Cryptophyte farming by symbiotic ciliate host detected in situ.

Protist-alga symbiosis is widespread in the ocean, but its characteristics and function in situ remain largely unexplored. Here we report the symbiosis of the ciliate Mesodinium rubrum with cryptophyte cells during a red-tide bloom in Long Island Sound. In contrast to the current notion that Mesodinium retains cryptophyte chloroplasts or organelles, our multiapproach analyses reveal that in this bloom the endosymbiotic Teleaulax amphioxeia cells were intact and expressing genes of membrane transporters, nucleus-to-cytoplasm RNA transporters, and all major metabolic pathways. Among the most highly expressed were ammonium transporters in both organisms, indicating cooperative acquisition of ammonium as a major N nutrient, and genes for photosynthesis and cell division in the cryptophyte, showing active population proliferation of the endosymbiont. We posit this as a "Mesodinium-farming-Teleaulax" relationship, a model of protist-alga symbiosis worth further investigation by metatranscriptomic technology.

Space station image captures a red tide ciliate bloom at high spectral and spatial resolution.

Mesodinium rubrum is a globally distributed nontoxic ciliate that is known to produce intense red-colored blooms using enslaved chloroplasts from its algal prey. Although frequent enough to have been observed by Darwin, blooms of M. rubrum are notoriously difficult to quantify because M. rubrum can aggregate into massive clouds of rusty-red water in a very short time due to its high growth rates and rapid swimming behavior and can disaggregate just as quickly by vertical or horizontal dispersion. A September 2012 hyperspectral image from the Hyperspectral Imager for the Coastal Ocean sensor aboard the International Space Station captured a dense red tide of M. rubrum (10(6) cells per liter) in surface waters of western Long Island Sound. Genetic data confirmed the identity of the chloroplast as a cryptophyte that was actively photosynthesizing. Microscopy indicated extremely high abundance of its yellow fluorescing signature pigment phycoerythrin. Spectral absorption and fluorescence features were related to ancillary photosynthetic pigments unique to this organism that cannot be observed with traditional satellites. Cell abundance was estimated at a resolution of 100 m using an algorithm based on the distinctive yellow fluorescence of phycoerythrin. Future development of hyperspectral satellites will allow for better enumeration of bloom-forming coastal plankton, the associated physical mechanisms, and contributions to marine productivity.

The Synonymy of the Toxic Dinoflagellates Prorocentrum mexicanum and P. rhathymum and the Description of P. steidingerae sp. nov. (Prorocentrales, Dinophyceae).

Prorocentrum mexicanum and P. rhathymum are toxicologically important dinoflagellates, but their relationship is not well defined. We investigated strains from Puerto Rico and Brazil by light and scanning electron microscopies. We provide molecular data from a strain isolated near the type locality of P. rhathymum, and the first morphological and molecular data from the South Atlantic Ocean. The rRNA gene (rDNA) sequences of the Puerto Rican and Brazilian strains were identical, and their morphologies fit the description of P. rhathymum. In the molecular phylogenies, the globally distributed populations under the names P. mexicanum and P. rhathymum are intermixed and branched together, except for several divergent strains from Florida and Cuba. We examined the original descriptions and iconotypes of the species Prorocentrum maximum, P. brochii, P. mexicanum, and P. rhathymum. We conclude that P. maximum sensu Schiller's figure 41a corresponds to the earlier description of this species; the split of P. mexicanum and P. rhathymum was based on a misidentification because P. mexicanum sensu Cortés-Altamirano & Sierra-Beltrán corresponds to P. texanum var. cuspidatum; and P. rhathymum is a junior synonym of P. mexicanum. Several Floridian and Cuban strains correspond to a new species, which we describe as Prorocentrum steidingerae sp. nov.

Morphological and molecular characterization of Ptychodiscus noctiluca revealed the polyphyletic nature of the order Ptychodiscales (Dinophyceae).

