Table 3.
The influence of siderophore and saccharide release on iron chemistry and availability in aquatic environments.
| Siderophores | Saccharides (EPS, TEP) |
|---|---|
| RESULTING IRON SPECIES | |
| Strongly bound organic dFe & cFe Fe(III)L | Organically bound/adsorbed dFe, cFe, & pFe |
| IRON SPECIES ACTED UPON | |
| dFe, cFe, & pFe | dFe & cFe |
| IMPACT | |
| • Maintain Fe in solution • Fe proximity to cell (amphiphilic) • Particulate Fe dissolution |
• Maintain Fe in solution or promote its aggregation and export from photic zone • Fe proximity to cell |
| SUBSEQUENT TRANSFORMATIONS | |
| Photochemical reduction | • Photochemical reduction • Ligand exchange • Adsorption/desorption of dFe |
| ORGANISMS AT PLAY | |
| Heterotrophic bacteria, fresh water phytoplankton | Phytoplankton, Bacteria, Viruses, Zooplankton |
| BIOAVAILABILITY | |
| Varies between complexes and organisms but probably lower compared to Fe′ | As high as Fe′ for all studied organisms |
| REFERENCE | |
| a–f | g–m |
dFe, dissolved iron; cFe, colloidal iron; pFe, particulate Fe.
References: a. Sandy and Butler (2009), b. Vraspir and Butler (2009), c. Holmén and Casey (1996), d. Martinez et al. (2000), e. Kraemer et al. (2005), f. Barbeau et al. (2003), g. Hassler et al. (2011a), h. Hassler and Schoemann (2009), i. Steigenberger et al. (2010), j. Passow (2002), k. Strmecki et al. (2010), l. Berman-Frank et al. (2007), m. Decho (1990).