bluuebunny/crossref_metadata_2025_split huggingface dataset:
FACTORS AFFECTING SURFACE ALKALINE PHOSPHATASE ACTIVITY IN THE BROWN ALGAFUCUS SPIRALISAT A NORTH SEA INTERTIDAL SITE (TYNE SANDS, SCOTLAND)1
Authors: Hernández Ignacio , Christmas Martin , Yelloly Julia M. , Whitton Brian A. 
Published: October 2004

ABSTRACTSurface alkaline phosphatase activity (APA) was measured in the tips ofFucus spiralisL. thalli over an approximately 1‐year period, using small plants from upper littoral rock pools at a site on the east coast of Scotland. Maximum APA (4.4 μmol p‐NP·g dry wt−1·h−1) occurred in April, coincident with a sharp increase in tissue N:P ratio of the tips and the probable period of most rapid growth. Enzymatic activity was not correlated with any of the physical and chemical factors (temperature, pH, external phosphate, salinity) measured in the pools or nutrient concentrations (C, N, P) in the apical part of the thallus. No obvious correlation was found between APA and the position of a plant on the shore. However, APA was significantly higher in plants emersed at low tide than in plants submerged during the whole tidal cycle. There was a significant positive correlation between APA and tissue P within a single thallus, with the highest value at the tip (which includes the meristematic zone). Changes in APA ofFucus spiralisappear to result from a complex interaction of biotic and environmental factors, including stress by emersion, growth period, rapid changes in tissue nutrient content and N:P ratio, and regzon of thallus.
AKINETE FORMATION IN PLANKTONIC ANABAENA SPP. (CYANOBACTEFUA) BY TREATMENT WITH LOW TEMPERATURE1
Authors: Li Renhui , Watanabe Masayuki , Watanabe Makoto M. 
Published: October 2004

ABSTRACTThe effects of temperature, light intensity and nutrient depletion on akinete formation in seven strains of planktonic Anabaena spp.: A. mucosa TAC426; A. crassa TAC436; A. spiroides TAC443 and TAC444; A. flosaquae TAC446; and A. ucrainica TAC448 and TAC449 were examined. A Marked Pfft of temperature on akinete formation was observed at 40 μmol photons·m−2·sec−1 and nutrient‐sufficient conditions. At 20° C, akinetes did not develop in A. mucosa TAC426, A. crassa TAC436, A. spiroides TAC443, A. flos‐aquae TAC446, or A. ucrainica TAC449 but were formed at frequencies of a little over 11% (ratio of filaments with akinetes to total filaments) in A. spiroides TAC444 and A. ucrainica TAC448. None of the strains fmd akinetes or heterocysts at 30° C and 35° C. At lower temperature (10° C and 15° C), akinetes developed in all the strains at maximum frequencies of 13.4–77.4% during the late exponential phase or late exponential to stationary phases of growth. With only one exception, low light or nutrient deletion did not lead to the induction of akinete diferentiation at 20° C. Only akinete formation in A. flosaquae TAC446 was induced by nitrogen deletion with a frequency of 12.1%, similar to that induced by low temperature, but the initiation of akinete formation in the strain was delayed compared to treatment with low temperature. These results show that temperature was the most important environmental factor triggering akinete formation in these species. In A. crassa TAC436 and A. spiroides TAC443 and TAC444, akinetes developed during the late exponential growth phase even though heterocysts were formed at a 100% frequency (ratio of filaments with heterocysts to total filaments) throughout the entire growth phase. In A. mucosa TAC426, A. flos‐aquae TAC446, and A. ucrainica TAC448 and TAC449, there was a positive correlation between heterocyst and akinete formation, suggesting that the presence of a heterocyst may play a role in akinete formation.
ADSORPTION AND UPTAKE OF COPPER BY THE GREEN ALGA SCENEDESMUS SUBSPICATUS (CHLOROPHYTA)1
Authors: Knauer Katja , Behra Renata , Sigg Laura 
Published: October 2004

