Accelerated uptake by phytoplankton of iron bound to humic acids

Chen, Min; Wang, Wen‐Xiong

doi:10.3354/ab00064

Cited by 45 publications

(25 citation statements)

References 66 publications

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“…3), which is consistent with previous research (Gorham et al 1998). DOC binds Fe and although opinions diverge on whether this complex is bioavailable (Maranger and Pullin 2003), there has been mounting evidence that organically complexed Fe is readily utilized by diatoms (Matsunaga et al 1998, Kuma et al 1999, Deein et al 2002, Chen and Wang 2008. The strongly positive relationship between DOC and DR observed in the present large-scale study provides compelling support of this notion, i.e., had the chelation of Fe by DOC led to Fe-limited conditions in streams, diatoms would have responded negatively to elevated concentrations of DOC.…”

Section: Discussionsupporting

confidence: 80%

A distinct latitudinal gradient of diatom diversity is linked to resource supply

Passy

2010

Ecology

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Abstract. For over 200 years, scientists have recognized the nearly ubiquitous poleward decline of species richness, but none of the theories explaining its occurrence has been widely accepted. In this continental study of U.S. running waters, I report an exception to this general pattern, i.e., a U-shaped latitudinal distribution of diatom richness (DR), equally high in subtropical and temperate regions. This gradient is linked unequivocally to corresponding trends in basin and stream properties with impact on resource supply. Specifically, DR distribution was related to wetland area, soil composition, and forest cover in the watershed, which affected iron, manganese, and macronutrient fluxes into streams. These results imply that the large-scale biodiversity patterns of freshwater protists, which are seasonal, highly dispersive, and sheltered by their environment from extreme temperature fluctuations, are resource driven in contrast to more advanced, perennial, and terrestrial organisms with biogeography strongly influenced by climate. The finding that wetlands, through iron export, control DR in streams has important environmental implications. It suggests that wetlands loss, already exceeding 52 million hectares in the conterminous United States alone, poses a threat not only to local biota, but also to biodiversity of major stream producers with potentially harmful consequences for the entire ecosystem.

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Section: Discussionsupporting

confidence: 80%

A distinct latitudinal gradient of diatom diversity is linked to resource supply

Passy

2010

Ecology

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“…In contrast, biologically produced exopolymeric substances (Hassler et al, 2011a;Hassler et al, in press), and terrestrial material such as humic and fulvic substances (Laglera et al, 2007;Laglera and van den Berg, 2009) are important compounds contributing to the pools of HS-like and iron binding organic ligands in the Southern Ocean (Chen and Wang, 2008;Laglera et al, 2007;Hassler et al, 2011a). The presence of these substances can stimulate phytoplankton growth by enhancing iron solubility and/or accelerating iron uptake (Chen and Wang, 2008;Kuma et al, 1999;Hassler et al, 2011a;Hassler et al, 2014). Even though the nature of HS-like material likely differs inshore from offshore stations, the contribution of HS-like compounds relative to Chl a was similarly high between offshore (22711 mg mg À 1 ) and inshore stations (15724 mg mg À 1 , Fig.…”

Section: Locationmentioning

confidence: 88%

Physiological characteristics of open ocean and coastal phytoplankton communities of Western Antarctic Peninsula and Drake Passage waters

Trimborn

Hoppe

Taylor

et al. 2015

Deep Sea Research Part I: Oceanographic Research Papers

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Photophysiological processes as well as uptake characteristics of iron and inorganic carbon were studied in inshore phytoplankton assemblages of the Western Antarctic Peninsula (WAP) and offshore assemblages of the Drake Passage. Chlorophyll a concentrations and primary productivity decreased from in- to offshore waters. The inverse relationship between low maximum quantum yields of photochemistry in PSII (Fv/Fm) and large sizes of functional absorption cross sections (σPSII) in offshore communities indicated iron-limitation. Congruently, the negative correlation between Fv/Fm values and iron uptake rates across our sampling locations suggest an overall better iron uptake capacity in iron-limited pelagic phytoplankton communities. Highest iron uptake capacities could be related to relative abundances of the haptophyte Phaeocystis antarctica. As chlorophyll a-specific concentrations of humic-like substances were similarly high in offshore and inshore stations, we suggest humic-like substances may play an important role in iron chemistry in both coastal and pelagic phytoplankton assemblages. Regarding inorganic carbon uptake kinetics, the measured maximum short-term uptake rates (Vmax(CO2)) and apparent half-saturation constants (K1/2(CO2)) did not differ between offshore and inshore phytoplankton. Moreover, Vmax(CO2) and K1/2(CO2) did not exhibit any CO2-dependent trend over the natural pCO2 range from 237 to 507 µatm. K1/2(CO2) strongly varied among the sampled phytoplankton communities, ranging between 3.5 and 35.3 µmol L−1 CO2. While in many of the sampled phytoplankton communities, the operation of carbon-concentrating mechanisms (CCMs) was indicated by low K1/2(CO2) values relative to ambient CO2 concentrations, some coastal sites exhibited higher values, suggesting down-regulated CCMs. Overall, our results demonstrate a complex interplay between photophysiological processes, iron and carbon uptake of phytoplankton communities of the WAP and the Drake Passage

