bluuebunny/crossref_metadata_2025 huggingface dataset:
Burning Influences on Wiregrass (Aristida beyrichiana) Restoration Plantings: Natural Seedling Recruitment and Survival
Authors: Mulligan Maureen K. , Kirkman L. Katherine
Published: March 2003

Regeneration and expansion ofAristida beyrichianaandAristida stricta(wiregrass) populations in remaining fire‐maintainedPinus palustris(longleaf pine) stands of the southeastern United States has become an objective of land managers. Although growing‐season fire is required for successful wiregrass seed production, studies examining naturally occurring wiregrass seedling dynamics are few. This study investigates how seedling survivorship is affected by season of burn, seedling size, time since germination, and proximity to adult plants. Restoration at this research site was begun in 1992 with the planting of containerized longleaf pine and wiregrass seedlings. Study plots were established in November 1997 after a growing‐season prescribed fire (June 1996) that resulted in successful seed production and seedling recruitment. Burn treatment plots included (1) no burn (control), (2) fire in the dormant season of the first year after germination (March 1998), (3) fire in the growing season of the first year after germination (August 1998), and (4) fire in the growing season of the second year after germination (July 1999). Seedling mortality increased with growing season burning and close proximity to planted adults. Natural seedling recruitment continued into the second year after initial seed‐drop in all plots, which verifies that wiregrass seed banking occurs for a minimum of 2 years after seed drop. Where wiregrass management objectives include population expansion, seedling recruits should be allowed 1 to 2 years post‐germination without growing season fire for successful establishment.
Prescribed Fire and Herbicide Effects on Soil Processes During Barrens Restoration
Authors: Rhoades Chuck , Barnes Thomas , Washburn Brian
Published: March 2003

Prescribed fire has become a common tool of natural area managers for removal of non‐indigenous invasive species and maintenance of barrens plant communities. Certain non‐native species, such as tall fescue (Festuca arundinacea), tolerate fire and may require additional removal treatments. We studied changes in soil N and C dynamics after prescribed fire and herbicide application in remnant barrens in west central Kentucky. The effects of a single spring burn post‐emergence herbicide, combined fire and herbicide treatments, and an unburned no‐herbicide control were compared on five replicate blocks. In fire‐plus‐herbicide plots, fescue averaged 8% at the end of the growing season compared with 46% fescue cover in control plots. The extent of bare soil increased from near 0 in control to 11% in burned plots and 25% in fire‐plus‐herbicide plots. Over the course of the growing season, fire had little effect on soil N pools or processes. Fire caused a decline in soil CO2flux in parallel to decreased soil moisture. When applied alone, herbicide increased plant‐available soil N slightly but had no effect on soil respiration, moisture, or temperature. Fire‐plus‐herbicide significantly increased plant‐available soil N and net N transformation rates; soil respiration declined by 33%. Removal of non‐native plants modified the chemical, physical, and biological soil conditions that control availability of plant nutrients and influence plant species performance and community composition.
Restoration of Highly Impacted Subalpine Campsites in the Eagle Cap Wilderness, Oregon
Authors: Zabinski Catherine A. , DeLuca Thomas H. , Cole David N. , Moynahan October Seastone
Published: March 2003

The effects of intensive recreation impacts and restoration amendments on soil parameters were assessed at four campsites in the Eagle Cap Wilderness, northeastern Oregon. Sites (2,215‐ to 2,300‐m elevation) are characterized by shallow granitic soils, anAbies lasiocarpa/Pinus albicaulisoverstory, and aVaccinium scopariumunderstory. In fall 1995, plots were established at four campsites on three subalpine lakes in which soils were scarified, compost amended, and planted to native species. In summer 1998, we sampled surface soils (0–15 cm) on undisturbed sites (between and under vegetation) and unamended and compost‐amended campsite soils. Samples were analyzed for total organic C, total N, potentially mineralizable N (PMN), NH4, soil moisture, microbial biomass, basal 5‐day respiration rates, and microbial community carbon utilization profiles. Unamended campsite soils had significantly lower levels of PMN, microbial biomass, basal respiration, and number of substrates metabolized in carbon utilization profiles. Compost addition elevated all these impacted parameters on campsite soils, although the increase in basal respiration rate was neither statistically significant nor sufficient to approach rates found underneath vegetation on undisturbed soils. Only the number of substrates metabolized in the carbon utilization profiles was significantly higher on compost‐amended soils than on undisturbed soils. Levels of PMN indicate that campsite soils may lack sufficient N for rapid plant regeneration, whereas amended and undisturbed soils contained adequate quantities of available N. This work suggests that compost amendments can ameliorate impacts to soil chemistry and microbial populations caused by camping, without exceeding the N fertility found on undisturbed soils.
Physical Evolution of Restored Breached Levee Salt Marshes in the San Francisco Bay Estuary
Authors: Williams Philip B. , Orr Michelle K.
Published: March 2003

