Showing papers in "Journal of Phycology in 1983"
TL;DR: The functional‐form group approach appears to have powerful capabilities in that it can indicate important morphological‐metabolic‐ecological interactions in a given community, where the macroalgae are known, without the need to examine each population in detail and without being constrained to a specific habitat or geographical region.
Abstract: Predictions of an evolutionary model were examined for 43 tropical macroalgae using a functional-form group approach. The ranking from high to low primary producers (Sheet- and Filamentous-Groups > Coarsely Branched- and Thick Leathery-Groups > Jointed Calcareous- and Crustose-Groups), and data from the literature, support the hypothesis that persistent forms which allocate resources for environmental resistance, interference competition or antiherbivory defenses do so at the cost of lower primary production rates. The results for percent thallus lost to fish grazing over a 24 h period support the hypothesis that members of the Thick Leathery-, Jointed Calcareous- and Crustose-Groups have evolved antipredator defenses, with a tendency for decreasing herbivore resistance toward the Sheet- and Filamentous-Groups. The most heavily-calcified species (e.g. crustose corallines) ranked among the most grazer resistant as did the thick rubbery or leathery species. The ranking of functional-form group means for resistance to predation was as follows: Filamentous-Group (62% lost-24 h−1), Sheet-Group (42%), Coarsely Branched-Group (33%), Jointed Calcareous-Group (10%), Thick Leathery-Group (7%) and Crustose-Group (0%), in accordance with the hypothesis. The algal groups generally showed an increase in mean penetration toughness from filaments (<200 g-cm−2 to shear thallus) to sheets (216 g·cm2), coarsely branched forms (328 g·cm−2) and thick leathery species (1800 g·cm−2) in agreement with the predictions of the model. Contrary to earlier findings, there was no consistent gradation between the first four groups (i.e. fleshy algae) based on calorific values. However, in partial support of the functional-form model, a seven-fold difference was noted when the mean for these groups (1.7 kcal·g−1) was compared with that of the Jointed Calcareous- and Crustose-Groups (0.2 kcal·g−1. The functional-form group approach appears to have powerful capabilities in that it can indicate important morphological-metabolic-ecological interactions in a given community, where the macroalgae are known, without the need to examine each population in detail and without being constrained to a specific habitat or geographical region.
274 citations
TL;DR: Diatom colonization was initialed within 1 h on the upstream side of substrata in riffles, while the tap face was colonized first in pools, and vertically positioned species remained dominant throughout the 3 wk period in the pool.
Abstract: Light and scanning electron microscopy were utilized to quality diatom colonization in Oak Creek, Arizona. Aluminum SEM stubs with and without plexiglass discs were anchored into rocks. Early colonization on five stub microzones was examined at hourly intervals; weekly intervals of up to 3 wk were employed to record community development in pool find riffle. Plexiglass was more suitable for microbial colonization than aluminum. Organic matter and bacteria were important surface pre-conditioning agents while fungi were instrumental in trap/ting cells during early stages of colonization in the riffle. Diatom colonization was initialed within 1 h on the upstream side of substrata in riffles, while the tap face was colonized first in pools. Colonization moved rapidly to the perimeter in each system. Early colonization of-side microzones was considerably more asymmetric in the riffle than, pool. At Idler stages (2 wk) diatoms with their associated mucilage and algal filaments contributed to the stability of the microbial communities. Horizontally positioned species (Achnanthes, Cocconeis) were early colonizers in both systems while vertically positioned species (Gomphonema, Nitzschia) were more important in later successional stages (3 wk) in the riffle. Horizontally positioned species remained dominant throughout the 3 wk period in the pool. After 3 wk, diversity was normally greater in the pool while density was higher in the riffle. Detrital microcosms containing viable microbiol assemblages frequently collected on tin-upstream face of substrata in the riffle. The random nature by which these detrital microcoms contact downstream substrata greatly contribute to the spatial variation of periphyton in streams. These detrital microcosms expedite repeated colonization in lotic systems.
174 citations
TL;DR: These bottom ice communities have higher primary productivity than typical brash ice communities; they are also accessible to marine herbivores and so may be more important to the Antarctic marine food chain than previously supposed.
Abstract: The structure, productivity and heterotrophic potential of an extensive microalgal community growing on the underside of sea ice near the Australian Antarctic Station of Casey, are described Underwater observations made near the Australian Antarctic stations of Davis and Mawson are also reported This community develops during September, is largely suspended from the bottom surface of annual sea ice and often extends into the underlying water column as conspicuous strands up to 15 cm long The algal community structure in the strands is dominated by an unidentified tube diatom belonging to the Amphipleura/Berkeleya group and chains of a species of Entomoneis cf Amphiprora paludosa var hyperborea (Grunow) Cleve Unlike previously described bottom ice environments, a brash ice layer under the hard sea ice is absent Living cells, predominantly Nitzschia frigida Grunow, also occur in microbrine channels in the bottom 3 cm of the ice Maximal primary production rates of 81 μg C · L-1· h-1 occurred during November, then began declining near the end of December Minimal rates (28 μg C · L-1· h-1) were reached in mid-January and coincided with changes in the physical structure of the sea ice and in the stability of the water column An abundant epibacterial community associated with the microalgal strands assimilated 3H-labelled amino acids suggesting significant heterotrophic recycling of dissolved organic matter Turnover times of assimilated amino acids in the bottom ice community averaged 55 h during November while negligible turnover of these substrates occurred in the water column 15 m below the ice These bottom ice communities have higher primary productivity than typical brash ice communities; they are also accessible to marine herbivores and so may be more important to the Antarctic marine food chain than previously supposed
97 citations
TL;DR: In all experiments, these photosynthetic properties were independent of spectral distribution (color) and in most experiments were dependent on irradiance, which does not conform to the predictions of the theory of complementary chromatic adaptation for seaweeds.
