bluuebunny/crossref_metadata_2025 huggingface dataset:
Serum Albumin as a Marker for Disease Activity in Patients with Systemic Lupus Erythematosus
Authors: YIP JONATHAN , AGHDASSI ELAHEH , SU JIANDONG , LOU WENDY , REICH HEATHER , BARGMAN JOANNE , SCHOLEY JAMES , GLADMAN DAFNA D. , UROWITZ MURRAY B. , FORTIN PAUL R.
Published: June 2010

Objective.

To determine whether serum albumin reflects disease activity in patients with systemic lupus erythematosus (SLE) with and without nephritis (LN, LNN), and whether serum albumin could be a surrogate marker of SLE disease activity overall. There is currently no clinical “gold standard” in the assessment of disease activity in SLE.

Methods.

Patients with ≥ 3 clinic visits within a maximum followup period of 10 years were selected from the University of Toronto Lupus Clinic database. Subjects were divided into 3 groups: LN-B, those with nephritis defined by histological findings on renal biopsies; LN-L, those with nephritis defined by laboratory abnormalities in the absence of biopsy; and LNN, those without nephritis. In a subanalysis, the renal groups were further stratified by proteinuria status. The associations of SLE-Disease Activity Index (SLEDAI-2K) with serum albumin and dsDNA were examined using the mixed model regression analysis.

Results.

A total of 1078 patients were studied: 89.1% female, 71.5% white, mean age 33.6 (SD 12.6) years, and with median baseline SLEDAI-2K of 8. Serum albumin was more significantly associated with SLEDAI in LN-B and LN-L. The association was also present but weaker in the LNN group. In all LN, the associations between serum albumin and SLEDAI-2K were stronger in those with proteinuria.

Conclusion.

In patients with SLE, higher SLEDAI was associated with lower serum albumin levels.
Le paysage, outil de territorialisation et d'aménagement incomplet pour les forêts méditerranéennes ?
Authors: Fourault-Cauët Véronique
Published: June 2010

Cet article porte sur la valeur opératoire du paysage dans l’aménagement forestier méditerranéen. Est-il une simple notion discursive, ou un objectif, voire le moteur de l’aménagement ? Le paysage est certes au cœur des enjeux de ces boisements : accrus, demande sociale, biodiversité etc. Il s’est de fait s’est imposé dans les discours forestiers. Mais il joue encore un rôle modeste dans les pratiques concrètes d’aménagement. Localement, la notion est mal connue. Le modèle paysager méditerranéen, l’héritage sylvicole de l’Europe du Nord, le flou de la notion expliquent ces gradations. Enfin, les approches paysagistes actuelles posent des difficultés structurelles, en prônant une conception réticulaire du paysage peu compatible avec la gestion des territoires.
Littérature et conversation au XXe siècle : Proust (encore)
Authors: Héron Pierre-Marie
Published: June 2010

L’article propose une relecture de la relation de Proust à Sainte-Beuve, à partir du Contre Sainte-Beuve et d’ À l’ombre des jeunes filles en fleurs . Le refus de concevoir la littérature comme un prolongement de la conversation et d’écrire pour un public se révèle moins tranché qu’il n’y paraît dans le premier volume, où la méthode critique de l’aîné est à la fois pastichée et caricaturée. Sur l’exemple de Bergotte, étudié (d’une manière toute beuvienne) dans son œuvre écrite et dans sa conversation, le divorce s’assouplit de fait dans le second au profit d’une simple hiérarchie de plans ménageant des continuités, reflet de celle existant en réalité entre moi social et moi génial. Demeure une ambivalence majeure, incarnée par la duchesse de Guermantes, vis-à-vis de la conversation « à la française », art de parler réconciliant l’originalité de vision avec le charme.
La dialectique, entre logique et rhétorique
Authors: Keiff Laurent , Rahman Shahid
Published: June 2010

Nous montrons dans cet article comment les approches dynamiques en logique contemporaine ont retrouvé, quoique sous d ’ autres attendus, une configuration théorique qu ’ on peut attribuer à Aristote au moment de la rédaction des Topiques . Dans cette configuration, la logique et la rhétorique  –  ou au moins la dialectique  –  se complètent dans le cadre conceptuel homogène offert par la dialectique, entendue comme une certaine forme relativement codifiée de débat critique. L ’ idée principale est qu ’ aujourd ’ hui, de même qu ’ alors, la dialectique est le cadre dans lequel il est possible de penser le rapport entre la logique et les formes générales de l ’ argumentation d ’ une part, et entre la logique et la théorie de la connaissance scientifique d ’ autre part.
Les enjeux philosophiques de la topique juridique selon Perelman
Authors: Melcer Alain
Published: June 2010

Juriste de formation logicienne, longtemps influencé par le positivisme logique, Chaim Perelman a d ’ abord pensé qu ’ il était possible d ’ étendre l ’ analyse du raisonnement formel à l ’ argumentation pratique, juridique et morale. L ’ abandon de ce projet est ce qui l ’ a conduit à redécouvrir la topique juridique et à proposer, sous le titre de « nouvelle rhétorique », un retour à la Rhétorique et aux Topiques d ’ Aristote.
La rhétorique : art de la preuve ou art de la persuasion ?
Authors: Danblon Emmanuelle
Published: June 2010

