Gymnodinium litoralis sp. nov. (Dinophyceae), a newly identified bloom-forming dinoflagellate from the NW Mediterranean Sea

Recurrent high-biomass blooms of a gymnodinioid species have been periodically recorded at different sites in the NW Mediterranean Sea (Catalan and Sardinian coast), causing intense discolorations of the water. In this study, several strains of the causative organism were isolated and subsequently studied with respect to the morphology of the vegetative cells and different life cycle stages, pigments profile, and molecular phylogeny. Based on phylogenetic analyses, the strains were placed within the Gymnodinium sensu stricto clade. The species possessed a horseshoe-shaped apical groove running anticlockwise around the apex and the major accessory pigment was identified as peridinin. These characteristics place the organism within the Gymnodinium genus, as defined today, although some other characteristics, such as vesicular chambers in the nuclear envelope and a nuclear fibrous connective were not observed. Morphologically, the isolates highly resemble Gyrodinium vorax (Biecheler) but major differences with the latter suggest that they comprise a new species, Gymnodinium litoralis sp. nov. The resting cyst of this species is described herein from field samples of the Catalan and Sardinian coast; pellicle cysts were observed in field samples and also in cultures. This species recurrently produces high biomass blooms (>10⁶ cell L⁻¹) in summer along several beaches and coastal lagoons in the NW Mediterranean Sea (L’Estartit, La Muga River mouth, and Corru S’Ittiri). Knowledge about its geographic distribution is limited, since the precise identification of G. litoralis from the field or fixed samples can be difficult. Therefore we expect that molecular studies will reveal a much wider distribution of the species.     

Early warning of toxic dinoflagellate blooms of Gymnodinium catenatum in southern Tasmanian waters

Blooms of the toxic dinoflagellate Gymnodinium catenatum (acausative organism of paralytic shellfish poisoning) in theDerwent and Huon estuaries of southern Tasmania, Australia,are predictable, annually recurrent events in the period Januaryto June (late summer to early winter). However, their spatialdistribution, duration and magnitude exhibit significant interannualvariability. High shellfish toxicities in 1986, 1991 and 1993(>8000 µ.g paralytic shellfish poisoning per 100 gshellfish meat) also coincided with the greatest spatial extentof shellfish toxicity (up to 35 shellfish farms closed for periodsup to 6 months). An exploratory analysis of the results of ashellfish toxin monitoring programme conducted from 1986 to1994, and of available hydrological and meteorological datafor the region, indicates that a significant G.catenatum bloomin Tasmanian waters can only develop within a permissive seasonalwater temperature window (>14°C at the time of bloominitiation) requiring a rainfall event as a trigger (Huon Riverdischarge, measured at Frying Pan Creek, must exceed 100 000megalitres over a 3-week period) and a calm stable water columnfor sustained development (windspeed <5 m s^–1 for periodsof 5 days or more). Once established, dinoflagellate populationsare subject to disturbance by turbulence caused by high windstress;this explains the incidence in some years of multiple shellfishtoxicity peaks. In winter months declining water temperatures(<10°C) and increasing windstress are responsible forthe termination of seasonal dinoflagellate blooms.     

Phylogenetic relations of the dinoflagellate Gymnodinium baicalense from Lake Baikal

Freshwater dinoflagellates still remain poorly studied by modern biological methods. This lack of knowledge prevents us from understanding the evolution and colonization patterns of these ecologically important protists. Gymnodinium baicalense is the most abundant, and possibly endemic, planktonic dinoflagellate from the ancient Lake Baikal. This dinoflagellate species blooms in the spring under the ice. This study analyzed the origin of this Baikalian dinoflagellate using three markers (two ribosomal and one mitochondrial DNA). It was found that this species is a true member of the order Gymnodiniales and has close relatives in the glacial melt waters of the Arctic Ocean. It seems that G. baicalense has diversified relatively recently from the arctic marine gymnodinioids. These results shed light on dinoflagellate biogeography and their colonizations in Lake Baikala biodiversity hotspot.     

