Showing papers in "Journal of Phycology in 1986"
TL;DR: A distinctive precapture swimming behavior is also deseribed foe six species, suggesting that the dinoflagellates are selective grazers.
Abstract: The feeding of 18 species of thrcale hetrophi dinoflagellates from three genera (Protoperidininm, Oblea, Zygabikodinium) can all be described within one general framework These species engulf diatoms and other prey with a pseudopod (herein terned a “Pallium”)which originates at the flagellar pore in the sulcus The pallium is a highly plastic, membranous organ which rasily strethes to accommodate spines and many as 58 diatom cells in a chain The contents of the phytoplanklon prey are liquified and transporued throughthe pallioum typically within 7 to 30 minutes of capture (although feeding may last 2 h) teaving an intact but empty cell wall or frustule Thus far, with few exceptions, Protoperidinium specises have been observed feeding inly on diatoms, whereas two diplopsaloid species feed on dinoflagellates and prasinophytes as well In four species from the three genera studied a capture filament has been observed that connects the food to the dinoflagellate prior to extension of the pallium, sometimes allowing the cell to pull the food while swimming A distinctive precapture swimming behavior is also deseribed foe six species, suggesting that the dinoflagellates are selective grazers
381 citations
TL;DR: Although the laboratory systems had many species in common during the realy stages of colonization, the experimental treatments generated differences in rates of community development, and the applicability of traditional successional theory to develoopmental patterns in lotic periphyton assemblages is discussed.
Abstract: Effects of current velocity and light energy on the taxonomica and physiognomic characteristics of periphyton assemblages were investigated in laboratory streams. The initial rate of colonization was related to current velocity, while the effects of light energy accounted for differences in species composition by the end of the experiment. Although the laboratory systems had many species in common during the realy stages of colonization, the experimental treatments generated differences in rates of communitydevelopment. synedra spp. were the early coloniters of the substrate, followed by an understory of Achnanthes spp. After day 16, Stigeoclonium tenue developed in the streams exposed to the higher photon flux density, but was rare in the shaded streams. The applicability of traditional successional theory to develoopmental patterns in lotic periphyton assemblages is discussed.
165 citations
TL;DR: It was observed that the lag period for rejuvenation increased with resting cell age (depth of burial in sediments), and in the 14C uptake studies, label was initially observed in condensed state cells, but gradually progressed to the more differentiated forms.
Abstract: Resting cells of Melosira granulate (Ehr.) Ralfs were collected from the anoxic sediments of Douglas Lake, Michigan. Sediment containing M. granulata was inoculated into distilled water and incubated in a growth chamber for one week during which observations were made on the cytological differentiation process. Cells classified as “condensed,” i.e. containing a dark brown cytoplasmic mass were identified as resting cells. The differentiation process consisted of a series of gradual cytological changes that included elongation of the cytoplasmic mass and recognition of definable organelles to the point where the cells were non-distinguishable from water column vegetative cells. Differentiating cells accumulated large polyphosphate and lipid granules. However, these granules disappeared just prior to cell division. The complete differentiation or rejuvenation sequence occurred in some cells in less than 24 h. However, not all dormant cells rejuvenated at the same time and it was observed that the lag period for rejuvenation increased with resting cell age (depth of burial in sediments). In the 14C uptake studies, label was initially observed in condensed state cells. The label gradually progressed to the more differentiated forms. Total carbon uptake during the rejuvenation process was initially lower in the rejuvenating cells, but roughly equal to water column populations after 8 h, indicating a period of high metabolic activity in the rejuvenating cells between 1 and 8 h.
103 citations
TL;DR: The compensation point for growth of Phaeodactylum tricornutum Bohlin is less than 1 μmol, and growth at low PFDs does not appear to reduce the maximum quantum efficiency of photosynthesis or to greatly inhibit the potential for light‐saturated, carbon‐specific photosynthesis.
Abstract: The compensation point for growth of Phaeodactylum tricornutum Bohlin is less than 1 μmol. m−2s−1. Growth at low PFDs (<3.5 μmol. m−2.s−1) does not appear to reduce the maximum quantum efficiency of photosynthesis (om) or to greatly inhibit the potential for light-saturated, carbon-specific photosynthesis (Pmc). The value for om in P. tricornutum is 0.10–0.12 mol O2-mol photon−1, independent of acclimation PFD between 0.75 and 200 μmol.m−2.s−1 in nutrient-sufficient cultures. Pmc in cells of P. tricornutum acclimated to PFDs <3.5 μmol m−2−s−1 is approximately 50% of the highest value obtained in nutrient-sufficient cultures acclimated to growth-rate-saturating PFDs. In addition, growth at low PFDs does not severely restrict the ability of cells to respond to an increase in light level. Cultures acclimated to growth at lees than 1% of the light-saturated growth rate respond rapidly to a shift-up in PFD after a short initial lag period and achieve exponential growth rates of 1.0 d−1 (65% of the light- and nutrient-saturated maximum growth rate) at both 40 and 200 μmol.m−2.s−1
99 citations
TL;DR: The stoichiometry of electron transport complexes changes in response to growth PFD and this change is correlated with the response flexlbility of algal photosynthesis in diverse light environments.
