For cell density estimation, 10 μL of algal culture was mixed with 30 μL of Lugol’s solution (Sigma-Aldrich, St. Louis, MO, United States) and the cell number was counted in duplicate using a light microscope (BX43, Olympus, Tokyo, Japan) and a hemacytometer (Improved Neubauer, Boeco, Germany) as mentioned above. The cell density was calculated according to the manufacturer’s manual and expressed as units of 106⋅ mL–1.
After 6 h of treatments, the viability of algal cells was estimated by loading 2 μL of cell suspension on TAP agar plates, and incubating the plates for 72 h at 28°C under illumination at 50 μmol⋅ m–2⋅ s–1 intensity. The colonies were imaged with a digital Nikon camera, and the final composite images were constructed using Adobe Photoshop (Adobe Systems, San Jose, CA, United States). Together with cell density curve, the cell viability assessed by growth ability (the color and size of the colony) was used to evaluate the effects of chemical challenges.
After 6 h of treatments, the viability of algal cells was estimated by loading 2 μL of cell suspension on TAP agar plates, and incubating the plates for 72 h at 28°C under illumination at 50 μmol