The Complete Plastid Genome Sequence of the Haptophyte Emiliania huxleyi: a Comparison to Other Plastid Genomes

The complete nucleotide sequence of the plastid genome of thehaptophyte Emiliania huxleyi has been determined. E. huxleyiis the most abundant coccolithophorid and has a key role inthe carbon cycle. It is also implicated in the production ofdimethylsulphide (DMS), which is involved in cloud nucleationand may affect the global climate. Here, we report the plastidgenome sequence of this ecologically and economically importantspecies and compare its gene content and arrangement to otherknown plastid genomes. The genome is circular and consists of105,309 bp with an inverted repeat of 4,841 bp. In terms ofboth genome size and gene content E. huxleyi cpDNA is substantiallysmaller than any other from the red plastid lineage. The geneticinformation is densely packed, with 86.8% of the genome specifying110 identified protein-coding genes, 9 open reading frames,28 different tRNAs, and 3 rRNAs. A detailed comparison to otherplastid genomes, based on gene content, gene function, and genecluster analysis is discussed. These analyses suggest a closerelationship of the E. huxleyi cpDNA to the chlorophyll c-containingplastids from heterokonts and cryptophytes, and they supportthe origin of the chromophyte plastids from the red algal lineage.     

Bloom of Emiliania huxleyi (Prymnesiophyceae) in the western South Atlantic Ocean

A monospecific bloom of the coccolithophorid Emiliania huxleyi(Lohmann) Hay & Mohler (Prymnesiophyceae) was detected offRio de La Plata at 36°S and 54°W in November 1989. Thecell densities observed were up to 6x10⁵ cells I^–1. Thisis the first record of a bloom of E.huxleyi in the area.     

Immunochemical characterization for eukaryotic ultraplankton from the Atlantic and Pacific oceans

The eukaryotic algae are an important component of the ultraplankton(<5 µm diameter cells) and contribute substantiallyto the photosynthetic biomass of the oceans. Because of theirsmall size, individual species cannot be easily distinguishedby traditional or epifluorescence microscopy. To examine thecomposition of the eukaryotic ultraplankton assemblage, immunofluorescenceprobes produced to strains thought to be representative of theultraplankton (Emiliania huxleyi clone BT-6; Pycnococcus provasoliiclone     

Patterns of carbon and nitrogen uptake during blooms of Emiliania huxleyi in two Norwegian fjords

Blooms of the coccolithophorid Emiliania huxleyi were monitoredin two land-locked fjords, Fauskangerpollen and Nordåsvannet(Western Norway), in May 1993. The chemical composition of particulatematter, size-fractionated photosynthesis, calcification, nitrogenuptake rates and the patterns of macromolecular synthesis wereexamined during the peak and decline of E.huxleyi blooms. Thetemporal evolution of the bloom in Fauskangerpollen was definedby a gradual decrease in cell abundance and cell-specific calcificationrates, and by increasing numbers of empty coccospheres and theratio detached coccoliths/living cells. A large proportion ofthe nitrogen required for microplankton growth was suppliedby aminonium and dissolved organic compounds such as urea and,as a consequence, the f-ratios were low (0.2). In general, nitrogenuptake patterns were consistent with ambient concentrationsof nitrogenous species. The photosynthetic carbon metabolismof E.huxleyi dominated phytoplankton assemblages was characterizedby high carbon allocation into lipids and relatively low carbonincorporation into protein as compared with diatom-dominatedassemblages. Consequently, the organic C/nitrogen uptake ratiodetermined stoichiometrically was significantly higher (up to10.8) when coccolithophorids were dominant than in diatom-basedor mixed-phyto-plankton assemblages. These carbon incorporationpatterns were reflected in differences in the chemical compositionof particulate matter.     

The Distribution of Silicon Deposits in the Roots of Molinia caerulea (L.) Moench. and Sorghum bicolor (L.) Moench.

