bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE INABILITY OF THE TEXAS “BROWN TIDE” ALGA TO USE NITRATE AND THE ROLE OF NITROGEN IN THE INITIATION OF A PERSISTENT BLOOM OF THIS ORGANISM1
Authors: DeYoe Hudson R. , Suttle Curtis A. 
Published: October 2004

ABSTRACTA planktonic alga similar in general morphology and pigments to Aureococcus anophagefferens Hargraves and Sieburth has caused persistent and ecologically damaging blooms along the south Texas coast. Experiments using 100 μM NO3−, NO2−, and NH4+ demonstrated that the alga could not use NO3− for growth but could use NO2− and NH4+. Doubling iron or trace metal concentrations did not permit growth on NO3−. Chemical composition data for cultures grown in excess NO3− or NH4+, respectively, were as follows: N·cell−1 (0.88 vs. 1.3 pg), C:N ratio (25:1 vs. 6.4:1), C:chlorophyll a (chl a) (560:1 vs. 44:1), and chl a·cell−1 (0.033 vs. 0.16 pg). These data imply that cells supplied with NO3− were N‐starved. Culture addition of 10 mM final concentration chlorate (a nitrate analog) did not affect the Texas isolate while NO3− utilizing A. anophagefferens was lysed, suggesting that the NO3− reductase of the Texas isolate is nonfunctional. Rates of primary productivity determined during a dense bloom indicated that light‐saturated growth rates were ca. 0.45 d−1, which is similar to maximum rates determined in laboratory experiments (0.58 d−1± 0.16). However, chemical composition data were consistent with the growth rate of these cells being limited by N availability (C:N 28, C:chl a 176, chl a·cell−1 0.019). Calculations based on a mass balance for nitrogen suggest that the bloom was triggered by an input of ca. 69 μM NH4+ that resulted from an extensive die‐off of benthos and fish.
EFFECTS OF TEMPERATURE ON GROWTH, LIGHT ABSORPTION, AND QUANTUM YIELD IN DUNALIELLA TERTIOLECTA (CHLOROPHYCEAE)1
Authors: Sosik Heidi M. , Mitchell B. Greg 
Published: October 2004

ABSTRACTThe effects of growth temperature on the marine chlorophyte Dunaliella tertiolecta Butcher were studied to provide a more mechanistic understanding of the role of environmental factors in regulating bio‐optical properties of phytoplankton. Specific attention was focused on quantities that are relevant for modeling of growth and photosynthesis. Characteristics including chlorophyll a (chl z)‐specific light absorption (a*ph(λ)), C:chl a ratio, and quantum yield for growth (φμ) varied as functions of temperature under conditions of excess light and nutrients. As temperature increased over the range examined (12°‐28°C), intracellular concentrations of chl a increased by a factor of 2 and a*ph(λ) values decreased by more than 50% at blue to green wavelengths. The lower values of a*ph(λ) were due to both a decrease in the abundance of accessory pigments relative to chl a and an increase in pigment package effects arising from higher intracellular pigment concentrations. Intracellular pigment concentration increased as a consequence of higher cellular pigment quotas combined with lower cell volume. At high growth temperatures, slightly more light was absorbed on a per‐cell‐C basis, but the dramatic increases in growth rate from μ= 0.5 d−1 at 12° C to μ= 2.2 d−1 at 28°C were primarily due to an increase in φμ (0.015–0.041 mol C (mol quanta)−1). By comparison with previous work on this species, we conclude the effects of temperature on a*ph(λ) and φμ are comparable to those observed for light and nutrient limitation. Patterns of variability in a*ph(λ)and φμ as a function of growth rate at different temperatures are similar to those previously documented for this species grown at the same irradiance but under a range of nitrogen‐limited conditions. These results are discussed in the context of implications for bio‐optical modeling of aquatic primary production by phytoplankton.
PROGRESSION OF SPERMATIAL NUCLEAR DIVISION REQUIRES CALCIUM INFLUX DURING FERTILIZATION OF THE RED ALGA PALMARIA SP.1
Authors: Mine Ichiro , Tatewaki Masakazu 
Published: October 2004

