Which is the real resting cyst of Cochlodinium polykrikoides Margalef (Gymnodiniales, Dinophyceae)?

Abstract

The ichthyotoxic dinoflagellate Cochlodinium polykrikoides Margalef is the most notorious causative species of dense blooms that have occurred annually in Korean coastal waters. These dense blooms have caused major economic losses to the aquaculture industry: USD $7 million in 1993, USD $60 million in 1995 and USD $4-19 million in 2000-2003, 2007 and 2012 (NFRDI, 2012). For this reason, intensive research projects funded by the Korean government were initiated to clarify the mechanisms behind the outbreak of C. polykrikoides blooms. However, most of these research projects have concentrated exclusively on understanding the introduction and origin of vegetative cells of C. polykrikoides. This is because Matsuoka et al. (2010) reported that the outbreaks of dense blooms in Asian coastal areas, such as in Korea and Japan, might be related to the transportation of vegetative cells of C. polykrikoides by the Tsushima Warm Current, and the researchers suspected that the resting cysts of C. polykrikoides are present in natural sediments, despite the fact that the production of resting cysts by C. polykrikoides has been confirmed by laboratory experiments. This study first provides the morphological features of resting cyst of Cochlodinium polykrikoides collected from natural sediments in Tongyeong coastal area, Korea. The evidence for resting cyst of C. polykrikoides is provided using the morphological and phylogenetic datauaculture industry: USD $7 million in 1993, USD $60 million in 1995 and USD $4-19 million in 2000-2003, 2007 and 2012 (NFRDI, 2012). For this reason, intensive research projects funded by the Korean government were initiated to clarify the mechanisms behind the outbreak of C. polykrikoides blooms. However, most of these research projects have concentrated exclusively on understanding the introduction and origin of vegetative cells of C. polykrikoides. This is because Matsuoka et al. (2010) reported that the outbreaks of dense blooms in Asian coastal areas, such as in Korea and Japan, might be related to the transportation of vegetative cells of C. polykrikoides by the Tsushima Warm Current, and the researchers suspected that the resting cysts of C. polykrikoides are present in natural sediments, despite the fact that the production of resting cysts by C. polykrikoides has been confirmed by laboratory experiments. This study first provides the morphological features of resting cyst of Cochlodinium polykrikoides collected from natural sediments in Tongyeong coastal area, Korea. The evidence for resting cyst of C. polykrikoides is provided using the morphological and phylogenetic data