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The occurrence of mycothalli, symbioses between liverworts and fungi bearing similarities to mycorrhizas, is poorly documented in sub-Antarctica, and biogeographical patterns in Serendipita, one of the main fungal genera forming the symbiosis, remain understudied. Here, 83 specimens of 16 leafy liverwort species in eight families were hence sampled from 12 sites on the Thatcher Peninsula on sub-Antarctic South Georgia and were examined for mycothalli. Staining and epifluorescence microscopy were used to enumerate fungal structures in liverwort tissues, and PCR amplification and sequencing of fungal ribosomal DNA were used to determine the taxonomic and biogeographical affinities of the fungi present in plants. Stained hyphal coils, a defining feature of the symbiosis, were found to be frequent (>40 % of stem length colonised) in Barbilophozia hatcheri (Anastrophyllaceae), Cephaloziella varians (Cephaloziellaceae) and Lophoziopsis excisa (Lophoziaceae). Analyses of fungal ITS2 region sequences showed that a single species of Serendipita, based on a 3 % cut-off for sequence divergence, was a frequent colonist of B. hatcheri, C. varians and L. excisa, and that a further 18 basidiomycete and ascomycete taxa colonised other liverwort species. Principal component analysis and analysis of variance indicated that the presence of the Serendipita species was positively associated with the occurrence of stained hyphal coils in stem epidermal cells. Phylogenetic analyses, incorporating worldwide accessions from leafy liverwort-associated Serendipita, showed that the same species, which also occurs in Chile, mainland Europe and on Svalbard, is apparently the sole symbiont of sub- and maritime Antarctic leafy liverworts, and indicated much higher species richness of the genus outside Antarctica.

For more than five decades, research has been conducted at Ny-Ålesund, in Svalbard, Norway, to understand the structure and functioning of High-Arctic ecosystems and the profound impacts on them of environmental change. Terrestrial, freshwater, glacial and marine ecosystems are accessible year-round from Ny-Ålesund, providing unique opportunities for interdisciplinary observational and experimental studies along physical, chemical, hydrological and climatic gradients. Here, we synthesize terrestrial and freshwater research at Ny-Ålesund and review current knowledge of biodiversity patterns, species population dynamics and interactions, ecosystem processes, biogeochemical cycles and anthropogenic impacts. There is now strong evidence of past and ongoing biotic changes caused by climate change, including negative effects on populations of many taxa and impacts of rain-on-snow events across multiple trophic levels. While species-level characteristics and responses are well understood for macro-organisms, major knowledge gaps exist for microbes, invertebrates and ecosystem-level processes. In order to fill current knowledge gaps, we recommend (1) maintaining monitoring efforts, while establishing a long-term ecosystem-based monitoring programme; (2) gaining a mechanistic understanding of environmental change impacts on processes and linkages in food webs; (3) identifying trophic interactions and cascades across ecosystems; and (4) integrating long-term data on microbial, invertebrate and freshwater communities, along with measurements of carbon and nutrient fluxes among soils, atmosphere, freshwaters and the marine environment. The synthesis here shows that the Ny-Ålesund study system has the characteristics needed to fill these gaps in knowledge, thereby enhancing our understanding of High-Arctic ecosystems and their responses to environmental variability and change.

Mineral extraction is known to affect soil fungi in polar environments, but it is unknown how long these effects persist. Here, by amplifying the internal transcribed spacer regions of rRNA genes in soil fungi, we compared soil fungal community in intact natural tundra with that in a nearby former coal mining area, abandoned 52 years previously, on Svalbard in the High Arctic. Compared with those in intact tundra, soils in the former mining area were more acidic and had lower plant coverage. Despite of similar diversity in the two areas, the fungal community was dominated by Basidiomycota in the intact tundra, but by Ascomycota in the former mining area. Ectomycorrhizal genera formed a major part of the tundra community, but were notably less abundant in the mining area. The principal variation among samples was soil pH. Surprisingly, network connectivity analysis indicated that the fungal community in the former mining area had greater network connectivity than that in the tundra area. Overall, the ecosystem in the former mining area has made only limited recovery towards the natural tundra state even after more than five decades. It is unclear whether the recovery of the fungal community is limited more by the low primary productivity, slow migration of fungi and plants, or slow changes in soil parameters. Our findings emphasize the susceptibility of polar ecosystems to disturbance, given their particularly slow recovery back towards the natural state. © 2022 Soil Science Society of China.

Mineral extraction is known to affect soil fungi in polar environments, but it is unknown how long these effects persist. Here, by amplifying the internal transcribed spacer regions of rRNA genes in soil fungi, we compared soil fungal community in intact natural tundra with that in a nearby former coal mining area, abandoned 52 years previously, on Svalbard in the High Arctic. Compared with those in intact tundra, soils in the former mining area were more acidic and had lower plant coverage. Despite of similar diversity in the two areas, the fungal community was dominated by Basidiomycota in the intact tundra, but by Ascomycota in the former mining area. Ectomycorrhizal genera formed a major part of the tundra community, but were notably less abundant in the mining area. The principal variation among samples was soil pH. Surprisingly, network connectivity analysis indicated that the fungal community in the former mining area had greater network connectivity than that in the tundra area. Overall, the ecosystem in the former mining area has made only limited recovery towards the natural tundra state even after more than five decades. It is unclear whether the recovery of the fungal community is limited more by the low primary productivity, slow migration of fungi and plants, or slow changes in soil parameters. Our findings emphasize the susceptibility of polar ecosystems to disturbance, given their particularly slow recovery back towards the natural state. © 2022 Soil Science Society of China.

For more than five decades, research has been conducted at Ny-Ålesund, in Svalbard, Norway, to understand the structure and functioning of High-Arctic ecosystems and the profound impacts on them of environmental change. Terrestrial, freshwater, glacial and marine ecosystems are accessible year-round from Ny-Ålesund, providing unique opportunities for interdisciplinary observational and experimental studies along physical, chemical, hydrological and climatic gradients. Here, we synthesize terrestrial and freshwater research at Ny-Ålesund and review current knowledge of biodiversity patterns, species population dynamics and interactions, ecosystem processes, biogeochemical cycles and anthropogenic impacts. There is now strong evidence of past and ongoing biotic changes caused by climate change, including negative effects on populations of many taxa and impacts of rain-on-snow events across multiple trophic levels. While species-level characteristics and responses are well understood for macro-organisms, major knowledge gaps exist for microbes, invertebrates and ecosystem-level processes. In order to fill current knowledge gaps, we recommend (1) maintaining monitoring efforts, while establishing a long-term ecosystem-based monitoring programme; (2) gaining a mechanistic understanding of environmental change impacts on processes and linkages in food webs; (3) identifying trophic interactions and cascades across ecosystems; and (4) integrating long-term data on microbial, invertebrate and freshwater communities, along with measurements of carbon and nutrient fluxes among soils, atmosphere, freshwaters and the marine environment. The synthesis here shows that the Ny-Ålesund study system has the characteristics needed to fill these gaps in knowledge, thereby enhancing our understanding of High-Arctic ecosystems and their responses to environmental variability and change.