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“…6). Fe' concentrations do play an important role, however, when interpreting uptake/growth inhibition by the addition of excess ligands such as EDTA or humic acid that have weaker binding constants than DFB (Shaked et al 2005, Chen & Wang 2008.…”

Section: Region 3 Competition By Excess Dfbthe Reductive Pathwaymentioning

confidence: 99%

“…Another facet of Fe-limitation in grow-out incubations is that the iron-replete cells from the Gulf may require sufficient acclimation time before they can access FeDFB. Iron-replete diatoms Thalassiosira oceanica and T .pseudonana (Maldonado & Price 2001, Chen & Wang 2008 have been shown to take up organically bound iron less readily than iron-starved cells. This has been put down to the activation of a high affinity uptake system under iron stress.…”

Section: Region 2 Titration Of Natural Fe By Dfb -Fedfb Bioavailabilitymentioning

confidence: 99%

“…DFB is also a very convenient Fe-ligand, characterized by a high affinity for Fe (buffering no Fe' when applied at equimolar ratios), fast binding (rapidly exchanges the natural Fe pools) and photo-inertness (no transient Fe') and can therefore address the uptake of organically bound iron exclusively. While several marine organisms, both prokaryotic and eukaryotic, have been shown to acquire DFB-bound iron (FeDFB; Allnutt & Bonner 1987a, Soria-Dengg & Horstmann 1995, Maldonado & Price 2001, Shaked et al 2005, Chen & Wang 2008, its application in representing naturally occurring organically bound iron has been complicated by the fact that DFB has been widely used to bind iron and induce iron limitation in different oceanic regions and culture based experiments (Wells et al 1994, Wells 1999, Eldridge et al 2004.…”

Section: Introductionmentioning

confidence: 99%

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Probing the bioavailability of organically bound iron: a case study in the Synechococcus-rich waters of the Gulf of Aqaba

Lis¹,

Shaked²

2009

Aquat. Microb. Ecol.

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The bioavailability of organically chelated and ambient iron to phytoplankton in the Gulf of Aqaba was examined in 2 sets of grow-out incubations amended with major nutrients and increasing concentrations of the model organic ligand desferrioxamine B (DFB). Short-term uptake of pre-complexed 55 FeDFB was then conducted with the DFB-incubated natural populations. Since incubation communities were dominated by Synechococcus spp., short-term FeDFB uptake experiments with Synechococcus WH8102 cultures complemented the field study. The role of extracellular reduction in FeDFB acquisition was studied in accordance with the Fe(II)s model (Shaked et al. 2005) by applying large excesses of DFB. Ambient iron was found adequate in meeting natural phytoplankton iron demands in incubations containing major nutrients. A gradually increasing iron-stress response was observed as DFB concentration increased and titrated out ambient iron. Nevertheless, both natural phytoplankton and Synechococcus WH8102 cultures were able to acquire DFB-bound iron. FeDFB uptake rates were inhibited by large excesses of DFB. This may indicate the operation of an extracellular reduction step in the acquisition of FeDFB by natural populations in the Gulf of Aqaba and Synechococcus WH8102.

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Accelerated uptake by phytoplankton of iron bound to humic acids

Cited by 45 publications

References 66 publications

A distinct latitudinal gradient of diatom diversity is linked to resource supply

A distinct latitudinal gradient of diatom diversity is linked to resource supply

Physiological characteristics of open ocean and coastal phytoplankton communities of Western Antarctic Peninsula and Drake Passage waters

Probing the bioavailability of organically bound iron: a case study in the Synechococcus-rich waters of the Gulf of Aqaba

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