bluuebunny/crossref_metadata_2025_split huggingface dataset:
GRADIENT ANALYSIS OF DIATOM ASSEMBLAGES IN WESTERN KENTUCKY WETLANDS1
Authors: Pan Yangdong , Stevenson R. Jan 
Published: October 2004

ABSTRACTDiatom and water chemistry data from 35 wetland sites in western Kentucky were used to assess diatoms as indicators of ecological conditions in wetlands. The wetlands were affected by different degrees of acid mine drainage and agriculture. Canonical correspondence analysis indicated that the distribution of diatoms was highly correlated with conductivity and total phosphorus (TP), two variables commonly associated with acidic mine drainage and agriculture, respectively.Diatom‐based inference models were developed for use as quantitative indicators of two important environmental variables in wetlands: conductivity and TP. Diatom‐inferred conductivity and TP values were highly correlated with measured values. Cross‐validation with jackknifing procedures suggested that high apparent r2 between inferred and measured conductivity was overly optimistic and should be treated with caution. Jackknifing‐derived TP inference models performed poorly in predicting TP toward the ends of low and high TP concentrations. In general, the conductivity inference models based on plankton had better predictability than those based on epiphyton. Epiphyton‐based inference models can predict TP better than plankton. Therefore, diatoms in planktonic and epiphytic assemblages could provide complementary information on ecological conditions.Our data suggest that diatoms can reflect major regional environmental gradients and therefore can be used as indicators of the ecological conditions in wetlands. Quantitative inference models with known predictive power can aid the development of realistic and ecologically sound biotic indices for this region.
CHANGES IN THE PLANKTONIC DIATOM FLORA OF A LARGE MOUNTAIN LAKE IN RESPONSE TO FERTILIZATION1
Authors: Yang Jing‐Rong , Pick Frances R. , Hamilton Paul B. 
Published: October 2004

ABSTRACTFertilization (phosphorus and nitrogen) of Kootenay Lake, British Columbia, was begun in 1992 in an attempt to increase food resources for declining stocks of kokanee salmon. In 1992 and 1993, significant changes in diatom abundance, species composition, diversity, and morphology of individual species were observed in the fertilized North Arm in comparison to the unfertilized South Arm. Effects of fertilization were most obvious during the spring. During summer stratification, fertilization did not result in significant changes in total abundance, but changes in species composition were observed. In 1993, with continued fertilization of the North Arm, diatom abundance in both spring and summer was significantly higher than at the same sites in 1992. No significant differences were observed in the unfertilized South Arm. Diatom abundance was significantly correlated with dissolved inorganic nitrogen (positive) and dissolved reactive silica (negative). Diatom assemblages in the fertilized North Arm in both the spring and summer of 1993 were dominated by Asterionella formosa and Fragilaria crotonensis, taxa considered mesotrophic. Abundance of the oligotrophic taxa Rhizosolenia eriensis and Cyclotella michiganiana was higher in the South Arm than in the North Arm. Differences in diatom assemblages between the two arms in both years were further summarized by multivariate statistical analyses. Morphological variations in two small Cyclotella species (C. comensis and C. cf. pseudostelligera) were observed between the fertilized and “control” stations. Populations of both species from fertilized stations exhibited stronger silicification with coarser striations and a smaller mean size.
MAXIMUM AMMONIUM UPTAKE RATES OF SCENEDESMUS QUADRICAUDA (CHLOROPHYTA) AND MICROCYSTIS NOVACEKII (CYANOBACTERIA) GROWN UNDER NITROGEN LIMITATION AND IMPLICATIONS FOR COMPETITION1
Authors: Watanabe Taku , Miyazaki Tatsuo 
Published: October 2004

