Phosphorus dynamics in the North Pacific subtropical gyre

Abstract

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 22:185-198 (2000) - doi:10.3354/ame022185 Phosphorus dynamics in the North Pacific subtropical gyre Karin Björkman*, Angie L. Thomson-Bulldis**, David M. Karl Department of Oceanography, School of Ocean & Earth Science & Technology (SOEST), University of Hawaii, Honolulu, Hawaii 96822, USA *E-mail: bjorkman@soest.hawaii.edu **Present address: College of Education, University of Washington, Seattle, Washington 98195, USA ABSTRACT: Phosphorus (P) dynamics were studied during several research cruises to Stn ALOHA and in the ŒClimax region¹ of the North Pacific subtropical gyre (NPSG) in 1996-1997. The aim of this study was to: (1) investigate the coupled uptake and regeneration of inorganic phosphate (Pi) and the production of dissolved organic phosphorus (DOP), (2) quantify the size of the biologically available P (BAP) pool, and (3) estimate the relative bioavailability of select organic P compounds to the natural microbial assemblages. At all stations, the microbial community was dominated by prokaryotes (>99.5% of total cell numbers); Prochlorococcus spp. was the dominant pigmented group (>97% by numbers), comprising 20 to 30% of the total prokaryotic population. Phosphate uptake rates were 3.0 to 8.2 nM d-1 (median = 3.5 nM d-1) and P pool turnover times ranged from 2 to 40 d (median = 9 d). The BAP pool generally exceeded the Pi pool, suggesting rapid turnover of at least a portion of the much larger DOP pool. The net production of DOP was approximately 10 to 40% of the net P uptake. Both the dissolved and the particulate organic matter pools were enriched in carbon (C) and nitrogen (N) relative to P, compared to the Redfield molar stoichiometry of 106C:16N:1P. The half-saturation constant, Km, values for Pi uptake were higher than the ambient Pi pool concentrations, and uptake rates were positively correlated with exogenous Pi additions over the range tested (Pi = 25 to 250 nM). The bioavailabilities of exogenous adenine and guanine nucleotides were generally higher than other organic P compounds we tested. The net Pi regeneration rate from nucleotides was up to 50 times higher than the net Pi uptake rates, indicating a large potential for the regeneration of Pi from specific organic compounds. These P pool dynamics observed in the NPSG are consistent with a microbial community currently under P control. KEY WORDS: Phosphate uptake rates · Turnover rates · Bioavailable phosphorus · Bacteria · North Pacific Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 22, No. 2. Online publication date: September 08, 2000 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2000 Inter-Research.