Rodney D. Seppelt

Loss of soluble carbohydrates and changes in freezing point of Antarctic bryophytes after leaching and repeated freeze-thaw cycles

Healthy samples of Grimmia antarctici (turf and cushion ecodemes), Ceratodon purpureus, Bryum pseudotriquetrum and Cephaloziella exiliflora were collected in late summer in Wilkes Land together with senescing and dead G. antarctici material. Plant material was subjected to leaching in water and up to 16 freeze-thaw cycles. Gas chromatography revealed that following 16 days immersion, loss of carbohydrates (mainly glucose and fructose) was relatively low ( c. 10–29% of the total sugar pool) for healthy material, with the loss of 69% from the dead G. antarctici material. Freeze-thaw cycles greatly increased rates of sucrose leakage and led to a 2–3 times rise in total sugar loss in all samples except the dead brown tissue which was not significantly different from the leached control treatment. After 16 freeze-thaw cycles Bryum pseudotriquetrum had lost 65% of total sugar pool. Losses for other species were below 28%. Differential thermal analyses showed freezing points of tissue varied from −8.3 to −3.5°C with dead material having the highest freezing temperatures. There was no significant correlation within species of freezing temperature changes with progressive sugar loss. The results are discussed in relation to nutrient cycling, soil microbial activity and the viability of bryophyte species in the Antarctic environment.

The broad-scale distribution of microfungi in the Windmill Islands region, continental Antarctica

Abstract Microfungi were isolated from soils, mosses, algae and lichens in the Windmill Islands region of Antarctica. From a total of 1,228 isolates, 22 genera were identified. The most frequently isolated fungi from mosses were Mycelia sterilia (47% of total isolates), Phoma spp. (18%), Penicillium spp. (11%), Chrysosporium spp. (7%) and Thelebolus microsporus (6%). Mycelia sterilia, Penicillium spp., Mortierella spp., Chrysosporium cf. pannorum and Thelebolus microsporus were also frequently isolated from algae. Fungal distribution and diversity were poor in samples of lichens, compared to samples from mosses and algae. The frequency of occurrence of microfungi was most often associated with strong biotic influence. There was a marked increase in fungal diversity in human-disturbed sites. Twelve taxa were restricted to soils from near the Australian Casey Station, suggesting significant introduction of fungi into this environment by human activities. Away from the station, fungal distribution appeared to be related to substrata and nutrient status rather than dispersal opportunities. Suggestions for future research and the need for constant monitoring to clarify the role of human disturbance on Antarctic fungi are discussed.

Chlorophyll a fluorescence and CO2 exchange of Umbilicaria aprina under extreme light stress in the cold

Abstract A lichen growing in a continental Antarctic region with low temperatures and strong irradiance in summer was investigated for evidence of photoinhibition. Field experiments with Umbilicaria aprina from a sheltered site with heavy snowpack showed no effects of photoinhibition when the lichen was exposed to strong sun irradiance for nearly 11 h a day. This was evident from CO2 exchange and simultaneous chlorophyll a fluorescence measurements. CO2 exchange was also not affected if quartz glass allowing greater UV penetration, was used as a lid for the cuvette. The dependency of net photosynthesis on photosynthetic photon flux density suggests that the lichen is photophilous.

Polyol and sugar content of terrestrial plants from continental Antarctica

Ethanol extractable polyols and sugars from the dominant cryptogams of the Windmill Islands, Willies Land, East Antarctica, were characterized and quantified by gas liquid chromatography. Arabitol, ribitol and mannitol were the major low molecular weight carbohydrates extracted from all eight species of lichen analysed. Total extractable carbohydrate levels (20-60 mg g −1 dry weight) were comparable to those for temperate lichens. Extracts of four common bryophyte species were dominated by sucrose, glucose and fructose; little polyhydric alcohol was detected except in the liverwort Cephaloziella exiliflora which contained a substantial proportion of mannitol (...)

Photosynthetic responses of three common mosses from continental Antarctica

Predicting the effects of climate change on Antarctic terrestrial vegetation requires a better knowledge of the ecophysiology of common moss species. In this paper we provide a comprehensive matrix for photosynthesis and major environmental parameters for three dominant Antarctic moss species (Bryum subrotundifolium, B. pseudotriquetrum and Ceratodon purpureus). Using locations in southern Victoria Land, (Granite Harbour, 77°S) and northern Victoria Land (Cape Hallett, 72°S) we determined the responses of net photosynthesis and dark respiration to thallus water content, thallus temperature, photosynthetic photon flux densities and CO2 concentration over several summer seasons. The studies also included microclimate recordings at all sites where the research was carried out in field laboratories. Plant temperature was influenced predominantly by the water regime at the site with dry mosses being warmer. Optimal temperatures for net photosynthesis were 13.7°C, 12.0°C and 6.6°C for B. subrotundifolium, B. pseudotriquetrum and C. purpureus, respectively and fall within the known range for Antarctic mosses. Maximal net photosynthesis at 10°C ranked as B. subrotundifolium > B. pseudotriquetrum > C. purpureus. Net photosynthesis was strongly depressed at subzero temperatures but was substantial at 0°C. Net photosynthesis of the mosses was not saturated by light at optimal water content and thallus temperature. Response of net photosynthesis to increase in water content was as expected for mosses although B. subrotundifolium showed a large depression (60%) at the highest hydrations. Net photosynthesis of both B. subrotundifolium and B. pseudotriquetrum showed a large response to increase in CO2 concentration and this rose with increase in temperature; saturation was not reached for B. pseudotriquetrum at 20°C. There was a high level of variability for species at the same sites in different years and between different locations. This was substantial enough to make prediction of the effects of climate change very difficult at the moment.

