Iron associated with exopolymeric substances is highly bioavailable to oceanic phytoplankton

Hassler, CS; Norman, L; Mancuso Nichols, CA; Clementson, LA; Robinson, C; Schoemann, V; Watson, RJ; Doblin, MA

Iron associated with exopolymeric substances is highly bioavailable to oceanic phytoplankton

Hassler, CS Norman, L Mancuso Nichols, CA Clementson, LA Robinson, C

Schoemann, V Watson, RJ Doblin, MA

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Publication Type:: Journal Article
Citation:: Marine Chemistry, 2015, 173 pp. 136 - 147
Issue Date:: 2015-07-01

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Field	Value	Language
dc.contributor.author	Hassler, CS	en_US
dc.contributor.author	Norman, L	en_US
dc.contributor.author	Mancuso Nichols, CA	en_US
dc.contributor.author	Clementson, LA	en_US
dc.contributor.author	Robinson, C https://orcid.org/0000-0001-8519-5641	en_US
dc.contributor.author	Schoemann, V	en_US
dc.contributor.author	Watson, RJ	en_US
dc.contributor.author	Doblin, MA https://orcid.org/0000-0001-8750-3433	en_US
dc.date.issued	2015-07-01	en_US
dc.identifier.citation	Marine Chemistry, 2015, 173 pp. 136 - 147	en_US
dc.identifier.issn	0304-4203	en_US
dc.identifier.uri	http://hdl.handle.net/10453/35885
dc.description.abstract	© 2014 Elsevier B.V. Growth limitation of marine algae due to lack of iron occurs in up to 40% of the global ocean. Despite important advances on the impact of organic compounds on iron biogeochemistry, their roles in controlling iron availability to prokaryotic and eukaryotic phytoplankton remain unclear. Whether algal and bacterial exopolymeric substances (EPS) include organic ligands which may help iron-limited phytoplankton growth remains an unknown. If so, then EPS could relieve phytoplankton iron limitation with implications for the biological carbon pump and hence the regulation of atmospheric CO<inf>2</inf>. Here we compared the biological impact of algal, bacterial and in situ EPS with model compounds, a siderophore and two saccharides on biological parameters including, iron bioavailability, phytoplankton growth, photo-physiology and community structure. Laboratory and field experiments demonstrated that EPS produced by marine microorganisms are efficient in sustaining biological iron uptake as well as algal growth, and can affect natural phytoplankton community structure. Our data suggest that natural phytoplankton growth enhancement in the presence of EPS was not solely due to highly bioavailable iron forms, but also because EPS contains other micronutrients. Stronger ligands were detected following iron-siderophore enrichments (log K<inf>Fe'L</inf>=12.0) and weaker ligands were measured in the presence of EPS (log K<inf>Fe'L</inf>=10.4-11.0). The trend of the conditional stability constants of organic ligands did not seem to be affected as a result of biological activity and photo-chemistry during our four day incubations. The shift in the phytoplankton community observed during our field experiments was not uniformly observed between different sites rendering it difficult to extrapolate which functional group(s) would benefit the most from iron bound to EPS.	en_US
dc.relation	http://purl.org/au-research/grants/arc/DP1092892
dc.relation.ispartof	Marine Chemistry	en_US
dc.relation.isbasedon	10.1016/j.marchem.2014.10.002	en_US
dc.subject.classification	Oceanography	en_US
dc.title	Iron associated with exopolymeric substances is highly bioavailable to oceanic phytoplankton	en_US
dc.type	Journal Article
utslib.citation.volume	173	en_US
utslib.for	0399 Other Chemical Sciences	en_US
utslib.for	0402 Geochemistry	en_US
utslib.for	0405 Oceanography	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
pubs.organisational-group	/University of Technology Sydney/Strength - C3 - Climate Change Cluster
utslib.copyright.status	closed_access
pubs.publication-status	Published	en_US
pubs.volume	173	en_US

Abstract:

© 2014 Elsevier B.V. Growth limitation of marine algae due to lack of iron occurs in up to 40% of the global ocean. Despite important advances on the impact of organic compounds on iron biogeochemistry, their roles in controlling iron availability to prokaryotic and eukaryotic phytoplankton remain unclear. Whether algal and bacterial exopolymeric substances (EPS) include organic ligands which may help iron-limited phytoplankton growth remains an unknown. If so, then EPS could relieve phytoplankton iron limitation with implications for the biological carbon pump and hence the regulation of atmospheric CO2. Here we compared the biological impact of algal, bacterial and in situ EPS with model compounds, a siderophore and two saccharides on biological parameters including, iron bioavailability, phytoplankton growth, photo-physiology and community structure. Laboratory and field experiments demonstrated that EPS produced by marine microorganisms are efficient in sustaining biological iron uptake as well as algal growth, and can affect natural phytoplankton community structure. Our data suggest that natural phytoplankton growth enhancement in the presence of EPS was not solely due to highly bioavailable iron forms, but also because EPS contains other micronutrients. Stronger ligands were detected following iron-siderophore enrichments (log KFe'L=12.0) and weaker ligands were measured in the presence of EPS (log KFe'L=10.4-11.0). The trend of the conditional stability constants of organic ligands did not seem to be affected as a result of biological activity and photo-chemistry during our four day incubations. The shift in the phytoplankton community observed during our field experiments was not uniformly observed between different sites rendering it difficult to extrapolate which functional group(s) would benefit the most from iron bound to EPS.

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