Varying Temperature Regimes Research Articles

Reconstructing Century-long Snow Regimes Using Estimates of High Arctic Salix arctica Radial Growth

Using a combination of microscopic examination and electronic scanning and printing, we analyzed the impacts of early spring snow cover extent and temperature during the growing season on the annual radial growth in arctic willow (Salix arctica Pallas) in the Zackenberg valley, High Arctic Northeast Greenland. So far, only little dendroclimatological research has been conducted on Salix arctica, and the species constitutes a yet-untapped resource for climate reconstruction in the Arctic. We obtained reliable annual radial growth measurements from a total of 43 Salix arctica stem samples and analyzed these in a mixed model to determine the limiting climatic factors. We found that early spring snow cover extent impacted the annual growth significantly, whereas variable temperature regimes seemed unimportant. Following the building of a site chronology for the Zackenberg valley, the early spring snow cover extent during the last century was reconstructed.

Effects of constant and varying temperatures on the development of blue swimmer crab ( Portunus pelagicus) larvae: Laboratory observations and field predictions for temperate coastal waters

Temperature is widely held to be a critical factor for the development of marine invertebrate larvae. We investigated three specific aspects of this relationship for the blue swimmer crab, Portunus pelagicus, in a temperate gulf: (1) the effects of different but temporally constant temperatures on the survival and developmental period of larvae reared in the laboratory, (2) the effects of varying temperatures on the survival and developmental period of larvae reared in the laboratory, and (3) prediction of larval developmental periods under seasonal temperature changes found in the field. Temperature had a marked effect on larval survival. At constant temperatures of 22.5 and 25 °C larval survival was far greater than at lower temperatures down to 17 °C, and developmental period of the larval period was inversely related to (constant) temperature. However, larvae in temperate coastal waters will usually be exposed to seasonally varying, rather than constant, temperatures. To account for this, a larval developmental period model was created and then verified in the laboratory by rearing larvae under varying temperatures. Results of this work demonstrated that developmental periods were markedly different under constant versus varying temperature regimes. Using different temperature simulations for a temperate gulf (Gulf St Vincent, South Australia), the developmental period model predicted that in years of ‘average’ seasonal temperature changes, total larval developmental period could range from 26 to 45 days depending on the day of hatching. In such cases, peak postlarval settlement was predicted to occur between mid January and mid March. Results from this study also predict that larval survival (and thus postlarval settlement) will be maximised in years with abnormally warm summers. Whilst the developmental period model was used to make predictions of developmental period for P. pelagicus in a temperate gulf, it could readily be adapted to predict developmental periods in other coastal environments.

In situ electrochemical-NMR spectroscopy. Reduction of aromatic halides.

A three-electrode, two-compartment cylindrical electrochemical cell has been constructed for in situ operation in a 500 MHz 1H NMR spectrometer. The cell was designed around a standard 10-mm sample tube holder and is lowered into position within the magnet by height-adjustable aluminum rods that support the wires connecting the potentiostat to the working, auxiliary and reference electrodes. The electrochemical cell functions under diffusion-controlled conditions in nonspinning mode and is able to operate under variable temperature and oxygen-free regimes. The working electrode consists of a 10-nm-thick gold film deposited onto the surface of a 7.49-mm-o.d. glass NMR tube that is located directly within the radio frequency coils of the NMR probe. The NMR spectra were collected simultaneously to the current flowing during the electrolysis with typical NMR line widths being approximately 2 Hz. The highly symmetrical nature of the cell design meant that probe tuning and gradient shimming changed minimally between experiments, which allowed standard shim sets to be saved and recalled for later use, thereby greatly reducing the time taken for tuning processes. Insertion and removal of the cell from within the magnet is achieved within a few seconds, which combined with the rapid shimming process makes the cell suitable for routine operation. The cell was used to study the in situ reduction of 9-bromoanthracene, 9-chloroanthracene, and 4-bromobenzophenone in deuterated acetonitrile with tetrabutylammonium hexafluorophosphate as the supporting electrolyte.