Previous studies have shown changes to the frequencies of hyphal coils and other fungal structures in leafy liverwort tissues across latitudinal transects through Antarctica. Although suggestive of a role of temperature in determining the frequencies of fungal structures, these studies could not exclude the possibility that other factors which alter at lower latitudes—notably liquid water availability—were responsible for the observed patterns of fungal colonisation. Here, in a field experiment in maritime Antarctica, the effects of warming with open top chambers (OTCs) on the frequencies of fungal structures in the leafy liverwort Cephaloziella varians were determined. At five samplings of the experiment taking place 5–10 years after its deployment, OTCs, which increased the summertime temperature of C. varians mats by 1.1 °C, but had no measurable effects on mat moisture concentration, were found to double the frequencies of fine hyphal coils in liverwort tissues. Over the duration of the experiment, the OTCs also significantly increased the frequency of rhizoids on C. varians stems, but had no effects on the frequencies of coarse hyphal coils, dark septate hyphae, hyaline septate hyphae, or hyphal colonisation of rhizoids. Given that C. varians can be recovered from frozen peatbank cores, it is proposed that the abundance of fine hyphal coils in its tissues might be used as a signal of recent climate warming on the Antarctic Peninsula.

Previous studies have shown changes to the frequencies of hyphal coils and other fungal structures in leafy liverwort tissues across latitudinal transects through Antarctica. Although suggestive of a role of temperature in determining the frequencies of fungal structures, these studies could not exclude the possibility that other factors which alter at lower latitudes—notably liquid water availability—were responsible for the observed patterns of fungal colonisation. Here, in a field experiment in maritime Antarctica, the effects of warming with open top chambers (OTCs) on the frequencies of fungal structures in the leafy liverwort Cephaloziella varians were determined. At five samplings of the experiment taking place 5–10 years after its deployment, OTCs, which increased the summertime temperature of C. varians mats by 1.1 °C, but had no measurable effects on mat moisture concentration, were found to double the frequencies of fine hyphal coils in liverwort tissues. Over the duration of the experiment, the OTCs also significantly increased the frequency of rhizoids on C. varians stems, but had no effects on the frequencies of coarse hyphal coils, dark septate hyphae, hyaline septate hyphae, or hyphal colonisation of rhizoids. Given that C. varians can be recovered from frozen peatbank cores, it is proposed that the abundance of fine hyphal coils in its tissues might be used as a signal of recent climate warming on the Antarctic Peninsula.

BackgroundThe emergence of antibiotic-resistant pathogens has created an urgent need for novel antimicrobial treatments. Advances in next-generation sequencing have opened new frontiers for discovery programmes for natural products allowing the exploitation of a larger fraction of the microbial community. Polyketide (PK) and non-ribosomal pepetide (NRP) natural products have been reported to be related to compounds with antimicrobial and anticancer activities. We report here a new culture-independent approach to explore bacterial biosynthetic diversity and determine bacterial phyla in the microbial community associated with PK and NRP diversity in selected soils.ResultsThrough amplicon sequencing, we explored the microbial diversity (16S rRNA gene) of 13 soils from Antarctica, Africa, Europe and a Caribbean island and correlated this with the amplicon diversity of the adenylation (A) and ketosynthase (KS) domains within functional genes coding for non-ribosomal peptide synthetases (NRPSs) and polyketide synthases (PKSs), which are involved in the production of NRP and PK, respectively. Mantel and Procrustes correlation analyses with microbial taxonomic data identified not only the well-studied phyla Actinobacteria and Proteobacteria, but also, interestingly, the less biotechnologically exploited phyla Verrucomicrobia and Bacteroidetes, as potential sources harbouring diverse A and KS domains. Some soils, notably that from Antarctica, provided evidence of endemic diversity, whilst others, such as those from Europe, clustered together. In particular, the majority of the domain reads from Antarctica remained unmatched to known sequences suggesting they could encode enzymes for potentially novel PK and NRP.ConclusionsThe approach presented here highlights potential sources of metabolic novelty in the environment which will be a useful precursor to metagenomic biosynthetic gene cluster mining for PKs and NRPs which could provide leads for new antimicrobial metabolites.

Soil microbial communities in the Arctic, one of the most rapidly warming regions on Earth, play an important role in a range of ecological processes. This report describes initial studies of natural soil bacterial diversity at a High Arctic site on Svalbard, as part of a long-term field environmental manipulation study. The impact of increased soil temperature and water availability on soil microbial communities was investigated. The manipulation experiment, using open-top chambers, was installed in late summer 2014, and the soils were sampled soon after snow melt in July 2015. High throughput sequencing of 16S rRNA genes showed relatively uniform diversity across the study area and revealed no significant initial effect of treatments on bacterial communities over the first 10-month autumn–winter–spring manipulation period.

Soil microbial communities in the Arctic, one of the most rapidly warming regions on Earth, play an important role in a range of ecological processes. This report describes initial studies of natural soil bacterial diversity at a High Arctic site on Svalbard, as part of a long-term field environmental manipulation study. The impact of increased soil temperature and water availability on soil microbial communities was investigated. The manipulation experiment, using open-top chambers, was installed in late summer 2014, and the soils were sampled soon after snow melt in July 2015. High throughput sequencing of 16S rRNA genes showed relatively uniform diversity across the study area and revealed no significant initial effect of treatments on bacterial communities over the first 10-month autumn–winter–spring manipulation period.

l-isomeric amino acids and oligopeptides are thought to represent a key nitrogen (N) source for plants and soil microorganisms, bypassing the need to take up inorganic N, whilst self-cycling of d-enantiomers within peptidoglycan-containing bacteria may provide a further short circuit within the N cycle. Here we use stable isotope profiling (SIP) to identify the fate of organic N within soil microbial communities. We followed the incorporation of 13C-labelled d- or l-labelled amino acids/peptides into phospholipid fatty acids (PLFAs). l-alanine and its peptides were taken up more rapidly than d-enantiomers by Gram-positive bacteria with 13C incorporation being predominantly into anteiso- and iso-fatty acids typically associated with Gram-positive bacteria. d-enantiomer uptake was found not to differ significantly between the microbial groups, providing little support for the view that soil bacteria may self-cycle d-forms of amino acids and peptides. There was no consistent association between peptide chain length and incorporation. The concentrations of l- and d-isomeric amino acids in soil solution were 866 nM and 72 nM, respectively. We conclude that Gram-positive bacteria appear to be the primary competitors for l-enantiomeric forms of amino acids and their peptides, but that both d- and l-enantiomers are available N and C sources for bacteria and fungi.

