The growth rate of Mychonastes ruminatus Simpson et Van Valkenburg under various light, temperature and salinity regimes

Abstract

Optimal growth conditions of temperature, light and salinity were determined for Mychonastes ruminatus. At a light intensity of 1·9 mW cm^-2 (28,600 lx) in 15‰. salinity medium, the alga grew at temperatures between 5·0°C and 30·0°C with a maximal doubling rate of 1·67/day at 25·0°C. Light saturation at 25·0°C was 0·78 mW/cm² (11,750 lx) at 15‰. salinity. These values for optimal temperature and light saturation are similar to those obtained for other Chlorophycean algae.

The effect of salinity on growth rates has been studied primarily on marine Chrysophytes and seaweeds with few reports for green unicellular algae. Mychonastes ruminatus grew in salinities between 1·0 and 30·0‰.. Growth declined below 10·0‰. and above 20·0‰. and was nearly constant between these salinities. The mechanisms of salt tolerance in algal cells are discussed with special reference to the suitability of M. ruminatus to test the theory of an ATPase mediated K⁺ pump.