ABSTRACTWe measured maximum ammonium uptake rates of the green alga Scenedesmus quadricauda (Turpin) Brébisson and the blue‐green alga Microcystis novacekii (Kom.) Comp. grown in nitrogen (ammonium)–limited chemostats. Maximum uptake rates per cellular carbon were larger in S. quadricauda than in M. novacekii. These rates increased with increased specific growth rates. Maximum uptake rates per cellular nitrogen were also larger in S. quadricauda than in M. novacekii. The maximum uptake rates per cellular nitrogen were nearly constant against increased cellular N:C ratios under nitrogen‐limited conditions. The higher maximum uptake rates indicate that S. quadricauda had higher uptake abilities for ammonium than M. novacekii when grown under nitrogen limitation. We examined the competition between both species under two distinct nutrient supply modes, using measured maximum uptake values and computer simulations. Microcystis novacekii prevailed in the small‐pulse, high‐frequency nutrient supply mode, whereas S. quadricauda became competitively superior in the large‐pulse, low‐frequency nutrient supply mode. These results indicate that we could control nuisance blooms of blue‐green algae in lakes and reservoirs by changing the nutrient supply modes.
EVOLUTIONARY AND ECOLOGICAL DIFFERENTIATION IN THE PANTROPICAL TO WARM‐TEMPERATE SEAWEED DIGENEA SIMPLEX (RHODOPHYTA)1
Authors: Pakker Hans , Klerk Hans , van Campen Jan Hein , Olsen Jeanine L. , Breeman Anneke M. 
Published: October 2004

ABSTRACTGenetic differentiation among geographic isolates of the pantropical to warm‐temperate red alga Digenea simplex (Wulfen) C. Agardh was investigated using random amplified polymorphic DNA (RAPD) markers, crossing studies, and temperature tolerances experiments. Eleven isolates representing populations from the Caribbean, eastern Atlantic, and Indo‐West Pacific were compared. RAPD analysis clearly revealed an Indo‐West Pacific group, a Caribbean/Cape Verde Islands group, and a Canary Islands group. Crossing studies showed different levels of inter fertility. In most crosses between Western Australian and Atlantic isolates, no hybrid tetrasporophytes were formed. In crosses between Caribbean and Cape Verde Islands isolates, tetrasporophytes developed, but the viability of tetraspores was reduced. Full sexual compatibility was observed among Cape Verde Islands isolates and among isolates from Bonaire. Temperature tolerance studies indicate that Pacific isolates have a broader temperature survival range than Atlantic isolates, which may be correlated to local temperature extremes. Despite the reduced level of sexual compatibility between Caribbean and Cape Verde Islands isolates, their shared position in the RAPD analysis and similar temperature responses suggest trans‐Atlantic dispersal in the near geological past. In addition to their discrete position in the RAPD distance analysis, the Canary Islands isolates were significantly more cold‐tolerant than the other Atlantic isolates. This finding is consistent with the hypothesis that the Canary Islands were recolonized from cold‐adapted eastern Mediterranean populations after the last Pleistocene glaciation.
THE EVOLUTION OF PARASITISM IN THE RED ALGAE: MOLECULAR COMPARISONS OF ADELPHOPARASITES AND THEIR HOSTS1
Authors: Goff Lynda J. , Moon Debra A. , Nyvall Pi , Stache Birgit , Mangin Katrina , Zuccarello Giuseppe 
Published: October 2004

