Going with the Flow: Spatial Distributions of Juvenile Coho Salmon Track an Annually Shifting Mosaic of Water Temperature

A critical challenge for ecologists is to understand the functional significance of habitat heterogeneity and connectivity for mobile animals. Here, we explore how a thermo-regulating fish responds to annual variation in the spatial patterning of thermal and trophic resources. In a third-order stream in coastal Alaska, juvenile coho salmon forage on sockeye salmon eggs at night in cold water and then move to warmer water to increase their digestive capacity. We mapped the spatial distributions of water temperature, juvenile coho salmon, and spawning sockeye salmon across a 5-year period during which summer discharge varied by greater than fivefold. In low flow years, warm water (9–12°C) was only available in thalweg (that is, main-channel) habitat at least approximately 400 m upstream of the cooler habitat (3–7°C) where sockeye salmon spawned. In high flow years, the entire stream thalweg was isothermal at 7–8°C, but inundated off-channel areas generated warm habitats (9–12°C) laterally adjacent to the downstream regions where sockeye salmon spawned. The daytime spatial distribution of juvenile coho salmon shifted from headwater thalweg habitats in low flow years, to downstream off-channel habitats in high flow years. In all years, the majority of juvenile coho salmon sampled during the daytime were found in warm habitat units without sockeye salmon present, yet they exhibited diet contents comprised virtually entirely of sockeye salmon eggs. Thus, thermoregulatory movements by coho salmon were able to track an annually shifting mosaic of water temperature. Our results demonstrate how the spatial habitat heterogeneity and connectivity of intact floodplains can in turn buffer aquatic organisms from high levels of temporal variation in habitat conditions and resource abundance.     

The Effect of Temperature on the Growth of Cocksfoot (Dactylis glomerata L.)

The growth of cocksfoot at 14°, 22°, and 26° C wasmeasured at weekly intervals over a period of six weeks. Initially,the relative growth rates increased with increase in temperature,but during the final three weeks they were little differentat all three temperatures. The reduction in relative growthrates with time at 22° and 26° were associated withincreases in size which were partly reflected by reductionsin the leaf-area ratios. It is also likely that at 26° changesin the photosynthetic capacity of leaves, perhaps associatedwith decreasing concentrations of mineral nutrients, contributedto the decreased relative growth rates. Leaf expansion and increase in cell numbers were estimated overtwo-day periods at temperatures ranging from 5° to 30°C. Leaf expansion increased with increase in temperature throughoutthis range; extrapolation suggested that it would cease at temperaturesbelow 3° C. The optimum temperature for cell division appearedto be between 20° and 25°C. Different physiological processes appeared to be involved inthe temperature responses of plants of different sizes and histories.With young plants these responses resulted in a large overalleffect of temperature on the growth rate; with older plantsof the same size there appeared to be several compensatory responsesso that variation in temperature over an apprecaible range hadlittle overall effect.     

Changes in gape frequency, siphon activity and thermal response in the freshwater bivalves Anodonta cygnea and Margaritifera falcata

Physiologically-driven rhythms in bivalve molluscs are predictedto vary as a function of metabolic rate and temperature, incontrast to genetically predisposed biological clocks. Theserhythms can be evaluated using long-term video monitoring techniquesunder controlled conditions in laboratory aquaria. The bivalvesAnodonta cygnea and Margaritifera falcata were used to evaluatethe effect of temperature on rhythms in gape and the formationof siphons at the mantle edge. Frequency and duration of shellclosure vary with temperature in both species, but with differentresponses. Mean duration of intervals of valve closure decreasesas temperature rises in both species, and is consistent withphysiological limitation by increased biological oxygen demand.For A. cygnea, cumulative gape duration peaks at 25°C, withless time spent closed than at any other temperature, but increasingtemperatures correspond to an increase in gape frequency witha strong increase observed at 31°C. In contrast, frequencyof adduction and valve closure peak at 25°C in M. falcata,and continuous gaping is observed above 29.5°C. This physiologicalstress is consistent with evidence from sclerochronologically-calibratedstable isotope studies of shells, where growth breaks in manymarine taxa coincide with maximum temperatures above 31°Cas derived for ¹⁸O_carbonate. The results of this study suggestthat these growth breaks may be due to physiological limitationsin oxygen uptake and metabolic activity, rather than being adirect consequence of elevated temperature alone. (Received 17 March 2008; accepted 3 October 2008)     

