Respiratory metabolism of Alaskozetes antarcticus

first_imgMeasurements of oxygen consumption in all post-embryonic life stages of U.K. cultured Alaskozetes antarcticus (Acari: Cryptostigmata) showed that log10 respiration rate was linearly related to log10 live weight, while loge metabolic rate was linearly related to the reciprocal of the absolute temperature over the range 273–283°K, although the magnitude of response to temperature shown by different life stages was found to vary. Differences were apparent between cultured animals and previous measurements made on field animals, especially in respect of the relationship between respiration rate and live weight. The data were found to support the hypothesis of cold adaptation by means of metabolic rate elevation and a possible mechanism in discussed.last_img

Temperature and basal metabolism in two Antarctic marine herbivores

first_imgV̇o2 was measured for specimens of the Antarctic brachiopod Liothyrella uva and limpet Nacella concinna, using couloximetric techniques. Time-course studies revealed different responses to starvation by each species. N. concinna initially responded with a rise in V̇o2 (68%) which lasted for ≈ 14 days, followed by a decline to a steady (basal) level which was reached 30–50 days after the start. The fed V̇o2 was 1.29 times the basal rate. L. uva did not show the initial rise in V̇o2 but exhibited a steady decline, resulting i basal rates after 25–30 days. Both species did, however, show a similar response in basal V̇o2 to 1.5 °C increments in temperature. This was a rise in V̇o2 to a peak which was reached between 2 and 7 days after the rise in temperature, followed by a decline to another steady level. In both species, acclimated and acute V̇o2 showed larger responses to 1.5 °C increments at lower temperatures than at higher ones. Acclimated V̇o2 essentially rose with each temperature increment to a plateau in both species and remained at those levels until the upper lethal temperature was reached. The brachiopods survived from an initial starting temperature of − 1.5 to 4.5 °C while the limpets had a much larger temperature range, from − 1.5 to 9.0 °C. Q10 coefficients reflected these patterns, declining with temperature. The highest figures for L. uva were obtained at the − 1.5 to 0.0 °C step and were 1.97 for acclimated rates and 9.73 for acute responses. The overall Q10 values ( − 1.5 to 3.0 °C) were 1.46 and 3.09, respectively. For N. concinna, the − 1.5 to 0.0 °C values were 3.17 (acclimated) and 34.19 (acute) and the overall figures (− 1.5 to 9.0 °C) were 2.41 and 15.62, respectively. This suggests that low Q10 values (≤2.5) are appropriate for use with cold-water species.last_img read more

Ground observations and possible source regions of two types of Pc 1-2 micropulsations at very high latitudes

first_imgWe have used 1-year’s data from the recently installed Magnetometer Array for Cusp and Cleft Studies (MACCS) in Arctic Canada and from two stations of the developing “conjugate” array of Automated Geophysical Observatories (AGOs) in Antarctica to study ULF waves in the Pc 1–2 (100–600 mHz) frequency band at cusp and polar cap latitudes (Λ ∼ 74° – 80°). In this paper we focus on the spectral properties and latitudinal and local time distributions of Pc 1–2 events observed during 1994 and use these along with several case studies to infer the source locations of the two major wave types we have observed. We found little variation in center-band frequency of the Pc 1–2 waves we observed, but the average event bandwidth was distinctly wider at stations near 80° MLAT than at stations near 75° MLAT. Broadband waves, with diffuse spectral character, dominated at the higher latitudes, but their occurrence was confined at most stations to within 4 hours of local magnetic noon. Waves with narrower bandwidth were much more common in our data set, and were the statistically dominant wave type at the lower-latitude MACCS stations. Their occurrence was also limited to the dayside but extended both later and more widely in local time than the more broadband waves. These multistation observations, combined with data from the DMSP, IMP 8, and Geotail satellites, suggest the possibility that these two wave types originate in quite different regions near the magnetospheric boundary; the more narrowband waves in the subsolar and postnoon equatorial region, and the more broadband waves in the high-latitude plasma mantle (and possibly at the poleward edge of the cusp). The cusp itself appears to not be a significant source of Pc 1–2 wave activity that can be detected by ground observatories.last_img read more