ABSTRACTIn several groups of parasites including insect, flowering plant, fungal, and red algal parasites, morphological similarities of the parasites and their specific hosts have led to hypotheses that these parasites evolved from their hosts. But these conclusions have been criticized because the morphological features shared by parasite and host may be the result of convergent evolution. In this study, we examine the hypothesis, originally put forth by Setchell, that adelphoparasitic red algae, that is, parasitic red algae that are morphologically very similar to their hosts, evolved from their specific red algal hosts. Rather than comparing morphological features of parasites and hosts, small‐subunit 18S nuclear ribosomal DNA and the internal transcribed spacer regions (ITSs) of the nuclear ribosomal repeat are compared for five parasites, their hosts, and related nonhosts from four red algal orders. These comparisons reveal that each of these adelphoparasites has evolved either directly from the host on which it is currently found, or it evolved from some other taxon that is closely related to the modern host. The parasites Gardneriella tuberifera, Rhodymeniocolax botryoides, and probably Gracilariophila oryzoides evolved from their respective hosts Sarcodiotheca gaudichaudii, Rhodymenia pacifica, and Gracilariopsis lemaneiformis, respectively. The parasite Faucheocolax attenuata evolved from either Fauchea laciniata or Fauchea fryeana and subsequently radiated onto the other host species. Presently this parasite is found on both hosts. Lastly, some parasitic genera such as Plocamiocolax are polyphyletic in their origins. A species of Plocamiocolax from an Antarctic Plocamium cartilagineum appears to have evolved from its host whereas the common Plocamiocolax pulvinata that occurs along the west coast of North America likely evolved from Plocamium violaceum and radiated secondarily onto its present day host, Plocamium cartilagineum.
PORPHYRA REDIVIVA SP. NOV. (RHODOPHYTA): A NEW SPECIES FROM NORTHEAST PACIFIC SALT MARSHES1
Authors: Stiller John W. , Waaland J. Robert 
Published: October 2004

ABSTRACTA new species, Porphyra rediviva (Bangiales, Rhodophyta), is described from the northeast Pacific based on morphological, cytological, reproductive, ecological, and molecular characters. This species occurs at high intertidal levels in salt marshes along the coasts of Washington, Oregon, and northern California and exhibits a growth optimum at reduced salinity. It is further distinguished by a distinct demarcation between male and female sectors of the gametophytic thalli of epilithic specimens. The species is found most commonly in the drift or trapped in Salicornia beds, but these detached blades never have been found with sporangia or gametangia. Molecular analyses using restriction fragment length polymorphism patterns of polymerase chain reaction–amplified ribosomal DNA (rDNA) show that this salt marsh Porphyra is conspecific throughout its range and is distinct from other Pacific Porphyra species with similar reproductive patterns. Based on molecular data, P. rediviva is related most closely to P. purpurea from the North Atlantic. Fixed rDNA polymorphisms between the two taxa, however, support ecological and cytological evidence that they should be considered different species.
FIRST INSIGHTS INTO IMPROVEMENT OF EICOSAPENTAENOIC ACID CONTENT IN PHAEODACTYLUM TRICORNUTUM (BACILLARIOPHYCEAE) BY INDUCED MUTAGENESIS1
Authors: Alonso Diego López , Segura del Castillo Clara I. , Grima Emilia Molina , Cohen Zvi 
Published: October 2004

ABSTRACTA strain improvement program was initiated based on mutagenesis with the goal of commercial production of eicosapentaenoic acid (EPA)from EPA‐overproducing microalgal strains. Two rounds of mutation and selection were conducted using Phaeodactylum tricornutum Bohlin UTEX #640 as the parent strain. After the first round of mutagenesis, a putative mutant (provisionally labeled 114) was obtained. The EPA content (% of dry weight) of this mutant strain was 37% higher than that of the wild type. 114 was further mutated and another putative mutant (provisionally called II242) was isolated, the EPA content of which was 44% higher than that of the wild type. When cultured with aeration in 1‐L flasks, EPA content of the wild type and putative mutants 114 and II242 was, 17.3 mg · g−1, 31.5mg · g−1, and 38.6 mg · g−1 dry biomass, respectively. EPA productivity was 3.48 mg · L−1· d−1 4.01 mg · L−1· d−1, and 4.98 mg · L−1· d−1 respectively. These figures compare favorably with many other promising EPA‐producing microorganisms and suggest that the use of a single methodology such as mutation and selection is a way to improve the polyunsaturated fatty acid content of microalgae and other microorganisms.
A METHOD FOR THE CRYOCONSERVATION OF DUNALIELLA SALINA (CHLOROPHYCEAE): EFFECT OF GLYCEROL AND COLD ADAPTATION1
Authors: Mortain‐Bertrand Anne , Etchart Freddy , Boucaud Marie‐Thérèse de 
Published: October 2004

