The cyanobacterial community of polygon soils at an inland Antarctic nunatak

Inland Antarctic terrestrial ecosystems and biodiversity are poorly understood in comparison with Antarctic coastal regions. Microorganisms, as primary colonists, are integral to Antarctic soil ecosystem development, essential for pedogenesis and structuring the soil, and providing the nutrients necessary for the subsequent establishment of macroorganisms. This study analysed the microbial communities present in polygon soils of Coal Nunatak (Alexander Island, at the southern limit of the maritime Antarctic). Soils were analysed across three polygons (centre and margins) and at three depths (0-1, 1-2, 2-5 cm). Cyanobacterial communities were characterised using two complementary molecular biological approaches, temperature gradient gel electrophoresis and clone library analysis. The three polygons exhibited conspicuous differences in community composition, both between different polygons and spatially (horizontally and vertically) within a single polygon. Comparison of our data with that from previous studies using classical culture and morphological identification techniques clearly shows the need for more intensive research on patterns of microbial diversity in terrestrial habitats throughout the Antarctic. The majority of the 17 cyanobacterial genera identified at Coal Nunatak are thought to have ubiquitous distributions, while none are known only from the Antarctic. Three of the genera present are also known to be capable of being lichen photobionts

Aerial dispersal of lichen soredia in the maritime Antarctic

An aerobiological monitoring programme was carried out for over a year on Signy Island, South Orkney Islands, Antarctica. Collections were made using arrays of rotorod samplers at three sites. Lichen soredia were found to be the most abundant air borne propagules, more so than ascospores, the sexual propagules of lichen fungi. The dominance of soredia over ascospores appeared to decrease with increasing maturity of fellfield sites. No correlations were found with temperature, relative humidity or wind speed. Collections at 1 m above ground level were shown not to be significantly different to those at 0·15 m at two of the sites. Size range distribution also differed at two of the sites. Soredial clumps in excess of 100 μm in diameter were collected at 1 m above ground level and at some distance from potential source plants, though most fell in the range 30–60 μm. Peaks in numbers of air borne soredia were found after winter snow melt, demonstrating that soredial production continues at subzero temperature

Antarctic crabs: invasion or endurance?

Recent scientific interest following the “discovery” of lithodid crabs around Antarctica has centred on a hypothesis that these crabs might be poised to invade the Antarctic shelf if the recent warming trend continues, potentially decimating its native fauna. This “invasion hypothesis” suggests that decapod crabs were driven out of Antarctica 40–15 million years ago and are only now returning as “warm” enough habitats become available. The hypothesis is based on a geographically and spatially poor fossil record of a different group of crabs (Brachyura), and examination of relatively few Recent lithodid samples from the Antarctic slope. In this paper, we examine the existing lithodid fossil record and present the distribution and biogeographic patterns derived from over 16,000 records of Recent Southern Hemisphere crabs and lobsters. Globally, the lithodid fossil record consists of only two known specimens, neither of which comes from the Antarctic. Recent records show that 22 species of crabs and lobsters have been reported from the Southern Ocean, with 12 species found south of 60°S. All are restricted to waters warmer than 0°C, with their Antarctic distribution limited to the areas of seafloor dominated by Circumpolar Deep Water (CDW). Currently, CDW extends further and shallower onto the West Antarctic shelf than the known distribution ranges of most lithodid species examined. Geological evidence suggests that West Antarctic shelf could have been available for colonisation during the last 9,000 years. Distribution patterns, species richness, and levels of endemism all suggest that, rather than becoming extinct and recently re-invading from outside Antarctica, the lithodid crabs have likely persisted, and even radiated, on or near to Antarctic slope. We conclude there is no evidence for a modern-day “crab invasion”. We recommend a repeated targeted lithodid sampling program along the West Antarctic shelf to fully test the validity of the “invasion hypothesis”

Shallow benthic communities of South Georgia Island

Benthic communities in several fjords and sheltered bays of the north coast of South Georgia Island were examined using SCUBA and shore sampling in November 2004. It is one of the most northerly islands within the Polar Front and its well studied, terrestrial biota is described as sub Antarctic. The intertidal and subtidal zones and their fauna are, by comparison, little known. We describe the composition of the substratum and benthic communities of sites in several northern bays, including an exceptional community in the extremely sheltered Moraine Fjord with a 2 m sill at its entrance. In this, like those in some other fjordic systems, some taxa occur shallower than elsewhere, and in this instance, get large and are probably old. Elsewhere, we found the coastal fauna was fairly similar to Antarctic shallow communities in the southern Scotia Arc and Peninsula region. Of the taxa we found, we identified 53 to genus and 41 to species. Most of these were typical Antarctic shallow benthic taxa. Certain flatworms, nemerteans, bivalve and gastropod molluscs, amphipod and isopod crustaceans, asteroid echinoderms and stalked ascidians were very abundant, but some normally common Antarctic higher taxa and species were notably absent or rare