3.2 Small- and large-scale experiments with Ulva fenestrata treated with GeO 2

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

μmol0.20

(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

− − s200

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.

Fresh weight (FW)-based contents of chlorophyll a (Chl a), chlorophyll b (Chl b), total chlorophylls (Chl a + b) and the Chl a -to- b ratio (Chl a / b). Data are means ± standard deviations of three replicates per treatment (n = 3). Different lowercase letters behind the data in each column indicate statistically significant differences of the pigments between the GeO 2 concentrations (P <0.001, 1-way ANOVA, Tukey-Kramer HSD post-hoc test).

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).