bluuebunny/crossref_metadata_2025 huggingface dataset:
COMPARATIVE PHOTOSYNTHESIS OF TWO SPECIES OF INTERTIDAL EPIPHYTIC MACROALGAE ON MANGROVE ROOTS DURING SUBMERSION AND EMERSION
Authors: Peña Enrique J. , Zingmark Richard , Nietch Christopher
Published: March 2003

Photosynthesis and dark respiration rates were measured in water and in air, and the capacity to recover photosynthetic activity from emersion stress was examined for two species of intertidal, epiphytic macroalgae—Bostrychia calliptera (Montagne) Montagne and Caloglossa leprieurii (Montagne) J. Agardh—collected on prop roots of the red mangrove Rhizophora mangle L. in Buenaventura Bay, Pacific coast of Colombia. In both species, net photosynthetic rates were significantly higher under submersed conditions. Maximum photosynthetic rates (Pmax) in water and in air were highest in B. calliptera, 126 ± 4 versus 52 ± 9 μmol O2·mg chl a−1·h−1, respectively. In C. leprieurii, Pmax of submerged plants in water and in air were 98 ± 9 versus 30 ± 11 μmol O2·mg chla−1·h−1. The photoinhibition model of Platt et al. (1980) was used to fit the experimental data in both water and air for both species. Photoinhibition occurred at irradiance as low as 200 μmol·m−2·s−1. The photosynthesis–light response curves demonstrated an adaptation to shaded habitats for both species, as light compensation points in water and air for both species were below 17 ± 5 μmol·m−2·s−1. The rate of dehydration was significantly lower in thalli of B. calliptera compared to C. leprieurii. An increase of photosynthetic activity in B. calliptera was evident between 5% and 15% water loss, but rates decreased thereafter with declining water content. In C. leprieurii, desiccation negatively influenced photosynthetic rates that significantly decreased linearly with declining water content. In B. calliptera, net photosynthesis reached zero only at a water content between 29% and 35%, whereas in C. leprieurii no net photosynthesis occurred in plants containing less than about 50% of their relative water content. Resubmerged plants ofB. calliptera exhibited 100% photosynthetic recovery after 45 min, whereas C. leprieurii recovered 100% at about 120 min. On the basis of the comparison of rates of light‐saturated net photosynthesis for B. calliptera in air versus in water, aerial photosynthetic activity ranged from 35% to 42% of that in water, whereas the emersed photosynthetic capacity of C. leprieurii ranged from 24% to 29% of that in water. Using tidal predictions and the emersed photosynthetic rates, a carbon balance model was constructed for both species over a single daylight period. The calculations indicated that emersed photosynthesis increased average daily carbon production of B. calliptera by 17% and C. leprieuri by 12%. The physiological responses to desiccation stress and the photosynthetic recovery capacities between species correlated with, and may determine, their vertical distribution in the mangrove habitats of Buenaventura Bay.
LIPID CLASS DISTRIBUTION OF HIGHLY UNSATURATED LONG CHAIN FATTY ACIDS IN MARINE DINOFLAGELLATES
Authors: Leblond Jeffrey D. , Chapman Peter J.
Published: March 2003

The very long chain highly unsaturated C28 fatty acids, octacosaheptaenoic [28:7(n‐6)] and octacosaoctaenoic acid [28:8(n‐3)], were found to be associated with phospholipids, obtained by fractionation of total lipid extracts into distinct lipid classes, in 4 and 6, respectively, of 16 examined dinoflagellates. An interfraction comparison of fatty acids associated with phospholipids and glycolipids has also shown that the phospholipid fractions contained the majority (over 75% in 12 of 16 strains) of docosahexaenoic acid [22:6(n‐3)] and traces of tetracosanoic acid (24:0). By contrast, the highly unsaturated C18 fatty acids octadecatetraenoic [18:4(n‐3)] and octadecapentaenoic acid [18:5(n‐3)] were primarily recovered from a chloroplast‐associated glycolipid fraction comprised of monogalactosyldiacylglycerol, digalactosyldiacylglycerol, and sulfoquinovosyldiacylglycerol. In 12 of 16 strains, an interfraction comparison showed that over 90% of 18:5(n‐3) was found to be associated with glycolipids. These findings indicate that the C28 fatty acids are located and probably synthesized in the cytoplasm or in an organelle other than the chloroplast, possibly with 22:6(n‐3) and 24:0 as precursors, whereas the C18 fatty acids 18:4(n‐3) and 18:5(n‐3) are glycolipid constituents apparently synthesized within the chloroplast. The function(s) of these C28 fatty acids as components of phospholipids in cellular membranes is currently unknown.
STRUCTURE AND DISTRIBUTION OF GLUCOMANNAN AND SULFATED GLUCAN IN THE CELL WALLS OF THE RED ALGA KAPPAPHYCUS ALVAREZII (GIGARTINALES, RHODOPHYTA)
Authors: Lechat Hervé , Amat Mireille , Mazoyer Jacques , Buléon Alain , Lahaye Marc
Published: March 2003

