bluuebunny/crossref_metadata_2025 huggingface dataset:
IFN-αβ and Self-MHC Divert CD8 T Cells into a Distinct Differentiation Pathway Characterized by Rapid Acquisition of Effector Functions
Authors: Marshall Heather D. , Prince Amanda L. , Berg Leslie J. , Welsh Raymond M.
Published: July 2010

Nonvirus-specific bystander CD8 T cells bathe in an inflammatory environment during viral infections. To determine whether bystander CD8 T cells are affected by these environments, we examined P14, HY, and OT-I TCR transgenic CD8 T cells sensitized in vivo by IFN-αβ–inducing viral infections or by polyinosinic:polycytidylic acid. These sensitized cells rapidly exerted effector functions, such as IFN-γ production and degranulation, on contact with their high-affinity cognate Ag. Sensitization required self-MHC I and indirect effects of IFN-αβ, which together upregulated the T-box transcription factor Eomesodermin, potentially enabling the T cells to rapidly transcribe CTL effector genes and behave like memory cells rather than naive T cells. IL-12, IL-15, IL-18, and IFN-γ were not individually required for sensitization to produce IFN-γ, but IL-15 was required for upregulation of granzyme B. These experiments indicate that naive CD8 T cells receive signals from self-MHC and IFN-αβ and that, by this process, CD8 T cell responses to viral infection can undergo distinct differentiation pathways, depending on the timing of Ag encounter during the virus-induced IFN response.
A Controlled, Randomized-Blinded Clinical Trial to Assess the Efficacy of a Nitric Oxide Releasing Patch in the Treatment of Cutaneous Leishmaniasis by Leishmania (V.) panamensis
Authors: López-Jaramillo Patricio , Rincón Melvin Y. , García Ronald G. , Silva Sandra Y. , Smith Erin , Kampeerapappun Piyaporn , García Carlos , Smith Daniel J. , López Marcos , Vélez Iván D.
Published: July 2010

A topical nanofiber nitric oxide (NO) releasing patch (≈3.5 μmol NO/cm2/day for 20 days, NOP) was compared with intramuscular meglumine antimoniate (Glucantime, 20 mg/kg/day for 20 days) for the treatment of cutaneous leishmaniasis (CL) caused by Leishmania (V.) panamensis in Santander and Tolima, Colombia. A double-blind, randomized, placebo-controlled, clinical trial was conducted to determine whether the NOP is as effective as Glucantime for the treatment of CL. Patients were randomly assigned to Glucantime and placebo patches or NOP and placebo of Glucantime. The cure rates after a 3-month follow-up were 94.8% for the group that received Glucantime compared with 37.1% in the NOP group. Despite the lower efficacy of the NOP versus Glucantime, a significantly lower frequency of non-serious adverse events and a reduced variation in serum markers were observed in patients treated with NOP. Treatment of CL with NOP resulted in a lower effectiveness compared with Glucantime; however, the low frequency of adverse events and the facility of topic administration justify the development of new generations of NOP systems for the treatment of CL.
Use of Statewide Hospital Discharge Data to Evaluate the Economic Burden of Neurocysticercosis in Los Angeles County (1991–2008)
Authors: Croker Curtis , Reporter Roshan , Mascola Laurene
Published: July 2010

Statewide hospital discharge data were used to assess the economic burden of neurocysticercosis in Los Angeles County (LAC) from 1991 through 2008. A neurocysticercosis hospitalization was defined as having a discharge diagnosis of cysticercosis in addition to convulsions, seizures, hydrocephalus, cerebral edema or cerebral cysts. This study identified 3,937 neurocysticercosis hospitalizations, with the number of annual hospitalizations remaining relatively unchanged over the study period (R2 = 0.01), averaging 219 per year (range 180–264). The total of all neurocysticercosis hospitalization charges over the study period was $136.2 million, averaging $7.9 million per year. The average charge per patient was $37.6 thousand and the most common payment method was Medicaid (43.9%), followed by private insurance (24.5%). The average length of stay was 7.2 days. The substantial number of hospitalizations and significant economic cost underscore the importance of neurocysticercosis in LAC.
Serologic and Molecular Characteristics of Hepatitis B Virus among School Children in East Java, Indonesia
Authors: Utsumi Takako , Yano Yoshihiko , Lusida Maria Inge , Amin Mochamad , Soetjipto  , Hotta Hak , Hayashi Yoshitake
Published: July 2010

Universal childhood hepatitis B vaccination was introduced in Indonesia in 1997; by 2008, coverage was estimated to be 78%. This study aimed to investigate the serologic status and virologic characteristics of hepatitis B virus (HBV) among the children in East Java. A total of 229 healthy children born during 1994–1999 were enrolled in this study. Overall, 3.1% were positive for hepatitis B surface antigen (HBsAg) and 23.6% were positive for antibody to HBsAg (anti-HBs). HBV DNA was detected in 5 of 222 HBsAg-negative carriers, which were suggested to be cases of occult HBV infection. A single amino substitution (T126I) in the S region was frequently found. HBV infection remains endemic, and the prevalence of anti-HBs remains insufficient among children in East Java, Indonesia.
Visceral Leishmaniasis Treated with Antimonials/Paromomycin followed by Itraconazole/Miltefosine after Standard Therapy Failures in a Human Immunodeficiency Virus–Infected Patient
Authors: Barragán Patricia , López-Velez Rogelio , Olmo Montserrat , Podzamczer Daniel
Published: July 2010

