Rapid Temperature Fluctuations Research Articles

Bloom dynamics in a seasonally forced phytoplankton–zooplankton model: Trigger mechanisms and timing effects

With the aim of describing annually recurring phytoplankton blooms we discuss an extension of the phytoplankton–zooplankton model introduced by [Truscott, J.E., Brindley, J., 1994. Ocean plankton populations as excitable media. Bull. Math. Biol. 56, 981–998]. The extension is a seasonal forcing of the phytoplankton growth rate driven by an oscillating temperature via a Q 10 law. We observe bistable long-term behaviour of the ecological system, i.e. a bloom and non-bloom mode, the importance of timing, and noise-induced switchings between the bloom and non-bloom mode. We link the model results to existing Helgoland Roads long-term data series by analysing the latter using the novel method of bloom-triggered averaging, a tool borrowed from signal analysis of neurophysiological recordings. We find that on an average blooms are correlated with rapid upward temperature fluctuations and speculate on their possible role as trigger mechanisms.

Body temperature fluctuations in free-ranging eastern foxsnakes (Elaphe gloydi) during cold-water swimming

We examined the thermal biology of free-ranging terrestrial eastern foxsnakes (Elaphe gloydi Conant, 1940) that were voluntarily swimming in cold water during spring, in Georgian Bay, Ontario, Canada. Using temperature-sensitive radiotelemetry, we recorded body temperatures of foxsnakes during 12 cold-water swims, and subsequent warming on shore. During these swims, water temperatures were from 11 to 22 °C and distances of 85–1330 m were travelled. Snakes that were in cold water long enough equilibrated with water temperature and did not maintain a body temperature above ambient. The largest observed drop in body temperature was 22.6 °C (over 11 min) and the largest increase was 23 °C (over 66 min). Such large, rapid temperature fluctuations have not previously been reported in detail from snakes in the field. Twice as many telemetry observations as expected occurred between 1200 and 1400, suggesting that snakes chose to swim midday. Additionally, our results suggest that foxsnakes bask to raise their body temperature prior to swimming in cold water. We compared swimming speed and the coefficient of temperature change among foxsnakes and other snake species. Swimming speed was positively correlated with water temperature, similar to other findings. We found no clear trend between mass and the coefficients of cooling and warming; however, snakes cooled in water 2.8–8.6 times faster than they warmed in air.

Limonius californicus

<i>Limonius californicus</i>

Thermal habitat experienced by Atlantic salmon (Salmo salar L.) kelts in coastal Newfoundland waters

AbstractThermal habitat was recorded by data storage tags (DSTs) applied to Atlantic salmon (Salmo salar L.) kelts during their seaward migration in the spring of 1998 at enumeration facilities in Highlands River, Humber River, Western Arm Brook, and Campbellton River, Newfoundland. In total, 139 DSTs were applied and data were downloaded from eleven of the recovered tags. The recovered tags had been applied at Highlands, Campbellton and Western Arm rivers and recovered in the coastal waters of Newfoundland and Québec and at the enumeration facilities at Highlands and Campbellton rivers. Water temperatures experienced by the fish were recorded for periods of 62–118 days at resolutions of 15–30 min. The data from the sea record on the DSTs were analysed for temperature patterns in relation to migration behaviour and diurnal movement of the fish. A variety of patterns were exhibited on the temperature records suggesting that the fish were behaving in various ways at different times. For Campbellton and Highlands fish over the course of some 24 h periods, night‐time temperatures changed little and were among the highest daily temperatures experienced by the fish, whereas daytime temperatures often showed dramatic and frequent shifts in temperature presumably as the fish rapidly and frequently changed depth. For the Western Arm Brook fish, rapid fluctuations in temperature occurred sometimes during the day and night without a consistent diurnal pattern. We also considered large‐scale aspects of the data by examining oceanographic conditions in relation to the temperatures recorded by the tags.

