bluuebunny/crossref_metadata_2025 huggingface dataset:
EFFECT OF GROWTH IN ACID MEDIA ON THE MORPHOLOGY, HYDROGEN-ION CONCENTRATION, VISCOSITY, AND PERMEABILITY OF WATER HYACINTH AND FROGBIT ROOT CELLS
Authors: Minshall Wm. Harold , Scarth G. W.
Published: August 2008

Roots of water hyacinth (Eichhornia crassipes (Mart.) Soims.) and frogbit (Hydrocharis morsus-ranae L.) when grown In solution cultures adjusted to pH 3.5, 4.0, 5.0, 6.0, and 6.5 did not suffer decidedly adverse, direct effects from hydrogen ions except at extreme acidities represented by a pH value of less than 4. During cool weather the plants were able to grow at a somewhat higher concentration of hydrogen ions than was possible in the warm summer months. The boundary between good growth and toxicity was a narrow one. Extreme acidity, short of the critical point, inhibited the growth of the roots by decreasing cell division and cell elongation. In the roots investigated, cell division at pH 3.5 was reduced to one-half of the rate at pH 5.0 and this reduction accounted for three-quarters of the inhibition in the growth of the roots. When grown in a highly acid medium, root cells acquired a resistance to the hydrogen ions. Water hyacinth meristem cells from the highly acid media exhibited a pronounced resistance to hydrochloric acid. It is suggested that this increased resistance is due to the cells having acquired a greater impermeability to the acids. Determination of the pH of expressed root juices revealed that, although all of the saps were decidedly less acid than were the media in which the plants were grown, roots grown in an extremely acid medium had a slightly more acid sap than those grown in a less acid one. A comparison of rates of streaming and the action of protoplasts during plasmolysis indicated that extreme acidity in the growth medium increased the viscosity of the cytoplasm of root cells. No significant difference was noted in the osmotic pressure of the root cells from the different cultures. The absolute permeability of frogbit root hairs to thiourea, as calculated from the formula [Formula: see text], did not vary significantly from.0012 millimoles per square centimeter of surface per hour per molar concentration difference for plants grown within the range of pH 3.6 to pH 6.0.
CLOSTERIUM IN CENTRAL CANADA
Authors: Hughes Elwyn O.
Published: August 2008

Fifty-seven species and varieties of Closterium are reported from Manitoba and Ontario. Previous reports from central, eastern, and arctic Canada are cited. Each species is illustrated and measurements are given from the author's material. The text and catalogue of species include notes on taxonomy of the genus. Two new species, four new varieties, and one new form are described.
FREQUENCY OF MICRONUCLEI IN POLLEN QUARTETS OF COMMON WHEAT MONOSOMICS
Authors: Morrison J. W. , Unrau John
Published: August 2008

The frequency with which 20 different monosomes of the common wheat variety, Chinese Spring, formed micronuclei in pollen quartets was determined. It was found that unless the study was made at an early developmental stage characterized by a distinct cell wall surrounding the quartets, the counts were unreliable, because some micronuclei were lost. The frequency of micronucleus formation was similar for anthers of a floret, florets of a spike, and plants of a monosome. Among the monosomes studied, there were three groups of three and four of two in which the total frequency of quartets with micronuclei, and the distribution of numbers of micronuclei per quartet, were strikingly similar. In the case of the groups of three, two monosomes were from the A and B genomes while one was from the D genome. This is interpreted as evidence of homoeology of chromosomes of a group and also that such chromosomes have undergone less change than those that do not form such series.
MICROCALORIMETRIC STUDIES ON GERMINATIONS OF CEREALS
Authors: Prat H.
Published: August 2008

Experiments have been performed on seedlings of many species of cultivated plants with a new Tian-Calvet microcalorimeter installed at the University of Montreal. The characteristic elements of the curve of thermogenesis are first described on wheat germinations and their variations discussed in function of temperature, preliminary dehydration, substances in solution in the soaking liquid: salts, alcohol, auxins, etc. Then comparisons are made between germinative thermogeneses of oats, rye, barley, corn, flax, tomatoes, etc., showing the numerous possible applications of microcalorimetry in plant studies and agronomy.
ECOLOGICAL STUDY OF THE PEAT BOGS OF EASTERN NORTH AMERICA: I. STRUCTURE AND EVOLUTION OF VEGETATION
Authors: Dansereau Pierre , Segadas-Vianna Fernando
Published: August 2008

It is attempted to clearly distinguish between bogs on the one hand and swamps and marshes on the other. The principal elements and factors are listed in Eastern North America where bogs are frequent. This first paper attempts a general outline of the dynamics of bog vegetation in this region and describes the structures of the communities involved. The biotope is considered the smallest piece in the association mosaic and its physical and biological aspects are emphasized. Two recent systems (Küchler's and Dansereau's) are applied to individualize the most important and widespread synecological units. Further studies involving climatic relationships on a geographical scale and phytosociological measurements at the quadrat level will permit a refocusing of some of the phenomena which are described and interpreted here.
INHERITANCE OF RESISTANCE TO USTILAGO NUDA IN BARLEY
Authors: Skoropad William P. , Johnson L. P. V.
Published: August 2008

