bluuebunny/crossref_metadata_2025 huggingface dataset:
Disease‐ and Performance‐Related Traits of Ethylene‐Insensitive Soybean
Authors: Bent Andrew F. , Hoffman Thomas K. , Schmidt J. Scott , Hartman Glen L. , Hoffman David D. , Xue Ping , Tucker Mark L.
Published: July 2010

Ethylene controls many beneficial responses in plants but also promotes chlorosis, senescence, disease, and fruit over‐ripening. The present study compared previously isolated ethylene‐insensitive lines of soybean [Glycine max (L.) Merr.] to their isogenic, ethylene‐sensitive parent with respect to disease resistance, seed yield, and other field performance traits. In laboratory tests, ethylene insensitivity reduced root colonization by soybean cyst nematode. Using healthy young plants, ethylene‐insensitivity also reduced ethylene‐activated leaf chlorosis and abscission. However, in the field, leaf chlorophyll and late‐season senescence were not altered, suggesting that ethylene is not a main determinant of late‐season senescence of soybean leaves. Field studies also revealed no changes in susceptibility to Septoria brown spot disease (caused by Septoria glycines Hemmi), flowering date, plant height, or seed total protein and oil concentration. Field studies did demonstrate elevated susceptibility to white mold disease [Sclerotinia sclerotiorum (Lib.) deBary], poor stand establishment in some but not all environments, altered plant architecture, and earlier maturity date in the ethylene‐insensitive lines. Seed yield was notably undependable, being similar to the parental line in some field locations but significantly reduced in most environments. To avoid these negative impacts on overall performance, manipulation of plant ethylene responses should be targeted to specific tissues, growth stages, or growth environments.
Evaluating the Reliability of Structure Outputs in Case of Relatedness between Individuals
Authors: Camus‐Kulandaivelu Létizia , Veyrieras Jean‐Baptiste , Gouesnard Brigitte , Charcosset Alain , Manicacci Domenica
Published: July 2010

Inference of population structure from neutral marker loci is a key issue for association genetics. However, the presence of highly related individuals, commonly observed in breeders' panels, may lead to deviation from model hypotheses and therefore unreliable group assignment. The present note proposes a tool to help interpret Structure software outputs on populations that include highly related individuals, such as plant breeding material. We ran Structure software on simple sequence repeat (SSR) data from two maize (Zea mays L. ssp. mays) inbred panels. We propose a criterion to evaluate Structure stability based on Euclidian distance between outputs. This approach shows a high stability across runs for the panel composed of first cycle inbred lines. On the contrary, the presence of highly related individuals in the second panel induces strong instability in Structure outputs.
Development and Evaluation of a Core Subset of the USDA Rice Germplasm Collection
Authors: Yan WenGui , Rutger J. Neil , Bryant Rolfe J. , Bockelman Harold E. , Fjellstrom Robert G. , Chen Ming‐Hsuan , Tai Thomas H. , McClung Anna M.
Published: July 2010

A valuable core collection that is a subset of a whole germplasm collection should capture most of the variation present in the whole collection, while allowing for more efficient evaluation and management due to smaller size. The United States Department of Agriculture (USDA) rice (Oryza sativa L.) core subset (RCS), assembled by stratified random sampling, consists of 1790 entries from 114 countries and represents approximately 10% of the 18412 accessions in the rice whole collection (RWC). Data for this study were obtained from the USDA germplasm system at www.ars‐grin.gov for the RWC and from an evaluation conducted in 2002 for the RCS. Comparative analysis for frequency distributions of 14 descriptors demonstrated that the RCS was highly correlated with the RWC (r = 0.94, P < 0.0001). Thus, information drawn from the RCS could be effectively used to assess the RWC with 88% certainty. Correlation coefficients between the RCS and the RWC for eight descriptors were ≥ 0.9, indicating that the RCS was highly representative of the RWC. Correlation coefficients for the other six descriptors were lower (0.65–0.88), but still significant.
On a Class of Contest Success Functions
Authors: Jia Hao
Published: July 2010

In this article, I analyze a class of contest success functions (CSFs) that satisfy Luce's Choice Axiom. I show that the functional forms of these CSFs can be fully identified if they are characterized by a partial differential equation (PDE), which has several intuitive economic interpretations. This PDE approach provides foundations for popular CSFs and their generalizations.
Adaptation to Impacts of Climate Change on Aeroallergens and Allergic Respiratory Diseases
Authors: Beggs Paul J.
Published: July 2010

Climate change has the potential to have many significant impacts on aeroallergens such as pollen and mould spores, and therefore related diseases such as asthma and allergic rhinitis. This paper critically reviews this topic, with a focus on the potential adaptation measures that have been identified to date. These are aeroallergen monitoring; aeroallergen forecasting; allergenic plant management; planting practices and policies; urban/settlement planning; building design and heating, ventilating, and air-conditioning (HVAC); access to health care and medications; education; and research.
Thin Film Deposition Using Energetic Ions
Authors: Manova Darina , Gerlach Jürgen W. , Mändl Stephan
Published: July 2010

