bluuebunny/crossref_metadata_2025 huggingface dataset:
COORDINATNE NUCLEAR AND CHLOROPLAST DIVISION IN UNILOCULAR SPORANGIA OF LAMINARIA ANGUSTATA (LAMINARIALES, PHAEOPHYCEAE)1
Authors: Motomura Taizo , Ichimura Terunobu , Melkonian Michael
Published: October 2004

ARSTRACT

Changes in the number of nuclei and chloroplasts were examined during the process of unispore formation in unilocular sporangia of Laminaria angustata. Just before meiosis, eight chloroplasts were always present in unilocular sporangial mother cells. The number of chloroplasts remained constant through meiosis. After the resulting four nuclei divided again (third nuclear division), a close association between a nucleus and a chloroplast developed among each of the eight nuclei and eight chloroplasts. The eight chloroplasts divided ahost synchronously before the synchronous division of the eight nuclei. Following the 16 nucleate stage with 16 chloroplasts and the final 32 nucleate stage with 32 chloroplasts, 32 unispores, each with a nucleus and a chloroplast, were fomd in unilocular sporangza of L. angustata. Immunofluorescence microscopy using an anti‐centrin antibody showed that two anticentrin‐stained structures (as future mitotic poles) occurred adjacent to each of the premitotic four nuclei, and each spot was located near a chloroplast. Therefore, after the third division, each of the eight nuclei established close contact with a chloroplast presumably mediated by the centrosomes.
PHYLOGENETIC ANALYSIS OFYAMAGISHLELLAANDPLATYDORINA(VOLVOCACEAE, CHLOROPHYTA) BASED ON rbcLGENE SEQUENCES1
Authors: Nozaki Hisayoshi , Ito Motomi , Sano Ryosuke , Uchida Hidenobu , Watanabe Makoto M. , Takahashi Hidenori , Kuroiwa Tsuneyoshi
Published: October 2004

Yamagishiella, based onPandorina unicoccaRayburn et Starr, is distinguished fromEudorinaby its isogamous sexual reproduction, whereasPlatydorinaexhibits anisogamous sexual reproduction. In the present study, we sequenced the large subunit of ribulose‐1,5‐bisphosphate carboxylase/oxygenase (rbcL) genes from five Japanese and North American strains of Y. unicocca (Rayburn et Starr) Nozaki, twoPlatydorina caudataKofoid strains, and two strains ofEudorina unicoccaG. M. Smith, as well as eight related colonial and unicellular species. Phylogenetic trees were constructed based on these sequence data and on previously published rbcL gene sequences from 23 volvocalean species in order to deduce phylogenetic relationships within the colonial Volvocales, with particular regard to the phylogenetic positions and status of the generaYamagishiellaandPlatydorina.Two robust monophyletic groups of the anisogamous/oogamous volvocacean species were resolved in the maximum‐parsimony tree as well as in the neighbor‐joining distance tree. One of the two groups comprises three species ofVolvoxsectionVolvox,whereas the other is composed of other sections ofVolvoxas well as of all the species ofEudorinaandPleodorina. Platydorina,however, was positioned outside these two monopliyletic groups. Therefore, derivation of thePlatydorinalineage may be earlier than that of such anisogamous/oogamous groups, or orgin of “anisogamy with sperm packets” inPlatydorinamay be independent of sperm packet evolution inEudorina, Pleodorina,andVolvox.It was also resolved with high bootstrap values that all of theY. unicoccastrains form a monophyletic group positioned outside the large monophyletic group includingEudorinaandPleodorina.These reject the possibility of the reverse evolution of isogamy from anisogamy to give rise toYamagishiellawithin the lineage of Eudorina.
DIVERSITY AND PHYLOGENETIC PLACEMENT OF BRACTEACOCCUS TEREG (CHLOROPHYCEAE, CHLOROPHYTA) BASED ON 18S RIBOSOMAL RNA GENE SEQUENCE DATA1
Authors: Lewis Louise A.
Published: October 2004

Sequence data from the nuclear small‐subunit ribosomal RNA gene was obtained for nine strains of Bracteacoccus Tereg, representing at least five morphological species and four distinct geographic locations. These, along with sequence data from two additional chlorophycean taxa, Spongiochloris spongiosa Starr and Ascochloris multinucleata Bold et MacEntee, and 48 published sequences from green algal taxa, were used to determine the phylogenetic placement of Bracteacoccus with respect to other chlorophycean green algae. Results support the monophyly of Bracteacoccus strains, contrasting with patterns observed so far for many other coccoid green algae. The range of variation among Bracteacoccus strains is similar to that of other congeners. Basal body orientation in Bracteacoccus has been interpreted as clockwise; however, the 18S data point to a relationship between Bracteacoccus and taxa with the directly opposed configuration of the flagellar apparatus. No close relationship was found to the multinucleated green coccoids with clockwise orientation of basal bodies, such as Spongiochloris, or to those with parallel basal bodies, such as Spermatozopsis. However, 18S data confirm that the motile and vegetative cells of Bracteacoccus are structurally distinct from the representatives of sphaeroplealean families currently studied. It is premature to reclassify Bracteacoccus until 18S comparisons can be made with additional sphaeroplealean taxa and with algae with similar flagellar structure such as Dictyochloris and Heterochlamydomonas.
PHYLOGENYAND HISTORICAL ECOLOGY OF THE DESMARESTIACEAE (PHAEOPHYCEAE) SUPPORT A SOUTHERN HEMISPHERE ORIGIN1
Authors: Peters Akira F. , van Oppen Madeleine J. H. , Wiencke Christian , Stam Wytze T. , Olsen Jeanine L.
Published: October 2004

