bluuebunny/crossref_metadata_2025 huggingface dataset:
Uptake of N, P and S in fertilized pasture herbage and herbage yield response to fertilizer as affected by soil nutrients
Authors: McCartney D. H. , Bittman S. , Horton P. R. , Waddington J. , Nuttall W. F.
Published: April 2011

Uptake of N, P and S nutrients in the herbage of different pasture species were determined at eight sites within pastures located on Luvisolic soils in northeastern Saskatchewan, Canada. Also, the nutrient status of the soil was related to herbage yield response to N, P and S fertilizers. Soil tests would be used to establish the initial response to ferilizer and thereafter, nutrients removed from the soil could be replaced by fertilizer. Experiments in the study included one site with bromegrass (Bromus inermis Leyss.) and alfalfa (Medicago media Pers.), six sites on a pasture mixture (Bromus inermis Leyss., Festuca rubra L., Poa pratensis L. and Medicago media Pers.) and one site with Russian wildrye (Psathyrostachys juncea (Fisch.) Nevski) at both Pathlow and Pleasantdale pastures. Nitrogen and P fertilizers were applied at 0, 45 and 90 kg N ha−1 in combination with P at 0 and 20 kg ha−1. Sulphur treatments included 90N–20P–2-S (sulphate source, kg S ha−1) on pasture mixture sites and two treatments of 90N–20P–23S and 90N–20P–45S (elemental source, kg S ha−1) on bromegrass and alfalfa. Maximum uptake of nutrients were 103.6 kg N, 11.5 kg P and 5.2 kg S ha−1 with the application of 90N–20P–45S (kg ha) on the bromegrass–alfalfa pasture. The controls resulted in the lowest uptake of 20.2 kg N, 1.9 kg P (pasture mixture) and 1.5 kg S ha−1 (bromegrass and alfalfa). Yield response to N and P fertilizers (percentage yield over control) was related to soil tests for N, P and S (r2 = 0.42). Herbage yield increase (log10 mean of years) from S fertilizer over the control was negatively related to the soil test for S on six sites (r2 = 0.77). Uptake of N, P and S in herbage gave an adequate estimate of nutrient removal and the amount of fertilizer to apply to maintain soil nutrient levels. Key words: pasture, N, P, S, herbage, soil tests, yield
Soil compaction induced by careful logging in the claybelt region of northwestern Quebec (Canada)
Authors: Brais S. , Camiré C.
Published: April 2011

Soil compaction induced by forest harvesting operations can reduce site productivity. Intensity, extent and persistence of soil compaction were assessed on fine- to medium- and coarse-textured soils. Severe compaction took place in the wheel track section of the skid trails. On fine- to medium-textured soils, half of the effects on the 0- to 10-cm and 10- to 20-cm mineral soil bulk densities (+11 and +8%) and half of the changes in the 10-cm depth soil strength (+69%) occurred in the course of the first two skidding cycles (cycle of half impact). On coarse soils, half of the effect on the 0- to 10-cm bulk density (+11%) occurred during the first three passes. Cycles of half impact for soil strength were 9, 14, 7 and 6 for the 2.5-, 5-, 10-, and 20-cm depths and corresponded to increases of 235, 402, 157 and 103% respectively. Compaction was more limited between track sections of trails. Six to twelve years following clearcutting on fine- to medium-textured soils, 0- to 10-cm soil bulk density was less in the skid trails than on the undisturbed sections of cutovers. Careful logging on moist, fine- to medium-textured soils is the safest way to limit the extent of soil compaction. On coarse-textured soils, spreading the traffic remains a valid option. Key words: Soil compaction, bulk density, soil strength, forest harvesting, careful logging
Sorption of clopyralid, dicamba and MCPA by two soils with conventional and no-till management
Authors: Shang C. , Arshad M. A.
Published: April 2011

Sorption is one of the key processes controlling the fate of agrochemicals in soil systems. The sorption of agrochemicals on a soil matrix can be affected by changes in chemical and physical properties caused by different tillage practices. Clopyralid (3,6-dichloro-2-pyridinecarboxylic acid), dicamba (3,6-dichloro-2-methoxybenzoic acid), and MCPA ((4-chloro-2-methylphenoxy)acetic acid), weakly acidic herbicides, are commonly used to control broadleaf weeds in crop production. The sorption of the three herbicides by surface soils (0–5 cm) from different tillage systems was studied by batch equilibrium. Of the herbicides used, MCPA was sorbed on soil in the greatest quantity, dicamba was the least sorbed, and the sorption was dependent on the pKa values of herbicides. In a sandy loam soil, more herbicide was sorbed under no-tillage (NT) than conventional tillage (CT). However, in a clay soil the difference in herbicide sorption between the two tillage systems was not consistent. The results can be explained in terms of changes in soil pH and organic matter content. The presence of clopyralid and MCPA lowered the sorption of dicamba, and MCPA was more effective than clopyralid in competing for sorption sites with dicamba. Key words: Herbicide sorption, clopyralid, dicamba, MCPA, tillage
Tillage and N source influence soil-emitted nitrous oxide in the Alberta Parkland region
Authors: Lemke R. L. , Izaurralde R. C. , Nyborg M. , Solberg E. D.
Published: April 2011