Abstract: The effect of light quantity (irradiance) on the photosynthetic physiology of seven seaweed species was distinguished from the effect of light quality (color). Plants were grown in outdoor, continuous-flow tanks, at irradiances saturating and limiting to growth, and in spectral distributions that were either broadband (white) or narrowband (green). The green light field complemented the absorptance spectrum of phycoerythrin and approximated the spectral distribution of a submarine light field in turbid coastal water near the compensation depth. Physiological measurements, made after 6–15 days growth, included light-harvesting pigment densities, instantaneous photosynthesis-light relationships and growth rate. In all experiments, these photosynthetic properties were independent of spectral distribution (color) and in most experiments were dependent on irradiance. These data do not conform to the predictions of the theory of complementary chromatic adaptation for seaweeds.
90 citations
TL;DR: The morphology of the valve of Coscinodiscus wailesii and the development of its siliceous architecture, studied in the SEM and TEM, is compared with valve formation in Thalassiosira eccentrica and variation in girdle bands is discussed with respect to cell division.
Abstract: The morphology of the valve of Coscinodiscus wailesii and the development of its siliceous architecture, studied in the SEM and TEM, is compared with valve formation in Thalassiosira eccentrica (Ehrenberg) Cleve Though the areolae-architecture of these two species differs in such that the cribrum is proximal and the foramen distal in T eccentrica, and in C wailesii the cribrum is distal and the foramen proximal, the formation of their complex loculate system is similar, displacing a centrifugal growth pattern with respect to the valve, and a proximal to distal, sequentially During base layer formation a hitherto undescribed rib system outlines the prospective areolae The vertical differentiation is in principle the same as in T eccentrica and also the cribra are formed centripetally in relation to the areolae in both species The location of the cribra at the proximal or distal side, therefore, seems to be of minor importance for the sequence of silica deposition Variation in girdle bands is discussed with respect to cell division The prophasic nuclear migration from the interphase position to the girdle bands, where mitosis is performed, seems to be necessary for triggering the formation of the unilateral cleavage furrow that later forms a cleavage ring with excentric position The divided nuclei migrate with the ingrowing cleavage furrow to the center of the newly created protoplasmic surfaces to initiate valve formation
75 citations
TL;DR: Tissue nitrogen was assessed monthly for 16 months in five species of perennial macroalgae representing three phyla at one location in Rhode Island Sound and showed a remarkable similarity in their pattern of seasonal fluctuation in both nitrate and total nitrogen.
Abstract: Tissue nitrogen was assessed monthly for 16 months in five species of perennial macroalgae representing three phyla at one location in Rhode Island Sound. The species showed a remarkable similarity in their pattern of seasonal fluctuation in both nitrate and total nitrogen. The period of greatest accumulation (January through March) coincided with the period of highest concentration of inorganic nitrogen in the water, and for most of these algae it was also the time of-least growth. Conversely, the period of lowest tissue nitrogen (50% of the winter value, May through July) coincided with the period of lowest inorganic nitrogen in the water and highest algal growth. The greatest accumulation of nitrate was found in Laminaria saccharina (L.) Lamour. (80 μmol·g dry wt.−1), four times as much as that measured simultaneously in the other species and 560 times the ambient concentration. By April the concentration of internal nitrate had dropped to nearly undetectable levels, but in August it began to accumulate again—a pattern that was repeated in Chondrus crispus Stackh. In Ascophyllum nodosum (L.) Le Jolis, Fucus vesiculosus L. and Codium fragile subsp. tomentosoides (Van Goor) Silva, the period of negligible internal nitrate level extended from March to December. The greatest concentration of total tissue nitrogen was measured in C. crispus (4.8% dry wt.), double the maximum in L. saccharina (2.3% dry wt.).
70 citations
TL;DR: It is demonstrated that in axenic cultures many species of seaweeds produce active extracellular substances which play an important role in growth and Morphogenesis of other species of decomposing seaweeds.
Abstract: The typical morphology of Monostroma oxyspermum (Kutz.) Doty is lost in axenic culture. In synthetic media of the ASP type, it grows as a colony-like mass composed of round cells with numerous rhizoids. Such a mass is a fragile structure which falls apart upon shaking, or slight touch, into small cell-groups and single cells or cells with a long rhizoid. Only temporary saccate or monostromatic fronds appear and reach 1–2 mm in length when grown in enriched seawater media, but disintegrate and become a colony-like mass. The typical morphology is easily restored by adding at specific intervals filtrates of bacterial cultures and supernatant medium from axenic brown and red algal cultures to the basal medium (ASP7), or by reinfecting the Monostroma with an appropriate bacterial flora. Furthermore, the typical morphology in also maintained by bialgal cultures between Monostroma and other axenic strains of various species of seaweeds except the species belonging to the Chlorophyceae. Monostroma thus appears to utilize some substances released by most species of brown and red algae for its typical growth. Active substances released by bacteria, brown and red algae have not yet been identified and purified. However, it is demonstrated that in axenic cultures many species of seaweeds produce active extracellular substances which play an important role in growth and Morphogenesis of other species of seaweeds.
