Performance of Chlorella sorokiniana under simulated extreme winter conditions

High annual microalgae productivities can only be achieved if solar light is efficiently used through the different seasons. During winter the productivity is low because of the light and temperature conditions. The productivity and photosynthetic efficiency of Chlorella sorokiniana were assessed under the worst-case scenario found during winter time in Huelva, south of Spain. The maximum light intensity (800?μmol photons m^-2 s^-1) and temperature (20°C) during winter were simulated in a lab-scale photobioreactor with a short light-path of 14?mm. Chemostat conditions were applied and the results were compared with a temperature-controlled situation at 38°C (optimal growth temperature for C. sorokiniana). When temperature was optimal the highest productivity was found at a dilution rate of 0.18 h^-1 (P _v?=?0.28?g Kg^-1 h^-1), and the biomass yield on light energy was high (Y _x,E?=?1.2?g?mol^-1 photons supplied). However, at suboptimal temperature, the specific growth rate of C. sorokiniana was surprisingly low, not being able to support continuous operation at a dilution rate higher than 0.02 h^-1. The slow metabolism under suboptimal temperature resulted in a decline of the light energy requirements of the cells. Consequently, the maximum winter irradiance was experienced as excessive, leading to a low photosynthetic efficiency and productivity (Y _x,E?=?0.5?g mol^-1 photons supplied, P _v?=?0.1?g Kg^-1 h^-1). At suboptimal temperature a higher carotenoid-to-chlorophyll ratio was observed indicating the activation of light-dissipating processes. We conclude that temperature control and/or light dilution during winter time will enhance the productivity.     

Survival types of high mountain plants under extreme temperatures

Extreme temperatures are a main factor limiting plant growth in high mountain habitats. During winter, the risk of frost damage is highest at windblown and often snow-free sites. During summer, actively growing plants are particularly endangered by episodic cold spells, but also by short-term overheating. The current review gives an overview of extreme temperatures in the European Alps and observations of temperature damage on plants in their natural habitats. Furthermore, seasonal time courses of frost and heat resistance derived from laboratory tests on different plant growth forms are presented. Study species were the cushion plants Silene acaulis, Minuartia sedoides, Saxifraga oppositifolia and Carex firma collected on wind-exposed ridges; the rosette plant Soldanella alpina collected on snow-protected sites, and three Sempervivum species collected in xerothermic habitats.     

Reproduction of rock pigeon exposed to extreme ambient temperatures

1. The breeding biology of rock pigeon (Columba livia) exposed to ambient temperatures (Ta) between 50 and 60 degrees C was investigated. 2. Four families accomplished three complete life cycles after long term daily exposure to extreme Ta, with about 100% success. 3. The steady state temperatures in the nest were 60, 58, 53 and 44.6 degrees C in the air, substrate surface, underwing, and in the egg's microenvironment, respectively. 4. At thermal conditions between 30 and 60 degrees C, egg temperature (Tegg) was regulated between 36.8 +/- 0.8 (S.D.) and 41.7 +/- 0.4 (S.D.). Tegg increases by 0.163 degrees C/1 degree C rise in Ta. 5. Mean Tb of the nonincubating parent exposed to 30-60 degrees C is 41.6 +/- 0.6 degrees C (S.D.). Under the same conditions the incubating parent regulated a significantly (P less than 0.01) lower Tb (38.8 degrees C) at 45 degrees C Ta and about 1 degree C lower Tb at 30 and 60 degrees C Ta, respectively. 6. By comparing the differences between fast (5 min) cooling of hot egg (44.8 degrees C) to slow heating (60-90 min), we could demonstrate the high sensitivity of the incubating parent to the danger of embryo overheating. 7. The significance of the adaptive behavioral and physiological mechanisms in breeding under extreme thermal conditions are discussed.     

Demographic effects of extreme winter weather in the barn owl

Extreme weather events can lead to immediate catastrophic mortality. Due to their rare occurrence, however, the long-term impacts of such events for ecological processes are unclear. We examined the effect of extreme winters on barn owl (Tyto alba) survival and reproduction in Switzerland over a 68-year period (∼20 generations). This long-term data set allowed us to compare events that occurred only once in several decades to more frequent events. Winter harshness explained 17 and 49% of the variance in juvenile and adult survival, respectively, and the two harshest winters were associated with major population crashes caused by simultaneous low juvenile and adult survival. These two winters increased the correlation between juvenile and adult survival from 0.63 to 0.69. Overall, survival decreased non-linearly with increasing winter harshness in adults, and linearly in juveniles. In contrast, brood size was not related to the harshness of the preceding winter. Our results thus reveal complex interactions between climate and demography. The relationship between weather and survival observed during regular years is likely to underestimate the importance of climate variation for population dynamics.     