Two new polysaccharides were isolated from the cell walls of the carrageenan producing red seaweed Kappaphycus alvarezii (Doty) Doty. They were characterized by chemical analyses, enzymatic degradations, and nuclear magnetic resonance spectroscopy. One was a 4.0 M NaOH soluble β‐(1,4)‐d‐glucomannan that mostly precipitated upon neutralization and dialysis. It was composed of about 82 residues, and 70% of its glucose and mannose were released by a commercial cellulase enzyme complex. The disaccharide β‐d‐Man (1→4) d‐Glc was recovered from the hydrolysate during the first hours of degradation and confirmed the chemical structure of the polysaccharide. The other polysaccharide was extracted with 1.5 M NaOH and was identified as a sulfated glucan of degree of polymerization of about 180 1,4‐linked β‐glucose containing 10% 1,3‐linkages. The sulfate was located on C‐6 of 64% of the 4‐linked glucose residues. A third alkali‐soluble polysaccharide rich in galactose was also detected. The distribution of the glucomannan and galactose containing polysaccharides was inversely related to the algal cell size. Potential functions of these alkali‐soluble polymers are discussed in the context of cell wall polysaccharide assembly.
TRANSITION TO A LAND FLORA: A MOLECULAR PHYLOGENETIC PERSPECTIVE
Authors: Qiu Yin‐Long , Lee Jungho
Published: March 2003

Phylogenetic analyses of morphoultrastructural characters and DNA sequences of chloroplast, mitochondrial, and nuclear genes and investigations of genomic structural features in both organellar genomes have clarified several difficult issues in charophyte and bryophyte phylogenies. Mesostigma seems to represent the first lineage of streptophytes, and Charales are a derived member of charophytes. Liverworts and hornworts both are candidates for the basal‐most lineage in land plants according to analyses of morphoultrastructural and sequence data, but mitochondrial intron distribution favors the former. Takakia is likely a basal moss. More studies using both multigene sequence analyses and genomic structural characters will significantly improve our understanding of the origin and early evolution of land plants.
PHYLOGENY OF THE CONJUGATING GREEN ALGAE (ZYGNEMOPHYCEAE) BASED ON rbc  L SEQUENCES
Authors: McCourt Richard M. , Karol Kenneth G. , Bell Jeremy , Helm‐Bychowski Kathleen M. , Grajewska Anna , Wojciechowski Martin F. , Hoshaw Robert W.
Published: March 2003

Sequences of the gene encoding the large subunit of RUBISCO (rbcL) for 30 genera in the six currently recognized families of conjugating green algae (Desmidiaceae, Gonatozygaceae, Mesotaeniaceae, Peniaceae, and Zygnemataceae) were analyzed using maximum parsimony and maximum likelihood; bootstrap replications were performed as a measure of support for clades. Other Charophyceae sensu Mattox and Stewart and representative land plants were used as outgroups. All analyses supported the monophyly of the conjugating green algae. The Desmidiales, or placoderm desmids, constitute a monophyletic group, with moderate to strong support for the four component families of this assemblage (Closteriaceae, Desmidiaceae, Gonatozygaceae, and Peniaceae). The analyses showed that the two families of Zygnematales (Mesotaeniaceae, Zygnemataceae), which have plesiomorphic, unornamented and unsegmented cell walls, are not monophyletic. However, combined taxa of these two traditional families may constitute a monophyletic group. Partitioning the data by codon position revealed no significant differences across all positions or between partitions of positions one and two versus position three. The trees resulting from parsimony analyses using first plus second positions versus third position differed only in topology of branches with poor bootstrap support. The tree derived from third positions only was more resolved than the tree derived from first and second positions. The rbcL‐based phylogeny is largely congruent with published analyses of small subunit rDNA sequences for the Zygnematales. The molecular data do not support hypotheses of monophyly for groups of extant unicellular and filamentous or colonial desmid genera exhibiting a common cell shape. A trend is evident from simple omniradiate cell shapes to taxa with lobed cell and plastid shapes, which supports the hypothesis that chloroplast shape evolved generally from simple to complex. The data imply that multicellular placoderm desmids are monophyletic. Several anomalous placements of genera were found, including the saccoderm desmid Roya in the Gonatozygaceae and the zygnematacean Entransia in the Coleochaetales. The former is strongly supported, although the latter is not, and Entransia's phylogenetic position warrants further study.
Active transport of CO2 by three species of marine microalgae
Authors: Huertas I. Emma , Colman Brian , Espie George S. , Lubian Luis M.
Published: March 2003

The occurrence of an active CO2 transport system and of carbonic anhydrase (CA) has been investigated by mass spectrometry in the marine, unicellular rhodophyte Porphyridium cruentum (S.F. Gray) Naegeli and two marine chlorophytes Nannochloris atomus Butcher and Nannochloris maculata Butcher. Illumination of darkened cells incubated with 100 μM H13CO3− caused a rapid initial drop, followed by a slower decline in the extracellular CO2 concentration. Addition of bovine CA to the medium raised the CO2 concentration by restoring the HCO3−–CO2 equilibrium, indicating that cells were taking up CO2 and were maintaining the CO2 concentration in the medium below its equilibrium value during photosynthesis. Darkening the cell suspensions caused a rapid increase in the extracellular CO2 concentration in all three species, indicating that the cells had accumulated an internal pool of unfixed inorganic carbon. CA activity was detected by monitoring the rate of exchange of 18O from 13C18O2 into water. Exchange of 18O was rapid in darkened cell suspensions, but was not inhibited by 500 μM acetazolamide, a membrane‐impermeable inhibitor of CA, indicating that external CA activity was not present in any of these species. In all three species, the rate of exchange was completely inhibited by 500 μM ethoxyzolamide, a membrane‐permeable CA‐inhibitor, showing that an intracellular CA was present. These results demonstrate that the three species are capable of CO2 uptake by active transport for use as a carbon source for photosynthesis.
SEQUENCE ANALYSIS OF THE ITS‐2 REGION: A TOOL TO IDENTIFY STRAINS OF SCENEDESMUS (CHLOROPHYCEAE)
Authors: Van Hannen Erik J. , Lürling Miquel , Van Donk Ellen
Published: March 2003

