scholarly journals Intra-specific variation in lichen secondary compounds across environmental gradients on Signy Island, maritime Antarctic

Polar Biology ◽  
2021 ◽  
Author(s):  
Stef Bokhorst ◽  
Johan Asplund ◽  
Peter Convey
Keyword(s):  
Acid Concentration ◽  
Environmental Gradients ◽  
Usnic Acid ◽  
Secondary Compounds ◽  
Maritime Antarctic ◽  
Orkney Islands ◽  
Solar Exposure ◽  
Signy Island ◽  
Specific Variation ◽  
Gyrophoric Acid

AbstractLichens produce various carbon-based secondary compounds (CBSCs) in response to abiotic conditions and herbivory. Although lichen CBSCs have received considerable attention with regard to responses to UV-B exposure, very little is known about intra-specific variation across environmental gradients and their role in protection against herbivory in the Antarctic. Here we report on the variation in CBSCs of two widely distributed and common Antarctic lichens, Usnea antarctica and Umbilicaria antarctica, between sites with different solar exposure (NW–SE) and along natural nitrogen (N) gradients which are associated with changing lichen-invertebrate associations on Signy Island (South Orkney Islands, maritime Antarctic). Fumarprotocetraric and usnic acid concentrations in Usnea showed no relationships with solar exposure, lichen-N or associated invertebrate abundance. However, fumarprotocetraric acid concentration was 13 times higher at inland sites compared to coastal sites along the N-gradients. Gyrophoric acid concentration in Umbilicaria was 33% lower in sun-facing (northerly exposed) habitats compared to more shaded (south-facing) rocks and declined with elevation. Gyrophoric acid concentration was positively correlated with the abundance and species richness of associated microarthropods, similar to the patterns found with lichen N. This initial investigation indicates that there can be large intraspecific variation in lichen CBSC concentrations across relative short distances (< 500 m) on Signy Island and raises further questions regarding current understanding of the role of CBSCs in Antarctic lichens in relation to biotic and abiotic pressures.

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.

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.

scholarly journals Primary succession of lichen and bryophyte communities following glacial recession on Signy Island, South Orkney Islands, Maritime Antarctic

2012 ◽  
Vol 24 (4) ◽  
pp. 323-336 ◽  
Author(s):  
Sergio E. Favero-Longo ◽  
M. Roger Worland ◽  
Peter Convey ◽  
Ronald I. Lewis Smith ◽  
Rosanna Piervittori ◽  
...  
Keyword(s):  
Primary Succession ◽  
Environmental Parameters ◽  
Local Scale ◽  
Ice Age ◽  
Maritime Antarctic ◽  
Late 20Th Century ◽  
Continuous Increase ◽  
Orkney Islands ◽  
Signy Island ◽  
Recent Climate

AbstractA directional primary succession with moderate species replacement was quantitatively characterized on Signy Island in zones of a glacial valley corresponding to their age since deglaciation. A continuous increase in diversity and abundance of lichens and bryophytes was observed between terrains deglaciated in the late 20th century, to areas where deglaciation followed the Little Ice Age, and others thought to be ice-free since soon after the Last Glacial Maximum. Classification (UPGMA) and ordination (principal co-ordinate analysis) of vegetation data identified three different stages of development: a) pioneer communities, which rapidly develop in a few decades, b) immature communities developing on three to four century old terrains, and c) a climax stage (Polytrichum strictum-Chorisodontium aciphyllum community) developing on the oldest terrains, but only where local-scale environmental features are more favourable. Multivariate analysis including environmental parameters (canonical correspondence analysis) indicated terrain age as being the dominant controlling factor, with other environmental factors also exhibiting significant conditional effects (duration of snow cover, surface stoniness). These findings not only quantitatively verify reports of the rapid colonization of Maritime Antarctic terrains following recent climate amelioration and associated decrease in glacial extent, but also show how local-scale environmental resistance may slow or even prevent vegetation succession from pioneer to more mature stages in future.

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.

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.