Photosynthetic field capacity of cyanobacteria of a tropical inselberg of the Guiana Highlands

Photosynthesis of cyanobacteria is well characterized under laboratory conditions. We present a detailed study of photosynthetic capacity of cyanobacterial communities measured under natural conditions using chlorophyll fluorescence techniques. Cyanobacteria of extensive and diverse communities grow epi- and endolithically on the bare rock of inselbergs in the tropics where they are exposed to extreme and rapid fluctuations in irradiance, temperature and water availability. Extreme and rapidly changing environmental conditions impose various stresses on cyanobacteria and lead to small-scale niches of different communities along the furrows of an inselberg in French Guiana. These different cyanobacterial communities can easily be separated from each other by their species composition. Moreover, cyanobacteria of these zonal areas show significantly different rates of apparent quantum yield of photosystem II (PSII), are differently adapted to utilize early morning light energy and have different strategies to face rapid cycles of desiccation. These different physiological strategies have led to the development of different cyanobacterial communities in distinct zones which are determined by different resistance to dehydration, water transport and storage capacity. In spite of the extreme environmental conditions with very high solar radiation, predawn measurements of potential quantum yield of PS II showed that they are not photoinhibited. We describe the manifold photosynthetic strategies that have developed in cyanobacteria under these extreme and highly fluctuating natural conditions.

Ultrathin Tropical Tropopause Clouds (UTTCs): II. Stabilization mechanisms

Abstract. Mechanisms by which subvisible cirrus clouds (SVCs) might contribute to dehydration close to the tropical tropopause are not well understood. Recently Ultrathin Tropical Tropopause Clouds (UTTCs) with optical depths around 10-4 have been detected in the western Indian ocean. These clouds cover thousands of square kilometers as 200-300 m thick distinct and homogeneous layer just below the tropical tropopause. In their condensed phase UTTCs contain only 1-5% of the total water, and essentially no nitric acid. A new cloud stabilization mechanism is required to explain this small fraction of the condensed water content in the clouds and their small vertical thickness. This work suggests a mechanism, which forces the particles into a thin layer, based on upwelling of the air of some mm/s to balance the ice particles, supersaturation with respect to ice above and subsaturation below the UTTC. In situ measurements suggest that these requirements are fulfilled. The basic physical properties of this mechanism are explored by means of a single particle model. Comprehensive 1-D cloud simulations demonstrate this stabilization mechanism to be robust against rapid temperature fluctuations of +/- 0.5 K. However, rapid warming (Δ T &gt; 2 K) leads to evaporation of the UTTC, while rapid cooling (Δ T &lt; -2 K) leads to destabilization of the particles with the potential for significant dehydration below the cloud

Antarctic Holocene climate change: A benthic foraminiferal stable isotope record from Palmer Deep

The first moderate‐ to high‐resolution Holocene marine stable isotope record from the nearshore Antarctic continental shelf (Ocean Drilling Program (ODP) Hole 1098B) suggests sensitivity of the western Antarctic Peninsula hydrography to westerly wind strength and El Niño‐Southern Oscillation (ENSO)‐like climate variability. Despite proximity to corrosive Antarctic water masses, sufficient CaCO3 in Palmer Deep sediments exists to provide a high‐quality stable isotopic record (especially in the late Holocene). Coherence of benthic foraminifer δ18O, δ13C, sedimentologic, and CaCO3 fluctuations suggests that rapid (&lt;20 years) Palmer Deep bottom water temperature fluctuations of 1°–1.5°C are associated with competitive interactions between two dominant oceanographic/climatic states. An abrupt shift from a warmer, stable Upper Circumpolar Deep Water (UCDW) state to a cooler, variable shelf water state occurred at ∼3.6 ka. Palmer Deep bottom waters oscillated between UCDW and shelf water‐dominated states between ∼3.6 and 0.05 ka. Cool shelf water intervals correlate with Neoglacial events, the most recent and largest being the Little Ice Age (LIA; ∼0.7–0.2 ka). Similarities between Palmer Deep and global Holocene records and the rapidity of inferred bottom water fluctuations suggest that western Antarctic Peninsula shelf hydrography has not been controlled by thermohaline reorganizations but by variable strength and/or position of the Southern Hemisphere westerly wind field. We suggest that these atmospheric perturbations may have originated in the low‐latitude tropical Pacific.

