Mélange within subduction–accretion complex rocks of Fredriksen Island, South Orkney Islands

first_imgSummary. A m´lange on Fredriksen Island, South Orkney Islands, is part of a Mesozoic subduction- accretion complex which formed along the western, Pacific side of Gondwana. It consists of a chaotic arrangement of irregular sized blocks, up to 8 m across, of basic pillow lava, chert, felsite and epiclastic sandstone in a pervasively sheared cataclastic matrix. Inclusions are typically lozenge-shaped and are characteristic of a tectonic m´lange. As the m´lange incorporates both possible ocean floor material that was accreted on to the continental margin and inner slope basin sediments it probably formed beneath the trench-slope basin along a shear zone at a high level in the subduction complex.last_img

The distribution, abundance and community structure of marine birds in southern Drake Passage and Bransfield Strait, Antarctica

first_imgWe studied the distribution and abundance of marine birds in Bransfield Strait and southern Drake Passage during January and February 1985. We identified clusters of bird species, “communities” with similar distributions, and examined the extent to which the distributions of these seabird communities reflected the underlying physical oceanography of the region. Based on temperature, salinity and silicon data, we identified 11 water masses which resulted from varying degrees of mixing of water from the Pacific Basin, the Bellingshausen Sea, the Weddell Sea and terrestrial runoff. Seabird species assemblages were associated with contiguous clusters of water masses, suggesting a response by the birds to apparently subtle differences in their marine habitat.last_img

Gastropod predation patterns in Pliocene and Recent pectinid bivalves from Antarctica and New Zealand

first_imgBoreholes in the large, extinct Antarctic Neogene pectinid Zygochlamys anderssoni suggest that this scallop was preyed upon by a large predatory muricid gastropod impossibly a Trophon species). The holes occur in mature individuals, which contrasts with the situation in modern Zygochlamys delicatula from New Zealand, where gastropod predation is apparently restricted to juveniles only. This difference is ascribed to dissimilarities in the lifestyles of these scallops; whereas the former was probably byssally attached throughout ontogeny, adults of the latter become tree living after an initial period of byssal attachment. During the late Pliocene, a change towards higher motility in Chlamys‐like pectinids of the Southern Ocean may have caused the loss of an important food source for the larger muricids.last_img read more

Initial comparisons of planetary waves in the stratosphere, mesosphere and ionosphere over Antarctica

first_imgPlanetary wave signatures, with periods of approximately 16, 10 and 5 days have been observed at altitudes ranging from 30 km to 220 km over Halley (76°S, 26°W), Antarctica. A comparative analysis of these signatures in the stratosphere, mesosphere and ionosphere has been conducted on a continuous 130‐day data sequence in the austral winter of 1997. This analysis utilises stratospheric European Centre for Medium‐Range Weather Forecasts (ECMWF) operational analyses, mesospheric Imaging Doppler Interferometer (IDI) data and ionospheric sounding data. The development and decay of these planetary waves were characterised as a function of altitude by selecting period ranges corresponding to each of the 16‐day, 10‐day and 5‐day normal mode oscillations from a wavelet analysis. The observations suggest ducting of the quasi 16‐day planetary wave from stratospheric mid‐latitudes to mesospheric high‐latitudes and a strong link between planetary waves in the mesosphere and F2‐region.last_img read more

Modelling in molecular biology: describing transcription regulatory networks at different scales

first_imgApproaches to describe gene regulation networks can be categorized by increasing detail, as network parts lists, network topology models, network control logic models or dynamic models. We discuss the current state of the art for each of these approaches. We study the relationship between different topology models, and give examples how they can be used to infer functional annotations for genes of unknown function. We introduce a new simple way of describing dynamic models called finite state linear model (FSLM). We discuss the gap between the parts list and topology models on one hand, and network logic and dynamic models, on the other hand. The first two classes of models have reached a genome-wide scale, while for the other model classes high-throughput technologies are yet to make a major impact.last_img read more

Use of geolocators reveals previously unknown Chinese and Korean scaly-sided merganser wintering sites

first_imgWe determined, for the first time, individual linkages between breeding areas of nesting female scaly-sided mergansers Mergus squamatus in the Russian Far East and their previously unknown wintering grounds in coastal Korea and inland China. Geolocators were deployed on nesting females caught and recaptured on nests along a 40-km stretch of the Kievka River. Mean positions for brood-rearing females during the summer were on average within 61.9 km of the nest site, suggesting reasonable device accuracy for subsequent location of winter quarters. Geolocation data showed that most birds wintered on freshwater habitats throughout mainland China, straddling an area 830 km E−W and 1100 km N−S. Most wintered in discrete mountainous areas with extensive timber cover, large rivers and low human population density. Three birds tracked in more than one season returned to within 25−150 km of previous wintering areas in successive years, suggesting winter fidelity to catchments if not specific sites. A single female from the adjacent Avvakumovka catchment wintered on saltwater in Korea, at least 1300 km east of Chinese wintering birds. Most sea duck species (Tribe Mergini) form pairs away from breeding areas, suggesting that this high level of winter dispersal amongst close-nesting females is a potential mechanism to maintain gene flow in this threatened species that has specialist habitat requirements. Hence, female scaly-sided mergansers disperse widely from breeding areas, but show fidelity to nesting areas and winter quarterslast_img read more