One important recent trend in deposition technology is the continuous expansion of available processes towards higher ion assistance with the subsequent beneficial effects to film properties. Nowadays, a multitude of processes, including laser ablation and deposition, vacuum arc deposition, ion assisted deposition, high power impulse magnetron sputtering and plasma immersion ion implantation, are available. However, there are obstacles to overcome in all technologies, including line-of-sight processes, particle contaminations and low growth rates, which lead to ongoing process refinements and development of new methods. Concerning the deposited thin films, control of energetic ion bombardment leads to improved adhesion, reduced substrate temperatures, control of intrinsic stress within the films as well as adjustment of surface texture, phase formation and nanotopography. This review illustrates recent trends for both areas; plasma process and solid state surface processes.
Reducing Pull-In Voltage by Adjusting Gap Shape in Electrostatically Actuated Cantilever and Fixed-Fixed Beams
Authors: Haluzan Darcy T. , Klymyshyn David M. , Achenbach Sven , Börner Martin
Published: July 2010

A gap with variable geometry is presented for both cantilever beam and fixed-fixed beam actuators as a method to reduce the pull-in voltage while maintaining a required displacement. The method is applicable to beams oriented either in a plane parallel to or perpendicular to a substrate, but is most suitable for vertically oriented (lateral) beams fabricated with a high aspect ratio process where variable gap geometry can be implemented directly in the layout. Finite element simulations are used to determine the pull-in voltages of these modified structures. The simulator is verified against theoretical pull-in voltage equations as well as previously published finite element simulations. By simply varying the gap in a linear fashion the pull-in voltage can be reduced by 37.2% in the cantilever beam case and 29.6% in the fixed-fixed beam case over a structure with a constant gap. This can be reduced a further 4.8% by using a polynomial gap shape (n = 4/3) for the cantilever beam and 1.2% for the fixed-fixed beam by flattening the bottom of the linearly varying gap.
Synthesis and Antiviral Bioactivity of Chiral Thioureas Containing Leucine and Phosphonate Moieties
Authors: Liu Jingzi , Yang Song , Li Xiangyang , Fan Huitao , Bhadury Pinaki , Xu Weiming , Wu Jian , Wang Zhencao
Published: July 2010

A series of novel chiral thioureas 3a-n bearing leucine and phosphonate moieties were synthesized in excellent yields. The structures of the compounds were completely characterized by elemental analysis, IR, 1H-, 13C-, 31P- and 19F-NMR spectral data. A half-leaf method was used to determine the in vivo protective and curative efficacies of the title products against tobacco mosaic virus (TMV). The compounds 3l and 3n displayed good in vivo protection and curative effects against TMV with inhibitory rates of 60.1, 62.8% (protection) and 56.7, 53.6% (curative) at 0.5 mg/mL, respectively. To the best of our knowledge, this is the first report on the antiviral activity of chiral thioureas containing leucine and phosphonate moieties.
Is there Emergence of Clinical HBV Resistance Under Long-Term HBV Combination Therapy? A Challenging Case Report
Authors: Schewe Knud , Noah Christian , Sirma Hüseyin , Schmiedel Stefan , Van Lunzen Jan , Rockstroh Jürgen Kurt , Schildgen Oliver
Published: July 2010

A first case of clinical tenofovir (TDF) HBV resistance in an HIV/HBV coinfected patient who developed an acute flare of hepatitis B is reported. The clinical course was accompanied by signs of acute liver failure after being on successful HBV treatment with tenofovir and persistently undetectable HBV-DNA viral load for over five years.
Characteristics of Effective Simulated Clinical Experience Instructors: Interviews with Undergraduate Nursing Students
Authors: Parsh Bridget
Published: July 2010

Effective clinical nursing instructors are essential for maximizing nursing students’ educational experience. Due to a shortage of clinical placement sites and advancements in technology, nursing students are increasingly learning clinical judgment and decision making in the simulated clinical experience (SCE) with human patient simulators. In this environment, SCE instructors help students acquire knowledge and skills in decision making in a controlled, risk-free, hospital-like clinical environment. Using informal student interviews, this study examined nursing student perceptions of the characteristics of an effective instructor in the simulated clinical experience. To capture information about the characteristics of effective SCE instructors, interviews were conducted with students (
N
= 8) from two universities in Northern California. All participants had experience working with human patient simulators in the simulation laboratory. Students identified six themes for SCE instructors: Personality, Teaching Ability, Evaluation, Nursing Competence, Interpersonal Relationships, and Realism. Further research on the similarities and differences of this new educational environment is recommended.
Women’s Responses to Unemployment of Their Spouse
Authors: Frank Deborah I.
Published: July 2010

The current economic recession has resulted in extremely high rates of unemployment, with the majority of those losing jobs being men. There is much research exploring how men respond to unemployment, but little examines how wives experience this crisis. Although nearly half of the workforce is now female, many women are co-providers, not sole providers. This article uses a historical perspective within a framework of role theory to help psychiatric nurse clinicians understand the possible responses of women who seek counseling after their spouses become unemployed. Counseling interventions are suggested, and an individual example is presented. Directions for future research are noted.
Prácticas de ciudadanía europea. El uso estratégico de las identidades en la participación política de los inmigrantes comunitarios
Authors: Janoschka Michael
Published: July 2010

