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This study provides the first morphological features of resting cysts of Cochlodinium polykrikoides collected from Korean coastal sediments. Evidence for the existence of resting cysts of C. polykrikoides is based on the morphological and molecular phylogenetic data of the germinated cells and a resting cyst. The morphology of the resting cysts differed from that reported previously in sediments and culture experiments. The distinct feature is that the cyst body was covered by the reticulate ornaments and spines. [ABSTRACT FROM AUTHOR]

Abstract: To investigate dinoflagellate cysts as indicators of salinity or eutrophication and to document the historical occurrence of ellipsoidal Alexandrium cysts in the Korean coastal areas, we studied a sediment core from Yeoja Bay. The analyzed dinoflagellate cysts include over 30 taxa commonly reported from other temperate regions. Cluster analysis based on dinoflagellate cyst assemblages indicated two main time intervals: from the mid-1990s to 2006 (Zone II) and from the early 1900s to early 1990s (Zone I). The total cyst concentration increased sharply in Zone II, to reach approximately five times the level in Zone I. The salinity in Yeoja Bay increased after 1995 (from 28 to 31psu), possibly due to a stronger intrusion of the Tsushima Warm Current. The increase in salinity coincided with increases in the abundance of Brigantedinium spp. and Selenopemphix nephroides. In addition, ellipsoidal Alexandrium cysts have occurred since the 1980s and increased in abundance since the mid-1990s, when a paralytic shellfish poisoning outbreak and increases in ellipsoidal Alexandrium cysts were recorded in several Korean and Japanese coastal areas. This suggests that ellipsoidal Alexandrium cysts may have been carried to the Korean coast, including Yeoja Bay, by the current system, possibly the Tsushima Warm Current, and that the current system may influence the growth of Alexandrium cysts. [ABSTRACT FROM AUTHOR]

Abstract: An unarmored dinoflagellate Cochlodinium polykrikoides has formed red tides responsible for fish mass mortalities especially in coastal areas of western Japan and southern Korea almost every summer to autumn. In laboratory culture, the optimum temperature for growth of the species is ca. 27°C. Since the species cannot survive in water of temperatures of less than 10°C, it was considered to over-winter in some certain regions as a motile form or resting cyst, and expand its distribution after the temperature increases to a level tolerable for growth. To determine the over-wintering regions and migration pattern of C. polykrikoides, occurrences of the motile cells were surveyed in the coastal and offshore areas of western Kyushu, Japan and south coast of the Korean Peninsula from April 2006 to August 2008. Cells of C. polykrikoides were found at 14 sites during the investigated period. Motile cells occurred throughout the year in Usuka Bay, Hirado of West Japan. From offshore regions of the Goto Islands and off Shin-Nagasaki Fishing Port, motile cells of C. polykrikoides were first detected from late May, and continuously occurred until February in Nama Bay of the Kami-Goto Islands. This first appearance was before red tides of C. polykrikoides reported at coastal areas in western Kyushu. In Korea, this species was first observed in May and disappeared after October in 2007. These occurrence patterns imply that Usuka Bay in Hirado is one of the over-wintering regions in western Kyushu, and also this species is possibly transported into the northern part of the East China Sea by the Tsushima Warm Current every year. [ABSTRACT FROM AUTHOR]

Abstract: Dinoflagellate cysts acquired from sediment cores were analyzed in order to reconstruct historical nutrient levels in Gamak Bay, Korea and Ariake Bay, Japan. Dinoflagellate cyst assemblages in Gamak Bay were characterized by high proportions of heterotrophic cysts such as Brigantedinium spp., Protoperidinium americanum and Polykrikos cysts, which suggested that nutrients levels may have already been high before 1970s, and then increased further to the hypertrophic conditions of the 1990s. In contrast, dinoflagellate cyst assemblages in Ariake Bay were characterized by high relative abundances of Lingulodinium machaerophorum and Spiniferites spp., which suggested that nutrient levels in Ariake Bay had increased gradually since the mid 1960s, and may have been significantly enhanced by the mid 1980s. Dinoflagellate cyst assemblages reflecting environmental changes in the two bays are contrasting, perhaps due to different nutrient enrichment mechanisms. This suggests that the indicators of nutrient levels encoded in dinoflagellate cyst assemblages may exhibit site-specific information. [ABSTRACT FROM AUTHOR]