Cet article propose une nouvelle enquête sur l ’ ancien concept de preuve rhétorique. Seront examinées les notions suivantes : le tekmerion (l ’ indice), le paradeigma (l ’ exemple) et le topos (lieu), afin d ’ éclairer leur lien apparemment paradoxal avec la persuasion et la validité. Le propos est de montrer qu ’ un tel paradoxe peut être résolu grâce à une conception stratifiée de la rationalité, où la raison archaïque soutient la persuasion, tandis que la raison moderne fonde la validité.
«Presque chacun ressemble à l'embryon»
Authors: Moussa Sarga
Published: June 2010

Résumé L’ Essai sur l’inégalité des races humaines (1853-1855) radicalise un discours raciologique qui, au xix e siècle, insiste sur la séparation et la hiérarchie des «races », dont les mélanges conduiraient à la dégénérescence. Paradoxalement, La Danseuse de Shamakha , la première des Nouvelles asiatiques (1876), n’illustre guère l’idée de supériorité de la «race» blanche. Bien qu’issue du Caucase, berceau des mythiques «Arians», l’héroïne musulmane est tiraillée entre la défense de son identité ethnique (elle appartient à la fière tribu des lesghys) et son amour pour des hommes qui excèdent ce cadre, que ce soit son cousin Mourad, devenu Assanoff depuis qu’il sert dans l’armée russe (mais ce triste produit du «métissage» ne peut plus revenir à son identité de départ…), ou l’exilé espagnol Moreno, dans lequel la danseuse reconnaît une image de sa propre nostalgie (mais elle meurt de cet amour). Il y a chez Gobineau à la fois un universalisme tragique et le désir de croire à une élite des déracinés – nouvelle famille dont les valeurs aristocratiques (courage, honneur…) transcenderaient les clivages ethniques, religieux ou linguistiques.
Forclore la violence à l'écran : l'écriture cinématographique des « années de plomb » italiennes et la forclusion de la violence politique
Authors: D’Errico Dora
Published: June 2010

Résumé De nombreux cinéastes italiens choisissent aujourd’hui, après une période de silence relatif, de rouvrir la page des années Soixante-dix. Une observation a guidé notre analyse de ce renouveau cinématographique : le glissement net qui, en vingt ans, s’est opéré dans le portrait du terroriste ; d’une figure invisible, mêlée au corps social, telle qu’on la voit dans les films des années Quatre-vingt, elle est désormais hyper individualisée, et auscultée avec les outils du psychologue et du criminologue. Répondant au malaise collectif, aux plaies encore ouvertes par les difficiles années de plomb, ainsi qu’aux vides laissés par une « historiographie à trous », les films se multiplient aujourd’hui et proposent des images mémorielles et des récits collectifs autour desquels la société italienne peut se réunir. Cette visée pacificatrice témoigne d’un nouvel usage de l’image qui entend forclore et délimiter la violence historique.
Living with New Media Technology
Authors: Wong Andrew
Published: June 2010

This chapter considers the collective information behavior of the poor in Bangladesh. It examines the mobile phone as the central node and seeks to understand the construction of collectiveness by examining the collective-mediated learning, sharing and experimenting among the poor. Three brief cases provide the background and illustrate the elements of a Learn, Share and Experiment model. Against this tapestry of multiple perspectives, collective-mediated learning, sharing and experimenting enable the poor to be cost-efficient and socially productive. In conclusion there is an urgent need for all researchers to reexamine and rethink the poor’s collective information behavior as new media technology spreads deeper into their lives. Without it, we may miss the opportunity to discover something useful that will eventually lift them out of poverty.
Contributors and Lurkers
Authors: Beamish Anne
Published: June 2010

The long-term sustainability of online communities depends on the active participation and contribution of its members, but we have limited knowledge about why individuals do not post and how online communities can differ. This chapter presents an exploratory case study of contribution rates and lurking in a professional international online community that focuses on architecture and design in the Islamic world. The purpose of this study was to gain a deeper understanding of the community and the lurking behavior of its members. Using a web-based survey and log files, it asked three primary questions: Who contributes? Where do they contribute? And what reasons do members give for not contributing?
On the Challenges of Collaborative Data Processing
Authors: Noël Sylvie , Lemire Daniel
Published: June 2010

The last 30 years have seen the creation of a variety of electronic collaboration tools for science and business. Some of the best-known collaboration tools support text editing (e.g., wikis). Wikipedia’s success shows that large-scale collaboration can produce highly valuable content. Meanwhile much structured data is being collected and made publicly available. We have never had access to more powerful databases and statistical packages. Is large-scale collaborative data analysis now possible? Using a quantitative analysis of Web 2.0 data visualization sites, the authors find evidence that at least moderate open collaboration occurs. The authors then explore some of the limiting factors of collaboration over data.
Why Do We Need to Share Information?
Authors: Ikeya Nozomi , Awamura Norihisa , Sakai Shinichiro
Published: June 2010

In order to study collaborative information behaviour (e.g. information search, creation, and sharing) in the work environment, it is important that we take into consideration its embedded nature in collaborative work, however not many studies have actually taken this into consideration. In conducting fieldwork, we studied group task management in the work of IT product hardware designers. The study shows how understanding the details of information activities embedded in task management allowed us to generate some ideas for transforming task management into a more collaborative activity, and for reembedding task management more thoroughly into their work practices together with the practitioners. The paper discusses how taking an ethnomethodological approach can be fruitful for researchers who want to gain a close understanding of actual collaborative information activities and their embedded nature in work, and how understandings of this kind can be important for developing ideas for transforming practice, both with or without the introduction of technology.
Collaborative Information Behavior in Completely Online Groups
Authors: Goggins Sean , Erdelez Sanda
Published: June 2010