La política local es un campo de negociación e intercambio social en el cual se perciben de forma destacada las profundas transformaciones que la sociedad española vivió a partir de los procesos masivos de inmigración de la última década. Este texto debatirá, a través de un análisis empírico de las formas de participación política en la costa mediterránea, qué alcance y magnitud de cambio introduce el derecho de voto activo y pasivo de extranjeros comunitarios. Para ese análisis, se efectúa un enlace conceptual entre la participación política a nivel local y algunas nociones teóricas como la ciudadanía europea. Los dos conceptos claves del debate, es decir, la ciudadanía europea y las referencias a identidades europeas, se piensan como una práctica diaria que se expresa activamente en cuestiones de índole político a nivel local.
BMO-Estimates for Maximal Operators via Approximations of the
Identity with Non-Doubling Measures
Authors: Yang Dachun , Yang Dongyong
Published: July 2010

Let μ be a nonnegative Radon measure on ℝd that satisfies the growth condition that there exist constants
C0 > 0 and n ∈ (0, d] such
that for all x ∈ ℝd and r > 0,
μ(B(x,
r)) ≤ C0rn, where B(x, r)
is the open ball centered at x and having radius
r. In this paper, the authors prove that if
f belongs to the BMO-type space RBMO(μ)
of Tolsa, then the homogeneous maximal function S( f ) (when ℝd is not an initial cube) and the inhomogeneous maximal function ℳS( f ) (when ℝd is an initial cube) associated with a given approximation of the
identity S of Tolsa are either infinite everywhere or
finite almost everywhere, and in the latter case, S and ℳS are bounded from RBMO(μ) to the BLO-type space
RBLO(μ). The authors also prove that the inhomogeneous
maximal operator ℳS is bounded from the local BMO-type space rbmo(μ)
to the local BLO-type space rblo(μ).
Extension of the type/token distinction to document structure
Authors: Huitfeldt Claus , Marcoux Yves , Sperberg-McQueen C. M.
Published: July 2010

The type/token distinction introduced by C. S. Peirce and taken up by many others is familiar when applied to individual symbols or characters in a writing system, and also when applied at a higher level to words (and word-like objects).

Some writers apply the distinction not only at some basic or foundational level but also as a description of higher levels of organization. This paper follows their example by outlining a concrete extension of the type/token distinction to all levels of document organization, specifying that higher-level types may contain sequences of lower-level types, and similarly for higher- and lower-level tokens. We further extend the usual model of types and tokens by allowing higher-level types to contain not just sequences of (lower-level) types but also sets, bags, conjunctions and disjunctions of types. This allows the system to deal gracefully both with indeterminate documents (e.g., a manuscript in which it is not clear whether a given mark on the page represents a 'c' or a 't') and with intentionally polyvalent documents, in which some marks are to be read as tokens of more than one type, as in the “ambigram”, a sort of combination puzzle and calligraphic artwork in which the shapes on the page may be read in different ways, or the same way, in different directions.

This account of document structure in terms of types and tokens is similar in many ways to that offered by SGML, XML, and other systems of descriptive markup. On this view, SGML and XML elements are, strictly speaking, types (and tokens) in Peirce's sense of those words. Some techniques developed in other areas to which the type/token distinction is relevant may be useful in work on markup languages (and vice versa).
A Streaming XSLT Processor
Authors: Kay Michael
Published: July 2010

Existing XSLT implementations build a tree representation of the source document in memory, and are therefore limited to processing of documents that fit in memory. With many transformations, however, there is a direct correspondence between the order of information in the output, and the order of the corresponding information in the input. In such cases it ought to be possible to perform the transformation without allocating memory to the entire source tree.

The XSL Working Group within W3C has been working on a new version of the language designed to make streamed implementations feasible, and the author, who is editor of that specification, has at the same time been working on the implementation of streaming in the Saxon XSLT processor. This paper describes how far this work has progressed, and the way in which the implementation is structured. It adopts a chronological approach to the exposition, explaining how the streaming features have gradually developed from small beginnings.
Multi-structured documents and the emergence of annotations vocabularies
Authors: Portier Pierre-Édouard , Calabretto Sylvie
Published: July 2010

The construction of multi-structured documents often implies the definition of annotations vocabularies. Moreover, in a multi-users context, the growth of these vocabularies has to be controlled. Therefore, we propose using the trace of users activity to limit this growth and to document the vocabularies. For example, a user will be able to follow and annotate a term in the context of its surrounding actions from its creation to the last time it was used. From a broader point of view, this work is grounded on our Web based philological platform, DINAH, and is mainly motivated by our collaboration with a group of philosophers studying the handwritten manuscripts of Jean-Toussaint Desanti.
Stone soup
Authors: Sperberg-McQueen C. M.
Published: July 2010

Reflections on making the best of unpromising situations.
Where XForms Meets the Glass
Authors: Wiecha Charlie , Akolkar Rahul , Spyker Andrew
Published: July 2010

We have observed two prevalent design paradigms for web applications: those who start from an existing data or process definition and project from that outward toward the user, and those conversely who start from a sense of desired user experience and derive from that required data and process elements. Design methods which seem natural to one community may look overly abstract, layered with unnecessary separation of concerns, and academic to no purpose. Conversely, others may be frustrated by a seeming lack of concern for reuse, valid content, and support for multiple design roles all of which may argue for additional architectural layers. Due to affinity of current web presentation technology to JSON encoded data, many times the choice to start with user experience precludes re-use of existing XML data. We present an approach to bridging this methodology and data divide by working within the conventions of existing web application frameworks to introduce incremental separation of concerns such as Model-View layering with interfaces and behavior suited to the introduction of XML-based technologies such as XForms at the model layer. In this way we hope to provide incremental means to adopt first a separation of concerns that supports packaging and reuse of model data and behavior, and secondly an XML-based technology for such data models that supports convenient projection of existing business data and process definitions to the client for user interaction.
The sustainability of the scholarly edition in a digital world
Authors: Hajo Cathy Moran
Published: July 2010

