Temporal variation of 2-MIB and geosmin production by Pseudanabaena galeata and Phormidium ambiguum exposed to high-intensity light.

This study demonstrated the temporal variation of 2-methylisoborneol (2-MIB) and geosmin (GSM) production of two filamentous cyanobacteria species Pseudanabaena galeata (NIES-512; planktonic) and Phormidium ambiguum (NIES-2119; benthic) exposed to high light intensity (950-1000 μmol m-2  s-1 photosynthetically active radiation). The production of 2-MIB and GSM was quantified together with oxidative stress, chlorophyll content, and cellular protein content. The relative chlorophyll bleaching and cell degradations were compared through microscopic images. The 2-MIB production of P. galeata increased by over 42 ± 17% on the second day of exposure and remained leveled through the exposure period. P. ambiguum showed a continuous increase of 2-MIB until the 10th day, recording a 95 ± 4% increment. The GSM production was elevated until the fourth day of exposure by 46 ± 10% for P. galeata and by 74 ± 21% on the second day for P. ambiguum and reduced with prolonged exposure for both species. The chlorophyll content of P. galeata was reduced by 62 ± 7% on the second day, and that of P. ambiguum was reduced by 52 ± 9% on the fourth day and remained low. Protein and H2 O2 contents of both species were changed inconsistently. Exposure to high-intensity light can photobleach and deteriorate cells of both species, but elevations in odorous compounds can be expected.