Biostimulatory capacity of dissolved iron for cyanophycean blooms in a nitrogen-rich reservoir

Studies of the concentration of available nutrients (nitrate-nitrogen, inorganic phosphate and dissolved iron) in Perris lake, Calif., combined with counts of the numbers of blue-green algae (Cyanophyta), are reported. Despite favourable climatic conditions, algal blooms had not reached the expected intensity, owing to an unfavourable balance of nutrients. Laboratory experiments on the stimulatory effect of iron suggest that a deficiency of this element was probably responsible for the absence of blooms under natural conditions.