Ichthyotoxic Cochlodinium polykrikoides red tides offshore in the South Sea, Korea in 2014: I. Temporal variations in three-dimensional distributions of red-tide organisms and environmental factors

Abstract

The ichthyotoxic Cochlodinium polykrikoides red tides have caused great economic losses in the aquaculture industry in the waters of Korea and other countries. Predicting outbreak of C. polykrikoides red tides 1-2 weeks in advance is a critical step in minimizing losses. In the South Sea of Korea, large C. polykrikoides red tide patches have often been recorded offshore and transported to nearshore waters. To explore the processes of offshore C. polykrikoides red tides, temporal variations in 3-dimensional (3-D) distributions of red tide organisms and environmental parameters were investigated by analyzing 4,432 water samples collected from 2-5 depths of 60 stations in the South Sea, Korea 16 times from May to Nov, 2014. In the study area, the vegetative cells of C. polykrikoides were found as early as May 7, but C. polykrikoides red tide patches were observed from Aug 21 until Oct 9. Cochlodinium red tides occurred in both inner and outer stations. Prior to the occurrence of large C. polykrikoides red tides, the phototrophic dinoflagellates Prorocentrum donghaiense (Jun 12 to Jul 11), Ceratium furca (Jul 11 to Aug 21), and Alexandrium fraterculus (Aug 21) formed red tides in sequence, and diatom red tides formed 2-3 times without a certain distinct pattern. The temperature for the optimal growth of these four red tide dinoflagellates is known to be similar. Thus, the sequence of the maximum growth rates of P. donghaiense > C. furca > A. fraterculus > C. polykrikoides may be partially responsible for this sequence of red tides in the inner stations following high nutrients input in the surface waters because of heavy rains. Furthermore, Cochlodinium red tides formed and persisted at the outer stations when NO 3 concentrations of the surface waters were <2 µM and thermocline depths were >20 m with the retreat of deep cold waters, and the abundance of the competing red-tide species was relatively low. The sequence of the maximum swimming speeds and thus potential reachable depths of C. polykrikoides > A. fraterculus

Mapping distribution of cysts of recent dinoflagellate and Cochlodinium polykrikoides using next-generation sequencing and morphological approaches in South Sea, Korea

“… 30 and Jeong et al . 33 emphasised that C. polykrikoides blooms developed after accumulation of cysts transported from other places. In particular, Lee et al .…”

Interactions between the Newly Described Small‐ and Fast‐Swimming Mixotrophic Dinoflagellate Yihiella yeosuensis and Common Heterotrophic Protists

“…; Jeong et al. ; Park et al. ; Shumway ; Turner and Anderson ), they have a very large genomic DNA and a large number of genes (e.g.…”

Synergistic Effect of Multi-Sensor Data on the Detection of Margalefidinium polykrikoides in the South Sea of Korea

“…Offshore waters has clear characteristic (Case-1 waters) due to the Kuroshio Current, but exhibits complex water characteristic in that the contents of SPM and CDOM increase toward coastal areas [16]. The depth range was 8-25 m in coastal areas and 27-54 m in offshore areas [7]. M. polykrikoides blooms occurred quite frequently in the study area.…”

“…M. polykrikoides is a relatively slow growing red tide organism. Therefore, it may not be able to outgrow red tide diatoms, flagellates, and other dinoflagellates under the same environmental conditions [7]. However, M. polykrikoides has the ability to swim fast and can theoretically reach 50 m in depth.…”

“…This species first bloomed in the South Sea of Korea (SSK) and has expanded to the West Sea (Yellow Sea) and East Sea (Sea of Japan) [6]. In the SSK, large-scale M. polykrikoides blooms that form offshore are often transported to coastal waters and gradually accumulate there [7]. This movement is caused by physical factors such as tidal currents, typhoons, wind, and the biological characteristics of red tide species.…”