The planktonic dinoflagellate Ptychodiscus noctiluca combined distinctive morphological features such as a disk-shaped anteroposteriorly compressed cell body and an apical carina, together with a flexible and tough cell covering, suggesting intermediate characteristics between thecate and naked dinoflagellates. Ptychodiscus noctiluca was examined by light, epifluorescence, and scanning electron microscopy from specimens collected in the Mediterranean Sea and the North and South Atlantic Ocean. Ptychodiscus noctiluca showed a straight apical groove that bisected the carina, a cell covering with a polygonal surface reticulum, nucleus without capsule, sulcal intrusion in the episome, sulcal ventral flange, and yellowish-green chloroplasts that are shared characters with Brachidinium/Karenia. The cell division was the typical binary fission of gymnodinioid dinoflagellates, although exceptionally in an oblique transversal axis. We examined the intraspecific variability during incubation experiments. In the fattened cells, termed as Ptychodiscus carinatus, chloroplasts transformed into dark granules, and the cell acquired the swollen and smaller stage, termed as P. inflatus. Ptychodiscus carinatus, P. inflatus, and Diplocystis antarctica are synonyms of P. noctiluca. Molecular phylogeny based on the SSU rDNA sequence revealed that Ptychodiscus branched within the short-branching dinokaryotic dinoflagellates as an independent lineage with affinity to Brachidinium/Karenia and Karlodinium/Takayama in a generally poorly resolved clade. Our results indicated that the order Ptychodiscales, established for unarmored dinoflagellates with a strongly developed pellicle, has artificially grouped thecate dinoflagellates (Kolkwitziella, Herdmania), naked dinoflagellates with thick cell covering (Balechina, Cucumeridinium) and other insufficiently known unarmored genera with typical cell coverings (Brachidinium, Ceratoperidinium).

In situ diets of the bloom-forming dinoflagellate Noctiluca scintillans in Daya Bay.

Red Noctiluca scintillans is a common heterotrophic dinoflagellate that forms blooms in temperate, subtropical, and tropical coastal ecosystems. The diet of this species plays an important role in its cell growth, development, and reproduction. Because limited gene diversity data are available regarding prey of this species, its diet in Daya Bay during a boreal winter bloom is reported using an integrated approach involving light microscopy, single cell isolation and plastid 16S rDNA cloning, and 18S rDNA V4 and V9 region amplification using isolated cells and environmental DNA as templates with high-throughput sequencing. While conventional light microscopy reveals the diet of this species to comprise Coscinodiscus sp. and Stephanopyxis turris (diatoms), copepod eggs, and detritus, plastid gene diversity identifies a diet comprising diatoms, cyanobacteria, and bacteria, and 18S rDNA high-throughput sequencing reveals a diet comprising 36 eukaryote families (primarily copepods, as well as diatoms, dinoflagellates, Ochrophyta, Haptophytes, Chordata, Cercozoans, Chlorophyta, Polychaeta, and ciliates). Dietary staples include copepods, diatoms, dinoflagellates, Ochrophyta, and Synechococcus. High copepod abundance in prey may reflect their relatively high abundance in environmental seawater. Thus, N. scintillans is generally omnivorous but prefers dominant phytoplankton taxa, including Rhizosoleniaceae, Leptocylindraceae, and Cymatosiraceae (diatoms), as well as Gonyaulacaceae (dinoflagellates). An integrated multi-disciplinary approach provides a more comprehensive picture of N. scintillans diet in Daya Bay, and an improved understanding of this species' ecological niche and trophic role in marine ecosystems.

Different photosynthetic responses of haploid and diploid Emiliania huxleyi (Prymnesiophyceae) to high light and ultraviolet radiation.

Solar radiation varies quantitatively and qualitatively while penetrating through the seawater column and thus is one of the most important environmental factors shaping the vertical distribution pattern of phytoplankton. The haploid and diploid life-cycle phases of coccolithophores might have different vertical distribution preferences. Therefore, the two phases respond differently to high solar photosynthetically active radiation (PAR, 400-700 nm) and ultraviolet radiation (UVR, 280-400 nm). To test this, the haploid and diploid Emiliania huxleyi were exposed to oversaturating irradiance. In the presence of PAR alone, the effective quantum yield was reduced by 10% more due to the higher damage rate of photosystem II in haploid cells than in diploid cells. The addition of UVR resulted in further inhibition of the quantum yield for both haploid and diploid cells in the first 25 min, partly because of the increased damage of photosystem II. Intriguingly, this UVR-induced inhibition of the haploid cells completely recovered half an hour later. This recovery was confirmed by the comparable maximum quantum yields, maximum relative electron transport rates and yields of the haploid cells treated with PAR and PAR + UVR. Our data indicated that photosynthesis of the haploid phase was more sensitive to high visible light than the diploid phase but resistant to UVR-induced inhibition, reflecting the ecological niches to which this species adapts.