Since 1972 over 940 ha (2,300 ac) of leveed former salt marsh sites around San Francisco Bay have been restored to tidal action, purposely or through natural processes. The evolution of these sites can inform predictions of rates of marshplain evolution and establishment of tidal channel systems. A review of the history of 15 re‐flooded sites ranging in size from 18 to 220 ha (45 to 550 ac) and in age from 2 to 29 years indicates that marshplain vegetation with more than 50% cover was established at nine of the sites within 4 to 20 years. The remaining six sites aged 2 to approximately 20 years continue to be less than 50% vegetated. The evolution of these sites is consistent with the following simple conceptual model of the physical evolution of restored tidal marshes in subsided breached sites. Initially, deposition of estuarine sediment builds up mudflats that allow vegetation establishment once elevations are high enough for vegetation to survive. Sites that are initially lower in the tidal frame take longer to vegetate than those that are initially higher. Three factors appear to retard the time frame for vegetation establishment: limited estuarine suspended sediment supply, erosion of deposited estuarine muds by internally generated wind waves, and restricted tidal exchange. These factors affect evolution more significantly in larger sites. The comparatively short time frame for vegetation colonization and marshplain evolution experienced in earlier, smaller, and/or less subsided breached levee restorations may not necessarily be replicable by simple levee breaching on larger subsided restoration sites now being planned. Our review of the 15 sites also indicates that the formation of tidal channels within the marshes is greatly dependent on whether and how high the site was filled before breaching. Filled sites at high intertidal elevations (above approximately 0.3 m below mean higher high water) can vegetate quickly but after several decades may show little development of tidal channels.
Assessing Stream Ecosystem Rehabilitation: Limitations of Community Structure Data
Authors: Brooks Shane S. , Palmer Margaret A. , Cardinale Brad J. , Swan Christopher M. , Ribblett Suzanna
Published: March 2003

Inappropriate land use practices, pollutants, exploitation, and overpopulation have simplified stream habitats and degraded water quality worldwide. Management agencies are now being tasked to ameliorate impacts and restore stream “health,” yet there is a dearth of rigorous scientific methods and theory on which to base sound restoration design and monitoring. Despite this, many localized restoration projects are being constructed to stabilize erosion and enhance habitat heterogeneity in streams. Many restoration attempts adopt the paradigm that increasing habitat heterogeneity will lead to restoration of biotic diversity, yet there have been few studies that have manipulatedvariationof a physical parameter independent of the mean to isolate the effects of heterogeneityper se. We conducted a field experiment to mimic restoration of habitat heterogeneity in a shallow. stony stream. By using an experimental approach rather than a detailed assessment of existing restoration work, we were able to control the starting conditions of replicate riffles so that organism responses could be unambiguously attributed to the heterogeneity treatments. We successfully manipulated thevariabilityof streambed particle sizes and consequently near‐bed flow characteristics of entire riffles. These factors define axes of habitat heterogeneity at scales relevant to the resident macroinvertebrate fauna. Despite this, we were unable to distinguish differences in community structure between high and low habitat heterogeneity treatments. Power analysis indicated that macroinvertebrate populations were more sensitive to individual site conditions at each riffle than to the heterogeneity treatments, suggesting that increasing habitat heterogeneity may be an ineffective technique if the restoration goals are to promote macroinvertebrate recovery in denuded streams. With extremely high variability between replicate riffles, monitoring programs for localized restoration projects or point source impacts are unlikely to detect gradual shifts in community structure until the differences between the reference and treatment sites are extreme. Innovative measurement of other parameters, such as ecosystem function variables (e.g., production, respiration, decomposition), may be more appropriate indicators of change at local scales.
Sciatic inflammatory neuritis (SIN): Behavioral allodynia is paralleled by peri‐sciatic proinflammatory cytokine and superoxide production
Authors: Gazda Lawrence S. , Milligan Erin D. , Hansen Michael K. , Twining Carin M. , Poulos Nicholas M. , Chacur Marucia , O'Connor Kevin A. , Armstrong Charles , Maier Steven F. , Watkins Linda R. , Myers Robert R.
Published: March 2003

Abstract  We have recently developed a model of sciatic inflammatory neuritis (SIN) to assess how immune activation near peripheral nerves influences somatosensory processing. Administration of zymosan (yeast cell walls) around a single sciatic nerve produces dose‐dependent low‐threshold mechanical allodynia without thermal hyperalgesia. Low (4 μg) doses produce both territorial and extraterritorial allodynia restricted to the injected hindleg. In contrast, higher (40 μg) doses produce territorial and extraterritorial allodynias of both hindlegs, an effect not accounted for by systemic spread of the zymosan. The aim of these experiments was to determine whether these behavioral allodynias were correlated with immunological and/or anatomical changes in or around the sciatic nerve. These experiments reveal that zymosan‐induced bilateral allodynia was associated with the following: (a) increased release of both interleukin‐1β and tumor necrosis factor‐α from peri‐sciatic immune cells; (b) increased release of reactive oxygen species from peri‐sciatic immune cells; (c) no change in circulating levels of proinflammatory cytokine; (d) no apparent zymosan‐induced influx of immune cells into the sciatic nerve from the endoneurial blood vessels; (e) mild edema of the sciatic, which was predominantly restricted to superficial regions closest to the peri‐sciatic immune cells; and (f) no anatomic evidence of changes in either the ipsilateral saphenous nerve or contralateral sciatic nerve that could account for the appearance of extraterritorial or contralateral (“mirror”) allodynia, respectively. No reliable differences were found when the low‐dose zymosan was compared with vehicle controls. Taken together, these data suggest that substances released by peri‐sciatic immune cells may induce changes in the sciatic nerve, leading to the appearance of bilateral allodynia.
Neurolymphomatosis associated with muscle and cerebral involvement caused by natural killer cell lymphoma: a case report and review of literature
Authors: Odabasi Zeki , Parrott James H. , Reddy Vishnu V.B. , Oh Shin J.
Published: March 2003

Abstract  We report a biopsy‐proven case of neurolymphomatosis (NL) presenting with sensory motor axonal polyneuropathy, polymyositis, and cerebral involvement.