A re-assessment of high elevation treeline positions and their explanation

In this review I first compile data for the worldwide position of climate-driven alpine treelines. Causes for treeline formation are then discussed with a global perspective. Available evidence suggests a combination of a general thermal boundary for tree growth, with regionally variable “modulatory” forces, including the presence of certain taxa. Much of the explanatory evidence found in the literature relates to these modulatory aspects at regional scales, whereas no good explanations emerged for the more fundamental global pattern related to temperature per se, on which this review is focused. I hypothesize that the life form “tree” is limited at treeline altitudes by the potential investment, rather than production, of assimilates (growth as such, rather than photosynthesis or the carbon balance, being limited). In shoots coupled to a cold atmosphere, meristem activity is suggested to be limited for much of the time, especially at night. By reducing soil heat flux during the growing season the forest canopy negatively affects root zone temperature. The lower threshold temperature for tissue growth and development appears to be higher than 3°C and lower than 10°C, possibly in the 5.5–7.5°C range, most commonly associated with seasonal means of air temperature at treeline positions. The physiological and developmental mechanisms responsible have yet to be analyzed. Root zone temperature, though largely unknown, is likely to be most critical. Received: 3 October 1997 / Accepted: 14 April 1998     

Effect of Temperature on Net Assimilation Rate

Net assimilation rates and other growth attributes were comparedfor rape, sunflower, and maize plants growing widely spacedat temperatures of 10°, 16°, 22°, 28°, and 34°C, in light of 3, 000 f.c. intensity. The optimum temperature for net assimilation rate lay between20° and 30° C, and was lowest for rape and highest formaize. The temperature coefficient of the net assimilation ratewas lower than that of the relative growth-rate, especiallyin rape and sunflower, corresponding to an increase in leaf-arearatio with in temperature. This arose to an increase in leaf-arearatio with rise in temperature. This mcrease arose through changeinleafarea/leaf weight; temperature had little effect on leafweight/plant weight. In moderate to warm conditions the net assimilation rate variedlittle with temperature: by only± 10 per cent between12° and 30° C for rape, and 23° and 36° C formaize. This agrees with observations in natural climates whichsuggest that temperature is generally less important than lightin controlling net assimilation rates, except in cool climates.In natural climates, as in these controlled climates, relativegrowth-rate is more temperature-dependent.     

Effects of Temperature on the In vivo Assay of Nitrate Reductase in some C3 and C4Species

Nitrate reductase (NR) activity was measuredin vivo in differentcrop species at 25–60 °C. Highest NR activity wasobserved at 40 °C in pigeon pea, cowpea, sunflower, sesameand sorghum, 45 °C in maize and 50 °C in bajra. At higherincubation temperatures NR activity declined in all species.In mung bean the optimum incubation temperature varied withthe season. In the summer crop of mung beans, NR activity wasmaximum at 50 °C while in the rainy season crop 30 °Cwas the optimum incubation temperature. NR in sesame was relativelyheat-tolerant. The results indicate that 30 °C is not theoptimum incubation temperature for all crop species. Nitrate reductase, temperature, in vivo assay     

O2bullet production at 37{degrees}C plays a critical role in depressing tetanic force of isolated rat and mouse skeletal muscle

