossover analysis matched by period, and case-crossover analysis matched by the confounding factor, i.e., average temperature or pollutant concentration. The graphical representation of the response surface, generated by the interaction term between these factors added to the Poisson regression model, was interpreted to evaluate the synergistic effect of the risk factors.RESULTSNo differences were observed between the results of the case-crossover and time-series analyses. The percentage change in the relative risk of cardiovascular and respiratory mortality was 0.85% (0.45;1.25) and 1.60% (0.74;2.46), respectively, due to an increase of 10 μg/m3 in the PM10 concentration. The pattern of correlation of the temperature with cardiovascular mortality was U-shaped and that with respiratory mortality was J-shaped, indicating an increased relative risk at high temperatures. The values for the interaction term indicated a higher relative risk for cardiovascular and respiratory mortalities at low temperatures and high temperatures, respectively, when the pollution levels reached approximately 60 μg/m3.CONCLUSIONSThe positive association standardized in the Poisson regression model for pollutant concentration is not confounded by temperature, and the effect of temperature is not confounded by the pollutant levels in the time-series analysis. The simultaneous exposure to different levels of environmental factors can create synergistic effects that are as disturbing as those caused by extreme concentrations.

Synergistic effects of temperature, diet and colony size on the competitive ability of two ant species

AbstractMultiple biotic and abiotic factors influence species coexistence and co‐occurrence patterns. In a competitive environment, for example, temperature and diet variation may modify both foraging behaviour and aggression, thereby changing competitive interactions and species co‐occurrence patterns. In New Zealand, two endemic ant species (Prolasius advenus and Monomorium antarcticum) often form allopatric distributions; though also periodically do co‐occur in the same habitat. Here, we performed a long‐term laboratory experiment in an attempt to understand how diet, colony size and environmental conditions may influence these co‐occurrence patterns. The consequences of temperature and diet variation differed between P. advenus and M. antarcticum. Colonies of P. advenus exhibited increased aggression and foraging activities at higher temperatures. In addition, P. advenus colonies augmented their foraging activities when deprived of a carbohydrate‐rich food source. Conversely, small M. antarcticum colonies exhibited higher aggression than when in large colonies, and increased their foraging activities at lower temperatures. The modulation of aggression and foraging behaviour may influence the likelihood of small P. advenus and M. antarcticum colonies persisting in the long term. Our results are compatible with the hypothesis that the environment is likely to be a strong filter for the negative co‐occurrence patterns we observe between P. advenus and M. antarcticum in New Zealand. Furthermore, this study provides a mechanistic explanation for potential impacts of climate warming on community structure. Environmental modification of aggression and foraging behaviour could potentially alter competitive interactions and influence community assembly.

Effects of temperature on intraspecific competition in ectotherms.

Understanding how temperature influences population regulation through its effects on intraspecific competition is an important question for which there is currently little theory or data. Here we develop a theoretical framework for elucidating temperature effects on competition that integrates mechanistic descriptions of life-history trait responses to temperature with population models that realistically capture the variable developmental delays that characterize ectotherm life cycles. This framework yields testable comparative predictions about how intraspecific competition affects reproduction, development, and mortality under alternative hypotheses about the temperature dependence of competition. The key finding is that ectotherm population regulation in seasonal environments depends crucially on the mechanisms by which temperature affects competition. When competition is strongest at temperatures optimal for reproduction, effects of temperature and competition act antagonistically, leading to more complex dynamics than when competition is temperature independent. When the strength of competition increases with temperature past the optimal temperature for reproduction, effects of temperature and competition act synergistically, leading to dynamics qualitatively similar to those when competition is temperature independent. Paradoxically, antagonistic effects yield a higher population floor despite greater fluctuations. These findings have important implications for predicting effects of climate warming on population regulation. Synergistic effects of temperature and competition can predispose populations to stochastic extinction by lowering minimum population sizes, while antagonistic effects can increase the potential for population outbreaks through greater fluctuations in abundance.

