bluuebunny/crossref_metadata_2025 huggingface dataset:
SEXUAL REPRODUCTION OFPERIDINIUM GATUNENSE(DINOPHYCEAE)1
Authors: Pfiester Lois A.
Published: August 2007

Sexual reproduction was induced in the dinoflagellatePeridinium gatunenseNygaard when exponentially growing cells were inoculated into nitrogen deficient medium. Small thecate cells produced by division of vegetative cells then acted as gametes. Thecae of fusing gametes broke in the girdle region and were lost. Zygotes thus formed remained motile 3–5 days during which time they enlarged slightly with the newly formed theca becoming warty. Three to 5 days following plasmogamy the zygote became nonmotile, the protoplast contracted, and the cell wall thickened. Hypnozygotes with 4 nuclei were observedca.10–12 h following formation. Meiosis was inferred. Hypnozygotes germinated within 12 h of formation producing 2 vegetative cells which divided within a 24 h period. Attempts to induce sexual reproduction by inoculation of cells into media deficient in a number of basic elements other than N were unsuccessful.
THE EFFECTS OF SOME ECOLOGICAL FACTORS ON CELL SIZE OF THE HOT SPRING ALGA SYNECHOCOCCUS LIVIDUS (CYANOPHYTA)1
Authors: Kullberg Russell G.
Published: August 2007

Algae were sampled along temperature gradients of 30 thermal springs in Colorado, Idaho, Montana and Wyoming. From a maximum temperature of 74.5 C downstream, to ca. 62 C, the diversity of the algae was limited to the various forms of Synechococcus lividus Copeland; from ca. 62 to 40–45 C it coexisted with other algae. When S. lividus was in direct sunlight the mean length was greatest at the highest temperatures of its existence, becoming shorter as the water cooled; the mean reduction in length was 0.132 μm for each 1 C reduction in temperature. The cells in a shaded stream did not exhibit the reduction in size with reduced temperature, but remained about the same length from 73 C downstream to 45 C. The longer cells from the highest temperatures of their existence in any stream could not become established in the cooler water downstream, so the range of cell lengths (diversity) became less as the water cooled. Unknown dissolved substance(s) depressed the upper temperature limit in two streams and had a reverse effect on the expected length–temperature relationship; the shortest cells were at the higher temperatures. Generally, total dissolved substances had a positive effect on the length; the longest cells were in the water with the highest total dissolved solids (TDS) at the upper temperature limits of 70–74.5 C. In the temperature range of 55–60 C the higher TDS were not as effective in developing longer cells.
STRUCTURAL, CHEMICAL AND ECOLOGICAL STUDIES ON IRIDESCENCE IN IRIDAEA (RHODOPHYTA)1
Authors: Gerwick William H. , Lang Norma J.
Published: August 2007

Transmission electron microscopy of the iridescent algae Iridaea flaccida (S & G) Silva, Iridaea cordata (Turn.) Bory var. cordata and I. cordata var. splendens (S & G) Abbott reveals a multilaminated cuticle covering the thallus. Experimental results show the cuticle: a) can be isolated intact by mechanical scraping or NaOH treatment; b) is iridescent by itself and the denuded thallus is not; and, c) is isolated without any subtending polysaccharide layer, cell walls, or cells. This cuticle acts as a thin layer producing the constructive and destructive light interference which is seen as iridescence. It is formed of alternating electron opaque and translucent layers with a total thickness of 0.5–1.6 μm. Analysis of mechanically isolated cuticle shows that it is composed of protein (50%), carbohydrate (ca. 40%), inorganic salts (5%) and some fatty acids (less than 1.0%). The electron opaque layers may correspond to protein‐rich regions and the electron translucent ones to regions rich in carbohydrates. The cuticle does not appear to affect photosynthesis or respiration, but rather, may protect the alga from physical factors such as desiccation and from predator injury. It is likely that the iridescence in other foliaceous red algae is caused by a similar structure.
ULTRASTRUCTURE OF A CHAIN‐FORMING DIATOM PHAEODACTYLUM TRICORNUTUM1
Authors: Borowitzka Michael A. , Chiappino Mary Louise , Volcani Benjamin E.
Published: August 2007

The ultrastructure of a chain‐forming clone of the polymorphic diatom Phaeodactylum tricornutum Bohlin has been studied by scanning and transmission electron microscopy. Both fusiform and tri‐radiate cells are capable of forming chains. The cells, lacking any silica shell, are attached to each other at the central region of the theca, leaving the arms free. Neither homogenization nor sonication completely disrupts the chains. The attachment is due to fusion of the cell wall in the central region of the cell during cell wall deposition. This fusion results from failure of the cytoplasmic cleavage furrow to separate the plasma membranes of the two daughter cells sufficiently so that a single wall is deposited instead of two separate walls. Possible explanations for this are discussed.
NITRATE UPTAKE KINETICS AND CLONAL VARIABILITY IN THE NERITIC DIATOMBIDDULPHIA AURITA1
Authors: Underhill Peter A.
Published: August 2007

Nitrate uptake experiments were conducted at 18 and 25 C on subtropical and temperate isolates of the neritic diatomBiddulphia aurita(Lyngb.) Breb. & Godey. Two clones (STX‐88 and B1) were grown in a 12:12 LD cycle in NO3‐limited continuous cultures used for uptake experiments. The half‐saturation constant (Ks) and the maximum NO3‐ uptake rate (Vm) were measured under conditions in which external NO3‐ concentration controlled uptake rate. The kinetic constants for both clones were higher at the higher temperature. The subtropical clone (STX‐88) had lower kinetic values than temperate clone (B1) at both temperatures. The differences appear to be of adaptive significance since STX‐88 has a NO3‐ uptake system, described by its lower Ksvalue, which minimizes the double stress effects of high temperature‐low NO3‐ concentration conditions characteristic of its habitat. Cytoplasmic enzyme electrophoretic analyses were conducted on the clones. Differences in banding patterns and mobilities showed evidence of allelic substitution. The results suggest genetic variation at the intraspecific level.
GROWTH OF A MARINE DIATOM AND A HAPTOPHYCEAN ALGA ON PHENYLALANINE OR TYROSINE SERVING AS SOLE NITROGEN SOURCE1
Authors: Landymore Arthur F. , Antia Naval J.
Published: August 2007

