bluuebunny/crossref_metadata_2025 huggingface dataset:
A Unified Smart City Model (USCM) for Smart City Conceptualization and Benchmarking
Authors: Anthopoulos Leonidas , Janssen Marijn , Weerakkody Vishanth
Published: August 2016

Smart cities have attracted an extensive and emerging interest from both science and industry with an increasing number of international examples emerging from all over the world. However, despite the significant role that smart cities can play to deal with recent urban challenges, the concept has been being criticized for not being able to realize its potential and for being a vendor hype. This paper reviews different conceptualization, benchmarks and evaluations of the smart city concept. Eight different classes of smart city conceptualization models have been discovered, which structure the unified conceptualization model and concern smart city facilities (i.e., energy, water, IoT etc.), services (i.e., health, education etc.), governance, planning and management, architecture, data and people. Benchmarking though is still ambiguous and different perspectives are followed by the researchers that measure -and recently monitor- various factors, which somehow exceed typical technological or urban characteristics. This can be attributed to the broadness of the smart city concept. This paper sheds light to parameters that can be measured and controlled in an attempt to improve smart city potential and leaves space for corresponding future research. More specifically, smart city progress, local capacity, vulnerabilities for resilience and policy impact are only some of the variants that scholars pay attention to measure and control.
Reputation, Image, and Social Media as Determinants of e-Reputation
Authors: Castellano Sylvaine , Khelladi Insaf
Published: August 2016

Although the Internet represents great opportunities for businesses, some firms that are evolving in the luxury industry were initially reluctant to engage in digital activities. However, over the past few years, digital natives represent a main reason for these firms to start adopting online strategies. Specifically, reputation and image are inherent to the luxury industry, and with social media, they are considered the determinants of e-reputation. Using an online survey design, the authors find that the influence of reputation, image and social media on e-reputation differs based on the status of the luxury brand (traditional compared with modern) and that digital natives moderate these links.
Analysis of a Double Pendulum System with Joint Actuation by a Non-Linear Control
Authors: Pereira M.C. , Weber H.I.
Published: August 2016

This article presents the study of a double pendulum system with distributed mass carrying an actuator at the joint between the two rods. This actuator can move the outer rod in order to inject or remove energy from the system, which is modeled as a body with variable position of the center of mass. The objective of this work is to develop a control technique that can make the pendulum swing up and rotate itself, similar to many other double pendulum investigations, but in the present case without any actuation on the fixed joint. The system is modeled with Simulink® software, using the parameters of a real model.
Dynamics of Starting of Vibrating Machines with Unbalanced Vibroexciters on Solid Body with Flat Vibrations
Authors: Yaroshevich N.P. , Zabrodets I.P. , Yaroshevich T.S.
Published: August 2016

Expressions for vibration moments (additional dynamic loading caused by the vibrations of bearing body) during the passage of resonant zone by vibration machines with the flat vibrations of bearing body both with one arbitrarily located vibration exciter and with two self-synchronization vibration exciters for the different modes of starting are got in an analytical form. Possibilities of improvement of process of running approach of vibration machines with unbalanced vibration exciters are demonstrated by using of methods of the "double" (in case of one vibration exciter) and "separate" starting of electric motors (in case of two vibration exciters). It is shown that the first method is based on using of semislow vibrations arising in the resonant zone. The necessary condition of the successful using of this method is motion on the rotor of exciter in the moment of the repeated including of engine of rotary-type vibration moment. The conditions when the separate starting is effective are shown. Conclusions and practical recommendations that allow to facilitate starting of vibration machines with an unbalanced drive are pointed.
Lock-Time Behavior of Charge Pump PLLs Employing Oscillators with Non-Linear Frequency Tuning Characteristics
Authors: Demir Oguz , Ozturk Cemile Duygu , Altun G. Yesa , Taskiran Abidin , Selcuk Gokhun
Published: August 2016

In this paper we investigate the lock time behavior of charge pump phase locked loops (CP-PLLs) which employ voltage controlled oscillators (VCOs) with non-linear frequency tuning characteristics. Since non-linear tuning characteristics leads to variable tuning gain (Kvco), we extend the state space analysis of PLLs to account for tuning gain variations. The frequency behavior is approximated by a polynomial which fits the equally spaced data points of tuning curve best in a least-square sense. We have analytically evaluated the integrals arising from high order terms in polynomial representation and migrated to state space analysis. The method is validated by simulating the lock-time process of a VCO with varying tuning gain and comparing the results with commercial PLL simulation software.
Automatic Control Technique for EMC Analysis Using the Scripting Language of HFSS
Authors: Chen Dan , Wan Jian Ping , Yang Feng Yuan , Yang Peng Hui , Qin Yu Jian
Published: August 2016

The electromagnetic compatibility (EMC) of the whole system should be guaranteed to ensure the electronic and electrical equipments can work without interference from each other. The article introduces the scripting language of HFSS and details the architecture of automatic control technique for EMC. Finally, the antenna isolation analysis among 3 wire monopole antennas set on an oval carrier was taken as an example to demonstrate the calculation process.
Reconsidering the Freedom Charter, the black theology of liberation and the African proverb about the locust’s head in the context of poverty in South Africa
Authors: Mtshiselwa Ndikho
Published: August 2016