Abstract: Chlamydomonas reinhardtii was grown at photon flux densities (PFDs) ranging from 47 to 400 μE.m-2 s-1. The total cellular content of chlorophyll (Chl) was twice as high in the low light (LL) versus high light (HL) grown cells. On an equal Chl basis, photosystem II (PSII) and cytochrome f (Cyt f) content was higher in HL cells, but photosystem I (PSI) concentration displayed little variation with the light intensity during cell growth. Consequently, there was a shift in the ratio of PSII / PSI and Cyt / PSI from near unity in LL cells to greater than two in HL cells. The functional Chl antenna size of PSII and PSI ranged from 460 and 170 Chl (a + b)in HL-grown cells to 620 and 370 Chl (a+ b)in LL-grown cells, respectively. The initial slope of the Chl-specific photosyn-thesis-irradiance (P-I) curve was similar in LL- and HL-grown cells, but the light saturated rate of photosynthesis was lower under LL. The response to low light was beneficial at the cellular level, since there was an enhancement of photosynthesis in LL. The PFD for the onset of light saturation, 1 was a factor of 2 lower in LL- relative to HL-grown photosythetic membranes. Since growth PFD varied by a factor of ten, photosynthesis shifted from being light-limited in the LL regime to light-saturated in the HL regime. The requirement for balanced absorption of light by the two photosystems constrains the PSII / PSI ratio to near unity when growth is light-limited, but such a constraint does not apply in HL conditions. Instead the concentration of individual electron transport complexes way be related to the pool size necessary for maximum rates of steady-state electron transport. Thus the stoichiometry of electron transport complexes changes in response to growth PFD and this change is correlated with the response flexlbility of algal photosynthesis in diverse light environments.
93 citations
TL;DR: Fluorescence induction and photosynthesis‐irradiance experiments examined the potential effects of salinity and temperature on the physiology of ice algae and showed the rise in in vivo fluorescence intensity during a period of millineconds.
Abstract: The measurement of Photosynthetic rates of algae growing on the undersurface of 1. 7 m thick ice in the Canadian Arctic (Resolute Passage. N.W.T.) presents several problems. During the preparation of samples for physiological measurements, the ice algae may he exposed to salinity and temperature shocks. Fluorescence induction (the rise in in vivo Chl a fluorescence intensity during a period of millineconds) and photosynthesis-irradiance (PI) experiments examined the potential effects of salinity and temperature on the physiology of ice algae.
Experimental suspensions were routinely prepared by scraping one part ire crystals (11–14%0 salinity) and attached algae from the bottom ice into four parts filtered seawater (32%0 salinity). giving a final salinity of 28–31%0. Post-dilution of melted ice scrapings with seawater suppressed photosynthetic 14C-fixation and decreased ADCMU (the area above the fluorescence induction curve measured in the presence of the inhibitor DCMC: an estimate of photosynthetic capacity) by a factor of 3–16. due to the low salinity of the melted ice scrapings. Fluorescence induction and PI experiments showed that the ice algae had a salinity optimum near 30%0, close to the ambient seawater salinity, Experiments in which the Chl a concentration was manipulated showed that ADCMU, Pam (Chl a-normalized rate of photosynthesis at light saturation), and a (photosynthetic efficiency) declined with increasing Chl a concentration. Ice algae tolerated heating (l.5°C-min-1) up to 17° C, above which ADCMU’decreased with sample temperature.
78 citations
TL;DR: Tight coupling of seaweed wrowth and chemical composition may therefor be relatively rare in natural waters where growth can be simultaneously limited by light, temperature, and N.
Abstract: The effects of light on growth, RuBPCase activity, and chemical composition of Ulva curvata (Kutz.) De Toni and U.Lactuca L. were examined at a range of temperatures and N-supply levels. Groeth of Ulva speices becomes more light-dependent with increasing temperature and N. The effect of light on RuBPcase is N-dependent, with a positive correlation under N-sufficient and a negative correlation under N-limited conditions. Light effects on pigment levels and ratios may be independent of effects on growth rate. These interactions uncouple growth rate from RuBPCase and pigments, and thus from tissue%N. The limits of variability of the growth-%N relationship can be described by a parabola. Under relative light or temperature-limitation, %N is negatively, growth increase with increasing %N. Tight coupling of seaweed wrowth and chemical composition may therefor be relatively rare in natural waters where growth can be simultaneously limited by light, temperature, and N.
