Response surface analysis of the combined effects of exposure and acclimation temperatures on filtration, oxygen consumption and scope for growth in the oyster Ostrea edulis

Acclimation at 5 degrees C intervals between 5degrees and 20 degrees C was used to determine the acute effects of temperature on energy balance In the oyster Ostrea edulis (L.). Rate-temperature curves for filtration showed evidence of lateral translation, maintaining a thermal optimum above the temperature of acclimation. No significant difference was found in food assimilation efficiency over the acclimation regime, the mean value being 76.43 + 9.71 % S. D. A low metabolic rate is maintained up to an acclimation temperature of 20'C; beyond 20 "C however, metabolic costs rise sharply. As a result, filtration efficiency and cost of filtration both achive a thermal optimum beween 15"and 20 "C. Scope for growth, as defined by the difference between assimilation ration and energy cost of metabolism, remained positive over the entire acclimated range at the experimental ration level. Stepwise linear regression analysis of the data produced a model relating assimilation ration, oxygen consumption and scope for growth to interactions between acclimation and exposure temperatures. Maximum growth rate is predicted at an acclimation temperature (T',)f approximately 17 "C and following exposure to short-term increases of temperature (T,.) to approximately 25 "C, much as might be anticipated during summer in very shallow water