bluuebunny/crossref_metadata_2025 huggingface dataset:
Seismic attenuation structure of the top half of the inner core beneath the northeastern Pacific
Authors: Iritani R. , Takeuchi N. , Kawakatsu H.
Published: October 2010

We present a 1‐D seismic attenuation model of the top 600 km of the inner core beneath the northeastern Pacific. We employ a waveform inversion method for attenuation parameters based on simulated annealing that enables us to analyze complicated waveforms contaminated by phase overlaps. The method also allows analysis of PKP(DF) in distant ranges where only single core phase is present. The resultant data set is about five times larger compared with our previous study. The inverted model shows a gradual increase of the attenuation from the ICB to 200–250 km depth that coincides with a gradual increase of the P‐wave velocity in the same depth range. The attenuation decreases from this depth range, and thus shows a peak around 200–250 km. A possible relation of these observations to the growth process of the inner core in the western hemisphere of the inner core is discussed.
Dependence of solar proton events on their associated activities: Flare parameters
Authors: Park Jinhye , Moon Y.‐J. , Lee D. H. , Youn Saepoom
Published: October 2010

In this study we have examined the occurrence probability of solar proton events and their peak fluxes depending on three flare parameters (X‐ray peak flux, longitude, and impulsive time). For this we used NOAA solar energetic particle events from 1976 to 2006 and their associated X‐ray flare data. As a result, we selected 166 proton events that were associated with major flares: 85 events associated with X‐class flares and 81 events associated with M‐class flares. The occurrence probability especially strongly depends on three parameters as follows. (1) We found that about only 3.5% (1.9% for M‐class and 21.3% for X‐class) of the flares are associated with the proton events. (2) It is also found that this fraction strongly depends on longitude; for example, the fraction for 30°W < L ≤ 90°W is about three times larger than that for 30°E < L ≤ 90°E. (3) We also note that the occurrence probability of solar proton events associated with long‐duration (≥0.3 h) flares is about 2 (X‐class flare) to 7 (M‐class flare) times larger than that with short‐duration (<0.3 h) flares. (4) The largest difference is found between the eastern short‐duration M‐class flare group (0.3%) and the western long‐duration X‐class flare group (46.5%). In addition, the relationship between X‐ray flare peak flux and proton peak flux as well as its correlation coefficient are strongly dependent on longitude and impulsive time.
Rate of radial transport of plasma in Saturn's inner magnetosphere
Authors: Chen Y. , Hill T. W. , Rymer A. M. , Wilson R. J.
Published: October 2010

In the inner part of a rapidly rotating magnetosphere such as that of Saturn, the major observable signature of radial plasma convection is a series of longitudinally localized injections and simultaneous drift dispersions of hot tenuous plasma from the outer magnetosphere. The Cassini Plasma Spectrometer (CAPS) and the Cassini Magnetospheric Imaging Instrument (MIMI) have observed signatures of these processes frequently, thus providing direct evidence for Saturn's magnetospheric convective motions, in which the radial transport of plasma comprises hot, tenuous plasma moving inward and cooler, denser plasma moving outward. On the basis of an extended statistical sample of these injection/dispersion events, we find that the inflow channels occupy only a small fraction (∼7%) of the total available longitudinal space, indicating that the inflow speed is much larger than the outflow speed. We assume that the plasma is largely confined to a thin equatorial sheet and calculate its thickness by deriving the centrifugal scale height profile based on the CAPS observations. We also present the radial and longitudinal dependences of flux tube mass content as well as the total ion mass between 5 and 10 Saturn radii. Combining these results, we estimate a global plasma mass outflow rate ∼280 kg/s.
Joule heating and nitric oxide in the thermosphere, 2
Authors: Barth Charles A.
Published: October 2010

During geomagnetic storms, gravity waves propagate from the polar regions toward the equator heating the thermosphere at 140 km and higher. These gravity waves are produced by Joule heating that occurs at latitudes of 60° and higher. The heating leads to an increase in the density of nitric oxide at 140 km in the thermosphere. On some occasions, the increased nitric oxide diffuses downward to the 110 km level causing the nitric oxide density at that level to increase substantially. Two and a half years (11 March 1998–30 September 2000) of Student Nitric Oxide Explorer (SNOE) observations of nitric oxide were examined to look for occurrences of increased nitric oxide produced by Joule heating initiated gravity waves and to determine how often downflow of nitric oxide occurs. The results of this study show that gravity wave heating occurs frequently, about 12–14% of the time at 40° latitude. For about 50% of these events, downflow of nitric oxide from 140 km to 110–120 km occurs the following day. About 2–3% of the time, gravity waves propagate all the way to the 20°N and S latitude band around the equator. On special occasions, downflow of nitric oxide occurs at the equator as the result of Joule heating occurring in the polar regions. This happened on five occasions during the two and a half year period in 1998–2000.
Spatial scales of climate response to inhomogeneous radiative forcing
Authors: Shindell Drew , Schulz Michael , Ming Yi , Takemura Toshihiko , Faluvegi Greg , Ramaswamy V.
Published: October 2010