While South Africa attained liberation from the apartheid rule in 1994, the legacy of colonialism and apartheid – in the form of poverty and economic inequality – continues to haunt black South Africans. The aim of this article is to make a case for the equitable sharing of South Africa’s mineral wealth amongst all its citizens with the view to alleviate poverty. Firstly, this article provides a reflection on the Freedom Charter and suggests that the values of the Charter, for instance, the sharing of resources and wealth, are relevant in South Africa today. Secondly, it is argued in the present article that the preferential option for the poor which is upheld in the black theology of liberation is equally relevant in post-apartheid South Africa where many black South Africans remain poor. Thirdly, this article argues that the African proverb, Bana ba motho ba ngwathelana hlogo ya tšie [The siblings share the head of a locust], also echoes the idea of equitable sharing of resources with a view to alleviate poverty. Lastly, the author submits that the idea of equitable sharing of resources and wealth that is echoed in the Freedom Charter, the black theology of liberation and the African wise saying support the equitable redistribution of the mineral wealth to the benefit of all South Africans.
Occurrence of Needlestick and Injuries among Health-care Workers of a Tertiary Care Teaching Hospital in North India
Authors: Goel Varun , Kumar Dinesh , Lingaiah Raghavendra , Singh Sarman
Published: August 2016

Introduction: Occupational hazards such as accidental exposure to sharp, cuts, and splashes are common among health-care workers (HCWs).

Aims and Objectives: To determine the occurrence of self-reported occupational exposures to these hazards and to know the prevalent practices following the exposure. The second aim was to know the baseline antibody levels against hepatitis B virus (HBV), hepatitis C virus (HCV), and human immunodeficiency virus (HIV) immediately after these accidents.

Methods: An observational prospective study was done in the HCWs of a tertiary care academic health organization of North India from January 2011 to December 2013. At the time of self-reporting of injury, a questionnaire was administered. Blood sample of HCWs and of the source, if identified, was collected for baseline HBV, HCV, and HIV serum markers. The exposed HCWs were followed up and repeat testing was done after 3–4 weeks for seroconversion up to 6 months.

Results: A total of 476 injuries were reported. Needlestick injury of fingers was the most common. Doctors were found to have the highest exposure rate (73.7%) distantly followed by nurses (19.1%). A significant number of the HCWs (125, 26.3%) vaccinated in past had hepatitis B surface antibody (anti-HBs) titers ≥10 mIU/mL (protection defined as anti-HBs level ≥10 mIU/ml). Only 44 sources were found to be seropositive (11 for HIV, 9 for HCV, and 24 for HBV). No seroconversion was seen in any of the exposed HCWs after 6 months.

Conclusions: The incidence of needlestick and sharp injuries is most often encountered in emergency wards. Anti-HBs titers were suboptimal in many of the HCWs requiring a booster dose of HBV vaccination.
Primary Nasal Tuberculosis: Resurgence or Coincidence − A Report of Four Cases with Review of Literature
Authors: Khan Sabina , Pujani Mukta , Jetley Sujata
Published: August 2016

Background: Primary nasal tuberculosis (TB) is a rare form of TB even in areas with high TB incidence. It is timely diagnosis and proper management are often delayed due to its rarity and nonspecific clinical presentation.

Aim: The aim of the study was to review histopathologically diagnosed cases of nasal TB over a period of 1 year and to describe its clinical presentation, diagnostic workup, the importance of histopathological diagnosis along with a brief review of the literature.

Materials and Methods: This was a retrospective study done in the Department of Pathology of a Tertiary Care Hospital of Delhi over a period of 1 year where all the cases with histopathological diagnosis of nasal TB were reviewed. Patients’ clinical details, investigations and treatment details along with follow‑up were obtained from the medical records section. For each case, routine hematoxylin and eosin stain were studied along with Ziehl–Neelson staining.

Results: A total of four patients were diagnosed with nasal TB histopathologically. Patients’ age ranged from 5 to 34 with an equal male to female ratio. All patients were immunocompetent. Primary nasal TB was seen in all of the four cases. None of the cases, it was clinically suspected, and histopathology was the mainstay of diagnosis. All the cases were treated with antituberculous treatment and showed considerable improvement.

Conclusions: Although nasal TB is rare, it should be considered in the differential diagnosis of chronic nasal symptoms and granulomatous lesions of the nose. Histopathology plays an important role in the diagnosis of these clinically unsuspecting cases of nasal TB.
Implementation of a Screening Program for Patients at Risk for Posttraumatic Stress Disorder
Authors: Roberts Carmen R. , Wofford Joanie E. , Hoy Haley M. , Faddis Mitchell N.
Published: August 2016

Introduction

Implantable cardioverter defibrillator (ICD) recipients who suffer from posttraumatic stress disorder (PTSD) are known to be associated with significant cardiac-specific mortality. Clinical observations suggest that PTSD is frequently undetected in ICD recipients followed up at electrophysiology (EP) outpatient clinics. Early recognition of PTSD is important to reduce the risk of serious manifestations on patient outcomes.