The marine diatom Navicula incerta Hustedt and the haptophyte Isochrysis galbana Parke, both accustomed to grow on nitrate, were tested for their adaptive capacity for growth in axenic culture on 0.025–2.0 mM l‐, d‐, and dl‐isomers of phenylalanine and tyrosine as sole nitrogen sources. The diatom showed immediate and excellent growth (superior to nitrate) on l‐phenylalanine and l‐tyrosine but required prolonged periods of adaptation before growing on the d‐isomers, which growth was considerably slower. Isochrysis showed good growth on l‐phenylalanine after short adaptation, fair growth on low but poor growth on high concentrations of l‐tyrosine and no growth on the d‐isomers of both amino acids. The racemate (dl‐mixture) of each amino acid produced growth responses, from both algae, inferior to those of the corresponding l‐isomer, indicating competitive inhibition from the d‐isomer in the presence of equal amounts of its counterpart. Increasing tyrosine concentration was beneficial to growth of Navicula but markedly inhibitory or toxic to that of Isochrysis. Phenylalanine concentration appeared to benefit growth of both algae. Ecological considerations suggest that N. incerta may be habituated to utilize both aromatic amino acids in its native milieu.
IN SITU PRESERVATION OF THE TRANSVERSE FLAGELLUM OF PERIDINIUM CINCTUM (DINOPHYCEAE) FOR SCANNING ELECTRON MICROSCOPY1
Authors: Berdach James T.
Published: August 2007

Three‐dimensional structure of the transverse flagellum was studied by means of scanning electron microscopy (SEM) in Peridinium cinctum (O.F.M.) Ehrenberg. Several fixation and dehydration procedures were compared. Cells fixed, rapidly in 1% osmium tetroxide and critical‐point dried showed accurate preservation of structural features seen in living cells; in particular, both transverse and posterior flagella were retained in the furrows on the cell surface. Osmium‐fixed and freeze‐dried, samples were prone to cellular collapse and loss of flagella. Glutar‐aldehyde‐fixed and critical‐point dried cells showed a layer of material covering the thecal plates, most conspicuously over the girdle region; flagella were absent. Stereo‐pair micrographs illustrate the 3‐dimensional configuration of the transverse flagellum. Modifications of previous structural models are proposed.
DIFFERENT CHEMICAL TYPES OF PLOCAMIUM VIOLACEUM (RHODOPHYTA) FROM THE MONTEREY BAY REGION, CALIFORNIA1
Authors: Crews Phillip , Campbell Lisa , Heron Elaine
Published: August 2007

Differences in the halogenated natural products of Plocamium violaceum Farlow can be noted from different sites in the Monterey Bay region, California. Specimens from the northern region produce a set of alicyclic halogenated monoterpenes which are not synthesized by those from the southern region. Instead, the latter elaborates a set of acyclic halogenated monoterpenes not observed from the former. This situation is invariant regardless of life history forms or different seasons. Similarly, the composition of halogenated monoterpene structures from P. cartilagineum (L.) Dixon varies at different locations. From the data presented herein we conclude that at least two chemical types can be identified for P. violaceum based upon differences in their halogenated products. Thus we suggest that the north Monterey form can be designated as chemotype α and the southern one as chemotype β.
DISTRIBUTION OF DIATOMS IN THE PLANKTON OF YAQUINA ESTUARY, OREGON1
Authors: Karentz Deneb , McIntire C. David
Published: August 2007

The distributional patterns of diatoms in the plankton of the Yaqnina Estuary, Oregon, were, investigated and related to selected climatic and hydrographic factors. Distribution was strongly influenced by seasonal patterns of rainfall resulting in the introduction of a large volume of fresh water into the estuary during fall and winter. Plankton assemblages in spring, summer and fall had fewer diatom species and exhibited a more rapid rate of change in species composition than in winter. Winter assemblages were further characterized by many pennate diatoms, apparently dislodged from the benthos during periods of high freshwater discharge and silt loads. A statistical measure of community difference indicated an increase in taxonomic homogeneity among assemblages throughout the estuary with the onset of the rainy season in late fall and a gradual transition to a more heterogeneous system again during late spring. Canonical correlation ordered 20 prominent diatom taxa along the salinity gradient and identified possible relationships among certain taxa and selected environmental variables, namely visible light energy and temperature. Redundancy in the species data given the environmental data was only 40%, emphasizing the difficulty in demonstrating a quantitive relationship between plankton dynamics in the field and concurrent measurements of chemical and physical variables.
EFFECTS OF LIGHT INTENSITY AND TEMPERATURE ONCRYPTOMONAS OVATA(CRYPTOPHYCEAE) GROWTH AND NUTRIENT UPTAKE RATES1
Authors: Cloern James E.
Published: August 2007