This chapter situates collaborative information behavior in completely online groups as a phenomenon distinct from prior work understanding collaborative information behavior in face-to-face groups, free and open source software groups and Wikipedia groups. The unexpected diversity of information resources utilized by completely online group members is analyzed through Sonnenwald’s Information Horizons theory. Information practices of completely online group members are described, and the key themes of groups as information resources, the influence of tool change on collaborative information behavior online, and the focusing potential of collaborative information tools for completely online group work are explicated. Future research directions that explore the potential of COGs for distributed innovation; new types of collaborative information behavior and breaking down the digital divide are reviewed.
Building a Learning Community
Authors: Scown Philip
Published: June 2010

Typically education is a process that is done to students. The work reported here relates to students who collaborate in the education process so that they become educators of later students. This collaboration takes the form of development of re-usable learning objects (RLOs) that are firstly used to assess each student’s understanding, but which are then to be used for the education of subsequent cohorts. This approach is based on a range of pedagogic concerns with motivational and social aspects of teaching. Students are given the options of producing a written or a video assignment. They make this decision in the knowledge that their work will be used to instruct students who will come after them. The video is relatively short at 5 – 10 minutes in length. Once assessed the video is added to a library for later use. Students report that they enjoy these assessments and that it is valuable to see the work of previous students.
Feline Neonatal Isoerythrolysis and the Importance of Feline Blood Types
Authors: Silvestre-Ferreira Ana C. , Pastor Josep
Published: June 2010

Although feline neonatal isoerythrolysis is rare, associated mortality rate is high. It results from mating of type B blood queens with type A or AB blood toms. A comprehensive review on feline blood types and feline neonatal isoerythrolysis physiopathology, clinical features, diagnosis, treatment, and prevention is covered.
Stable constant-mean-curvature hypersurfaces are area minimizing in small $L^1$ neighborhoods
Authors: Morgan Frank , Ros Antonio
Published: June 2010

We prove that a strictly stable oriented constant-mean-curvature hypersurface in a smooth closed manifold of dimension less than or equal to 7 is uniquely homologically area minimizing for ﬁxed volume in a small _L_1 neighborhood, proving a conjecture of Choksi and Sternberg.
On the existence of mean curvature ﬂow with transport term
Authors: Liu Chun , Sato Norifumi , Tonegawa Yoshihiro
Published: June 2010

We prove the global-in-time existence of weak solution for a hypersurface evolution problem where the velocity is the sum of the mean curvature and arbitrarily given non-smooth vector ﬁeld in a suitable Sobolev space. The approximate solution is obtained by the Allen–Cahn equation with transport term. By establishing the density ratio upper bound on the phase boundary measure it is shown that the limiting surface moves with the desired velocity in the sense of Brakke.
Evaluation of RepliVAX WN, a Single-Cycle Flavivirus Vaccine, in a Non-Human Primate Model of West Nile Virus Infection
Authors: Widman Douglas G. , Ishikawa Tomohiro , Giavedoni Luis D. , Hodara Vida L. , Garza Melissa de la , Montalbo Jessica A. , Travassos Da Rosa Amelia P. , Tesh Robert B. , Patterson Jean L. , Carrion Ricardo , Bourne Nigel , Mason Peter W.
Published: June 2010

West Nile virus (WNV) causes serious neurologic disease, but no licensed vaccines are available to prevent this disease in humans. We have developed RepliVAX WN, a single-cycle flavivirus with an expected safety profile superior to other types of live-attenuated viral vaccines. In this report we describe studies examining RepliVAX WN safety, potency, and efficacy in a non-human primate model of WNV infection. A single immunization of four rhesus macaques with RepliVAX WN was safe and elicited detectable neutralizing antibody titers and IgM and IgG responses, and IgG titers were increased in two animals that received a second immunization. After challenge with WNV, three of four immunized animals were completely protected from viremia, and the remaining animal showed minimal viremia on one day. In contrast, the unvaccinated animal developed viremia that lasted six days. These results demonstrate the efficacy and safety of RepliVAX WN in this primate model of WNV infection.
The Incremental Cost-Effectiveness of Engaging Private Practitioners to Refer Tuberculosis Suspects to DOTS Services in Jogjakarta, Indonesia
Authors: Mahendradhata Yodi , Probandari Ari , Ahmad Riris A. , Utarini Adi , Trisnantoro Laksono , Lindholm Lars , van der Werf Marieke J. , Kimerling Michael , Boelaert Marleen , Johns Benjamin , Van der Stuyft Patrick
Published: June 2010

