Iron nutrition of Trichodesmium

Rueter, John G.; Hutchins, David A.; Smith, Randall W.; Unsworth, Nancy L.

doi:10.1007/978-94-015-7977-3_19

Cited by 102 publications

(85 citation statements)

References 32 publications

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“…However, iron is likely to regulate the phytoplankton growth rate and biomass in the equatorial region of the Pacific (Landry et al, 1997) and may play an important role in regulating diazotrophic growth. N 2 fixation is an ironintensive metabolic process compared to the assimilation of fixed forms of nitrogen, since nitrogenase, the enzyme for nitrogen fixation, has a high iron content (Rueter et al, 1990(Rueter et al, , 1992Paerl et al, 1994). Other issues to be explored in the future are the vertical migration of Trichodesmium colonies, which allows an incorporation of inorganic phosphorus from greater depths (Karl et al, 1992;Letelier and Karl, 1998) and the utilization of dissolved organic phosphorus (Yentsch et al, 1972).…”

Section: Discussionmentioning

confidence: 99%

A deterministic model for N2 fixation at stn. ALOHA in the subtropical North Pacific Ocean

Fennel

Spitz

Letelier

et al. 2001

Deep Sea Research Part II: Topical Studies in Oceanography

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Marine N 2 fixation by diazotrophic microorganisms is a key process in biogeochemical cycling and yields an important input of new nitrogen into the tropical and subtropical surface ocean. However, it is only poorly accounted for in current numerical models. We present a simple biological model that explicitly includes N 2 fixation by diazotrophic phytoplankton. The model employs a mechanistic parameterization of N 2 fixation based on physiological responses of Trichodesmium to physical conditions of the environment. The model is conceived to allow shifts in nitrogen versus phosphorus control of the plankton community by resolving the biogeochemical cycles of both elements. Typical N : P ratios were assigned to the different functional groups to capture variations in the N : P stoichiometries of inorganic and organic matter pools. The biological model was coupled to a 1D physical model of the upper ocean. A simulation was performed at stn. ALOHA (22145 0 N, 1581W) in the subtropical North Pacific Ocean, where intense blooms of Trichodesmium occurred during the last decade. The model captures essential features of the biological system including the vertical structure and seasonal course of chlorophyll, the seasonal cycle and interannual differences in diazotrophic biomass, the mean vertical particle flux, and an oscillation in the relative importance of nitrogen versus phosphorus. We regard this model as a step towards a mechanistic tool to assess the magnitude of marine N 2 fixation and to explore hypotheses on its effect on carbon sequestration from the atmosphere. r

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Section: Discussionmentioning

confidence: 99%

A deterministic model for N2 fixation at stn. ALOHA in the subtropical North Pacific Ocean

Fennel

Spitz

Letelier

et al. 2001

Deep Sea Research Part II: Topical Studies in Oceanography

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“…We assume that the diazotrophs have adapted to relatively efficient iron uptake due to their larger iron demands. In addition, Trichodesmium colonies may be able to extract additional iron from dust particles (Reuter et al, 1992), a process not accounted for in our model.…”

Section: Ecosystem Modelmentioning

confidence: 99%

“…It has been argued that iron requirements for diazotrophs are much higher than for other phytoplankton due to the iron requirements of N fixation (Raven, 1988;Reuter et al, 1992). Kustka et al (2002) recently estimated that the iron requirement for Trichodesmium is B8 times that of eukaryotic phytoplankton based on theoretical calculations in conjunction with field measurements.…”

Section: Ecosystem Modelmentioning

confidence: 99%

“…This translates to a broad range of Fe/C ratios between 28 and 438 mmol/mol. Dust particles stuck to colonies as described by Reuter et al (1992) could have resulted in an overestimation of iron content in some samples. There was no significant correlation between iron content and nitrogen fixation rates (Orcutt et al, 2001), implying that the Trichodesmium colonies were generally iron-replete even at the wintertime Fe/C ratios of B47 mmol/mol.…”

Section: Ecosystem Modelmentioning

confidence: 99%

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An intermediate complexity marine ecosystem model for the global domain

