taxonID	type	description	language	source
03C39459FFD2FFBFF420FD82FAD6FC63.taxon	description	After 22 days of seawater cultivation in 1 l glass beakers, brown biofilms of Fragilariopsis oceanica became clearly visible on the bottom and walls of the beakers of both the control (0 mg l − 1) and the lowest GeO 2 concentration (0.003 mg l − 1) with 27.13 mg DW m − 2 and 24.23 mg DW m − 2, respectively. In contrast, all GeO 2 concentrations ≥ 0.014 mg l − 1 had lower diatom biomass (6.56 mg DW m − 2) than the control and 0.003 mg GeO 2 l − 1 (P <0.0001, 1 - way ANOVA; Figure 2).	en	Rautenberger, Ralf (2024): Germanium dioxide as agent to control the biofouling diatom Fragilariopsis oceanica for the cultivation of Ulva fenestrata (Chlorophyta). Botanica Marina (Warsaw, Poland) 67 (2): 93-100, DOI: 10.1515/bot-2023-0075, URL: http://dx.doi.org/10.1515/bot-2023-0075
03C39459FFD2FFBEF420FBB0FB0DFB31.taxon	description	In the small-scale experiment, the RGR and all three photosynthetic parameters of Ulva fenestrata were statistically similar between the control (0 mg GeO 2 l − 1) and the 3 GeO 2) standard deviations. Lowercase letters above columns indicate statistically significant differences between the treatments (P <0.001, 1 - way ANOVA, Tukey-Kramer HSD post-hoc test). 20 photons 0.25 0.30) 15 − 1 1 − % d ETR μmol 0.20 (10 0.15 RGR 5 α electrons 0.05 0.10 0 μmol 0.00 0 0.022 0.223 2.235 (0 0.022 0.223 2.235 Figure 3: Physiological parameters of the small-scale cultivation of Ulva fenestrata with GeO 2. 40)) 1 (A) Relative growth rates (RGR), 1 − − s 200 s 2 (B) photosynthetic electron transport − 2 − m 30 m efficiencies (α ETR), (C) maximum electron ETR electrons max 20 photons 150 100 transport fenestrata saturation rates after points (small-scale ETR of max photosynthesis) and cultivation (D) light (E k () 5 of days Ulva) 10 μmol μmol (E (k 50 in tions 1 - l glass at 140 beakers µmol photons with four m − 2 GeO s − 1 2 and concentra- 9 ° C. 0 0 Data are means of three replicates per treat- 0 0.022 0.223 2.235 0 0.022 0.223 2.235 ment (n = 3) and error bars represent standard GeO 2 concentration (mg L− 1) GeO 2 concentration (mg L− 1) deviations. concentrations tested between 0.022 and 2.235 mg l − 1 (Figure 3). In addition, the contents of Chl a and Chl b in U. fenestrata remained unaffected by the presence of different GeO 2 concentrations in the seawater (Table 1). However, there was slight decrease in the Chl a / b ratio of U. fenestrata from 1.61 ± 0.08 in the control by 10 – 15 % in the presence of GeO 2 (P = 0.0208, 1 - way ANOVA; Table 1). In the large-scale experiment, the RGR, all three photosynthetic parameters, and the chlorophyll contents, including the Chl a / b ratio of U. fenestrata, were statistically similar between the control and the two tested GeO 2 concentrations after 14 days of cultivation (Figure 4 and Table 1). However, the addition of GeO 2 to the seawater decreased the density of F. oceanica on the wall surfaces of the Plexiglass water tanks by 36 – 43 % at 0.223 – 2.235 mg GeO 2 l − 1 compared to the control (P = 0.0077, 1 - way ANOVA; Figure 5).	en	Rautenberger, Ralf (2024): Germanium dioxide as agent to control the biofouling diatom Fragilariopsis oceanica for the cultivation of Ulva fenestrata (Chlorophyta). Botanica Marina (Warsaw, Poland) 67 (2): 93-100, DOI: 10.1515/bot-2023-0075, URL: http://dx.doi.org/10.1515/bot-2023-0075