The relationship between water chemistry and surface sediment diatom assemblages in maritime Antarctic lakes

1993 ◽  
Vol 5 (4) ◽  
pp. 339-348 ◽  
Author(s):  
V. J. Jones ◽  
S. Juggins ◽  
J. C. Ellis-Evans
Keyword(s):  
Water Chemistry ◽  
Transfer Functions ◽  
Environmental Gradients ◽  
Species Abundance ◽  
South Shetland Islands ◽  
Diatom Species ◽  
Maritime Antarctic ◽  
Diatom Assemblages ◽  
Lake Chemistry ◽  
Orkney Islands

Maritime Antarctic freshwater lakes and their catchments are inherently simple systems in an environment which is characterized by strong seasonality. Such lakes offer excellent opportunities to study the interaction of water chemistry and plant communities. The response of diatom species to environmental gradients was assessed by constructing a diatom and water chemistry dataset from 59 lakes at two locations (Livingston Island, South Shetland Islands and Signy Island, South Orkney Islands). Results indicate that diatom species abundance is predominately related to nutrient and salinity gradients. The dataset will be used to create transfer functions which can be applied to sediment core diatom assemblages to reconstruct historical patterns of lake chemistry.

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.

Interactions between climate, vegetation and the active layer in soils at two Maritime Antarctic sites

2006 ◽  
Vol 18 (3) ◽  
pp. 323-333 ◽  
Author(s):  
N. Cannone ◽  
J.C. Ellis Evans ◽  
R. Strachan ◽  
M. Guglielmin
Keyword(s):  
Layer Thickness ◽  
Active Layer ◽  
Air Temperature ◽  
Vegetation Type ◽  
Ground Surface ◽  
Active Layer Thickness ◽  
Maritime Antarctic ◽  
Orkney Islands ◽  
Signy Island ◽  
Air Temperatures

In the summer 2000–01, thermal monitoring of the permafrost active layer within various terrestrial sites covered by lichen, moss or grasses was undertaken at Jubany (King George Island) and Signy Island in the Maritime Antarctic. The results demonstrated the buffering effect of vegetation on ground surface temperature (GST) and the relationship between vegetation and active layer thickness. Vegetation type and coverage influenced the GST in both locations with highest variations and values in the Deschampsia and Usnea sites and the lowest variations and values in the Jubany moss site. Active layer thickness ranged from 57 cm (Jubany moss site) to 227 cm (Signy Deschampsia site). Active layer thickness data from Signy were compared with data collected at the same location four decades earlier. Using a regression equation for air temperature versus ground surface temperatures the patterns of changing air temperature over time suggest that the active layer thickness increased c. 30 cm between 1963 and 1990 and then decreased 30 cm between 1990 and 2000. The documented increased rate of warming (2°C ± 1) since 1950 for air temperatures recorded in the South Orkney Islands suggests that the overall trend of active layer thickness increase will be around 1 cm year−1.

scholarly journals Biogeochemical responses to nutrient, moisture and temperature manipulations of soil from Signy Island, South Orkney Islands in the Maritime Antarctic

2014 ◽  
Vol 26 (5) ◽  
pp. 513-520 ◽  
Author(s):  
Sun Benhua ◽  
P.G. Dennis ◽  
V.A. Laudicina ◽  
V.J. Ord ◽  
S.P. Rushton ◽  
...  
Keyword(s):  
N Mineralization ◽  
Soil Microbial Activity ◽  
Organic Substrates ◽  
Maritime Antarctic ◽  
Soil Microbial ◽  
Orkney Islands ◽  
Signy Island ◽  
Microbial Responses ◽  
C And N ◽  
C And N Cycling

AbstractWe have investigated how the microbially-driven processes of carbon (C) mineralization (respiration) and nitrogen (N) mineralization/immobilization in a soil from the northern Maritime Antarctic respond to differences in water availability (20% and 80% water-holding capacity) and temperature (5°C and 15°C) in the presence and absence of different organic substrates (2 mg C as either glucose, glycine or tryptone soy broth (TSB) powder (a complex microbial growth medium)) in a controlled laboratory experiment over 175 days. Soil respiration and N mineralization/immobilization in the presence of a C-rich substrate (glucose) increased with increases in water and temperature. These factors were influential individually and had an additive effect when applied together. For the N-rich substrates (glycine and TSB), microbial responses to increased water or temperature alone were weak or not significant, but these factors interacted to give significantly positive increases when applied together. These data indicate that under the expected changes in environmental conditions in the Maritime Antarctic, where temperature and the availability of water and organic substrates will probably increase, soil microbial activity will lead to more rapid C and N cycling and have a positive feedback on these biogeochemical processes, particularly where or when these factors increase concurrently.

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.

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