66 citations
TL;DR: Skeletonema costatum (Grev.) Cl. exhibits an asexual means, of increasing cell size that is more common than auxosporulation, that accounts for the genetic stability of S. costatum in culture and for the deficiency of heterozygotes in natural populations.
Abstract: Skeletonema costatum (Grev.) Cl. exhibits an asexual means, of increasing cell size that is more common than auxosporulation. This phenomenon accounts for the genetic stability of S. costatum in culture and for the deficiency of heterozygotes in natural populations, and has important implications far the life history of this species.
65 citations
TL;DR: The diatom clone 13–1 isolated from the Sargasso Sea by Dr. R. L. Guillard is described as a separate species, Thalassiosira oceanica sp.
Abstract: The diatom clone 13–1 isolated from the Sargasso Sea by Dr. R. R. L. Guillard as Cyclotella nana Hust. or Thalassiosira pseudonana Hasle and Heimdal is described as a separate species, Thalassiosira oceanica sp. nov. An amplified diagnosis of Thalassiosira partheneia Schrader is given, and a comparison of the two species is made based on light and electron microscopy. Similarities are present in the apparent distribution pattern, cell size, and girdle structure. Differences are present in the shape of the areolae of the valvocopula and the copula, in the structure of the vela of these bands, in the texture of the external valve surface, in the morphology of the strutted processes, in the location of the labiate process, in the distance between the marginal strutted processes, and by the presence of a marginal ridge in T. oceanica. Fifteen nanoplanktonic (maximum diameter = 20 UmUm) Thalassiosira species are listed, among them T. oceanica and T. partheneia.
63 citations
TL;DR: Plants grown at 60 and 140 μE·–2s–1 showed higher light compensation and saturation points, suggesting that the variations in pigment composition found between the different treatments determine the photosynthetic responses at sub–optimal photon fluence rates.
Abstract: The optimal photon fluence rate for growth of tha llus tips of Gracilaria sp. was low (about 100 μE·–2·1); higher photon fluence rates inhibited growth. Both phycoerythrin (PE) and chlorophyll (chl) contents decreased with increasing photon fluence rates (up to 100 μE·–m–2s–1) in a fashion inverse to the growth response. Chl/PE ratios varied directly as the growth response over a larger photon fluence rate range. The peak chl/PE ratios were obtained at a photon fluence rate optimal for growth, suggesting that this parameter may be used to estimate in situ growth rates. A low compensation point (about 7 μE·–2s–1) was observed for low light (15 μE·–2s–1) grown plants. This compensation point was also obtained for growth in the long–term (5–6 weeks) experiments. Plants grown at 60 and 140 μE·–2s–1 showed higher light compensation and saturation points, suggesting that the variations in pigment composition found between the different treatments determine the photosynthetic responses at sub–optimal photon fluence rates. Photosynthetic rates at light saturation were the same, on a biomass basis, for plants grown at the various photon fluence rates. Thus, the photosynthetic dark reactions were not influenced by previous light regimes. It is suggested that maximal photosynthetic rates expressed on a biomass basis better reflect the potential productivity at tight saturation than if expressed on a pigment basis. Gracilaria sp. grew better under non–filtered fluorescent and greenish than under reddish and blue–enriched light of equal and sub–optimal photon, fluence rate. However, the pigment relations of the algae did not change in a direction complementary to the light composition at which they grew. This, together with the relatively higher photosynthetic rates under reddish and blueish light for plants previously grown under reddish and blueish light, suggests that adaptations to variouslight spectra are based on mechanisms different from complementary chromatic adaptation of the pigments.
62 citations
TL;DR: The growth rate of Laminaria saccharina (L.) Lamour is dependent on inorganic nitrogen in culture and most enzyme activities followed a hyperbolic curve resembling those described by the Michaelis‐Menten equation, with different half‐saturation constants.
Abstract: The growth rate of Laminaria saccharina (L.) Lamour. is dependent on inorganic nitrogen in culture. Growth rates were saturated between 5 and 10 μmol · L−1 nitrate. The activities of ribulose-1,5 bisphosphate carboxylase, phosphoenolpyruvate carboxykinase, mannitol-1-phosphate dehydrogenase, nitrate reductase and glutamine synthetase also varied with the concentration of inorganic nitrogen in the medium. All enzyme activities were lowest at 2.5 μmol · L−1 nitrate (the lowest concentration used) increasing to a maximum activity between 10 and 30 μmol · L−1 nitrate. Most enzyme activities followed a hyperbolic curve resembling those described by the Michaelis-Menten equation, with different half-saturation constants.
TL;DR: The physiological behavior of phycoerythrin‐deficient mutants of the red seaweed Gracilaria tikvahiae is compared to that of their wild types and the data do not conform with the predictions of the theory of complementary chromatic adaptation for seaweeds.
Abstract: The physiological behavior of phycoerythrin-deficient mutants of the red seaweed Gracilaria tikvahiae (Mc-Lachlan 1979) is compared to that of their wild types The mutants are phenotypically green while the wild types are red Cloned scions were grown factorially at irradiances saturating and limiting to growth, and spectral distributions which were broadband (white) and narrowband (green) The green light field complements the absorptance spectrum of phycoerythrin Experiments were performed in an outdoor continuous flow system Physiological measurements included light-harvesting pigment composition, instantaneous photosynthesis-light relationships and growth In all cases, the mutants performed as their wild type progenitors Further, physiological responses occurring in no less than 8 days were dependent solely on irradiance (“intensity”), and were independent of spectral distribution (“color”) The data do not conform with the predictions of the theory of complementary chromatic adaptation for seaweeds
TL;DR: The adaptive significance of a life‐history strategy, expressed as divergent morphological forms, was examined for the heteromorphic alga Scytosiphon lomentaria and indicates that selection in the crust form has tended to increase allocation of materials to nonpigmented structural tissue at the expense of photosynthetic tissue and reduced production rates.
