Rate Of Temperature Decline Research Articles

Study on the Thermal and Dielectric Properties of SrTiO3/Epoxy Nanocomposites

SrTiO3/epoxy nanocomposites are prepared using the facile solution-processing technique by incorporating SrTiO3 nanoparticles with different weight fractions into the epoxy resin host. The morphology of the nanoparticles and composites, as well as the thermal conduction characteristics and electrical properties of the composites were investigated via conventional testing methods. The thermal conductivity increased along with the SrTiO3 weight fractions, and the thermal conductivity of the SrTiO3/epoxy composite with 40 wt % weight fraction increased to 0.52 W/mK. The dielectric constant increased along with the weight fractions and decreased along with frequency, thereby suggesting that the interfacial and dipole polarization do not follow the changes in the electrical field direction at high frequency. The dielectric constants at 1 kHz frequency increased along with temperature. Surface breakdown tests illustrated further improvements in the thermal and electrical properties of the composites. In the same time span of 40 s, the 40 wt % nanocomposite demonstrated a rapid temperature decline rate of 6.77 °C/s, which was 47% faster than that of the pure epoxy sample. The surface breakdown voltage also increased along with the weight fractions. The functional composites can solve the key problem in the intelligentization, miniaturization, and high-efficiency of the gas-insulated switchgear, which warrants further research.

Ondansetron and promethazine have differential effects on hypothermic responses to LiCl administration and to provocative motion in rats

We have recently reported that provocative motion (rotation in a home cage) causes hypothermic responses in rats (1), similar to hypothermic responses induced by motion sickness in humans. Since in rats many chemical emetic stimuli also provoke hypothermia, we hypothesized that a fall in body temperature may reflect a “nausea-like” state in these animals. As rats do not possess an emetic reflex, we now employed a pharmacological approach to test this hypothesis. It is well known that in humans nausea during motion sickness and chemically-induced nausea have differential sensitivity to anti-emetics. We thus tested whether hypothermia induced in rats by provocative motion (rotation at 0.7 Hz) and by the emetic LiCl (10 mg/kg i.p. at 0.15 M) have similar differential sensitivity. Both provocations caused comparable robust falls in core body temperature (−1.9 ± 0.3 °C and −2.0 ± 0.2 °C for chemical and motion provocations, respectively). LiCl-induced hypothermia was completely prevented by ondansetron (a 5-HT3 receptor antagonist that reduces chemotherapy-induced nausea), but was entirely insensitive to promethazine (a histamine-H1 receptor antagonist that is commonly used to treat motion sickness). Conversely, motion-induced hypothermia was unaffected by ondansetron but promethazine reduced the rate of temperature decline from 0.20 ± 0.02 to 0.11 ± 0.03 °C/min (p < 0.05) with a trend to decrease the magnitude. We conclude that this differential pharmacological sensitivity of the hypothermic responses of vestibular vs. chemical etiology in rats mirrors observations in humans, and thus supports the idea that a “nausea-like” state in rodents is associated with disturbances in thermoregulation.

Ondansetron and promethazine have differential effects on hypothermic responses to lithium chloride administration and to provocative motion in rats

