Database of diazotrophs in global ocean: abundance, biomass and nitrogen fixation rates

By Ya‐Wei Luo, S. Doney, L. Anderson, M. Benavides, I. Berman‐Frank, A. Bode, S. Bonnet, Kjärstin H. Boström, D. Böttjer, D. Capone and 39 more. 2012

395 citations recorded by the source corpus.

Abstract. Marine N2 fixing microorganisms, termed diazotrophs, are a key functional group in marine pelagic ecosystems. The biological fixation of dinitrogen (N2) to bioavailable nitrogen provides an important new source of nitrogen for pelagic marine ecosystems and influences primary productivity and organic matter export to the deep ocean. As one of a series of efforts to collect biomass and rates specific to different phytoplankton functional groups, we have constructed a database on diazotrophic organisms in the global pelagic upper ocean by compiling about 12 000 direct field measurements of cyanobacterial diazotroph abundances (based on microscopic cell counts or qPCR assays targeting the nifH genes) and N2 fixation rates. Biomass conversion factors are estimated based on cell sizes to convert abundance data to diazotrophic biomass. The database is limited spatially, lacking large regions of the ocean especially in the Indian Ocean. The data are approximately log-normal distributed, and large variances exist in most sub-databases with non-zero values differing 5 to 8 orders of magnitude. Reporting the geometric mean and the range of one geometric standard error below and above the geometric mean, the pelagic N2 fixation rate in the global ocean is estimated to be 62 (52–73) Tg N yr−1 and the pelagic diazotrophic biomass in the global ocean is estimated to be 2.1 (1.4–3.1) Tg C from cell counts and to 89 (43–150) Tg C from nifH-based abundances. Reporting the arithmetic mean and one standard error instead, these three global estimates are 140 p 9.2 Tg N yr−1, 18 p 1.8 Tg C and 590 p 70 Tg C, respectively. Uncertainties related to biomass conversion factors can change the estimate of geometric mean pelagic diazotrophic biomass in the global ocean by about p70%. It was recently established that the most commonly applied method used to measure N2 fixation has underestimated the true rates. As a result, one can expect that future rate measurements will shift the mean N2 fixation rate upward and may result in significantly higher estimates for the global N2 fixation. The evolving database can nevertheless be used to study spatial and temporal distributions and variations of marine N2 fixation, to validate geochemical estimates and to parameterize and validate biogeochemical models, keeping in mind that future rate measurements may rise in the future. The database is stored in PANGAEA ( doi:10.1594/PANGAEA.774851 ).

Subfields: Ecology, Oceanography

View Paper: https://www.semanticscholar.org/paper/6888840835b9fdcd577a33c358279505542c3f11

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Citations in the corpus

Ecological niches of open ocean phytoplankton taxa (2015, background): “Additionally, the investigated genus Richelia represents heterocystous diazotrophs (Luo et al. 2012).”
Iron, phosphorus, and nitrogen supply ratios define the biogeography of nitrogen fixation (2013, background): “latitude oceans, where diazotrophs are typically found (Luo et al. 2012).”
Diversity and activity of nitrogen‐fixing communities across ocean basins (2017, background): “Though historically understudied as an environment for diazotrophs (Luo et al. 2012), focus on the ESP increased after a numerical model predicted high NFR in the region (Deutsch et al. 2007).”
New insights into the ecology of the globally significant uncultured nitrogen-fixing symbiont UCYN-A (2016, background): “Compared to Trichodesmium, which tends to be more abundant in the upper water column (Luo et al. 2012), UCYN-A were found to occupy greater depths (down to ~150 m) and were present at higher latitudes, extending the previously known N2 fixation domains (Moisander et al.”