bluuebunny/crossref_metadata_2025_split huggingface dataset:
MICROSENSOR STUDIES OF OXYGEN AND LIGHT DISTRIBUTION IN THE GREEN MACROALGA CODIUM FRAGILE1
Authors: Lassen Carsten , Bebout Leslie E. , Paerl Hans W. , Jørgensen Bo B. 
Published: October 2004

ABSTRACTScalar irradiance, oxygen concentration, and oxygenic photosynthesis were measured at 0.1 mm spatial resolution within the tissue of the siphonous green macroalga Codium fragile subsp. tomentosoides (van Goor) Silva by fiber‐optic scalar irradiance microsensors and oxygen microelectrodes. The scalar irradiance of visible light was strongly attenuated in the outer 0.2 mm of the tissue but was nearly constant for the subsequent 1.0 mm of photo‐synthetic tissue. Far‐red scalar irradiance at 750 nm increased below the tissue surface to a maximum of 200% of incident irradiance at 1.2 mm depth due to multiple scattering in the medullary tissue. The constant intensity of visible light below 0.2 mm was thus a result of the combined effects of absorption and backscattering from the medulla.The oxygen exchange between the alga and the surrounding water was diffusion‐limited with a steep O2gradient inside and around the alga. In darkness, the tissue below 0.6 mm became anoxic, and endophytic extracellular space provided an environment where anoxygenic microbial processes may occur. When illuminated at 160 nmol photons·−2·−1, O2 concentrations exceeded ambient levels throughout the thallus, with a maximum of 250% of air saturation just below the surface. The amplitude of oxygen variation was buffered by gas bubbles formed in the medullary tissue.
PICOPHYTOPLANKTON BIOMASS IN RELATION TO LAKE TROPHIC STATE AND THE TN:TP RATIO OF LAKE WATER IN JAPAN1
Authors: Takamura Noriko , Nojiri Yukihiro 
Published: October 2004

ABSTRACTPicophytoplankton biomass and its contribution to total phytoplankton biomass were investigated in relation to the nutrient concentration and total N: total P ratio of the epilimnetic waters of 42 Japanese lakes during the warm season in 1991 (April–October). Picophytoplankton biomass (as chlorophyll a) in meso‐, eu‐, and hypertrophic lakes was significantly higher than those observed in oligotrophic lakes. However, picophytoplankton biomass increased significantly with increased total P concentrations in all systems excluding hypertrophic lakes. Picophytoplankton contribution to total chlorophyll a content was significantly higher in oligo‐ and mesotrophic lakes than in eu‐ and hypertrophic lakes and was inversely correlated with total P concentrations in lake water. Picophytoplankton contribution to the total phytoplankton biomass was positively (r = 0.54, n = 42, P = 0.0003) correlated with the total N: total P ratio of lake waters. Each lake trophic type, with the exception of hypertrophic lakes, showed this trend, although the correlation was not significant. We suggest that picophytoplankton contribution is influenced by the total N: total P ratio rather than lake trophic state; however, picophytoplankton were of little importance in hypertrophic lakes.
USE OF RIBOSOMAL DNA INTERNAL TRANSCRIBED SPACERS FOR PHYLOGENETIC STUDIES IN DIATOMS1
Authors: Zechman Frederick W. , Zimmer Elizabeth A. , Theriot Edward C. 
Published: October 2004