The occurrence of silica in relation to meristematic zones andthe thickening of the endodermis in the roots of Molinia caerulea(L.) Moench. and Sorghum bicolor (L.) Moench. has been investigatedby means of the electron-probe microanalyser and the scanningelectron microscope. In proximal regions of mature roots ofM. caerulea, the central strengthening tissue of the stele,the vessel walls, the endodermis and the sub-epidermal sclerenchymaare areas of heavy accumulation. The distal regions of suchroots are relatively free of silicon and show little thickeningof the inner tangential walls of the endodermis or of the cellsof the strengthening tissues. The thickening of these elementsis shown to be associated with their location and the age ofthe root. In the proximal regions of S. bicolor, silicon is detected andlargely confined to the inner tangential walls of the endodermiswhich display some thickening. In addition, discrete and evenly-distributeddeposits varying in size partly fill the lumen of this layer.Some cells exhibit a number of smaller protrusions. High magnificationsof these lumen deposits show a distinct granular structure incontrast to the very uniform pattern of the wall deposits. The results are compared with deposits in grass leaves and inflorescencebracts and in woody perennials. The presence of silicon in additionto suberin, lignin and polyphenols in the thickened endodermalwall is also discussed in relation to the recognized functionof the endodermis.     

Spatial dynamics of coccolithophore assemblages in the Equatorial Western-Central Pacific Ocean

The spatial distribution of living coccolithophores was studied in the Western-Central Equatorial Pacific Ocean during November–December, 1990 and September–October, 1992. The highest local concentration of coccolithophores occurred at the thermocline in well-stratified waters, but at sea-surface level in dynamic waters. In total, 111 coccolithophore taxa were recognized, some of which exhibited hydrographically controlled variation in their absolute abundance. Gephyrocapsa oceanica and Oolithotus antillarum were abundant in the upwelling front. Most of the lower photic dwellers were abundant in the tropical to subtropical stations regardless of the water stratification. The coccolithophore flora of well-stratified waters could be distinguished from the upwelling front flora by the higher abundance of Umbellosphaera irregularis and lower abundance of G. oceanica. The temperature mixed-water flora was characterized by a high abundance of Emiliania huxleyi. The vertical distribution of all coccolithophore taxa, except three placolith-bearing species, Gephyrocapsa ericsonii, G. oceanica and E. huxleyi, was controlled by upper photic-zone temperature and water stratification. The upper or lower vertical distribution limits of many coccolithophore taxa coincided with the top of the thermocline. The most common 27 taxa were grouped into four ecological groups, Upper Photic-zone Group (UPG), Middle Photic-zone Group (MPG), Lower Photic-zone Group (LPG) and Omnipresent Group (OPG), on the basis of their vertical distribution. By analyzing the hydrographic control on the vertical distribution of these four ecological groups, four ecological assemblages were recognized: High Temperature; Warm Oligotrophic; Warm Eutrophic; and Temperate Mixed-water Assemblages. In equatorial waters, the total coccolithophore assemblage across the photic-zone was controlled by the population in the upper photic-zone. The UPG monopolized the upper photic-zone flora in the High Temperature Assemblage. In the Warn Oligotrophic-water Assemblage, common OPG accompanied abundant UPG in the upper photic-zone. The upper photic-zone of the Warm Eutrophic Assemblage consisted of UPG, MPG and OPG.Emiliania huxleyi and Gephyrocapsa oceanica, the major component of OPG, displayed intra-specific morphological variations. G. oceanica Type 1 was restricted to the upper photic-zone of well-stratified oligotrophic waters. Conversely, in these waters E. huxleyi Type C and G. oceanica Type 2 only occurred below the thermocline. These two taxa also coexist with G. oceanica Type 3 and E. huxleyi Type A in the upper photic zone of dynamic waters.     