The genetic distances between several strains of Scenedesmus obliquus (Turp.) Kütz., S. acutus Hortobagyi, and S. naegelii Chod. calculated from ITS‐2 sequences were found to be smaller than the genetic distances within other strains of Scenedesmus—that is, in S. acuminatus (Lagerh.) Chod. and S. pectinatus Meyen. These results confirm that the studied strains were not properly identified and should be renamed S. obliquus, as already suggested in other studies.
MIXOTROPHIC GROWTH MODIFIES THE RESPONSE OF SPIRULINA (ARTHROSPIRA) PLATENSIS (CYANOBACTERIA) CELLS TO LIGHT
Authors: Vonshak Avigad , Cheung Suk Man , Chen Feng
Published: March 2003

Spirulina (Arthrospira) platensis (Nordstedt) Geitler cells grown under mixotrophic conditions exhibit a modified response to light. The maximal photosynthetic rate and the light saturation value of mixotrophic cultures were higher than those of the photoautotrophic cultures. Dark respiration and light compensation point were also significantly higher in the mixotrophically grown cells. As expected, the mixotrophic cultures grew faster and achieved a higher biomass concentration than the photoautotrophic cultures. In contrast, the growth rate of the photoautotrophic cultures was more sensitive to light. The differences between the two cultures were also apparent in their responses to exposure to high photon flux density of 3000 μmol·m−2·s−1. The light‐dependent O2 evolution rate and the maximal efficiency of photosystem II photochemistry declined more rapidly in photoautotrophically grown than in mixotrophically grown cells as a result of exposure to high photon flux density. Although both cultures recovered from the high photon flux density stress, the mixotrophic culture recovered faster and to a higher extent. Based on the above results, growth of S. platensis with a fixed carbon source has a significant effect on photosynthetic activity.
NUTRIENT CONTROLS ON NITROGEN UPTAKE AND METABOLISM BY NATURAL POPULATIONS AND CULTURES OF TRICHODESMIUM (CYANOBACTERIA)
Authors: Mulholland Margaret R. , Ohki Kaori , Capone Douglas G.
Published: March 2003

The effects of inorganic nutrient (ammonium [NH4+] and nitrate [NO3−]) and amino acid (glutamate [glu] and glutamine [gln]) additions on rates of N2 fixation, N uptake, glutamine synthetase (GS) activity, and concentrations of intracellular pools of gln and glu were examined in natural and cultured populations of Trichodesmium. Additions of 1 μM glu, gln, NO3−, or NH4+ did not affect short‐term rates of N2 fixation. This may be an important factor that allows for continued N2 fixation in oligotrophic areas where recycling processes are active. N2 fixation rates decreased when nutrients were supplied at higher concentrations (e.g. 10 μM). Uptake of combined N (NH4+, NO3−, and amino acids) by Trichodesmium was stimulated by increased concentrations. For NO3−, proportional increases in NO3− uptake and decreases in N2 fixation were observed when additions were made to cultures before the onset of the light period. GS activity did not change much in response to the addition of NH4+, NO3−, glu, or gln. GS is necessary for N metabolism, and the bulk of this enzyme pool may be conserved. Intracellular pools of glu and gln varied in response to 10 μM additions of NH4+, glu, or gln. Cells incubated with NH4+ became depleted in intracellular glu and enriched with intracellular gln. The increase in the gln/glu ratio corresponded to a decrease in the rate of N2 fixation. Although the gln/glu ratio decreased in cells exposed to the amino acids, there was only a corresponding decrease in N2 fixation after the gln addition. The results presented here suggest that combined N concentrations on the order of 1 μM do not affect rates of N2 fixation and metabolism, although higher concentrations (e.g. 10 μM) can. Moreover, these effects are exerted through products of NH4+ assimilation rather than exogenous N, as has been suggested for other species. These results may help explain how cultures of Trichodesmium are able to simultaneously fix N2 and take up NH4+ and how natural populations continue to fix N2 once combined N concentrations increase within a bloom.
EFFECT OF OLIGOMYCIN ON DARK RESPIRATION IN THE MARINE DIATOM PHAEODACTYLUM TRICORNUTUM (BACILLARIOPHYCEAE): IMPLICATIONS FOR DETERMINATION OF MAINTENANCE RESPIRATION
Authors: Rees T. Alwyn V.
Published: March 2003

