bluuebunny/crossref_metadata_2025 huggingface dataset:
Dejando atrás las fronteras. Las políticas migratorias ante las exigencias de la justicia global
Authors: Velasco Juan Carlos
Published: July 2010

En este artículo se abordan las recíprocas implicaciones normativas existentes entre las concepciones de la justicia global y de la ciudadanía, por un lado, y la definición de las políticas migratorias, por otro. La exploración se hace en cuatro pasos: se ofrecen algunas razones para superar el enfoque estadocéntrico de la teoría de la justicia; se presentan la pobreza mundial y los flujos migratorios generados por ella como cuestiones ineludibles para una teoría de la justicia; se analizan los obstáculos que las fronteras estatales representan a la hora de implementar una concepción global de la justicia; y, finalmente, se argumenta a favor de redefinir la noción de ciudadanía de modo que constituya el horizonte normativo de las políticas migratorias.
Integración: una cuestión de derechos
Authors: Añón María José
Published: July 2010

Este artículo tiene por objeto llevar a cabo un análisis comparativo entre el Plan Estratégico de Ciudadanía e Integración (2007-2010) y el Anteproyecto de Ley española de Extranjería. Es propósito del mismo analizar, en primer lugar, en qué sentido el concepto de integración introducido como principio general en el Anteproyecto es coherente con el concepto plasmado en el plan. En segundo término, se trata de examinar el sentido en el que queda plasmada la noción de integración en algunas de las disposiciones que introduce la reforma especialmente en materia de derechos fundamentales. Todo ello llevará, finalmente, a valorar las relaciones de implicación y de tensión entre las políticas migratorias de control y las políticas de integración de las personas migrantes.
De indeseables a ilegales: una aproximación a la irregularidad migratoria
Authors: González Cámara Noelia
Published: July 2010

La hipótesis que vertebra este trabajo consiste en que la migración irregular no es la mera consecuencia de entrar sin autorización en un Estado sino un producto de medidas legales y políticas. Se sostendrá que las migraciones no autorizadas no tienen un referente estático, más bien dicho referente ha evolucionado en función de las circunstancias socio-históricas. El objetivo es, a la luz de las interpretaciones sobre la producción de irregularidad migratoria realizadas por historiadores y sociólogos, contribuir a la desnaturalización del uso del término “migración irregular”. Para alcanzar este objetivo se propone realizar una serie de precisiones conceptuales que clarifiquen las distintas formas de designar este fenómeno, así como los supuestos que incluye. A partir de ahí se revisará cómo se ha llevado a cabo la identificación de determinados flujos como irregulares y su evolución en Estados Unidos, Francia, Reino Unido y Alemania tras la Segunda Guerra Mundial.
La biblioteca de Pedro Salinas
Authors: González García Juana María
Published: July 2010

La biblioteca personal del poeta Pedro Salinas previa a la Guerra Civil española, ha permanecido prácticamente desconocida hasta el momento para los investigadores y estudiosos de su obra creativa. Conservada entre el fondo documental del Instituto madrileño de Secundaria Cervantes, este conjunto de libros tiene, sin embargo, un gran interés. En este trabajo se publican tanto el catálogo de libros del poeta, resultado de una lenta tarea de clasificación y estudio de los textos así como las convenientes reflexiones en torno a su historia y características.
Requirement for Inducible Nitric Oxide Synthase in Chronic Allergen Exposure-Induced Pulmonary Fibrosis but Not Inflammation
Authors: Naura Amarjit S. , Zerfaoui Mourad , Kim Hogyoung , Abd Elmageed Zakaria Y. , Rodriguez Paulo C. , Hans Chetan P. , Ju Jihang , Errami Youssef , Park Jiwon , Ochoa Augusto C. , Boulares A. Hamid
Published: July 2010

The role of inducible NO synthase (iNOS) in allergic airway inflammation remains elusive. We tested the hypothesis that iNOS plays different roles during acute versus chronic airway inflammation. Acute and chronic mouse models of OVA-induced airway inflammation were used to conduct the study. We showed that iNOS deletion was associated with a reduction in eosinophilia, mucus hypersecretion, and IL-5 and IL-13 production upon the acute protocol. Such protection was completely abolished upon the chronic protocol. Interestingly, pulmonary fibrosis observed in wild-type mice under the chronic protocol was completely absent in iNOS−/− mice despite persistent IL-5 and IL-13 production, suggesting that these cytokines were insufficient for pulmonary fibrosis. Such protection was associated with reduced collagen synthesis and indirect but severe TGF-β modulation as confirmed using primary lung smooth muscle cells. Although activation of matrix metalloproteinase-2/-9 exhibited little change, the large tissue inhibitor of metalloproteinase-2 (TIMP-2) increase detected in wild-type mice was absent in the iNOS−/− counterparts. The regulatory effect of iNOS on TIMP-2 may be mediated by peroxynitrite, as the latter reversed TIMP-2 expression in iNOS−/− lung smooth muscle cells and fibroblasts, suggesting that the iNOS–TIMP-2 link may explain the protective effect of iNOS-knockout against pulmonary fibrosis. Analysis of lung sections from chronically OVA-exposed iNOS−/− mice revealed evidence of residual but significant protein nitration, prevalent oxidative DNA damage, and poly(ADP-ribose) polymerase-1 activation. Such tissue damage, inflammatory cell recruitment, and mucus hypersecretion may be associated with substantial arginase expression and activity. The results in this study exemplify the complexity of the role of iNOS in asthma and the preservation of its potential as a therapeutic a target.
Long-Term Human CD34+ Stem Cell-Engrafted Nonobese Diabetic/SCID/IL-2Rγnull Mice Show Impaired CD8+ T Cell Maintenance and a Functional Arrest of Immature NK Cells
Authors: André Maya C. , Erbacher Annika , Gille Christian , Schmauke Vanessa , Goecke Barbara , Hohberger Alexander , Mang Philippa , Wilhelm Ayline , Mueller Ingo , Herr Wolfgang , Lang Peter , Handgretinger Rupert , Hartwig Udo F.
Published: July 2010