We aimed to evaluate the incremental cost-effectiveness of engaging private practitioners (PPs) to refer tuberculosis (TB) suspects to public health centers in Jogjakarta, Indonesia. Effectiveness was assessed for TB suspects notified between May 2004 and April 2005. Private practitioners referred 1,064 TB suspects, of which 57.5% failed to reach a health center. The smear-positive rate among patients reaching a health center was 61.8%. Two hundred eighty (280) out of a total of 1,306 (21.4%) new smear-positive cases were enrolled through the PPs strategy. The incremental cost-effectiveness ratio per smear-positive case successfully treated for the PPs strategy was US$351.66 (95% CI 322.84–601.33). On the basis of an acceptability curve using the National TB control program's willingness-to-pay threshold (US$448.61), we estimate the probability that the PPs strategy is cost-effective at 66.8%. The strategy of engaging PPs was incrementally cost-effective, although under specific conditions, most importantly a well-functioning public directly observed treatment, short-course (DOTS) program.
Bacterial Loads and Antibody Responses in BALB/c Mice Infected with Low and High Doses of Burkholderia pseudomallei
Authors: Srisurat Nuttiya , Sermswan Rasana W. , Tatawasart Unchalee , Wongratanacheewin Surasakdi
Published: June 2010

Profiles of Burkholderia pseudomallei persistence and antibodies in blood, spleen, liver, and lungs of infected BALB/c mice were investigated. Animals were infected intraperitoneally with low (6 colony-forming units) or high (230 colony-forming units) doses of B. pseudomallei. In the high-dose infected group, bacteria were found by culture in 100% of blood, liver, spleen and lung samples at 24 and 48 hours after infections; blood samples were 100% positive by polymerase chain reaction after 60 hours. Antibody responses in the high-dose infected group were low. These responses were detected in the low-dose infected group after 5 days, peaked at 7–14 days, and showed persistence until 28 days post-infection. Bacterial loads and antibody profiles varied according to the level of bacterial infections. This kinetic study, although in animals, provides crucial knowledge that might be useful for the development of a sensitive and specific diagnostic assay for patients with melioidosis.
Molecular-Based Assay for Simultaneous Detection of Four Plasmodium spp. and Wuchereria bancrofti Infections
Authors: Mehlotra Rajeev K. , Gray Laurie R. , Blood-Zikursh Melinda J. , Kloos Zachary , Henry-Halldin Cara N. , Tisch Daniel J. , Thomsen Edward , Reimer Lisa , Kastens Will , Baea Manasseh , Baea Kaye , Baisor Moses , Tarongka Nandao , Kazura James W. , Zimmerman Peter A.
Published: June 2010

Four major malaria-causing Plasmodium spp. and lymphatic filariasis-causing Wuchereria bancrofti are co-endemic in many tropical and sub-tropical regions. Among molecular diagnostic assays, multiplex polymerase chain reaction (PCR)–based assays for the simultaneous detection of DNAs from these parasite species are currently available only for P. falciparum and W. bancrofti or P. vivax and W. bancrofti. Using a post-PCR oligonucleotide ligation detection reaction–fluorescent microsphere assay (LDR-FMA), we developed a multiplex assay that has the capability to simultaneously detect all four Plasmodium spp. and W. bancrofti infections in blood samples. Compared with microfilarial positivity in the blood, the LDR-FMA assay is highly concordant (91%), sensitive (86%), and specific (94%), and has high reproducibility for Plasmodium spp. (85–93%) and W. bancrofti (90%) diagnoses. The development of this assay for the simultaneous diagnosis of multiple parasitic infections enables efficient screening of large numbers of human blood and mosquito samples from co-endemic areas.
Can Daytime Use of Bed Nets Not Treated with Insecticide Reduce the Risk of Dengue Hemorrhagic Fever Among Children in Vietnam?
Authors: Tsuzuki Ataru , Thiem Vu Dinh , Suzuki Motoi , Yanai Hideki , Matsubayashi Toru , Yoshida Lay-Myint , Tho Le Huu , Minh Truong Tan , Anh Dang Duc , Kilgore Paul E. , Takagi Masahiro , Ariyoshi Koya
Published: June 2010

The purpose of this study was to investigate the prevalence of bed net use and elucidate the effect of daytime bed net use on preventing dengue hemorrhagic fever (DHF) among children in Vietnam. We conducted a population-based cross-sectional survey and a matched case–control study in Khanh Hoa Province where not only some pre-schoolchildren but also some school children, who take a nap during lunch break prior to returning to school, used bed nets during the day. Among 36,901 children 2–10 years of age, most used untreated bed nets during the night (98.3%) compared with 8.4% during the day. The results of the case–control study, which defined 151 cases who were hospitalized with DHF in the provincial hospitals and 604 age-matched neighborhood controls, did not support our hypothesis that children using untreated bed nets during the day are less likely to be hospitalized with DHF (adjusted odds ratio = 0.56, 95% confidence interval = 0.23–1.39).
An Insight into the Sialotranscriptome of Simulium nigrimanum, a Black Fly Associated with Fogo Selvagem in South America
Authors: Ribeiro José M. C. , Valenzuela Jesus G. , Pham Van M. , Kleeman Lindsay , Barbian Kent D. , Favreau Amanda J. , Eaton Donald P. , Aoki Valeria , Hans-Filho Gunter , Rivitti Evandro A. , Diaz Luis A.
Published: June 2010

