bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Sphagnum peat and copper sulfate on productivity of a Ferro-Humic Podzol
Authors: Parent L. E. , Li Hong , Tremblay C. , Tahiri R. , Karam A.
Published: April 2011

Sphagnum peat is an abundant resource in the Quebec boreal zone and can be used to improve water retention in sandy soils of low productivity. Our objective was to select a peat application rate suitable for growing potato (Solanum tuberosum L. 'Superior') and barley (Hordeum vulgare L. 'Chapais') on a ferro-humic podzol. The experiment was conducted in Mistassini, Quebec, from 1994 to 1997. Organic matter content (OMC) of a Parent loamy sand was 2.7–2.9% initially. Peat was applied to small plots in a 2-yr potato and 2-yr barley rotation at rates of 0 (control), 29, 48 and 68 t ha−1 on a dry weight basis. A cupric fertilizer trial (0 vs. 2.2 kg Cu ha−1) was combined with the peat treatments. A yearly potato–barley rotation was also established in a nearby field receiving 25 t peat ha−1. The arable layer of peat-amended soils was stratified into a 5.3- to 14.8-cm thick upper layer (A1) down to the limit of peat incorporation, and an underlying layer (A2), averaging 15 cm in thickness, keeping the original soil properties. The highest tuber yield, but reduced tuber specific gravity, were obtained with the 48 t ha−1 treatment compared with the control and the 29 t ha−1 treatments. Peat rates excceeding 29 t ha−1 reduced yield and quality of the barley crop. The Cu concentration in barley and potato diagnostic tissues decreased as peat rate increased. Copper was needed to counteract the detrimental effects of peat amendments on maturation, yield and quality of barley. At field scale, peat increased the lower limit of soil water content for starting irrigation from 0.12 m3m−3 in the control to 0.15 m3m−3 in the peat-amended soil. Irrigation rate should be augmented at each passage, and frequency of waterings diminished, in peat-amended soils compared with the control, due to increased water storage capacity. Peat improved the productivity of the sandy soil up to 4–5% OMC, but could induce Cu shortage in barley. Key words: Soil water, potato, Solanum tuberosum L., barley, Hordeum vulgare L.
A lysimeter system for monitoring soil solution chemistry
Authors: Titus B. D. , Kingston D. G. O. , Pitt C. M. , Mahendrappa M. K.
Published: April 2011

In northern temperate and boreal zones, long-term sampling of the soil solution using lysimeter systems requires (i) a lysimeter that can be installed with a minimum of soil disturbance, (ii) a lysimeter that is small enough to install in stony soil but large enough to representatively sample the soil solution, (iii) a system with a constant tension that integrates soil solution sample collection over time, and (iv) a system that will not break under freezing conditions. A lysimeter system that meets these requirements was designed, and consists of a lysimeter (a fritted glass plate mounted on a glass casing) connected in series to a sample bottle and a tension-generating unit. The glass casing of the lysimeter has two ports: a drainage port for continuous flow of soil solution to the sample bottle, and an access port that can be used (i) for air entry to facilitate complete sample retrieval, (ii) for cleaning, (iii) for re-wetting the fritted glass plate, or (iv) for winterizing the lysimeter with alcohol. A 1-m hanging water column was used to supply a constant tension of approximately 10 kPa. A potential 93% efficiency rate of sample collection can be achieved, and the systems are capable of sampling soil solution beneath organic horizons, as well as in the rooting zone of mineral horizons. The system is presently being used to evaluate the effects of different harvesting and silvicultural treatments on nutrient cycling processes in the soil. Almost 700 of these lysimeter systems are in use in the Atlantic provinces of Canada. The lysimeters have been functioning satisfactorily for over 10 yr and are suitable for long-term monitoring of the soil solution. Key words: Lysimeter design, soil monitoring methodology, nutrient cycling
Soil water regimes of rotationally grazed perennial and annual forages
Authors: Twerdoff D. A. , Chanasyk D. S. , Naeth M. A. , Baron V. S. , Mapfumo E.
Published: April 2011

To maintain a sustainable agricultural system, management practices such as grazing must ensure adequate soil water for plant growth, yet minimize the risk of soil erosion. The objective of this study was to characterize the soil water regime of perennial and annual forages under three grazing intensities (heavy, medium and light). The study was conducted at the Lacombe Research Station, Alberta, on an Orthic Black Chernozem of loam to silt loam texture. The forages used were smooth bromegrass (Bromus inermis L. 'Carlton'), meadow bromegrass (Bromus riparius L. 'Paddock'), a mixture of triticale (X Triticosecale Wittmack 'Pika') and barley (Hordeum vulgare L. 'AC Lacombe') and triticale. Soil water measurements were conducted between April and October of 1994 and 1995 using a neutron scattering hydroprobe to a depth of 90 cm. Surface (0–7.5 cm) soil water was more responsive to grazing intensity than soil water accumulated to various depths. For all grazing treatments and forages, both surface soil water and accumulated soil water generally fluctuated between field capacity and wilting point during the growing season. Although plant water status was not determined, no visual permanent wilting of forages was observed during the study. Differences in evapotranspiration (ET), as determined by differences in soil water were evident among forage species but not grazing intensities, with perennials having high ET in spring and annuals having high ET in summer. Estimated values of water-use efficiency (WUE) were greater for perennials than for annuals and grazing effects on WUE were minimal. From a management perspective, grazing of annuals and perennials altered soil water dynamics but still maintained adequate soil water for plant growth. Key words: Evapotranspiration, forages, grazing intensity, water-use efficiency
Soil microbial biomass and enzyme activity following liquid hog manure application in a long-term field trial
Authors: Lalande R. , Gagnon B. , Simard R. R. , Côté D.
Published: April 2011