The distances over which localized radiative forcing influences surface temperature have not been well characterized. We present a general methodology to analyze the spatial scales of the forcing/response relationship and apply it to simulations of historical aerosol forcing and response in four climate models. We find that the surface temperature response is not strongly sensitive to the longitude of forcing but is fairly sensitive to latitude. Surface temperature responses in the Arctic and the Southern Hemisphere extratropics, where forcing was small, show little relationship to local forcing. Restricting the analysis to 30°S–60°N, where nearly all the forcing was applied, shows that forcing strongly influences response out to ∼4500 km away examining all directions. The meridional length of influence is somewhat shorter (∼3500 km or 30°), while it extends out to at least 12,000 km in the zonal direction. Substantial divergences between the models are seen over the oceans, whose physical representations differ greatly among the models. Length scales are quite consistent over 30°S–60°N land areas, however, despite differences in both the forcing applied and the physics of the models themselves. The results suggest that better understanding of regionally inhomogeneous radiative forcing would lead to improved projections of regional climate change over land areas. They also provide quantitative estimates of the spatial extent of the climate impacts of pollutants, which can extend thousands of kilometers beyond polluted areas, especially in the zonal direction.
Green synthesis of gold nanoparticles by the marine microalga Tetraselmis suecica
Authors: Shakibaie Mojtaba , Forootanfar Hamid , Mollazadeh‐Moghaddam Kamyar , Bagherzadeh Zahra , Nafissi‐Varcheh Nastaran , Shahverdi Ahmad Reza , Faramarzi Mohammad Ali
Published: October 2010

The application of green‐synthesis principles is one of the most impressive research fields for the production of nanoparticles. Different kinds of biological systems have been used for this purpose. In the present study, AuNPs (gold nanoparticles) were prepared within a short time period using a fresh cell extract of the marine microalga Tetraselmis suecica as a reducing agent of HAuCl4 (chloroauric acid) solution. The UV–visible spectrum of the aqueous medium containing AuNPs indicated a peak at 530 nm, corresponding to the surface plasmon absorbance of AuNPs. The X‐ray diffraction pattern also showed a Bragg reflection related to AuNPs. Fourier‐transform infrared spectroscopy was performed for analysis of surface functional groups of AuNPs. Transmission electron microscopy and particle‐size‐distribution patterns determined by the laser‐light‐scattering method confirmed the formation of well‐dispersed AuNPs. The most frequent size of particles was 79 nm.
Erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA) blocks differentiation and maintains the expression of pluripotency markers in human embryonic stem cells
Authors: Burton Peter , Adams David R. , Abraham Achamma , Allcock Robert W. , Jiang Zhong , McCahill Angela , Gilmour Jane , McAbney John , Kaupisch Alexandra , Kane Nicole M. , Baillie George S. , Baker Andrew H. , Milligan Graeme , Houslay Miles D. , Mountford Joanne C.
Published: October 2010

hESCs (human embryonic stem cells) have enormous potential for use in pharmaceutical development and therapeutics; however, to realize this potential, there is a requirement for simple and reproducible cell culture methods that provide adequate numbers of cells of suitable quality. We have discovered a novel way of blocking the spontaneous differentiation of hESCs in the absence of exogenous cytokines by supplementing feeder-free conditions with EHNA [erythro-9-(2-hydroxy-3-nonyl)adenine], an established inhibitor of ADA (adenosine deaminase) and cyclic nucleotide PDE2 (phosphodiesterase 2). hESCs maintained in feeder-free conditions with EHNA for more than ten passages showed no reduction in hESC-associated markers including NANOG, POU5F1 (POU domain class 5 transcription factor 1, also known as Oct-4) and SSEA4 (stage-specific embryonic antigen 4) compared with cells maintained in feeder-free conditions containing bFGF (basic fibroblast growth factor). Spontaneous differentiation was reversibly suppressed by the addition of EHNA, but, upon removing EHNA, hESC populations underwent efficient spontaneous, multi-lineage and directed differentiation. EHNA also acts as a strong blocker of directed neuronal differentiation. Chemically distinct inhibitors of ADA and PDE2 lacked the capacity of EHNA to suppress hESC differentiation, suggesting that the effect is not driven by inhibition of either ADA or PDE2. Preliminary structure–activity relationship analysis found the differentiation-blocking properties of EHNA to reside in a pharmacophore comprising a close adenine mimetic with an extended hydrophobic substituent in the 8- or 9-position. We conclude that EHNA and simple 9-alkyladenines can block directed neuronal and spontaneous differentiation in the absence of exogenous cytokine addition, and may provide a useful replacement for bFGF in large-scale or cGMP-compliant processes.
Ephrin-B3 binds to a sulfated cell-surface receptor
Authors: Holen Halvor L. , Zernichow Lillian , Fjelland Kristine E. , Evenroed Ida M. , Prydz Kristian , Tveit Heidi , Aasheim Hans-Christian
Published: October 2010

The ephrins are a family of proteins known to bind the Eph (erythropoietin-producing hepatocellular) receptor tyrosine kinase family. In the present paper, we provide data showing that ephrin-B3 binds a sulfated cell-surface protein on HEK-293T (human embryonic kidney-293 cells expressing the large T-antigen of simian virus 40) and HeLa cells, a binding that is nearly completely blocked by treatment of these cell lines with chlorate or heparinase, or by addition of the heavily sulfated glycosaminoglycan heparin. This indicates that heparan sulfate on these cells is essential for cell-surface binding of ephrin-B3. Heparin did not affect ephrin-B3 binding to EphB receptors expressed on transfected HEK-293T cells, indicating further that ephrin-B3 binds an alternative receptor which is a heparan sulfate proteoglycan. Site-directed mutagenesis analysis revealed that Arg178 and Lys179 are important for heparin binding of ephrin-B3 and also for ephrin-B3 binding to cells. These amino acids, when introduced in the non-heparin-binding ephrin-B1, conferred the heparin-binding property. Functional studies reveal that ephrin-B3 binding to cells induces cellular signalling and influences cell rounding and cell spreading. In conclusion, our data provide evidence for an unknown ephrin-B3-binding cell-surface proteoglycan involved in cellular signalling.
Conformation states of the neuronal porosome complex
Authors: Cho Jin Won , Lee Jin‐Sook , Jena Bhanu P.
Published: October 2010