68 citations
TL;DR: Thalassiodira oceanica Hasle, isolated from a lou'‐managanese oceanic enviorment, was capable of better growth at low manganese ion concentrations that T. Pseudonana hasle and Heimdal, and appeared to be under negative feedback control in both species.
Abstract: Growth rate, cellular manganese concentration and mangfanese uptake kinetics were measured as functions of the free manganese ion concentration in the medium for two centric diatoms. Thalassiodira oceanica Hasle, isolated from a lou'-managanese oceanic enviorment. was capable of better growth at low manganese ion concentrations that T. pseudonana hasle and Heimdal, islated from higt.manganese estuatine waters. This was dur to the oceanic species’ greater avility to accumulate manganese at low free ion concentrations and to grow well at lower cellular manganese concentions. Manganese up take in both species followed classical saturation kinestics, and Vmax but not K, Uaried with the managanese ion concentration in the growth medium. The Ks of managanese uptake for T. Oceanica (10-795 M) was one-seventh of that for T. Pseudonana. accouning for T. oceanica's greater ablility to accumulate managaese at low gree ion concentrations.Vmax appeared to be under negative feedback control in both species and six- to twelve-fold variations in this parameter allowed cells to regulate cellular managanese at nearly constant valies at manganese ion concentrations in the vicinity of and somewhat below Kr The range in free manganese ion concenteations over which regukation occurred was diffrent for the two species, and coincided with the in free manganese ion concentrations of the natural habitat of each species.
68 citations
TL;DR: Over the course of one year the volatile organic biogenic substances found in the water of a eutrophied shallow lake were determined by gas chromatographic and mass spectrometric methods and exhibited marked dynamics in the lake.
Abstract: Over the course of one year the volatile organic biogenic substances (VOBS) found in the water of a eutrophied shallow lake were determined by gas chromatographic and mass spectrometric methods. The substances detected belonged to nor-carotenoids, terpenoids, unsaturated hydrocarbons, ketones, and aldehydes. The occurrence of particular VOBS correlated with the frequency with which certain phytoplankton species were recorded. The latter showed a well developed succession in that year. The following correspondences were found: β-cyclocitral and Microcystis; heptadec-cis 5-ene and Oscillatoria redekei; geosmin and argosmin and Aphanizomenon gracile; hepta-trans, cis 2,4-dienal, deca-trans, cis 2,4-dienal and Dinobryon; octa-trans, cis 1,3,5-triene and Asterionella formosa. Dictyopterenes and ectocarpene were only detected in high amounts in one sample obtained in August. The VOBS exhibited marked dynamics in the lake and usually were rapidly eliminated from the water body.
64 citations
TL;DR: The widespread distribution of certain algae in endolithic habitats of the Colorado Plateau and their presence in rocks at quite distant locations suggests that the endolithic habitat may be utilized by algae whenever it provides more favorable conditions than the surrounding surfaces.
Abstract: Eighteen taxa, including representatives of both eukaryotic and prokaryotic genera, were isolated from below the surface of eight sandstones in four semi-desert and cold temperate biomes of northern Arizona, southern Utah and Western New Mexico. The algae occurred as uniform well defined bands in light-colored sandstones and also as scattered patches in dark sandstones. The algal communities varied in generic composition, chlorophyll a content, and location within the different sandstones. Biomass, estimated by chlorophyll a content, was approximately two to twenty-fold greater than reported for cryptoendolithic algal bands in a cold desert habitat. The widespread distribution of certain algae in endolithic habitats of the Colorado Plateau and their presence in rocks at quite distant locations suggests that the endolithic habitat may he utilized by algae whenever it provides more favorable conditions than the surrounding surfaces.
58 citations
TL;DR: Plants exhibited an annual growth pattern and reached maximum values between May and June and only blade thickness continued to increase tthrooughout the ovservation period.
Abstract: Laminaria saccharina (L) Lamour. Sporophytes were monitored monthly from October 1982 to September 1983 to investigate reproduction phenology and relationshiops to growth paatterns aaat its southern limit of distribution in the northwest Atlantic Ocean (Long Island Soundd). Plants exhibited an annual growth pattern. Growth raate, bladelehgth, maximum width, area, stiipe lehgth an wet weight swhoed the same seasonal pattern and reached maximum values between May and June. Only blade thickness continued to increase tthrooughout the ovservation period. Blade dissintegration occurred dduring August and September.