Liquid hog manure (LHM) addition to soils in corn silage (Zea mays L.) production may benefit microbial activity by providing C and other nutrients. The objective of this study was to compare the effects of a LHM application to that of inorganic fertilizers (IF) on the biological activity of a Le Bras silt loam soil (Humic Gleysol) under continuous corn production and LHM fertilization. Amounts of 0 to 120 m3 LHM ha−1 and 150 N–150 P2O5–150 K2O kg ha−1 were applied to silage corn. The 0- to 15-cm and 15- to 30-cm soil layers were sampled 28 d after the 18th yearly LHM application. The LHM inputs, particularly at 90 m3 ha−1, resulted in higher enzyme activities and microbial biomass C (MBC) than IF or the unamended control in the 0- to 15-cm soil layer. The 90 m3 LHM ha−1 also gave higher microbial biomass N (MBN) than IF in this soil layer. Application of LHM had no effect on the activities of the enzymes studied or on the MBC and MBN contents in the 15- to 30-cm layer. Ammonifier population was highest with 60 m3 LHM ha−1 in both soil layers. Nitrifier population was not affected by LHM in the top soil layer, but was linearly increased by LHM rates in the 15- to 30-cm layer. This study showed that LHM addition may enhance enzyme activities, microbial biomass and the N mineralizer population in the plow layer of a soil in a corn silage monoculture. Key words: Corn, pig slurry, microbial biomass, monoculture, soil enzyme
Prediction of soil salinity risk by digital terrain modeling in the Canadian prairies
Authors: Florinsky I. V. , Eilers R. G. , Lelyk G. W.
Published: April 2011

Soil salinisation is a typical problem for the Canadian prairies. At macro-topographic scale, build-up of salts occurs in depressions. However, this relationship is not displayed on existing small-scale maps of soil salinity. To improve these maps, one can use a concept of accumulation, transition and dissipation zones of the landsurface. The concept allows one to reveal depressions (topographically expressed accumulation zones) using digital models of horizontal and vertical curvatures, or accumulation and mean curvatures derived from a digital elevation model. We applied the concept of accumulation, transition and dissipation zones to improve an existing small-scale map of the salinity risk index for the prairies and adjacent areas. A comparison of the old and the improved maps demonstrated that once data on depressions have been taken into account, areas marked by salinity risk decreased significantly. We suggest that the method used may prevent an overestimation in predictions of soil cover degradation due to salinisation. The method used can also reveal saline areas linked with discharges of saline aquifers. This is because sites marked by high discharges of groundwater usually relate to sites of intensive fracturing of geological materials, which are closely associated with topographically expressed accumulation zones. Key words: Digital terrain models, topography, soil salinisation, mapping
Comment on: Application of 13C CPMAS NMR techniques in "Petroleum residues as water-repellent substances in weathered nonwettable oil-contaminated soils" (Roy et al. 1999) and recent related studies
Authors: Preston Caroline M.
Published: April 2011

not available
Comparison of samplers for the biological characterization of the sea surface microlayer
Authors: Agogué Hélène , Casamayor Emilio O. , Joux Fabien , Obernosterer Ingrid , Dupuy Christine , Lantoine François , Catala Philippe , Weinbauer Markus G. , Reinthaler Thomas , Herndl Gerhard J. , Lebaron Philippe
Published: April 2011

The surface film of the hydrosphere covers more than 70% of the world's surface. The sea surface microlayer (SML) or “skin” of the ocean is a sink for natural and anthropogenic material originating from the atmosphere and the water column. Organisms living in this SML are called “neuston.” Our knowledge of the biology of the SML is still in its infancy. Research of the sea surface microlayer requires the use of appropriate sampling techniques and strategies, and the question of what is the most suitable device has not yet been answered. In the present study, we have compared the efficiency of the Harvey glass plate (GP) and the Garrett metal screen (MS) to analyze a wide range of microbiological parameters in SML samples collected at two coastal stations in the NW Mediterranean Sea. Two types of membranes (Teflon and polycarbonate) were also used to collect bacterioneuston. The MS was the most appropriate technique for most biological parameters providing higher enrichment factors as compared to the GP and, therefore, the highest enrichment factors compared with underlying waters (UW). Control experiments with UW demonstrated that the enrichment reported for the MS was not biased by any selectivity of the sampler itself. Therefore, we recommend the use of the MS when the aim is to compare different biological parameters. In contrast, there is clear evidence that hydrophobic and hydrophilic membranes have an important drawback and should not be used for quantification purposes.
An efficient method for γ‐spectrometric determination of radium‐226,228 via manganese fibers
Authors: Dulaiova Henrieta , Burnett William C.
Published: April 2011

