Effects of Environmental Factors on the Zoospore Release and Germling Growth of the Green Macroalga Chaetomorpha linum

Effects of environmental factors on the zoospore release and germling growth of Chaetomorpha linum were examined. Zoospore release and germling growth experiments were carried out under a combination of temperatures × irradiances, and a single factor of irradiances, salinities, daylength and nutrients (nitrogen, phosphorus). Zoospore release was maximal under condition of 20℃ × 100 μmol photons m −2 s −1 in a factorial experiment (temperatures × irradiances), at 100 μmol photons m −2 s −1 in irradiance experiment and at 34 psu in salinity conditions. After 24 days in culture, germling growth was maximal at 25℃ × 100 μmol photons m −2 s −1 in temperatures × irradiances and at normal seawater (34 psu) in salinity. Germling growth is faster at higher irradiance under same temperature condition and it increased with increasing daylengths (8−16 h). Chaetomorpha linum grew in wide range of N and P concentrations. The growth of germling was maximal at 50 μM PO₄ 3− and 40 μM NH₄ + . Germling growth was more effective under nitrogen addition than phosphorus addition in culture. In conclusion, optimal environmental conditions for zoospore release were 20℃, 100 μmol photons m −2 s −1 , and 34 psu. In addition, the optimal germling growth was observed at 25℃, 100 μmol photons m −2 s −1 , 34 psu, 16 h, 50 μM (PO₄ 3− ) and 40 μM(NH₄ + ).