Climate change in the western Antarctic Peninsula since 1945: observations and possible causes

first_imgTemperature records from stations on the west coast of the Antarctic Peninsula show a very high level of interannual variability and, over the last 50 years, larger warming trends than are seen elsewhere in Antarctica. In this paper we investigate the role of atmospheric circulation variability and sea-ice extent variations in drivingthese changes. Owing to a lack of independent data, the reliability of Antarctic atmospheric analyses produced in the 1950s and 1960s cannot be readily established, but examination of the available data suggests that there has been an increase in the northerly component of the circulation over the Peninsula since the late 1950s. Few observations of sea-ice extent are available prior to 1973, but the limited data available indicate that the iceedge to the west of the Peninsula lay to the north of recently observed extremes during the very cold conditions prevailing in the late 1950s. The ultimate cause of the atmospheric circulation changes remains to be determined and may lie outside the Antarctic region.last_img read more

Frozen in time

first_imgStudying ice chemistry may not sound very exciting – after all, isn’t ice just frozen water? Almost true, but glaciers and ice sheets, along with snow, contain traces of everything in the atmosphere. All the impurities remain as long as the ice persists. The central parts of the Antarctic ice sheet are over 3 km thick. By drilling right through it, scientists have obtained layers of ice that are over 800 000 years old. Each layer contains a story about the composition of the atmosphere and the climate that the Earth was experiencing at that time. Extraction of this information requires painstaking analysis of the tiny quantities of impurities. A good understanding of the physical and chemical processes that take material from the atmosphere into the ice is also needed.last_img read more

Aerosol deposited in East Antarctica over the last glacial cycle: detailed apportionment of continental and sea-salt contributions

first_imgThe major ions, sodium (Na+), calcium (Ca2+), and chloride (Cl−), deposited in central Antarctica and preserved in ice cores originate from both marine and continental sources. They provide important proxy records, helping to reconstruct past climatic processes. However, it is difficult to clearly separate the individual contributions from the two sources, particularly the continental one during glacial periods. On the basis of Na+ and Ca2+ records at an unprecedented resolution from the European Project for Ice Coring in Antarctica (EPICA) Dome C ice core back to the penultimate glacial period, mean ion mass ratios were deduced for the continental and the sea-salt aerosol body over East Antarctica. The sea-salt ion mass ratios are in the range predicted for both wind-induced bubble bursting of breaking waves on the open ocean and sea ice brine-derived aerosols, respectively, thus allowing no clear decision on the contribution of sea ice to the central Antarctic sea-salt aerosol. The continental ion mass ratios point to a substantial contribution by halide aerosols, which is in agreement with the source properties in southern South America, although these ratios do not rule out the continental shelf exposed during glacial stages as an additional source. While during cold glacial periods continental sources accounted for more than 90% of the total Ca2+ input, this contribution was highly variable during the remaining glacial periods covarying with the Antarctic warm events. During the Holocene it was less than 50%, but it was significantly higher during the last interglacial period. The sea-salt aerosol contribution to the total Na+ input, which was mostly dominant and higher than 90%, was reduced to only two thirds during the last two glacial maxima and the period around 60 ka. Thus the glacial continental Na+ contribution appears to be more important than previously assumed, implying that Na+ records not corrected for continental Na+ do not represent a pure marine signal at the East Antarctic plateau during glacial times.last_img read more

Rates of warming and the global sensitivity of shallow water marine invertebrates to elevated temperature

first_imgAssessing the sensitivity of ectotherms to variability in their environment is a key challenge, especially in the face of rapid warming of the Earth’s surface. Comparing the upper temperature limits of species from different regions, at different rates of warming, has recently been developed as a method to estimate the long term sensitivity of shallow marine fauna. This paper presents the first preliminary data from four tropical Ascension Island, five temperate New Zealand and six Antarctic McMurdo Sound species. The slopes and intercepts of these three assemblages fitted within the overall pattern for previously measured assemblages from high temperature tolerance in tropical fauna and a shallow slope, to low temperature tolerance and a steep slope in Antarctic fauna. Despite the tropical oceanic Ascension Island being subject to upwelling events, the fit of the intercept and slope within the overall assemblage pattern suggests that the upwelling is sufficiently predictable for the fauna to have evolved the plasticity to respond. This contrasts with previously analysed species from the Peruvian upwelling region, which had a steeper slope than other temperate fauna. The speed and capacity of faunal assemblages to acclimatize their physiology is likely to determine the shape of the rates of warming relationship, and will be a key mechanism underpinning vulnerability to climate warming.last_img read more

Lateral meltwater transfer across an Antarctic ice shelf.

