Showing papers in "Journal of Phycology in 1979"
TL;DR: It is established that Aquil is suitable for physiological experiments with a variety of marine phytoplankters representing all major phyla and modifications of the basic recipe and design of chemically defined media in general are discussed.
Abstract: The medium Aquil and its variations have been successfully used for trace metal studies of marine phytoplankton (diatoms and dinoflagellates) over the past three years. Here, the recipes, the methods of preparation and the chemical composition of Aquil are presented in detail. To permit complete definition of chemical speciation of the various components as calculated from thermodynamic equilibria, trace element contamination is controlled and the formation of precipitates and adsorbates is avoided. It is established that Aquil is suitable for physiological experiments with a variety of marine phytoplankters representing all major phyla. Modifications of the basic recipe and design of chemically defined media in general are discussed.
371 citations
TL;DR: Compared in two populations of Laminaria longicruris de la Pylaie in Shag Bay, Nova Scotia, Canada, it is concluded that lower productivity of the exposed coast population is the result of adaptation to high intensity water movement.
Abstract: Blade elongation was compared in two populations of Laminaria longicruris de la Pylaie in Shag Bay, Nova Scotia, Canada; one population was exposed to and the other sheltered from high intensity water movement. The maximum and minimum elongation rates were similar for the two populations, but the sheltered coast plants grew more rapidly during 8 mo of the year. Measurements of internal inorganic nitrogen (NO3−+ NO2−) reserves and dry organic weight indicated that low concentrations of dissolved nutrients in summer and low levels of illumination in fall and winter were more limiting to growth at the exposed site than the sheltered site. Transplant experiments provided evidence that morphological differences between the exposed and sheltered coast plants accounted at least partially for their different responses to varying nutrient conditions and light levels. It is concluded that lower productivity of the exposed coast population is the result of adaptation to high intensity water movement.
205 citations
TL;DR: Phytoplankton growth rate in response to irradiance can be approximated by a hyperbola defined by three coefficients: i) initial slope (α); ii) asymptote (μm); and, iii) X‐axis intercept or compensation irradiance (Ic).
Abstract: Phytoplankton growth rate in response to irradiance can be approximated by a hyperbola defined by three coefficients: i) initial slope (α); ii) asymptote (μm); and, iii) X-axis intercept or compensation irradiance (Ic). To mathematically represent the interaction of temperature and irradiance on growth rate, one must describe the relationship between these constants and temperature. The marine diatom, Skeletonema costatum (Greville) Cleve, was grown in unialgal culture at different levels of irradiance and 2-3 photoperiods at 0, 5, 10, 16 and 22 C. The value of Ic is ca. 1.0 ly·day−1 or less at all temperatures. The initial slope (div·ly−1) is a “u-shaped” function of temperature described by the second degree polynomial, α= 0.25–0.02T+0.001T2. Within the range 0–10 C, μm (div·day−1) is an exponential function of temperature described by the equation, μm= 0.48 exp (0.126T). At each temperature and selected levels of irradiance, cell size and cellular content of C, N and chl a were determined. The C:chl a and N:chl a ratios increased with irradiance because of increases in C and decreases in chl a. At lower temperatures (0, 5, 10 C), the rate of increase of both ratios with irradiance was greater than at the higher temperatures (16, 22 C). Cellular content of N was independent of irradiance and temperature, and the C:N ratio ranged from 5 to 8 with a slight tendency to lower values at low irradiance. Cell volume was not influenced by either temperature or irradiance.
151 citations
TL;DR: The available evidence shows that photosynthetic responses cannot reliably be used in short‐term enrichments but changes in respiration or ATP content may be useful in certain circumstances.
Abstract: Changes in net photosynthesis, dark respiration, ATP content, and some other aspects of composition were measured following phosphate or ammonium addition to cultures of the green alga Scenedesmus quadricauda (Turp.) Breb. deficient in phosphorus or nitrogen. The deficient nutrient was rapidly taken up. Light-saturated net photosynthesis was depressed below the pre-addition rate during nutrient uptake and did not increase markedly above that rate until several hours after uptake was complete. Dark respiration, on the other hand, was markedly stimulated during uptake of the deficient nutrient and to a lesser extent after uptake was complete. Phosphate addition to P-deficient cells caused a large increase in the ATP content within 2–4 h of addition, whereas ammonium addition to N-deficient cells caused much less or no increase in ATP content. Short-term enrichment experiments to detect nutrient limitations are evaluated in the light of these and similar results taken from the literature. The available evidence shows that photosynthetic responses cannot reliably be used in short-term enrichments but changes in respiration or ATP content may be useful in certain circumstances.