The effects of thermal scarification and seed storage on germination of four heathland species

The germination responses of 4 shrubs, Erica arborea, E. australis and Daboecia cantabrica (Ericaceae) and Genistella tridentata (Papilloneaceae) in relation to variable light and temperature regimes was determined for freshly harvested and 1 year-old seeds. Temperature treatments consisted of 5 levels of heat from 60 °C to 140 °C and two levels of exposure time, 2 and 4 min. We also examined the effects of stratification on germination of Erica arborea and E. australis. The seeds of Erica arborea were the first to begin germinating and the freshly collected ones reached the highest level of germination with light. The seed viability of E. arborea was affected by storage, decreasing germinative capacity, while mean germination in Erica australis ssp. aragonensis was lowest. However, the stored E. australis seeds germinated better than the fresh ones. Germination response to ageing varies in Daboecia cantabrica depending on heat pretreatment. A significantly positive effect of high temperature and exposure time on germination was shown in Daboecia cantabrica and Genistella tridentata. Cold pre-treatment of seeds did not enhance germination.

Seasonal photosynthetic temperature responses and changes in δ13C under varying temperature regimes in leaf-succulent and drought-deciduous shrubs from the Succulent Karoo

Temperatures in the Succulent Karoo, South Africa, are predicted to increase by 1–3°C over the next 50 years. Four species from the semi-arid Succulent Karoo were grown under differing temperature regimes in order to determine their photosynthetic acclimation potential, using gas exchange and carbon stable isotope composition (δ 13 C) techniques. Three species are evergreen leaf succulent shrubs ( Zygophyllum prismatocarpum E. Mey. ex. Sond., Stoeberia utilis (L. Bolus) Van Jaarsveld and Ruschia spinosa (L.) Dehn), and one species is a drought-deciduous shrub ( Tripteris sinuata (DC.) [previously Osteospermum sinuatum (DC.) Norl.]). Plants were not subjected to water stress, and thus operated in the C 3 photosynthetic mode. It was predicted that the photosynthetic temperature optima (Topt) and the δ 13 C values would increase with an increase in growth temperature (treatment) and seasonal temperature regimes in the evergreen, but not in the drought-deciduous species. However, both growth forms showed photosynthetic acclimation {increasing Topt) in response to increasing temperature. δ 13 C also increased with increasing temperature in all species, indicating improved intrinsic water use efficiency. It is unlikely that photosynthetic capacity of these shrubs will be negatively impacted by increasing temperatures alone and their responses to climate change may depend more on simultaneous changes in water supply.

Temperature, growth and seasonal succession of phytoplankton in Lake Baikal, Siberia

1. Growth rates of two dominant Lake Baikal phytoplankton, the winter diatom Aulacoseira baicalensis and the summer cyanobacterium Synechocystis limnetica, were measured in the laboratory under varied temperature and light regimes to determine the potential role of these abiotic factors in seasonal species succession in the lake. 2. Aulacoseira baicalensis grew best at low temperature and not at all above 8 °C. Its maximum instantaneous growth rate was 0.15 d -1 recorded at 2-3 °C. Cells grew faster as temperature decreased, apparently in contrast to conventional Q 10 -based temperature-growth relationships. 3. The picoplankter Synechocystis limnetica did not grow at 2-3 or 5-6 °C, but grew at a rate of 0.24 d -1 at the highest incubation temperature of 17 °C. Maximum growth rate was 0.35 d -1 at 8 °C. 4. Saturation irradiances (I k ) for growth of Aulacoseira baicalensis and Synechocystis limnetica were near pre-acclimation values of 40 μmol m -2 s -1 . At temperatures conducive to growth, both phytoplankters grew at all irradiances tested, except for A. baicalensis which would not grow at values above 300 μmol m -2 s -1 at 8 °C. 5. We conclude that temperature is a major driving force for the seasonal succession of species in Lake Baikal. Other factors, including vertical mixing of the water column and grazing by zooplankton, may also play important roles.