Phylogenetic relationships in the Desmarestiales (Phaeophyceae) were inferred among the monotypic Arthrocladia (Arthrocladiaceae) and 27 isolates from Desmarestiaceae, representing 17 taxa of Desmarestia and the monotypic Antarctic genera Himantothallus and Phaeurus. Phaeurus and Arthrocladia were used as outgroups. Parsimony analyses of nuclear ribosomal DNA internal transcribed spacer (ITS1 and ITS2) sequences, in which gaps were both included and excluded, yielded well‐resolved trees with a consistent general branching pattern. A parallel analysis of nine morphological and life‐history characters and three ecological characters yielded a similar tree but provided little resolution in the terminal clades. The position of the monotypic Arthrocladia villosa within the Desmarestiales is consistent with monophyly for the order, but its position as the most primitive desmarestialean is not resolvable from the molecular data set. The basal position of Phaeurus, the Antarctic Desmarestia species, and Himantothallus is consistent with the hypothesis of a Southern Hemisphere origin for the family Desmarestiaceae. The more recent Northern Hemisphere “aculeata” clade evolved from an Antarctic ancestor. A “D. aculeata‐like” species was ancestral to a lineage characterized by annual sporophytes with high sulfuric acid content, which radiated into many species, widely distributed in both hemispheres. Mapping of morphological and ecological characters onto the molecular tree confirm the informativeness of sulfuric acid‐containing vacuoles and unilocular sporangial types. There is good congruence between phylogenetic tree topology and temperature impints in relation to biogeographic distribution, supporting the theory that temperature tolerance is a conservative trait.
PHYLOGENETIC AFFINITIES OF THE SARCINOCHRYSIDALES AND CHRYSOMERIDALES (HETEROKONTA) BASED ON ANALYSES OF MOLECULAR AND COMBINED DATA1
Authors: Saunders Gary W. , Potter Daniel , Andersen Robert A.
Published: October 2004

Small‐subunit ribosomal RNA nucleotide sequences were inferred for Giraudyopsis stellifera Dangeard (Chrysomeridales), as well as for Pulvinaria sp. and Sarcinochrysis marina Geitler (Sarcinochrysidales,). Phylogenetic analyses of the molecular data indicate that the former is weakly related to the Phaeophyceae/Xanthophyceae clade, whereas the latter two have affinities to the Pelagophyceae, and the Sarcinochrysidales sensu stricto is transferred to this class. A recent study proposed that the Pelagophyceae belongs to a larger assemblage of chromophytic species characterized by reduced flagellar apparatuses. Although the flagellar apparatus characterizing the Sarcinochrysidales is reduced relative to the Chysomeridaels and some other chromophytes, it is the most complicated to be associated with “the reduced flagellar apparatus” lineage. Cladistic analyses of a traditional data set (largely ultrastructural features of the flagellar apparatus) and a combined traditional/molecular data set were used to assess the evolutionary trends of reduction in the flagellar apparatus within the heterokont chromophytes.
SEASONAL PATTERNS OF PHOTOSYNTHESIS AND LIGHT‐INDEPENDENT CARBON FIXATION IN MARINE MACROPHYTES1
Authors: Cabello‐Pasini Alejandro , Alberte Randall S.
Published: October 2004

The contribution of light‐independent carbon fixation (LICF) to the overall carbon gain and the seasonal patterns of maximum photosynthesis (Pmax and LICF were characterized in a broad taxonomic range of macrophytes from Monterey Bay, California. Pmax and LICF rates (nmol C.g filtered seawater−1.min−1) varied among species and taxonomic groups examined, and as a function of tissue type in the phaeophyte Laminaria setchellii Silva (Phaeophyceae). On average, Pmax values were higher in the Rhodophyta, whereas LICF rates were greater in the Phaeophyceae. LICF rates were generally less than 5% of Pmax in the marine macrophytes studied and, as a consequence, cannot fully compensate for respiratory carbon losses, which usually are greater than 10% of Pmax. All species studied possessed the highest Pmax and LICF rates when irradiance levels were highest and decreased during periods of low incident irradiance. Seasonal patterns of Pmax and LICF in most of the macrophytes from the stenothermal environment of Monterey Bay were strongly correlated with photosynthetic photon flux rather than seawater temperature. The concomitant decrease of LICF and Pmax rates in all species examined argues against LICF playing a major role in carbon acquisition under light‐limiting conditions as suggested previously. Rather, the strong positive correlation of Pmax and LICF indicates the direct coupling of photosynthate (e.g. 3‐phosphoglyceric acid) generation with production of substrates for LICF reactions. Our results also suggest that LICF might be a useful indicator of photosynthetic metabolism in marine macrophytes.
LATITUDINAL TRENDS IN THE GROWTH AND REPRODUCTIVE SEASONALITY OF DELESSERIA SANGUINEA, MEMBRANOPTERA ALATA, AND PHYCODRYS RUBENS (RHODOPHYTA)1
Authors: Molenaar F. J. , Breeman A. M.
Published: October 2004

The seasonality of Delesseria sanguinea, Membranoptera alata, and Phycodrys rubens (Rhodophyta) was studied at Helgoland (North Sea, Germany) and Roscoff (Brittany, France). Plants were collected at bimonthly intervals, and growth and reproduction were monitored. Growth of blades was observed mainly in spring, although small blades were found on plants of M. alata and P. rubens all year round. In summer, plants started to degenerate and in autumn they became fertile. The reproductive season of D. sanguinea lasted from October to February/April at both locations, whereas reproductive plants of M. alata and P. rubens were found until April at Helgoland and until June and August, respectively, in Roscoff: Lower winter temperatures at Helgoland than at Rascoff may have caused these differences in the duration of the reproductive season. Using published data, the seasonal patterns at Helgoland and Roscoff were compared to those found at other locations (e.g. Barents Sea; Maine, USA; Isle of Man, UK) and local temperature/daylength conditions. Blade growth was synchronized across all populations and occurred in spring, when temperatures were usually still suboptimal for growth. Maximum reproduction was generally found in the colder half of the year but started earlier in autumn in the Barents Sea. Adaptive strategies in the seasonal control of growth and reproduction are discussed. Adequate timing of the history events (e.g. appearance of juveniles in spring) appears more important than maximal growth and reproduction of adults during the season with the most favorable temperatures.
FLOW VISUALIZATION AROUND SINGLE‐ AND MULTIPLE‐BLADED SEAWEEDS WITH VARIOUS MORPHOLOGIES1
Authors: Hurd Catriona L. , Stevens Craig L.
Published: October 2004

