2013 年 15 巻 Supplement 号 p. 160-165
Faster water-flow conditions mitigates photosynthetic stress on zooxanthellate coral species Acropora digitifera, especially under excessive light and high water temperature conditions. Until now, it has remained yet unconfirmed that the effect can be seen on coral species inhabiting similar environments. Here we report on the presence of differential effects of water flow among shallow-inhabiting scleractinian corals in Okinawa, Japan. Using Diving-PAM (pulse amplitude modulation) chlorophyll fluorometers, we compared the dynamics in maximal photochemical efficiencies of photosystem II (Fv/Fm) of five coral species under two flow conditions (<3 cm s-1 and 20 cm s-1). Surprisingly, two out of five coral species showed almost no effects, while water flow exhibited significant mitigating effects in three species such as in A. digitifera. Our results imply that the period of limited water motion (e.g. doldrums-like periods) with strong light conditions would result in variable responses among shallow-inhibiting coral species. We suggest that the presence of water flow allows the coexistence of stress-susceptible corals together with more tolerant ones in similar habitats.