Visceral leishmaniasis is an opportunistic infection that affects human immunodeficiency virus–infected persons in leishmaniasis-endemic areas. The standard treatment may not be effective and relapses are common. We report the case of a human immunodeficiency virus-1–infected patient who had several relapses of visceral leishmaniasis after treatment with standard therapies and responded to a combined therapy.
Survey for Tick-Borne Zoonoses in the State of Espirito Santo, Southeastern Brazil
Authors: Spolidorio Mariana G. , Labruna Marcelo B. , Machado Rosangela Z. , Moraes-Filho Jonas , Zago Augusto M. , Donatele Dirlei M. , Pinheiro Sônia R. , Silveira Iara , Caliari Késia M. , Yoshinari Natalino H.
Published: July 2010

Blood samples collected from 201 humans, 92 dogs, and 27 horses in the state of Espirito Santo, Brazil, were tested by polymerase chain reaction, indirect immunofluorescence assays, and indirect enzyme-linked immunosorbent assay for tick-borne diseases (rickettsiosis, ehrlichiosis, anaplasmosis, borreliosis, babesiosis). Our results indicated that the surveyed counties are endemic for spotted fever group rickettsiosis because sera from 70 (34.8%) humans, 7 (7.6%) dogs, and 7 (25.9%) horses were reactive to at least one of the six Rickettsia species tested. Although there was evidence of ehrlichiosis (Ehrlichia canis) and babesiosis (Babesia canis vogeli, Theileria equi) in domestic animals, no human was positive for babesiosis and only four individuals were serologically positive for E. canis. Borrelia burgdorferi-serologic reactive sera were rare among humans and horses, but encompassed 51% of the canine samples, suggesting that dogs and their ticks can be part of the epidemiological cycle of the causative agent of the Brazilian zoonosis, named Baggio-Yoshinari Syndrome.
Identification of a Hyperendemic Area for Trypanosoma cruzi Infection in Central Veracruz, Mexico
Authors: Ramos-Ligonio Angel , López-Monteon Aracely , Guzmán-Gómez Daniel , Rosales-Encina José Luis , Limón-Flores Yairh , Dumonteil Eric
Published: July 2010

The state of Veracruz, Mexico, is a well-recognized endemic region for Chagas disease, but the geographic distribution of the disease and its magnitude are still poorly documented. We evaluated the seroprevalence of Trypanosoma cruzi infection in the sanitary jurisdictions of Cordoba and Cosamaloapan in central Veracruz. A total of 654 serum samples from 19 rural localities were tested by using four tests: two enzyme-linked immunosorbent assays, an indirect immunofluorescent, and Western blotting. Overall, 110 (16.8%) of 654 samples were positive for T. cruzi by ≥ 2 tests (95% confidence interval = 14.2–19.9%). The municipality of Tezonapa in the jurisdiction of Cordoba was identified as a potential hyperendemic region with seroprevalence rates ≤ 45% in young children. No cases were detected in the jurisdiction of Cosamaloapan. Further studies should help clarify T. cruzi transmission dynamics in Tezonapa. The magnitude of T. cruzi infection rate in this region calls for the urgent implementation of extensive epidemiologic surveillance and control programs.
Analysis of the mdr-1 Gene in Patients Co-Infected with Onchocerca volvulus and Loa loa Who Experienced a Post-Ivermectin Serious Adverse Event
Authors: Bourguinat Catherine , Kamgno Joseph , Boussinesq Michel , Mackenzie Charles D. , Prichard Roger K. , Geary Timothy G.
Published: July 2010

Ivermectin (IVM) is exceptionally safe in humans, and is used for mass treatment of onchocerciasis and lymphatic filariasis. However, cases of encephalopathy, sometimes fatal, have been reported in a small number of individuals who harbored large numbers of Loa loa microfilariae (mf). A loss-of-function mutation in the mdr-1 gene in some dog breeds and in mice leads to accumulation of the drug in the brain, causing coma and death. This hypothesis was tested in four individuals from Cameroon who experienced a post-IVM serious adverse event (SAE) and in nine non-SAE matched controls. No loss-of-function mutation was detected in mdr-1 in any subject. However, haplotypes, associated with altered drug disposition, were present as homozygotes in two of the SAE patients (50%), but absent as homozygotes in the controls (0%). An association of high Loa mf load and a genetic predisposition to altered IVM distribution could be involved in IVM SAEs.
Short Course Combination Therapy for Giardiasis after Nitroimidazole Failure
Authors: Lopez-Velez Rogelio , Batlle Carolina , Jiménez Carolina , Navarro Miriam , Norman Francesca , Perez-Molina Jose
Published: July 2010

Recommended first line treatments for giardiasis include the nitroimidazoles and, recently, nitazoxanide. For refractory cases, a combination of two or more drugs may be a viable approach. A review of 10 patients with giardiasis refractory to nitroimidazoles with response to a short course (< 2 weeks), combined treatment is presented.
Rocky Mountain Spotted Fever in the United States, 2000–2007: Interpreting Contemporary Increases in Incidence
Authors: Openshaw John J. , Swerdlow David L. , Krebs John W. , Holman Robert C. , Mandel Eric , Harvey Alexis , Haberling Dana , Massung Robert F. , McQuiston Jennifer H.
Published: July 2010