Allogeneic hematopoietic stem cell transplantation represents the most effective form of immunotherapy for chemorefractory diseases. However, animal models have been missing that allow evaluation of donor-patient–specific graft-versus-leukemia effects. Thus, we sought to establish a patient-tailored humanized mouse model that would result in long-term engraftment of various lymphocytic lineages and would serve as a donor-specific surrogate. Following transfer of donor-derived peripheral blood stem cells into NOD/SCID/IL-2Rγnull (NSG) mice with supplementation of human IL-7, we could demonstrate robust engraftment and multilineage differentiation comparable to earlier studies using cord blood stem cells. Phenotypical and functional analyses of lymphoid lineages revealed that >20 wk posthematopoietic stem cell transplantation, the majority of T lymphocytes consisted of memory-type CD4+ T cells capable of inducing specific immune functions, whereas CD8+ T cells were only present in low numbers. Analysis of NSG-derived NK cells revealed the expression of constitutively activated CD56brightCD16− killer Ig-like receptornegative NK cells that exhibited functional impairments. Thus, the data presented in this study demonstrate that humanized NSG mice can be successfully used to develop a xenotransplantation model that might allow patient-tailored treatment strategies in the future, but also highlight the need to improve this model, for example, by coadministration of differentiation-promoting cytokines and induction of human MHC molecules to complement existing deficiencies in NK and CD8+ T cell development.
Essential Role of Endogenous Heat Shock Protein 90 of Dendritic Cells in Antigen Cross-Presentation
Authors: Ichiyanagi Tomoko , Imai Takashi , Kajiwara Chiaki , Mizukami Shusaku , Nakai Akira , Nakayama Toshinori , Udono Heiichiro
Published: July 2010

Extracellular HSP90 associated with Ag peptides have been demonstrated to efficiently cross-prime T cells, following internalization by dendritic cells (DCs). In addition, the nature of cell-associated Ags required for cross-priming is implicated as peptides and proteins chaperoned by heat shock protein (HSP). However, the role of endogenous HSP in DCs during cross-presentation remains elusive. In this paper, we show that endogenous HSP90 is essential for cross-presentation of both soluble and cell-associated Ags in DCs. Cross-presentation of soluble OVA and OVA-loaded transporter associated with Ag processing-1–deficient cells by bone marrow-derived DCs and DC-like cell line DC2.4 was profoundly blocked by HSP90 inhibitors, whereas presentation of endogenously expressed OVA was only partially suppressed. Assays using small interfering RNA and heat shock factor-1–deficient DCs (with defective expression of HSP90α) revealed the pivotal role of HSP90α in cross-presentation. The results suggest that in addition to HSP90 in Ag donor cells, endogenous HSP90 in DCs plays an essential role during Ag cross-presentation and, moreover, points to a link between heat shock factor-1–dependent induction of HSP90α within DC and cytotoxic T cell immunity.
GILT Accelerates Autoimmunity to the Melanoma Antigen Tyrosinase-Related Protein 1
Authors: Rausch Matthew P. , Irvine Kari R. , Antony Paul A. , Restifo Nicholas P. , Cresswell Peter , Hastings K. Taraszka
Published: July 2010

Melanocyte differentiation Ags, including tyrosinase-related protein (TRP) 1, are relevant to both autoimmune skin depigmentation (vitiligo) and tumor immunity, because they are expressed by both benign melanocytes and many malignant melanomas. Melanoma patients generate CD4+ T cells that specifically recognize these proteins. TRP1 contains internal disulfide bonds and is presented by MHC class II molecules. γ-IFN–inducible lysosomal thiol reductase (GILT) facilitates the generation of class II-binding peptides by the endocytic reduction of protein disulfide bonds. We show in this study that GILT is required for efficient MHC class II-restricted processing of a TRP1 epitope in vitro and accelerates the onset of vitiligo in TRP1-specific TCR transgenic mice. The presence of GILT confers a small increase in the percentage of autoreactive T cells with an effector memory phenotype that may contribute to earlier disease onset. The onset of vitiligo is associated with a greater increase in the percentage of autoreactive T cells with an effector memory phenotype. Given that many self and tumor Ags have disulfide bonds and are presented on MHC class II, GILT is likely to be important in the pathogenesis of other CD4+ T cell-mediated autoimmune diseases and for the development of effective cancer immunotherapy.
A Virtualization-Based Retrieval and Update API for XML-Encoded Corpora
Authors: Briquet Cyril , Renders Pascale , Petitjean Etienne
Published: July 2010

