Methodological Underestimation of Oceanic Nitrogen Fixation Rates
Autor: | Tobias Großkopf, Douglas W.R. Wallace, Wiebke Mohr, Julie LaRoche |
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Jazyk: | angličtina |
Rok vydání: | 2010 |
Předmět: |
0106 biological sciences
010504 meteorology & atmospheric sciences Nitrogen Bubble Science Oceans and Seas chemistry.chemical_element Soil science Cyanobacteria 01 natural sciences Fixation (surgical) Marine and Aquatic Sciences/Microbiology TRACER Nitrogen Fixation Botany Marine and Aquatic Sciences/Biological Oceanography Seawater Biomass Nitrogen cycle 0105 earth and related environmental sciences Multidisciplinary Nitrogen Isotopes 010604 marine biology & hydrobiology Crocosphaera watsonii Marine and Aquatic Sciences/Biogeochemistry Kinetics chemistry 13. Climate action Isotope Labeling Nitrogen fixation Environmental science Medicine Research Article |
Zdroj: | PLoS ONE PLoS ONE, 5 (9). e12583. PLoS ONE, Vol 5, Iss 9, p e12583 (2010) |
ISSN: | 1932-6203 |
Popis: | The two commonly applied methods to assess dinitrogen (N(2)) fixation rates are the (15)N(2)-tracer addition and the acetylene reduction assay (ARA). Discrepancies between the two methods as well as inconsistencies between N(2) fixation rates and biomass/growth rates in culture experiments have been attributed to variable excretion of recently fixed N(2). Here we demonstrate that the (15)N(2)-tracer addition method underestimates N(2) fixation rates significantly when the (15)N(2) tracer is introduced as a gas bubble. The injected (15)N(2) gas bubble does not attain equilibrium with the surrounding water leading to a (15)N(2) concentration lower than assumed by the method used to calculate (15)N(2)-fixation rates. The resulting magnitude of underestimation varies with the incubation time, to a lesser extent on the amount of injected gas and is sensitive to the timing of the bubble injection relative to diel N(2) fixation patterns. Here, we propose and test a modified (15)N(2) tracer method based on the addition of (15)N(2)-enriched seawater that provides an instantaneous, constant enrichment and allows more accurate calculation of N(2) fixation rates for both field and laboratory studies. We hypothesise that application of N(2) fixation measurements using this modified method will significantly reduce the apparent imbalances in the oceanic fixed-nitrogen budget. |
Databáze: | OpenAIRE |
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