bluuebunny/crossref_metadata_2025 huggingface dataset:
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

Sequence 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

Knowledge 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

The 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

The 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

Twenty‐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

Lipid 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

We 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

The 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

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

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

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

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.
SPONTANEOUS AND STIMULATED BIOLUMINESCENCE OF THE DINOFLAGELLATE CERATOCORYS HORRZDA (PERIDINIALES)1
Authors: Latz Michael I. , Lee Andrea O.
Published: October 2004

This is the first report of spontaneous bioluminescence in the autotrophic dinoflagellate Ceratocorys horrida von Stein. Bioluminescence was measured, using an automated data acquisition system, in a strain of cultured cells isolated from the Sargasso Sea. Ceratocorys horrida is only the second dinoflagellate species to exhibit rhythmicity in the rate of spontaneous flashing, flash quantum flux (intensity), and level of spontaneous glowing. The rate of spontaneous flashing was maximal during hours 2–4 of the dark phase [i.e. circadian time (CT)16–18 for a 14:10 h LD cycle (LD14:10)], with approximately 2% of the population flashing‐min−1, a rate approximately one order of magnitude greater than that of the dinoflagellate Gonyaulax polyedra. Flash quantum flux was also maximal during this period. Spontaneous flashes were 134 ms in duration with a maximum flux (intensity) of 3.1×109 quanta‐s−1. Light emission presumably originated from blue fluorescent microsources distributed in the cell periphery and not from the spines. Values of both spontaneous flash rate and maximum flux were independent of cell concentration. Isolated cells also produced spontaneous flashes. Spontaneous glowing was dim except for a peak of 6.4× 104quanta‐s−1 cell−1, which occurred at CT22.9 for LD14:10 and at CT22.8 for LD12:12. The total integrated emission of spontaneous flashing and glowing during the dark phase was 4×109 quantacell−1, equivalent to the total stimulable luminescence. The rhythms for C. horrida flash and glow behavior were similar to those of Gonyaulax polyedra, although flash rate and quantum flux were greater. Spontaneous bioluminescence in C. horrida may be a circadian rhythm because it persisted for at least three cycles in constant dark conditions. This is also the first detailed study of the stimulated bioluminescence of C. horrida, which also displayed a diurnal rhythm. Cultures exhibited >200 times more mechanically stimulated bioluminescence during the dark phase than during the light phase. Mechanical stimulation during the dark phase resulted in 6.7 flashes. cell−1; flashes were brighter and longer in duration than spontaneous flashes. Cruise‐collected cells exhibited variability in quantum flux with few differences in flash kinetics. The role of dinoflagellate spontaneous bioluminescence in the dynamics of near‐surface oceanic communities is unknown, but it may be an important source of natural in situ bioluminescence.
DIVISION APPARATUS OF THE CHLOROPLAST IN NANNOCHLORIS BACILLARIS (CHLOROPHYTA)1
Authors: Ogawa Satoko , Ueda Katsumi , Noguchi Tetsuko
Published: October 2004

Chloroplast division in Nannochloris bacillaris Naumann (Chlorophyta) was examined by electron microscopy after preparation of samples by freeze‐substitution. A pair of belts appeared on the surface of the outer and inner envelope membranes at the middle of the chloroplast. These belts seemed to be constructed of thin fibrils that run parallel to the longitudinal direction of the belts. The outer fibrillar belt increased in width as the constriction of the chloroplast advanced. It appears that the fibrillar belt is the division apparatus of the chloroplast. It encircles the chloroplast and finally divides the chloroplast in two as the diameter of the belt decreases.
DNA:ATP RATIOS IN MARINE MICROALGAE AND BACTERIA: IMPLICATIONS FOR GROWTH RATE ESTIMATES BASED ON RATES OF DNA SYNTHESIS1
Authors: Jones David R. , Karl David M. , Laws Edward A.
Published: October 2004