Abstract: The adaptive significance of a life-history strategy, expressed as divergent morphological forms, was examined for the heteromorphic alga Scytosiphon lomentaria. Successional studies were performed by physically clearing mature, temporally-constant intertidal communities on San Clemente I., California. At week six, after clearing, complanate thalli dominated the successional plots (mean cover = 23.5%) and began to decline as the cylindrical form became abundant. The latter attained its peak cover (82.3%) at week 13, whereupon it too began a precipitous reduction. The crustose ralfsioid form appeared surprisingly early (4–13 wks) in trace amounts but did not achieve its greatest cover (85.0%) until week 43. The ranking from high to low primary productivity (cylindrical form = 8.1 mg C · g dry. wt-1·h-1, complanate form = 6.5 mg, crustose form = 0.5 mg) corresponded closely with the data for photosynthetic vs. structural components (cylindrical = 92.3% pigmented, complanate = 65.3%, crustose = 32.0%). This finding indicates that selection in the crust form, which is more readily accessible to epilithic grazers, has tended to increase allocation of materials to nonpigmented structural tissue at the expense of photosynthetic tissue and reduced production rates. The results for thallus losses to urchin grazing over 48 h were complanate form = 82.7% lost, cylindrical = 81.4% and crustose = 16.2%, which correlates with the calorific contents of the three forms (i.e. complanate = 4.97 kcal · ash-free g dry wt.-1, cylindrical = 4.46 kcal and crustose = 3.55 kcal). The crustose form had tougher thalli (26 g · mm-2 to penetrate thallus) than either the complanate form (12 g) or the cylindrical form (15 g). It is likely that opposing selective factors have resulted in the evolutionary divergences observed in algae with heteromorphic life histories. Previous work may have overemphasized the selective role of grazing because the crustose form is also adapted to withstand physical forces (sand-scouring, burial and wave-shearing) or as an overwintering stage under physiologically stressful conditions.
TL;DR: The results from crossing experiments showed that two virtually non‐interbreeding populations with a high degree of geographical separation exist in the north‐eastern Atlantic and placed Agardh in synonymy with Gigartina stellata (Stackhouse in Withering) Batters.
Abstract: Fourteen isolates of the crustose marine red alga Petrocelis cruenta J. Agardh from various localities in the British Isles, France (including the type locality), Spain and Portugal gave rise in culture to dioecious foliose plants identifiable as Gigartina stellata (Stackhouse) Batters although two isolates formed only sterile foliose blades. A total of 145 isolates of Gigartina stellata were also grown in culture from various localities in the U.S.A. (Maine), the British Isles, Iceland, Denmark, France, Spain and Portugal using both carpospores and vegetative blade apices. Two basic types of life history were found among these isolates: a direct-type life history involving the formation of further foliose plants from carpospores, some isolates of which also form spermatangia on the same papillae as the cystocarps; and a heteromorphic-type in which only crustose plants resembling Petrocelis cruenta are formed from carpospores. Only heteromorphic-type life histories were found from Spain and Portugal. Both life history types were found in plants from the U.S.A., the British Isles and northern France. Only direct-type life histories were found in plants from Iceland and Denmark. Some Petrocelis-like crusts derived from field collected G. stellata carpospores and Petrocelis crusts of hybrid progeny formed tetrasporangia in 8:16 h LD, 10° C but not in 8:16 h LD, 15° C; 16:8 h LD 10° C or 15° C; and 10:6.5:1: 6.5 h LDLD, 10° C. The spores thus formed were viable and produced normal dioecious male and female gametophytes. Short day and low temperature conditions appear necessary for tetrasporogenesis. The results from crossing experiments with 32 male and 27 female isolates of the heteromorphic-type derived from both G. stellata and P. cruenta showed that two virtually non-interbreeding populations with a high degree of geographical separation exist in the north-eastern Atlantic. Morphological differences between plants from each population are described. On the basis of culture and crossing results, Petrocelis cruenta J. Agardh is placed in synonymy with Gigartina stellata (Stackhouse in Withering) Batters.
TL;DR: Evidence that these algae with high cellular iron quotas are effectively Fe deficient is provided by a decrease in the cytochrome f/chlorophyll a ratio and a much greater decrease in NO3‐ reductase activity than in aldolase activity or H14C03 assimilation.
Abstract: Cadmium inhibits iron uptake and assimilation in the coastal diatom Thalassiosira weissflogii Grun. The effect of cadmium on short term Fe uptake fits ft competitive binding model:
where (Fe3+) and (Cd2++) tire the free ferric and cadmium ion concentrations, respectively. The apparent binding constant Kcds, is calculated to be ca. lO8.2M-1 compared to a Kfe of lO19 M-1. At low free ferric ion concentrations. interference of cadmium with iron transport (at pCd = 8 and pFe* < 20) results in a simultaneous decrease in growth rate and Fe accumulation to a level known 1o limit growth. Upon decreasing the free cadmium ion concentration, cells accumulate a large amount oj iron prior to resumption of normal growth. At higher free ferric ion concentrations (pFe* < 20) normal or elevated Fe quotas are absented but “luxury consumption” of iron still occurs upon reversal of toxicity. Evidence that these algae with high cellular iron quotas are effectively Fe deficient is provided by a decrease in the cytochrome f/chlorophyll a ratio and a much greater decrease in NO3- reductase activity than in aldolase activity or H14C03 assimilation. Under the conditions of this study, cadmium had little effect on Si accumulation. The transport of methylamine (an analog of NH+4) is unaffected by short term exposure to high free cadmium ion concentration but is greatly inhibited upon long term (97 h) exposure.