The inheritance of resistance to loose smut races Tr and Ts (a new race) was studied in several barley crosses and backcrosses in which the varieties Jet and Titan were the resistant parents. Jet is resistant to race Tr and race Ts, Titan to race Tr only. Genetical analyses were based (a) on a classification of F2 plants according to the smut reaction of their F3 progeny, and (b) on the reaction of selfed generation backcrosses involving recessive (susceptible) parents. The resistance of Titan and of Jet to Tr was found in each case to be due to a single, dominant gene, designated as Un and Un3, respectively. The resistance of Jet to Ts was also found to be due to a single, dominant gene. This is probably a "new" gene and has been provisionally designated Un6. Resistance was found to be determined by the genetic constitution of the developing embryo rather than by that of surrounding floral structures.
PHYSIOLOGICAL AND BIOCHEMICAL STUDIES IN PLANT METABOLISM: VI. THE EFFECT OF ONTOGENY ON THE PHYSIOLOGICAL HETEROGENEITY IN THE FIRST LEAF OF WHEAT
Authors: Roberts D. W. A.
Published: August 2008

The respiration rate, R.Q., and the water content of each of the developing quarters of the first leaf of Khapli wheat have been measured at different ages and found to change as the tissue ages. In general the respiration rate declines as the tissue ages. The R.Q. is usually close to unity except in the basal quarter around the fifth day. The water content of the quarters tends to decline as the mature leaves become older. In the basal quarter of four- and five-day-old leaves the oxygen uptake appears to reach its peak when calculated on a dry weight basis. In the five-day-old leaves the rate of water uptake is very high and the R.Q. very low. These properties are thought to be correlated with the phase of elongation which is occurring in this quarter at that stage.
PERSISTENCE OF RHIZOCTONIA SOLANI KÜHN IN SOIL
Authors: Sanford G. B.
Published: August 2008

The effect of different living host and nonhost plants 21 days old, soil amendments, and Trichoderma lignorum (Tode) Harz on the persistence of a heavy artificial infestation of Rhizoctonia solani Kühn in a natural virgin Edmonton black loam of optimum moisture content, held at 61° F., was studied under controlled laboratory conditions, A disease rating of host plants was found to be a satisfactory measure of the persistence of R. solani, whereas data from buried glass slides and from root colonization of indicator plants were unreliable for the purpose intended. In natural, unamended soil, a heavy infestation of T. lignorum did not check the growth of R. solani perceptibly, but with the addition of cornmeal it was practically suppressed for several days. In the presence of living potato plants, R. solani persisted as well in natural untreated soil as it did when cornmeal, sodium nitrate, or calcium hydroxide was added. The living or dead roots of potato or wheat plants did not aid or suppress the pathogen. Apparently R. solani disappeared from the soil in 120 days or less when associated with wheat, oat, barley, or corn plants replanted every 21 days, but it was still fairly abundant in soils bearing potato, bean, or pea plants. When potato plants were absent, a heavy soil infestation in the late autumn practically disappeared by the following June. Results indicate that R. solani depends essentially on parasitic nutrition for its persistence in the soil. The hyphae of R. solani commonly inhabited the living roots of host and nonhost plants, but no nutritional relationship with them was detected.
STUDIES ON THE FORMATION OF VITAMIN C IN SLICES OF POTATO TISSUE
Authors: Asselbergs E. A. M. , Francis F. J.
Published: August 2008

When slices of potato tissue are stored for two days at 23 °C. in moist chambers or in aerated distilled water, the vitamin C content increases 100-300% as measured by the method of Roe et al. The increase does not occur in slices from freshly harvested potatoes. The physiological condition of the potatoes at the time of the experiment is important in determining the amount of increase in slices from potatoes stored for several months. Experiments with auxins and mannitol solutions show that there is no direct relationship between the process of water uptake and vitamin C formation. Solutions of indoleacetic acid and naphthaleneacetic acid increase the amount of vitamin formed. The results of experiments with potassium cyanide, sodium azide, malachite green, 8-hydroxyquinoline, sodium diethyldithiocarbamate and 2,4-dinitrophenol suggest that the formation of vitamin C is not directly related to any of the enzyme systems inhibited by the above chemicals. Infiltration of potato slices with solutions of fumaric and malic acid results in an increased formation of vitamin C as compared with the water controls.
INHIBITION OF THE BACTERIOSTATIC ACTION OF LAURYLAMINE SACCHARINATE BY ORGANIC MATTER
Authors: Gray P. H. H. , Taylor L. J.
Published: August 2008

Laurylamine saccharinate has been tested for its bacteriostatic powers against 30 species of bacteria, namely, 6 Gram-positive micrococci, 12 Gram-positive and 12 Gram-negative 'rods'. The compound was used in concentrations of 0.0005, 0.001, and 0.005% in plain broth, broth with glycerol, and broth with glycerol and skim milk, these adjuncts representing progressively increasing amounts of organic matter. The Gram-negative bacteria were the most resistant. The bacteriostatic action of the laurylamine was progressively reduced by the organic matter. Staphylococcus aureus was not killed by 0.005% laurylamine in the medium containing skim milk. Media containing phenol were used as a measure of comparison, and similar effects of organic matter were observed. Agar also reduced the bacteriostatic power of the laurylamine.
RADIATION-INDUCED MUTATIONS IN WHEAT AND BARLEY
Authors: Arnason T. J. , Person C. O. , Naylor J. M.
Published: August 2008