Pemphigus foliaceus is a life threatening skin disease that is associated with autoimmunity to desmoglein, a skin protein involved in the adhesion of keratinocytes. This disease is endemic in certain areas of South America, suggesting the mediation of environmental factors triggering autoimmunity. Among the possible environmental factors, exposure to bites of black flies, in particular Simulium nigrimanum has been suggested. In this work, we describe the sialotranscriptome of adult female S. nigrimanum flies. It reveals the complexity of the salivary potion of this insect, comprised by over 70 distinct genes within over 30 protein families, including several novel families, even when compared with the previously described sialotranscriptome of the autogenous black fly, S. vittatum. The uncovering of this sialotranscriptome provides a platform for testing pemphigus patient sera against recombinant salivary proteins from S. nigrimanum and for the discovery of novel pharmacologically active compounds.
Identification of Stage Biomarkers for Human African Trypanosomiasis
Authors: Amin Daniel Ndem , Ngoyi Dieudonné Mumba , Nhkwachi Gondwe-Mphepo , Palomba Maria , Rottenberg Martin , Büscher Philippe , Kristensson Krister , Masocha Willias
Published: June 2010

Human African trypanosomiasis (HAT), caused by infection with sub-species of Trypanosoma brucei (T. b.), manifests as a hemolymphatic stage followed by an encephalitic stage. The distinction of the two stages needs improvement as drugs used for the late stage are highly toxic. Transcripts encoding 16 secreted proteins differentially expressed in the brains of mice at late stage T. b. brucei infection when the early stage drug suramin is no longer effective and different to immunoglobulins, chemokines, and cytokines, were selected by microarray analysis. Lipocalin 2 and secretory leukocyte peptidase inhibitor (SLPI) mRNA showed the highest differential expression in mice. These transcripts were also upregulated in brains from infected rats. Lipocalin 2 was increased in cerebrospinal fluid (CSF) from rats during late stage T. b. brucei infection. Protein levels of lipocalin 2, SLPI, and the chemokine CXCL10 were found increased in CSF from Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense late stage HAT compared to early stage.
Imported Enteric Fever: Case Series from the Hospital for Tropical Diseases, London, United Kingdom
Authors: Patel Trupti A. , Armstrong Margaret , Morris-Jones Stephen D. , Wright Stephen G. , Doherty Tom
Published: June 2010

Our current knowledge of the clinical characteristics of enteric fever is drawn mainly from population-based studies in disease-endemic countries, and there are limited data published on cases in returning travelers. We report the clinical characteristics of enteric fever in 92 travelers returning to London, United Kingdom. Salmonella typhi and S. paratyphi resulted in an almost indistinguishable clinical picture. Rose spots and relative bradycardia were found only in a few patients. A total of 91% of the patients had a normal leukocyte count, which was associated with a markedly increased level of alanine aminotransferase in 82%. A total of 57% of the S. typhi isolates had decreased susceptibility to ciprofloxacin and resistance to nalidixic acid; these isolates were from southern Asia. Thirty percent were multidrug resistant; all were from southern Asia and Nigeria. None of the paratyphoid isolates were multidrug resistant but rates of decreased susceptibility to fluoroquinolones were higher than in S. typhi (74%).
Growth limitation in young Euphausia superba under field conditions
Authors: Ross Robin M. , Quetin Langdon B. , Baker Karen S. , Vernet Maria , Smith Raymond C.
Published: June 2010

Growth rates of late furcilia and juvenile Antarctic krill (Euphausia superba Dana) in the spring and summer were related to food quantity and quality. The 4 yr covered by this study (1991–1992, 1993–1994, 1994–1995, and 1995–1996) were part of the seasonal time series of the Palmer Long‐Term Ecological Research program. Chlorophyll a concentrations represented food quantity, and accessory photosynthetic pigments represented phytoplank‐ton community composition or food quality. Instantaneous growth rates reflected the in situ nutritional history of the previous intermolt period. The response of krill to the food environment was seen on temporal scales of days to weeks. Percent growth per intermolt period (percentage growth IMP−1 ( varied significantly both within and between years, ranging from ∼2 to 10% IMP−1. Percent growth IMP−1 increased with increasing chlorophyll a (Chl a), reaching a maximum of 9.3% IMP−1 above a critical concentration of about 3.5 mg m 23 . Maximum growth was reached in only 2 yr, 1991–1992 and 1995–1996. In a multiple regression analysis, total Chl a and prymnesiophyte‐Chl a explained over 71% of the temporal variance in growth. In general, highest growth was found toward the end of diatom blooms and lowest during periods of low phytoplankton biomass or blooms dominated by cryptophytes and prymnesiophytes. The results of this study support the hypothesis that maximum growth rates are only possible during diatom blooms and that production in Antarctic krill is limited by both food quantity and quality.
Phytoplankton species diversity control through competitive exclusion and physical disturbances
Authors: Hambright K. David , Zohary Tamar
Published: June 2010

Competitive exclusion theory suggests that phytoplankton species number in an assemblage at equilibrium will be limited to the number of simultaneously limiting resources, generally three or fewer. However, natural phyto‐plankton assemblages usually exhibit high species diversity, hence the concept of Hutchinson's “paradox of the plankton”. Recent works have suggested that this apparent paradox is a result of disturbances intermediate in frequency relative to the time period necessary for species succession to lead to equilibrium conditions (sensu Connell's intermediate disturbance hypothesis [IDH]). Moreover, evidence indicates that disturbances of intermediate intensities are also conducive to maintenance of high species diversity in phytoplankton communities. Using a long‐term data record from hypereutrophic subtropical Hartbeespoort Dam (South Africa) that was typically dominated by a single species, but annually subjected to physical disturbance, we demonstrate here that disturbances can indeed enhance phytoplankton species diversity. However, these data fail to support Connell's IDH per se, as moderate‐and high‐intensity disturbances yielded similarly high species diversity. These data also suggest that community resilience (the ability or time to return to predisturbed conditions) is negatively related to disturbance intensity, such that higher intensity disturbances maintained high diversity for longer periods of time relative to lower intensity disturbances.
The role of nutrients in decomposition of a thecate dinoflagellate
Authors: Zohary Tamar , Güde Hans , Pollingher Utsa , Kaplan Bina , Pinkas Riki , Hadas Ora
Published: June 2010

