Antarctic seabird and seal monitoring studies

first_imgThe need to investigate and understand the nature of changes in abundance of economically important marine living resources has been widely recognized. They may be naturally occurring fluctuations, cycles or undirectional processes, or changes in response to artificial influences such as pollution or commercial harvesting. As direct investigation of status and population structure of some of these resources can often prove difficult, or incompatible with continuing exploitation, attention has also focussed on the identification and study of more convenient species which may be used as indices of environmental change.last_img read more

Variation in foraging effort by lactating Antarctic fur seals: response to simulated increased foraging costs

first_imgSeasonally breeding predators, which are limited in the time available for provisioning young at a central location, and by the fasting abilities of the young, are likely to maximize energy delivery to the young by maximizing the rate of energy delivery averaged over the whole period of investment. Reduction in food availability or increased foraging costs will alter the optimal behavior of individuals. This study examined the behavioral adaptations of a diving predator, the Antarctic fur seal, to increased foraging costs during lactation. One group of mothers (n=5, treatment) was fitted with additional drag to increase the cost of transport in comparison with a control group (n=8). At the scales of the individual dives, the treatment group made more shorter, shallower (< 30 m) dives. Compensation for slower swimming speeds was achieved by diving at a steeper angle. Overall, diving behavior conformed to several specific theoretical predictions but there were also departures from theory, particularly concerning swimming speed during diving. Diving behavior appears to be adjusted to maximize the proportion of time spent at the bottom of dives. At the scale of diving bouts, no difference was observed between the treatment and control groups in terms of the frequency and duration of bouts and there was also no difference between the two groups in terms of the proportion of time spent diving. At the scale of complete foraging cycles, time taken to return to the pup was significantly longer in the treatment group but there was no difference in the rate of delivery of energy (measured from pup growth rate) to the pups in each group. Since mothers in the treatment group did not use significantly more body reserves, we conclude that behavioral adjustments at the scale of individual dives allowed mothers in the treatment group to compensate for the additional foraging costs. Pup growth rate appears to be less sensitive to the foraging conditions experienced by mothers than foraging trip duration.last_img read more

The behavior of the electric field within the substorm current wedge

first_imgWe use the Goose Bay HF radar to investigate the behavior of the electric field within the substorm current wedge for a small substorm (< 200 nT) which occurred on February 15, 1992. Mid- and high-latitude magnetometer data helped to locate the radar backscatter with respect to the longitudes and latitudes of the substorm currents, as well as describing the time development of the substorm itself. Velocities in the portion of the field of view of the Goose Bay HF radar closest to the Frederikshab magnetometer in Greenland were compared directly with the ionospheric currents inferred from the magnetometer. During the early growth phase, the plasma flow and current gradually increased in response to the DP2 electric field and are related by an estimated effective height-integrated conductivity, Σ*, ∼ 1 S. The plasma flow and current continued to increase in the same proportion (i.e., Σ* was still ∼ 1 S) as the electrojet intensified in stages during the late growth/early expansion phase. In this interval there was probably a pseudo-breakup which established a longitudinally and latitudinally narrow substorm current wedge. The increased plasma flow and current measured at Frederikshab are attributed to the superposition of the pseudo-breakup/current wedge electric field on the preexisting DP2 electric field. Evidently, the enhanced ionospheric conductivity strip usually associated with the current wedge is initially located equatorward of Frederikshab, since its effect is not apparent at that location. During the expansion phase proper, a clearly resolved current wedge expanded so that the radar backscatter lay within it. The expansion led to an increased current over Frederikshab, but a slightly suppressed plasma flow, related by an increased Σ* ∼ 4 S: the effect of the precipitation induced conductivity strip now apparent. It is suggested that near-Earth current disruption may play a significant role in the onset of this particular substorm, which occurred during a nonstorm time interval.last_img read more

Evolution of the Scotia Sea region: relevance to broad-band seismology

first_imgThis paper reports briefly an attempt to examine the tectonic evolution of the Scotia Sea region, in thecontext of the use of broad-band seismological techniques there. Such techniques can determine present plateboundaries, and examine crustal and upper mantle velocities and velocity anisotropy. Some studies are already underway (e.g. Vuan et al., 1999; Mueller, 1999; in press) and additional work is planned. An understanding of Scotia Seaevolution should allow future work to become more focussed.last_img read more