DNA: ATP and carbon: DNA (C:DNA) ratios were measured in a total of 14 species of marine microalgae and bacteria. Comparison of several DNA assay methods with results obtained with cultures uniformly labeled with 33P indicated that by far the most accurate results were obtained using diaminobenzoic acid (DABA) or diphen‐ylamine, with DABA having the highest precision. Both the Hoechst and DAPI methods seriously underestimated DNA concentrations in algal cultures. Average DNA: ATP ratios in the algal and bacterial cultures were I7 and 34 by weight, respectively, with almost all values lying in the range of 10–40. DNA: ATP ratios in the microalgae showed no correlation with growth conditions but varied by about a factor of 3 among species. C:DNA ratios for individual species of microalgae and bacteria ranged from 21 to 155 by weight and averaged 50 for the microalgae and bacteria taken together. Growth rates of microalgal species grown in cyclostats were estimated to within 8% of dilution rates when calculated from the uptake of 3H‐adenine and the DNA: ATP ratio of the species. Use of the 3H‐adenine method for estimating microalgal growth rates in the field may thus be a useful tool for investigating the physiology of microalgae in nature.
DISTURBANCE OF STREAM PERIPHYTON BY PERTURBATIONS IN SHEAR STRESS: TIME TO STRUCTURAL FAILURE AND DIFFERENCES IN COMMUNITY RESISTANCE1
Authors: Biggs Barry J.F. , Thomsen Henrik A.
Published: October 2004

The resistance of stream periphyton to structural disturbance by increases in shear stress (simulating a spate) was investigated in a laboratory flow tank. We monitored loss of biomass from a filamentous community (dominated by Melosira varians) under four different levels of shear stress. In each case, any loss that was going to occur did so within 10 min for this community. In a second experiment, we tested the resistance of four different communities (two dominated by nonfilamentous diatoms and two dominated by filamentous green algae/diatoms) to increases in shear stress. Nine different levels of shear stress were used, ranging from 1‐ to 70‐fold higher than the conditions to which the communities were acclimated. All communities were 14 days old, but some differences in initial biomass occurred that influenced the degree of resistance independently of species composition. Overall, the nonfilamentous diatom communities were the most resistant, and the filamentous communities were the least resistant. The kinetics of the sloughing process varied among community types, with a community dominated by Melosira varians/Gom‐phonema parvulum losing 50% of its biomass with only a 3‐fold increase in shear stress. In contrast, a community dominated by the nonfilamentous diatoms Fragilaria vaucheriae/Cymbella minuta lost <50% of its biomass after a 70‐fold increase in shear stress. Shear stresses required for 50% loss of biomass for the different communities were as follows: 3.6 Newtons.m−2 for the Melosira varians/Gomphonema parvulum community, 10.0 N.m−2 for the Spirogyra sp./Gomphoneis her‐culeana/Ulothrix zonata community, 50.6 N.m−2 for the Fragilaria construens/Cymbella minuta/Ach‐nanthes minutissima community, and >90.0 N.m−2for the Fragilaria vaucheriae/Cymbella minuta community. These results show that spates without bedload movement can potentially have widely differing disturbance effects on periphyton loss among streams depending on the initial taxonomic composition of resident communities. These results have important implications for stream ecosystem analysis and modeling.
IDENTIFICATION OF A MYOSIN‐LIKE PROTEIN IN CHLAMYDOMONAS REINHARDTII (CHLOROPHYTA)1
Authors: La Claire John W. , Chen Richard , Herrin David L.
Published: October 2004

A myosin‐like protein was identified in vegetative cells of the unicellular green alga Chlamydomonas reinhardtii Dangeard. Polyclonal antibodies affinity purified against the heavy chain of slime‐mold myosin recognized a 180,000 Mr protein in western blots of total protein extracts from three different strains, including cyt‐1, a cytokinesis‐defective mutant. Immunoblots of isolated chloroplasts indicated that some of the cellular myosin fractionated with chloroplasts, whereas tubulin did not. Evidence for the presence of at least one myosin gene was obtained by probing Southern blots of genomic DNA with a myosin heavy‐chain gene fragment isolated from the green alga Ernodesmis verticillata (Kützing) Børgesen. Collectively, the immunological and molecular data identify at least one myosin heavy‐chain gene and a myosin‐like protein in vegetative cells of the model organism Chlamydomonas.
A SEASONAL COMPARISON OF CARBON, NITROGEN, AND PIGMENT CONTENT IN LAMINARIA SOLIDUNGULA AND L. SACCHARINA (PHAEOPHYTA) IN THE ALASKAN ARCTIC1
Authors: Henley William J. , Dunton Kenneth H.
Published: October 2004