We recently reported that provocative motion (rotation in a home cage) causes hypothermic responses in rats, similar to the hypothermic responses associated with motion sickness in humans. Many stimuli inducing emesis in species with an emetic reflex also provoke hypothermia in the rat, therefore we hypothesized that a fall in body temperature may reflect a “nausea-like” state in these animals. As rats do not possess an emetic reflex, we employed a pharmacological approach to test this hypothesis. In humans, motion- and chemically-induced nausea have differential sensitivity to anti-emetics. We thus tested whether the hypothermia induced in rats by provocative motion (rotation at 0.7 Hz) and by the emetic LiCl (63 mg/kg i.p.) have a similar differential pharmacological sensitivity. Both provocations caused a comparable robust fall in core body temperature (−1.9 ± 0.3°C and −2.0 ± 0.2°C for chemical and motion provocations, respectively). LiCl−induced hypothermia was completely prevented by ondansetron (2mg/kg, i.p., a 5-HT3 receptor antagonist that reduces cancer chemotherapy-induced nausea and vomiting), but was insensitive to promethazine (10 mg/kg, i.p., a predominantly histamine-H1 and muscarinic receptor antagonist that is commonly used to treat motion sickness). Conversely, motion-induced hypothermia was unaffected by ondansetron but promethazine reduced the rate of temperature decline from 0.20 ± 0.02 to 0.11 ± 0.03°C/min (P < 0.05) with a trend to decrease the magnitude. We conclude that this differential pharmacological sensitivity of the hypothermic responses of vestibular vs. chemical etiology in rats mirrors the observations in other pre-clinical models and humans, and thus supports the idea that a “nausea-like” state in rodents is associated with disturbances in thermoregulation.

Influence of rapid chilling on biochemical parameters governing the water‐holding capacity of pork longissimus dorsi

SummaryThe aim of this study was to investigate the effects of rapid chilling (RC) of carcasses on the quality of pork longissimus dorsi (LD) compared to conventional chilling (CC). Carcasses subjected to RC were chilled at −20 °C for 1.5 h and then moved to 4 °C until 24 h post‐mortem, while carcasses that were CC were placed directly in a chill at 4 °C for 24 h post‐mortem. RC accelerated the rates of temperature decline post‐mortem (P &lt; 0.01) and increased pH values at 1.5 and 8 h post‐mortem (P &lt; 0.05). RC could significantly decrease the denaturation of myosin and sarcoplasmic proteins during post‐mortem ageing. Samples of RC had a significant lower purge loss compared to CC group during post‐mortem ageing (P &lt; 0.05). Our study implies that RC could influence the biochemical changes of pork LD which may further regulate water‐holding capacity during post‐mortem ageing.

Effects of forage silage species on yearling growth performance, carcass and meat quality, and nutrient composition in a forage based beef production system

Berthiaume, R., Lafrenière, C., Girard, C., Campbell, C. P., Pivotto, L. M. and Mandell, I. B. 2015. Effects of forage silage species on yearling growth performance, carcass and meat quality, and nutrient composition in a forage based beef production system. Can. J. Anim. Sci. 95: 173–187. Forty weaned, crossbred beef calves (predominantly Angus and Simmental) were forage-finished using all-silage diets (red clover–timothy versus tall fescue) to examine forage species’ effects on growth performance, carcass traits, meat quality, and nutrient composition. Weaned calves (257 d of age) were forage-finished using red clover–timothy or tall fescue silage and harvested at approximately 1 yr of age. During carcass processing, one side from each carcass was covered with a polyliner to examine if reducing rates of chilling could compensate for limited fat cover expected from low dietary energy contents fed, and limited time on feed. Longissimus thoracis, semimembranosus, and semitendinosus steaks were aged 10, 14, and 21 d to examine effects on Warner–Bratzler shear force values while fatty acid and vitamin B12 composition were determined on 10-d-aged steaks. Average daily gain, feed efficiency, hot carcass weights, and longissimus muscle area were greater (P&lt;0.03) when cattle were fed red clover–timothy versus tall fescue silage, most likely due to the higher protein content of red clover–timothy silage. Shear force was greater (P&lt;0.002) in steaks from all muscles evaluated from cattle fed tall fescue versus red clover–timothy silage. In comparison to 10-d-aged steaks, 14 d of ageing were needed to reduce (P&lt;0.001) shear force for longissimus steaks, while 21 d of ageing were needed to reduce (P&lt;0.001) shear force for semitendinosus steaks. Use of a polyliner decreased (P=0.0001) the rate of temperature decline at selected carcass sites, but did not reduce shear force values. The percent of n-3 fatty acids and polyunsaturated fatty acid/saturated fatty acid ratio were greater (P&lt;0.04) in longissimus from cattle fed red clover–timothy versus feeding tall fescue silage. Feeding red clover–timothy silage improved growth performance, carcass, shear force, and fatty acid composition traits versus feeding tall fescue silage.

