Taxonomy and Physiology of Oxyrrhis marina and Oxyrrhis maritima in Korean Waters

Abstract

The genus Oxyrrhis is a heterotrophic dinoflagellate found in diverse marine environments. Oxyrrhis spp. have received attention owing to their ecological and industrial importance, high lipid contents, and docosahexaenoic acid formation. To the best of our knowledge, contrary to O. marina, ecophysiological characterization studies on O. maritima have not yet been reported. Therefore, we investigated the taxonomy and ecophysiology of four strains of O. marina from coastal waters and two strains of O. maritima from the littoral tidepool waters of Korea. Based on phylogenetic trees constructed using internal transcribed spacer ribosomal DNA (ITS rDNA) and SSU rDNA of dinoflagellates, the clade of all four O. marina strains was divergent from that of the two O. maritima strains. We measured the growth rates of both species at various water temperatures (10–36 °C), salinities (5–90), and light intensities (0–100 µE·m−2·s−1). The lowest (O. marina and O. maritima: 10 °C) and highest temperatures (O. marina: <35 °C, O. maritima: >35 °C) revealed that O. maritima has more tolerance to high salinity. This study provides a basis for understanding the ecophysiology of O. marina and O. maritima and their population dynamics in marine ecosystems.