Laminaria solidungula and L. saccharina inhabit the Beaufort Sea in the Alaskan High Arctic. Laminaria solidungula is an Arctic endemic, whereas L. saccharina extends from north temperate Pacific and Atlantic waters to the Arctic. Previous studies have shown that the two species have different seasonal timing of growth, but little comparative physiological information exists. As a first step in characterizing these two species from a mixed Arctic population, we measured variations in carbon, nitrogen, and photosynthetic pigment content in blade tissue from plants collected under the fast ice in April and during the open water Period in late July, Both species exhibited seasonal differences in many measured variables; seasonal differences in L. solidungula were most pronounced in growing basal blades. For example, the molar CIN ratio of basal blades averaged 11 in April and 21 in July for L. solidungula and 11.5 in April and 28 in July for L. saccharina. Basal and mature second blades differed in pigment content in April but not in July: chlorophyll a + c in L. solidungula basal and mature second blades averaged 19 and 27 nmol.cm−2 in April and 30 and 29 nmol. cm−2 in July, respectively. The corresponding values for L. saccharina were 17 and 29 nmol.cm−2 in April and 16 and 16 nmol.cm−2 in July (95% confidence intervals approximately 1–3 nmol. cm −2). Carotenoids exhibited similar patterns. Species differences in pigments, carbon, and nitrogen were minor and were probably effects rather than causes of the different seasonal patterns of growth and development. The primary difference between the two species may be the ability of L. solidungula to retain multiple metabolically active blades and to fuel areal growth with stored carbohydrates during winter near‐darkness, whereas L. saccharina growth is more closely tied to active photosynthesis in the growing basal blade. The cause of old blade retention in L. solidungula and the possibility of other physiological differences between the two species, including gametophytes, remain to be determined.
CHARACTERIZATION OF THE LIGHT‐HARVESTING COMPLEX OFGIRAUDYOPSIS STELLIFER(CHRYSOPHYCEAE) AND EFFECTS OF LIGHT STRESS1
Authors: Lichtlé Christiane , Arsalane Wafa , Duval Jean Claude , Passaquet Chantal
Published: October 2004

The light‐harvesting complex (LHC) ofGiraudyopsis stelliferDangeard was isolated on a sucrose density gradient after digitonin treatment, and the pigment composition was analyzed by reverse‐phase high‐pressure liquid chromatography. The LHC is a chlorophyll (Chl) a/c/fucoxanthin/violaxanthin complex, depleted of β‐carotene, comparable to the LHC of Fucophyceae. The excitation transfer from Chlcand fucoxanthin to Chlais efficient in whole cells. Immunological reactions indicate a close relationship between Chrysophyceae and Fucophyceae. The immunocytochemical labeling confirms the lack of segregation of the LHC in the appressed membranes of the three associated thylakoids and its localization in the intrapyrenoid thylakoid. The violaxanthin‐antheraxanthin‐zeaxanthin cycle is operative in the cells and efficiently protects photosystem II reaction centers against photoinhibition.
CELL DIVISION IN THE DINOFLAGELLATE GAMBIERDISCUS TOXICUS IS PHASED TO THE DIURNAL CYCLE AND ACCOMPANIED BY ACTIVATION OF THE CELL CYCLE REGULATORY PROTEIN, CDC2 KINASE1
Authors: van Dolah Frances M. , Leighfield Tod A. , Sandel H. Daniel , Hsu Chuin Kang
Published: October 2004

The cell division cycle in several pelagic dinoflagellate species has been shown to be phased with the diurnal cycle, suggesting that their cell cycle may be regulated by a circadian clock. In this study, we examined the cell cycle of an epibenthic dinoflagellate, Gambierdiscus toxicus Adachi and Fukuyo (Dinophyceae), and found that cell division was similarly phased to the diurnal cycle. Cell division occurred during a 3‐h window beginning 6 h after the onset of the dark phase. Cell cycle progression in higher eukaryotes is regulated by a cell cycle regulatory protein complex consisting of cyclin and the cyclin‐dependent kinase CDC2. In this report, we identified a CDC2‐like kinase in G. toxicus that displays activity in vitro against a known substrate of CDC2 kinase, histone H1. As in higher eukaryotes, CDC2 kinase was expressed constitutively in G. toxicus throughout the cell cycle, but it was activated only late in the dark phase, concurrent with the presence of mitotic cells. These results indicate that cell division in G. toxicus is regulated by molecular controls similar to those found in higher eukaryotes.
PSEUDO‐NITZSCHIA PUNGENS AND P. MULTISERIES (BACILLARIOPHYCEAE): NOMENCLATURAL HISTORY, MORPHOLOGY, AND DISTRIBUTION1
Authors: Hasle Grethe Rytter
Published: October 2004

