Gonyaulax species (Dinophyceae) from Korean coastal waters: Morphology, phylogeny, and effects of temperature and salinity on growth

Abstract

The genus Gonyaulax Diesing was established with Gonyaulax spinifera (Claparède ＆ J. Lachmann) Diesing as the type species. Since the first description, more than 120 species have been described however many species in the genus have been transferred to other genera. Gonyaulx species have been widely examined, because some Gonyaulax species form dense blooms or red tide patches that can cause large-scale fish mortality, and are well known as the yessotoxin producer. However, in Korean coastal waters, little is known about the morphological and phylogenetic characterization on Gonyaulax species, and the relationship between environmental conditions and their growth in Korean coastal waters. Four Gonyaulax species isolated from Korean coastal waters and the East China Sea were examined using light and scanning electron microscope and their rDNA (SSU, ITS and LSU) were sequenced. In addition, the effects of temperature and salinity on growth of the isolates of Gonyaulax species were investigated, based on the laboratory experiments. Morphological and phylogenetic data revealed that the isolates of Gonyaulax species belong to G. digitalis, G. membranacea, and two ribotypes of G. polygramma, respectively. Maximum growth rates of these species were observed in temperatures of 20-25 ℃ and in salinity of 25-35, which ranged from 0.17 to 0.42 day-1. G. digitalis and G. membranacea could grow at low temperatures of 10 and 15 ℃, and G. polygramma grew in a wide range of temperature (15-30℃) however there were significant differences between growth characterizations of two ribotypes of G. polygramma. These findings can be useful for better understanding classification of species in seasonal occurrence of genus Gonyaulax.