Iron toxicity in Chlamydomonas in relation to P limitation

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The green flagellate algal species Chlamydomonas acidophila faces co-limiting conditions in a multi-stress environment. In this proposal, co-limiting conditions for inorganic P (Pi) and inorganic carbon (CO2) as well as survival in lakes with high iron concentrations (multi-stress) are the central topics.In the very acidic lakes, growth of C. acidophila is potentially limited by Pi and/or CO2. In ongoing laboratory experiments, a trade-off in the acquisition of either Pi or CO2 was revealed, that was more strongly related to the cellular P quota (Qp) than to the external nutrient concentration. This correlation enhanced our understanding of the dynamics of natural phytoplankton populations possibly co-limited for Pi and CO2. First data show a high tolerance for high iron concentrations on the growth and photosynthetic yield of C. acidophila, but also negative effects. For example, high extemal Fe concentrations resulted in a cellular Pi-limitation. Other results showed a negative correlation between enhanced cellular Fe accumulations and the chlorophyll content. In a 3rd year of the project GA401/12, I want to finalise the experimental work on a co-limitation, and study the physiological response (e.g. Fe accumulation and location, C, P and Fe cell quotas and photosynthesis) of C acidophila to different ambient P:Fe ratios with the aim to unravel mechanisms of iron tolerance and the impact of Fe accumulation on the ecophysiology of our model algal species.