Oligomycin is an inhibitor of the mitochondrial ATP synthase. In nitrogen‐replete cells of the marine diatom Phaeodactylum tricornutum Bohlin, the rate of dark respiration was high and markedly inhibited (62%–74%) in the presence of oligomycin. In contrast, the rate of dark respiration in nitrogen‐deprived cells was about half that in nitrogen‐replete cells but was only slightly inhibited (16%–30%) by oligomycin. Consistent with these effects on rates of dark respiration, oligomycin decreased the ATP level and the ATP:ADP ratio by about 40% in nitrogen‐replete cells incubated in darkness but had a negligible effect on the ATP level and ATP:ADP ratio in nitrogen‐deprived cells. In sodium and nitrogen‐deprived cells, the rate of dark respiration was greater than that in nitrogen‐replete cells, but there was little effect of oligomycin on the rate of dark respiration. In light‐limited cells, the rate of dark respiration was similar to that in nitrogen‐deprived cells, but the inhibition (57%) in the presence of oligomycin was greater. These results suggest that most of the O2 consumption by nitrogen‐replete cells was linked to mitochondrial ATP synthesis and that the rate of mitochondrial ATP synthesis in nitrogen‐deprived and sodium and nitrogen‐deprived cells was low. The potential implications of these results for our understanding of maintenance respiration are discussed.
THE γ SUBUNITS OF PHYCOERYTHRIN FROM A RED ALGA: POSITION IN PHYCOBILISOMES AND SEQUENCE CHARACTERIZATION
Authors: Apt Kirk E. , Metzner Sandra , Grossman Arthur R.
Published: March 2003

Aglaothamnion neglectum Feldman‐Mazoyer has two γ subunits, γ31 and γ33, that are associated with phycoerythrin in the light‐harvesting phycobilisomes. We demonstrate that these subunits are spatially separated within the phycobilisome, with the γ31 subunit present at the distal end of phycobilisome rods and the γ33 subunit present on the proximal end. These subunits are thought to link phycoerythrin hexamers together in the rod substructure, serving a role analogous to that of linker polypeptides of cyanobacteria (although unlike the cyanobacterial linker polypeptides they are chromophorylated). The sequencing of tryptic polypeptides of the γ subunits enabled us to prepare oligonucleotides encoding different regions of γ31. These oligonucleotides were used as primers to generate a probe for isolating a γ31 cDNA clone. Characterization of the cDNA clone predicts a polypeptide of 280 amino acids with a 42 amino acid presequence that is characteristic of a transit peptide, the peptide that targets proteins to chloroplasts of vascular plants. The γ31 subunit has 50% similarity to the previously characterized γ33 subunit but has no identifiable similarity to functionally related polypeptides present in cyanobacterial phycobilisomes or to any other polypeptides in the databases. A repeat of 95 amino acids is present in the red algal γ subunit sequences, suggesting that these proteins were generated by a gene duplication followed by fusion of the duplicate sequences.
PHYLOGENETIC RELATIONSHIPS WITHIN CLADOPHORALES (ULVOPHYCEAE, CHLOROPHYTA) INFERRED FROM 18S rRNA GENE SEQUENCES, WITH SPECIAL REFERENCE TOAEGAGROPILA LINNAEI  1
Authors: Hanyuda Takeaki , Wakana Isamu , Arai Shogo , Miyaji Kazuyuki , Watano Yasuyuki , Ueda Kunihiko
Published: March 2003

The phylogenetic position of a freshwater green alga,Aegagropila linnaei(Cladophorales, Ulvophyceae), was investigated using nuclear 18S rRNA gene sequences. This alga has usually been calledCladophora aegagropila(L.) Rabenhorst orCladophora sauteri(Nees ex Kütz.) Kütz. Based on morphology, it was formerly classified into the sectionAegagropilaor into the subgenusAegagropila, together with several marine species of the genusCladophora.This classification is not supported by the present phylogenetic analyses in which two very distinct Cladophorales clades are recognized.Aegagropila linnaeigroups together in a well‐supported clade withCladophorasp.,Pithophorasp.,Chaetomorpha okamurae,Arnoldiella conchophila,Wittrockiella lyallii, andCladophora conchopheria. Aegagropila linnaeiand its closely related species share some ultrastructural and biochemical characteristics, like pyrenoid structure, carotenoid composition, and cell wall composition. Freshwater species, included in the analysis, were located in two distantly related lineages, indicating that adaptation from a marine to a freshwater habitat has happened at least twice independently in the Cladophorales.
PHYLOGENY OF THE GENUS COLEOCHAETE (COLEOCHAETALES, CHAROPHYTA) AND RELATED TAXA INFERRED BY ANALYSIS OF THE CHLOROPLAST GENE rbcL1
Authors: Delwiche Charles F. , Karol Kenneth G. , Cimino Matthew T. , Sytsma Kenneth J.
Published: March 2003

The genus Coleochaete Bréb. is considered to be a key taxon in the evolution of green algae and embryophytes (land plants), but only a few of the approximately 15 species have been studied with molecular phylogenetic methods. We report here the sequences of the gene rbcL from six new cultures of Coleochaete and two of Chaetosphaeridium Klebahn. These sequences were combined with 32 additional sequences, and phylogenetic analyses were performed with maximum likelihood, distance optimality, and parsimony methods. Important subgroups within Coleochaete include two primary lineages, one marked by fully corticated zygotes and the other by naked or weakly corticated zygotes. In the first lineage there is a subclade with tightly joined filaments and distinctive (“T‐shaped”) cell division, an assemblage of strains that resembles the endophytic species Coleochaete nitellarum Jost, and a clade with loosely joined filaments and “Y‐shaped” cell divisions. Consistent with recent multigene phylogenies, these analyses support the monophyly of the Coleochaetales, place the Charales as the sister taxon to land plants, and indicate that Chaetosphaeridium is far more closely related to Coleochaete than to Mesostigma Lauterborn.
THE LIFE CYCLE AND TOXICITY OF PFIESTERIA PISCICIDA REVISITED1
Authors: Burkholder JoAnn M. , Glasgow Howard B.
Published: March 2003

