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Antarctic Continent (antarctic + continent)
Selected AbstractsOffshore spatial segregation in giant petrels Macronectes spp.: differences between species, sexes and seasonsAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue S1 2007J. González-Solís Abstract 1.Investigations were made to determine whether the two giant petrel species segregate by gender and species in relation to the stage of the annual cycle. The individual foraging behaviour of 14 male and 11 female northern giant petrels (Macronectes halli) and 13 male and 15 female southern giant petrels (M. giganteus) breeding at South Georgia were tracked over 1 year using geolocators (global location sensing loggers). 2.Males of both species showed a flexible foraging strategy, switching from coastal to pelagic habits, probably governed by spatio-temporal changes in carrion availability. In contrast, marine areas exploited by females were more consistent over the year and similar for the two species, with most foraging locations concentrated over the same pelagic waters. 3.This study provides support for the differences in foraging between sexes as the main mechanism reducing intraspecific competition. Although the two species are morphologically similar and can easily access each other's foraging habitat, they differ in the foraging areas exploited. Thus, interspecific competition seems mainly relaxed by spatial segregation, particularly between males in winter, probably mediated by different competitive abilities and physical tolerances to temperature and winds. Foraging southern giant petrels from South Georgia were not restricted to the areas within the line of equidistance to other colonies, but their foraging range overlapped with feeding grounds of conspecifics breeding in the Falkland Islands and the Antarctic Continent. 4.Taken together, these findings suggest that foraging selection on marine habitat heterogeneity reduces interspecific competition, whereas carrion availability reduces intersexual competition, in giant petrels. Copyright © 2008 John Wiley & Sons, Ltd. [source] Antarctic climate change during the last 50 yearsINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 3 2005John Turner Abstract An erratum has been published for this article in International Journal of Climatology 25 (8) 2005, 1147,1148. The Reference Antarctic Data for Environmental Research (READER) project data set of monthly mean Antarctic near-surface temperature, mean sea-level pressure (MSLP) and wind speed has been used to investigate trends in these quantities over the last 50 years for 19 stations with long records. Eleven of these had warming trends and seven had cooling trends in their annual data (one station had too little data to allow an annual trend to be computed), indicating the spatial complexity of change that has occurred across the Antarctic in recent decades. The Antarctic Peninsula has experienced a major warming over the last 50 years, with temperatures at Faraday/Vernadsky station having increased at a rate of 0.56 °C decade,1 over the year and 1.09 °C decade,1 during the winter; both figures are statistically significant at less than the 5% level. Overlapping 30 year trends of annual mean temperatures indicate that, at all but two of the 10 coastal stations for which trends could be computed back to 1961, the warming trend was greater (or the cooling trend less) during the 1961,90 period compared with 1971,2000. All the continental stations for which MSLP data were available show negative trends in the annual mean pressures over the full length of their records, which we attribute to the trend in recent decades towards the Southern Hemisphere annular mode (SAM) being in its high-index state. Except for Halley, where the trends are constant, the MSLP trends for all stations on the Antarctic continent for 1971,2000 were more negative than for 1961,90. All but two of the coastal stations have recorded increasing mean wind speeds over recent decades, which is also consistent with the change in the nature of the SAM. Copyright © 2005 Royal Meteorological Society [source] Distribution and temporal variability of 500 hPa cyclone characteristics in the Southern HemisphereINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 2 2002Murray Keable Abstract A 40 year period (1958,97) of US National Centers for Environmental Prediction reanalysis data has been used to diagnose the behaviour and variability of 500 hPa extratropical cyclones for the Southern Hemisphere using a Lagrangian perspective. The ,finding' and ,tracking' of these systems were performed using a fully automated scheme. Seasonal distributions of system density, cyclone formation (cyclogenesis), decay (cyclolysis), cyclone