Zero tillage systems are receiving attention as possible strategies for sequestering atmospheric carbon. This benefit may be offset by increased N2O emissions, which have been reported for soils under zero tillage (ZT) compared to those under more intensive tillage (IT). Comparisons of N2O emissions from the two systems have been restricted to the growing season, but substantial losses of N2O have been reported during spring thaw events in many regions. Inorganic and organic additions of nitrogen and fallowing have also been shown to increase levels of soil-emitted N2O. The objectives for this study were: (i) to confirm that losses of N2O are higher under ZT than under IT in Alberta Parkland agroecosystems; (ii) to compare the relative influence of urea fertilizer (56 or 100 kg N ha−1), field pea residue (dry matter at 5 Mg ha−1), sheep manure (dry matter at 40 Mg ha−1) additions, and fallow on total N2O losses; and (iii) to investigate possible interactions between fertility and tillage treatments. Gas samples were collected using vented soil covers at three sites near Edmonton, Alberta during 1993, 1994, and 1995. Gas samples were analyzed using a gas chromatograph equipped with a 63Ni electron capture detector. Estimated annual N2O loss ranged from 0.1 to 4.0 kg N ha−1. Emissions during summer were slightly higher, similar, or lower on ZT compared to those under IT, but were consistently lower on ZT plots during spring thaw. Combined estimates (spring plus summer) of N2O loss under ZT were equal to or lower than those under IT. Highest overall losses were observed on fallow plots, followed by fertilizer, pea residue, and then either manure or control plots. We conclude that ZT management systems have potential for reducing agricultural greenhouse gas emissions in the Alberta Parkland region. Key words: Nitrous oxide, thawing soil, tillage, nitrogen fertilizer, manure, fallow
Relationship between soybean seed selenium and harvested grain selenium
Authors: Gupta Umesh C. , MacLeod J. A.
Published: April 2011

Field experiments were conducted on sandy loam soils in Prince Edward Island (PEI) with two cultivars of soybeans at two locations to determine the relationship between Se concentration in the seed sown and the Se concentration found in the harvested soybean crop. Seeds containing a range of Se from 0.78 to 38.5 mg kg−1 were used. These variable concentrations of seed Se were obtained in field experiments by varying the rates of seed and foliar applied Se. Grain Se concentration increased with increased Se concentration in the planted seed. A high proportion of the variation in Se concentration in the harvested soybean crop was explained by variation in the Se content of the planted seed (R2 = 0.98). The regression was calculated using averages of cultivars for both locations. From the regression equation it could be predicted that planting seed containing 24 mg Se kg−1 would produce a soybean crop containing 0.5 mg Se kg−1. When used at 200 kg soybean per tonne ration this would provide a Se concentration of 0.1 mg kg−1 assuming negligible contributions from other ingredients. Selenium concentration of 0.1 mg kg−1 in animal ration is considered adequate to protect livestock from Se deficiency diseases. Key words: Podzol soils, seed-applied Se, grain Se
In situ application of the 15NO3− isotope pairing technique to measure denitrification in sediments at the surface water‐groundwater interface
Authors: Sanders Ian A. , Trimmer Mark
Published: April 2011

There is a need to understand the hydro‐ecological significance of surface‐subsurface interactions, including denitrification, in sediments in permeable catchments. Measurement of denitrification in such sediments is complicated by the NO3− reduction zone being relatively deep in the sediment (a few to tens of centimeters), there being 2 significant sources of NO3− (the overlying water and the underlying groundwater) and, in some environments, the impact of macrophytes such as Ranunculus. These factors negate the collection of sediment cores for measuring denitrification by traditional techniques. Instead, we have developed a minipore water probe system that can be used to identify NO3− reduction zones and measure in situ rates of denitrification based on spiking sediment pore waters with 15NO3− followed by a short incubation time (15 min) and subsequent quantification of 29N2 and 30N2. Given the short incubation time, we suggest that the technique can be applied to pore waters with significant advective flow, and present results for fine sand sediments from the River Frome (Dorset, England). The limitations of the technique, including a low depth resolution (2 cm) and intrusion of pore water from outside the sample target depth, are calculated and discussed. Accepting the disturbance caused by the initial insertion of the probes, which is transient, this approach enables denitrification to be quantified under close to in situ conditions without the use of inhibitors and without destruction or isolation of the sediment.
Application of environmental sample processor (ESP) methodology for quantifying Pseudo‐nitzschia australis using ribosomal RNA‐targeted probes in sandwich and fluorescent in situ hybridization formats
Authors: Greenfield Dianne I. , Marin Roman , Jensen Scott , Massion Eugene , Roman Brent , Feldman Jason , Scholin Christopher A.
Published: April 2011