ABSTRACTSequence variation of ribosomal DNA internal transcribed spacers (ITS) among populations, species, and genera of the diatom genus Stephanodiscus was investigated. ITS 1 and ITS 2, including the 5.8S gene, were sequenced from geographically distant and nearby populations of S. niagarae Ehrenberg. In addition, repeats from S. hantzschii Grunow and Cyclotella meneghiniana Kützing were sequenced to determine the taxonomic range over which the ITS region could be used for diatom systematics. The morphologically distinct S. yellowstonensis Theriot & Stoermer, thought to have evolved from S. niagarae in Yellowstone Lake between 12,000 and 8000 years ago, also was sequenced to assess its relationship to nearby S. niagarae populations. The organization and relative sizes of ITS 1 and ITS 2 in Stephanodiscus species were similar to those reported for other eukaryotes. In general, ITS 2 was slightly larger and more variable than ITS 1. Cladistic analysis of ITS sequences did not resolve relationships of nearby S. niagarae and S. yellowstonensis populations. However, central North American S. niagarae populations were in a clade supported by two nucleotide changes. For Cyclotella, much of the ITS region was not alignable with that for Stephanodiscus species; therefore, generic‐level comparison within the Thalassiosiraceae may not be possible. The variation (95–96% similarity) between S. hantzschii and other Stephanodiscus species suggests that interspecific relationships could be assessed with ITS sequences. Although S. yellowstonensis is morphologically distinct from S. niagarae, no autapomorphic nucleotide sites were identified. Two S. niagarae populations (Heart and Lewis Lakes), however, did possess autapomorphic ITS sites.
TOLERANCE OF SIX MARINE MICROALGAE TO THE CRYOPROTECTANTS DIMETHYL SULFOXIDE AND METHANOL1
Authors: Cañavate J. Pedro , Lubian Luis M. 
Published: October 2004

ABSTRACTKnowledge of tolerance to cryoprotectants is important in determining viability after biological freezing of algae. Six taxonomically diverse marine microalgae were evaluated for their tolerance to the widely used cryoprotectants dimethyl sulfoxide (DMSO) and methanol. Tetraselmis chuii Butcher survived exposure to 30% (v/v) DMSO and 25% methanol for periods of up to 4 h. All other species were more sensitive to high concentrations of these cryoprotectants. DMSO was lethal at 25% after a 15‐min exposure of Rhodomonas baltica Karsten, Isochrysis off. galbana (strain T‐ISO) Parke, and Nannochloropsis gaditana Lubian. Nannochloris atomus Butcher could tolerate only a 1‐min exposure at this concentration; Chaetoceros gracilis Schutt completely lost viability when exposed to 20% for 60 min. Safe concentrations for DMSO incubations were similar (about 5% lower) to lethal thresholds. Methanol incubations did not significantly decrease cell viability at concentrations of 5% (1 min) for R. baltica, 25% (up to 60 min) for T. chuii, 15% (up to 120 min) for I. galbana, 5% (up to 60 min) for N. gaditana, 15% (up to 240 min) for Ch. gracilis, and 15% (up to 120 min) for N. atomus. Nannochloris atomus has the potential to be cryopreserved without the need for any cryoprotectant. The other five species were clearly dependent on a 15% DMSO preincubation to achieve a growth response after thawing from −196° C. Only N. atomus and N. gaditana could be grown after being cryopreserved in the presence of 5% methanol.
POLYAMINE TRANSPORT IN THE SEAWEED ULVA RIGIDA (CHLOROPHYTA)1
Authors: Badini Lorenza , Pistocchi Rossella , Bagni Nello 
Published: October 2004

ABSTRACTThe excessive growth of Ulva rigida C. Agardh, a green seaweed present in the Northern Adriatic Sea, is a problem for the inhabitants and the economy of the region. As information about hormonal control of growth in seaweeds is scarce, our aim was to investigate the presence of endogenous polyamines and their absorption by algal cells and to correlate the findings with terrestrial plants. Free polyamines (putrescine, spermidine, and spermine) were present endogenously in the algal thallus at concentrations ranging from 4 to 134 μM. Putrescine and spermidine were also present in the seawater in which the alga usually grows at concentrations between 0 and 0.9 μM. Uptake of labeled polyamines occurred, but it was inhibited by cations present in the seawater. Uptake was investigated also by incubation in distilled water. In this case, uptake displayed characteristics similar to those observed in higher plant systems. Uptake studies in seawater showed that polyamine accumulation in algal cells occurred and that it followed a concentration gradient and displayed linear kinetics. The mechanism proposed that of a passive uptake, as indicated also by the inability of metabolic inhibitors to block transport. There was evidence for polyamine binding to external cell sites, but polyamine uptake by protoplasts as well as polyamine translocation and secretion by the whole thallus was also demonstrated. Since cultured and actively growing thallus discs displayed a higher uptake ability than freshly collected ones, a role for polyamines in sustaining growth is discussed.
THE IMPACT OF STORM‐FLOW ON RIVER BIOFILM ARCHITECTURE1
Authors: Blenkinsopp Sandra A. , Lock Maurice A. 
Published: October 2004