Rocky Mountain spotted fever (RMSF), a potentially fatal tick-borne infection caused by Rickettsia rickettsii, is considered a notifiable condition in the United States. During 2000 to 2007, the annual reported incidence of RMSF increased from 1.7 to 7 cases per million persons from 2000 to 2007, the highest rate ever recorded. American Indians had a significantly higher incidence than other race groups. Children 5–9 years of age appeared at highest risk for fatal outcome. Enzyme-linked immunosorbent assays became more widely available beginning in 2004 and were used to diagnose 38% of cases during 2005–2007. The proportion of cases classified as confirmed RMSF decreased from 15% in 2000 to 4% in 2007. Concomitantly, case fatality decreased from 2.2% to 0.3%. The decreasing proportion of confirmed cases and cases with fatal outcome suggests that changes in diagnostic and surveillance practices may be influencing the observed increase in reported incidence rates.
Environmental and Biological Factors Influencing Culex pipiens quinquefasciatus (Diptera: Culicidae) Vector Competence for West Nile Virus
Authors: Richards Stephanie L. , Lord Cynthia C. , Pesko Kendra N. , Tabachnick Walter J.
Published: July 2010

Interactions between environmental and biological factors affect the vector competence of Culex pipiens quinquefasciatus for West Nile virus. Three age cohorts from two Cx. p. quinquefasciatus colonies were fed blood containing a low- or high-virus dose, and each group was held at two different extrinsic incubation temperatures (EIT) for 13 days. The colonies differed in the way that they responded to the effects of the environment on vector competence. The effects of mosquito age on aspects of vector competence were dependent on the EIT and dose, and they changed depending on the colony. Complex interactions must be considered in laboratory studies of vector competence, because the extent of the genetic and environmental variation controlling vector competence in nature is largely unknown. Differences in the environmental (EIT and dose) and biological (mosquito age and colony) effects from previous studies of Cx. p. quinquefasciatus vector competence for St. Louis encephalitis virus are discussed.
Indigenous Plasmodium ovale Malaria in Bangladesh
Authors: Fuehrer Hans-Peter , Starzengruber Peter , Swoboda Paul , Khan Wasif Ali , Matt Julia , Ley Benedikt , Thriemer Kamala , Haque Rashidul , Yunus Emran Bin , Hossain Shah Monir , Walochnik Julia , Noedl Harald
Published: July 2010

In spite of the high prevalence of malaria in Southeastern Bangladesh, there remains a significant shortage of information regarding the presence of three of five human malaria parasites: Plasmodium ovale, P. malariae, and P. knowlesi. The presence of P. ovale and P. knowlesi has previously never been reported from Bangladesh. We used a genus- and species-specific nested polymerase chain reaction, targeting highly conserved regions of the small subunit ribosomal RNA (SSU rRNA) gene, to investigate the presence of malaria parasites in a total number of 379 patient samples in a survey of patients with febrile illnesses in the Chittagong Hill Tracts in Southeastern Bangladesh. We identified the first cases of P. ovale in Bangladesh. They were confirmed by sequence analysis; 189 of 379 samples (49.9%; 95% confidence interval = 44.9–54.9%) were positive for Plasmodium sp. by PCR. P. falciparum monoinfections accounted for 68.3% (61.3–74.5%), followed by P. vivax (15.3%; 10.9–21.2%), P. malariae (1.6%; 0.5–4.6%), P. ovale (1.6%; 0.5–4.6%), and mixed infections (13.2%; 9.1–18.8%). We found no evidence of P. knowlesi in this region.
Hepatitis B Infection and Association with Other Sexually Transmitted Infections Among Men Who Have Sex with Men in Peru
Authors: Lama Javier R. , Agurto Hellen S. , Guanira Juan V. , Ganoza Carmela , Casapia Martin , Ojeda Nora , Ortiz Abner , Zamalloa Victoria , Suarez-Ognio Luis , Cabezas Cesar , Sanchez Jose L. , Sanchez Jorge
Published: July 2010

To assess the epidemiology of hepatitis B virus (HBV) infection among men who have sex with men (MSM) in Peru, we evaluated the prevalence and associated risk factors for HBV serologic markers among participants of a HIV sentinel surveillance conducted in 2002–2003. The standardized prevalences for total antibodies to hepatitis B core antigen (anti-HBc) and hepatitis B surface antigen (HBsAg) were 20.2% and 2.8%, respectively. Individuals with human immunodeficiency virus (HIV-1) infection had significantly higher anti-HBc (44.3% versus 19.3%) and HBsAg (9.5% versus 2.3%) prevalences than uninfected men. Increasing age (adjusted odds ratio [AOR] = 1.06), versatile sexual role (AOR = 1.59), sex in exchange for money/gifts (AOR = 1.58), syphilis (AOR = 1.74), HIV-1 infection (AOR = 1.64), and herpes simplex virus type 2 (HSV-2, AOR = 2.77) infection were independently associated with anti-HBc positivity, whereas only HIV-1 infection (AOR = 3.51) and generalized lymph node enlargement (AOR = 3.72) were associated with HBsAg positivity. Pre-existing HBV infection is very common among Peruvian MSM and was correlated with sexual risk factors. MSM in Peru constitute a target population for further HBV preventive and treatment interventions.
Sulfadoxine-Pyrimethamine–Based Intermittent Preventive Treatment, Bed Net Use, and Antenatal Care during Pregnancy: Demographic Trends and Impact on the Health of Newborns in the Kassena Nankana District, Northeastern Ghana
Authors: Oduro Abraham R. , Fryauff David J. , Koram Kwadwo A. , Rogers William O. , Anto Francis , Atuguba Frank , Anyorigiya Thomas , Adjuik Martin , Ansah Patrick , Hodgson Abraham , Nkrumah Francis
Published: July 2010

