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

Abstract

Acclimation at 5 CO intervals betwec,n 5" and 20 "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 laterdl translation, maintaining a thermal optimum above the temperat~lre of accllmation. No significant difference was found in food assimilation efficiency over the acclimation regime, the mean value belng 76.43 + 9.71 % S. D. A low metabol~c 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 achic>\e a thermal o p t ~m u n ~ between 15"and 20 "C. Scope for growth, a s defined by the difference between ass~n~ilatetl ration and energy cost of metabohsm, remained positive over the rntlre ~~c c l i m a t e d range at the experimental ration level. Stepwise linear regression analysis of the data produced a model relating assim~latetl ration, oxygen consumption and scope for growth to interactions between acclimation and exposure temperatures. Maxin~um growth rate is predicted at an accllmation temperature (T',) of approximately 17 "C and following exposure to short-term increases of temperature (T,.) to approximately 25 "C, much a s might be dntlcipated during summer in very shallow water