134 citations
TL;DR: The observations that O. thiebautii represents only a small fraction of total phy toplankton biomass and that its growth rate is 10–100 times slower than that of the other indigenous phytoplankon, strongly suggest that N2 fixation by this alga is a virtually insignificant component of the nitrogenous nutrition for the phy Topolankton of the North Atlantic central gyre in late Spring.
Abstract: Physiological rate measurements were made with Oscillatoria thiebautii (Gom.) Geitler in the subtropical north Atlantic Ocean between Spain and Bermuda during May and June of 1975. The near surface C:N fixation ratios averaged 6.5, and the cellular composition ratio was 6.2, suggesting that N2 fixation is the major path of nitrogenous nutrition for this alga. Compared to other oceanic phytoplankters, it has a low affinity for orthophosphate at oceanic concentrations (ks= 9.0); however, it has a high potential for utilizing phosphomonoesters (170–300 ng atoms P ·μg chl a−1· h−1). Maximal photosynthesis occurred at 450–700 μ Einstein · m−2· s−1, and was inhibited by full sunlight. Calculated cell division rates (ca. 180 days) suggest that relative to other phytoplankters in this oceanic region, O. thiebautii must be subjected to negligible grazing pressure. No major differences in C, N, chl a or ATP were observed between the tuft (fusiform) and puff (spherical) colonies. ATP concentrations relative to other cellular constituents varied greatly between colonies, suggesting a general inter-colony physiological variability in the open Atlantic. With increasing depth in the euphotic zone, there was no evidence for chromatic adaption. The observations that O. thiebautii represents only a small fraction of total phytoplankton biomass and that its growth rate is 10–100 times slower than that of the other indigenous phytoplankton, strongly suggest that N2 fixation by this alga is a virtually insignificant component of the nitrogenous nutrition for the phytoplankton of the North Atlantic central gyre in late Spring.
126 citations
TL;DR: Intraspecific differences in division periodicity were found among eight clones of the diatom Thalassiosira pseudonana (Hustedt) Hasle & Heimdal and six clone of the coccolithophore Emiliania huxleyi (Lohm.) Hay & Mohler.
Abstract: The division rates of 26 clonal cultures representing 13 species of planktonic marine algae (6 diatoms, 2 flagellated chrysophytes, 2 coccolithophores, 1 cryptomonad flagellate, I dinoflagellate, 1 green alga) were determined every 2 h for 48 h during exponential growth on a 14:10 LD cycle in nutrient-replete batch culture. Cyclic oscillations in the division rate were detectable in 22 of these clones. Of 14 diatom clones examined, four displayed nearly constant division rates throughout the LD cycle and ten showed strong periodicity favoring division during the light periods. In contrast, all other algae (12 clones) exhibited division rate maxima during periods of darkness, and clearly detectable decreases in cell number for time intervals of 4–8 h during periods of illumination. Intraspecific differences in division periodicity were found among eight clones of the diatom Thalassiosira pseudonana (Hustedt) Hasle & Heimdal and six clones of the coccolithophore Emiliania huxleyi (Lohm.) Hay & Mohler.
112 citations
TL;DR: The reduction and methylation of arsenate to dimethylarsinic acid by the cell produces a stable, non‐toxic compound.
Abstract: Arsenate is taken up readily by Skeletonema costatum (Greville) Cleve due to its chemical similarity to phosphate, and it inhibits primary productivity at concentrations as low as 67 nM when the phosphate concentration is low. A phosphate enrichment of greater than 0.3 ..mu..M alleviates this inhibition; however, the arsenate stress causes an increase in the cell's requirement for phosphorus. Arsenite is also toxic to Skeletonema at similar concentrations. Methylated species, such as dimethylarsinic acid, did not affect cell productivity at the levels examined. Thus, the reduction and methylation of arsenate to dimithylarsinic acid by the cell produces a stable, non-toxic compound.
103 citations
TL;DR: The C budget for this ciliate indicates that the daily contribution to the particulate food chain is large, although not as great as is indicated by short incubations.