Demographics and health practices of 2,232 pregnant women in rural northeastern Ghana and characteristics of their 2,279 newborns were analyzed to determine benefits associated with intermittent preventive treatment (IPTp), antenatal care, and/or bed net use during pregnancy. More than half reported bed net use, 90% reported at least two antenatal care visits, and > 82% took at least one IPTp dose of sulfadoxine-pyrimethamine. Most used a bed net and IPTp (45%) or IPTp alone (38%). Low birth weight (< 2,500 grams) characterized 18.3% of the newborns and was significantly associated with female sex, Nankam ethnicity, first-born status, and multiple births. Among newborns of primigravidae, IPTp was associated with a significantly greater birth weight, significantly fewer low birth weight newborns, improved hemoglobin levels, and less anemia. Babies of multigravidae derived no benefit to birth weight or hemoglobin level from single or multiple doses of sulfadoxine-pyrimethamine during pregnancy. No differences or benefits were seen when a bed net was the only protective factor.
Unmasking Leprosy: An Unusual Immune Reconstitution Inflammatory Syndrome in a Patient Infected with Human Immunodeficiency Virus
Authors: Bussone Guillaume , Charlier Caroline , Bille Emmanuelle , Caux Frédéric , Lévy Annie , Viard Jean-Paul , Lecuit Marc , Lortholary Olivier
Published: July 2010

Immune reconstitution inflammatory syndrome (IRIS) has become a frequent and potentially severe complication after initiation of following antiretroviral therapy (ART) in patients infected with human immunodeficiency virus (HIV). IRIS can unmask a previously clinically silent infection, such as tuberculosis, as recently described for Mycobacterium infections. We describe a case in a patient from Côte d'Ivoire living in France in whom skin papular lesions developed after initiation of ART. These lesions were associated with microbiologically proven leprosy. Thus, latent leprosy can appear as IRIS, and leprosy-associated IRIS should be considered in HIV-infected patients from areas endemic for leprosy.
Development of a deep chlorophyll maximum of Heterocapsa triquetra Ehrenb. at the entrance to the Gulf of Finland
Authors: Kononen Kaisa , Huttunen Maija , Hällfors Seija , Gentien Patrick , Lunven Michel , Huttula Timo , Laanemets Jaan , Lilover Madis , Pavelson Juss , Stips Adolf
Published: July 2010

The development of a deep chlorophyll maximum (DCM) at a depth of 30–35 m was followed during a 15‐d case study in July 1998 at the entrance to the Gulf of Finland. The study consisted of three 18–24‐h periods of biological (chlorophyll a, phytoplankton, primary production), chemical (nitrate, phosphate) and physical (CTD, turbulence, vertical particle size distribution) measurements at an anchor station and six mesoscale towed CTD/ fluorometer mappings over the surrounding area. Exceptionally cold and windy weather led to a red tide of the dinoflagellate Heterocapsa triquetra instead of the cyanobacterial bloom that frequently occurs in late summer. Comparison of the estimated amount of nitrogen required for an H. triquetra bloom biomass with external loading affirmed that the bloom had been formed on the basis of the nitrate pool below the thermocline. The development of the bloom, therefore, led to the extremely deep nitracline. The DCM formed by H. triquetra developed at the top of the nitracline at an illumination of <0.1% of the sea surface illumination. A temperature‐salinity analysis showed that the DCM was not caused by intrusions from inshore regions. It was concluded that the DCM was formed as a result of changing migratory behavior of H. triquetra after an upwelling event that fertilized the upper layer with phosphorus.
Phytoplankton primary production and photosynthetic parameters in reservoirs along a gradient of watershed land use
Authors: Knoll Lesley B. , Vanni Michael J. , Renwick William H.
Published: July 2010

We investigated how watershed land use (a gradient of agricultural vs. forested land) relates to phytoplankton primary production (PPr) and photosynthetic parameters in 12 reservoirs in Ohio and examined spatial variation in these parameters. Shallow sites near stream inflows had higher light attenuation, total phosphorus (TP), chlorophyll, nonvolatile suspended solids (NVSS), light‐saturated photosynthesis (PBm), and volumetric PPr than deeper sites near dam outflows, but areal PPr and the initial slope of the photosynthesis‐irradiance curve (αB) were not significantly different between sites. Mean mixed layer irradiance and the severity of light limitation did not differ between sites because shallower depths compensated for higher light attenuation at inflow sites. Watershed land use (percent agriculture) was only weakly (but significantly) related to mean annual PPr, TP, and chlorophyll, but there was a well‐defined upper limit to the effect of land use on all three of these parameters. Multiple regression showed that inclusion of additional watershed factors (the ratio of watershed land area to reservoir volume and the ratio of cropland area to number of livestock) greatly increased the variance explained compared to land use alone. TP and chlorophyll were highly correlated with each other and with PPr. Comparison of our TP‐chlorophyll, TP‐PPr, and chlorophyll‐PPr regressions with those of other studies suggests that reservoirs have lower PPr per unit TP than natural lakes, probably because of lower light intensity and higher concentrations of nonalgal P in reservoirs.
Urease activity in cultures and field populations of the toxic dinoflagellate Alexandrium
Authors: Dyhrman Sonya T. , Anderson Donald M.
Published: July 2010