Porosomes are the universal secretory machinery of the cell plasma membrane, where membrane‐bound secretory vesicles transiently dock and fuse to expel intravesicular contents to the environment during cell secretion. In neurons, 12‐ to 17‐nm cup‐shaped lipoprotein structures possessing a central plug are present at the presynaptic membrane, where 40–50 nm in diameter synaptic vesicles transiently dock and fuse to release neurotransmitters. The neuronal porosome complex has been isolated, its composition determined and it has been both structurally and functionally reconstituted in artificial lipid membranes. Earlier studies using AFM (atomic force microscopy), EM (electron microscopy), electron density and 3D contour mapping provide the structure and assembly of proteins within the neuronal porosome complex at the nanoscale level. A set of eight protein units lining the neuronal porosome cup is present, each connected via spoke‐like elements to a central plug, hypothesized for the rapid opening and closing of the structure to the outside. In the present study, ultrahigh‐resolution imaging of the presynaptic membrane of isolated synaptosome preparations demonstrate, for the first time, the presence of neuronal porosomes in both their open and close conformations. The results suggests that the central plug is retracted into the porosome cup in its open conformation and pushed outward to seal the porosome opening, supporting the hypothesis that it operates as the opening–closing device of the complex.
Clinical Experience with Molecular Adsorbent Recirculating System (MARS) in Patients with Drug‐induced Liver Failure
Authors: Zhou Xin‐min , Miao Ji‐yan , Yang Yan , Zhao Ling , Wang Xin , Xu Li , Ding Jie , Wu Kai‐chun , Fan Dai‐ming , Wang Min‐min
Published: October 2010

Abstract:  The molecular adsorbent recirculating system (MARS) is a novel extracorporeal technique for liver support. We report the clinical results in a group of fourteen patients with drug‐induced liver failure. Fourteen patients, aged 22–83 years, with acute or subacute liver failure [mean Child–Turcotte–Pugh (CTP) score 11 (range 8–15)] due to the intake of various drugs (diet pill overdose—2; Chinese traditional medicine (CTM)—4; antibiotic, paracetamol, tuberculostatic, or vasodilator abuse—8) were treated with one to seven sessions of MARS. Beneficial effects such as the improvement of encephalopathy and prothrombin activity, as well as a reduction of bilirubin and ammonia were recorded during MARS treatments. Thirteen out of fourteen patients survived the hospitalization (93%), and two of the discharged patients died during the follow‐up of 6–12 months. The overall survival rate was about 79%. MARS therapy can contribute to the improved treatment of drug‐induced liver failure patients.
N‐ASSIMILATION IN THE NOXIOUS FLAGELLATE HETEROSIGMA CARTERAE (RAPHIDOPHYCEAE): DEPENDENCE ON LIGHT, N‐SOURCE, AND PHYSIOLOGICAL STATE1
Authors: Clark Darren R. , Flynn Kevin J.
Published: October 2010

The capabilities of the diel vertically migrating flagellate Heterosigma carterae Hulburt for assimilating ammonium and nitrate into cell‐N in light and in darkness were studied using cells of different N‐status. Ammonium utilization in darkness, except by N‐replete cells, attained>50% of use in the light. However, the capacity to use nitrate was poor in darkness, and less than 20% of nitrate‐N that was taken up in darkness was then actually incorporated into cell‐N. The ability to assimilate N in darkness improved as N‐status (N:C) declined, concurrent with an increasing content of water‐soluble carbohydrate. This carbohydrate was used to support dark N‐assimilation. Cells held in darkness for over a day and that had halted nitrate‐uptake were still capable of taking up ammonium. Furthermore, the act of taking up ammonium appeared to make available a source of C to support nitrate uptake that was previously unavailable. The implications of these results for the ecophysiology of this organism and for the construction of mathematical models of algal growth are considered.
UPTAKE OF INORGANIC CARBON BY CLADOPHORA GLOMERATA (CHLOROPHYTA) FROM THE BALTIC SEA1
Authors: Choo Kyung‐sil , Snoeijs Pauli , Pedersén Marianne
Published: October 2010

Carbon uptake in the green macroalga Cladophora glomerata (L.) Kütz. from the brackish Baltic Sea was studied by recording changes in pH, alkalinity, and inorganic carbon concentration of the seawater medium during photosynthesis. The use of specific inhibitors identified three uptake mechanisms: 1) dehydration of HCO3− into CO2 by periplasmic carbonic anhydrase, followed by diffusion of CO2 into the cell; 2) direct uptake of HCO3− via a 4,4′‐diisothiocyanato‐stilbene‐2,2′‐disulfonate‐sensitive mechanism; and 3) uptake of inorganic carbon by the involvement of a vanadate‐sensitive P‐type H+‐ATPase (proton pump). A decrease in the alkalinity of the seawater medium during carbon uptake, except when treated with vanadate, indicated a net uptake of the ionic species contributing to alkalinity (i.e. HCO3−, CO32−, and OH−) from the medium, where OH− influx is equivalent to H+ efflux. This would suggest that the proton pump is involved in HCO3− transport. We also show that the proton pump can be induced by carbon limitation. The inducibility of carbon uptake in C. glomerata may partly explain why this species is so successful in the upper littoral zone of the Baltic Sea. Usually, carbon limitation is not a problem in the upper littoral of the sea. However, it may occur frequently within dense Cladophora belts with high photosynthetic rates that create high pH and low carbon concentrations in the alga's microenvironment.
LIGHT AND ELECTRON MICROSCOPIC OBSERVATIONS OF PREFERENTIAL DESTRUCTION OF CHLOROPLAST AND MITOCHONDRIAL DNA AT EARLY MALE GAMETOGENESIS OF THE ANISOGAMOUS GREEN ALGADERBESIA TENUISSIMA(CHLOROPHYTA)1
Authors: Lee Sang‐Hee , Motomura Taizo , Ichimura Terunobu
Published: October 2010

