Thermal compensation of metabolism in the temperate coral, Plesiastrea versipora (Lamarck, 1816)

Plesiastrea versipora is a hermatypic coral with a distribution that extend s to the southern limit for hermatypic corals. The normal annual temperatur e range for this coral in Port Phillip Bay (Victoria) (approximately 10-21 degreesC) is well below the physiological optimum for the majority of herma typic corals (25-29 degreesC). The rate of photosynthesis and respiration i n Plesiastrea generally increased with temperature before levelling out at the higher temperatures, with Q(10) data suggesting that both photosynthesi s and respiration in Plesiastrea acclimate to changing temperatures. Respir ation showed a similar trend to photosynthesis, with respect to temperature , but with a slightly lower rate of increase. Photosynthetic rate in Plesia strea is comparable with that of reef corals despite lower temperatures and irradiance. When expressed as a function of chlorophyll a content photosyn thesis approached perfect temperature compensation with prolonged exposure to various temperatures. Temperature-dependent changes with chlorophyll con tent may be responsible for temperature related changes in photosynthetic r ate. This may be a mechanism for stabilising the symbiotic relationship ove r a wide temperature range. Autotrophic ability, estimated from photosynthe sis/respiration (P/R) ratios, was greatest at higher temperatures and was o nly slightly less than that of reef corals. At low temperatures Plesiastrea may be dependent on heterotrophic feeding. (C) 2001 Elsevier Science B.V. All rights reserved.