Nitrogen availability is an important factor controlling phytoplankton abundance and species composition in marine waters. In addition to inorganic nitrogen, some phytoplankton species can use dissolved organic nitrogen sources such as urea for growth. Herein we demonstrate that axenic laboratory cultures of the toxic dinoflagellate, Alexandrium fundyense strain CB301A and A. catenella strain TN9A were able to grow on urea as a sole nitrogen source in the presence of nickel. This nickel dependence suggests that these Alexandrium species hydrolyze urea into ammonia with the enzyme urease rather than adenosine triphosphate urea amidolyase. Cells grown on urea had lower toxin content (15%‐30%) than f/2‐grown cells. In A. fundyense the urease enzyme appears to be nitrogen‐regulated. In culture experiments, enzyme activity was highest in nitrate‐starved and urea‐grown (replete) cells, whereas activity was undetectable in f/2‐grown (replete) and phosphate‐starved cells. Urease activity in ammonia‐grown (replete) cells was also depressed. Urease activity also appeared to increase with decreasing nitrate‐limited growth rate in semicontinuous cultures. May and June cruises in the Gulf of Maine followed the yearly bloom of A. fundyense. On average, inorganic nitrogen concentrations in May were higher than in June, whereas cell abundances, urea concentrations, and urease activity in May were lower than in June. The latter measurements relied on an immunomagnetic bead separation to isolate living A. fundyense cells from mixed phytoplankton samples for analysis. The differences between May and June suggest that urea may be important for Alexandrium nutrition as inorganic nitrogen concentrations in surface water decline.
Resource quality effects on life histories of Daphnia
Authors: Becker Claes , Boersma Maarten
Published: July 2010

We investigated the changes in life histories imposed on the water flea, Daphnia magna, due to biochemical and mineral limitations. Phosphorus‐deficient Scenedesmus obliquus were incubated with or without a single essential fatty acid, eicosapentaenoic acid (EPA). Additionally, the algae were spiked with dissolved phosphorus to create a range of C: P ratios from 600 to 200. This procedure created the possibility to study the importance of different essential resources. We found that somatic growth is retarded until a C: P ratio (molar) ~350 is reached. Adding more phosphorus did not further increase growth. At the same time, at high C: P ratios the addition of EPA did not make a difference in growth, whereas below the nutrient threshold (C : P = 350), the fatty acid had a strong positive impact on growth. In a second experiment we studied how the food conditions (with regard to EPA) affected the growth and investment in reproduction and whether this effect was passed on to the next generation. We found that animals fed EPA made an earlier and larger investment in reproduction. Also, the EPA‐enriched animals had a higher mortality. The juveniles from mothers fed EPA‐enriched algae had a higher growth rate than neonates from control mothers.
Response of freshwater microcosm communities to nutrients, fish, and elevated temperature during winter and summer
Authors: McKee D. , Atkinson D. , Collings S. E. , Eaton J. W. , Gill A. B. , Harvey I. , Hatton K. , Heyes T. , Wilson D. , Moss B.
Published: July 2010

Under conditions of stress, shallow freshwater ecosystems can undergo a state change characterized by the rapid loss of macrophytes and subsequent dominance of phytoplankton. Elevated water temperature may promote such change. Here we report the impact of two warming regimes (continuous 3°C above ambient and 3°C above ambient during summer only), with two nutrient loadings and the presence or absence of fish, on 48 microcosm ecosystems created to mimic shallow pond environments. We found that warming did not significantly encourage phytoplankton blooms, even in combination with increased nutrients and fish. Instead, macrophyte communities remained dominant. Macrophyte‐associated invertebrates (gastropods and ostracods) increased in numbers in the warmed microcosms, potentially helping to stabilize the macrophyte communities. Nevertheless, warming produced trends in water chemistry that could be problematic. It increased phosphorus concentrations, total alkalinity, and conductivity. It decreased pH and oxygen saturation and increased the frequency of severe deoxygenation. These trends were largely independent of the other experimental treatments and support the suggestion that moderate warming has the potential to exacerbate existing eutrophication problems.
Effect of ultraviolet light on dissolved nitrogen transformations in coastal lagoon water
Authors: Buffam Ishi , McGlathery Karen J.
Published: July 2010

The effect of ultraviolet radiation on the production of inorganic nitrogen, urea, and amino acids from aquatic dissolved organic matter (DOM) was investigated for waters from Hog Island Bay, a coastal lagoon in Virginia. Waters representing distinct sources of DOM to the lagoon were subjected to UV light mimicking the natural solar spectrum. Dissolved organic nitrogen concentrations did not change measurably during the 36‐h incubation, while calculated dissolved organic carbon concentrations dropped by up to 17%, resulting in decreases in estimated C/N for some samples. Nitrate and urea levels were not consistently altered in the light, while ammonium photoproduction rates of up to 0.032 µmol N L−1 h−1 were observed. Changes in dissolved free amino acids were measured in a groundwater sample obtained from a shoreline seep, and this sample exhibited photoproduction of glycine and alanine at rates of 0.8–1.1 nmol N L−1 h−1. The rates of ammonium and amino acid formation, when scaled up to estimate photoproduction in the lagoon system, appeared to be minor relative to other sources to and fluxes within the system.
Seasonal cycle of copper speciation in Gullmar Fjord, Sweden
Authors: Croot Peter L.
Published: July 2010

