It is immensely difficult to sample and accurately count microalgal cells that grow attached to the substratum or culture vessel. The cells are scraped from the sur­face using a spatula to dislodge them into a suspension. The cells are then care­fully homogenized so as to separate the cell clumps, and this can result in the death of some cells. The cells that are clumped are indistinguishable from single cells, and therefore cell enumeration may be inaccurate (Guillard and Sieracki, 2005). Colonies of Microcystis aeruginosa were separated to a homogenous cell suspension by alkaline hydrolysis with 0.01 M KOH at 80°C for about 30 minutes, but higher molarities of KOH resulted in cell loss (Box, 1981). In addition, complete separation of colonies to single cells was achieved by heating at 80°C for 30 minutes followed by 30 seconds of vortex-mixing (Box, 1981). Furthermore, in these studies, sonica — tion (20 KHz, c. 50W) did not completely reduce the colonies to single cells, and this procedure resulted in cell death on some occasions (Box, 1981).

It has been reported that the efficiency of the method for separating the colonies into a single-cell suspension relies on the microalgal cells used (Box, 1981). The accuracy of enumerating microalgal cells displaying colonial growth is hindered if there is no uniformity in the number of cells per colony. In addition, the cells cannot be sufficiently distinguished from each other, thus compromising accuracy. The enu­meration of dividing microalgal cells is subject to inherent inaccuracies.