Succession phenomenon of two dinoflagellates Cochlodinium polykrikoides and Alexandrium affine in the southern sea of Korea in summer of 2017

Abstract

We investigated the succession patterns of both HAB species in the southern sea of Korea and performed a bioassay using C. polykrikoides and A. affine to evaluate their competitive relationship. From June to August, the surface water temperature increased from 17.4°C to 27.9°C, the salinity decreased from 34.2 to 30.8. C. polykrikoides dominated in July however, A. affine reached bloom levels in August. The growth experiments were carried out at six water temperature (15,20, 22.5, 25, 27.5 and 30°C) and six salinity (20, 24, 26, 28, 30 and 32) levels. At 25°C, the maximum growth rate for C. polykrikoides (0.31 day-1) was measured at a salinity of 32, and for A. affine (0.43 day-1) at a salinity of 30. C. polykrikoides cells died within 2 days at 30°C, while A. affine maintained high growth rates (0.35