Radium isotope activities are typically at such low levels in natural waters, especially in seawater, that their measurement requires preconcentration from very large samples. Many investigators accomplish this by passing large volumes (20 to 150 L) of seawater or groundwater through a cartridge loaded with MnO2‐impregnated acrylic fiber. We describe here a new approach for converting “Mn fiber” into a form suitable for measurement of long‐lived 226Ra and 228Ra by γ‐spectrometry. The fiber is packed into custom‐made crucibles manufactured from stainless‐steel sheets. The fiber is then ashed at 550°C resulting in a sample mass reduction of approximately 90%. The crucibles are subsequently folded to enclose the ash, pressed using a hydraulic press, and sealed on top with silicon caulking to prevent radon escape. This procedure has an advantage over similar techniques because there is no sample transfer needed, and it is very time efficient. Radium‐228 is determined by counting photopeaks at 338 and 911 keV from its daughter 228Ac (T1/2 = 6.1 h). Radium‐226 is determined either by its photopeak at 186 keV (clear from interferences from 235U as U is not extracted on Mn fiber from oxidizing waters) or by counting the more abundant photopeaks from the granddaughters 214Bi and 214Pb after a 3‐week in‐growth period. A recent International Atomic Energy Agency intercomparison study for radium determination in water as well as comparison to the traditional radon emanation method showed that this technique provided good results and is appropriate for radium measurements in natural waters.
Mapping coastal optical and biogeochemical variability using an autonomous underwater vehicle and a new bio‐optical inversion algorithm
Authors: Brown Catherine A. , Huot Yannick , Purcell Michael J. , Cullen John J. , Lewis Marlon R.
Published: April 2011

Autonomous underwater vehicles (AUVs) can map water conditions at high spatial (horizontal and vertical) and temporal resolution, including under cloudy conditions when satellite and airborne remote sensing are not feasible. Applications of this technology are numerous, and harnessing the full potential of AUV platforms for oceanographic research will require innovative sampling and data processing techniques, particularly in shallow littoral environments. We deployed a passive radiometer on a small AUV called the Remote Environmental Monitoring UnitS (REMUS; Hydroid) to demonstrate a novel method that uses one optical sensor at depth to characterize variability in underwater clarity and the constituents of coastal seawater (i.e., dissolved organic material, algal biomass, and other particles). This approach uses spectral differences between attenuation coefficients that are computed from ratios of downwelling irradiance measured at one depth assuming a constant shape, but not magnitude, for the solar irradiance spectrum at the surface. A spectral inversion model provides estimates of the absorption coefficients (m−1) of the constituents above the sensor. There is no requirement for sensors at the ocean surface using this approach and, compared to inversion methods for subsurface reflectance, the effects of bottom reflectance in shallow waters are minimal. Maps of biooptical properties at high spatial resolution demonstrate that our approach can be used for characterizing shallow and highly variable coastal waters. This simple and robust technique is also applicable to other in situ sampling platforms (e.g., gliders, moorings, Argo floats).
Quantifying porewater exchange across the sediment‐water interface in the deep sea with in situ tracer studies
Authors: Rao Alexandra M. F. , Jahnke Richard A.
Published: April 2011

A numerical model of NaBr tracer transport in benthic flux chamber incubations has been developed to simulate temporal changes in chamber water tracer concentrations and applied to four deep sea locations: the California and North Carolina margins, the Ceara rise, and the Cape Verde plateau. Model variables include the chamber volume (which determines the initial tracer concentration), and rates of diffusive and nonlocal exchange across the sediment‐water interface. Chamber volume and solute exchange rate estimates were obtained by optimizing the fit between observations and model results using a χ2 statistical scheme. We observe enhanced solute exchange in regions with high organic carbon rain rates, over a wide range of bottom water oxygen concentrations. Furthermore, our results demonstrate that solute exchange rates cannot be assumed constant, even within relatively short deployments. In six of 22 cases, chamber volumes and corresponding benthic solute fluxes derived from model fits were more than 20% greater than values calculated using linear extrapolations of chamber tracer concentration‐time relationships. To avoid this discrepancy, future benthic chamber studies should seek to minimize the time interval between tracer injection and sampling while maintaining sufficient time to achieve complete homogenization of the tracer in the chamber waters.
Measuring carbon isotope ratios of microphytobenthos using compound‐specific stable isotope analysis of phytol
Authors: Oakes Joanne M. , Revill Andrew T. , Connolly Rod M. , Blackburn Susan I.
Published: April 2011

Carbon stable isotope analysis is one of the most common methods for validating theories about the role microphytobenthos (MPB) plays in estuarine food webs. However, difficulties extracting MPB from sediments to determine a pure isotope signature have hampered such studies. We have developed compound‐specific isotope analysis (CSIA) of phytol δ13C (δ13Cphytol) as an accurate proxy for δ13C of bulk MPB (δ13Cbulk). In most circumstances MPB is the dominant source of phytol in estuarine sediments, particularly in shallow water environments, so our method circumvents the need to extract MPB. We have demonstrated in the laboratory the relationship between δ13Cphytol and δ13Cbulk, and could predict δ13Cbulk within 1.8‰ (95% CI) of observed values at moderate replication (n = 5). If water temperature is included, δ13Cphytol predicts δ13Cbulk within 1.3‰. With greater replication (n = 10), predictions are extremely good (within 1.0‰). A two‐source mixing model assessed the usefulness of each method for estimating MPB contribution to consumer nutrition. At moderate replication (n = 5), for a gap between MPB and another producer of 6.0‰, estimates were more precise (i.e., 95% CIs were smaller) when both δ13Cphytol and temperature were used (95% CI 0.40) rather than only δ13Cphytol (0.46). The greatest difference in precision was for a gap of 6.0‰, close to the average gap in the literature (5.5‰). Given the difficulty of extracting MPB from sediment, carbon isotope studies of food webs could benefit by using CSIA of phytol, especially in conjunction with simple measurements of water temperature. The advance in methodology will allow a reevaluation of the trophic importance of MPB.
Flow‐through chamber method for clearance rate measurements in bivalves: design and validation of individual chambers and mesocosm
Authors: Filgueira R. , Labarta U. , Fernandez‐Reiriz M. J.
Published: April 2011