TL;DR: The apical cells of Sphacelaria tribuloides Menegh are larger than other thallus cells, contain more organelles and appear polarized, and microtubules traverse the thin cytoplasmic strands which, in both interphase and cytokinetic cells, meander among the vacuoles of the basal pole of the cell and the internuclear space.
Abstract: The apical cells of Sphacelaria tribuloides Menegh. are larger than other thallus cells, contain more organelles and appear polarized. Their tip portion, where they grow, contains a well developed Golgi apparatus, abundant endoplasmic reticulum (ER) membranes, mitochondria, chloroplasts and a large number of small vacuoles. It seems likely that a continuous flow of membranous material from the ER membranes to the dictyosomes and from the latter to the plasmalemma of the extending tip portion takes place. In contrast, the basal pole possesses fewer organelles and is occupied mainly by large-sized, sometimes central vacuoles. The apical cells undergo two distinct types of highly asymmetrical differential divisions giving rise to cells of the thallus and hair initials. During the early stages of mitosis the nuclear envelope remains intact, except for fenestrated poles. Microtubules pass through the fenestrae into the nucleoplasm. During meta-phase, a typical chromosome plate is organized. The sites of attachment of spindle microtubules to the chromosomes are structurally different from the rest of the chromosomes. At late anaphase, the nuclear envelope breaks down completely. During telophase, a new membrane encloses the chromosomes which are decondensed and the nucleoli are reorganized. Cytokinesis proceeds long after mitosis at a stage in which the nuclei have increased in size and have moved farther apart. A membranous furrow develops centripetally, without the participation of microtubules. However, microtubules traverse the thin cytoplasmic strands which, in both interphase and cytokinetic cells, meander among the vacuoles of the basal pole of the cell and the internuclear space. Dictyosomes appear to be involved in the subsequent wall deposition.
TL;DR: Both species exhibited submersed photosynthesis‐light relationships and dark respiration rates similar to those established for other closely related intertidal, fucoids, but H. harveyanus thalli contained more water when fully hydrated and lost water more slowly during dehydration, thus suggesting greater photosynthetic potential during field conditions of emersion.
Abstract: Rates of net photosynthesis and dark respiration were determined under submersed and emerged conditions for Hesperophycus harveyanus S & G and Pelvetia fastigiata f gracilis (Decne) S & G Both species exhibited submersed photosynthesis-light relationships and dark respiration rates similar to those established for other closely related intertidal, fucoids Maximal net photosynthesis of H harveyanus (021 mmol O2 g dry wt-1· h-1; 018 mmol CO2 g dry wt-1· h-1) was similar to that of P fastigiata f gracilis (017 mmol O2 g dry wt-1· h-1; 014 mmol CO2 g dry wt -1· h-1) Light saturation occurred between 150 and 250 μE · m-2· s-1 for H harveyanus and between 75 and 150 μE · m-2· s-1 for P fastigiata f gracilis; photon flux densities required for compensation were 64 and 92 μE · m-2· s-1, respectively Photoinhibition was not observed for either species The light-saturated, submersed net photosynthetic performances of both species varied significantly with temperature Greatest photosynthetic rates were obtained at 23° C for H harveyanus and at 18° C for P fastigiata f gracilis Under emersed conditions, the maximal net photosynthetic rate and the photon flux densities required for saturation were greater for H harveyanus (008 mmol CO2 g dry wt-1· h-1; 260 to 700 μE · m-2· s-1) than for P fastigiata f gracilis (002 mmol CO2g dry wt-1· h-1; 72 to 125 μE · m-2· s-1) However, for both species, emersed photosynthetic rates were much lower (14–44%) than those obtained under submersed conditions Desiccation negatively influenced emersed photosynthesis, of both species, but H harveyanus thalli contained more water when fully hydrated and lost water more slowly during dehydration, thus suggesting greater photosynthetic potential during field conditions of emersion
TL;DR: It is proposed that the morphogenetic machinery of NitzSchia and Hantzschia have a common origin, with present Nitzschiae having undergone considerable diversification at the intracellular level, causing the unstable cell symmetry exhibited by several modern species.