The decomposition of freeze‐dried whole cells and empty thecae of the dinoflagellate Peridinium gatunense Nygaard originating from dense blooms in Lake Kinneret (Israel) was followed experimentally under controlled conditions in the lab. The two materials (whole cells; empty thecae) were suspended in replicate bottles containing nutrient‐poor epilimnetic water from the lake. After 7 d, nutrients (N, P, and trace metals) were added to half the bottles. We followed the changes with time in dry weight, the dynamics of nutrients, microbial abundances and a range of microbial activities including leucine incorporation rates and activities of hydrolytic enzymes. Because of the low N and P content of thecae (C:N:P atomic ratios >3000:19:1) relative to protoplasts (276:51:1), the microbial utilization of thecae was expected to depend much more on the availability of external nutrient sources than the utilization of protoplasts. Indeed, decomposition of thecae did not occur in the absence of external nutrients but was rapid (1–2 d to their disappearance) after nutrients were added. In contrast, almost no stimulating effect of nutrient addition was observed for the decomposition of whole cells. The results suggest that intensive regenerative nutrient cycling or external nutrient inputs are a necessary precondition for an efficient trophic transfer of the energy stored in blooms of thecate dinoflagellates. The high nutrient demands of microbial degradation imply furthermore a competition for nutrients between heterotrophic degradative and phototrophic productive processes. Because of the generally assumed stronger competitive ability of heterotrophic bacteria, reduced primary production is expected as an indirect result of dinoflagellate bloom degradation. Indeed, reduced primary production is observed in Lake Kinneret every summer after the decline of the annual Peridinium bloom in June–July.
Biological implications of surf‐zone flow complexity
Authors: Gaylord Brian
Published: June 2010

Wave action imposes potentially large hydrodynamic forces on intertidal plants and animals, and can act as a primary agent of disturbance. It has also been proposed that rapid water accelerations produced by breaking waves might constrain the sizes to which intertidal organisms can grow. However, despite the proven ecological importance of surf‐zone flows, few actual measurements of forces imposed on plants or animals by waves in nature have been conducted. In this study, real‐time wave forces acting on individuals of the rockweed Pelvetia compressa and a sea urchin Strongylocentrotus purpuratus are recorded in the field. These measured forces are compared with values predicted from theory using laboratory‐determined shape factors (i.e., drag and added mass coefficients) and simultaneous flow measurements conducted adjacent to the deployed samples. Results demonstrate that models predicting large contributions of force due to water's acceleration are likely inaccurate, most probably because such models fail to account for the small spatial scales of surf‐zone accelerations. This likely eliminates any capacity for intertidal hydrodynamic accelerational forces to limit size, contrary to previous conjectures. Data also suggest that wave‐induced forces predicted from simple fluid dynamic expressions can, but sometimes do not, reflect accurately the forces applied. Together these findings imply that although traditional hydrodynamic theory may indeed provide a valuable tool for predicting forces imposed on immersed surf‐zone organisms, such approaches must be used with caution. Finally, the field recordings suggest that sharp, transient forces arising from the impingement of waves directly on non‐submerged organisms may in general impose the most severe loadings experienced by intertidal plants and animals, a possibility that to date has received little attention. The precise consequences of such brief forces depend on the level of flexibility or rigidity of an organism's construction.
Phosorus availability in an acidified watershed‐lake ecosystem
Authors: Kopáček Jiřĺ , Hejzlar Josef , Borovec Jakub , Porcal Petr , Kotorova Ivana
Published: June 2010

Acid precipitation has been shown to reduce phosphorus (P) outputs from terrestrial sources. We present field evidence that the in‐lake P cycle may also be disrupted in atmospherically acidified watershed‐lake ecosystems. Plešné Lake in the Bohemian Forest is an acidified forest lake with epilimnetic pH of 4.5–4.9, total P concentration of ∼10 μg L−1, and pronounced anoxia above the bottom during winter and summer stratification periods. The water chemistry of the anoxic zone develops in a predictable way: After depletion of dissolved oxygen, concentrations of nitrate and sulfate decrease while concentrations of ammonium, iron, alkalinity, and pH increase; the only exception to the general pattern is a permanently low concentration of dissolved reactive P (<1 μg L−1 ) above the sediment.