Providing support for flexible automated tagging of text-oriented XML documents (i.e. text with intersparsed markup) is a challenging issue. This requires support for tag-aware full text search (i.e. the capability to skip some tags or make invisible whole sections of the document), match points, and transparent updates. An API addressing this issue is described. Based on the virtualization of selected sections of the XML document, the API produces a tag-aware representation, backed by the document, that is transparently searchable (using keyword search or regular expressions) and updatable, offering support for natural linguistic reasoning.
Multi-channel eBook production as a function of diverse target device capabilities
Authors: Freese Eric
Published: July 2010

Publishers have a history of managing data for the long-term. In the past this meant warehouses of proof sheets. As the publishing process became electronic, assets were archived on tape or disk in the event of a need to re-release (perhaps due to a popular subsequent movie or other event). However, the challenge shifted from storage of materials to file compatibility and management of software versions. Then along came XML, which offered a vendor-agnostic format in which to, at a minimum, archive data if not becoming the format in which the data was authored. Now that publishers find themselves in the midst of an eBook boom they find themselves, yet again, dealing with managing different formats and, to complicate matters, dealing with different implementations of the same standard. This paper will discuss the current state of the trade, textbook, and journal publishing industry as it pertains to creating eBooks for current and backlist resources. It will also discuss the challenges faced by publishers as the technology continues to move forward toward “enhanced eBooks” at a pace faster than the standards can be updated.

A sample project will be presented which presents the challenges of producing eBooks in the current environment as well as demonstrates how current standards might support the next generation of eBooks.
XHTML Dialects: Interchange over domain vocabularies through upward expansion
Authors: Hennum Erik
Published: July 2010

The XML community exhibits a persistent tension between the value of sharing (motivating standards) and the value of individuation (motivating customization of those standards). Some communities resolve this tension through particular emphasis on customizations that produce subsets of base vocabularies. Current practices for defining subset vocabularies, however, have limitations that reduce the value of this approach. This paper proposes enhancing the XML ecosystem with a general-purpose mechanism for defining and managing subset extensions of a vocabulary. The proposal makes use of Semantic Web strategies — in particular, asserting new type relations for existing type definitions and simplifying content models — to identify commonality for variant vocabularies. This approach has particular promise for extending XHTML as illustrated with a few microformats.
Greasing the Wheels: Overcoming User Resistance to XML
Authors: Harvey Betty , Lee David A. , Newcomb Steven , Sall Kenneth B. , Walmsley Priscilla
Published: July 2010

While Balisage may be filled with people who are not only comfortable working in XML, many of us are more comfortable with XML than with spreadsheets, word processors, or pens. But many of the users we work with find XML confusing or intimidating and resist learning about XML and using XML tools. This discussion will focus on how to overcome user resistance to XML, including ways to hide the XML, or at least the full complexity of the XML, from end users.
Freestyle Markup Language
Authors: Pondorf Denis , Witt Andreas
Published: July 2010

This paper provides a new generation of a markup language by introducing the Freestyle Markup Language (FML). Demands placed on the language are elaborated, considering current standards and discussions. Conception, a grammatical definition, a corresponding object graph and the bi-directional unambiguous transformation between these two congruent representation forms are set up. The result of this paper is a fundamental definition of a completely new markup language, consolidating many deficiency-discourses and experiences into one particular implementation concept, encouraging the evolution of markup.
Refining the Taxonomy of XML Schema Languages. A new Approach for Categorizing XML Schema Languages in Terms of Processing Complexity.
Authors: Stührenberg Maik , Wurm Christian
Published: July 2010

This paper presents a refined taxonomy of XML schema languages based on the work by Murata et al., 2005. It can be seen as first building block for a more elaborate formal analysis of XML and its accompanied specifications, in this case: XML schema languages such as DTD, XSD and RELAX NG.
Vertical distribution of aggregates (>110 µm) and mesoscale activity in the northeastern Atlantic: Effects on the deep vertical export of surface carbon
Authors: Guidi Lionel , Stemmann Lars , Legendre Louis , Picheral Marc , Prieur Louis , Gorsky Gabriel
Published: July 2010

Spatial and temporal variability in the distribution of marine aggregates (>110 mm) was studied using underwater video profilers in an area off the Iberian Peninsula and Azores Islands dominated by mesoscale and submesocale hydrodynamics in winter, spring, and summer 2001. In the 0‐200‐m layer, aggregates were most abundant in spring (100‐120 mg dry weight [dry wt] m‐3) and lowest during summer and winter (1‐10 mg dry wt mm‐3). In the deeper layers (down to 1,000 m), the seasonal pattern was different, with concentrations highest in spring and summer, and lowest in winter (e.g., at 800 m, 5‐10 mg dry wt mm‐3 in spring and summer; 1‐5 mg dry wt mm‐3 in winter). The seasonal change in the abundance of aggregates in the upper 1,000 m was consistent with changes in the composition and intensity of the particulate flux recorded in sediment traps and with seasonal changes in the surface phytoplankton community. In an area dominated by eddies, surface accumulation of aggregates and export down to 1,000 m occur at mesoscale distances (<100 km). The occurrence of a rich aggregate layer may be related to mesoscale activity in water flow that drives nutrient inputs, phytoplankton production, and the formation of large aggregates. Such spatially constrained zones of massive export may be typical of frontal open‐sea systems, and may have been missed by conventional sediment trap moorings, which cannot resolve export at this mesoscale level.
Effects of upstream lakes on dissolved organic matter in streams
Authors: Larson James H. , Frost Paul C. , Zheng Zhiyu , Johnston Carol A. , Bridgham Scott D. , Lodge David M. , Lamberti Gary A.
Published: July 2010