Water flow was visualized around 10 seaweeds with various morphologies to determine the onset of turbulence and to estimate the scales of motion generated by the seaweeds themselves. For single‐bladed specimens of the kelps Laminaria setchellii, Costaria costatum, Macrocystis integrifolia, and Alaria marginata, the transition from a laminar to turbulent velocity boundary layer occurred at mainstream velocities of 1.5 cm.s−1. Transition to turbulence fm multiple‐bladed specimens of M. integrifolia, Nereocystis luetkeana, Egregia menziesii, and Fucus gardneri occurred at 2.5–3 cm‐s−1 and at 5 cm.s−1 for the coarsely branched red seaweed, Gelidium coulteri. Flow features such as separation, recirculating eddies, and Von Kánncán vortex streets were observed around various morphologtcal features. We suggest that in the field, flow around larger macroalgae such as kelp is mostly turbulent and that many seaweeds will lie within the wakes of neighboring macroalgae. For small, branched seaweeds such as G. coulteri, however, the meshlike structure may damp turbulence within the thallus, thereby increasing the mainstream velocity at which the transition to turbulence occurs.
PHOTOINHIBITION AND RECOVERY AFTER HIGH LIGHT STRESS IN DIFFERENT DEVELOPMENTAL AND LIFE‐HISTORY STAGES OF LAMINARIA SACCHARINA (PHAEOPHYTA)1,2
Authors: Hanelt Dieter , Wiencke Christian , Karsten Ulf , Nultsch Wilhelm
Published: October 2004

The capacity to cope with high light stress was investigated in different life‐history and developmental stages of Laminaria saccharina Lamour. sporophytes and gametophytes. Changes in photosynthetic efficiency and in the level of photoinhibition were measured by in vivo fluorescence changes of photosystem II. Pigment content was studied using high performance liquid chromatography. Additionally, the morphology of the various developmental stages during the life cycle was studied by light microscopy in relation to the photosynthetic parameters.

High light stress (2 h, 500 μmol.m‐2.s−1) induced photoinhibition of photosynthesis with fast kinetics in older sporophytes and gametophytes. In contrast, the absolute degree of photoinhibition after light stress was higher in younger than in older sporophytes. Photosynthesis recovered faster in older sporophytes and gametophytes compared to young sporophytes. In very young sporophytes, photosynthesis did not recover fully even after 12 h exposure to low light, indicating severe photodamage. Kinetics of recovery in old sporophytes and in gametophytes showed a fast and a slow phase, whereas younger sporophytes recovered only with a slow phase, The fast phase is indicative of a decline of the photoprotective process, whereas the slow phase indicates a recovery from photodamage. The capacity to cope with high light stress in Laminaria sporophytes increased with increasing age of the thalli. The gametophytes are less sensitive to high light stress and may be selected to endure unfavorable white light conditions.

Investigation of the xanthophylls showed that the higher resistance to high light is not caused solely by a higher content of xanthophyll cycle pigments. Additionally, changes in the thallus structure during the development of the sporophytes seemed to cause a higher resistance to high light. The observed changes in the ability to cope with high light in the different life‐history and developmental stages of Laminaria saccharina may influence the distribution of the species on the shore.
THE SIGNIFICANCE OF INTRACELLULAR SELF‐SHADING ON THE BIOOPTICAL PROPERTIES OF BROWN, RED, AND GREEN MACROALGAE1
Authors: Orzymski Joe , Johnsen Geir , Sakshaug Egil
Published: October 2004

The spectral light absorption and fluorescence excitation spectra from thalli (in vivo) and thylakoid micelles (no intracellular self‐shading) from the macroalgae Laminaria digitata (L.) Edmonson, Palmaria palmata (L.) Kuntze, and Ulva sp. were examined. In all the examined species, the intracellular self‐shading (i.e. the package effect) was highly significant to the extent that absorption peaks related to individual pigments were significantly suppressed. Thus, for studies related to taxonomy and physiology, “unpacked”spectra may be more informative. Thylakoid micelle preparations offer opportunities to examine more closely species‐specific differences in the packaging effect, light harvesting and utilization, and pigmentation. As well, the thylakoid micelles, when analyzed with biochemical assays or fluoromtry, may provide insight into components of the photosynthetic machinery that are specific to different classes of mncroalgne. We present the Chl a‐specific absorption coefficients and the corresponding fluorescence excitation spectra of macroalgal thylakoid micelles for the three species.
PHACOTUS LENTICULARIS (CHLAMYDOMONADALES, PHACOTACEAE) ZOOSPORES REQUIRE EXTERNAL SUPERSATURATION OF CALCIUM CARBONATE FOR CALCIFICATION IN CULTURE1,2
Authors: Hepperle Dominik , Krienitz Lothar
Published: October 2004

