| Summary: | A CO2 enrichment mesocosm study was carried out in Bergen, Norway in May 2006. This study investigates differences in alpha-proteobacteria diversity between acidified and non-acidified mesocosms. IVIetagenomic fosmid, 600bp alphaproteobacterial specific and full-length 16S rDNA clone libraries were constructed. The fosmid and fulllength 16S rDNA libraries were screened for alphaproteobacterial 16S rRNA genes. Phylogenetic analyses revealed a greater diversity of alphaproteobacteria from nonacidified clones in all three methods. ANOSIM statistical analysis confirmed a weak but highly significant (p < 0.01) treatment effect in all libraries. However, in the metagenomic fosmid method, differences between treatments for a specific Roseobacter clade were responsible for the observed statistical significance. In the 600bp and full length 16S rDNA libraries, the treatment effect was a result of the presence or absence of different taxa in each sample. All three methods revealed the same general community structure indicating hierarchical taxonomic trends were conserved with the different techniques. This demonstrates that the effects seen in this study result from treatment not methodological effects. This study concludes that alpha-proteobacteria populations exposed to an increase in PCO2 and concomitant reduction in pH for just 17 days experience small but significant changes which were manifested as an apparent loss of phylogenetic diversity and a shift in the dominance of specific strains. Faculty of Science
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