*3.2. Morphological Observation*

The morphological changes of the algal cells were observed using a Leica DM750 light microscope (Leica Microsystems, Wetzlar, Germany) and photos were taken with a Leica ICC50 W camera (Leica Microsystems, Wetzlar, Germany).

#### *3.3. Determination of Cell Number*

The samples were fixed with Lugol's iodine solution first. Then, cell numbers were counted using a Neubauer improved cell counting chamber under Leica DM750 light microscope and measured as cells mL−1.

The daily percentage growth rate of nonmotile cells (% day−1) was calculated as follows:

$$\text{Daily percentage growth rate of nonmotile cells } \left( \% \text{ day}^{-1} \right) = \frac{\frac{\mathcal{C}\_{\text{Ml}}}{\mathcal{C}\_{\text{Tl}}} \times 100\%}{t} \tag{1}$$

where *CNt* and *CTt* were the nonmotile cells number and total cells number on day t, respectively.