Reproductive sporophytes occurred throughout the observation period; the greatest frequency of appearance occurred in October (43.8%) and June (37.8%). The blade area covered by sori ranged from 2.4% (Janaury) to 6.1% (August). Meiospore release under laboratory conditions was maximum in May and minimum in July. No meio-spores were released in August Sporulation was not correlated with meristematic growth of nitrogen content How ever, reproductive plants were generally larger and thicker throughout the sporulation period, and had a greater carbort content is spring than nonreproductive plants. Fecundity and reproductive success of female gametophytes were maximum in spring and minimum in winter. The growth of early sporophyte stages in the laboratory was greatest in early spring; however, juvenile macroscopic stages were hardly observed in the field during summer months due to warm water temperatures. “Over-summering” of gamelophytes and / or microscopic sporophytes may account for the annual cycle of Laminaria at its southern limit of distribution.
TL;DR: An Iridaea cordata (Turner) Bory population made up of 83% gametophytes and 17% tetrasporophytes demonstrated little variation in these proportions over three years, contrasting with an expectation that alternations of generations, as demonstrated by culture studies, should result in equal numbers of isomorphic generations.
Abstract: An Iridaea cordata (Turner) Bory population made up of 83% gametophytes and 17% tetrasporophytes demonstrated little variation in these proportions over three years. These data contrast with an expectation that alternations of generations, as demonstrated by culture studies, should result in equal numbers of isomorphic generations. Analyses of reproductive and demographic attributes of the population were made to better understand the role of alternation of generations in this population.
Growth and mortality rates in the summer could not account for the success of gametophytes. however, size class frequencies demonstrated that tetrasporophytes were smaller individuals. Sporelings recruited into this intertidal region and made up 20% of the spring population numbers. Even with this level of recruitment, gametophyte-to-tetrasporophyte ratios did not change. Perennating holdfasts regenerated 80% of the spring number and 90% of the total blade area. Consequently, perennation and differential survival of gametophyte spores or sporelings are proposed as mechanisms maintaining gatnetophyte dominance in this San Juan Island, Washington population.
TL;DR: It is demonstrated that turbulence strongly influences the community structure of periphyton on both micro and macro scale levels.
Abstract: Microdistributional patterns of attached algal communities on Cladophora and glass slides were compared under varying disturbance regimes in the Upper Mississippi River, using light and scanning electron microscopy. Localized physical disturbance, induced by boat traffic and wind-generated wave action in the main channel, inhibited development of complex attached algal communities and maintained an adnate flora with two-dimensional architecture. In contrast, communities protected from disturbance developed a more complex, three-dimensional architecture. A high degree of architectural similarity was observed between communities on Cladophora and glass substrates exposed to similar levels of disturbance. Communities exposed to severe disturbance resembled ones in early stages of colonization and development, whereas less disturbed communities were similar to ones in advanced stages of development. These results demonstrated that turbulence strongly influences the community structure of periphyton on both micro and macro scale levels.
TL;DR: This is the first report of protoplast isolation and cell division in a commercially important, phycocolloid‐producing red seaweed, as well as for a member of the Florideophycidae.
Abstract: Methods were developed for the isolation of large numbers of healthy protoplasts from two species of the agarophyte Gracilaria; G. tikvahiae McLachlan and G. lemaneiformis (Bory) Weber-van Bosse. This is the first report of protoplast isolation and cell division in a commercially important, phycocolloid-producing red seaweed, as well as for a member of the Florideophycidae. The optimal enzyme composition for cell wall digestion and protoplast viability consisted of 3% Onozuka R-10, 3% Macerozyme R-10, 1% agarase and 0.5% Pectolyase Y- 23 dissolved in a 60% seawater osmoticum containing 1.0 M mannitol. The complete removal of the cell wall was confirmed by several different methods, including electron microscopic examination, and the absence of Calcofluor White (for cellulose) and TBO (for sulfated polysaccharide) staining. Spontaneous protoplast fusion was observed on several occasions. Protoplast viability was dependent upon the strain and age of the parent material, as well as the mannitol concentration of the enzyme osmoticum. Cell wall regeneration generally occurred in 2-6 days; cell division in 5-10 days. Protoplast-produced cell masses up to the 16-32 cell stage have been grown in culture. However, efforts to regenerate whole plants have been unsuccessful to date.
TL;DR: The red marine alga Gracilaria sp. (collected on Israel's Mediterranean shore) was grown in the laboratory under controlled conditions and the total agar content was higher in algae grown in natural seawater than in those grown in enriched seawater and decreased only slightly with increasing irradiance.