Shipborne oceanic high-spectral-resolution lidar for accurate estimation of seawater depth-resolved optical properties.

Lidar techniques present a distinctive ability to resolve vertical structure of optical properties within the upper water column at both day- and night-time. However, accuracy challenges remain for existing lidar instruments due to the ill-posed nature of elastic backscatter lidar retrievals and multiple scattering. Here we demonstrate the high performance of, to the best of our knowledge, the first shipborne oceanic high-spectral-resolution lidar (HSRL) and illustrate a multiple scattering correction algorithm to rigorously address the above challenges in estimating the depth-resolved diffuse attenuation coefficient Kd and the particulate backscattering coefficient bbp at 532 nm. HSRL data were collected during day- and night-time within the coastal areas of East China Sea and South China Sea, which are connected by the Taiwan Strait. Results include vertical profiles from open ocean waters to moderate turbid waters and first lidar continuous observation of diel vertical distribution of thin layers at a fixed station. The root-mean-square relative differences between the HSRL and coincident in situ measurements are 5.6% and 9.1% for Kd and bbp, respectively, corresponding to an improvement of 2.7-13.5 and 4.9-44.1 times, respectively, with respect to elastic backscatter lidar methods. Shipborne oceanic HSRLs with high performance are expected to be of paramount importance for the construction of 3D map of ocean ecosystem.

Two functionally distinct ciliates dwelling in Acropora corals in the South China Sea near Sanya, Hainan Province, China.

We detected and characterized two distinct scuticociliate ciliates inside Acropora corals in the South China Sea. One, voraciously foraging on Symbiodinium, resembled the brown band disease of ciliates. The other, which is closely related to Paranophrys magna, grazed on detritus instead of Symbiodinium. These two ciliates may serve contrasting functions (competitor versus "cleaner") in the coral-ciliate-Symbiodinium triangular relationship.

Flourishing deep-sea AAP bacteria detected by flow cytometric sorting and molecular analysis.

Pigmented bacteria cells, including aerobic anoxygenic phototrophic (AAP) bacteria, contribute significantly to secondary production and aquatic carbon cycling but their distribution in the deep sea is still not well understood, especially in the South China Sea. In this study, microscopic, flow cytometric, and molecular analyses were carried out to investigate the abundance and diversity of AAP bacteria at seven stations in the South China Sea. The results revealed the existence of bacteriochlorophyll-containing bacteria below 500 m from two of seven stations. Flow cytometric analysis detected red and infra-red fluorescence under blue (488 nm) light excitation from fluorescent cells. Blue light-excited red fluorescence of these cells from the 1000 m depth at station E403 were verified using epifluorescence microscopy. Based on fluorescence and side scatter features, fluorescent cells were sorted and subjected to molecular analysis. DNA was extracted from these sorted cells from both stations for PCR amplification using 16S rDNA primers. Sequencing of the PCR products showed that the sorted cells from the 1000 m depth at station E403 belonged to the genus Porphyrobacter. The cell population sorted from 500 m at station E703 contained Sphingomonas and a Methylobacterium-like taxon. All these three taxa belong to aerobic anoxygenic phototrophic alpha-proteobacteria. Using flow cytometric analysis, we found that the abundance of Porphyrobacter sp. at 1000 m was 2.71-2.95×104 cells mL-1 whereas cell counts of Sphingomonas sp. and Methylobacterium at 500 m were about 3.75-4.12×105 cells mL-1. These results indicate that albeit not ubiquitous in deep water, bacteriochlorophyll-containing bacteria can be abundant in the deep-sea aphotic zone.

Fukuyoa paulensis gen. et sp. nov., a new genus for the globular species of the dinoflagellate Gambierdiscus (Dinophyceae).