We examined the effects of upstream lakes on dissolved organic matter (DOM) quantity and the absorbance of ultraviolet (UV) radiation in the streams of northern Michigan. We assessed DOM concentration and absorbance in 15 streams with upstream lakes and 17 streams without upstream lakes located in the same geographic region in May and August 2003. In addition, we estimated watershed land cover and morphology to assess the possibility that other landscape variables could account for DOM differences between the two stream types. The concentration of dissolved organic carbon, its UVB absorbance, and its molar absorbtivity (absorbance per unit carbon) were all significantly lower in streams with upstream lakes than in streams with no lakes. Strong predictive relationships existed between upstream watershed metrics and stream DOM properties, but varied by season and the presence of upstream lakes. DOM quantity and UV‐absorbing ability were related to different watershed metrics, with DOM quantity being strongly related to terrestrial watershed metrics, whereas UV‐absorbing ability was most strongly related to percent water surface area. Upstream lakes strongly influence downstream DOM potentially because of their long water residence times, which could increase opportunities for DOM processing. Upstream lakes represent a strong landscape predictor of stream DOM properties that is not directly tied to terrestrial DOM sources and processing.
Stable isotopic detection of ammonium and nitrate assimilation by phytoplankton in the Waquoit Bay estuarine system
Authors: York Joanna K. , Tomasky Gabrielle , Valiela Ivan , Repeta Daniel J.
Published: July 2010

We measured concentration and δ15N of chlorophyll a (Chl a), NO3‐, and NH4+ along a salinity gradient in Childs River, Massachusetts, in winter, spring, and summer. We used the δ15N of Chl a as a proxy for the phytoplankton δ15N to minimize potential ambiguities from other material in seston. NO3‐ concentration ranged from 0 to 50 µmol L21 and NH4+ from 0 to 8 µmol L‐1; both forms decreased with increasing salinity. NO3‐ concentration was generally higher than NH4+. Chl a concentrations ranged between 1 and 15 mg m‐3 in winterspring and had a summer midestuarine peak of 95 mg m‐3. The δ15N of NO3‐ and NH4+ ranged from ‐10‰ to +7‰ and ‐3‰ to +13‰, respectively, and decreased approximately linearly with increasing salinity. The δ15N of NO3‐ reflected the predominance of groundwater as the source of NO3‐ to the estuary, whereas the δ15N of NH4+ indicated that regeneration was the main NH4+ source. Throughout the estuary, NO3‐ was isotopically lighter than NH4+. Phytoplankton δ15N increased from winter to summer and was relatively invariant with salinity, in contrast to the δ15N of dissolved inorganic nitrogen. A comparison of the δ15N of phytoplankton, NO3‐, and NH4+ indicated that phytoplankton in Childs River derived 53% to 97% of their N from NH4+. Phytoplankton acquired their stable nitrogen isotopic ratio upstream, then maintained that ratio during downstream transport. The fractionation factor for phytoplankton NH4+ uptake was +4.0‰ ± 0.6‰, which was in the lower range of other estimates, indicating that phytoplankton might have been N limited.
Summer algal blooms in shallow estuaries: Definition, mechanisms, and link to eutrophication
Authors: Carstensen Jacob , Henriksen Peter , Heiskanen Anna-Stiina
Published: July 2010

We propose a definition for identification of blooms and use this definition to investigate the underlying mechanisms of summer blooms and their link to nutrient enrichment. Blooms were defined as chlorophyll a observations deviating significantly from a normal seasonal cycle; the frequency and magnitude of these deviating observations characterized bloom frequency and intensity. The definition was applied to a large monitoring data set from five estuaries in Denmark with at least biweekly sampling. Four mechanisms with links to nutrient enrichment were identified as sources of summer blooms: (1) advection from biomass‐rich inner estuary, (2) resuspension of nutrients and algae from sediments, (3) nutrient releases from sediments during hypoxic conditions, and (4) decoupling of benthic grazers. Summer blooms were mostly dominated by diatoms, and in 33% of the bloom samples the dominating species was also dominant prior to the bloom. Only four species (Cerataulina pelagica, Chaetoceros socialis/radians, Prorocentrum micans, and Prorocentrum minimum) typically (>50% of blooms) increased their biomass proportion during bloom initiations. Bloom frequency and intensity decreased from 1989 to 2004, corresponding to decreases in nutrient inputs and concentrations, but only bloom frequency could be directly linked to the actual total nitrogen concentrations, whereas bloom intensities depended on site‐specific features, particularly a threshold response for stations exposed to hypoxia. Bloom frequency has increased over longer timescales in response to nutrient enrichment.
In situ feeding and metabolism of glass sponges (Hexactinellida, Porifera) studied in a deep temperate fjord with a remotely operated submersible
Authors: Yahel Gitai , Whitney Frank , Reiswig Henry M. , Eerkes-Medrano Dafne I. , Leys Sally P.
Published: July 2010