first_imgSurface meltwater on ice shelves can exist as slush, it can pond in lakes or crevasses, or it can flow in surface streams and rivers. The collapse of the Larsen B Ice Shelf in 2002 has been attributed to the sudden drainage of similar to 3000 surface lakes and has highlighted the potential for surface water to cause ice-shelf instability. Surface meltwater systems have been identified across numerous Antarctic ice shelves, although the extent to which these systems impact ice-shelf instability is poorly constrained. To better understand the role of surface meltwater systems on ice shelves, it is important to track their seasonal development, monitoring the fluctuations in surface water volume and the transfer of water across ice-shelf surfaces. Here, we use Landsat 8 and Sentinel-2 imagery to track surface meltwater across the Nivlisen Ice Shelf in the 2016-2017 melt season. We develop the Fully Automated Supraglacial-Water Tracking algorithm for Ice Shelves (FASTISh) and use it to identify and track the development of 1598 water bodies, which we classify as either circular or linear. The total volume of surface meltwater peaks on 26 January 2017 at 5.5 x 10(7) m(3). At this time, 63 % of the total volume is held within two linear surface meltwater systems, which are up to 27 km long, are orientated along the ice shelf’s north-south axis, and follow the surface slope. Over the course of the melt season, they appear to migrate away from the grounding line, while growing in size and enveloping smaller water bodies. This suggests there is large-scale lateral water transfer through the surface meltwater system and the firn pack towards the ice-shelf front during the summer.last_img read more

Utah Division I Male Athletes Conclude NCAA Track & Field Championships

first_img Written by Brad James June 8, 2018 /Sports News – Local Utah Division I Male Athletes Conclude NCAA Track & Field Championships FacebookTwitterLinkedInEmailEUGENE, Ore.-Friday at Hayward Field, the NCAA men’s track and field championships drew to a conclusion and while the Georgia Bulldogs emerged as national champions for the first time in program history, several Utah-based athletes excelled as well on the final day of competition.The Utah State men placed a respectable 18th overall in the standings, tied with Big Ten Conference athletic powerhouse Penn State with 15 points. The BYU men also showed well, placing 40th overall with 7 points.In the men’s 3000-meter steeplechase, BYU’s Matt Owens and Clayson Shumway placed sixth and seventh, respectively in the final standings in this event.Several Cougars male athletes also fared well in the 5000-meter run Friday with Rory Linkletter placing 8th overall in this event. BYU’s Clayton Young placed 12th and Connor McMillan rounded out the event finishing in 24th place.The women will exclusively compete Saturday to conclude the NCAA championship meet with Utah’s Grayson Murphy and Utah State’s Cierra Simmons both in prime position to contend for a national title in the 3000-meter steeplechase. Tags: BYU Cougars/Cierra Simmons/Clayson Shumway/Clayton Young/Connor McMillan/Georgia Bulldogs/Grayson Murphy/Matt Owens/NCAA Championships/Rory Linkletter/Utah State Aggieslast_img read more

BYU Men’s Basketball Faces Mississippi State On Road Saturday

first_img Brad James Tags: Ben Howland/BYU Men’s Basketball/Cincinnati/Clemson/Lamar Peters/Mississippi State Bulldogs/Quinndary Weatherspoon/TJ Haws/UCLA/Weber State/Yoeli Childs Written by FacebookTwitterLinkedInEmailSTARKVILLE, Miss.-Saturday, BYU men’s basketball faces Mississippi State in their final non-conference game of the season and perhaps their toughest game to date.The 8-6 Cougars are facing an 11-1 Bulldogs squad that has collected wins against tough squads such as Cincinnati and Clemson.The Cougars bring in plenty of firepower to this one as their 84.8 points per game rank them 15th nationally. They are also 33rd nationally in assists per game (16.9), 14th in assist-turnover ratio and 51st in field goal percentage at 48 percent. The Cougars are also giving up 77.1 points per game.The Cougars’ statistical leader remains junior forward Yoeli Childs (22.1 points, 10.6 rebounds per game) while junior guard TJ Haws posts 17.5 points per game.Over the course of the past five games, Haws has stepped up by posting 21 points and 5.4 assists per game. He is also shooting 59.3 percent from the field in this span, including 50 percent behind the arc and 88 percent at the foul line.The Bulldogs, coached by Weber State graduate and former UCLA coach Ben Howland, score 78.2 points per game and only surrender 65.5 points per contest.Mississippi State’s leading scorer is senior guard Quinndary Weatherspoon (16.4 points, 5.3 rebounds per game), while junior guard Lamar Peters (14.3 points) also excels for Howland’s squad.The Cougars and Bulldogs are meeting for the third time in history as the series is tied 1-1. December 27, 2018 /Sports News – Local BYU Men’s Basketball Faces Mississippi State On Road Saturdaylast_img read more