Vectorial transport of toxins from the dinoflagellate Gymnodinium breve through copepods to fish

Toxins from the dinoflagellate Gymnodinium breve were tracedthrough experimental food chains from dinoflagellates, throughcopepod grazers, to juvenile fish. The generality of this foodweb transfer was demonstrated using three different combinationsof copepods and juvenile fish during different seasons. Fishwere not exposed directly to the toxic dinoflagellates but werefed toxin-laden copepods in order to examine sublethal vectorialintoxication. Toxins were shown to move from fish viscera tomuscle tissue within periods of 2–6 h to 25 h. A new toxindetection method was used in this first stepwise demonstrationof multi-trophic-level intoxication of a planktonic food chainby G.breve. Micellar electrokinetic capillary electrophoresiswith laser-induced fluorescence allowed measurements of toxinsat trace levels and nanoliter-sized volumes critical for planktonicfood web transfer studies.     

Morphological variation and phylogenetic analysis of the dinoflagellate Gymnodinium aureolum from a tributary of Chesapeake Bay

Cultures of four strains of the dinoflagellate Gymnodinium aureolum (Hulburt) G. Hansen were established from the Elizabeth River, a tidal tributary of the Chesapeake Bay, USA. Light microscopy, scanning electron microscopy, nuclear-encoded large sub-unit rDNA sequencing, and culturing observations were conducted to further characterize this species. Observations of morphology included: a multiple structured apical groove; a peduncle located between the emerging points of the two flagella; pentagonal and hexagonal vesicles on the amphiesma; production and germination of resting cysts; variation in the location of the nucleus within the center of the cell; a longitudinal ventral concavity; and considerable variation in cell width/length and overall cell size. A fish bioassay using juvenile sheepshead minnows detected no ichthyotoxicity from any of the strains over a 48-h period. Molecular analysis confirmed the dinoflagellate was conspecific with G. aureolum strains from around the world, and formed a cluster along with several other Gymnodinium species. Morphological evidence suggests that further research is necessary to examine the relationship between G. aureolum and a possibly closely related species Gymnodinium maguelonnense.     

Coupling planktonic and benthic shifts during a bloom of Alexandrium catenella in southern Chile: Implications for bloom dynamics and recurrence

Cell abundances and distributions of Alexandrium catenella resting cysts in recent sediments were studied along time at two locations in the Chilean Inland Sea exposed to different oceanographic conditions: Low Bay, which is much more open to the ocean than the more interior and protected Ovalada Island. The bloom began in interior areas but maximum cyst concentrations were recorded in locations more open to the ocean, at the end of the Moraleda channel. Our results showed a time lapse of around 3 months from the bloom peak (planktonic population) until the number of resting cysts in the sediments reached a maximum. Three months later, less than 10% of the A. catenella cysts remained in the sediments. Maximum cyst numbers in the water column occurred one month after the planktonic peak, when no cells were present. The dinoflagellate assemblage at both study sites was dominated by heterotrophic cysts, except during the A. catenella bloom. CCA analyses of species composition and environmental factors indicated that the frequency of A. catenella blooms was associated with low temperatures, but not with salinity, chlorophyll a concentration, and predator presence (measured as clam biomass). However, resting cyst distribution was only related to cell abundance and location. The occurrence of A. catenella cysts was also associated with that of cysts from the toxic species Protoceratium reticulatum. By shedding light on the ecological requirements of A. catenella blooms, our observations support the relevance of encystment as a mechanism of bloom termination and show a very fast depletion of cysts from the sediments (<3 months), which suggest a small role for resting cyst deposits in the recurrence of A. catenella blooms in this area.     

Rhodotorula grinbergsii sp. nov. isolated from decayed wood in the evergreen rainy Valdivian forest of southern Chile

An unusual Rhodotorula isolated from decayed wood of Eucryphia cordifolia Cav. is described and illustrated. This species differs enough from all accepted Rhodotorula species (1–5) to warrant its establishment as a new species, Rhodotorula grinbergsii sp. nov.The DNA base composition of this species was not calculated, since our laboratory is not properly equipped for that purpose.     