In nature, zoospores of the chlamydophycean genus Phacotus Perty usually have a calcified lorica. The only cultured species, Phacotus lenticularis (Ehrenberg) Stein, did not readily calcify in artificial media. To overcome this deficiency, we developed an artificial culture medium (N‐HS) in which Phacotus lenticularis formed mineralized loricae, as under natural conditions. Calcification of Phacotus (strain Krienitz 91/1) was achieved in a medium containing the ionic concentrations found in natural habitats (i.e. Lake Haussee and Lake Stechlin), hard‐water lakes of the Baltic Lake District (Germany). The N‐HS medium contained extremely low phosphate concentrations and high calcium and magnesium concentrations compared with common culture media, but the concentrations were similar to those in the lakes. Calcium carbonate in N‐HS medium was dissolved up to the saturation concentration (saturation index = 1). Supersaturation was achieved by the addition of ultra‐alkaline compounds (Na2SiO3 or NaOH). The medium with the highest super‐saturation had a saturation index of 118 and was extremely supersaturated with respect to calcium carbonate. In that medium and in modified media with less of the sodium compounds (lower supersaturations), calcification of zoospores was observed. To determine the effects of sodium and silicon compounds on calcification, various other silicon and sodium compounds were tested but were shown to be ineffective. In conclusion, calcification of Phacotus lenticularis depends directly on the degree of calcium carbonate supersaturation of the medium, but the fundamental mineralization pattern does not. Our study shows that calcification in Phacotus lenticularis can be triggered and controlled by supersaturation of calcium carbonate.
SOURCES OF INORGANIC CARBON FOR PHOTOSYNTHESIS BY THREE SPECIES OF MARINE DIATOM1
Authors: Korb Rebecca E. , Saville Peter J. , Johnston Andrew M. , Raven John A.
Published: October 2004

The utilization of inorganic carbon by three species of marine diatom, Skeletonema costatum (Grev.) Cleve. Ditylum brightwellii (West) Grun., and Chaetoceros calcitrans Paulsen was investigated using an inorganic carbon isotopic disequilibnum technique and inorganic carbon dose‐response curves. Stable carbon isotope data of the diatoms are also presented. Observed rates of photosynthetic oxygen evolution were greater than could be accounted for by the theoretical rate of CO2 supply from the uncatalyzed dehydration of HCO3− in the external medium, suggesting use of HCO3− as an inorganic carbon source. Data from the isotopic disequilibrium experiment demonstrate the use of both HCO3− and CO2 for photosynthesis. Carbon isotope discrimination values support the use of HCO3− by the diatoms.
CHARACTERIZATION OF MORPHOSPECIES AND STRAINS OFMICROCYSTIS(CYANOBACTERIA) FROM NATURAL POPULATIONS AND LABORATORY CLONES USING CELL PROBES (LECTINS AND ANTIBODIES)1
Authors: Lópa‐Rodas Victoria , Costa Eduardo
Published: October 2004

The genus Microcystis (cyanobacteria) includes toxic and bloom‐forming morphotypes which are usually arranged into species based on morphological features. Immunofluorescence assays using polyclonal and preadsorbed antibodies, as well as FITC‐labebd lectins were used to characterize three morphospeciesof Microcystis (M. viridis, M. wesenbergii,andM. aeruginosa)from natural populations (several lakes/reservoirs in Denmark and Spain) and laboratory clones. The cell probes used were unaffected by the different phases of the cell division cycle, growth phase, or environmental factors, such as culture medium, light, or temperature. Anhbody and lectin binding patterns were specific to each clone. In nature, the cell probes were useful tools to characterizeMicrocystispopulations. Antibodies and lectins revealed geographic differentiation within the same morphospecies. Differentiation was moderate among nearby locales and intensified among areas distant from one another. Microcystis aeruginosa from Spain has very different cell surface antigens and lectin binding sites thanM. aeruginosafrom Denmark. A taxonomy ofMicrocystisbased on cell probes reveals some discrepancies with classical morphospecies. The binding affinities were more closely related to the geographic origin of the tested material than to the morphospecies identification. Different morphospecies from the same lake in some cases were more similar than the same morphospecies from different lakes. Microcystis viridis andM. aeruginosafrom Danish lakes appeared to be closely related species, whereasM. wesenbergiiemerged as a different species.
LINKAGE OF 5S RIBOSOMAL DNA TO OTHER rDNAS IN THE CHROMOPHYTIC ALGAE AND RELATED TAXA1
Authors: Kawai Hiroshi , Nakayama Takeshi , Inouye Isao , Kato Atsushi
Published: October 2004

Gene organization within the nuclear ribosomal DNA cistron and linkage of the 5S rDNA gene to the cistron were surveyed in 20 taxa of protists representing most of the Chromophyta (stramenopiles) and representatives of the Dinophyceae (alveolata) and Euglenophyceae. The intergenic spacer, which separates adjacent cistrons, was first PCR‐amplified from total DNA using primers anchored in the 3’end of the large subunit and the 5’end of the small subunit in the next downstream cistron. Presence of the 5S gene in the cistron was determined by a second round of PCR using primers anchored in the large subunit and the 5S gene. where 5S‐linked rDNA was not detected in the cistron, the presence of 5S tandem repeating units were confirmed by the PCR of 5S‐5S fragments from the total DNA. Results show that most of the Chromophyta, as well as Opalina, Proteromonas (colorless stramenopiles), Dinophyceae, and Euglenophyceae have a 5S‐linked type of rDNA organization. In contrast, only tandem repeats of 5S rDNA were detected in Bacillariophyceae and Synurophyceae. The occurrence of 5S‐unlinked rDNA is hypothesized to be the result of secondary transfer from an ancestral, linked 5S type. The 5S‐linked type of rDNA organization is apparently common in protists. Given the fact that most of these protists have mitochondria with tubular or discoid cristae, as compared with flattened cristae common in higher plants and animals, we conclude that the 5S‐linked type of rDNA diverged at a very early stage in the evolution of eukaryotes.
BIOGEOGRAPHYOF BATRACHOSPERMUM GELATINOSUM (BATRACHOSPERMALES, RHODOPHYTA) IN NORTH AMERICA BASED ON MOLECULAR AND MORPHOLOGICAL DATA1
Authors: Vis Morgan L. , Sheath Robert G.
Published: October 2004