Specific growth rate ofCryptomonas ovatavar.palustrisPringsheim was measured in batch culture at 14 light‐temperature combinations. Both the maximum growth rate (μm) and optimum light intensity(Iopt)fit an empirical function that increases exponentially with temperature up to an optimum(Topt),then declines rapidly as temperature exceedsTopt.Incorporation of these functions into Steele's growth equation gives a good estimate of specific growth rate over a wide range of temperature and light intensity. Rates of phosphate, ammonium and nitrate uptake were measured separately at 16 combinations of irradiance and temperature and following a spike addition of all starved cells initially took up nutrient at a rapid rate. This transitory surge was followed by a period of steady, substrate‐saturated uptake that persisted until external nutrient concentration fell. Substrate‐saturated NO3−‐uptake proceeded at very slow rates in the dark and was stimulated by both increased temperature and irradiance; NH4+‐uptake apparently proceeded at a basal rate at 8 and l4 C and was also stimulated by increased temperature and irradiance. Rates of NH4−‐uptake were much higher than NO3−‐uptake at all light‐temperature combinations. Below 20 C, PO4−3‐uptake was more rapid in dark than in light, but was light enhanced at 26 C.
EFFECT OF TEMPERATURE ON LIGHT‐LIMITED GROWTH AND CHEMICAL COMPOSITION OF SKELETONEMA COSTATUM (BACILLARIOPHYCEAE)1
Authors: Yoder James A.
Published: August 2007

Phytoplankton growth rate in response to irradiance can be approximated by a hyperbola defined by three coefficients: i) initial slope (α); ii) asymptote (μm); and, iii) X‐axis intercept or compensation irradiance (Ic). To mathematically represent the interaction of temperature and irradiance on growth rate, one must describe the relationship between these constants and temperature. The marine diatom, Skeletonema costatum (Greville) Cleve, was grown in unialgal culture at different levels of irradiance and 2‐3 photoperiods at 0, 5, 10, 16 and 22 C. The value of Ic is ca. 1.0 ly·day−1 or less at all temperatures. The initial slope (div·ly−1) is a “u‐shaped” function of temperature described by the second degree polynomial, α= 0.25–0.02T+0.001T2. Within the range 0–10 C, μm (div·day−1) is an exponential function of temperature described by the equation, μm= 0.48 exp (0.126T). At each temperature and selected levels of irradiance, cell size and cellular content of C, N and chl a were determined. The C:chl a and N:chl a ratios increased with irradiance because of increases in C and decreases in chl a. At lower temperatures (0, 5, 10 C), the rate of increase of both ratios with irradiance was greater than at the higher temperatures (16, 22 C). Cellular content of N was independent of irradiance and temperature, and the C:N ratio ranged from 5 to 8 with a slight tendency to lower values at low irradiance. Cell volume was not influenced by either temperature or irradiance.
MECHANISMS OF RAPID PHOTOSYNTHETIC ADAPTATION IN NATURAL PHYTOPLANKTON COMMUNITIES. I. REDISTRIBUTION OF EXCITATION ENERGY BETWEEN PHOTOSYSTEMS I AND II1
Authors: Vincent Warwick F.
Published: August 2007

An inverse linear relationship between chlorophyll fluorescence yield (R) and light intensity was recorded in the near‐surface waters of six lakes (New Zealand, England) of greatly different trophic status and phytoplankton species composition. This surface depression of R values could be removed by incubation of samples in dim light or darkness and was not observed in situ below a threshold irradiance (146 μEin ·m−2·s−1 for Lake Taupo, New Zealand). The time course of chlorophyll fluorescence depression and recovery in response to light treatment was measured in samples from Lake Windermere (England). Fluorescence exponentially decreased upon exposure to bright light and the response was 100% (5 m samples) or 83% (dim light‐adapted 0 m samples) complete within 2 min. An increase in R values in the dim light occurred after a lag of 60 s and the rate of increase decreased exponentially with time. Full recovery took 15 min or more. Deep (6.5 m) populations from Lake Windermere exhibited large, time‐dependent variations in chlorophyll fluorescence over the first 25 s of exposure to 450 nm light, whereas surface populations did not. These data were interpreted in terms of decreased spillover from PSII to PSI with increasing depth, to a minimum at the threshold light intensity below which cells are in light state 1.
PIGMENTATION AND MORPHOLOGY OF A MARINE GYRODINIUM (DINOPHYCEAE) WITH A MAJOR CAROTENOID DIFFERENT FROM PERIDININ AND FUCOXANTHIN1
Authors: Bjørnland T. , Tangen Karl
Published: August 2007

Chlorophylls and carotenoids of a small unarmoured dinoftagellate (Gyrodinium sp.‐A) isolated from the Oslofjord, Norway, were investigated by thin‐layer chromatography, visible light spectrophotometry, proton magnetic resonance and mass spectrometry and simple chemical reactions. Besides chlorophyll a, chlorophyll c, β,β‐carotene, diatoxanthin and diadinoxanthin, the species possessed three xanthophylls that could not be correlated with carotenoids previously reported from dinoflagellates. The main carotenoid was different from peridinin and fucoxanthin, both of which are reported as the main characteristic carotenoids in photoautotrophic dinoflagellates. No trace of peridinin could be detected in the pigment extract. A morphological description of the organism based on light microscopy is presented, and the relationship with other small gymnodinioid (Gymnodinium spp.) species is discussed. The preliminary results indicate that this Gyrodinium may be a previously undescribed species.
POTASSIUM IN POLYPHOSPHATE BODIES OF CHLORELLA PYRENOIDOSA (CHLOROPHYCEAE) AS DETERMINED BY X‐RAY MICROANALYSIS1
Authors: Adamec Jan , Peverly John H. , Parthasarathy Mandayam V.
Published: August 2007

Potassium is an important component information of polyphosphate bodies (PB) by Chlorella pyrenoidosa Chick. However, it was not detected in PB by X‐ray energy dispersive microanalyses when the specimens were subjected to a standard preparation procedure for transmission electron microscopy. Intact cells were incinerated at 350 C on stainless steel grids coated with silicon monoxide. X‐ray spectra from PB showed conspicuous peaks of energy counts in the Kα lines for phosphorus and potassium. It is proposed that potassium is a major cationic component of PB in C. pyrenoidosa grown in potassium sufficient medium.
CRITICAL LEVELS OF LIGHT AND TEMPERATURE REGULATING THE GAMETOGENESIS OF THREELAMINARIASPECIES (PHAEOPHYCEAE)1
Authors: Lüning Klaus
Published: August 2007