Ours is the second reported case of NL caused by natural killer‐cell lymphoma defined by morphology and immunophenotyping. For 3 months, the patient developed stocking‐glove distribution of hypesthesia, subacute progressive weakness and mental deterioration. EMG showed severe sensorimotor mixed axonal‐demyelinating polyradiculoneuropathy. Lumbar puncture revealed mildly high protein level with normal glucose and cell count. Sural nerve biopsy demonstrated lymphomatous axonal neuropathy and muscle biopsy was indicative of lymphomatous polymyositis. Brain MRI revealed multiple white matter lesions, consistent either with progressive multifocal leukoencephalopathy or cerebral lymphoma. Bone marrow biopsy showed neoplastic infiltrates. The patient died of multiple organ failure prior to initiation of chemotherapy.
Degeneration and regeneration of the peripheral nervous system: From Augustus Waller's observations to neuroinflammation
Authors: Stoll Guido , Jander Sebastian , Myers Robert R.
Published: March 2003

Abstract  This review article on the degeneration and regeneration of peripheral nerve fibers was presented as a Plenary Lecture at the 2001 meeting of the Peripheral Nerve Society. It is accompanied by a reprint of Augustus Waller's 1850 article, which gave rise to the pathologic process termed Wallerian degeneration. This review is focused on the role of neuroinflammation in Wallerian degeneration and how immune mediators contribute to both axonal degeneration and regeneration. Similarities and differences between the PNS and CNS in terms of inflammation and microglial activation after nerve injury are discussed, and point towards progress in understanding the failure of nerve fiber regeneration in the CNS.
LR white post‐embedding colloidal gold method to immunostain MBP, P0, NF and S100 in glutaraldehyde fixed peripheral nerve tissue
Authors: Keita Mahamane , Magy Laurent , Richard Laurence , Piaser Martine , Vallat Jean‐Michel
Published: March 2003

Abstract  A variety of immunocytochemical techniques are now widely used for the electron and light microscopic examination of biological samples. They are employed routinely for investigating the role of certain proteins in nervous tissue. Immunoelectron microscopic studies require the tissue to be fixed and embedded in a solid support, which may disrupt cellular structures and destroy crucial antigens. A technique of post‐embedding with LR white resin has been developed, and it has been shown that certain antigens tolerate fixation with glutaraldehyde. In this study, we optimized a previous post‐embedding method using low‐water‐miscible low‐temperature embedding resin (LR white) to immunostain MBP, P0, NF and S100 proteins in peripheral nerves fixed with a relatively high concentration of glutaraldehyde found to be compatible with the morphology of normally compacted nerve fibers from humans and adult animals. The main difference in the procedures described here from previous ones is the elimination of vibratome sectioning, rendering this immunostaining technique more accessible to neuropathological laboratories using standard equipment for the ultrastructural study of peripheral nerves. It may prove of value for localization and quantification of these proteins in normal and pathological conditions.
POPULATION DYNAMICS OF MICROALGAE IN THE UPPER LAND‐FAST SEA ICE AT A SNOW‐FREE LOCATION
Authors: Stoecker Diane K. , Gustafson Daniel E. , Black Megan M. D. , Baier Christine T.
Published: March 2003

The population dynamics of interior ice microalgae were investigated at a snow‐free site on annual land‐fast sea ice in McMurdo Sound, Antarctica, during the austral spring and summer of 1995–96. A dynamic successional sequence was observed with life history transformations playing an important role. During late November and early December (austral spring), cryo‐ and halotolerant dinoflagellates and chrysophytes bloomed in brine channels within the upper ice. At this time, competition and grazing pressure are low because of the inability of most marine species to grow under the extreme environmental conditions found in the upper ice during the austral spring. In November and December, dinoflagellates, chrysophytes, and prasinophytes contributed an average of 66%, 44%, and <1% of the phytoflagellate biomass, respectively. Both the dinoflagellates and the chrysophytes encysted in December, with cyst formation most intense just prior to surface melt and flushing of the ice. The cysts appear to be an adaptation for survival and dispersal in the plankton during ice decay and/or overwintering in the sea ice. In January (austral summer), when ice temperatures were similar to those in the water column, pennate diatoms replaced flagellates as the photosynthetic dominants in the upper sea ice. The upper land‐fast sea ice undergoes dramatic seasonal changes in light availability, temperature, brine salinity, and inorganic nutrient availability. Ephemeral blooms of cyst‐forming phytoflagellates exploit this habitat in the austral spring, when both inorganic nutrients and light are available but temperatures <−2° C and brine salinities elevated.
THE CIRCADIAN RHYTHM OF BIOLUMINESCENCE IN PYROCYSTIS IS NOT DUE TO DIFFERENCES IN THE AMOUNT OF LUCIFERASE: A COMPARATIVE STUDY OF THREE BIOLUMINESCENT MARINE DINOFLAGELLATES
Authors: Knaust Rosemarie , Urbig Thomas , Li Liming , Taylor Walter , Hastings J. Woodland
Published: March 2003

The biochemistry and circadian regulation of luminescence in two Pyrocystis species, P. lunula Hulburt and P. noctiluca Murray et Haeckel, were compared with a well‐studied species, Gonyaulax polyedra Stein. All exhibit circadian rhythms and all have similar luciferins and luciferases. However, the Pyrocystis species lack a second protein involved in the reaction in Gonyaulax, the luciferin (substrate) binding protein, which sequesters the luciferin at the cytoplasmic pH and releases it upon acidification, thus controlling the characteristic flashing, which is similar in the three species. More striking is the difference in the circadian regulation of luminescence, which in Gonyaulax involves the daily synthesis and destruction of the two proteins, along with the luminous organelles (scintillons) from which light is emitted, and which are present in all species. In the Pyrocystis species, the amount of luciferase is the same in extracts made during the day and night phases; its circadian regulation in vivo may be attributed to a change in its localization from day to night phase.
COMPETITION BETWEEN A PROCHLOROPHYTE AND A CYANOBACTERIUM UNDER VARIOUS PHOSPHORUS REGIMES: COMPARISON WITH THE DROOP MODEL
Authors: Ducobu Hélène , Huisman Jef , Jonker Richard R. , Mur Luuc R.
Published: March 2003