The effectiveness of absorbed radiophosphorus for mutation induction in wheat and barley has been studied. The P32was supplied to seedlings and to young plants. Chromosome aberrations found in groups of several cells at meiosis were counted but single cell aberrations were not. Following some dosages of P32, as many as one-third of the treated plants were found to have blocks or clusters of aberrant cells. Samples of R2(progeny of treated) plants of vulgare wheat and of common barley were also examined for the presence of chromosome aberrations at meiosis. The samples consisted of 143 wheat and 128 barley plants. Approximately 8 to 19% of wheat and 6 to 11% of barley plants of different treatment groups had aberrations. Phenotypic mutants were found in barley, einkorn, and vulgare wheat. Chlorophyll mutants occurred in all of these though no albinos were produced in vulgare. The R2and R3of vulgare, consisting of 10,443 plants from 258 treated R1plants, included 15 recognized mutants. The original mutants did not breed true. Offspring of some mutants included only mutant and normal-appearing plants. Other mutants gave a variety of new phenotypic forms; some of these are true-breeding. Nearly all of the wheat mutants gave evidence of chromosome aberrations. Most of the phenotypic changes are therefore attributed to changed gene balance rather than to gene mutation.A few mutations have also been obtained by irradiating wheat and barley seeds with high-energy X rays from the betatron. Two such mutants in wheat were found to have undergone chromosome breakage and rearrangement.
Daytime Exposure to Fish Predation for Littoral Benthic Organisms in Unproductive Lakes
Authors: Collins Nicholas C.
Published: August 2008

Fish activity near the bottom was monitored in two central Ontario lakes using time-lapse video equipment. Predation risk for benthic invertebrates was measured as the frequency of fish entries into a hypothetical cylinder with dimensions such that an imaginary 2–3 mm invertebrate at the bottom-center of the cylinder would be within the detection radius of any fish entering the space. By this criterion, risk of predation is high, even in lakes with low fish densities. For 7 d of data spread over different lakes, sites, and months, the median rate of exposure of the hypothetical invertebrate to passing fish was 14.2 times/h; the median rate of exposure to fish that stopped or turned as if foraging was 3 times/h. Exposure to benthivorous fish varied markedly between two lakes in June and within a lake between June and August. Changes in the fish species, sizes, and level of activity all contributed to the variance. Exposure to fish also varied markedly among days, within a day, and among sites within a lake. Differences in predation risk between two neighboring sites were consistent for several days, suggesting that some of the patchiness in benthic invertebrate composition might be generated by patchy fish exploitation. The high median levels of exposure to fish suggest that benthic organisms should spend a high proportion of their time in risk-reducing positions or behaviors, so that competition among fish caused by resource depression will be important.
Role of Exposure Duration in Hydrogen Ion Toxicity to Brook (Salvelinus fontinalis) and Rainbow Trout (Salmo gairdneri)
Authors: Curtis Lawrence R. , Seim Wayne K. , Siddens Lisbeth K. , Meager Debra A. , Carchman Richard A. , Carter Walter H. , Chapman Gary A.
Published: August 2008

Acidification of streams and rivers associated with rainstorm or snowmelt events is often episodic as are many environmental introductions of toxic substances. We examined the toxicity of continuous or intermittent exposures to sulfuric acid (H+) to brook trout (Salvelinus fontinalis) embryos, alevins, and fry. Acute toxicity tests were conducted with juvenile rainbow trout (Salmo gairdneri). These studies permitted evaluation of key components of intermittent exposures (toxicant concentration, exposure duration, and recovery period) on mortality, reduced growth, and perturbed electrolyte balance. Lethality of H+ markedly changed with developmental stage of brook trout. Resistance of the chorion to H+ penetration probably protected embryonic fish, while hatching and onset of active swimming exacerbated H+ toxicity. Response surface methods demonstrated that between pH 4 and 7, time–concentration relationships for H+ toxicity were greatly influenced by exposure duration and peak concentration but little by length of recovery period. Daily pulses at pH 4 with duration as short 4.5 h produced marked mortality after 90 d. This did not occur after 4–60 d of testing. Whole-body Na+, K+, and Ca2+ concentrations of brook trout were negatively correlated with mean H+ concentrations after 90 d of exposure. Cation depletion appeared to be a more sensitive index of chronic, sublethal H+ toxicity than reduced growth.
Trace Element Analysis of Fish Sagittae as an Aid to Stock Identifications: Pink Snapper (Chrysophrys auratus) in Western Australian Waters
Authors: Edmonds J. S. , Moran M. J. , Caputi N. , Morita M.
Published: August 2008

Concentrations of trace elements in the sagittal otoliths of pink snapper (Chrysophrys auratus) from seven locations along the coast of Western Australia were measured by inductively coupled plasma atomic emission spectrometry (ICP-AES). Canonical variate (discriminant) analyses of the concentrations of eight elements (Na, Mg, Si, P, S, K, Fe, and Sr) from all fish when corrected for fish length showed the pattern of concentrations to be specific to the location of capture of the fish. Trace elements are likely to be irreversibly deposited in the sagittae during growth and should provide an integrated environmental history of each fish. Differences in elemental composition may thus be useful for identifying nonmixing groups of fish that may be regarded as separate stocks for some fisheries management purposes.
Oxygen Availability Provides a Signal for Hatching in the Rainbow Trout (Salmo gairdneri) Embryo
Authors: Latham Keith E. , Just John J.
Published: August 2008