Gametophytes of threeLaminariaspecies occurring near Helgoland, North Sea, were cultivated 4 wk in a 12:12 LD regime at different temperatures in artificial light fields, and in the sea at different water depths. In the artificial light fields underwater spectral distribution was simulated according to Jerlov water Types 5, 7, 9. Blue light in the simulated light fields amounted to 17, 12 or 4% of total quanta. The rate of vegetative growth did not depend on spectral distribution, was light‐saturated at 4–6 W · m−2, and increased with temperature up to 15 C.L. saccharina(L.) Lamour. exhibited the highest tolerance towards temperature, light and UV. Gametophytes survived 1 wk at 21 C ± 0.1, but not 22 C ± 0.1. Gametophytes ofL. hyperborea(Gunn.) Fosl. andL. digitata(Huds.) Lamour. survived 1 wk at 20 C ± 0.1, but not at 21 C ± 0.1. In sunlight, and in the light field of a xenon lamp, 50% ofL. saccharinagametophytes were killed by a quantum dose of 50 μEin · cm−2, and 100% of the plants by 90 μEin · cm−2. Approximately half of these quantum doses killed the corresponding percent of the other species gametophytes. Appreciably higher quantum doses were survived in visible light, with red being the most detrimental. Fertility depended on a critical quantum dose of blue light which decreased almost exponentially with decreasing temperature. The quantum dose (400–512 nm) required for induction of fertilization of 50% of the female gametophytes (males react similarly) was 90 μEin · cm−2at 5 C, 110 μEin · cm−2at 10 C, 230 (560 inL. digitata)μEin · cm−2at 15 C, and 560 (L. hyperborea)or about 850 (other 2 species) μEin · cm−2at 18 C. In the sea the gametophytes survived the dark winter months in the unicellular stage, with almost no vegetative growth of the primary cell, due to lack of light. In early spring the female gametophytes matured in the unicellular, and the males in a few‐celled stage at the depth of 2 m, as did the laboratory cultures under conditions inducing maximal fertility.
RELATIONSHIP BETWEEN NUCLEO‐CYTOPLASMIC RATIO AND FINAL CELL VOLUME IN MICRASTERIAS CRUX‐MELITENSIS (DESMIDIACEAE, CHLOROPHYTA)1
Authors: Sana Momoyo , Ueda Katsumi
Published: August 2007

In Micrasterias crux‐melitensis (Ehrbg.) Hass., small parental half‐cells produced daughter half‐cells larger than themselves. As the volume of the parental half‐cells decreased, the volume ratio of daughter to parental half‐cells increased; the larger the nucleo‐cytoplasmic ratio of parental half‐cells, the larger the volume of the daughter half‐cells. Small daughter half‐cells grew larger than expected when cytoplasm of other cells was incorporated. The number of dictyosomes was almost the same for cells of different volumes. Results obtained seem to suggest that the volume of daughter cells is determined by the balance between the gradient of mRNA and the quantity of cytoplasm.
FINE STRUCTURE OF CALONEIS AMPHISBAENA (BACILLARIOPHYCEAE)1
Authors: Edgar Lesley A.
Published: August 2007

The structure of the motile pennate diatom Caloneis amphisbaena Cleve is described, with emphasis on the lateral, lobed pyrenoid with neither a limiting membrane nor penetration by thylakoids, an interphase nucleus with centers of condensed chromatin, paired dictyosomes, and mitochondria cradled within the chambers of the valve. Microfilaments forming two bundles which lie beneath each raphe slit are of the same size and appearance as actin microfilaments associated with other motile systems.
A GRADIENT IN BENTHIC INTERTIDAL ALGAL ASSEMBLAGES ALONG THE SOUTHERN CALIFORNIA COAST1
Authors: Thom Ronald M.
Published: August 2007

Based on an analysis floristic data, a gradient appears to exist in the composition of intertidal algae along the 450 km of southern California coastline immediately south of Point Conception. Reciprocal averaging ordination of the algal flora at 51 sites in this area suggests that the gradient is not strictly latitudinal. Variation from a latitudinal gradient occurs ca. 60‐80 km south of Point Conception. An ordination of frequently occurring species indicated that compositional changes are substantial when sites at the extreme north and south are compared, but that the changes are gradual and continuous. Possible explanations for the gradient are discussed, and these include: sea temperature, upwelling, sand movement, human disturbance (i.e., pollution, trampling), and wave action.
ELECTROPHORETIC ANALYSIS OF GENETIC VARIATION IN THE CHAROPHYTA. I. GENE DUPLICATION VIA POLYPLOIDY1
Authors: Grant Michael C. , Proctor Vernon W.
Published: August 2007

Electrophoretic analysis of 12 species ofCharaindicates that functional gene duplication via polyploidy has commonly occurred in the genus. Duplication has been followed by differentiation of the loci encoding phosphoglucose isomerase (PGI). This has led directly to generation of substantial levels of genie variation both within and between taxa. A simple genetic model is proposed to account for the large array of PGI phenotypes encountered in natural populations. Constraints imposed by the reproductive biology of members of the genus, such as selfing, appear to have resulted in selective premiums on intrinsic mechanisms of generating genetic variation. Levels of variation in PGI were higher than would be predicted on the basis of charophyte reproductive characteristics; haploid loci segregate approximately two alleles within each species.
PERIODICITY OF EPIPELIC UNICELLULAR VOLVOCALES (CHLOROPHYCEAE) IN A SHALLOW ACID POOL1
Authors: Happey‐Wood Christine M.
Published: August 2007

