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.

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.

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.

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.

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.

Summer gregarine infection in Antarctic krill Euphausia superba in the Dumont D’Urville Sea,East Antarctic

Antarctic krill Euphausia superba plays a key role in the Antarctic food web.The trophic linkage between krill and other macro-organisms has been studied in the past decades,but the variability of parasites in krill is less studied and remains poorly understood.Therefore,it is important to understand the factors that influence abundance and infection of parasites in krill.Moreover,the relationship between the infection intensity of parasite and krill diet needs to be clarified,which is helpful for understanding the role of parasite in the food web.We investigated the abundance of the highly prevalent gregarine parasites in the digestive tract of krill and the factors influencing the gregarine infection to krill in the East Antarctic.The infection rate of Cephaloidophora pacifica Avdeev,1985 to krill(n=50 individuals)was 94%.The results of generalized linear model show the infection intensity of C.pacifica to the host was related significantly to the station,krill size,and maturity stage,but not the food species and abundance in the stomach of krill.Abundance of C.pacifica in krill differed among stations,and the lowest abundance occurred in the station nearest to the coast.Gregarines abundance varied among sexual maturity stages of krill and increased with krill size.

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.

Distribution characteristic and variation trend of planktonic dinoflagellate in the Taiwan Strait from 2006 to 2007

Based on 4 cruise surveys from July 2006 to October 2007 in the Taiwan Strait, the species composition, community structure and spatio-temporal distribution of dinoflagellate were studied. A total of 131 dinoflagellates belonging to 18 genera were identified. The population was dominated by hyperthermal and hyperhaline species accounting for 72.52% of the total species. Eurythermal and euryhaline species were the second most common one accounting for 25.19% of the total species. It was only 2.29% for neritic species. The maximum species number occurred in summer, while the maximum cell density appeared in spring. The average dinoflagellate cell density was 404.96x104 cells/m3. It showed that the dinof]agellate cell density increased from the nearshore waters to the open sea and from the north to the south. Compared with the results during 1984-1985, the horizontal distribution pattern and seaeonal variation of the dinofiagellate have not changed significantly, but the dinoflagellate cell density increased by 3.01 times. Further analysis of the dinoflagellate abundance variations both in the spatial and temporal aspects, indicated that the abundance of dinoflagellate increased more significantly in cold seasons, and there was a larger increase in the north of the Taiwan Strait. Besides, the dinoflagellate community structure changed notably. It showed that the diversity and evenness index were relatively high, and the proportion of dinoflageliate cell density to the total phytoplankton increased.

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.

I mpact of several harmful algal bloom(HAB) causing species, on life history characteristics of rotifer Brachionus plicatilis Müller

In recent years, harmful algal blooms(HABs) have occurred frequently along the coast of China, and have been exhibiting succession from diatom- to dinofl agellate-dominated blooms. To examine the eff ects of dif ferent diatom and dinofl agellate HABs, the life history parameters of rotifers(B rachionus plicatilis Müller) were measured after exposure to dif ferent concentrations of HAB species. The HAB species examined included a diatom(S keletonema costatum) and four dinofl agellates( Prorocentrum donghaiense, Alexandrium catenella, Prorocentrum lima and Karlodinium venefi cum). Compared with the control treatment(CT), the diatom S. costatum showed no adverse impacts on rotifers. Exposure to dinofl agellates at densities equivalent to those measured in the fi eld resulted in a reduction in all the life history parameters measured. This included a reduction in: lifetime egg production(CT: 20.34 eggs/ind.) reduced to 10.11, 3.22, 4.17, 7.16 eggs/ind., life span(CT: 394.53 h) reduced to 261.11, 162.90, 203.67, 196 h, net reproductive rate(CT: 19.51/ind.) reduced to 3.01, 1.26, 3.53, 5.96/ind., fi nite rate of increase(CT: 1.47/d) reduced to 1.16, 1.03, 1.33, 1.38/d, and intrinsic rate of population increase(CT: 0.39/d) reduced to 0.15, 0.03, 0.28, 0.32/d, for the dinofl agellates P. donghaiense, A. catenella, P. lima and K. venefi cum, respectively. The results showed that the diatom S. costatum had no detrimental consequences on the reproduction and growth of B. plicatilis, however, the four dinofl agellates tested did show adverse ef fects. This suggests that dinofl agellate HABs may suppress microzooplankton, resulting in an increase in algal numbers.

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.

Dinoflagellate Cysts Records from Core Samples of Modern Marine Sediment at the Luoyuan Bay Mouth

Thirty species of dinoflagellate cysts in 15 genus are identified from KMZK5 Core samples of recent marine sediment at the Luoyuan Bay mouth, Fujian. All of these dinoflagellate cysts are first recorded in the Luyuan Bay, 12 species of them are not distributing in the near sea area such as Sansha Bay and Minjiang estuary, including 6 kinds of toxic species, such as Alexandrium affine, A. minutum, A. tamarense, Gonyaulax spinifera, Gymnodinium catenatum and Scrippsiella trochoidea. The abundance and vertical distribution characterestics of the main and the toxic dinoflgellate cysts are also studied in the paper.