ABSTRACTThe unicellular green alga Dunaliella salina Teod. was frozen according to the following procedure: 3 days cold adaptation at 4°C, addition of 3.5 M glycerol as a cryoprotectant, slow cooling to –40°C, immersion in liquid nitrogen, and rapid thawing. The survival rate was higher when cells were grown, before freezing, in the presence of 2 M NaCl instead of 1 M NaCl (78 and 48% survival, respectively). This difference is probably due to the intracellular amount of glycerol, which increases with external NaCl concentration and, therefore, may enhance cell protection. Although cells grown in 4 M NaCl accumulated a large amount of glycerol in response to osmotic stress, they did not withstand freezing. The use of cryoprotectant was absolutely necessary for the cells to recover from storage at –196°C. Glycerol was used because it is naturally produced by Dunaliella salina and therefore is not toxic. Provided it was added slowly to avoid osmotic shock, 3.5 M glycerol gave better results than 1M glycerol (48 and 18% survival, respectively).Cold adaptation in the dark increased postthaw viability. Cells grown in 1 M or 2 M NaCl had a survival rate of 48 and 78%, respectively, when cold‐adapted, against 10 and 42% when not cold‐adapted. This adaptation could be due to the synthesis, at low temperature, of specific proteins because two bands (28–29 kDa) appeared when electrophoretically separated proteins from cold‐adapted cells and control cells were compared. Also, it could be due to the degradation of starch that occurs in the dark and leads to glycerol accumulation. Our procedure has never been used to cryopreserve microalgae and could enhance reported survival rates.
THE STORAGE GLUCAN OFPHAEOCYSTIS GLOBOSA(PRYMNESIOPHYCEAE) CELLS1
Authors: Janse Ingmar , van Rijssel Marion , van Hall Pieter‐Jan , Gerwig Gerrit J. , Gottschal Jan C. , Prins Rudolf A. 
Published: October 2004

ABSTRACTA non‐colony‐forming axenic strain ofPhaeocystis globosa(Harlot) Lagerheim was shown to produce a water‐soluble β‐d‐glucan. This glucan consisted of about 20 glucose units, mainly (l→3)‐linked, with branching at position 6. Therefore, it can be classified as a chrysolaminaran. Glucan production occurred mainly during the stationary growth phase and resulted in concentrations as high as 76 pg glucose per cell. When cultures were deprived of light the glucans were consumed, which supports their possible role as compounds used for temporary storage of energy.
CHANGES IN CELL COMPOSITION AND LIPID METABOLISM MEDIATED BY SODIUM AND NITROGEN AVAILABILITY IN THE MARINE DIATOM PHAEODACTYLUM TRICORNUTUM (BACILLARIOPHYCEAE)1
Authors: Larson Tony R. , Rees T. Alwyn V. 
Published: October 2004

