Species Diversity Of Phytoplankton In Yellow Sea And Bohai Sea And Molecular Identification Of Microalgal Isolates

Yellow Sea and Bohai Sea are superior in natural conditions and complex inecological environments. Numerous fish grounds and aquaulturing areas of Chinalocate at these two seas. They are also important sources of energy producingmicroalgae; they are very rich in phytoplanktonic diversity. In combination with two(summer and winter) multidisciplinary oceanographic surveying cruises, the speciesdiversities of phytoplankton in Yellow Sea and Bohai Sea were determined usingnet-collected seawater samples; and pure microalgal isolates were obtained andidentified with molecular method. The results will facilitate the exploitation ofmicroalgal resources of Chinese coastal seawaters.The major findings included:(1) A total of44species in30genera,4phyla were identified in fixed summersamples. The abundance of these species ranged from0.71×10~2to83.79×10~4cells/Lwith an everage3.81×10~4cells/L. In fixed winter samples, a total of55species in30genera,4phyla were identified. The abundance of the identified species variedbetween1.25×10~2and47.54×10~4cells/L with an average3.46×10~4cells/L. Diatomand dinoflagellate were found to be dominants in both summer and winter seawaters.The identified species can be divided into either low temperature and low salinity, lowtemperature and high salinity, high temperature and low salinity preferring, hightemperature and high salinity and eurysalinity and eurythermy ecological types, orcoastal, offshore and estuarial types. Coscinodiscus sp. and Paralia sulcatadominanted both summer and winter seawaters.(2) From summer seawater, at least160microalgal species were isolated andpurified with macromanipulation, streak plating and serial dilution approaches incombination. In comparison with the identified in fixed samples, the isolates were usually smaller. Paralia sulcata and Skeletonema costatum were two species whichwere both identified in fixed sample and isolated from seawater.(3) The microalgal isolated were further identified with molecular methods with15of them assigned to phyla bigyra and chlorophyta, respectively. It was found thatstrain74belonged to phylum chlorophyta, class prasinophyceae, orderpseudoscourifeldials and family pycnococcaceae; it claded with Pseudoscourfieldiamaria, Pycnococcus provasolii, and Pycnococcus sp.; strains118,119and136belonged to phylum chlorophyta, class chlorophyta, order chlorellales, familychlorellaceae and genus nannochloris; they clustered with Nannochloris maculata;and strain49belonged to phylum bigyra, class bicosea, order bicosecida, familycafeteriacea and gunus pseudobodo; it merged with Pseudobodo tremulans as a clade.Strain86was Caetiellus parvulus DQ230538which belongs to class bicosea, orderbicosecida, family siluaniaceae and genus caetiellus. Strains30and34were Cafeteriaroenbergensis; they showed a similarity of100%in their maker sequences with thatof known Cafeteria roenbergensis AY827849in phylum bigyra, class bicosea, orderbicosecida, family cafeteriaceae and genus caetiellus. Among the isolates,Pseudobodo tremulans was found previously in the costal seawater of Australian,Denmark, Canada, Brazil, British and Sweden. It was isolated for the first time fromChinese coastal seawater in this study.