Abstract: Extensive blooms of the autotrophic ciliate Mesodinium rubrum (Lohmann) occurred in the Peru coastal upwelling region at 15°S latitude in March through May 1977 and contributed significantly to the organic productivity of the region. From observations made during the JOINT-II oceanographic expedition, a budget of the carbon flux of these unusual photosynthetic organisms can be constructed. The light dependent C fixation was determined with short (1 h) incubations because of the organisms' sensitivity to confinement and rapid nutrient exhaustion. Maximum photosynthesis occurred at 50% of incident light with a maximum rate of particulate C synthesis of 2187 mg C · m−3· h−1. The specific carbon uptake rates were also high with a maximum light saturated value of 16.8 mg C ·(mg chl a)−1· h−1. The rate of excretion of dissolved organic C at the productivity maximum ranged from 16.1 to 181.1 mg C · m−3· h−1. The range of percent excretion was 1.8–12.5% the total C fixed, similar to the range found in both motile and nonmotile phytoplankton assemblages. Respiration, determined by the decrease in particulate C in the dark, averaged 4.6% of the previously fixed photosynthetic C · h−1. M. rubrum actively took up amino acids and naturally occurring dissolved organic carbon. The C budget for this ciliate indicates that the daily contribution to the particulate food chain is large, although not as great as is indicated by short incubations. The contribution of M. rubrum to the productivity and elemental fluxes of upwelling and coastal ecosystems has been seriously underestimated.
84 citations
TL;DR: The tetrasporangial initial in Palmaria palmata (L.) O. Kuntze arises from a cortex cell which enlarges and deposits a protein‐rich wall layer, which undergoes mitosis to form a tetraporocyte and a stalk cell.
Abstract: The tetrasporangial initial in Palmaria palmata (L.) O. Kuntze (formerly Rhodymenia palmata (L.) Greville) arises from a cortex cell which enlarges and deposits a protein-rich wall layer. This cell undergoes mitosis to form a tetrasporocyte and a stalk cell. Synaptonemal complexes are formed in the sporocyte nucleus while in the cytoplasm floridean starch is deposited in association with ER or with particles presumed to be ribosomes. Microbody-like structures become numerous between the nuclear envelope and perinuclear ER, and clusters of non-membranous, spherical structures also are associated with the nucleus. Chromatin condensation is reversed following pachytene and a prolonged diffuse stage ensues, when dictyosomes and ER produce vesicles which deposit mucilage rich in sulfated and acidic polysaccharides around the tetrasporocyte. A conspicuous lenticular thickening of the mucilage sheath develops at the apical end of the sporangium. Dictyosomes are frequently associated with mitochondria which may be associated with chloroplasts. Following nuclear divisions the tetrasporocyte is cleaved into four spores by sequentially initiated, but simultaneously completed periclinal and anticlinal furrows. When mucilage deposition ceases, the dictyosomes begin to produce vesicles with glycoprotein-rich contents. These vesicles are abundant in released tetraspores, and they probably contain adhesive material aiding in the attachment of the liberated spores.
84 citations
TL;DR: The growth response of C. erosa in culture provides insight into the abundance and distribution of cryptomonads and other small algal flagellates in nature.
Abstract: Cryptomonas erosa Skuja, a planktonic alga, was grown in batch culture at different combinations of light intensity and temperature, under nutrient saturation Growth was maximal (12 divisions · day−1) at 235 C and 0043 ly · min−1, declining sharply with temperature (0025 divisions-day−1 at 1 C) With decreasing temperature, the cells showed both light saturation and inhibition at much reduced light intensities At the same time the compensation light intensity for growth declined towards a minimum of slightly above 04 × 10−4 ly · min−1 (~1 ft-c) at 1 C or <01 ly · day−1 (PAR) Cell division was more adversely affected by low temperature than carbon uptake, and the resulting excess production of photosynthate was both stored and excreted Extreme storage of carbohydrates resulted in cell volumes and carbon content ca 22 and 30 × greater, respectively, than the maxima observed for cells incubated in the dark, whereas, at growth inhibitory light levels, as much as 57% of the total assimilated carbon was excreted A marked increase in cell pigment was observed at the lowest light levels (<10−3 ly · min−1), at high temperature The growth response of C erosa in culture provides insight into the abundance and distribution of cryptomonads and other small algal flagellates in nature
79 citations
TL;DR: The production of thick walled zygates in culture implies that such resting stages in marine sediments could serve as a source stock for blooms and the existence of benthic “seed beds” consisting of hypnozygotes is now plausible.