ABSTRACTDuring fertilization of the red alga Palmaria sp. (Palmariales), the prophase‐arrested nucleus of the uninucleate spermatium resumes its division after direct attachment of the spermatium to the trichogyne of a carpogonium. Treatments that reduce Ca2+ influx inhibit the progression of spermatial nuclear division. The ratio of the number of spermatia released from prophase arrest (those in meta‐phase to binucleate stages) to the total spermatia attached to trichogynes was significantly reduced by incubating the spermatia in the culture solution having low Ca2+ concentration. Similar inhibition was observed by addition of either inorganic (La3+ and Co2+) or organic (nifedipine and tetramethrin) Ca2+ channel inhibitors to the culture solution containing 10 mM Ca2+. These results indicate that the prophase/metaphase transition of spermatial nuclear division requires an influx of Ca2+ and suggest that Ca2+ acts as a second messenger to the mechanical or chemical stimulus that initiates mitotic progression of spermatia in this alga.
RESTRICTION FRAGMENT LENGTH POLYMORPHISM OF RIBOSOMAL DNA INTERNAL TRANSCRIBED SPACER AND 5.8S REGIONS IN JAPANESE ALEXANDRIUM SPECIES (DINOPHYCEAE)1
Authors: Adachi Masao , Sako Yoshihiko , Ishida Yuzaburo 
Published: October 2004

ABSTRACTThe 5.8S ribosomal RNA (rDNA) gene and flanking internal transcribed spacers (ITS1 and ITS2)from 9 isolates of Alexandrium catenella (Whedon and Kofoid) Taylor, 11 isolates of A. tamarense (Lebour) Taylor, and single isolates of A. affine (Inoue et Fukuyo) Balech, A. insuetum Balech, and A. pseudogonyaulax (Biecheler) Horiguchi ex Yuki et Fukuyo comb. nov. from various locations in Japan were amplified using the polymerase chain reaction (PCR) and subjected to restriction fragment‐length polymorphism (RFLP) analysis. PCR products from all strains were approximately 610 bp, inclusive of a limited region of the 18S and 28S rRNA coding regions. RFLP analysis using four restriction enzymes revealed six distinct classes of rDNA (“ITS types”). Restriction patterns of A. catenella were uniform at the intra‐specific level and clearly distinguishable from those of A. tamarense. The patterns associated with A. tamarense (“tamarense group”) were also uniform except for one strain, WKS‐1. Some restriction fragments from WKS‐1 were in common with those of A. catenella or A. tamarense, whereas some were distinct from all Alexandrium species tested. Alexandrium affine, A. insuetum, and A. pseudogonyaulax carry unique ITS types. The ITSs of the “tamarense group” exhibit sequence heterogeneity. In contrast, the ITSs of all other isolates (including WKS‐1) appear homogeneous. RFLP analysis of the 5.8S rDNA and flanking ITSs regions from Alexandrium species reveals useful taxonomic and genetic markers at the species and/or population levels.
MOLECULAR PHYLOGENETIC ANALYSIS OF rbcL IN THE PRYMNESIOPHYTA1
Authors: Fujiwara Shoko , Sawada Mitsuhiro , Someya Junichiro , Minaka Nobuhiro , Kawachi Masanobu , Inouye Isao 
Published: October 2004

