GEOSMIN AND 2-METHYLISOBORNEOL PRODUCTION BY CYANOBACTERIA IN FISH PONDS IN THE SOUTHEASTERN UNITED-STATES

Levels of geosmin and 2-methylisoborneol and composition of phytoplankton communities were determined for water samples collected from 35 fish ponds at Auburn, Alabama, and 34 ponds in west-central Mississippi. In Auburn ponds, geosmin levels ranged from 0.05 to 8.9-mu-g/l but 2-methylisoborneol was never detected. Highest geosmin concentrations were measured in ponds with plankton blooms dominated by Anabaena species with straight trichomes. In Mississippi ponds, 2-methylisoborneol levels ranged from 0.05 to 76-mu-g/l. Highest 2-methylisoborneol concentrations were associated with blooms of Oscillatoria cf. chalybea, a cyanobacterium that produces 2-methylisoborneol in unialgal culture. Geosmin was found infrequently in Mississippi pond waters; geosmin levels ranging from 0.05 to 6.25-mu-g/l could be associated with blooms of Anabaena spiroides, and always concurred with 2-methylisoborneol concentrations ranging from 0.45 to 3.25-mu-g/l. Neither geosmin nor 2-methylisoborneol at either location could be associated with phytoplankton blooms of Aphanizomenon flos-aquae, Oscillatoria agardhii, Raphidiopsis brookii, or Microcystis aeruginosa.