In Vitro Growth and Photosynthesis of Three Edible Seaweeds, Betaphycus gelatinus , Eucheuma serra and Meristotheca papulosa (Solieriaceae, Rhodophyta)

Three species of Solieriaceae (Rhodophyta), Betaphycus gelatinus, Eucheuma serra and Meristotheca papulosa are economically important species, that are found in subtropical to tropical waters and are well represented in the coastal area of Ryukyu and Kyushu Islands of Japan. This study was motivated by the need to establish basic information regarding their physiology, in order to design a cultivation system. Two experiments were conducted to determine how five temperature treatments of 16, 20, 24, 28 and 32℃ influenced growth and photosynthesis, as determined by a dissolved oxygen sensor. An additional experiment examined how nine irradiance levels of 0, 13, 26, 48, 68, 168, 248, 342 and 536μmol photon m-2 s-1 at 24℃ influenced photosynthetic rates. Optimal relative growth rates of B. gelatinus and E. serra under 90μmol photon m-2 s-1 occurred from 24℃ and 28℃, while for M. papulosa it ranged from 20℃ and 24℃. Maximum photosynthetic rates (Pmax) for B. gelatinus, E. serra and M. papulosa were 135.0, 65.0 and 52.4μg O2 (mg chl-a)-1 min-1 , respectively and saturated beyond 94.9, 69.4 and 35.4μmol photon m-2 s-1 , respectively. These characteristic results were closely related to their depth of the habitat and local distribution in southern Japan, and provide information required to design their mass-cultivation systems.