Abstract: The red marine alga Gracilaria sp. (collected on Israel's Mediterranean shore) was grown in the laboratory under controlled conditions. The effects of the medium (natural seawater or enriched seawater) and of irradiance on the following parameters were studied: growth rate, dry weight, content of pigments, CO2 fixation rate, starch content, and the quality and quantity of agar. The total agar content was higher in algae grown in natural seawater than in those grown in enriched seawater and decreased only slightly with increasing irradiance. The agar composition was also different in algae grown in the two media. The starch content was higher in algae grown in natural seawater than in algae grown in enriched seawater, and in algae in both media it increased with increasing irradiance. Since the starch content in Gracilaria can reach 21% on a dry weight basis, it is important to correct for in when determining the agar content.
TL;DR: The results suggest that development of pyrenoid starch is generally correlated with growth under low CO2 conditions, whereas CO2‐effects on lamellar stacking are species dependent.
Abstract: Effects of CO2 concentration during growth on intracellular structure were studied with ftve species of Chlorella and Scenedesmus obliquus. Cells grown under ordinary air conditions (low-CO2 cells) had a well developed pyrenoid surrounded by starch, while those grown under high CO2 conditions (high-CO2 cells) had a less developed pyrenoid or no detectable pyrenoid. Two mitochondria, one at each side of the neck of the projection of the chloroplast close to the pyrenoid, were found in low CO2 cells of C. vulgaris 11h. Usually, lamellar stacks extended in parallel in the chloroplast of low-CO2 cells of C. vulgaris 11h, while a grana-like structure was found in high-CO2 cells. However, in C. pyrenoidosa, grana like structures were found more commonly in low-CO2 cells than in high-CO2 cells. These results suggest that development of pyrenoid starch is generally correlated with growth under low CO2 conditions, whereas CO2-effects on lamellar stacking are species dependent.
TL;DR: Comparisons of dark fixation at high (8.0) and low (5.2) pH suggest that bicarbonate ions are used as a source of inorganic carbon.
Abstract: The characteristics of dark carbon fixation by Ascophyllum nodosum were investigated. In longitudinal profile the maximum rates of dark and light dependent fixation are found at the apex. The use of Michaelis-Menten kinetics did not suitably describe the relationship between the uptake rate in the dark and the total inorganic carbon concentration. Dark fixation was saturated at a total inorganic carbon concentration [TIC] of 2.5 mM. The use of the Hill-Whittingham equation to describe the uptake curve indicates that the process is diffusion limited. Comparisons of dark fixation at high (8.0) and low (5.2) pH suggest that bicarbonate ions are used as a source of inorganic carbon. The transfer of 14C, fixed in the dark, from the ethanol soluble to the insoluble fraction was relatively slow irrespective of the light treatment during the chase period. Ascophyllum nodosum displays a small diel fluctuation in the pH of aqueous extracts and titratable acidity similar to that displayed by CAM plants. The significance of dark fixation to the overall carbon budget is discussed.
TL;DR: Fifteen freshwater cryptomonad species were freeze‐dried and examined with the scanning electron microscope and Cryptomonas spp.
Abstract: Fifteen freshwater cryptomonad species were freeze-dried and examined with the scanning electron microscope. Surveys of cell surfaces revealed four general cell types. Chroomonas type cells lack a furrow but possess a shallow vestibular depression where the flagella are inserted. The presence of a gullet could not be detected. Cryptomonas spp. displayed three morphological types, all lacking gullets. The first type of Cryptomonas has a simple, shallow furrow with ridges that apparently can close to form a raphe but an oval opening or stoma remains at the posterior end and an opening from the vestibulum is formed at the anterior end. The second Cryptomonas type consists of a complex furrow with furrow ridges and folds that extend almost two-thirds of the cell length. A sloma is present in the central region of the closed furrow. The folds apparently can separate thereby exposing the underlying furrow. The third type of Cryptomonas possesses a simple, non-closing furrow. At the anterior end there is a vestibular ligule which extends from the dorsalleft side of the cell and covers the region of the vestibulum where the contractile vacuole discharges.
TL;DR: Cultured, actively growing cells of Odentella sinensis secrete mucilage, forming gelatinous masses; the mucilage can be visualised with Alcian Blue.
Abstract: Cultured, actively growing cells of Odentella sinensis secrete mucilage, forming gelatinous masses; the mucilage can be visualised with Alcian Blue. When examined live with the light microscope, many cells exhibited continuous small shuffing and rocking movements that could last for long periods (30-40 min); the cells, however, were not translocated and remained relatively fixed in position with respect to their neighbours.