Biogeography and microhabitat variation in temperate algal‐invertebrate symbioses: zooxanthellae and zoochlorellae in two Pacific intertidal sea anemones, Anthopleura elegantissima and A. xanthogrammica

Abstract. Temperate sea anemones in the genus Anthopleura are unique among cnidarians in harboring two phylogenetically distinct symbiotic algae, zooxanthellae (golden‐brown dinophytes, Symbiodinium) and zoochlorellae (green chlorophytes). To determine whether their physiological differences generate patterns in anemone habitat and biogeographic distribution, we sampled symbiotic algae in the small clonal A. elegantissima and the large solitary A. xanthogrammica at 8 field sites (and the other large solitary Anthopleura species at one site) spanning 18° of latitude along 2500 km of the Pacific coast of North America. We found that zoochlorellae predominate in low intertidal habitats and northerly latitudes and in A. xanthogrammica, while zooxanthellae constitute the majority of symbionts in high intertidal habitats and more southerly latitudes and in A. elegantissima. These data are consistent with published predictions based on photosynthetic efficiency of the two algae under varied temperature and light regimes in the laboratory. This anemone‐algal system provides a potential biological signal of benthic intertidal communities' responses to El Niño events and long‐term climate changes in the Pacific.

Predicting germination response of four cool-season range grasses to field-variable temperature regimes

Germination of non-dormant seeds under variable-temperature conditions can be predicted from constant-temperature germination data if it is assumed that instantaneous germination rate is independent of thermal history. Thermal-response models of this type have not been validated under simulated field-variable temperature conditions that vary in diurnal pattern, diurnal range and longer-term trends in mean–daily temperature. The purpose of this experiment was to evaluate germination response of thickspike wheatgrass ( Elymus lanceolatus), bluebunch wheatgrass ( Pseudoroegneria spicata), Sandberg bluegrass ( Poa sandbergii) and bottlebrush squirreltail ( Elymus elymoides) under both constant and field-variable temperature regimes in the laboratory. It was hypothesized that the thermal history assumption was valid and that constant-temperature data could be used to accurately estimate field-variable temperature response. Seeds were germinated at seven constant temperatures between 5 and 35°C, and under 18 variable-temperature regimes simulating six planting dates at three field sites. Predictions of germination time under variable-temperature conditions were accurate to within a fraction of 1 day up to a cumulative germination percentage of 70% for thickspike wheatgrass, 60% for bluebunch wheatgrass, 55% for Sandberg bluegrass and 70% for bottlebrush squirreltail. It was concluded that, for the variable-temperature regimes tested in this experiment, the thermal-history assumption was valid for earlier-germinating subpopulations.

Predicting high-frequency upwelling: Spatial and temporal patterns of temperature anomalies on a Florida coral reef

High-frequency measurements reveal a rapidly changing, highly variable temperature regime on the slope of Conch Reef, a coral reef in the upper Florida Keys, USA. Water temperatures 1 m above the reef were measured at 20 min intervals at 21 and 33 m depths from 1992 through 1997, for all of 1992 at 7 m depth and 1997 at 10 m. While the annual variation in dailyaveraged temperatures was approximately 10°C in most years (Winter lows near 20°C to Summer highs near 30°C), temperature fluctuations as large as 6 to 10°C were recorded within individual days. Temperature variation is concentrated at semi-diurnal internal tidal frequencies, with a variety of mechanisms including internal tides, internal tidal bores, and cold water intrusions most likely related to variability of the Florida Current influencing high-frequency upwelling at this site. An analysis of extreme values in the long-term temperature records is used to predict return times for cold water upwelling events at depths of 7, 21, and 33 m. This analysis provides quantitative, seasonal estimates for among-depth differences in the extent of cool water pulsing. Return times for cooling events are shorter in May through September than in October through April, and decrease markedly with increasing depth on the reef slope. In Summer, the predicted median return times for a -3°C temperature anomaly are 136, 14, and 7 days at 7, 21, and 33 m depths, respectively. Predictable physical forcing arising from upwelling of cool water may be an important source of externally derived nutrients and suspended particles for this coral reef. The methods and results presented here should be applicable to a range of studies of temperature variation and nutrient dynamics in the Florida Keys and other regions.