This in‐lake P inactivation can be explained by the acidification of soils in the watershed and subsequent precip‐itation of Al in the lake. The suggested mechanism is as follows: atmospheric deposition of strong acids has resulted in strong acidification and nitrogen saturation of soils in the Plešné Lake watershed and, consequently, in high terrestrial losses of Al (0.78–1.04 mg L−1 ), SO42− (4.5–7.7 mg L−1 ), and NO3− (0.48 –1.15 mg L−1 NO3 ‐N) to the lake. Biological removal of NO3− and SO42− by both assimilatory and dissimilatory reduction contributes greatly to the total in‐lake alkalinity generation and to the increase in water pH. Under higher pH, ionic Al species hydrolyze and form colloidal Al hydroxides (Alpart), which coagulate dissolved organic carbon and adsorb orthophosphate in the water column. The Al hydroxides settle and increase the P sorption capacity of the sediment. The elevated content of fresh Al oxyhydroxides in the surface sediment reduces P release to the water column after orthophosphate liberation from ferric oxyhydroxides during anoxia, because Alpart complexes are not sensitive to redox changes. The example of Plešné Lake shows that atmospheric acidification of a watershed‐lake ecosystem may provide the natural conditions for in‐lake P inactivation similar to the lake restoration technique based on the artificial addition of Al salt to the water column.
Further evidence of elemental composition as an indicator of the bioavailability of humic substances to bacteria
Authors: Hunt A. P. , Parry J. D. , Hamilton‐Taylor J.
Published: June 2010

Batch culture experiments examined the ability of an isolated bacterial community to utilize four humic substances with similar molecular size but variable elemental composition. Univariate and multivariate linear regression analysis of the results provided evidence of a significant positive relationship between the N:C ratio and bacterial concentrations. In contrast, neither H:C nor O:C ratios were significant predictors of humic substances bioavailability, and their inclusion in the multivariate model provided no further explanatory power compared with the univariate model using N:C as the single independent variable. These findings suggest that N:C ratios provide the best indicator of bioavailability for complex, recalcitrant carbon moieties typical of many aquatic systems.
Light sensitivity in larval fishes: Implications for vertical zonation in the pelagic zone
Authors: Job Suresh D. , Bellwood David R.
Published: June 2010

Larval fishes exhibit marked vertical zonation patterns that are important in planktonic predator‐prey interactions. This zonation has been related to both proximate physical (e.g., light intensity) and ultimate biological factors (e.g., predator risk, prey availability). We hypothesize that changes in visual sensitivity and feeding performance in larval fishes provide a constraint on depth distributions and that this constraint may represent the major determinant of vertical distribution patterns. To test the generality of the relationship between larval age and visual sensitivity, larvae were obtained from captive breeding adults of seven species (three Apogonidae and four Pomacentridae). The lowest light intensity at which feeding behavior occurred was measured using infrared video techniques with natural prey items. The visual sensitivity of the larvae, measured as initiation of feeding, increased by about 3 orders‐of‐magnitude during the larval phase. The abilities of the larvae were broadly similar within families, but there were marked differences between families. Pomacentrids were about an order‐of‐magnitude less light‐sensitive than apogonids. Larval apogonids are potentially capable of feeding at a depth of about 100 m in clear tropical waters at 4 mm standard length (SL) and to 200 m at 12 mm SL. The patterns of ontogenetic and phylogenetic differences in light sensitivity are consistent with field observations on the vertical distributions of larvae in these taxa.
Response of life history traits to food conditions in a cyclopoid copepod from an oligotrophic environment
Authors: Makino Wataru , Ban Syuhei
Published: June 2010

The Cyclops sp. responses of life history traits (growth, development, and reproduction) to food conditions from oligotrophic Lake Toya were analyzed by rearing animals individually under four food regimes:three densities of the alga Cryptomonas tetrapyrenoidosa and nauplii of the calanoid copepod Eurytemora affinis as prey in an algal suspension. Cyclops sp. grew successfully from newborn nauplii to adults when algal density was ≥4 × 103 cells ml‐1 . Development time was shorter and body length larger in the high‐density (H) treatment (4 × 104 cells ml‐1 ) than in medium‐density (M) treatment (4 × 103 cells ml−1) until the early copepodite stages. In late copepodite stages, females tended to grow more slowly but tended to be larger in the M treatment than in the H treatment. However, stage‐specific growth rates were similar among treatments during development, suggesting a trade‐off between body size and development time. Although the egg production rate was higher in the M treatment than in the H treatment, it depended on female body size regardless of the food regime. Furthermore, the weight‐specific egg production rate was the same among treatments, indicating egg production was not affected by the algal concentrations tested. Addition of copepod prey influenced neither postembryonic development time nor body size, and egg production rates were comparable to those reared with an algal diet. These results reveal that even older copepodites and adults, which are generally thought to be predacious, do not necessarily require animal prey for growth and reproduction, and that Cyclops sp. can complete its life cycle on an algal diet alone. For female Cyclops sp., reduction of algal density resulted in slow development and large body size, which might be an adaptation to the oligotrophic environment, the original habitat of the copepod.
Measuring life‐history omnivory in the opossum shrimp, Mysis relicta, with stable nitrogen isotopes
Authors: Branstrator Donn K. , Cabana Gilbert , Mazumder Asit , Rasmussen Joseph B.
Published: June 2010

Mysis relicta is a species of omnivorous zooplankton that has been implicated over the last several decades in important food‐web processes such as the lengthening of food chains, the mobilization of benthic contaminants to the pelagic, and the restructuring of community dynamics. We used stable nitrogen isotopes (δ15N) to quantify ontogenetic diet shifting of M. relicta in five North American lakes. Analyses indicated that M. relicta measuring >1.5 cm were elevated, on average, 0.73 trophic levels above conspecifics measuring <1‐cm length, and 0.57 trophic levels above conspecifics measuring <1 but >1.5‐cm length. This pattern suggests a trend toward increasing carnivory with maturity, which is consistent with the results of previous conventional approaches to diet analysis in this species. Our results should be useful to modelers concerned with quantifying the effects of M. relicta on energy transfer and contaminant bioaccumulation in food chains.
Size distribution of marine submicron particles determined by flow field‐flow fractionation
Authors: Vaillancourt Robert D. , Balch William M.
Published: June 2010

