*2.4. Nitrogen Limitation Experiment*

In order to investigate the effect of nitrogen limitation on the growth and nutrient removal of these two species, a total of 18 side-arm flasks including three replicates for each treatment were prepared. Each flask contained 500 mL culture medium with GeO2 and 5 g thalli. These two species were incubated for 4 days after three different periods of nitrogen limitation (1, 2, and 3 day). We used nitrogen-deficient seawater (NO3-N: 5 mg L<sup>−</sup>1) to achieve different nitrogen levels in the algae. During the 4-day experiment, a temperature of 23 ◦C, a 12:12-h light/dark cycle, and an irradiance of 100 μmol photon m–2 s–1 were maintained. The RGR and removal rates of NO3-N and PO4-P were calculated in the same way as described above.

#### *2.5. Statistical Analysis*

Two-way analysis of variances (ANOVA) were used to analyze the effects of desiccation and the species, water velocity and the species, and nitrogen limitation and the species on the RGR and NO3-N and PO4-P removal rates. Prior to the ANOVA tests, all of the data were confirmed to show a normal distribution and homogeneity of variance. When a significant difference was identified by the ANOVA, Tukey's multiple comparisons test was used to determine which levels of each factor produced significant differences (*p* < 0.05). All of the analyses were performed using STATISTICA version 7.0 software.

#### **3. Results**