Methods

All ICD recipients aged 19 years or older at the Washington University School of Medicine (WASHU) EP clinic, a large urban EP clinic, were invited to participate in the project. An informed consent letter with an attached primary care: posttraumatic stress disorder (PC: PTSD) survey was offered to the participants who met the inclusion criteria. Those who completed the survey were included in the project. Individuals with positive survey result were offered a referral to mental health services. Comparisons between PTSD and non-PTSD patients were done using a two-sample t-test for continuous variables. Using Fisher's exact test, PTSD prevalence was compared to the study by Ladwig et al in which prevalence was determined as the proportion of patients with positive findings of PTSD ( n = 38/147). All analyses were conducted using SAS v9.4. The proportion of patients having PTSD was determined and an exact 95% confidence interval was evaluated based on the binomial distribution.

Results

Using a convenience sample, 50 ICD recipients (33 males and 17 females) were enrolled. The project had a 30-day outcome period. Nine (18%) of the 50 participants had positive PC: PTSD findings and all these nine participants were referred to a mental health specialist. The current project demonstrated an 18% (9/50) PTSD prevalence rate when compared to a 26% (38/147) prevalence rate in the study by Ladwig et al ( P = 0.34). Although this project did not demonstrate 20% PTSD prevalence rate, as hypothesized, the 18% PTSD prevalence rate is consistent with previous research.

Conclusion

The prevalence of PTSD noted in the current project is consistent with previous research and validates underrecognition of PTSD in ICD patients. Offering a referral to all ICD recipients at EP clinic visits with a positive PC: PTSD screening to a mental health specialist is an important step in reducing the risk of serious manifestations on patient outcomes.
Plasma Tryptophan and the Kynurenine–Tryptophan Ratio are Associated with the Acquisition of Statural Growth Deficits and Oral Vaccine Underperformance in Populations with Environmental Enteropathy
Authors: Kosek Margaret N. , Mduma Estomih , Kosek Peter S. , Lee Gwenyth O. , Svensen Erling , Pan William K. Y. , Olortegui Maribel Paredes , Bream Jay H. , Patil Crystal , Asayag Cesar Ramal , Sanchez Graciela Meza , Caulfield Laura E. , Gratz Jean , Yori Pablo Peñataro
Published: August 2016

Early childhood enteric infections have adverse impacts on child growth and can inhibit normal mucosal responses to oral vaccines, two critical components of environmental enteropathy. To evaluate the role of indoleamine 2,3-dioxygenase 1 (IDO1) activity and its relationship with these outcomes, we measured tryptophan and the kynurenine–tryptophan ratio (KTR) in two longitudinal birth cohorts with a high prevalence of stunting. Children in rural Peru and Tanzania (N = 494) contributed 1,251 plasma samples at 3, 7, 15, and 24 months of age and monthly anthropometrics from 0 to 36 months of age. Tryptophan concentrations were directly associated with linear growth from 1 to 8 months after biomarker assessment. A 1-SD increase in tryptophan concentration was associated with a gain in length-for-age Z-score (LAZ) of 0.17 over the next 6 months in Peru (95% confidence interval [CI] = 0.11–0.23, P < 0.001) and a gain in LAZ of 0.13 Z-scores in Tanzania (95% CI = 0.03–0.22, P = 0.009). Vaccine responsiveness data were available for Peru only. An increase in kynurenine by 1 μM was associated with a 1.63 (95% CI = 1.13–2.34) increase in the odds of failure to poliovirus type 1, but there was no association with tetanus vaccine response. A KTR of 52 was 76% sensitive and 50% specific in predicting failure of response to serotype 1 of the oral polio vaccine. KTR was associated with systemic markers of inflammation, but also interleukin-10, supporting the association between IDO1 activity and immunotolerance. These results strongly suggest that the activity of IDO1 is implicated in the pathophysiology of environmental enteropathy, and demonstrates the utility of tryptophan and kynurenine as biomarkers for this syndrome, particularly in identifying those at risk for hyporesponsivity to oral vaccines.
RADIOCARBON IN THE PACIFIC AND INDIAN OCEANS AND ITS RELATION TO DEEP WATER MOVEMENTS1
Authors: Bien G. S. , Rakestraw N. W. , Suess H. E.
Published: August 2016

Since 1948, carbon‐14 measurements on the bicarbonate of ocean water samples from the Pacific and Indian oceans have been carried out at the Scripps Institution of Oceanography, La Jolla, California. Previous reports of the results of these investigations have been confirmed and amended by many recent measurements. The method of extracting CO2 from ocean water has been modified and perfected over the past years. The most notable results of the measurements concern the 14C content of deep ocean water which can be interpreted unambiguously by considering the aging of the water during the time of movement from the Weddell Sea eastward and then northward into the North Pacific Ocean.
ABSOLUTE DYNAMIC TOPOGRAPHY1
Authors: von Arx William S.
Published: August 2016

Dynamic sections could be made absolute if, between each pair of oceanographic stations, the inclination of any isobaric surface were known with reference to any coextensive geopotential surface. Various methods for accomplishing this measurement are cited with particular emphasis on gravimetric and inertio‐optical techniques. An observational procedure is outlined in principle, and the difficulties of such measurements are discussed in the light of recent experiments at sea.
THE AGE AND DEVELOPMENT OF THE PROVINCELANDS HOOK, OUTER CAPE COD, MASSACHUSETTS1
Authors: Zeigler John M. , Tuttle Sherwood D. , Tasha Herman J. , Giese Graham S.
Published: August 2016