There is an ongoing discussion in the scientific literature about methodological aspects of clearance rate (CR) measurement with regard to bivalves, especially when the CR is measured by flow‐through chamber method. In the present paper, an experimental chamber, a mesocosm system, and a validation protocol have been developed for determining the CR using the flow‐through method. The procedure consisted of a preliminary analysis of the fluid dynamics in the interior of the chamber and a statistical analysis of the CR measurement in the mussel Mytilus galloprovincialis L at different water inflows. This allowed the performance of the chamber for each flow to be identified. The performance of the chamber for all the flows studied was also modeled simultaneously by means of Ivlev curve. The protocol, applied to an individual cylindrical experimental chamber (ICEC) (radius 71 mm, height 76 mm, volume 1200 mL), established that the ICEC complies with all the requirements for CR measurement using the flow‐through chamber method, provided that the percentage of particles cleared is approximately 20% (minimum 13%, maximum 25%). In agreement with the allometric relationship between length and volume of Mytilus galloprovincialis, 3 types of ICEC were designed for CR measurement on individuals of 20 to 85 mm length. After validation of the ICEC, the performance of a mesocosm system used regularly by our group (box raft experimental chamber or BREC) was evaluated. Three comparative measurements were carried out for the ICEC and BREC, two in situ and one in the laboratory. No statistically significant differences were observed between the experimental systems for the CR determinations, which validates the BREC for CR measurement using the flow‐through chamber method.
Expression of glutamine synthetase and glutamate dehydrogenase by marine bacterioplankton: Assay optimizations and efficacy for assessing nitrogen to carbon metabolic balance in situ
Authors: Hoch Matthew P. , Snyder Richard A. , Jeffrey Wade H. , Dillon Kevin S. , Coffin Richard B.
Published: April 2011

Expression of glutamate metabolism enzymes, glutamate dehydrogenase (GDH), and glutamine synthetase (GS) are proposed to yield information on the nitrogen (N) to carbon (C) metabolic balance within bacterioplankton communities. Whole‐cell assay conditions were optimized, and reactions were linear with time and biomass. Enzyme activities were assayed in seawater cultures from four ecosystems of contrasting trophic state amended with different regimes of glucose, amino acids, and ammonium (NH4+) to validate expression patterns of GDH and GS in various combinations of N and C limitation or excess. In three of four experiments, glucose amendment enhanced GS expression by 2‐fold but repressed GDH by 10% to 40% relative to the control. In contrast, addition of amino acids or NH4+ resulted in 20% to 90% repression of GS and enhanced GDH expression by 20% to 900%. The GDH:GS activity ratio (×10−3) ranged from 6 to 22 in glucose added treatments and 63 to 264 in NH4+‐amended treatments and appears to be a more sensitive index of bacterial N bioavailability relative to C supply than either enzyme alone. Cluster analysis was used to identify the condition of ambient bacterio‐plankton by matching enzyme expression with the validation results. This enzymatic approach overcomes some of the biases and limitations of other methods for assessing N metabolism in marine bacteria while providing unique information to further understand constraints of bacterioplankton respiration, production, and N flux.
Evaluation of a lifetime‐based optode to measure oxygen in aquatic systems
Authors: Tengberg Anders , Hovdenes Jostein , Andersson Henrik Johan , Brocandel Olivier , Diaz Robert , Hebert David , Arnerich Tony , Huber Christian , Körtzinger Arne , Khripounoff Alexis , Rey Francisco , Rönning Christer , Schimanski Jens , Sommer Stefan , Stangelmayer Achim
Published: April 2011

In this article, we evaluate the performance of a commercially available lifetime‐based optode and compare it with data obtained by other methods. We performed a set of 10 different tests, including targeted laboratory evaluations and field studies, covering a wide range of situations from shallow coastal waters and wastewater treatment plants to abyssal depths. Our principal conclusion is that, owing to high accuracy (± 2 µM), long‐term stability (more than 20 months), lack of pressure hysteresis, and limited cross‐sensitivity, this method is overall more suitable for oxygen monitoring than other methods.
Laser ablation ICP‐MS analysis of larval shell in softshell clams (Mya arenaria) poses challenges for natural tag studies
Authors: Strasser C.A. , Thorrold S.R. , Starczak V.R. , Mullineaux L.S.
Published: April 2011