Abstract: The sexual cycle of Gonyaulax monilata Howell was observed in stationary cultures and in nitrogen-deficient medium. The armored, isogamous gametes fuse in a characteristic manner with cingula at oblique angles. Nuclear fusion lags slightly behind cytoplasmic fusion. The zygote enlarges for several days. The dark, double-flagellated planozygote encysts within 1–3 wk. Early hypnozygotes are round to ovoid and contain lipid and one or two large golden-yellow globules. As the hypnozygote matures, the globules become smaller and the cytoplasm darkens and pulls from the wall. All cysts examined contained only one nucleus. A very dark, uninucleate post-hypnozygotic cell escapes through an archeopyle and within 24 h divides into daughter cells which divide in 24–48 h forming a small chain. The production of thick walled zygates in culture implies that such resting stages in marine sediments could serve as a source stock for blooms. This species causes toxic red tides and the existence of benthic “seed beds” consisting of hypnozygotes is now plausible.
TL;DR: The results showed that the degree of synchrony is highest for cells grown under optimal conditions, and this light‐dark synchronization system was evaluated and compared with those described in the literature using probit analysis of the time course of DNA synthesis, nuclear and cytoplasmic division and sporulation.
Abstract: Chlamydomonas reinhardtii Dangeard was synchronized at optimal growth conditions under a 12:4 LD regime at 35 C and 20,000 lx with serial dilution to a standard starting cell density of (1.4 ± 0.2) × 106 cells/ml. Synchronous growth and division were characterized by measuring cell number, cell volume and size distribution, dry weight, protein, carbon, nitrogen, chlorophyll, carotenoids, nucleic acids, nuclear and cytoplasmic division during the vegetative life cycle. The main properties of the present system are: Exponential growth with high productivity, high degrees of synchrony and reproducibility during repeated life cycles. The degree of synchrony of this light-dark synchronization system was evaluated and compared with those described in the literature using probit analysis of the time course of DNA synthesis, nuclear and cytoplasmic division and sporulation (increase in cell number). The results showed that the degree of synchrony is highest for cells grown under optimal conditions.
TL;DR: Polyphosphate bodies containing lead were induced in laboratory cultures of Diatoma tenue var.
Abstract: Polyphosphate bodies containing lead were induced in laboratory cultures of Diatoma tenue var elongatum Lyngb by the addition of phosphorus and 005 mug-atoms/l Pb to P deficient medium Morphometric analysis of cells exposed to Pb showed a significant decrease in number of mitochondria with a concomitant increase in their volume and an increase in membranous organelles in the vacuole compared to phoshorus starved and phosphorus sufficient controls Exposure of cultures to 008 mug-atoms/l copper resulted in reduction of the number of polyphosphate bodies formed during luxury uptake but no other significant morphological changes in cellular organelles Ecological implications of the interactions between nutrients and low level trace metal contamination are discussed
TL;DR: The preliminary results indicate that this Gyrodinium may be a previously undescribed species, which possessed three xanthophylls that could not be correlated with carotenoids previously reported from dinoflagellates.
Abstract: Chlorophylls and carotenoids of a small unarmoured dinoftagellate (Gyrodinium sp.-A) isolated from the Oslofjord, Norway, were investigated by thin-layer chromatography, visible light spectrophotometry, proton magnetic resonance and mass spectrometry and simple chemical reactions. Besides chlorophyll a, chlorophyll c, β,β-carotene, diatoxanthin and diadinoxanthin, the species possessed three xanthophylls that could not be correlated with carotenoids previously reported from dinoflagellates. The main carotenoid was different from peridinin and fucoxanthin, both of which are reported as the main characteristic carotenoids in photoautotrophic dinoflagellates. No trace of peridinin could be detected in the pigment extract. A morphological description of the organism based on light microscopy is presented, and the relationship with other small gymnodinioid (Gymnodinium spp.) species is discussed. The preliminary results indicate that this Gyrodinium may be a previously undescribed species.
TL;DR: Deep populations from Lake Windermere exhibited large, time‐dependent variations in chlorophyll fluorescence over the first 25 s of exposure to 450 nm light, whereas surface populations did not, and data were interpreted in terms of decreased spillover from PSII to PSI with increasing depth, to a minimum at the threshold light intensity below which cells are in light state 1.
