Photosynthesis and respiration rates of the reef corals
Pocillopora damicornis (Linn.), Montipora verrucosa (Lamarck), Porites compressa Dana and Fungia scutaria Lamarck were measured under controlled temperatures. Results indicate that coral m e t a b o l i s m is closely adapted to ambient temperature conditions. Tropical corals m e a s u r e d at Enewetak, Marshall Islands, showed greater primary production compared to maintenance requirements at elevated temperatures than did subtropical varieties of the same species in Hawaii. P h o t o s y n t h e s i s : r e s p i r a t i o n (P:R) ratios were significantly and negatively related with temperature between 18 ~ and 31~ for all Hawaiian corals, whereas at Enewetak this ratio generally showed a curvilinear r e l a t i o n s h i p for this temperature range. Extrapolations of P:R regressions on temperatures to a value of 2.0 (estimated as a m i n i m u m required for long-term functional autotrophy) coincide for Hawaiian specimens with published upper lethal temperatures. Extrapolation of P:R regressions for Enewetak specimens at temperatures above 25~ suggests lethal temperatures for these corals to be 2 to 5 C ~ higher than for Hawaiian corals, in good agreement with recent experimental findings. Interspecific differences in P:R temperature regressions for Hawaiian corals correlating with upper lethal temperature tolerances are described.