Burning characteristics of low-cost safety charcoal briquettes made from wood residues and soil for domestic use

Handmade charcoal briquettes made from harvesting residues and soil were tested for their burning characteristics. The soil was added as a fire retarder to decrease the maximum burning temperature and temperature decline rate. In this way the danger of fire to the surroundings is minimized and the potential usefulness, e.g. for cooking purposes, is maximized. Briquettes with different coal to soil ratios were made and tested for energy, ash and volatile content, as well as burning characteristics, such as maximum temperature, coal temperature, the time required to reach those temperatures and the temperature decline rate. Clear correlations between soil content and most of these properties could be found. For example, a higher soil content clearly resulted in lower maximum temperatures, a longer burning time and a slower temperature decline, which makes this type of charcoal briquettes a suitable fuel for domestic purposes.

Optimisation of temperature observational well selection

In wellbore climatology the method of temperature inversion to determine the trends in ground surface temperature history (GSTH) assumes that the process of a well’s thermal recovery is practically completed. However, for deep wells (>100–300 m) the drilling process, due to the lengthy period of drilling fluid circulation, greatly alters the temperature of formation immediately surrounding the well. As a result, the determination of the formation temperature (with a specified absolute accuracy) at any depth requires a lengthy period of shut-in time. The objective of this study is to determine how long it takes before the error caused by mud circulation is small compared to the change arising from the change in surface temperature. In this paper we suggest two techniques, Slider’s method and utilisation of the γ-function, which enable us to estimate the rate of temperature decline and the difference between the formation and shut-in temperatures.

Evaluating juvenile thermal tolerance as a constraint on adult range of gray snapper (Lutjanus griseus): A combined laboratory, field and modeling approach

Climate change is expected to cause a poleward shift of many temperate species, however, a mechanistic understanding of how temperature and species' life histories interact to produce observed adult range is often lacking. We evaluated the hypothesis that juvenile thermal tolerance determines northern range in gray snapper (Lutjanus griseus), a species commonly caught as juveniles along the US Atlantic coast well north of their adult distribution, using a combined laboratory, field and modeling approach. The cumulative degree days below 17°C (CDD<17) survived by individuals maintained in the laboratory under ambient seasonal cooling conditions were used to quantify the chronic effects of prolonged but non-lethal low temperatures. Under ambient conditions, juveniles stopped feeding below 11.3°C, and the mean temperature at death was 10.2°C (+/−0.74S.D.). The CDD<17 endured by individuals ranged from 61.9 to 138.8 (83.54+/−22.44S.D.), and was positively related to fish size. The relation between CDD<17 and fish size was extrapolated to the maximum juvenile size in fall to provide an upper limit for survival in the wild (CDD<17=210days). Acute low temperature tolerance was evaluated in a second experiment that exposed juveniles to a constant rate of temperature decline (3°Cd−1), where feeding ceased at 10.3°C and death occurred at 7.0°C (+/−0.45S.D.). These thermal thresholds were combined with winter estuarine temperature data at 12 sites to evaluate potential overwinter survival along the US Atlantic coast. Of a total of 134 site-year combinations categorized based on the acute and chronic thresholds, the CDD<17 threshold (>210days) was more limiting than the acute threshold (minimum daily temperature<7.0°C) to survival of juveniles for a given site-year. To evaluate the relationship between juvenile thermal tolerance criteria and adult distributions, we quantified adult distribution using field observations in the western Atlantic Ocean compiled from a database of recreational divers. There was a strong correspondence between observations of adult gray snapper from the database of recreational divers vs. latitude with that of the predicted survival of juveniles vs. latitude from our analysis. The agreement between the laboratory-derived thermal tolerance metrics, the spatial distribution of winter temperature, and the distribution of adult gray snapper support the hypothesis that the adult range of gray snapper is largely limited by the overwinter survival of juveniles. Understanding the interaction between physiology and range is important for forecasting the impacts of climate change on other species of fish where juvenile tolerances are critical in determining range, particularly in seasonal systems.