Glass sponges are conspicuous inhabitants of benthic communities in the cool waters of the Antarctic and north Pacific continental shelf. We used an ROV outfitted with a new device for simultaneous sampling of water inhaled and exhaled by the sponges to provide the first data on the nutritional ecology and metabolism of two glass sponge species in their natural deep‐water habitat (120–160 m). Aphrocallistes vastus and Rhabdocalyptus dawsoni were found to be mostly bacteriovores, removing up to 95% of the bacteria (median removal was 79% for both species) and heterotrophic protists (<10 µm) from the water they filter. The relatively scarce microbial cells were efficiently selected from a ‘soup’ of suspended clay and detritus particles (microorganisms accounted for ~1% of the total ambient suspended solids). Removal of planktonic microorganisms (2.2 ± 1.3 µmol carbon [C] C L−1 and 0.37 ± 0.17 µmol nitrogen [N] L−1) accounted for the entire total organic C uptake and ammonium excretion by both species, with no evidence for dissolved organic uptake. Similar results were obtained in laboratory experiments in which dissolved organic C was directly measured. Despite the massive siliceous sponge skeleton, silica uptake was below detection levels (0.28 µmol L−1), supporting previous suggestions of low growth rates in Hexactinellida. Reported mean sponge abundances of >1 individual m−2 indicate that the sponge filtering activity may significantly affect the deep microbial community and benthic‐pelagic mass exchange in some north‐east Pacific fjords.
Large‐scale variability in surface bacterial carbon demand and growth efficiency in the subtropical northeast Atlantic Ocean
Authors: Alonso-Sáez Laura , Gasol Josep M. , Arístegui Javier , Vilas Juan C. , Vaqué Dolors , Duarte Carlos M. , Agustí Susana
Published: July 2010

We present surface estimates of bacterial respiration, bacterial heterotrophic production (BHP), and bacterial growth efficiency (BGE), and their relationship with nutrient availability, along a trophic gradient from coastal upwelling waters to the open‐ocean waters of the eastern North Atlantic. Bacterial respiration generally ranged between 10 and 30 µg C L−1 d−1 and was relatively unaffected by nutrient enrichment. In contrast, BHP showed higher variability (more than one order‐of‐magnitude range) and was affected by carbon and/or phosphorus additions in different regions. Empirical bacterial carbon‐to‐leucine (Leu) conversion factors (CFs) (range, 0.02–1.29 kg C mol Leu−1) decreased from the coast to the open ocean, largely influencing the BHP estimates in oligotrophic waters. We found high percentages of Leu respiration in oceanic waters (average 68% of Leu taken up by bacteria), possibly related to the low CFs found offshore. Empirical CFs were highly correlated to BGE (Pearson correlation coefficient r = 0.86, n = 12, p < 0.0004, log‐log transformed), which varied between 1% in offshore waters and 56% in the upwelling waters. Empirical CFs could be critical not only for accurately constraining BHP, but probably also for predicting BGE in oceanic waters.
Seasonal shifts in chemotype composition of Microcystis sp. communities in the pelagial and the sediment of a shallow reservoir
Authors: Welker Martin , Šejnohová Lenka , Némethová Danka , Döhren Hanšvon , Jarkovský Jiří , Maršálek Blahoslav
Published: July 2010

The various oligopeptides produced by individual Microcystis clones enable the classification of individual colonies of Microcystis in distinct peptide chemotypes. The dynamics and diversity of coexisting chemotypes are regarded as major factors influencing the microcystin‐content of blooms of this potentially toxic cyanobacterial genus. We compared the chemotype composition in planktonic and benthic Microcystis communities in Brno reservoir (Czech Republic) from July to November 2004 by single‐colony mass spectrometry (n = 783). Ninety‐two peptides were selected to characterize 37 chemotypes as revealed by K‐means clustering. In the course of the season the Microcystis community became significantly less diverse (linear regression of Shannon indices, p < 0.001) in the pelagic, and in November two chemotypes—both of which did not contain microcystins—accounted for nearly 80% of the colonies. In contrast, other chemotypes that were dominant in the pelagic in July were no longer encountered after August, whereas some chemotypes that never accounted for high relative abundances were encountered throughout the season. The shift to some few dominant chemotypes in the pelagic was also reflected by changes in the benthic community where the same chemotypes increased in relative abundances. Nonetheless, chemotypes were identified in the sediment in July and November that were never found in plankton samples. A principal component analysis revealed that communities in the pelagial and the benthal were very different in July but converged during the season because of the deposition of dominant planktonic chemotypes in the sediment. In accordance with the declining percentage of toxin‐producing Microcystis colonies, the microcystin content of seston samples decreased significantly from 0.9 mg g‐1 dry weight to levels below the detection limit (linear regression, p < 0.001).
The role of surface vertical mixing in phytoplankton distribution in a stratified reservoir
Authors: Serra T. , Vidal J. , Casamitjana X. , Soler M. , Colomer J.
Published: July 2010

We investigated convection caused by surface cooling and mixing attributable to wind shear stress and their roles as agents for the transport of phytoplankton cells in the water column by carrying out two daily surveys during the stratified period of the Sau reservoir. Green algae, diatoms, and cryptophyceae were the dominant phytoplankton communities during the surveys carried out in the middle (July) and end (September) of the stratified period. We show that a system with a linear stratification and that is subject to weak surface forcing, with weak winds “4 m s‐1 and low energy dissipation rate values of the order of 10‐8 m2 s‐3 or lower, enables the formation of thin phytoplankton layers. These layers quickly disappear when water parcels mix because there is a medium external forcing (convection) induced by the night surface cooling, which is characterized by energy dissipation rates on the order of ~5 x 10‐8 m2 s‐3. During both surveys the wind generated internal waves during the entire diurnal cycle. During the day, and because of the weak winds, phytoplankton layers rise in the water column up to a depth determined by both solar heating and internal waves. In contrast, during the night phytoplankton mixes down to a depth determined by both convection and internal waves. These internal waves, together with the wind‐driven current generated at the surface, seem to be the agents responsible for the horizontal transport of phytoplankton across the reservoir.
Photochemical control of copper complexation by dissolved organic matter in Rocky Mountain streams, Colorado
Authors: Brooks Marjorie L. , McKnight Diane M. , Clements William H.
Published: July 2010