The occurrence, periodicity and growth of twenty species of unicellular Volvocales on sediments in an acidic pool are described. Minimum populations were recorded in winter, but during the rest of the year standing crops fluctuated rapidly. The greatest species diversity and primary productivity occurred in late spring‐early summer and in autumn, when maximum numbers of Chlamydomonas spp. and Chloromonas spp. increased exponentially on the sediments. The chlamydomonads were more numerous in the epipelon than other major algal components such as diatoms, euglenoids, bluegreen algae and desmids. Growth of the chlamydomonad population occurred after the period of maximum diatom standing crop. Evidence shows that rates of primary production were greater in late spring and late summer when species diversity and standing crop or apparent growth rates of unicellular Volvocales were high. Thus these algae which are normally neglected may be more important in primary productivity than previously believed since they grow during periods when larger algae are scarce. Analysis of the data using the multivariate technique of Reciprocal Averaging confirmed seasonal periodicity in this community of epipelic flagellates. It also identified species with distinctive ecological requirements. A relationship between the bicarbonate‐alkalinity of the overlying water and the chlamydomonad population was demonstrated by ordination analysis.
OLISTHODISCUS LUTEUS (CHRYSOPHYCEAE). IV. EFFECTS OF LIGHT INTENSITY AND TEMPERATURE ON PHOTOSYNTHESIS, AND CELLULAR COMPOSITION1
Authors: Tomas Carmelo R.
Published: August 2007

The effect of light intensity and temperature on photosynthesis, chlorophyll a, and cellular concentrations of nitrogen and carbon in an axenic clone of Olisthodiscus luteus Carter following incubation in both indoor and outdoor growth chambers was determined. Populations were grown outdoors and photosynthesis determined in a graded series of light intensities yielding 4–524 total ly (per 6 h) and temperatures from 5 to 23 C and indoors at 0.3–40 total ly and 5–30 C. In both series, photosynthesis was saturated at low light (∼10 total ly or 0.028 ly · min −1) and showed only slight inhibition at the higher light intensities. Chlorophyll a·cell−1 had a maximum at 15 C with declining values at extremes of temperature. Carbon and nitrogen were more variable between indoor and outdoor experiments. Populations incubated indoors increased their carbon (130–225 pg·cell−1) and nitrogen (23–35 pg·cell−1) content as a function of light and temperature from 5 to 20 C. The outdoor series had increases in cellular N and C as a function of light and temperature below 14 C but maximum C·cell−1 (175 pg) and N·cell−1 (>27 pg) as well as wide variations in assimilation number occurred between 14–21 C. Assimilation numbers (<1.0–4.7) were similar to those measured in natural populations. Ratios for C and N had a similar relationship in both indoor and outdoor experiments. Growth calculated from photosynthesis results agreed with growth based on cell number for the 24 h period preceding incubations in the indoor series but was consistently overestimated in the outdoor series. The low light saturation indoors, lack of inhibition at high intensities, and variations between 14–21 C in the outdoor series suggest features important to survival of O. luteus in natural waters.
A MORPHOLOGICAL STUDY OF FIMBRIFOLIUM, A NEW GENUS IN THE CYSTOCLONIACEAE (GIGARTINALES, RHODOPHYTA)1
Authors: Hansen Gayle I.
Published: August 2007

Fimbrifolium is described as a new genus for the taxon, Rhodophyllis dichotoma (Lepechin) Gobi. Vegetatively, Fimbrifolium dichotomum is similar to some species of Rhodophyllis and Craspedocarpus, but reproductively it differs from these genera in three main features: the carposporophyte develops with the first gonimoblast initial produced in an outward direction away from the axis; at maturity, the carposporophyte consists of a central fusion cell with outwardly radiating chains of carposporangia and inwardly radiating nutritive filaments; and, in the mature tetrasporophyte, tetrasporangia are borne in an intercalary position in cortical rosette‐filaments. The relative importance of these features as generic characteristics in the family is discussed.
SYSTEMATICS OF THE ZYGNEMATACEAE (CHLOROPHYCEAE). II. ZYGOSPORE‐WALL STRUCTURE IN SIROGONIUM AND A TAXONOMIC PROPOSAL1
Authors: Hoshaw Robert W.
Published: August 2007

Zygospore‐wall structure is described for nine species of Sirogonium using the light microscope and scanning electron microscopy (SEM) on spores from cultures and on glycerin‐preserved spores from field collections. Zygospores possess four distinctive wall layers with the innermost and outermost smooth and composed of cellulose. The two median wall layers are pigmented and the innermost of these may be conspicuously ornamented as in Sirogonium ceylanicum Wittrock, S. hui (Li) Transeau, S. melanosporum (Randhawa) Transeau, S. ventersicum Transeau, S. pseudofloridanum (Prescott) Transeau and S. illinoisense (Transeau) G. M. Smith. Inner median wall layers of S. floridanum (Transeau) G. M. Smith, S. sticticum (J. E. Smith) Kützing and S. tenuis (Nordstedt) Transeau lack distinctive ornamentation, but possess minor depressions or small raised areas on their surfaces. Types of ornamentation revealed by SEM are compared with earlier light microscope observations and the interpretations from SEM are used to construct improved taxonomic keys to Sirogonium.
FORMATION OF RESTING SPORES BY LEPTOCYLINDRUS DANICUS (BACILLARIOPHYCEAE) IN A CONTROLLED EXPERIMENTAL ECOSYSTEM1
Authors: Davis Curtiss O. , Hollibaugh James T. , Seibert Don L. R. , Thomas William H. , Harrison Paul J.
Published: August 2007