Critical Thermal Minima of age‐0 Australian bass, Macquaria novemaculeata, fingerlings: implications for stocking programmes

Abstract Fishes are often stocked outside natural distribution ranges with inadequate information on target streams, particularly thermal regimes. Australian bass, Macquaria novemaculeata (Steindachner), is a catadromous species that is regularly stocked into upland reaches of rivers and impoundments in south‐eastern Australia. Critical Thermal Minima (CTMin) were determined for age‐0 Australian bass fingerlings with a mean fork length of 64.4 ± 0.4 mm and weighing 3.8 ± 0.8 g. Four treatments were used, including three replicate aquaria for each treatment. Fingerlings were acclimated at either 8 or 15 °C at densities of 15 fish in 56‐L glass aquaria. Water temperatures were then decreased at either 1 °C day−1 or 1 °C h−1 until loss of equilibrium (LOE), which occurred between 3 and 7 °C. Mean CTMin among treatments was 3.22–4.64 °C and was influenced by acclimation temperature and rate of temperature decline. Fingerlings acclimated at 8 °C subjected to a temperature decline of 1 °C h−1 experienced highest LOE temperature. Post‐LOE mortality among treatments was highest at 100% in the 8 °C acclimation with a 1 °C day−1 temperature decline. Mortalities following LOE occurred within 5 days. The results suggest that stocking age‐0 Australian bass is unlikely to be successful in areas where winter temperatures fall below 6 °C.

Rapid chilling has no detrimental effect on the tenderness of low-voltage electrically stimulated M. longissimus in Chinese bulls

This study investigated the effect of pre-rigor rapid chilling (RC) on the rate of pH and temperature decline, shear force values and ultrastructure of M. longissimus from beef carcasses exposed to electrical stimulation (ES). Chinese bull carcasses were electrically stimulated, and the alternate sides of the carcasses either were chilled conventionally (CC, 0–4°C, air speed 0.5m/s for 24h) or they underwent RC (−14±1°C, air speed 3m/s for 2h and then cooled under CC conditions until 24h post-mortem). The results showed that RC increased the rate of temperature decline (P<0.05) and decreased the rate of pH decline (P<0.05). There were no significant differences in the shear force value and sarcomere length of M. longissimus between the two treatments (P>0.05). The results of this study indicate that RC has no detrimental impact on the tenderness of beef carcasses exposed to ES.

Thermal tolerance experiments help establish survival probabilities for tilapia, a group of potentially invasive aquatic species

Summary1. Estimating the probability of establishment is an important step toward managing ecological risk posed by natural or intentional introductions. Species introductions in certain geographic areas may pose less of a threat when environmental conditions are unlikely to promote long‐term establishment. Species commonly referred to as ‘tilapia’ have become widespread in certain areas of the southeastern United States, yet concerns remain regarding their potential spread to other areas.2. We created a model to predict the survival of tilapia in Georgia (U.S.A.) based on individual ‘thermal experience’. Laboratory experiments were conducted to measure the duration of survival of two strains of tilapia, Oreochromis nilotica and O. nilotica × O. aureus hybrids, exposed to a variety of temperature regimes with three minimum temperatures and two rates of temperature decline.3. We used Mayfield hierarchical logistic regression (MHLR) to describe the daily probability of survival as a function of the rate of temperature decline, average sustained temperature, tilapia strain and mass–length ratio.4. Tilapia generally survived constant minimum temperatures over 12 °C but survival rate was mediated by the rate of decline, mass–length ratio and strain. For every 1 °C increase in minimum temperature, tilapia were 2.76 times more likely to survive. Fish exposed to rapid temperature decline were less likely to survive than those exposed to slowly decreasing temperature. More robust fish (higher mass–length ratio) were more likely to survive, and strain had a minimal effect despite being supported by the best MHLR model.5. Our model can be used to estimate survival probability for tilapia under known surface water temperature regimes. Using MLHR in conjunction with experimental tolerance data may be useful for estimating the likelihood of establishment of potentially invasive species.