The ecophysiology and competitive behavior of the prochlorophyte Prochlorothrix hollandica Burger‐Wiersma, Stal et Mur, and the cyanobacterium Planktothrix agardhii Anagn. et Kom. were investigated in phosphorus‐limited continuous cultures. When the species were exposed to successive saturating pulses of P, the maximal P uptake rate decreased linearly with an increase in the P cell quota. Prochlorothrix had a higher maximal P uptake rate, a lower half‐saturation constant for P uptake, higher maximal cell quota for P, and slightly lower minimal cell quota for P than Planktothrix. These data indicate that Prochlorothrix is an affinity and storage strategist, at least when compared to Planktothrix. On the other hand, Prochlorothrix had a lower maximal growth rate than Planktothrix. On the basis of these ecophysiological parameters, we developed a Droop model to predict the time course and outcome of competition under various P regimes. The model predictions were in line with the results of competition experiments under three different P‐limited conditions (continuous P supply, 4‐day pulse period, 12‐day pulse period). Prochlorothrix competitively displaced Planktothrix under both a constant and a pulsed P supply, and competitive displacement of Planktothrix was slowest in the experiment with a 12‐day pulse period. In the pulsed experiments, the mean filament lengths and chl a fluorescence of the species oscillated at the same frequency as the pulse additions. In contrast to the Droop model, the predictions of the Monod model were not in line with the outcome of the competition experiments. Our results demonstrate that Prochlorothrix is a very good competitor for P and that the time course and outcome of competition for P in a variable environment can be predicted on the basis of the P uptake and storage characteristics of the species.
COMMUNITY DYNAMICS AND METABOLISM OF BENTHIC ALGAE COLONIZING WOOD AND ROCK SUBSTRATA IN A FOREST STREAM
Authors: Sabater Sergi , Gregory Stan V. , Sedell James R.
Published: March 2003

Colonization dynamics and metabolism of algal communities on wood (small pieces of Douglas fir) and artificial rock (tiles) substrata were investigated in an open reach in Mack Creek, Cascade Mountain Range, Oregon, for 42 days. Chlorophyll a concentration was not significantly different between the two algal communities (ANOVA, P= 0.119). Even though differences in cell densities were not significantly different between the two algal communities (ANOVA, P= 0.063), biovolume and diversity were greater in epixylic than in epilithic communities (ANOVA, P= 0.011 and 0.002, respectively). The same algal taxa occurred on both substrata, but some of them (e.g. Ceratoneis arcus Grun., Cymbella minuta Hilse ex Rabh., Zygnema sp.) were more numerous on wood, whereas a few others preferred tiles (e.g. Achnanthes lanceolata (Bréb.) Grun.). Scanning electron microscopy revealed a much higher surface roughness on wood, which likely led to a patchy distribution of the algae and the development of stalked diatom species. However, adnate species adapted much better to the mainly flat surfaces of tiles. Net community primary productivity (NCPP) measured in 42‐day‐old substrata was moderate on tiles but negative on wood. Community respiration (CR) was significantly higher on wood than on tiles. Epixylic algal communities exhibited greater nitrogen demand than epilithic communities after ammonium addition. NCPP shifted to positive values on wood but did not increase on tiles. Despite metabolic differences, the variations between the two communities are more closely related to the physical characteristics of the substrata and the attachment abilities of the algal taxa.
MOLECULAR EVIDENCE FROM nrDNA ITS SEQUENCES THAT LAMINARIOCOLAX (PHAEOPHYCEAE, ECTOCARPALES SENSU LATO) IS A WORLDWIDE CLADE OF CLOSELY RELATED KELP ENDOPHYTES
Authors: Burkhardt Elke , Peters Akira F.
Published: March 2003

Marine brown algae living as endophytes in macroalgae are morphologically simple and their taxonomy is particularly difficult. A molecular phylogeny for endophytic taxa isolated from kelps and red algae, and for putative epiphytic and free‐living relatives, was inferred from partial small subunit and complete internal transcribed spacer nuclear ribosomal DNA sequences. It has revealed the following results. (1) Three species of endophytes isolated from members of the Laminariales are closely related. They form a clade together with the epi‐endophytic species Laminariocolax tomentosoides (Farlow) Kylin. Members of the clade possess uniseriate plurilocular sporangia, and they may form erect filaments. Laminariocolax eckloniae sp. nov., occurring in the South African host Ecklonia maxima (Osbeck) Papenfuss, is described. The new combinations, Laminariocolax aecidioides (Rosenvinge) comb. nov. and L. macrocystis (Peters) comb. nov., are proposed for two taxa previously classified in Gononema and Streblonema, respectively. (2) The genus Laminariocolax occurs worldwide in temperate areas, and the phylogeny of the taxa studied is in agreement with biogeographic distribution. (3) Laminariocolax belongs to the Ectocarpales sensu lato. The genus is more closely related to Chordaria than to Dictyosiphon, Ectocarpus, or Scytosiphon. (4) Two brown endophytes (Streblonema spp.), isolated from red algae, are closely related to each other and may form a sister clade to Laminariocolax.
A PHYLOGENETIC STUDY OF THE CORALLINALES (RHODOPHYTA) BASED ON NUCLEAR SMALL‐SUBUNIT rRNA GENE SEQUENCES
Authors: Bailey J. Craig , Chapman Russell L.
Published: March 2003