ABSTRACTThe nucleotide sequences of rbcL genes encoding the large subunit of ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco) were determined from six species of Prymnesiophyta to clarify their phylogenetic relationships. Molecular phylogenetic trees were constructed using PAUP (Phylogenetic Analysis Using Parsimony). These analyses suggest that the Prymnesiophyta, except for the Pavlovales, area relatively stable monophyletic group. Pleurochrysis carterae, included in the Isochrysidales, is a sister species of a monophyletic group consisting of other members of the Isochrysidales, Gephyrocapsa oceanica and Emiliania huxleyi, members of the Coccosphaerales, Calyptrosphaera sphaeroidea and Umbilicosphaera sibogae var. foliosa, and a member of the Prymnesiales, Chrysochromulina hirta. The nucleotide sequence of rbcL from G. oceanica was identical to that from E. huxleyi within the region examined. Our trees show that G. oceanica and E. huxleyi are more closely related to C. hirta than to U. sibogae, C. sphaeroidea, and P. carterae. These results suggest that orders in the Prymnesiophyceae, including the above‐mentioned genera, should be redefined.
CHARACTERIZATION OF OCEANIC PHOTOSYNTHETIC PICOEUKARYOTES BY FLOW CYTOMETRY1
Authors: Simon Nathalie , Barlow Raymond G. , Marie Dominique , Partensky Frédéric , Vaulot Daniel 
Published: October 2004

ABSTRACTTo interpret flow cytometric data that are routinely obtained on natural oceanic communities, 23 strains of photosynthetic picoeukaryotes belonging to four classes (Prasinophyceae, Chlorophyceae, Pelagophyceae, and Prymnesiophyceae) and six pigment types were investigated for their light scattering in the forward and right‐angle directions, chlorophyll fluorescence, and DNA content as measured by flow cytometry. Cell she was assessed by Coulter counter, and pigment composition was measured by reverse‐phase high‐performance liquid chromatography. The size and GC% of the nuclear genome of cultured picoeukaryotes was measured from the fluorescence of DNA‐specific dyes. Using these two parameters, we could discriminate species within pigment groups. DNA staining of preserved natural samples may also prove useful in discriminating cooccurring populations in situ as long as the communities are not too complex. Using the relationships that we established between size and light‐scattering properties of the cells, we estimated equivalent diameters of picoeukaryotes in natural populations to be between 1.3 and 2 μm. Chlorophyll a content was between 6 and 16 fg·cel−1 as calculated from relationships that we established between chlorophyll a content and red fluorescence of the cultured strains. With respect to size, chlorophyll a content, and pigment composition, Pelagomonas sp. strains (Pelagophyceae) appeared to be the most representative of the natural communities in subtropical ocean waters. In contrast, green coccoid strains, which often outcompete other strains in culture, might only be minor contributors to these communities.
TRANSIENT AMMONIUM UPTAKE IN THE MACROALGA ULVA LACTUCA (CHLOROPHYTA): NATURE, REGULATION, AND THE CONSEQUENCES FOR CHOICE OF MEASURING TECHNIQUE1
Authors: Pedersen Morten Foldager 
Published: October 2004

ABSTRACTThe nature of transient ammonium uptake by the macroalga Ulva lactuca L. was studied from the depletion of ammonium after single additions of ammonium to batch cultures. The experiments were carried out by the application of two different experimental setups: the “multiple flask” and the “perturbation” techniques. Uptake rate was nonlinear with time, and three distinct, succeeding phases of uptake were identified: 1) “surge” uptake, i.e. transiently enhanced uptake that lasted for a few hours only, followed by 2) “internally” controlled uptake, a relatively constant phase occurring at high substrate concentrations, and finally 3) the “externally” controlled uptake phase, which was substrate‐dependent and occurred at low substrate concentrations. Surge uptake occurred over a broad range of substrate concentrations but was concentration‐dependent and, so, equalled externally controlled uptake rates at substrate concentrations below 3–10 μM. The transient nature of ammonium uptake rate seemed related to rapid changes in small intracellular pools of inorganic nitrogen or amino acids rather than to changes in total N content of the algae. The transient nature of ammonium uptake has important implications for the measurement of uptake rates when either of the two standard methods, the multiple flask and the perturbation technique, are used, and I recommend that a combination of the two methods be used for future uptake experiments.
PHYLOGENY OF THE GENUS PYRAMIMONAS (PRASINOPHYCEAE, CHLOROPHYTA) INFERRED FROM THE rbcL GENE1
Authors: Daugbjerg Niels , Moestrup Øjvind , Arctander Peter 
Published: October 2004