centre velocity and intensity/strength are presented. System density is shown to exhibit a maximum in the surface circumpolar trough region and over the Antarctic continent. A broad band of enhanced cyclone system density was evident across the South Pacific from southeast Australia to South America in all seasons, most markedly in winter. As this feature appears also at the surface level, strong vertical consistency of these cyclones in the low and middle troposphere is indicated. Velocities of cyclone centres were found to peak in the latitudes 50,55 °S, and 500 hPa systems appeared to move on average in a much more zonal (easterly) direction than their sea-level counterparts. The mean number of midlatitude cyclones per analysis has exhibited a significant downward trend over the record, with particularly low values observed in the early 1980s. Offsetting this trend have been increases in three measures of mean cyclone vigour. Three orographic features, in particular, are seen to influence the behaviour of 500 hPa cyclones: the mountains of New Zealand, the Antarctic Peninsula and the southern Andes. Over most of Antarctica the rate of cyclogenesis exceeds that of cyclolysis, indicating that many of the cyclones being formed in the vortex are actually exported out (i.e. to the north) of the continent. In the subtropics, considerable numbers of systems are formed in the Mozambique Sea region, but these tend to be quasi-stationary features. Copyright © 2002 Royal Meteorological Society. [source] Contrasting effects of the extent of sea-ice on the breeding performance of an Antarctic top predator, the Snow Petrel Pagodroma niveaJOURNAL OF AVIAN BIOLOGY, Issue 4 2001Christophe Barbraud Recent studies have shown that the Antarctic Circumpolar Wave and the related sea-ice cover around the Antarctic continent may have a profound effect on the lower trophic levels of the marine environment. In particular, extensive sea-ice cover enhances the survival of krill. However, the effects of sea-ice cover on top predators remain poorly understood. Using time series from 1973 to 1999, we examine the influence of regional sea-ice extent on a number of indices of breeding performance of an avian predator, the Snow Petrel, in Antarctica. The percentage of breeding pairs was highly variable and there were fewer birds breeding when sea-ice cover was extensive during July. By contrast, overall breeding success and fledgling body condition were improved during years with extensive sea-ice cover during the preceding November and July,September. These results indicate that the same sea-ice conditions may have different effects on the breeding performance of a species. The overall increase in winter sea-ice extent during the last decade appears to have resulted in an overall improvement of the quality of fledglings produced, and thus probably of future recruitment. [source] Evidence for a lacustrine faunal refuge in the Larsemann Hills, East Antarctica, during the Last Glacial MaximumJOURNAL OF BIOGEOGRAPHY, Issue 7 2006Louise Cromer Abstract Aim, There is no previous direct evidence for the occurrence of lacustrine refuges for invertebrate fauna in Antarctica spanning the Last Glacial Maximum (LGM). In the absence of verified LGM lacustrine refuges many species are believed to result from Holocene dispersal from sub-Antarctic islands and continents further north. If freshwater lake environments were present throughout the LGM, extant freshwater species may have been associated with Antarctica prior to this glacial period. This study looked at faunal microfossils in a sediment core from an Antarctic freshwater lake. This lake is unusual in that, unlike most Antarctic lakes, the sediment record extends to c. 130,000 yr bp, i.e. prior to the LGM. Location, Lake Reid, Larsemann Hills, East Antarctica (76°23, E; 69°23, S). Methods, Palaeofaunal communities in Lake Reid were identified through examination of faunal microfossils in a sediment core that extended to c. 130,000 yr bp. Results, Ephippia and mandibles from the cladoceran Daphniopsis studeri and loricae of the rotifer Notholca sp. were found at all depths in the sediment, indicating that these two species have been present in the lake for up to 130,000 years. Copepod mandibles were also present in the older section of the core, yet were absent from the most recent sediments, indicating extinction of this species from Lake Reid during the LGM. Main conclusion, The presence of D. studeri and Notholca sp. microfossils throughout the entire Lake Reid core is the first direct evidence of a glacial lacustrine refugium for invertebrate animals in Antarctica, and indicates the presence of a relict fauna on the Antarctic continent. [source] The Ultraviolet Radiation Environment of