Interaction between Carbon and Sulfur Cycles in Antarctic Stratified Lakes and Fjords
---- Public Summary from Project ----
The lakes and fjords of the Vestfold Hills region of Antarctica provide unique ecosystems for studying environmental changes in Antarctica over the past 8000 years. Studies of the changes in organic matter composition in sediment cores provide information how the microbial and plankton communities have changed over time in response to varying chemical and ... physical conditions. Our study will provide new information about how the cycles of the biologically-important elements carbon and sulfur are linked and why some sediments can preserve large amounts of organic carbon. This information will be useful for studies of palaeoclimate and will also provide valuable insights into the processes that produce petroleum source rocks.
From the abstracts of the referenced papers:
Preserved ribosomal DNA of planktonic phototrophic algae was recovered from Holocene anoxic sediments of Ace Lake (Antarctica), and the ancient community members were identified based on comparative sequence analysis. The similar concentration profiles of DNA of haptophytes and their traditional lipid biomarkers (alkenones and alkenoates) revealed that fossil rDNA also served as quantitative biomarkers in this environment. The DNA data clearly revealed the presence of six novel phylotypes related to known alkenone and alkenoate-biosynthesising haptophytes with Isochrysis galbana UIO 102 as their closest relative. The relative abundance of these phylotypes changed as the lake chemistry, particularly salinity, evolved over time. Changes in the alkenone distributions reflect these population changes rather than a physiological response to salinity by a single halophyte. Using this novel palaeo-ecological approach of combining data from lipid biomarkers and preserved DNA, we showed that the post-glacial development of Ace Lake from freshwater basin to marine inlet and the present-day lacustrine saline system caused major qualitative and quantitative changes in the biodiversity of the planktonic populations over time.
Post-glacial Ace Lake (Vestfold Hills, Antarctica), which was initially a freshwater lake and then an open marine system, is currently a meromictic basin with anoxic, sulfidic and methane-saturated bottom waters. Lipid and 16S ribosomal RNA gene stratigraphy of up to 10,400-year-old sediment core samples from the lake revealed that these environmentally induced chemical and physical changes caused clear shifts in the species composition of archaea and aerobic methanotrophic bacteria. The combined presence of lipids specific for methanogenic archaea and molecular remains of aerobic methanotrophic bacteria (13C-depleted delta8(14)-sterols and 16S rRNA genes) revealed that an active methane cycle occurred in Ace Lake during the last 3000 calendar years and that the extant methanotrophs were most likely introduced when it became a marine inlet (9400 y BP); rDNA sequences showed 100% sequence similarity with Methanosarcinales species from freshwater environments and were the source of sn-2- and sn3-hydroxyarchaeols. Archaeal phylotypes related to uncultivated Archaea associated with various marine environments were recovered from the present-day anoxic water column and sediments deposited during the meromictic and marine period.
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See the referenced papers for details.
Dates provided in temporal coverage are approximate only. Year and month are correct.
Copies of the referenced papers are available for download from the provided URL to AAD staff only.
DNA sequences are available via Genbank (see the url below) with the following accession numbers:
Section 2.9. page 229 of the EPSL paper: GenBank acc. numbers AY303351-AY303357
Section 2.10 page 1155 of the Org. Geochem paper: GenBank acc. numbers AY291536-AY291564
Data Set Progress
+61 3 6232 5281
+61 3 6232 5123
john.volkman at csiro.au
GPO BOX 1538
CSIRO Marine and Atmospheric Research
Province or State:
Coolen, M.J.L., Muyzer, G., Rijpstra, W.I.C., Schouten, S., Volkman, J.K. and Sinninghe Damsté, J.S. (2004), Combined DNA and lipid analyses of sediments reveal changes in Holocene haptophyte and diatom populations in an Antarctic lake., Earth and Planetary Science Letters, 223, 225-239
Coolen, M.J.L., Hopmans, E.C., Rijpstra, W.I.C., Muyzer, G., Schouten, S., Volkman, J.K. and Sinninghe Damsté, J.S. (2004), Evolution of the methane cycle in Ace Lake (Antarctica) during the Holocene: response of methanogens and methanotrophs to environmental change., Organic Geochemistry, 35, 1151-1167
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