Abstract: An inverse linear relationship between chlorophyll fluorescence yield (R) and light intensity was recorded in the near-surface waters of six lakes (New Zealand, England) of greatly different trophic status and phytoplankton species composition. This surface depression of R values could be removed by incubation of samples in dim light or darkness and was not observed in situ below a threshold irradiance (146 μEin ·m−2·s−1 for Lake Taupo, New Zealand). The time course of chlorophyll fluorescence depression and recovery in response to light treatment was measured in samples from Lake Windermere (England). Fluorescence exponentially decreased upon exposure to bright light and the response was 100% (5 m samples) or 83% (dim light-adapted 0 m samples) complete within 2 min. An increase in R values in the dim light occurred after a lag of 60 s and the rate of increase decreased exponentially with time. Full recovery took 15 min or more. Deep (6.5 m) populations from Lake Windermere exhibited large, time-dependent variations in chlorophyll fluorescence over the first 25 s of exposure to 450 nm light, whereas surface populations did not. These data were interpreted in terms of decreased spillover from PSII to PSI with increasing depth, to a minimum at the threshold light intensity below which cells are in light state 1.
TL;DR: Kinetic evidence from this study suggests that Selenastrum will not be growth competitive with some other common aquatic heterotrophs and autotrophS when Pi limits microbial growth in lakes.
Abstract: Most theoretical studies of phytoplankton growth in aquatic environments assume that relative nutrient utilization abilities regulate species composition. The steady-state phosphate-limited growth kinetics of Selenastrum capricornutum Printz were examined using continuous cultures to characterize the green alga's ability to compete for orthophosphate (Pi) when Pi limits growth. The maximal specific growth rate for Selenastrum at 20 C was 1.20 day−1, and the concentration where half maximal growth rate occurs was 40 nM Pi. There was an apparent threshold of 10 nM Pi. Cell yields varied inversely with growth rate; thus ability to utilize Pi could not be characterized in terms of the Monod half-saturation constant and maximal growth rate. Instead, we computed the Pi affinity from steady-state flux vs. external Pi concentrations. This affinity was 2.8 l·mg dry wt−1· day−1 for Selenastrum. Kinetic evidence from this study suggests that Selenastrum will not be growth competitive with some other common aquatic heterotrophs and autotrophs when Pi limits microbial growth in lakes.
TL;DR: Two marine diatoms were studied singly and in mixed culture and Thalassiosira pseudonana (Hust.) Hade & Heimdal was capable of a higher growth rate (μmax) than Phaeodactylum tricornutum Bohlin.
Abstract: Two marine diatoms were studied singly and in mixed culture. Thalassiosira pseudonana (Hust.) Hade & Heimdal was capable of a higher growth rate (μmax) than Phaeodactylum tricornutum Bohlin. In two-species batch cultures P. tricornutum took over in the latter portion of the exponential phase, possibly due to allelopathy. The filtrate from this species caused an initial lag phase and a reduced terminal population density for T. pseudonana. Two-species continuous cultures showed verification of these interactions. At high dilution rate (i.e., high growth rate) P. tricornutum washed out when added at low density, whereas T. pseudonana maintained constant cell density. However, when sufficient density of P. tricornutum was added as a contaminant, both species washed out. At a lower dilution rate P. tricornutum increased in density when added and eventually reached a stable population; T. pseudonana then washed out.
TL;DR: The diel pattern of cell division, cell carbon, adenine nucleotides and vertical migration was determined for laboratory cultures of the photosynthetic marine dinoflagellate, Ceratium furca (Ehr.), suggesting that the vertical migration pattern is independent of a phototactic response and may be under the control of an endogenous rhythm.