The chemical speciation of dissolved Cu was investigated by voltammetric methods in Gullmar Fjord, Sweden, over the course of a year from September 1996 until August 1997. Sampling was carried out on a roughly monthly basis, with an intensive survey carried out in May 1997. Surface water temperatures ranged from 21 to 22°C, whereas bottom waters in the fjord were approximately 6°C throughout. Macronutrient concentrations in the fjord during the period of the survey were investigated independently by the Göteborgs och Bohus lä4ns Vattenvårdsförbund (Water Quality Association of Göteborg and Bohus). Surface phosphate concentrations were highest in early spring with low levels (<0.1 mmol kg‐1) over the late spring and summer. Nitrate and silicate showed a similar pattern to phosphate with the exception of high concentrations encountered in surface waters when low salinity plumes caused by runoff were encountered. A period of calm, sunny weather in January 1997 saw the initiation of the spring bloom some 2 months earlier than usual. Dissolved Cu speciation was dominated by organic complexation (over 99.8%) throughout this study. Strong Cu binding ligands (log K > 12.5) were not detected during the winter or early spring and could be related to the temperature‐related seasonal appearance of the cyanobacterium Synechoccocus in these waters. The appearance of the strong Cu ligands led to a decrease in the concentration of free copper, resulting in a seasonal cycle for free copper in the fjord. This is the first study to examine Cu speciation over an annual cycle in a coastal environment.
Observations of a negatively buoyant river plume in a large lake
Authors: Churchill James H. , Ralph Elise A. , Cates Angela M. , Budd Judith W. , Urban Noel R.
Published: July 2010

Although seldom studied, negatively buoyant river plumes may be common within large lakes, especially during spring when lake and river waters are near the temperature of maximum fresh water density (4°C) and relatively warm river discharge can be denser than the receiving lake water. Here we examine a negatively buoyant plume entering Lake Superior from the Ontonagon River during late March 2000. Because of small temperature related density differences, the sediment load carried by the river made an appreciable contribution to the plume‐edge density field and significantly impacted plume‐edge dynamics. Particle‐related density gradients were responsible for roughly one‐third of the geostrophic velocity shear at the plume edge. As a result of the small width (50 m) of the Ontonagon River mouth, the emerging river water was not deflected by rotational effects. Its movement appeared to have been primarily controlled by the wind‐driven coastal current. Our analysis indicates that the frequent reversals of this current should effectively limit the plumeÂ's alongshore extent and may result in a continuous coastal band of turbid water extending alongshore in either direction from the river mouth.
Nutrient limitation on a planktonic rotifer: Life history consequences and starvation resistance
Authors: Ramos‐RodrÍguez EloÍsa , Conde‐Porcuna José M.
Published: July 2010

Nutrient content of plants is low relative to that of herbivores. Dietary nutrients can limit the growth and reproduction of herbivores. We studied life history consequences and starvation resistance for a common planktonic rotifer, Keratella cochlearis, feeding on algae grown on nutrient‐limited media. A strain of Cryptomonas was grown on three types of growth medium with nitrogen (N) and phosphorus (P) adjusted to produce N‐limiting, P‐limiting, and nutrient‐sufficient conditions. The analysis of nutrient content of Cryptomonas cells grown on nutrient‐limited conditions showed that those algae exhibited higher P content than algae growing on a nutrient‐sufficient medium. However, Cryptomonas reached lower densities in nutrient‐limited media. The life history responses of Keratella to food quality were examined with low and high food availability. Our study showed that the interaction of food quantity and quality had a significant effect on rotifer growth rates. We observed, at low food levels, that Keratella growth rates were highest when the algae were grown under P limitation. The lowest rotifer growth rates were obtained when the rotifer fed on Cryptomonas grown in nutrient‐sufficient conditions. Our study also showed that starvation resistance was higher for those rotifers fed on N‐limited Cryptomonas. In natural situations, rotifers could even grow better under nutrient‐limited conditions if this group of algae is dominant in the phytoplankton community. Moreover, differences in starvation resistance could be critical in determining competitive outcome and community structure in nutrient‐variable environments.
A carbon isotope method to quantify groundwater discharge at the land‐sea interface
Authors: Gramling C. M. , McCorkle D. C. , Mulligan A. E. , Woods T. L.
Published: July 2010

We present a new method to characterize and quantify groundwater discharge to estuaries and the coastal ocean. Using data from the Pages Creek estuary in the Cape Fear region of southeastern North Carolina, we show that the concentration and carbon isotopic composition (Δ14C and Δ13C values) of dissolved inorganic carbon (DIC) can provide a tracer of a single, well‐defined component of the surface water‐groundwater system in coastal regions— the integrated freshwater discharge to an estuary from confined aquifers. Groundwater from the two shallowest confined aquifers in the Cape Fear region (the Castle Hayne and the Peedee) has DIC Δ14C values ranging from −282‰ to −829‰, significantly lower than the radiocarbon content of surficial (water table) groundwater, rivers and streams, and seawater in the area (Δ14C = −38‰ to +97‰). DIC additions from salt marsh decomposition and DIC removal via photosynthesis and gas evasion can influence estuarine DIC concentrations and DIC Δ13C values. However, none of these processes results in strongly depleted DIC Δ14C values. Because artesian springs are the only significant low‐Δ14C DIC input to the Pages Creek estuary, flood‐ebb 14C budgets provide a direct measure of the fraction of the total freshwater inputs to the Pages Creek estuary that is derived from artesian discharge. With this method, we have observed a striking range in the relative contribution of artesian flow to the Pages Creek estuary freshwater budget. During November 1999 and April 2001 (both periods of low precipitation in southeastern North Carolina), artesian groundwater discharge could account for essentially all of the Pages Creek freshwater inputs. In contrast, during July 2000 (a period of high precipitation in this region), artesian groundwater made a negligible contribution to the creek’s freshwater budget.
Gas transfer velocities measured at low wind speed over a lake
Authors: Crusius John , Wanninkhof Rik
Published: July 2010

