한국연안에서 분리한 와편모류 Alexandrium affine의 물리화학적 환경요인에 대한 생장반응 연구

Abstract

Physiological experiments on physicochemical factors were conducted to identify physiological characteristic of Alexnadrium affine. The effects of temperature, salinity and irradiance on the growth of dinoflagellate Alexandrium affine isolated from South Sea, Korea were examined in the laboratory. Growth was examined under the following combinations of temperature and salinity: 10, 15, 20, 25 and 30℃, and 10, 15, 20, 25, 30 and 35 psu. No growth was observed with a temperature of 10℃ and a salinity of 10 psu. The maximum growth rate, 0.69 day-1, was obtained at 25℃ and 25 psu. The optimum growth range (≥80% of maximum specific growth rate) of A. affine was 20 ∼ 25℃ in temperature and 20 ∼ 35 psu in salinity. This result indicated that A. affine is euryhaline organism. In light experiments, cell growth of A. affine was conducted with constant temperature (25℃) and salinity (25 psu) under light photon flux densities (PFD) of 10, 20, 50, 75, 100, 150, 200 and 300 μmol m-2 s-1. A. affine was did not growth at irradiance ≤ 10 μmol m-2 s-1. Photoinhibition did not occur at 300 μmol m-2 s-1, which was the maximum irradiance used in this study. The irradiance-growth curve was described as μ = 0.75·(I+4.25)/(I-65.5) at 25℃ and 25 psu. The half-saturation photon flux density(PFD) (KS) was 57.0 and compensation PFD (IC) was 4.25 μmol m-2 s-1. The result of the present study indicate that A. affine has advantage physiological characteristic to the interspecific competition at the embayment and costal areas of South Sea, Korea in summer. Nutrient ability was examined under the following concentration of nitrate and phosphate: 1, 3, 5, 10, 30, 50, 80 μM, and 0.1, 0.3, 0.5, 0.8, 1, 2, 3 μM. The results of Nutrient ability experiments based on batch culture showed that the half saturation constant (Ks) of A. affine on nitrate (NO3-) and phosphate (PO42-) were 17.6 ∼ 22.0 μM and 3.88 ∼ 4.12 μM, respectively. These Ks values are higher than those reported for diatoms and other flagellates. Although the maximum specific growth rate (μmax) of A. affine was lower than diatoms, it was higher than those of other flagellates. Therefore, our results indicate that the DIP and DIN level in the study area was too low to support A. affine blooms. Thus, A. affine is a poor competitor in terms of inorganic nutrient use and is unlikely to form blooms in Tongyeong Bay. However, A. affine were able to grow using dissolved organic nutrient compounds such as urea and glycerol phosphate as well as dissolved inorganic nutrient. As a result of this experiment, the physiological characteristic of A. affine is euryhaline, and it is possible to grow at high water temperature and low light intensity. This species might be able to grow using DOM. These physiological characteristics would have been beneficial in competing with other species in the environment of high temperature, high salinity and low nutrient environment in the Tongyeong region.