Gametogenesis in male and female gametophytes was studied by light microscopy and EM in the dioecious multinucleate green algaDerbesia tenuissima(Moris & De Notaris) P. Crouan & H. Crouan, where male and female gametes differ in size. Gametogenesis was divided into five stages: 32 h (stage 1), 24 h (stage 2), 16 h (stage 3), 8 h (stage 4), and 0.5 h (stage 5) before gamete release. At stage 1, the first sign of gametogenesis observed was the aggregation of gametophyte protoplasm to form putative gametangia. At stage 2, gametangia were separated from the vegetative protoplasm of gametophytes. Morphological changes of nuclei and organelles occurred at this early stage of male gametogenesis, and organelle DNA degenerated. At stage 3, male organelle DNA had completely degenerated, whereas in female gametangia, organelle DNA continued to exist in both chloroplasts and mitochondria. Gametogenesis was almost completed at stage 4 and fully at stage 5. Small male gametes had a DNA‐containing nucleus and a large mitochondrion and one or several degenerated chloroplasts. The mitochondria and plastids were devoid of DNA. The large female gametes had a nucleus and multiple organelles, all of which contained their own DNA. Thus, degeneration of chloroplast DNA along with morphological changes of organelles occurred at male gametogenesis in anisogamous green algae (BryopsisandD. tenuissima), in contrast with previous studies in isogamous green algae (Chlamydomonas,Acetabularia caliculus, andDictyosphaeria cavernosa) in which degeneration of chloroplast DNA occurred after zygote formation.
EFFECT OF TAXON SAMPLING, CHARACTER WEIGHTING, AND COMBINED DATA ON THE INTERPRETATION OF RELATIONSHIPS AMONG THE HETEROKONT ALGAE1
Authors: Goertzen Leslie R. , Theriot Edward C.
Published: October 2010

Nuclear ribosomal small subunit and chloroplastrbcL sequence data for heterokont algae and potential outgroup taxa were analyzed separately and together using maximum parsimony. A series of taxon sampling and character weighting experiments was performed. Traditional classes (e.g. diatoms, Phaeophyceae, etc.) were monophyletic in most analyses of either data set and in analyses of combined data. Relationships among classes and of heterokont algae to outgroup taxa were sensitive to taxon sampling. Bootstrap (BS) values were not always predictive of stability of nodes in taxon sampling experiments or between analyses of different data sets. Reweighting sites by the rescaled consistency index artificially inflates BS values in the analysis ofrbcL data. Inclusion of the third codon position fromrbcL enhanced signal despite the superficial appearance of mutational saturation. Incongruence between data sets was largely due to placement of a few problematic taxa, and so data were combined. BS values for the combined analysis were much higher than for analyses of each data set alone, although combining data did not improve support for heterokont monophyly.
COMPOSITION, DISTRIBUTION, AND ABUNDANCE OF DEEP‐WATER (>30 m) MACROALGAE IN CENTRAL CALIFORNIA1
Authors: Spalding Heather , Foster Michael S. , Heine John N.
Published: October 2010

The deep‐water macroalgal assemblage was described at 14 sites off the central California coast during 1999 and 2000 from SCUBA and remotely operated vehicle sampling. The stipitate kelp Pleurophycus gardneri Setchell & Gardner, previously thought to be rare in the region, was abundant from 30 to 45 m, forming kelp beds below the well‐known giant kelp forests. Macroalgae typically formed three broadly overlapping zones usually characterized by one or a few visually dominant taxa: 1) the upper “Pleurophycus zone” (30–45 m) of stipitate kelps and Desmarestia spp. with a high percent cover of corallines, low cover of uncalcified red algae, and rare green algae; 2) a middle “Maripelta zone” (40–55 m) with other uncalcified red algae and infrequent corallines and green algae; and 3) a zone (55–75 m) of infrequent patches of nongeniculate coralline algae. The green alga Palmophyllum umbracola Nelson & Ryan, not previously reported from the Northeast Pacific, was found over the entire geographical range sampled from 35 to 54 m. Year‐round profiles of water column irradiance revealed unexpectedly clear water with an average K0 of 0.106·m−1. The low percent surface irradiance found at the average lower macroalgal depth limits in this study (0.56% for brown algae, 0.12% for uncalcified red algae, and 0.01% for nongeniculate coralline algae) and lack of large grazers suggest that light controls the lower distributional limits. The ubiquitous distribution, perennial nature, and similar lower depth limits of deep‐water macroalgal assemblages at all sites suggest that these assemblages are a common persistent part of the benthic biota in this region.
NITROGEN LIMITATION EFFECTS OF DIFFERENT NITROGEN SOURCES ON NUTRITIONAL QUALITY OF TWO FRESHWATER ORGANISMS,SCENEDESMUS QUADRICAUDA(CHLOROPHYCEAE) ANDSYNECHOCOCCUSSP. (CYANOPHYCEAE)
Authors: Ahlgren Gunnel , Hyenstrand Per
Published: October 2010