Biocontained Mortality Compost Using Liquid Manure

During disease outbreaks, composting has been used to safely dispose of carcasses and infectious solid manure. However, optimized methods have not been established to use liquid manure (> 80% water content, WC) from dairies as the substrate for mortality composting. In April of 2007, a 3×2 factorial study was conducted in wooden compost bins (240 × 240 × 140 cm) lined with 0.5 mm plastic to a height of 50 cm. Three levels (LO, 95 kg; MED, 236 kg; HI, 606 kg wet wt.) of liquid manure (91% WC) were applied to barley straw containing a single calf mortality (avg. wt 130 kg). Compost temperature and carcass degradation were evaluated in each bin over 52 d. As an indication of compost efficiency, viability of 4 types of weed seeds (wild buckwheat, Polygonium convolvulus L, BW; dandelion, Taraxacum officinale, DL; stinkweed, Thlaspi arvense L., SW; and wild oat, Avena fatua, WO) was determined from seeds retained at the laboratory (Control) or from those placed in sealed nylon bags (50 μm pore size) embedded at 3 locations in each bin. Initial C: N ratios ranged from 58:1 (HI) to 68:1 (LO), while initial WC was 64, 52 and 42% for the HI, MED and LO treatments, respectively. Rate of compost heating and peak temperature (58.6 vs. 46.5°C) was increased (P < 0.05) for HI as compared to LO. Rate of temperature decline was lower (P < 0.05) and calf decomposition was visibly superior for HI as compared to LO. Viability of WO was eliminated by all compost treatments, but that of BW increased (P < 0.05) in MED and LO as compared to Control. Although HI did not eliminate BW viability, this treatment showed the the most promise for incorporating liquid manure as a substrate in contained mortality compost.

Crystallization of binary carboxylic acids characterized with streaming potential measurement

AbstractThe streaming potential of supersaturated solution of binary carboxylic acids, which have even carbon atoms, was determined to characterize crystallization under different temperatures. The value of the streaming potential was related to the type and solubility of the acids and the starting temperature of crystallization, and was easily influenced by the pressure difference of the liquid or the rate of temperature decline. When the temperature was declined to the point where a crystal nucleus appeared, the streaming potential reached the minimum. Thereafter, as the temperature was sequentially lowered, some minicrystals grew, and the streaming potential presented an ascendant tendency. The higher the starting temperature of the acids saturated solution, the higher is the temperature corresponding to the streaming potential minimum. The less the carbon atoms in the acids and the greater the solubility of the acids are, the higher is the temperature of the streaming potential minimum. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Comparison of cooling methods to induce and maintain normo- and hypothermia in intensive care unit patients: a prospective intervention study

