Concentric fungal rings in antarctic moss communities

first_imgCertain Antarctic moss communities often have a pattern of concentric arcs or rings on their surfaces which can be up to 5 m in diameter. These are caused by fungal infection and show many similarities to those previously reported from the Arctic. The fungus appears not to spread through the moss uniformly but in a series of rapid advances, resulting in parallel stripes of infected moss; the reasons for this pattern remain unclear. During the seasons studied 2–6 infection stripes were produced per year, resulting in an average rate of advance of 8 cm yr−1. Three species of ascomycete have been found associated with these rings.last_img read more

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Cold shock injury in Tetrahymena pyriformis

first_imgThe ciliated protozoan Tetrahymena pyriformis has been used to study the biochemistry of cellular injury induced by rapid cooling (cold shock). Cellular viability was found to depend on the time and temperature of cold exposure, and the rate of cooling. During cooling to −7.5 °C, in the absence of ice, an optimal rate of cooling of 2.5 °C min−1 was observed; at both faster and slower cooling the recovery decreased. Following acclimation at a reduced temprature (10 °C) the viability following rapid cooling was significantly different from that of cultures maintained at 20 °C. Analysis of the phospholipid fatty acids from cells grown at 10 °C demonstrated that, at the reduced temperature, there was an increase in the average degree of fatty acyl unsaturation. Cold-shock injury in Tetrahymena is associated with membrane thermotropic events which are determined by temperature per se, whereas viability is a function of the rate of cooling. A hypothesis of injury is presented in which the presence of gel-phase lipid within the membrane is not the critical event, but it is the pattern of nucleation within the membrane which ultimately determines the extent of cellular injury.last_img read more

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Comparison of krill (Euphausia superba) density estimates using 38 and 120 kHz echosounders

first_imgA series of observations, using a dual-frequency calibrated echosounder operating at 38 and 120 kHz, of a patch of Euphausia superba close to South Georgia in 1986 is described. Sea state is shown to cause significant noise close to the surface, but to cause no significant signal attenuation. There is a consistent difference of ∼5 dB between the signal levels at the two frequencies which is in line with the difference noted from independent observations, theoretical models and in studies on encaged aggregations of krill.last_img read more

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Temporal scales of foraging in a marine predator

first_imgThe pattern of prey distribution can profoundly affect the foraging behavior and success of a predator. In pelagic marine ecosystems, where prey is often patchily distributed, predators must be able to adapt quickly to changes in the spatial patterning of prey. Antarctic fur seals feed primarily on krill, which is patchily distributed. When combined with information about swimming speed on the surface, the time taken for a fur seal to locate a new patch after leaving an old one is an indication of the distance between patches. The frequency distribution of intervals between bouts of foraging showed that fur seals foraged at two spatial distributions: (1) a fine—scale (median distance 0.18—0.27 km) represented by short (5 min) travel durations. In a study lasting 5 yr, the distributions of travel durations between bouts of feeding changed between years. These changes suggested that the structure and/or the spatial distribution of krill swarms varied between years. The behavior of fur seals suggested that there was overall clumping of prey at the fine—scale, but there was a more even spacing of prey patches at the meso—scale level. Only in 1 yr of the study (1990/1991) were there indications that fur seals had difficulty in finding enough food. Fur seal behavior suggested that there was no reduction in the number of prey patches available in that year but that prey patches were of poorer quality. The study showed how predator behavior can provide valuable information about the functional relationship between prey dispersion and predator performance.last_img read more

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Slice of intraoceanic arc: insights from the first multichannel seismic reflection profile across the South Sandwich island arc

first_imgWe present the first multichannel seismic (MCS) reflection line that crosses the South Sandwich Trench, South Sandwich island arc, and East Scotia Sea backarc basin. The line is used in combination with earthquake catalogue data to interpret the strain distribution across the Sandwich plate and the relationship of forearc structures to processes operating at the trench. The MCS data reveal a 1.2-km-high fault scarp associated with a 20-km-wide arcward-tilted block in the mid-forearc; these features indicate large-scale gravitational collapse, and earthquake data are consistent with trench-normal extension at shallow depth in this area. There is, however, little evidence of distributed extension within the interior of the Sandwich plate. The MCS data show a small frontal wedge that achieves its maximum thickness only 18 km from the trench. Backarc magnetic data, mid-forearc extension, and the small size of the frontal wedge are all consistent with long-term and ongoing subduction erosion. Earthquake data suggest that this erosion is taking place in an environment of low interplate stress.last_img read more

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Biologging, remotely-sensed oceanography and the continuous plankton recorder reveal the environmental determinants of a seabird wintering hotspot

first_imgMarine environments are greatly affected by climate change, and understanding how this perturbation affects marine vertebrates is a major issue. In this context, it is essential to identify the environmental drivers of animal distribution. Here, we focused on the little auk (Alle alle), one of the world’s most numerous seabirds and a major component in Arctic food webs. Using a multidisciplinary approach, we show how little auks adopt specific migratory strategies and balance environmental constraints to optimize their energy budgets. Miniature electronic loggers indicate that after breeding, birds from East Greenland migrate >2000 km to overwinter in a restricted area off Newfoundland. Synoptic data available from the Continuous Plankton Recorder (CPR) indicate that this region harbours some of the highest densities of the copepod Calanus finmarchicus found in the North Atlantic during winter. Examination of large-scale climatic and oceanographic data suggests that little auks favour patches of high copepod abundance in areas where air temperature ranges from 0°C to 5°C. These results greatly advance our understanding of animal responses to extreme environmental constraints, and highlight that information on habitat preference is key to identifying critical areas for marine conservation.last_img read more

