bluuebunny/crossref_metadata_2025 huggingface dataset:
ENVIRONMENTAL FACTORS INFLUENCING DIATOM CELL MOTILITY1
Authors: Cohn Stanley A. , Disparti Nicholas C.
Published: October 2004

This article describes the effect of various environmental conditions on the speed of freshwater diatoms. The diatoms display a wide distribution of cell speeds, from 0 to > 20 μm·s−l, as indicated by both the distribution of speeds within a cell population as well as the distribution of 1‐s interval speeds of individual cells. Cell length has little or no effect on cell speed, as the speed of large postconjugal populations ofCraticulaand smaller preconjugal cell populations were not significantly different. The diatoms showed a broad pH tolerance, withCraticula spp.andNitzschia spp.displaying active motility between pH 3 and 12 and pH 4 and 10, respectively, with velocity maxima for both species at approximately pH 7. In contrast to previous reports on marine diatoms, these freshwater diatoms do not require millimolar levels of external calcium for motility, as bothCraticula spp.andNitzschia spp.showed significant motility in distilled water (<0.5 μM calcium) for up to 5 h. Although addition of ≥500 μM of EGTA inhibited motility, this inhibition did not appear to be due to calcium chelation, as EGTA solutions preincubated with up to 20‐fold excess calcium, magnesium, or both still inhibited motility with the same dose‐dependent response as EGTA alone. Moreover, significant motility was restored by rinsing EGTA‐treated cells in distilled water, Ca‐free medium, or regular diatom medium. The calcium channel inhibitors lanthanum and ruthenium red also inhibited motility in a dose‐dependent manner, suggesting that regulation of internal calcium stores may be important in motility.Craticulamotility also declines rapidly in medium ≥50 mOsM while the isotonic concentration appears to be 100–120 mOsM, suggesting that movement may require the plasma membrane to be exerting a force ≥50–70 mOsM osmotic pressure (1–1.5 atm) against the cell wall.
EFFECT OF TEMPERATURE AND IRRADIANCE ON GROWTH OF HAEMATOCOCCUS PLUVIALIS (CHLOROPHYCEAE)1
Authors: Fan Lu , Vonshak Avigad , Boussiba Sammy
Published: October 2004

The growth characteristics of Haematococcus pluvialis Flotow were determined in batch culture. Optimal temperature for growth of the alga was between 25° and 28°C, at which the specific growth rate was 0.054 h−1. At higher temperatures, no cell division was observed, and cell diameter increased from 5 to 25 μm. The saturated irradiance for growth of the alga was 90 μmol quanta · m−2·s−1; under higher irradiances (e.g. 400 μmol quanta·m−2·s−1) astaxanthin accumulation was induced. Growth rate, cell cycle, and astaxanthin accumulation were significantly affected by growth conditions. Careful attention should be given to the use of optimal growth conditions when studying these processes.
VARIABILITY OF PHOTOSYSTEM II QUANTUM YIELD AND RELATED PROCESSES IN CHLORELLA PYRENOIDOSA (CHLOROPHYTA) ACCLIMATED TO AN OSCILLATING LIGHT REGIME SIMULATING A MIXED PHOTIC ZONE1
Authors: Kroon Bernd M. A.
Published: October 2004

The regulation of photosystem II (PSII)‐related parameters was characterized for Chlorella pyrenoidosa Chick grown in continuous nutrient‐replete culture and acclimated to a light field simulating fluctuations of a natural environment. The maximum quantum yield for charge separation at PSII showed a light‐driven decrease during the first half of the photoperiod when incident irradiance (integrated hourly) was increasing to a midday maximum, This change was accompanied by a decrease in the effective cross‐section for all PSIIs and the connectivity between PSIIs, while the cross‐section for inactive centers increased. Furthermore, a decrease in the number of active PSII centers and the amount of QB bound to D1 became evident. During the second half of the day, as irradiance declined toward the end of the photoperiod, all the observed changes in PSII photochemistry were reversed. The low quantum yield values at the middle of the photoperiod returned to 85% of the value at the end of the photoperiod by the addition of far‐red light, suggesting that a State I–II–I transition took place during the day. Measured rates of oxygen production correlated well with fluorescence‐derived estimates of photosynthesis. The overall results suggest that PSII photochemistry is optimized to minimize the susceptibility to photoinhibition and to allow balanced growth under fluctuating irradiation and that the impact of these alterations on primary production can be adequately monitored through bio‐optical measurements alone.
TAXONOMY AND ULTRASTRUCTURE OFGOMPHONEIS MESTASP. NOV. (BACILLARIOPHYTA), A NEW EPILITHIC DIATOM FROM THE MESTA RIVER, BULGARIA1
Authors: Passy‐Tolar Sophia I. , Lowe Rex L.
Published: October 2004