ABSTRACTCopper (II) accumulation has been investigated in the green alga Scenedesmus subspicatus G. Brinkmann considering both adsorption and uptake kinetics. Experiments were conducted in a Cu‐ and PH‐buffered medium at different free Cu2+ concentrations that were neither growth limiting nor toxic. We distinguished between adsorption on the cell surface and intracellular uptake by extracting copper from the cells with EDTA. Data from short‐term experiments were compared with data obtained from experiments under steady state conditions. The accumulation of Cu can be described by two processes, an initial fast adsorption occurring within a minute followed by a slower intracellular uptake. Metal uptake followed Michaelis‐Menten kinetics and is mediated by two systems, one with low and the other with high affinity. The maximum uptake rates (1.30 × 10−‐10 mol·[g dry wt algae]−1· min−1, 3.67 × 10−‐9 mol·[g dry wt algae]−1·min−1), and the half‐saturation constants (6.84 × 10−‐14 M, 2.82 × 10−‐12 M) for the two uptake systems were determined using the Lineweaver‐Burk plot. The calculated maximum concentration of binding sites on the surface of the algae is initially higher (9.0 × 10−‐6 mol Cu.[g dry wt algae]−1) than under steady state conditions (2.9 × 10−‐6 mol Cu·[g dry wt algae]−1). This suggests that the initial binding to the algal surface comprises the binding to specific transport ligands as well as to inert adsorption sites. The conditional stability constant of the Cu binding to surface ligands was calculated as log KCu= 11.0 at pH 7.9. This freshwater alga has a high ability to accumulate Cu, reflecting its adaptation to the bioavailable concentration of copper.
AN UNUSUAL PHYCOCYANOBILIN‐CONTAINING PHYCOERYTHRIN OF SEVERAL BLUISH‐COLORED, ACROCHAETIOID, FRESHWATER RED ALGAL SPECIES1
Authors: Glazer Alexander N. , Chan Crystal F. , West John A. 
Published: October 2004

ABSTRACTThe reproductive biology and phycobiliproteins of four different culture isolates of the freshwater algaeAudouinellaand‘Chantransia’were investigated.‘Chantransia’sp. (3585/UTEX 2623) and Audouinella macrospora (Wood) Sheath et Burkholder (3394,3395) from California and Minnesota reproduced only by monospores. However, A. macrospora (3603/Necchi 1) reproduced by monosporangia that formed successive generations of theAudouinellaphase, andBatrachospermumshoots developed from the basal and erect systems. The major light‐harvesting phycobiliprotein in all of these isolates was a phycocyanobilin‐containing phycoerythrin not previously detected in red algae or cyanobacteria. As in the commonly found R‐ and B‐phycoerythrins, Audouinella phycoerythrin had a native molecular mass of ∼ 240,000 and was made up of α, β, and γ subunits. Audouinella phycoerythrin carried two phycoerythrobilins on the α subunit; one phycourobilin, one phycoerythrobilin, and one phycocyanobilin on the β subunit; and one phycourobilin and two phycoerythrobilins on the γ subunit. With excitation at 495, 563, or 603 nm, the fluorescence emission peak ofAudouinellaphycoerythrin was at 626 nm, showing that phycocyanobilin was the terminal energy acceptor.
BICARBONATE UTILIZATION BY MARINE PHYTOPLANKTON SPECIES
Authors: Nimer Nabil A. , Iglesias‐Rodriguez M. Debora , Merrett Michael J. 
Published: October 2004

ABSTRACTThe contribution of bicarbonate to total dissolved inorganic carbon (DIC) utilization was investigated using 18 marine phytoplankton species, including members of Bacillariophyceae, Dinophyceae, Prymnesiophyceae, and Raphidophyceae, under carbon‐replete or ‐limited conditions. Extracellular carbonic anhydrase (CA) was assayed as an indicator of extracellular CA‐catalyzed HCO−3 utilization. For some species, extracellular CA was constitutive, in others activity was detected under conditions of carbon limitation, and in others, even under carbon‐limited conditions, activity was not detected. In species without extracellular CA, direct HCO−3 uptake was investigated using a pH drift technique in a closed system, DIC measurements, and the use of the anion exchange inhibitor 4′4′‐diisothiocyanatostilbene‐2,2‐disulfonic acid (DLDS). Three of these species (Chaetoceros compressus, Thalassiosira pseudonana, and Glenodinium foliaceum) gave a pH drift not inhibited by DIDS, but cultures of Chrysochromulina kappa, Gephrocapsa oceanica, and Coccolithus pelagicus, in which DLDS inhibited DIC uptake, did not give a pH drift. This result shows that direct HCO3− transport may occur by an anion exchange‐type mechanism in some species but not others. Of the eighteen species investigated, only Heterosigma akashiwo did not have the potential for direct uptake or extracellular CA‐catalyzed HCO−3 utilization.
IN VIVO MEASUREMENT OF ACTIVE OXYGEN PRODUCTION IN THE BROWN ALGA FUCUS EVANESCENS USING 2′,7′‐DICHLOROHYDROFLUORESCEIN DIACETATE1
Authors: Collén Jonas , Davison Ian R. 
Published: October 2004

