Philip M. Novis

Controls on the distribution of productivity and organic resources in Antarctic Dry Valley soils

The Antarctic Dry Valleys are regarded as one of the harshest terrestrial habitats on Earth because of the extremely cold and dry conditions. Despite the extreme environment and scarcity of conspicuous primary producers, the soils contain organic carbon and heterotrophic micro-organisms and invertebrates. Potential sources of organic compounds to sustain soil organisms include in situ primary production by micro-organisms and mosses, spatial subsidies from lacustrine and marine-derived detritus, and temporal subsidies (‘legacies’) from ancient lake deposits. The contributions from these sources at different sites are likely to be influenced by local environmental conditions, especially soil moisture content, position in the landscape in relation to lake level oscillations and legacies from previous geomorphic processes. Here we review the abiotic factors that influence biological activity in Dry Valley soils and present a conceptual model that summarizes mechanisms leading to organic resources therein.

Isotopic evidence for the provenance and turnover of organic carbon by soil microorganisms in the Antarctic dry valleys.

The extremely cold and arid Antarctic dry valleys are one of the most environmentally harsh terrestrial ecosystems supporting organisms in which the biogeochemical transformations of carbon are exclusively driven by microorganisms. The natural abundance of (13)C and (15)N in source organic materials and soils have been examined to obtain evidence for the provenance of the soil organic matter and the C loss as CO(2) during extended incubation (approximately 1200 days at 10 degrees C under moist conditions) has been used to determine the potential decay of soil organic C. The organic matter in soils remote from sources of liquid water or where lacustrine productivity was low had isotope signatures characteristic of endolithic (lichen) sources, whereas at more sheltered and productive sites, the organic matter in the soils that was a mixture mainly lacustrine detritus and moss-derived organic matter. Soil organic C declined by up to 42% during extended incubation under laboratory conditions (equivalent to 50-73 years in the field on a thermal time basis), indicating relatively fast turnover, consistent with previous studies indicating mean residence times for soil organic C in dry valley soils in the range 52-123 years and also with recent inputs of relatively labile source materials.

The Distribution of Elongation Factor‐1 Alpha (EF‐1α), Elongation Factor‐Like (EFL), and a Non‐Canonical Genetic Code in the Ulvophyceae: Discrete Genetic Characters Support a Consistent Phylogenetic Framework

ABSTRACT. The systematics of the green algal class Ulvophyceae have been difficult to resolve with ultrastructural and molecular phylogenetic analyses. Therefore, we investigated relationships among ulvophycean orders by determining the distribution of two discrete genetic characters previously identified only in the order Dasycladales. First, Acetabularia acetabulum uses the core translation GTPase Elongation Factor 1α (EF‐1α) while most Chlorophyta instead possess the related GTPase Elongation Factor‐Like (EFL). Second, the nuclear genomes of dasycladaleans A. acetabulum and Batophora oerstedii use a rare non‐canonical genetic code in which the canonical termination codons TAA and TAG instead encode glutamine. Representatives of Ulvales and Ulotrichales were found to encode EFL, while Caulerpales, Dasycladales, Siphonocladales, and Ignatius tetrasporus were found to encode EF‐1α, in congruence with the two major lineages previously proposed for the Ulvophyceae. The EF‐1α of I. tetrasporus supports its relationship with Caulerpales/Dasycladales/Siphonocladales, in agreement with ultrastructural evidence, but contrary to certain small subunit rRNA analyses that place it with Ulvales/Ulotrichales. The same non‐canonical genetic code previously described in A. acetabulum was observed in EF‐1α sequences from Parvocaulis pusillus (Dasycladales), Chaetomorpha coliformis, and Cladophora cf. crinalis (Siphonocladales), whereas Caulerpales use the universal code. This supports a sister relationship between Siphonocladales and Dasycladales and further refines our understanding of ulvophycean phylogeny.

TWO SNOW SPECIES OF THE QUADRIFLAGELLATE GREEN ALGA CHLAINOMONAS (CHLOROPHYTA, VOLVOCALES): ULTRASTRUCTURE AND PHYLOGENETIC POSITION WITHIN THE CHLOROMONAS CLADE1

The quadriflagellate snow alga Chlainomonas Christen, distributed in New Zealand and North America, has several unusual structural attributes. A process assumed to be cytokinesis involves extrusion of protoplasm from the parent through a narrow canal, C. kolii (J. T. Hardy et Curl) Hoham produces a net‐like outer envelope rather than a cell wall, and the flagellar basal apparatus of Chlainomonas consists of two semi‐independent pairs of basal bodies. Structural connections between basal body pairs appear minimal, but a connecting system different from that observed in other genera exists within each pair. Phylogenetic analysis using rbcL sequences places Chlainomonas in the Chloromonas clade, other known members of which are all biflagellate. Chlainomonas is split into two robust lineages, with New Zealand collections sharing an origin with northern North American collections. Although the quadriflagellate condition is regarded as ancestral in the Chlorophyceae, we speculate—based on ultrastructural and molecular data presented here—that Chlainomonas represents a derived form that has arisen from fusion of two ancestral biflagellate cells. Other explanations (for example, that Chlainomonas represents a diploid form of a biflagellate species) are remotely possible but are presently at odds with extensive observations of field material. Improvements in techniques for experimental manipulation of these sensitive cryophiles will be required to fully characterize their structure and progress our understanding of their biology.