The Provincelands Hook, an area of marshes and dunes, was built out from the northern end of the glacial deposits of Outer Cape Cod. The hook, a wedge 60 m at its thickest, of marine, beach, and dune material, rests in part on Tertiary Coastal Plain sediments that are probably only an isolated patch on the crystalline basement. About 18,000 years ago, when late Tazewell ice melted away from the region of present day Cape Cod, the Gulf of Maine was filled with ice, and Georges Bank was above sea level. Between 18,000 and 6,000 years ago, sand that eroded from the coast was moved along the east side of Cape Cod from north to south, where it accumulated as a part of the sand wave complex southeast of the cape. Waves from the east and southeast that would have tended to move sand northward along the Capo were blocked by Georges Shoals and Nantucket Shoals. By 6,000 years ago, sea level had so risen that deeper water over Georges Bank permitted more waves to reach Cape Cod from the east and southeast. The dominant direction of littoral drift which had been to the south, then received a strong north component and material moved northward, accumulating to form the Provincelands Hook.

Based on 14C dates and other evidence, the hook formed between 6,000 years ago and the present and is still growing. Shoreline reconstructions are guided by 14C dates, well information, regional topography, and known behavior of hooks. It is noted that hooks are characteristic features of Cape Cod spits and tend to trap lakes behind them. The depressions containing lakes in the modern Provincelands are interpreted as low areas trapped behind hooks. A change in the growth habits of spits is thought to have taken place about 2,000 years ago, coinciding with the abrupt decrease in the rate of rise of sea level.
A MOORED STABLE PLATFORM FOR AIR–SEA INTERACTION STUDIES1
Authors: Doe L. A. E. , Brooke John
Published: August 2016

A stable, moored platform for use in water up to 90 m deep under moderate sea and weather conditions is described. Its use in studies of air–sea interactions is proposed.
STUDIES ON THE DECOMPOSITION OF ORGANIC DETRITUS DERIVED FROM THE TURTLE GRASS THALASSIA TESTUDINUM1
Authors: Fenchel Tom
Published: August 2016

A study was made of the quantitative composition of the microbial communities living on detrital particles derived from the turtle grass Thalassia testudinum. The number of organisms on and the rate of oxygen consumption of the detritus are approximately proportional to the total surface area. Field samples of detritus harbored about 3 × 109 bacteria, 5 × 107 flagellates, 5 × 104 ciliates, and 2 × 107 diatoms and consumed from 0.7 to 1.4 mg 02/hr per g dry wt.

The detritus‐consuming amphipod Parhyalella whelpleyi feeds on detrital particles and on its own fecal pellets but it only uses the microorganisms; the dead plant residue passes undigested through the intestine. After a few days the microbial communities living on fecal pellets are qualitatively and quantitatively comparable to those living on other detrital particles.

The amphipods decrease the particle size of the detritus thereby increasing its total surface and thus the microbial activity. In less than 4 days, the mechanical activity of the amphipods may increase the detrital O2 uptake by 110% of their own metabolic rate. Measurements of respiratory rates of the amphipods will therefore give a much too low estimate of their total role in the ecosystem.
THE EFFECT OF A DEPOSIT‐FEEDING AMPHIPOD ON THE METABOLISM OF BENTHIC MICROFLORA1
Authors: Hargrave Barry T.
Published: August 2016

The density of a deposit‐feeding amphipod Hyalella azteca was varied experimentally in undisturbed sediment cores taken from Marion Lake, British Columbia. Epibenthic algal production, total community respiration, and bacterial oxygen consumption were measured after 48‐hr in situ incubation. As density increased community respiration also increased, in a nonlinear manner. Epibenthic algal production was stimulated within the range of natural amphipod densities, but declined at higher densities. Bacterial respiration was stimulated at amphipod densities up to four times those observed in the lake and also declined at higher densities.

These data were used to compare microflora production with Hyalella’s daily calorific requirement at various densities. At natural densities, less than 10% of daily microflora production would be required to supply the energy necessary for observed rates of amphipod growth, respiration, and egg production.

Fecal pellets produced by Hyalella were rapidly colonized by microorganisms. Autotrophic microorganisms increased, while respiration of heterotrophic microorganisms and solution decreased organic content of feces. Dissolved organic compounds excreted by Hyalella significantly increased the rate of recolonization of fecal material.
RECORDING DENSITOMETRY OF X‐RADIOGRAPHS FOR THE STUDY OF CRYPTIC LAMINATIONS IN THE SEDIMENT OF LAKE WASHINGTON
Authors: EDMONDSON W. T. , ALLISON DAVID E.
Published: August 2016

X‐radiographs of cores of sediment from Lake Washington reveal prominent laminations not visible to the eye. Measurement of the film density with a recording densitometer provides an exact and objective record of these laminations. The strongest band, at a depth of about 16 cm in the central part of the lake, is attributed to the lowering of the lake level in 1916. The mean rate of deposition therefore has been about 3.1 mm/yr.

The most prominent bands more recent than 1916 are too few to be annual, but the fine structure of these bands shown by the densitometer record may result from annual variations in deposition.