Ultrastructural examination of these cells showed prominent aggregations of mucilage vesicles, derived from the Golgi bodies, at the base of the labiate processes, each of which is close to an elevation bearing an ocellus. In Ditylum brightwellii, similar aggreations of these vesides were also located at teh labiate processes; this diatom, too, secretes mucilage but does not have ocelli. We conclude that the movements observed in O. sinenisis are an indirect result of active muilage secretion through the labiate process. It has been suggested that the raphe may have evolved from the labiate process; our conclusion, therefore, has phylogenetic implications, suggesting a functional as well as a morphological relationship between the two valve structures.
TL;DR: It is recommended that attention should be paid to the occurrences and possibility of toxic bloom of M. viridis from the standpoint of water management and public health.
Abstract: Lethal toxicity (intraperitoneal, mouse) was examined in relation to Species composition of samples containing bloom-forming Microcystis populations from natural waters and correlated with toxicity of laboratory strains of four Microcystis formas and species. Toxicity was not always associated with the presence of M. aeruginosa f. aeruginosa Elenkin. A sample with almost all cells of M. aeruginosa f. aeruginosa showed no toxicity, However samples comprised of a high percentage of M. viridis Lemmermann often showed lethal toxicity. Toxicity tests were done on culture strains M. aeruginosa f aeruginosa, M. aeruginosa f flos-aquae Elenkin, M. viridis and M. wesenbergii Kamarek. All five cultured strains of M. viridis were found to be toxic, while only one out of nine strains of M. aeruginosa f. aeruginosa was toxic. Six strains of M. wesenbergii showed no toxicity, It is recommended that attention should be paid to the occurrences and possibility of toxic bloom of M. viridis from the standpoint of water management and public health.
TL;DR: Standard bright field or phaseconrast microsocopy could not reliably distinguish the cyanobacteria within Hemiaulus spp.
Abstract: The presence of nitrogen–Fixing cyanobacterial endophytes, such as Richelia intracellularis Schmidit commonly observed within several species of Rhizosolenia, in nitrogen-limited oceanic waters has obvious implications both for the host organism(s) and for the entire planktonic assemblage. Recently, epi-fluorescent examination of pllankton samples collected off Oahu, Hawaii, in september 1982 revealed R. intracellularis within the diatoms Hemiaulus membranaceus Cleve and H. hauckii Grunow as well as its expected presence within Rhizosolennia spp. Richelia intracellularis coccurred with within Hemiaulus spp. at frequenccies (ca.80%)comparable to those noted for Rhizosolenia spp. Standard bright field or phaseconrast microsocopy could not reliably distinguish the cyanobacteria within Hemiaulus spp. If this association is common, the occurrence of R.intracellularis (and its significance in the nitrogen dynamics of the ocean)may have been greatly underestimated in previous studies.
TL;DR: Within 15 months or less of the eruption, algal communities were established throughout the blast impact area, but as a result of the initial and continued disturbance these communities remained in an early successional stage.
Abstract: Mt. St. Helens, a volcanic peak in the Cascade Range in southern Washington erupted violently on May 18, 1980, causing enormous damage to both terrestrial and aquatic ecosystems. The initial explosion evaporated, scoured or buried all springs and streams in the blast impact area. Ash fall and erosion from defoliated hillsides subsequently filled most of the lotic habitats with organic debris and volcanic ash. Recolonization of springs and streams by algae occurred quickly in areas where erosion through the ash progressed down to bedrock. Within 15 months or less of the eruption, algal communities were established throughout the blast impact area. However, as a result of the initial and continued disturbance these communities remained in an early successional stage. Floral assemblages were highly variable except that they were composed mostly of diatoms, with Achnanthes minutissima dominating most lotic sites. Springs showed the most rapid development toward stable floras.
TL;DR: It is concluded that chrysophycean flagellates may have a perennation strategy quite different from that of the majority of planktonic diatoms, dinoflageLLates, and green algae for which resting cyst production requires an exogenous trigger usually associated with physiological stress and periods of negative growth.
Abstract: Sexual reproduction of the common planktonic chrysophyte Synura petersenii is described from observations made on clonal isolates grown in defined culture. Sexual fusion was isogamous and heterothallic, with cells of normal appearance from compatible clones serving as hologametes. No special culture conditions were required to induce sexual behavior; actively growing cell populations appeared to be continually receptive to mating when mixed with a sufficient number of cells from a compatible clone. A single, bipolar mating group was documented containing five of the seven clones tested. Zygotic statospores were found to be binucleate and to contain 4 chloroplasts at maturity. Production rates of zygospores were low for even the most highly compatible clones, with batch culture yields ranging from 1-20% of final cell density under the culture conditions utilized. Six of the clones tested were also capable of very low frequency (0.001-0.01%) homothallic statospore production but the reproductive significance of these cysts remains enigmatic. The dynamics of sexual encystment suggest that the process proceeds during periods of active population growth and is density dependent. Based on the characteristics of cyst induction and encystment dynamics, it is concluded that chrysophycean flagellates may have a perennation strategy quite different from that of the majority of planktonic diatoms, dinoflagellates, and green algae for which resting cyst production requires an exogenous trigger usually associated with physiological stress and periods of negative growth.
