Abstract: The formation of resting spores plays an important role in redtide causive alga of population succession, conservation, distribution and dispersal. The effects of nitrogen (N) and silicon (Si) limitation on the resting spore formation of Chaetoceros compressus were studied. Resting spores of C. compressus formed earlier and developed in higher speed under low N concentration (50 μmol•L-1) than that under high N concentration (100 μmol•L^-1), while no resting spores were observed with the 500 μmol•L^-1 N concentration. N-depletion is one of the indispensable conditions for resting spore formation of diatoms. Resting spores can be formed in C. compressus species when the N concentrations in the medium reduced to be lower than 10μmol•L^-1. And abundant Si is needed for the formations of resting spores which are induced by N- depletion. No resting spores of C. compressus formed when Si concentrations in the medium was lower than 23μmol•L-1, even if the N concentrations are low enough. These results showed that the formation of diatom resting spores was related not only with N concentration, but also with Si concentration.

Key words: Chaetoceros compressus, nitrogen, resting spores, silicon