Iron availability limits the ocean nitrogen inventory stabilizing feedbacks between marine denitrification and nitrogen fixation

By J. K. Moore, S. Doney. 2007

206 citations recorded by the source corpus.

Recent upward revisions in key sink/source terms for fixed nitrogen (N) in the oceans imply a short residence time and strong negative feedbacks involving denitrification and N fixation to prevent large swings in the ocean N inventory over timescales of a few centuries. We tested the strength of these feedbacks in a global biogeochemical elemental cycling (BEC) ocean model that includes water column denitrification and an explicit N fixing phytoplankton group. In the northern Indian Ocean and over longer timescales in the tropical Atlantic, we find strong stabilizing feedbacks that minimize changes in marine N inventory over timescales of ∼30–200 years. In these regions high atmospheric dust/iron inputs lead to phosphorus limitation of diazotrophs, and thus a tight link between N fixation and surface water N/P ratios. Maintenance of the oxygen minimum zones in these basins depends on N fixation driven export. The stabilizing feedbacks in other regions are significant but weaker owing to iron limitation of the diazotrophs. Thus Fe limitation appears to restrict the ability of N fixation to compensate for changes in denitrification in the current climate, perhaps leading the oceans to lose fixed N. We suggest that iron is the ultimate limiting nutrient leading to nitrogen being the proximate limiting nutrient over wide regions today. Iron stress was at least partially alleviated during more dusty, glacial times, leading to a higher marine N inventory, increased export production, and perhaps widespread phosphorus limitation of the phytoplankton community. The increased efficiency of the biological pump would have contributed to the glacial drawdown in atmospheric CO2.

Subfields: Ecology, Oceanography

View Paper: https://www.semanticscholar.org/paper/dd0a4dfab3d6e5524d2561a812b49641dc520efd

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Citations in the corpus

Interconnection of nitrogen fixers and iron in the Pacific Ocean: Theory and numerical simulations (2012, methodology): “The modulation of global nitrogen fixation by variations in the aeolian supply of iron has been illustrated in sensitivity studies using numerical models [Moore and Doney, 2007; Moore et al., 2006; Krishnamurthy et al., 2009; Monteiro et al., 2011].”
Distribution of diverse nitrogen fixers in the global ocean (2010, background): “…models parameterize their diazotrophic functional types to only grow in warm waters [i.e.,Moore et al., 2004, 2006; Breitbarth et al., 2007; Moore and Doney, 2007] or stratification conditions [Hood et al., 2004], here this feature is an emergent result of the “self‐assembling” model…”