Taxonomy and phylogeny of a new kleptoplastidal dinoflagellate, Gymnodinium myriopyrenoides sp. nov. (Gymnodiniales, Dinophyceae), and its cryptophyte symbiont

A new kleptoplastidal dinoflagellate, Gymnodinium myriopyrenoides sp. nov., was described using light microscopy, electron microscopy and phylogengetic analysis based on partial LSU rDNA sequences. Cells were dorsiventrally flattened, elongate-elliptical in ventral view. There was no displacement of the cingulum encircling the anterior part of the cell. The cingulum was curved posteriorly at the terminal junction with the sulcus. The sulcus was generally narrow but expanded in the posterior end. The epicone possessed an apical groove made of one and one-half counterclockwise revolutions. Phylogenetic analysis based on LSU rDNA showed that the sequence of G. myriopyrenoides was included in the Gymnodiniales sensu stricto clade and had special affinities with the species Amphidinium poecilochroum and Gymnodinium acidotum, which also harbor kleptochloroplasts. Phylogenetic analysis based on plastid-encoded SSU rDNA and ultrastructural observations suggested that the symbionts of G. myriopyrenoides were cryptophytes of the genus Chroomonas or Hemiselmis. Organelles including the nucleus, the nucleomorph, mitochondria, Golgi bodies and large chloroplasts remained in the cytoplasm of the symbionts, but not the periplast, ejectosomes or flagellar apparatus. The symbiotic level of G. myriopyrenoides was estimated to be a relatively early stage in the unarmored kleptoplastidal dinoflagellates.     

Life cycle,behavior and morphology of a new tide pool dinoflagellate,Gymnodinium pyrenoidosum sp. nov. (Gymnodiniales,Pyrrhophyta)

A new tide pool dinoflagellate,Gymnodinium pyrenoidosum Horiguchi et Chihara sp. nov. is described from central Japan. It was found to form dense blooms with a characteristic greenish color from April to November. The species exhibits a characteristic diurnal vertical migration and an alternation of a motile with a nonmotile phase, which are dependent on light intensity and tidal movement. Cells of the motile phase are unarmored and relatively small. They have a single, reticulate chloroplast, orange stigma situated near the sulcus and conspicuous pyrenoid in epicone. The alga reproduces itself by means of zoospores which are produced by the bipartition of protoplasm within the parent cell wall during the nonmotile stage which occurs at night. The occurrence of another type of motile cell, termed a macroswarmer, which differs from normal zoospore in size and shape has also been demonstrated.     

Rhodotorula nothofagi sp. nov., isolated from decayed wood in the evergreen rainy Valdivian forest of southern Chile

An unusual Rhodotorula isolated from decayed wood of Nothofagus obliqua (Mirb.) Blume is described and illustrated. This species differs from all accepted Rhodotorula species (1–7, 10) to warrant its establishment as a new species, Rhodotorula nothofagi sp. nov.Postgraduate student from the Instituto de Ecología y de Evolución, Universidad Austral de Chile, Valdivia.     

Pichia scaptomyzae sp. nov., isolated from Scaptomyza multispinosa Malloch (Diptera) in southern Chile

A novel representative of the yeast genus Pichia which has been isolated from the intestinal tract of the fly Scaptomyza multispinosa Malloch, (species of Chilian diptera frequenting meadows where Ranunculus repens L. are abundant), is described and illustrated. The strain differs from all accepted Pichia species (1–11) to warrant its establishment as a new species: Pichia scaptomyzae sp. nov.     

Harmful dinoflagellate blooms caused by Cochlodinium sp.: Global expansion and ecological strategies facilitating bloom formation

