Hobart

Seminar abstract

Friday 8 June 2007, 11.30 am
CSIRO Auditorium, Hobart

Christel Hassler
Post Doctoral Fellow
CSIRO

Use of cyanobacterial bioreporters to measure iron bioavailability and limitation in aquatic systems

Iron is an essential nutrient known to limit primary productivity in vast regions of the oceans such as the Southern Ocean. Given the important nutritive role of Fe for the phytoplankton and its effects in the global carbon cycle, much interest has been focused on understanding Fe uptake and limitation to phytoplankton.

Iron bioavailability to phytoplankton is a challenge due to the low solubility of Fe(III), an active redox cycle, slow reaction kinetics, important associations of Fe(III) with poorly defined organic ligands that can be photo-degraded under natural conditions (releasing Fe(III) as well as active oxygen species), and highly specific biological uptake strategies. Given the spatial variability of natural phytoplankton communities, iron bioaccumulation experiments done at different time or location cannot be quantitatively compared.

The recent development of a Fe-dependent cyanobacterial bioreporter(s) presents the unique advantage of providing a sensitive and rapid (12 h) measurement of Fe bioavailability at the scale of living organisms. Previous trials of these bioreporters in the Laurentian Great Lakes, Southern Ocean and Baltic Sea gave promising results in respect to the use of bioreporters to highlight iron limitation in natural waters. Nonetheless, bioreporters are whole living micro-organisms for which factors controlling iron bioavailability, as well as iron intracellular mechanisms, are still poorly understood. Deep characterization is therefore needed in order to accurately interpret the measure given by bioreporters: (1) assessment of the influence of global biophysicochemical parameters (e.g. growth condition, levels of macronutrients, light, temperature, biomass used), (2) assessment of the influence of iron chemistry on the response of the bioreporter. Such characterization is required to define robustness, limitation and optimal use of the bioreporter. Furthermore, the knowledge of the specific bioavailability of organically bound iron is critical in using the most relevant chemical form of iron to relate the response of the bioreporter.

These points will be discussed in light of the characterization performed for both fresh- and sea-water bioreporters. In addition, the optimal procedure for using bioreporters to gain quantitative information about iron bioavailability will be discussed. Finally some actual caveats and limitations will be presented, along with the prospect of increasing our knowledge of in-situ iron bioavailability, especially in the Southern Ocean.

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Location:
CSIRO = Marine Laboratories Auditorium, Castray Esplanade, Hobart

For further information, or to schedule a seminar, contact:
To schedule a seminar, contact:
Karen Wild-Allen, (Oceanographic seminars) CSIRO Marine and Atmospheric Research (03) 6232 5010
Thomas Kunz, (Biological seminars) CSIRO Marine and Atmospheric Research
(03) 6232 5076
Annabel Ozimec (seminar administrator) CSIRO Marine and Atmospheric Research (03) 6232 5462
Sandra Zicus, Antarctic Climate and Ecosystems CRC (03) 6226 7888
Margaret Hazelwood, Institute of Antarctic and Southern Ocean Studies (IASOS) University of Tasmania (03) 6226 2971

Last updated 1/06/07