l-isomeric amino acids and oligopeptides are thought to represent a key nitrogen (N) source for plants and soil microorganisms, bypassing the need to take up inorganic N, whilst self-cycling of d-enantiomers within peptidoglycan-containing bacteria may provide a further short circuit within the N cycle. Here we use stable isotope profiling (SIP) to identify the fate of organic N within soil microbial communities. We followed the incorporation of 13C-labelled d- or l-labelled amino acids/peptides into phospholipid fatty acids (PLFAs). l-alanine and its peptides were taken up more rapidly than d-enantiomers by Gram-positive bacteria with 13C incorporation being predominantly into anteiso- and iso-fatty acids typically associated with Gram-positive bacteria. d-enantiomer uptake was found not to differ significantly between the microbial groups, providing little support for the view that soil bacteria may self-cycle d-forms of amino acids and peptides. There was no consistent association between peptide chain length and incorporation. The concentrations of l- and d-isomeric amino acids in soil solution were 866 nM and 72 nM, respectively. We conclude that Gram-positive bacteria appear to be the primary competitors for l-enantiomeric forms of amino acids and their peptides, but that both d- and l-enantiomers are available N and C sources for bacteria and fungi.

Antarctica is not a single ecological model. Substantial differences in the temperature, precipitation (which combine to affect the available water) and radiation determine the distribution and the habit of primary producers that in turn structure the trophic. Because terrestrial primary production is operating at environmental extremes in some parts of Antarctica, particularly in continental Antarctica, the spatial and temporal subsidies to the terrestrial stock of organic carbon make proportionately larger contributions to contemporary carbon cycling

We 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.

Forty-four herbarium specimens of the hepatic Barbilophozia hatcheri, collected from across the entire range of the species in Antarctica (54–68 °S), were examined for fungal colonisation. Mycothalli, consisting of hyaline hyphae in rhizoids or hyphal coils in rhizoid bases and stem medullary cells, were present in 42 specimens. The frequencies of mycothalli declined at higher latitudes and were associated positively with annual air temperatures. In contrast, the frequency of dark septate hyphae on stems increased at higher latitudes. Sequencing of ITS regions of fungal rRNA genes amplified from B. hatcheri from 54 °S, 61 °S and 68 °S indicated that Cladophialophora species colonised plants at higher latitudes, but that most fungi had >99 % homology with members of Sebacinales clade B, with best matches to mycobionts of B. lycopodioides, Lophoziopsis excisa and Protolophozia crispata. We propose the use of herbarium specimens of mycothalli as proxies for climate change in Antarctica.

Antarctica is not a single ecological model. Substantial differences in the temperature, precipitation (which combine to affect the available water) and radiation determine the distribution and the habit of primary producers that in turn structure the trophic. Because terrestrial primary production is operating at environmental extremes in some parts of Antarctica, particularly in continental Antarctica, the spatial and temporal subsidies to the terrestrial stock of organic carbon make proportionately larger contributions to contemporary carbon cycling

We 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.

Forty-four herbarium specimens of the hepatic Barbilophozia hatcheri, collected from across the entire range of the species in Antarctica (54–68 °S), were examined for fungal colonisation. Mycothalli, consisting of hyaline hyphae in rhizoids or hyphal coils in rhizoid bases and stem medullary cells, were present in 42 specimens. The frequencies of mycothalli declined at higher latitudes and were associated positively with annual air temperatures. In contrast, the frequency of dark septate hyphae on stems increased at higher latitudes. Sequencing of ITS regions of fungal rRNA genes amplified from B. hatcheri from 54 °S, 61 °S and 68 °S indicated that Cladophialophora species colonised plants at higher latitudes, but that most fungi had >99 % homology with members of Sebacinales clade B, with best matches to mycobionts of B. lycopodioides, Lophoziopsis excisa and Protolophozia crispata. We propose the use of herbarium specimens of mycothalli as proxies for climate change in Antarctica.

The biology and ecology of Cephaloziella varians, the most widespread and abundant liverwort in Antarctica, are reviewed. A description of the species is given, together with information on its geographical distribution, reproduction, habitats, associated organisms and responses to environmental stresses. Characteristics of its photosynthetic physiology are also presented, including data on oxygen evolution rates and chlorophyll a fluorescence parameters. Substratum and tissue chemistry, water relations and pigments are discussed, along with recent data demonstrating that the dark pigment in the apical leaves of C. varians is the anthocyanidin riccionidin A. Recent studies showing that the ericoid mycorrhizal symbiont Rhizoscyphus ericae is present in the tissues of the plant at a wide range of locations in the maritime and sub-Antarctic are also described. It is evident, from the literature reviewed, that C. varians has several adaptations that enable it to survive in the Antarctic biome, explaining its survival at higher latitudes than any other hepatic. The species' major adaptations include the synthesis of riccionidin A in apical leaves, enabling efficient heat absorption and protection from photoinhibition, and the presence in stems and rhizoids of fungal hyphae, which are potentially beneficial to the hepatic's nutrition and possibly also synthesize cryoprotectants.

The biology and ecology of Cephaloziella varians, the most widespread and abundant liverwort in Antarctica, are reviewed. A description of the species is given, together with information on its geographical distribution, reproduction, habitats, associated organisms and responses to environmental stresses. Characteristics of its photosynthetic physiology are also presented, including data on oxygen evolution rates and chlorophyll a fluorescence parameters. Substratum and tissue chemistry, water relations and pigments are discussed, along with recent data demonstrating that the dark pigment in the apical leaves of C. varians is the anthocyanidin riccionidin A. Recent studies showing that the ericoid mycorrhizal symbiont Rhizoscyphus ericae is present in the tissues of the plant at a wide range of locations in the maritime and sub-Antarctic are also described. It is evident, from the literature reviewed, that C. varians has several adaptations that enable it to survive in the Antarctic biome, explaining its survival at higher latitudes than any other hepatic. The species' major adaptations include the synthesis of riccionidin A in apical leaves, enabling efficient heat absorption and protection from photoinhibition, and the presence in stems and rhizoids of fungal hyphae, which are potentially beneficial to the hepatic's nutrition and possibly also synthesize cryoprotectants.