In this contribution, we assess the application of methodology used in a novel in situ remote sampling platform, the environmental sample processor (ESP), for the identification and enumeration of a harmful algal species, the domoic acid‐producing diatom Pseudo‐nitzschia australis, using 2 molecular assays: a sandwich hybridization assay (SHA) and fluorescent in situ hybridization (FISH). Both the SHA and FISH assays were initially designed as laboratory‐based methods that are now emulated in the ESP. Response of the SHA to a range of concentrations of P. australis using the laboratory (96‐well plate) and ESP (DNA probe array) formats showed that the two were highly correlated. Enumeration of cells filtered and archived for FISH using a manifold designed for laboratory applications agreed well with counts of cells filtered and archived in the ESP at ≥2.5 × 104 cells L−1. At lower concentrations, it becomes statistically unlikely to derive a reliable abundance estimate, suggesting that FISH is better suited for qualitative analyses unless the target organism is very abundant. We also assessed the suitability of an oligonucleotide as synthetic target sequence to act as a SHA reagent quality control and internal standard for the plate assay. This was successful, but the probe and/or associated reagents were stable for only ~60 days. Our results show that the ESP is capable of detecting P. australis in near real‐time and also supports whole‐cell archival samples, making it a potentially useful tool for future research and monitoring initiatives.
Application of high‐temperature fusion for analysis of major and trace elements in marine sediment trap samples
Authors: Huang Suilou , Sholkovitz Edward R. , Conte Maureen H.
Published: April 2011

Multielemental information is important for a broad range of ocean biogeochemical studies, yet the quantity of sample material available for analysis is often extremely limited. Here we describe a simple, rapid, and accurate method for multielemental analyses of oceanic sediment trap material. This method involves high‐temperature fusion using a lithium metaborate flux for sample digestion and elemental quantification using high‐resolution inductively coupled plasma mass spectrometry (HR‐ICP‐MS). Each analysis consumes only 1 to 2 mg of sample material yet enables simultaneous measurements of 18 elements (Mg, Al, Si, P, Ca, Sc, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Sr, Cd, Ba, and Pb) with accuracy of > 90% for most elements. The fusion method introduces minimal contamination when appropriate sample handling and procedural precautions are employed. Elemental quantification of samples prepared for ICP‐MS analysis using fusion agrees well with those prepared using acid digestion. Additionally, the fusion method has several advantages over acid digestion. No highly toxic reagents like hydrofluoric acid are used. Refractory mineral dissolution is more complete. Si, Ca, and other trace elements can be analyzed without potential losses due to coprecipitation with CaF2. The simplicity and reproducibility of the procedure makes it especially suitable for routine, ongoing analyses of oceanic particulate materials.
A submersible imaging‐in‐flow instrument to analyze nano‐and microplankton: Imaging FlowCytobot
Authors: Olson Robert J. , Sosik Heidi M.
Published: April 2011

A fundamental understanding of the interaction between physical and biological factors that regulate plankton species composition requires, first of all, detailed and sustained observations. Only now is it becoming possible to acquire these types of observations, as we develop and deploy instruments that can continuously monitor individual organisms in the ocean. Our research group can measure and count the smallest phytoplankton cells using a submersible flow cytometer (FlowCytobot), in which optical properties of individual suspended cells are recorded as they pass through a focused laser beam. However, FlowCytobot cannot efficiently sample or identify the much larger cells (10 to >100 µm) that often dominate the plankton in coastal waters. Because these larger cells often have recognizable morphologies, we have developed a second submersible flow cytometer, with imaging capability and increased water sampling rate (typically, 5 mL seawater analyzed every 20 min), to characterize these nano‐ and microplankton. Like the original, Imaging FlowCytobot can operate unattended for months at a time; it obtains power from and communicates with a shore laboratory, so we can monitor results and modify sampling procedures when needed. Imaging FlowCytobot was successfully tested for 2 months in Woods Hole Harbor and is presently deployed alongside FlowCytobot at the Martha's Vineyard Coastal Observatory. These combined approaches will allow continuous long‐term observations of plankton community structure over a wide range of cell sizes and types, and help to elucidate the processes and interactions that control the life cycles of individual species.
Effect of filtration on the total alkalinity of open‐ocean seawater
Authors: Chanson Mareva , Millero Frank J.
Published: April 2011

Total alkalinity (TA) of filtered and unfiltered samples was measured during the P16N 2006 cruise in the Pacific Ocean and the I9N 2007 cruise in the Indian Ocean. Although filtering coastal water samples may be important to remove the contributions of phytoplankton and bacteria on the measured TA, it is not the case for open ocean samples. In this study, our results show that the at‐sea measured total alkalinity of filtered and unfiltered samples were not statistically different. Measurements of 180 samples of surface, oxygen minimum, and deep waters in the Pacific and Indian oceans for unfiltered and filtered agreed to ±2 µmol kg−1. Therefore, the findings of this article show that it is not necessary to filter seawater samples when measuring total alkalinity in the open ocean.
Laboratory measurements of light scattering from marine particles
Authors: Lotsberg J.K. , Marken, E. , Stamnes J.J. , Erga S.R. , Aursland K. , Olseng C.
Published: April 2011

We present an improved technique for measurements of the volume‐scattering function (VSF) for marine particles, which include added spectral information, a novel optical design of the sample container, and two new ways of eliminating unwanted reflections. The novel optical design enables us to measure an angular range comparable to the largest angular range previously reported. Our improved setup eliminates the need for an empirically based data correction and reveals interesting characteristics of the VSF for different phytoplankton species. Measurements with our improved setup provide information that is important to understand and simulate radiative transfer in the ocean.
In situ field measurements of aquatic animal‐fluid interactions using a Self‐Contained Underwater Velocimetry Apparatus (SCUVA)
Authors: Katija Kakani , Dabiri John O.
Published: April 2011