ABSTRACTA 1089‐basepair fragment (approx. 75%) of the large subunit of the chloroplast‐encoded gene, ribulose‐1,5‐bis‐phosphate carboxylase/oxygenase (rbcL), was sequenced from 16 species of the genus Pyramimonas Schmarda. Electron microscopic and biochemical studies of Pyramimonas, one of the most morphologically diverse genera within the potential sister groups to the chlorophyll a‐ and b‐containing plants, suggest that this genus consists of at least four separate subgenera. Using the homologous sequence of rbcL from Cymbomonas tetramitiformis Schiller (Halosphaeraceae) as an outgroup and applying the maximum likelihood method, we show that the inferred topology is congruent with traditional delimitations of the taxa based on observations of periplast, internal ultrastructure, and biochemical features. A bootstrap analysis also supports division at the subgeneric level; however, the low bootstrap support associated with the deep nodes precludes resolution of these branches. A maximum likelihood relative rate test revealed that the rbcL gene in these single‐celled green flagellates has a heterogeneous rate of substitution. The rbcL gene in species of the subgenus Pyramimonas has evolved at an accelerated rate relative to that of congenerics.
ISOLATION AND REGENERATION OF HAPLOID PROTOPLASTS FROM BANGIA ATROPURPUREA (RHODOPHYTA) WITH MARINE BACTERIAL ENZYMES1
Authors: Araki Toshiyoshi , Hayakawa Michio , Tamaru Yutaka , Yoshimatsu Keiji , Morishita Tatsuo 
Published: October 2004

ABSTRACTThree kinds of enzymes, agarase, β‐1,4‐mannanase, and β‐1,3‐xylanase, required for isolation of protoplasts from the red alga Bangia atropurpurea (Roth) C. Ag. were prepared from bacterial culture fluids of Vibrio sp. PO‐303, Vibrio sp. MA‐138, and Alcaligenes sp. XY‐234, respectively, isolated from the sea environment. The optimal pH of all enzymes was around 7.5. Suitable conditions for protoplast isolation from B. atropurpurea were examined. The pretreatment of the fronds with pa‐pain solution (20 mM Mes buffer, pH 7.5, containing 2% papain and 0.5 M mannitol) contributed to successful protoplast isolation. When razor‐cut fragments of the fronds (about 200 mg in fresh weight) immersed in 20 mM Mes buffer, 7.5, containing 0.5 M mannitol and one unit each of agarase, β‐1,4‐mannanase, and β‐1,3‐xylanase were incubated at 22°C for 90 min with gentle agitation, 5.7 × 106 protoplasts were released from them. Many protoplasts regenerated into fronds of regular or irregular shape.
THE ECOLOGY OFNOSTOC
Authors: Dodds Walter K. , Gudder Dolly A. , Mollenhauer Dieter 
Published: October 2004