ABSTRACTIntracellular production of active oxygen in the brown alga Fucus evanescens C. Ag. was studied by measuring the capacity for in vivo conversion of 2′,7′‐dichlorohydrofluorescein diacetate (DCFH‐DA) to the fluorescent dye 2′,7′‐dichlorofluorescein (DCF), both in emersed and immersed seaweeds. Algae were incubated in seawater containing DCFH‐DA under a range of conditions, and it was also possible to load algae with DCFH‐DA and then follow subsequent DCF production in emersed tissue. DCF formation was linear for at least 2 h in both darkness and light, with the rate of formation increasing with the light level. DCF formation was temperature dependent. It also increased when algae were treated with H2O2 or methyl viologen (paraquat), which disrupts photosystem 1 electron transport and increases O−2 production. Exogenous catalase reduced in vivo DCF production, presumably by lowering cellular concentrations of H2O2. Hydrogen peroxide was released into the seawater by illuminated algae resulting in external dye conversion to DCF. However, this does not interfere with in vivo measurement of DCF by loaded, washed algae because DCF leakage appeared to be negligible. Internal DCF did not affect photosynthetic oxygen production relative to untreated controls. Overall, our data suggest that DCFH‐DA is a potentially very useful probe for studying active oxygen metabolism in seaweeds subjected to environmental stresses.
FEEDING IN PERANEMA TRICHOPHORUM REVISITED (EUGLENOPHYTA)1
Authors: Triemer Richard E. 
Published: October 2004

ABSTRACTFeeding in Peranema trichophorum (Ehrenberg 1838) Stein 1878 was first observed over a century ago, yet there is still contention over how the feeding apparatus is used in feeding. Using video microscopy and scanning microscopy, this study documents two types of feeding. Peranema may engulf prey cells whole. Immotile cells are preferred, but moving cells occasionally are engulfed. Details of the early stages of engulfment are presented using scanning electron microscopy. A second method of feeding begins with the attachment of Peranema to a prey cell. The rods of the feeding apparatus then are repeatedly scraped over the surface of the prey until a tear occurs in the cell. The feeding apparatus is inserted into the opening and the internal cell contents are sucked out. The anterior flagellum is inserted into the prey to help remove the cell's contents.
THE CHITINOUS NATURE OF FILAMENTS EJECTED BY PHAEOCYSTIS (PRYMNESIOPHYCEAE)1
Authors: Chrétiennot‐Dinet Marie‐JosèPhe , Giraud‐Guille Marie‐Madeleine , Vaulot Daniel , Putaux Jean‐Luc , Saito Yukie , Chanzy Henri 
Published: October 2004

ABSTRACTFilaments ejected by Phaeocystis globosa Scherffel, organized in star‐like structures, were observed and analyzed before and after their discharge from cells. Ultrastructural observations obtained after cryofixation and cryosubstitution led to a model for their storage within the cell and for their ejection from the cell. Electron diffraction analysis on the ejected filaments demonstrated their chitinous composition. This technique indicated without ambiguity that each filament was in fact a whisker‐like α‐chitin crystal, with the axes of the corresponding polymer chains aligned with the filament's axis. X‐ray microanalysis of the mats of filaments indicated that the silica content suggested by earlier workers was an artifact resulting from the filtration procedure.
GROWTH‐CONTROLLED OSCILLATION IN ACTIVITY OF HISTONE H1 KINASE DURING THE CELL CYCLE OF CHLAMYDOMONAS REINHARDTII (CHLOROPHYTA)1
Authors: Zachleder Vilém , Schläfli Oliver , Boschetti Arminio 
Published: October 2004

