Phylogenetic diversity of dinoflagellates in polar regions

Because of the limitations of sampling and seasonal study in polar regions, knowledge of dinoflagellate diversity, distribution and ecology are limited. Dinoflagellates have been incidentally reported from polar regions during some seasons and some populations have been reported as components of microalgae. Surveys of molecular diversity link the genotype of dinoflagellates from polar regions with environmental adaptation. In this study, 37 positive clones of dinoflagellates collected from different sites were used for genotype analysis, providing new insights into the biodiversity and distribution of these species based on 18S rRNA sequencing. Diverse genotypes were recorded for the summer season in Kongsfjorden （high Arctic） whilst a single novel genotype of dinoflagellate was recorded from winter samples from the Antarctic Ocean. Data from ice cores suggests that this single dinoflagellate genotype was adapted to extreme cold and clone library screening found that it was occasionally the only microbial eukaryotic genotype found in winter ice cores. The findings of this study could improve our understanding of the diverse dinoflagellate genotypes occurring in these perennially cold microbial ecosystems.

Co-monitoring bacterial and dinoflagellates communities by denaturing gradient gel electrophoresis (DGGE) and SSU rRNA sequencing during a dinoflagellates bloom

Dinoflagellates are unicellular eukaryotic protists that dominate in all coastal waters, and are also present in oceanic waters. Despite the central importance of dinoflagellates in global primary production, the relationship between dinoflagellates and bacteria are still poorly understood. In order to understand the ecological interaction between bacterial and dinoflagellates communities, denaturing gradient gel electrophoresis (DGGE) and SSU rRNA sequencing were applied to monitoring the population dynamics of bacteria and dinoflagellates from the onset to disappearance of a dinoflagellates bloom occurred in Baltimore Inner Harbor, from April 15 to 24,2002. Although Prorocentrum minimum was the major bloom forming species under the light microscopy, DGGE method with dinoflagellate specific primers demonstrated that Prorocentrum micans, Gymnodinium galatheanum and Gyrodinium uncatenum were also present during the bloom. Population shifts among the minor dinoflagellate groups were observed. DGGE of PCR-amplified 16S rRNA gene fragments indicated that cyanobacteria, α, β, γ-proteobacteria, Flavobacterium Bacteroides-Cytophaga (FBC), and Planctomcetes were the major components of bacterial assemblages during the bloom. DGGE analysis showed that Cytophagales and α-proteobacteria played important roles at different stages of dinoflagellates bloom. DGGE can be used as a rapid tool to simultaneously monitor population dynamics of both bacterial and dinoflagellates communities in aquatic environments, which is demonstrated here.

Biodiversity and distribution of benthic dinoflagellates in tropical Zhongsha Islands,South China Sea

Benthic dinoflagellates have attracted increasing attention in recent years because of their toxicity and ability to form extensive harmful algal blooms.Ostreopsis producing palytoxin and its analogs,Gambierdiscus producing ciguatera toxins,and Prorocentrum producing okadaic acid and dinophysis toxins,have been concerned as serious human poisonings.We explored the benthic dinoflagellate biodiversity and distribution characteristics of a series of tropical reefs in 20-40-m water depth in wet season in the Zhongsha Islands in South China Sea using morphological,phylogenetic,and cell counting methods.Results show that benthic dinoflagellates in the islands are rich in biodiversity and 15 species from genera Amphidinium,Coolia,Ostreopsis,and Prorocentrum were identifi ed:Amphidinium carterae,A.magnum,A.massartii,A.operculatum,Coolia canariensis,C.malayensis,C.palmyrensis,C.tropicalis,Ostreopsis cf.ovata,Prorocentrum concavum,P.cf.sculptile,P.emarginatum,P.hof fmannianum,P.lima,and P.rhathymum.Among them,A.magnum is reported for the first time in Chinese waters.The abundance of benthic dinoflagellates was relatively low at 88-4345 cells/100 cm^(2) on sediment and 10-91 cells/g on macroalgae.Prorocentrum and Amphidinium were the dominant and subdominant genera,respectively.It is speculated that the low abundance of benthic dinoflagellates is closely related to the scarcity of macroalgae and stronger water motion at the depth>15 m in Zhongsha Islands.This study expanded the study in biodiversity of benthic dinoflagellates in Chinese waters,and revealed the distribution characteristics of harmful benthic microalgae in reef habitats.