A new species from the diatom genusGomphoneis, G. mesta, was described following morphological and ultra‐structural analyses of its frustules by light and scanning electron microscopy. The valve striation consisting of double rows of areolae and the presence of longitudinal lines dictate the systematic position of this taxon in the genusGomphoneis.The set of features that distinguishesG.mesta from allied taxa is small valves, 26.5–81.6 μm in length and 7–12.5 μm in width, lanceolate to clavate shape, with a broadly lanceolate axial area, and longitudinal lines positioned next to the valve margins, thus contributing to a general thickening of the valve outline. When compared to other members of the genus,G. mestamost resemblesG. magnaKociolek & Stoermer.Gomphoneis mestadominates the epilithic community, growing in the Cherna Mesta, a pristine high‐mountainous tributary of the Mesta River in Bulgaria. The species has been also found as small populations in all other benthic habitats of the Cherna Mesta and in a few locations along the Mesta River.
A LOW‐VOLUME FLOW TANK FOR MEASURING NUTRIENT UPTAKE BY LARGE MACROPHYTES1
Authors: Hurd Catriona L. , Quick Michael , Stevens Craig L. , Laval Bernard E. , Harrison Paul J. , Druehl Louis D.
Published: October 2004

A recirculating flow‐tank was designed and tested to measure inorganic nutrient uptake by, and visualize the movement of seawater around, large macrophytes. The tank volume was small (46 L), and a propeller drive produced unidirectional mean flow. A turbulence reduction section dampened turbulence in the test section to a low level, so that water movement within this region was virtually laminar. The test section of the tank was wider than that of previous designs, allowing whole blades of Macrocystis integrifolia Bory and juvenile plants of Nereocystis luetkeana (Mert.) Post, et Rupr. to be placed in the flow, away from the influence of velocity boundary layers associated with the tank walls. The tank's use in macroalgae nutrient uptake and flow visualization experiments was demonstrated.
EVOLUTION OF THE ANTARCTIC MARINE BENTHIC ALGAL FLORA
Authors: Clayton Margaret N.
Published: October 2004

There are many logistic difficulties associated with studying Antarctic marine algae and, as a consequence, the taxonomic information available is far from comprehensive and any generalizations should be regarded with caution. The Antarctic marine benthic flora is characterized by a low species richness. Biogeographical characteristics of the flora are outlined. There is a high degree of endemism, possibly around 35–40%. Other major floristic elements are a group of species with a distribution extending to Tierra del Fuego and subantarctic islands, a group spread through temperate regions of the Southern Hemisphere, and a cosmopolitan group. Ecological observations show that ice has a major effect on the occurrence and distribution of algae, and ecophysiological studies indicate that Antarctic macroalgae possess various adaptations to ice, low temperatures, and strongly seasonal light conditions. Possible trends in the evolution of the Antarctic benthic marine flora, including a reduction in species richness and the origins of biogeographical links with subantarctic and temperate regions of the Southern Hemisphere, are discussed in the context of tectonic and climatic changes over the past 100 million years. A comparison is made with studies on the evolution of shallow‐water marine fauna.
BIOGEOGRAPHIC ANALYSIS OF THE ARMORED PLANKTONIC DINOFLAGELLATECERATIUMIN THE NORTH ATLANTIC AND ADJACENT SEAS1
Authors: Dodge John D. , Marshall Harold G.
Published: October 2004

The distribution of the dinoflagellate genusCeratiumSchrank (Dinophyceae) in the North Atlantic and adjacent seas was studied by a combination of new observations on a large number of plankton samples collected from the northeastern Atlantic and North Sea, data from cruises off the east coast of North America and Caribbean Sea, and reports in the literature of the past 90 years. Seventy species were recorded, and their distribution was examined by several methods. Distribution maps were plotted for all species, and from these the ranges of temperature tolerance were derived. The 240 sets of data, which took the form of lists of species present in 5° latitude / longitude blocks obtained from the new work and the published material, were analyzed by clustering and ordination multivariate techniques using the programs Twinspan and Decorana.