We investigated whether laser ablation inductively coupled plasma mass spectrometry (ICP‐MS) could be used to quantify larval shell compositions of softshell clams, Mya arenaria. The composition of aragonitic otoliths has been used as a natural tag to identify natal habitat in connectivity studies of fish. If it is possible to measure larval shell reliably, this technique could also be applied to marine bivalves. To determine whether the first larval shell (prodissoconch I) could be measured independent of underlying material, we conducted laboratory experiments in which larval M. arenaria were exposed to enrichments of the stable isotope 138Ba during different stages in shell development. We were unable to isolate the chemical signature of the prodissoconch I from subsequent life stages in all combinations of shell preparation and instrument settings. Typical instrument settings burned through the prodissoconch I on a post‐settlement juvenile and at least 9 d of second larval shell (prodissoconch II) growth. Our results suggest instrumental and technical improvements are needed before laser ablation ICP‐MS can be useful for connectivity studies that require analysis of larval shell on a post‐settlement M. arenaria juvenile. Laser burn‐through is potentially a problem in any connectivity study where it is necessary to assay the small amounts of shell material that are deposited before a larva disperses away from its natal location.
Submersible operated peepers for collecting porewater from deep‐sea sediments
Authors: Dattagupta Sharmishtha , Telesnicki Guy , Luley Kathryn , Predmore Benjamin , McGinley Michael , Fisher Charles R.
Published: April 2011

Peepers are a common alternative to push cores for collecting porewater from shallow aquatic environments such as lakes, streams, and wetlands but are infrequently used to sample deep‐sea sediments due to design limitations. In this study, a peeper was developed to obtain porewater from precisely located positions on the deep‐sea floor using remotely operated or manned submersibles. The sample cells of the peepers can be sealed closed after they are deoxygenated on board a ship to ensure that they remain anoxic until peepers are deployed at the deep‐sea sampling location. Similarly, peeper cells can be closed at the end of an incubation period to maintain sample integrity during submersible recovery and until sample processing. Each peeper can be used to collect samples from 10 cm above the sediment water interface and at 10 cm intervals down to 60 cm depth in the sediment, and can provide sufficient volume for multiple chemical analyses, including stable isotope ratio determinations.
The use of wet chemical oxidation with high‐amplification isotope ratio mass spectrometry (WCO‐IRMS) to measure stable isotope values of dissolved organic carbon in seawater
Authors: Osburn Christopher L. , St‐Jean Gilles
Published: April 2011

Few measurements of the carbon stable isotope value (δ13C) of marine dissolved organic carbon (DOC), the largest pool of reduced carbon in the ocean, have been made because of analytical obstacles due to the interference of halides and the low amount of DOC in seawater. By using concentrated persulfate in a wet chemical oxidation organic carbon analyzer coupled to an isotope ratio mass spectrometry (WCO‐IRMS) the analytical obstacles are overcome. Key to this method is reducing the persulfate blank and increasing the IRMS signal with larger amplifier gain resistors. After these simple modifications, a 2 mL sample provides enough signal to make precise measurements of DOC concentration and δ13C value on up to 15 samples per day. Sodium persulfate (1.68 mol L−1) is cleaned by pre‐heating and sparging with ultrahigh purity helium. In the WCO analyzer, 6 mL cleaned persulfate is added to 2 mL sample at 98°C for 8.5 min to completely oxidize DOC to CO2. After quantitative measurement by nondispersive IR, the gases contained in the exhaust are swept through a cleanup reactor, separated by a GC column and introduced to the IRMS for δ13C measurement. Complete recovery of the DOC and δ13C values was confirmed with two DOC standards added individually to seawater. IRMS precision was confirmed by measuring a range of sea water samples. On several coastal water samples measured using this system, δ13C‐DOC values ranging from −22‰ to −25‰. These results were consistent with published reports of seawater δ13C‐DOC using other methods.
A novel and robust device for repeated small‐scale oxygen measurement in riverine sediments—implications for advanced environmental surveys
Authors: Riss H. Wolfgang , Meyer Elisabeth I. , Niepagenkemper Olaf
Published: April 2011

A novel sampling methodology was developed to measure in situ oxygen concentrations at well‐defined spatial resolutions in riverine sediments. Stainless steel tubes of different length, perforated and shielded at the lower end, and bundled in units, were inserted into the streambed to serve as long‐term sampling points. The samplers were given a physically robust design to withstand a certain degree of bed load discharge. Oxygen measurements were obtained by introducing into the sampling tubes a fine tolerance metal tube containing a fiber optic oxygen sensor (optode). Small volumes of interstitial water were withdrawn and the partial pressure of dissolved oxygen in the sample water was measured continuously as it passed the oxygen sensor. The optode has distinct advantages over previous oxygen sensors in that it neither consumes oxygen nor requires a significant flow of water past the sensor to obtain reliable readings. A sample volume of less than 1 cm3 is sufficient to obtain interstitial water with a purity of more than 97%. Residual water from inside the steel tubes caused only a low contamination level. Measurement bias as a consequence of vacuum withdrawal and consequent changes to atmospheric pressure did not exceed one percent under normal conditions. The measurement technique presented in this paper offers advantages over previous methodologies in that it permits more accurate in situ oxygen measurement at smaller spatial scales and especially at low oxygen levels. After installation of the sampling tubes in the streambed, and following an initial stabilization period (approx. 40 d), field measurements revealed vertical and horizontal variability in interstitial oxygen concentrations. Installed sample arrays allowed repeat measurement of interstitial conditions over a 12‐month period.
Mass‐spectrometer bias in stable isotope ecology
Authors: Mill Aileen C. , Sweeting Christopher J. , Barnes Carolyn , Al‐Habsi Saoud H. , MacNeil M. Aaron
Published: April 2011