Fourier-transform Raman spectroscopic studies of chronological change in stromatolitic cores from Antarctic lake sediments

first_imgThe Fourier transform-Raman spectra of two lacustrine sediment cores from Antarctic sites are reported. The Lake Hoare specimens were predominantly calcium carbonate, quartz and β-carotene, with chlorophyll and calcium sulphate being noted as minor components. No evidence was found for iron (III) oxide or oxy-hydroxide bands. The Lake Nella specimens, in contrast, contain chlorophyll and quartz predominantly, but the absence of β-carotene is noteworthy. Here, the presence of haematite and a haematite–goethite mixture have been identified, with weaker features such as those of scytonemin, characteristic of cyanobacterial mats. The Raman spectra indicate that two different types of lake chemistry have been operating and several reasons are proposed for this.last_img read more

Disturbance, colonization and development of Antarctic benthic communities

first_imgA decade has yielded much progress in understanding polar disturbance and community recovery—mainly through quantifying ice scour rates, other disturbance levels, larval abundance and diversity, colonization rates and response of benthos to predicted climate change. The continental shelf around Antarctica is clearly subject to massive disturbance, but remarkably across so many scales. In summer, millions of icebergs from sizes smaller than cars to larger than countries ground out and gouge the sea floor and crush the benthic communities there, while the highest wind speeds create the highest waves to pound the coast. In winter, the calm associated with the sea surface freezing creates the clearest marine water in the world. But in winter, an ice foot encases coastal life and anchor ice rips benthos from the sea floor. Over tens and hundreds of thousands of years, glaciations have done the same on continental scales—ice sheets have bulldozed the seabed and the zoobenthos to edge of shelves. We detail and rank modern disturbance levels (from most to least): ice; asteroid impacts; sediment instability; wind/wave action; pollution; UV irradiation; volcanism; trawling; non-indigenous species; freshwater inundation; and temperature stress. Benthic organisms have had to recolonize local scourings and continental shelves repeatedly, yet a decade of studies have demonstrated that they have (compared with lower latitudes) slow tempos of reproduction, colonization and growth. Despite massive disturbance levels and slow recolonization potential, the Antarctic shelf has a much richer fauna than would be expected for its area. Now, West Antarctica is among the fastest warming regions and its organisms face new rapid changes. In the next century, temperature stress and non-indigenous species will drastically rise to become dominant disturbances to the Antarctic life. Here, we describe the potential for benthic organisms to respond to disturbance, focusing particularly on what we know now that we did not a decade ago.last_img read more

Interannual variability in phytoplankton biomass and species composition in northern Marguerite Bay (West Antarctic Peninsula) is governed by both winter sea ice cover and summer stratification

first_imgThe rapid warming of the West Antarctic Peninsula region has led to reduced sea ice cover and enhanced glacial melt water input. This has potential implications for marine ecosystems, notably phytoplankton growth, biomass, and composition. Fifteen years (1997–2012) of year-round size fractionated chlorophyll a (Chl a), phytoplankton pigment fingerprinting and environmental data were analyzed to identify the relationship between sea ice cover, water column stability and phytoplankton dynamics in northern Marguerite Bay, Antarctica. Over the investigated period, both summer (December–February) and winter biomass declined significantly, 38.5% and 33.3% respectively. Winter phytoplankton biomass was low (< 0.25 μg Chl a L−1) and consisted on average of 69% diatoms, 5% cryptophytes, and 20% haptophytes. Summers following winters with low (< 65 days) sea ice cover were characterized by decreased stratification strength and relatively low (median  20 μm) fraction was strongly decreased in the low biomass years, from 92% to 39%, coinciding with a smaller diatom fraction in favor of nanophytoplankton ( 95%) during summers with average-to-high biomass. We advance a conceptual model whereby low winter sea ice cover leads to low phytoplankton biomass and enhanced proportions of nanophytoplankton, when this coincides with reduced stratification during summer. These changes are likely to have a strong effect on the entire Antarctic marine food web, including krill biomass, and distribution.last_img read more

