Effect of EDTA on Growth of the Marine Diatom Ditylum brightwellii (West) Grunow

Abstract

The presence of a chelating agent such as EDTA was shown to be necessary for growth of D. brightwellii in SiO₂, Stosch-modified Schreiber medium irrespective of initial cell concentration, temperature and illuminance. Growth increased with increasing EDTA concentration up to about 2 × 10^-6M above which growth was independent of EDTA concentration. The reason for lack of growth of D. brightwellii in the absence of EDTA was investigated using various methods of sterilization, filtration and modification of the composition of culture media. Filtration of seawater may either remove essential constituents which may be replaced by EDTA or introduce contaminants such as heavy metals. From a model describing the speciation of heavy metals in the culture medium, it was concluded that the beneficial effect of added EDTA was not due to a reduction in metal toxicity.