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.

Comparative study of hydrographic conditions for algal bloom formation in the coastal waters of east and west of Hong Kong during 1998

Phytoplankton abundance was found to be positively correlated with seasonal changes of seawater temperature in Port Shelter and Lamma Channel, Hong Kong in 1998. Rising water temperature from around 20℃ to 25℃ coincided with an increase in phytoplankton abundance at both locations. Heavy rains from June to September reduced salinity from 30 to 20, but the decrease in salinity was not correlated with a decline in phytoplankton abundance. In spring 1998, over 0.6×10^6 cells dm^-3 and 0.1× 10^6 cells dm^-3 of the dinoflagellate, Gymnodinium mikimotoi Miyake et Kominami ex Oda occurred in the coastal waters of Port Shelter and Lamina Channel, respectively. High abundance of the dinoflagellate Ceratium furca （Ehr.） Claparede et Lachmann （〉1×10^6 cells dm^-3） produced long-lasting blooms in the waters of Port Shelter from September to October in 1998. The abundances of both diatoms and dinoflagellates were significantly lower in the waters of Lamina Channel than those in Port Shelter due to the less frequent blooms in 1998. Hydrographic conditions such as stable water masses and water column stratification were the main reasons for the differences in the algal abundance and bloom frequency found between the two locations since neither of the two areas appeared to be nutrient-limited. This type water condition for the formation of algal bloom in Port Shelter has not been reported previously and it is not a general case for many bays along China＇s coast where algal bloom occurs as well.

Geographical distribution of red and green Noctiluca scintillans

The dinoflagellate Noctiluca scintillans is one of the most important and abundant red tide organisms and it is distributed world-wide. It occurs in two forms. Red Noctiluca is heterotrophic and fills the role of one of the microzooplankton grazers in the foodweb. In contrast, green Noctiluca contains a photosynthetic symbiont Pedinomonas noctilucae （a prasinophyte）, but it also feeds on other plankton when the food supply is abundant. In this review, we document the global distribution of these two forms and include the first maps of their global distribution. Red Noctiluca occurs widely in the temperate to sub-tropical coastal regions of the world. It occurs over a wide temperature range of about 10℃ to 25℃ and at higher salinities （generally not in estuaries）. It is particularly abundant in high productivity areas such as upwelling or eutrophic areas where diatoms dominate since they are its preferred food source. Green Noctiluca is much more restricted to a temperature range of 25℃-30℃ and mainly occurs in tropical waters of Southeast Asia, Bay of Bengal （east coast of India）, in the eastern, western and northern Arabian Sea, the Red Sea, and recently it has become very abundant in the Gulf of Oman. Red and green Noctiluca do overlap in their distribution in the eastern, northern and western Arabian Sea with a seasonal shift from green Noctiluca in the cooler winter convective mixing, higher productivity season, to red Noctiluca in the more oligotrophic warmer summer season.

Effects of ambient DIN:DIP ratio on the nitrogen uptake of harmful dinoflagellate Prorocentrum minimum and Prorocentrum donghaiense in turbidistat

The effects of varying nitrogen （N）： phosphorus （P） ratios on the growth and N-uptake and assimilation of the harmful dinoflagellates Prorocentrum minimum and Prorocentrum donghaiense were examined in turbidistat culture experiments. Algal cultures were supplied with media containing PO4^3- in various concentrations to obtain a wide range of N：P ratios. Experiments to determine rates of N uptake and assimilation of different N sources （NO^3-, NH4^＋, urea and glycine by P. minimum and NO3^-, NH4^＋ by P. donghaiense） were conducted using ^15-N tracer techniques at each N：P ratio. The growth rates suggested nutrient limitation at both high and low N：P ratios relative to the Redfield ratio. On a diel basis, the growth of both species was regulated by the light-dark cycle, which may be a result of regulation of both lightdependent growth and light-independent nutrient uptake. Maximum growth rates of both species always occurred at the beginning of light phase. In P-rich medium （low N：P ratio）, both species had higher N assimilation rates, suggesting N limitation. Low assimilation coefficients at high N：P ratios suggested P limitation of N uptake and assimilation. NO3 ^-and NH4^＋ contributed more than 90% of the total N uptake of P. minimum. Reduced N sources were more quickly assimilated than NO3^-. Highest average daily growth rates were recorded near an N：P ratio of 12 for both species. The N uptake rates of cultures at N：P ratios near Redfield ratio were more balanced with growth rates. The linkage between growth rates and N uptake/assimilation rates were conceptually described by the variation of cell N quota. The N：P ratios affect the N uptake and growth of Prorocentrum spp., and may regulate their bloom progression in eutrophic ecosystems.