Pseudo‐nitzschia pungens f: multiseries is raised in rank from form to species based on morphological, physiological, and genetic features. Distinctive details of the valve face striae, the valve mantle, and the girdle of P. pungens and P. multiseries are outlined. The nomenclatural history and the distribution of the two species and their relationship to other species of the genus are discussed.
CARBON AVAILABILITY AND THE PATTERN OF CYANOBACTERIAL DOMINANCE IN ENRICHED LOW‐CARBON LAKES1
Authors: Klemer Andrew R. , Hendzel Len L. , Findlay David L. , Hedin Randy A. , Mageau Michael T. , Konopka Allan
Published: October 2004

We hypothesize that the pattern of cyanobacterial dominance in experimentally enriched, low‐carbon lakes is related not only to the resultant N:P ratio but also to the availability of carbon for gas‐vesicle synthesis. We tested this hypothesis by determining the buoyancy responses of a highly gas‐vacuolate, N2‐fixing cyanobacterium to P enrichment with and without induced C limitation. Enrichment of samples of Aphanizomenon schindleri (Kling et al. 1994) from blooms in Lake 227 with combinations of C, N, and P produced rapid buoyancy reductions in P treatments, reductions that were reversed within a generation time in treatments that included C or C and N as well as P. These responses are the first of their kind to be observed in experiments with lake populations of cyano‐bacteria. The rapid buoyancy reductions were associated with polyphosphate accumulations in P‐treated A. schindleri. Differences in buoyancy status after one generation time were linked to differences in relative gas vacuolation between samples treated with P only and samples treated with C and N as well as P. These results may explain the relative success of different types of cyanobacteria in newly enriched, low‐carbon lakes. The availability of C for gasvesicle synthesis may determine whether a low N:P ratio induces N2 fixation by benthic or by planktonic cyanobacteria and whether a high NP ratio leads to dominance by non‐gas‐vacuolate or by highly gas‐vacuolate, non‐N2‐fixers.
INFLUENCE OF FLUCTUATING PHOSPHATE SUPPLY ON THE REGULATION OF PHOSPHATE UPTAKE BY THE BLUE‐GREEN ALGA ANACYSTZS NIDULANS1
Authors: Falkner Gernot , Wagner Ferdinand , Small John Victor , Falkner Renate
Published: October 2004

The blue‐green alga Anacystis nidulans Drouet (Synechococcus leopoliensis Raciborski) cultivated under phosphate‐limited conditions adopts a threshold value in the nanomolar range below which uptake ceases. In this study, we investigated the influence of phosphate pulses on the regulation of uptake behavior during reestablishment of the threshold value. Short‐term pulses had only a slight effect on uptake kinetics and, hence, on the threshold value, even if the population had been exposed several times to elevated concentrations above the steady‐state level in the growth medium. The threshold value was also practically insensitive to the amount of phosphate stored during these short‐term fluctuations. Long‐term phosphate pulses resulted in a transition to a metastable state that was characterized by a severalfold higher threshold value. This transition, apparently an adaptation to the transiently elevated phosphate concentrations, was further studied by following the influx of 32P‐phosphate at constant external concentrations and was shown to be complete after a period of 10–20 min. After adaptation to pulses, the uptake behavior followed a linear flow‐force relation over a wide range of external concentrations. This behavior was explained by the simultaneous operation of at least two uptake systems with different, but coordinated kinetic parameters. This linear flow‐force relation facilitated a direct determination of the threshold value from uptake measurements. For applicability in the field the force‐flow relation can be a diagnostic tool to assay for fluctuating phosphate and to establish threshold values below the normal measurable range.
SPECTRAL CHARACTERIZATION OF NEW CHLOROPHYLLCPIGMENTS ISOLATED FROMEMILIANIA HUXLEYI(PRYMNESIOPHYCEAE) BY HIGH‐PERFORMANCE LIQUID CHROMATOGRAPHY1
Authors: Garrido José L. , Zapata Manuel , Muñiz Susana
Published: October 2004

Pigment extracts from the prymnesiophyteEmiliania huxleyi (Lohm.) Hay & Mohler (CCMP 370) were analyzed using a new chromatographic method based on the use of polymeric octadecylsilica columns, which split both the chlorophyllc3peak and phytol‐substituted chlorophyllc‐like peak into two fractions. The pigments corresponding to each of these fractions were isolated. The spectra and chromatographic behavior suggest that chlorophyll c3fromE. huxleyiis a mixture of two different compounds whereas the splitting of the phytol‐substituted c‐like pigment could be the result of the equilibrium of two forms showing the same absorption spectrum. The method allowed, as well, the detection of magnesium 3,8‐divinylpheoporphy‐rin a, monomethyl ester in the prymnesiophytesE. huxleyi (CCMP 370) andPrymnesium parvumCarter (CCMP 708) and the chrysophytePelagococcus subviridisNorris (CCMP 1429).
COLINEARITY OF CHLOROPLAST GENOMES IN DIVERGENT ECOTYYES OF THE MARINE DIATOM SKELETONEMA COSTATUM (BACILLARIOPHYTA)1
Authors: Stabile Joseph E. , Gallagher Jane C. , Wurtzel Eleanore T.
Published: October 2004