Abstract: The relationship of cell organelles to valve morphogenesis was investigated in three species of Nitzschia. One, N. sigmoidea (Nitzsch) W. Sm., showed consistent ability to generate both nitzschioid and hantzschioid symmetry in daughter cells following cytokinesis; the other two maintained nitzschioid symmetry stably. From previous work with Hantzschia, a certain sequence of events could be anticipated in the cytoplasm. In two significant areas–the behavior of the Microtubule Center (MC) and its microtubule (MT) system, and the central origin of the silicalemma–not only were the results unexpected, but the three species showed fundamental differences among themselves. In N. sigmoidea, the silicalemma (and the future raphe region) arises centrally on the cleavage furrow, and after some lateral expansion, the silicalemmas and their associated organelles move in opposite directions in daughter cells, so that the raphe and the raphe canals end up along the girdle side of the cell as expected. However, the MCs never become associated with their silicalemma, remaining throughout near the girdle bands. In N. sigma (Kutz) W. Sm., the silicalemmas arise centrally and after lateral growth, move in opposite directions to generate nitzschioid symmetry. In this case, the MCs move to the vicinity of but never close to the silicalemmas, and follow them distantly during their lateral movement. In N. tryblionella Hantzsch, the new silicalemmas arise opposite one another, on one side of the daughter cells; each MC soon moves very close to its silicalemma, and remains thus through most of valve morphogenesis. Later, only one silicalemma/MC complex moves laterally, establishing the nitzschioid symmetry in both daughter cells. In all three species, as in Hantzschia, linear arrays of mitochondria aligned along MTs occupy the forming raphe canal, and microfilaments line the outer edge of the expanding silicalemma. The fibulae (the wall struts arching across the raphe canal) in Hantzschia always grow from the valve surface to the girdle surface of the forming valves. In these three Nitzschiae, this invariably happens in only one daughter cell of any pair; in the other, all the fibulae grow from the girdle surface to the valve surface. An explanation of these variations is proposed: that the morphogenetic machinery of Nitzschia and Hantzschia have a common origin, with present Nitzschiae having undergone considerable diversification at the intracellular level, causing the unstable cell symmetry exhibited by several modern species. Perhaps a taxonomic distinction between Hantzschia and Nitzschia lies in whether the morphogenetic machinery associated with valve morphogenesis moves laterally in the same or in opposite directions.
TL;DR: The counterclockwise absolute orientation of components, and terminal caps, may be the most consistent flagellar apparatus features of ulvophycean green algae, while variations in other features previously considered diagnostic for the Ulvophyceae may serve instead to identify discrete lineages within this class.
Abstract: The flagellar apparatuses of the quadriflagellate zoo-spores and biflagellate female gametes of the marine chaetophoracean alga Entocladia viridis Reinke are significantly different from those of algae belonging to Chaetophoraceae sensu stricto, but closely resemble those of ulvacean genera. These differences permit the taxonomic reassignment of certain marine chaetophoracean genera and an evaluation of the flagellar apparatus features used to characterize the class Ulvophyceae. Critical features of the zoospore include arrangement of the four basal bodies into an upper and a lower pair with the proximal ends of the upper basal bodies overlapping, terminal caps, proximal sheaths connected to one another by striated bands, and a cruciate microtubular rootlet system having a 3-2–3-2 alternation pattern and striated microtubule-associated components that accompany the two-membered rootlets. An indistinct distal fiber occurs just anterior to the basal bodies, and is closely associated with the insertion into the flagellar apparatus of the three-membered rootlets. The flagellar apparatus demonstrates 180° rotational symmetry, and its components show counterclockwise absolute orientation when viewed from above. Newly described features include the prominently bilobed structure of the terminal caps on the upper basal body pair, and the presence of both a granular zone and an additional single microtubule anterior to each of the four rootlets, an arrangement termed the “stacked rootlet configuration.” Rhizoplasts were not observed and are presumed to be absent. The gamete is identical, except for the absence of the lower basal body pair and the presence of an electron-dense membrane associated structure that resembles the mating structure found in Ulva gametes. These findings, correlated with life history data, sporangial and gametangial structure and developmental patterns, chloroplast pigment arrays, and vegetative cell ultrastructural features, compel the removal of Entocladia viridis and similar members of the marine Chaetophoraceae to a separate family, the Ulvellaceae. The latter is referred to the order Ulvales of the Ulvophyceae. The counterclockwise absolute orientation of components, and terminal caps, may be the most consistent flagellar apparatus features of ulvophycean green algae, while variations in other features previously considered diagnostic for the Ulvophyceae may serve instead to identify discrete lineages within this class.
TL;DR: The validity of a recent nutrient‐based modal of algal photosynthesis was tested using phosphorus‐limited semi‐continuous cultures of the green alga, Scenedesmus quadricauda, and data suggest that the cell quota model is a valid empirical description of the photosynthetic behavior of nutrient‐limited cells.
Abstract: The validity of a recent nutrient-based modal of algal photosynthesis was tested using phosphorus-limited semi-continuous cultures of the green alga, Scenedesmus quadricauda. The data suggest that light-saturate photosynthesis (P opt, mg C · mg chla−1· h−1) is a hyperbolic function of cellular phosphorus quota (Qp), whether Qp is expressed per unit cellular chlorophyll a, per unit dry weight, or per cell number. Furthermore, the light availability during growth appears to have little effect on these hyperbolic relationships over the range of light intensities studied here (65–110 μE · m−2· s−1). These data, and data presented from other published studies, suggest that the cell quota model is a valid empirical description of the photosynthetic behavior of nutrient-limited cells.
TL;DR: Whole cell photosynthesis showed that the rates of oxygen evolution were greatly in excess of the rate of CO2 supply from the spontaneous dehydration of HCO3− in the medium, indicating that bicarbonate is utilized by the cell to support this photosynthetic rate.
