Authors:Ben J. Dilley; David W. Hedding, Dominic A.W. Henry, Kalinka Rexer-Huber, Graham C. Parker, Stefan Schoombie, Alexis Osborne, Peter G. Ryan Pages: 231 - 242 Abstract: We compared systematic and random survey techniques to estimate breeding population sizes of burrow-nesting petrel species on Marion Island. White-chinned (Procellaria aequinoctialis) and blue (Halobaena caerulea) petrel population sizes were estimated in systematic surveys (which attempt to count every colony) in 2009 and 2012, respectively. In 2015, we counted burrows of white-chinned, blue and great-winged (Pterodroma macroptera) petrels within 52 randomized strip transects (25 m wide, total 144 km). Burrow densities were extrapolated by Geographic Information System-derived habitat attributes (geology, vegetation, slope, elevation, aspect) to generate island-wide burrow estimates. Great-winged petrel burrows were found singly or in small groups at low densities (2 burrows ha−1); white-chinned petrel burrows were in loose clusters at moderate densities (3 burrows ha−1); and blue petrel burrows were in tight clusters at high densities (13 burrows ha−1). The random survey estimated 58% more white-chinned petrels but 42% fewer blue petrels than the systematic surveys. The results suggest that random transects are best suited for species that are widely distributed at low densities, but become increasingly poor for estimating population sizes of species with clustered distributions. Repeated fixed transects provide a robust way to monitor changes in colony density and area, but might fail to detect the formation/disappearance of new colonies. PubDate: 2019-10-01T00:00:00.000Z DOI: 10.1017/S0954102019000300 Issue No:Vol. 31, No. 5 (2019)
Dissostichus+mawsoni+in+the+Ross+Sea+region&rft.title=Antarctic+Science&rft.issn=0954-1020&rft.date=2019&rft.volume=31&rft.spage=243&rft.epage=253&rft.aulast=Parker&rft.aufirst=Steven&rft.au=Steven+J.+Parker&rft.au=Darren+W.+Stevens,+Laura+Ghigliotti,+Mario+La+Mesa,+Davide+Di+Blasi,+Marino+Vacchi&rft_id=info:doi/10.1017/S0954102019000282">Winter spawning of Antarctic toothfish Dissostichus mawsoni in the Ross Sea region
Authors:Steven J. Parker; Darren W. Stevens, Laura Ghigliotti, Mario La Mesa, Davide Di Blasi, Marino Vacchi Pages: 243 - 253 Abstract: A survey of Antarctic toothfish (Dissostichus mawsoni) was conducted in the northern Ross Sea region during the winter of 2016 to document the timing and location of spawning activity, to collect biological information about reproductive status during the spawning season and to look for temporal signals in biological data from D. mawsoni that may indicate a spawning migration of mature toothfish from the continental slope region to the northern Ross Sea region. The 58 day survey showed that spawning of D. mawsoni began on some seamounts by early July. No changes were detected between winter and summer in length, age, sex ratio or condition factor distributions for D. mawsoni in the northern Ross Sea as hypothesized following a spawning migration from the slope to the northern Ross Sea region. These results suggest that the distribution of D. mawsoni in the Ross Sea is mainly accomplished through ontogenetic migration and not annual return spawning migrations. PubDate: 2019-10-01T00:00:00.000Z DOI: 10.1017/S0954102019000282 Issue No:Vol. 31, No. 5 (2019)
Authors:Victor C.S. Badaró; Setembrino Petri Pages: 254 - 262 Abstract: Here we describe new microfossil assemblages for the Miocene Hobbs Glacier Formation and the first possibly indigenous assemblages for the Plio-Pleistocene Weddell Sea Formation on Seymour Island, West Antarctica. The assemblages are composed mainly of foraminifers, but radiolarians, calcitarchs and poriferan sclerites are also present. For the Hobbs Glacier Formation, we report the foraminifers Bolivina sp., Oolina globosa and Rosalina cf. globularis; and for the Weddell Sea Formation, we report Favulina hexagona, Globigerinita