ABSTRACTSynchronous cultures of the cell wall‐less mutant Chlamydomonas reinhardtii Dangeard cw 15 were grown under different mean irradiances and different illumination regimes, which produced cell cycles that differed in the number of daughter cells released from one mother cell, in the length of the cell cycle, and in the growth rate. During the cell cycle, the cells reached several commitment points whose number and timing differed according to the particular pattern of the cell cycle. The cell volume was used as a growth parameter and increased in a stepwise manner. Each of the steps consisted of periods of both fast and slow growth. Growth usually stopped when the cells attained a volume twice that of the preceding step. Reaching particular commitment points was coupled with the position of these points in the enlargement of cell volume. Changes in the activity of histone H1 kinase were noted during the cell cycles of all experimental variants, and the activities were compared with the timing of various commitment points. It was found that kinase activity varied markedly within a single cell cycle, attaining maximal values when the cellular volume had doubled. Each peak in kinase activity slightly preceded the commitment to an individual sequence of reproductive events. In addition to the oscillations related to cell growth, a peak of kinase activity always occurred toward the end of the cell cycle when multiple rounds of DNA replication, mitosis, and cell division occurred.
TWO MORPHOLOGICALLY SIMILAR BIOLOGICAL SPECIES: CHONDRUS PINNULATUS AND C. ARMATUS (GIGARTINACEAE, RHODOPHYTA)1
Authors: Brodie Juliet , Masuda Michio , Mine Ichiro , Guiry Michael D. 
Published: October 2004

ABSTRACTThe nature of the relationship between Chondrus pinnulatus (Harvey) Okamura f. pinnulatus and C. pinnulatus f. armatus (Harvey) Yamada et Mikami (Gigartinaceae, Rhodophyta) was investigated by comparative analysis of their biogeography, phenologies, life histories, gross and vegetative morphology, crossability, and upper thermal tolerance. The forma pinnulatus has a more northerly distribution in Japan and adjacent waters, exhibiting adaptation to the cooler regions, whereas the forma armatus has a more southerly range. The latter may be the result of a higher thermal tolerance. Both formae have a Polysiphonia‐type life history and are similar in their internal vegetative morphology. They can, however, be distinguished by gross morphology: forma pinnulatus has wide, flattened axes, compressed to flattened ultimate segments and proliferations, while forma armatus has narrow, compressed to subterete axes and subterete to terete ultimate segments and proliferations. These differences persist in laboratory culture. All intraformae crosses were positive, with carpospores from the cross developing into fertile F1 tetrasporophytes releasing tetraspores that developed into dioecious F1 gametophytes, the female gametophytes of which formed normal cystocarps. This suggests that members of populations of each forma freely interbreed. Among interformae crosses, only some offspring derived from geographically distant strains bore normal cystocarps in the F1 female gametophytes. Other crosses showed that interbreeding between populations of these two formae was blocked by various isolating mechanisms: incompatibility, hybrid inviability, and hybrid sterility. Reproductive isolation between f. pinnulatus and f. armatus is virtually complete in wild populations, because hybrid populations have not been found in the wild. In addition, these two entities can be considered biological species that are also referred to the taxonomic species, C. armatus and C. pinnulatus, because they do not overlap with regard to the morphology of the ultimate segments and proliferations. Subtle (but significant) gross morphological differences, partial interfertility between the two species, and deleterious hybridization in the area in which they occur sympatrically suggest that their evolutionary divergence was relatively recent.
DNA EXTRACTION AND RAPD MARKERS TO ASSESS THE GENETIC SIMILARITY AMONG GELIDIUM SESQUIPEDALE (RHODOPHYTA) POPULATIONS1
Authors: Alberto Filipe , Santos Rui , Leitão José M. 
Published: October 2004

ABSTRACTA simple method developed for genomic DNA isolation from fungus was tested on the red alga, Gelidium sesquipedale (Clem.) Born et Thur., which is commercially exploited for its high sulfated polysaccharide (agar) content. This method is faster, cheaper, and less toxic than conventional phenol/chloroform methods. Random amplified polymorphic DNA (RAPD) amplifications were performed successfully without the necessity of purifying the DNA. RAPD markers were used to investigate the genetic similarity among three natural populations of G. sesquipedale from southern Portugal. Bulked‐genomic DNA samples of 15 different individuals were made in each population. These can be conceived of as a sample of the population DNA. Of the 62 primers screened, 41 produced bands and 22 revealed polymorphisms. Genetic similarities among populations were high. Populations that are further away from each other have the lowest similarity coefficients, whereas the intermediate Ingrina population, located on the south coast, showed higher genetic similarity with the Odeceixe population located on the southwest coast, than with the São Rafael southern population. This suggests a higher genetic flow between Odeceixe and Ingrina or the result may be a founder effect in the sense that the species has propagated from the east coast to the south coast of Portugal. We conclude that the use of this isolation method with RAPD analysis is appropriate to characterize the genetic variability of this commercial species along its geographical distribution. Large sample sizes can be screened at a relatively low cost. Finding genetic markers for commercial populations of G. sesquipedale may be of industrial interest.
ICE NUCLEATION IN SEAWEEDS IN RELATION TO VERTICAL ZONATION1
Authors: Lundheim Rolv 
Published: October 2004