We describe the development of a Self‐Contained Underwater Velocimetry Apparatus (SCUVA) that enables a single SCUBA diver to make in situ digital particle image velocimetry (DPIV) measurements of animal‐fluid interactions in real time. The device is demonstrated in a study of the dynamics of Aurelia labiata jellyfish swimming in the coastal waters of Long Beach, California. We analyze the DPIV measurements by computing the kinetic energy in the flow field induced by an animal's swimming motions. As a proof‐of‐concept, we compare these results with an existing theoretical model and find that the results are consistent with one another. However, SCUVA provides details regarding the temporal evolution of the energetics during the swimming cycle, unlike the model. These results suggest the usefulness of SCUVA as a method to obtain quantitative field measurements of in situ animal‐fluid interactions.
Quality control in the analysis of lake sediments for spheroidal carbonaceous particles
Authors: Rose Neil L.
Published: April 2011

The use of spheroidal carbonaceous particles (SCPs) in environmental studies as a means to identify atmospherically deposited contamination, or as a technique to provide a chronology for lake sediment cores, is rapidly increasing. However, currently there are no internationally accepted quality controls for this methodology. No reference standard exists to provide inter‐calibration, and no standardized criteria for identification have been proposed. This paper addresses these issues. It is suggested that morphology (spheroidal but not spherical), color (black only), depth (i.e., three‐dimensional rather than disc‐like), and porosity (characteristic when present) should be used as criteria for SCP identification under the light microscope. A sediment reference material for SCP analysis has also been developed. Two hundred ten replicate analytical measurements were made on a homogenized sediment material resulting in a reliable estimate of the mean SCP concentration of 6005 ± 70 SCP per gram dry sediment (gDM−1). This material is available to SCP analysts for quality control purposes.
A Bayesian compositional estimator for microbial taxonomy based on biomarkers
Authors: Van den Meersche Karel , Soetaert Karline , Middelburg Jack J.
Published: April 2011

Determination of microbial taxonomy based on lipid or pigment spectra requires use of a compositional estimator. We present a new approach based on Bayesian inference and an implementation in the open software platform R. The Bayesian Compositional Estimator (BCE) aims not only to obtain a maximum likelihood solution, but also to provide a complete estimate of the taxonomic composition, including probability distributions and dependencies between estimated values. BCE results are compared with those obtained with CHEMTAX. The BCE has not only a similar accuracy, but also extracts more information from the data, the most obvious being standard deviation and covariance estimates.
Application of an inexpensive and high‐throughput genomic DNA extraction method for the molecular ecology of zooplanktonic diapausing eggs
Authors: Montero‐Pau Javier , Gómez Africa , Muñoz Joaquín
Published: April 2011

We describe the application of a simple, low‐cost, and effective method of DNA extraction (hot sodium hydroxide and Tris, HotSHOT) to the diapausing propagules of continental aquatic invertebrates for its use in PCR amplification. We illustrate the use of the technique in cladocerans, rotifers, anostracans, notostracans, and copepod diapausing eggs. We compare the performance of the HotSHOT technique to the currently most widely used method for DNA extraction of zooplankton eggs and individuals, the chelating resin (or Chelex) technique. The HotSHOT technique overcomes several of the problems posed by Chelex and permits easy optimization for its use with 96‐well plates for high‐throughput DNA extraction and subsequent genetic characterization. We foresee a wide use of this technique in the future from DNA barcoding of diapausing stages to the genetic characterization of the diapausing egg banks of continental aquatic invertebrates.
Influence of handling stress and fasting on estimates of ammonium excretion by tadpoles and fish: recommendations for designing excretion experiments
Authors: Whiles Matt R. , Huryn Alexander D. , Taylor Brad W. , Reeve John D.
Published: April 2011

Excretion rate estimates are important for linking consumers to biogeochemical processes. Short‐term incubations in chambers are a common approach for studies. This, however, may result in inaccuracies due to a welldocumented decline in excretion with time, which is often attributed to fasting. An alternative explanation, however, is that excretion slows during recovery from handling stress. Whereas shorter incubations may reduce fasting effects, longer incubations can allow for recovery from handling. Although both views have merit and are not mutually exclusive, attempts to identify optimal incubation times are lacking. We examined effects of handling stress and fasting on NH4+ excretion by omnivorous tadpoles and predatory fish. Fasting did not influence tadpole excretion for at least 6 h. Rather, handling stress appeared to cause initially elevated excretion, and thus longer incubations were appropriate. Fasting and handling stress influenced fish excretion, and intermediate incubations (~30 min) appeared most appropriate. We also found that ammonium measurements were confounded by increasing concentrations of excretory products in longer incubations. We recommend that studies include incubation time trials and correct for potential matrix effects. Effects of handling and fasting likely vary with organism and experimental procedures, and both can be accounted for using the procedures we describe.
NH4‐Digiscan: an in situ and laboratory ammonium analyzer for estuarine, coastal, and shelf waters
Authors: Plant J. N. , Johnson K. S. , Needoba J. A. , Coletti L. J.
Published: April 2011