TL;DR: It is proposed that polyploidy may be of widespread occurrence in Spirogyra with plane end walls and that associated morphological plasticity may account for the high apparent specied diversity and survival of the genus in a wider variety of microhabitats than occupied by other Zygnemataceae.
Abstract: Large-scale collections of Zygnemataceae in the continental United States of America were made between March and August in 1982, 1983, and 1984. Collections were made on a 31000-km transect through 35 states. Zygnemataceae were found at 318 sites was inspected. Temperature average 19°C and pH averaged 6.1 over all sites. Algal strains in collections were identified to genus, characterized for filament width, chloroplast number, and end wall type, then photographed and isolated into unialgal culture. Spirogyra was the most common genus collected(632 strains), followed in abundance by Zygnema (174 Strains) and Mougeotia (135 strains). These three genera contained 95% of the strains collected and were equally widely distributed. Strains of the three genera frequently occurred together; no genus displayed evidence of habitat specialization among the three habitat types: flowing water, permanent ponds or lakes, and temporary pools. In Spirogyra, strains with plane (flat) end walls were four times more abundant than those with replicate (interlocking) end walls. Spirogyra with plane end walls showed more variation in filament width than Zygnema, Mougeotia, or Spirogyra with replicate end walls. In Spirogyra with plane end walls, filament width was correlted with nuclear DNA content and number of strains found per collection site was twice that of other genera or Spirogyra, with replicate end walls. Spirogyra strains wider than 70 μm were more frequent on the northern part of the transect. It is proposed that polyploidy may be of widespread occurrence in Spirogyra with plane end walls and that associated morphological plasticity may account for the high apparent specied diversity and survival of the genus in a wider variety of microhabitats than occupied by other Zygnemataceae.
TL;DR: The uptake and incorporation of tritiated thymidine (3H‐TdR) by axenic laboratory cultures of marine diatoms and dinoflagellates was measured and appears to accurately indicate the timing of DNA synthesis.
Abstract: The uptake and incorporation of tritiated thymidine (3H-TdR) by axenic laboratory cultures of marine diatoms and dinoflagellates was measured. 3H-TdR was incorporated into nucleic acids by all four algae examined during a two to six hour period prior to cytokinesis and not during other times of the cell cycle. Between 90-95% of the 3H label incorporated into (cold trichloroacetic acid insoluble) nucleic acids was recovered from DNA. Incorporation of 3H-TdR appears to accurately indicate the timing of DNA synthesis. The incorporation of 3H-TdR by eucaryotic algae during long term (24 h) incubations does not generally preclude using 3H-TdR uptake to estimate bacterial production and growth during short term incubations.
TL;DR: May and June bioassays suggest that Bay water could not support sexuality (hence spore formation) in L. danicus during this period, and Examination of the early June data indicates the replacement of one population by another.
Abstract: A field study to assess resting spore importance in long-and short-term population dynamics of Leptocylindrus danicus (Ehr.) Gran was carried out, based on the observation that germinating spores produce only vegelative cells of maximum diameter. From May through November 1978. L. danicus was present in lower Narragansett Bay, but resting spores were not found. May and June bioassays suggest that Bay water could not support sexuality (hence spore formation) in L. danicus during this period. Mean valve diameter decreased abruptly in early June. as did cell number. When mean valve diameter increased abruptly in August, with no resting spores seen, 70 additional clonal isolates showed that one clone had the “normal” sexual and spore-forming life cycle while 69 clones had an “alternate” life cycle lacking sperm and spore formation. Valvar fine structure of the two types differed with respect to the presence or absence of a subcentral valvar pore, and a new subspecific taxon is here distinguished: variety apora. Examination of the early June data indicates the replacement of one population by another. Populations of L. danicus may be sporadically introduced into Narragansett Bay from Gulf Stream rings.
TL;DR: Growth efficiencey N. americana, calculated as the ratio between specific growth rates and rates of gross photosynthesis, increased with an increase in salinity with a maximum at the predicted optimum temperature and salinity of 25°C and 32‰, suggesting and uncoupling between photosynthesis and growth at nonoptimum growth conditions.