The film density is strongly correlated with the dry weight and mineral residue of the sediment.
A SIMPLE PISTON CORER FOR SAMPLING SAND BEACHES
Authors: CUBIT JOHN
Published: August 2016

A corer is described that penetrates most wet sands without difficulty and can be used for taking deep samples in sand beaches.
AN INEXPENSIVE MICROSAMPLER1
Authors: BAKER A. L.
Published: August 2016

A phytoplankton sampling device is described that collects samples at relatively close depth intervals (10 cm). This device is simple, transportable, easy to construct, and low in cost.
210Pb dating and the recent geologic history of Crystal Bay, Lake Minnetonka, Minnesota1
Authors: Murchie Scott L.
Published: August 2016

210Pb dating of five cores from Crystal Bay, Lake Minnetonka, was used to examine the geologic history of the basin during the last century. A lakewide 210Pb budget and the basinwide average cumulative activities of 210Pb within time‐stratigraphic units were estimated from multiple cores. Ages of time‐stratigraphic markers and sediment accumulation rates of time‐stratigraphic units were calculated from a constant‐flux 210Pb‐dating model.

The basinwide bulk‐sediment accumulation rate was found to have increased from 0.003 g cm−2 yr−1 before settlement to 0.07 g cm−2 yr−1 for the period from 1962 to 1983. Since settlement of the surrounding area, profundal sediment became highly calcareous and accumulation of littoral marl began.

Intensity of focusing of sediment to the center of Crystal Bay decreased as basinwide sediment accumulation rates increased. Light organic sediment was also found to be more intensely focused than heavier siliceous or calcareous sediment. Accumulation of sediment spread to regions shallower than 5 m as the rate of sedimentation exceeded the rate of sediment resuspension at that depth, about 4 mm yr−1.
Denitrification in freshwater and coastal marine ecosystems: Ecological and geochemical significance
Authors: Seitzinger Sybil P.
Published: August 2016

Denitrification occurs in essentially all river, lake, and coastal marine ecosystems that have been studied. In general, the range of denitrification rates measured in coastal marine sediments is greater than that measured in lake or river sediments. In various estuarine and coastal marine sediments, rates commonly range between 50 and 250 µmol N m−2 h−1, with extremes from 0 to 1,067. Rates of denitrification in lake sediments measured at near‐ambient conditions range from 2 to 171 µmol N m−2 h−1. Denitrification rates in river and stream sediments range from 0 to 345 µmol N m−2 h−1. The higher rates are from systems that receive substantial amounts of anthropogenic nutrient input. In lakes, denitrification also occurs in low oxygen hypolimnetic waters, where rates generally range from 0.2 to 1.9 µmol N liter−1 d−1. In lakes where denitrification rates in both the water and sediments have been measured, denitrification is greater in the sediments.

The major source of nitrate for denitrification in most river, lake, and coastal marine sediments underlying an aerobic water column is nitrate produced in the sediments, not nitrate diffusing into the sediments from the overlying water. During the mineralization of organic matter in sediments, a major portion of the mineralized nitrogen is lost from the ecosystem via denitrification. In freshwater sediments, denitrification appears to remove a larger percentage of the mineralized nitrogen. N2 fluxes accounted for 76–100% of the sediment‐water nitrogen flux in rivers and lakes, but only 15–70% in estuarine and coastal marine sediments. Benthic N2O fluxes were always small compared to N, fluxes.

The loss of nitrogen via denitrification exceeds the input of nitrogen via N2 fixation in almost all river, lake, and coastal marine ecosystems in which both processes have been measured.

Denitrification is also important relative to other inputs of fixed N in both freshwater and coastal marine ecosystems. In the two rivers where both denitrification measurements and N input data were available, denitrification removed an amount of nitrogen equivalent to 7 and 35% of the external nitrogen loading. In six lakes and six estuaries where data are available, denitrification is estimated to remove an amount of nitrogen equivalent to between 1 and 36% of the input to the lakes and between 20 and 50% of the input to the estuaries.
Comparative ecology of marine and freshwater phytoplankton1
Authors: Kilham Peter , Hecky Robert E.
Published: August 2016

Examination of models of nutrient‐limited growth and uptake, nutrient patchiness, resource competition, and r‐ and K‐selection with respect to marine and freshwater phytoplankton indicates that organisms from both habitats are ecologically similar. However, there are differences in the physiology and ecology of phytoplankton within a given habitat (either marine or freshwater) during the course of succession. Even though the identity and basic ecology of organisms that are present early and late in successional sequences are generally known, little is known about their physiology. Marked differences in uptake ability, storage capacity, and growth and loss rates will be found for phytoplankton that can be ranked along an r‐ through K‐selection continuum. This continuum can serve as a unifying concept in phytoplankton ecology.
Bioturbation and porosity gradients
Authors: Mulsow Sandor , Boudreau Bernard P. , Smith John A.
Published: August 2016

Ubiquitous porosity gradients have a potentially important effect on the mixing of particle‐bound tracers, such as 210Pb Mass‐depth coordinates cannot be used to deal with these effects if values of the traditional mixing coefficient, DB are required. This paper compares and evaluates three different means of dealing directly with porosity gradients while modeling bioturbation, i.e. mean constant porosity, interphase mixing (porosity mixed), and intraphase mixing (porosity not mixed). We apply these models to 11 different 210Pb profiles collected at various depths and times on the eastern Canadian Margin. A statistical analysis of the resulting best fits shows that these models produce equivalent mixing coefficient values for 55% of the profiles. For the remaining 45% of the profiles, the interphase mixing model predicts the existence of well‐mixed near‐surface zones on the time scale of 210Pb decay, a phenomenon not predicted by the other models. Unfortunately, our tracer dataset by itself cannot be used to establish which mixing mode is actually operative at each station.
Organisms' response in a chronically polluted lake supports hypothesized link between stress and size
Authors: Cattaneo Antonella , Asioli Alessandra , Comoli Patrizia , Manca Marina
Published: August 2016

