Addition of inorganic or organic phosphorus enhances nitrogen and carbon fixation in the oligotrophic North Pacific

作者：Watkins Brandt Katie S; Letelier Ricardo M; Spitz Yvette H; Church Matthew J; Boettjer Daniela; White Angelicque E^*

来源：Marine Ecology Progress Series, 2011, 432: 17-29.

DOI：10.3354/meps09147

• Phosphorus
• Nitrogen fixation
• Dissolved organic matter

We present a spatially extensive record of dinitrogen (N-2) fixation rates and distributions of N-2 fixing microorganisms along with the results of exogenous phosphorus (P) addition experiments conducted during a series of cruises in the North Pacific Subtropical Gyre (NPSG). We measured the N-2 and carbon (C) fixation rates of natural plankton assemblages in response to the addition of methylphosphonate (MPn), a dissolved organic phosphorus (DOP) compound, and dissolved inorganic phosphorus (DIP). Results are compared to parallel unamended controls. These experiments produced 3 major findings: (1) MPn and DIP were utilized with equal metabolic efficiency over a single photoperiod, (2) the bulk of the enhanced N-2 fixation rates were within the range of those previously reported in the NPSG, suggesting that P levels in this region can be saturating but were not at the time of sampling and (3) MPn and DIP additions stimulated C fixation rates beyond estimated contributions by diazotrophs, and hence both DIP and bioavailable DOP additions could lead to enhancement of net primary productivity on short time-scales. Our results suggest that the rate of N-2 fixation in our study region may have been restricted by the availability and/or the composition of the total P pool (inorganic and organic P) during our field season.

• 出版日期2011