Relationship between the maximum standing crop of musty-odor producing algae and nutrient concentrations in the southern basin water of Lake Biwa

In order to make clear the growth characteristics of musty-odor producing a lgae (Oscillatoria tenuis, Phormidium tenue and Anabaena macrospora), we ex amined the correlation between the maximum growth number (MGN) of each alga and nutrient concentrations, with the unialgal culture method using a 0.45 mu m pore size membrane-filtered lake water. We found that the MGN of Lake Biwa water was limited by soluble phosphorus concentration. In order to verify the results, we examined out the relation between the ma ximum standing crop (MSC) of musty-odor producing algae in the southern bas in of Lake Biwa and nutrient concentrations of our 12-year (1983-1994) obse rvation data. The MSC of P. tenue showed a positive correlation with the N: P ratio, On the other hand, The MSC of O. tenuis showed a strong positive c orrelation with the phosphorus concentration, and a positive correlation wi th the iron and soluble phosphorus concentration, but a strong negative cor relation with the N:P ratio. When the phosphorus concentration is over 0.03 0 mg/l, O. tenuis will probably be over 10 filaments/ml. The optimum N:P ra tio range was 10 to 20. (C) 1999 Published by Elsevier Science Ltd on behal f of the IAWQ. All rights reserved.