Stable isotope analysis (SIA) is recognized as a powerful analytical tool with numerous ecological applications. This has been highlighted by the increase in popularity of the isotope ratio mass spectrometry (IRMS) technique and the large number of studies reporting isotopic data. Comparisons of new isotopic data with previously published results and the use of large volumes of isotopic ratios in meta‐analyses to explain isotopic variance are commonplace. Such data often originate from different IRMS instruments and are assumed to be readily comparable as all instruments are calibrated to International Atomic Energy Agency (IAEA) standards. To test the validity of this assumption, we analyzed a single ecological sample (homogenized cod muscle, Gadus morhua) on eight anonymous IRMS instruments and found significant variation in both δ15N and δ13C. We used a one‐way analysis of variance (ANOVA) with random effects to estimate the average variability of laboratory results within and among instruments. Overall, 74% of variation in δ15N and 35% of variation in δ13C of a single ecological sample was explained by differences in the IRMS instrument used. In light of these findings, researchers are encouraged to submit their own sample reference to provide an independent check on variation between runs and between instruments; consistent discrepancies between instruments should be corrected through linear regression. Comparisons of data obtained from multiple instruments should acknowledge inter‐instrument variation as a potential source of error.
A microfluidic chemotaxis assay to study microbial behavior in diffusing nutrient patches
Authors: Seymour J.R. , Ahmed T. , Marcos  , Stocker R.
Published: April 2011

The nutrient environment experienced by planktonic microorganisms is patchy at spatiotemporal scales commensurate with their motility (µm – cm), and the efficiency with which chemotactic microbes can exploit this heterogeneous seascape influences trophodynamics and nutrient cycling rates in aquatic environments. Yet, methodological limitations have largely prevented direct examinations of microbial behavior within heterogeneous microenvironments. We used soft lithography to fabricate a microfluidic‐based chemotaxis assay to study the foraging response of aquatic microbes to diffusing microscale nutrient patches. The transparency, biocompatibility, and simplicity of microfluidic devices make them ideally suited for microbial ecology studies. A microinjector was used to create a 300 µm‐wide nutrient band, simulating a pulse release of solutes. The chemotactic response of microbes to the diffusing patch was measured at the population and single‐cell level. In contrast to traditional chemotaxis assays, this technique permits the assessment and quantification of chemotaxis toward a potential attractant in real time, enabling rapid screening of multiple chemicals. Furthermore, detailed information on chemotactic behavior can be obtained by tracking individual organisms. Here, we applied this microassay to study the chemotactic behavior of a range of aquatic microorganisms, including three marine bacterial isolates, a species of phagotrophic flagellate, and a species of phytoplankton. Each organism exhibited a rapid chemotactic response to a variety of chemical compounds, suggesting that many marine microbes are adapted to life within patchy microenvironments. The chemotaxis assay described here was found to be a flexible platform for studying both the specific case of microbes foraging within patchy habitats and as a broadly applicable tool for rapidly assessing and quantifying microbial chemotaxis.
Calculating the conductivity of natural waters
Authors: Pawlowicz Rich
Published: April 2011

An algorithm is developed to compute the conductivity of lake and dilute ocean water from measured chemical composition at arbitrary temperature and pressure. The complex mixed electrolyte is considered as a sum of binary electrolytes rather than a sum of ions. Effects of ion association are included, and it is found that pairing effects are important in natural freshwaters. Bounds on the accuracy of the algorithm for specific classes of binary electrolytes are assessed and it is estimated that the algorithm has an overall accuracy of better than 2% for salinities less than about 4 g L−1. Comparison with seawater conductivities is much better than 1%, but predicted conductivities of some published analyses of river waters are about 3% too high. Some of this difference may be due to a lack of data on ion pairing effects between bivalent metals and bicarbonate, but also may result from uncertainties in the measured chemical composition and measured conductivity. An iterative procedure incorporating this algorithm is used to compute reference conductivity at 25°C and salinity from in situ measurements of conductivity in waters where only relative amounts of ions are known. It is found that the conversion to reference conductivity is reasonably independent (to within about 1%) of the ionic composition for most world river waters, but is somewhat different than that for KCl solutions. However, derived salinities are quite sensitive to the composition, and the ratio of ionic salinity to reference conductivity varies between 0.6 and 0.9 mg L−1 (µS cm−1)−1.
Fluorescent lectin assay to quantify particulate marine polysaccharides on 96‐well filtration plates
Authors: Uthicke Sven , Llewellyn Lyndon , Eder Florian
Published: April 2011