ABSTRACTThe impact of storm‐flow on river biofilm architecture was investigated using transmission (TEM) and scanning (SEM) electron microscopy. TEM resin substrata were colonized under light‐grown (LG) or dark‐grown (DG) conditions for 33 weeks in the Clywedog River, North Wales, prior to exposure to ambient‐flow (approx. 60 cm·s−1) or storm‐flow (approx. 235 cm·s−1+ river sediment) in a laboratory flume. Line transect methodology was used to quantify information from TEM ultrathin sections of LG material. In the LG ambient‐flow biofilm, bacteria were more abundant directly adjacent to the substratum and were noticeably denser directly under the adnate diatom Cocconeis. Higher in the biofilm, the bacteria were loosely dispersed in the matrix between other cells. Cyanobacteria occurred most frequently as single cells but were also found in large “palisade” formations adjacent to the substratum. Significant horizontal and vertical nearest‐neighbor associations were noted for both bacteria and cyanobacteria. Cells of Cocconeis were common adjacent to the substratum, providing shelter to, and often elevated upon, an “organic pad” of bacteria, cyanobacteria, and densely staining exopolysaccharide. Cyanobacteria and Cocconeis were resistant to removal by storm‐flow, but Cocconeis frustules were sometimes damaged. Bacteria in the LG storm‐flow samples were less common adjacent to the substratum and were sometimes more dispersed higher in the biofilm than in ambient‐flow samples. We suggest that storm‐flow hydrodynamic forces may redistribute bacteria adjacent to the substratum into higher areas of the biofilm. In addition, bacteria and the exopolysaccharide matrix were sometimes removed down to the substratum by storm‐flow, unless beneath Cocconeis. The DG biofilm consisted almost entirely of bacteria. Storm‐flow only removed surface growth from DG biofilms, and SEM revealed peritrich stalk abrasion and “blow‐down.” Pre‐disturbance biofilm architecture appears to influence the form of destruction. We suggest that the “microcosms” of Cocconeis and their underlying cells not only serve as an inoculum to recolonize the surface when conditions permit but enhance immigration by interrupting flow patterns across the surface.
DISTRIBUTION AND SYSTEMATICS OFBATRACHOSPERMUM(BATRACHOSPERMALES, RHODOPHYTA) IN NORTH AMERICA. 6. SECTIONTURFOSA1
Authors: Sheath Robert G. , Vis Morgan L. , Cole Kathleen M. 
Published: October 2004