Non‐equilibrium compositions of liquid polar stratospheric clouds in gravity waves

On 25 January 1998 mountain induced gravity waves developed over Scandinavia leading to the formation of mesoscale polar stratospheric clouds (PSCs). Balloon‐borne mass spectrometric measurements of particle composition and optical backscatter measurements were performed above Kiruna/Sweden. PSCs were encountered twice, showing a correlated increase in the condensed phase water, nitric acid and the backscatter ratio. Thermodynamic modeling allows the PSC particles to be unambiguously identified as supercooled ternary solution (STS) droplets, but cannot account for the measured scatter in the particulate HNO3∶H2O mole ratio. Simultaneous temperature measurements show that the particles were subject to rapid atmospheric temperature fluctuations of ±1 K and cooling/heating rates exceeding 1 K/min caused by the gravity waves. Micro‐physical non‐equilibrium modeling of STS droplet distributions reveals that the observed temperature perturbations cause particle compositions in close agreement with the measured HNO3∶H2O variations. Non‐equilibrium compositions of liquid PSC particles are thus a principal stratospheric characteristic related to gravity waves affecting particle evolution.

The effects of high temperature on isoprene synthesis in oak leaves

ABSTRACTIsoprene emission from plants is highly temperature sensitive and is common in forest canopy species that experience rapid leaf temperature fluctuations. Isoprene emission declines with temperature above 35 °C but the temperature at which the decline begins varies between 35 and 44 °C. This variability is caused by the rate at which leaf temperature is increased during measurement with lower temperatures associated with longer measurement cycles. To investigate this we exposed leaves of red oak (Quercus rubra L.) to temperature regimes of 35–45 °C for periods of 20–60 min. Isoprene emission increased during the first 10 min of high temperature exposure and then decreased over the next 10 min until it reached steady state. This phenomenon was common at temperatures above 35 °C but was not noticeable at temperatures below that. The response was reversible within 30 min by lowering leaf temperature to 30 °C. Because there is no storage of isoprene inside the leaf, this behaviour indicates regulation of isoprene synthesis in the leaf. We demonstrated that the variability in isoprene decline results from regulation and explains the variability in the temperature response. This is consistent with our theory that isoprene protects leaves from damage caused by rapid temperature fluctuations.

Effects of tidally driven temperature fluctuations on shallow-water acoustic communications at 18 kHz

A communications experiment was conducted to investigate the effects of oceanographic fluctuations on high-frequency acoustic transmissions. Source transmissions containing broadband channel probes and phase-shift-keyed (PSK) communication sequences were carried out in 100-m water depth using a stationary 18-kHz source and a stationary 64-hydrophone receive array. Thermistor string data indicate the presence of high-frequency temperature fluctuations generated by the internal tide as it progresses along the continental shelf. Data are analyzed from three periods when the thermal activity is: (1) absent; (2) confined to the lower water column; and (3) confined to the mid-water column. Because of a downward refracting profile, ray paths are most dense near the bottom, which maximizes wavefront interaction with the fluctuating temperature field during period 2. Statistics of the individual ray paths indicate a strong dependence of the temporal correlation on the presence and location of the thermal activity. Ray paths interacting strongly with the portion of the water column exhibiting rapid temperature fluctuations have coherence times of a few tens of seconds, whereas the correlation remain high over the 60-s observation window when the temperature structure is stable. Because of calm sea surface conditions, surface interacting rays are also highly correlated over this time. Spatial coherence estimates and eigenvalue analysis of the array cross-spectral density matrix further indicate that the thermal activity decorrelates the signal in space. Binary PSK (BPSK) data are processed for each of the three periods using two receiver structures: (1) a multichannel decision feedback equalizer and (2) a single-channel decision feedback equalizer preceded by an eigenvector beamformer which projects the data onto the first empirical orthogonal function. Performance of the two receivers is comparable except during period 2. During this period, the eigenvector beamformer performance suffers due to the spatial decorrelation of the signal imposed by the temperature fluctuations.

