bluuebunny/crossref_metadata_2025_split huggingface dataset:
COMPETITIVE INTERACTIONS BETWEEN THE OPPORTUNISTIC MACROALGAE CLADOPHORA VAGABUNDA (CHLOROPHYTA) AND GRACILARIA TIKVAHIAE (RHODOPHYTA) UNDER EUTROPHIC CONDITIONS1
Authors: Peckol Paulette , Rivers Jennifer S. 
Published: October 2004

ABSTRACT In a eutrophic embayment (Waquoit Bay, Massachusetts), Cladophora vagabunda (L.) van den Hoek occurs in thick (sometimes > 1 kg dry wt ‐m−2), nearly monospecific unattached mats in deeper regions (2 m), whereas Grac‐ilaria tikvahiae McLachlan is largely restricted to shallow (<1 m) areas. We explored these distribution patterns, investigating competitive interactions between these opportunistic species by varying the limiting resource, photon flux density (PFD), and species composition under conditions of N sufficiency in microcosms. Under lower biomass loadings, neither species showed a difference in growth rates in single‐ and mixed‐species stands. With a 25% increase in initial biomass loading, Gracilaria tikvahiae had significantly higher growth rates under saturating PFD and consistently showed greater performance when grown in single‐species rather than in mixed‐species stands. While growth rate was 2×greater for C. vagabunda in single‐species than in mixed‐species stands at saturating PFD, this pattern was reversed under limiting irradi‐ances. In mixed‐species stands at high PFD (comparable to shallow regions of the bay), the growth rate of G. tikvahiae was over 4×higher than that of C. vagabunda. Cladophora vagabunda grew at a faster rate than G. tikvahiae only in the low PFD, mixed‐species treatment. Results of this study suggest that the observed distributional patterns of these macroalgae are due in part to interspecific exploitative competition but that tolerance of low PFD by C. vagabunda has led to dominance of these species in distinctive regions of the embayment.
PHOSPHORUS AND NITROGEN NUTRITION IN CHONDRUS CRISPUS (RHODOPHYTA): EFFECTS ON TOTAL PHOSPHORUS AND NITROGEN CONTENT, CARRAGEENAN PRODUCTION, AND PHOTOSYNTHETIC PIGMENTS AND METABOLISM1
Authors: Chopin Thierry , Gallant Trevor , Davison Ian 
Published: October 2004

ABSTRACT The existence of a phenomenon in phosphorus (P) nutrition comparable to the “Neish effect” in nitrogen (N) nutrition (an inverse relation between seawater N enrichment and carrageenan content) was investigated in the temperate red alga Chondrus crispus Stackhouse. Plants were preconditioned for 17 d and then cultured under varying enrichments of P (0, 3, 6, 10, 15 μM P·wk−1) and a constant N enrichment (53.5 μM N·wk−1) for 5 wk. Tissue total P, tissue total N, and carrageenan contents were then determined. Identical experiments were performed using C. crispus collected during the fall, winter, spring, and summer seasons. The procedure was repeated using material collected during the following fall season and cultured under constant P (6 μM P·wk−1) and varying N enrichments (0, 3, 6, 10, 25 μM N·wk−1). In the fall (P) experiment, carrageenan content was the highest [53.1 ± 0.3% DW (dry weight)], and tissue total P content was the lowest (1.71 ± 0.27 mg P·g DW−1) in plants that received no P enrichment. Carrageenan content was stable (46.1 ± 1.8% DW) for plants given enrichments of 3 μM P·wk−1 and greater. Thus, a decrease in carrageenan content, concomitant with an increase in tissue total P content, was observed, but only at tissue total P levels below 2 mg P·g DW−1. As these levels were always higher than 2 mg P·g DW−1 in the winter, spring, and summer experiments, carrageenan content remained constant within each season at 46.2 ± 1.3, 43.1 m 0.7, and 44.5 ± 0.6% DW, respectively. Nitrogen enrichment of plants collected in the fall did not affect carrageenan content, which was stable at 49.3 ± 0.9% DW. When these plants were compared with those of the previous fall experiment (6 μM P·wk−1 and 53.5 μM N·wk−1), a slight increase in carrageenan content was noted. Thus, at sufficiently high concentration, N also decreased carrageenan content in C. crispus. Phosphorus nutrition had no significant effect on photosynthesis versus irradiance parameters (Pmax, α, Rd, Ic, and Ik), the contents of the photosynthetic pigments chlorophyll‐a, phycoerythrin (PE), phycocyanin (PC), and allophycocyanin (APC), and the ratios PE:APC and PC:APC. In contrast, N nutrition affected both Pmaxand the photosynthetic pigment contents. The data indicate that N limitation reduces the number of phycobilisomes but not their size. The greater reduction in phycobiliprotein than chlorophyll‐acontent corroborates the natural bleaching phenomenon regularly observed in C. crispus populations during summer when N levels are generally low in seawater. These results suggest that C. crispus in the temperate waters of the Bay of Fundy may experience N limitation, but P limitation is unlikely.
DISTRIBUTION OF THE XANTHOPHYLL LOROXANTHIN IN DESMIDS (CHAROPHYCEAE, CHLOROPHYTA)1
Authors: Donohue Christine M. , Fawley Maroin W. 
Published: October 2004