We investigated photochemical, seasonal, and source effects on copper (Cu) complexation by dissolved organic matter (DOM). Cu‐DOM complexation regulates Cu toxicity by decreasing the activity of the cupric ion ({Cu2+}), the most bioavailable Cu species. However, DOM is photochemically unstable under solar insolation. We analyzed Cu‐DOM complexation before and after photooxidation of DOM collected from six rivers during spring runoff and late summer (n = 12 DOM samples). After irradiation of DOM for 24 h in a solar simulator (~4 d of ambient insolation), we analyzed Cu‐DOM complexation during potentiometric titrations of Cu into dissolved organic carbon concentrations of 5 mg L−1. In 10 DOM samples across the range of titrations (Cu, 7.8 x 10−8 to 8.7 x 10−6 mol L−1), photooxidation of DOM decreased Cu complexation, increasing {Cu2+} by an average of 156% ± 28% (mean ± SE). In one DOM sample, irradiation had no net effect on {Cu2+} (6% ± 12%), whereas in another Cu complexation was enhanced (30% ± 4%). Cu complexation that was indistinguishable before irradiation decreased significantly more during photooxidation of DOM in spring (185% ± 25%) than in summer (74% ± 14%). The specific ultraviolet absorption coefficient at 254 nm explained ~60% of the variation in conditional stability constants of Cu‐DOM complexes regardless of DOM source, season, or extent of photooxidation. During a simulated contaminant event where 1.5 x 10−6 mol L−1 Cu was added to site waters, water chemistry reduced bioavailability in 6 of 12 cases to below the {Cu2+} expected to cause 50% mortality ({Cu2+}LC50) in larval fish. However, after 6 d of photooxidation, none of the site waters remained below {Cu2+}LC50.
Phosphorus availability, phytoplankton community dynamics, and taxon‐specific phosphorus status in the Gulf of Aqaba, Red Sea
Authors: Mackey Katherine R. M. , Labiosa Rochelle G. , Calhoun Mike , Street Joseph H. , Post Anton F. , Paytan Adina
Published: July 2010

The relationships among phytoplankton taxon‐specific phosphorus‐status, phytoplankton community composition, and nutrient levels were assessed over three seasons in the Gulf of Aqaba, Red Sea. During summer and fall, stratified surface waters were depleted of nutrients, and picophytoplankton populations comprised the majority of cells (80% and 88%, respectively). In winter, surface nutrient concentrations were higher and larger phytoplankton were more abundant (63%). Cell‐specific alkaline phosphatase activity (APA) derived from enzyme‐labeled fluorescence was consistently low (<5%) in the picophytoplankton population throughout the year, whereas larger cells expressed increased APA (up to 68% labeling in some taxa) during the summer and fall but less in the winter. A nutrient addition bioassay during the fall showed that after addition of orthophosphate along with a nitrogen source, APA in larger cells was reduced by half relative to the control, whereas the APA of picophytoplankton groups remained low (<1%) across all treatments. These results indicate that the most abundant phytoplankton in the gulf are not limited by orthophosphate, and only some subpopulations (particularly of larger cells) exhibit orthophosphate limitation throughout the year, and more so in the summer and fall. Our results indicate that orthophosphate availability influences phytoplankton ecology, correlating with shifts in phytoplankton community structure and the nutrient status of individual cells. The role of dissolved organic phosphorus as an important phosphorus source for marine phytoplankton in oligotrophic settings and the need for evaluating nutrient limitation at the taxa and/or single cell level (rather than inferring it from nutrient concentrations and ratios or bulk enzyme activity measurements) are highlighted.
Chemical defense of the red tide dinoflagellate Karenia brevis against rotifer grazing
Authors: Kubanek Julia , Snell Terry W. , Pirkle Christen
Published: July 2010

In order to test whether phytoplankton such as the red tide dinoflagellate Karenia brevis negatively affect rotifer grazers and what mechanisms are involved in these interactions, we conducted laboratory feeding experiments using K. brevis cultured from Gulf of Mexico coastal waters and two species of rotifers, one cooccurring and the other from an inland sea in Russia. The co‐occurring rotifer Brachionus ibericus did not ingest K. brevis as a sole diet but tolerated K. brevis in a diet mixed with Rhodomonas lens, whereas the allopatric rotifer, Brachionus plicatilis, rejected K. brevis in either diet, although B. plicatilis started feeding on the mixed diet after a delay of 4 days. The deterrence of K. brevis was mediated by its cellular organic extracts and not by exudates, with compounds other than brevetoxins PbTx‐2, PbTx‐3, and PbTx‐9 implicated in deterrence. The finding that closely related rotifers respond differently to K. brevis and to its chemical defense suggests that a shared evolutionary history may have led B. ibericus to tolerate K. brevis in a mixed diet.
Simulated light regimes affect feeding and metabolism of Antarctic krill, Euphausia superba
Authors: Teschke Mathias , Kawaguchi So , Meyer Bettina
Published: July 2010

