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Aquatic Microbial Ecology

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AME 75:1-13 (2015)  -  DOI:

Bacterial and archaeal biogeography of the deep chlorophyll maximum in the South Pacific Gyre

Emily A. Walsh1,*, David C. Smith1, Mitchell L. Sogin2, Steven D’Hondt

1Graduate School of Oceanography, University of Rhode Island, Narragansett Bay Campus, 215 South Ferry Road, Narragansett, RI 02882, USA
2Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543, USA
*Corresponding author:

ABSTRACT: We used 16S rRNA gene tag pyrosequencing to examine the biogeography of bacterial and archaeal community composition in the deep chlorophyll maximum (DCM) of the South Pacific Gyre (SPG), the largest and most oligotrophic region of the world ocean. Dominant DCM bacterial taxa, including Prochlorococcus, SAR11, SAR406, and SAR86, were present at each sampled site in similar proportions, although the sites are separated by thousands of kilometers and up to 100 m in water depth. Marine Group II (MGII) and MGIII Euryarcheota dominated the archaeal assemblages of the DCM at these sites. Bray-Curtis indices show that assemblage composition of these sites is >70% similar for Bacteria and >80% similar for Archaea. Despite these similarities, communities of the central SPG, the western SPG margin, and the southern SPG margin are distinguishable from each other. Comparison of our bacterial results to samples from the DCM of the North Pacific Gyre (NPG) and the relatively nutrient- and chlorophyll-rich Equatorial Pacific (EQP) shows that DCM bacterial assemblage composition is >50% similar throughout all 3 regions. Nonetheless, the SPG, NPG, and EQP assemblages are statistically distinct from each other (ANOSIM, p = 0.001), with the communities of the 2 gyres resembling each other more closely than either resembles the EQP community (which lives geographically between them). Variation in assemblage composition correlates with sea-surface chlorophyll concentration (r2 = 0.71, p < 0.003). This study demonstrates that the DCM horizons of different oceanic regions harbor statistically distinct communities that are consistent within regions for thousands of kilometers.

KEY WORDS: South Pacific Gyre · Microbial biogeography · Microbial diversity · Deep chlorophyll maximum · Pyrosequencing

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Cite this article as: Walsh EA, Smith DC, Sogin ML, D’Hondt S (2015) Bacterial and archaeal biogeography of the deep chlorophyll maximum in the South Pacific Gyre. Aquat Microb Ecol 75:1-13.

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