Analysis of the individual species showed that surface water temperature is the most important factor determining distribution and the number of species in a particular area. Warm water and /or low latitudes have many more species than cold waters and/or high latitudes. For example, at 5°N there are on average 23 species per block, whereas at 60° N there are only 8 species. On the basis of this work, theCeratiumspecies are divided into Group 1, Arctic‐temperate species normally only found in water of less than 15°C; Group 2, cosmopolitan species, which are found virtually everywhere and are the species most likely to form blooms or “brown water”; Group 3, intermediate species, which extend into neither the coldest nor the warmest water; Group 4, temperate‐tropical species, which have a lower temperature boundary of 5°–12° C; Group 5, warm‐temperate‐tropical species with a lower temperature boundary of 14°–15°C; and Group 6, tropical species, which are rarely found in water of less than 20° C.

Analysis of the sample sites also confirmed the predominant influence of temperature, and the Atlantic Ocean was divided into four biogeographical zones of which the boundaries follow isotherms of surface water temperature. Zone 1 consists of the Arctic and subarctic area, with the southern boundary closely following the 10° mean annual temperature (MAT) line. Zone 2 is an intermediate or cold‐temperate zone, of which the southern boundary follows the winter 10° C MAT isotherm or the similarly placed summer 15° isotherm. Zone 3 is the warm‐temperate or subtropical zone, which is very broad. The southern boundary closely follows the 25°C summer isotherm. Zone 4 is the tropical zone, where water temperature is never likely to be much less than 23°C. These findings are discussed in relation to experimental work and environmental observations. We suggest that the genusCeratiumprovides an excellent tool for defining ocean currents and temperature changes and may become of value in studies of global change.
BUOYANCY REGULATION IN THE COLONIAL DIAZOTROPHIC CYANOBACTERIUM TRICHODESMIUM TENUE: ULTRASTRUCTURE AND STORAGE OF CARBOHYDRATE, POLYPHOSPHATE, AND NITROGEN1
Authors: Romans Kristen M. , Carpenter Edward J. , Bergman Birgitta
Published: October 2004

Trichodesmium tenue Wille (1904) was examined using transmission electron microscopy to determine the role of carbohydrate, phosphorus, and nitrogen storage in buoyancy regulation. Carbohydrate storage area (mean = 2.06 ± 0.61 [SE] μm2; 6.62% of total cell area) in negatively buoyant colonies (NBCs) was significantly higher (P < 0.001) than in positively buoyant colonies (PBCs) (mean = 0.38 ± 0.06 μm2; 0.73%). Distinct diel periodicity of carbohydrate content was found in NBCs demonstrated by an increase from darkness to afternoon. Polyphosphate content was significantly higher (P < 0.001) in NBCs, with a mean of 0.44± 0.10 μm2 (1.54%), as compared to PBCs, with a mean of 0.14 ± 0.05 μm2 (0.24%). Polyphosphate content increased in NBCs from morning to evening, and PBCs had a 10% decrease from morning to afternoon. Calculations indicated that averaged effects of polyphosphate on increased cell density is approximately 20% of that from carbohydrate accumulation. Density contribution due to ballast weight of carbohydrate and polyphosphate indicated that NBCs were 12 times more dense than PBCs. Mean area of cyanophycin granules (N storage) was not significantly different between PBCs and NBCs. In conclusion, Trichodesmium tenue can regulate buoyancy by carbohydrate ballasting similar to that noted in limnetic cyanobacteria. Polyphosphate storage and possibly nitrogen storage products play a significant role in buoyancy regulation.
TEMPERATURE‐DEPENDENT CHANGES IN COLONY SIZE OF THE FRESHWATER PENNATE DIATOM ASTERIONELLA FORMOSA (BACILLARIOPHYCEAE) AND THEIR POSSIBLE ECOLOGICAL IMPLICATIONS1
Authors: Hayakawa Toshiyuki , Kudoh Sakae , Suzuki Yoshihiro , Takahashi Masayuki
Published: October 2004