Distribution of indicator dinoflagellates in the East China Sea

-The material discussed in this paper is from four cruises which were carried out in May -June, 1986 (spring), July -August, 1987(summer) .October -November, 1988(autumn)and December, 1987(winter)respectively. Identified dinoflagellates were 141 species (including varieties and forms) belonging to 18 genera.According to the distribution and ecological characteristics of dinoflagellates species, we can divide them into three groups: 1) Hyporhaline-neritic group: they are distributed only in type Ⅲ and typeⅣ water and they perform an evident function indicating continental coast water; 2) Eurythermic-euryhaline group represented by Protoperidinium depressum, Gentium fusus, etc. They are fond of perching in mixing water which character is similar to that of coast water even though they are distributed in different water systems; 3) Hyperthermic-hyperhaline group: on the basis of varying degrees to which they tolerate temperature and salinity, we can divide them into two sub-groups: euryhyperthermic-euryhyperha-line subgroup and stenohyperthermic- stenohyperhaline subgroup. The first subgroup is represented by Pyrocystis pseudoxoctiluca whose adaptability reaction occurred with the changing of hydrographic environment. The second subgroup is tropic oceanic species which can serve as a good indicator for Kuroshio in the East China Sea. Its biological boundary coincides well with the hydrographic boundary of Kuroshio water.

Molecular Assessment of Athecate Dinoflagellates of the Order Gymnodiniales (Dinophyceae) in Todos Santos Bay, Baja California México

The Gymnodiniales are the most important group of athecate dinoflagellates both for its abundance and distribution and for the harmful potential of several of its species. Although morphologically it is well known, phylogenetically it has been very little studied. HABs impact important coastal activities in Todos Santos Bay, so a detailed characterization of potentially toxic phytoplankton species is crucial in monitoring surveys. Therefore, the aim of the present study was to carry out a molecular assessment to the morphospecies of Gymnodiniales currently recorded in Todos Santos Bay, from which discussed their phylogenetic relationships. 120 samples were obtained from monthly samplings during 2019 to 2020. For all of them, 18 s small subunit (SSU) and 28 s large subunit (LSU) genes of rDNA were amplified and sequenced using single-cell PCR. Also, they were photographed. A phylogenetic analysis was performed on MrBayes from the combined 18 s - 28 s data set. The presence of 15 phylogenetic entities was confirmed, four of which constituted new records for the Mexican Pacific, as well as three harmful species, one toxic and two bloom-forming. Our molecular results evidenced the need to re-evaluate the current taxonomic system of athecate dinoflagellates at all hierarchical levels, integrating them with morphological evidence without preponderance of this criterion over taxonomic decisions.

Spatio-temporal Variability of Dinoflagellates in Different Salinity Regimes in the Coast of Rakhine

Regarding the spatial and seasonal variations of dinoflagellates in different salinities regimes,Prorocentrum rostratum showed a strong correlation with high salinity(≥29 ppt.).However,P.micans had a negative correlation with salinity.In Dinophysoids,Dinophysis caudata showed a wide salinity tolerance than other species in the group.D.miles,Ornithocercus magnificus,O.steinii,and O.thumii showed a strong correlation with salinity.In Gonyaulacoids,Ceratium furca,C.fusus,C.horridum,C.trichoceros,C.tripos,Gonyaulax polygramma,G.spinifera,and Pyrophacus magnificus showed a strong correlation with salinity.In Peridinoids,Protoperidinium depressum,P.oblongum,P.oceanicum,P.pyreforme,and Podolampus palmipes showed a strong correlation with salinity.In Gymnodinoid and Noctilucoid,Gyrodinium estuariale and N.scintillans showed a strong correlation with salinity.