ABSTRACT Forty‐seven species of desmids, representing all four families, were examined for the presence of the xanthophyll loroxanthin by reverse‐phase high‐performance liquid chromatography. In the Desmidiaceae 28 of the 35 species examined possessed loroxanthin, and in the Mesotaeniaceae two of the six examined had loroxanthin present. All six species of the families Peniaceae and Closteriaceae examined possessed loroxanthin. Although the distribution of loroxanthin appears to be disjunct in the desmids and does not have strict taxonomic significance, it does follow a coherent pattern consistent with current ideas on desmid phylogeny. This pattern suggests that loroxanthin synthesis probably evolved once in the desmid lineage, with one or more subsequent reversals.
REDOX SENSITIVITY AND LIGHT MODULATION OF ENZYME ACTIVITY IN THE RHODOPHYTES GRACILARIA TIKVAHIAE AND CHONDRUS CRISPUS1
Authors: Pacold Michael E. , Anderson Louise E. , Li Dong , Stevens Fred J. 
Published: October 2004

ABSTRACT One of the cysteine residues believed to be necessary for reductive light activation is lacking in the only red algal NADP‐linked glyceraldehyde‐3‐P dehydrogenases for which sequences are available, namely Gracilaria verrucosa (Hudson) Papenfuss and Chondrus crispus Stackhouse. Consistent with the mechanism of light modulation proposed for this enzyme, which involves reduction of domain movement‐restricting disulfide bonds, it is not reductively activated in Chondrus crispus extracts, and it is not light‐activated in whole cells or dithiothreitol (DTT) activated in extracts of the North American species Gracilaria tikvahiae McLachlan. Fructosebisphosphatase and glucose‐6‐P dehydrogenase, two enzymes for which sequence information from these algae is not yet available, are both activated in crude extracts by DTT treatment, but only fructosebisphosphatase is light‐activated in intact Gracilaria.
A LINKED 5S rRNA GENE IN SCYTOSIPHON LOMENTARIA (SCYTOSIPHONALES, PHAEOPHYCEAE)1
Authors: Kawai Hiroshi , Muto Hideki , Fujii Tetsuya , Kato Atsushi 
Published: October 2004