Understanding and accurately predicting the fate of carbon and nitrogen in the terrestrial biosphere remains a central goal in ecosystem science. Amino acids represent a key pool of C and N in soil, and their availability to plants and microorganisms has been implicated as a major driver in regulating ecosystem functioning. Because of potential differences in biological diversity and litter quality, it has been thought that soils from different latitudes and plant communities may possess intrinsically different capacities to perform key functions such as the turnover of amino acids. In this study we measured the soil solution concentration and microbial mineralization of amino acids in soils collected from 40 latitudinal points from the Arctic through to Antarctica. Our results showed that soil solution amino acid concentrations were relatively similar between sites and not strongly related to latitude. In addition, when constraints of temperature and moisture were removed, we demonstrate that soils worldwide possess a similar innate capacity to rapidly mineralize amino acids. Similarly, we show that the internal partitioning of amino acid-C into catabolic and anabolic processes is conservative in microbial communities and independent of global position. This supports the view that the conversion of high molecular weight ( MW) organic matter to low MW compounds is the rate limiting step in organic matter breakdown in most ecosystems.

Understanding and accurately predicting the fate of carbon and nitrogen in the terrestrial biosphere remains a central goal in ecosystem science. Amino acids represent a key pool of C and N in soil, and their availability to plants and microorganisms has been implicated as a major driver in regulating ecosystem functioning. Because of potential differences in biological diversity and litter quality, it has been thought that soils from different latitudes and plant communities may possess intrinsically different capacities to perform key functions such as the turnover of amino acids. In this study we measured the soil solution concentration and microbial mineralization of amino acids in soils collected from 40 latitudinal points from the Arctic through to Antarctica. Our results showed that soil solution amino acid concentrations were relatively similar between sites and not strongly related to latitude. In addition, when constraints of temperature and moisture were removed, we demonstrate that soils worldwide possess a similar innate capacity to rapidly mineralize amino acids. Similarly, we show that the internal partitioning of amino acid-C into catabolic and anabolic processes is conservative in microbial communities and independent of global position. This supports the view that the conversion of high molecular weight ( MW) organic matter to low MW compounds is the rate limiting step in organic matter breakdown in most ecosystems.

PCR amplification of ITS1-5.8S-ITS2 regions of rDNA followed by cloning was used to determine the fungi present in soil from three sites at Mars Oasis in the southern maritime Antarctic. The soils sampled were adjacent to, or distant from, a meltwater pond, and had moisture contents of 8 %, 3.6 % and 2.5 %. Sequences bearing close similarity to Chytridiales were commonly recorded in clone libraries from the wettest soil. In contrast, sequences from the driest soil matched closely with ectomycorrhizal members of the Helotiales and less closely with Serendipita-like Sebacinales, Tetracladium and ascomycetous black yeasts, such as Rhinociadiella- and Cladophialophora-like fungi and members of the Verrucariales. Sequences loosely similar to Tetracladium, Arrhenia and Omphalina were frequently recovered from the soil of moderate moisture content. our study corroborates research from the Dry Valleys indicating that soil moisture has an important influence on the composition of Antarctic soil fungal communities. (C) 2008 Elsevier Ltd and The British Mycological Society

We review the distributions and functions of mycorrhizas and dark septate root endophytes in polar regions. Arbuscular mycorrhizas (AM) are present in the Arctic and Antarctic to 82 ºN and 63 ºS, respectively, with fine endophyte being the dominant form of AM in roots at higher latitudes. Ecto- (ECM) and ericoid (ERM) mycorrhizas both occur in the Arctic to 79 ºN, owing to the presence of species of Salix, Dryas, Vaccinium and Cassiope to this latitude. ECM and ERM are not present in Antarctic ecosystems, owing to an absence of suitable hosts. Arbutoid and orchid mycorrhizas are infrequent in the Arctic, whilst the latter is present at one location in the sub-Antarctic. Data from studies of AM, ECM and ERM colonisation along a latitudinal transect through the Arctic indicate that the frequency of plant species not colonised by mycorrhizas increases at higher latitudes, largely owing to an increase in non-mycorrhizal and a decrease in obligately mycorrhizal plant families at more northerly locations. A separate group of root- and rhizoid-associated fungi, the dark septate root endophytes (DSE), are widespread to 82 ºN and 77 ºS, and are apparently more frequent than mycorrhizal fungi in polar regions. The functions of DSE are largely unclear, but studies suggest beneficial effects on plant growth under defined conditions. We advocate further research into the effects of DSE on their host plants in polar regions.

PCR amplification of ITS1-5.8S-ITS2 regions of rDNA followed by cloning was used to determine the fungi present in soil from three sites at Mars Oasis in the southern maritime Antarctic. The soils sampled were adjacent to, or distant from, a meltwater pond, and had moisture contents of 8 %, 3.6 % and 2.5 %. Sequences bearing close similarity to Chytridiales were commonly recorded in clone libraries from the wettest soil. In contrast, sequences from the driest soil matched closely with ectomycorrhizal members of the Helotiales and less closely with Serendipita-like Sebacinales, Tetracladium and ascomycetous black yeasts, such as Rhinociadiella- and Cladophialophora-like fungi and members of the Verrucariales. Sequences loosely similar to Tetracladium, Arrhenia and Omphalina were frequently recovered from the soil of moderate moisture content. our study corroborates research from the Dry Valleys indicating that soil moisture has an important influence on the composition of Antarctic soil fungal communities. (C) 2008 Elsevier Ltd and The British Mycological Society

Understanding and accurately predicting the fate of carbon and nitrogen in the terrestrial biosphere remains a central goal in ecosystem science. Amino acids represent a key pool of C and N in soil, and their availability to plants and microorganisms has been implicated as a major driver in regulating ecosystem functioning. Because of potential differences in biological diversity and litter quality, it has been thought that soils from different latitudes and plant communities may possess intrinsically different capacities to perform key functions such as the turnover of amino acids. In this study we measured the soil solution concentration and microbial mineralization of amino acids in soils collected from 40 latitudinal points from the Arctic through to Antarctica. Our results showed that soil solution amino acid concentrations were relatively similar between sites and not strongly related to latitude. In addition, when constraints of temperature and moisture were removed, we demonstrate that soils worldwide possess a similar innate capacity to rapidly mineralize amino acids. Similarly, we show that the internal partitioning of amino acid-C into catabolic and anabolic processes is conservative in microbial communities and independent of global position. This supports the view that the conversion of high molecular weight ( MW) organic matter to low MW compounds is the rate limiting step in organic matter breakdown in most ecosystems.