Preliminary Palynostratigraphic Data on the Middle Albian-Lower Cenomanian of the Tarfaya Basin, Southwest Morocco

The Tarfaya-Laayoune-Boujdour basin is of great interest to oil exploration;on this aspect, there has been exploration by the Moroccan National Office of Hydrocarbons and Mining, which has shown indices of oil and/or gas recorded in most wells drilled in the Moroccan Atlantic margin. FD-1 well, object of this study, is one of these wells located in the offshore Tarfaya-Laayoune-Boujdour basin. A palynological examination of the processed samples revealed the existence of organic palynomorphs, well conserved and rich in dinoflagellate cysts. The latter are composed of worldwide marker taxa of high stratigraphic resolutions. Thus, the middle upper Albian (3408 - 3408.5 m) is determined by the presence of Cribroperidinium tensiftense, Tehamadinium coummia, Spiniferella cornuta, Chichaouadinium vestitum, Dinopterygium alatum and Litosphaeridium arundum. The upper Albian (3406.5 - 3408 m) is characterized by the FOs of marker taxa: Cyclonephelium chabaca, Cribroperidinium auctificum and Chichaouadinium vestitum. Lastly, the upper Albian-lower Cenomanian transition is defined between 3404 m and 3406.50 m, as suggested by the FOs of Chichaouadinium boydii, Dinopterygium tuberculatum, Sepispinula ancorifera, Litosphaeridium conispinum, Prolixosphaeridium conulum and Xenascus ceratioides.

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.

Species composition and abundance of dinoflagellates from the coastal waters of Pakistan

Objective:To assess the community structure,seasonal dynamics of dinoflagellates population with environmental conditions in the nutrient-rich and polluted coastal waters off,Karachi.Methods:Sampling sites were located from Karachi harbour(Station A)and Mouth of Manora Channel(Station B).Total 180 replicate samples were collected at 1-m depth through Niskin bottle sampler(1.7 L)and fixed with 2%lugol’s preservative then examined under light inverted microscopy,scanning electron and epiflourescence microscope.Results:The environmental conditions,such as temperature[(20-27)°C],salinity[(35-40)psu],chlorophyll a[(1-103)μg/L],pH(6.03-8.13)and dissolve oxygen[(0.7-5.5)mg/L]were recorded from both stations.A total of 96 species were identified into potential harmful toxic/non-toxic bloom forming species and cysts producer.Total dinoflagellate cells between two coastal sites were much concentrated at the adjacent area of mouth of Manora Channel compare to harbor site.The dinoflagellate cell concentration ranging from 20 to~55000 cells/L and the maximum values observed in two season,(~55000 cells/L)in autumn and(~3000 cells/L)in winter season.Gyrodinium sp.was the predominant taxa with the maximum abundance(48166 cells/L)observed in autumn season following by Scrippsiella trochoidea(1200 cells/L),Alexandrium ostenfeldii(3000 cells/L)in winter season,and Ceratium furca(640 cells/L),Protoperidinium steinii(780 cells/L),Ceratium fusus(906 cells/L),Pyrophacus steinii(840 cells/L),Gonyaulax spinifera(666 cells/L),Alexandrium tamarense(520 cells/L)and Dinophysis caudata(393 cells/L)in summer and spring season.Statistically,abundance of dinoflagellates correlated significant to chlorophyll a with chlorophyll a and temperature but inverse relation to salinity and pH observed from both sites.Conclusions:The present study reports on the prevalence and significance of harmful algae bloom forming taxa in the area which would be available for the coastal zone managers and fishery industry to inform them of possible threat and damage that can be caused by any blooms to,for example,fishery industry,and environmental and human health.

