Protist diversity and biogeography in the Pacific sector of the Southern Ocean

• Main Author: Wolf, Christian
• Format: Thesis
• Language: unknown
• Published: 2013
• Subjects: Amundsen Sea; Antarc*; Antarctic; Ross Sea; Southern Ocean
• Online Access: https://epic.awi.de/id/eprint/34202/; https://epic.awi.de/id/eprint/34202/2/Dissertation_ChristianWolf_2012.pdf; https://hdl.handle.net/10013/epic.43313; https://hdl.handle.net/10013/epic.43313.d002

The objectives of this thesis were the establishment of molecular approaches in the diversity investigation of eukaryotic protists in the Southern Ocean, the comparison of different approaches and the delivery of a comprehensive and taxon detailed overview of protist assemblages in the Pacific sector of the Southern Ocean, especially in the Amundsen Sea. The molecular approaches used to achieve these goals were automated ribosomal intergenic spacer analysis (ARISA), sequencing of 18S rRNA gene clone libraries and 454-pyrosequencing. The comparison of 18S rRNA clone library sequences with the results of 454-pyrosequencing was conducted with four Arctic water samples, focusing on picoplankton (0.4-3 μm), and with one Antarctic water sample, covering the whole size spectrum (>0.2 μm). It turned out that the two methods delivered different results. Both approaches discovered phylotypes that were not found with the other approach. The abundant biosphere, defined by the 454-pyrosequencing approach, was not fully recovered by the clone library approach. The cloning approach was biased against several groups, e.g. haptophytes in the Arctic samples and diatoms in the Antarctic sample. In summary, prior cloning data have to be handled with care, when compared with 454-pyrosequencing data. Additionally, cloning data are only of limited suitability to serve as a backbone for phylogenetic analysis of 454-pyrosequencing data. The results of this comparison led to the decision to use ARISA and 454-pyrosequencing for the further protist diversity investigations. First, the hypothesis that distinct protist community assemblages characterize large-scale water masses was tested. The composition and biogeography of late summer eukaryotic protist assemblages along a transect from the coast of New Zealand to the eastern Ross Sea was determined. ARISA and 454-pyrosequencing were used in combination with flow cytometry and pigment measurements via high performance liquid chromatography (HPLC) to study the protist assemblage. ...