ABSTRACTThe effects of nitrogen starvation in the presence or absence of sodium in the culture medium were monitored in batch cultures of the marine diatom Phaeodactylum tricornutum Bohlin. During nitrogen starvation in the presence of sodium, cell nitrogen and chlorophyll a decreased, mainly as a consequence of continued cell division. These decreases were accompanied by decreases in the rates of photosynthesis and respiration. There was no change in either cell volume or carbohydrate, but both carbon and lipid increased. During nitrogen starvation in the absence of sodium, cell division ceased. Cell nitrogen and chlorophyll a remained constant, and respiration did not decrease, but the changes in the photosynthetic rate and the lipid content per cell were similar to cultures that were nitrogen‐starved in the presence of sodium. The carbon‐to‐nitrogen ratio increased in both cultures. Nitrogen, in the form of nitrate, and sodium were resupplied to cultures that had been preconditioned in nitrogen‐ and sodium‐deficient medium for 5 d. Control cultures to which neither nitrate or sodium were added remained in a static state with respect to cell number, volume, and carbohydrate but showed slight increases in lipid. Cells in cultures to which 10 mM nitrate alone was added showed a similar response to cultures where no additions were made. Cells in cultures to which 50 mM sodium alone was added divided for 2 d, with concomitant small decreases in all measured constituents. Cell division resumed in cultures to which both sodium and nitrate were added. The lipid content fell dramatically in these cells and was correlated to metabolic oxidation via measured increases in the activity of the glyoxylate cycle enzyme, isocitrate lyase. We conclude that lipids are stored as a function of decreased growth rate and are metabolized to a small extent when cell division resumes. However, much higher rates of metabolism occur if cell division resumes in the presence of a nitrogen source.
CHANGES IN INTRACELLULAR NITROGEN POOLS AND FEEDBACK CONTROLS ON NITROGEN UPTAKE IN CHAETOMORPHA LINUM (CHLOROPHYTA)1
Authors: McGlathery Karen J. , Pedersen Morten Foldager , Borum Jens 
Published: October 2004

ABSTRACTChanges in the size of intracellular nitrogen pools and the potential feedback by these pools on maximum N uptake (NH4+ and NO3−) rates were determined for Chaetomorpha linum (Müller) Kützing grown sequentially under nutrient‐saturating and nutrient‐limiting conditions. The size of individual pools in N‐sufficient algae could be ranked as residual organic N (RON) comprised mainly of amino acids and amino compounds > protein N > NO3− > NH4+ > chlorophyll N. When the external N supply was removed, growth rates remained high and individual N pools were depleted at exponential rates that reflected both dilution of existing pools by the addition of new biomass from growth and movement between the pools. Calculated fluxes between the tissue N pools showed that the protein pool increased throughout the N depletion period and thus did not serve a storage function. RON was the largest storage reserve; nitrate was the second largest, but more temporary, storage pool that was depleted within 10 days. Upon N resupply, the RON pool increased 3 × faster than either the inorganic or protein pools, suggesting that protein synthesis was the rate‐limiting step in N assimilation and caused a buildup of intermediate storage compounds. Maximum uptake rates for both NH4+ and NO3− varied inversely with macroalgal N status and appeared to be controlled by changes in small intracellular N pools. Uptake of NO3− showed an initial lag phase, but the initial uptake of NH4+ was enhanced and was present only when the intracellular NH4+ pool was depleted in the absence of an external N supply. A strong negative correlation between the RON pool size and maximum assimilation uptake rates for both NH4+ and NO3− suggested a feedback control on assimilation uptake by the buildup and depletion of organic compounds. Enhanced uptake and the accumulation of N as simple organic compounds or nitrate both provide a temporary mechanism to buffer against the asynchrony of N supply and demand in C. linum.
MODULATION OF THE HEAT SHOCK UBIQUITIN POOL IN SKELETONEMA COSTATUM (BACILLARIOPHYCEAE)1
Authors: Penna Antonella , Crinelli Rita , Magnani Mauro 
Published: October 2004