Food quality for grazers has been related to mineral (nitrogen, phosphorus) and biochemical (amino acids, fatty acids) constituents. The aim of the study was to examine the influence of different nitrogen sources on these constituents in two organisms, the green algaScenedesmus quadricaudaTurp. and the cyanobacteriumSynechococcussp., commonly used in feeding experiments. The two organisms were grown in continuous cultures at different growth rates. Nitrate or ammonium salts were used as nitrogen sources under both replete and limited conditions. Carbon content (mg·g−1dry weight) was stable in both organisms independent of nitrogen source, nitrogen limitation, and growth rate. Nitrogen content decreased with limitation and growth rate inScenedesmusand to a lesser degree inSynechococcus, whereas changes in phosphorus content were not statistically significant. The relative proportions of amino acids (% of total amino acids) were relatively stable in both organisms, whereas the proportions of fatty acids varied with growth rate and limitation. Fatty acid content was much lower inSynechococcusthan inScenedesmus. At N limitation, polyunsaturated fatty acids (PUFAs) showed lower levels in both organisms. The change occurred in the ω3 PUFA (linolenic acid) of the green alga and in the ω6 PUFA (linoleic acid) of the cyanobacterium. The difference in the response of N limitation in the two organisms may be traced to the different composition of the chloroplast membranes (the prokaryotic way) and the microsomal membranes (the eukaryotic way) where the desaturation takes place.
MORPHOLOGY AND LIFE HISTORY OF SCYTOSIPHON LOMENTARIA (SCYTOSIPHONACEAE, PHAEOPHYCEAE) FROM THE AZORES1
Authors: Parente Manuela Isabel , Neto Ana Isabel , Fletcher Robert Lawson
Published: October 2010

Morphological and culture studies of Scytosiphon lomentaria (Lyngbye) Link and Microspongium gelatinosum Reinke (Scytosiphonaceae, Phaeophyceae) were undertaken on material collected on the Island of São Miguel, Azores, where both species were commonly found. Erect thalli of S. lomentaria collected in the field were up to 33 cm long and 2.3 mm wide, tubular, hollow, and commonly constricted at intervals. The plurilocular sporangia were positioned in continuous sori on the thallus surface. Ascocysts were present. In the field, M. gelatinosum formed crustose to slightly pulvinate plants, were spongy in texture, and dark brown to black in color, which were circular or irregularly spreading over several centimeters and firmly attached to the substratum. Sessile unilocular sporangia were located in sori on the crust surface. In culture S. lomentaria plurispores developed into Microspongium‐like crustose prostrate thalli that formed unilocular sporangia. Unispores developed into new erect thalli that formed plurilocular sporangia. Sexual reproduction was not observed. In culture, M. gelatinosum unispores developed into erect thalli identical with S. lomentaria. These results are similar to those reported for other areas and suggest the occurrence in the Azorean plants of a monophasic and heteromorphic life history, involving both entities studied.
THE MESOZOIC RADIATION OF EUKARYOTIC ALGAE: THE PORTABLE PLASTID HYPOTHESIS1
Authors: Grzebyk Daniel , Schofield Oscar , Vetriani Costantino , Falkowski Paul G.
Published: October 2010

Although all chloroplasts appear to have been derived from a common ancestor, a major schism occurred early in the evolution of eukaryotic algae that gave rise to red and green photoautotrophic lineages. In Paleozoic and earlier times, the fossil record suggests that oceanic eukaryotic phytoplankton were dominated by the green (chl b‐containing) algal line. However, following the end‐Permian extinction, a diverse group of eukaryotic phytoplankton evolved from secondary symbiotic associations in the red (chl c‐containing) line and subsequently rose to ecological prominence. In the contemporary oceans, red eukaryotic phytoplankton taxa continue to dominate marine pelagic food webs, whereas the green line is relegated to comparatively minor ecological and biogeochemical roles. To help elucidate why the oceans are not dominated by green taxa, we analyzed and compared whole plastid genomes in both the red and green lineages. Our results suggest that whereas all algal plastids retain a core set of genes, red plastids retain a complementary set of genes that potentially confer more capacity to autonomously express proteins regulating oxygenic photosynthetic and energy transduction pathways. We hypothesize that specific gene losses in the primary endosymbiotic green plastid reduced its portability for subsequent symbiotic associations. This corollary of the plastid “enslavement” hypothesis may have limited subsequent evolutionary advances in the green lineage while simultaneously providing a competitive advantage to the red lineage.
PHYLOGENETIC EVIDENCE FOR THE CRYPTOPHYTE ORIGIN OF THE PLASTID OF DINOPHYSIS (DINOPHYSIALES, DINOPHYCEAE)1
Authors: Hackett Jeremiah D. , Maranda Lucie , Yoon Hwan Su , Bhattacharya Debashish
Published: October 2010

Photosynthetic members of the genus Dinophysis Ehrenberg contain a plastid of uncertain origin. Ultrastructure and pigment analyses suggest that the two‐membrane‐bound plastid of Dinophysis spp. has been acquired through endosymbiosis from a cryptophyte. However, these organisms do not survive in culture, raising the possibility that Dinophysis spp. have a transient kleptoplast. To test the origin and permanence of the plastid of Dinophysis, we sequenced plastid‐encoded psbA and small subunit rDNA from single‐cell isolates of D. acuminata Claparède et Lachman, D. acuta Ehrenberg, and D. norvegica Claparède et Lachman. Phylogenetic analyses confirm the cryptophyte origin of the plastid. Plastid sequences from different populations isolated at different times are monophyletic with robust support and show limited polymorphism. DNA sequencing also revealed plastid sequences of florideophyte origin, indicating that Dinophysis may be feeding on red algae.
DIFFERENCES IN LIFE‐HISTORY CHARACTERISTICS ARE CONSISTENT WITH THE VERTICAL DISTRIBUTION PATTERN OF FUCUS SERRATUS AND FUCUS VESICULOSUS (FUCALES, PHAEOPHYCEAE) IN THE CENTRAL BALTIC SEA
Authors: Malm Torleif , Kautsky Lena
Published: October 2010

