Influence of Iodine and Bromine on Growth of Some Red Algae in Axenic Culture

Some red algae in axenic culture have been cultivated with different additions of iodine and bromine. Polysiphonia urceolata appeared to have an absolute demand for iodine. Additions could be made either as organically bound iodine or as inorganic iodine. A linear correlation between amount of added iodide and growth was found for iodide concentrations from 1 μmol up to at least 8 μmμmumol per 1. Nemalion proved to be indifferent to iodide additions, while Goniotrichum elegans was inhibited by concentrations higher than 0.4 μumol per 1, which corresponds to that of natural seawater. High additions of iodine generally inhibited growth of nonaxenic algae. Acrochaetium made an exception, being stimulated by 4 μumol per I. Bromine in the same concentration as that of seawater, viz. 814.3 μmol pa 1 inhibited growth of most species, but amounts smaller than 50 μumol had in some experiments a slightly increasing effect. Bromine seems, however, not to play an essential part in the metabolism of Polysiphonia urceolata.