Scholarly editions must be used for generations; by nature they require a stable long-term publication format. Some editors have eagerly embraced digital editing and XML, but many more editors remain unconvinced that digital publications can last as long as printed books. Community standards and DTDs for editions have not been widely adopted and editors lack consensus about what a digital edition should be. XML's stability and sustainability is critical to efforts to go beyond “the book,” and to develop new ways of presenting texts and scholarly commentary. To build 21st century editions, we need tools to make XML encoding easier, to encourage collaboration, to exploit social media, and to separate transcriptions of texts from the editorial scholarship applied to them.
Dissolved organic matter in abyssal sediments: Core recovery artifacts
Authors: Hall Per O. J. , Brunnegård Jenny , Hulthe Gustaf , Martin William R. , Stahl Henrik , Tengberg Anders
Published: July 2010

We report measurements of pore‐water dissolved organic carbon (DOC), dissolved organic nitrogen, total dissolved carbohydrates, dissolved free monosaccharides, and ammonium in recovered deep‐sea sediments from the Porcupine Abyssal Plain (PAP), Northeast Atlantic. There were distinct maxima close to the sediment‐water interface of these constituents at all times of the year. The very high diffusive effluxes calculated from these porewater distributions were not compatible with simultaneous sediment trap measurements of particulate organic carbon, nitrogen, and carbohydrate fluxes toward the seafloor. Effluxes calculated from pore‐water DOC distributions in recovered cores from another Atlantic deep‐sea site, showing almost identical maxima as those at PAP, were more than an order of magnitude greater than simultaneous in situ chamber DOC flux measurements. We suggest that the dissolved organic matter maxima are predominantly artifacts induced by lysis of, or leakage from, mainly bacterial biomass resulting from decompression and/or warming during recovery of the sediment cores from the abyssal seafloor. Temperature elevation during core recovery from the abyss gives a N2 saturation of about 150%, and the combined effect of warming and decompression results in a CO2 saturation of about 135%, which together plausibly are associated with bubble formation creating cell bursting. Previous estimates of microbial biomass in abyssal sediments may be underestimates because of the difficulty of counting lysed bacterial cells. Since exoenzymes are inducible, previous measurements of their activities in recovered abyssal sediments may be overestimates.
Pathways of anaerobic carbon cycling across an ombrotrophic‐minerotrophic peatland gradient
Authors: Keller Jason K. , Bridgham Scott D.
Published: July 2010

Peatland soils represent globally significant stores of carbon, and understanding carbon cycling pathways in these ecosystems has important implications for global climate change. We measured aceticlastic and autotrophic methanogenesis, sulfate reduction, denitrification, and iron reduction in a bog, an intermediate fen, and a rich fen in the Upper Peninsula of Michigan for one growing season. In 3‐d anaerobic incubations of slurried peat, denitrification and iron reduction were minor components of anaerobic carbon mineralization. Experiments using 14C‐labeled methanogenic substrates showed that methanogenesis in these peatlands was primarily through the aceticlastic pathway, except early in the growing season in more ombrotrophic peatlands, where the autotrophic pathway was dominant or codominant. Overall, methane production was responsible for 3‐70% of anaerobic carbon mineralization. Sulfate reduction accounted for 0‐26% of anaerobic carbon mineralization, suggesting a rapid turnover of a very small sulfate pool. A large percentage of anaerobic carbon mineralization (from 29% to 85%) was unexplained by any measured process, which could have resulted from fermentation or possibly from the use of organic molecules (e.g., humic acids) as alternative electron acceptors.
Evidence for visual constraints in large marine fish stocks
Authors: Aksnes Dag L.
Published: July 2010

I tested the hypothesis that the abundance of visually constrained fish stocks relate inversely to light attenuation for the Black Sea, where long time series of fish stocks and Secchi depths are available. Variation in Secchi depth accounted for 76–85% of the variation in combined fish biomass, which is higher than any other correlations previously reported for large fish stocks and a single environmental variable. Fish biomass scaled linearly with Secchi depth, which is consistent with the visual constraints hypothesis. Two alternative hypotheses, one involving a trophic cascade that affects water clarity and another assuming the effect of water clarity on fish catches, were not consistent with the observations. Although causal factors other than visual constraints cannot be excluded, the results clearly suggest that changes in water clarity must be considered in analyses of marine ecosystem change and regime shifts.
Hydrologic forcing of submarine groundwater discharge: Insight from a seasonal study of radium isotopes in a groundwater‐dominated salt marsh estuary
Authors: Charette Matthew A.
Published: July 2010