ABSTRACT The complete nucleotide sequence of the transcribed and nontranscribed regions of the ribosomal RNA (rRNA) gene in the brown alga Scytosiphon lomentaria (Lyngbye) Link (Scytosiphonales, Phaeophyceae) is presented. Each rDNA repeating unit is about 8.3 kb in length and contains a 5S rRNA gene sequence in the same repeating unit as the 18S, 5.8S, and 25S rDNA. The 5S rDNA is located downstream from the 25S and arranged in the same transcriptional direction as the larger rDNAs. The 5S rDNA of Scytosiphon lomentaria shares 96.9–100% sequence similarity with 5S rRNA gene sequences of other brown algal species. Based on the very high sequence similarity of the Scytosiphon 5S rDNA to those of other chromophytes, the presence of a RNA polymerase III termination site (TTTTT) in the 3’flanking region of 5S, and indirect evidence of the lack of an unlinked 5S rDNA, we conclude that the linked 5S rRNA gene in Scytosiphon is functional. This is the first report of a presence of linked 5S rRNA gene in multicellular photosynthetic eukaryotes. Recent reports of the presence of linked 5S rRNA genes in all eukaryotes are reviewed, and the possibility that the Chromophyta lineage originally had a linked 5S rDNA as ancestor is discussed.
SEQUENCES OF THE RRN18 GENES OF CHLAMYDOMONAS HUMICOLA AND C. DYSOSMOS ARE IDENTICAL, IN AGREEMENT WITH THEIR COMBINATION IN THE SPECIES C. APPLANATA (CHLOROPHYTA)1
Authors: Gordon Julie , Rumpf Robert , Shank Samuel L. , Vernon Dawne , William Birky C. 
Published: October 2004

ABSTRACT The nuclear Rrn18 gene coding for small‐subunit ribosomal RNA was amplified from Chlamydomonas humicola and C. dysosmos. The sequences were identical, in agreement with the combination of these two species under the name C. applanata on morphological and physiological grounds by Ettl and Schlösser (1992).
SPECIES COMPOSITION, BIOMASS, AND NUTRIENT CONTENT OF PERIPHYTON IN THE FLORIDA EVERGLADES1
Authors: Vymazal Jan , Richardson Curtis J. 
Published: October 2004

ABSTRACT Periphyton biomass, nutrient dynamics in the biomass, and species composition were studied in two Florida Everglades sloughs from August 1991 to August 1992. Periphyton biomass on macrophytes was strongly season‐dependent. Maximum biomasses, 1180, 161, and 59 g dry mass.m−2 on Eleocharis vivipara, E. cellulosa, and Nymphaea odorata, respectively, occurred in summer and early autumn; winter and spring periphyton biomass was very low (practically not measurable). Periphyton was dominated by blue‐green algae (cyanobacteria) during the summer and autumn; diatoms dominated during the winter and spring. Green algae occurred mostly during the summer and autumn, but their growth was sparse and did not contribute significantly to periphyton biomass. Nitrogen‐to‐phosphorus ratios in the periphyton were very high (59–121:1), suggesting phosphorus limitation of periphyton growth. The periphyton contained large concentrations of calcium (up to 22.3% on dry mass basis) especially in late summer and autumn.
ENHANCEMENT OF INTRACELLULAR PROLINE LEVEL IN CELLS OF ANACYSTIS NIDULANS (CYANOBACTERIA) EXPOSED TO DELETERIOUS CONCENTRATIONS OF COPPER1
Authors: Wu Jiunn‐Tzong , Chang Shih‐Chieh , Chen Kuang‐Sin 
Published: October 2004

ABSTRACT The intracellular proline level in Anacystis nidulans cells was enhanced when the cells were exposed to sublethal concentrations of Cu2+; the degree of enhancement was positively related to the concentration of Cu2+. Analysis by high‐performance liquid chromatography confirmed that the enhancement of proline levels was the most pronounced change in the composition of the free amino acid pool during copper treatment. A direct supply of exogenous proline to the cultures lowered the inhibitory influence of Cu2+on the growth of cells. Further experiments showed that the supply of exogenous proline lowered the leakage of potassium ions from cells exposed to deleterious concentrations of Cu2+. The inhibition of potassium leakage was particularly pronounced when proline was supplied prior to Cu2+treatment. The present study suggests that enhanced proline protects cell membranes from being affected by deleterious concentrations of Cu2+.
PSEUDO‐NITZSCHIA PUNGENS AND P. MULTISENES (BACILLARIOPHYCEAE): NUCLEAR RIBOSOMAL DNAS AND SPECIES DIFFERENCES1
Authors: Manhart James R. , Fryxell Greta A. , Villac M. Célia , Segura Linda Y. 
Published: October 2004