Abstract: Various physiological characteristics of photosynthesis in the unicellular red alga Porphyridium cruentum Naegeli have been investigated. The rate of photosynthesis was optimal at 25° C and pH 7.5 and was not inhibited by 21% oxygen over a temperature range of 5 to 35° C. Kinetics of whole cell photosynthesis as a function of substrate concentration gave a K1/2, (CO2) of 0.3 μM. CO2 compensation point, measured in a closed system at pH 7.5, was a constant 6.7 mL · L−1 over the temperature range 15 to 30° C and was unaffected by O2 concentration. Whole cell photosynthesis, measured in a closed system at alkaline pH, showed that the rates of oxygen evolution were greatly in excess of the rate of CO2 supply from the spontaneous dehydration of HCO3− in the medium. This indicates that bicarbonate is utilized by the cell to support this photosynthetic rate. These physiological characteristics of Porphyridium cruentum are consistent with the hypothesis that this alga transports bicarbonate across the plasmalemma.
TL;DR: It appears that this organism fixes atmospheric N2 only at the minimum concentration required to maintain a μ, and the rate of acetylene reduction rate increased with μ in both N2‐ and nitrate‐grown cells, but the rate was lower in nitrate.
Abstract: The effects of N2, nitrate and ammonia as N sources were investigated in P-limited and nutrient-sufficient cultures of Anabaena flos-aquae (Lyngb.) Breb. The maximum growth rate (μm) was highest at 1.34 d−1 with ammonia, compared to 1.18 with nitrate and 0.95 d−1 with N2. There was no difference in P requirement between N2 and nitrate cultures. Under P-limited conditions, the increase in cell P with growth rate (μ) was identical. With N2 as the N source, cell-N concentrations in P-limited cells increased with μ as did cell P, and the cellular N:P ratio remained the same (14) within the range of μ examined. With nitrate, however, cell N concentrations were high and independent of n, except at a low μ. It appears that this organism fixes atmospheric N2 only at the minimum concentration required to maintain a μ. The acetylene reduction rate increased with μ in both N2- and nitrate-grown cells, but the rate was lower in nitrate. Under P-limitation, there was no difference in net C-fixation rate per cell between N2 and nitrate cultures at a given μ. However, the rate per unit of chlorophyll a (chl a) was higher in N2 than in nitrate cultures, and the rate was independent of μ with N2 but was a linear function of nitrate supplied. The maximum C-fixation rate in nutrient sufficient cells was highest with ammonia, followed by nitrate and N2. The cellular chl a concentration was correlated with the total cell-N concentrations regardless of H and the source of N.
TL;DR: Dunaliella tertiolecta (Butcher) was grown in chemostat culture over a wide range of ammonium limited growth rates and the magnitude and duration of photosynthetic suppression was related to the concentration of added ammonium.
Abstract: Dunaliella tertiolecta (Butcher) was grown in chemostat culture over a wide range of ammonium limited growth rates. The addition of ammonium caused a rapid temporary suppression of photosynthetic carbon fixation. The magnitude of ammonium induced photosynthetic suppression increased with the severity of ammonium limitation. Cells growing at rates greater than ca. 80%μmax exhibited no photosynthetic suppression in response to additions of the limiting nutrient. The duration of photosynthetic suppression was related to the concentration of added ammonium. Immediately following the suppression, photosynthesis was enhanced with respect to the controls. The eventual degree of enhancement increased with the concentration of added ammonium. Steady-state cellular chlorophyll concentrations, photosynthetic rates, and assimilation numbers are reported.
TL;DR: The present study indicates that the first two weeks of substrate exposure in the summer represented a colonization phase followed by rapid microsuccession and percent transmittance through the growth layer correlated significantly with cell density and ash‐free dry weight.
Abstract: Adverse weather and resultant turbulence caused sloughing of attached diatom communities during the first two weeks of colonization on artificial substrates. In contrast to Pacific macroalgal systems, older communities (8–12 d) were the most affected by wave action. Ash-free dry weight of the periphyton and diatom cell density generally increased, except following periods of high turbulence when losses of up to 80% occurred. The maximum cell density (4 × 105 diatoms · cm−2) and ash-free dry weight (2.9 mg · cm−2) are among the highest reported for similar conditions. Percent transmittance through the growth layer correlated significantly with cell density and ash-free dry weight and is recommended as a rapid method for measuring the relative accumulation of periphyton. Diatom diversity generally increased throughout the study period and did not clearly reflect the effects of disturbance as did standing crop. Comparisons of diatom diversity and community composition indicated that the three overlapping growth series were not significantly different and samples collected on the same date were not more similar than those of identical age. Combined with previous evidence, the present study indicates that the first two weeks of substrate exposure in the summer represented a colonization phase followed by rapid microsuccession.
TL;DR: The results and additional data in the literature indicate that phytoplankton C and RNA concentrations can be estimated to within a factor of two by multiplying ATP concentrations by 311 and 35, respectively, in N limited systems, and by 341 and 36, respectively in PO43‐ limited systems.
Abstract: The feasibility of estimating phytoplankton carbon and RNA concentrations from measurements of ATP and chlorophyll a (chl a) concentrations was studied using chemostat populations of the marine diatom Thalassiosira weissflogii (Grunow) Fryxell & Hasle (= T. fluviatilis Hustedt). C:ATP and RNA:ATP ratios were studied for six additional marine species in batch culture representing five classes of phytoplankton. Statistical analyses revealed that both the growth rate and the factor limiting growth (NO3-, NH4+, PO43- or light) could alter C:ATP, RNA: ATP, C:chl a and RNA:chl a ratios by amounts which were large compared to measurement error. An analysis of variance of the batch culture results indicated that both species and the source of inorganic nitrogen (NO3-, or NH4+) had a significant effect on C:ATP and RNA:ATP ratios. Light had less of an influence on C:ATP and RNA:ATP ratios than on C:chl a and RNA:chl a ratios, and for this reason we feel that phytoplankton C and RNA concentrations can be estimated with greater reliability from ATP than from chl a measurements. The range of C:ATP and RNA:ATP values found for T. weissflogii under a variety of growth conditions was similar to that for the six additional species grown in batch culture, suggesting that this range of values is indicative of the extremes likely to occur in living cells. Our results and additional data in the literature indicate that phytoplankton C and RNA concentrations can be estimated to within a factor of two by multiplying ATP concentrations by 311 and 35, respectively, in N limited systems, and by 341 and 36, respectively in PO43- limited systems.
