Microalgal communities from ornithogenic soils at Cierva Point, Antarctic Peninsula

Unrecognized diversity and distribution of soil algae from Maritime Antarctica (Fildes Peninsula, King George Island)

Introduction

Eukaryotic algae in the top few centimeters of fellfield soils of ice-free Maritime Antarctica have many important effects on their habitat, such as being significant drivers of organic matter input into the soils and reducing the impact of wind erosion by soil aggregate formation. To better understand the diversity and distribution of Antarctic terrestrial algae, we performed a pilot study on the surface soils of Meseta, an ice-free plateau mountain crest of Fildes Peninsula, King George Island, being hardly influenced by the marine realm and anthropogenic disturbances. It is openly exposed to microbial colonization from outside Antarctica and connected to the much harsher and dryer ice-free zones of the continental Antarctic. A temperate reference site under mild land use, SchF, was included to further test for the Meseta algae distribution in a contrasting environment.

Methods

We employed a paired-end metabarcoding analysis based on amplicons of the highly variable nuclear-encoded ITS2 rDNA region, complemented by a clone library approach. It targeted the four algal classes, Chlorophyceae, Trebouxiophyceae, Ulvophyceae, and Xanthophyceae, representing key groups of cold-adapted soil algae.

Results

A surprisingly high diversity of 830 algal OTUs was revealed, assigned to 58 genera in the four targeted algal classes. Members of the green algal class Trebouxiophyceae predominated in the soil algae communities. The major part of the algal biodiversity, 86.1% of all algal OTUs, could not be identified at the species level due to insufficient representation in reference sequence databases. The classes Ulvophyceae and Xanthophyceae exhibited the most unknown species diversity. About 9% of the Meseta algae species diversity was shared with that of the temperate reference site in Germany.

Discussion

In the small portion of algal OTUs for which their distribution could be assessed, the entire ITS2 sequence identity with references shows that the soil algae likely have a wide distribution beyond the Polar regions. They probably originated from soil algae propagule banks in far southern regions, transported by aeolian transport over long distances. The dynamics and severity of environmental conditions at the soil surface, determined by high wind currents, and the soil algae's high adaptability to harsh environmental conditions may account for the high similarity of soil algal communities between the northern and southern parts of the Meseta.

Microcystin production by oscillatorialean cyanobacteria isolated from cryopreserved Antarctic mats

Twenty cyanobacterial strains of eight morphospecies isolated from deep-frozen (-15 °C) mat samples originally collected on Ross Island, in Victoria Land, and on the McMurdo Ice Shelf were screened for the presence of genes encoding for production of anatoxins, cylindrospermopsin, microcystin/nodularin and saxitoxin. One strain of each of Microcoleus autumnalis and Phormidesmis priestleyi and two strains of Wilmottia murrayi were found to produce microcystin. No toxin production was detected in the other 16 strains representing five species. The four toxin-producing strains were characterised using both morphological and molecular approaches. Phylogenetic analyses using partial 16S rRNA sequences were consistent with the morphological identification of all four strains. They were all found to contain a fragment of the mcyE gene, which is involved in microcystin biosynthesis. ELISA analysis of extracts from cultures of these strains confirmed the presence of low concentrations of microcystin: 0.35 μg/L in M. autumnalis, <0.15 μg/L in P. priestleyi, 1.60 μg/L in W. murrayi strain 1 and 0.9 μg/L in W. murrayi strain 2. This study includes the first report of microcystin synthesis by W. murrayi.

The influence of penguin activity on soil diatom assemblages on King George Island, Antarctica with the description of a new Luticola species

Background

Ice-free areas in the Antarctic region are strongly limited. The presence of marine mammals and birds in those areas influence soil properties and vegetation composition. Studies on the terrestrial diatom flora in soils influenced by sea birds in the Maritime Antarctic region are scarce.

Methods

Samples were collected from two transects on the western shore of the Admiralty Bay region. Light and scanning electron microscopic observations and statistical analyses were conducted to consider the impact of penguin rookeries on soil diatom assemblages.

Results

The disturbance associated with the presence of penguin rookeries clearly influences the soil diatom diversity. Assemblages from areas with the highest nutrient input were characterized by a much lower diversity with only few species dominating the flora. One of recorded taxa could not be assigned to any of the known species. Therefore, based on the combination of morphological features analyzed using light and scanning electron microscopes and comparison with similar taxa in the Antarctic region and worldwide, the species is described hereby as new to science-Luticola kaweckae sp.nov. The new species is characteristic for soil habitats with strong penguin influence.

Diversity and distribution of tardigrades in soils of Edmonson Point (Northern Victoria Land, continental Antarctica)

This work contributes to the knowledge on distribution, diversity and ecology of the Antarctic soil biota. Different soil habitats from several ice-free coastal sites were sampled along the Victoria Land across 7° of latitude from 71° to 78°S during five austral summer seasons between 2003/04 and 2011/12. In this paper we report preliminary data on soil tardigrades (water bears) from Edmondson Point, Northern Victoria Land. Tardigrades were found to be present in 23 of the 41 examined soil samples (56%). Their presence was associated exclusively with soil samples collected from bryophytes communities and under cyanobacterial mats, whereas they were completely absent in fellfield and ornithogenic soils. Tardigrades were least numerous among all soil micrometazoans, their abundance in the positive samples was very variable and ranged from 3 to 1824 individuals per 100 g of soil DW. High water content seemed to be the major factor determining occurrence of tardigrades in the soils investigated. On the other hand low water content and toxic compounds from penguin guano seemed to act as a strong constraint on their existence in the Antarctic soils. Taxonomic evaluation of the extracted tardigrades revealed presence of only two species belonging to class Eutardigrada: Acutuncus antarcticus (Richters, 1904) and Milnesium antarcticum Tumanov, 2006. While A. antarcticus has already been reported previously as the most widespread and abundant tardigrade across the Victoria Land, the information on M. antarcticum is novel, both for Victoria Land and the continental Antarctica.

Relationships between the Arctic and the Antarctic cyanobacteria; three Phormidium-like strains evaluated by a polyphasic approach

Selected strains of filamentous Phormidium-like cyanobacteria isolated from two Arctic regions (Ellesmere Island, High Canadian Arctic and Svalbard) and from Antarctica (Antarctic peninsula, South Shetland Islands and South Orkney Islands) were studied. The polyphasic approach used included phenotypic observations of morphological features and genotypic analyses (restriction fragment length polymorphism of 16S rRNA gene, internal transcribed space, 16S rRNA gene sequence analysis). Although genotypes generally correspond to observed morphotypes, the genetic analyses revealed a high degree of biodiversity that could not be unveiled using solely morphological evaluations. According to the phylogenetic analysis, the three clones were divided into two major clades, indicating that the phylogenetic distance between Arct-Ph5/Ant-Ph68 and Ant-Ph58 was so large they belonged to different genera. The polyphyletic position of strains of the genus Phormidium was confirmed by this study, attesting the need to entirely revise classification in this taxon in the future.