Abundance and phylogenetic identity of archaeoplankton in the permanent oxygen minimum zone of the eastern tropical South Pacific

• Published in: FEMS microbiology ecology 2011-11, Vol.78 (2), p.314-326
• Main Authors: Belmar, Lucy, Molina, Verónica, Ulloa, Osvaldo
• Format: Article
• Language: English
• Subjects: Ammonium; Animal, plant and microbial ecology; Archaea - classification; Archaea - genetics; Archaea - growth & development; Biological and medical sciences; Community structure; crenarchaea; Ecology; euryarchaea; Fundamental and applied biological sciences. Psychology; Genes, rRNA; Hydrothermal Vents - microbiology; Microbial ecology; Microbiology; Molecular Sequence Data; Oxygen - analysis; Phylogeny; Plankton - classification; Plankton - genetics; Plankton - growth & development; Relative abundance; Seawater - chemistry; Seawater - microbiology; suboxic; Tropical Climate; Water column
• ISSN: 0168-6496; 1574-6941
• DOI: 10.1111/j.1574-6941.2011.01159.x

Abstract We assessed the abundance and molecular phylogeny of archaeoplankton in the oxygen minimum zone (OMZ) of the eastern tropical South Pacific, using specific-probe hybridization and phylogenetic analysis of the SSU-rRNA gene. Euryarchaea from Marine Group-II (MG-II) were most abundant in the surface oxic layer, representing 4.0±2.0% of the total picoplankton, while crenarchaea from Group I.1a (G-I.1a) peaked at the oxyclines, with a relative abundance of 8.1±4.3% (upper oxycline). In most of the stations, the abundance of both the groups decreased at the core of the OMZ, where a secondary maximum in cell density is commonly observed. The majority of the phylotypes affiliated with one of three groups: MG-II, euryarchaeal Marine Group-III (MG-III) and G-I.1a (75.9%, 12.8% and 10.3%, respectively). While MG-II phylotypes were found throughout the water column and G-I.1a ones were predominantly found within the oxyclines, MG-III phylotypes came almost exclusively from the OMZ core. Higher archaeal richness was found within the OMZ, with some of the exclusive lineages grouping with sequences from the deep ocean and hydrothermal vents. Moreover, G-I.1a sequences from the OMZ grouped into a different subcluster from the aerobic ammonium-oxidizerNitrosopumilus maritimus. Thus, the community structure of archaeoplankton in OMZs is rich and distinct, with G-I.1a members particularly prominent at the oxyclines.