Evolution and structure of a shelf coccolithophore bloom in the Western English Channel

The physical factors associated with the development, advectionand disappearance of a shelf bloom of the coccolithophore Emilianiahuxleyi were investigated in the Western English Channel inJune 1992 from an early reflective stage to a mature and dissipativephase (3–4 weeks lifetime) in conjunction with thermaland visible satellite imagery [Advanced Very High ResolutionRadiometer (AVHRR)]. The physical processes that appeared importantin patch evolution and structure were differential stratificationin an area of weak tidal currents, initial zero resultant windconditions (allowing local bloom development), later strengtheningNE winds (driving a coastal warm surface current). entrainmentof the bloom water into the anticyclonic tidal circulation aroundthe Isles of Scilly, and finally bloom dispersal by mixing andflow divergence. Sea-truth results simultaneous with the satelliteimages on 25 and 26 June were examined in relation to the bloomintensity and vertical structure (E.huxleyi cells, detachedcoccoliths and empty coccospheres). Bloom conditions were characterizedby sections of temperature, chlorophyll a, inorganic nutrients,particulate organic and inorganic carbon, and carbon to nitrogenatom ratio. The phytoplankton composition of non-coccolithophorespecies presented significant variations inside and outsidethe bloom. Measurements of beam attenuation coefficient (660nm),diffuse attenuation coefficient [Photosynthetically active radiation(PAR)] and reflectance spectra (415–660 nm) were usedto analyse the extent to which the bloom changed the local opticalproperties. Optical measurements at sea were correlated withcoccolith concentration in order to quantify concentration estimatesderived from remote sensing reflectance measurements.     

Observations on pigments and morphology of Gyrodinium aureolum Hulburt, a marine dinoflagellate containing 19' -hexanoyloxyfucoxanthin as the main carotenoid

Gyrodinium aureolum, a common "red tide" dinoflagellate in Europeanwaters often associated with fish mortality, was isolated fromthe Oslofjord, Norway, and analysed for chlorophylls and carotenoids.Besides chlorophyll a and c the following carotenoids were characterizedby thin-layer chromatography, visible light spectrophotometryand mass spectrometry: ß,-carotene, ß,ß-carotene,djatoxanthin, diadinoxanthin, 19'-hexanoyloxyfucoxanthin and3 xanthophylls which could not be correlated with hitherto structurallyknown carotenoids from dinoflagellates. G. aureolum deviatesfrom most dinoflagellates by the lack of peridinin, but showsaffinity with Gyrodinium sp.-A by the possession of 19'-hexanoyloxyfucoxanthin. Preliminary light microscopical observations on the internalstructure indicate that G. aureolum is uni-nucleate with a typicaldinokaryotic nucleus containing continually condensed chromosomes.The chloroplasts seem to possess an internal pyrenoid like someother dinoflagellates with deviating carotenoid pigmentation.The similarity in carotenoid pigmentation and chloroplast structureof Emiliania huxleyi (Prymnesiophyceae) and Gyrodinium sp.-Aand G.aureolum (Dinophyceae) is pointed out. The potential chemotaxonomicvalue of the carotenoid composition in establishing identitywith morphologically similar and ichthyotoxic dinoflagellatesis briefly discussed.     

Evidence for the Involvement of Mitochondrial Respiration in Calcification in a Marine Coccolithophorid, Emiliania huxleyi

In the marine coccolithophorid, Emiliania huxleyi, CaCO₃ productionunder illumination showed a lag phase for about 3 h and thenincreased greatly. During the lag phase the rate of CaCO₃ productionin the light was similar to that in the dark. The productionof CaCO₃ in the dark was inhibited by the addition of 170 µMCCCP, 1 mM KCN and 1 mM SHAM. These results suggest that a littleproduction of CaCO₃ is supported by energy from mitochondrialrespiration, but that large amount of CaCO₃ production requiresphotosynthesis. ¹Present address: SDS Biotech K.K., Tsukuba Technology Center,Midorigahara 2-1, Tsukuba, Ibaraki, 300-26 Japan     