Biological and Molecular Geochemical Evidence for Dinoflagellate Ancestors in the Upper Sinian-Cambrian

Dinoflagellates are single celled organisms that reflect the ecological conditions in modern oceans and lakes. Their earliest undisputed fossil record suggests that dinoflagellates originated from the Middle Triassic (c. 240 Ma ago). However, the presence of molecular biomarkers (dinosterane, 4α-methyl-24-ethylcholestane and tria-romatic dinosteroids) in rock extracts and coccoid dinoflagellate fossils from the upper Sinian to Cambrian of the Tarim basin confirms the hypothesis that dinoflagellates have an ancient origin, and predate the oldest undisputed dinoflagellate fossils at least by 300 Ma, as early as the late Sinian-Cambrian.

Effects of Ultraviolet(UV)Radiation on Outdoor-and Indoor-Cultured Prorocentrum lima,a Toxic Benthic Dinoflagellate

The effects of different types of ultraviolet(UV)radiation(UVR,wavelength=280-400 nm)and light intensities on cell growth,pigment composition,UV-absorbing compounds(UVACs),and chlorophyll a(Chl a)fluorescence were studied in dinoflag-ellate Prorocentrum lima cultured outdoors for 16 days and indoors for 18 days.In the outdoor experiment,UVA radiation(320-400 nm)increased the growth rate of this dinoflagellate when solar light intensities were<12%;decreased growth rates were observed when intensities were>12%.Exposure to UVB radiation(280-320 nm)alleviated the negative effects of UVA.In the indoor ex-periment,UVA and low doses of UVB enhanced growth rates.Addition of low doses of UVB to UVA exposure resulted in higher contents of Chl a and photoprotective pigments compared with UVA exposure only.The results of both experiments showed that UVB is the primary signal of UVAC synthesis.High-dose UVB exposure accelerated growth rates when UVAC contents were maintained at high levels,suggesting that the latter plays a key role in UVR damage protection.Furthermore,the repair rate was en-hanced by UVB exposure after 16 days of culture.This study confirms the positive effects of UVA and UVB on the growth of P.lima,with the latter enhancing the photoprotective and recovery pathways of the species.

Morphology and distribution of Pronoctiluca (Dinoflagellata, incertae sedis) in the Pacific Ocean

The diversity and distribution of Pronoctiluca, a marine dinoflagellate of enigmatic systematic position, was studied in the vicinity of the Kuroshio and Oyashio Currents, the Philippines, Celebes, Sulu and South China Seas, western and central equatorial and southeast Pacific Ocean. The abundance of Pronoctiluca was high- er, with a wide vertical distribution, in eutrophic temperate regions, whereas it was nearly absent in surface waters of oligotrophic tropical regions. Most of the specimens corresponded to P. spinifera. Pronoctiluca pelagica, covered by hyaline layers and with no flagella, is considered as an encysted form. The bipartition was only observed in P. acuta-P, spinifera forms, that together with the occurrence of intermediate forms between P. spinifera and P. pelagica suggest that they may correspond to developmental stages of a single species. Pronoctiluca is essential to understanding the evolutionary history of the alveolates.

Distribution of dinoflagellate cysts in Yellow Sea sediments

To investigate the distribution, abundance, and species composition of dinoflagellate cysts in the Yellow Sea, surface sediment samples were collected at 37 sites, including the Korean dump site. Twenty-one di- noflagellate cyst taxa were identified, with the assemblages dominated mainly by Spiniferites bulloideus, Operculodinium centrocarpum, and cyst of Alexandrium catenella/tarnarense type. A high frequency of O. centrocarpum in the Yellow Sea was observed for the first time, and it is likely that this can be attributed to the dynamics of the Yellow Sea Cold Water Mass and the Changjiang （Yangtze） River runoff. Total cyst concentrations ranged from 23 to 48 442 cysts/g dry weight, and high cyst concentrations were recorded adjacent to the dumping site. This result suggests that anthropogenic activities such as ocean dumping s- timulate the growth of dinoflagellates in the Yellow Sea, which in turn leads to high levels of dinoflagellate cyst production.

