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

Abstract

Respiration rates for the cladocerans Bythotrephes cederstroemi and Daphnia middendorffiana were measured over a broad range of temperatures. The data were fit to the model f(°K) Wb where f(°K) is a formulation based on enzyme activity as a function of temperature. The enzyme kinetic model better described the biological observations of respiration as a function of temperature than standard empirical models. The results indicate that Bythotrephes has characteristics of a stenotherm and that the arctic Daphnia middendorffiana has characteristics of a eurytherm based on the linear region of Arrhenius plots (where enzymes are fully active). Above 23°C, Bythotrephes was limited by inactivation of respiratory enzymes. Also, below 14°C, enzyme inactivation became significant and not fully compensated for. Daphnia middendorffiana has a temperature region from ~10 to 26°C in which the respiratory process was linear on an Arrhenius plot. Temperature-dependent and weight-specific respiration was described for each species with a formulation over a complete range of environmental temperatures. The formulation for temperature inactivation is applicable to all enzyme processes and should be used in aquatic studies requiring a broad temperature range.