Abstract: The physiological response of an estuarine clone of Nitzschia americana Fryx3ell was measured under experimental conditions of temperature and salinity which represent the average range of these variables in the Cape Fear River Estuary, North Carolina. The influence of temperature (10, 15, 20, 25, 30°C) and salinity (8, 15, 20, 26, 32‰) on specific growth rates, μ, and parameters of photosynthesis-irradiance curves, α, and Pmax were measured during maximum and minimum rates of diurnal photosynthesis using axenic semi-continuous batch cultures maintained at an irradiance saturating for photosynthesis (140 μE m-2·s-1). There was an increase in μ with increasing temperature up to a broad uptimum (25 ± 2.5°C), above which μ gradually declined. At the predicted optimum temperature of 25°C, μ increased as a linear function of salinity. oth light-limited (α) amd light-saturated (Pmax) rates of photosynthesis increased as salinity decreased. The effect of temperature on a and Pmax was complex and dependent on salinity. Pmax exhibited a diurnal periodicity, whereas estimates of a were not significantly different between sampling periods. Growth efficiencey opf N. americana, calculated as the ratio between specific growth rates and rates of gross photosynthesis, increased with an increase in salinity with a maximum at the predicted optimum temperature and salinity of 25°C and 32‰, suggesting and uncoupling between photosynthesis and growth at nonoptimum growth conditions.
TL;DR: This paper records previously unreported morphological detail of Cyclostephanos and speculates that structure of the punctum, labiate process and strutted process may enhance diagnosis of the freshwater genera of the Thalassiosiraceae Lebour emend.
Abstract: Two new species of the diatom genus Cyclostephanos Round are described from Pliocene fossil deposits in western North America. Cyclostephanos undatus is distinguished from other Cyclostephanos species by its tangentially undulate valve face; Cyclostephanos fenestratus is distinguished by its extremely shallow alveoli. This paper records previously unreported morphological detail of Cyclostephanos and speculates that structure of the punctum, labiate process and strutted process may enhance diagnosis of the freshwater genera of the Thalassiosiraceae Lebour emend. Hasle. Cyclostephanos undatus is similar to several Cyclotella species, but its external costae are raised and its alveolar morphology is similar to that of Cyclostephanos dubius (Fricke) Round. Cyclostephanos fenestratus is similar in external view to Stephanodiscus Ehrenb. However, the two species described here have flat cribra covering the mantle puncta and the labiate processes appear to lack external tubes, whereas Stephanodiscus species have domed mantle cribra and external tubes.
TL;DR: The ultrastructural features of the dormant, condensed state in resting cells of M, granulata are similar to those described for hypnospores and could provide a population of cells which could easily revert should environmental conditions become adverse.
Abstract: Detailed cytological changes that accompany the rejuvenation of resting cells of Melosira granulata were studied with the electron microscope. Dormant and viable cells that we previously classified as the condensed state generally contain definable chloroplasts, mitochondria, a nucleus and other cytoplasmic remnants. However, there appears to be a continuous cytoplasmic degradation spectrum and some cells which appear intensely colored with the light microscope have discontinuous chloroplast membranes and few other cytoplasmic remnants. Rejuvenation of viable dormant cells is initially accompanied by the accumulation of both lipids and polyphosphates. In the earliest stages of expansion, these storage products are dispersed throughout the cell. In later stages of expansion, the lipids appear to be coalesced into larger droplets which are easily identified at the light microscope level. The fully expanded stage is characterized by the normal complement of organelles and their arrangement at the periphery of the cells and central cytoplasmic bridge. These cells appear both anabolically and catabolically active as evidenced by the abundance of endoplasmic reticulum, ribosomes and secretory and lytic vesicles. Prior to cell division, both lipids and polyphosphates a re reduced or absent in the cells. The ultrastructural features of the dormant, condensed state in resting cells of M, granulata are similar to those described for hypnospores. A rejuvenation sequence that produces cytological features common to resting state formation could provide a population of cells which could easily revert should environmental conditions become adverse.
TL;DR: Electron microscopic studies demonstrate that the pyrenoid disperses concomitantly with the period of paramylon increase, and the distribution of ruBisCO in the clocrplast is directly related to pyrenoids dispersal.
Abstract: A System has been developed to study the photoheterotrophic synthesis of paramylon, a β-1,3 glucan storage product found in the euglenoid flagellates. The amount of paramylon in the cells is controlled by manipulating the levels of nutrients in the culture medium. During experimental conditions, when cells are transferred from an incomplete to a complete medium, the transferred from an incomplete to a complete medium, the paramylon concentration increases at least seven-fold relative to the controls. Electron microscopic studies demonstrate that the pyrenoid disperses concomitantly with the period of paramylon increase. The pyrenoid of Euglena is labeled by a ribulose-1,5 bisphosphate carboxylase-oxygenase(Ru-BisCO)antibody. The distribution of ruBisCO in the clocrplast is directly related to pyrenoid dispersal.