Effect of Temperature and Light on the Photosynthetic Performance of Two Edible Seaweeds: Meristotheca coacta Okamura and Meristotheca papulosa J. Agardh (Solieriaceae, Rhodophyta)

The photosynthetic performance of two species of Meristotheca (Solieriaceae, Rhodophyta), M. coacta and M. papulosa, was investigated under a variety of temperature and light conditions to derive basic information regarding their physiology. A pulse amplitude modulated-chlorophyll fluorometer (Imaging-PAM) was used to generate rapid light curves (RLCs) to provide the relative electron transport rates (rETR) over 21 levels of photosynthetic active radiation (PAR), ranging from 0 to 1,078μmol photons m-2 s-1 at 14 temperatures (i.e., from 8 to 34℃). The initial slope (α), photoinhibition (β) and coefficient (γ) was calculated by fitting the RLCs to a nonlinear model of the form rETR=γ(1-exp(-α･PAR/γ)) (exp(-β･PAR/γ)) using a two-level hierarchical Bayesian model. Both species required temperatures ranging from 18 to 28℃ to maintain optimal photosynthetic activity, as revealed by the estimated model parameters. The optimal PAR (PARopt) increased with increasing temperature. Meristotheca coacta and M. papulosa can be considered well-adapted to the current natural light and temperature conditions of southern Kyushu, Japan. Finding in this study should be useful to the design and manage mariculture programs to conserve the natural resources.