Suppressive effect of germanium dioxide on diatom contamination during cultivation of Saccharina japonica young sporophytes

Abstract:

In the present study, using the chlorophyll fluorescence technique, the suppressive effect of germanium dioxide (GeO₂)on Nitzschia sp. contamination during the cultivation of Saccharina japonica seedling was investigated with the photosystem II maximum fluorescence yield (Fv/Fm) as the index. The results showed that: 1) When the concentration was above 5mg/L, GeO₂ affected Fv/Fm value of Nitzschia sp. significantly, whereas when the concentration was 15mg/L or above，GeO₂ had lethal effect on Nitzschia sp.; 2) To the young sporophytes of S. japonica, GeO₂ at concentrations of 20mg/L or above affected the Fv/Fm value significantly, whereas GeO₂ at concentrations of 30mg/L or above had lethal effect on young sporophytes; 3) To the young sporophytes contaminated by Nitzschia sp.，the Fv/Fm value was affected significantly by GeO₂ at concentrations of 15 mg/L or above , while the contaminated young sporophytes died when GeO₂ concentration was 20 mg/L or above. Comparatively, GeO₂ at concentrations of 5～15 mg/L could suppress the photosynthesis of Nitzschia sp. significantly, but only had a minor effect on photosynthesis of S. japonica young sporophytes. Therefore, GeO₂ at concentrations of 5～15 mg/L could prevent the Nitzschia sp. contamination during the cultivation of S. japonica young sporophytes. The results obtained from the present study could provide the basis for preventing the Nitzschia sp. contamination during the cultivation of S. japonica young sporophytes.