To find out whether the decrease in muscle performance of isolated mammalian skeletal muscle associated with the increase in temperature toward physiological levels is related to the increase in muscle superoxide (O₂^–) production, O₂^– released extracellularly by intact isolated rat and mouse extensor digitorum longus (EDL) muscles was measured at 22, 32, and 37°C in Krebs-Ringer solution, and tetanic force was measured in both preparations at 22 and 37°C under the same conditions. The rate of O₂^– production increased marginally when the temperature was increased from 22 to 32°C, but increased fivefold when the temperature was increased from 22 to 37°C in both rat and mouse preparations. This increase was accompanied by a marked decrease in tetanic force after 30 min incubation at 37°C in both rat and mouse EDL muscles. Tetanic force remained largely depressed after return to 22°C for up to 120 min. The specific maximum Ca²⁺-activated force measured in mechanically skinned fibers after the temperature treatment was markedly depressed in mouse fibers but was not significantly depressed in rat muscle fibers. The resting membrane and intracellular action potentials were, however, significantly affected by the temperature treatment in the rat fibers. The effects of the temperature treatment on tetanic force, maximum Ca²⁺-activated force, and membrane potential were largely prevented by 1 mM Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl), a membrane-permeable superoxide dismutase mimetic, indicating that the increased O₂^– production at physiological temperatures is largely responsible for the observed depression in tetanic force at 37°C by affecting the contractile apparatus and plasma membrane. intact mammalian muscle; physiological temperature; superoxide; excitation-contraction coupling; maximum Ca²⁺-activated force; muscle excitability; cytochrome c assay     

Germination of Stored Cassava Seed at Constant and Alternating Temperatures

Cassava seed is only capable of germinating over a restrictedrange of constant temperatures. During storage the optimum constanttemperature for germination decreases from about 35 to 30 °Cor possibly less. The rate at which the optimum temperaturechanges during dry storage increases with increase in storagetemperature over the range 0 to 40 °C. Some alternating-temperatureregimes (16 h at the lower temperature; 8 h at the higher temperature)can provide conditions as favourable for germination as theoptimum constant temperatures. Furthermore, it has been shownthat temperature alternation itself is stimulatory because whenthe range of the alternation does not include the optimum constanttemperature value, percentage germination is often higher thancould be obtained at any constant temperature within the range,though this stimulatory response declines during storage. Forthese reasons it is provisionally recommended that cassava seedshould be germinated at 25/35 °C which is as stimulatorya treatment as any which has so far been investigated and hasthe advantage of encompassing the range over which the optimumconstant temperature changes during storage. Manihot esculenta Crantz, cassava, germination, dormancy, seed viability, storage of seeds, after-ripening     

Development of endothermy in a tasmanian marsupial, Bettongia gaimardi and its response to cold and noradrenaline

Marsupials at birth are ectothermic and gradually attain the ability to change their metabolic heat production during pouch life. How this process occurs in the bettong has been measured on 13 pouch young from week 1 until 3 weeks after pouch vacation (week 18). Oxygen consumption was measured at 35 °C (pouch temperature) and at 22 °C. The results at 35 °C showed an increase in metabolic rate from week 1 until week 12 when there was a decrease to near adult levels after pouch vacation. At 22 °C young bettongs had a lower metabolic rate (compared with measurements made at 35 °C) until week 9 after which there was an increase above measurements made at 35 °C. Noradrenaline had little effect until week 10 after which the metabolic rate (although measured at 35 °C) paralleled the levels measured at 22 °C. The free thyroxine level was low in early pouch life, increased to a peak at week 12 then decreased. Thermal conductance increased until week 10 after which it decreased, reaching values similar to those of adult bettongs by week 20. The results indicate that non-shivering thermogenesis occurs in this macropodoid marsupial. This phenomenon may be a phylogenetic difference between macropodid and non-macropodid marsupials as also suggested by Nicol et al. (1997). Accepted: 19 February 1998     

Growth and Development in the Young Tomato: III. THE EFFECT OF NIGHT AND DAY TEMPERATURES ON VEGETATIVE GROWTH