Conflicting classifications for the Corallinales were tested by analyzing partial sequences for the nuclear small‐subunit ribosomal RNA (SSU) gene of 35 species of coralline algae. Parsimony and likelihood analyses of these data yielded congruent hypotheses that are inconsistent with classifications for the group that include as many as eight subfamilies. Four major clades are resolved within the order, including the early‐diverging Sporolithaceae as well as the Melobesioideae and Corallinoideae. The fourth clade, which is supported robustly, includes both nongeniculate and geniculate species classified in the subfamilies Mastophoroideae, Metagoniolithoideae, Lithophylloideae, and Amphiroideae. Molecular and morphological data support the proposal that the latter two subfamilies are sister taxa. Although relationships among some genera are not resolved clearly, the order of branching of taxa among and within the four principal lineages is concordant with paleontological evidence for the group. Relationships inferred among genera within each of the clades is discussed. Seven morphological characters delimiting higher taxonomic groups within the order were combined with the sequence data, analyzed, and optimized onto the resulting tree(s). Except for the presence or absence of genicula, all other characters were found to be phylogenetically informative. Genicula are nonhomologous structures that evolved independently in the Amphiroideae, Corallinoideae, and Metagoniolithoideae. The phenetic practice of separating coralline algae into two categories solely on the basis of the presence or absence of genicula does not accurately reflect the evolutionary history of the group.
EFFECTS OF ENVIRONMENTAL CONDITIONS ON GROWTH AND LIPID ACCUMULATION IN NITZSCHIA COMMUNIS (BACILLARIOPHYCEAE)
Authors: Dempster Thomas A. , Sommerfeld Milton R.
Published: March 2003

Microalgae from natural saline habitats in the southwestern United States were isolated and screened for rapid growth potential and ability to store intracellular neutral lipid, a precursor for renewable liquid fuel sources. After preliminary screening of isolated strains, Nitzschia communis (Rabenhorst) was selected for optimization of growth rate and lipid yield. Nitzschia communis was subjected to two media types (SERI I, II) with different major ion compositions designed to mimic natural saline groundwater aquifers in the arid Southwest. Growth rates were determined through 4 days of logarithmic growth, followed by 2 days of physiological stress (nitrogen deprivation) and subsequent measurement of neutral lipid accumulation. Poststress intracellular neutral lipid increases were documented by utilizing the fluorochrome Nile Red with fluorometric analysis and epifluorescent microscopy. Growth rate was slightly higher in SERI Type I medium, whereas lipid yield was higher in SERI Type II medium. Rapid growth and appreciable lipid yields were observed over a broad range of temperatures (20°–30° C) and specific conductances (10–70 mS·cm−1). The highest lipid yields were observed at elevated conductances (between 40 mS·cm−1 and 70 mS·cm−1). Substitution of individual salt concentrations from SERI Type II into SERI Type I medium indicated that increased lipid yield in Type I medium was associated with a reduction in MgCl2 concentration.
GRAZER‐INDUCED DEFENSE IN SCENEDESMUS OBLIQUUS (CHLOROPHYCAEA)
Authors: Lürling M.
Published: March 2003

The non‐spiny Scenedesmus obliquus may express considerable phenotypic plasticity in response to changes in their environment. When exposed to chemicals released from the grazer Ceriodaphnia, unicellular S. obliquus populations were rapidly transformed into colonial ones. The morphological response appeared strongly correlated with the amount of algae grazed upon by the Ceriodaphnia. The induced S. obliquus colonies were protected against grazing, as were large spined Scenedesmus, whereas unicellular S. obliquus and spined Scenedesmus remained vulnerable to grazing by Ceriodaphnia. Growth rates of unicellular and induced‐colonial S. obliquus populations were identical. However, sinking rates were significantly higher for the induced‐colonial S. obliquus. Hence, the phenomenon of grazer‐induced colony formation in S. obliquus can be interpreted as an inducible defense at the expense of higher sinking losses.
PROTEIN EXPRESSION DURING HEAT STRESS IN THERMO‐INTOLERANT AND THERMO‐TOLERANT DIATOMS
Authors: Rousch J. M. , Bingham S.E. , Sommerfeld M.R.
Published: March 2003

To better understand how diatoms are capable of responding to environmental stress, protein expression during heat treatment of a thermo‐intolerant (Phaeodactylum tricornutum) and thermo‐tolerant (Chaetoceros muelleri) diatom (Chrysophyta) was investigated. The stress response is a universal and conserved mechanism of cell survival to unfavorable conditions. Typically, a 10 to 15° C temperature elevation above cell growth optimal causes constitutively expressed proteins to decrease and heat shock proteins (HSPs) to increase. HSPs are categorized by molecular weight among five classes with each apparently specialized for a particular function that enhances cell survival. One‐dimensional SDS‐PAGE of diatoms subjected to heat treatment revealed that P. tricornutum exhibited a typical stress response, but C. muelleri did not exhibit a characteristic response even at a greatly elevated temperature (50° C). This result was confirmed by total soluble protein assays. Chaetoceros muelleri may contain higher basal levels of HSPs than P. tricornutum allowing C. muelleri to better tolerate elevated temperatures. Western blot analysis using pea HSP70 (70 kDa) antisera of heat‐treated P. tricornutum and C. muelleri validated the hypothesis that thermo‐tolerant cells contain higher levels of constitutively expressed HSPs. Two‐dimensional gel electrophoresis of heat‐treated cells indicate that the small HSPs (17–30 kDa) played a role in the stress response similar to that found in vascular plants. Ongoing work is focused on the manipulation of the stress response through over‐expression of key hsp genes.
IDENTIFICATION OF THE CYTOKININ ISOPENTENYLADENINE IN A STRAIN OF ARTHRONEMA AFRICANUM (CYANOBACTERIA)
Authors: Stirk Wendy A. , Ördög Vince , Van Staden Johannes
Published: March 2003