Changes in colony size (cell number per colony) of Asterionella Formosa Hass. were experimentally evaluated in relation to water temperature using two types of clones having colony sizes of four or eight cells. The clones were isolated from two different temperate freshwater lakes. Both clones showed the same general trend with changing temperature. Most of the colonies were normal in size at low temperatures, but colony size was twice as large at high temperatures. Variable colony sizes were present at low percentages. Colony separation occurred at the oldest connection within the colony after cell division. Culture experiments showed that the rates of specific growth and colony separation were balanced except for a rather short period of time when the temperature was changed. Optical and scanning electron micrography did not show any distinctive morphological structure at the point of connection except for porelli and mucilage pads. Seasonal changes in colony size of A. formosa observed in a freshwater lake are discussed based on these temperature results.
IDENTIFICATION OF MARINE DINOFLAGELLATES USING FLUORESCENT LECTINS1
Authors: Costas Eduardo , Rodas Victoria López
Published: October 2004

Toxic and nontoxic species of marine dinoflagellates were characterized using fluorescent lectins. Lectin binding was detected by epifluorescence as well as spectrofluorometry. The binding assay of fluorescent lectins readily differentiated between morphologically similar species (i.e the toxic dinoflagellate Gymnodinium catenatum and the nontoxic Gymnodinium sp.). Lectins appear to be a useful tool to distinguish among different clones of the same species and, thus, possibly as a tool in dinoflagellate identification. Moreover, the lectins used show that thecate species have more binding sites and diversity in glycan moieties than athecate species.
MORPHOLOGY, PLOIDY, PIGMENT COMPOSITION, AND GENOME SIZE OF CULTURED STRAINS OFPHAEOCYSTIS(PRYMNESIOPHYCEAE)1
Authors: Vaulot Daniel , Birrien Jean‐Louis , Marie Dominique , Casotti Raffaella , Veldhuis Marcel J. W. , Kraay Gijsbert W. , Chrétiennot‐Dinet Marie‐Josèphe
Published: October 2004

We examined cell morphology, ploidy level, cell size, pigment composition, and genome size in 16 cultured strains ofPhaeocystisLagerheim. Two strains originated from the Antarctic, 3 from the tropical Western Atlantic, and 11 from temperate regions (Eastern Atlantic, English Channel, North Sea, and Mediterranean Sea). Thirteen strains made colonies morphologically similar toP. glo‐bosaScherffel, whereas three never formed colonies under any circumstances. Five‐rayed star‐like structures with filaments were observed in 11 strains. In several strains, two ploidy levels were observed, one (haploid) linked to flagellates and one (diploid) linked to colonies. Cell size did not appear to be a very good criterion for distinguishing strains since size distributions overlapped. Pigment analysis by reversed‐phase‐high‐performance liquid chroma‐tography allowed the strains to be grouped into three clusters that differed from each other mainly by the relative proportions of three carotenoids: fucoxanthin, 19′‐hex‐anoyloxyfucoxanthin, and diadinoxanthin. All strains contained low levels of 19′‐butanoyloxyfucoxanthin. Differences in genome size measured by flow cytometry delimited at least five groups. On the basis of both pigment composition and genome size, six clusters were defined, one corresponding to an Antarctic species (possibly P. antarc‐tica), one toP. globosa, and the rest probably to several yet‐undescribed species or subspecies. Two main conclusions emerge from this study. First, the taxonomy of the genusPhaeocystisneeds to be clarified through a combination of morphological, biochemical, and molecular studies. Second, sexuality is a prevalent phenomenon inPhaeocystis, but controls of the sexual cycle are most likely strain‐dependent.
PSEUDO‐NITZSCHIA AS A GENUS DISTINCT FROM NITZSCHIA (BACILLARIOPHYCEAE)1
Authors: Hasle Grethe Rytter
Published: October 2004

Morphologic, diagnostic characters of the subgenus Nitzschia, genus Nitzschia Hassall 1845, and the marine planktonic genus Pseudo‐nitzschia H. Peragallo in H. & M. Peragallo 1900 were compared. Colony formation by overlap of cell ends; weakly silicified, shallow, and flattened valves; an extremely eccentric raphe, not elevated above the general level of the valve; lack of con‐opea; and striated girdle bands characterize Pseudo‐nitzschia as a natural group and a genus separate from Nitzschia.
ULTRAVIOLET‐B RADIATION EFFECTS ON INORGANIC NITROGEN UPTAKE BY NATURAL ASSEMBLAGES OF OCEANIC PLANKTON1
Authors: Behrenfeld Michael J. , Lean David R. S. , Lee Henry
Published: October 2004