Despite use of excellent molecular techniques, Litaker et al. (2002) cannot provide insights about the life history of toxic Pfiesteria piscicida because they showed no data in support of having used toxic strains; rather they presented evidence that they used non‐inducible strains. Litaker et al. did not find amoeboid stages or a chrysophyte‐like cyst stage in several cultures and unequivocally concluded that the stages do not exist in all P. piscicida strains. Thus, they did not consider the tenet that absence of evidence does not constitute proof of absence. Apparent discrepancies between the research by Litaker et al. and previous research on Pfiesteria can be resolved as follows: First, Litaker et al. did not use toxic strains. We have reported findings (similar to Litaker et al.) showing few amoeboid transformations in non‐inducible strains, which manifest some but not all of the forms that have been documented in some toxic strains. We, and others, have documented active toxicity to fish, transformations to amoebae, and chrysophyte‐like cysts in some clonal toxic strains. Second, the data from several recent publications, which were available but not mentioned by Litaker et al. or by Coats (2002) in accompanying commentary, have verified P. piscicida amoebae, chrysophyte‐like cysts, and other stages in some toxic strains through a combination of approaches including PCR data from clonal cultures.
SEXUAL REPRODUCTION, MATING SYSTEM, AND PROTOPLAST DYNAMICS OF SEMINAVIS (BACILLARIOPHYCEAE)1
Authors: Chepurnov Victor A. , Mann David G. , Vyverman Wim , Sabbe Koen , Danielidis Daniel B.
Published: March 2003

Cell division, the mating system, and auxosporulation were studied in the marine epipelic diatom Seminavis cf. robusta Danielidis & D. G. Mann. The interphase protoplast contains two girdle‐appressed chloroplasts, each with an elongate bar‐like pyrenoid, and also a central nucleus, located in a bridge between two vacuoles. Before cell division, the chloroplasts divide transversely and translocate onto the valves. The nucleus relocates to the ventral side for mitosis. After cytokinesis and valve formation, the chloroplasts move back to the girdle, showing a constant clockwise movement relative to the epitheca of the daughter cell. Seminavis cf. robusta is dioecious, and sexual reproduction is possible once cells are less than 50 μm. In crosses of compatible clones, gametangia pair laterally, without the formation of a copulation envelope, and produce two gametes apiece. The intensity of sexualization increases as cells reduce further in size below the 50‐μm threshold. At plasmogamy, the gametangia dehisce fully and the gametes, which were morphologically and behaviorally isogamous, fuse in the space between the gametangial thecae. The auxospore forms a transverse and longitudinal perizonium. After expansion is complete, there is an unequal contraction of the protoplast within the perizonium, creating the asymmetrical shape of the vegetative cell. Apart from this last feature, almost all characteristics exhibited by the live cell and auxospores of Seminavis agree with what is found in Navicula sensu stricto, supporting the classification of both in the Naviculaceae. Haploid parthenogenesis and polyploid auxospores were found, lending support to the view that change in ploidy may be a significant mechanism in diatom evolution.
ARRESTED DEVELOPMENT OF GIANT KELP (MACROCYSTIS PYRIFERA, PHAEOPHYCEAE) EMBRYONIC SPOROPHYTES: A MECHANISM FOR DELAYED RECRUITMENT IN PERENNIAL KELPS?1
Authors: Kinlan Brian P. , Graham Michael H. , Sala Enric , Dayton Paul K.
Published: March 2003

Delayed recruitment of microscopic stages in response to cyclical cues is critical to the population dynamics of many annual and seasonally reproducing perennial seaweeds. Microscopic stages may play a similar role in continuously reproducing perennials in which adult sporophytes are subject to episodic mortality, if they can respond directly to the unpredictable onset and relaxation of unfavorable conditions. We experimentally evaluated the potential for temporary reduction in limiting resources (light, nutrients) to directly delay recruitment of giant kelp (Macrocystis pyrifera (L.) C.A. Agardh) gametophytes and embryonic sporophytes. Laboratory cultures were subjected to limiting conditions of light and nutrients for 1 month and then exposed to nonlimiting conditions for 10 days. Gametophytes in all treatments failed to recruit to sporophytes after 2 weeks, suggesting they are not a source of delayed recruitment in giant kelp. Sporophytes in light‐limited treatments, however, survived and grew significantly slower than non–light‐limited controls. When stimulated with light, light‐limited sporophytes grew from 2 to>10 times faster than unstimulated controls depending on nutrient availability. These results suggest that limiting resources can delay recruitment of embryonic giant kelp sporophytes for at least 1 month. Flexible timing of recruitment from embryonic sporophytes may enhance persistence of continuously reproducing perennial species when mac‐ roscopic adults are subject to episodic large‐scale removals.
Biological Weighting Functions for the Effect of UV Radiation on Carbon Partitioning in Microalgae
Authors: Franklin L. A. , Neale P. J.
Published: March 2003

