A model for temperature correction of size-specific respiration in Bythotrephes cederstroemi and Daphnia middendorffiana

Respiration rates for the cladocerans Bythotrephescederstroemi and Daphnia middendorffianawere measured over a broad range of temperatures. The data were fit to themodel f(K)W^b wheref(°K) is a formulation based on enzymeactivity as a function of temperature. The enzyme kinetic model betterdescribed the biological observations of respiration as a function oftemperature than standard empirical models. The results indicate thatBythotrephes has characteristics of a stenotherm andthat the arctic Daphnia middendorffiana hascharacteristics of a eurytherm based on the linear region of Arrheniusplots (where enzymes are fully active). Above 23°C,Bythotrephes was limited by inactivation ofrespiratory enzymes. Also, below 14°C, enzyme inactivation becamesignificant and not fully compensated for. Daphniamiddendorffiana has a temperature region from 10 to26°C in which the respiratory process was linear on an Arrheniusplot. Temperature-dependent and weight-specific respiration was describedfor each species with a formulation over a complete range of environmentaltemperatures. The formulation for temperature inactivation is applicable toall enzyme processes and should be used in aquatic studies requiring abroad temperature range.