Ultraviolet‐B radiation (UVBR: 290‐320 nm) inhibited ammonium uptake (pNH4) and nitrate uptake (pNO3) in natural plankton assemblages collected during a transect from 37° N to 55° N in the Pacific Ocean. Comparison of responses in pNH4to ambient solar‐ and lamp‐enhanced UVBR spectra allowed calculation of an action spectrum for pNH4inhibition. The slope of the action spectrum for Pnh4is half as steep as action spectra for UVBR inhibition of photosynthetic carbon uptake. Consequently, WBR‐induced photoinhibition of pNH4extends to greater depths than inhibition of carbon fixation due to the greater relative effect of longer UVBR wavelengths. Inhibition of pNH4was dependent upon UVBR dose when doses were weighted by the pNH4action spectrum. Dependence of WBR inhibition of pNH4on dose rate was not apparent. We found that near‐surface pNH4and pNO3can be overestimated in excess of 50% when measured using standard incubation vessels made of UVBR‐absorbing materials such as polycarbonate.
EFFECTS OF SMALL‐SCALE TURBULENCE ON PHOTOSYNTHESIS, PIGMENTATION, CELL DIVISION, AND CELL SIZE IN THE MARINE DINOFLAGELLATE GOMAULAX POLYEDRA (DINOPHYCEAE)1
Authors: Thomas William H. , Vernet Maria , Gibson Carl H.
Published: October 2004

Several experiments were conducted to understand better the physiological mechanisms underlying growth inhibition of the dinoflagellate Gonyaulax polyedra Stein due to small‐scale turbulence shear. To measure photosynthetic 14C uptake, a “phytoplankton wheel” device for rotating cultures in closed bottles was used. Turbulence was quantified biologically in the bottles by comparing growth inhibition with that in cultures with constant shear between a fixed cylinder and an outer concentric rotating cylinder (a stable Couette flow). At saturating irradiances, particulate photosynthesis (Psat) or photosynthesis per unit chlorophyll (PBsat) were not inhibited completely at the highest turbulence level (26.6 rad.s−1), and photosynthesis was less sensitive than growth. Photosynthesis per cell (PCsat) was increased by turbulence. In three experiments on the effects of turbulence on photosynthesis versus irradiance curves, the slope of the curve, α, for particulate photosynthesis at limiting irradiances did not change. Photosynthesis per unit chlorophyll per unit irradiance (αB) decreased at high (but not intermediate) turbulence levels. Photosynthesis per cell per unit irradiance, αC, increased with turbulence, suggesting an increase in photosynthetic efficiency in turbulent cultures. In two of the three experiments, respiration rates increased with turbulence, and in one experiment excretion of photosynthetically fixed 14C was not affected by motion. Ratios of accessory pigments to chlorophyll a did not change with turbulence, but pigments per cell and per dry weight increased with turbulence. These findings suggest little or no disruption of the photosynthetic apparatus. When turbulence was applied for 1 week, β‐carotene increased while peridinin and diadinoxanthin decreased, suggesting inhibition of synthesis of these latter pigments by prolonged turbulence. Since cell numbers did not increase or decreased during turbulent 72–h incubations, cell division was inhibited and also the cells were very much enlarged. Increases in αC per cell suggest that, in the sea, photo synthetic metabolism can persist efficiently without cell division during turbulent episodes. After turbulence ceases or reaches low levels again, cells can then divide and blooms may form. Thus, blooms can come or go fairly rapidly in the ocean depending on the degree of wave‐ and wind‐induced turbulence.
PERIPHYTIC DIATOM ASSEMBLAGES FROM HIGH ARCTIC PONDS1
Authors: Douglas Marianne S. V. , Smol John P.
Published: October 2004