We review the distributions and functions of mycorrhizas and dark septate root endophytes in polar regions. Arbuscular mycorrhizas (AM) are present in the Arctic and Antarctic to 82 ºN and 63 ºS, respectively, with fine endophyte being the dominant form of AM in roots at higher latitudes. Ecto- (ECM) and ericoid (ERM) mycorrhizas both occur in the Arctic to 79 ºN, owing to the presence of species of Salix, Dryas, Vaccinium and Cassiope to this latitude. ECM and ERM are not present in Antarctic ecosystems, owing to an absence of suitable hosts. Arbutoid and orchid mycorrhizas are infrequent in the Arctic, whilst the latter is present at one location in the sub-Antarctic. Data from studies of AM, ECM and ERM colonisation along a latitudinal transect through the Arctic indicate that the frequency of plant species not colonised by mycorrhizas increases at higher latitudes, largely owing to an increase in non-mycorrhizal and a decrease in obligately mycorrhizal plant families at more northerly locations. A separate group of root- and rhizoid-associated fungi, the dark septate root endophytes (DSE), are widespread to 82 ºN and 77 ºS, and are apparently more frequent than mycorrhizal fungi in polar regions. The functions of DSE are largely unclear, but studies suggest beneficial effects on plant growth under defined conditions. We advocate further research into the effects of DSE on their host plants in polar regions.

The pathogenicity of an isolate of a Pythium species from Signy Island in the South Orkney Islands was tested against the Antarctic hairgrass Deschampsia antarctica. The isolate was found to infect plants at 8ºC and to cause foliar and root symptoms similar to those seen in other Pythium infections in grasses. Analysis of ribosomal RNA sequences placed it, together with another isolate from Antarctica, in a clade that included the known snow moulds caused by Pythium spp. Sporangia and oogonia were produced in culture, but the isolate differed from other Pythium spp. in producing chlamydospores in older cultures and plant tissue. This is the first report of a pathogen of an eukaryotic vascular plant in the maritime Antarctic region.

The two native Antarctic vascular plant species, Colobanthus quitensis and Deschampsia antarctica, were sampled from 15 points along a 1480 km latitudinal transect from South Georgia (54°S, 36°W) through to the Léonie Islands on the western Antarctic Peninsula (67°S, 68°W). Roots of plants were cleared and stained and fungal structures recorded. The commonest type of fungal association was that formed by dark septate endophytes (DSE): 32% and 27% of the root lengths of C. quitensis and D. antarctica were colonized by hyphae of these fungi, respectively. Hyaline and stained septate hyphae were also common in roots. Coarse and fine arbuscular mycorrhiza (AM) occurred in the roots of both plant species from South Georgia, and fine AM colonization with occasional arbuscules was also sporadically recorded in roots from the South Shetland Islands, suggesting functional associations between higher plants and AM symbionts. Fungal abundances were not associated with soil chemistry, but AM abundance was associated with seasonal surface air temperature, with lower colonization in more southerly, colder habitats. We conclude that DSE are widespread, and that AM fungi are sparse but present and decline in abundance at higher latitudes, in the roots of C. quitensis and D. antarctica.

The two native Antarctic vascular plant species, Colobanthus quitensis and Deschampsia antarctica, were sampled from 15 points along a 1480 km latitudinal transect from South Georgia (54°S, 36°W) through to the Léonie Islands on the western Antarctic Peninsula (67°S, 68°W). Roots of plants were cleared and stained and fungal structures recorded. The commonest type of fungal association was that formed by dark septate endophytes (DSE): 32% and 27% of the root lengths of C. quitensis and D. antarctica were colonized by hyphae of these fungi, respectively. Hyaline and stained septate hyphae were also common in roots. Coarse and fine arbuscular mycorrhiza (AM) occurred in the roots of both plant species from South Georgia, and fine AM colonization with occasional arbuscules was also sporadically recorded in roots from the South Shetland Islands, suggesting functional associations between higher plants and AM symbionts. Fungal abundances were not associated with soil chemistry, but AM abundance was associated with seasonal surface air temperature, with lower colonization in more southerly, colder habitats. We conclude that DSE are widespread, and that AM fungi are sparse but present and decline in abundance at higher latitudes, in the roots of C. quitensis and D. antarctica.

The pathogenicity of an isolate of a Pythium species from Signy Island in the South Orkney Islands was tested against the Antarctic hairgrass Deschampsia antarctica. The isolate was found to infect plants at 8ºC and to cause foliar and root symptoms similar to those seen in other Pythium infections in grasses. Analysis of ribosomal RNA sequences placed it, together with another isolate from Antarctica, in a clade that included the known snow moulds caused by Pythium spp. Sporangia and oogonia were produced in culture, but the isolate differed from other Pythium spp. in producing chlamydospores in older cultures and plant tissue. This is the first report of a pathogen of an eukaryotic vascular plant in the maritime Antarctic region.

A recent study identified a fungal isolate from the Antarctic leafy liverwort Cephaloziella varians as the ericoid mycorrhizal associate Rhizoscyphus ericae. However, nothing is known about the wider Antarctic distribution of R. ericae in C. varians, and inoculation experiments confirming the ability of the fungus to form coils in the liverwort are lacking. Using direct isolation and baiting with Vaccinium macrocarpon seedlings, fungi were isolated from C. varians sampled from eight sites across a 1875-km transect through sub- and maritime Antarctica. The ability of an isolate to form coils in aseptically grown C. varians was also tested. Fungi with 98–99% sequence identity to R. ericae internal transcribed spacer (ITS) region and partial large subunit ribosomal (r)DNA sequences were frequently isolated from C. varians at all sites sampled. The EF4/Fung5 primer set did not amplify small subunit rDNA from three of five R. ericae isolates, probably accounting for the reported absence of the fungus from C. varians in a previous study. Rhizoscyphus ericae was found to colonize aseptically-grown C. varians intracellularly, forming hyphal coils. This study shows that the association between R. ericae and C. varians is apparently widespread in Antarctica, and confirms that R. ericae is at least in part responsible for the formation of the coils observed in rhizoids of field-collected C. varians.

