Iron in the Sargasso Sea (Bermuda Atlantic Time‐series Study region) during summer: Eolian imprint, spatiotemporal variability, and ecological implications

Sedwick, Peter N.; Church, Thomas M.; Bowie, Andrew R.; Marsay, Chris M.; Ussher, Simon J.; Achilles, Katherine M.; Lethaby, Paul; Johnson, Rodney J.; Sarin, M.M.; McGillicuddy, Dennis J.

doi:10.1029/2004gb002445

Cited by 141 publications

(201 citation statements)

References 75 publications

(113 reference statements)

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“…Consistent with our observations, Sedwick et al (2005) reported higher levels of iron in Sargasso Sea summer surface waters compared to the spring, presumably from eolian input from the Saharan desert. The periplasmic iron-binding transporter was one of only two periplasmic substratebinding proteins not observed in the metaproteomic data, the other being a protein of uncertain substrate specificity.…”

Section: Sargasso Sea Metaproteomicssupporting

confidence: 91%

Transport functions dominate the SAR11 metaproteome at low-nutrient extremes in the Sargasso Sea

et al. 2008

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The northwestern Sargasso Sea undergoes annual cycles of productivity with increased production in spring corresponding to periods of upwelling, and oligotrophy in summer and autumn, when the water column becomes highly stratified. The biological productivity of this region is reduced during stratified periods as a result of low concentrations of phosphorus and nitrogen in the euphotic zone. To better understand the mechanisms of microbial survival in this oligotrophic environment, we used capillary liquid chromatography (LC)-tandem mass spectrometry to detect microbial proteins in surface samples collected in September 2005. A total of 2215 peptides that mapped to 236 SAR11 proteins, 1911 peptides that mapped to 402 Prochlorococcus proteins and 2407 peptides that mapped to 404 Synechococcus proteins were detected. Mass spectra from SAR11 periplasmic substrate-binding proteins accounted for a disproportionately large fraction of the peptides detected, consistent with observations that these extremely small cells devote a large proportion of their volume to periplasm. Abundances were highest for periplasmic substrate-binding proteins for phosphate, amino acids, phosphonate, sugars and spermidine. Proteins implicated in the prevention of oxidative damage and protein refolding were also abundant. Our findings support the view that competition for multiple nutrients in oligotrophic systems is extreme, but nutrient flux is sufficient to sustain microbial community activity.

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Section: Sargasso Sea Metaproteomicssupporting

confidence: 91%

Transport functions dominate the SAR11 metaproteome at low-nutrient extremes in the Sargasso Sea

et al. 2008

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“…There is evidence based on the OMI Aerosol Index and MODIS observations that forest fires in Tasmania (Australia) may have led to a greater proportion of soluble Fe in aerosols sampled on the northeastern leg Guieu et al, 2005). It is possible that soluble iron deposition fluxes measured on the ship did not reflect Fe fluxes that fueled the observed NCP, and also that the fraction of bioavailable Fe was greater than that determined through the instantaneous leaching approach (Baker and Croot, 2010;Sedwick et al, 2005;Buck et al, 2006). A greater proportion of bioavailable iron, as parameterized in many atmospheric deposition models (e.g.…”

Section: Ncp Vs Aeolian Fe Deposition Estimatesmentioning

confidence: 99%

The influence of iron and light on net community production in the Subantarctic and Polar Frontal Zones

et al. 2011

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The roles of iron and light in controlling biomass and primary productivity are clearly established in the Southern Ocean. However, their influence on net community production (NCP) and carbon export remains to be quantified. To improve our understanding of NCP and carbon export production in the Subantarctic Zone (SAZ) and the northern reaches of the Polar Frontal Zone (PFZ), we conducted continuous onboard determinations of NCP as part of the Sub-Antarctic Sensitivity to Environmental Change (SAZ-Sense) study, which occurred in January–February 2007. Biological O2 supersaturation was derived from measuring O2/Ar ratios by equilibrator inlet mass spectrometry. Based on these continuous measurements, NCP during the austral summer 2007 in the Australian SAZ was approximately 43 mmol O2 m−2 d−1. NCP showed significant spatial variability, with larger values near the Subtropical front, and a general southward decrease. For shallower mixed layers (<50 m), dissolved Fe concentrations and Fe sufficiency, estimated from variable fluorescence, correlated strongly with NCP. The strong correlation between NCP and dissolved Fe may be difficult to interpret because of the correlation of dissolved Fe to MLD and because the concentration of iron may not be a good indicator of its availability. At stations with deeper mixed layers, NCP was consistently low, regardless of iron sufficiency, consistent with light availability also being an important control of NCP. Our new observations provide independent evidence for the critical roles of iron and light in mediating carbon export from the Southern Ocean mixed layer

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“…Light limitation in the lower euphotic zone would be expected to accelerate this process (Lomas and Lipschultz 2006). Indeed, work by Sedwick et al (2005) at several locations in the Sargasso Sea revealed that the lowest Fe concentration consistently occurred at or around the depth of PNM. While several studies have shown that some phytoplankton can substitute flavodoxin, which does not require Fe, for ferrodoxin under Fe-limiting conditions (La Roche et al 1995), the work of Milligan and Harrison (2000) has indicated that despite making flavodoxin, T. pseudonana also released nitrite under similar conditions.…”

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confidence: 99%

The speciation of copper across active gradients in nitrogen‐cycle processes in the eastern tropical South Pacific

Jacquot

Kondo

Knapp

et al. 2013

Limnology & Oceanography

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Copper (Cu) complexation and distribution were characterized using competitive ligand exchange adsorptive cathodic stripping voltammetry and isotope dilution inductively coupled plasma mass spectrometry along two transects (20uS and 10uS) in the eastern tropical South Pacific. In the southern and westernmost stations, Cu showed upper water column depletion to values as low as , 0.26 nmol L 21 , the lowest concentrations ever reported. However, Cu levels were much higher within the secondary nitrite maxima of the oxygen minimum zone (OMZ) in the northern (10uS) transect. The enrichment of Cu in the reducing conditions of the OMZ has not been reported before and probably reflects remineralization and offshore transport from the shelf. Free [Cu 2+ ] was typically low throughout the water column, ranging from about 3.15 3 10 215 mol L 21 to 1.34 3 10 213 mol L 21 , and depth profiles exhibited similar features to those for dissolved Cu, though they showed more variability near the surface. Offshore and beyond the influence of the OMZ, the lowest dissolved and free [Cu 2+ ] was within the primary nitrite maxima (PNM), where ammonia oxidation and nitrate reduction rates are important. This finding is of interest because the two competing explanations for the PNM-iron limitation of diatoms and high rates of ammonia oxidation relative to nitrite oxidation-have high Cu requirements. The low concentrations of free Cu 2+ measured here could impose significant constraints on the rates of these processes.

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Iron in the Sargasso Sea (Bermuda Atlantic Time‐series Study region) during summer: Eolian imprint, spatiotemporal variability, and ecological implications

Cited by 141 publications

References 75 publications

Transport functions dominate the SAR11 metaproteome at low-nutrient extremes in the Sargasso Sea

Transport functions dominate the SAR11 metaproteome at low-nutrient extremes in the Sargasso Sea

The influence of iron and light on net community production in the Subantarctic and Polar Frontal Zones

The speciation of copper across active gradients in nitrogen‐cycle processes in the eastern tropical South Pacific

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