Abstract: The diel pattern of cell division, cell carbon, adenine nucleotides and vertical migration was determined for laboratory cultures of the photosynthetic marine dinoflagellate, Ceratium furca (Ehr.) Clap. and Lachm., entrained on an alternating 12:12 LD schedule at 20 C. Cell division was initiated during the latter portion of the dark period with ca. 30% of the population undergoing division. Cell C increased during the light period and exhibited a linear decrease with a loss of 33% during the dark period. ATP . cell/sup -1/ increased during the light period and decreased by Ca. 40 to 50% during the dark period. The diel patterns of cell C and ATP tended to buffer the magnitude of the change in C:ATP ratios around an overall mean value of 89. There was no obvious trend in the concentration of (GTP + UTP) . cell /sup -1/ over the cell cycle. The cellular adenylate energy charge was maintained at values between 0.8 to 0.9 throughout the 24 h LD cycle, despite a ca. 40% decrease in total adenylates (A/sub T/ = ATP + ADP + AMP) during the dark period on 12:12 LD, and over a 68% decrease in ATP during 42 h of continuousmore » darkness. These data lend experimental support to the theory of cellular metabolic control by the adenine nucleotides. With lateral illumination on 12:12 LD cycles, the cells began to concentrate at the surface of the experimental tubes shortly before the lights were turned on, and at the bottom of the tubes shortly before the lights were extinguished. This patterncontinued for 6 days in continuous darkness, suggesting that the vertical migration pattern is independent of a phototactic response and may be under the control of an endogenous rhythm.« less
TL;DR: Comparison of gaseous contents of young and old nonaxenic cultures of filamentous algae in the divisions Chlorophyta and Xanthophyta showed DMS occurred only in aged cultures and was probably produced by bacteria utilizing substances from senescent algal cells.
Abstract: Dimethyl sulfide (DMS) was found to be the principle biogenic sulfur compound in a freshwater environment. Endemic and non-endemic algae were cultured under axenic and nonaxenic conditions in defined media. Sulfur gas analysis of culture fluids indicated that members of the Cyanophyta were probable sources of DMS whereas representatives of the divisions Chlorophyta, Xanthophyta and Bacillariophyta apparently did not produce this compound. Comparison of gaseous contents of young and old nonaxenic cultures of filamentous algae in the divisions Chlorophyta and Xanthophyta showed DMS occurred only in aged cultures and was probably produced by bacteria utilizing substances from senescent algal cells. Data suggest that the composition of the algal community determines whether DMS is algal and/or bacterial in origin.
TL;DR: The validity of Heiberg's genus Paralia is confirmed and a type slide of the species is designated and two kinds of heterovalvy were observed and the taxonomic significance of one of these is discussed.
Abstract: Light and electron microscopy were used to investigate the complex structure of the frustule of Paralia sulcata (Ehrenb.) Cleve. Rimoportulae are reported for the first time in this diatom and two types of linking processes are described. The ease with which the cingulum is lost is explained with regard to its attachment to the valve. Two kinds of heterovalvy were observed and the taxonomic significance of one of these is discussed. The validity of Heiberg's genus Paralia is confirmed and a type slide of the species is designated.
TL;DR: Chlorophyll a:b ratios for Chlorella capsulata Guillard, Bold & MacEntee, Chlorosarcinopsis halophila, Nannochloris atomus Butcher and Micromonas pusilla (Butcher) Manton & Parke support the hypothesis that marine algae have lower chlorophyll b containing plants.
Abstract: Chlorophyll a:b ratios for Chlorella capsulata Guillard, Bold & MacEntee, Chlorosarcinopsis halophila Guillard, Bold,& MacEntee, Nannochloris atomus Butcher and Micromonas pusilla (Butcher) Manton & Parke were found to be 1.74, 2.46, 1.89, and 1.53, respectively. Compared to previously published values in marine planktonic algae, these ratios are similar to the average value (2.17, SD = 1.12) reported for 25 species in 15 genera. Both the new data and previously published data support the hypothesis that marine algae have lower chlorophyll a:b ratios than do other chlorophyll b containing plants.
TL;DR: The “double thecae” or “internal septa” of Eunotia soleirolii (Kütz.) Rabenh, are shown to represent the theCae of resting spores, as characterized by their physiology, as well as morphology.
Abstract: The “double thecae” or “internal septa” of Eunotia soleirolii (Kutz.) Rabenh, are shown to represent the thecae of resting spores, as characterized by their physiology, as well as morphology. They differ from all resting spores of centric diatoms by the formation of both their valves as a result of unequal cell divisions; and, from the majority of centric spores by the presence of several girdle bands in both their thecae. Spore formation can be induced by high or low pH, high temperature (24 C), and iron, silica, phosphate or nitrate deficiencies, whereas low temperatures defer it. Spores do not germinate directly, but dormancy can be removed by dark treatments (–2 to 15 C) for a minimum of 4–5 wk. Longer dark treatments result in higher germination rates. At 15 C, a minimum of 2 mo is required and 4 mo is better. Heat treatments (27–42 C) are ineffective, but may shorten the dormancy-breaking subsequent cold period. Instances of secondary dormancy, as well as relative dormancy, were observed. Germination usually occurs in the light between 2 and 21 C. An equal division of the spore is followed by unequal divisions of both new cells with only the two resulting large cells being viable. The experiences in the laboratory aided the discovery of stages of spore germination in nature.