Fifteen populations of the widespread fieshwater red alga Batrachospermum gelatinosum (L.) De Candolle were sampled throughout the geographic range in North America from central Alabama, U.S.A. (33° N), to Ellesmere Island, Northwest Territories (NWT), Canada (80° N). Analysis of ribosomal DNA internal transcribed spacer (ITS) 1 and 2 sequences yielded a parsimony tree with a large polytomy consisting of most populations plus a branch with one Nova Scotia and two NWT populations. The nucleotide variation, both within the polytomy and within the branch, was small (< 1%). The sequence divergence between the branch and polytomy was 3%. The lengths of the ITS 1 and 2 sequences of B. gelatinosum, 216–229 and 448–458 base pairs, respectively, fall within the very broad ranges reported for other red algae. The cluster analysis of 11 morphometric characteristics revealed three groupings of populations, partly based on geographic distribution. All tundra, eastern boreal forest, and mid‐western hemlock‐hardwood populations were in one grouping, whereas the deciduous forest, coastal plain, and eastern hemlock‐hardwood populations were in a second. How ever, one deciduous forest population from Rhode Island, U.S.A. was unassociated. There was considerable overlap in morphometric characteristics among the three groupings. Based on this fact and the relatively small nucleotade variation in ITS sequences, we conclude that B. gelatinosum is a morphologically variable and geographically widespread species that is a valid taxonomic entity.
CELLULAR DNA CONTENT OF MARINE PHYTOPLANKTON USING TWO NEW FLUOROCHROMES: TAXONOMIC AND ECOLOGICAL IMPLICATIONS1
Authors: Veldhuis Marcel J. W. , Cucci Terry L. , Sieracki Michael E.
Published: October 2004

Two new fluorochromes, PicoGreen® and SYTOX Green™ stain (Molecular Probes, Inc.), are useful with flow cytometry for quantitative detection of cellular DNA in a variety of marina phytoplankton. The basic instrument configuration of modern low‐power flow cytometers (15 mW, 488 nm excitation) is sensitive enough to detect the DNA signal in nearly all of the 121 strains (from 12 taxonomic classes)examined. The major advantages of these dyes over others are 1)suitability for direct use in seawater, 2)green fluorescence emission of the DNA‐dye complex (wavelength 525 ± 15 nm) showing no overlap with the autofluorescence of the plankton pigments in the red band, 3) high fluorescence yield of the DNA‐dye complex with an increase in fluorescence > 100‐fold compared to the unstained cell, and 4)dyes can be used to quantify double‐stranded DNA. The high sensitivity allowed the quantification of the DNA of the smallest known phyto‐plankter (Prochlorococcus) as well as bacteria found in some of the algal cultures. Of the 12 taxonomic classes tested, only the 3 Nannochloropsis spp. (Eustagmatophyceae) stained poorly, and a few members of the Chlorophyceae and Pelagophyceae showed poor staining occasionally. In general, maximal fluorescence was achieved within 15 min after addition of the dye. Although the PicoGreen dye stained some living phytoplankton species, preservation is recommended for quantitation. SYTOX Green did not stain live cells. The combination of the dyes, therefore, allows the discrimination between live and dead cells in some algal groups (Prochlorococcus, diatoms, prasinophytes, and pelagophytes). Paraformaldehyde was preferred over glutaraldehyde for fixation to avoid (induced) green autofluorescence.

Total DNA values measured in 90 algal species (ca. 121 strains) varied by a factor of 20,000. The lowest values were found in Prochlorococcus and the highest in a large dinoflagellate (Prorocentrum micans). DNA content appears to be a scaleable cell component covarying with the carbon and nitrogen contents of the phytoplankton cells. This covariation allows the total DNA content to be used as an accurate, independent estimate of total cell carbon biomass in unicellular pelagic phytoplankton.
NONDESTRUCTIVE TRACING OF MIGRATORY RHYTHMS OF INTERTIDAL BENTHIC MICROALGAE USING IN VIVO CHLOROPHYLL A FLUORESCENCE1,2
Authors: Serôdio João , Marques da Silva Jorge , Catarino Fernando
Published: October 2004

In vivo chlorophyll (Chl) a fluorescence was measured in undisturbed intertidal sediments with the purpose of tracing the vertical migratory rhythms of benthic microalgae. A pulse amplitude fluorometer, an instrument which does not require physical contact with the sample, was used, thus allowing successive measurements to be taken on the same sample without causing any type of disturbance to the sediment structure. The basis of the method is the possibility to detect changes in the Chl a concentration near the sediment surface caused by the vertical movement of the microalgae. This requires the verification of two conditions: the possibility to follow changes in the sediment Chl a content from fluorescence intensity, and a sediment photic depth smaller than the vertical distances covered by the moving microalgae. Both conditions were experimentally verified in intertidal muddy sediments of the Tagus estuary, Portugal. In vivo fluorescence was shown to vary linearly with the sediment Chl a content, and the sediment photic depth was estimated to reach 0.27 mm, a value clearly smaller than the reported depths for microalgal migrations. Sediment samples kept under in situ conditions exhibited large hourly Variations (over 400%) in the Chl a fluorescence intensity, which were closely synchronized with the daytime periods of emersion. The rhythmic fluctuations in Chl a fluorescence were confirmed further to represent microalgal migration by (1) its endogenous nature (fluorescence continued to follow diurnal and tidal cycles after removal of environmental stimuli), (2) its dependence on the vertical distribution of the microalgal population within the sediment (vertically homogenized samples failed to display fluorescence variations), and (3) the lack of significant temperature and light effects on the fluorescence emission under in situ conditions (tested in three species representative of the main groups found in the studied microphytobenthic communities—the diatom Phaeodactylum tricornutum (Böhlin), the cyanobacterium Spirulina maxima (Setch. et Gard.), and the euglenophyte Euglena granulata (Klebs) Lemm.). The results obtained indicate that, in spite of the potential concurrent effects of factors other than the Chl a concentration on the fluorescence intensity, in vivo Chl a fluorescence can be used to trace nondestructively the migratory behavior of benthic microalgae.
GENETIC VARIABILITY AND SPATIAL SEPARATION IN THE SEA PALM KELP POSTELSIA PALMAEFORMIS (PHAEOPHYCEAE) AS ASSESSED WITH M13 FINGERPRINTS AND RAPDS1
Authors: Coyer James A. , Ohen Jeanine L. , Stam Wytze T.
Published: October 2004