UV radiation clearly inhibits phytoplankton photosynthesis, with direct effects on both photosystem II and the enzyme, Rubisco, that catalyses the first reaction of the photosynthetic carbon reduction cycle. The subsequent partitioning of fixed carbon into macromolecular pools (carbohydrates, lipids, and proteins) is also affected by UV exposure, although relative changes in allocation are not well‐documented and vary considerably. The wavelength specificity of inhibition of photosynthesis has been described by spectral weighting functions, or biological weighting functions (BWFs) that combine the effect of UV radiation with interactive effects of longer wavelengths. BWFs permit one to compare the effects of different radiation sources or various ozone depletion scenarios. However, no data are available from which BWFs for partitioning can be determined, as experimental techniques have varied widely. These BWFs are essential for predicting the effects of increased UV‐B on other trophic levels, and for analyzing the cost and benefit of synthesizing protective compounds. Using a polychromatic approach, we are developing BWFs for the partitioning of 14C in Thalassiosira pseudonana (3H) at photosynthetically saturating irradiance. We are comparing these functions to BWFs calculated from simultaneous measurements of primary productivity. We have found consistent differences in sensitivity to UV exposure among the pools, and are testing these differences for significance using a variety of model and calculation approaches.
Three New Species of Gracilariopsis (Gracilariales, Rhodophyta) From the North‐Western Atlantic
Authors: Gurgel C. F. D. , Fredericq S.
Published: March 2003

A recent molecular phylogenetic study inferred from chloroplast‐encoded rbcL sequence analyses based on 20 specimens of Gracilariopsis. Dawson 1949 worldwide confirmed the monophyly of the genus and revealed the existence of three new Caribbean species (Gurgel et al. J. Phycol., submitted). Gracilariopsis sp. 1 collected in the Mexican Gulf of Mexico is sister to G. tenuifrons. Gracilariopsis sp. 2 collected in Caribbean Panama (Colón City) and Venezuela (Paraguana Península) is morphologically closely related to G. panamensis. Gracilariopsis sp. 3 collected in Venezuela (La Vela de Coro) is distinct from all other terete and stringy species that characterize the genus by being a flat‐foliose taxon; it also shows a basal topology with uncertain phylogenetic relationship to an undetermined species from Japan and China and to G. heteroclada from the Philippines. The lack of clear‐cut vegetative and reproductive features among the species coupled with a high degree of thallus plasticity may account for the fact that genetically distinct species were not previously recognized as taxonomically distinct. Our molecular and morphological studies reveal that the diversity of Gracilariopsis species in the western Atlantic and probably in the rest of the world is currently underestimated. Morphologically detailed descriptions for all three new species are provided.
Bioassessment of Stream‐Water Quality Using Benthic and Planktonic Algae Collected Along an Urban Intensity Gradient in the Eastern Cornbelt Plains Ecoregion, Ohio, USA
Authors: Hambrook J. A.
Published: March 2003

Algae possess many attributes that make them ideal organisms to employ in water‐quality investigations. They are ubiquitous, ecologically important, and sensitive to a broad range of stressors; moreover, they respond rapidly to changes in water quality. As part of the USGS National Water Quality Assessment (NAWQA) Program, two methods of analyzing stream‐dwelling algae were used to assess relations among nutrient concentrations, algae, and overall biological integrity of streams along a gradient from agricultural to urban land cover. One method is based on algal production (chlorophyll a, biomass, and 48‐h measures of dissolved oxygen), whereas the other is based on algal community assemblages (species abundance, biovolume, and autecology). Quantitative periphyton and phytoplankton samples were collected from 30 stream reaches in small watersheds (drainage area 7.7–188.7 km2) in south‐west Ohio, during July 2000. Phytoplankton Chl a ranged from 0.5 mg/L in an urban area to 43 mg/L in an agricultural basin, whereas the epilithic periphyton Chl a ranged from 2 mg/m2 in an urban area to 142 mg/m2 in an agricultural basin. Spearman correlations were used to indicate relations between the physical, chemical, and biological factors and measures of algal production. Multivariate analysis of algal species abundance and metrics will be used to characterize gradients of algal community response relative to chemical and landscape factors. Results will be discussed in relation to the influence of urban land‐use intensity and the US Environmental Protection Agency nutrient criteria proposed for this region. The extent to which the algal production and community structure results are useful for bioassessment of stream health will be evaluated with regard to understanding community responses to organic enrichment, dissolved oxygen, specific conductance, light availability, pesticide concentrations, and the monitoring of watershed management practices.
Impacts of Reduced Salinity on Seagrasses in Indian River Lagoon
Authors: Hanisak M. D.
Published: March 2003

From November 1993 to November 1995, a study was conducted in Indian River Lagoon (IRL) to determine relationships of light attenuation, water quality, and seagrass at sites representing a range of water quality conditions. There were considerable interannual differences at the sites. The most striking event occurred at a station in northern Banana River, an area of IRL considered the least anthropogenically impacted. This station had a well‐developed, multispecies seagrass bed (Halodule wrightii and Syringodium filiforme, with small quantities of Halophila englemannii). Throughout the first year, salinity was stable (90% of weekly values ranged from 26 to 32 ppt). Beginning in November 1994, the cover, shoot density, and biomass of all three species declined precipitously due to sharply reduced salinities associated with high rainfall and run‐off. Salinities during the following year varied little and remained low (90% of weekly values ranged from 13.5 to 19.8 ppt). The lack of recovery to earlier salinity levels was due to the long residence time (about 1 year) in that portion of IRL. Seagrass cover, shoot density, and biomass reached minima in May 1995. By August 1995, Halodule began to recover, but nearly 8 years later, Syringodium has not recovered to 1994 levels.
Synchrotron‐Based Infrared Imaging of Euglena Gracilis Single Cells
Authors: Hirschmugl C. , Bunta M. , Holt J. , Giordano M. , Skilirov A. , Strickler J. R.
Published: March 2003