Epiphytic, epilithic, and surface sediment diatom assemblages were identified and enumerated from 35 study ponds on CapeHerschel (78°37″N, 74°42″W), east‐central Ellesmere Island, Canada. All the sites are shallow (maximum depth <2 m), clear, oligotrophic, and freshwater. The ponds freeze completely for 10 months of the year. Major ion concentrations are relatively similar among the 35 sites, although environmental gradients exist. Over 130 diatom taxa from 28 genera were identified in the periphyton samples. Marked differences in species composition were evident among the ponds. Moreover, many of the diatoms exhibited varying degrees of microhabitat specificity. Variance partitioning by canonical correspondence analysis showed that 26% of the total variance exhibited by diatom species composition could be accounted for by the measured environmental variables (i.e. 10.2% by habitat and 15.8% by water chemistry). Pondwater alkalinity best explained the distribution of taxa, and weighted averaging regression and calibration were used to develop a transfer function to infer pondwater alkalinity from the diatom assemblages. Other important environmental variables included [Na+] for the epilithic and [SiO2] for the epiphytic assemblages.
CHRYSOPHYTE POPULATION AND ENCYSTMENT PATTERNS IN TWO CANADIAN LAKES1
Authors: Agbeti Michael D. , Smol John P.
Published: October 2004

The dynamics of chrysophyte populations and the onset of encystment in relation to several physical, chemical, and biological variables were studied in two Canadian lakes, Lake Opinicon (LO) and Upper Rock Lake (URL). LO is shallow and polymictic during the ice‐free season, whereas URL is deep and dimictic. Seasonal patterns of many limnological variables, as well as species composition and seasonal dynamics of chrysophyte assemblages, were broadly similar in both lakes. Three groups of chrysophytes were recognized: 1) taxa that were more abundant during ice cover and/or early spring and occasionally in late fall (Dinobryon spp. Ehrenberg and Synura spinosa Korsh), 2) taxa that seemed to prefer moderately warm water proglena americana Calkins and Ochromonas sp. Wyssotzki) and had maximum densities in late summer and occasionally in the fall, and 3) taxa that occurred in low numbers and did not exhibit any discernible seasonality in the two lakes (Mallomonas spp. Perty). Encystment rarely occurred during ice cover in both lakes. Stomatocyst concentrations were highest shortly after ice breakup (late April or early May), declined to trace levels by June, and remained at those levels until the end of the sampling season (late November). Encystment rates (cyst concentrations) were higher in dimictic URL. Encystment in both lakes coincided with concurrent changes in physical and chemical variables and chrysophyte vegetative cell densities, but it was not possible to pinpoint the exact conditions responsible for triggering encystment. Only a small proportion of chrysophytes encysted. Cyst production within a lake may vary from year to year.
PRELIMINARY INVESTIGATIONS INTO THE STRUCTURE AND ACTIVITY OF RIBULOSE BISPHOSPHATE CARBOXYLASE FROM TWO PHOTOSYNTHETIC DINOFLAGELLATES1
Authors: Whitney Spencer M. , Yellowlees David
Published: October 2004

Ribulose bisphosphate carboxylase / oxygenase (Rubisco) from the dinoflagellates Symbiodinium sp. Freudenthal and Amphidinium carterae Hulburt rapidly loses activity following cell lysis. Evidence presented indicates that this is not due to proteolysis. Using the tight binding inhibitor [14C] carboxyarabinitol bisphosphate as a marker, the Rubisco large subunit (LSu) from Symbiodinium sp. was purified. The subunit molecular weight was 56 kDa, while non‐denaturing polyacrylamide gel electrophoresis indicated that the purified protein had a molecular weight significantly less than that expected of the intact hexadecameric protein. No trace of the small subunit was apparent. The initial loss of carboxylase activity following cell lysis may be due to instability of the quaternary structure of the enzyme. Antibodies prepared to the purified LSU cross‐reacted with LSus from other dinoflagellates but not with the LSus of higher plants, diatoms, and other chromophytic algae. This suggests that the LSu of at least some dinoflagellates is antigenically different from that of other eukaryotes.
A NEW SPECIES OF ENSICULIFERA, E. IMARIENSE (DINOPHYCEAE), PRODUCING ORGANIC‐WALLED CYSTS1
Authors: Kobayashi Satoru , Matsuoka Kazumi
Published: October 2004

We describe a new organic‐walled resting cyst from surface sediments of Imari Bay in western Japan. The cysts are spherical, 23–29 pm in diameter, and their surface is covered with spinous to membranous ornaments that are 5–7 μm long and 1.5–2.2 μm wide. The ornaments vary from slender and bifurcate to membranous and multifurcate distal extremities. No archeopyle was observed. The cyst shape is variable in both natural samples and clonal cultures.

