scientific article | Proceedings of the Seventh International Coral Reef Symposium
Masuda K, Goto M, Maruyama Tadashi, Miyachi S
Characteristics of biomass change. and the photosynthetic response of solitary corals, Fun- gia repanda, F. echinata and their zooxanthellae were studied in order to clarify their adaptation to lower light environment in deeper habitat. The Fungia were collected from 1 to 50 m depths in Ngedebus Coral Garden of Palau. The chlorophyll a contents in the algae increased with depth, whereas the chlorophyll a contents per surface area of the coral did not change significantly with depth. Protein contents per surface area de- creased with depth. Maximum gross photosynthetic rate (Pmax) and dark respiration rate (R) normal- ized by surface area of the corals were negatively correlated with the depth, while the values of the initial slope of the curve (a) did not show any clear correlation with the depth. Compensation light in- tensity (Ic) and the light intensity at which the in- itial slope of the curve intercepts the horizontal asymptote (Ik) decreased with depth. In isolated zooxanthellae, it is deduced from changes in Pmax and a that they adapt to low light intensity by changing photosynthetic unit size. Both Ic and Ik decreased with the depth as in the intact corals. The reduction of protein,per surface area of the corals in deeper habitats implies the decrease of host animal tissues. Decrease in Ic can be explained by reduction of R/area which could be due to the decrease in animal tissues. These photoadapta- tional responses of intact Fungia were shown to be a combination of the photoadaptation of symbiotic algae and the decrease of host animal tissue. These adaptational mechanisms seem to allow the Fungia to have wide vertical distribution where light in- tensity spans more than two orders of magnitude.
Republic of Palau