Effect of nitrogen source and acclimatization on specific growth rates of microalgae determined by a high-throughput in vivo microplate autofluorescence method

Specific growth rates (SGR) of freshwater algaespecies (Chlorella vulgaris, Auxenochlorella protothecoides,and Chlorella sorokiniana) and the marine speciesNannochloropsis oculata on various nitrogen sources (ammoniumcarbonate, ammonium chloride, sodium nitrate, andurea) could be determined by in vivo chlorophyll-a autofluorescence.These preferences could be determined before large pH changes occurred in the media, with no significant difference(P>0.05) between buffered and non-buffered media. In all algal species, acclimatization was observed with no significant difference (P>0.05) between SGRs of the second and third cultivations. ANOVA of SGRs in the acclimatized second and third cultivations revealed preferences for nitrogen sources among most of the algae; C. vulgaris preferred sodiumnitrate over other nitrogen sources, A. protothecoides adapted to urea after no growth in the first cultivation, and the SGRs of N. oculata showed an aversion for sodium nitrateover other nitrogen sources (P<0.05).