A seasonal study of radium‐derived submarine groundwater discharge (SGD) and associated nitrogen fluxes was carried out in a salt marsh estuary between 2001 and 2003 (Pamet River Estuary, Massachusetts). Twelvehour time series of salinity and radium at the estuary inlet were used to determine the relative importance of fresh versus saline SGD, respectively. The distinct radium (228Ra : 226Ra) isotopic signature of marsh peat pore water and aquifer‐derived brackish groundwater was used to further partition the Ra‐derived SGD estimate. Of these three groundwater sources, only the marsh‐derived groundwater was constant across time. The ratio of brackish to fresh SGD was inversely correlated with water table elevation in the aquifer, suggesting that Ra‐derived SGD was enhanced during dry periods. The various SGD fluxes were responsible for an average annual dissolved inorganic nitrogen (DIN) input of between 1.7 mol m−2 yr−1 and 7.1 mol m−2 yr−1 and a soluble reactive phosphate (SRP) flux of 0.13‐0.54 mol m−2 yr−1. Approximately 30% of the SGD‐derived DIN and SRP flux is exported to coastal waters (Cape Cod Bay), whereas 70% is retained by the salt marsh ecosystem.
Focusing of phytodetritus deposition beneath a deep‐ocean front, Chatham Rise, New Zealand
Authors: Nodder Scott D. , Duineveld Gerard C. A. , Pilditch Conrad A. , Sutton Philip J. , Probert P. Keith , Lavaleye Marc S. S. , Witbaard Rob , Chang F. Hoe , Hall Julie A. , Richardson Ken M.
Published: July 2010

In October 2001, we observed a deep‐ocean phytodetritus deposition event on Chatham Rise beneath the Subtropical Front (STF). The origin of this phytodetritus was probably an extensive phytoplankton bloom that occurred in the STF in the preceding weeks. We assessed the spatial distribution of the deposition event using video images from benthic lander and epibenthic trawl deployments and sediment pigment analyses at six sites on a north—south transect across Chatham Rise. High surficial sediment chlorophyll a concentrations were restricted spatially to the southern flank of Chatham Rise (350–1,200‐m depth) with the highest values centered at ~750‐m water depth (750 S). This southern 750 S site was also the only site where macroscopic phytodetritus was observed, coincident with elevated benthic biomass and sediment community respiration rates. At 750 S, phytodetritus resuspension was observed on video and corroborated by current meter, sediment trap, and optical backscatter measurements, suggesting a threshold erosion current speed for phytodetritus of ~10 cm s−1, equivalent to a shear velocity of 0.5 cm s−1 and similar to other deep‐ocean studies elsewhere. The restriction of macroscopic phytodetritus deposition to 750 S was related to a zone of current convergence within the STF and lower near‐bed current speeds observed across ~1‐day that promoted deposition. Observations of high benthic biomass and respiration on the southern flank of Chatham Rise suggest that this focusing process is important in fueling the energy demands of benthic communities, in association with the general west‐east advection of organic matter within the STF itself. Such physical focusing of labile organic matter deposition may be an important process in other highly productive frontal systems.
Unexpected underestimation of primary productivity by 18O and 14C methods in a lake: Implications for slow diffusion of isotope tracers in and out of cells
Authors: Yacobi Yosef Z. , Perel Naomi , Barkan Eugeni , Luz Boaz
Published: July 2010

By use of in situ bottle incubations, we determined three variables for the characterization of plankton community primary productivity in Lake Kinneret, Israel: (1) H218O‐based primary productivity (18OP), measured by 34O2 (18O16O) evolution; (2) radiocarbon‐uptake‐based primary productivity (14CP); and (3) net O2 production (NOP), calculated from the rate of O2 : Ar change. Six experiments were conducted in the fall, a period that is characterized by thermocline deepening, erosion of the hypolimnion, and eventual introduction of high concentration of reduced substances into the epilimnion. An additional experiment was conducted in spring. In comparison to net O2 evolution, the tracer‐based methods severely underestimated primary productivity in the fall. This is indicated by unusually high NOP: 18OP and NOP: 14CP ratios (1–2.2 and 2–4, respectively). The latter is considerably different than the typical values of aquatic environments (~1.4). In contrast to these ratios, the 18OP: 14CP appears normal (1.6–2.9) and not significantly different from previous results in the lake. Ammonium was the major nitrogen source in the fall experiments, and there is no reason to assume that the cellular composition of phytoplankton was exceptional. It is therefore unlikely that the high NOP: 14CP ratio represents genuine ratios of oxygen and carbon metabolism. We suggest that an explanation accounting for the high values of both NOP: 18O P and NOP: 14CP can be slow diffusion of the tracers in and out of phytoplankton cells.
Kinetics of phosphorus in Daphnia at different food concentrations and carbon:phosphorus ratios
Authors: He Xuejia , Wang Wen-Xiong
Published: July 2010

We examined the assimilation efficiency, excretion, and efflux of phosphorus (P) in adults and juveniles of Daphnia magna under different food levels (2–40 µg P L−1) and dietary carbon : phosphorus (C : P) ratios (90‐930 in molar) with Chlamydomonas reinhardtii as food. The P assimilation efficiencies calculated by regression analysis were 38‐85% and 66‐89% for adults and juveniles, respectively, and were constant at food concentrations >24 µg P L−1, but increased significantly when the diet shifted from P‐sufficiency to P‐deficiency. The mass‐specific excretion rate of adults and juveniles was 1.1‐33.2 ng P mg dry weight (DW)−1 h−1 and 3.0‐63.4 ng P mg DW−1 h−1, respectively, and was influenced by the food concentration and decreased with an increase in dietary C: P ratio. The efflux rate constants of the adults and juveniles were 0.182‐0.298 d−1 and 0.096‐0.185 d−1, respectively. Food concentration did not affect the efflux, but an increase in dietary C: P ratio reduced the P efflux, suggesting stoichiometric regulation. Among the different routes involved in P loss from Daphnia, molting was the most important, contributing 44‐75% of the total loss for the juveniles and adults. The mass specific loss rates were 13‐54 ng P mg−1 h−1 and 45‐110 ng P mg−1 h−1. The relative and absolute P loss from each compartment (except the dissolved P release in adults) was independent of food concentration. Increasing the dietary C: P ratio decreased the mass‐specific release rates by molting, dissolved P release, and reproduction, indicating the animals' endeavor to maintain P stoichiometric homeostasis.
Molecular quantification of differential ingestion and particle trapping rates by the appendicularian Oikopleura dioica as a function of prey size and shape
Authors: Troedsson Christofer , Frischer Marc E. , Nejstgaard Jens C. , Thompson Eric M.
Published: July 2010