Photosynthetic biocathode enhances the power output of a sediment-type microbial fuel cell

Conventional microbial fuel cells (MFCs) consist of biological anodes and abiotic cathodes separated by a proton-exchange membrane. The abiotic cathode usually catalyses the reduction of oxygen to produce water by means of expensive catalysts such as platinum.1 The cathodic reaction is often limiting in MFCs and researchers are now focusing on efficient, low-cost catalysts to improve oxygen reduction at the cathode. This paper describes a photosynthetic biocathode in a sediment-type MFC constructed without a proton-exchange membrane. The carbon and stainless steel cathode did not contain any catalyst, but was covered in a biofilm composed of a complex community including microalgae and cyanobacteria. Although electroactive species were detected in the cathode biofilm, no biocatalysis of oxygen reduction was observed. Enhancement of the current output was mostly due to the production of pure oxygen near the cathode surface by the photosynthetic biofilm. Photosynthesis could produce dissolved oxygen levels approximately four times higher than oxygen levels obtained by aeration. The MFC was able to generate a maximum power density of 11 mW/m2 (projected anode area) over six months without feeding.

New records of snow algae for New zealand, from Mt Philistine, Arthur's Pass National Park

Abstract Eight out of nine species of snow algae occurring on Mt Philistine, Arthurs Pass National Park, are new records for New Zealand. Chlainomonas kolii, reported previously in snow beneath tree canopies in the USA, is responsible for blooms which colour the snow red. Chloromonas rubroleosa, which is found in red snow dominated by C. kolii, also occurs in continental Antarctica. Three other species of Chloromonas, including the relatively common bipolar alga previously known as Scotiella antarctica, occur in other snowfields on the mountain. The widely reported Raphidonema nivale was identified in cultures from many snow samples. Two species of chrysophyceans, Chromulina cf. elegans and Chrysophyceae sp. 2 (a cyst, of which the life cycle is not understood) occur in Mt Philistine snow. The few previous investigations of New Zealand snow algae have suffered from lack of culturing and observation of living material. Results presented here show that many more sites require detailed study using these techniques to improve our understanding of the biogeography of New Zealand snow algae, and for comparison with floras elsewhere to be meaningful.

New records of microalgae from the New Zealand alpine zone, and their distribution and dispersal

Abstract Chrysocapsa flavescens (Chrysophyceae), Botrydiopsis constricta (Xanthophyceae), and Chlamydomonas pseudogloeogama (Chlorophyceae) were recovered from the alpine zone and constitute new records for New Zealand. Pseudococcomyxa simplex and Stichococcus sp. were also found and subjected to molecular phylogenetic analysis for the first time. Klebsormidium dissectum was isolated for the first time from the alpine zone. RbcL sequences suggest a mix of range restrictions in these taxa, from very little (C. pseudogloeogama, highly similar to a Czech strain) to a well‐supported clade of New Zealand strains (K. dissectum). This mix of biogeographic patterns in these “soft algae” reflects those of the diatom flora, although evidence for widespread range restriction is presently less compelling. Despite the challenges posed by the difficulty of undertaking surveys of microbes, and a paucity of molecular data for many taxa, we suggest Baas Beckings widely quoted biogeographical tenet can be reconciled with both biogeographic structure and long‐distance dispersal under a simple probabilistic framework.

New records of Spirogyra and Zygnema (Charophyceae, Chlorophyta) in New Zealand

Abstract Filamentous zygnematalean algae frequently dominate periphyton assemblages in New Zealand streams, yet only 10 reliable species records of the most common genera, Spirogyra and Zygnema, exist. One of these species, S. clavata, was found again in a new survey of stream habitats, mainly in the South Island. Ten further species (nine of Spirogyra and one of Zygnema) are also described and identified. Morphology and interfertility are affected by polyploid series in Spirogyra, making current species concepts unsatisfactory. Identifications in this study emphasise zygospore ornamentation, which is the most stable and conserved character known.

Alpine Scenedesmaceae from New Zealand: new taxonomy

Cultures from samples collected from the alpine zone in Canyon Creek, Canterbury, New Zealand, revealed three taxa belonging to Scenedesmaceae. Identifications were made based on morphological data (light microscopy and transmission and scanning electron microscopy) and sequences of 18S ribosomal DNA. Desmodesmus abundans is a commonly recorded species worldwide and in New Zealand, but Desmodesmus granulatus is a new record for this country. Coelastrella multistriata var. grandicosta is described as new to science. Cryptodesmus ellipsoideus, previously isolated from the alpine zone at Arthurs Pass, is transferred to Coelastrella ellipsoidea on the basis of new ultrastructural and molecular information. Analysis of 18S ribosomal DNA in Coelastrella indicates likely intragenomic recombination and possible horizontal transfer of introns between taxa in this genus. http://zoobank.org/urn:lsid:zoobank.org:pub:2D9CA9F7-72DE-462B-8201-2725F4F9C91F

Microbial responses to carbon and nitrogen supplementation in an Antarctic dry valley soil

Abstract The soils of the McMurdo Dry Valleys are exposed to extremely dry and cold conditions. Nevertheless, they contain active biological communities that contribute to the biogeochemical processes. We have used ester-linked fatty acid (ELFA) analysis to investigate the effects of additions of carbon and nitrogen in glucose and ammonium chloride, respectively, on the soil microbial community in a field experiment lasting three years in the Garwood Valley. In the control treatment, the total ELFA concentration was small by comparison with temperate soils, but very large when expressed relative to the soil organic carbon concentration, indicating efficient conversion of soil organic carbon into microbial biomass and rapid turnover of soil organic carbon. The ELFA concentrations increased significantly in response to carbon additions, indicating that carbon supply was the main constraint to microbial activity. The large ELFA concentrations relative to soil organic carbon and the increases in ELFA response to organic carbon addition are both interpreted as evidence for the soil microbial community containing organisms with efficient scavenging mechanisms for carbon. The diversity of the ELFA profiles declined in response to organic carbon addition, suggesting the responses were driven by a portion of the community increasing in dominance whilst others declined.