Most of the available support for the hypothesis that pollutants' effects depend on size comes from shortterm experiments. We applied a size‐based approach to the analysis of the fossil remains of Lago d'Orta in Northern Italy, a lake that has been polluted with copper, other metals, and acid for more than 50 yr. Once this pollution began, the size distribution of diatoms, thecamoebians, and cladocerans shifted to smaller individuals. These changes in size reflected shifts in the taxonomic composition of the assemblages, but we also observed reduction of body size within a single taxon (the diatom Achnanthes minutissima). These reductions in the average size across three communities from different kingdoms and trophic levels provide strong evidence that chronically stressed environments select for smaller organisms.
Reply to comment by Boudreau on: What controls the mixed‐layer depth in deep‐sea sediments? The importance of POC flux
Authors: Smith Craig R. , Rabouille Christophe
Published: August 2016

#N/A
Variations in Synechococcus cell quotas of phosphorus, sulfur, manganese, iron, nickel, and zinc within mesoscale eddies in the Sargasso Sea
Authors: Twining Benjamin S. , Nuñez-Milland Daliangelis , Vogt Stefan , Johnson Rodney S. , Sedwick Peter N.
Published: August 2016

The quotas of P, S, Mn, Fe, Ni, and Zn in individual Synechococcus cells collected from the surface and deep chlorophyll maximum (DCM) layer of three mesoscale eddies in the Sargasso Sea were measured using synchrotron X‐ray fluorescence microscopy. Cells in a mode‐water eddy had significantly higher P (57 ± 10 amol) and Mn (28 ± 7 zmol) cell quotas than cells collected from a cyclone (22 ±2 amol and 10 ± 1 zmol, respectively) or anticyclone (25 ± 3 amol and 18 ± 3 zmol, respectively). Conversely, Ni and Zn quotas were significantly higher in the cells from the anticyclone (92 ± 19 and 561 ± 150 zmol, respectively) than in cells from the cyclonic (25 ± 4 and 35 ± 7 zmol, respectively) or mode‐water (30 ± 9 and 21 ± 8 zmol, respectively) eddies. These changes may reflect biochemical responses (e.g., production of urease and alkaline phosphatase) to gradients in inorganic N and P supplies. Cellular quotas of Fe (111 ± 17 zmol in the cyclone) and S (52 ± 6 amol in the cyclone) did not vary significantly among eddies despite two‐ to threefold higher dissolved and particulate Fe concentrations in the anticylone. Cells collected from 10‐m depth contained approximately 80% more Ni and S than cells collected from the DCM, potentially reflecting cell responses to heightened oxidative stress. Depthrelated trends varied by eddy for the other elements. Cellular P and Zn varied significantly during repeated samplings of the cyclone, with quotas of both elements dropping as bulk chlorophyll biomass in the DCM increased. These data demonstrate the dynamic responses of phytoplankton elemental composition to physical and chemical environmental gradients.
Upward phosphorus transport by Daphnia diel vertical migration
Authors: Haupt Florian , Stockenreiter Maria , Reichwaldt Elke S. , Baumgartner Michaela , Lampert Winfried , Boersma Maarten , Stibor Herwig
Published: August 2016

In many lakes, zooplankton show a distinct diel vertical migration (DVM) behavior, especially during periods of stratification. Excretion products of these zooplankton could potentially cause an upward nutrient transport and consequent nutrient enrichment for phytoplankton in the epilimnion. We quantified the upward transport of phosphorus by the cladoceran Daphnia DVM experimentally by adding a radioactive tracer (33P) to the hypolimnion of large indoor mesocosms and measuring tracer accumulation in the epilimnion over time. During the daytime, when all Daphnia were found in the hypolimnion, no phosphorus transport from the hypolimnion into the epilimnion took place. As soon as the Daphnia started their upward migration, around dusk, we observed a continuous increase in phosphorus concentration in the epilimnion. The amount of phosphorus transported was in a biologically meaningful range. Our results strongly suggest that Daphnia vertical migration presents a continuous nutrient supply for the epilimnion.
The effect of increased nitrate loading on nitrate reduction via denitrification and DNRA in salt marsh sediments
Authors: Koop-Jakobsen Ketil , Giblin Anne E.
Published: August 2016