Isopentenyladenine was isolated from a strain of the cyanobacterium Arthronema africanum (Schwabe et Simons) Komárek et Lukavský using a combination of biological and chemophysical techniques, including the soybean callus bioassay, cation exchange resin chromatography, paper chromatography, HPLC, and GC‐MS. Positive identification of the major biologically active compound was achieved.
REPRODUCTIVE SUCCESS OF FUCUS VESICULOSUS (PHAEOPHYCEAE) IN THE BALTIC SEA
Authors: Serrão Ester A. , Brawley Susan H. , Hedman Jenny , Kautsky Lena , Samuelsson Göran
Published: March 2003

Marine organisms colonizing brackish habitats such as the Baltic Sea must cope with the negative effects of low salinities on reproductive success because these may reduce gamete viability and/or increase polyspermy. Reproductive characteristics of the marine seaweed Fucus vesiculosus L. were studied in several brackish habitats, particularly in the northern Baltic Sea, to understand its ability to reproduce where few other marine species survive. Polyspermy and fertilization success were variable at the boundary of the continuous distribution of F. vesiculosus in the Baltic Sea, and polyspermy was high (10%–30%) when fertilization was successful. A strong female bias (80%–86%, ca. 5.5:1) was found at the northernmost limit of Baltic F. vesiculosus. Electrophysiological studies showed that many eggs have a high input resistance (519 ± 150 MΩ[mean ± SE, n = 14] at Drivan, 1995), which may be helpful in preventing polyspermy in this brackish habitat. The polyspermy block remains sodium‐dependent in the northern Baltic. Sperm bound quickly to northern Baltic eggs in natural water, but fertilization was delayed compared to marine F. vesiculosus. A subset of northern Baltic eggs studied during an optimal reproductive period (7–11 July 1995) had a membrane potential (Em) of ca. −100 mV and an effective fertilization potential (FP) of ca. 2 min with a plateau of −25 mV, but repolarized too rapidly for the FP to be protective. Pronuclear migration and cell wall secretion occurred more slowly in Baltic than in marine zygotes. The reproductive success of theseboundary populations may be dependent upon windows of opportunity when there are favorable combinations of the levels of salinity, water motion, population density, and sex ratio. These factors and the short duration of the reproductive season in the northern Baltic Sea may result in reproductive failure in some years.
GENETIC, MORPHOLOGICAL, AND TOXICOLOGICAL VARIATION AMONG GLOBALLY DISTRIBUTED STRAINS OF NODULARIA (CYANOBACTERIA)
Authors: Bolch Christopher J. S. , Orr Philip T. , Jones Gary J. , Blackburn Susan I.
Published: March 2003

Morphological, toxicological, and genetic variation was examined among 19 strains of Nodularia. The strains examined could be morphologically discriminated into four groups corresponding to N. spumigena Mertens, N. sphaerocarpa Bornet et Flahault, and two strains that did not clearly correspond to currently accepted Nodularia species. Genetic variation was examined using nucleotide sequencing of the phycocyanin intergenic spacer region (cpcBA‐IGS) and RAPD‐PCR. The PCR‐RFLP of the cpcBA‐IGS differentiated four genotypes corresponding to the four morphological groups. However, nucleotide sequencing of 598 bp of the 690‐bp fragment showed that one of the three strains corresponding to N. sphaerocarpa (PCC 7804) was genetically divergent from the other two, suggesting that it constitutes a distinct species. Nucleotide variation within the morphospecies groups was limited (<1%), and all 14 Australian strains of N. spumigena possessed identical cpcBA‐IGS sequences. The RAPD‐PCR differentiated the same groups as the cpcBA sequencing and discriminated each of the seven different Australian populations of N. spumigena. Strains from within a bloom appeared genetically identical; however, strains isolated from different blooms could be separated into either a western or a southeastern Australian cluster, with one strain from western Australia showing considerable genetic divergence. The pattern of variation suggests that individual blooms of N. spumigena are clonal but also that Australian N. spumigena populations are genetically distinct from each other. Examination of genetic distance within and between blooms and within and between morphological groups showed clear genetic dicontinuities that, in combination with the cpcBA‐IGS data, suggest that Nodularia contains genetically distinct morphospecies rather than a continuous cline of genetic variation. Furthermore, these morphospecies are genetically variable, exhibiting hierarchical patterns of genetic variation on regional and global scales. Production of the hepatotoxin nodularin was not restricted to one genetic lineage but was distributed across three of the five genotypic groups. A strain of N. spumigena from a nontoxic Australian population was found to fall within the range of genetic variation for other toxic Australian strains and appears to be a unique nontoxic strain that might have arisen by loss of toxin production capacity.
PHOTOSYNTHESIS IN AN EXTREME SHADE ENVIRONMENT: BENTHIC MICROBIAL MATS FROM LAKE HOARE, A PERMANENTLY ICE‐COVERED ANTARCTIC LAKE
Authors: Hawes Ian , Schwarz Anne‐Maree
Published: March 2003

