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

Aim: 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 new to Korea. o Methodology: 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 trans cribeds pacer (ITS) sequences of rDNA. The growth characteristics of these species through the effect of temperature, nitrate concentration and light intensity were investigated. Results: These two species have different cell shape, size and caudus morphology. The nuclear ITS rDNA sequences of specimens had 99% identity with G. depressum and G. semen recorded at Gen Bank. Gonyostomum depressum had the highest growth rate at 21C, nitrate concentration of 1,000 μM, and light intensity of 120 μmol photons m^-2s^-1. G. semen showed the highest growth rate at 21ºC, 120 μmol photons m^-2 s^-1 and nitrate concentration of 100 μM, respectively. Interpretation: Water temperature seems to be important in controlling the distribution and growth of G. depressum and G. semen.