Temporal changes in community composition of heterotrophic bacteria during in situ iron enrichment in the western subarctic Pacific (SEEDS-II) |
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| Institution: | 1. Department of Earth and Ocean Sciences, University of South Carolina, Columbia, SC 29208, USA;2. Department of Ocean Sciences, University of California, Santa Cruz, CA 95064, USA;3. Department of Earth Science, University of Southern California, Los Angeles, CA 90089, USA;1. Royal Netherlands Institute for Sea Research, Den Burg, The Netherlands;2. Laboratoire de Glaciologie, Université Libre de Bruxelles, Brussels, Belgium;3. Department of Ocean Ecosystems, University of Groningen, Groningen, The Netherlands;1. CESAM, Departamento de Física, Universidade de Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal;2. MARETEC, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal;3. Hidromod, Rua Rui Teles Palhinha, nº 4, 1°, 2740-278 Porto Salvo, Portugal |
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| Abstract: | Little is known about the effects of iron enrichment in high-nitrate low-chlorophyll (HNLC) waters on the community composition of heterotrophic bacteria, which are crucial to nutrient recycling and microbial food webs. Using denaturing gradient gel electrophoresis (DGGE) of 16S rDNA fragments, we investigated the heterotrophic eubacterial community composition in surface waters during an in situ iron-enrichment experiment (SEEDS-II) in the western subarctic Pacific in the summer of 2004. DGGE fingerprints representing the community composition of eubacteria differed inside and outside the iron-enriched patch. Sequencing of DGGE bands revealed that at least five phylotypes of α-proteobacteria including Roseobacter, Cytophaga-Flavobacteria-Bacteroides (CFB), γ-proteobacteria, and Actinobacteria occurred in almost all samples from the iron-enriched patch. Diatoms did not bloom during SEEDS-II, but the eubacterial composition in the iron-enriched patch was similar to that in diatom blooms observed previously. Although dissolved organic carbon (DOC) accumulation was not detected in surface waters during SEEDS-II, growth of the Roseobacter clade might have been particularly stimulated after iron additions. Two identified phylotypes of CFB were closely related to the genus Saprospira, whose algicidal activity might degrade the phytoplankton assemblages increased by iron enrichment. These results suggest that the responses of heterotrophic bacteria to iron enrichment could differ among phylotypes during SEEDS-II. |
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