The hatching of rainbow trout (Salmo gairdneri) embryos can be stimulated by subjecting them to low oxygen partial pressures [Formula: see text] during the final days of incubation or delayed by elevating [Formula: see text]. Most embryos develop the ability to hatch between days 26 and 27 of incubation at 12 °C. During this time, similar hatching frequencies are obtained at any [Formula: see text] below a critical value in the 94–135 mm Hg (6.5–9.3 mg/L) range (1 mm Hg = 133.322 Pa). The [Formula: see text] required for continued incubation increases with developmental time such that hatching cannot be delayed beyond day 30 at 12 °C. These results indicate that oxygen availability influences the time at which trout embryos hatch and that hatching occurs when hatchable embryos are confronted with an ambient [Formula: see text] that is inadequate to satisfy aerobic metabolic requirements.
Phosphorus Reservoirs in the St. Lawrence Upper Estuary
Authors: Lucotte Marc
Published: August 2008

A first-order phosphorus (P) budget is presented for the St. Lawrence Upper Estuary. The upwelled intermediate waters of the Laurentian Trough contribute 90% of the dissolved P source to the estuary whereas the St. Lawrence River carries in most of the particulate P. The dissolved P flux to the estuary (~80 000 t∙yr−1) is about 10 times larger than the particulate one (~5000 t∙yr−1, more than half being detrital apatite). However, the dissolved and particulate estuarine P reservoirs are of the same order of magnitude (~3000 t) because of the short residence time of the water masses relative to that of the solid matter. This rapid water mass turnover is responsible for the conservative behavior of dissolved orthophosphate (PO4) throughout the estuary; dissolved PO4 concentrations are not significantly affected by the biogeochemical exchange reactions involving particulate P. Approximately 500 and 300 t PO4∙yr−1 are respectively adsorbed on the flocculating iron hydroxide colloids and desorbed from marsh deposits. Marsh macrophytes are the main P consumers in the estuary (~100 t∙yr−1), but detectable PO4 changes attributable to this biological uptake are confined to the areas near the marshes.
Influence of Environmental Factors and Piscivory in Structuring Fish Assemblages of Small Alberta Lakes
Authors: Robinson Clifford L. K. , Tonn William M.
Published: August 2008

We surveyed 45 small lakes in central Alberta to determine if discrete, repeatable types of fish assemblages exist, to identify the main environmental and biotic processes likely responsible for assemblage-level patterns, and to compare and contrast Alberta patterns with those observed in other regions of North America. Overall, 11 species of fish were caught in 36 lakes; nine lakes were fishless. Hierarchical classification and detrended correspondence analysis of fish species presence/absence identified two main assemblage types, characterized by northern pike (Esox lucius) and yellow perch (Perca flavescens) versus brook stickleback (Culaea inconstans) and fathead minnow (Pimephales promelas). Pike/perch lakes were significantly deeper and larger than lakes of the stickleback/fathead assemblage type; however, a subset of the former group lacking yellow perch was environmentally similar to stickleback/fathead lakes. Piscivory by northern pike appears to be the dominant process maintaining nearly complete negative associations between members of the two assemblage types. Despite environmental and faunal-richness differences, our results were not unlike those from southern Ontario and northern Wisconsin. For small boreal lakes of North America, piscivory and processes related to a small number of environmental variables, such as maximum depth, surface area, and isolation, appear to be most important in structuring fish assemblages.
Phytoplankton, Nutrients, and Primary Production in Fertilized and Natural Lakes at Saqvaqjuac, N.W.T.
Authors: Welch Harold E. , Legauit John A. , Kling Hedy J.
Published: August 2008

Whole-lake phosphorus (P) and nitrogen (N) addition experiments at Saqvaqjuac, N.W.T. (63°N in the central Canadian arctic), showed that the lakes were P limited but required both P and N for increased production. Photosynthetic response to 0.1 g P and 1.0 g N∙m−2∙yr−1 was immediate (15→30 g C∙m−2∙yr−1), with simultaneous increases in protozoa, while oligotrophic chrysophyte assemblages gave way to volvocalean greens. Cyanophytes were not important during P-only or P and N additions or in oligotrophic lakes, but formed permanent blooms in several naturally mesotrophic lakes near sea level. Retention of P was naturally low, but high during P addition. Silicon (Si) retention was always very high. Chlorophyll: P ratios were similar to those of subarctic and north-temperate lakes. Saturation light intensity (Ik) tracked surface light flux with a 2- to 3-wk delay, averaging 15 E∙m−2∙s−1 in winter and peaking at 140 E∙m−2∙s−1 in July. Comparison of our data with those for lakes in the Experimental Lakes Area (northwestern Ontario, 50°N) and Char Lake (75°N) shows that with increasing latitude, in small lakes, (a) phytoplankton production decreases, (b) phytoplankton production per unit light decreases less sharply, and (c) the proportion of primary production occurring beneath ice cover increases.
A Robust Method for Parameter Estimation from Catch and Effort Data
Authors: Ludwig D. , Walters C. J.
Published: August 2008