Vegetative cells are small and ovoid, 17–25 μm long and 14–21 μm wide, and are yellow‐brown in color. The epitheca is conical with a conspicuous apical horn, and the hypotheca is hemispherical. The cingular transitional plate has a needle‐like spine at its anterior right corner. The plate formula is Po, X, 4″3a, 7″, 5c, 5s 5″and 2″.

Although vegetative cells of the present species correspond to Ensiculifera, it is distinct from other species in producing no calcareous cysts. No species of Ensiculifera has been reported to produce cysts composed of only an organic wall. The present species is provisionally placed in the genus Ensiculifera as E. imariense sp. nov.
SEASONAL GROWTH, BIOMASS, AND REPRODUCTIVE BEHAVIOR OF THREE SPECIES OF RED ALGAE IN GODAVARI ESTUARY, INDIA1
Authors: Narasimha Rao G. Mohan
Published: October 2004

Growth and different phases in the life histories of Bos‐trychia tenella (Vohl.) J. Ag., Caloglossa leprieurii (Mont.) J. Ag., and Catenella impudica (Mont.) J. Ag. were estimated for 23 months from January 1986 to December 1987 in the Gautami Godavari estuary of lndia. Seasonal data on hydrographical conditions, biomass, and plant length were collected from three stations in this estuary. Biomass was minimum in August and September and maximum in January and February, as was frond length of tetrasporic and vegetative plants. Temperatures of 24°–27°C and salinities of 5–20 ppt coincided with optimal growth for all three algae. In all three species, tetrasporophytes were present in all months of the year without any seasonal periodicity, and nearly 50% of the plants were tetrasporophytes. The gametophytes of B. tenella and C. leprieurii and cystocarpic plants of C. impudica occurred from October to May, with greatest abundance in January. The abundance of spermatangial and cystocarpic plants in the populations of B. tenella and C. leprieurii ranged from 3 to 15%. Spermatangial plants of Catenella impudica could not be identified, and the abundance of cystocarpic plants was very low.
SUMMER DECLINE OF ULVA LACTUCA (CHLOROPHYTA) IN A EUTROPHIC EMBAYMENT: INTERACTIVE EFFECTS OF TEMPERATURE AND NITROGEN AVAILABILITY?1
Authors: Rivers Jennifer S. , Peckol Paulette
Published: October 2004

Throughout the summer, abundance of Ulva lactuca L. declined while biomass of Cladophora vagabunda (L.) van den Hoek and Gracilaria tikvahiae McLachlan increased in a New England embayment undergoing eu‐trophication (Waquoit Bay, Massachusetts). We investigated the physiological basis for the summer dieback, focusing on temporal variations in photosynthetic performance and tissue nitrogen (N). We also compared photosynthetic and N uptake capabilities of U. lactuca with other abundant species in this eutrophic system. Photosynthetic egiciency and capacity of U. lactuca declined markedly at 25°C, compared with a spring (15°C) peak in photosynthetic performance; Pmax was 4.6 ± 0.3 and 1.8 ± 0.6 μmol O2.m−2.s−1 during spring and summer, respectively. Notably, summer pmax of other abundant species of the embayment was 1.5–3 × higher than that measured for U. lactuca. Ulva lactuca showed a signifciant photosynthetic response to dissolved inorganic carbon enrichment during summer, when water‐column‐dissolved CO2 levels were 20% of spring values. Although ammonium uptake rates of U. lactuca were extremely high at both subsaturating (15μM) and saturating (75 μM) N concentrations, as predicted by the functional‐form hypothesis, tissue N fell to 1% by late summer. We suggest that a carbon imbalance, initiated by rising water temperatures and declining water‐column N; thermal stress; and biological factors (competition, grazing) all contribute to the recurrent summer decline of U. lactuca in this shallow, eutrophic embayment. Thus, while the morphology of U. lactuca might be considered a successful strategy for disturbed, or “stressed” (sensu Littler and Littler 1980), habitats, its inability to persist and flourish in this environment emphasizes the complexity of factors at work in natural systems.
COMPETITIVE INTERACTIONS BETWEEN THE OPPORTUNISTIC MACROALGAE CLADOPHORA VAGABUNDA (CHLOROPHYTA) AND GRACILARIA TIKVAHIAE (RHODOPHYTA) UNDER EUTROPHIC CONDITIONS1
Authors: Peckol Paulette , Rivers Jennifer S.
Published: October 2004

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

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

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

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

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

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

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

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

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

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

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

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