Physioecology of zooplankton. III. Effects of phytoplankton concentration,temperature, and body size on the metabolic rate ofCalanus pacificus

Weight-specific rates of oxygen consumption of actively feeding copepodite stages ofCalanus pacificus Brodsky were measured under various combination of phytoplankton concentration and temperature. The rate decreased logarithmically with a logarithmic increase in dry body weight of copepods, and the relationship between these variables was described using a log-transformed allometric equation. The body-size dependence of the metabolic rate was independent of changes in food concentration and temperature, but the metabolic level increased linearly with a logarithmic increase in temperature and was not significantly affected by changes in food concentration. Respiration rates measured in this study forC. pacificus were about twice as high as rates reported for unfed closely related species of the same genus. An analysis of the metabolic cost of feeding processes suggests that metabolic models derived from feeding models may be of little ecological value at present.Contribution No. 1129 from the Department of Oceanography, University of Washington, Seattle, Washington 98195, USA