Observations on the effects of germanium dioxide on the growth of macro-algae and diatoms

Abstract

Growth of various species of macro-algae and diatoms was measured in culture in a range of concentrations of germanium dioxide. Growth of Laminaria saccharina was inhibited measurably at concentrations above 0.22 mg GeO2 l−1 and very markedly inhibited above 1.1 mg GeO2 l−1. Fucus spiralis was measurably inhibited at concentrations above 0.22 mg GeO2 l−1, as was Ulva lactuca at concentrations above 2.2 mg GeO2 l−1. The Rhodophyta tested (Polysiphonia urceolata, Porphyra umbilicalis, Chondrus crispus) showed no inhibition by GeO2. Most diatoms tested were strongly inhibited by concentrations of 0.134 mg GeO2 l−1. It is suggested that the majority of diatoms can be controlled without inhibiting the growth of most cultures of species of Phaeophyta or Chlorophyta by short-term application of GeO2 in concentrations of 0.045–0.179 mg GeO2 l−1 (0.01–0.04 ml sat. GeO2 soln. l−1) instead of the much higher concentrations previously suggested.