Leptocylindrus danicus Cleve became the dominant phytoplankton species, comprising 70–80% of the total assemblage, in one of the CEPEX Controlled Experimental Ecosystems (CEE) at Saanich Inlet, British Columbia (Canada). In the first week of June, when nitrate levels were reduced below 0.5 μm, the majority of the L. danicus cells present in the CEE formed resting spores. The spores were heavily armored with spines and appeared to sink unmolested to the bottom of the CEE. Four continuous cultures were started with an inoculum from the CEE and, in a 24 h period when N became depleted, 86% of the L. danicus present (∼80% of the total phytoplankton assemblage) formed resting spores. A daily dilution culture with nutrients kept at saturating levels was started at the same time from the same inoculum and continued for 2 wk beyond the spore formation event in the N‐limited cultures. No spores were observed in the nutrient‐saturated culture, indicating that N limitation was necessary to trigger spore formation. Spores were kept in the dark at 3 and 10 C. After 36 and 97 days, a large percentage of the spores germinated. After 214 days, >1% of the spores were still capable of germination. Laboratory studies with L. danicus isolated from the CEE confirmed that N limitation was the primary factor triggering spore formation. Microscope observations of these cultures indicated that the spores were formed by auxospores following sexual reproduction.
DIATOM MINERALIZATION OF SILICIC ACID. V. ENERGETIC AND MACROMOLECULAR REQUIREMENTS FOR Si(OH)4 MINERALIZATION EVENTS DURING THE CELL CYCLE OF NAVICULA PELLICULOSA1
Authors: Sullivan Cornelius W.
Published: August 2007

The reactions and processes which underlie the silicification mechanism (incorporation of soluble pool Si into insoluble material) in the diatom Navicula pelliculosa (Bréb.) Hilse are quite sensitive to low temperature. Furthermore incorporation is completely blocked in 66Ge‐Si(OH)4 preloaded cells treated with an inhibitor of oxidative phosphorylation (2,4‐dinitrophenol) or a sulfhydryl blocking agent (N ‐ethylmaleimide). De novo protein synthesis is not required for incorporation in cells preloaded 3 h, but cycloheximide added to cells preloaded 1 h inhibits incorporation after 2 h. These results are interpreted to indicate that purely chemical reactions, which are uncoupled from cellular metabolism, cannot completely account for Si(OH)4 polycondensation during silica frustule morphogenesis in the diatom. A temperature sensitive cellular process or reaction, postcytokinesis, is also postulated to be required before silicification can occur.
USE OF METHYLAMMONIUM AS AN AMMONIUM ANALOGUE IN NITROGEN TRANSPORT AND ASSIMILATION STUDIES WITHCYCLOTELLA CRYPTICA(BACILLARIOPHYCEAE)1
Authors: Wheeler Patricia A.
Published: August 2007

The effect of methylammonium on the utilization of other nitrogen sources and the characteristics of methylammonium uptake byCyclotella crypticaReimann, Lewin, and Guillard were examined. Methylammonium prevented growth on nitrate, nitrite, and arginine, but did not affect growth on ammonium or glutamine. Methylammonium was taken up rapidly by what appears to be an ammonium transport system. Transport followed saturable kinetics, was specific for ammonium and methylammonium, and appeared to be subject to nitrogen regulation. Transport rates were hyperbolically related to external Na+and strongly inhibited by high external concentrations of K+. These results support the use of methylammonium as an ammonium analogue, as an inhibitor of the utilization of some forms of nitrogen, and in the analysis of the mechanism and regulation of ammonium transport.
BROMOPEROXIDASES AND HALOGENATED LIPIDS IN MARINE ALGAE1
Authors: Hewson William D. , Hager Lowell P.
Published: August 2007

Using the facilities of the RIV Alpha Helix, marine algae were collected and immediately sampled for the presence of peroxidase enzymes capable of performing electrophilic bromination via the oxidation of bromide ion. Algae were also sampled for halogenated neutral lipids. A spectrophotometric assay employing monochlorodimedone was used to measure the level of enzymatic bromination, and an automated halogen analyzer was used to determine the level of lipid halogen. Of 72 algae tested for bromoperoxidase, 55 were active; moreover 27 of 102 algae contained significant levels of lipid halogen. For 67 algae there was sufficient sample to complete both assays. A comparison of the reds, browns and greens showed the Rhodophyta to be the richest in both bromoperoxidase and lipid halogen levels while the Phaeophyta was the poorest. pH optima in the range pH 5 to 8 were determined for a few of the more active algal bromoperoxidases. Cyanide inhibited the bromination of monochlorodimedone but inhibition could not be distinguished from the possibility of competition by cyanide for electrophilic bromination.
GROWTH OF A COCCOID NANOPLANKTER (EUSTIGMATOPHYCEAE) FROM THE CHESAPEAKE BAY AS INFLUENCED BY LIGHT, TEMPERATURE, SALINITY AND NITROGEN SOURCE IN FACTORIAL COMBINATION1
Authors: Terlizzi Daniel E. , Karlander Edward P.
Published: August 2007

Division rates of Nannochloris oculata Droop (Chesapeake Bay clone) were recorded in semicontinuous cultures grown at 81 combinations of light intensity, temperature, salinity and nitrogen source. A maximal growth rate of 2.1 doublings 1 day occurred at 30 C, 15‰ salinity with a light intensity of 11,300 lux (1.350 mW/cm2) using ammonium or urea as nitrogen sources. Several generalizations about the autecology of this organism result: (1) salinity optima were between 5–15‰ in all instances. (2) the lack of growth at 10 C and the universal improvement in growth with temperature elevation to 30 C indicates a rather high temperature optimum. (3) there is a trend of decreasing light optimum with temperature decreases below the optimum.

The source of nitrogen providing the best growth was shown to be dependent on light, temperature, salinity and interactions among these variables. For nitrate and ammonium cultures, temperature had the greatest influence on growth rate, followed by light and then salinity. For urea cultures, the order was temperature, salinity, then light. Interactions of all combinations of variables were significant with the temperature‐salinity‐light interaction most pronounced with urea cultures. Demonstration of interactions among environmental variables and nitrogen nutrition suggests that some conclusions based on surveys employing fixed variables alone may be unreliable.
31P‐NMR DIFFERENTIATION BETWEEN INTRACELLULAR PHOSPHATE POOLS IN COSMARIUM (CHLOROPHYTA)1
Authors: Elgavish A. , Elgavish G. A.
Published: August 2007

31P nuclear magnetic resonance (NMR) spectroscopy of intact Cosmarium sp. cells is presented as a suitable tool for the differentiation of intracellular accumulation pools of polyphosphates.