ABSTRACT The region of the nuclear ribosomal DNA (rDNA) operon containing the small subunit (SSU), internal transcribed spacer 1 (ITS1), and a portion of the 5.8s rDNA gene was sequenced in one isolate each of Pseudo‐nitzschia multiseries (Hasle) Hasle and Pseudo‐nitzschia pungens (Grunow in Cleve & Möller) Hasle. The SSUs of these two species were highly similar, differing only in 14 point mutations and one insertion/deletion in 1774 bp. The ITS1 sequences were more variable, with 57 point mutations and three insertion/deletions in 257 bp. There were no differences in 44 bp of the 5.8S sequences. Restriction fragment patterns (RFPs) for the restriction endonucleases HaeIII, Hha1, and Rsa1 for 13 isolates of P. multiseries from the Atlantic, Pacific, and Gulf coasts of the United States and 16 isolates of P. pungens from the three coasts of the United States, in addition to Japan and China, were compared. There were differences between the RFPs of P. multiseries and P. pungens that corresponded to sites mapped by the DNA sequences, but no infraspecific variation in RFPs was observed for either species. The differences in RFPs correlate with morphological, immunological, and other rDNA differences and support the recognition of these taxa as separate species.
MORPHOLOGY AND ECOLOGY OF THE MARINE DINOFLAGELLATEOSTREOPSIS LABENSSP. NOV. (DINOPHYCEAE)1
Authors: Faust Maria A. , Morton Steve L. 
Published: October 2004

ABSTRACTA new species, Ostreopsis labensFaust et Morton sp. nov., is described from three marine habitats: lagoonal water and lagoonal sand from the barrier reef of Belize, and associated with macroalgae from coral reef habitats of Oshigaki and Iriomote Islands, Japan. Dimensions ofOstreopsis labenscells are 60–86 μm long, 70–80 μm wide, and 81–110 μm in dorsoventral depth. Cells are broadly ovoid, anterioposteriorly compressed bearing a spherical nucleus and many chloroplasts. The epitheca is convex and composed of three apical plates, seven precingular plates, and an apical pore plate. The cingulum is composed of six plates. The hypotheca is constructed of five postcingular plates, one posterior intercalary, and two antapical plates. The sulcus is small, recessed, and hidden and exhibits a ventral pore and a ridged, curved plate. The thecal arrangement of O. labensis Po, 3′, 7″ 6C, 6S(?), Vp, Rp, 5″, 1p, 2″. Only one sulcal list is present. The thecal plates have a smooth surface with distinct round pores. The intercalary band between the thecal plates is smooth. A row of marginal pores line the lipped cingulum. Ostreopsisspecies are anteroposteriorly flattened, photosynthetic, benthic dinoflagellates that are more diverse in ecology than previously known. Ostreopsis labensis capable of living in three marine habitats: in the water column, in sand, and on macroalgal surfaces. It was most numerous in sand and less in lagoonal waters, and only a few cells were associated with macroalgae. Light and scanning electron microscopy studies revealed engulfed cells withinO. labens,which indicates mixotrophic/phagotrophic behavior. A ventral opening situated in the cingulum ofO. labensexhibits size variability; it may serve as an opening for engulfiing food particles because it varies in size. We propose that ingestion of prey byO. labensoccurs through the ventral opening, the proposed feeding apparatus of this species, which is similar to the function of the peduncle‐like structure of mixotrophic dinoflagellates. The behavior ofO. labensappears similar to that previously described forDinophysisspecies.
PROTEIN PHOSPHATASE INHIBITORY ACTIVITY IN EXTRACTS OF CULTURED BLUE‐GREEN ALGAE (CYANOPHYTA)1
Authors: Honkanen Richard E. , Caplan Faith R. , Baker Kathleen K. , Baldwin Cynthia L. , Bobzin Steven C. , Bolis Christine M. , Cabrera Gabriela M. , Johnson Louis A. , Jung Jee H. , Larsen Linda K. , Levine Ira A. , Moore Richard E. , Nelson Carrie S. , Patterson Gregory M. L. , Tschappat Kathryn D. , Tuang Grace D. , Boynton Alton L. , Arment Anthony R. , An Jisi , Carmichael Wayne W. , Rodland Karin D. , Magun Bruce E. , Lewin Ralph A. 
Published: October 2004

