The extreme environment of the Great Salt Plains (GSP) results in low algal biomass, such that natural selection is likely driven by survival of multiple abiotic stresses rather than rapid growth and biotic interactions. The objective of this study was to determine the effect of combined salinity stress and iron limitation on growth and photosynthesis in the green alga, Picochlorum oklahomensis isolated from the GSP habitat. Algal cells were grown in batch cultures under iron sufficiency or iron limitation at salinities of 10, 50 and 100 ppt in artificial seawater (AS 100) medium. Cells were physiologically characterized by growth rates, cell density, photosynthetic light-response curves (oxygen evolution), pigment composition and the chlorophyll fluorescence parameters Fv/Fm, ФPSII, qP and NPQ. P. oklahomensis cultured in no added Fe exhibit smaller inhibition by 100 ppt salinity relative to 10 ppt. Thus, high salinity appears to be reduced under low nutrient conditions. Fe stress resulted in qualitative differences in physiological response. The interaction between salinity and low iron is consistent with a general stress response that concurrently protects against several abiotic stress factors.
Key words: Iron limitation, salinity stress, Picochlorum sp.
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