Tomato seedlings were grown in a 12-hour day at constant andalternating day and night temperatures ranging from 10°to 30° C. The pattern of results was similar at light intensitiesof 400 and 800 f.c. The maximum rate of dryweight accumulationoccurred at a constant temperature close to 25° C. The effectsof day and night temperatures on total dry weight showed a considerabledegree of independence. The optimum day temperature was 25°C irrespective of the night temperature; the optimum night temperatureincreased from 18° to 25° C over the whole range ofday temperature. On average, day temperature affected totaldry weight twice as much as night temperature. High night temperaturesto some extent compensated for low day temperatures. The optimumday and night temperatures for leaf growth were both 25°C. On average day temperature affected leaf growth one and ahalf times as much as night temperature. By 12-hourly sampling it was shown that the cotyledons and leavesgrow throughout both day and night and that high night temperatureaccelerates nocturnal growth (cotyledons by cell expansion,young leaves by cell multiplication). Plants having receivedonly one night at 25° C, as compared with 15° C, showa slightly greater assimilation during the following light period,apparently as a consequence of increased photosynthetic surface.The respiratory loss in dry weight during darkness was not significantlyaffected by temperature over the range 15–25° C.     

The Effect of Temperature and Carbon Metabolism on Sucrose Uptake by Detached Tomato Fruits

The effect of temperature on sucrose uptake, and changes inlevels of starch, hexoses and sucrose in detached tomato fruitswas used to investigate the role of the sink in regulation ofcarbon import. Sucrose uptake was lower at 5 °C and greaterat 40 °C than at 25 °C. Conversion of radioactive componentsto starch was lower at both 5 °C and 40 °C than at 25°C, while the levels of non-radioactive starch was similarat all three temperatures. There was a depletion of glucoseand fructose in fruits at 40 °C. Uptake of sucrose froman agar medium by detached tomato fruits was negatively correlatedwith initial sucrose content of the fruit. The results indicatethat carbon import by tomato fruits is largely determined bysucrose levels which can be affected by metabolic activity. Lycopersicon esculentum L., tomato, fruit, sucrose uptake, temperature, carbon metabolism     

Physiological acclimation to decreased water temperature and the relative importance of water viscosity in determining the feeding performance of larvae of a serpulid polychaete

Ambient temperature exerts both physiological and mechanicaleffects on the rates of functional processes of small aquaticectotherms. Physiological effects of temperature result fromits influence on the rates of chemical reactions. Mechanicaleffects of temperature result from the inverse relationshipbetween the temperature of water and its dynamic viscosity.We measured the relative importance of these components of temperatureon the feeding performance of polychaete larvae. Cohorts oflarvae were reared for 24 h at 20°C and 10°C in treatmentswhere the physiological and mechanical effects of these temperatureswere separated. The feeding performance of these larvae wassubsequently measured in treatments where these components oftemperature were similarly partitioned. Cold-reared larvae displayedcomplete acclimation of feeding performance to the physiologicaleffects of decreased temperature: thus, increased viscositywas responsible for 100% of the difference in feeding performancebetween 20°C and 10°C. The physiological ability ofsmall aquatic ectotherms to acclimate functional processes totemperature variation may be greater than previously thought,and these results have implications for understanding the responsesof aquatic ectotherms’ to global temperature change.     

Acclimation of chlorophyll biosynthetic reactions to temperature stress in cucumber (Cucumis sativus L.)