Infrared (IR) microspectroscopy is used to examine and identify the chemistry in individual living cells of Euglena gracilis. The spectra provide relative concentrations of lipids, proteins and carbohydrates in the specimen. Diffraction‐limited, spatially resolved IR images of single cells of the microalga were measured using synchrotron radiation as a bright IR source. These contour maps reveal the distributions of the proteins, lipids and carbohydrates including the phospholipids, sugars and paramylon. We compare the images with the biochemistry for E. gracilis. We also present the IR images for two different cells, which were exposed to different culture conditions prior to the measurements. The overall trends observed for the two specimens are in qualitative agreement with the hypothesis that there was a significantly reduced concentration of nitrogen in the culture as a function of time. Importantly, this study demonstrates the potential to examine changes in the chemistry of living cells while modifying environmental stimuli.
Chlororespiration in Green Algae Isolated From Desert Crusts
Authors: Lewis L. A. , Cardon Z. G. , Tyser D.
Published: March 2003

Photosynthetic organisms enduring extreme temperatures, low water availability, or high light require photoprotective mechanisms to prevent sustained damage to photosynthetic machinery. Green microalgae living in desert crust communities of the south‐western US experience all these environmental stresses, yet photophysiological studies of green algae in the literature have focused on only a handful of common aquatic and marine species. We are examining the variation in green algal photoprotective mechanisms that is the result of natural selection acting independently in multiple lineages of highly diverse desert green algae (Chlorophyta) within the classes Chlorophyceae and Trebouxiophyceae. We have found that unusually extensive dark reduction of the plastoquinone pool is a prominent photophysiological feature among these desert algae; this reduction may be linked with enhanced chlororespiration. Recently, chlororespiration in higher plants has been linked through mutant analysis to control of the carotenoid synthetic pathway, heat stress, and starch metabolism among other pathways, though the function of chlororespiration remains controversial. Given that green algae and higher plants are monophyletic, analysis of potential chlororespiration in desert green algae may help decipher the evolution of the chlororespiratory process as well as its potential role in photoprotection in desert habitats.
How Age and Daytime Activities Are Related to Insomnia in the General Population: Consequences for Older People
Authors: Ohayon Maurice M. , Zulley Jurgen , Guilleminault Christian , Smirne Salvatore , Priest Robert G.
Published: March 2003

OBJECTIVES: To determine the role of activity status and social life satisfaction on the report of insomnia symptoms and sleeping habits.

DESIGN: Cross‐sectional telephone survey using the Sleep‐EVAL knowledge base system.

SETTING: Representative samples of three general populations (United Kingdom, Germany, and Italy).

PARTICIPANTS: 13,057 subjects age 15 and older: 4,972 in the United Kingdom, 4,115 in Germany, and 3,970 in Italy. These subjects were representative of 160 million inhabitants.

MEASUREMENTS: Clinical questionnaire on insomnia and investigation of associated pathologies (psychiatric and neurological disorders).

RESULTS: Insomnia symptoms were reported by more than one‐third of the population age 65 and older. Multivariate models showed that age was not a predictive factor of insomnia symptoms when controlling for activity status and social life satisfaction. The level of activity and social interactions had no influence on napping, but age was found to have a significant positive effect on napping.

CONCLUSIONS: These results indicate that the aging process per se is not responsible for the increase of insomnia often reported in older people. Instead, inactivity, dissatisfaction with social life, and the presence of organic diseases and mental disorders were the best predictors of insomnia, age being insignificant. Healthy older people (i.e., without organic or mental pathologies) have a prevalence of insomnia symptoms similar to that observed in younger people. Moreover, being active and satisfied with social life are protective factors against insomnia at any age.
Visual Risk Factors for Falls in Older People
Authors: Lord Stephen R. , Dayhew Julia
Published: March 2003

OBJECTIVES: To determine the tests most predictive of falls in community‐dwelling older people from a range of visual screening tests (high and low contrast visual acuity, edge contrast sensitivity, depth perception, and visual field size). To determine whether one or more of these visual measures, in association with measures of sensation, strength, reaction time, and balance, can accurately predict falls in this group.

DESIGN: Prospective cohort study of 12 months duration.

SETTING: Falls and Balance Laboratory, Prince of Wales Medical Research Institute.

PARTICIPANTS: 156 community‐dwelling men and women age 63 to 90 (mean age 76.5, standard deviation = 5.1).

MEASUREMENTS: Screening tests of vision, sensation, strength, reaction time and balance, falls.

RESULTS: Of the 148 subjects available at follow‐up, 64 (43.2%) reported falling, with 32 (21.7%) reporting multiple falls. Multiple fallers had decreased vision, as indicated by all visual tests, with impaired depth perception, contrast sensitivity, and low‐contrast visual acuity being the strongest risk factors. Subjects with good vision in both eyes had the lowest rate of falls, whereas those with good vision in one eye and only moderate or poor vision in the other eye had elevated falling rates—equivalent to those with moderate or poor vision in both eyes. Discriminant analysis revealed that impaired depth perception, slow reaction time, and increased body sway on a compliant surface were significantly and independently associated with falls. These variables correctly classified 76% of the cases, with similar sensitivity and specificity.

CONCLUSION: The study findings indicate that impaired vision is an important and independent risk factor for falls. Adequate depth perception and distant‐edge‐contrast sensitivity, in particular, appear to be important for maintaining balance and detecting and avoiding hazards in the environment.
Genetic and Environmental Influences on Self‐Reported Reduced Hearing in the Old and Oldest Old
Authors: Christensen Kaare , Frederiksen Henrik , Hoffman Howard J.
Published: March 2003

OBJECTIVES: The aim of the present twin study was to estimate the relative importance of genetic and environmental factors in variation in self‐reported reduced hearing among the old and the oldest old.