A major settlement event associated with minor meteorologic and oceanographic fluctuations

Settlement of ophiuroids (Ophiopholis aculeata, Ophiura spp.) was measured using artificial collectors at 3-day intervals during their annual 2-week settlement period in July-August 1993 in St. Margaret's Bay, Nova Scotia. Hydrographic (temperature, salinity, current velocity, wave height and period) and meteorologic conditions (atmospheric pressure and wind velocity) were recorded concurrently at the site or at nearby locations. A major settlement pulse occurred over one 3-day period, with declining settlement over the following 6 days. This pulse was associated with a shift in current direction and preceded by rapid temperature and salinity fluctuations. Similar changes in temperature occurred at a second site (4.5 km away), indicating at least bay-scale forcing. This period was characterised by the passage of weak atmospheric pressure gradients and a low-energy sea state. These meteorologic and oceanographic fluctuations were within the normal range for this time of year, indicating that major settlement events can occur at scales of days in association with minor fluctuations in the physical environment.

PHYSICAL ANALOGS AND PERFORMANCE OF A BOX MODEL FOR COMPOSITION AND GROWTH OF H 2SO 4/H 2O AND HNO 3/H 2SO 4/H 2O AEROSOL IN THE STRATOSPHERE

A physical box model simulating the aerosol particle evolution along air mass trajectories is developed to provide a tool for interpreting the local observations of stratospheric aerosols (i.e., polar stratospheric clouds). The model calculates the composition and the size distributions of H 2SO 4/H 2O and HNO 3/H 2SO 4/H 2O liquid droplets. The parameterization of the physical processes affecting the dynamics of HNO 3 and H 2SO 4 solid hydrates and ice particle size distributions is also included, but not used. This work is restricted to some speculations about the liquid to solid transition, according to existing theories. The evolution of liquid particles is simulated taking into account nucleation, diffusive condensation/evaporation and coagulation. This paper reports the physical and numerical details of the model, which are discussed within the framework of the current understanding of the stratospheric aerosol physics. Performance and limitations of the model are discussed on the basis of the evolution of particle size, and composition along synthetic air mass thermal histories. Size distributions and size-dependent acid weight fractions of the liquid stratospheric aerosols consisting of HNO 3/H 2SO 4/H 2O are calculated in the cases of air mass thermal histories with different cooling rates and with rapid temperature fluctuations.

Evolutionary significance of isopreneemission from mosses

Isoprene emission has been documented and characterized from species in all major groups of vascular plants. We report in our survey that isoprene emission is much more common in mosses and ferns than later divergent land plants but is absent in liverworts and hornworts. The light and temperature responses of isoprene emission from Sphagnum capillifolium (Ehrh.) Hedw. are similar to those of other land plants. Isoprene increases thermotolerance of S. capillifolium to the same extent seen in higher plants as measured by chlorophyll fluorescence. Sphagnum species in a northern Wisconsin bog experienced large temperature fluctuations similar to those reported in tree canopies. Since isoprene has been shown to help plants cope with large, rapid temperature fluctuations, we hypothesize the thermal and correlated dessication stress experienced by early land plants provided the selective pressure for the evolution of light-dependent isoprene emission in the ancestors of modern mosses. As plants radiated into different habitats, this capacity was lost multiple times in favor of other thermal protective mechanisms.