The adaptive responses of the greening process of plants to temperature stress were studied in cucumber (Cucumis sativus L. cv. Poinsette) seedlings grown at ambient (25 °C), low (7 °C) and high (42 °C) temperatures. Plastids isolated from these seedlings were incubated at different temperatures and the net syntheses of various tetrapyrroles were monitored. In plastids isolated from control seedlings grown at 25 °C, the optimum temperature for synthesis of Mg-protoporphyrin IX monoester or protochlorophyllide was 35 °C. Temperature maxima for Mg-protoporphyrin IX monoester and protochlorophyllide syntheses were shifted to 30 °C in chill-stressed seedlings. The net synthesis of total tetrapyrroles was severely reduced in heat-stressed seedlings and the optimum temperature for Mg-protoporphyrin IX monoester or protochlorophyllide synthesis shifted slightly towards higher temperatures, i.e. a broader peak was observed. To further study the temperature acclimation of seedlings with respect to the greening process, tetrapyrrole biosynthesis was monitored at 25 °C after pre-heating the plastids (28–70 °C) isolated from control, chill- and heat-stressed seedlings. In comparison to 28 °C-pre-heated plastids the percent inhibition of protochlorophyllide synthesis in 40 °C-pre-heated plastids was higher than for the control (25 °C-grown) in chill-stressed seedlings and lower than for the control in heat-stressed seedlings. Maximum synthesis of total tetrapyrroles and protoporphyrin IX was observed when chloroplasts were heated at 50 °C, which was probably due to heat-induced activation of the enzymes involved in protoporphyrin IX synthesis. Prominent shoulders towards lower or higher temperatures were seen in chill-stressed or heat-stressed seedlings, respectively. The shift in optimum temperature for tetrapyrrole biosynthesis in chill- and heat-stressed seedlings was probably due to acclimation of membranes possibly undergoing desaturation or saturation of membrane lipids. Proteins synthesized in response to temperature-stress may also play an important role in conferring stress-tolerance in plants. Received: 8 October 1998 / Accepted: 19 November 1998     

Thermophilic protease-producing Geobacillus from Buranga hot springs in Western Uganda

Two proteolytic thermophilic aerobic bacterial strains, PA-9 and PA-5, were isolated from Buranga hot springs in western Uganda. The cells were rods, approximately 10–12 μm in length and 3 μm in width. Isolate PA-9 grew at between 38°C and 68°C (optimum, 62°C), and PA-5 grew at between 37°C and 72°C (optimum, 60°C). Both isolates grew optimally at pH 7.5–8.5. Their 16S rRNA gene sequences indicated that they belong to the newly described genus Geobacillus. Zymogram analysis of the crude enzyme extracts revealed the presence of two extracellular proteases for isolate PA-5, and at least eight for isolate PA-9. The optimum temperature and pH for casein-degrading activity were 70°C, pH 6.5 for isolate PA-9, but caseinolytic activity could also be observed at 2°C. In the case of isolate PA-5, optimal activity was observed over a temperature and pH range of 50–70°C and pH 5–10, respectively. Received: 26 November 2001 / Accepted: 12 December 2001     

Simultaneous saccharification and fermentation of cellulose for lactic acid production

Lactic acid production from α-cellulose by simultaneous saccharification and fermentation (SSF) was studied. The cellulose was converted in a batch SSF using cellulase enzyme Cytolase CL to produce glucose sugar andLactobacillus delbrueckii to ferment the glucose to lactic acid. The effects of temperature, pH, yeast extract loading, and lactic acid inhibition were studied to determine the optimum conditions for the batch processing. Cellulose was converted efficiently to lactic acid, and enzymatic hydrolysis was the rate controlling step in the SSF. The highest conversion rate was obtained at 46°C and pH 5.0. The observed yield of lactic acid from α-cellulose was 0.90 at 72 hours. The optimum pH of the SSF was coincident with that of enzymatic hydrolysis. The optimum temperature of the SSF was chosen as the highest temperature the microorganism could withstand. The optimum yeast extract loading was found to be 2.5 g/L. Lactic acid was observed to be inhibitory to the microorganisms’ activity.     