The chloroplast genomes of three isolates of the marine diatom Skeletonema costatum (Grev.) Cleve were mapped and found to be 131 ± 2 kb with inverted repeats (IRs) of approximately 20 kb. In contrast to higher plants, the psbA gene mapped to the IR, and rbcS mapped to the same fragment as the rbcL gene in the large single‐copy region. The maps of the three isolates were colinear and revealed as many as 20 site mutations out of a total of 47 sites. The number of site mutations among isolates was consistent with previous data on their genetic diversity and physiology. Comparisons of gene order among our maps and those of three other diatom species showed that closely related genera retained similar gene orders but that more distantly related taxa exhibited extensive rearrangements. We conclude that simple restriction fragment analysis of chloroplast DNA is useful in comparative studies of diatom populations and species but that other analytical methods are more appropriate for phylogenetic studies at higher levels.
INHERITANCE AND MEIOTIC ELIMINATION OF A VIRUS GENOME IN THE HOST ECTOCARPUS SZLZCULOSUS (PHAEOPHYCEAE)1
Authors: Bräutigam Martin , Klein Michael , Knippers Rolf , Müller Dieter G.
Published: October 2004

The marine brown alga Ectocarpus siliculosus (Dillwyn) Lyngbye is frequently infected by a latent DNA virus that multiplies in modified sporangia and gametangia of the host. We describe a polymerase chain reaction (PCR) procedure for the amplification and detection of viral DNA in Ectocarpus. PCR analysis of parents and progeny plants confirmed that virus DNA passes through meiosis like a Mendelian trait. An infected sporophyte produced equal numbers of gametophytes with and without the viral genome. Thus, meiosis in sexual populations of the host acts as a mechanism for the creation of virus‐free progeny.
SPATIAL DYNAMICS OF A HIMANTHALIA ELONGATA (FUCALES, PHAEOPHYTA) POPULATION
Authors: Creed Joel C.
Published: October 2004

In dense monospecific stands of plants intraspecific competition usually results in self‐thinning, the concurrent increase in biomass and decrease in density over time. Self‐thinning may also result in a change in the spatial pattern of individuals, but so far the spatial dynamics of marine plants has not been investigated. The brown alga Himanthalia elongata (L.) S. F. Gray forms dense monospecific stands on many northern temperate rocky shores, and various attributes (including its simple form) facilitated the study of the spatial dynamics of this species.

The spatial pattern of settling zygotes was examined in the laboratory. In the absence of water movement, substratum heterogeneity, and a point source, zygotes usually settled in clumps rather than randomly. Within the clumps zygotes appeared to be regularly distributed at a scale similar to the size of the zygotes themselves. Furthermore, the clumps themselves seemed to be regularly distributed. On the shore, well‐established stands of “button‐stage” Himanthalia populations were examined during a period of extensive growth and self‐thinning. Individual plants were initially highly regular in spatial pattern but became less so over time. The pattern of plants dying during self‐thinning was also highly regular and probably reflected existing spatial regularity. However, using a hypothesis of mortality as a random event, I found that smaller plants had a less than average survival potential, while larger plants had a greater than average chance. A consideration of the spatial pattern of plants alive at the end of the study revealed regularity at a scale of 2–7 mm but a random spatial pattern at larger scales, which might indicate a small sphere of influence of competing individuals. The best predictor of mean nearest neighbor distances in the populations was mean plant diameter.
CARBONIC ANHYDRASE ACTIVITY IN THE BLOOM‐FORMING DINOFLAGELLATE PERIDINIUM GATUNENSE
Authors: Berman‐Frank Ilana , Kaplan Aaron , Zohary Tamar , Dubinsky Zvy
Published: October 2004