Abundance and distribution of dinoflagellate cysts in Xiamen Western Harbor

In a grid investigation, dinoflagellate cysts were collected from sediments in Xiamen Western Harbor in May of 2000, from which five species of cysts were identified: Alexandrium tamarensis, A. minutum, Lingulodinium polyedra, Gonyaulax scrippsae and Gymnodinium catenatum, account for about 21% in the species composition. The quanti-tative analysis of the sediments shows that the number of dinoflagellate cysts varies from 51 to 256 cysts/g of sediment, the highest value (>200 cysts/g) being recorded at the stations of the central part of the bay, while the lowest (<100 cysts/g) at the bay mouth. A good linear relationship is found between cyst amount and fine-grained sediments. Complex physiognomies on the seabed, topographty in the bay and weak water exchange are the main factors not only in cyst accumulation but also in their distribution pattern, and have resulted in the difference in cyst densities between the inner bay and the outer bay in the harbor.

Dinoflagellate cysts in recent marine sediment from Guangxi, China

Total of 33 species of dinoflagellate cysts were discovered from surface sediment in the sea region of Guangxi, among them 12 cyst types (Diplopsalopsis sp. 1, D. sp. 2, D. sp. 3, Cochlodinium sp., Protoperidinium sp. 1, P. sp. 2, P. compressum, Scrippsiella sp. 1, S. sp. 2, Alexandrium sp. 1, A. sp. 2, A. sp. 3) were first reported from the South China Sea. And one cyst type (Cochlodinium sp.) was first reported in the world. Scrippsiella trochoidea is the dominant species in this area, accounting for 45% of all the cysts. There are 2 cysts of toxic dinoflagellate (Alexandrium tamarensis and Gymnodinium catenatum) But there is no relationship between cyst number and grain size distribution.

Long-term nutrient variation trends and their potential impact on phytoplankton in the southern Yellow Sea,China

The concentration and composition of nutrients,such as N,P,and Si,respond to biogeochemical processes and in turn,impact the phytoplanktons'community structure and primary production.In this study,historical data was systematically analyzed to identify long-term variations in nutrient trends,red tide frequency,phytoplankton community abundance,and dominant species succession in the southern Yellow Sea(SYS).Results showed that N/P concentration ratios dramatically increased as a function of increasing dissolved inorganic nitrogen concentrations,and Si/N concentration ratios were generally larger than 1,indicating that N limitation morphed to P limitation and potentially to Si limitation,which impacted the phytoplankton community.Furthermore,inter-annual trends over the past 50 years show that phytoplankton community abundance has been higher in spring and summer,relative to autumn and winter.Moreover,with respect to red tide frequency,diatom abundance gradually decreased,while that of dinoflagellates gradually increased.Dominant species succession showed that the phytoplankton community exhibited an evident tendency to transform from diatoms to dinoflagellates.These research results clearly depict the presence of an important correlation between the phytoplankton community and nutrient structure in the SYS.

Preliminary study on taxonomy of dinoflagellate cysts from major estuary and bays of Fujian Province, China

According to the morphology, wall structure, color, ornamentation, etc., 25 species belonging to 9 genera are identified and described from 144 sediment samples of the Xiamen Harbor, the mouth of the Minjiang River and the Sansha Bay. Among them there are 2 toxic species: Alexandrium minutun,A. tamarenes, 4 harmful species: Alexandrium affine,Lingulodinium polX drum, Scrippsiella trochoide,Gonyaulax spinifera. It shows that 11 species of dinoflagellate cysts (Alexandrium affine, A. minutum, Diplopelta cf. parva, Polykrikos cf. schwartzii, protoceratium reticulatum, Protoperidinium minutum, P. cf. minutum, P. cf americanum and Alexandrium sp., Protoperidinium sp. 1, P. sp. 2) are first recorded along the coast of Fujian Province, China. These newly discovered species might be transported to the coastal sea of Fujian Province by ballast water of international trade vessels.