Rattlesnake denning: theoretical considerations on winter temperatures

Aggregations of over-wintering rattlesnakes are considered as a hypothetical metabolic unit. Estimates of fat consumption are utilized to predict heat production during the denning season. Previously determined temperature heat production curves allow prediction of a mean body temperature for the winter season which is around 15°C above the ambient den site temperature. An estimate from the previously derived relationship between heat production per unit surface area and body temperature predicts a reduction in aggregate effective surface area of 40 % of the summed surface areas of the individual animals constituting the hypothetical aggregation.     

Response of microbial communities of Lake Baikal to extreme temperatures

The survival rate, metabolic activity, and ability for growth of microbial communities of Lake Baikal after exposure to extremely low temperatures (freeze-thawing) for different lengths of time have been first studied. It has been shown that short-term freezing (1-3 days) inhibits the growth and activity of microbial communities. The quantity of microorganisms increased after 7- and 15-day freezing. In the periods of maximums, the total number of microorganisms in the test samples was twice as high as in the control. It was established that after more prolonged freezing the microorganisms required more time after thawing to adapt to new conditions. In the variants with 7- and 15-day freezing, the activities of defrosted microbial communities were three or more times higher than in the control. The survival rate and activity of Baikal microorganisms after freeze-thawing confirms the fact that the Baikal microbial communities are highly resistant to this type of stress impact.     

Response of microbial communities of Lake Baikal to extreme temperatures

The survival rate, metabolic activity, and ability for growth of microbial communities of Lake Baikal have been first studied after exposure to extremely low temperatures (freeze-thawing) for different lengths of time. It has been shown that short-term freezing (1–3 days) inhibits the growth and activity of microbial communities. The quantity of microorganisms increased after 7-and 15-day freezing. In the periods of maximums, the total number of microorganisms in the test samples was twice as high as in the control. It was established that after more prolonged freezing the microorganisms required more time after thawing to adapt to new conditions. In the variants with 7-and 15-day freezing, the activities of defrosted microbial communities were three or more times higher than in the control. The survival rate and activity of Baikal microorganisms after freeze-thawing confirms the fact that the Baikal microbial communities are highly resistant to this type of stress impact.     

Determination of unfrozen water in winter cereals at subfreezing temperatures

The freezing of water in acclimated and nonacclimated cereals was studied using pulsed nuclear magnetic resonance spectroscopy. The quantity of unfreezable water per unit dry matter was not strongly dependent on the degree of cold acclimation. In contrast, the fraction of water frozen which was tolerated by nonacclimated winter cereals and by an acclimated spring wheat (Triticum aestivum L.) was less than in acclimated hardy cereals. The freezing curves had the following form:L_T = L₀ΔTm/T + KL_T and L₀ are liquid water per unit dry matter at T and 0 C, respectively. ΔTm is the melting point depression and K is the liquid water which does not freeze.     

Sex reversal of the newt Triturus cristatus reared at extreme temperatures

Crested newt larvae were reared at defined temperatures, either from uncleaved eggs or from early feeding larvae, until metamorphosis when sexual differentiation had occurred. Trials at 18-24 degrees C showed a 1:1 sex ratio. A higher temperature trial produced more males than females, including some XX neomales. Lower temperatures resulted in a significant excess of females, including XY neofemales. Sex reversal only occurred in about half the possible cases on average. Extreme temperatures must perturb the normal XX/XY system of sex determination, to reveal either an ancestral ZZ/ZW system or a still more primitive environmental control. It is suggested that neofemales (but not neomales) could occur in nature.     

The association of extreme temperatures and the incidence of tuberculosis in Japan

Seasonal variation in the incidence of tuberculosis (TB) has been widely assumed. However, few studies have investigated the association between extreme temperatures and the incidence of TB. We collected data on cases of TB and mean temperature in Fukuoka, Japan for 2008–2012 and used time-series analyses to assess the possible relationship of extreme temperatures with TB incident cases, adjusting for seasonal and interannual variation. Our analysis revealed that the occurrence of extreme heat temperature events resulted in a significant increase in the number of TB cases (relative risk (RR) 1.20, 95 % confidence interval (CI) 1.01–1.43). We also found that the occurrence of extreme cold temperature events resulted in a significant increase in the number of TB cases (RR 1.23, 95 % CI 1.05–1.45). Sex and age did not modify the effect of either heat or cold extremes. Our study provides quantitative evidence that the number of TB cases increased significantly with extreme heat and cold temperatures. The results may help public health officials predict extreme temperature-related TB incidence and prepare for the implementation of preventive public health interventions.     