ABSTRACT A large‐scale screening program was initiated to evaluate laboratory‐cultured blue‐green algae (cyanobacteria) as a source of novel compounds with inhibitory activity against certain serine/threonine protein phosphatases. Over 1600 extracts, representing 816 cyanophyte strains with broad habitat and taxonomic diversity, were screened. Inhibitors were identified in extracts produced from all orders tested except Chamaesiphonales, and the family Stigonemataceae was found to contain proportionally more inhibitors as compared to the total screen.
INTERNAL NITRATE CONCENTRATIONS IN SINGLE CELLS OF LARGE PHYTOPLANKTON FROM THE SARGASSO SEA1
Authors: Villareal Tracy A. , Lipschultz Fredric 
Published: October 2004

ABSTRACT Nitrate concentrations within individual cells of Ethmodiscus, Pyrocystis, and Halosphaera and chains of Rhizosolenia were determined from samples collected in the Sargasso Sea. In all cases, field populations exhibited a wide range of internal nitrate concentrations (INCs) within a single sampling date. Halosphaera INCs reached 100 mM, in contrast to diatom and dinoflagellate INCs, which did not exceed 22 mM. Sinking Rhizosolenia, Ethmodiscus and Pyrocystis had significantly lower internal NO3‐ pools than did floating cells (P< 0.05). Ethmodiscus incubations in surface seawater resulted in a dramatic reduction in the proportion of high INC cells concurrent with decreases in average INCs and an increased proportion of sinking cells. Population buoyancy was inversely related to INC, and negatively buoyant cells rarely exceeded I mM INC, suggesting that a critical INC threshold may exist. The photosynthetic parameters Pmax and α decreased with time as internal NO3‐‐ Pools were depleted. Internal nitrate depletion rates were consistent with oxygen production rates during this time. Based on the known characteristics of Pyrocystis and Ethmodiscus, we conclude that virtually all of the > 100 μm‐sized phytoplankton present in the Sargasso Sea can vertically migrate. However, the appropriate time scale for migrators such as Halosphaera that reproduce by swarmer formation is unclear and may be significantly different than the other taxa studied. Changes in the frequency distributions, buoyancy‐internal pool relationships, and general P‐1 photosynthesis‐irradiance time series data in Ethmodiscus suggest that nutrient limitation is related to these migrations. High INC appears to be a fundamental property of the largest microalgal cells present in oligotrophic seas and suggests that nitrate transport by these nonmotile cells is widespread.
IMPACT OF ULTRAVIOLET‐B RADIATION ON PHOTOSYSTEM II ACTIVITY AND ITS RELATIONSHIP TO THE INHIBITION OF CARBON FIXATION RATES FOR ANTARCTIC ICE ALGAE COMMUNITIES1
Authors: Schofield Oscar , Kroon Bernd M. A. , Prézelin Barbara B. 
Published: October 2004