To investigate whether particles are ingested or merely trapped in the house of the appendicularian Oikopleura dioica, we developed a real‐time quantitative polymerase chain reaction (qPCR) assay and applied it in a controlled study where O. dioica was fed three types of algae at different concentrations. At particle concentrations ranging from 100 to 10,000 cells mL−1, highest ingestion efficiencies (75‐96%) were observed with the smallest algal species (Isochrysis sp.) compared to the larger cryptophyte Rhinomonas sp. (2‐87%) and a similar sized but spiny diatom, Chaetoceros calcitrans (4‐65%). When prey were mixed, the presence of C. calcitrans inhibited ingestion of Rhinomonas sp. but not the smaller Isochrysis sp., suggesting that C. calcitrans clogged the inlet filter and mechanically hindered ingestion of larger algae. O. dioica is adapted to feed on smaller particles at low (nonbloom) concentrations and may thus be subjected to bottom‐up regulation by larger spiny or colonial prey that typically dominate late‐stage phytoplankton blooms.
Significant year‐round effect of small mixotrophic flagellates on bacterioplankton in an oligotrophic coastal system
Authors: Unrein Fernando , Massana Ramon , Alonso-Sáez Laura , Gasol Josep M.
Published: July 2010

The seasonal variation in the grazing effect of mixotrophic flagellates on bacterioplankton was assessed during an annual cycle in an oligotrophic coastal station in the northwest Mediterranean Sea. Ingestion rates of fluorescently labeled bacteria were estimated for different size categories of phytoflagellates (PF) and heterotrophic flagellates (HF) in short‐term experiments and compared with long‐term grazing estimates and published empirical models. The mixotrophic flagellates included haptophyte‐like cells, cryptophytes, and dinoflagellates. The group‐specific grazing rates (SGR) averaged 1.1 (3–5 µm PF), 1.3 (5–20 µm PF), 4.0 (<5 µm HF), and 15.4 bacteria individual−1 h−1 (5‐20 µm HF). Lower SGR but higher abundances of PF resulted in an average mixotroph contribution of 50% to the total flagellate grazing. Remarkably, the effect was relatively high all through the year (35–65%). Regardless of the presence of chloroplasts, flagellates <5 mm in size accounted, on average, for about 80% of total flagellate bacterivory and ingested a large percentage of their cell carbon per day from bacteria. Soluble reactive phosphorus concentration was negatively correlated with the ingestion rate of both groups of PF, suggesting that mixotrophic flagellates would be using their phagotrophic capability to obtain phosphorus when this nutrient is limiting. HF grazing activity showed a marked seasonality, with grazing being higher during the warmer seasons, and clearance rates were positively correlated with water temperature. Total bacterivory accounted for most of the bacterial production. Short‐term and long‐term bacterivory measurements were highly correlated, confirming that the smallest flagellates were the main causative agent of bacterial loss. The bacterivory values were also well correlated to a published empirical model that considers HF as the only bacterivorous. However, this model underestimated (up to 50%) total flagellate grazing during periods of high effect of mixotrophic flagellates.
Enhanced methane oxidation in an estuarine turbidity maximum
Authors: Abril Gwenaël , Commarieu Marc-Vincent , Guérin Frédéric
Published: July 2010

Methane and suspended particulate matter (SPM) concentrations, monitored bimonthly during one hydrological year (2003–2004) along 70 km transects in the tidal regions of the Garonne and Dordogne rivers (SW France), showed a significant negative correlation, both spatially and temporally. During spring in clear waters (SPM < 50 mg L−1), methane production was first evidenced by a net increase in methane concentrations, in parallel with temperature and a decrease in river flow. In summer, as soon as the estuarine turbidity maximum (ETM) appeared and SPM concentrations exceeded 100 mg L−1, methane concentrations decreased from ~600 to ~30 nmol L−1 in one month. More downstream in the turbid Gironde estuary, methane concentrations were occasionally below atmospheric equilibrium. In dark microcosms, high methane consumption was observed in samples from the ETM with SPM concentrations >2,000 mg L−1, but not after removing the SPM by settling (SPM = 16 mg L−1), nor in a sample collected few kilometers upstream, with SPM = 3 mg L−1. Methane oxidation was also able to draw down methane concentrations below half the atmospheric equilibrium value in an ETM sample. Suspended clays in the ETM enhance methane oxidation and strongly reduce methane fluxes to the atmosphere.
A long‐term chlorophyll dataset reveals regime shift in North Sea phytoplankton biomass unconnected to nutrient levels
Authors: McQuatters-Gollop Abigail , Raitsos Dionysios E. , Edwards Martin , Pradhan Yaswant , Mee Laurence D. , Lavender Samantha J. , Attrill Martin J.
Published: July 2010

