Impacts of atmospheric nutrient deposition on marine productivity: Roles of nitrogen, phosphorus, and iron

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Date

2011-06-23

Author

Okin, Gregory S.
Baker, Alex R.
Tegen, Ina
Mahowald, Natalie M.
Dentener, Frank J.
Duce, Robert A.
Galloway, James N.
Hunter, Keith
Kanakidou, Maria
Kubilay, Nilgun
Prospero, Joseph M.
Sarin, Manmohan
Surapipith, Vanisa
Uematsu, Mitsuo
Zhu, Tong

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Nutrients are supplied to the mixed layer of the open ocean by either atmospheric deposition or mixing from deeper waters, and these nutrients drive nitrogen and carbon fixation. To evaluate the importance of atmospheric deposition, we estimate marine nitrogen and carbon fixation from present-day simulations of atmospheric deposition of nitrogen, phosphorus, and iron. These are compared with observed rates of marine nitrogen and carbon fixation. We find that Fe deposition is more important than P deposition in supporting N fixation. Estimated rates of atmospherically supported carbon fixation are considerably lower than rates of marine carbon fixation derived from remote sensing, indicating the subsidiary role atmospheric deposition plays in total C uptake by the oceans. Nonetheless, in high-nutrient, low-chlorophyll areas, the contribution of atmospheric deposition of Fe to the surface ocean could account for about 50% of C fixation. In marine areas typically thought to be N limited, potential C fixation supported by atmospheric deposition of N is only similar to 1%-2% of observed rates. Although these systems are N-limited, the amount of N supplied from below appears to be much larger than that deposited from above. Atmospheric deposition of Fe has the potential to augment atmospherically supported rates of C fixation in N-limited areas. In these areas, atmospheric Fe relieves the Fe limitation of diazotrophic organisms, thus contributing to the rate of N fixation. The most important uncertainties in understanding the relative importance of different atmospheric nutrients are poorly understood speciation and solubility of Fe as well as the N: Fe ratio of diazotrophic organisms.

Subject Keywords

Atmospheric Science, Global and Planetary Change, General Environmental Science, Environmental Chemistry

URI

https://hdl.handle.net/11511/68604

Journal

GLOBAL BIOGEOCHEMICAL CYCLES

DOI

https://doi.org/10.1029/2010gb003858

Collections

Graduate School of Marine Sciences, Article

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Citation Formats

G. S. Okin et al., “Impacts of atmospheric nutrient deposition on marine productivity: Roles of nitrogen, phosphorus, and iron,” GLOBAL BIOGEOCHEMICAL CYCLES, pp. 0–0, 2011, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/68604.