The relationship between gas transfer velocity and wind speed was evaluated at low wind speeds by quantifying the rate of evasion of the deliberate tracer, SF6, from a small oligotrophic lake. Several possible relationships between gas transfer velocity and low wind speed were evaluated by using 1‐min‐averaged wind speeds as a measure of the instantaneous wind speed values. Gas transfer velocities in this data set can be estimated virtually equally well by assuming any of three widely used relationships between k600 and winds referenced to 10‐m height, U10: (1) a bilinear dependence with a break in the slope at ~3.7 m s−1, which resulted in the best fit; (2) a power dependence; and (3) a constant transfer velocity for U10 < ~3.7 m s−1, with a linear dependence on wind speed at higher wind speeds. The lack of a unique relationship between transfer velocity and wind speed at low wind speeds suggests that other processes, such as convective cooling, contribute significantly to gas exchange when the wind speeds are low. All three proposed relationships clearly show a strong dependence on wind for winds > 3.7 m s−1 which, coupled with the typical variability in instantaneous wind speeds observed in the field, leads to average transfer velocity estimates that are higher than those predicted for steady wind trends. The transfer velocities predicted by the bilinear steady wind relationship for U10 < ~3.7 m s−1 are virtually identical to the theoretical predictions for transfer across a smooth surface.
Does 234Th/238U disequilibrium provide an accurate record of the export flux of particulate organic carbon from the upper ocean?
Authors: Moran S. B. , Weinstein S. E. , Edmonds H. N. , Smith J. N. , Kelly R. P. , Pilson M. E. Q. , Harrison W. G.
Published: July 2010

The magnitude of the flux of biogenic particulate organic carbon (POC) exported from the surface waters of the world ocean and remineralized at depth is critical to constraining models of the global carbon cycle, yet remains controversial. The use of upper ocean sediment traps is still one of the primary tools for determining this export flux, although trap fluxes have been shown to vary significantly because of hydrodynamic and sample collection biases. Over the past decade, 234Th increasingly has been used as a tracer to estimate POC export from the euphotic zone by multiplying the depth‐integrated 234Th flux by the POC/234Th ratio of sinking particles. The accuracy of this technique is highly dependent on the natural variability in the POC/234Th ratio and 234Th flux, yet the significance of this variability to estimates of POC export remains uncertain. Based on an analysis of new 234Th and POC data from the Labrador Sea and a review of 25 previous independent field studies, we report that POC export fluxes can vary 2–10 times or more solely because of variability in the POC/234Th ratio and procedures used to estimate the 234Th flux. Recommended improvements include studies of the biological, chemical, and physical mechanisms controlling 234Th‐organic matter interactions in seawater; detailed comparisons of POC/234Th ratios in size‐fractionated and sediment trap material; increased spatial and temporal sampling density of234Th; and more standardized procedures to calculate the 234Th export flux.
Methane bubbles in Lake Kinneret: Quantification and temporal and spatial heterogeneity
Authors: Ostrovsky Ilia
Published: July 2010

The amount of methane bubbles rising from the bottom of Lake Kinneret was quantified by using a dual‐beam echo sounder. Both echo‐counting (EC) and echo integration (EI) techniques were implemented. Bubbles can confound the identification of fish targets because their acoustic sizes strongly overlap. Analysis of vertical changes in densities in the anoxic hypolimnion (with no fish) indicated that multiple targets were most abundant near the bottom, which caused an essential bias of bubble density estimates by EC. EI was a reliable tool for assessment of bubble density near the bottom. In the upper part of the water column, both techniques provided similar estimates of density of targets (mainly bubbles) because they were measured between dense fish schools during the daytime. The mean acoustic size of rising bubbles decreased in the hypolimnion but increased in the epilimnion, suggesting change in the relative importance of factors controlling gas volume. In summer and fall 2001, the bubbles became predominant echo‐reflecting objects in the epilimnion. Temporal and spatial changes in bubble densities were highly heterogeneous, suggesting strong variability in factors affecting the gas ebullition. This variability should be taken into consideration when attempting to quantify the methane ebullition and assessing fish abundance in aquatic systems.
Relationship of nitrogen isotope fractionation to phytoplankton size and iron availability during the Southern Ocean Iron RElease Experiment (SOIREE)
Authors: Karsh K. L. , Trull T. W. , Lourey M. J. , Sigman D. M.
Published: July 2010

The 15N composition of sediments has been used as a proxy for nitrate utilization in surface waters to assess the role of Southern Ocean export production in glacial/interglacial changes in atmospheric CO2 concentration. Interpretation has relied on a temporally constant isotope effect (ε) associated with uptake and assimilation of nitrate by phytoplankton. To investigate the reliability of this approach, we examined the relationships between the 15N compositions of dissolved nitrate, bulk and size‐fractionated (200, 70, 20, 5, 1 µm) suspended particulate organic nitrogen (PON), and sinking particles obtained from sediment traps during the Southern Ocean iron release experiment (SOIREE). We found variations in phytoplankton nitrogen isotopic compositions with both cell size and iron availability. δ15NPON increased by >2‰ with increasing size, both within and outside the ironenriched patch. In comparison to unfertilized waters, δ15NPON within the iron‐fertilized patch was a further 3–4‰ higher in those size fractions dominated by large diatoms (20–70, 70–200 µm). We speculate that this iron response might result from (1) variation in ε of nitrate utilization or (2) an iron‐stimulated shift from ammonium‐based to nitrate‐based production. Comparing the δ15N of the large diatom—dominated size fractions to the δ15N of nitrate suggests relatively low ε values of 4–5‰, in contrast to estimated values of 7–10‰ from seasonal nitrate depletion and export production. This suggests that higher glacial δ15N in Southern Ocean sediments could, in part, reflect increases in iron availability, dominant cell size, and possibly growth rates, and these effects must be considered in any quantitative scaling of δ15N variations, including those of diatom‐bound δ15N, to the extent of nitrate utilization.
Photochemical reactivity of siderophores produced by marine heterotrophic bacteria and cyanobacteria based on characteristic Fe(III) binding groups
Authors: Barbeau Katherine , Rue Eden L. , Trick Charles G. , Bruland Kenneth W. , Butler Alison
Published: July 2010