Sensitivity of the meiofaunal copepod Tisbe longicornis to K2Cr2O7 under varying temperature regimes.

Sensitivity of the meiofaunal copepod Tisbe longicornis to K2Cr2O7 under varying temperature regimes.

Measuring the Sensitivity of an Indirect Predator Gut Content ELISA: Detectability of Prey Remains in Relation to Predator Species, Temperature, Time, and Meal Size

The gut contents of three species of insect predators that were fed either a variable or a fixed number of pink bollworm eggs but held at variable time and temperature regimes were assayed by an indirect enzyme-linked immunosorbent assay (ELISA). The sensitivity and efficacy of the monoclonal antibody-based ELISA was dependent on the predator species examined. Small predators were more immunoresponsive to the ELISA than large predators. Furthermore, the assay sensitivity was dependent on the number of prey consumed, elapsed time after feeding, and temperature at which the predators were held. The smaller predator species retained recognizable traces of prey remains for longer periods than larger predator species. The ELISA efficacy decreased with increasing ambient temperature. A series of regression equations have been developed to estimate the median detection interval of prey in a predator's gut that takes into account the predator species examined, the quantity of prey consumed, and ambient after-meal temperature.

Effect of short-term temperature and shading on fruit-set, seed and berry development in model vines of V. vinifera, cvs Chardonnay and Shiraz

Small Chardonnay and Shiraz vines were grown under controlled environment conditions at 25/20°C and 400 μE/(m2.s) radiant energy. These conditions were interrupted for some plants for one week, at two periods near flowering, by imposing reduced temperatures (17°/14°C or 12°/9°C) and shading (8, 40 or 72% light reduction), in factorial combinations. Fruit‐set was reduced by exposure to the lower temperature regime in both cultivars (confirming the results of a previous experiment) and tended also to decrease with increasing intensity of shading. Seed characteristics were examined only in Chardonnay where total number of seeds per berry was not affected by any of the treatments. However, pre‐flowering exposure to 12°/9°C resulted in fewer berries with one or two sinker seeds and more berries with floater seeds and, overall, in a greater proportions of seeds being floaters. Shading had little effect on seed development. Berries on vines exposed to 12°/9°C, at both stages of development, had lower pericarp and seed weights compared with those treated with 17°/14°C or 25°/20°C. At harvest, pericarp weight and seed weight per berry were positively correlated; the linear regression for berries exposed to the higher temperature regimes had a significantly steeper slope than that for berries exposed to the lowest temperature regime. It is concluded that differences in pericarp weight were due to differing cell numbers. These differences may have developed firstly in the ovary due to a direct effect of exposure to varying temperature regimes, and secondly in the developing berry after fruit‐set because of variation in the stimulatory activity of the seeds, caused by residual effects of pre‐flowering temperature conditions on ovule and seed development.

Partitioning of chloride ion in the germinating seed of two forage legumes under varied salinity and temperature regimes

Abstract Laboratory studies were conducted to investigate the partitioning of chloride (Cl) ions in the germinating seed of two forage legumes, Sesbania (Sesbania sesban) and Snail Medic (Medicago scutellata), under varied salinities and temperatures. Seeds were placed in Petri dishes containing 20 mL of saline solutions of varied electrical conductivities (0.01, 6.4, 12.2, 17.4, 22.6, 27.2, and 32.1 d/Sm) prepared with sodium chloride (NaCl). The germination temperatures were 10, 20, 30, and 40°C. Germination counts were taken every two days for eight days and the result was used to calculate germination rate index. On Day 8, seeds were separated into seed coat, cotyledon, and embryo, and analyzed separately for Cl. Generally, Cl concentration increased in the different seed components with increase in salinity and temperature. High Cl accumulation in the embryo was associated with germination failure. However, apart from the toxic effect of high embryo Cl content, high temperatures may also have a direc...