03C39459FFD3FFB8F454F952FDEDFE16.taxon	description	20 photons 0.4 1) 15 1 − 0.3 − d % ETR μmol (10 0.2 RGR 5 α electrons 0.1 0 μmol 0.0 0 0.223 2.235 (0 0.223 2.235 Figure 4: Physiological parameters of the large-scale cultivation of Ulva fenestrata with GeO 2. 100 1) 300 (A) Relative growth rates (RGR), − 1) − s 2 s 250 (B) photosynthetic electron transport 802 − mmefficiencies (α ETR max − electrons 40 60 photons 100 200 150 transport fenestrata saturation rates after points ETR large-scale (ETR), of (C max photosynthesis) maximum) and cultivation (D) electron light (E k (14) of days Ulva) μmol (20 E (μmol k 50 0 in concentrations 100 - l Plexiglass at 140 water µmol tanks photons with three m − 2 s GeO − 1 2 0 and 12 ° C. Data are means of three replicates 0 0.223 2.235 0 0.223 2.235 per treatment (n = 3) and error bars represent GeO 2 concentration (mg L− 1) GeO 2 concentration (mg L− 1) standard deviations. 2 Toxicological studies have shown species- and strain-specific responses of diatoms to GeO 2. While concentrations of up to 1 mg GeO 2 l − 1 inhibited the growth of highly silicified diatom species (e. g. Amphiphora paludosa, Cylindrotheca fusiformis), diatoms with a low degree of silicified cell walls (e. g. Phaeodactylum tricornutum) were insensitive even to 10 GeO 2 mg l − 1 (Lewin 1966; Markham and Hagmeier 1982; Tatewaki and Mizuno 1979). By using these results as benchmark for the present study, F. oceanica seems to be highly sensitive to GeO 2 because its growth was inhibited at a low concentration of 0.014 mg GeO 2 l − 1. Assuming that Si uptake in F. oceanica is mediated by SITs at low Si concentrations in seawater (<30 µM) as shown for Thalassiosira pseudonana (Thamatrakoln and Hildebrand 2008), a growth inhibition by GeO 2 could have been expected because the seawater Si concentration used was approx. 2.1 µM (Busch et al. 2014). However, if Si was added to the seawater according to formulation of the ESNW medium with a final concentration of 106 µM, a different result would have been observed because diffusive Si uptake predominates at higher Si concentrations (Thamatrakoln and Hildebrand 2008). Interestingly, the use of GeO 2 in the glass beakers and Plexiglass water tanks showed different effects on F. oceanica. While low GeO 2 concentration inhibited the growth of F. oceanica, the colonisation of the Plexiglass walls by F. oceanica could not be fully prevented even by the use of 2.235 mg GeO 2 l − 1. This could be possibly ascribed to the different physical surface properties between glass and Plexiglass. Insoluble extracellular polymeric substances (EPS) secreted by diatoms allow them to adsorb better on hydrophobic surfaces such as Plexiglass than on the hydrophilic surfaces of the glass beakers (Finlay et al. 2013; Holland et al. 2004; Krishnan et al. 2006; reviewed by Thompson and Coates 2017). In addition, EPS-rich biofilms from Roseobacter and S ul fi tobacter, which are associated with Ulva, could have enhanced the attachment of F. oceanica on the Plexiglass walls (Bruckner et al. 2011; Buhmann et al. 2016; Spoerner et al. 2012). Thus, the bacterial biofilms could help F. oceanica to overcome the negative effects of GeO 2. Other factors such as the different treatments of the glass beakers (acid-washed) and water tanks (hand washing and sodium hypochlorite) prior to the experiments could also have contributed to the different outcomes of the two experiments. Nevertheless, since the large-scale experiment showed a considerable reduction in diatom density on the Plexiglass surfaces by 0.223 mg GeO 2 l − 1 (f. c.), the costs for the biomass production of U. fenestrata are expected to be lower than without employing any GeO 2 at all.	en	Rautenberger, Ralf (2024): Germanium dioxide as agent to control the biofouling diatom Fragilariopsis oceanica for the cultivation of Ulva fenestrata (Chlorophyta). Botanica Marina (Warsaw, Poland) 67 (2): 93-100, DOI: 10.1515/bot-2023-0075, URL: http://dx.doi.org/10.1515/bot-2023-0075