The NH4‐Digiscan is an in situ analyzer designed for measuring ammonium in estuarine, coastal, and shelf waters at depths of less than 3 m. This wet chemical analyzer uses micro‐solenoid pumps to propel sample and reagents, a gas diffusion cell to isolate the analyte from the matrix, and a conductivity detector for analyte detection. Instrument measurements are stable for deployments of at least 30 d. In estuarine and coastal waters, the analyzer is capable of sampling hourly and has a detection limit of 0.2 µM. In shelf waters, the NH4‐Digiscan can be configured to have a detection limit of 0.014 µM. The simple chemistry, in situ capability, and high resolution sampling minimizes the use of toxic reagents, minimizes many of the problems plaguing ammonium analyses, and adequately captures the high temporal variability of coastal waters, which is often undersampled. The analyzer has been successfully deployed on coastal moorings, benthic flux chambers, and on a drifter 500 km west of Monterey Bay, California. The system can also be easily configured for laboratory bench top analysis of discrete samples.
A sea‐going continuous culture system for investigating phytoplankton community response to macro‐ and micro‐nutrient manipulations
Authors: Pickell Lisa D. , Wells Mark L. , Trick Charles G. , Cochlan William P.
Published: April 2011

Continuous cultures can provide refined insights on the response of phytoplankton communities to small changes in nutrient flux, however are logistically more challenging to perform at sea than batch cultures. Here we describe the design and successful testing of a new continuous culture system for shipboard experiments using natural phytoplankton communities. Using this system, we studied the effects of nitrate amendments in coastal waters of the Pacific Northwest, and low‐level iron additions in High Nitrate, Low Chlorophyll (HNLC) waters of the subarctic Pacific. With nitrate amendments the coastal phytoplankton community showed proportional increases in chlorophyll biomass and appeared to achieve dynamic steady state as biomass, nutrient drawdown, and photo‐physiology stabilized after 4 d. In contrast, biomass did not reach steady state with iron amendment in the 10‐d HNLC experiment, however a major transition in dominant phytoplankton from small autotrophic flagellates to the toxigenic diatom Pseudo‐nitzschia was observed. This new continuous culture design demonstrated high precision in flow rates, good mixing within culture vessels, and was simple to operate at sea. This system provides an effective platform for investigating small changes in macro‐ and micro‐nutrient flux on the growth of individual phytoplankton species and, in turn, the trajectory of planktonic ecosystems.
Hydroacoustic assessment of fish abundance in the presence of gas bubbles
Authors: Ostrovsky Ilia
Published: April 2011

Methane ebullition from bottom sediments is abundant in many productive water bodies. The occurrence of the methane bubbles in the water column may cause erroneous quantification of fish densities in aquatic ecosystems when using hydroacoustic methods, since the target strength (TS) of bubbles strongly overlaps with that of fish. In this study, an approach that allows separation of TS distributions of fish and bubbles is proposed. The method was applied to data collected in a shallow reservoir with a 120‐kHz echo sounder. Separation between fish and bubbles was based on the difference in their trajectories on echograms. To distinguish the target trajectories, the water column was sampled at low boat speed at restricted locations. Sampling was also carried out at high boat speed to assess the abundance and TS distribution of all targets in the entire reservoir. The information from the two different sampling modes was integrated in a simple mathematical algorithm, which allowed calculating bubble and fish densities in the reservoir. The total abundance of gas bubbles was higher than the density of fish. The elaborated method can be useful for quantification of dominant objects when spatial distributions are heterogeneous.
Improved, high‐throughput approach for phosphorus speciation in natural sediments via the SEDEX sequential extraction method
Authors: Ruttenberg K.C. , Ogawa N.O. , Tamburini F. , Briggs R.A. , Colasacco N.D. , Joyce E.
Published: April 2011

A novel approach for implementation of sequential extraction methods using a multisample, solid‐phase extraction manifold (SPExMan) successfully addresses several chronic problems typical of sequential extraction methods, including (1) sample loss during supernatant removal and (2) the time‐ and work‐intensive nature of sequential extraction protocols. Supernatant is removed from SPExMan reaction vessels through an integrated filter base, eliminating the possibility of sample loss during supernatant collection. Vacuum manifold filtration makes it possible to filter multiple samples simultaneously. These two features of the design result in minimal residual volume between steps, eliminating the need for wash steps in between principle extraction steps and for residual volume correction. The SPExMan system was evaluated for the SEDEX method of quantifying different forms of phosphorus in sediments. Results from three different sediment samples analyzed via the classical centrifuge/syringe filtration SEDEX method and the SPExMan‐SEDEX method agree well, indicating that the SPExMan design is robust for performance of sequential extraction methods, and that SPExMan‐SEDEX data can be directly compared with classical SEDEX data. Overall, sample throughput is greatly increased by the SPExMan approach. Materials chosen for the SPExMan system are compatible with a wide range of chemical extractants, including corrosives and organic solvents.
Metabolic profiling reveals growth stage variability in diatom exudates
Authors: Barofsky Alexandra , Vidoudez Charles , Pohnert Georg
Published: April 2011