Habitat microclimates drive fine‐scale variation in extreme temperatures

Most multicellular terrestrial organisms experience climate at scales of millimetres to metres, yet most species‐climate associations are analysed at resolutions of kilometres or more. Because individuals experience heterogeneous microclimates in the landscape, species sometimes survive where the average background climate appears unsuitable, and equally may be eliminated from sites within apparently suitable grid cells where microclimatic extremes are intolerable. Local vegetation structure and topography can be important determinants of fine‐resolution microclimate, but a literature search revealed that the vast majority of bioclimate studies do not include fine‐scale habitat information, let alone a representation of how habitat affects microclimate. In this paper, we show that habitat type (grassland, heathland, deciduous woodland) is a major modifier of the temperature extremes experienced by organisms. We recorded differences among these habitats of more than 5°C in monthly temperature maxima and minima, and of 10°C in thermal range, on a par with the level of warming expected for extreme future climate change scenarios. Comparable differences were found in relation to variation in local topography (slope and aspect). Hence, we argue that the microclimatic effects of habitat and topography must be included in studies if we are to obtain sufficiently detailed projections of the ecological impacts of climate change to develop detailed adaptation strategies for the conservation of biodiversity.     

Functional adaptations of the bacterial chaperone trigger factor to extreme environmental temperatures

Trigger factor (TF) is the first molecular chaperone interacting cotranslationally with virtually all nascent polypeptides synthesized by the ribosome in bacteria. Thermal adaptation of chaperone function was investigated in TFs from the Antarctic psychrophile Pseudoalteromonas haloplanktis, the mesophile Escherichia coli and the hyperthermophile Thermotoga maritima. This series covers nearly all temperatures encountered by bacteria. Although structurally homologous, these TFs display strikingly distinct properties that are related to the bacterial environmental temperature. The hyperthermophilic TF strongly binds model proteins during their folding and protects them from heat‐induced misfolding and aggregation. It decreases the folding rate and counteracts the fast folding rate imposed by high temperature. It also functions as a carrier of partially folded proteins for delivery to downstream chaperones ensuring final maturation. By contrast, the psychrophilic TF displays weak chaperone activities, showing that these functions are less important in cold conditions because protein folding, misfolding and aggregation are slowed down at low temperature. It efficiently catalyses prolyl isomerization at low temperature as a result of its increased cellular concentration rather than from an improved activity. Some chaperone properties of the mesophilic TF possibly reflect its function as a cold shock protein in E. coli.     

Impact of extreme and fluctuating temperatures on aphid–parasitoid dynamics

Climate change is predicted to increase the occurrence of extreme temperature events. We constructed a stage‐structured Leslie matrix model with intra‐generational dynamics to explore the impact of extreme and fluctuating temperatures on host–parasitoid dynamics. We varied three temperature parameters to generate a range of temperature regimes that varied in their daily maximum temperatures, the number of warmer‐than‐average days and the autocorrelation of those warmer‐than‐average days. All three temperature parameters influenced host–parasitoid dynamics. Increasing the frequency of warmer than average days and the degree of autocorrelation only exerted significant impacts on host– parasitoid dynamics when daily maximum temperatures were sufficient to produce temperature‐dependent mortality. The effects of increasing autocorrelation of daily temperatures were dependent on the maximum daily temperatures and the frequency of warmer than average days. When daily maximum temperatures were severely warm, but the frequency of those severely warm days was low, increasing autocorrelation increased the probability that the aphids and parasitoids will persist, but when the frequency of severely warm days is increased, increasing autocorrelation decreases the probability that the populations will persist. These temperature phenomena exert significant effects on host–parasitoid dynamics in addition to those effects produced by changes in mean temperatures and warrant further investigation at the community level.     