GETTING AUTO EXHAUSTS TO PRISTINE

In many regards, catalytic converters found on today's automobiles do a darn good job of converting pollutants in engine emissions to benign products. Though they're subjected to severe and rapid temperature fluctuations, constant road and engine vibration, and enormous numbers of on-off cycles, these durable, mobile chemical reactors already reduce emissions of hydrocarbons, carbon monoxide, and nitrogen oxides (NO x ) by more than 95%. But legislators continue to call for cleaner air and even more stringent vehicle-emissions standards. To meet the evertightening demands, automotive catalysis researchers are examining a range of new emissions-abatement technologies, catalyst materials, and engine-operation strategies as they aim to make tomorrow's cars and trucks ever more pollution free. In a typical well-tuned engine, incomplete combustion of gasoline tends to produce exhaust gas mixtures containing (by volume) 1 to 2% CO, 500 to 1,000 ppm hydrocarbons, and up to a few thousand ppm NO x . Allowed to pa...

A major settlement event associated with minor meteorologic and oceanographic fluctuations

Settlement of ophiuroids (Ophiopholis aculeata, Ophiura spp.) was measured using artificial collectors at 3-day intervals during their annual 2-week settlement period in July-August 1993 in St. Margaret's Bay, Nova Scotia. Hydrographic (temperature, salinity, current velocity, wave height and period) and meteorologic conditions (atmospheric pressure and wind velocity) were recorded concurrently at the site or at nearby locations. A major settlement pulse occurred over one 3-day period, with declining settlement over the following 6 days. This pulse was associated with a shift in current direction and preceded by rapid temperature and salinity fluctuations. Similar changes in temperature occurred at a second site (4.5 km away), indicating at least bay-scale forcing. This period was characterised by the passage of weak atmospheric pressure gradients and a low-energy sea state. These meteorologic and oceanographic fluctuations were within the normal range for this time of year, indicating that major settleme...

The regulation of isoprene emission responses to rapid leaf temperature fluctuations

Isoprene emission from leaves is temperature dependent and may protect leaves from damage at high temperatures. We measured the temperature of white oak (Quercus alba L.) leaves at the top of the canopy. The largest short‐term changes in leaf temperature were associated with changes in solar radiation. During these episodes, leaf temperature changed with a 1 min time constant, a measure of the rate of temperature change. We imposed rapid temperature fluctuations on leaves to study the effect of temperature change rate on isoprene emission. Leaf temperature changed with a 16 s time constant; isoprene responded more slowly with a 37 s time constant. This time constant was slow enough to cause a lag in isoprene emission when leaf temperature fluctuated rapidly but isoprene emission changed quickly enough to follow the large temperature changes observed in the oak canopy. This is consistent with the theory that isoprene functions to protect leaves from short periods of high temperature. Time constant analysis also revealed that there are two processes that cause isoprene emission to increase with leaf temperature. The fastest process likely reflects the influence of temperature on reaction kinetics, while the slower process may reflect the activation of an enzyme.

Correlation between Arabian Sea and Greenland climate oscillations of the past 110,000 years

Palaeoclimate studies have revealed the general high-frequency instability of Late Pleistocene climate—for example, the so-called Dansgaard–Oeschger and Heinrich events—on timescales of a few millennia, centuries or even decades1,11. Here we present evidence for a general relationship between low-latitude monsoonal climate variability and the rapid temperature fluctuations of high northern latitudes that are recorded in the Greenland ice records. Sediment cores from the northeastern Arabian Sea show laminated, organic-carbon-rich bands, reflecting strong monsoon-induced biological productivity, that correlate with the mild interstadial climate events in the northern North Atlantic region. In contrast, periods of lowered southwest monsoonal intensity, indicated by bioturbated, organic-carbon-poor bands, are associated with intervals of high-latitude atmospheric cooling and the injection of melt water into the North Atlantic basin. Our records suggest that Dansgaard–Oeschger and Heinrich events are strongly expressed in low-latitude (monsoonal) climate variability, suggesting the importance of common forcing agents such as atmospheric moisture and other greenhouse gases.