The antagonistic and synergistic effects of temperature during solar disinfection of synthetic secondary effluent

A 4-factor, multilevel, full factorial design of 240 experiments was performed in order to investigate the effect of temperature on the inactivation efficiency of spiked Escherichia coli in simulated solar disinfection of a synthetic secondary effluent. The initial population of the microorganisms was 103, 104, 105 and 106 CFU/mL, the exposure time 1, 2, 3 and 4 h, the treatment temperature 20, 30, 40, 50 and 60 °C and the sunlight intensity 0, 800 and 1200 W/m2. Radical changes in bacterial behavior, process efficiency and remaining populations were observed, while treating effluents in discreet temperatures. Elevating treatment temperature from 20 to 40 °C drastically impaired disinfection. Thermal inactivation with no regrowth predominated at 50 °C and total inactivation of microorganisms was observed at 60 °C in non-irradiated samples. Irradiation at 800 and 1200 W/m2 much increased inactivation efficiency, especially at 50 and 60 °C, proving sensitive light-temperature synergy at those temperatures. Total inactivation was achieved within 4 h under a range of treatment conditions, including all samples at 1200 W/m2, or 60 °C samples at 800 W/m2. Also, 99.9–100% efficiencies and final population below 1000 CFU/100 mL were obtained at 800 W/m2 and temperatures of 50 °C and above. Treatment time, temperature and intensity are the critical parameters for the disinfection process, while initial population is insignificant for removal efficiency. An explanation of the mechanism of the process as well as a general linear model predicting the outcome of the experiments is also suggested.

Telomeric attrition with age and temperature in Eastern mosquitofish (Gambusia holbrooki)

Telomeric attrition has repeatedly been found to correlate with the ageing of organisms; however, recent research is increasingly showing that the determinants of attrition dynamics are not well understood. This study examined the relative telomere lengths in Eastern mosquitofish, Gambusia holbrooki, kept at different temperatures and at different ages. Newly born fry were randomly selected for one of four treatment groups: 20, 30, 20-30, and 30-20 °C, where the third and fourth treatment groups were gradually changed from their starting temperature to their final temperature between days 10 and 14. Telomere length was measured, and it was found that length decreased with age and that fish exposed to the 20 °C treatment had significantly shorter telomeres than those that received the 30-20 °C treatment. Telomeric attrition with age agrees with results previously found in studies of telomeres; however, the variation in attrition with temperature was not simply predictable and may be the synergistic effects of temperature and some other factor.

Synergy in the effects of temperature and air pollution on mortality in 8 European cities. Results from the PHASE project.

Background: Numerous studies have associated excess heat or cold with increased mortality. Air pollution, especially particulate matter and ozone also deteriorate human health. Their joint effects, though, are less well studied and understood. Aim: Within the PHASE project, we used data from 8 European cities (Athens, Barcelona, Budapest, Helsinki, Paris, Rome, Stockholm and Valencia) to investigate possible synergistic effects of temperature and air pollution on mortality. Methods: City-specific Poisson regression models controlling for seasonality and other confounders were used separately for summer (April-September) and winter (October-March). Maximum apparent temperature was the exposure variable in summer, while minimum was used in winter. Based on previous results, threshold terms for summer and linear temperature terms for winter were used. Interaction terms between temperature and pollution variables were included in the models to investigate synergy on all cause, cardiovascular and respiratory mortality, in all ages and by age group. Results: Initial results provide evidence for synergy in several participating cities. For example, significant positive interaction between high temperature and PM10 was found in Athens and Paris, concerning both total and cardiovascular mortality in all ages. In Athens, significant synergy was also detected between high temperature and ozone on cardiovascular mortality in all ages. In Paris and Stockholm, a significant positive interaction between high temperature and ozone was found on total mortality in all ages. Conclusions: There is evidence for higher impact on mortality on days with both high temperature and high ozone or PM10 concentration, although this was not consistent across all cities. These findings should have implications on policy-making in Europe.

