Temperature functions in biology and their application to algal growth constants

Various kinds of temperature rules have been proposed for biological use, but reasons for choosing one before another have seldom been given. Arguments for such choices should include both theoretical and mathematical-statistical aspects. In this paper the relationships of algal growth constants, such as ~t (maximum specific growth rate), q0 (minimum nutrient content of the algae), Y (yield coefficient) and Ks (halfsaturation constant for growth) with temperature (t) were investigated. The growth constants were estimated from growth experiments with the green alga Scenedesmus quadricauda performed in batch and P-limited chemostat cultures at t between 3 and 25°C. Additional growth data from different algal populations were estimated from 14C experiments in an incubator and in the field (0-20°C). The dependence of both (A and AZ (assimilation number) on t was generally described better by Belehradek's equation based on a "physical view", i.e., the rate of biological processes is more likely controlled by physical processes such as diffusion and viscosity than by equations of Berthelot's or Van't Hoff-Arrhenius' types, which were derived from chemical processes. Within smaller t intervals, Burckhardt-Harvey's equation (linear) often gave an equally good fit. For Scenedesmus the parameter q0 can be described by a 2nd degree polynomial. The limit value of Y at ,t = 0 versus t can also be best described by Belehradek's equation. Both Ks and Y at ut = seem to be independent of t. Many examples from zoology also show statistically the most accurate fit to Belehradek's equation. On the whole, biological processes seldom show exponential increases with t. For example, the RGT-rule (Q0l), which is so widely used even today, often gives artificial "breaks" in the temperature coefficients. An equation of Belehradek's type should therefore be more generally accepted, also because its parameters appear to have some ecological significance.