On the rocky shores of southeast Sweden, in the central Baltic Sea, the brown seaweed species Fucus serratus L. and Fucus vesiculosus L. form dense constantly submerged stands. The relative proportion of the two species in the belt is shifting both vertically and geographically. Our hypothesis is that differences in life‐history characteristics and the tolerance to physical factors such as wave force, freezing, and light may alter the competitive outcome between the two species with increasing wave exposure. This study included a combination of field studies and laboratory experiments. In sheltered locations, F. serratus and F. vesiculosus grow in mixed stands from 0.5 to 3 m deep, whereas at exposed sites F. vesiculosus grow from 0.5 to 2 m deep and F. serratus mainly from 1 to 5 m deep. The two Fucus species differed markedly in their tolerance to physical stress as well as in a number of reproductive and vegetative characteristics. Tolerance to freezing and wave action was higher in F. vesiculosus compared with F. serratus. Fucus vesiculosus also produced 10 times more eggs per receptacle, allocated significantly more tissue per frond for reproduction, and produced more reproductive fronds per individual than did F. serratus. In addition, the survival rate of F. vesiculosus germlings was slightly higher than that of F. serratus germlings during the first year. These differences in life history characteristics are suggested to partly explain the observed distribution patterns of the two Fucus species in the Baltic Sea.
MULTIMINERAL CALCAREOUS DEPOSITS IN THE MARINE ALGA ACETABULARIA ACETABULUM (CHLOROPHYTA; DASYCLADACEAE)
Authors: Kingsley Roni J. , Van Gilder Rachel , LeGeros Racquel Z. , Watabe Norimitsu
Published: October 2010

The ultrastructure and mineralogy of cultured and wild specimens of the green algae Acetabularia acetabulum were studied. Sites of calcification were clarified using TEM and SEM. Minerology was determined via electron diffraction, energy‐dispersive x‐ray microanalysis, and Fourier transform infrared spectral analyses of the calcareous deposits. These deposits were found covering the surface and within the cell wall of the cultured juveniles and adult wild specimens of A. acetabulum. Deposits within and directly over the wall were amorphous calcium carbonate (ACC) in granular form. In‐wall and outer cell wall ACC appear to develop independently from each other. The formation of the in‐wall ACC may be mediated by the wall structure and/or chemistry, whereas mucin may be the factor mediating formation of outer cell wall ACC. In contrast to the stable in‐wall ACC, outer cell wall ACC could be transitory, transforming into aragonite. In cultured cells, a small amount of monohydrocalcite crystals and calcite were found. It is possible that these were transformation products of ACC. In wild specimens, whewellite (calcium oxalate monohydrate) was present inside and outside of the cap wall. It is unclear if whewellite is present within the cytoplasm. Local and temporal differences in the microenvironments for the multiphase mineralization are suggested.
CHARACTERIZATION OF MICROBIALITE‐FORMING CYANOBACTERIA IN A TROPICAL LAGOON: TIKEHAU ATOLL, TUAMOTU, FRENCH POLYNESIA
Authors: Abed Raeid M. M. , Golubic Stjepko , Garcia‐Pichel Ferran , Camoin Gilbert F. , Sprachta Sophie
Published: October 2010

Natural populations of benthic cyanobacteria in the lagoon of Tikehau Atoll in French Polynesia were studied using a polyphasic approach that combined field observations, LM, culturing, and molecular sequencing. The approach assessed their phenotypic (morphotypic and ecological) and genotypic diversity. Partial sequences (approximately 450 bp long) of the PCR‐amplified 16S rRNA gene were obtained from both natural and cultured populations using cyanobacteria‐specific primers. The sequences obtained clustered into six separate phylogenetic clusters in relation to the complete set of 16S rRNA sequences available in public databases. Phylogenetic clustering correlated in many cases with some morphological characteristics. For example, Spirulina subsalsa could be identified to the morphospecies level using both molecular and microscopic approaches. Morphotypes identified as Symploca hydnoides (Kütz. ex Gomont) TK22, Phormidium sp. TK1, and P. laysanense (Lemmerman) TK14 formed a distinct cluster. The morphogenus Hydrocoleum (Blennothrix) clustered interestingly close to the morphologically similar, but planktonic, marine cyanobacterium Trichodesmium, suggesting a relationship. Other sequences belonging to morphotaxa with very narrow trichomes were found to be polyphyletic. Enrichment cultures, with inoculum obtained from field populations, were followed over a period of 18 months. Dominance in all cultures shifted over time in favor of a set of cyanobacterial strains with narrow trichomes, which were phenotypically and phylogenetically different from natural populations dominating the original samples. Sequences from strains enriched by cultivation clustered into two well‐defined phylogenetic groups, possibly identifying new taxa. These clusters may represent a niche of opportunistic species, evolved to exploit short‐term nutrient spikes in the environment.
MORPHOLOGY, REPRODUCTION, AND THE 18S rRNA GENE SEQUENCE OF PIHIELLA LIAGORACIPHILA GEN. ET SP. NOV. (RHODOPHYTA), THE SO‐CALLED ‘MONOSPORANGIAL DISCS’ ASSOCIATED WITH MEMBERS OF THE LIAGORACEAE (RHODOPHYTA), AND PROPOSAL OF THE PIHIELLALES ORD. NOV.
Authors: Huisman John M. , Sherwood Alison R. , Abbott Isabella A.
Published: October 2010

