Effects of ocean acidification on the growth of Saccharina japonica in the sporophyte and gametophyte stages

Aims of this study were examined the effects of global warming and ocean acidification on the sporophyte photosynthesis and gametophyte growth of cultivation algae, Saccharina japonica. Photosynthesis efficiency (Fv/Fm) of... [ view full abstract ]

Aims of this study were examined the effects of global warming and ocean acidification on the sporophyte photosynthesis and gametophyte growth of cultivation algae, Saccharina japonica. Photosynthesis efficiency (Fv/Fm) of sporophytic frond discs (Ø 1cm) was measured after five day incubation under combination of three pCO2 (380, 750, 1000 ppm) × four temperature (5, 10, 15, 20 ℃) × two irradiance levels (40, 80 μmol m-2s-1). Growth was estimated with length of female gametophytes after 10 days in culture in the same environmental conditions except two temperature levels of 15 and 20 ℃. Fv/Fm value of S. japonica sporophyte was 0.63 in 380 ppm, increased to 0.67 in 750 ppm and then decreased 0.55 in 1000 ppm. Also, Fv/Fm values of S. japonica grown in the temperature of 5~15 ℃ (0.63~0.66) were significantly greater than 0.55 of 20 ℃ but no differences were found between irradiance levels. Female gametophytes of S. japonica was 2-3 times long under lower 380 ppm (39.40 μm) and getting grew slow with increasing pCO2 concentration: 15.60 μm in 750 ppm and 12.73 μm in 1000 ppm. At 15 and 20 ℃, the growth of S. japonica gametophytes were quite similar. In conclusion, photosynthesis of S. japonica sporophyte was enhanced as pCO2 concentration was increased from 380 ppm to 750 ppm. Gametophytes of both species grew well in 380 ppm. The growth of S. japonica gametophytes was not different between temperatures of 15 and 20 ℃.