Heart rate and estimated energy expenditure of flapping and gliding in black-browed albatrosses

first_imgAlbatrosses are known to expend only a small amount of energy during flight. The low energy cost of albatross flight has been attributed to energy-efficient gliding (soaring) with sporadic flapping, although little is known about how much time and energy albatrosses expend in flapping versus gliding during cruising flight. Here, we examined the heart rates (used as an instantaneous index of energy expenditure) and flapping activities of free-ranging black-browed albatrosses (Thalassarche melanophrys) to estimate the energy cost of flapping as well as time spent in flapping activities. The heart rate of albatrosses during flight (144 beats min-1) was similar to that while sitting on the water (150 beats min-1). In contrast, heart rate was much higher during takeoff and landing (ca. 200 beats min-1). Heart rate during cruising flight was linearly correlated with the number of wing flaps per minute, suggesting an extra energy burden of flapping. Albatrosses expend only 4.6% ± 1.4% of their time in flapping during cruising flight, which was significantly lower than those during and shortly after takeoff (9.8% ± 3.5%). Flapping activity, which amounted to just 4.6% of the time in flight, accounted for 13.3% of the total energy expenditure during cruising flight. These results support the idea that albatrosses achieve energy-efficient flight by reducing the time spent in flapping activity, which is associated with high energy expenditure.last_img read more

Chemical fingerprints encode mother-offspring similarity, colony membership, relatedness and genetic quality in fur seals

first_imgChemical communication underpins virtually all aspects of vertebrate social life, yet remains poorly understood because of its highly complex mechanistic basis. We therefore used chemical fingerprinting of skin swabs and genetic analysis to explore the chemical cues that may underlie mother–offspring recognition in colonially breeding Antarctic fur seals. By sampling mother–offspring pairs from two different colonies, using a variety of statistical approaches and genotyping a large panel of microsatellite loci, we show that colony membership, mother–offspring similarity, heterozygosity, and genetic relatedness are all chemically encoded. Moreover, chemical similarity between mothers and offspring reflects a combination of genetic and environmental influences, the former partly encoded by substances resembling known pheromones. Our findings reveal the diversity of information contained within chemical fingerprints and have implications for understanding mother–offspring communication, kin recognition, and mate choice.last_img read more

Diatom communities in the High Arctic aquatic habitats of northern Spitsbergen (Svalbard)

first_imgAs High Arctic environments are particularly sensitive to global and regional climate changes, a growing number of studies have focused on that region. It has been shown that living and fossil diatoms can be successfully used to track environmental changes in polar habitats. Nevertheless, the diatom flora of many Arctic areas remains unknown. The present study set out to examine the diatom flora in the rarely visited and near-pristine zone of northern Spitsbergen. Examination by light and scanning electron microscopy of 25 sediment samples, collected in fjords, tidal plains and lakes, indicated significant differences between the diatom assemblages identified in lakes located within different fjord watersheds. Altogether, 96 diatom taxa (46 genera) were found. The most abundant species (Achnanthidium minutissimum, Staurosirella pinnata and Nitzschia alpina) occurred in at least eight of the 11 investigated lakes. Assemblages from the Woodfjorden region were characterized by the presence of Cavinula pseudoscutiformis and Encyonema reichardtii, along with Navicula spp., which coincided with relatively low conductivity (34–58.7 µS cm−1) and near-neutral pH (7.2–7.5). Diatom assemblages found in the Wijdefjorden area were typically characterized by Denticula kuetzingii and Nitzschia inconspicua, with these lakes generally having higher water conductivity (>184 µS cm−1) and pH (7.5–8.1) conditions. Conductivity, biogenic silica concentration and water temperature were indicated as significant predictors of diatom community species composition and structure. No diatom frustules were found in fjord and tidal plain sediments. The effects of selected environmental factors on diatom assemblage formation are discussed.last_img read more

Scoreboard roundup — 4/11/18

first_imgApril 12, 2018 /Sports News – National Scoreboard roundup — 4/11/18 Written by FacebookTwitterLinkedInEmailiStock/Thinkstock(NEW YORK) — Here are the scores from yesterday’s sports events:    INTERLEAGUE Final  Oakland  16  L-A Dodgers   6    AMERICAN LEAGUE Final  Minnesota       9  Houston       8 Final  Chi White Sox   2  Tampa Bay     1 Final  Seattle         4  Kansas City   2 Final  Cleveland       5  Detroit       1 Final  Baltimore       5  Toronto       3 Final  N-Y Yankees    10  Boston        7 Final  L-A Angels      7  Texas         2    NATIONAL LEAGUE Final  Atlanta        5  Washington      3, 12 Innings Final  Milwaukee      3  St. Louis       2 Final  Colorado       6  San Diego       4 Final  Arizona        7  San Francisco   3 Final  Philadelphia   4  Cincinnati      3, 12 Innings Final  N-Y Mets       4  Miami           1 Final  Chi Cubs      13  Pittsburgh      5     NATIONAL BASKETBALL ASSOCIATION PLAYOFFS Final OT  Minnesota      112  Denver         106 Final  Detroit        119  Chicago         87 Final  N-Y Knicks     110  Cleveland       98 Final OT  Miami          116  Toronto        109 Final  Philadelphia   130  Milwaukee       95 Final  New Orleans    122  San Antonio     98 Final  Oklahoma City  137  Memphis        123 Final  Orlando        101  Washington      92 Final  Boston         110  Brooklyn        97 Final  Sacramento      96  Houston         83 Final  L.A. Lakers    115  L.A. Clippers  100 Final  Portland       102  Utah            93    NATIONAL HOCKEY LEAGUE PLAYOFFS Final  Pittsburgh   7  Philadelphia   0 Final  Winnipeg     3  Minnesota      2 Final  Vegas        1  L.A. Kings     0Copyright © 2018, ABC Radio. All rights reserved.center_img Beau Lundlast_img read more