We measured the responses of pigments and chlorophyll a fluorescence parameters of the Antarctic leafy liverwort Cephaloziella varians to snowmelt during austral spring 2005 at Rothera Point on the western Antarctic Peninsula. Although no changes to the concentrations of UV-B photoprotective pigments were detected during snowmelt, chlorophyll and carotenoid concentrations and maximum photosystem (PS)II yield (F v /F m) were respectively 88, 60 and 144% higher in the tissues of the liverwort that had recently emerged from snow than in those under a 10 cm depth of snow. A laboratory experiment similarly showed that effective PSII yield increased rapidly within the first 45 min after plants sampled from under snow were removed to an illuminated growth cabinet. The pigmentation and PSII yields of plants during snowmelt were also compared with those of plants in January, during the middle of the growing season at Rothera Point. During snowmelt, plants had lower F v /F m values, chlorophyll a/b ratios and concentrations of UV-B photoprotective pigments and carotenoids than during mid-season, suggesting that although there is some recovery of PSII activity and increases in concentrations of photosynthetic pigments during snowmelt, the metabolism of C. varians is restricted during this period.

We examined the influence of elevated UV-B radiation on the extractability of carbohydrates from leaf litter of Quercus robur. Saplings were exposed to a 30% elevation above the ambient level of erythemally weighted UV-B (280–315 nm) radiation for eight months at an outdoor facility. UV-B radiation was applied under arrays of fluorescent lamps filtered with cellulose diacetate, which transmitted both UV-B and UV-A (315–400 nm) radiation. Saplings were also exposed to elevated UV-A radiation under arrays of polyester-filtered lamps and to ambient radiation under arrays of non-energised lamps. Abscised leaves were collected, ground and sequentially treated with seven solvents in order to fractionate extractable carbohydrates based on the way in which they are held in the cell wall. Elevated UV-B radiation reduced the extractability of carbohydrates from cell walls of Q. robur. Sodium phosphate buffer at pH 7 extracted 10% less total carbohydrate from leaf material exposed during growth to elevated UV-B radiation under cellulose diacetate-filtered lamps than from leaf material grown under polyester-filtered and non-energised lamps. The cumulative amount of carbohydrate released by sequential extraction with phosphate buffer, CDTA, urea and sodium carbonate was between 5.1% and 7.8% lower from leaf material grown under cellulose diacetate-filtered lamps relative to that from leaves grown under non-energised lamps. Abscised leaves were also digested with Driselase, an enzyme mixture extracted from a basidiomycete fungus. No effects of elevated UV radiation were recorded on the amount of carbohydrate released by Driselase digestion. Regression analyses, using data from a previous field decomposition study, suggested that reduced availability of carbohydrates enhanced the colonisation of Q. robur litter by basidiomycete fungi, which then accelerated the decomposition rate of the litter in soil. We recommend that future studies into the effects of UV-B radiation on plant li

1. Predicting the effects of warming and species loss on ecosystems are two significant challenges currently facing ecologists. However, little is known of the interactive effects of these two factors. We hence tested whether or not warming and species loss interact to influence productivity and dissolved nitrogen concentrations in model Antarctic microbial food webs. Food webs, consisting of a uniform bacterial community and mixtures of six, four, two and zero bacterivorous flagellate species, drawn randomly from a pool of six flagellate species isolated from an Antarctic freshwater lake, were grown in soil extract suspension medium held in microcosms for 252 h. Half of the microcosms were kept at 4 °C and half were warmed to 8 °C over the first 36 h and then held at this temperature. 2. After 252 h there were significant interactive effects of flagellate species loss and warming on the abundance of bacterial prey and the concentration of ammonium in the medium: bacterial abundances were reduced by 75% and NH4-N concentrations were doubled in mixtures inoculated with six and four flagellate species, compared with those inoculated with two species, but only in warmed microcosms. This difference in response was apparently largely owing to the absence of Bodo saltans and Spumella putida, species with high grazing activities and growth rates, from most replicates of the warmed two species mixtures. 3. Evidence for an apparent complementarity effect was also found, with B. saltans and Spongomonas uvella growing more rapidly at 4 °C in mixtures of six species than in those of four species. 4. Data from a separate experiment, in which the flagellate species were grown in single-species culture under food-saturated conditions, confirmed that the logarithmic growth rates of B. saltans and S. putida were the highest of each of the six species at both 4 °C and 8 °C. 5. We broadly conclude from our data that random species loss from food webs or communities is likely to alter

Although soil-borne bacteria represent the world's greatest source of biological diversity, it is not well understood whether extreme environmental conditions, such as those found in Antarctic habitats, result in reduced soil-borne microbial diversity. To address this issue, patterns of bacterial diversity were studied in soils sampled along a > 3200 km southern polar transect spanning a gradient of increased climate severity over 27° of latitude. Vegetated and fell-field plots were sampled at the Falkland (51°S), South Georgia (54°S), Signy (60°S) and Anchorage Islands (67°S), while bare frost-sorted soil polygons were examined at Fossil Bluff (71°S), Mars Oasis (72°S), Coal Nunatak (72°S) and the Ellsworth Mountains (78°S). Bacterial 16S rRNA gene sequences were recovered subsequent to direct DNA extraction from soil, polymerase chain reaction amplification and cloning. Although bacterial diversity was observed to decline with increased latitude, habitat-specific patterns appeared to also be important. Namely, a negative relationship was found between bacterial diversity and latitude for fell-field soils, but no such pattern was observed for vegetated sites. The Mars Oasis site, previously identified as a biodiversity hotspot within this region, proved exceptional within the study transect, with unusually high bacterial diversity. In independent analyses, geographical distance and vegetation cover were found to significantly influence bacterial community composition. These results provide insight into the factors shaping the composition of bacterial communities in Antarctic terrestrial habitats and support the notion that bacterial diversity declines with increased climatic severity., Although soil-borne bacteria represent the world's greatest source of biological diversity, it is not well understood whether extreme environmental conditions, such as those found in Antarctic habitats, result in reduced soil-borne microbial diversity. To address this issue, patterns of bacterial diversity were studied in soils sampled along a > 3200 km southern polar transect spanning a gradient of increased climate severity over 27° of latitude. Vegetated and fell-field plots were sampled at the Falkland (51°S), South Georgia (54°S), Signy (60°S) and Anchorage Islands (67°S), while bare frost-sorted soil polygons were examined at Fossil Bluff (71°S), Mars Oasis (72°S), Coal Nunatak (72°S) and the Ellsworth Mountains (78°S). Bacterial 16S rRNA gene sequences were recovered subsequent to direct DNA extraction from soil, polymerase chain reaction amplification and cloning. Although bacterial diversity was observed to decline with increased latitude, habitat-specific patterns appeared to also be important. Namely, a negative relationship was found between bacterial diversity and latitude for fell-field soils, but no such pattern was observed for vegetated sites. The Mars Oasis site, previously identified as a biodiversity hotspot within this region, proved exceptional within the study transect, with unusually high bacterial diversity. In independent analyses, geographical distance and vegetation cover were found to significantly influence bacterial community composition. These results provide insight into the factors shaping the composition of bacterial communities in Antarctic terrestrial habitats and support the notion that bacterial diversity declines with increased climatic severity.

