Effect of Light and Temperature Interactions on Growth Ofcryptomonas Erosa(cryptophyceae)1

Cryptomonas erosaSkuja, a planktonic alga, was grown in batch culture at different combinations of light intensity and temperature, under nutrient saturation. Growth was maximal (1.2 divisions · day−1) at 23.5 C and 0.043 ly · min−1, declining sharply with temperature (0.025 divisions‐day−1at 1 C). With decreasing temperature, the cells showed both light saturation and inhibition at much reduced light intensities. At the same time the compensation light intensity for growth declined towards a minimum of slightly above 0.4 × 10−4ly · min−1(~1 ft‐c) at 1 C or <0.1 ly · day−1(PAR). Cell division was more adversely affected by low temperature than carbon uptake, and the resulting excess production of photosynthate was both stored and excreted. Extreme storage of carbohydrates resulted in cell volumes and carbon content ca. 22 and 30 × greater, respectively, than the maxima observed for cells incubated in the dark, whereas, at growth inhibitory light levels, as much as 57% of the total assimilated carbon was excreted. A marked increase in cell pigment was observed at the lowest light levels (<10−3ly · min−1), at high temperature. The growth response ofC. erosain culture provides insight into the abundance and distribution of cryptomonads and other small algal flagellates in nature.