Values for K, the coefficient of vertical eddy diffusion in the thermocline of lake 227, a small, highly stratified, and artificially eutrophied lake in northwestern Ontario, Canada, are presented. Three methods: the classical temperature method of McEwen, a dye method, and a new method using a RAGAPOS (Radon Gas Point Source), were used. Results ranged from 2 × 10−4 cm2/sec by the Rn method to 34 ×10−4 cm2/sec by temperature method; the dye method resulted in an average value of 12 × 10−4 cm2/sec. The recycling of ΣCO2 resulting from particulate degradation below the epilimnion was calculated. The results ranged from 8 to 53% of the net loss of carbon from the empilinion depending on the K value used. Results from the radon method are considered to be more accurate than results from the temperature method.