Our aim was to develop a method to more broadly quantify particulate polysaccharides (PPs) to complement Alcian blue quantification of transparent exopolymer particles (TEPs), which are a subset of the ocean's pool of PPs. We used fluorescently labeled concanavalin A (FITC‐conA), which is a lectin (a group of proteins that bind polysaccharides) and propose a method using 96‐well filtration plate technology. ConA binds polysaccharides that contain the commonly occurring saccharides glucose and mannose. Using gum xanthan as a standard and field samples from the Great Barrier Reef (GBR), we demonstrated that marine particles (>0.4 µm) bound FITC‐conA in a concentration‐dependent manner. Particulate polysaccharides measured by FITC‐conA and Alcian blue (TEP only) in samples from 11 locations in the GBR were significantly correlated (R2 = 0.61, P = 0.003). The lectin‐based measurements were on average 80% higher, probably because Alcian blue stains acidic polysaccharides only, whereas lectins stain a broader polysaccharide spectrum. FITC‐conA measurements of PPs in the wet season were on average 54% higher than in the dry season. PP concentrations correlated to concentrations of chlorophyll a, pheophytin, and particulate nitrogen, suggesting phytoplankton as an important source of PPs. Small volumes and few working steps enabled miniaturization of the FITC‐conA protocol into a 96‐well plate format, which provides for rapid sample throughput. In addition, there is extensive scope for further development using different lectins, naturally sourced standards, or filter size and capacity.
In vivo electron transport system activity: a method to estimate respiration in natural marine microbial planktonic communities
Authors: Martínez‐García Sandra , Fernández Emilio , Aranguren‐Gassis María , Teira Eva
Published: April 2011

Oxygen consumption during in vitro dark bottle incubations is the most common method to estimate planktonic respiration. This method is time consuming and labor instensive and, consequently, the database of planktonic respiration rates is scarce. Electron Transport System (ETS) activity measurement has gained acceptance as a routine technique to estimate respiration due to its high sensitivity. However, the in vitro ETS assay commonly used yields potential rates. Hence, the empirically determined ratio between in situ respiration and potential ETS activity is not constant, varying over two orders of magnitude, highly limiting the routine application of this technique to estimate microbial respiration. We hypothesized that in vivo ETS activity should be a reliable estimator of in situ respiration in marine plankton communities. The aim of this study was to develop a methodology to estimate in vivo ETS activity rates by using tetrazolium salt 2‐para (iodo‐phenyl)‐3(nitrophenyl)‐5(phenyl)tetrazolium chloride (INT) as electron acceptor. We established a procedure to apply the in vivo INT reduction method to natural marine microplankton samples. Optimum incubation times were found to be lower than 2–6 h, even for oligotrophic waters. The method was tested in natural waters, covering a very wide range of respiration rates and trophic conditions. A significant linear relationship was found between in situ respiration and in vivo INT reduction. Moreover, the ratio between oxygen consumption and INT reduction was constant across contrasting environments, which reveals the INT reduction method as a simple, quick, sensitive, and robust technique suitable to substantially improve the microbial plankton respiration database.
A particle separator used to concentrate Dinoflagellate cysts from sediment
Authors: Smith Barry C. , Persson Agneta , Wikfors Gary H.
Published: April 2011

A device has been developed to separate and collect large numbers of dinoflagellate cysts from sediment samples of several liters volume. The apparatus consists of a 152.5 × 44.5 × 38‐cm fiberglass tank with a 20‐µm screen inserted diagonally across the long dimension, creating an inclined plane as the bottom of a settling tank. A peristaltic pump delivers resuspended bottom material to the top of the deep end of the tank. The particles settle according to mass and friction as the water moves to a drain near the top center of the shallow end of the screen. The desired particles can be vacuumed from specific areas of the screen and further refined with a final sieving step. More than 16 L marine mud were processed in this apparatus at one time. In a reference sediment sample collected from beneath New Haven Harbor (Connecticut, USA), cyst recovery was 25% for living cysts. The sediment in the uppermost part of the sorter had approximately 376 times more cysts/mL than the sediment originally added. The cyst fraction (particles 20‐100 µm) contained ten times more cysts in the uppermost part of the sorter than at the middle or lower ends. Cysts within the cyst‐rich zone of the separator settled differently depending upon species, size, and morphology.
Analysis of cooking spices in natural waters
Authors: Keil Richard G. , Neibauer Jacquelyn A.
Published: April 2011

An isolation and quantification technique is presented for the analysis of semi‐volatile spices and scents in aquatic waters including thymol, eugenol, limonene, carvacrol, vanillin, and cinnamaldehyde. Compounds are isolated from natural waters by solid phase extraction onto Waters Oasis HLB columns and eluted into ethyl acetate. Recovery efficiencies are >70% for most target compounds. Comparison with liquid‐liquid extraction and C‐18 solid phase extraction indicates that HLB cartridges are more robust and provide equal or better recoveries for target compounds relative to other approaches. Because the compounds are semi‐volatile and prone to losses during solvent evaporation, we do not dry the samples completely before quantification by gas chromatography mass spectrometry. Compounds are analyzed using selected ion monitoring with a sensitivity ~1 pg compound per injection. This equates to a sensitivity of about 2–200 ng L−1 in natural waters, or part‐per‐billion levels. Column loading and matrix effects are minimal and are accounted for by careful monitoring of volumes and by standard additions during GC analysis. Environmental samples (treated sewage, lake, stream, and fjord samples) show a wide range of compounds and quantities, most in the 10–10,000 ng L−1 range. The artificial spice ethylvanillin, which is commonly used as an internal standard in analysis of woody lignin samples, is found in some natural waters. This is likely a result of the industrial‐scale production of this compound for culinary and pharmaceutical use.
Volunteers@your library: benefits and pitfalls of volunteers in hospital libraries
Authors: McDiarmid Mary , Auster Ethel W
Published: April 2011

