Effects of germanium dioxide, an inhibitor of diatom growth, on the microscopic laboratory cultivation stage of the kelp, Laminaria saccharina

Abstract

The kelp, Laminaria saccharina, is an economically and biologically valuable seaweed used in integrated multi-trophic aquaculture. The development of the initial microscopic phase of the life cycle of this species is carried out in the laboratory. A treatment of germanium dioxide (GeO 2 ) can be applied to algal laboratory cultures to inhibit the growth of contaminating diatoms. Previous studies reported inhibitory effects also affecting the macroscopic stage of the life cycle of L. saccharina, the sporophyte, but the effects on the microscopic gametophytic life stage are unknown. To determine the effects, cultures of L. saccharina were treated with varying concentrations of GeO 2 and the resulting lengths and surface area of the juvenile sporophytes produced were measured. It was determined that GeO 2 follows a typical dose-effect pattern, increasing the growth rate of juvenile sporophytes until a critical point at which an inhibitory effect was observed. To obtain juvenile sporophytes ready for deployment to aquaculture sites in the shortest time and to successfully reduce diatom contamination, it was determined that a concentration between 0.10 and 0.50 mL of GeO 2 per litre of seawater, applied at day 8, was the most efficient.

Efecto inhibidor del dióxido de germanio sobre el biofouling del puerto de Mar del Plata

“…Sin embargo, en la gran mayoría de los casos el efecto observado sobre las algas es claramente inhibidor [16][17][18]. El desarrollo de E. intestinalis y Ectocarpus sp.…”

Protocol for seaweed decontamination to isolate unialgal cultures

“…The absence of diatoms in the culture was verified after adding this solution for two weeks. The GeO 2 concentration employed was based on Shea & Chopin (2007), who recommended the addition of 0.0004 to 0.0022 mg of germanium dioxide per liter of seawater to prevent diatom growth without compromising the development of the microscopic phase of Laminaria saccharina (Linnaeus) J.V. Lamour in culture.…”

Effect of GeO2on embryo development and photosynthesis in Fucus vesiculosus (Phaeophyceae)

“…This seems counterintuitive; however, Lewin (1966) showed that GeO 2 , though extremely deleterious for diatoms, had no negative influence on energy metabolism of the cells, and even at 400 mg L -1 GeO 2 , cell respiration did not decrease. Shea and Chopin (2007) also reported that low concentrations of GeO 2 (up to 0.5 mg L -1 ) might sometimes have a slightly positive effect on growth of brown algae. After 5 days, F v /F m and rETR max significantly decreased in Ge-treated embryos, relative to control.…”

“…In addition, the omission of Si from the growth media for brown algae has no apparent deleterious effects (McLachlan 1977). Thus the physiological basis for Ge toxicity in brown algae is unlikely to be similar to that in diatoms, and Shea and Chopin (2007) even reported positive growth responses of low concentrations of GeO 2 on S. latissima (L.) Lane et al (as Laminaria). More recently Mizuta and Yasui (2011) showed extensive silicon localization in sporophyte tissue of S. japonica (Areschoug) Lane et al There have been several studies on the direct effects of Ge on algal growth and morphology (McLachlan 1977, Yang 1993, Shea and Chopin 2007.…”

“…Thus the physiological basis for Ge toxicity in brown algae is unlikely to be similar to that in diatoms, and Shea and Chopin (2007) even reported positive growth responses of low concentrations of GeO 2 on S. latissima (L.) Lane et al (as Laminaria). More recently Mizuta and Yasui (2011) showed extensive silicon localization in sporophyte tissue of S. japonica (Areschoug) Lane et al There have been several studies on the direct effects of Ge on algal growth and morphology (McLachlan 1977, Yang 1993, Shea and Chopin 2007. In this paper we examine the effects of GeO 2 on developing embryos of F. vesiculosus L. during the first 10 days following fertilization from the perspective of both morphological changes and photosynthetic physiology.…”