ABSTRACTImmunoblotting experiments performed with an anti‐ubiquitin antibody revealed that Skeletonema costatum (Grev.) Cleve cells contained free ubiquitin as well as ubiquitin conjugated to various endogenous proteins. A temperature shift from 18° to 30°C greatly increased the total amount of ubiquitin and particularly the ubiquitin fraction in high molecular mass conjugates. A solid‐phase immunoassay indicated values of 0.031 ± 0.004 pmol·10−6 cells for free ubiquitin and 0.046 ± 0.004 pmol·10−6 cells for conjugated ubiquitin for cells grown at 18°C, and 0.056 ± 0.008pmol·10−6cells and 0.21 ± 0.03 pmol·10−6cells, respectively, after a temperature increase from 18° to 30°C. Cell‐free extracts of S. costatum were equally able to form thiol ester linkages with 125I‐ubiquitin in an adenosine triphosphate–dependent manner at 18° C and at 30°C. Cell‐free extracts were also able to conjugate 125I‐ubiquitin to endogenous proteins, but the ubiquitin conjugation rate at 30°C was lower than at 18°C. Incubation of S. costatum for 3 h at 30°C and then for 3 h at 18°C resulted in the formation of high amounts of ubiquitin conjugates, suggesting that partially inactive or denaturated proteins accumulate during heat stress. These denaturated proteins are then conjugated to ubiquitin very efficiently when the physiological temperature is restored. Thus, S. costatum cells contain ubiquitin and an active ubiquitin conjugation system responding to stress conditions (temperature stress). The intracellular concentration of ubiquitin conjugates is most likely limited by the availability of protein substrates to be conjugated rather than by ubiquitin‐conjugating activity.
ANALYSIS OF ALEXANDRIUM (DINOPHYCEAE) SPECIES USING SEQUENCES OF THE 5.8S RIBOSOMAL DNA AND INTERNAL TRANSCRIBED SPACER REGIONS1
Authors: Adachi Masao , Sake Yoshihiko , Ishida Yuzaburo 
Published: October 2004

ABSTRACTThe 5.8S ribosomal RNA gene (rDNA) and flanking internal transcribed spacers 1 and 2 (ITS1 and ITS2) from 7 isolates of Alexandrium catenella (Wedon et Kofoid) Taylor, 13 isolates of A. tamarense (Lebour) Balech, 2 isolates of A. affine (Fukuyo et Inoue) Balech, and single isolates of A. fundyense Balech, A. insuetum Balech, and A. pseudogonyaulax (Biecheler) Horiguchi ex Yuki et Fukuyo comb. nov. from Japan, Thailand, and the United States were amplified using the polymerase chain reaction (PCR), sequenced, and subjected to phylogenetic analysis. The sequences ranged from 518 to 535 base pairs (bp) exclusive of the 18S and 28S rDNA coding regions. Sequence comparisons revealed seven divergent “ITS types” designated as follows: 1) catenella type, 2) tamarense type, 3) WKS‐1 type, 4) Thai type, 5) affine type, 6) insuetum type, and 7) pseudogonyaulax type. Isolates of the tamarense type from various locations in Japan and the United States and of A. fundyense from the United States were closely related to each other and were clearly divergent from isolates of A. tamarense WKS‐1 (WKS‐I type) or A. tamarense CU‐15 (Thai type). These latter two strains carried unique ITS types, although they were not distinguishable from isolates of the tamarense type by morphological criteria. Distance values between isolates of the tamarense type and the WKS‐1 or Thai type were quite high (about 0.21 and 0.39, respectively). Seven isolates of A. catenella from Japan (catenella type) clearly diverged from the other ITS types already mentioned. Distance values between isolates of the catenella type were extremely low (<0.01), whereas distance values of ITS between the catenella type and the tamarense, WKS‐1, or Thai type were 0.17, 0.18, and 0.40, respectively. Isolates of A. affine, A. insuetum, and A. pseudogonyaulax all carried unique ITS types. The ITSs of the tamarense type exhibited two distinct ITS sets, the “A gene” and the “B gene.” The two sequences occurred in a 1:1 ratio in PCR products. In contrast, the ITSs of all other isolates appeared homogeneous. Sequence comparisons also showed that the variations in the 3′ end of ITS1 (150‐177 bp) were low within each ITS type but extremely high between ITS types. The number of different nucleotides among the seven Alexandrium types in this 28‐bp region is more than 10. High diversity of this region may facilitate the design of DNA probes specific for each ITS type/species of Alexandrium.