The cold trichloroacetic acid (TCA) insoluble fraction is shown to contain most of the total cellular phosphate in the phosphate rich Cosmarium cells. Moreover, evidence from a 31 P‐NMR study and electron microscopic observations of cold TCA treated Cosmarium cells indicate that this fraction consists mostly of polyphosphates which seem to retain the native morphological structure observed in the untreated cells. The determination of orthophosphate in the hot water extract of Cosmarium cells did not measure the polyphosphate pools. Determination of total phosphorus content in the hot water extract rendered a value three times higher than the frequently used orthophosphate determination procedure. However, as revealed by the 31P‐NMR spectra and the chemical analyses of the extract and of the treated cells, even total phosphorus in the extract measured only 30% of the total cellular phosphorus. 31P‐NMR enabled the unequivocal chemical identification of the major phosphate compounds in the hot water extract (“Surplus P”) as orthophosphate and polyphosphates of about 10 phosphate units chainlength. More than 70% of the accumulation pool of polyphosphates was still in the cells after extraction. However, the electron microscopy study revealed that the native granular structure of polyphosphates had been destroyed by the hot water extraction procedure.
INFLUENCE OF ENVIRONMENTAL FACTORS AND POPULATION COMPOSITION ON THE TIMING OF CELL DIVISION IN THALASSIOSIRA FLUVIATILIS (BACILLARIOPHYCEAE) GROWN ON LIGHT/DARK CYCLES1
Authors: Chisholm Sallie W. , Costello John C.
Published: August 2007

Cell division patterns in Thalassiosira fluviatilis grown in a cyclostat were analyzed as a function of temperature, photoperiod, nutrient limitation and average cell size of the population. Typical cell division patterns in populations doubling more than once per day had multiple peaks in division rate each day, with the lowest rates always being greater than zero. Division bursts occurred in both light and dark periods with relative intensities depending on growth conditions. Multiple peaks in division rate were also found, when population growth rates were reduced to less than one doubling per day by lowering temperature, nutrients, or photoperiod and the degree of division phasing was not enhanced. Temperature and nutrient limitation shifted the timing of the major division burst relative to the light/dark cycle.

Average cell volume of the inoculum was found to be a significant determinant of the average population growth rate and the timing and magnitude of the peaks in division rate. The results are interpreted in the context of a cell cycle model in which generation times are “quantized” into values separated by a constant time interval.
GROWTH‐INHIBITORS AND GROWTH‐PROMOTERS IN ENTEROMORPHA COMPRESS A (CHLOROPHYTA)1
Authors: Niemann Dorothea I. , Dörffling Karl
Published: August 2007

Methanol extracts from the alga Enteromorpha compressa (L.) Grev. contain substances which inhibit the elongation of Lepidium roots. Chromatographic separation of the inhibiting substances revealed that one of the inhibitory zones of the chromatograms had properties of the so‐called inhibitor β. Neither abscisic acid (ABA) nor lunularic acid proved to be responsible for the growth‐inhibiting property of this zone.

Moreover, the extracts contain substances which promote the elongation of Avena coleoptile segments. One of these substances could be tentatively identified as indole‐3‐acetic acid by thin‐layer and gas‐liquid chromatography. (In addition to indole‐3‐acetic acid a second growth‐promoting factor with the properties of the so‐called accelerator α could be detected.)
VALVE AND BAND MORPHOLOGY OF SOME FRESHWATER DIATOMS. III. PRE‐ AND POST‐AUXOSPORE FRUSTULES AND THE INITIAL CELL OFMELOSIRA ROESEANA1
Authors: Roemer Stephen C. , Rosowski James R.
Published: August 2007

Frustules of a clonal culture ofMelosira roeseanaRabenh. were examined with light and scanning electron microscopy. Vegetative valves in the post‐auxospore (full size) stage exhibit a larger width/length ratio than those in the pre‐auxospore (size‐reduced) stage. Cells form chains by linking spines of adjacent valves which occur at the periphery of the valve face‐mantle junction. Three or jour large pores occur at the center of the valve face, with the diameter of each pore tapering from the inner to the outer valve surface; these pores are often occluded by siliceous processes. Features ofM. roeseana,not shown previously forMelosira,include a “stepped” mantle, on only one of the two valves resulting from the same cell division, flattened processes attached to short siliceous stalks on the valve face, disk‐like processes on the mantle, and an open girdle band with up to eight antiligulae. Siliceous scales on the surface of the initial cell are remnants of the auxospore wall. The epivalve of the initial cell is larger in diameter than the hypovalve, and both valves lack linking spines and a step on the valve surface. The initial, cell epicingulum consists of only two bands; the hypocingulum has up to seven. Initial cells with four or more hypocingular bands divide to form new post‐auxospore filaments.Melosira roeseanashould not be included in the genusMelosiraas it is presently defined by the type species,M. nurnmuloidesC. Ag. Major differences include irregular linking spines, a closed pseudoloculate valve construction, and labiate processes on the valve face and mantle ofM. nummuloides,compared with well‐defined linking spines, a valve constructed of a basal siliceous layer perforated by poroid areolae, and labiate processes lacking on the valve ofM. roeseana.
DISTRIBUTION AND SALINITY ADAPTATIONS OF BANGIA ATROPURPUREA (RHODOPHYTA), A PUTATIVE MIGRANT INTO THE LAURENTIAN GREAT LAKES1
Authors: Sheath Robert G. , Cole Kathleen M.
Published: August 2007