We studied the patterns of waterborne metabolites released by diatom cultures during different growth phases. A carefully optimized enrichment procedure for metabolites from seawater medium facilitated the generation of large‐scale sample sets that could be used for metabolic profiling. Samples from cartridge enrichments were directly submitted to ultraperformance liquid chromatography (UPLC) coupled with time‐of‐flight mass spectrometry (TOF‐MS). Metabolic profiling revealed distinct patterns of metabolite release depending on the growth phases of the major bloom‐forming diatoms Skeletonema marinoi and Thalassiosira pseudonana. Principal component analysis (PCA) enabled the recognition of specific metabolites that were only temporarily released by growing algal cultures. The exometabolome of the cells was complex and variable. The kinetics of metabolite release of some compounds resembles those of signal molecules involved in quorum sensing by bacteria. The introduced exometabolome investigation will help unravel the implications of release patterns of potential infochemicals for plankton ecology.
Quantifying phosphorus uptake using pulse and steady‐state approaches in streams
Authors: Powers Stephen M. , Stanley Emily H. , Lottig Noah R.
Published: April 2011

Steady‐state approaches to the study of stream nutrient processing have several limitations. Dynamic (time series) approaches are more flexible, and allow interpretation of nutrient additions introduced as unsteady slugs (pulses). We compared soluble reactive phosphorus (SRP) uptake metrics from experimental nutrient pulses modeled dynamically with those from continuous injections modeled with a steady‐state approach. For six southern Wisconsin streams, uptake metrics from these two methods were similar despite low nutrient demand. Linear regression of paired‐pulse versus steady‐state estimates of the first‐order uptake coefficient (λ; r2 = 0.84, slope = 1.21) and uptake velocity (vf; r2 = 0.95, slope = 1.03) were highly significant. There was a tendency for slightly higher uptake with pulses, possibly due to P sorption. Sampling across five stations of one stream yielded a similar longitudinal pattern between experimental pulse SRP flux and steady‐state (plateau) SRP concentration. Conservative transport parameters for pulse and continuously injected tracer data were also similar. These results suggest that unsteady nutrient amendments can provide usable nutrient uptake values, even in low‐uptake situations for which uncertainty is high. The flexibility of dynamic approaches to nutrient spiraling facilitates research in poorly understood situations, including conditions of high water residence time, high discharge, and changing discharge or background chemistry.
Use of an armored RNA standard to measure microcystin synthetase E gene expression in toxic Microcystis sp. by reverse‐transcription QPCR
Authors: Rueckert Andreas , Cary S. Craig
Published: April 2011

Microcystin is a secondary metabolic peptide toxin known to cause hepatotoxicosis and carcinogenicity in vertebrates. It is produced by various bloom‐forming cyanobacterial species constituting a serious threat to the quality of freshwater reservoirs worldwide. There is an intense interest to understand the biological function of microcystin and the regulatory mechanism behind its biosynthesis in order to develop strategies for freshwater management. To date, changes in toxin production in response to various environmental parameters have been studied using direct toxin analysis. Despite extensive research over the past two decades, the function of microcystin remains poorly understood. In this study, we developed an alternative method to study the regulation of microcystin production in toxic Microcystis sp. (and alternatively in Anabaena sp.) at the level of gene expression targeting microcystin synthetase E (mcyE) transcripts. We developed a durable and ribonuclease‐resistant armored RNA standard to monitor for the integrity of all nucleic acid processing steps including extraction, reverse transcription, amplification, and detection. The armored RNA was designed to consist of the mcyE target matrix with a unique internal probe‐binding sequence. To validate the efficacy of the method, we conducted a comprehensive survey of mcyE expression profiling in batch cultures of Microcystis sp. during exponential, linear, and stationary growth phase. Our transcriptional analysis indicates a growth‐phase‐dependent expression of mcyE, with the maximal level of expression observed during mid‐log growth. With progressing age of the cultures, mcyE was gradually down‐regulated, with expression levels having declined by more than three orders of magnitude during the stationary growth phase.
Sampling requirements and the implications of reduced sampling effort for the estimation of annual zooplankton population and community dynamics in north temperate lakes
Authors: Rusak James A. , Montz Pamela K.
Published: April 2011

Detecting and understanding long‐term changes in zooplankton populations and communities requires sound sampling strategies and reliable estimates of annual abundance. We use a long‐term, highly resolved data set from four north‐temperate lakes to investigate the sampling requirements necessary to precisely quantify common zooplankton species and taxonomic aggregates as well as the influence that a reduced sampling regime has on our ability to investigate changes in community structure. Sample sizes required for estimating mean annual abundance (precision of 20%) ranged from 4–7 samples per year for total crustacean zooplankton abundance to as many as 34–86 samples per year for individual rotifer species, depending on the lake. Despite these often onerous sampling requirements for some taxa, patterns of population abundance were typically quite similar when compared using reduced (five samples per year) and extended (14 samples per year on average) data sets. The same 3‐fold reduction in sampling produced taxa‐specific shifts in community structure ranging between 6% to 20% for two‐dimensional solutions and between 9% to 21% in three dimensions, depending on the lake. Although community structure was not significantly different between reduced and extended sampling scenarios, we found that the correlations between taxa and ordination axes could change and that these differences increased with the dimensionality of the ordination. Although individual investigators need to determine acceptable boundaries of sampling precision based on the objectives of their study, it appears that enumerating 5–10 sample events per year may adequately document long‐term changes in populations and communities on an annual basis in many lakes.
Estimates of phosphorus entrainment in Lake Mendota: a comparison of one‐dimensional and three‐dimensional approaches
Authors: Kamarainen Amy M. , Yuan Hengliang , Wu Chin H. , Carpenter Stephen R.
Published: April 2011

