Sources of edaphic cyanobacterial diversity in the Dry Valleys of Eastern Antarctica

Abstract

Cyanobacteria are major components of Antarctic Dry Valley ecosystems. Their occurrence in lakes and ponds is well documented, however, less is known about their distribution in edaphic environments. There has been considerable debate about the contribution of aquatic organic matter derived largely from cyanobacteria to terrestrial ecosystems. In this study, automated rRNA intergenic spacer analysis (ARISA) and 16S rRNA gene clone libraries were used to investigate cyanobacterial diversity in a range of soil environments within the Miers and Beacon Valleys. These data were used to elucidate the input of aquatic cyanobacteria to soil communities. Thirty-eight samples were collected from a variety of soil environments including dry and moist soils, hypoliths and lake and hydroterrestrial microbial mats. The results from the ARISA and 16S rRNA clone library analysis demonstrated that diverse cyanobacterial communities exist within the mineral soils of the Miers Valley. The soil samples from Beacon Valley were depauparate in cyanobacterial signals. Within Miers Valley, significant portions (29%-58%) of ARISA fragment lengths found in aquatic cyanobacterial mats were also present in soil and hypolith samples, indicating that lacustrine and hydroterrestrial cyanobacteria play a significant role in structuring soil communities. The influence of abiotic variables on the community structure of soil samples was assessed using BEST analysis. The results of BEST analysis of samples from within Miers Valley showed that total percentage of carbon content was the most important variable in explaining differences in cyanobacterial community structure. The BEST analyses indicated that four elements contributed significantly to species compositional differences between valleys. We suggest that the complete absence of lakes or ponds from Beacon Valley is a contributing factor to the low cyanobacterial component of these soils.

Microbiology of Eutrophic (Ornithogenic and Hydrocarbon-Contaminated) Soil

“…The similarity of cyanobacterial phylotypes in Dry Valley soils to local lake and hydroterrestrial cyanobacterial mat phylotypes supports suggestions that soils are seeded directly through wind dispersal of mat communities Wood et al 2008). In particular, Leptolyngbya spp., which are dominant in microbial mats across the Dry Valleys , are commonly detected in the surrounding soils (Aislabie et al , 2008.…”

“…Community fingerprinting and sequencing were completed using Cyanobacteria-specific PCR primers to analyze distributions in Beacon Valley and Miers Valley soils. Cyanobacterial signatures were below detection or limited to a single phylotype in samples analyzed from Beacon Valley, despite having higher average soil water content than samples collected from Miers Valley, where several phylotypes, grouping to the orders Chroococcales, Nostocales, and Oscillatoriales, were observed (Wood et al 2008). Variation in cyanobacterial community structures was best explained by differences in elemental composition of soils (Wood et al 2008).…”

“…In contrast to the findings in Northern Victoria Land (Niederberger et al 2008), the distribution of Cyanobacteria in the Dry Valleys was not found to be related to soil water content (Wood et al 2008). Community fingerprinting and sequencing were completed using Cyanobacteria-specific PCR primers to analyze distributions in Beacon Valley and Miers Valley soils.…”

“…Mat samples have been shown to be capable of remaining dormant for many years and returning to activity in the presence of water (Vincent and Howard-Williams 1986), suggesting that windblown mat material not only provides important nutrients to the surrounding soils, but also disseminates potentially active bacterial species throughout the valley floor. The absence of hydrological features (ponds and lakes) in the Beacon Valley compared to Miers Valley was considered an important factor in explaining the differences in cyanobacterial compositions between the two valleys (Wood et al 2008). Heterotrophic bacteria in microbial mats, which include representatives of the phyla Actinobacteria, Proteobacteria, Bacteroidetes, Firmicutes, and Deinococcus-Thermus (Brambilla et al 2001;Van Trappen et al 2002;Rojas et al 2009;Peeters et al 2011), may be similarly redistributed by aeolian processes in Antarctic ecosystems.…”

“…This biomass accumulates at the edges of these water bodies where it is freeze-dried and can be blown throughout the valley distributing organisms and providing carbon and nitrogen subsidies to areas of low productivity (Parker et al 1982;Elberling and Brandt 2003;Moorhead et al 2003;Nkem et al 2006;Hopkins et al 2006a;Barrett et al 2006b;Wood et al 2008). The size of these aquatic systems, along with wind intensity and direction, influence the relative contribution of these sources to valley-wide nutrient cycling and productivity (Hopkins et al 2006a, b).…”