The optimal temperature for the H. pluvialis strain used in the present study was 20C; maintaining such a low temperature under high illumination conditions requires increased energy, and, therefore, higher cultivation temperatures would be desirable if the object is to decrease production costs. In fact, many industrial outdoor cultivation operations are conducted in tropical climatic regions where, on average, light intensity and temperature are too high for uncontrolled algal cultivation. In an effort to increase efficiency of the overall astaxanthin production, in the present study we first attempted to elucidate how temperature affects cell growth