The Induction of Contractile Root Activity in Sauromatum guttatum (Araceae)

Abstract:Contraction of Sauromatum guttatum roots creates a slow, downward underground corm movement, the corm be‐coming covered by a greater amount of soil, and the geophilous plant surviving the dormancy period at a safer soil position. Corm movement of Sauromatum guttatum is only possible if root contraction results in pulling activity. This pulling activity can be quantified using the lifting technique. Measurements of the pulling activity are shown as working curves over time and as the maximum work of a single contractile root. Our results show that root activity varies in individuals cultivated under different parameter conditions. It can be shown that two factors induce root contraction: first, rapid temperature fluctuations during the preceding growth period; second, illumination of the sheath leaves during the actual growth period. However, light induction is, as found here, more important and hierarchically superior, for the temperature effect is only seen in plants whose sheath leaves are not illuminated. Mobility of S. guttatum plants can thus be described as photo‐movement. If the light effect is not present, the mobility of S. guttatum may become thermo‐movement. However, at present, there is no indication that this movement is oriented to the direction of stimulus.

Influence of melt-temperature fluctuations on striation formation in large-scale Czochralski Si growth systems

The effects of melt-temperature fluctuations on growth striations in crystals grown in a commercial-scale growth system were studied by an analysis of the fast-Fourier-transform (FFT) method applied to the melt-temperature fluctuations and to the growth striations as evaluated by X-ray topography and spreading-resistance (SR) methods. The period of the growth striations observed in crystals corresponded exactly to that of temperature fluctuations in the melt; however, the amplitude of these growth striations decreased when temperature fluctuations with a constant amplitude occurred rapidly. This phenomenon results from a delay in the response of the microscopic growth rate to rapid temperature fluctuations. The amplitude of melt-temperature fluctuations and the peak height of the FFT power spectra were observed to decrease in the radial direction toward the crystal center, and this trend was also observed for growth striations. It was concluded that temporal thermal fluctuations caused by melt convection are preserved in growth striations for crystals grown in large growth systems.

Exposure of goldsinny, rock cook and corkwing wrasse to low temperature and low salinity: survival, blood physiology and seasonal variation

Wrasse used as cleaner fish with farmed Atlantic salmon Salmo salar can be subjected to large and rapid temperature and salinity fluctuations in late autumn and early winter, when summer-warmed surface water is affected by early snowmelt episodes. Because of their containment in sea cages, wrasse which are essentially acclimated to summer temperatures may be rapidly exposed to winter conditions. Short-term tolerance of low temperature and low salinity by three species of wrasse, goldsinny Ctenolabrus rupestris rock cook Centrolabrus exoletus corkwing Crenilabrus melops caught during the summer, and winter-caught corkwing, was investigated. A 3–day period at 30 or 32‰ salinity and temperature 8, 6 or 4° C (for summer-caught fish; 4° C only for winter-caught) was followed by a decline in salinity to 24, 16 or 8‰ over c. 36 h, followed by a further 24 h at these salinities held constant, at each of the three temperatures. Controls in 30 or 32‰ were maintained at 8, 6 or 4° C. Mortality of summer-caught corkwing and rock cook was high at 4° C, whereas the influence of salinity on mortality was small. Mortality of goldsinny was low or zero in all treatments. Surviving corkwing and rock cook after 3 days at 4° C and 32‰ salinity had elevated plasma osmolality: in summer-caught corkwing, plasma [Cl°] and [Na+] were high, whereas in rock cook only [Na+] was high. Haematocrit was low in summer-caught corkwing, high in rock cook. In survivors of all three species at the end of the experiment, values of all these parameters were comparable with those of fish at the beginning of the experiment, except that survivors at low salinity (8, 16‰) had low plasma osmolality, at all temperatures, and in surviving rock cook in these treatments haematocrit was high and plasma [Cl−] was low. Winter-caught corkwing had higher osmolality, [Na+] and [Cl−] than summer-caught corkwing; there was no difference in haematocrit. Survival of wintercaught corkwing exposed to four salinities at 4° C was much higher than that of summercaught corkwing under the same conditions. Little change in blood physiology was recorded for winter-caught corkwing, with only fish subjected to 8‰ and 4° C showing signs of osmoregulatory stress. The interspecific and seasonal differences in survival and blood physiology at low temperature and low salinity are discussed in relation to wrasse survival over winter, both in the field and in salmon farms.