Taxonomic studies of Achnanthes (Bacillariophyta) in freshwater maritime antarctic lakes

1994 ◽  
Vol 72 (12) ◽  
pp. 1735-1748 ◽  
Author(s):  
D. R. Oppenheim
Keyword(s):  
Trophic Status ◽  
Maritime Antarctic ◽  
Widespread Occurrence ◽  
Orkney Islands ◽  
Signy Island ◽  
South Orkney Islands ◽  
Algal Material ◽  
Taxonomic Studies ◽  
One New Species ◽  
Eleven Species

Eleven species of Achnanthes from Signy Island, South Orkney Islands are described including one new species. Benthic algal material from a range of shallow lakes of varying trophic status was examined by light microscopy and scanning electron microscopy. Detail of morphology is provided with an overview of the taxonomic literature for each species. In all cases source descriptions are cited, and where possible holotype and lectotype material was examined. The variation between populations inhabiting different lakes is considered. An examination of the geographical distribution of Achnanthes in southern latitudes from the literature confirms numerous records of widespread occurrence in freshwater environments in sub-antarctic regions but not from higher latitudes. Key words: Achnanthes, Antarctic, taxonomy, benthic, phytogeography.

A fern cultured from Antarctic glacier detritus

2013 ◽  
Vol 26 (4) ◽  
pp. 341-344 ◽  
Author(s):  
R.I. Lewis Smith
Keyword(s):  
Maritime Antarctic ◽  
Orkney Islands ◽  
Ice Cap ◽  
Signy Island ◽  
South Orkney Islands ◽  
Mode Of Transport

AbstractA fem, Elaphoglossum hybridum (Bory) Brack., has been cultured from mineral sediment in cryoconite holes in the ice cap of Signy Island, South Orkney Islands. Its provenance, mode of transport to its Maritime Antarctic destination and the significance of viable exotic propagules as potential colonists are discussed.

The terrestrial invertebrate fauna of the Maritime Antarctic

1967 ◽  
Vol 252 (777) ◽  
pp. 261-278 ◽  
Keyword(s):  
Limiting Factor ◽  
Maritime Antarctic ◽  
Invertebrate Fauna ◽  
Orkney Islands ◽  
Signy Island ◽  
South Orkney Islands ◽  
Terrestrial Habitats ◽  
Community Variation ◽  
The Antarctic ◽  
Basic Similarity

During the period from 18 January to 31 M arch 1964 the author was able to visit certain islands on the Scotia Ridge and parts of the Antarctic Peninsula. Apart from South Georgia, all the areas lie within the Maritime Antarctic region (Holdgate 1964). At each locality an attempt was made to ascertain the composition of the meiofauna from as many terrestrial habitats as possible and, when time permitted, quantitative sampling was carried out. During the previous two years a similar but more detailed study was carried out at Signy Island, South Orkney Islands, but the bulk of these data will be presented elsewhere. Figure 32 shows all the areas visited with the month and number of quantitative samples taken. It was only possible to spend a few hours at certain localities. The Maritime Antarctic is, by definition (Holdgate 1964), a region bounded by isotherms and supporting a limited but typical vegetation. The types of plant communities have already been discussed (Longton, this Discussion, p. 213) and it is clear that whilst a considerable amount of species and community variation exists there is a basic similarity throughout the region. This general uniformity of climate and vegetation would together appear to offer a similar set of terrestrial habitat conditions. If dispersal were not a limiting factor, one would also expect the invertebrate fauna of such habitats to exhibit a uniform pattern. In fact it does not.

Chemistry of streams of Signy Island, maritime Antarctic: sources of major ions

1997 ◽  
Vol 9 (1) ◽  
pp. 3-11 ◽  
Author(s):  
A.P. Caulkett ◽  
J.C. Ellis-Evans
Keyword(s):  
Major Ions ◽  
Maritime Antarctic ◽  
General Study ◽  
Orkney Islands ◽  
Signy Island ◽  
South Orkney Islands ◽  
Dissolved Ions

A general study of the streams of Signy Island, South Orkney Islands, was undertaken to identify the effects of catchment, distance from source, and time on concentrations of dissolved ions. In the majority of cases catchment did not affect the chemistry of streams, although marine-derived ions were affected by distance from the sea. Na+, K+, Mg2+, Ca2+, Cl− and NH4+were derived from the thawing of the winter snowpack. NO3− was derived from areas of permanent ice. SiO44−, Ca2+, Mg2+ and CO2−3 were derived from crustal weathering. Although PO43− was also derived from crustal weathering, it was released as a pulse related to the thawing of the soil.