We measured the responses of pigments and chlorophyll a fluorescence parameters of the Antarctic leafy liverwort Cephaloziella varians to snowmelt during austral spring 2005 at Rothera Point on the western Antarctic Peninsula. Although no changes to the concentrations of UV-B photoprotective pigments were detected during snowmelt, chlorophyll and carotenoid concentrations and maximum photosystem (PS)II yield (F v /F m) were respectively 88, 60 and 144% higher in the tissues of the liverwort that had recently emerged from snow than in those under a 10 cm depth of snow. A laboratory experiment similarly showed that effective PSII yield increased rapidly within the first 45 min after plants sampled from under snow were removed to an illuminated growth cabinet. The pigmentation and PSII yields of plants during snowmelt were also compared with those of plants in January, during the middle of the growing season at Rothera Point. During snowmelt, plants had lower F v /F m values, chlorophyll a/b ratios and concentrations of UV-B photoprotective pigments and carotenoids than during mid-season, suggesting that although there is some recovery of PSII activity and increases in concentrations of photosynthetic pigments during snowmelt, the metabolism of C. varians is restricted during this period.

A recent study identified a fungal isolate from the Antarctic leafy liverwort Cephaloziella varians as the ericoid mycorrhizal associate Rhizoscyphus ericae. However, nothing is known about the wider Antarctic distribution of R. ericae in C. varians, and inoculation experiments confirming the ability of the fungus to form coils in the liverwort are lacking. Using direct isolation and baiting with Vaccinium macrocarpon seedlings, fungi were isolated from C. varians sampled from eight sites across a 1875-km transect through sub- and maritime Antarctica. The ability of an isolate to form coils in aseptically grown C. varians was also tested. Fungi with 98–99% sequence identity to R. ericae internal transcribed spacer (ITS) region and partial large subunit ribosomal (r)DNA sequences were frequently isolated from C. varians at all sites sampled. The EF4/Fung5 primer set did not amplify small subunit rDNA from three of five R. ericae isolates, probably accounting for the reported absence of the fungus from C. varians in a previous study. Rhizoscyphus ericae was found to colonize aseptically-grown C. varians intracellularly, forming hyphal coils. This study shows that the association between R. ericae and C. varians is apparently widespread in Antarctica, and confirms that R. ericae is at least in part responsible for the formation of the coils observed in rhizoids of field-collected C. varians.

1. Predicting the effects of warming and species loss on ecosystems are two significant challenges currently facing ecologists. However, little is known of the interactive effects of these two factors. We hence tested whether or not warming and species loss interact to influence productivity and dissolved nitrogen concentrations in model Antarctic microbial food webs. Food webs, consisting of a uniform bacterial community and mixtures of six, four, two and zero bacterivorous flagellate species, drawn randomly from a pool of six flagellate species isolated from an Antarctic freshwater lake, were grown in soil extract suspension medium held in microcosms for 252 h. Half of the microcosms were kept at 4 °C and half were warmed to 8 °C over the first 36 h and then held at this temperature. 2. After 252 h there were significant interactive effects of flagellate species loss and warming on the abundance of bacterial prey and the concentration of ammonium in the medium: bacterial abundances were reduced by 75% and NH4-N concentrations were doubled in mixtures inoculated with six and four flagellate species, compared with those inoculated with two species, but only in warmed microcosms. This difference in response was apparently largely owing to the absence of Bodo saltans and Spumella putida, species with high grazing activities and growth rates, from most replicates of the warmed two species mixtures. 3. Evidence for an apparent complementarity effect was also found, with B. saltans and Spongomonas uvella growing more rapidly at 4 °C in mixtures of six species than in those of four species. 4. Data from a separate experiment, in which the flagellate species were grown in single-species culture under food-saturated conditions, confirmed that the logarithmic growth rates of B. saltans and S. putida were the highest of each of the six species at both 4 °C and 8 °C. 5. We broadly conclude from our data that random species loss from food webs or communities is likely to alter

We examined the influence of elevated UV-B radiation on the extractability of carbohydrates from leaf litter of Quercus robur. Saplings were exposed to a 30% elevation above the ambient level of erythemally weighted UV-B (280–315 nm) radiation for eight months at an outdoor facility. UV-B radiation was applied under arrays of fluorescent lamps filtered with cellulose diacetate, which transmitted both UV-B and UV-A (315–400 nm) radiation. Saplings were also exposed to elevated UV-A radiation under arrays of polyester-filtered lamps and to ambient radiation under arrays of non-energised lamps. Abscised leaves were collected, ground and sequentially treated with seven solvents in order to fractionate extractable carbohydrates based on the way in which they are held in the cell wall. Elevated UV-B radiation reduced the extractability of carbohydrates from cell walls of Q. robur. Sodium phosphate buffer at pH 7 extracted 10% less total carbohydrate from leaf material exposed during growth to elevated UV-B radiation under cellulose diacetate-filtered lamps than from leaf material grown under polyester-filtered and non-energised lamps. The cumulative amount of carbohydrate released by sequential extraction with phosphate buffer, CDTA, urea and sodium carbonate was between 5.1% and 7.8% lower from leaf material grown under cellulose diacetate-filtered lamps relative to that from leaves grown under non-energised lamps. Abscised leaves were also digested with Driselase, an enzyme mixture extracted from a basidiomycete fungus. No effects of elevated UV radiation were recorded on the amount of carbohydrate released by Driselase digestion. Regression analyses, using data from a previous field decomposition study, suggested that reduced availability of carbohydrates enhanced the colonisation of Q. robur litter by basidiomycete fungi, which then accelerated the decomposition rate of the litter in soil. We recommend that future studies into the effects of UV-B radiation on plant li

A sample of the liverwort Cephaloziella varians was collected on 1 January 1999 at Rothera Point on the Wright Peninsula, Adelaide Island, western Antarctic Peninsula and was partially dried and then frozen at −80°C. The sample was rapidly defrosted to c. 10°C after six years and two months of storage at this temperature. Nematodes, tardigrades and a bdelloid rotifer present in the sample were found to have survived. Of the 159 nematodes recovered from the sample, 49 (31%) were alive: of the tardigrades and rotifers, two of 15 (13%) and one of 48 (2%) had survived, respectively. A Chi-square test showed that there was a significant association between nematode taxon and survival: a greater proportion of Coomansus gerlachei individuals were alive than of Rhyssocolpus paradoxus. A Chi-square test also showed that there was a significant association between phylum and survival: a significantly greater proportion of nematodes or tardigrades were alive than of bdelloid rotifers. We conclude that Antarctic soil metazoans are capable of surviving long-term exposure to low sub-zero temperatures and that there may be taxon-specific effects of freezing on survival.

