Nitrogen fixation-enhanced carbon sequestration in low nitrate, low chlorophyll seascapes
Karl, D.M.; Letelier, R.M. (2008). Nitrogen fixation-enhanced carbon sequestration in low nitrate, low chlorophyll seascapes. Mar. Ecol. Prog. Ser. 364: 257-268. http://dx.doi.org/10.3354/meps07547
In: Marine Ecology Progress Series. Inter-Research: Oldendorf/Luhe. ISSN 0171-8630; e-ISSN 1616-1599, more
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| Keywords |
Algal blooms
Analysis > Quantitative analysis
Aquatic communities > Plankton > Phytoplankton
Biological production > Primary production
Carbon sequestration
Chemical compounds > Nitrogen compounds > Nitrates
Chemical reactions > Nitrogen fixation
Concentration (composition)
Cycles > Chemical cycles > Geochemical cycle > Biogeochemical cycle > Nutrient cycles > Carbon cycle
Distribution > Geographical distribution > Vertical distribution
Inorganic matter > Carbon > Inorganic carbon > Dissolved inorganic matter > Dissolved inorganic carbon
Microorganisms
Microorganisms > Bacteria
Motion > Water motion > Circulation > Water circulation > Ocean circulation > Gyres
Motion > Water motion > Vertical water movement > Upwelling
Nutrients (mineral)
Organic compounds > Carbohydrates > Glycosides > Pigments > Photosynthetic pigments > Chlorophylls
Quantitative analysis
Quantitative analysis
Seawater
Bacillariophyceae [WoRMS]; Bacillariophyceae [WoRMS]
Marine/Coastal |
| Author keywords |
N-2 fixation; diazotroph; nutrients; carbon sequestration; North Pacificgyre |
| Authors | | Top |
- Karl, D.M.
- Letelier, R.M.
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| Abstract |
The magnitude of fluxes in the carbon cycle of subtropical and tropical marine habitats is determined by the supply of inorganic nutrients. These habitats have low sea-surface concentrations of nitrate (NO3-) and chlorophyll (dubbed LNLC regions), sustain relatively low rates of organic matter production and export, and represent global ocean minima in carbon sequestration potential. The low NO3- resupply should select for nitrogen (N-2)-fixing bacteria, termed diazotrophs, provided all other growth-limiting nutrients are available. Several recent field efforts have been aimed at enhancing N-2 fixation in LNLC regions through mesoscale fertilization with iron and phosphorus (or both) and we hypothesize herein that controlled upwelling of nutrient-enriched deep water may also be effective. Based on a quantitative assessment of the vertical distribution of N-O(3)-, phosphate (PO43-) and dissolved inorganic carbon (DIC) at Station ALOHA (22 degrees 45' N, 158 degrees W), we hypothesize that the process of controlled upwelling of low NO3-:PO43- seawater may lead to enhanced N2 fixation, organic matter production and net carbon sequestration. Furthermore, based on a long-term (20 yr) data set from Station ALOHA, we predict that the upwelling of water from a depth of 300 to 350 m during summer months will trigger a 2-stage phytoplankton bloom. The first stage will be characterized by a NO3--supported Redfield ratio (e.g. C-106:N-16:P by atoms) diatom bloom. Following quantitative NO3- removal, the residual PO43- from the low N:P (<16:1) upwelled nutrient pulse will stimulate a N-2-fixing bacterial bloom, leading to net sequestration of carbon. However, any strategic benefit of controlled upwelling for enhancing the long-term carbon sequestration will depend on the spatial and temporal uncoupling of organic matter production and remineralization, which is ultimately controlled by the microbial response to these perturbations. |
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