ABSTRACTThe ice nucleation temperatures of thallus fragments of different macroalgal species were investigated. The samples were collected from the littoral zone on a rocky shore in Trondheimsfjord, central Norway. Thallus fragments of species growing in the upper parts of the eulittoral zone had lower ice nucleation temperatures than those of species living in the lower eulittoral zone and in the upper sublittoral zone. Samples collected in the winter had lower nucleation temperatures than samples from the same species collected in the summer, which indicates that the seaweeds are removing or inactivating ice nucleators as a part of their cold hardiness strategy.
EPIPHYTE‐GRAZER INTERACTIONS ON ZOSTERA MARINA (ANTHOPHYTA: MONOCOTYLEDONES): EFFECTS OF DENSITY ON COMMUNITY FUNCTION1
Authors: Nelson Timothy A. 
Published: October 2004

ABSTRACTInteractions between algal epiphytes and their grazers can have a significant impact on the structure and function of eelgrass (Zostera marina L.) meadows. In Puget Sound, the herbivorous gastropod Lacuna variegata Carpenter and its congeners appear to remove large quantities of the epiphytic community from eelgrass blades. When snails at typical field densities were used in microcosms, Lacuna significantly reduced epiphytic biomass and areal productivity. Biomass‐specific productivity of the epiphytic community showed an increasing trend with increasing snail density. Epiphytic productivity increased nonlinearly with increasing epiphytic biomass. The commonly used logistic population growth formula adequately described this relationship. Grazing rate also increased nonlinearly with increasing epiphytic biomass. The Hailing equation adequately described the relationship between grazing rate and epiphytic biomass. The proportion of the epiphytic biomass found on the oldest blade of an eelgrass shoot was related linearly to epiphytic biomass, suggesting that a constant fraction of the epiphytic community is lost regardless of epiphytic density. Lacuna clearly removed large quantities of epiphytic material from eelgrass blades, significantly altering community function. Modified Lotka‐Volterra equations, incorporating the logistic growth form and Hailing grazing equation, should prove useful in modeling the epiphyte–grazer interaction.
SEASONAL VARIATION OF PHOTOSYNTHETIC PERFORMANCE AND LIGHT ATTENUATION INULVACANOPIES FROM PALMONES RIVER ESTUARY1
Authors: Vergara Juan J. , Pérez‐Lloréns J. Lucas , Peralta Gloria , Hernández Ignacio , Niell F. Xavier 
Published: October 2004

ABSTRACTThe primary production ofUlvapopulations relies on their photosynthetic performance, which is dependent on the light availability under natural conditions. This study concerns the light attenuation characteristics inUlvacanopies and the seasonal photosynthetic performance of two different species (Ulva rotundataBlid.,Ulva curvata(Kütz.) De Toni) blooming in the Palmones river estuary. Light within canopies differed from that reaching the surface. Light availability was reduced through the water column (at high tide) andUlvacanopies. In addition, light was spectrally filtered. As a result, the photosynthetically usable radiation (PUR) was further attenuated throughUlvacanopies, increasing the photosynthetically active radiation/PUR ratio. The muddy sediment deposited on and between theUlvathalli also drastically restricted the light availability. ThickUlvamats are frequently found covering the intertidal mudflats, and therefore, thalli within these mats may be subjected to steep light gradients. As a consequence, individualUlvagrowth rates cannot be extrapolated to estimate the primary production ofUlvacanopies. Interspecific differences were observed for light‐saturated photosynthetic rates (Pmax) and light compensation points (LCP), withUlva curvatagenerally displaying higher values than didU. rotundata. For both species, maxima were recorded in winter for Pmax, quantum yield, chlorophyll content, and absorptance, whereas minima were found in summer. Dark respiration (Rd) was not seasonally affected, and a maximum LCPwas found in summer. To extrapolate these data to field situations, the temperature dependence of photosynthesis should be considered. The Q10values were 2.44 for Rdand 1.79 for Pmax, whereas the photosynthesis rate at subsaturating light levels was unaffected. The Q10values showed an enhanced respiratory rate in summer and a minimum in winter, whereas the seasonal differences on Pmaxwere damped.