Factors driving the biogeographic distribution of two temperate Australian damselfishes and ramifications for range shifts

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 484:189-202 (2013) - DOI: https://doi.org/10.3354/meps10300 Factors driving the biogeographic distribution of two temperate Australian damselfishes and ramifications for range shifts Ronen Galaiduk1,*, Will F. Figueira1,2, Michael J. Kingsford3, Belinda G. Curley2 1School of Biological Sciences, Marine Ecology Laboratories, A11, University of Sydney, New South Wales 2006, Australia 2Sydney Institute of Marine Science, Building 22, Chowder Bay Road, Mosman, New South Wales 2088, Australia 3School of Marine and Tropical Biology and ARC Centre of Excellence for Coral Reef Studies, James Cook University, Queensland 4811, Australia *Email: rgal2782@uni.sydney.edu.au ABSTRACT: The distribution and abundance of marine organisms is determined by interactions among numerous abiotic and biotic factors that operate across multiple spatial scales. This study focused on 2 endemic temperate damselfishes Parma microlepis and P. unifasciata, which have a similar ecology but only partially overlapping (~3° of latitude) biogeographical and depth ranges. The synergistic effects of temperature, competition and habitat use on patterns of abundance, distribution and growth were investigated using a combination of mensurative and manipulative field and laboratory experiments. Evidence suggests that the current ranges of both species are driven largely by latitudinal and depth variations in habitat types and not by thermal regimes. P. microlepis was shown to be a slower-growing, long-lived species (to 37 yr) that appears to be specialised in using urchin-grazed barrens. In contrast, P. unifasciata is a shorter-lived species (to 12 yr) and more of a habitat generalist. Where the ranges of these 2 species overlap, competitive interactions appear to drive patterns of habitat use, with P. microlepis potentially excluding P. unifasciata from urchin-grazed barrens habitat. Mesocosm laboratory experiments indicated that the outcome of competitive interactions between these 2 species is temperature-dependent, with P. microlepis dominance increasing at higher temperatures. This study clarifies the important role of habitat in determining latitudinal ranges of these 2 species. It also highlights the need to consider temperature-dependent behavioural interactions to properly understand future potential shifts in species ranges that may result from global climate change. KEY WORDS: Damselfishes · Parma microlepis · Parma unifasciata · Biological distribution · Range expansion · Global warming Full text in pdf format PreviousNextCite this article as: Galaiduk R, Figueira WF, Kingsford MJ, Curley BG (2013) Factors driving the biogeographic distribution of two temperate Australian damselfishes and ramifications for range shifts. Mar Ecol Prog Ser 484:189-202. https://doi.org/10.3354/meps10300 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 484. Online publication date: June 12, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Mutual stimulation of temperature and light effects on C 4 phosphoenolpyruvate carboxylase in leaf discs and leaves of Amaranthus hypochondriacus

This article reports marked modulation of the activity and regulatory properties of phosphoenolpyruvate carboxylase (PEPC) by temperature and light in leaf discs as well as leaves of Amaranthus hypochondriacus. The activity of PEPC increased by 1.7-fold at 45 degrees C over 25 degrees C. Warm temperature also stimulated the photoactivation of PEPC. The activation by light of PEPC was 1.9-fold at 25 degrees C and increased to 2.2-fold at 45 degrees C. The sensitivity of PEPC to its inhibitor malate was less and the activation by glucose-6-phosphate (G-6-P) or inorganic phosphate (Pi) was more at 45 degrees C than that at 25 degrees C. These effects of temperature were quite pronounced in light. Similar responses were observed when detached leaves were exposed to varying ambient temperature (dry heat). The activity of PEPC increased by 1.6-fold at 45 degrees C over 25 degrees C in the dark. The activation of PEPC by light was 2.1-fold at 25 degrees C and increased to 2.6-fold at 45 degrees C. Inhibition by malate was less and activation by G-6-P or Pi was more at 45 degrees C than that at 25 degrees C. Thus, there was a marked modulation of not only the activity but also the regulatory properties of the enzyme by temperature and light, independently as well as cooperatively with each other. Further experiments suggested that PEPC was able to memorize to a significant extent the changes induced by warm temperature and that these changes were complemented by subsequent illumination. These effects were not due to changes in PEPC protein levels. We conclude that temperature and light can modulate PEPC activity and regulatory properties not only individually but also in a significantly cooperative manner with each other. As significant increases in temperature are common during daytime in tropical or subtropical conditions, we suggest that the synergistic effects of temperature and light are quite relevant in optimizing the activity of PEPC in leaves of C(4) plants.