Saccharides enhance iron bioavailability to Southern Ocean phytoplankton
Iron limits primary productivity in vast regions of the ocean. Giventhat marine phytoplankton contribute up to 40% of global biologicalcarbon fixation, it is important to understand what parameterscontrol the availability of iron (iron bioavailability) to theseorganisms. Most studies on iron bioavai...
| Published in: | Proceedings of the National Academy of Sciences |
|---|---|
| Main Authors: | , , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Natl Acad Sciences
2011
|
| Subjects: | |
| Online Access: | https://doi.org/10.1073/pnas.1010963108 http://www.ncbi.nlm.nih.gov/pubmed/21169217 http://ecite.utas.edu.au/95613 |
| Summary: | Iron limits primary productivity in vast regions of the ocean. Giventhat marine phytoplankton contribute up to 40% of global biologicalcarbon fixation, it is important to understand what parameterscontrol the availability of iron (iron bioavailability) to theseorganisms. Most studies on iron bioavailability have focused on therole of siderophores; however, eukaryotic phytoplankton do notproduce or release siderophores. Here, we report on the pivotalrole of saccharideswhich may act like an organic ligandin enhancingiron bioavailability to a Southern Ocean cultured diatom,a prymnesiophyte, as well as to natural populations of eukaryoticphytoplankton. Addition of a monosaccharide (>2 nM of glucuronicacid, GLU) to natural planktonic assemblages from both the polarfront and subantarctic zones resulted in an increase in iron bioavailabilityfor eukaryotic phytoplankton, relative to bacterioplankton.The enhanced iron bioavailability observed for several groupsof eukaryotic phytoplankton (i.e., cultured and natural populations)using three saccharides, suggests it is a common phenomenon. Increasediron bioavailability resulted from the combination of saccharidesforming highly bioavailable organic associations with ironand increasing iron solubility, mainly as colloidal iron. As saccharidesare ubiquitous, present at nanomolar to micromolar concentrations,and produced by biota in surface waters, they also satisfythe prerequisites to be important constituents of the poorly definedligand soup, known to weakly bind iron. Our findings pointto an additional type of organic ligand, controlling iron bioavailabilityto eukaryotic phytoplanktona key unknown in iron biogeochemistry. |
|---|