ABSTRACTTwenty‐one populations ofBatrachospermumsectionTurfosafrom North America were compared to nine type and two historically important specimens using multivariate morphometrics and image analysis. The protologues of six other infrageneric taxa were also compared. From this analysis, six species are recognized worldwide: B, de‐sikacharyiSankaran,B. gombakenseKumano et Ratnasabapathy,B. keratophytumBory de Saint‐Vincent [syn.B. vagumvar.keratophytum(Bory de Saint‐Vincent) Sirodot,B. gulbenkianumReis, andB. suevorumKützing nom. Meg.],B. sinense Jao, B. turfosumBory de Saint‐Vincent [syn.B. vagum(Roth) C. Agardh andB. vagumvar.undulato‐pedicellatumKumano et Watanabe], andB. vogesiacumF. G. Schultz ex Skuja [syn.B. vagumvar.flagelliformeSirodot,B. flagelliforme(Sirodot) Necchi], These species are distinguished on the basis of carposporophyte‐bearing branch cortication, secondary fascicle development, monoecy or dioecy, presence of spermatangia on involucral filaments and monosporangia, and dimensions of trichogynes and carposporangia. Peripheral cortication has been previously used to separate species in this section, but we observed that this feature is quite widespread in the section. Presence of indeterminate gonimoblast filaments has been reported for some taxa in sectionTurfosa, but no such structures were seen in any of the specimens examined. OnlyB. keratophytumhas been collected in North America, ranging from southwestern Greenland (64°N) to Louisiana (30° N).
THE RELATIONSHIP OF LIPIDS WITH LIGHT AND CHLOROPHYLL MEASUREMENTS IN FRESHWATER ALGAE AND PERIPHYTON1
Authors: Napolitano Guillermo E. 
Published: October 2004

ABSTRACTLipid content and lipid class composition were determined in stream periphyton and the filamentous green algae Cladophora sp. and Spirogyra sp, Sterols and phospholipids were compared to chlorophyll a (chl a) as predictors of biomass for stream periphyton and algae. Chlorophyll a, phospholipids, and sterols were each highly correlated with ash‐free dry mass (AFDM) (r2 > 0.98). Stream periphyton exposed naturally to high light (HL) and low light (LL) had chl a concentrations (μg chl a‐mg−1AFDM) of 7.9± 0.7 and 12.4 ± 2.9, respectively, while the sterol concentrations of these HL and LL stream periphyton (1.6 ± 0.4) were not significantly different (P > 0.05). Periphyton exposed to an irradiance of 300 μmol photons·m−2s−1 in the laboratory for 60 h had 5.6 ± 0.55 μg chl a·mg−1 AFDM, but the same periphyton exposed to 2% incident light for the same amount of time had 11.0 ± 0.56 μg chl a·mg−1 AFDM. Sterol concentrations in these periphyton communities remained unchanged (1.5 ± 0.3 μg·mg−1AFDM), Similar results (i.e. changes in chl a but stability of sterol concentrations in response to irradiance changes) were also found for Cladophora and Spirogyra in laboratory experiments. Sterols can be quantified rapidly from a few milligrams of algae and appear to be a useful predictor of eukaryote biomass, whereas cellular levels of chl a vary substantially with light conditions. Phospholipids (or phospholipid fatty acids) are considered to be a reliable measure of viable microbial biomass. Nevertheless, phospholipid content varied substantially and unpredictably among algae and periphyton under different light regimes. Irradiance also had a significant effect on storage lipids: HL Cladophora and HL periphyton had 2 × and 5 × greater concentrations of triacylglycerols, respectively, compared to their LL forms. HL and LL algae also differed in the concentration of several major fatty acids. These light‐induced changes in algal lipids and fatty acids have important implications for grazers.
CHARACTERIZATION OF TWO CHLORELLA VULGARIS (CHLOROPHYCEAE) STRAINS ISOLATED FROM WASTEWATER OXIDATION PONDS1
Authors: Post Anton F. , Cohen Iris , Romem Eitan 
Published: October 2004

ABSTRACTWe report here on the characterization and isolation of two ecotypes of Chlorella vulgaris Beyerinck that coexist in wastewater reservoirs. One ecotype (C1) contains high amounts of chlorophyll b, is capable of autotrophic growth, and can utilize only a few organic solutes for growth. The second ecotype (C2) contains low amounts of chlorophyll b, requires vitamin B12, and can support its growth with a broad range of organic compounds. Of the two ecotypes, the latter showed slower growth rates when light was the sole source of energy. Cells of C2‐type Chlorella attained higher photosynthetic activities than C1‐type cells at saturating irradiances. However, their low chlorophyll b content and lower light utilization efficiency suggest that C2‐type Chlorella contains relatively low amounts of light‐harvesting antennae, a disadvantage in severely light‐limited ecosystems like wastewater reservoirs. We hypothesize that the two Chlorella types coexist by adopting different lifestyles: C1‐type cells rely largely on their photosynthetic potential for energy conservation and growth, whereas C2‐type cells may exploit their heterotrophic properties for this purpose.
THE PHYSIOLOGICAL ECOLOGY OF A FRESHWATER DINOFLAGELLATE BLOOM POPULATION: VERTICAL MIGRATION, NITROGEN LIMITATION, AND NUTRIENT UPTAKE KINETICS1,2
Authors: Lieberman Oded S. , Shilo Moshe , van Rijn Jaap 
Published: October 2004