Postelsia palmaeformis Ruprecht is an annual species, occuring from southern California to Vancouver Island, Canada, in upper intertidal sites exposed to extreme wave shock. Because of its limited spore dispersal, discrete and inbred populations are likely on the local scale, yet dispersal of drifting and fertile thalli raises the possibility of outbred populations on a regional scale. M13 minisatellite DNA fingerprinting and random amplified polymorphic DNA (RAPD) marks were used in a complementary fashion to investigate genetic variability among 24 individuals on scales of clusters (= coalesced holdfasts). < 1 m, 10 m, 25 m, 16 km, and 250 km. Based on M13 fingerprinting, genetic relatedness within clusters was extremely high. Three of six clusters had at hast two identical individuals, and similarity values within five clusters were ≧0.90. Similarities between two of three clusters separated by < 1 m were significantly higher than between cluster pairs separated by 25 m and 250 km: however, the similarity between two clusters separated by 25 m was equivalent to the similarity between two clusters separated by 250 km. Thus, genetic relatedness as determined by M13 fingerprinting generally decreased as distance increased to 25 m. Conversely, RAPD data easily discriminated populations separated by 16 and 250 km but were not useful in discriminating individuals from < 1 to 25 m. Results from the complementary data sets suggest that most dispersal occurs over distances of 1–5 m, individuals within a cluster are siblings, and distinguishable biogeographic populations are present along the coast.
EXCYSTMENT AND GROWTH OF CHRYSOPHYTES AND DINOFLAGELLATES AT LOW TEMPERATURES AND HIGH SALINITIES IN ANTARCTIC SEA‐ICE1
Authors: Stoecker Diane K. , Gustafson Daniel E. , Merrell Jeffrey R. , Black Megan M. D. , Baier Christine T.
Published: October 2004

Extreme environmental conditions have been thought to limit algal growth in the upper sea‐ice. In McMurdo Sound, Antarctica, chrysophyte statocysts (stomatocysts) and dinoflagellate hypnozygotes (resting cysts) overwinter in first‐ and second‐year land‐fast sea‐ice exposed to temperatures of ‐20° C or lower. In early November, when temperatures in the upper ice are < −8°C and brine salinities are >126 psu, dinoflagellate cysts activate and shortly thereafter excyst. During early November, chrysophyte statocysts also begin to excyst. Net daily primary production occurs in the sea‐ice brine at temperatures as low as −7.1° C, at brine salinities as high as 129 psu, and at average photon flux densities as low as 5 μmol photons.m−2.s−1. Dinoflagellate densities were >106 vegetative cells.L−1 of ice while temperatures in the upper ice were between −6.8 and −5.8° C and brine salinities were ∼100 psu. Chrysophyte densities reached >106.L−1 of ice by early December. High densities of physiologically active clyo‐ and halotolerant algae can occur in the upper land‐fast sea‐ice under extreme conditions of temperature and salinity.
THE IDENTIFICATION AND PURIFICATION OF A CELL‐SURFACE ALKALINE PHOSPHATASE FROM THE DINOFLAGELLATE PROROCENTRUM MINIMUM (DINOPHYCEAE)1
Authors: Dyhrman Sonya T. , Palenik Brian P.
Published: October 2004

Two cell‐surface proteins were identtjied in the dinoflagellate Prorocentrum minimum (Pavillard) Schilkr strain CCMP 1329 that are evident in phosphate‐limited cultures, but not in nitrate‐limited cultures or cultures growing exponentially in complete media. These proteins were detected by labeling cell‐surface proteins with the biotinylating reagent succinimidyl 6‐(biotinamido) hexanoate. One protein, of appoximately 200,000 daltons was purified using differential centrifugation, detergent extraction, and gel filtration chromatography. This purified protein was able to hydrolyze orthophosphate groups from p‐nitrophenylphosphate at pH 8, indicating it is an alkaline phosphatase, although it is larger than other alkaline phosphatases isolated to date tom most microorganisms. This protein may be induced to help P. minimum cleave orthophosphate groups from organic forms of phosphate in marine environments. Ultimately, this protein could represent a unique antigen for developing an antibody probe for examining the relationships between phosphate stress and bloom formation in P. minimum, and perhaps other dinoflagellates, in the field.
IDENTIFICATION OF CYLINDROSPERMOPSIN IN APHANIZOMENON OVALISPORUM (CYANOPHYCEAE) ISOLATED FROM LAKE KINNERET, ISRAEL1
Authors: Banker R. , Carmeli S. , Hadas O. , Teltsch B. , Porat R. , Sukenik A.
Published: October 2004