The effect of different light regimes on physiological parameters (feeding activity, oxygen consumption, and activity of the metabolic enzyme malate dehydrogenase [MDH]) of Antarctic krill, Euphausia superba, was studied over 12 weeks under laboratory conditions. Krill were exposed to light‐cycle regimes of variable intensity to simulate Southern Ocean summer, autumn, and winter conditions, respectively, using: (1) continuous light (LL; 200 lux max), (2) 12‐h light and 12‐h darkness (LD 12 : 12; 50 lux max), and (3) continuous darkness (DD). In all experimental groups, the food concentration was kept at high levels (~ 800 µg C L−1). Krill exposed to LL and LD 12 : 12 showed an increase in all measured parameters over the experimental period. Physiological parameters of krill held under LD 12 : 12 showed a more consistent increase and remained below those of krill held under LL. No change was recorded for krill exposed to DD; clearance rates and daily C rations did not respond to the high food availability, and oxygen consumption rates and MDH activity were significantly lower (p < 0.05) than those of krill exposed to summer light condition. Thus, changes in the environmental light regime have an important effect on physiological parameters of krill, such as feeding and metabolic rates, and may indicate an inherent overwinter adaptation strategy triggered by the Antarctic light regime.
Characterization of suspended particles in Everglades wetlands
Authors: Noe Gregory B. , Harvey Judson W. , Saiers James E.
Published: July 2010

We report the concentration, phosphorus (P) and nitrogen (N) content, and size and chemical fractionation of fine suspended particles (0.2‐100 µm) and colloids (3 kilodalton [kDa]‐0.1 µm) in the surface water of Everglades wetlands along regional and P‐enrichment gradients. Total suspended sediment concentrations ranged from 0.7 to 2.7 mg L−1. Total particulate P concentrations increased from 0.05 µmol L21 to 0.31 µmol L−1 along the Penrichment gradient. Particles contained from 20% to 43% of total P but <12% of total N in surface water. Dissolved (<0.2 µm) organic N contained about 90% of total N, with the 3‐100‐kDa colloidal size class containing the most N of any size class. The 0.45‐2.7‐µm size fraction held the most particulate P at all sites, whereas particulate N was most abundant in the 2.7‐10‐µm size class at most sites. Standard chemical fractionation of particles identified acid‐hydrolyzable P as the most abundant species of particulate P, with little reactive or refractory organic P. Sequential chemical extraction revealed that about 65% of total particulate P was microbial, while about 25% was associated with humic and fulvic organic matter. The size and chemical fractionation information suggested that P‐rich particles mostly consisted of suspended bacteria. Suspended particles in Everglades wetlands were small in size and had low concentrations, yet they stored a large proportion of surface‐water P in intermediately reactive forms, but they held little N.
Optical effect on the nitracline in a coastal upwelling area
Authors: Aksnes Dag L. , Ohman Mark D. , Rivière Pascal
Published: July 2010

The transport of nitrate into the euphotic zone is an important regulator of primary production. This transport is facilitated by physical processes that involve the depth and the steepness of the nitracline, but transport is complicated by the dynamical nature of the euphotic zone. Here we derive an analytical model that predicts two optical effects of the euphotic zone on the nitracline: the nitracline depth should vary inversely with light attenuation for downwelling irradiance, and the nitracline steepness should be directly proportional to light attenuation. We show that observations of nitrate and Secchi depth, which have been obtained over 21 yr in the coastal upwelling region off Southern California (CalCOFI area), are consistent with these predictions. Chlorophyll a measurements also indicate an optical signature in the nitracline: while the amount of chlorophyll correlated poorly with the nitracline depth, the nitracline depth correlated strongly with the optical effect of chlorophyll, and the nonlinear nature of this relationship was consistent with the model prediction. These optical effects on the nitracline may involve positive feedback mechanisms with phytoplankton production that have implications for interpretation and modeling of primary production.
Hurricane signals in salt marsh sediments: Inorganic sources and soil volume
Authors: Turner R. Eugene , Swenson Erick M. , Milan Charles S. , Lee James M.
Published: July 2010

The inorganic content of 51 dated sediment cores from Mississippi River deltaic plain salt marsh wetlands peaks with the landfall of hurricanes. Variations in the inorganic sediment content demonstrate no temporal coherence with changes in either the Mississippi River suspended matter concentration or discharge, or with wetland losses on this coast. The inorganic matter brought to wetlands during hurricanes is sufficient to account for the accumulated inorganic sediment, and the volume averages 9% of the soil volume. A “sediment deficit” hypothesis, which makes a causal connection between a changing inorganic supply and the dramatically high wetland losses on this coast, is therefore rejected. Our results support the hypothesis that wetlands of an undeveloped coast receive the majority of their inorganic sediments from offshore and not from overbank flooding or through crevasses. Restoration and wetland maintenance (prevention) goals should be implemented with this in mind: the coastal wetland losses of the last century along this coast appear to be a consequence of the diminished accumulation of organic matter and not from variations in inorganic sediment loading.
Nitrogen dynamics in grassland streams along a gradient of agricultural development
Authors: Simon Kevin S. , Niyogi Dev K. , Frew Russell D. , Townsend Colin R.
Published: July 2010