ABSTRACTThe motile freshwater dinoflagellate Gymnodinium bogoriense Klebs., which forms dense blooms in Jezre'el Valley water reservoirs (Israel) appears to be physiologically suited to exploit stratified environments, where it outcompetes all other phytoplankton types. The dense summer blooms (“red tides”) were found to be nitrogen‐limited. The algae's competitive advantage, however, cannot result from superior uptake capabilities: its Ks (μmol NH4·L−1) for NH4 was higher and its Vmaxμmol NH4·mg chlorophyll a−1·h−1) was lower than other phytoplankton types commonly occurring in the region. The competitive advantage of G. bogoriense probably stems from other physiological capabilities: dark ammonia and phosphorus assimilation and the ability to undertake diel vertical migration cycles between the upper photic water layers during the day and nutrient‐rich deeper layers at night. These findings confirm the vertical nutrient retrieval hypothesis in migrating phytoplankton.
EFFECT OF NUTRIENT LIMITATION ON FATTY ACID AND LIPID CONTENT OF MARINE MICROALGAE1
Authors: Reitan Kjell Inge , Rainuzzo Jose R. , Olsen Yngvar 
Published: October 2004

ABSTRACT Phaeodactylum tricornutum and Chaetoceros sp. (Badllariophyceae), Isochrysis galbana (clone T‐Iso) and Pavlova lutheri (Prymnesiophyceae), Nannochloris atomus (Chlorophyceae), Tetraselmis sp. (Prasinophyceae), and Gymnodinum sp. (Dinophyceae) were cultured at different extents of nutrient‐limited growth: 50 and 5% of μmax. The lipid content of the algae was in the range 8.3–29.5% of dry matter and was generally higher in the Prymnesiophyceae than in the Prasinophyceae and the Chlorophyceae. Increasing extent of phosphorus limitation resulted in increased lipid content in the Bacillariophyceae and Prymnesiophyceae and decreased lipid content in the green flagellates N. atomus and Tetraselmis sp.The fatty acid composition of the algae showed taxonomic conformity, especially for the Bacillariophyceae, where the major fatty adds were 14:0, 16:0, 16:1, and 20:5n‐3. These fatty acids were dominant also in the Prymnesiophyceae together with 22:6n‐3. An exception was I. galbana, in which 18:1 was the major monounsaturated fatty add and 20:5n‐3 was absent. The fatty acids of N. atomus and Tetraselmis sp. varied somewhat, but 16:0, 16:1, 18:1, 18:3n‐3, and 20:5n‐3 were most abundant. Gymnodinum sp. contained mainly 16:0, 18:4n‐3, 20: 5n‐3, and 22:6n‐3. An increased level of nutrient limitation (probably phosphorus) resulted in a higher relative content of 16:0 and 18:1 and a lower relative content of 18:4n‐3, 20:5n‐3, and 22:6n‐3. The nutrient limitation probably reduced the synthesis of n‐3 polyunsaturated fatty acids.
THE NEAR‐SPINELESS TRACHELOMONAS GRANDIS (EUGLENOPHYCEAE) SUPERFICIALLY APPEARS SPINY BY ATTRACTING BACTERIA TO ITS SURFACE1,2
Authors: Rosowski James R. , Langenberg Willem G. 
Published: October 2004

