Phytoplankton ecology in the adjacent waters of the Daya Bay Nuclear Power Station in Guangdong in spring

The purpose of this study is to detail the ecological characteristics of phytoplankton in waters around the Daya Bay Nuclear Power Station in Guangdong (GNPS) (Fig. 1) in spring, the bloom period of algae. The collections with a small temporal scale of every three days were made during 30 cruises from March to May in 1987. Such an investigation has never been carried out before in China except that the seasonal distribution and composition of phytoplankton in these regions were reported in

Ecological provinces of spring phytoplankton in the Yellow Sea:species composition

Phytoplanktonic ecological provinces of the Yellow Sea（31.20°–39.23°N, 121.00°–125.16°E） is derived in terms of species composition and hydrological factors（temperature and salinity）. 173 samples were collected from 40 stations from April 28 to May 18, 2014, and a total of 185 phytoplanktonic algal species belonging to 81 genera of 7phyla were identified by Uterm？hl method. Phytoplankton abundance in surface waters is concentrated in the west coast of Korean Peninsula and Korea Bay, and communities in those areas are mainly composed of diatoms and cyanobacteria with dominant species of Cylindrotheca closterium, Synechocystis pevalekii, Chroomonas acuta,Paralia sulcata, Thalassiosira pacifica and Karenia mikimotoi, etc. The first ten dominant species of the investigation area are analyzed by multidimensional scaling（MDS） and cluster analysis, then the Yellow Sea is divided into five provinces from Province I（P-I） to Province V（P-V）. P-I includes the coastal areas near southern Liaodong Peninsula, with phytoplankton abundance of 35 420×10^3–36 163×10^3 cells/L and an average of 35 791×10~3 cells/L, and 99.84% of biomass is contributed by cyanobacteria. P-II is from Shandong Peninsula to Subei coastal area. Phytoplankton abundance is in a range of 2×10^3–48×10^3 cells/L with an average of 24×10^3cells/L, and 63.69% of biomass is contributed by diatoms. P-III represents the Changjiang（Yangtze River） Diluted Water. Phytoplankton abundance is 10×10^3–37×10^3 cells/L with an average of 24×10^3 cells/L, and 73.14% of biomass is contributed by diatoms. P-IV represents the area affected by the Yellow Sea Warm Current.Phytoplankton abundance ranges from 6×10^3 to 82×10^3 cells/L with an average of 28×10^3 cells/L, and 64.17% of biomass is contributed by diatoms. P-V represents the cold water mass of northern Yellow Sea. Phytoplankton abundance is in a range of 41×10^3–8 912×10^3 cells/L with an average of 1 763×10^3 cells/L, and 89.96% of biomass is contributed by diatoms. Overall, structures of phytoplankton community in spring are quite heterogeneous in different provinces. Canonical correspondence analysis（CCA） result illustrates the relationship between dominant species and environmental factors, and demonstrates that the main environmental factors that affect phytoplankton distribution are nitrate, temperature and salinity.

Vitamin B_(12)-auxotrophy in dinoflagellates caused by incomplete or absent cobalamin-independent methionine synthase genes(metE)

Dinoflagellates are responsible for most marine harmful algal blooms (HABs) and play vital roles in many ocean processes.More than 90% of dinoflagellates are vitamin B_(12) auxotrophs and that B_(12) availability can control dinoflagellate HABs,yet the genetic basis of B_(12) auxotrophy in dinoflagellates in the framework of the ecology of dinoflagellates and particularly HABs,which was the objective of this work.Here,we investigated the presence,phylogeny,and transcription of two methionine synthase genes(B_(12)-dependent metH and B_(12)-independent metE)via searching and assembling transcripts and genes from transcriptomic and genomic databases,cloning 38 cDNA isoforms of the two genes from 14 strains of dinoflagellates,measuring the expression at different scenarios of B_(12),and comprehensive phylogenetic analyses of more than 100 organisms.We found that 1)metH was present in all 58 dinoflagellates accessible and metE was present in 40 of 58 species,2)all metE genes lacked N-terminal domains,3)metE of dinoflagellates were phylogenetically distinct from other known metE genes,and 4)expression of metH in dinoflagellates was responsive to exogenous B_(12) levels while expression of metE was not responding as that of genuine metE genes.We conclude that most,hypothetically all,dinoflagellates have either non-functional metE genes lacking N-terminal domain for most species,or do not possess metE for other species,which provides the genetic basis for the widespread nature of B_(12) auxotrophy in dinoflagellates.The work elucidated a fundamental aspect of the nutritional ecology of dinoflagellates.