High Southern Latitudes: Springtime Behavior over a Decadal Timescale,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2005Yixiang Liao ABSTRACT Four spectroradiometers located at latitudes from 55° to 90°S conducted near-continuous measurements of ground-level solar ultraviolet irradiance from 1990 through 2001. The behavior during months from October through December is of special interest because this period includes the springtime loss in column ozone and the naturally large irradiances of early summer. Monthly integrated irradiances using biological weightings for erythema and damage to DNA show a distortion of the normal annual cycle in irradiance, with enhanced values occurring in October and November. In some cases, these irradiances exceed those near summer solstice in December. Changes in local cloudiness and column ozone both contribute significantly to interannual variability in erythemal irradiance. This is particularly the case at Palmer Station, near 65°S, where the monthly integrated erythemal irradiance in November 1997 was more than double that observed 5 years earlier. In general, at sites on the Antarctic continent, interannual variability in monthly integrated erythemal irradiance is greatest in November, when the observation for any given year can fall 40% above or below the multiyear mean. Near the tip of South America, interannual variability is approximately half that seen in Antarctica. [source] Stable isotope natural abundance of nitrous oxide emitted from Antarctic tundra soils: effects of sea animal excrement depositionsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 22 2008Renbin Zhu Nitrous oxide (N2O), a greenhouse gas, is mainly emitted from soils during the nitrification and denitrification processes. N2O stable isotope investigations can help to characterize the N2O sources and N2O production mechanisms. N2O isotope measurements have been conducted for different types of global terrestrial ecosystems. However, no isotopic data of N2O emitted from Antarctic tundra ecosystems have been reported although the coastal ice-free tundra around Antarctic continent is the largest sea animal colony on the global scale. Here, we report for the first time stable isotope composition of N2O emitted from Antarctic sea animal colonies (including penguin, seal and skua colonies) and normal tundra soils using insitu field observations and laboratory incubations, and we have analyzed the effects of sea animal excrement depositions on stable isotope natural abundance of N2O. For all the field sites, the soil-emitted N2O was 15N- and 18O-depleted compared with N2O in local ambient air. The mean , values of the soil-emitted N2O were ,15N,=,,13.5,±,3.2, and ,18O,=,26.2,±,1.4, for the penguin colony, ,15N,=,,11.5,±,5.1, and ,18O,=,26.4,±,3.5, for the skua colony and ,15N,=,,18.9,±,0.7, and ,18O,=,28.8,±,1.3, for the seal colony. In the soil incubations, the isotopic composition of N2O was measured under N2 and under ambient air conditions. The soils incubated under the ambient air emitted very little N2O (2.93,µg,N2ON,kg,1). Under N2 conditions, much more N2O was formed (9.74,µg,N2ON,kg,1), and the mean ,15N and ,18O values of N2O were ,19.1,±,8.0, and 21.3,±,4.3,, respectively, from penguin colony soils, and ,17.0,±,4.2, and 20.6,±,3.5,, respectively, from seal colony soils. The data from in situ field observations and laboratory experiments point to denitrification as the predominant N2O source from Antarctic sea animal colonies. Copyright © 2008 John Wiley & Sons, Ltd. [source] Biological invasions in the Antarctic: extent, impacts and implicationsBIOLOGICAL REVIEWS, Issue 1 2005Yves Frenot ABSTRACT Alien microbes, fungi, plants and animals occur on most of the sub-Antarctic islands and some parts of the Antarctic continent. These have arrived over approximately the last two centuries, coincident with human activity in the region. Introduction routes have varied, but are largely associated with movement of people and cargo in connection with industrial, national scientific program and tourist operations. The large majority of aliens are European in origin. They have both direct and indirect impacts on the functioning of species-poor Antarctic ecosystems, in particular including substantial loss of local biodiversity and changes to ecosystem processes. With rapid climate change occurring in some parts of Antarctica, elevated numbers of introductions and enhanced success of colonization by aliens are likely, with consequent increases in impacts on ecosystems. Mitigation measures that will substantially reduce the risk of introductions to Antarctica and the sub-Antarctic must focus on reducing propagule loads on humans, and their food, cargo, and transport vessels. [source] | ||||||||||