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Marine Ecology Progress Series

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MEPS 504:43-58 (2014)  -  DOI:

Microbial response to enhanced phosphorus cycling in the North Pacific Subtropical Gyre

Solange Duhamel1,2,*, Karin M. Björkman1, Joseph K. Doggett1, David M. Karl1

1Daniel K. Inouye Center for Microbial Oceanography: Research and Education (C-MORE), University of Hawaii, C-MORE Hale, 1950 East West Road, Honolulu, Hawaii 96822, USA
2Present address: Lamont-Doherty Earth Observatory, Division of Biology and Paleo Environment, Columbia University, PO Box 1000, 61 Route 9W, Palisades, New York 10964, USA
*Corresponding author:

ABSTRACT: Microbial community response to nitrogen (N) amendments and induced phosphorus (P) stress was investigated in the North Pacific Subtropical Gyre (NPSG). Samples amended with reduced sources of N, in the form of nitrate plus ammonium, showed significant increases in microbial cell abundance and biomass and decreases in dissolved inorganic phosphate (Pi) and silicate concentrations during an incubation period of 6 d. Primary productivity, P uptake rates (as both Pi and adenosine-5’-triphosphate [ATP]) and alkaline phosphatase activity (APA) all increased following N amendment. Dissolved organic P (DOP) concentrations did not change, but the large increase in APA and ATP uptake rates suggests that DOP was a dynamic pool and an important source for microbial P nutrition in P-stressed samples. Significant changes were also observed in the structure of the microbial community, with Synechococcus and picoalgae abundances increasing substantially in the N-amended treatments, while non-pigmented picoplankton abundances were unchanged. Data on P resource partitioning among groups of picoplankton separated by size using membrane filters of different porosities, or by scattering and fluorescence properties using flow cytometry sorting, indicate that Synechococcus could have a greater role in the NPSG P cycling following episodic N inputs. This experimental manipulation of nutrient loading combined with observations at the total population to the microbial group levels constitutes a unique approach to improve our understanding of microbial community structure and function in response to environmental forcing.

KEY WORDS: Phosphorus dynamics · Microbes · Flow cytometry cell sorting · North Pacific Subtropical Gyre

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Cite this article as: Duhamel S, Björkman KM, Doggett JK, Karl DM (2014) Microbial response to enhanced phosphorus cycling in the North Pacific Subtropical Gyre. Mar Ecol Prog Ser 504:43-58.

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