THE EFFECT OF TEMPERATURE ON CADMIUM KINETICS AND OXYGEN-CONSUMPTION IN SOIL ARTHROPODS

Soil arthropod species differ considerably in cadmium concentration and the way their burdens vary seasonally. The seasonal variation is often explained by variation in temperature and metabolic activity. To estimate the distribution of cadmium over the soil community and its annual fluxes through the different species, temperature responses of cadmium kinetics have to be taken into account. We examined the effect of temperature on consumption, number of fecal pellets, oxygen consumption, and cadmium kinetics in two common soil arthropod species, Platynothrus peltifer and Orchesella cincta. Accumulation and elimination of cadmium was analyzed by fitting a one-compartment model. Oxygen consumption was higher for Orchesella cincta than for Platynothrus peltifer. Consumption and number of fecal pellets increased considerably between 10 and 20-degrees-C. Oxygen consumption increased exponentially in both species. Cadmium kinetics of the species showed a different response to temperature. In Orchesella cincta, assimilation and excretion increased with temperature; in Platynothrus peltifer, assimilation increased with temperature whereas no effect was found for excretion. As a result, the equilibrium concentration remained constant in Orchesella cincta, whereas in Platynothrus peltifer it increased between 10 and 20-degrees-C. The results indicate that the effects of temperature on cadmium kinetics differ among soil arthropod species and that it is difficult to extrapolate results from one species to the whole soil arthropod community. Species equipped to store cadmium internally seem to respond in a more pronounced way to increased temperature than do species equipped to rapidly excrete cadmium. Because oxygen consumption and cadmium kinetics are not directly related, temperature responses of cadmium kinetics should be taken into account in calculating fluxes of metals through soil arthropod populations.