Extensive colonization of volcanic ash by an unusual form of Peltigera didactyla at Deception Island, maritime Antarctic

2005 ◽  
Vol 37 (4) ◽  
pp. 367-368 ◽  
Author(s):  
Ronald I. Lewis-Smith
Keyword(s):  
Volcanic Ash ◽  
Deception Island ◽  
Maritime Antarctic ◽  
Cosmopolitan Distribution ◽  
Orkney Islands ◽  
Signy Island ◽  
Unusual Form ◽  
South Orkney Islands ◽  
The Antarctic

Peltigera didactyla (With.) J. R. Laundon has a cosmopolitan distribution, but in the Antarctic it is very restricted and is nowhere common or abundant, occurring at a number of sites in the northern maritime Antarctic extending to 65°S (Øvstedal & Lewis-Smith, 2001). Within its Antarctic distribution it appears to be most frequent on Signy Island, South Orkney Islands. Typically, this species grows as small colonies amongst mosses in relatively dry, gravelly, sheltered habitats, forming aggregations of lobed sorediate thalli up to c. 10–15 (rarely to c. 25) cm diameter.

Theudium Austroatlanticum (Verrucariaceae), A New Species from the South Orkney Islands

1993 ◽  
Vol 25 (3) ◽  
pp. 271-277 ◽  
Author(s):  
Alan Orange
Keyword(s):  
New Species ◽  
The South ◽  
Orkney Islands ◽  
Signy Island ◽  
South Orkney Islands ◽  
A New Species

AbstractThelidium austroatlanticum sp. nov. is described from Signy island; it is characterized by an epilithic thallus, more or less appressed involucrellum, and 1-septate spores 30–40 μm long. Thelidium incavatum is also reported for Signy Island.

scholarly journals Snowmelt modelling on signy island, South Orkney Islands

1998 ◽  
Vol 26 ◽  
pp. 161-166 ◽  
Author(s):  
Michael J. Gardiner ◽  
J. Cynan Ellis-Evans ◽  
Malcolm G. Anderson ◽  
Martyn Tranter
Keyword(s):  
Snow Water Equivalent ◽  
Energy Content ◽  
Heat Fluxes ◽  
Geographical Information ◽  
Wave Radiation ◽  
Snow Pack ◽  
State Variables ◽  
Orkney Islands ◽  
Signy Island ◽  
South Orkney Islands

The ability of the Utah energy-balance and snowmelt model (UEB) to simulate decline in snow water equivalent (SWE) at an extreme location was assessed. Field data were collected at Paternoster Valley, Signy Island, South Orkney Islands (60°43′S) during the austral summer of 1996–97. This is the first application of UEB in a maritime Antarctic site. UEB is a physically based snow melt model using a lumped snow-pack representation with primary state variables SWE and snow pack-energy content(U).Meteorological inputs are air temperature, wind speed, humidity, precipitation and total incoming solar and longwave radiation. The Paternoster Valley catchment was subdivided into eight non-contiguous terrain classes for sampling and modelling using a geographical information system (GIS). Simulations of SWE in each of these classes were compared พ with field observations. It is shown that initialUand snow-surface thermal conductance(Ks)affect model simulations. Good approximations of SWE depletion are obtained using measured incoming solar radiation to drive the model but there are shortcomings in the characterization of long wave radiation and sensible-heat fluxes.

Colonization by Lichens and the Development of Lichen-Dominated Communities in the Maritime Antarctic

1995 ◽  
Vol 27 (6) ◽  
pp. 473-483 ◽  
Author(s):  
R.I. Lewis Smith
Keyword(s):  
Growth Rates ◽  
High Growth ◽  
Percentage Increase ◽  
Maritime Antarctic ◽  
Small Individual ◽  
Nitrogenous Compounds ◽  
Orkney Islands ◽  
Signy Island ◽  
Rhizocarpon Geographicum

AbstractThree long-term studies of lichen growth and colonization have been undertaken at Signy Island, South Orkney Islands, in the maritime Antarctic. Small individual thalli of several crustose species and uncolonized plots on 12 fresh rock surfaces were photographically monitored at intervals of 3–4 years over a period of up to 20 years. The development of Ochrolechia frigida colonies on a regenerating moss bank, recently uncovered by a receding glacier, was similarly monitored. The results indicate that many lichens growing in sites enriched by nitrogenous compounds derived from populations of sea birds, have relatively rapid colonization and growth rates. Mean percentage increase in thallus area can be as high as 15–32% per annum in some nitrophilous saxicolous species (e.g. Acarospora macrocyclos, Xanthoria elegans and species of Buellia and Caloplaca), but as low as, 0·4–4% in nitrophobous species (Lecanora physciella, Lecidea sp., Rhizocarpon geographicum). Umbilicaria antarctica and Usnea Antarctica also yielded data indicating high growth rates, with colonist plants reaching several centimetres after 20 years. Colonization by mixed assemblages of lichens of new rock surfaces can attain 40->90% cover after 20 years in nutrient-enriched sites, and even 20–25% in non-biotically influenced sites. Colonization by or increase in extant O. frigida on the regenerating moribund moss bank was also quite rapid. It is suggested that the exceptionally large thalli of several lichen species and the locally extensive dense lichen fellfield communities in the maritime Antarctic may be much younger than previously supposed.

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