Phosphate Compounds in Vertebrate Red Blood Cells

This review brings together and discusses the significance ofexisting information about water-soluble (small molecule) organicphosphate constituents of red blood cells in different vertebratespecies, with emphasis on 2,3 diphosphoglycerate (DPG), inositolpentaphosphate (IP₅) ATP and guanosine triphosphate (GTP), compoundswhich may play an important role in respiratory physiology bymodifying the affinity of hemoglobin for oxygen. Results onthe distribution and concentration of these compounds in redcells of vertebrate animals can be summarized as follows 1)DPG High in mammals (except cats and ruminants) Absent in crocodilianssquamata and fishes. High briefly in the bird embryo absentin adult. High briefly in turtle embryo low in juvenile lowto absent in adult 2 IP₅. High in birds. Absent in mammals,crocodilians squamata and fishes (with the exception of Arapaimagigas). Low in turtles 3 ATP Intermediate in mammals. High inbirds and turtles. Very high in squamata Intermediate to veryhigh in fishes. Low in crocodilians 4) GTP Very low in mammalsbirds, reptiles and amphibians (except for small pool in Ranatadpole). Low to very high in fishes.     

Short-term dynamics of a Melosira population in the plankton of an impoundment in central Chile

Relationships among the chlorophyll-specific photosyntheticbehaviour of a Melosira-dominated phytoplankton, net variationsin the quantity of Melosira in suspension, the rates of sinkingloss of Melosira cells and did fluctuations in water-columnstability were investigated in Embalse Rapel. central Chile.The short study was carried out during the autumnal equinoxialperiod (March. 1984) of maximal Melosira abundance to determinethe extent to which these various components might contributeto the distinctly bimodal seasonal distribution of phytoplanktonabundance in this reservoir. Diurnal photosynthetic productionwithin the illuminated layer and supposed column respirationwere found to be of a similar order, suggesting that net increasethrough cellular growth was already substantially limited byself-shading. Thus observed net changes in the standing populationmay have depended more on the relative magnitude of sinkingloss rates and recruitment through resuspension, which processesare profoundly influenced by alternations in wind-induced mixingand intense, near-surface, thermal stratification. As the relativefrequency and duration of these episodes vary during the year,so does the capacity of the Melosira to maintain or increaseits standing biomass. High cellular photosynthetic efficiencycoupled with rapid sinking rate appear to be of selective advantagewhen the cycle of alternation is approximately diel. The applicationof these findings to the seasonal distribution of M. granulatain the Rapel reservoir and to the ecology of planktonic Melosirapopulations elsewhere is briefly discussed.     

Biogeographic study of the planktonic communities of the Prince Edward Islands (Southern Ocean)

Microphytoplankton and zooplankton composition and distributionin the vicinity of the Prince Edward Islands and at the Sub-antarcticFront (SAF) were investigated in late austral summer (April/May)1996. Samples were collected for analysis of chlorophyll a concentration(Chi a), microphytoplankton and zooplankton abundance. Generally,the highest Chl a concentrations (up to 2.0 µg l^–1)and zooplankton densities (up to 192 ind. m^–3) were recordedat stations within the inter-island area while the lowest values(<0.4 µg l^–1) were observed at stations upstreamof the islands. High Chl a and zooplankton biomass values werealso associated with the SAF. Microphytoplankton were dominatedby chain-forming species of the genera Chaetoceros (mainly C.neglectus),Fragilariopsis spp. and the large diatom Dactyliosolen antarcticus.The zooplankton assemblages were always dominated by mesozooplanktonwhich at times contributed up to 98% of total zooplankton abundanceand up to 95% of total biomass. Among mesozooplankton, copepods,mainly Clausocalanus brevipes and Metridia lucens numericallydominated. Among the macrozooplankton euphausiids, mainly Euphausiavallentini, E.longirostis and Stylocheiron maximum, and chaetognaths(Sagitta gazellae) accounted for the bulk of abundance and biomass.Cluster and ordination analysis did not identify any distinctbiogeographic regions among either the microphytoplankton orzooplankton.     