The past two decades have witnessed an expansion in the reported occurrences of harmful algal blooms (HABs) caused by the dinoflagellate Cochlodinium. Prior to 1990, blooms had been primarily reported in Southeast Asia, with South Korea alone reporting more than $100M USD in annual fisheries losses during the 1990s. Since then, time blooms have expanded across Asia, Europe, and North America, with recognition of multiple species and ribotypes that exhibit similar ecophysiological and harmful characteristics. Here, we summarize the current state of knowledge regarding taxonomy, phylogeny, detection, distribution, ecophysiology, life history, food web interactions, and mitigation of blooms formed by Cochlodinium. We review this recent expansion of Cochlodinium blooms and characterize the ecological strategies utilized by Cochlodinium populations to form HABs. Although Cochlodinium is comprised of more than 40 species, we focus primarily on the two HAB-forming species, C. polykrikoides and C. fulvescens, specifically describing their flexible nutrient acquisition strategies, inhibition of grazing by inducing rapid mortality in a diverse set of predators, and allelopathic inhibition of a broad range of competing phytoplankton. Finally, we summarize the available information on prevention, control, and mitigation strategies specific to this genus, and discuss pressing questions regarding this increasingly important HAB organism.     

A recurrent and localized dinoflagellate bloom in a Mediterranean beach

A recurrent, prolonged and singular bloom of Alexandrium tayloriBalech in an open beach (La Fosca, Spain, NW Mediterranean)is described. Alexandrium taylori appears at several placesalong a wide area of the NW Mediterranean (Costa Brava) duringthe summer, reaching concentrations up to 10⁵ cells l^–1,but it only proliferates persistently, massively (densities>10⁶ cells l^–1) and recurrently during August in LaFosca beach. The A.taylori bloom can be considered a manifestationof large-scale proliferation in a restricted area, where couplingbetween resting cysts in the sediment and bloom outbreak isnot a major factor compared to the interaction of local environmentalconditions with the planktonic organism's life history. Fromobservations of environmental conditions (the environmentalwindow) and the multiscale spatio-temporal distributions andlife history of A.taylori, we describe the bloom dynamics andanswer some critical questions about the different phases ofthe bloom. Some of these answers are: (i) the source of theA.taylori population is widespread offshore and is not locateddirectly at the beach; (ii) high cell densities are reachedand maintained with a moderate in situ growth and low loss rates;(iii) temporary cysts act as a reserve of the population.     

Flagellar apparatus and nuclear chambers of the green dinoflagellate Gymnodinium chlorophorum

The green dinoflagellate Gymnodinium chlorophorum (BAH ME 100, the type culture) was reexamined with emphasis on the structure of the flagellar apparatus and nuclear envelope. Like other Gymnodinium species, G. chlorophorum possessed a nuclear fibrous connective linking the flagellar apparatus and the nucleus, albeit in a very reduced and unique form. Microtubules nucleated from the R3 flagellar root associated with the nuclear fibrous connective and terminated at the nucleus, a novel arrangement not known in any other dinoflagellate. Although overlooked by previous researchers, nuclear chambers were present in G. chlorophorum similar to those reported in Gymnodinium aureolum and Gymnodinium nolleri. In contrast to the type species of Gymnodinium, Gymnodinium fuscum, only one nuclear pore was present per chamber. The presence of a feeding tube (peduncle) suggests that G. chlorophorum is mixotrophic. Although the fine structure of G. chlorophorum revealed its affiliation to the Gymnodinium group the above discrepancies set it apart, indicating that it might belong in a different genus.     

Morphology,phylogeny and toxin profiles of Gymnodinium inusitatum sp. nov., Gymnodinium catenatum and Gymnodinium microreticulatum (Dinophyceae) from the Yellow Sea,China

Four Gymnodinium species have previously been reported to produce microreticulate cysts. Worldwide, Gymnodinium catenatum strains are conservative in terms of larger subunit (LSU) rDNA and internal transcribed spacer region (ITS) sequences, but only limited information on the molecular sequences of other species is available. In the present study, we explored the diversity of Gymnodinium by incubating microreticulate cysts collected from the Yellow Sea off China. A total of 18 strains of Gymnodinium, from three species, were established. Two of these were identified as Gymnodinium catenatum and Gymnodinium microreticulatum, and the third was described as a new species, Gymnodinium inusitatum. Motile cells of G. inusitatum are similar to those of Gymnodinium trapeziforme, but they only share 82.52% similarity in LSU sequences. Cysts of G. inusitatum are polygonal in shape, with its microreticulate wall composed of approximately 14 concave sections. G. microreticulatum strains differ from each other at 69 positions (88.00% similarity) in terms of ITS sequences, whereas all G. catenatum strains share identical ITS sequences and belonged to the global populations. Phylogenetic analyses, based on LSU sequences, revealed that Gymnodinium species that produce microreticulate cysts are monophyletic. Nevertheless, the genus as a whole appears to be polyphyletic. Paralytic shellfish toxins (PSTs) were found in all G. catenatum strains tested (dominated by 11-hydroxysulfate benzoate analogs and N-sulfocarmaboyl analogs) but not in any of the G. microreticulatum and G. inusitatum strains. Our results support the premise that cyst morphology is taxonomically informative and is a potential feature for subdividing the genus Gymnodinium.     