The problem of robust estimation of optimal effort levels from surplus production models is considered. A variety of models are used to generate data, for the purpose of testing estimation schemes. The result of an estimation is an estimate of the optimal effort. These efforts are compared using the expected discounted value of a deterministic stock, which corresponds to the model used to generate the data. Such a criterion takes into account not only the loss due to bias in the estimated optimal effort, but also the loss due to the variance of the estimator. Estimation is difficult if there is a lack of informative variation in effort levels or stock sizes. In such cases, the estimation scheme which maximizes the criterion described above sacrifices realism in the representation of the stock-production relationship in order to reduce the variance of the estimate of optimal effort. We present a composite estimation scheme which performs acceptably in all the cases we have examined, and whose performance degrades slowly as the amount of information in the data decreases.
Biochemical Genetic Comparison of Sockeye Salmon and Kokanee, the Anadromous and Nonanadromous forms of Oncorhynchus nerka
Authors: Foote Chris J. , Wood Chris C. , Withler Ruth E.
Published: August 2008

Twenty-three anadromous (sockeye salmon) and nonanadromous (kokanee) Oncorhynchus nerka populations were sampled from throughout British Columbia and examined electrophoretically at three to five polymorphic loci to test whether the forms represent distinct genetic lineages or whether they are polyphyletic. Sockeye and kokanee which spawn sympatrically in three different lake systems were also examined to determine whether the two forms belong to a single panmictic population. Our results support the hypothesis that sockeye and kokanee are polyphyletic. No genetic characters were found by which the forms could be separated consistently. Greater differences exist among O. nerka populations from different drainages than between sockeye and kokanee forms. Sympatric sockeye and kokanee were significantly different in all systems examined, demonstrating that genetic differences can persist in the absence of geographic barriers to gene flow. While sympatric sockeye and kokanee were genetically divergent, they showed greater genetic similarity to one another (in allele frequency and/or allele types) than they did to their own forms in neighbouring lakes. We argue that this genetic similarity between sympatric forms is the result of sympatric divergence of sockeye and kokanee.
Comparison of Meristic and Morphometric Characters among Spring- and Fall-Spawning Ecotypes of Cisco (Coregonus artedii) in Southern Quebec, Canada
Authors: Hénault Michel , Fortin Réjean
Published: August 2008

Meristic and morphometric phenotypes of the spring-spawning stock of ciscoes (Coregonus artedii) from lac des Écorces were compared with those of fall-spawning stocks from the same drainage basin. The spring spawners show almost complete nonoverlap in gillrakers compared with fall spawners (averages of 42.7 and 50.5, respectively). This large gap could indicate genotypic differences between these stocks. Spring spawners also show smaller numbers of lateral line scales and of dorsal and anal fin rays, which might be related to higher incubation temperatures. Based on the comparison of conventional and truss network measures, discriminant analyses performed separately on males and females showed that the head and cephalic structures are smaller in spring ciscoes; their thoracic region is also longer and their caudal peduncle narrower and shorter. A principal components analysis showed that the few fall-spawning ciscoes captured in lac des Écorces do not differ from the fall spawners occurring upriver: the spring-spawning population would thus be allopatric.
Soluble Fluorescence: Effects on Chlorophyll Determination at Different Salinities
Authors: Keller Aimee A. , Beatty Lynn L. , Weber Laura E. , Heil Cynthia A.
Published: August 2008

Measurements of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) enhanced fluorescence (FDCMU), provided reliable estimates of phytoplankton biomass along a salinity gradient when adjusted for soluble enhanced fluorescence (SDCMU, <1 μm size fraction). Positive linear relationships (P < 0.0001) were observed between FDCMU and extracted chlorophyll at salinities of ~0, 5, 10 and 30 in experimental mesocosms and the Pawcatuck River Estuary, Rhode Island, both before and after subtraction of SDCMU. Adjusting for SDCMU did not reduce variability in the FDCMU to extracted chlorophyll relationships or alter slopes of the regression equations at different salinities. Positive intercepts (which varied with salinity) were, however, reduced to zero after correction. Results further indicated that SDCMU decreased with increasing salinity (primarily as a result of dilution with seawater), that it was relatively constant at a given salinity, and was unrelated to total FDCMU. Relying solely on in vivo fluorescence techniques, without correction for soluble fluorescence, would thus increasingly lead to overestimates of phytoplankton biomass at decreasing salinities. Over the experimental period, 32% (range 8–93%) of total FDCMU was present in the soluble fraction (SDCMU), with the majority (83%) non-photosynthetic material and most likely dissolved humic substances. SDCMU and light extinction coefficients were significantly and positively related in the mesocosms and the field.
Reciprocal Diel Vertical Migration Behavior in Planktivores and Zooplankton in British Columbia Lakes
Authors: Levy David A.
Published: August 2008

Simultaneous comparison of planktivore and crustacean zooplankton distribution patterns in a set of British Columbia lakes suggested coupled diel vertical migration behavior in the two adjacent trophic levels. In lakes where juvenile sockeye salmon performed diel vertical migrations, most zooplankton were non-migratory and concentrated in shallow surface waters over the diel cycle. In contrast, in one lake where pelagic threespine sticklebacks were present, and where juvenile sockeye diel vertical migrations were periodically reversed, most zooplankton undertook diel vertical migrations. The presence of diel vertical migration behavior in zooplankton thus appears to be related to the presence or absence of the behavior in the predominant planktivores.
Sensory Mechanism and Selective Advantage for Diel Vertical Migration in Juvenile Sockeye Salmon, Oncorhynchus nerka
Authors: Levy David A.
Published: August 2008