ABSTRACT One goal of the Icecolors 1993 study was to determine whether or not photosystem II (PSII) was a major target site for photoinhibition by ultraviolet‐B radiation (QUVB, 280–320 nm) in natural communities. Second, the degree to which QUVBinhibition of PSII could account for QUVBeffects on whole cell rates of carbon fixation in phytoplankton was assessed. On 1 October, 1993, at Palmer Station (Antarctica), dense samples of a frazil ice algal community were collected and maintained outdoors in the presence or a bsence of QUVBand l or ultraviolet‐A (QUVB, 320–400 nm) radiation. Samples were then collected at intervals over the day to track the time course of UV inhibition of primary production. The ice algae were assessed for changes in pigment composition and rates of carbon fixation. The quantum yield of PSII (ØIIc°) was measured by Pulse Amplitude Modulated fluorometry. Over the day, ØIIc° declined due to increasing time‐integrated dose exposure of QUVB. The QUVB‐driven inhibition of ØIIc° increased from 4% in the early morning hours to a maximum of 23% at the end of the day. The QUVB photoinhibition of PSII quantum yield did not recover by 6 h after sunset. In contrast, photoinhibition by QUVA and photosynthetically available radiation (QPAR, 400–700 nm) recovered during the late afternoon. Flourescence‐based estimates of carbon fixation rates were linearly correlated (P =0.002, r2=0.45) with measured carbon fixation. Fluorescence overestimated the observed QUVB inhibition in measured carbon fixation rates by 8% in the morning hours; however, the discrepancy increased during the afternoon. Therefore, researchers should be cautious in using fluorescence measurements to infer ultraviolet inhibition for rates of carbon fixation until there is a greater understanding of the coupling of carbon metabolism to PSII activity for natural populations. Despite these current limitations, fluorescence‐based technologies represent powerful tools for studying the impact of the ozone hole on natural populations on spatial/ temporal scales not possible using conventional productivity techniques.
DIFFUSION BOUNDARY LAYER TRANSPORT IN GRACILARIA CONFERTA (RHODOPHYTA)1
Authors: Gonen Yael , Kimmel Eitan , Friedlander Michael 
Published: October 2004

ABSTRACT A theoretical framework on the combined effect of water velocity and solute concentration on the photosynthetic performance of the red alga Gracilaria conferta (Rhodophyta) is developed. This is based on the balance between the rate of transport through boundary layers and Michaelis‐Menten‐type equations for carbon consumption and for production of oxygen and hydroxyl ions. By comparing the theoretical models with experimental data, we found that the mechanism of enhancing photosynthetic rates by increasing water velocity cannot be attributed to enhanced bicarbonate and CO2 transport, nor to CO2 as a sole source of carbon. Velocity‐facilitated photosynthesis may be due to the enhanced removal of OH− ions, which inhibit photosynthesis when accumulated on the algal surface. Oxygen had no inhibitory effect on Gracilaria conferta.
STEROL, FATTY ACID, AND PIGMENT CHARACTERISTICS OF UTEX 2341, A MARINE EUSTIGMATOPHYTE IDENTIFIED PREVIOUSLY AS CHLORELLA MINUTISSIMA (CHLOROPHYCEAE)1
Authors: Gladu Patricia K. , Patterson Glenn W. , Wikfors Gary H. , Smith Barry C. 
Published: October 2004

ABSTRACT An examination of the sterols of UTEX 2341, a small (ca. 2μm), nonmotile unicellular marine alga identified as Chlorella minutissima Fott et Novakova, yielded results inconsistent with any of 35 Chlorella strains analyzed previously. UTEX 2341 contained cholesterol as the principal sterol, with 24‐methylenecholesterol, fucosterol, and isofucosterol also present; these are not dominant sterols in any other Chlorella species. Presence of eicosapentaenoic acid in UTEX 2341 also contrasted with fatty acids of Chlorella strains analyzed previously. Pigment analysis of UTEX 2341 revealed that it contained chlorophyll a, but not chlorophylls b or c; violaxanthin was the only major xanthophyll pigment. Both lipid and pigment compositions suggest that UTEX 2341 is not a member of the genus Chlorella but, rather, belongs in the Eustigmatophyceae; it may be Nannochloropsis sp. Cells with possible extracellular structures were present at an appreciable percentage of the stationary‐phase population studied; centrifuging removed or collapsed these structures. The high cholesterol and polyunsaturated fatty acid contents of UTEX 2341 make it attractive as a potential aquaculturefeed, provided it is, or can be made, digestible.