Stress relaxation properties of the cell wall of growing intact plants

The cell wall of dark-grown Avena coleoptiles and the epidermisof light-grown mungbean hypocotyls was subjected to stress-relaxationanalysis and the following results were obtained. 1. Actively growing apical regions of the organs, either coleoptilesor hypocotyls, had certain threshold values of minimum stress-relaxationtime, T_O, 0.04 sec for coleoptile cell wall and 0.03 sec forthe epidermal cell wall of hypocotyls. The cell wall of thebasal region of the organs, which were mature and not growing,had a higher value of To. 2. When the apical regions of the organs, either coleoptilesor hypocotyls, ceased to grow, their cell walls showed T_O valuesabove these thresholds. 3. The relaxation rate, b, was small in the cell wall of activelygrowing regions of the organs, compared with that of non-growingregions. 4. The maximum relaxation time, T_m, was variable and no significantrelationship with growth capacity was found. 5. The extensibility, mm/gr, was large not only in activelygrowing regions of the organs but also in fully grown regions,suggesting that the value represents complex properties of thecell wall including the history of cell wall extension. From these results, we concluded that biochemical modificationsoccur in the cell wall matrix of actively growing organs ofeither monocots or dicots, and these are the bases of the capacityof the cell wall to extend and are represented chiefly by T_oand possibly by b. (Received August 12, 1974; )     

Increased CO<Subscript>2</Subscript> and the effect of pH on growth and calcification of <Emphasis Type="Italic">Pleurochrysis carterae</Emphasis> and <Emphasis Type="Italic">Emiliania huxleyi</Emphasis> (Haptophyta) in semicontinuous cultures

The effects of changes in CO₂ and pH on biomass productivity and carbon uptake of Pleurochrysis carterae and Emiliania huxleyi in open raceway ponds and a plate photobioreactor were studied. The pH of P. carterae cultures increased during day and decreased at night, whereas the pH of E. huxleyi cultures showed no significant diurnal changes. P. carterae coccolith production occurs during the dark period, whereas in E. huxleyi, coccolith production is mainly during the day. Addition of CO₂ at constant pH (pH-stat) resulted in an increase in P. carterae biomass and coccolith productivity, while CO₂ addition lowered E. huxleyi biomass and coccolith production. Neither of these algae could grow at less than pH 7.5. Species-specific diurnal pH and pCO₂ variations could be indicative of significant differences in carbon uptake between these two species. While E. huxleyi has been suggested to be predominantly a bicarbonate user, our results indicate that P. carterae may be using CO₂ as the main C source for photosynthesis and calcification.     

Temperature-related diversity of shell colour in the intertidal gastropod Batillaria

The intertidal snail Batillaria exhibits remarkable variationin the shell colour within and among populations. Field studywas conducted to determine the factors in maintaining observedshell colour polymorphism. Geographical variations in shellcolour polymorphisms in B. attramentaria were significantlycorrelated with the temperature of the locality of the population.Darker morphs were predominant in colder regions, whereas lightermorphs increase their proportion in warmer regions. A consistentassociation was also found in B. multiformis that co-existedwith B. attramentaria. Strong predatory pressure imposed bydigenean trematode parasites was observed in B. attramentaria.However, it is unlikely to affect the colour variations, becauseno correlation exists between colour morphs and trematode parasitism.Although visual selection may also contribute to colour variationin Batillaria, no evidence is found for the existence of visualpredators that affect colour patterns of these snails. The deficitof variation in cold regions is possibly due to selection againstbrighter morphs, because bright colours reflect heat. Althoughdark shells absorb sunlight and may therefore be exposed tothe risks of overheating and drying up in a hot habitat, thedarkest morph was frequently observed in the warmer regions,suggesting that physical selection on the colour morphs canbe relaxed in the warmer environment. Our results suggest thatclimatic selection is one of the significant factors maintainingshell colour polymorphism in these intertidal snails. (Received 13 December 2006; accepted 14 April 2007)     

