Effects of salinity, temperature, and light intensity on the growth rates of two halophilic phytoflagellates in mixed culture

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Abstract
Growth rates of two halophilic phytoflagellates, Dunaliella euchlora Lerche and D. salina Teodoresco, were studied in mixed batch cultures grown in filtered, axenic brines from Lake Grassmere, New Zealand. Forty‐five combinations of temperature, salinity, and light intensity were used. A maximum growth rate of 1.50 doublings day‐1 was attained by D. salina at 26°C, 190 × 10‐3S at a light intensity of 126 μE m‐2 s‐1. D. euchlora showed maximum growth rate of 1.16 doublings day‐1 at 20°C, 120 × 10‐3S at a light intensity of 180 μE m‐2s‐1. Predicted maximum values of 1.41 and 1.14 doublings day‐1 respectively were obtained from regression models based on 45 replicate treatment combinations. In decreasing order of importance, temperature, salinity, and light intensity influence growth rates of brine algae. The optimum temperature for growth of both species increased as the salt concentration increased but decreased with increasing light intensity.