Red tide refers to when seawater is discolored red due to a mass bloom of phytoplankton – mainly cyanobacteria, diatoms, and dinoflagel- lates – in the ocean. Depending on the species of plankton, the color of the water can show tinges of yellowish brown, yellow, or grass green. Red tides cause great damage to marine ecosystems as they cause mass kills of coastal sh species all across the globe.
While diatoms were widely responsible for red tides along the Korean southern coast in the early 1990s, Cochlodinium polykrikoides (a species of dino agellates) has primarily been the cause since 1995. Red tides from Cochlodinium polykrikoides blooms occur in the clear waters between Narodo and Namhaedo and spread throughout the South Sea of Korea. In some years, they spread to the west coast and the East Sea as well.