Aphanizomenon ovalisporum (Forti) was identified and isolated from Lake Kinneret upon its first appearance as a dominant bloom in late 1994. This cyanobacterial species, not previously known to be toxic, was evaluated by a commonly used mouse bioassay and was demonstrated to induce toxic symptoms that were distinguishable from the typical symptoms of the neurotoxins previously reported in Aphanizomenon flos‐aquae (L.) Ralfs. Mice died 5–24 h after crude extracts were injected intraperitoneally, and the LD50 value was estimated as 465 mg dry wt biomass · kg−1 mouse. A toxicity‐guided fractionation of the active extract indicated that the potent substance is polar an nature. The structure of the active compound was determined by its mass spectrometry and NMR data. The compound was found to be the sulfate‐guanidinium zwitterion, cylindrospermopsin, previously isolated from the cyanobacterium Cylindrospermopsis raciborskii (Woloszynska) and recently also reported in Umezakia natans (Watanabe). This is the first time that Aphanizomenon ovalisporum has been reported to contain a toxic compound.
GROWTH, PHYSIOLOGY, AND ULTRASTRUCTURE OF A DIAZOTROPHIC CYANOBACTERIUM, CYANOTHECE SP. STRAIN ATCC 51142, IN MIXOTROPHIC AND CHEMOHETEROTROPHIC CULTURES1
Authors: Schneegurt Mark A. , Sherman Debra M. , Sherman Louis A.
Published: October 2004

The growth, physiology, and ultrastructure of the marine, unicellular, diazotrophic cyanobacterium, Cyanothece sp. strain ATCC 51142, was examined under mixotrophic and chemoheterotrophic conditions. Several organic substrates were tested for the capacity to support heterotrophic growth. Glycerol was the only substrate capable of enhancing mixotrophic growth in the light and supporting chemoheterotrophic growth in the dark. Dextrose enhanced mixotrophic growth but could not support chemoheterotrophic growth. Chemoheterotrophic cultures in continuous darkness grew faster and to higher densities than photoautotrophic cultures, thus demonstrating the great respiratory capacity of this cyanobacterial strain. Only small differences in the pigment content and ultrastructure of the heterotrophic strains were observed in comparison to photoautotrophic control strains. The chemoheterotrophic strain grown in continuous darkness and the mixotrophic strain grown in light/dark cycles exhibited daily metabolic oscillations in N2 fixation and glycogen accumulation similar to those manifested in photoautotrophic cultures grown in light/dark cycles or continuous light. This “temporal separation” helps protect O2‐sensitive N2 fixation from photosynthetic O2 evolution. The rationale for cyclic glycogen accumulation in cultures with an ample source of organic carbon substrate is unclear, but the observation of similar daily rhythmicities in cultures grown in light/dark cycles, continuous light, and continuous dark suggests an underlying circadian mechanism.
THE ZYGOSPORE WALL OF CHLAMYDOMONAS MONOICA (CHLOROPHYCEAE): MORPHOGENESIS AND EVIDENCE FOR THE PRESENCE OF SPOROPOLLENIN1
Authors: VanWinkle‐Swift Karen P. , Rickoll Wayne L.
Published: October 2004

Chlamydomonas monoica Strehlow is being developed as a model for genetic analysis of zygospore morphogenesis, and many relevant mutant strains are available. To provide the basis for interpreting the ultrastructural phenotypes of zygospore mutants, an analysis of wall morphogenesis in wildtype zygospores of C. monoica was undertaken. Following synthesis of a thick, fibrous, primary zygote wall, granular material accumulated between the plasma membrane and the primary zygote wall and aggregated into a repetitive array of electron‐opaque fibrous stripes. A new wall layer, the outer layer of the secondary zygospore wall, first appeared as segments with a fibrous outer surface overlying a well‐defined band of electron‐translucent material. These segments gave rise to an intact sheath adjacent to the plasma membrane. Beneath this sheath, electron‐opaque material (forming the inner layer of the secondary zygospore wall) accumulated unevenly and forced the surface sheath to undulate, creating a pattern of peaks and valleys that was exposed to the external environment 4 rupture and release of the primary zygote wall. The zygospore wall included material resistant to degradation by potassium hydroxide, 2‐aminoethanol, and acetolysis, but it was destroyed by exposure to chromic acid. These characteristics, in combination with the autofluorescence of untreated zygospore walls and their failure to stain with phloroglucinol, suggest that sporopollenin may be responsible for many of the resistant properties associated with the mature zygospore of Chlamydomonas.
PORGUENIA PERUVIANA GEN. ET SP. NOV., A MARINE CENTRIC DIATOM WITH AN UNUSUAL OCELLUS1
Authors: Sullivan Michael J.
Published: October 2004

A new diatom genus and species, Porguenia peruviana Sullivan, is described from an Eocene marine deposit from the Paracas Peninsula, Peru. The value outline is circular and the areolation is best described as pseudoloculate; spines of any type are lacking. A ring of elongated, densely packed rimoportulae is situated on the secondary marginal ridge. Externally, each rimoportula consists of a long, flattened, fluted upper portion supported by a shorter cylindrical stalk. The processes are winged and exhibit various degrees of curvature of the major axis. Typically, six reniform ocelli of unusual structure are situated centrifugally to the ring of rimoportulae and interrupt the true marginal ridge. Because the perforation plate differs from that of all other ocellus‐bearing diatoms, a new term has been introduced for this structure, the diaphoron. The placement and structure of this newly discovered “perforation plate” do not allow Porguenia to be placed in any circumscribed family, although the Triceratiaceae would appear at present to be the most closely related family.
SEASONAL EFFECT ON THE RELATIONSHIP BETWEEN THE PHOTOSYNTHETIC CAPACITY OF INTERTIDAL MICROPHYTOBENTHOS AND TEMPERATURE1
Authors: Blanchard Gérard F. , Guarini Jean‐Marc , Gros Philippe , Richard Pierre
Published: October 2004

