Physical forcing of nitrogen fixation and diazotroph community structure in the North Pacific subtropical gyre
By M. Church, C. Mahaffey, Ricardo M Letelier, R. Lukas, Jonathan P. Zehr, David M. Karl. 2009
215 citations recorded by the source corpus.
Dinitrogen (N2) fixing microorganisms (termed diazotrophs) exert important control on the ocean carbon cycle. However, despite increased awareness on the roles of these microorganisms in ocean biogeochemistry and ecology, the processes controlling variability in diazotroph distributions, abundances, and activities remain largely unknown. In this study, we examine 3 years (2004–2007) of approximately monthly measurements of upper ocean diazotroph community structure and rates of N2 fixation at Station ALOHA (22°45′N, 158°W), the field site for the Hawaii Ocean Time‐series program in the central North Pacific subtropical gyre (NPSG). The structure of the N2‐fixing microorganism assemblage varied widely in time with unicellular N2‐fixing microorganisms frequently dominating diazotroph abundances in the late winter and early spring, while filamentous microorganisms (specifically various heterocyst‐forming cyanobacteria and Trichodesmium spp.) fluctuated episodically during the summer. On average, a large fraction (∼80%) of the daily N2 fixation was partitioned into the biomass of <10 μm microorganisms. Rates of N2 fixation were variable in time, with peak N2 fixation frequently coinciding with periods when heterocystous N2‐fixing cyanobacteria were abundant. During the summer months when sea surface temperatures exceeded 25.2°C and concentrations of nitrate plus nitrite were at their annual minimum, rates of N2 fixation often increased during periods of positive sea surface height anomalies, as reflected in satellite altimetry. Our results suggest mesoscale physical forcing may comprise an important control on variability in N2 fixation and diazotroph community structure in the NPSG.
Subfields: Ecology, Oceanography
View Paper: https://www.semanticscholar.org/paper/e6964c0240eaa9e642dc7393da236bc7442d92c0
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Citations in the corpus
- Distribution of diverse nitrogen fixers in the global ocean (2010, unknown): “The model predicts a similar, late summer bloom of Trichodesmium in the subtropical North Pacific Ocean, as observed at the Hawaii Ocean Time‐Series [Goebel et al., 2007; Church et al., 2009].”
- New insights into the ecology of the globally significant uncultured nitrogen-fixing symbiont UCYN-A (2016, background): “…bulk seawater community into larger and smaller size fractions, it has been found that the smaller size fraction can at times dominate water column N2 fixation rates (Montoya et al. 2004, Garcia et al. 2007, Biegala & Raimbault 2008, Bonnet et al. 2009, Church et al. 2009, Benavides et al. 2011).”