Flow field‐flow fractionation (flow FFF) with power field‐strength programming was used to size fractionate submicron particles (colloids) in coastal seawater. All analyses used filtered seawater as carrier solution to preserve the native chemical environment of the colloids. Our fractograms show colloid size distributions with major peaks centered at 50 to 60 nm for samples that were size fractionated immediately following the preconcentration step. Preconcentrated samples that had aged for 2 to 5 d revealed the presence of an additional larger sized particle (or aggregate) peak with indeterminate size. Errors in colloid sizing may result if the physical and chemical behaviors of the particle size standards are not mimicked by those of the colloids during separation in the flow FFF channel. Particle detection using absorbance meters, such as the ultraviolet (UV) detector used here, greatly underestimates the contribution of smaller particles (ca. <100 nm) due to the exceedingly small optical efficiency of particles within this size‐refractive index domain.
Transport and degradation of phytoplankton in permeable sediment
Authors: Huettel Markus , Rusch Antje
Published: June 2010

In flume and field experiments we demonstrate that interfacial water flows, generated when bottom currents interact with sea bed topography, provide a fast and efficient pathway for the transport of suspended phytoplankton into subsurface layers of permeable sandy sediments. The advective transport, associated with small mounds and ripples as commonly found on shelf sediments, increased penetration depth of unicellular algae (Dunaliella spec.) into sandy sediment (permeability k = 4 × 10−11 m2) up to a factor of 7 and flux up to a factor of 9 relative to a smooth control sediment. The pore water flow field produced a distinct distribution pattern of particulate organic matter in the sediment with subsurface concentration maxima and zones depleted of algae. Flux chamber simulations of advective transport of algae into sands of different grain sizes revealed increasing fluxes, algal penetration depths, and degradation rates with increasing permeability of the sediment. Two experiments conducted in intertidal sand flats confirmed the importance of the advective interfacial transport of phytoplankton for natural settings, showing permeability‐dependent penetration of planktonic algae into embedded sand cores of different grain sizes. The significance of our results is discussed with respect to particulate organic matter flux and mineralization in shelf sands, and we suggest the concept of a decomposition layer.
The effect of dietary nitrogen content on trophic level 15N enrichment
Authors: Adams Thomas S. , Sterner Robert W.
Published: June 2010

Given the great potential value of stable isotopes in a variety of scientific investigations, surprisingly little attention has been paid to the underlying physiological and biochemical mechanisms that account for trophic increases in ;415N values. This has lead to a general call for controlled studies investigating the relationship between organismal diet and corresponding isotopic composition. We conducted a series of laboratory studies varying dietary nitrogen content and measuring corresponding variations in organismal ;415N values. Specifically, we investigated the relationship between the ;415N values of the anomopod crustacean, Daphnia magna, and the C:N ratio of its food, the green algae, Scenedesmus acutus. Daphnids were raised to a standard life stage on three types of S. acutus as food, which ranged in C:N (atomic) from 7.3 to 24.8. The average C:N of the daphnids was 6.0. 15N enrichment was found to be strongly linearly related to the C:N of the algae, ranging from nearly zero to approximately 6‰, which would normally be considered a span of almost two trophic levels. The d15N values of the daphnids and the diet‐tissue isotope fractionation factor, (Δdt = D. magna ;415N – S. acutus ;415N), were inversely related to the nitrogen content of the algae (R2 = 0.82 and 0.99 in two separate runs). To our knowledge, this is the first controlled study of nitrogen balance and d15N values in animals.
Functional response of the appendicularian Oikopleura dioica
Authors: Acuña José Luis , Kiefer Markus
Published: June 2010

Different concentrations of 14C radiolabeled cultures of the prymnesiophyte Isochrysis galbana (5.5 µm in size), the prasinophyte Tetraselmis suecica (9.5 µm), and the chlorophyte Chlorella sp. (3.5 µm) were offered as food to groups of 2–5 Oikopleura dioica to determine the response of clearance (CR) and ingestion (IR) rates to food concentration (FC). At high FCs of I. galbana, IR and CR of O. dioica decreased with age of the house. Aging had little effect on the functional response (FR) because most of the decrease in IR and CR occurred during the initial 10% of the house lifespan. The FR resembled a type II model for the IR and presented saturation and inhibition at high FC (>100 µg C L−1)of I. galbana. Fits of FR curves of the IR of animals weighing ca. 3 µg C ind−1 to a Michaelis Menten model yielded Imax (maximum IR) of 198 ± 28, 498 ± 171, and 489 ± 150 ng C ind−1 h−1 and Km (half saturation FC) of 38 ± 21, 225 ± 177, and 290 ± 205 µg C L−1 for the prey I. galbana, T. suecica, and Chlorella sp., respectively. The Km values are high and in two of three cases exceed the maximum concentration of ingestible particles found in the natural habitat, which suggests that O. dioica is adapted to high phytoplankton concentrations. In contrast with classical FR models, CR remained nearly constant for all concentrations. Particles cleared from suspension by O. dioica are ingested and transformed into fast‐sinking fecal pellets at low FC, while they are mainly accumulated into slow to fast‐sinking filter houses at high FC, which implies considerable shifts in the biogeochemical role of these animals with changing particle concentrations.