Blooms of Prorocentrum donghaiense reduced the species diversity of dinoflagellate community

Most of reported harmful algal blooms(HABs)of microalgae(75%)have been caused by dinoflagellates.Studies on the negative effects of HABs have generally focused on animals,valuable organisms in particular,and environmental factors such as dissolved oxygen and nutrients,but relatively fewer on community level,particularly that using metagenomic approach.In this study,we reported an investigation on the effects of a HAB caused by the dinoflagellate Prorocentrum donghaiense on the species diversity and community structure of the dinoflagellate sub-community via a pyrosequencing approach for the samples taken before,during,and after the bloom season of P.donghaiense in the East China Sea.We sequenced partial 28S rRNA gene of dinoflagellates for the field samples and evaluated the species richness and diversity indices of the dinoflagellate community,as a sub-community of the total phytoplankton.We obtained 800185 valid sequences(categorized into 560 operational taxonomic units,OTUs)of dinoflagellates from 50 samples and found that the biodiversity of dinoflagellate community was significantly reduced during the blooming period in comparison to that in pre-and after-blooming periods,as reflected in the four diversity indices:the species richness expressed as the number of OTUs,Chao1 index,Shannon index(evenness),and Gini-Simpson index.These four indices were all found to be negatively correlated to the cell density of the bloom species P.donghaiense.Correlation analyses also revealed that the P.donghaiense cell abundance was correlated negatively with NO3--N,and NO2--N,but positively with total nitrogen(TN)and total phosphorus(TP).Principal coordinates analysis(PCoA)showed that the community structure of dinoflagellates was markedly different among the different sampling periods,while the redundancy analysis(RDA)revealed P.donghaiense abundance,salinity,NO3--N,and SiO32-were the most four significant factors shaping the dinoflagellate community structure.Our results together demonstrated that HABs caused by the dinoflagellate P.donghaiense could strongly impact the aquatic ecosystem on the sub-community level which the blooming species belongs to.

Validation of reference genes for gene expression studies in the dinoflagellate Akashiwo sanguinea by quantitative real-time RT-PCR

The accurate measurement of gene expression via quantitative real-time reverse transcription PCR（q RT-PCR）heavily relies on the choice of valid reference gene（s） for data normalization. Resting cyst is the dormant stage in the life cycle of dinoflagellate, which plays crucial roles in HAB-forming dinoflagellate ecology. However, only limited investigations have been conducted on the reference gene selection in dinoflagellates. Gap remained in our knowledge about appropriate HKGs for normalizing gene expression in different life stages, which laid obstacles for the application of q RT-PCR to the HAB-forming group. In this study, six candidate reference genes,18 S ribosomal RNA（18S）, glyceraldehyde-3-phosphate dehydrogenase（GAPDH）, α-tubulin（TUA）, β-tubulin（TUB）, actin（ACT） and cytochrome oxidase subunit 1（COX1）, were evaluated for their expression stability with q RT-PCR and three statistical algorithms（Ge Norm, Norm Finder, and Best Keeper） for the cosmopolitan, harmful algal bloom-forming dinoflagellate Akashiwo sanguinea. Expression patterns were observed across 18 biological samples, including cells at resting stages（resting cysts）, different growth stages, in darkness, exposed to abscisic acid（ABA） and exposed to temperature stress. The results indicated that TUA, 18 S and GAPDH were relatively stable across all tested scenarios. While the best-recommended reference genes differed across experimental groups, the pairs of ACT and TUA, 18 S and GAPDH were the most reliable for cells at different growth stages and darkness treatment. The combination of TUA and TUB was the best choice for normalization in resting cysts and in ABA treatment, respectively. The pair of ACT and COX1 was suitable for temperature treatments. This study was the first to investigate the stable internal reference genes in dinoflagellates at different stages of life cycle,particularly in resting cysts. Our results provided useful information for selection of reference genes in dinoflagellates regarding quantification of gene expression at different experimental scenarios, which will facilitate more accurate and widespread use of q RT-PCR in gene analysis of dinoflagellates and help to design primers targeting orthologous genes in other algal species.