Taxonomy and effect of temperature, nutrients and light intensity on the growth of two freshwater algal species of Raphidophyceae new to Korea

The present study was conducted to understand the taxonomy and effect of environmental factors on the growth of two freshwater algal Raphidophyceae (Gonyostomum depressum and G. semen) that are newto Korea. Samples used in the culture experiments were isolated from two small ponds in Jeju Island and Kyungpook province of Korea. Species identification was based on morphology and nuclear internal transcribed spacer (ITS) sequences of rDNA. The growth characteristics of these species through the effect of temperature, nitrate concentration and light intensity wereinvestigated. These two species have different cell shape, size and caudus morphology. The nuclear ITS rDNA sequences of specimens had 99% identitywith G. depressum and G. semen recorded at GenBank. Gonyostomum depressum had the highest growth rate at 21°C, nitrate concentration of 1,000 mgr;M, and light intensity of 120 μmol photons mV. G. semen showed the highest growth rate at 21°C, 120 pmol photons m-2 s-1 and nitrate concentration of 100 μM, respectively. Water temperature seems to be important in controlling the distribution and growth of G. depressum and G. semen.