We investigated the composition of benthic microbial mats in permanently ice‐covered Lake Hoare, Antarctica, and their irradiance vs. photosynthetic oxygen exchange relationships. Mats could be subdivided into three distinct depth zones: a seasonally ice‐free “moat” zone and two under‐ice zones. The upper under‐ice zone extended from below the 3.5 m thick ice to approximately 13 m and the lower from below 13 m to 22 m. Moat mats were acclimated to the high irradiance they experienced during summer. They contained photoprotective pigments, predominantly those characteristic of cyanobacteria, and had high compensation and saturating irradiances (Ec and Ek) of 75 and 130 μmol photons·m−2·s−1, respectively. The moat mats used light inefficiently. The upper under‐ice community contained both cyanobacteria and diatoms. Within this zone, biomass (as pigments) increased with increasing depth, reaching a maximum at 10 m. Phycoerythrin was abundant in this zone, with shade acclimation and efficiency of utilization of incident light increasing with depth to a maximum of 0.06 mol C fixed·mol−1 incident photons under light‐limiting conditions. Precipitation of inorganic carbon as calcite was associated with this community, representing up to 50% of the carbon sequestered into the sediment. The lower under‐ice zone was characterized by a decline in pigment concentrations with depth and an increasing prevalence of diatoms. Photosynthesis in this community was highly shade acclimated and efficient, with Ec and Ek below 0.5 μmol·m−2·s−1 and 2 μmol·m−2·s−1, respectively, and maximum yields of 0.04 mol C fixed·mol−1 incident quanta. Carbon uptake in situ by both under‐ice and moat mats was estimated at up to 100 and 140 mg·m−2·day−1, based on the photosynthesis–irradiance curves, incident irradiance, and light attenuation by ice and the water column.
GC‐SIM‐MS DETECTION AND QUANTIFICATION OF FREE INDOLE‐3‐ACETIC ACID IN BACTERIAL GALLS ON THE MARINE ALGA PRIONITIS LANCEOLATA (RHODOPHYTA)
Authors: Ashen Jon B. , Cohen Jerry D. , Goff Lynda J.
Published: March 2003

Indole‐3‐acetic acid (IAA), a plant hormone necessary for terrestrial plant growth and development, was detected and quantified in the marine red alga Prionitis lanceolata Harvey (Halymeniaceae, Gigartinales, Rhodophyta) using gas chromatography–selective ion‐monitoring mass spectrometry (GC‐SIM‐MS). This allowed comparison of free IAA levels between the algal thallus and eubacterially induced galls on this alga characterized by abnormal algal growth and cell division and extensive, intercellular microbial proliferation. The levels of free IAA in the P. lanceolata thallus averaged 2.5 (±1.1) ng·g−1 fresh wt. Free IAA levels in galls were more variable, ranging from ca. 4 to 39 (8.3 ± 10.9) ng·g−1 fresh wt, but were significantly higher overall (P= 0.0022). The identity of the IAA in this marine florideophycean alga was confirmed by full scan GC‐MS analysis of both galls and thalli. The levels of free IAA in P. lanceolata were two to three orders of magnitude higher than those observed previously in the Rhodophyta. The origin of elevated IAA levels in P. lanceolata galls is unknown because it is possible that this compound is produced by either the gall‐inducing bacterial symbiont or the host alga.
ACCUMULATION OF FERREDOXIN AND FLAVODOXIN IN A MARINE DIATOM IN RESPONSE TO FE
Authors: McKay R. Michael L. , La Roche Julie , Yakunin Alexander F. , Durnford Dion G. , Geider Richard J.
Published: March 2003

Despite recognition that Fe availability is significant in regulating oceanic production in some regions, the biogeochemistry of this trace element is poorly understood. To complement contemporary methods of analytical chemistry, we have used an immunological approach to monitor the Fe nutrition of marine phytoplankton. In prokaryotes and numerous microalgae, the redox catalyst ferredoxin is functionally replaced by flavodoxin during periods of Fe deficiency. In this study, antibodies were raised against ferredoxin purified from a marine diatom, and their utility as a diagnostic indicator was assessed. A species survey demonstrated broad reactivity with both pennate and centric diatoms and additionally with several nondiatom taxa. In batch cultures of the diatom Phaeodactylum tricornutum Bohlin, in which Fe levels were varied, accumulation of ferredoxin varied with the physiological state of the culture; in unimpaired cells (Fv/Fm≥ 0.65), ferredoxin levels were high, whereas levels dropped markedly in cells experiencing even slight photochemical impairment. Accumulation of flavodoxin varied inversely with that of ferredoxin. An experiment was performed to demonstrate the temporal pattern of accumulation of ferredoxin upon recovery from Fe limitation. Prior to Fe amendment, cells were physiologically impaired (chlorotic, Fv/Fm < 0.3) and contained flavodoxin but no detectable ferredoxin. Following addition of Fe, constraints on photochemistry were relaxed within hours. Coinciding with this, levels of flavodoxin declined, whereas ferredoxin was accumulated to high levels within 8 h.
PHOTOSYNTHESIS AND CALCIFICATION BY EMILIANIA HUXLEYI (PRYMNESIOPHYCEAE) AS A FUNCTION OF INORGANIC CARBON SPECIES
Authors: Buitenhuis Erik T. , De Baar Hein J. W. , Veldhuis Marcel J. W.
Published: March 2003