ABSTRACT Trachelomonas grandis Singh has a mucilaginous, highly porous mineralized lorica (envelope) generally without ornamentation except occasionally for a few short, tapered, anterior or posterior spines. However, as our first cultures of this species aged, rod‐shaped structures appeared on the loricas. That these surface projections were bacteria was determined by scanning and transmission electron microscopy. The bacteria, 2‐6 μm long with rounded apices, were oriented perpendicular to the exterior lorica surface and were attached on one end by apically produced tie‐down fibers. The bacteria also secreted fibers over their entire surface, forming a network between them that collapsed during specimen preparation for scanning electron microscopy. The density of the surface bacteria increased with time until the lorica took on a “spiny” appearance superficially similar to lorica extensions of algal origin. In mature algal specimens, an estimated 1200‐1800 bacteria per lorica occurred as a monolayer, the maximum number related to the surface area of the lorica available for bacterial colonization. The bacteria, always motionless while attached, showed putative evidence of budding. Fission formed short chains of up to three cells on the lorica. Our cultures maintained this association for 8 years (1972‐1979). However, cultures ordered for further study in the past year have failed to develop loricas with more than just a few bacterial cells, and most have none.
THE MARINE MIXOTROPH DINOBRYON BALTICUM (CHRYSOPHYCEAE): PHAGOTROPHY AND SURVIVAL IN A COLD OCEAN1
Authors: McKenrie Cynthia H. , Deibel Don , Paranjape Madhu A. , Thompson Raymond J. 
Published: October 2004

ABSTRACT The marine chrysophyte Dinobryon balticum (Schzütt) Lemm. was one of the dominant members of the phytoplankton community (1.8×103 cells‐L−1) in June and July in Conception Bay, Newfoundland. Dinobryon balticum colonies were common only in samples from June and July. The cells were concentrated at 5 m (X±SD=1.11±4 × 105 cells.L−1) and at 40 m (3.32±2×104.L−1) depths. Colonies were composed of up to 560 cells with a mean (±SD) colony size of 10 ± 1 cells at 5 m and 40 ± 8 cells at 40 m. Fluorescent latex bead‐uptake experiments conducted with field samples indicated that this marine species was capable of phagotrophy and that twice as many Dinobryon cells were ingesting beads at 40 m than at 5 m, although the ingestion rates for those cells actively ingesting beads were similar at both depths. This chrysophyte was found in association with bacteria‐and nutrient‐rich microhabitats of microaggregates and fecal pellets. The cells and colonies observed in this study appeared to be healthy, as demonstrated by their appearance and their ability to ingest beads.
PREMATURE CHROMOSOME CONDENSATION OF THE KARYOGAMY‐BLOCKED SPERM PRONUCLEUS IN THE FERTILIZATION OF FUCUS DISTICHUS (FUCALES, PHAEOPHYCEAE)1
Authors: Motomura Taizo 
Published: October 2004

ABSTRACT Mitosis of egg and sperm pronuclei of Fucus distichus subsp. evanescens (C. Agardh)Powell was examined by fluorescence and electron microscopy when migration of the sperm pronucleus and, as a result, karyogamy were blocked by colchicine treatment after plasmogamy. Chromosome condensation was obsewed in both pronuclei Microspectrophotometric studies after staining the nuclei with mithramycin A clearly showed that DNA synthesis ocurred in the egg pronucleus but not in the sperm pronucleus. This means that chromosomes condensed prematurely in the sperm pronucleus (premature chromosome condensation). In some cases, the egg chromosomes became arranged on a metaphase plate, whereas the sperm chromosomes lay scattered near the egg pronucleus. Immuno fluorescence microscopy using anti‐β‐tubulin antibody confirmed that a normal spindle was formed at the egg pronucleus. A pair of centrioles existed at the two poles of this spindle. The sperm nuclear membrane disappeared, and microtubules radiated to the sperm chromosomes from one pole of the egg spindle.