Direct ethanol production from cellulosic materials at high temperature using the thermotolerant yeast Kluyveromyces marxianus displaying cellulolytic enzymes

To exploit cellulosic materials for fuel ethanol production, a microorganism capable of high temperature and simultaneous saccharification–fermentation has been required. However, a major drawback is the optimum temperature for the saccharification and fermentation. Most ethanol-fermenting microbes have an optimum temperature for ethanol fermentation ranging between 28 °C and 37 °C, while the activity of cellulolytic enzymes is highest at around 50 °C and significantly decreases with a decrease in temperature. Therefore, in the present study, a thermotolerant yeast, Kluyveromyces marxianus, which has high growth and fermentation at elevated temperatures, was used as a producer of ethanol from cellulose. The strain was genetically engineered to display Trichoderma reesei endoglucanase and Aspergillus aculeatus β-glucosidase on the cell surface, which successfully converts a cellulosic β-glucan to ethanol directly at 48 °C with a yield of 4.24 g/l from 10 g/l within 12 h. The yield (in grams of ethanol produced per gram of β-glucan consumed) was 0.47 g/g, which corresponds to 92.2% of the theoretical yield. This indicates that high-temperature cellulose fermentation to ethanol can be efficiently accomplished using a recombinant K. marxianus strain displaying thermostable cellulolytic enzymes on the cell surface.     

Response to Temperature in a Stand of Pearl Millet: 10. PARTITION OF ASSIMILATE

Effects of temperature on partition of assimilate between leaves,stems and panicles of pearl millet are analysed in terms ofa duration (t_w) over which a structure increased in weight,and a partition factor (p)—the fraction of new dry matterallocated to the structure during t_w. The value of tw was, forall structures, inversely proportional to temperature abovea base of 10 °C and below an optimum of 28 to 30 °C.For stems and panicles, the value of p was, with one exception,little affected by temperature. The dry weight of these structureswas, therefore, proportional to t_w, and decreased with risein temperature. (The exception was panicles at the lowest temperature,19 °C, for which p was reduced by 40% because few grainswere set.) For leaves, however, p increased with rise in temperature,counteracting the effect on t_w, such that dry weight changedlittle with temperature. The optimum temperature for reproductiveyield was 22 °C, but the proportion of the total dry matterallocated to reproductive structures changed little between22 °C and 31 °C. Key words: Pearl millet, temperature, thermal time, partitioning     

The Responsiveness to Temperature of the Extension Rates of Leaves of Wheat Growing in the Field under Different Levels of Nitrogen Fertilizer

The response of the rates of extension (LER) of wheat leaves(Triticum aestivum cv. Gamenya) to temperatures maintained fora short period was measured by changing the temperature of theextension zone and recording the changes in leaf length. Therange of temperatures used was from 4-38 °C. The LER ofall leaves responded to increases in temperature as field temperatureswere suboptimal. The data obtained from several series of measurementsover different ranges of temperature were combined to producea general response curve. The minimum temperature for LER wasconsidered to be approximately 0 °C, the optimum was 28.4°C, while the maximum was in excess of 38 °C. The responsivenessof LER to temperature, measured by the Q₁₀, declined exponentiallyfrom >6 at 5 °C to 2 at 20 °C. The Q₁₀ at 15 °Cwas not affected by nitrogen supply.     

Versuche über die Abhängigkeit der Atmung vonArenicola marina (Annelides Polychaeta) von Größe und Temperatur

A knowledge of the rate of oxygen consumption is very important for the evaluation of many physiological and ecological problems. Among the many factors affecting respiratory rate, water temperature and body size are particularly considered here. The modifying effects of body size may be expressed mathematically by the allometric formula: y=b · w ^a , where b represents the rate of O₂ consumption of an individual whose weight is expressed in a chosen metrical weight unity (i. e. in grams, ounces, etc.), anda represents the decrease of metabolic rate during growth. InArenicola the exponent is not the same at all temperatures tested. In most cases it lies between 0.7 and 0.8, i. e., between a weight proportional respiratory rate and a surface proportional one. Minimum values fora were found in experiments conducted in summer at 20° C and in spring at 15° C. They characterize an optimum efficiency of metabolism at these temperatures. Determinations of b demonstrated that metabolic rate ofArenicola is significantly less affected in spring (10° to 20° C) and autumn (10° to 25° C) than is usually known from biological processes. However, the temperature coefficients above and below these temperature ranges are very high. Another break in the temperature-rate curve could be demonstrated below 5° C in spring.