TL;DR: Chlamydomonas reinhardtii Dang, was grown in a chemostat culture under phosphate limitation and the steady state concentration of phosphate was below the detection limit (< 1 μg P/L) in all runs.
Abstract: Chlamydomonas reinhardtii Dang, was grown in a chemostat culture under phosphate limitation. The steady state concentration of phosphate was below the detection limit ( 0.12 h−1) and became attached to the wall of the culture vessel. They differed from the vegetative stage in both chemical composition and growth rate. Their contents of phosphorus and chlorophyll a were low, as in the vegetative cells, which grew at a low growth rate, whereas the ration Qpp/Qp and the activity of alkaline phosphatase were comparable with those of fast growing vegetative cells. The growth rate of the palmelloids was 0.03 h−1 whereas maximum growth rate (μm) for the vegetative cells was 0.21 h−1.
TL;DR: Changes in initial slope and pigment concentrations in the blade tissues suggest that, changes in the size or efficiency of electron transfer in the photosynthetic unit occur.
Abstract: The seasonal photosynthetic performances of three age classes of blades of Macrocystis integrifolia Bory were estimated by studying their photosynthetic rate vs. irradiance curves and pigment contents for 15 months. All blade types were irradiance-saturated between 25 and 70 μE · m−2· S−1. Young and mature blade tissues had higher photosynthetic maxima and initial slopes on an area basis than older blade tissue. The latter, however, had pigment concentrations similar to those in mature blade tissues. All these parameters varied on a seasonal basis. The photosynthetic maxima ranged from 0.1–0.8 μmol · C · cm−2· h−t and showed two peaks, one in late summer-early fall and the other in late winter. Changes in initial slope and pigment concentrations in the blade tissues suggest that, changes in the size or efficiency of electron transfer in the photosynthetic unit occur. These data are discussed in relation to changes in seawater temperature and nitrate concentrations.
TL;DR: The fatty acid, sterol and chlorophyll composition of the calcified, unicellular alga Thoracosphaera heimii (Lohmann) Kamptner are reported and the presence of 4,23,24‐termethyl‐5α‐cholest‐22E‐en‐3β‐ol (dinosterol) and the predominance of C18, C20 and C22 unsaturated fatty acids, including the acid 18:5ω3
Abstract: The fatty acid, sterol and chlorophyll composition of the calcified, unicellular alga Thoracosphaera heimii (Lohmann) Kamptner are reported. The presence of 4,23,24-termethyl-5α-cholest-22E-en-3β-ol (dinosterol), 4,23,24-trimethyl-5α-cholest-22E-en-3-one (dinosterone) and the predominance of C18, C20 and C22 unsaturated fatty acids, including the acid 18:5ω3, indicates that T. heimii is a dinoflagellate. The fatty acid: sterol ratio (1.3), is typical of dinoflagellates. The geochemical significance of dinosterone, the high relative concentration of 4-desmethyl-5α-stanols and the role of 23-methyl-5α-cholest-22E-en-3β-ol in the biosynthesis of dinosterol in T. heimii are also discussed.
TL;DR: It is postulate that at least some of the silica‐scaled algae including Mallomonas and Synura may be distinct from other Chrysophyceae based upon pigmentation and other characters described in the literature.
Abstract: We analyzed 34 strains representing 25 species of Chrysophyceae for chlorophylls c1 and c2 using thin-layer chromatography. Most organisms had both chlorophylls c1 and c2 in addition to chlorophyll a but 17 strains of 9 species of Synura and Mallomonas possessed only chlorophylls a and c1. These are the first chlorophyll c-bearing algae which lack chlorophyll c2. We postulate that at least some of the silica-scaled algae including Mallomonas and Synura may be distinct from other Chrysophyceae based upon pigmentation and other characters described in the literature.
TL;DR: Variation in the cyst morphology of a single species that may result from genetic differences among the vegetative clones involved and from variation in the temperature of the environment during cyst development is investigated.
Abstract: Many chrysophycean species produce resting cysts (statospores) with purportedly species-specific morphology. I investigated variation in the cyst morphology of a single species that may result from genetic differences among the vegetative clones involved and from variation in the temperature of the environment during cyst development. Populations of Dinobryon cylindricum Imhof cysts were produced under defined conditions in vitro and then sampled for morphological analysis based on SEM micrographs. Morphological data is presented and then used in a multivariate discriminant analysis to determine the utility of each morphological character in distinguishing the six populations studied. Results suggest that some features of cyst morphology (i.e. cyst diameter) are invariant among the populations, while other features show distinctive variation. The density of spines covering the cyst body as well as the morphology of those spines appear correlated to the specific clones involved, and thus may represent useful phenotypic genetic markers. The length and definition of both the spines and the cyst collar, on the other hand, are markedly influenced by encystment temperature. The implications of these findings for paleoecological studies is discussed.