Pihiella liagoraciphila gen. et sp. nov. (Rhodophyta) is described for a minute endo/epiphyte that is commonly associated with members of the Liagoraceae ( Nemaliales, Rhodophyta). Algae are discoid or subspherical and grow to a maximum diameter of 400 μm. Attachment is via isolated elongate rhizoids that penetrate into the loosely filamentous structure of the host or by a pad of several coalesced rhizoids where the host has a more cohesive cortex. Elongate surface hairs are common. Gametophytes are dioecious, the spermatangia arising on surface cells, and carpogonia with elongate trichogynes borne directly on undifferentiated surface supporting cells. Large sporangia form on stalk cells across the upper surface of the plants, these appearing to be either monosporangial or the result of fertilization of the carpogonia and equivalent to undivided zygotosporangia. Carposporophytes and tetrasporangia are unknown. 18S rRNA gene sequence analyses indicate that Pihiella constitutes a clade of long branch length most closely related to the Ahnfeltiales. The unique morphology and reproduction of Pihiella, combined with a substantial genetic divergence from the Ahnfeltiales, suggest that it is sufficiently distinct to warrant placement in a new family and order. We therefore describe the family Pihiellaceae and the order Pihiellales to accommodate the new genus.
EFFECT OF SEASONAL SEA ICE BREAKOUT ON THE PHOTOSYNTHESIS OF BENTHIC DIATOM MATS AT CASEY, ANTARCTICA1
Authors: Mcminn Andrew , Runcie John W. , Riddle Martin
Published: October 2010

Photosynthesis of marine benthic diatom mats was examined before and after sea ice breakout at a coastal site in eastern Antarctica (Casey). Before ice breakout the maximum under‐ice irradiance was between 2.5 and 8.2 μmol photons·m−2·s−1 and the benthic microalgal community was characterized by low Ek (12.1–32.3 μmol photons·m−2·s−1), low relETRmax (9.2–32.9), and high alpha (0.69–1.1). After breakout, 20 days later, the maximum irradiance had increased to between 293 and 840 μmol photons·m−2·s−1, Ek had increased by more than an order of magnitude (to 301–395 μmol photons·m−2·s−1), relETRmax had increased by more than five times (to 104–251), and alpha decreased by approximately 50% (to 0.42–0.68). During the same time interval the species composition of the mats changed, with a decline in the abundance of Trachyneis aspera (Karsten) Hustedt, Gyrosigma subsalsum Van Heurck, and Thalassiosira gracilis (Karsten) Hustedt and an increase in the abundance of Navicula glaciei Van Heurck. The benthic microalgal mats at Casey showed that species composition and photophysiology changed in response to the sudden natural increase in irradiance. This occurred through both succession shifts in the species composition of the mats and also an ability of individual cells to photoacclimate to the higher irradiances.
NITROGENOUS NUTRITION OF ALEXANDRIUM CATENELLA (DINOPHYCEAE) IN CULTURES AND IN THAU LAGOON, SOUTHERN FRANCE1
Authors: Collos Yves , Gagne Céline , Laabir Mohamed , Vaquer André , Cecchi Philippe , Souchu Philippe
Published: October 2010

Alexandrium catenella (Whedon et Kofoid) Balech was isolated from Thau lagoon (northern Mediterranean) and its growth and uptake characteristics measured for nitrate, ammonium, and urea. Although affinity constants did not indicate a preference for ammonium over nitrate, there was a strong inhibition of nitrate uptake by ammonium when both nitrogen (N) sources were present. Nitrogen budgets during growth in cultures revealed major imbalances between decreases in dissolved N and increases in particulate N, indicating excretion of dissolved organic N during the early part of the growth phase and uptake during the later part. A quasi‐unialgal bloom in November 2001 (4×106 cells·L−1) allowed measurements of uptake of nitrate, nitrite, ammonium, and urea; net and gross growth rate of A. catenella; and grazing rates on this organism. The affinity constants indicate that it is not a strong competitor for the N nutrients tested when these are in low concentrations (<10 μgat N·L−1), compared with other members of the phytoplankton community. Indirect evidence from cultures indicate that dissolved organic N compounds could be important in triggering those blooms. Finally, the strongly unbalanced growth observed in the field indicates that A. catenella exhibits a storage rather than a growth response to a nutrient pulse and is adapted to low frequency events such as the passage of frontal disturbances. The disappearance of A. catenella was due to grazing that balanced growth at the peak of the bloom.
ENDOGENOUS CYTOKININS IN THREE GENERA OF MICROALGAE FROM THE CHLOROPHYTA1
Authors: Ördög Vince , Stirk Wendy A. , Van Staden Johannes , Novák Ondřej , Strnad Miroslav
Published: October 2010

Nine axenic microalgal (Chlorophyta) strains from three genera (Protococcus, Chlorella, and Scenedesmus) were analyzed for endogenous cytokinins. Cytokinin‐like activity was detected using the excised cucumber cotyledon bioassay. Five strains showed no cytokinin‐like activity and four strains, low cytokinin‐like activity. Ethanolic extracts of the microalgae containing a mixture of deuterium‐labeled standards were purified using a combined DEAE‐Sephadex octadecysilica column and immunoaffinity column based on wide‐range specific mon‐oclonal antibodies and analyzed by HPLC linked to a micromass single quadrupole mass spectrometer with an electrospray interface and a photodiode array detector. There were similar trends in cytokinin profiles for the nine microalgal strains investigated, although concentrations did vary. Both isopentenyladenine and isopentenyladenosine were detected in all nine strains. cis‐Zeatin and cis‐zeatin riboside occurred at higher concentrations than the trans isomers, whereas trans‐zeatin‐O‐glucoside and trans‐zeatin riboside‐O‐glucoside were dominant over the cis isomers. Dihydrozeatin and its conjugates were not detected in any significant amounts. The aromatic benzyladenine always occurred at higher concentrations than benzyladenosine. The topolins were well represented with all three isomers (ortho, meta, and para) being detected, with ortho‐topolin and ortho‐topolin riboside occurring at higher concentrations than the other isomers. However, for the O‐glucosides, the meta isomers (meta‐topolin‐O‐glucoside and meta‐topolin riboside‐O‐glucoside) occurred at higher concentrations than the other isomers. No N‐glucosides were detected (isopentenyladenine‐9‐glucoside, zeatin‐9‐glucoside, dihydrozeatin‐9‐glucoside, benzyladenine‐9‐glucoside, ortho‐topolin‐9‐glucoside, and meta‐topolin‐9‐glucoside). Generally, zeatin and topolin conjugates were the dominant forms of isoprenoid and aromatic cytokinins, respectively. There was no distinct trend in the proportions of isoprenoid to aromatic cytokinins.
PHYTOPLANKTON DIVERSITY OF SHALLOW TIDAL LAKES: INFLUENCE OF PERIODIC SALINITY CHANGES ON DIVERSITY AND SPECIES NUMBER OF A NATURAL ASSEMBLAGE1
Authors: Flöder Sabine , Burns Carolyn W.
Published: October 2010

