Spatial and seasonal distributions of the phototrophic dinoflagellate Biecheleriopsis adriatica (Suessiaceae) in Korea

Abstract

The phototrophic dinoflagellate Biecheleriopsis adriatica is a small suessioid species characterized by a fragile thinwall. Although the morphology of this dinoflagellate is well established, there is currently little information availableon its distribution and the environmental factors that influence this distribution. Thus, to investigate the spatial andseasonal distributions of the vegetative cells of B. adriatica in Korean waters, surface water samples were collected on aseasonal basis from 28 stations in the East, West, and South Sea of Korea and Jeju Island from April 2015 to October 2018,and abundances of the vegetative cells of B. adriatica were quantified using quantitative real-time polymerase chainreactions, for which we developed the species-specific primer and probe set. Simultaneously, major environmentalparameters, including temperature, salinity, nutrient concentrations, and dissolved oxygen concentrations were measured. The vegetative cells of B. adriatica were detected at 20 of the 28 sampling stations: 19 stations in summer and 6 inautumn, although from no stations in either spring or winter. The ranges of water temperature and salinity at sites wherethis species was detected were 17.7-26.4°C and 9.9-34.3, respectively, whereas those of nitrate and phosphate concentrationswere not detectable-96.2 and 0.18-2.66 μM, respectively. Thus, the sites at which this species is found are characterizedby a narrow range of temperature, but wide ranges of salinity and concentrations of nitrate and phosphate. Thehighest abundance of the vegetative cells of B. adriatica was 41.7 cells mL-1, which was recorded in Jinhae Bay in July2018. In Jinhae Bay, the abundance of vegetative cells was significantly positively correlated with the concentration ofnitrate, but was negatively correlated with salinity. On the basis of these findings, it appears that the abundance of B. adriatica vegetative cells shows strong seasonality, and in Jinhae Bay, could be affected by the concentrations of nitrate.