Moore

Doney

Kleypas

et al. 2001

Deep Sea Research Part II: Topical Studies in Oceanography

486

536

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A new marine ecosystem model designed for the global domain is presented, and model output is compared with field data from nine different locations. Field data were collected as part of the international Joint Global Ocean Flux Study (JGOFS) program, and from historical time series stations. The field data include a wide variety of marine ecosystem types, including nitrogen-and iron-limited systems, and different physical environments from high latitudes to the mid-ocean gyres. Model output is generally in good agreement with field data from these diverse ecosystems. These results imply that the ecosystem model presented here can be reliably applied over the global domain.The model includes multiple potentially limiting nutrients that regulate phytoplankton growth rates. There are three phytoplankton classes, diatoms, diazotrophs, and a generic small phytoplankton class. Growth rates can be limited by available nitrogen, phosphorus, iron, and/or light levels. The diatoms can also be limited by silicon. The diazotrophs are capable of nitrogen fixation of N 2 gas and cannot be nitrogen-limited. Calcification by phytoplankton is parameterized as a variable fraction of primary production by the small phytoplankton group. There is one zooplankton class that grazes the three phytoplankton groups and a large detrital pool. The large detrital pool sinks out of the mixed layer, while a smaller detrital pool, representing dissolved organic matter and very small particulates, does not sink. Remineralization of the detrital pools is parameterized with a temperature-dependent function. We explicitly model the dissolved iron cycle in marine surface waters including inputs of iron from subsurface sources and from atmospheric dust deposition. r

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“…Rueter (1982) and Rueter et al (1992) argued that iron (Fe) is a primary factor limiting N 2 -fixation due to the high Fe requirement of the nitrogenase enzyme. This idea is supported by the early experimental work of Paerl et al (1994) and the general global correspondence between regions of high iron/dust deposition and high N 2 -fixation, e.g., N 2 -fixation rates are generally higher in the Atlantic than in the Pacific ; but see also Deutsch et al, 2006).…”

Section: Limitations On N 2 -Fixationmentioning

confidence: 99%

Modeling the impact of iron and phosphorus limitations on nitrogen fixation in the Atlantic Ocean

Coles

Hood

2007

Biogeosciences

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Abstract. The overarching goal of this study is to simulate subsurface N* (sensu, Gruber and Sarmiento, 1997; GS97) anomaly patterns in the North Atlantic Ocean and determine the basin wide rates of N 2 -fixation that are required to do so. We present results from a new Atlantic implementation of a coupled physical-biogeochemical model that includes an explicit, dynamic representation of N 2 -fixation with light, nitrogen, phosphorus and iron limitations, and variable stoichiometric ratios. The model is able to reproduce nitrogen, phosphorus and iron concentration variability to first order. The latter is achieved by incorporating iron deposition directly into the model's detrital iron compartment which allows the model to reproduce sharp near surface gradients in dissolved iron concentration off the west coast of Africa and deep dissolved iron concentrations that have been observed in recent observational studies. The model can reproduce the large scale N* anomaly patterns but requires relatively high rates of surface nitrogen fixation to do so (1.8×10 12 moles N yr −1 from 10 • N-30 • N, 3.4×10 12 moles N yr −1 from 25 • S-65 • N). In the model the surface nitrogen fixation rate patterns are not co-located with subsurface gradients in N*. Rather, the fixed nitrogen is advected away from its source prior to generating a subsurface N* anomaly. Changes in the phosphorus remineralization rate (relative to nitrogen) linearly determine the surface nitrogen fixation rate because they change the degree of phosphorus limitation, which is the dominant limitation in the Atlantic in the model. Phosphorus remineralization rate must be increased by about a factor of 2 (relative to nitrogen) in order to generate subsurface N* anomalies that are comparable to the observations. We conclude that N 2 -fixation rate estimates for the Atlantic (and globally) may need to be revised upward, which will help resolve imbalances in the Correspondence to: V. J. Coles

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Iron nutrition of Trichodesmium

Cited by 102 publications

References 32 publications

A deterministic model for N2 fixation at stn. ALOHA in the subtropical North Pacific Ocean

A deterministic model for N2 fixation at stn. ALOHA in the subtropical North Pacific Ocean

An intermediate complexity marine ecosystem model for the global domain

Modeling the impact of iron and phosphorus limitations on nitrogen fixation in the Atlantic Ocean

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