BackgroundTemperature management is used with increased frequency as a tool to mitigate neurological injury. Although frequently used, little is known about the optimal cooling methods for inducing and maintaining controlled normo- and hypothermia in the intensive care unit (ICU). In this study we compared the efficacy of several commercially available cooling devices for temperature management in ICU patients with various types of neurological injury.MethodsFifty adult ICU patients with an indication for controlled mild hypothermia or strict normothermia were prospectively enrolled. Ten patients in each group were assigned in consecutive order to conventional cooling (that is, rapid infusion of 30 ml/kg cold fluids, ice and/or coldpacks), cooling with water circulating blankets, air circulating blankets, water circulating gel-coated pads and an intravascular heat exchange system. In all patients the speed of cooling (expressed as°C/h) was measured. After the target temperature was reached, we measured the percentage of time the patient's temperature was 0.2°C below or above the target range. Rates of temperature decline over time were analyzed with one-way analysis of variance. Differences between groups were analyzed with one-way analysis of variance, with Bonferroni correction for multiple comparisons. A p < 0.05 was considered statistically significant.ResultsTemperature decline was significantly higher with the water-circulating blankets (1.33 ± 0.63°C/h), gel-pads (1.04 ± 0.14°C/h) and intravascular cooling (1.46 ± 0.42°C/h) compared to conventional cooling (0.31 ± 0.23°C/h) and the air-circulating blankets (0.18 ± 0.2°C/h) (p < 0.01). After the target temperature was reached, the intravascular cooling device was 11.2 ± 18.7% of the time out of range, which was significantly less compared to all other methods.ConclusionCooling with water-circulating blankets, gel-pads and intravascular cooling is more efficient compared to conventional cooling and air-circulating blankets. The intravascular cooling system is most reliable to maintain a stable temperature.

The influence of the rate of pH decline on the rate of ageing for pork. II: Interaction with chilling temperature

The influence of the rate of pH decline post slaughter on the rate of ageing of pork m. longissimus thoracis et lomborum was investigated. The rate of pH decline on 24 finisher pigs was manipulated by altering the method of stunning (carbon dioxide or electrical head to heart) and by the use of electrical stimulation (none or low voltage electrical stimulation (LVES) at 4 min post slaughter for either 15 s or 60 s). The rate of temperature decline was altered by chilling at 2 or 14 °C until rigor. The pH and temperature decline rates generated were designed to induce cold shortening at one extreme and protein denaturation at the other. The research results showed that the rate of pH decline was increased by electrical stimulation which in turn reduced cold shortening and improved tenderness. Chilling at 14 °C reduced the time to reach rigor by 1.3 h and resulted in a faster aging rate as indicated by a larger percentage change in WBSF from rigor to 4 days postmortem relative to carcases chilled at 2 °C. The greater tenderising effect appeared to be due to a combination of prevention of cold shortening and increased proteolysis. However, chilling slowly at 14 °C or the use of LVES for 60 s or any combination of these treatments did not induce protein denaturation.

Low-Temperature Tolerance of Age-0 Atlantic Croakers: Recruitment Implications for U.S. Mid-Atlantic Estuaries

Age-0 Atlantic croakers Micropogonias undulatus overwinter in Mid-Atlantic Bight (MAB) estuaries, where interannual variability in year-class strength is pronounced. Previous researchers have hypothesized that this variability is the result of cold-induced winter mortality of age-0 Atlantic croakers within estuarine nurseries. We tested this hypothesis by means of laboratory experiments designed to (1) estimate the effects of winter severity and duration on the probability of survival of age-0 fish, (2) determine the relationship between body size and cold tolerance, and (3) examine the effects of temperature decline rate and salinity on susceptibility to low-temperature mortality. Age-0 Atlantic croakers (15–65 mm standard length, SL) were collected from Delaware Bay during October, acclimated to 8°C in the laboratory, and then cooled (1.0°C/d) to treatment levels of 1, 3, 5, or 7°C that were designed to simulate varying levels of winter severity in MAB estuaries. Survival ranged from 0% at 1°C to 99.3% at 7°C, increasing dramatically between 3°C (1.3%) and 5°C (86.8%). Cold tolerance was size dependent, with smaller individuals surviving significantly longer than larger ones. The rate of temperature decline (1.0°C/d versus 0.2°C/d) did not affect survival at lower winter temperatures. Atlantic croakers remained intolerant of temperatures of 3°C or less even when these temperatures were approached gradually. Cold tolerance increased with increasing salinity, implying that the risk of overwinter mortality varies spatially along an estuarine salinity gradient. The mean survival duration at 3°C increased from 5.9 d at 2‰ to 14.7 d at 10‰ and to 17.1 d at 26‰. Our findings provide empirical support for the hypothesis that cold-induced overwinter mortality regulates the year-class strength and recruitment success of Atlantic croakers in the Mid-Atlantic Bight.