uvula, Globocassidulina cf. subglobosa and Psammosphaera fusca. The low abundance and diversity of microfossils, allied with the complex taphonomical processes that prevailed in Antarctic glacial–marine palaeoenvironments, make it impossible to define whether the assemblages are composed of a mixture of indigenous and re-elaborated specimens or exclusively of re-elaborated remains. Nevertheless, the indigenous nature of some specimens is suggested by their inherent fragility, excellent preservation and/or taxonomic association with indigenous assemblages from correlated strata. The taxonomic compositions are not directly comparable with other Antarctic assemblages, although most of the species were previously reported from pre-Quaternary or modern deposits of both West and East Antarctica. This lack of correspondence is probably due to preservation biases, but any further significance is hidden by the complex taphonomy of the deposits. PubDate: 2019-10-01T00:00:00.000Z DOI: 10.1017/S0954102019000294 Issue No:Vol. 31, No. 5 (2019)
Authors:Christopher P. McKay; Edward Balaban, Simon Abrahams, Nick Lewis Pages: 263 - 270 Abstract: Dry permafrost - ground with temperature always below 0°C and containing negligible ice - overlying ice-cemented ground has been reported in the Dry Valleys of Antarctica and on Mars. Here we report on a new site (79°49.213'S, 83°18.860'W, 718 m elevation) located on the side of Mount Dolence in Ellsworth Land, Antarctica. Year-round temperature and humidity measurements indicate that dry permafrost is present between depths of 13.5 and 49.0 cm - the location of ice-cemented ground. The mean annual frost point of the ice-cemented ground is -17.0 ± 0.2°C and the mean annual frost point of the atmosphere is -22.7 ± 1°C. The corresponding mean annual temperatures are -19.2°C and -20.3°C. Neither the temperature of the ice-cemented ground nor the air rise above freezing. Both the dry permafrost and the ice table may be habitable. In the dry soil at 3 cm depth there are 80 hours in the summer when temperature exceeds -5°C and water activity exceeds 0.8. At the ice table, temperature exceeds -10°C and water activity exceeds 0.8 for 35 hours in the year. The ice table and the dry permafrost above it would be considered a ‘Special Region’ on Mars. Further microbial investigation of this site is indicated. PubDate: 2019-10-01T00:00:00.000Z DOI: 10.1017/S0954102019000269 Issue No:Vol. 31, No. 5 (2019)
Authors:Benoit Faucher; Denis Lacelle, David A. Fisher, Dale T. Andersen, Christopher P. McKay Pages: 271 - 285 Abstract: Lake Untersee is one of the largest perennially ice-covered lakes in Dronning Maud Land. We investigated the energy and water mass balance of Lake Untersee to understand its state of equilibrium. The thickness of the ice cover is strongly correlated with sublimation rates; variations in sublimation rates across the ice cover are largely determined by wind-driven turbulent heat fluxes and the number of snow-covered days. Lake extent and water level have remained stable for the past 20 years, indicating that the water mass balance is in equilibrium. The lake is damned by the Anuchin Glacier and mass balance calculation suggest that subaqueous melting of terminus ice contributes 40–45% of the annual water budget; since there is no evidence of streams flowing into the lake, the lake must be connected to a groundwater system that contributes 55–60% in order to maintain the lake budget in balance. The groundwater likely flows at a rate of ~8.8 × 10−2 m3 s−1, a reasonable estimate given the range of subglacial water flux in the region. The fate of its well-sealed ice cover is likely tied to changes in wind regime, whereas changes in water budget are more closely linked to the response of surrounding glaciers to climate change. PubDate: 2019-10-01T00:00:00.000Z DOI: 10.1017/S0954102019000270 Issue No:Vol. 31, No. 5 (2019)
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