A sample of the liverwort Cephaloziella varians was collected on 1 January 1999 at Rothera Point on the Wright Peninsula, Adelaide Island, western Antarctic Peninsula and was partially dried and then frozen at −80°C. The sample was rapidly defrosted to c. 10°C after six years and two months of storage at this temperature. Nematodes, tardigrades and a bdelloid rotifer present in the sample were found to have survived. Of the 159 nematodes recovered from the sample, 49 (31%) were alive: of the tardigrades and rotifers, two of 15 (13%) and one of 48 (2%) had survived, respectively. A Chi-square test showed that there was a significant association between nematode taxon and survival: a greater proportion of Coomansus gerlachei individuals were alive than of Rhyssocolpus paradoxus. A Chi-square test also showed that there was a significant association between phylum and survival: a significantly greater proportion of nematodes or tardigrades were alive than of bdelloid rotifers. We conclude that Antarctic soil metazoans are capable of surviving long-term exposure to low sub-zero temperatures and that there may be taxon-specific effects of freezing on survival.

UV-B radiation (280–315 nm), incident on the leafy liverwort Cephaloziella varians growing at Rothera Point on the Western Antarctic Peninsula, was manipulated in late austral spring 1998 by screens consisting of a novel combination of Plexiglas panes and polyester sheets. The screens transmitted approximately 79, 68, 48, 41 and 31% of daily UV-B radiation dose. Plants from under and outside the screens were sampled seven times over 35 days. Correlative analyses indicated that concentrations of an anthocyanin-like pigment located in leaf tips were positively associated with UV-B transmission at the last two samplings, that concentrations of total chlorophylls were negatively associated with UV-B transmission at the final sampling, and that those of UV-B screening pigments were positively correlated with transmission at three intermediate samplings. Plants exposed to low UV-B transmission levels were visibly greener than those exposed to high transmission levels after approximately 23 days. The closest relationships between the treatment and concentrations of UV-B screening pigments were associated with increased ambient biologically weighted UV-B dose received by plants in the 5.5 h before each sampling, which coincided with the passage of the ozone hole over Rothera Point. As C. varians emerged from melting snow and ice, concentrations of the anthocyanin-like pigment and chlorophyll respectively increased and decreased faster in plants exposed to high transmission levels of UV-B, relative to those exposed to low UV-B transmission levels.

UV-B radiation (280–315 nm), incident on the leafy liverwort Cephaloziella varians growing at Rothera Point on the Western Antarctic Peninsula, was manipulated in late austral spring 1998 by screens consisting of a novel combination of Plexiglas panes and polyester sheets. The screens transmitted approximately 79, 68, 48, 41 and 31% of daily UV-B radiation dose. Plants from under and outside the screens were sampled seven times over 35 days. Correlative analyses indicated that concentrations of an anthocyanin-like pigment located in leaf tips were positively associated with UV-B transmission at the last two samplings, that concentrations of total chlorophylls were negatively associated with UV-B transmission at the final sampling, and that those of UV-B screening pigments were positively correlated with transmission at three intermediate samplings. Plants exposed to low UV-B transmission levels were visibly greener than those exposed to high transmission levels after approximately 23 days. The closest relationships between the treatment and concentrations of UV-B screening pigments were associated with increased ambient biologically weighted UV-B dose received by plants in the 5.5 h before each sampling, which coincided with the passage of the ozone hole over Rothera Point. As C. varians emerged from melting snow and ice, concentrations of the anthocyanin-like pigment and chlorophyll respectively increased and decreased faster in plants exposed to high transmission levels of UV-B, relative to those exposed to low UV-B transmission levels.

Changes to the radiative environment arising from stratospheric ozone (O3) depletion and subsequent associations between these changes and the pigmentation of the moss Andreaea regularis were measured in late austral spring and early summer 1998 at Rothera Point on the western Antarctic Peninsula (67 S, 68 W). A strong relationship between O3 column depth and the ratio of UV-B to PAR irradiance (FUV-B/FPAR) was recorded at ground level (r2 = 92%, P<0.001). Weaker, but significant, associations between O3 column depth and ground level unweighted and biologically effective UV-B radiation (UV-BBE) were also found. Regression analyses indicated that FUV-B/FPAR was the best predictor for concentrations of UV-B screening pigments and total carotenoids extracted from plant tissues. Concentrations of these pigments were loosely (r2 = c. 30%) but significantly (P<0.01) positively associated with FUV-B/FPAR. Concentrations of UV-B screening pigments were also positively associated with irradiances and daily doses of unweighted UV-B and UV-BBE radiation. The concentrations of chlorophylls a and b were apparently unaffected by O3 depletion. The data derived from this study suggest that changes to the radiative environment associated with stratospheric O3 depletion influence the pigmentation of A. regularis. As a corollary, flavonoids are shown to be present in tissues of A. regularis.

Changes to the radiative environment arising from stratospheric ozone (O3) depletion and subsequent associations between these changes and the pigmentation of the moss Andreaea regularis were measured in late austral spring and early summer 1998 at Rothera Point on the western Antarctic Peninsula (67 S, 68 W). A strong relationship between O3 column depth and the ratio of UV-B to PAR irradiance (FUV-B/FPAR) was recorded at ground level (r2 = 92%, P<0.001). Weaker, but significant, associations between O3 column depth and ground level unweighted and biologically effective UV-B radiation (UV-BBE) were also found. Regression analyses indicated that FUV-B/FPAR was the best predictor for concentrations of UV-B screening pigments and total carotenoids extracted from plant tissues. Concentrations of these pigments were loosely (r2 = c. 30%) but significantly (P<0.01) positively associated with FUV-B/FPAR. Concentrations of UV-B screening pigments were also positively associated with irradiances and daily doses of unweighted UV-B and UV-BBE radiation. The concentrations of chlorophylls a and b were apparently unaffected by O3 depletion. The data derived from this study suggest that changes to the radiative environment associated with stratospheric O3 depletion influence the pigmentation of A. regularis. As a corollary, flavonoids are shown to be present in tissues of A. regularis.