Effects of nutritional factors on the geosmin production of Lyngbya kuetzingii UTEX 1547 (Oscillatoriales, Cyanobacteria)

The effects of phosphate-P (PO4-P), nitrate-N (NO3-N), and calcium ion (Ca2+) on the geosmin production of Lyngbya kuetzingii UTEX 1547, a geosmin-producing cyanobacterium, were investigated. All nutrients had significant effects on geosmin production (P < 0.05). Of the three concentrations of PO4-P tested: 0, 0.20, and 5.44 mg l(-1) , the minimum geosmin concentration, mimimum geosmin per chlorophyll a (geosmin/Chl a), and maximum Chl a content were observed at 5.44 mg l(-1). The concentration and proportion of extracellular geosmin were also the lowest at 5.44 mg l(-1) PO4-P. Of the six concentrations of NO3-N (0, 2.47, 24.70, 82.50, 165.00, and 247.00 mg l(-1)), the geosmin concentrations were high at 82.50, 165.00, and 247.00 mg l(-1), and the highest geosmin/Chl a were observed at 0 and 2.47 mg NO3-N l(-1). The proportion of extracellular geosmin increased as the growth progressed at 165.00 and 247.00 mg NO3-N l(-1). With respect to Ca2+ ,geosmin concentrations were considerably greater at 97.96 and 979.60 mg Ca2+ l(-1) than those at 0 and 9.80 mg Ca2+ l(-1). The geosmin/Chl a values were highest at 979.60 mg Ca2+ l(-1) as the growth progressed, except in the calcium-deficient condition. The present study confirmed that nutritional factors can regulate geosmin production in cyanobacteria. This will help understand the dynamics of geosmin production in cyanobacteria and facilitate the management of geosmin contamination in surface waters.