Environmental and nutritional factors affecting geosmin synthesis by Anabaena sp.

A cyanobacterium isolated from a source-water reservoir during a spring odor and taste episode and identified as Anabaena sp. consistently produced geosmin during laboratory culture on modified BG-11 liquid medium. Maximal geosmin/biomass occurred at 20 degreesC and a light intensity of 17 muE/m(2)/s; geosmin/chl a values directly correlated with increasing light intensity (r(2) = 0.95, P<0.01). It was concluded that at 20C, increasing light intensity favors less chl a synthesis and higher geosmin synthesis; at 17 muE/m(2)/s, increasing temperature stimulates chl a production (to 25 degreesC) while repressing geosmin synthesis (above 20 degreesC). Nutritional factors promoting biomass, chl a, and geosmin synthesis by Anabaena sp. were also investigated. For cultures grown at 17 muE/m(2)/s and 20 degreesC for 20 days, both ammonium-N and nitrate-N generally enhanced the growth of Anabaena sp. Nitrate-N promoted more chl a production (r(2) = 0.99) than ammonium-N. Geosmin synthesis was directly correlated with ammonium-N concentrations (r(2) = 0.89), with low nitrate-N (123.5 mug/l) favoring maximal geosmin production (2.8 mug/l). Increasing nitrate-N concentrations promoted a three-fold increase in chin content with geosmin synthesis decreased by two-fold. Geosmin/mg biomass was directly related to ammonium-N concentration; high nitrate-N levels suppressed geosmin production. No geosmin was detected at or below 118 mug phosphate phosphorus/l. Geosmin, dry weight biomass, and chl a production were correlated with increasing phosphorus (P) concentration (r(2) = 0.76, 0.96 and 0.98, respectively). No geosmin was detected when copper was present in growth media at or above 6.92 mug Cu2+ /1 (CuSO4. 5H(2)O). Dry weight biomass and chl a production were negatively correlated with Cu2+ ion concentrations. (C) 2001 Elsevier Science Ltd. All rights reserved.