Ulva fenestrata

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), pp. 93-100 : 95-96

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.

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 ).

Figures

Figure 5: GeO2-dependent total diatom density present on the surfaces of Plexiglass water tanks after 14 days of large-scale cultivation of Ulva fenestrata. Data are means of three replicates per treatment (n = 3) and error bars represent 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).