ABSTRACTNostocis a genus of filamentous cyanobacteria that can form macroscopic or microscopic colonies and is common in both terrestrial and aquatic habitats. Much of the success ofNostocin terrestrial habitats is related to its ability to remain desiccated for months or years and fully recover metabolic activity within hours to days after re‐hydration with liquid water. Nostoccan also withstand repeated cycles of freezing and thawing and, thus, is an important component of extreme terrestrial habitats in the Arctic and Antarctic. The ability to fix atmospheric N2can provide an advantage in nitrogen‐poor environments. Nostocalso has the ability to screen damaging ultraviolet light in terrestrial and shallow benthic habitats. The genus potentially could be important in paddy rice culture because it fixes nitrogen that may later be released and used by plants; it also may play a role in soil formation and may increase nitrogen input to natural aquatic and terrestrial ecosystems. The abilities to survive in terrestrial habitats and fix N2are important in symbiotic interactions with fungi (lichens), liverworts, hornworts, mosses, ferns, cycads, and the angiospermGunnera. Nostocis somewhat resistant to predation; this probably is related to production of large amounts of sheath material, synthesis of microcystin‐like toxins by some strains, and formation of colonies that are too large for many algivores to consume. Some organisms can subsist onNostoc,although it may not be a preferred food source. Lytic cyanophages also infectNostoc,but little is known about population control ofNostocin its natural environment, Late Precambrian fossils resemblingNostochave been described, andNostocpossibly has been an important component of many terrestrial and aquatic communities since that time.
RESPONSE OF MICROALGAL EPIPHYTE COMMUNITIES TO NITRATE ENRICHMENT IN AN EELGRASS (ZOSTERA MARINA) MEADOW1
Authors: Coleman Virginia L. , Burkholder JoAnn M. 
Published: October 2004

ABSTRACT The community structure and productivity of epiphytic microalgae on field populations of eelgrass (Zostera marina L.) from a high flow regime were characterized under water‐column nitrate enrichment over a 30–d period during the autumn growing season for the macrophyte. Epiphyte communities in replicate low‐nitrogen sites (LOW‐N, median water‐column nitrate concentrations below detection) were compared to communities in replicate N‐enriched sites wherein nitrate was leached from clay pots filled with enriched agar (N‐ENRICH, median concentration ca. 6 μM NO3−‐N; pots replaced at 8– to 12–d intervals). In experimental chambers, total epiphyte community productivity as 14C‐bicarbonate uptake was determined from short‐term (3–h) laboratory assays. Track light microscope‐autoradiography enabled estimates of species‐specific productivity for abundant algal taxa. After 6 d in the LOW‐N and N‐ENRICH communities, the crustose adnate red alga Sahlingia subintegra (Rosenvinge) Kornmann was dominant in terms of cell number and codominant in biovolume. Photosynthetic dinoflagellates, not previously reported as abundant in eelgrass epiphyte communities, were dominant in biovolume contribution after both 6 and 30 d in LOW‐N communities. Nitrate enrichment stimulated the adnate monoraphid diatom Cocconeis placentula Ehr. but apparently inhibited dinoflagellates and the diatom Melosira sp. Total productivity of the epiphyte communities remained comparable in both the LOW‐N and N‐ENRICH sites. Shifts in community structure and species‐specific productivity, however, indicated a controlling influence of nitrate supply on microalgal epiphytes in the field eelgrass community.
IMPORTANCE OF RESTING STAGES IN DIATOM SEASONAL SUCCESSION1
Authors: McQuoid Melissa R. , Hobson Louis A. 
Published: October 2004

ABSTRACT The role of environmental factors in seasonal succession of six clones of marine diatoms was examined by testing effects of various combinations of temperature (5°, 10°, 15°, 20°C) and photoperiod (10, 12, 14, 16 h) on time to germination of resting stages and subsequent vegetative cell division rates. Resting stages were induced in batch cultures using a low nutrient medium and a cold, dark period. A three‐factor ANOVA showed that species, temperature, daylength, and their interactions signficantly (P =0.0001) injuenced germination time and division rate. Resting stages of Chaetoceros similis Cleve and Odontella aurita (Lyngbye) Agardh were most successful in producing populations of cells on warm, long days (20°C/16 h). Chaetoceros didymus Ehrenberg and C. cinctus Gran were most successful under more moderate conditions (15°C/14 h). Resting stages of Ditylum bright‐wellii (West) Grunow germinated and cells divided rapidly under all conditions. No consistent pattern was evident with Thalassiosira rotula Meunier. We compared results of the laboratory study with environmental conditions prevailing during the presence of these species in a British Columbia fjord. Favorable growth conditions determined for C. didymus, D. brightwellii, and T. rotula were similar to conditions present when these species were commonly found in the fjord.
PHYSIOLOGICAL PROFILES OF SYNECHOCOCCUS (CYANOPHYCEAE) IN IRON‐LIMITING CONTINUOUS CULTURES1
Authors: Wilhelm Steven W. , Trick Charles G. 
Published: October 2004