Differential sensitivity of planktonic trophic levels to extreme summer temperatures in boreal lakes

The stress–size hypothesis predicts that smaller organisms will be less sensitive to stress. Consequently, climate warming is expected to favour smaller taxa from lower trophic levels and smaller individuals within populations. To test these hypotheses, we surveyed zooplankton communities in 20 boreal lakes in Killarney Provincial Park, Canada during 2005 (an anomalously warm summer) and 2006 (a normal summer). Higher trophic levels had larger responses to warm temperatures supporting the stress–size hypothesis; however, rather than imposing negative effects, higher density and biomass were observed under warmer temperatures. As a result, larger taxa from higher trophic levels were disproportionately favoured with warming, precluding an expected shift towards smaller species. Proportionately greater increases in metabolic rates of larger organisms or altered biotic interactions (e.g. predation and competition) are possible explanations for shifts in biomass distribution. Warmer temperatures also favoured smaller individuals of the two most common species, in agreement with the stress–size hypothesis. Despite this, these populations had higher biomass in the warm summer. Therefore, reduced adult survivorship may have triggered these species to invest in reproduction over growth. Hence, warmer epilimnions, higher zooplankton biomass and smaller individuals within zooplankton populations may function as sensitive indicators of climate warming in boreal lakes.     

Effect of catholyte in culture media on cell growth at extreme temperatures]

The growth of Escherichia coli cells in media whose properties were changed by the action of direct current in the cathode compartment of a diaphragm electrolyzer was studied. For this purpose, the growth medium was preliminarily treated using different method of medium preparation under different treatment conditions. The biological activity of medium was estimated by measuring the effect of these solutions on cell growth. Cells were cultivated under extremal temperature conditions, 20 degrees C and 42 degrees C (optimal temperature 37 degrees C). It was shown that at low temperatures, the cell growth considerably increases as compared to control. At elevated temperatures, the acceleration of cell death occurred, whereas in the control the deceleration of cell growth and partial cell death were observed.     

Peripheral nerve at extreme low temperatures 2: Pharmacologic modulation of temperature effects

Changes in temperature have profound and clinically important effects on the peripheral nerve. In a previous paper, the effects of temperature on many properties of the peripheral nerve action potential (NAP) were explored including the NAP amplitude, conduction velocity and response to paired pulse stimulation. In this paper, the effects of pharmacologic manipulations on these parameters were explored in order to further understand the mechanisms of these effects.The reduction in conduction velocity with temperature was shown to be independent of the ionic composition of the perfusate and was unaffected by potassium or sodium channel blockade. This implies that the phenomenon of reduced conduction velocities at low temperature may be related to changes in the passive properties of the axon with temperature. Blockade of sodium channels and chronic membrane depolarization produced by high perfusate potassium concentrations or high dose 4-aminopyridine impair the resistance of the nerve to hypothermia and enhance the injury to the nerve produced by cycles of cooling and rewarming. This suggests the possibility that changes in the sodium inactivation channel may be responsible for the changes in the NAP amplitude with temperature and that prolonged sodium inactivation may lead more permanent changes in excitability.     

The effect of extreme temperatures and starvation on the body proportions of the rat

The effects of extremely cold and hot environments on body proportions of rats were studied. These effects included changes in the length of the tail, trunk, extremities, cranio-facial and nasal dimensions, in bone robusticity and bone shape, in the size of the ear and in some characteristics of the skin and hair. Since animals in both extreme temperatures fail to gain normal body weight, all changes were also studied in a group of starving rats. Because of the lower body weight and its concomitant reduction of body measurements, absolute values were avoided for analysis and all parameters were related to neurocranial length and trunk length. Such a triple experimental approach (response to cold, heat, and starvation) combined with a two-fold frame of reference (neurocranial length and trunk length), as well as statistical corrections for body weight loss, made it possible to differentiate between nutrition-specific and temperature-specific responses under conditions of extreme temperature exposure. Moreover, some attention was given to endocrine pathways involved in some morphological changes. The methodological advantages of a multi-experimental approach over a single-experimental technique were demonstrated.     

A system for studying the effects of naturally-occurring subzero temperatures on winter barley

Thermostatically-controlled, electrical soil heating cables were used to examine the effects of subzero temperatures on winter barley growing in plots outdoors. Plants in plots without heating cables were exposed to naturally-occurring subzero temperatures (unheated), while those in corresponding plots with the cables (heated) were protected from such temperatures. Measurements of soil, plant and air temperatures in heated and unheated plots showed that the system can, at least with the temperatures encountered during the measurement periods, prevent plant temperature from falling below the temperature set on the thermostat. A field experiment involving different cultivars and sowing dates showed that subzero temperatures experienced did not significantly affect individual plant grain yield or the number of fertile ears produced per plant. However, small, but statistically significant, effects of naturally-occurring subzero temperatures were found in relation to the number of grains per ear, thousand grain weight and harvest index. The nature of these effects varied, and were dependent upon cultivar and/or sowing date. Subzero temperatures were also responsible for reducing the numbers of established plants in late-sown plots through soil heaving. Possible uses of the soil heating cable system for temperature-related studies in the Gramineae are discussed.