DESIGN: Self‐reported hearing abilities of older twins assessed at intake interview in a population‐based longitudinal survey.

SETTING: Denmark.

PARTICIPANTS: Twins age 75 and older identified in the population‐based Danish Twin Registry in 1995. An interview was conducted with 77% of 3,099 individuals in the study population. In 1997 and 1999, a follow‐up contact to the survivors was made and an additional 2,778 twins, age 70–76, were included in the study.

MEASUREMENTS: Reduced hearing was assessed by the same question in all interview waves. Heritability (proportion of the population variance attributable to genetic variation) was estimated using structural‐equation analyses.

RESULTS: The prevalence of self‐reported reduced hearing corresponded to previous studies and showed the expected age and sex dependence. Concordance rates, odds ratios, and correlations were consistently higher for monozygotic twin pairs than for dizygotic twin pairs in all age and sex categories, indicating heritable effects. Structural‐equation analyses revealed a substantial heritability for self‐reported reduced hearing of 40% (95% CI = 19–53%). The remaining variation could be attributed to individuals' nonfamilial environments.

CONCLUSION: We found that genetic factors play an important role in self‐reported reduced hearing in both men and women age 70 and older. Because self‐reports of reduced hearing involve misclassification, this estimate of the genetic influence on hearing disabilities is probably conservative. Hence, genetic and environmental factors play a substantial role in reduced hearing among the old and oldest old. This suggests that clinical epidemiological studies of age‐related hearing loss should include not only information on environmental exposures but also on family history of hearing loss and, if possible, biological samples for future studies of candidate genes for hearing loss.
Problem Behavior in the Last Year of Life: Prevalence, Risks, and Care Receipt in Older Americans
Authors: Bedford Susan , Melzer David , Guralnik Jack
Published: March 2003

OBJECTIVES: To estimate the prevalence of problem behavior in the last year of life in older people and to explore risk factors and assess the effect of behaviors on access to care.

DESIGN: Retrospective analysis of data from the 1993 National Mortality Followback Survey, conducted by the National Center for Health Statistics (NCHS).

SETTING: Persons who resided and died in the United States (except South Dakota) in 1993.

PARTICIPANTS: Seven thousand six hundred and eighty‐four deaths in people age 65 and older were included, from which full informant interview data were available for 6,748 decedents (88%).

MEASUREMENTS: Informant data were collected on frequency of complaints about behavior from family members, complaints from others in the community, bizarre behavior, destroying property, violent threats or attempts, and temper tantrums.

RESULTS: Overall, 20% of decedents were reported as having any of the problem behaviors sometimes or often in the last year of life. Rates differed little by age at death or gender. Risks of having problem behaviors were higher for those with clinically diagnosed dementia, mental illness, alcohol abuse, and bronchitis or emphysema. A diagnosis of dementia had been made in 27% of those with behavior problems. Nursing homes or healthcare facilities were the usual residence of 32% of people with any behavior problems sometimes or often during their last year of life. Informants for decedents who had destroyed property or made violent threats were 2.3 times (95% confidence interval (CI) = 1.2–4.4) more likely to report that the subject had not received the care they had needed during the last year of life.

CONCLUSION: Problem behavior is relatively common in older people in the last year of life and is not confined to nursing home residents or people suffering from dementia.
Secular Trends in Self‐Reported Functioning, Need for Assistance and Attitudes Towards Life: 10‐Year Differences of Three Older Cohorts
Authors: Pitkala K. H. , Valvanne J. , Kulp S. , Strandberg T. E. , Tilvis R. S.
Published: March 2003

OBJECTIVES: To compare the self‐reported functional status of cohorts, born 10 years apart, when they were at equivalent ages: 75, 80, or 85.

DESIGN: Cross‐sectional mailed survey of three birth cohorts in 1989 and 1999.

PARTICIPANTS: Random samples of older home‐dwelling residents from birth cohorts 1904, 1909, and 1914 in 1989 (N = 685) and the birth cohorts 1914, 1919, and 1924 in 1999 (N = 2,047) were asked the same questions.

MEASUREMENTS: Self‐reported physical functioning, need for assistance in daily living, and attitudes toward life.

RESULTS: Among 85‐year‐olds born in 1914 there was a significantly larger proportion able to go outdoors compared with 85‐year‐olds born in 1904 (72.9% vs 60.6% in women (P < .01) and 84.6% vs 63.6 % in men (P < .01), respectively). Similar trends were observed between the oldest cohorts concerning the need for assistance. The amount of publicly funded domestic help had reduced in the two oldest cohorts in 1999 compared with 1989 (20.3% vs 29.8% in 85‐year‐old women born in 1914 vs 1904 (P < .05); and 10.2 % vs 25.0% in 85‐year‐old men born 1914 vs 1904 (P < .05), but at the same time 75‐year‐old women born in 1924 had increased the use of private domestic help compared with 75‐year‐old women born in 1914. Significantly larger proportions of both men and women had plans for the future in all the cohorts in 1999 than in 1989.

CONCLUSIONS: Consistent yet small differences between the corresponding cohorts suggest that physical functioning and more‐optimistic attitude toward life have increased and need for assistance has decreased over 10 years in the older population up to the age of 85.