The effects of increased nitrogen loading on denitrification and dissimilatory nitrate reduction to ammonium (DNRA) in marsh sediments were studied in permanently submerged subtidal creek sediments and on the tidally inundated vegetated marsh platform in Plum Island Sound estuary, Massachusetts. DNRA and denitrification in surface sediments were measured at all sites using whole‐core incubations and the isotope pairing technique, which allows distinction between denitrification of water column nitrate and coupled nitrification‐denitrification. On the marsh platform, denitrification was also measured at depth in the rhizosphere, using a new approach that combined the push‐pull method and the isotope pairing technique. In tidal creek sediments, fertilization increased denitrification of water column nitrate by approximately one order of magnitude, and coupled nitrification‐denitrification threefold. Coupled nitrification‐denitrification made a significant contribution to the total N2 production in the unfertilized creek but was of minor importance in the fertilized creek due to increased rates of denitrification of water column nitrate. In the surface sediment of the marsh platform, fertilization increased denitrification of water column nitrate by an order of magnitude during inundation of the marsh platform, about 12% of the day. However, coupled nitrification‐denitrification occurring at depth in the rhizosphere was the main denitrification pathway, accounting for more than 50% of the total N2 production in the fertilized as well as in the reference marsh. DNRA was measured in the surface sediment only, where it was comparable in magnitude to denitrification in the fertilized as well as in the unfertilized marsh.
A century of bottom‐up‐ and top‐down driven changes on a lake planktonic food web: A paleoecological and paleoisotopic study of Lake Annecy, France
Authors: Perga Marie-Elodie , Desmet Marc , Enters Dirk , Reyss Jean-Louis
Published: August 2016

We reconstructed the changes in the planktonic food web of an oligotrophic subalpine lake over the past century, combining paleoecological methods and historical monitoring data. Analyses of organic matter δ15N from sediment cores show that nutrient enrichment started in the 1910s and intensified from the 1930s. Subsequent changes in sediment organic carbon content and accumulation rates, carotenoid pigment concentrations, organic matter δ13C, and cladoceran subfossil remains show that excess nutrient inputs triggered bottom‐up‐driven increases in lake primary production, as well as in Daphnia abundance. Daphnia size, however, started to decrease in the late 1930s, indicating an increasing size‐selective predation from zooplanktivorous whitefish populations (Coregonus lavaretus) that had been fostered by stocking and increased food availability. Whitefish predation is likely to have indirectly facilitated the establishment of Bosmina longirostris. With decreasing nutrient concentrations, Daphnia abundance decreased, but their size declined, presumably due to an ongoing size‐selective predation. At this same time, Bosmina abundance doubled as a likely result of released interspecific competition from smaller Daphnia. δ15N analyses on subfossil cladoceran remains revealed that these changes in cladoceran community structure were accompanied by major changes in the food web. In spite of successful measures to reduce nutrient inputs from the late 1960s and reduced primary production, anoxia still occurs every summer at the lake bottom. These patterns are the consequence of a still relatively high export of phytoplankton‐derived organic matter to the sediment as a result of strong top‐down effects on the planktonic food chain.
The effect of pH on the uptake of zinc and cadmium in marine phytoplankton: Possible role of weak complexes
Authors: Xu Yan , Shi Dalin , Aristilde Ludmilla , Morel François M. M.
Published: August 2016

In natural samples from the New Jersey coast and the Gulf of Alaska, zinc (Zn) and cadmium (Cd) uptake rates by phytoplankton decreased on average about 30% as pH was decreased from 8.5 to 7.9 or 7.7, and the partial pressure of carbon dioxide (PCO2) increased accordingly. The underlying mechanism was explored with the model species, Thalassiosira weissflogii and Emiliania huxleyi, using ethylenediaminetetraacetic acid (EDTA), desferrioxamine B, phytochelatin, and cysteine as complexing agents. Experiments with single complexing agents did not reproduce the effect of pH seen in field samples, ruling out two possible mechanisms: a direct effect on the uptake machinery or down‐regulation of uptake at high PCO2. Zn and Cd bioavailability must thus somehow decrease at low pH in natural seawater, which is counterintuitive since the protonation of complexing agents at low pH should increase the total free concentration of metals. However, in the presence of both a strong and a weak complexing agent, metal uptake rate may decrease at low pH if formation of the weak complex decreases and the metal in the weak complex is more “available” than in the strong complex. We obtained proof of concept for such a two‐ligand mechanism for Zn uptake in the presence of EDTA + phytochelatin and EDTA + cysteine. Weak ligands that bind a small fraction of essential metals in surface seawater may thus be important in metal uptake by phytoplankton, and the dual effects of strong and weak complexing agents may control not just the magnitude but also the sign of the effect of pH‐PCO2 on metal uptake rates.
Solubility of iron in the Southern Ocean
Authors: Schlosser Christian , De La Rocha Christina L. , Streu Peter , Croot Peter L.
Published: August 2016

Iron solubility (cFeS) ranged from 0.4 to 1.5 nmol L−1, decreasing from south to north in three different Southern Ocean zones (the Coastal Zone, the Antarctic Zone, and the Polar Frontal Zone plus the Subantarctic Zone). This decrease was at times correlated with an increase in temperature. Organic Fe solubility (cFeS,org), which was obtained by subtracting from total measured Fe solubility the solubility of inorganic species of iron (Fe) at the measurement temperature (20°C), ranged from 0.3 to 1.3 nmol L−1, representing an average of 32 ± 14% of the concentration of ligands in the dissolved size fraction as determined via competitive ligand exchange‐absorptive cathodic stripping voltammetry (barring a handful of extremely high values from a transect run to the east of Prydz Bay). Values of cFeS were mainly lower than the predicted value for inorganic Fe solubility at the in situ temperature. Total in situ Fe solubility (cFeS,adj) was therefore estimated by adjusting for inorganic Fe solubility at in situ temperatures (between −2°C and +18°C). Because in situ temperatures in the Antarctic Circumpolar Current were mostly lower than +3°C, such cFeS,adj values, ranging from 0.5 to 1.8 nmol L−1, were roughly twice as large as cFeS,org. The adjustment relies heavily on model calculations of inorganic Fe solubility but, if correct, indicates that the bulk of the solubility of Fe in the cold waters of the Southern Ocean is tied to the solubility of inorganic Fe rather than to Fe ligands in the soluble size fraction.
Influence of geomorphic setting on the metabolism of Lake Huron fringing wetlands
Authors: Cooper Matthew J. , Steinman Alan D. , Uzarski Donald G.
Published: August 2016