Entrainment of phosphorus across the thermocline can be an important nutrient source for phytoplankton in stratified lakes. In eutrophic stratified lakes, seasonal entrainment can be responsible for delayed recovery following a decrease in external phosphorus load. We compared seasonal estimates of entrainment derived from single‐ and multilocation thermocline migration approaches. Entrainment estimates from these methods were similar. A sampling approach based on a single centralized location produced whole‐lake entrainment estimates in general agreement with the mean value from the multilocation approach (the single‐location approach reasonably reproduced patterns at a weekly and seasonal time scale). In this study, it was not essential to account for spatial variation in estimating annual rates of entrainment. We also estimated entrainment based on a three‐dimensional (3‐D) hydrodynamic model over a short period of significant thermocline migration. The 3‐D model was most useful in exposing spatial and temporal variation in temperature and phosphorus profiles that are otherwise difficult to observe. Spatial variation in phosphorus profiles was associated with upwelling of metalimnetic water represented by the 3‐D model. These transient dynamics, though a relatively small portion of an annual phosphorus budget, may supply nutrients to epilimnetic phytoplankton during periods of nutrient limitation. There is a need for further research that combines 3‐D hydrodynamic modeling with field collection of biological and chemical data.
Investigating information-seeking behaviors of primary care physicians who care for older depressed patients and their family caregivers: a pilot study
Authors: Dorsey Mary Jo , Detlefsen Ellen
Published: April 2011

Objective  To describe preliminary findings from a study of information-seeking behaviors of primary care physicians who care for elderly and depressed patients, and the correlation between what is sought versus what is provided to the patient and (or) caregiver. Setting  Physicians in two large ambulatory primary care practices throughout urban Pittsburgh, Pennsylvania, who take care of geriatric patients. Methods  Structured interviews, with common questions, will be conducted with 12 primary care physicians to determine patterns of information-seeking behaviors. Environmental scans of physicians' offices for evidence of their existing information behaviors will complement the information obtained from the interviews. Results  This pilot study provides an analysis of the resources primary care physicians use to seek information to provide to patients and caregivers. Analyses show types of information sought, time spent seeking information, and methods used to find information given to patients. Conclusions  With mounting evidence of the Internet being used for patient self care, it is essential to understand if primary care physicians understand the scope and breadth of information readily available to their patients. The primary care physician needs to be aware of the types of information made available to their patients and the caregivers who are inclined to obtain information for the patient.
The Flower Report: Libraries without walls – (almost) 20 years later
Authors: Chatterley Trish
Published: April 2011

In the 1987 report Libraries Without Walls: Blueprint for the Future, Muriel Armstrong Flower put in writing her vision for a library that was open to all Canadians. This paper discusses Flower's recommendations and their outcomes and offers commentary about the current state of Canadian health sciences librarianship. It also outlines recent progress made towards equality of access to health information for all.
Availability of electronic libraries in the health sciences in the Arabian Gulf region
Authors: Neves Karen , Bishawi Hakim
Published: April 2011

Health sciences libraries the world over have experienced an increase in the popularity and use of electronic resources in their collections. As the Internet has begun to invade even the remotest of areas, libraries in the health sciences are experiencing ever-increasing pressure to expand into the electronic environment. The Arabian Gulf region is no exception. In the Gulf Cooperation Council (GCC) countries (United Arab Emirates, Saudi Arabia, Bahrain, Qatar, Kuwait, and Oman) libraries are asked to serve the information needs of health practitioners with a diverse range of financial, electronic, and human resources. In some countries, both funding and infrastructure are excellent. In others, a lack of hardware, software, or financial resources have taken their toll on services. Through the use of online and fax questionnaires, this paper examines the availability of electronic resources in health libraries in the Gulf region and will look at the state of the art for such characteristics of digital libraries as a significant Web presence, ability to access resources at a distance, and the provision of library services using electronic media.
Harnessing history: Highlighting CHLA / ABSC capacity building through the Northern Alberta Health Libraries Association (NAHLA), 1985–2007
Authors: Chatterley Trish , Dorgan Marlene , Clifford Connie , Chan Liza , Varney Janice , Dingwall Orvie
Published: April 2011