The marine epiphytic dinoflagellate Gambierdiscus is a toxicologically important genus responsible for ciguatera fish poisoning, the principal cause of non-bacterial illness associated with fish consumption. The genus currently contains species exhibiting either globular or anterior-posteriorly compressed morphologies with marked differences in cell shape and plate arrangement. Here we report a third globular, epiphytic and tychoplanktonic species from the coasts of Ubatuba, Brazil. The new species can be distinguished from G. yasumotoi and G. ruetzleri by its broader first apical plate that occupies a larger portion of the epitheca. Accordingly, phylogenetic trees from small subunit (SSU) and large subunit (LSU) ribosomal DNA sequences also showed strongly supported separation of the new species from the G. yasumotoi/G. ruetzleri group albeit with short distance. The molecular phylogenies, which included new sequences of the planktonic species Goniodoma polyedricum, further indicated that the globular species of Gambierdiscus formed a tight clade, clearly separated (with strong bootstrap support) from the clade of lenticular species including the type for Gambierdiscus. The morphological and molecular data in concert support the split of Gambierdiscus sensu lato into two genera. Gambierdiscus sensu stricto should be reserved for the species with lenticular shapes, highly compressed anterioposteriorly, with short-shank fishhook apical pore plate, large 2' plate, low and ascending cingular displacement, and pouch-like sulcal morphology. The new genus name Fukuyoa gen. nov. should be applied to the globular species, slightly laterally compressed, with long-shank fishhook apical pore plate, large 1' plate, greater and descending cingular displacement, and not pouch-like vertically-oriented sulcal morphology. Fukuyoa contains the new species Fukuyoa paulensis gen. et sp. nov., and F. yasumotoi comb. nov. and F. ruetzleri comb. nov.

Apical groove type and molecular phylogeny suggests reclassification of Cochlodinium geminatum as Polykrikos geminatum.

Traditionally Cocholodinium and Gymnodinium sensu lato clade are distinguished based on the cingulum turn number, which has been increasingly recognized to be inadequate for Gymnodiniales genus classification. This has been improved by the combination of the apical groove characteristics and molecular phylogeny, which has led to the erection of several new genera (Takayama, Akashiwo, Karenia, and Karlodinium). Taking the apical groove characteristics and molecular phylogeny combined approach, we reexamined the historically taxonomically uncertain species Cochlodinium geminatum that formed massive blooms in Pearl River Estuary, China, in recent years. Samples were collected from a bloom in 2011 for morphological, characteristic pigment, and molecular analyses. We found that the cingulum in this species wraps around the cell body about 1.2 turns on average but can appear under the light microscopy to be >1.5 turns after the cells have been preserved. The shape of its apical groove, however, was stably an open-ended anticlockwise loop of kidney bean shape, similar to that of Polykrikos. Furthermore, the molecular phylogenetic analysis using 18S rRNA-ITS-28S rRNA gene cistron we obtained in this study also consistently placed this species closest to Polykrikos within the Gymnodinium sensu stricto clade and set it far separated from the clade of Cochlodinium. These results suggest that this species should be transferred to Polykrikos as Polykrikos geminatum. Our results reiterate the need to use the combination of apical groove morphology and molecular phylogeny for the classification of species within the genus of Cochlodinium and other Gymnodiniales lineages.

Morphological and molecular characterization of the toxic dinoflagellate Ostreopsis cf. ovata (Gonyaulacales: Dinophyceae) from Brazil (South Atlantic Ocean) / Caracterización morfológica y molecular del dinoflagelado tóxico Ostreopsis cf. ovata (Gonyaulacales: Dinophyceae) en Brasil (Océano Atlántico Sur)

AbstractOstreopsis cf. ovata is a toxic epiphytic dinoflagellate widely distributed in warm waters that often co-occur with species of the genera Coolia, Fukuyoa, Gambierdiscus and Prorocentrum. We investigated a strain isolated from the coast of Ubatuba, Brazil (Southwest Atlantic Ocean) by light and epifluorescence microscopies; we also report molecular data based on the LSU rDNA and ITS markers. Cells were 35-65 µm in the dorso-ventral diameter and 20-40 µm wide. We obtained the sequence of a ~1 900 base pair region of the rRNA gene cistron. In the LSU rDNA phylogeny, the sequences under the names O. ovata and O. cf. ovata branched into three clades. The ITS marker showed greater resolving power and the sequences of O. ovata/O. cf. ovata split into five clades. Our ITS sequence branched in a clade with sequences of strains from the Mediterranean Sea, European Atlantic coasts, subtropical NE Atlantic, other sequences from Brazil at Rio de Janeiro, and a few sequences from Japan. The cell dimensions and thecal plate arrangement were under the variability range reported in other ocean regions. Our observations confirm O. cf. ovata as the most commonly recorded species of Ostreopsis in the SW Atlantic Ocean. Ostreopsis cf. ovata co-occurred with Coolia malayensis in Brazil and Asia, but it has been commonly reported from the Mediterranean Sea, where C. malayensis has not yet been recorded; while Coolia malayensis has been reported from the Caribbean Sea, but not O. ovata. With the current knowledge, it is difficult to understand the factors that determine the biogeography of the tropical epiphytic dinoflagellates. Rev. Biol. Trop. 65 (3): 1022-1032. Epub 2017 September 01.

