Halogenation of natural tufts gave no fruitful results. Using isolated filaments of Cladophora sp. showed that halogens cause changes in cell colour from green to yellow or even to colourless, very often damage to cell wall. Leaching of cell content also occurred, or contraction of cytoplasm was observed. Using dark field technique it was observed that the normal red fluorescence seen in healthy cells disappeared. Very high concentrations (50 mg/l and over) caused severe deformation of cells. In the absence of a recommended procedure for measuring viability of filamentous algae, one hundred cells were counted in each filament and a bioassay was performed at the end of each experiment. Addition of 5 mg/1 of halogens has caused some effect on the algae, while addition of copper sulphate at this concentration showed no effect at all. With higher concentrations of halogens or copper sulphate, cell damage was caused. Ten mg/1 chlorine for 2 hr, 10 mg/1 bromine for 10 hr or 10 mg/1 copper sulphate for 4 days of contact caused complete algal kill. © 1969.
