DIRECT CALORIMETRY OF AQUATIC ANIMALS - DYNAMIC-RESPONSE OF BIOLOGICAL PROCESSES

The theory of system identification was used to determine the time con stant tau of a 1 litre flow through differential calorimeter (Setaram GF 108) at a flow rate of 50 ml min(-1). By numerical differentiation the impulse response function g(t), the time derivative of the step re sponse f(t), was calculated. With the aid of the Prony method, the tim e constant a(2) of the time-discrete system of the decimated dataset w as calculated, giving a mean value of 0.7402 +/- 0.0044 (n = 4). This value was converted to the time constant tau of the time-continuous sy stem, giving a value of 33.25 +/- 0.65 min (n = 4). The description of the system agreed with a model for a first order process. For control of the time constant value, the step response f(t) and the impulse re sponse g(t) signal were simulated from the original block diagram u(t) which gave a suitable fit. Via the technique of deconvolution, the da tasets of a biological case study with goldfish (Carassius auratus L.) were desmeared to describe the dynamic responses of the biological pr ocesses in the calorimetric vessel with a much reduced time constant t au. Finally, the timescale on which the process of metabolic depressio n takes place in this species during anaerobiosis was estimated to be several minutes.