Life cycle of the ichthyotoxic dinoflagellate Cochlodinium polykrikoides in Korean coastal waters

Since 1995, blooms of the harmful dinoflagellate, Cochlodinium polykrikoides, have caused considerable mortality of aquatic organisms and economic loss in Korea. However, little is known about the life cycle of the species, except for the planktonic vegetative stage; therefore, the aim of this paper was to elucidate the life cycle of C. polykrikoides. Its life cycle has two morphologically different stages: an armored and an unarmored vegetative stage. Armored vegetative cells were found in seawater samples collected in late-November and developed into four-cell chained, unarmored vegetative cells under laboratory culture. In samples collected in late-May, both the armored and unarmored types (vegetative swimming stage) occurred; the former easily developed into an unarmored vegetative cell type, suggesting that the armoured–unarmored transition occurs as early as May. A presumptive resting cyst, round but folded at one side, was produced from armored type cells in laboratory conditions. It was also collected from natural bottom sediments, which suggests it is the dormant resting cyst of C. polykrikoides.     

Cyanopeptolin S, a sulfate-containing depsipeptide from a water bloom of Microcystis sp.

Abstract A new sulfated, cyclic depsipeptide, called cyanopeptolin S, from Microcystis sp. was isolated from a water bloom in the Auensee/Leipzig (Germany). The depsipeptide had a relative molecular mass of 925 and contained l-arginine, l-threonine, l-isoleucine, N-methyl-l-phenylalanine, a l-glutamic acid-δ-aldehyde ring system and a sulfated d-configurated glyceric acid as a side chain. The structure was elucidated by means of two-dimensional ¹H and ¹³C nuclear magnetic resonance spectroscopy, fast atom bombardment mass spectroscopy, Fourier transformed infrared spectroscopy and combined gas-liquid chromatography/mass spectrometry. Cyanopeptolin S inhibited trypsin with an IC₅₀≤ 0.2 μg ml⁻¹.     

The effect of growth phase on the lipid class,fatty acid and sterol composition in the marine dinoflagellate,Gymnodinium sp. in batch culture

We have studied the effects of growth phase on the lipid composition in batch cultures of Gymnodinium sp. CS-380/3 over 43 days of culturing. The lipid content increased two fold, from late logarithmic (day 6) to linear growth phase (day 22) then decreased at stationary phase (day 43) while the lipid yield (mg l(-1)) increased 30-fold from day 6 to 30 mg l(-1) at day 43. Changes in fatty acid content mirrored those observed for the total lipid, while the sterol content continued to increase with culture age through to stationary phase. The largest changes occurred in the lipid classes, especially the polar lipids and triacylglycerols (oil). The proportion of triacylglycerols increased from 8% (of total lipids) at day 6 to 30% at day 43, with a concomitant decrease in the polar lipid fraction. The proportions of 16:0 and DHA [22:6(n-3)] increased while those of 18:5(n-3) and EPA [20:5(n-3)] decreased with increasing culture age. The proportion of the major sterol, dinosterol, decreased from 41% (day 6) to 29% (day 43), while the major dinostanol epimer (23R,24R) increased from 33% (day 6) to 38% (day 22). Despite small changes in the proportion of the main sterols, the same sterols were present at all stages of growth, indicating their value as a chemotaxonomic tool for distinguishing between strains within the same genus. Growth phase could be a useful variable for optimising the oil and DHA content with potential for aquaculture feeds and a source of DHA-rich oils for nutraceuticals.