Siderophores, high‐affinity Fe(III) ligands produced by microorganisms to facilitate iron acquisition, might contribute significantly to dissolved Fe(III) complexation in ocean surface waters. In previous work, we demonstrated the photoreactivity of the ferric ion complexes of several α‐hydroxy carboxylic acid—containing siderophores produced by heterotrophic marine bacteria. Here, we expand on our earlier studies and detail the photoreactivity of additional siderophores produced by both heterotrophic marine bacteria and marine cyanobacteria, making comparisons to synthetic and terrestrial siderophores that lack the α‐hydroxy carboxylate group. Our results suggest that, in addition to secondary photochemical reaction pathways involving reactive oxygen species, direct photolysis of Fe(III)‐siderophore complexes might be a significant source of Fe(II) and reactive Fe(III) in ocean surface waters. Our findings further indicate that the photoreactivity of siderophores is primarily determined by the chemical structure of the Fe(III) binding groups that they possess—hydroxamate, catecholate, or α‐hydroxy carboxylate moieties. Hydroxamate groups are photochemically resistant regardless of Fe(III) complexation. Catecholates, in contrast, are susceptible to photooxidation in the uncomplexed form but stabilized against photooxidation when ferrated. α‐Hydroxy carboxylate groups are stable as the uncomplexed acid, but when coordinated to Fe(III), these moieties undergo light‐induced ligand oxidation and reduction of Fe(III) to Fe(II). These photochemical properties appear to determine the reactivity and fate of Fe(III)‐binding siderophores in ocean surface waters, which in turn might significantly influence the biogeochemical cycling of iron.
Lake metabolism: Relationships with dissolved organic carbon and phosphorus
Authors: Hanson Paul C. , Bade Darren L. , Carpenter Stephen R. , Kratz Timothy K.
Published: July 2010

Recent literature has suggested that for many lakes and rivers, the respiratory breakdown of organic matter (R) exceeds production of organic matter by photosynthesis (gross primary production [GPP]) within the water body. This metabolic balance (GPP > R; “heterotrophy”) implies that allochthonous organic matter supports a portion of the aquatic ecosystem's respiration. Evidence that many lakes are heterotrophic comes from diverse approaches, and debate remains over the circumstances in which heterotrophy exists. The methods used to estimate GPP and R and the limited extent of lake types studied, especially with respect to dissolved organic carbon (DOC) and total phosphorus (TP) concentrations, are two reasons for differing conclusions. We deployed O2 and CO2 sondes to measure diel gas dynamics in the surface waters of 25 lakes. From these data, we calculated GPP, R, and net ecosystem production (NEP = GPP − R). Over the broad range in TP and DOC among the lakes, diel CO2 and O2 changed on a near 1 : 1 molar ratio. Metabolism estimates from the two gases were comparable, except at high pH. Most lakes in our data set had negative NEP, but GPP and R appeared to be controlled by different factors. TP correlated strongly with GPP, whereas DOC correlated with R. At low DOC concentrations, GPP and R were nearly equal, but, at higher DOC, GPP and R uncoupled and lakes had negative NEP. Strong correlations between lake metabolism and landscape related variables suggest that allochthonous carbon influences lake metabolism.
Inorganic nitrogen transformations in the bed of the Shingobee River, Minnesota: Integrating hydrologic and biological processes using sediment perfusion cores
Authors: Sheibley Richard W. , Duff John H. , Jackman Alan P. , Triska Frank J.
Published: July 2010

Inorganic N transformations were examined in streambed sediments from the Shingobee River using sediment perfusion cores. The experimental design simulated groundwater‐stream water mixing within sediment cores, which provided a well‐defined one‐dimensional representation of in situ hydrologic conditions. Two distinct hydrologic and chemical settings were preserved in the sediment cores: the lowermost sediments, perfused with groundwater, remained anaerobic during the incubations, whereas the uppermost sediments, perfused with oxic water pumped from the overlying water column, simulated stream water penetration into the bed. The maintenance of oxic and anoxic zones formed a biologically active aerobic‐anaerobic interface. Ammonium (NH+4) dissolved in groundwater was transported conservatively through the lower core zone but was removed as it mixed with aerated recycle water. Concurrently, a small quantity of nitrate (NO−3 ) equaling ~25% of the NH+4 loss was produced in the upper sediments. The NH+4 and NO−3 profiles in the uppermost sediments resulted from coupled nitrification‐denitrification, because assimilation and sorption were negligible. We hypothesize that anaerobic microsites within the aerated upper sediments supported denitrification. Rates of nitrification and denitrification in the perfusion cores ranged 42–209 and 53–160 mg N m−2 day−1, respectively. The use of modified perfusion cores permitted the identification and quantification of N transformations and verified process control by surface water exchange into the shallow hyporheic zone of the Shingobee River.