During the 1980s, a rapid increase in the Phytoplankton Colour Index (PCI), a semiquantitative visual estimate of algal biomass, was observed in the North Sea as part of a regionwide regime shift. Two new data sets created from the relationship between the PCI and SeaWiFS chlorophyll a (Chl a) quantify differences in the previous and current regimes for both the anthropogenically affected coastal North Sea and the comparatively unaffected open North Sea. The new regime maintains a 13% higher Chl a concentration in the open North Sea and a 21% higher concentration in coastal North Sea waters. However, the current regime has lower total nitrogen and total phosphorus concentrations than the previous regime, although the molar N: P ratio in coastal waters is now well above the Redfield ratio and continually increasing. Besides becoming warmer, North Sea waters are also becoming clearer (i.e., less turbid), thereby allowing the normally light‐limited coastal phytoplankton to more effectively utilize lower concentrations of nutrients. Linear regression analyses indicate that winter Secchi depth and sea surface temperature are the most important predictors of coastal Chl a, while Atlantic inflow is the best predictor of open Chl a; nutrient concentrations are not a significant predictor in either model. Thus, despite decreasing nutrient concentrations, Chl a continues to increase, suggesting that climatic variability and water transparency may be more important than nutrient concentrations to phytoplankton production at the scale of this study.
Ultraviolet radiation negatively affects growth but not food quality of arctic diatoms
Authors: Leu Eva , Falk-Petersen Stig , Hessen Dag O.
Published: July 2010

We studied the short‐term effects of ultraviolet radiation (UV radiation, 280–400 nm) on the fatty acid composition and cellular stoichiometry of three dominant arctic diatom species (Thalassiosira antarctica var. borealis, Chaetoceros socialis, Bacterosira bathyomphala) in laboratory experiments. Photosynthetic efficiency during UV irradiation was inhibited 90%, which led to a substantial reduction in biomass. In contrast to results of previous studies, the percentage of total polyunsaturated fatty acids (PUFAs) did not decrease during UV exposure. Instead, the two major PUFAs, 16:4(n‐1) and 20:5(n‐3), of B. bathyomphala increased, and the PUFA content of T. antarctica and C. socialis did not change significantly. However, the monounsaturated fatty acid 16:1(n‐7) content in all three species substantially decreased during UV radiation. Since high concentrations of 16:1(n‐7) are usually associated with exponential growth under favorable conditions, UV radiation probably did not affect a specific type of fatty acid directly; the fatty acid profile rather reflected a general deterioration in the algal physiological state. The nutritional quality of the fatty acids did not decrease during UV exposure; the C: P and N: P ratios decreased by 50% in all species, whereas the C:N ratios increased slightly in two species. Our results indicate that UV radiation has strong negative effects on photosynthesis and biomass production, but not on food quality with regard to PUFAs and stoichiometry.
Patterns in the δ13C and δ15N signature of Ulva pertusa: Interaction between physical gradients and nutrient source pools
Authors: Cornelisen Christopher D. , Wing Stephen R. , Clark Kim L. , Hamish Bowman M. , Frew Russell D. , Hurd Catriona L.
Published: July 2010

Field surveys and laboratory experiments were used to investigate the influence of the physical environment on variability in δ13C and δ15N signatures of Ulva pertusa, an abundant macroalgae inhabiting the low salinity layer (LSL) of Doubtful Sound, a New Zealand fjord. Field surveys revealed significant spatial variability in δ13C (‐18% to ‐12%) and δ15N (0% to 6%). δ13C was enriched at high irradiance sites and depleted at the fjord’s wave‐exposed entrance. δ15N signatures increased from 0% at the fjord head where freshwater influence is greatest to an oceanic signature of 6% at the fjord entrance. δ15N also increased by up to 4% between 2‐m depth and the LSL‐seawater interface (4‐m depth); this pattern was less pronounced near the ocean. During laboratory experiments, δ13C of U. pertusa became significantly enriched under high levels of irradiance (>50 mmol quanta m−2 s−1). When exposed to high irradiance, increases in water motion rapidly depleted δ13C signatures by as much as 5%. Variability in δ13C of U. pertusa in Doubtful Sound is largely a function of the light regime, which influences rates of photosynthesis and in turn the algae’s dependence on HCO3−, an enriched source of carbon. However, increased water motion at the fjord entrance counteracts the influence of irradiance, leading to enhanced flux of CO2 and depleted δ13C signatures. Variation in δ15N of U. pertusa is less dependent on the physical environment and instead is driven by the source pool signature, which in turn varies between freshwater and marine sources of nitrogen.
Seasonal acclimatization of Asparagopsis taxiformis (Rhodophyta) from different biogeographic regions
Authors: Padilla-Gamiño Jacqueline L. , Carpenter Robert C.
Published: July 2010

