Who is the“murderer”of the bloom in coastal waters of Fujian,China,in 2019?

On May 24-29,2019,a bloom occurring in Pingtan coastal areas of Fujian Province caused mass mortality of cage-cultured fish(Plectorhinchus cinctus and Pagrosomus major).During the bloom,two major causative organisms were present:Prorocentrum donghaiense(at a concentration of 1.46×10^7 cells/L)and an unknown naked dinoflagellate(4.58×10^6 cells/L).The naked dinoflagellate was isolated and cultured in this study,and its morphological features were examined using light microscopy and scanning electron microscopy.The large subunit(LSU)of the rRNA gene and the internal transcribed spacer(ITS)region of the naked dinoflagellate were also sequenced for field bloom samples and lab culture strains(PT-A and PT-B).On the basis of its morphological characteristics and molecular sequences,the unknown naked dinoflagellate was identified as Karlodinium digitatum.According to the phylogenetic analysis,the Karl.digitatum was most closely related to Karlodinium australe and Karlodinium armiger,and the three species clustered into a single clade of Karlodinium with bootstrap/posterior probability values of 95%/0.99 and 86%/0.99 inferred from LSU and ITS sequences,respectively.Karl.digitatum was first reported as Karenia digitata,a new harmful algal species bloomed in Hong Kong,China,in 1998.In present study,we gave a detailed morphological and phylogenetic description of Karl.digitatum and submitted the molecular sequences of this species to GenBank for the first time.

Analysis of grey model between seawater environmentalessential factors and phytoplankon dynamics in the Dapeng Bay, the South China Sea

The relation between the dynamics of phytoplankton and essential environmental factors of seawater has been studied. According to the comparison between environmental factors of seawater. and on the basis of mathematical space theory and the four principles of normalization, even symmetry, globality and proximity, smoothing discrete function, the grey derivative and the grey differential equation have been defined, the grey models and relation to the factors (the seawater physical and chemical factors) were estimated. The calculation results indicate that zooplankton,Mn, Fe and dissolved oxygen are the moot important factors.