Control of post mortem pH decrease in pig muscles: experimental design and testing of animal models

From a series of experiments aimed at manipulating and relating the resting levels of glycogen and creatine phosphate (CP) in the live muscle four models were selected to induce different rates and extents of pH decrease post mortem in pig muscle. Model A served as the control, animals being slaughtered under minimal stress, in model B animals were subjected to 10 min treadmill exercise at 3.8 km/h immediately prior to stunning, in model C, animals were given 0.2 mg adrenaline/kg live weight 16 h prior to slaughter, and in model D they were given 0.3 mg adrenaline/kg live weight 16 h before slaughter and subjected to 5 min of treadmill exercise immediately before stunning. After slaughter, the decline in pH and temperature post mortem was recorded in M. longissimus dorsi (LD), M. biceps femoris (BF), M. semimembranosus (SM) and M. psoas major (PM) from 1 min to 24 h after bleeding. Significant differences in ultimate pH and the time course of pH decrease were observed, both as an effect of model as well as type of muscle. No differences in ultimate pH between model A and model B were observed in any of the muscles. Ultimate pH in the C and the D models were significantly higher than in A and B. In the B model lower pH values were observed from 1 min to 6 h post bleeding compared to the other three models. No differences in rate of pH decrease were observed between the A and the B models in any of the muscles. Within the A model no differences in ultimate pH between muscles were seen, indicating that the frequently observed differences in ultimate pH are caused by environmental factors rather than by differences in physiological and morphological characteristics. The exercise bouts caused elevated temperatures during the first hour after bleeding (model B and D). The BF muscle in all the models displayed the fastest rate of pH decrease and SM the slowest; a slower rate of temperature decline occurred in the BF than in the SM.

Direct effect of elevated CO(2) on nocturnal in situ leaf respiration in nine temperate deciduous tree species is small.

Direct (i.e., short-term) effects of elevated CO(2) on nocturnal in situ leaf respiration rate were measured in nine deciduous tree species (seven genera) in 20 3.5-4.0-h experiments. During the experiments, CO(2) concentration was alternated between 400 and 800 ppm (approximately 40 and 80 Pa of CO(2)). Data analysis accounted for effects on respiration rate of the normal decline in temperature with time after sunset. The median response to a 40-Pa increase in CO(2) was a 1.5% decrease in respiration rate, with responses ranging from a 5.6% inhibition to a 0.4% stimulation. Direct effects of elevated CO(2) on respiration were similar among the species. Thus, the response of nocturnal leaf respiration rate to a short-term CO(2) increase was small, and of little practical importance to the accuracy of measurements of respiration involving similar changes in CO(2) concentration during measurement. These direct respiratory responses of leaves to elevated CO(2) would translate into only slight, if any, effects on the carbon balance of temperate deciduous forests in a future atmosphere containing as much as 80 Pa CO(2).

Effects of the thermal environment on the temporal pattern of emergence of hatchling loggerhead turtles Caretta caretta