Penicillium species from terrestrial habitats in the Windmill Islands, East Antarctica, including a new species, Penicillium antarcticum

Abstract This paper documents the Penicillium species associated with the naturally occurring plants and animals in the Windmill Islands, East Antarctica. An attempt has been made to establish the species associations between the Penicillia and the mosses and birds. The species found are discussed briefly in terms of taxonomy and biological significance, and a new species, Penicillium antarcticum, is described.

Phytogeography of bryophyte and lichen vegetation in the Windmill Islands, Wilkes Land, Continental Antarctica

The distribution and frequency of bryophyte and lichen vegetation on ice-free regions of the Windmill Islands are presented using data derived from aerial photography and ground surveying. The qualitative and quantitative plant cover of sites are listed and related to the topography and major soil characteristics of each site. The richest associations of macrolichens and bryophytes occurred on the metamorphic northern peninsulas. Species richness and frequency was generally reduced on the charnockitic southern peninsula and the islands which have been deglaciated longer. Salinity varied significantly throughout the region with the highest levels in the northern islands reflecting the presence of penguin colonies. In such sites bryophytes and lichens were virtually absent. Wind blown sea-spray contributed far less salts than direct excretion from penguins. On the peninsulas snow cover and site exposure appeared to delimit plant distribution. Higher salt levels from sea-spray on the northern aspects of the peninsulas seemed to have negligible impact on vegetation patterns with the possible exception ofBiatorella cerebriformis which was encountered only inland. The total phosphorus and nitrogen levels of the skeletal soils were generally low except in eutrophic sites adjacent to penguin colonies. The vegetation patterns are discussed in terms of the climate, topography and species autecology.

Microclimatic conditions, meltwater moistening, and the distributional pattern of Buellia frigida on rock in a southern continental Antarctic habitat

Abstract The importance of snowmelt as a source of moisture for the crustose lichen Buellia frigida in the early austral summer was investigated at Cape Geology, Granite Harbour, southern Victoria Land (77°01′S, 162°32′E). Surface and air temperatures and irradiance were recorded on the surface of a slightly inclined granite boulder for 5 weeks. Observations were made of lichen thallus hydration during a 5-day period. The results confirmed the strong warming effect of high irradiance; the rock surface and hydrated lichen were up to 19K above air temperature and, overall, the rock surface averaged 5.5K warmer. Therefore water condensation on the rock surface (dew or hoarfrost) was not possible during that period. Thalli were moistened by meltwater from both a small area of snow pack and from occasional snowfalls. The distribution of lichen thalli on the rock surface can be explained by the frequency and duration of meltwater moistening. Despite the very high irradiance whilst moist, the lichens seem well adapted to the combination of hydration, low temperatures and strong light.

Lichen and moss communities of Botany Bay, Granite Harbour, Ross Sea, Antarctica.

Abstract Botany Bay is one of the richest sites for lichen and bryophyte biodiversity in continental Antarctica. A total of 29 lichen, nine moss and one liverwort species have been identified. The most extensive vegetation occurs on a sheltered raised beach terrace. Vegetation associations are described and compared to other continental Antarctic localities that also possess a rich vegetation cover. Ordination analysis clearly indicates the importance of the type of water supply, its regularity, the substrate type, and particularly in Botany Bay, the influence of nutrients derived from the local bird population in governing plant distribution and associations. A vegetation map has been produced and can be used as a baseline to assess vegetation changes over time.

Exposure and Nutrients As Delimiters of Lichen Communities in Continental Antarctica

Abstract Lichens dominate the terrestrial vegetation of the ice-free regions of continental Antarctica. Vegetation patterns were studied in the Windmill Islands Oasis, Wilkes Land, continental Antarctica, in relation to edaphic features to elucidate the factors that govern lichen distribution and abundance. Vegetation was studied on a low rounded knoll on Clark Peninsula some 3 km North East of the present Casey station. Substratum nutrient levels vary considerably across the knoll due to the presence of an abandoned penguin rookery on the crest and the uneven topography provides both sheltered and exposed sites. Along a 130 m-long transect crossing the knoll from South to North, a total of 25 species of lichen and one moss were identified, the vegetation being dominated by Umbilicaria decussata, Pseudephebe minuscula, Usnea sphacelata and U. antarctica. TWINSPAN analysis of species distributions identified six sociations, the distribution of which were related to substratum structure and chemistry. Several species were restricted to nutrient-rich zones while late-lying snow restricted all species to varying degrees.