The response of carbonic anhydrase (CA) activity in Peridinium gatunense Nygaard, the natural bloom‐forming dinoflagellate in Lake Kinneret, to diel and seasonal variations in environmental conditions was characterized under controlled laboratory experiments. Simulated diel cycles demonstrated large changes in the ambient concentration of dissolved CO2 and parallel changes in CA activity. The CA activity depended on the total concentrations of inorganic carbon (C1) and in particular on the dissolved CO2. Lowering the C1concentrations resulted in a large increase in CA activity within several hours. Light and photosynthesis were both required for the induction of CA activity. Under CO2 ‐limited conditions, the dependence of the photosynthetic rate on CA (estimated from the ratio of photosynthetic rates in the presence or absence of CA inhibitors) was greater in P. gatunense than in other eukaryotic microalgae. This points to the ecological significance of CA in photosynthetic carbon uptake mechanisms of a large, dominant alga in a natural ecosystem.
IMMUNOLOGICAL AND ULTRASTRUCTURAL CHARACTERIZATION OF THE PHOTOSYNTHETIC COMPLEXES OF THE PROCHLOROPHYTE PROCHLOROCOCCUS (OXYCHLOROBACTERIA)
Authors: Lichtlé Christiane , Thomas Jean Claude , Spilar Agnès , Partensky Frédéric
Published: October 2004

Ultrastructural features and immunological properties of some thylakoid proteins were examined in two strains of the prochlorophyte Prochlorococcus and compared to those of other photosynthetic prokaryotes and eukaryotes. Both strains exhibited two or three rows of tightly appressed thylakoidal membranes, located at the cell periphery. However, thylakoids were concentrically arranged in the strain from the Sargasso Sea (SARG) and horseshoe‐shaped in the Mediterranean isolate (CCMP 1378). Although lacking phycobilisomes, both cell types shared with cyanobacteria the presence of carboxysome‐like structures and glycogen granules as storage compounds.

The main thylakoid polypeptides separated by sodium dodecyl sulfate—polyacrylamide gel electrophoresis were characterized by Western blotting using several antibodies. The 30‐kDa polypeptide of the light‐harvesting complex (LHC) of Prochlorococcus showed a weak positive immunological cross‐reaction with an antibody raised against the 32‐kDa apoprotein of the LHC of the prochlorophyte Prochlorothrix hollandica. In contrast, it showed no immunological relationships with the chlorophyll a/b (Chl a/b) LHCs of green algae and higher plants. Protein membranes from Prochlorococcus strongly cross‐reacted with antibodies raised against reaction center polypeptides of photosystems II and I (PSs II and I) of other photosynthetic organisms, confirming the high degree of conservation of these basic compounds of the photosynthetic machinery during evolution. Immunolocalization of thylakoid proteins showed that the LHC proteins, the major PS II reaction center proteins (CP 43 and D2), and the PS I reaction center proteins were equally distributed within the thylakoid membranes in contrast to the segregation observed in higher plants and green alga thylakoids. We also identified ribulose‐1, 5‐bisphosphate carboxylase/oxygenase in the carboxysomes. These results suggest that Prochlorococcus is more closely related to cyanobacteria than to green plastids even though it contains Chl b.
CHROMOPHYTE PLASTID 16S RIBOSOMAL RNA GENES FOUND IN A CLONE LIBRARY FROM ATLANTIC OCEAN SEAWATER
Authors: Rappe' Michael S. , Kemp Paul F. , Giovannoni Stephen J.
Published: October 2004

In recent years, the cloning of ribosomal RNA genes from natural plankton communities has provided insight into the biodiversity of marine bacterioplankton. Small eukaryotic phytoplankton, like bacterioplankton, can be difficult to cultivate or identify routinely by morphological characteristics. We used bacteria‐specific 16S rRNA primers to amplify genes from picoplankton samples collected on 0.2–μm filters by filtration from a depth of 10 m in the pelagic region over the continental shelf off Cape Hatteras, North Carolina. Nucleic acid sequencing and probe hybridization revealed that chromophyte plastid genes comprised 25% of the genes in a library of 170 clones. The plastid genes belonged to two groups within the Chromophyta: the Prymnesiophyceae and the Bacillariophyceae. Comparisons revealed substantial diversity among the bacillariophyte gene sequences, but the species from which the genes originated could not be identified because few sequences from cultured bacillariophytes are available. The prymnesiophyte genes could not be identified either, although they were most similar (similarity = 0.94) to plastid genes from the coccolithophorid Emiliania huxleyi (Lohmann) Hay and Mohler strain PML92D. These results provide evidence of abundant chromophyte plastid 16S rRNA genes in the water over the continental shelf off Cape Hatteras. The results also suggest that plastid 16S rRNA genes may provide suitable genetic markers for studying phytoplankton biodiversity and biogeography.