Permalink : http://hdl.handle.net/2115/47537

KEYWORDS : Chattonella antiqua;Humic substance;Iron;Artificial medium;Culture experiment

　Humic subsatnces (HS) are major components of dissolved organic matter in aquatic systems and known to have a substantial influence on the trace metal speciation, and thus the bioavailability of trace elements. Trace metals, such as iron, frequently act as a crucial limiting factor for phytoplankton growth, and sometimes bloom developments in the sea.　The effects of HS on the growth of the harmful red tide phytoplankton, Chattonella antiqua were investigated by using of a chemically defined artificial medium. Humic acid (0.6, 6, 60 and 600 μg L-1) supplied with iron (541 μg L-1 of ferric chloride hexahydrate) had accelerative effects on the growth of C. antiqua. The growth yield was highest in the medium of 6 μg L-1 of humic acid, and 8 times larger than that in the control medium without humic acid. On the contrary, fulvic acid did not enhance the growth of C. antiqua. It is suggested that the composition and concentration of HS possibly affects the bloom developments of C. antiqua by controlling the iron availability. This is the first report of the effects of humic substances on the growth of C. antiqua, raising an insight into the growth physiology of this fish-killing species.