To test the possibility of inorganic carbon limitation of the marine unicellular alga Emiliania huxleyi (Lohmann) Hay and Mohler, its carbon acquisition was measured as a function of the different chemical species of inorganic carbon present in the medium. Because these different species are interdependent and covary in any experiment in which the speciation is changed, a set of experiments was performed to produce a multidimensional carbon uptake scheme for photosynthesis and calcification. This scheme shows that CO2 that is used for photosynthesis comes from two sources. The CO2 in seawater supports a modest rate of photosynthesis. The HCO is the major substrate for photosynthesis by intracellular production of CO2 (HCO+ H+→ CO2+ H2O → CH2O + O2). This use of HCO is possible because of the simultaneous calcification using a second HCO, which provides the required proton (HCO+ Ca2+→ CaCO3+ H+). The HCO is the only substrate for calcification. By distinguishing the two sources of CO2 used in photosynthesis, it was shown that E. huxleyi has a K½ for external CO2 of “only” 1.9 ± 0.5 μM (and a Vmax of 2.4 ± 0.1 pmol·cell−1·d−1). Thus, in seawater that is in equilibrium with the atmosphere ([CO2]= 14 μM, [HCO]= 1920 μM, at fCO2= 360 μatm, pH = 8, T = 15° C), photosynthesis is 90% saturated with external CO2. Under the same conditions, the rate of photosynthesis is doubled by the calcification route of CO2 supply (from 2.1 to 4.5 pmol·cell−1·d−1). However, photosynthesis is not fully saturated, as calcification has a K½ for HCO of 3256 ± 1402 μM and a Vmax of 6.4 ± 1.8 pmol·cell−1·d−1. The H+ that is produced during calcification is used with an efficiency of 0.97 ± 0.08, leading to the conclusion that it is used intracellularly. A maximum efficiency of 0.88 can be expected, as NO uptake generates a H+ sink (OH− source) for the cell. The success of E. huxleyi as a coccolithophorid may be related to the efficient coupling between H+ generation in calcification and CO2 fixation in photosynthesis.
GIANT KELP (MACROCYSTIS PYRIFERA, PHAEOPHYCEAE) RECRUITMENT NEAR ITS SOUTHERN LIMIT IN BAJA CALIFORNIA AFTER MASS DISAPPEARANCE DURING ENSO 1997–1998
Authors: Ladah Lydia B. , Zertuche‐González José A. , Hernández‐Carmona Gustavo
Published: March 2003

During the ENSO event of 1997–1998, density and population structure were evaluated in a Macrocystis pyrifera forest located in Bahía Tortugas, Baja California, Mexico, near the southern limit of the species’ distribution in the Northern Hemisphere. Observations in Bahía Tortugas were made quarterly from January 1997 to September 1998 using SCUBA diving surveys. No macroscopic plants were found in the Bahía Tortugas area from October 1997 to April 1998, a local absence of at least 7 months. Aerial surveys further suggest regional disappearance along most of the Baja California coast during the event. Unexpectedly, plants were found in Bahía Tortugas again in July 1998, in spite of the widespread disappearance of the species less than a year earlier. Long‐distance spore dispersal was an unlikely cause of the recruitment because: 1) the nearest spore source was more than 100 km away; 2) recruitment appeared to be simultaneous at many sites and occurred rapidly after the cessation of the ENSO event; and 3) the recruits occurred in the same areas as before disappearance. We suggest that a microscopic stage that was not visible during dive surveys survived the stressful conditions of ENSO and caused the recruitment event, supporting the hypothesis that a bank of microscopic forms can survive conditions stressful to macroscopic algae.
MORPHOLOGICAL AND GENETIC CHARACTERIZATION OF PHAEOCYSTIS CORDATA AND P. JAHNII (PRYMNESIOPHYCEAE), TWO NEW SPECIES FROM THE MEDITERRANEAN SEA
Authors: Zingone Adriana , Chrétiennot‐Dinet Marie‐Josèphe , Lange Martin , Medlin Linda
Published: March 2003

Two new Phaeocystis species recently discovered in the Mediterranean Sea are described using light and electron microscopy, and their systematic position is discussed on the basis of an analysis of their nuclear‐encoded small‐subunit ribosomal RNA gene (SSU rRNA) sequences. Phaeocystis cordata Zingone et Chrétiennot‐Dinet was observed only as flagellated unicells. Cells are heart shaped, with two flagella of slightly unequal length and a short haptonema. The cell body is covered with two layers of thin scales. The outermost layer scales are oval, with a faint radiating pattern, a raised rim, and a modest central knob. The inner‐layer scales are smaller and have a faint radiate pattern and an inflexed rim. Cells swim with their flagella close together, obscuring the haptonema, pushing the cell, and causing it to rotate about its longitudinal axis while moving forward. Phaeocystis jahnii Zingone was isolated as a nonmotile colony. It forms loose aggregates of cells embedded in a mucilaginous, presumably polysaccharide matrix without a definite shape or visible external envelope. The flagellated stage has the features typical of other Phaeocystis species. Cells are rounded in shape and slightly larger than P. cordata. The cell body is covered with extremely thin scales of two different sizes with a very faint radiating pattern toward their margin. Swimming behavior is similar to that of P. cordata, with the flagella in a posterior position as the cells swim. The SSU rRNA sequence analysis indicated that both species are distinct from other cultivated Phaeocystis species sequenced to date. Regions previously identified as specific for the genus Phaeocystis are not found in P. jahnii, and new genus‐specific regions have been identified. P. cordata is more closely related to the colonial species P. globosa, P. antarctica, and P. pouchetii and has branched prior to the divergence of the warm‐water P. globosa species complex from the cold‐water species P. antarctica and P. pouchetii. These results are discussed within a framework ofthe available data on the evolution of the world’s oceans.