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 189:251-261 (1999) - doi:10.3354/meps189251 Effects of the thermal environment on the temporal pattern of emergence of hatchling loggerhead turtles Caretta caretta Kathleen L. Moran*, Karen A. Bjorndal, Alan B. Bolten Archie Carr Center for Sea Turtle Research and Department of Zoology, University of Florida, PO Box 118525, Gainesville, Florida 32611, USA *E-mail: kmoran@zoo.ufl.edu ABSTRACT: Sea turtles deposit their eggs in beaches at a depth of about 50 cm and leave them to incubate for approximately 60 d. After that time, hatchlings emerge from the sand at night, both to avoid predation and to prevent overheating. Three hypotheses have been proposed regarding the thermal cues involved in emergence. Hatchlings emerge (1) after sand temperature falls below a critical threshold, (2) after a negative thermal gradient in the sand above the nest has been created, making upper sand cooler than sand below, or (3) in response to a rapid decrease in the temperature of the nest column. This study evaluated the cue(s) that loggerhead sea turtle Caretta caretta hatchlings use to emerge into a safe thermal environment. We collected thermal data at 5 depths in the sand from 150 loggerhead nests that had been relocated in Broward County, Florida. Hatchlings had a significant effect on sand temperatures due to metabolic heat. Therefore, to evaluate thermal cues, temperatures should be measured in nest columns and not adjacent to nests, as in previous studies. A critical threshold temperature existed, above which hatchlings did not emerge. The threshold temperature at 0 cm was 32.4°C, which is similar to upper thermal thresholds of swimming activity for loggerhead and green turtle Chelonia mydas hatchlings measured in other studies. Most hatchlings emerged after a reversal in the thermal gradients between sand depths, but no particular temperature differential existed between those depths that cued emergence. A delay occurred after both threshold and reversal cues before hatchlings emerged, which may protect hatchlings under rapidly changing environmental conditions. Most hatchlings emerged sooner after the threshold temperature had been reached than after the temperature gradient had been reversed, but the 2 cues cannot be completely distinguished without further research. Rate of temperature decline was not a cue because most hatchlings emerged when rates were close to zero. We conclude that the critical threshold temperature is the most probable cue and that the most probable mechanism for controlling time of emergence is physiological--that is, a thermal inhibition of coordinated muscle movement so that emergence from the sand is only possible below a critical temperature threshold. Emergence data from in situ nests support these thermal patterns in relocated nests. These results have important implications for management of beach habitat for nesting sea turtles. Human impacts, such as beach renourishment and beach-front development, can change the thermal characteristics of the nesting environment, and therefore affect temporal emergence patterns of hatchlings. KEY WORDS: Caretta caretta · Loggerhead sea turtle · Hatchling emergence · Thermal cue · Physiological response Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 189. Publication date: November 26, 1999 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1999 Inter-Research.

Effects of Ration Limitation and Low Temperature on Growth, Biochemical Condition, and Survival of Juvenile Summer Flounder from Two Atlantic Coast Nurseries

Laboratory experiments were conducted on juvenile summer flounder Paralichthys dentatus (25–80 mm total length) from Delaware and North Carolina nurseries to compare their responses to temperature and to ration limitation. Ad libitum feeding rates, maximum growth rates, and growth efficiency were measured at temperatures from 2 to 20°C. Although ad libitum feeding rates did not differ between fish from the two locations, North Carolina juveniles had higher maximum growth rates and growth efficiencies than Delaware juveniles between 6 and 18°C. Growth rates and changes in biochemical condition were also measured for different rations at temperatures that persist during the months following settlement (10–16°C). Survival was high (>98%) after 10–14 d of starvation and suboptimal rations at 10–16°C, but growth rates were highly dependent on feeding rates. Maintenance rations remained constant between 10 and 16°C, but scope for growth increased with temperature, Scope for growth of North Carolina juveniles was higher than that of Delaware juveniles between 10 and 16°C, and growth rates of North Carolina juveniles were more sensitive to changes in ration. Changes in RNA:DNA ratios over the course of each 10–14-d experiment depended primarily on ration; ratios increased as temperature and feeding rate increased. Low-temperature tolerance (at 1–4°C) of juveniles was highly dependent on the rate of temperature decline, not on feeding rate, Time until 50% mortality (LT50) varied from 14 d (–1.3°C/d, fast rate) to 31 d (–0.3°C/d, slow rate); North Carolina juveniles were significantly less tolerant of decreasing temperatures than were Delaware juveniles.