We measured gross primary productivity (GPP) and respiration (R) seasonally in benthic, water column, and epiphytic microhabitats of Lake Huron fringing wetlands. Spring areal GPP ranged from 33 to 103 mmol O2 m−2 d−1, spring R ranged from 16 to 110 mmol O2 m−2 d−1, and the water column was the most important microhabitat for both GPP and R on average. Summer GPP ranged from 40 to 131 mmol O2 m−2 d−1, R ranged from 25 to 155 mmol O2 m−2 d−1, and the water column and benthic microhabitats were equally important for GPP and R. Fall GPP ranged from < 1 to 19 mmol O2 m−2 d−1, and R ranged from < 1 to 47 mmol O2 m−2 d−1, with the benthic and water column microhabitats being equally important. Net metabolism (the difference between GPP and R) was close to zero at most wetlands, but when macrophyte productivity was accounted for, most wetlands appeared autotrophic. Both GPP and R were highest in deep wetlands protected from hydrologic energy and declined with increasing wave exposure. With increasing exposure, wetlands were restricted to shallower water and benthic GPP and R increased relative to water column GPP and R. This pattern persisted to intermediate levels of exposure, beyond which benthic GPP and R declined as a result of physical disturbance to the sediment. Coastal wetlands are hotspots of productivity in Lake Huron and hydrologic energy is an important driver of total metabolism rates, as well as the distribution of GPP and R among microhabitats.
Response of lotic microbial communities to altered water source and nutritional state in a glaciated alpine floodplain
Authors: Freimann Remo , Bürgmann Helmut , Findlay Stuart E. G. , Robinson Christopher T.
Published: August 2016

Factors driving bacterial community composition (BCC) and linkages to ecosystem function (EF) are a fundamental interest in microbial ecology. Climate warming is expected to cause a shift from glacial‐ to groundwater‐dominated water sources in alpine catchments due to receding glaciers, which is likely accompanied by a shift in BCC and EF. In this context, we performed a reciprocal transplant experiment of hyporheic sediments within a Swiss alpine floodplain. We assessed the influence of water source (groundwater = krenal, glacial water = kryal) and nutritional state (C, N, and P) on BCC and EF. Experimental response was tested using automated ribosomal intergenic spacer amplification and potential activities of eight different enzymes. BCC from both kryal and krenal systems was highly resistant to changes in water source, yet exhibited pronounced EF flexibility. Major factors determining BCC and EF response were sediment origin followed by seasonal variation in BCC. The gradient in seasonal change in BCC showed different strengths in the two water systems. Krenal BCC was more seasonally stable compared with kryal BCC, although functional plasticity showed the same extent in both. This difference in connectivity between BCC and EF suggests that krenal BCC was dominated by generalists, whereas kryal BCC was dominated by specialists. The weak effect of altered nutritional state on BCC and EF indicates a complex but hierarchically structured relationship among these factors. We conclude that microbial communities in alpine catchments are able to rapidly buffer the effect of shifts in water source on ecosystem functioning.
Historical changes in nutrient inputs from humans and anadromous fishes in New England's coastal watersheds
Authors: Twining Cornelia W. , West Derek C. , Post David M.
Published: August 2016

Prior to Euro‐American contact, anadromous alewives (Alosa pseudoharengus) were abundant throughout eastern North America. In the 400 yr since Euro‐American settlement began in the region, anadromous alewife populations have declined by an order of magnitude or more while human land use has simultaneously intensified. Here we asked how lake nutrient inputs in the southern New England region have changed over the past 400 yr by examining nutrient inputs to four lakes in coastal Connecticut that differ in their land‐use history and their history of accessibility to anadromous alewife. We estimated the flux of nitrogen and phosphorus from both anadromous alewife and the landscape and conducted a paleoecological analysis of stable isotopes (δ15N, total δ13C, organic δ13C) and nutrients (N : P, C : N, organic C) from lake sediment cores in each of our study watersheds. Nutrient loading models suggest that allochthonous nutrient inputs are now dominated by watershed land use and our paleoecological data also reflect major changes in human land use. Loading models also suggest that prior to Euro‐American contact, anadromous alewife runs historically provided up to 95% of allochthonous phosphorus inputs and up to 68% of allochthonous nitrogen inputs to the region's coastal lakes. However, paleoecological data suggest that even the large nutrient inputs from abundant past alewife populations may never have had the same long‐term effect on lake nutrient dynamics as those from the landscape due to the unique combination of the alewife's life history and coastal Connecticut's climate and geomorphology.