We studied the photosynthetic acclimatization of two populations of Asparagopsis taxiformis from two biogeographic regions (Santa Catalina Island, California, and Kaneohe Bay, Hawaii) in two seasons. We compared thermal variability between locations and estimated the environmental optima and tolerance limits of photosynthesis to understand the relationship between phenotypic plasticity and thermal variability at each location. Photosynthetic performance was assessed using oxygen evolution and pulsed amplitude modulated fluorometry to quantify responses to thermal variation. A. taxiformis from both locations had similar high temperature tolerances for maximum net photosynthesis (Pnetmax) and maximum relative electron transport rate rETRmax (~30°C), but different cold temperature tolerances. Respiration rates from both locations (summer and winter) always increased above 25°C. Chlorophyll fluorescence yield from dark‐adapted samples from both locations decreased at warmer temperatures in the winter and at colder temperatures during the summer. Populations exposed to greater thermal variability (across both short and long time scales) displayed greater capacity for photosynthetic acclimatization. A. taxiformis from California showed seasonal changes in photosynthetic performance within the environmental temperature range (14–21°C), whereas individuals from Hawaii did not. The narrower temperature tolerance (short‐term response) of subtropical Asparagopsis may make it more susceptible than temperate populations to the predicted increases in global sea surface temperatures. Acclimatization of photosynthesis may play an important role in enabling A. taxiformis to respond to a variable environment and to persist in different biogeographic regions.
The dynamics of phosphorus in turbid estuarine systems: Example of the Gironde estuary (France)
Authors: Deborde Jonathan , Anschutz Pierre , Chaillou Gwénaëlle , Etcheber Henri , Commarieu Marc-Vincent , Lecroart Pascal , Abril Gwenaël
Published: July 2010

Suspended particles and surface waters were collected in the Gironde estuary (southwestern France) along the salinity gradient. Dissolved inorganic phosphorus (DIP) was analyzed in the filtered surface waters. The suspended particles were sequentially leached to determine five fractions of phosphorus: exchangeable or loosely sorbed P, reactive Fe‐bound P, refractory Fe oxide‐bound P, P associated with apatite and carbonates, and organic P. Experiments were conducted to determine the effects of temperature, salinity, and DIP concentration on phosphorus sorption/desorption processes. The concentration and distribution of particulate phosphorus was homogeneous along the salinity gradient of the estuary, whereas it was variable in time and space in the freshwater part. DIP showed a rapid desorption of loosely sorbed P at low salinities. Desorption depended on suspended particle concentration, but not on DIP concentration. At high suspended particle concentrations, some exchangeable P remained linked to particles, until suspended particle concentration decreased downstream of the estuary. This delayed desorption of bioavailable P occurs in waters in which the penetration of light is sufficient to support photosynthesis and probably plays a major role in primary production at high salinities. Mineralization of organic phosphorus also releases available phosphorus, but this process is slow relative to the water residence time in the estuary. The budget of DIP, the loss of particulate P from the organic fraction, and the water residence time suggest that the dynamics of P in the Gironde estuary is well explained by the two processes of P release from particles to waters without P uptake.
Anaerobic ammonium oxidation in the Peruvian oxygen minimum zone
Authors: Hamersley M. Robert , Lavik Gaute , Woebken Dagmar , Rattray Jayne E. , Lam Phyllis , Hopmans Ellen C. , Damsté Jaap S. Sinninghe , Krüger Siegfried , Graco Michelle , Gutiérrez Dimitri , Kuypers Marcel M. M.
Published: July 2010

We investigated the microbial pathways of nitrogen (N) loss in an April 2005 transect through the Peruvian oxygen minimum zone (OMZ) at 12°S latitude using short anaerobic incubations with 15N‐labeled substrates and molecular‐ecological and lipid‐biomarker studies. In incubations with 15NH4+, immediate production of 14N15N, but not 15N15N, indicated that N2 was produced by the pairing of labeled 15NH4+ with in situ 14NO2− via anaerobic ammonium oxidation (anammox). Supporting this finding, we also found anammox‐related 16S ribosomal ribonucleic acid gene sequences similar to those previously known from other marine water columns in which anammox activity was measured. We identified and enumerated anammox bacteria via fluorescence in situ hybridization and quantitative polymerase chain reaction and found ladderane membrane lipids specific to anammox bacteria wherever anammox activity was measured by our isotope tracer method. However, in incubations with 15NO3− or 15NO2−, in which denitrification would have been expected to produce 15N15N by pairing of oxidized 15N ions, 15N15N production was not detected before 24 h, showing that denitrification of fixed N to N2 was not taking place in our samples. At the time and locality of our study, anammox, rather than denitrification, was responsible for N2 production in the Peruvian OMZ waters.
Diel vertical migration of individual jellyfish (Periphylla periphylla)
Authors: Kaartvedt Stein , Klevjer Thor A. , Torgersen Thomas , Sørnes Tom A. , Røstad Anders
Published: July 2010

Vertical migration of the mesopelagic jellyfish Periphylla periphylla (Scyphozoa: Coronatae) was studied by use of hull‐mounted and submerged echosounders in a ~440 m deep Norwegian fjord. The research vessel was kept at a fixed position so that individual jellyfish remained in the acoustic beam for prolonged periods in the low advective environment of the deep fjord basin. The population of jellyfish was divided into different vertical modes with different migration behavior. A scattering layer (SL) of P. periphylla was located at 150‐200 m during the day; it migrated coherently to the upper 50 m at night and returned to depth the next morning. A deeper SL seemed to remain below 250 m both day and night. However, focus on individuals revealed additional, asynchronous migration activity. A pulse of P. periphylla left upper layers already a few hours after sunset, and there was interchange of individuals between shallow and deep water throughout the night, including ascent of individuals from the apparent nonmigrating deepest SL. Vertical migration velocities were ~2 cm s−1 both during ascent and descent, irrespective of time. Different types of swimming behavior were reflected in the acoustic records, affecting the recorded backscatter.