Effect of Iron Stress, Light Stress, and Nitrogen Source on Physiological Aspects of Marine Red Tide Alga

Abstract

Effect of iron (Fe) stress, light stress, and nitrogen (N) source on physiological aspects of the marine red tide alga Heterosigma akashiwo was investigated in batch cultures. Cellular chlorophyll and carotenoid contents increased under low light stress and decreased under iron stress. A specific pigment was induced under light stress. Nitrate reductase and nitrite reductase activities of nitrate-grown cells decreased under iron and light stress, while those of ammonium-grown cells were negligible. The cell density and the growth rate decreased under Fe stress, and this decrease can be aggravated by light stress. Compared with ammonium-grown cells, nitrate-grown cells showed an increase in the cell density and the growth rate. Intracellular C:N ratios indicated that the Fe-stress effect on nitrate or ammonium did not specifically involve in the nitrate assimilatory pathway, and light stress would aggravate the Fe-stress effect.