The purpose of this survey was to explore the attitudes of hospital library managers toward the use of library volunteers. During April 2003 a questionnaire was mailed to 89 Ontario hospital library managers. One of the methods used to assess attitudes toward volunteers was to ask respondents to list two main benefits and pitfalls of using volunteers. Benefits of volunteer use identified by respondents included assisting with routine clerical tasks, saving staff time, providing an added value or service, assisting with a heavy workload, contributing to a positive public perception and promoting library service, keeping costs down, optimizing staff time, and doing special projects. Some of the pitfalls of volunteer use identified by respondents included unreliable volunteer attendance and commitment, and excessive training and retraining. The identification of volunteer benefits and pitfalls will help hospital library managers optimize the use of volunteers and implement changes in the way they manage volunteers.
Whatever happened to William Osler's library?
Authors: Lyons Christopher , Crawford David S
Published: April 2011

Sir William Osler bequeathed his library to McGill University in 1919, and the 8000 volumes arrived in Montreal a decade later. Then, as now, the collection consisted of both primary works (rare books) and secondary commentaries, and current works on the history of the health sciences. In the last 80 years, the collection has grown considerably, and the library now adds about 1000 books each year, mainly current publications, and receives 200 current serial titles. The Osler Library, which is one of the largest "history of medicine" libraries in the world and the largest in Canada, tries to collect current material on the history of the health sciences from all over the world and attempts to collect all medical history published in Canada. The Osler offers its resources to researchers through its Web site, publications, and Research Travel Grant program.
Investigation of cytochromes P450 in myxobacteria: Excavation of cytochromes P450 from the genome of Sorangium cellulosum So ce56
Authors: Khatri Yogan , Hannemann Frank , Perlova Olena , Müller Rolf , Bernhardt Rita
Published: April 2011

The exploitation of cytochromes P450 for novel biotechnological application and for the investigation of their physiological function is of great scientific interest in this post genomic era, where an extraordinary biodiversity of P450 genes has been derived from all forms of life. The study of P450s in the myxobacterium Sorangium cellulosum strain So ce56, the producer of novel secondary metabolites of pharmaceutical interest is the research topic, in which we were engaged since the beginning of its genome sequencing project. We herein disclosed the cytochrome P450 complements (CYPomes) of spore‐forming myxobacterial species, Stigmatella aurantiaca DW4/3‐1, Haliangium ochraceum DSM 14365 and Myxococcus xanthus DK1622, and their potential pharmaceutical significance has been discussed.
Overwintering strategies of Antarctic organisms
Authors: Cockell Charles S , Stokes M Dale , Korsmeyer Keith E
Published: April 2011

The extremity of winter conditions in the present-day polar regions is unique on Earth. Each year organisms are subjected to extremes of temperature and depending on latitude, prolonged periods of darkness. Organisms have adapted to these extremes through a variety of overwintering strategies that range from physiological changes to alterations in geographical distributions. Some adaptations are specific to just a few taxa, such as huddling by penguins, a strategy that is also seen in some Arctic mammals. However, other strategies are common to a wide diversity of taxa, such as fat storage throughout the winter or migratory avoidance behavior. Although many organisms have specifically adapted to polar conditions, it is also apparent that for many, survival of the Antarctic winter draws upon an inherent phenotypic plasticity particularly amongst the invertebrates. In this review the adaptations of a wide range of organisms to the polar winter environment are discussed. This review concentrates on the Antarctic, although the Arctic is discussed for comparison where appropriate.Keywords: winter, overwintering, polar, Arctic, Antarctic.
Long-term changes in the North Sea ecosystem
Authors: Clark R A , Frid C LJ
Published: April 2011

Long-term data on the North Sea ecosystem are available for phytoplanktonic, zooplanktonic, benthic, fish, and seabird communities. Temporal changes in these have been examined by numerous researchers over the course of the 20th century, their main objective being to determine how the interannual dynamics of these communities are controlled. Ultimately, long-term changes in the North Sea ecosystem appear to be driven by two wide-ranging, but separate processes. In the northern, western and central areas of the North Sea, long-term changes are predominantly influenced by climatic fluctuations. Here, primary productivity during a particular year is related to the effect of weather on the timing of stratification and the resulting spring bloom. In the southern and eastern areas of the North Sea, the lack of stratification and the large inputs of nutrients mean that primary productivity is more strongly influenced by variations in anthropogenic nutrient inputs, and is only weakly related to climatic variation. Long-term changes at higher trophic levels (zooplankton, benthic, fish, and seabirds) are generally affected by fluctuations in their food source (i.e., the lower trophic levels), although because of the high complexity of the North Sea ecosystem there are many exceptions to these general patterns. However, the weight of evidence shows that long-term changes in the ecosystem may ultimately be related to long-term changes in either climate or nutrients, although the long-term dynamics of certain taxa and communities do show evidence of being influenced by both anthropogenic factors and (or) internal factors such as competition and predation. Key words: long-term changes, North Sea, time series, climate change, ecosystem functioning, anthropogenic impacts.