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Timing and climate forcing of volcanic eruptions for the past 2,500 years

first_imgVolcanic eruptions contribute to climate variability, but quantifying these contributions has been limited by inconsistencies in the timing of atmospheric volcanic aerosol loading determined from ice cores and subsequent cooling from climate proxies such as tree rings. Here we resolve these inconsistencies and show that large eruptions in the tropics and high latitudes were primary drivers of interannual-to-decadal temperature variability in the Northern Hemisphere during the past 2,500 years. Our results are based on new records of atmospheric aerosol loading developed from high-resolution, multi-parameter measurements from an array of Greenland and Antarctic ice cores as well as distinctive age markers to constrain chronologies. Overall, cooling was proportional to the magnitude of volcanic forcing and persisted for up to ten years after some of the largest eruptive episodes. Our revised timescale more firmly implicates volcanic eruptions as catalysts in the major sixth-century pandemics, famines, and socioeconomic disruptions in Eurasia and Mesoamerica while allowing multi-millennium quantification of climate response to volcanic forcing.last_img read more

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Bacterial community composition and diversity respond to nutrient amendment but not warming in a southern maritime Antarctic soil

first_imgA resumption of climate warming in maritime Antarctica, arising from continued greenhouse gas emissions to the atmosphere, is predicted to lead to further expansions of plant populations across the region, with consequent increases in nutrient inputs to soils. Here, we test the main and interactive effects of warming, applied with open top chambers (OTCs), and nutrient amendment with tryptic soy broth (TSB), an artificial growth substrate, on bacterial community composition and diversity using Illumina sequencing of 16S rRNA genes in soil from a field experiment in the southern maritime Antarctic. Substantial effects of TSB application on bacterial communities were identified after 49 months, including reduced diversity, altered phylogenetic community assembly processes, increased Proteobacteria-to-Acidobacteria ratios and significant divergence in community composition, notably increases in the relative abundances of the gram-positive genera Arthrobacter, Paeniglutamicibacter and Planococcus. Contrary to previous observations from other maritime Antarctic field warming experiments, we recorded no effects of warming with OTCs, or interactive effects of OTCs and TSB application, on bacterial community composition or diversity. Based on these findings, we conclude that further warming of the maritime Antarctic is unlikely to influence soil bacterial community composition or diversity directly, but that increased nutrient inputs arising from enhanced plant growth across the region may affect the composition of soil bacterial communities, with possible effects on ecosystem productivity.last_img read more

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USU Soccer Adds To 2018 Soccer Roster

first_imgJune 1, 2018 /Sports News – Local USU Soccer Adds To 2018 Soccer Roster Tags: Emma Card/Heather Cairns/Imelda Williams/Kendyl Neus/USU Soccer FacebookTwitterLinkedInEmailLOGAN, Utah-Friday, with the Utah State women’s soccer program ready to commence its season in 2.5 months, head coach Heather Cairns announced additions to her roster.The new Aggies are Emma Card of Mapleton, Utah and Kendyl Neus of Gilbert, Ariz.Card comes to Logan as a four-year letter-winner at Maple Mountain High School and played a crucial role in the Golden Eagles winning the 2017 Class 5-A state championship. She was the star of a defense that surrendered only 26 goals and netted three shutouts en route to a 12-2-3 record and was also an all-academic honoree last season.Card has played club soccer for Utah FC for four seasons under head coach Eric Brady.News comes to Utah State after one season at Division II Fort Lewis of Durango, Colo., playing in 15 matches for the Skyhawks and posting nine starts.Starring at Higley High School, Neus led the Knights with 13 goals and 15 assists her senior season.Beyond this, the Aggies will welcome back returned LDS Church missionary Imelda Williams to the roster.The Timpanogos High School product played her freshman season at Logan in 2016 before departing for 18 months of service in Aguascalientes, Mexico.Williams will arrive back jut in time for the team to report for preseason training.Presently, the Aggies’ signing roster consists of 11 players with these additions. Written by Brad Jameslast_img read more

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Ramirez scores twice in 1st start since trade, LAFC beats RSL

first_img FacebookTwitterLinkedInEmailLOS ANGELES (AP) — Christian Ramirez scored his first two goals since joining Los Angeles FC in a trade last week, helping the expansion team beat Real Salt Lake 2-0 on Wednesday night.LAFC acquired the high-scoring forward from Minnesota United on Aug. 6. The Garden Grove, California, left as the leading goal-scorer in United’s short history. He has nine goals this season.LAFC (11-7-6) ended a five-game winless stretch, including two straight losses. Salt Lake (10-10-5) has just one win in its last six games, with three draws.In the 13th minute, Ramirez controlled a cross from Carlos Vela with the outside of his foot and sent it past Nick Rimando. Ramirez had an easy left-footed redirection of Eduard Atuesta’s cross in the 30th.RSL changed goalkeepers at halftime, giving 23-year-old Andrew Putna his first MLS minutes. He finished with four saves. August 15, 2018 /Sports News – Local Ramirez scores twice in 1st start since trade, LAFC beats RSL Tags: MLS/Real Salt Lake/Soccer Written by Associated Presslast_img read more

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