ABSTRACT We examined the physiology and biochemistry associated with the iron‐limited continuous culture of the halotolerant cyanobacterium Synechococcus PCC 7002. Biomass production, photosynthetic pigment levels, photosynthetic efficiency, and the production of hydroxamate‐ and catechol‐type siderophores are reported for cells grown over a range of available iron concentrations. The relationship between the yield of Synechococcus PCC 7002 in iron‐limited chemostats and the concentration of available iron was not linear. Synechococcus PCC 7002 expressed an inducible physiological response that led to alterations either in the cellular iron quotient or, more likely, in levels of available iron due to induced iron‐scavenging processes. During iron limitation these cyanobacteria produced components consistent with the activation of a high‐affinity iron transport system; both hydroxamate‐ and catechol‐type siderophores were detected. Iron‐limited Synechococcus PCC 7002 also reduced CO2 fixation rates from luxury levels to a rate that matched the cellular growth rate, presenting interesting implications for oceanic carbon flux models.
RELATIONSHIPS BETWEEN NITRATE REDUCTASE ACTIVITY AND RATES OF GROWTH AND NITRATE INCORPORATION UNDER STEADY‐STATE LIGHT OR NITRATE LIMITATION IN THE MARINE DIATOM THALASSIOSIRA PSEUDONANA (BACILLARIOPHYCEAE)1
Authors: Berges John A. , Harrison Paul J. 
Published: October 2004

ABSTRACT Although activity of the enzyme nitrate reductase (NR) can potentially be used to predict the rate of nitrate incorporation in field assemblages of marine phytoplankton, application of this index has met with little success because the relationship between the two rates is not well established under steady‐state conditions. To provide a basis for using NR activity measurements, the relationships among NR activity, growth rate, cell composition, and nitrate incorporation rate were examined in cultures of Thalassiosira pseudonana (Hustedt)Hasle and Heimdal, growing a) under steady‐state light limitation, b) during transitions between low and high irradiance (15 or 90 μmol quanta.m−2.s−1), and c) under steady‐state nitrate limitation. Using a modified assay for NR involving additions of bovine serum albumin to stabilize enzyme activity, NR activity in light‐limited cultures was positively and quantitatively related to calculated rates of nitrate incorporation, even in cultures that were apparently starved of selenium. During transitions in irradiance, growth rates acclimated to new conditions within 1 day; through the transition, the relationship between NR activity and nitrate incorporation rate remained quantitative. In nitrate‐limited chemostat cultures, NR activity was positively correlated with growth rate and with nitrate incorporation rates, but the relationship was not quantitative. NR activity exceeded nitrate incorporation rates at lower growth rates (<25% of nutrient‐replete growth rates), but chemostats operating at such low dilution rates may not represent ecologically relevant conditions for marine diatoms. The strong relationship between NR activity and nitrate incorporation provides support for the idea that NR is rate‐limiting for nitrate incorporation or is closely coupled to the rate‐limiting step. In an effort to determine a suitable variable for scaling NR activity, relationships between different cell components and growth rate were examined. These relationships differed depending on the limiting factor. For example, under light limitation, cell volume and cell carbon content increased significantly with increased growth rate, while under nitrate limitation cell volume and carbon content decreased as growth rates increased. Despite the differences found between cell composition and growth rate under light and nitrate limitation, the relationships between NR activity scaled to different compositional variables and growth rate did not differ between the limitations. In field situations where cell numbers are not easily determined, scaling NR activity to particulate nitrogen content may be the best alternative. These results establish a strong basis for pursuing NR activity measurements as indices of nitrate incorporation in the field.