Diel vertical migrations are commonly undertaken by juvenile sockeye salmon within pelagic lake nursery environments. Data from hydroacoustic surveys in British Columbia lakes are used to compare predictions from sensory mechanism and selective advantage theories for diel vertical migration with the performance of the animals under field conditions. The observations suggest that light and temperature controlled juvenile sockeye day and night depth positions respectively. A multifactor hypothesis, which interprets the migration as a three-way compromise between foraging, predator avoidance, and the optimization of nocturnal metabolic efficiency, provides the most realistic explanation for the selective advantage of the behavior.
Measuring Epilithic Bacterial Production In Streams
Authors: Hudson J. J. , Roff J. C. , Burnison B. K.
Published: August 2008

Techniques are presented for the measurement of bacterial production (by the rate of 3H-TdR incorporation into DNA), isotope dilution, time course of incorporation of nucleoside, and disturbance artifacts in natural epilithic (on rock) communities of headwater streams. The epilithon in riffles was subsampled by carefully chipping upper rock surfaces. Chips were placed in test tubes and incubated in situ. Test tubes were rotated to reduce the formation of artificial diffusion barriers to TdR transport. DNA was isolated using a double filtration technique. Summertime production had a range of 1.3–51 mg C∙m−2∙h−1 in five southern Ontario streams. Precursors to DNA synthesis, which diluted 3H-TdR, had a range of 63–440 nM. Incorporation of 3H-TdR was linear for at least 1 h. Disturbance artifacts did not appear from rock chipping or from extended sample rotation. The techniques can be applied to other microbial groups from various aquatic hard substrata.
Effects of Iron Cycling on 210Pb Dating of Sediments in an Adirondack Lake, USA
Authors: Gubala Chad P. , Engstrom Daniel R. , White Jeffrey R.
Published: August 2008

In three cores from an acidic lake in the Adirondack State Park of New York, iron cycling accounted for diagenetic enrichment of up to 14% of sediment dry mass. The accuracy of the sediment accumulation rates calculated from the constant rate of supply (c.r.s.) model and the dating and sediment accumulation rates calculated from the constant initial concentration (c.i.c.) 210Pb models were affected by post-depositional movement of iron about the sediment–water interface and through the sediment. Dating biases from iron diagenesis reached as high as 57% and biases to calculated sediment accumulation rates ranged up to approximately 15%. In general, however, the difference between the iron-corrected and uncorrected dating was not much greater than the error expected from routine analytical precision. However, under circumstances of low sediment accumulation rates and high iron enrichment, significant deviations in dating and sediment accumulation calculations for both c.r.s. and c.i.c. 210Pb models may become noteworthy.
Micrograzer Impact and Substrate Limitation of Bacterioplankton in Lake Michigan
Authors: Pernie Gwenyth Laird , Scavia Donald , Pace Michael L. , Carrick Hunter J.
Published: August 2008

We estimated Lake Michigan epilimnetic heterotrophic bacterial loss rates, predator size, and substrate limitation in 1986 and 1987. The bacterial growth rates were always enhanced by organic substrate additions indicating that bacterial growth is limited, to some degree, by substrate availablility. In this study we obtained loss rates and intrinsic growth rates each between 0.32 and 1.45 d−1. The grazers were predominantly picoplankton-size organisms, presumably heterotrophic flagellates. Using radiolabeled bacteria, only a small percentage (2–3%) of bacterial cells were incorporated into larger size fractions after 24 h. These results indicate that during our experiments heterotrophic bacteria were not a direct, significant, carbon source for the upper trophic levels.
Timing of Sea-Run Brown Trout (Salmo trutta) Smolt Migration: Effects of Climatic Variation
Authors: Bohlin Torgny , Dellefors Claes , Faremo Ulo
Published: August 2008

By trapping seaward migrating smolts of brown trout (Salmo trutta), we analyzed the timing of the run in a small stream in southwestern Sweden (58°N) during 1984–90 in relation to environmental factors. Ninety percent of the smolts were captured during a period of 28.7 d (SD 5.9), with median time ranging from April 26 to May 17. Using polynomial multiple regression, we found a positive relationship between the probability of migration per day and the number of degree-days, change in water level, temperature change during the preceding week, and mean annual fish length. Forty-seven percent of the variation was explained. The predicted probabilities were used to calculate the population fraction migrating per day for the seasons 1984–90. There was a close agreement between the observed and expected daily fraction of migrants. The model, with parameter values based on the observations from 1984–90, was also used to predict the daily migration in 1991. The result indicated that the model accurately predicts the smolt run (R2 = 0.40).
Estimation of Algal Succession in Lake Water Using HPLC Analysis of Pigments
Authors: Soma Yuko , Imaizumi Takashi , Yagi Kei-ichi , Kasuga Sei-ichi
Published: August 2008

Seasonal variation in algal biomass in lake water was estimated using HPLC analysis of pigments. Carotenoids/chlorophyll a ratios were determined for cultures of Anabena, Microcystis, green algae, diatoms, and Cryptomonas. The contributions of various algal taxa to the total chlorophyll a content of lake water were calculated using the average carotenoid/chlorophyll a ratios of fingerprint pigments. The pigment analysis reflected the observed trend in the numbers of algae in lake water and proved to be a useful supplementary approach to evaluate algal biomass.
Homing and Straying Patterns of Chinook Salmon (Oncorhynchus tshawytscha) from a New Zealand Hatchery: Spatial Distribution of Strays and Effects of Release Date
Authors: Unwin Martin J. , Quinn Thomas P.
Published: August 2008