In a survey of the distribution of Bangia atropurpurea (Roth) Ag. along the north and east shorelines of the Laurentian Great Lakes, it was observed that this species was concentrated in the lower lakes. Asexual reproduction by monospore formation was the only form of reproduction in these populations. First generation germlings derived from these spores grew in a wide range of salinities from 1 to 26‰, but the rate was inversely proportional to salinity. In addition, acclimation of parent plants to freshwater or marine media prior to sporulation affected growth rates of first generation germlings placed into a series of salinities. By the second and third generation, germlings with a lineage of seawater showed a preference for the higher salinities, 19 and 26‰ Plants collected in Lake Ontario exhibited no decline in photosynthetic rate as salinity was raised by 13‰ for 15 min. At 26‰ the rate was reduced by half and thylakoids were disrupted in the region of the pyrenoid. On the other hand, third generation plants with a history of seawater attained maximum photosynthetic rates at 26‰ and contained a normal thylakoid organization. Three chromosomes were observed in these plants, which agrees with some of the previous findings for marine Bangia. Origins and taxonomic status of Bangia growing In the Great Lakes are discussed in light of these findings.
POPULATION GENETICS OF SKELETONEMA COSTATUM (BACILLARIOPHYCEAE) IN NARRAGANSETT BAY1
Authors: Gallagher Jane C.
Published: August 2007

During a two year period 457 clones of the diatom Skeletonema costatum were isolated prior to and during the summer‐fall and winter‐spring blooms of this species in Narragansett Bay, R.I. Their allozyme banding patterns were examined for 5 enzyme loci. Genotypic frequencies indicated that the winter bloom populations were genetically different from the prevalent summer bloom populations of the same species. Genetic differences between seasonal blooms are as great as those found between species of terrestrial organisms, but are not accompanied by morphological variation. Although blooms have distinct prevalent forms, they are not genetically homogeneous. No single clone is ever representative of all populations of S. costatum. The dynamics of these allochronic populations appear to be governed by a form of cyclic natural selection, and are probably a regular feature of the cycles of abundance of this species in this area. These results cast doubt on some of the assumptions often made in the “autecological approach” to phytoplankton ecology. This study comprises the first quantitative examination of the population genetics of a microalga.
THE RELEASE OF GLYCOLATE BY A FRESHWATER DIATOM1
Authors: Colman Brian , Hosein Myda L.
Published: August 2007

Navicula pelliculosa (Breb) Hilse grown on 2% CO2 in air released glycolate when incubated in light in buffer pH 8.0 containing 10 mM bicarbonate. Excretion ceased about 90 min after transfer to air and no excretion was detected with air‐grown cells. These results indicate that glycolate release in this alga, as in species of other algal phyla, is an artifact of growth on high concentrations of CO2.
OPTIMUM N:P RATIOS AND COEXISTENCE OF PLANKTONIC ALGAE1
Authors: Rhee G‐Yull , Gotham Ivan J.
Published: August 2007

The optimum atomic ratio of N to P, the ratio at which one nutrient limitation changes over to the other, was determined in seven species of freshwater planktonic algae. The ratio varied over a wide range among species; the average for these species was 17. If the cellular nutrient ratios in marine species are comparable with those in freshwater organisms, Redfield's ratio of 15 is remarkably close to the average. Cellular N:P ratios varied over a 24‐h period under a light:dark cycle. The variation of the optimum ratio between species and diel change in cellular N:P ratios within a species could play an important role in population dynamics by enhancing the probability of coexistence of species.
TRACHELOMONAS HISPIDA VAR. CORONATA (EUGLENOPHYCEAE), II. ENVELOPE SUBSTRUCTURE1,2
Authors: West Larry K. , Walne Patricia L.
Published: August 2007

Envelopes of the mineralizing protist, Trachelomonas hispida var. coronata Lemm., were examined by light and electron microscopy and by electron diffraction analysis. The ellipsoidal hollow envelope is made of mineralized strands of mucilage (muci‐strands) that form a compact wall 0.2–4.0 μm thick, interspersed with numerous puncta 0.2–0.3 μm in diameter and, in some instances with tapered spines ca. 0.6 μm long and 0.7 μm wide at the base. The mucilage strands are cylindrical, anastomosing threads 20 nm thick. Electron‐dense, needle‐shaped mineral deposits form axial cores in the strands. Also, powdery granular mineral deposits are dispersed sparingly throughout the mucilage matrix. Micromicro‐electron diffraction analyses verify the crystalline nature of the needle‐shaped deposits, which are 4–9 nm thick and vary in length (20–100 nm). The mucilage strands and microcrystallites pervade the whole of the envelope matrix, including the spines, and may be preferentially oriented along the envelope surfaces.
EFFECT OF NITROGEN SUPPLY ON NITROGEN CONTENT AND GROWTH RATE OF JUVENILE MACROCYSTIS PYRIFERA (PHAEOPHYTA) SPOROPHYTES1
Authors: Wheeler Patricia A. , North Wheeler J.
Published: August 2007

The effect of nitrogen supply on nitrogen content and growth rate of juvenile Macrocystis pyrifera (L.) C. A. Agardh sporophytes was studied in two types of experiments: growth in continuously flowing mixtures of deep (nutrient‐rich) and surface (nutrient‐poor) seawater, and growth in batch cultures with alternate 7–10 day periods in deep and surface water. In the continuous flow experiments, the nitrogen content of the plants increased with the increased concentration of nitrate in the seawater. In the batch culture experiments, a lag period of 3–7 days often occurred before changes in the nitrogen supply were reflected in corresponding changes in the nitrogen content of the plants. Growth rates were a linear function of tissue nitrogen which varied between 1–3% dry weight. Saturation of growth rate as a function of tissue nitrogen did not occur, although tissue nitrogen levels did saturate as a function of external nitrate supply. Juvenile M. pyrifera sporophytes do not appear to “store” nitrogen. Total nitrogen varies from 1–6% dry weight in Laminariales and Fucales, but only some species of Laminaria appear to accumulate large pools of “surplus” nitrogen.