ResumenOstreopsis cf. ovata es un dinoflagelado tóxico epifítico de amplia distribución en aguas cálidas, que a menudo coincide con especies de los géneros Coolia, Fukuyoa, Gambierdiscus y Prorocentrum. Investigamos una cepa aislada en la costa de Ubatuba, Brasil (Atlántico sudoccidental) mediante microscopía óptica y de epifluorescencia. Obtuvimos una secuencia de una región de unos 1 900 pares de bases del cistrón del gen del ARN ribosómico. Las células tenían 35-65 µm de diámetro dorso-ventral y 20-40 µm de ancho. En la filogenia del marcador LSU rADN, las secuencias con los nombres O. ovata and O. cf. ovata se sitúan en tres grupos. El marcador ITS mostraba un mayor poder resolutivo y las secuencias de O. ovata/O. cf. ovata se separan en cinco grupos. Nuestra secuencia ITS se sitúa en un grupo con secuencias de cepas procedentes del Mar Mediterráneo, costas europeas Atlánticas, Atlántico subtropical nororiental, otras secuencias procedentes de Río de Janeiro en Brasil, y algunas secuencias de Japón. Las dimensiones celulares y la disposición de las placas tecales se sitúan en el rango de variabilidad descrito en otras regiones oceánicas. Nuestras observaciones confirman a O. cf. ovata como la especie más comúnmente registrada de Ostreopsis en el Atlántico sudoccidental. Ostreopsis cf. ovata coindice con Coolia malayensis en Brasil y Asia. Ostreopsis cf. ovata ha sido comúnmente encontrada en el Mar Mediterráneo, donde C. malayensis aún no ha sido registrada. Coolia malayensis has sido registrada en el Mar Caribe, donde O. ovata aún no ha sido encontrada. Es difícil comprender los factores que determinan la biogeografía de los dinoflagelados epífitos tropicales, a partir del conocimiento actual.

Nuclear, mitochondrial and plastid gene phylogenies of Dinophysis miles (Dinophyceae): evidence of variable types of chloroplasts.

The Dinophysis genus is an ecologically and evolutionarily important group of marine dinoflagellates, yet their molecular phylogenetic positions and ecological characteristics such as trophic modes remain poorly understood. Here, a population of Dinophysis miles var. indica was sampled from South China Sea in March 2010. Nuclear ribosomal RNA gene (rDNA) SSU, ITS1-5.8S-ITS2 and LSU, mitochondrial genes encoding cytochrome B (cob) and cytochrome C oxidase subunit I (cox1), and plastid rDNA SSU were PCR amplified and sequenced. Phylogenetic analyses based on cob, cox1, and the nuclear rRNA regions showed that D. miles was closely related to D. tripos and D. caudata while distinct from D. acuminata. Along with morphology the LSU and ITS1-5.8S-ITS2 molecular data confirmed that this population was D. miles var. indica. Furthermore, the result demonstrated that ITS1-5.8S-ITS2 fragment was the most effective region to distinguish D. miles from other Dinophysis species. Three distinct types of plastid rDNA sequences were detected, belonging to plastids of a cryptophyte, a haptophyte, and a cyanobacterium, respectively. This is the first documentation of three photosynthetic entities associated with a Dinophysis species. While the cyanobacterial sequence likely represented an ectosymbiont of the D. miles cells, the detection of the cryptophyte and haptophyte plastid sequences indicates that the natural assemblage of D. miles likely retain more than one type of plastids from its prey algae for temporary use in photosynthesis. The result, together with recent findings of plastid types in other Dinophysis species, suggests that more systematic research is required to understand the complex nutritional physiology of this genus of dinoflagellates.