Homing and straying patterns of fall chinook salmon (Oncorhynchus tshawytscha) released from the Glenariffe Salmon Research Station on the Rakaia River, New Zealand, are reported, based on coded-wire tag recoveries from the 1978–84 brood years. Of 17 671 tagged adults recovered, 87.9% returned to the Rakaia, and the rest were recovered from 12 other catchments up to 500 km away. The number of strays entering a given river increased with discharge and with proximity to the Rakaia, but most strays were recorded in catchments north of the Rakaia. A higher proportion of salmon released in winter, when the downriver migration of naturally produced chinook is a minimum, strayed to other catchments (14.9–20.6%) than did those released at other times of the year (3.6–7.6%). However, straying within the Rakaia catchment was largely unaffected by release date, suggesting that imprinting by fry to the natal tributary is separate from imprinting by smolts to the mainstem river. There was a complex interaction between age at maturity, release date, and straying rates; straying of 4-yr-old fish was more strongly influenced by release date than straying of younger fish. Notwithstanding this interaction, straying was more prevalent among older fish.
Effect of Tannins on Leaf Processing and Conditioning Rates in Aquatic Ecosystems: An Empirical Approach
Authors: Ostrofsky M. L.
Published: August 2008

Tannin concentrations were determined in the autumn-shed leaves of 48 species of deciduous trees. Chemical measures of tannins (total phenolics and condensed tannins) were significantly correlated with protein-precipitating capacity. None of these measures of tannin concentration, however, were significantly related to published leaf processing rates, measured as weight loss versus time, or to microbial colonization, measured as rates of lipid synthesis on conditioned leaves. These data suggest that the large variation seen in leaf processing rates is due to factors other than tannin concentration and that much of this variation is due to abiotic factors such as leaching and physical fragmentation. Microbial activity on leaves showed much less variation than did processing rates.
Experimental Analysis of Microhabitat Selection by Juvenile Steelhead (Oncorhynchus mykiss) and Coho Salmon (O. kisutch) in a British Columbia Stream
Authors: Fausch Kurt D.
Published: August 2008

Replicate experiments were conducted in the Salmon River, British Columbia, during early summer 1990 to test the relative importance of velocity refuge, visual isolation, and overhead cover to microhabitat selection by steelhead (Oncorhynchus mykiss) parr and age-0 coho salmon (O. kisutch). Four types of artificial Plexiglas structures, the first three of identical construction, had different portions painted to provide increasing habitat complexity: velocity refuge alone, velocity refuge with visual isolation, all three features combined, and overhead cover alone. Steelhead parr selected structures with overhead cover alone or all three features significantly more often than those without overhead cover. Steelhead also selected structures adjacent to the swiftest velocities available and closest to other natural overhead cover, which accounted for most differences in use of the same structure in different locations. In contrast, few age-0 coho salmon used any structures. Those that did selected the three types of structures with velocity refuge about equally, but significantly more often than those with overhead cover alone, regardless of their location. Field experiments such as this hold promise for elucidating mechanisms of habitat selection by stream salmonids.
Effects of Experimental Acidification on Zooplankton Population and Community Dynamics
Authors: Locke Andrea , Sprules W. Gary
Published: August 2008

We provide experimental evidence of indirect ecological changes occurring through alterations in both competitive and predatory interactions within zooplankton communities during acidification. Acidification experiments were conducted on zooplankton in 16-m3enclosures suspended in a Precambrian Shield lake in central Ontario in order to identify mechanisms of community change. Changes in abundance, body size, egg ratio, and lipid status in zooplankton populations reflected changes in biotic interactions during acidification to pH between 5.0 and 6.0. Abundance of small cladocerans (especially Bosmina longirostris) increased following acidification despite increases in abundance or dominance of their cyclopoid predators, increased reproduction of Bosmina, in the absence of detectable changes in edible phytoplankton biomass, suggests that this was due to competitive release from larger cladoceran species that did not survive acidification.
Age- and Density-Dependent Bathymetric Pattern of Atlantic Cod (Gadus morhua) in the Southern Gulf of St. Lawrence
Authors: Swain Douglas P.
Published: August 2008

I examined the bathymetric pattern of Alantic cod (Gadus morhua) in September in the southern Gulf of St. Lawrence for age groups 3–8+over the period 1971–91 using data from annual bottom trawl surveys. Mean age of cod tended to increase with depth in all years. The age-specific bathymetric patterns underlying this relationship differed markedly between periods of low and high abundance. When abundance was high, cod densities tended to be highest at intermediate depths, and the positive correlation between age and depth reflected a tendency for density to be highest in progressively deeper water for older fish. When abundance was low, density was either unrelated to depth or highest in shallow water, and the positive correlation between age and depth reflected a tendency for older cod to be more widely distributed than younger cod (i.e., density decreased less sharply with depth for older cod). I suggest explanations for this density dependence of cod bathymetric pattern and discuss these results in relation to the factors underlying habitat selection and bathymetric segregation by age in this population.
Environmental Sex Determination in Southern Brook Lamprey,Ichthyomyzon gagei
Authors: Beamish F. William H.
Published: August 2008