The influence of periodic salinity changes was investigated for 42 days under semicontinuous culture conditions with phosphorus limitation using phytoplankton assemblages from Lake Waihola, a tidally influenced shallow lake. To simulate tidal effects on the phytoplankton community, salinity in the cultures was increased in pulses at different intervals (3.5, 7, and 14 days), and these cultures were compared with those that experienced constant freshwater conditions. Salinity pulses significantly affected competition and succession with a major loss in diversity during the first days of the experiment due to the initial pulse that caused a transition from freshwater to brackish conditions in the cultures. After this initial phase, diversity index (H') and species number (Scorr) decreased less rapidly. The loss in H' and Scorr over time was highest under constant freshwater conditions and lowest in the treatment with an interval of 3.5 days between salinity pulses. At the end of the experiment, the combination of initial loss in H' and Scorr and the time course of H' and Scorr resulted in a U‐shaped relation between the interval length of salinity pulses and both H' and Scorrtemp1.txttemp1.txt. Our results indicate that salinity pulses at intervals of a few days tend to promote phytoplankton diversity. If saline intrusions in coastal freshwater systems occur only at spring tides, this will lead to decreases in diversity and species richness.
THE NEW GENUS YONAGUNIA KAWAGUCHI ET MASUDA (HALYMENIACEAE, RHODOPHYTA), BASED ON Y. TENUIFOLIA KAWAGUCHI ET MASUDA SP. NOV. FROM SOUTHERN JAPAN AND INCLUDING Y. FORMOSANA (OKAMURA) KAWAGUCHI ET MASUDA COMB. NOV. FROM SOUTHEAST ASIA1
Authors: Kawaguchi Shigeo , Shimada Satoshi , Wang Hong Wei , Masuda Michio
Published: October 2010

Yonagunia Kawaguchi et Masuda, gen. nov. (Halymeniaceae, Rhodophyta) is proposed to accommodate a new species, Yonagunia tenuifolia Kawaguchi et Masuda and the species currently known as Prionitis formosana (Okamura) Kawaguchi et Nguyen. Based on auxiliary cell ampullar features, Yonagunia is included in the group of genera with the simplest type of ampulla (the Grateloupia type) that comprises Dermocorynus, Grateloupia, Kintokiocolax, Phyllymenia, and Zymurgia. However, Yonagunia differs from these genera in the behavior of cells in the ampullar filaments immediately after diploidization, most cells of the primary and secondary filaments simultaneously dividing to form grape‐like clusters of small globular cells that subsequently elongate and produce involucral filaments to laxly surround the maturing carposporophyte. Yonagunia is resolved by our rbcL gene sequence analyses as one of five monophyletic clades within the Halymeniaceae (an Aeodes/Pachymenia, a Polyopes, a Carpopertis/Cryptonemia/Halymenia, a Yonagunia, and a Grateloupia clade) that is positioned as sister to the Grateloupia clade. Carpogonial branch apparatuses are identified as a potential taxonomic significance on the same level as auxiliary cell ampullae.
GENETIC DIFFERENTIATION AMONG POPULATIONS OF THE PLANKTONIC MARINE DIATOM DITYLUM BRIGHTWELLII (BACILLARIOPHYCEAE)1
Authors: Rynearson Tatiana A. , Virginia Armbrust E.
Published: October 2010

Population genetic structure was determined for the planktonic diatom Ditylum brightwellii (West) Grunow in two connected estuaries—Puget Sound and the Strait of Juan de Fuca (WA, USA). Three genetically distinct populations were detected that were characterized by different microsatellite allele distributions and unique alleles. Isolates from the two most genetically diverged populations displayed identical full‐length 18S rDNA sequences suggesting that either a single or two recently diverged species were sampled. The extent of genetic differentiation between populations was not correlated with distance between water samples or time between sampling. Instead, distinct populations were associated with different estuaries. In Puget Sound waters, one population was detected three times over the course of 28 months. Cells from this population were likely maintained inside Puget Sound over long periods through water recirculation within the Sound. In Strait of Juan de Fuca waters, two additional populations were detected. Maximum growth rates of Puget Sound isolates were significantly different from Strait of Juan de Fuca isolates, indicating that populations were composed of cells with different physiological capabilities. The genetic and physiological differentiation observed between populations from intermixing estuaries suggested that genetic exchange between populations was restricted through differential selection. Despite the potential for widespread dispersal in planktonic organisms, it appears that populations with distinct genetic and physiological characteristics can be maintained over long time periods through a combination of hydrology and differential selection.