The response of the photosynthetic capacity (Pmax) of microphytobenthos to short‐term variations of temperature (in the range 5–35° C) was assessed on a seasonal basis. The relationship is described mathematically, and relevant physiological parameters are identified: PMAX, the maximum value of Pmax achieved at Topl, the optimum temperature. Estimated values of Topt do not change significantly throughout the year and remain close to 25° C. It is thus concluded that Topt is not influenced by seasonal variations in the daily range of mud surface temperature. Identical conclusions hold for Tmax (ca. 38° C), the thermal threshold beyond which no photosynthesis occurs. Conversely, PMA estimates exhibit substantial variability: PMAX (mean ± root mean square error) is highest in April (11.18 ± 0.42 [μg C · [μg Chl a]−1· h−1) during the beginning of the annual increase in temperature, photoperiod, and maximum irradiance and is lowest in December (3.04 ± 0.16 μg C · [μg Chl a]−1· h−l). From an ecological point of view, the short‐term and seasonal variations of PMAX suggest that the microphytobenthic community takes advantage of the abiotic spring environmental conditions, allowing the onset of the bloom. Nevertheless, no “acclimation strategy” (i.e. shifts in Topt and Tmax that prevent temperature inhibition in summer or improve photosynthetic rates in winter) is apparent from our results.
PRIMARY PRODUCTION, CALCIFICATION, AND AIR‐SEA CO2 FLUXES OF A MACROALGAL‐DOMINATED CORAL REEF COMMUNITY (MOOREA, FRENCH POLYNESIA)1
Authors: Gattuso Jean‐Pierre , Payri Claude E. , Pichon Michel , Delesalle Bruno , Frankignoulle Michel
Published: October 2004

Community metabolism and air‐sea carbon dioxide (CO2) fluxes were investigated in July 1992 on a fringing reef at Moorea (French Polynesia). The benthic community was dominated by macroalgae (85% substratum cover) and comprised of Phaeophyceae Padina tenuis (Bory), Turbinaria ornata (Turner) J. Agardh, and Hydroclathrus clathratus Bory (Howe); Chlorophyta Halimeda incrassata f. ovata J. Agardh (Howe); and Ventricaria ventricosa J. Agardh (Olsen et West), as well as several Rhodophyta (Actinotrichia fragilis Forskál (Børgesen) and several species of encrusting coralline algae). Algal biomass was 171 g dry weight· m−2. Community gross production (Pg), respiration (R), and net calcification (G) were measured in an open‐top enclosure. Pg and R were respectively 248 and 240 mmol Co2·m−2·d−1, and there was a slight net dissolution of CaCO3 (0.8 mmol · m−2·d−1). This site was a sink for atmospheric CO2 (10 ± 4 mmol CO2·m−2·d−1), and the analysis of data from the literature suggests that this is a general feature of algal‐dominated reefs. Measurement of air‐sea CO2 fluxes in open water close to the enclosure demonstrated that changes in small‐scale hydrodynamics can lead to misleading conclusions. Net CO2 evasion to the atmosphere was measured on the fringing reef due to changes in the current pattern that drove water from the barrier reef (a C02 source) to the study site.
PATTERNS OF REPRODUCTION, GENETIC DIVERSITY, AND GENETIC DIFFERENTIATION IN CALIFORNIA POPULATIONS OF THE GENICULATE CORALLINE ALGA LITHOTHRIX ASPERGILLUM (RHODOPHYTA)1
Authors: Pearson Elizabeth A. , Murray Steven N.
Published: October 2004

The reproductive composition and genetic diversity of populations of the red seaweed Lithothrix aspergillum Gray (O. Corallinales) were studied at three southern California sites (Shaw's Cove and Treasure Island, Laguna Beach; Indian Rock, Santa Catalina Island) and at a fourth site (Bodega Bay) located in northern California. Sexually reproducing populations were confined to southern California. Diploid individuals were numerically dominant over haploid (gametophytic) individuals at all sites. Intertidal and subtidal subpopulations from Shaw's Cove differed in their reproductive profiles. Most intertidal specimens found on emersed surfaces were densely branched, turf‐forming, and bore tetrasporangial (68.6%), carposporangial (11.4%), or spermatangial (5.7%) conceptacles, reflecting a sexual life history; none produced asexual bispores. In contrast, 74.3% of the larger, loosely branched subtidal specimens bore bisporangial conceptacles indicative of asexual reproduction. Nearly 70% of the Indian Rock thalli showed no evidence of conceptacle formation. Only asexual, diploid bispore‐producing thalli were obtained from the Bodega Bay site. Genetic diversity (mean number of alleles per locus, percent of polymorphic loci, and average expected heterozygosity) of diploid L. aspergillum populations varied with life‐history characteristics and geographic location. A total of 30 alleles was inferred from zymograms of 16 loci examined by starch‐gel electrophoresis; of these loci, 11 were polymorphic. The genetic diversity of sexual, diploid populations of L. aspergillum (alleles per locus [A/L] = 1.4‐1.5; percent polymorphic loci [%P] = 37.5‐50.0) was relatively high compared with other red seaweeds. Lowest diversity (A/L = 1.0; %P = 0.0) occurred in the exclusively asexual Bodega Bay population which consisted of genetic clones. All sexual L. aspergillum populations deviated significantly from Hardy‐Wein‐berg expectations due to lower than expected heterozygosity. Genetic differentiation (Wright's Fstatistic [FST]; Nei's Genetic Distance [D]) among sexually reproducing southern California populations was low (FST= 0.030) on a local scale (ca. 5 km), suggesting high levels of gene flow, but high genetic differention (FST= 0.390 and 0.406) occurred among southern California populations separated by ca. 70 km. Very high genetic differentiation (FST= 0.583–0.683) was obtained between northern and southern California populations separated by 700–760 km. Our genetic and reproductive data suggest that the L. aspergillum population from Bodega Bay is sustained by perennation, vegetative propagation, or asexual reproduction by bispores and may represent an isolated remnant or a population established by a founder event.