TL;DR: Comparisons of the nutrient dynamics of O. luteus to other phytoplankton species and the ecological implications as related to the phy Topolankton community of Narragansett Bay (Rhode Island) are discussed.
Abstract: Uptake and assimilation of nitrogen and phosphorus were studied in Olisthodiscus luteus Carter. A diel periodicity in nitrate reductase activity was observed in log and stationary phase cultures; there was a 10-fold difference in magnitude between maximum and minimum rates, but other cellular features such as chlorophyll a, carbon, nitrogen, C:N ratio (atoms) · cell−1 were less variable. Ks values (~2 μM) for uptake of nitrate-N and ammonium-N were observed. Phosphorus assimilated · cell−1· day−1 varied with declining external phosphorus concentrations; growth rates <0.5 divisions · day−1 were common at <0.5 μM PO4-P. Phosphate uptake rates (Ks= 1.0–1.98 μM) varied with culture age and showed multiphasic kinetic features. Alkaline phosphatase activity was not detected. Comparisons of the nutrient dynamics of O. luteus to other phytoplankton species and the ecological implications as related to the phytoplankton community of Narragansett Bay (Rhode Island) are discussed.
TL;DR: Two species of marine diatoms were grown in batch and continuous cultures on four different nitrogen compounds and carbon and nitrogen uptake were measured simultaneously with the stable isotopes 13C and 15N, finding that nitrite generally had the greatest inhibitory effect on C uptake.
Abstract: Two species of marine diatoms, Skeletonema costatum (Grev.) Cleve and Phaeodactylum tricornutum Bohlin were grown in batch and continuous cultures on four different nitrogen compounds (nitrate, nitrite, ammonium, urea). Carbon and nitrogen uptake were measured simultaneously with the stable isotopes 13C and 15N. Nitrogen uptake generally increased with N concentration in the medium, but no clear difference existed between the N sources. Carbon fixation was decreased for up to 5 h following the addition of the N compound. Nitrite generally had the greatest inhibitory effect on C uptake. Carbon-to-nitrogen uptake ratios decreased with increasing dissolved N concentration, becoming lower than one in nutrient-limited cultures. In contrast, batch cultures exhibited C:N uptake ratios greater than one. These effects are essentially short-term and differ from long-term influences of the N source on the cellular chemical composition.
TL;DR: It appears that certain euryhaline algae may consist of ecotypes, each of which has some capacity for physiological adaptation to salinity variations.
Abstract: Laboratory culture studies on the euryhalinity of Bostrychia radicans Montagne and Caloglossa leprieurii (Montagne) J. Agardh from the mouth and head of the Mullica River estuary, New Jersey, revealed both species probably have ecotypes whose growth patterns correlate with the salinity regime of their habitat in nature. Significant growth differences of tetrasporelings were determined in response to four salinities (5, 15, 25, 35%c) even after acclimation periods of the tetrasporophytes from 6 mo–2 yr in laboratory culture. However, one isolate of Bostrychia and both isolates of Caloglossa also demonstrated some capability for physiological adaptation to salinity changes although this was less significant statistically than their ecotypic response. It thus appears that certain euryhaline algae may consist of ecotypes, each of which has some capacity for physiological adaptation to salinity variations.
TL;DR: Synarthrophyton gen. nov. is described based on southern Australian material of Melobesia patena Hooker fils & Harvey, which shows features intermediate between Mesophyllum Lemoine and Lithothamnium Philippi.
Abstract: Synarthrophyton gen. nov. is described based on southern Australian material of Melobesia patena Hooker fils & Harvey, which shows features intermediate between Mesophyllum Lemoine and Lithothamnium Philippi. It has the thin-walled rounded epithallial cells and coaxial hypothallium characteristic of Mesophyllum and the type of procarp and male structures common to Lithothamnium. Synarthrophyton is unique within the subfamily Melobesioideae (J. E. Areschoug) Yendo because it displays secondary pit connections. Details of the vegetative and reproductive morphology of S. patena (Hooker fils. & Harvey) comb. nov. are given and its taxonomic position in the Corallinaceae Lamouroux discussed.
