Microalgal cells must be preserved after sampling, most preferably in Lugol’s iodine solution before counting, to arrest the movement of some live cells around the counting chambers, for example, flagellates and diatoms, and therefore hampering accurate enumeration. Other methods of preservation, such as the use of aldehydes,

saline ethanol, and freezing, can also be adopted for a wide range of phytoplankton. Microalgal preservation is recommended so as to prevent cell disintegration and to avoid any changes in cell population size due to zooplankton grazing (Hotzel and Croome, 1999).