Sex ratios were determined for 20 populations of southern brook lamprey larvae, Ichthyomyzon gagei, collected from throughout much of their range in the southeastern United States. Ratios varied between 9 and 49% males. Differential mortality was an unlikely factor, as sex ratios were similar among age groups within each population. Environmental sex determination is suggested. Sex ratio varied with growth (expressed as length of larvae at specific ages), larval density, pH, and annual mean temperature of the natal stream. Generally, under conditions promoting rapid growth, the percentage of males varied directly with density and inversely with temperature. Where growth was slow, the percentage of males declined as larval density increased, the response being less at low than at high pH. Temperature had little effect when larval growth was slow. The percentage of males declined when growth was rapid under otherwise similar environmental conditions.
Structure of the Body-Size Spectrum of the Biomass in Aquatic Ecosystems: A Consequence of Allometry in Predator–Prey Interactions
Authors: Thiebaux M. L. , Dickie L. M.
Published: August 2008

An equation describing predator–prey trophic energy transfers and production within the body-size spectrum of the biomass of aquatic ecosystems is formulated using allometric functions of body size. Its solution is the sum of two parts. One is a quadratic term that gives parabolic domes of biomass, in accordance with observations in nature. A second part, which seems not to have been recognized earlier, is a periodic function of log body size having significant potential for interpreting sample data reflecting ecosystem dynamics. The formulation is fitted to fish data from a small lake to demonstrate the applicability of the basic model to observations and to examine the scales of interaction of the measures of ecosystem dynamics that may be derived from them.
Strontium Microstructure in Scales of Freshwater and Estuarine Striped Bass (Morone saxatilis) Detected by Laser Ablation Mass Spectrometry
Authors: Coutant Charles C. , Chen C. H.
Published: August 2008

A laser ablation microprobe with mass spectrometry was used to examine the variability of Sr concentration among and within scales of striped bass (Morone saxatilis). These exploratory studies demonstrated that the technique is capable of showing differences that we relate to environmental conditions. There were marked differences in scale Sr concentrations at high spatial resolution between striped bass from freshwater reservoirs in Tennessee (low Sr) and the Roanoke River – Albemarle Sound estuary system in North Carolina (high Sr). A peak in Sr concentration was found near the scale focus of striped bass collected in the freshwater Roanoke River (but not in scales from reservoir fish) that may identify saltwater parentage or estuarine rearing. In fish from the Roanoke River and Albemarle Sound, we observed spatial variations across annuli that might reflect movements between fresh and saline water. There was a typical Sr profile with depth through the estuarine scales that exhibited a peak of unresolved significance near the inside surface. Laser ablation mass spectrometry of Sr in fish scales appears to be a valuable technique for life history analyses.
Convenient synthesis of ferrocene amines via Cu-catalyzed coupling reaction
Authors: Wu Jinsheng , Li Xiaolong , Yang Mingyu , Gao Yujie , Lv Qianru , Chen Baohua
Published: August 2008

An efficient copper-catalyzed Ullmann-type cross-coupling reaction without ligand of iodo-ferrocene with amines has been reported. In this process, a range of ferrocenyl amine compounds have been prepared in moderate to good yields.Key words: amines, iodo-ferrocene, cross-coupling, copper, Ullmann coupling.
Chemical-constituent diversity of Tridax procumbens
Authors: Chen Wen-Hao , Ma Xing-Ming , Wu Quan-Xiang , Shi Yan-Ping
Published: August 2008

Three new phytochemicals, a polyacetylene, 1,2-dihydrodendroarboreol B (1), an ionone derivative, (3S,5R,6S,7E)-3-tetradecanoate-5,6-epoxy-β-ionone (4), and a flavonol diglycoside, quercetagetin-3,6,4′-trimethoxy-7-O-neohesperidoside (38), along with 35 known compounds with diverse structures, were isolated from the EtOH extract of the aerial parts of Tridax procumbens. The structures of 1, 4, and 38 were determined on the basis of comprehensive methods including UV, IR, NMR, HR-ESI-MS, and CD, and by comparison of the spectroscopic data with those reported for structurally related compounds. Compounds 4, (3S,5R,6S,7E)-5,6-epoxy-3-hydroxy-7-megastigmene-9-one (5), and icariside B1 (12) were tested for their abilities to inhibit SGC-7901 and HL-60 cells. The antioxidant activities of quercetagetin-3,6,4′-trimethoxyl-7-O-β-D-glucopyranoside (36), quercetin-3-methoxyl-4′-O-β-D-glucoside (37), and 38 were evaluated by measuring their free-radical-scavenging effects, using the DPPH free-radical method.Key words: Tridax procumbens, polyacetylene, ionone, flavonol, cytotoxicity, antioxidant activities.
Mechanistic principles and applications of resonance energy transfer
Authors: Andrews David L
Published: August 2008

Resonance energy transfer is the primary mechanism for the migration of electronic excitation in the condensed phase. Well-known in the particular context of molecular photochemistry, it is a phenomenon whose much wider prevalence in both natural and synthetic materials has only slowly been appreciated, and for which the fundamental theory and understanding have witnessed major advances in recent years. With the growing to maturity of a robust theoretical foundation, the latest developments have led to a more complete and thorough identification of key principles. The present review first describes the context and general features of energy transfer, then focusing on its electrodynamic, optical, and photophysical characteristics. The particular role the mechanism plays in photosynthetic materials and synthetic analogue polymers is then discussed, followed by a summary of its primarily biological structure determination applications. Lastly, several possible methods are described, by the means of which all-optical switching might be effected through the control and application of resonance energy transfer in suitably fabricated nanostructures.Key words: FRET, Förster energy transfer, photophysics, fluorescence, laser.