Physiological responses of Dunaliella salina and Dunaliella viridis, isolated from solar saltworks on the Yucatan Peninsula, were studied. Optimal growth temperature for D. salina was 22 degrees C (3.06 x 10(6) cells mL(-1)) and 26 degrees C for D. viridis (4.04 x 10(6) Cells mL(-1)). Total carotenoid content in D. salina increased with temperature to a maximum of 35.14 pg cell(-1) at 38 degrees C. Dunaliella salina of-carotene and P-carotene content was 0.083 +/-0.003 and 0.598 +/- 0.020 mg 100 g dry wt(-1) respectively, whereas lower values were found in D. viridis cultured under same experimental conditions (0.018 +/- 0.002 and 0.136 +/- 0.012 mg 100 g dry wt-1 respectively). The highest specific growth rate in D. salina was obtained at 10% NaCl (0.28 d(-1)), while its cell volume increased from 524 to 2066.93 mu m(3) when cultured from 10% to 35% NaCl. Maximum photosynthetic rates were attained when increasing from optimal growing temperature to 30 degrees C for D. viridis (108 nmol O-2 mu g chl a h(-1)) and D. salina (139 nmol O-2 mu g chl a h(-1)). Photosynthetic responses to temperature variations indicated physiological adjustments in both species, with higher acclimation in D. salina. Evaluation of physiological attributes of these species will be used for to carry out mass cultivation. (c) 2006 Elsevier Ltd. All rights reserved.