TL;DR: Silicic acid taken up from the growth medium by Navicula pelliculosa (Bréb.) Hilse was shown to enter at least two compartments: i) soluble pools; ii) insoluble fraction comprised predominantly of the silica frustule.
Abstract: Silicic acid taken up from the growth medium by Navicula pelliculosa (Breb.) Hilse was shown to enter at least two compartments: i) soluble pools; ii) insoluble fraction comprised predominantly of the silica frustule. Soluble Si pools were extracted by a variety of agents from cells uniformly labeled for ten generations in medium containing 68Ge-Si(OH)4. 100 C water soluble and 0 C perchloric acid (PCA) soluble Si pools of 680 mM Si·l−1 and 490 mM Si·l−1 cell water represented 13 and 9%, respectively, of total, cell Si in exponential growth phase cells. Uniformly labeled cells synchronized by the combined synchronization technique accumulate at the cell cycle stage where silica frustule development is initiated. These cells contain water and PCA soluble pools of 10 nmol Si·106 cells−1 and-8.8 nmol Si·106 cells−1, respectively. On addition of Si(OH)4, a rapid uptake ensues allowing the Si pool to expand 2.5-fold, apparently to provide precursors of the silica frustule.
TL;DR: Uptake of 14C‐methylamine can be used as a highly sensitive measure of NH4+ uptake activity and should be a useful tool for studying NH4+, and the results suggest that methylamine enters the algal tissue via a specific mediated transport system.
Abstract: The ammonium analogue, methylamine, is taken up rapidly from dilute solution by Macrocystis pyrifera (L.) C. A. Agardh. /sup 14/C-methylamine was used to characterize the transport system, with respect to dependence on external concentration, temperature, pH and substrate specificity. The results suggest that methylamine enters the algal tissue via a specific mediated transport system. Uptake of methylamine showed no consistent relation to the N content of the plant tissue, but was highly dependent on the portion of plant sampled and severely affected by cutting the tissue. The strong inhibition of methylamine uptake by ammonium and lesser inhibition by other alkylamines suggests that the uptake system functions as an ammonium permease. Uptake of /sup 14/C-methylamine can be used as a highly sensitive measure of NH/sub 4//sup +/ uptake activity and should be a useful tool for studying NH/sub 4//sup +/ uptake in the laboratory and field.
TL;DR: It appears that D. dichotoma maintains its populations near its northern distribution limit on the East Coast of North America by undergoing dormancy after germling establishment, and releasing aplanospores unaffected by temperature and photoperiod.
Abstract: The mechanism of yearly repopulation of Dictyota dichotoma (Hudson) Lamouroux in the inshore waters of North Carolina was studied in the field and in laboratory experiments. It was demonstrated that D. dichotoma is maintained throughout the year at this location and does not require yearly immigrations. A young germling stage was shown to function as the overwintering structure. Although release of aplanospores was unaffected by temperature and photoperiod, subsequent germination and establishment required warm conditions. If germlings were allowed to grow to the 7–9 cell stage under summer conditions, they could survive 21 wk of winter conditions. Transfer of 21 wk old winterized germlings to summer conditions resulted in the rapid production of erect blades. It therefore appears that D. dichotoma maintains its populations near its northern distribution limit on the East Coast of North America by undergoing dormancy after germling establishment.
TL;DR: Pronuclear migration in Fucus distichus spp.
Abstract: Pronuclear migration in Fucus distichus spp. edentatus (de la Pyl.) Powell is blocked by incubation of fertilized eggs in colchicine (1 mg/ml) and Nocodazole (2 μg/ ml). Rhizoids form prior to decondensation of the sperm chromatin in eggs in which pronuclear fusion is blocked. This occurs during continuous colchicine incubation as well as in eggs recovering from a short treatment with either drug following fertilization. During recovery of the cells, the sperm and egg chromosomes condense, and the sperm chromosomes migrate toward the egg pronucleus. The delay in migration following removal of colchicine is as much as 24 h and is even slower following removal of Nocodazole. The egg chromosomes form a metaphase plate in treated cells while the sperm chromosomes are still distant in the cytoplasm. This suggests that egg centrioles are important in the mitotic division of the zygote, not sperm centrioles. The effect of colchicine treatment on the mitotic plane and cytokinesis is also discussed.