Fruit-set on small Chardonnay and Shiraz vines grown under varying temperature regimes between budburst and flowering

Small Chardonnay and Shiraz vines were grown under controlled conditions at 25°/20°C day/night temperatures but transferred for one week to 17°/14°C or 12°/9°C at four stages of growth between budburst and flowering. In Chardonnay, half the vines were given supplementary pollination with pollen produced under favourable conditions. Per cent fruit‐set and berry number per bunch of Chardonnay were reduced by about one third to one half by 12°/9°C, applied just before and at the early stage of flowering. At these stages, and with this low‐temperature treatment, supplementary pollination had significant positive effects. Total seed number per berry was not affected by treatment, but the proportion of hollow seeds increased in the treatments which suffered reduced set. This resulted in a positive relation between the number of functional seeds per berry and the number of berries per bunch. In Shiraz, the differences between the various treatment means were small and mostly not significant. It is concluded that the reduction in fruit‐set of Chardonnay due to cool temperatures near flowering is due to detrimental effects on both pollen and ovules.

Influence of Temperature Variations on Rate of Development in Insects: Analysis of Case Studies from Entomological Literature

Case studies on development-time data collected at constant and varying temperatures in a number of insects have been analyzed in a comparative manner to investigate the effects of temperature variations on rate of development. Sources of experimental errors are many and are not always adequately controlled. For statistical analysis, the more common problems include the assumption of a linear relationship between temperature and development rate over the whole temperature range and extrapolation or subjective vertical cutoff of the rate function in rate summation for varying temperatures. Development-time data of 26 species were selected for the analysis. For each species, the expected development time under each varying temperature regime was estimated by integrating constant temperature development rates over the 24-h varying temperature cycle. These estimates were then compared with the development times observed under the corresponding varying temperature regimes, and the significance of the differences was evaluated. The results as a whole suggest that the differences in development times between constant and varying temperatures could usually be accounted for by the effect of rate summation based on the curvilinear relationship between temperature and rate of development. The possible physiological mechanisms that act in addition to the rate-summation effect are briefly discussed. Finally, the need for more extensive and detailed investigations in this area of study is indicated.

Variable versus constant temperature acclimation regimes: Effects on hemoglobin isomorph profile in goldfish,Carassius auratus

Goldfish,Carassius auratus, were acclimated for 2 to 3.5 weeks to three temperature regimes: [1] temporally-constant (10, 20 and 30°C), [2] diurnally-cycling (20 ± 10°C) and [3] randomly-fluctuating (± 2°C at approximately 2h intervals between extremes of 10 and 30°C). No significant differences in hematocrit were evident. Hemoglobin levels in fish at constant 30°C and under randomly fluctuating temperature were significantly elevated. Of the three hemoglobin isomorphs observed, the two minor components (G1, G3) tended to decrease in relative abundance with increase in constant temperature, but increased under varying temperature regimes. The converse was true of the principal hemoglobin, G2. Extent of isomorph variation was correlated with extent of temperature variability. These observations confirm that temperature variability significantly effects thermoacclimatory response. The functional significance of changes in isomorph abundances during the acclimatory process is considered.

EVOLUTIONARY ADAPTATION TO TEMPERATURE. III. ADAPTATION OF ESCHERICHIA COLI TO A TEMPORALLY VARYING ENVIRONMENT.

Six lines of the bacterium Escherichia coli were propagated for 2,000 generations in a temporally varying environment. The imposed environmental regime consisted of alternating days at 32°C and 42°C, with rapid transitions between them. These derived lines are competitively superior to their ancestor in this variable temperature regime. We also measured changes in the fitness of these lines, relative to their common ancestor, in both the constant (32°C and 42°C) and transition (from 32°C to 42°C and from 42°C to 32°C) components of this temporally varying environment, to determine whether the bacteria had adapted to the particular constant temperatures or the transitions between them, or both. The experimentally evolved lines had significantly improved fitness in each of the constant environmental components (32°C and 42°C). However, the experimental lines had not improved in making the sudden temperature transitions that were a potentially important aspect of the temporally variable environment. In fact, fitness in making at least one of the transitions (between 32°C and 42°C) unexpectedly decreased. This reduced adaptation to the abrupt transitions between these temperatures is probably a pleiotropic effect of mutations that were responsible for the increased fitness at the component temperatures. Among the six experimental lines, significant heterogeneity occurred in their adaptation to the constant and transition components of the variable environment.

