Differential effects of typhoons on ichthyotoxic Cochlodinium polykrikoides red tides in the South Sea of Korea during 2012–2014

Abstract

The harmful dinoflagellate Cochlodinium polykrikoides is known to cause fish death by gill-clogging when its abundance exceeds approximately 1000 cellsml−1. Thus, red tides of this dinoflagellate have caused considerable loss in the aquaculture industry worldwide. Typhoons carrying strong winds and heavy rains may alter the process of red tide events. To investigate the effects of typhoons on C. polykrikoides red tides, daily variations in the abundance of C. polykrikoides, and wind speeds in three study areas in the South Sea of Korea were analyzed during the periods of C. polykrikoides red tides and the passage of 14 typhoons during 2012–2014. The typhoons differentially affected Cochlodinium red tides during the study period, and the daily maximum wind speed generated by the typhoon was critical. Four typhoons with daily maximum wind speeds of >14ms−1 eliminated Cochlodinium red tides, while three typhoons with daily maximum wind speed of 5–14ms−1 only lowered the abundance. However, other typhoons with daily maximum wind speeds of <5ms−1 had no marked effect on the Cochlodinium abundance. Therefore, typhoons may sometimes eliminate C. polykrikoides red tide events, or reduce cell abundances to a level that is not harmful to caged fish cultivated in aquaculture industries. Thus, typhoons should be considered when compiling red tide dynamics and fish-kill models.