Inter-strain differences in nitrogen use by the coccolithophore Emiliania huxleyi, and consequences for predation by a planktonic ciliate

Four strains of the coccolithophore Emiliania huxleyi (CCMP strains 370, 373, 374, 379) were tested for their ability to grow on various nitrogen sources. All strains grew on ammonium, nitrate, and urea, although growth of CCMP379 on urea was low. Responses to other dissolved organic nitrogen (DON) sources varied. CCMP379 did not grow on any DON source other than urea. All other strains grew on one of the two tested amino acids: CCMP370 and CCMP373 on glutamine, and CCMP374 on alanine. All three of these strains also grew on hypoxanthine; in addition, two grew well on acetamide and one on ethanolamine. E. huxleyi strains also differed in their susceptibility to predation by the ciliate Strobilidium sp. CCMP374 was ingested at substantially higher rates than CCMP373 regardless of E. huxleyi growth condition. Ciliate feeding rates also depended on E. huxleyi growth condition. For CCMP374, feeding rates were 2× higher on growing E. huxleyi cells than on non-growing cells (average 27.5 versus 15.6 cells ciliate⁻¹ h⁻¹, respectively). For CCMP373, a relationship between E. huxleyi growth rate and ciliate feeding rate was not evident, but E. huxleyi grown on some N sources (ammonium, nitrate, urea) were ingested at consistently higher rates than E. huxleyi grown on other sources (ethanolamine, glutamine). Interstrain differences in the ability to utilize DON and resist predation may contribute to maintenance of high genetic diversity within this cosmopolitan, bloom-forming species.     

Spatial and temporal patterns of phytoplankton composition in subtropical coastal lagoon, the Indian River Lagoon, Florida, USA

A 2 year study of the phytoplankton community was carried outin the Indian River Lagoon, USA. In terms of biovolume, thephytoplankton community was generally dominated by dinoflagellates,diatoms or cyanobacteria. Mean phytoplankton standing cropswere highest in the most flow-restricted regions of the lagoon,which had the lowest mean salinity values and comparativelyhigh total nitrogen:total phosphorus ratios. In this region,blooms of dinoflagellates were common in the first year of thestudy, which was characterized by an El Niño event thatyielded exceptionally high rainfall levels and freshwater outflow.Picoplanktonic cyanobacteria blooms became more prominent inthe second year of the study, which was characterized by belowaverage rainfall conditions. In unrestricted flow regions ofthe lagoon, located near inlets to the Atlantic Ocean, diatomswere most often the dominant taxa. Regions of intermediate waterturnover rates and high external loading of phosphorus had aprevalence of diatom blooms. However, the average phytoplanktonstanding crops in the latter regions did not reach the levelsexperienced in the flow-restricted parts of the lagoon. In termsof individual phytoplankton taxa, the most common bloom-formingdiatoms in the Indian River Lagoon system included: Skeletonemacostatum, Dactyliosolen fragilissimus, Skeletonema menzelii,Cerataulina pelagica, Odontella regia, Chaetoceros lorenzianus,Rhizosolenia setigera and Thalassionema nitzschioides. The majorbloom-forming dinoflagellate species included: Pheopolykrikoshartmannii, Akashiwo sanguinea, Prorocentrum micans, the potentiallytoxic species Pyrodinium bahamense var. bahamense and Prorocentrumminimum. Several picoplanktonic cyanobacteria were also prominentmembers of the phytoplankton community, including Synechococcuselongates. The spatial and temporal patterns observed in someof these dominant species were attributable to patterns in keyenvironmental variables, including salinity, temperature andnutrient concentrations.