The emperor penguin – vulnerable to projected rates of warming and sea ice loss

first_imgWe argue the need to improve climate change forecasting for ecology, and importantly, how to relate long-term projections to conservation. As an example, we discuss the need for effective management of one species, the emperor penguin, Aptenodyptes forsteri. This species is unique amongst birds in that its breeding habit is critically dependent upon seasonal fast ice. Here, we review its vulnerability to ongoing and projected climate change, given that sea ice is susceptible to changes in winds and temperatures. We consider published projections of future emperor penguin population status in response to changing environments. Furthermore, we evaluate the current IUCN Red List status for the species, and recommend that its status be changed to Vulnerable, based on different modelling projections of population decrease of ≥50% over the current century, and the specific traits of the species. We conclude that current conservation measures are inadequate to protect the species under future projected scenarios. Only a reduction in anthropogenic greenhouse gas emissions will reduce threats to the emperor penguin from altered wind regimes, rising temperatures and melting sea ice; until such time, other conservation actions are necessary, including increased spatial protection at breeding sites and foraging locations. The designation of large-scale marine spatial protection across its range would benefit the species, particularly in areas that have a high probability of becoming future climate change refugia. We also recommend that the emperor penguin is listed by the Antarctic Treaty as an Antarctic Specially Protected Species, with development of a species Action Plan.last_img read more

Rates and mechanisms of turbulent mixing in a coastal embayment of the West Antarctic Peninsula

first_imgQuantifying and understanding the processes driving turbulent mixing around Antarctica is key to closing the Southern Ocean’s heat budget, an essential component of the global climate system. In 2016, a glider deployed in Ryder Bay, West Antarctic Peninsula, collected hydrographic and microstructure data, obtaining some of the first direct measurements of turbulent kinetic energy dissipation off West Antarctica. Elevated dissipation O(10−8) W kg−1 is found above a topographic ridge separating the 520 m‐deep bay, where values are O(10−10) W kg−1, from a deep fjord of the continental shelf, suggesting the ridge is important in driving upward mixing of warm Circumpolar Deep Water. Twelve glider transects reveal significant temporal variability in hydrographic and dissipation conditions. Mooring‐based current and nearby meteorological data are used to attribute thermocline shoaling (deepening) to Ekman upwelling (downwelling) at Ryder Bay’s southern boundary, driven by ∼ 3‐day‐long south‐westward (north‐westward) wind events. Anticyclonic winds generated near‐inertial shear in the bay’s upper layers, causing elevated bay‐wide shear and dissipation ∼ 1.7 days later. High dissipation over the ridge appears to be controlled hydraulically, being co‐located (and moving) with steeply sloping isopycnals. These are observed in ∼ 60% of the transects, with a corresponding mean upward heat flux of ∼ 2.4 W m−2. The ridge therefore provides sustained heat to the base of the thermocline, which can be released into overlying waters during the bay‐wide, thermocline‐focused dissipation events (mean heat flux of ∼ 1.3 W m−2). This highlights the role of ridges, which are widespread across the West Antarctic Peninsula, in the regional heat budget.last_img read more

Former all-star Ilya Kovalchuk returns to NHL with the Los Angeles Kings

first_imgJune 23, 2018 /Sports News – National Former all-star Ilya Kovalchuk returns to NHL with the Los Angeles Kings Beau Lund FacebookTwitterLinkedInEmailiStock/Thinkstock(LOS ANGELES) — Former NHL all-star Ilya Kovalchuk, who left the league to play professionally in Russia, has agreed to join the Los Angeles Kings on a three-year deal, according to ESPN.ESPN adds that Kovalchuk will receive $6.25 annually on the deal. Kovalchuk left the NHL in 2013 to play for SKA St. Petersburg in the Kontinental Hockey League (KHL).Kovalchuk’s services were in high demand upon announcing his interest in returning to the NHL. He led the KHL in points last year, according to ESPN, and was a top goal-scorer during his first 11 seasons in the NHL. He additionally was named MVP at the 2018 Olympics in Pyeongchang.Vice president and general manager Rob Blake said in a statement “We are excited to add Ilya to the LA Kings organization. He gives us an added element of skill and scoring along with a desire to win. We will withhold further comment until July 1.”Copyright © 2018, ABC Radio. All rights reserved.center_img Written bylast_img read more