We examined nitrogen (N) uptake in seven grassland streams lying in catchments along a gradient (0–84%) of agricultural land use in New Zealand using a stable isotope (15N) addition of NH4+ to quantify whole‐stream uptake rates and uptake by specific compartments within the streams. Whole‐stream uptake of NH4+ ranged from 1.2 mmol N m−2 min−1 to 7.9 mmol N m−2 min−1 and showed no evidence of strong saturation of uptake with increasing NH4+ availability along the land use gradient. The relatively simple pattern of increasing N uptake along the gradient occurred despite substantial shifts in uptake among community members. Uptake of NH4+ by epilithic biofilms followed a subsidy‐stress relationship, with highest uptake rates at intermediate levels of pastoral development and lowest uptake rates at high pastoral development. At high (>60%) pastoral development, reduced uptake by epilithon was compensated for by enhanced uptake by macrophytes. Compensatory uptake can play an important role in streams when community composition is reorganized by human activity.
Nitrogen and oxygen isotopic signatures of subsurface nitrate seaward of the Florida Keys reef tract
Authors: Leichter James J. , Wankel Scott , Paytan Adina , Hanson Katharine , Miller Steven , Altabet Mark A.
Published: July 2010

Hydrographic and nutrient structure and the nitrogen and oxygen isotopic compositions (d15N and d18O) of the nitrate pool seaward of the Florida Keys reef tract were measured in Summer 2003. Nitrate and soluble reactive phosphate concentrations were tightly associated with depth and temperature and were close to 0 in surface waters, increased to 2–10 µmol L−1 and 0.1–1.0 µmol L−1, respectively, at intermediate depths associated with the thermocline and 15–25 µmol L−1 and 1.0–1.5 µmol L−1, respectively, in deeper water. Ammonium concentrations were low (0–0.6 µmol L−1) at all depths. Dissolved organic carbon concentrations ranged from 70–120 µmol L−1 near the surface to 40–60 µmol L−1 below the thermocline. Mean nitrate δ15N was 4.78% (±0.05) overall and varied from 4.24%(±0.07) within the chlorophyll maximum layer at 50–70 m depth to 5.26% (±0.05) below the thermocline at 150–242 m depth. Mean δ18O mean was 3.26% (±0.08) and varied from 4.89% (±0.14) within the chlorophyll maximum layer to 3.02% (±0.07) below the thermocline. These observations suggest an oceanic, deep‐water nitrate source below the thermocline, a mix of sources from upwelling and N2 fixation, and the effects of fractionation associated with uptake by primary producers within the thermocline. The water column nitrate isotopic data support the general hypothesis that primary producers on the Florida Keys reef tract directly utilize the transiently available subsurface nitrate pool.
Phosphonate metabolism by Trichodesmium IMS101 and the production of greenhouse gases
Authors: White A. E. , Karl D. M. , Björkman K. M. , Beversdorf L. J. , Letelier R. M.
Published: July 2010

Herein we present the results of a series of laboratory experiments conducted to delineate the relationship between dissolved organic phosphorus (DOP) utilization and organic matter production by the model diazotroph Trichodesmium IMS101. The rate and ratio of Trichodesmium carbon (C) and nitrogen (N) production driven by phosphorus (P) derived from select phosphonates and P monoesters were not found to be significantly different than growth rates based on dissolved inorganic phosphorus (DIP). Conversely, despite the observed similarities in C and N fixation rates between parallel DIP and DOP incubations, cultures grown solely on methylphosphonate (MPn) had reduced maximal P content per unit chlorophyll a or C relative to cultures grown on P monoesters or DIP. So while Trichodesmium IMS101 appears to be able to maintain similar rates of growth on DIP and select DOP substrates, the P uptake efficiency and, hence, the P content per cell is greater for growth on DIP or tested P monoesters relative to growth on the phosphonate MPn. The primary conclusion arising from these results is that neither the observation of P monoester hydrolysis nor highly P‐deficient organic matter or expression of phosphonate hydrolyzing genes can be interpreted to indicate P limitation of C or N fixation of Trichodesmium spp. under light‐saturated, DIP‐deficient conditions.
Functional response of carbon absorption efficiency in the pelagic calanoid copepod Acartia tonsa
Authors: Thor Peter , Wendt Ida
Published: July 2010

We constructed a general relationship between prey concentration and absorption efficiency (AE; previously termed assimilation efficiency) in the cosmopolitan calanoid copepod Acartia tonsa. The relationships between observed AEs and prey concentrations developed differently on different prey species. While AEs decreased asymptotically with prey concentration on the cryptophyte Rhodomonas baltica, the chlorophyte Dunaliella tertiolecta generated a v‐shaped response, whereas AEs remained constant on the diatom Thalassiosira weissflogii. We used these observations to develop a mechanistic gut model in which gut carbon concentrations depend on ingestion rate and either egestion rate or absorption rate. To investigate which rate was more important for AE, two different model modes were run: absorption was set to vary according to absorptive enzyme kinetics and egestion set to relate linearly to gut carbon concentration, or the contrary, egestion was set to vary according to enzyme kinetics and absorption set to relate linearly to gut concentration. This approach revealed that copepod carbon AE is controlled primarily by egestion rate kinetics and is independent of absorptive enzyme kinetics. Accordingly, we suggest a simplified regression model for the functional response of AE in pelagic copepods based solely on rates of ingestion and egestion.