First Step in European Corn Borer (Lepidoptera: Pyralidae) Diapause Mechanistic Modeling: Wing Disks Development Model

Taking into account the limits of previous models proposed to predict European corn borer, Ostrinia nubilalis (Hubner) infestation time, complementary research in physiology, population dynamic, and modeling was used to propose a mechanistic model to describe this phenomenon. Diapause is the main process that determines infestation time in this pest. Recent work on diapause has demonstrated the heterogeneity of this development phase. This model describes the first phase of the diapause process, wing disk development. The model proposed consists of two parts; the first component takes into account the influence of temperature as a nonlinear function and the second (normal distributions) represents the variability in development time among a population for each stage. This model has been estimated by maximum likelihood from laboratory data obtained with a destructive sampling under three variable sinusoidal temperature regimes 9–21, 12–34, and 18–42°C with a photoperiod of 12:12 (L:D) hallowing diapause induction. This unique model describes the development under these different temperature ranges with a 2% precision (0.5 d) and has been validated under field conditions. The development of populations ending their development before winter is correctly represented (10% precision). The model is not adapted to describe the population ending their development after winter. The estimated model correctly predicts diapause development for temperatures above 4°C. This report presents novel data in modeling research and demontrates a convincing correlation between laboratory and field collected data.

Temperature-Dependent Growth Model for Eggs and Larvae of Cephalcia arvensis (Hymenoptera: Pamphiliidae)

The sawfly, Cephalcia arvensis Panzer, is a pest of the Norway spruce (Picea abies Karst.) and has caused large outbreaks in Europe. The variability in the diapause length and the adaptability of the immature stages to a wide range of temperatures makes it difficult to predict the attacks and the phenology. In this paper, the effects of variable temperature regimes on both embryonic and larval development are studied in a natural environment. The experimental conditions covered the whole temperature range of the areas colonized by the pest. Several models were considered and their estimation were performed using the DEVAR software program applied to natural fluctuating temperatures. Before the application of DEVAR, its predictive power was tested using hypothetical data sets. The program was able to find parameter values leading to an excellent model fit. Four models were validated using data from three generations of natural populations of the pest. All models gave a good prediction for both embryos and larvae in all the years considered. The model can be usefully applied in population dynamics and in timing the application of both insecticides and entomopathogenic nematodes against the pest.

Phenotypic plasticity and genetic variability in annual Zizania spp. along a latitudinal gradient

Bulk seed collections were made from six populations of Zizania spp. (two Z. palustris and four Z. aquatica) along the Atlantic seaboard from northern New Brunswick, Canada, to southern Georgia, U.S.A. Ten plants per population were cultivated in each of two greenhouse chambers differing in temperature, and 20 – 80 seedlings from each population were assayed for 14 isozyme loci. Mean values for a suite of phenological and morphometric traits showed clinal variation in association with the latitudinal gradient. Magnitudes and patterns of plasticity for the same traits did not show clinal variation in response to varying temperature regimes but were different in the two species. Plants from Z. palustris populations responded to elevated temperatures by delaying flowering, increasing stem size, and decreasing proportional reproductive effort; Z. aquatica populations were generally much less sensitive to the temperature differential, but where responses were observed they were typically opposite to those described for Z. palustris. The species were also differentiated by allelic composition of the populations. There was no systematic relationship between degree of heterozygosity at isozyme loci and magnitudes of plasticity for morphometric traits. There was no evidence for the coordinated divergence of Zizania populations for trait means and magnitudes and patterns of plasticity. It is suggested that ecological differences, possibly characteristic differences in intensity and consistency of competitive pressure, may account for the contrasting patterns of plasticity in Z. palustris and Z. aquatica. Key words: Zizania, phenotypic plasticity, latitude, genetic variability.