Objective – The purpose of the Northern Alberta Health Libraries Association (NAHLA) History Project was to capture, collect, and document the history of NAHLA, record and share the process with other Canadian Health Libraries Association / Association des bibliothèques de la santé du Canada (CHLA / ABSC) chapters, and systematically organize NAHLA documents for delivery to the Provincial Archives of Alberta. Methods – The methodology employed for this project is described in detail in the CHLA / ABSC Fact Sheet “Reporting Your Chapter History: The Process”, available at the CHLA/ABSC Web site (http://www.chla-absc.ca). Results – During the course of the project, the History Group uncovered the very active and successful 23-year history of NAHLA. The History Group captured the story of the chapter’s origins, identified political actions and educational offerings, and learned of members’ perspectives about what NAHLA meant to them personally and professionally. Reviewing the Association chronology revealed changes in the focus of NAHLA over the years; those trends are also discussed. Discussion – The process of compiling and documenting a local association history can be a rewarding and enlightening experience. It leads to the long term preservation of knowledge of the association’s origins and development. The authors hope the present article will inspire other chapters to initiate similar projects to preserve their own local histories.
An Akaike-type information criterion for model selection under inequality constraints
Authors: Kuiper R. M. , Hoijtink H. , Silvapulle M. J.
Published: April 2011

The Akaike information criterion for model selection presupposes that the parameter space is not subject to order restrictions or inequality constraints. Anraku (1999) proposed a modified version of this criterion, called the order-restricted information criterion, for model selection in the one-way analysis of variance model when the population means are monotonic. We propose a generalization of this to the case when the population means may be restricted by a mixture of linear equality and inequality constraints. If the model has no inequality constraints, then the generalized order-restricted information criterion coincides with the Akaike information criterion. Thus, the former extends the applicability of the latter to model selection in multi-way analysis of variance models when some models may have inequality constraints while others may not. Simulation shows that the information criterion proposed in this paper performs well in selecting the correct model.
Does shortening the training on Integrated Management of Childhood Illness guidelines reduce its effectiveness? A systematic review
Authors: Rowe Alexander K , Rowe Samantha Y , Holloway Kathleen A , Ivanovska Verica , Muhe Lulu , Lambrechts Thierry
Published: April 2011

Objective Implementation of the Integrated Management of Childhood Illness (IMCI) strategy with an 11-day training course for health workers improves care for ill children in outpatient settings in developing countries. The 11-day course duration is recommended by the World Health Organization, which developed IMCI. Our aim was to determine if shortening the training (to reduce cost) reduces its effectiveness.

Methods We conducted a systematic review to compare IMCI's effectiveness with standard training (duration ≥11 days) versus shortened training (5–10 days). Studies were identified from a search of MEDLINE, two existing systematic reviews, and by contacting investigators. We included published or unpublished studies that evaluated IMCI's effectiveness in developing countries and reported quantitative measures of health worker practices related to managing ill children under 5 years old in public or private health facilities. Summary measures were the median of effect sizes for all outcomes from a given study, and the percentage of patients needing oral antimicrobials or rehydration who were treated according to IMCI guidelines.

Findings Twenty-nine studies were included. Direct comparisons from three studies showed little difference between standard and shortened training. Indirect comparisons from 26 studies revealed that effect sizes for standard training versus no IMCI were greater than shortened training versus no IMCI. Across all comparisons, differences ranged from -3 to +23 percentage-points, and our best estimate was a 2 to 16 percentage-point advantage for standard training. No result was statistically significant. After IMCI training (of any duration), 34% of ill children needing oral antimicrobials or rehydration were not receiving these treatments according to IMCI guidelines.

Conclusions Based on limited evidence, standard IMCI training seemed more effective than shortened training, although the difference might be small. As sizable performance gaps often existed after IMCI training, countries should consider implementing other interventions to support health workers after training, regardless of training duration.
Nitrogen deposition and effects on European forests
Authors: Erisman J W , Vries W de
Published: April 2011

Hypotheses about the impacts of elevated atmospheric deposition of nitrogen on the forest ecosystem include an increased sensitivity to natural stress, impacts on roots, reduced species diversity of the ground vegetation, reduced growth, and unbalanced nutritional status due to eutrophication and acidification. The impact of N deposition has gained in ecological importance during recent decades, in part due to the steady decline in S emissions. Results of throughfall and deposition measurements at 163 plots in Europe show that total deposition of S and N compounds ranged from 100 to 3000 mol ha1yr1in approximately 90% of the plots, but values up to 40008000 mol ha1yr1were also observed. Approximately 50% of the plots received N inputs, dominated by NH4, above 1000 mol ha1yr1, which is a deposition level at which species diversity of the ground vegetation may be at risk. Results of inputoutput budgets for plots concentrated in Northern and Western Europe indicate that nitrate leaching starts to occur at throughfall inputs above 10 kg ha1yr1, specifically in soils with C/N ratios in the humus layer below 25. Examples are given of field evidence for impacts of elevated N deposition, including elevated N contents in foliage and soil, Al release in soil response to increased nitrate concentrations, reduced shoot/root ratios, and a reduction in species diversity. Although knowledge about the response of forest ecosystems to N inputs has increased over the last decade, there is still a lack of information on the dynamics of N accumulation and related critical N loads in a range of environmental conditions. Furthermore, a European-wide perspective of N saturation in forest ecosystems is still lacking.Key words: nitrogen, deposition, inputoutput budgets, nitrogen status, forests, effects.