bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection and quantification of Pseudo‐nitzschia australis in cultured and natural populations using LSU rRNA‐targeted probes
Authors: Scholin Christopher , Miller Peter , Buck Kurt , Chavez Francisco , Harris Paul , Haydock Paul , Howard Judith , Cangelosi Gerard
Published: May 2010

Pseudo‐nitzschia australis Frenguelli is a marine pennate diatom associated with the production of domoic acid— a neuroexcitatory amino acid linked to illness and mortality of humans and wildlife. Distinguishing P. australis from its co‐occurring congeners is labor intensive and time consuming because of a requirement for scanning electron microscopy. Here, we apply large‐subunit ribosomal RNA (LSU rRNA)‐targeted oligonucleotides in whole‐cell and sandwich hybridization formats to identify and enumerate this species collected from pure cultures and natural populations. Whole‐cell hybridization employed fluorescently labeled probes, filter‐based sample processing, and epifluorescence microscopy to enumerate labeled cells. In contrast, sandwich hybridization was accomplished by homogenizing cells in a chaotropic solution and performing two hybridization reactions: capture of LSU rRNA using an oligonucieotide coupled to a macroscopic solid support and binding of signal probe to a region of LSU rRNA near that of the capture site. Sandwich hybrids were detected colorimetrically; color intensity was proportional to the abundance of target species in the original sample. The sandwich hybridization assay was semiautomated with a robotic processor. Both whole‐cell and sandwich hybridization are useful techniques for identifying P. australis as it occurs in nature. Sandwich hybridization potentially offers the most rapid and simple means to accomplish this task when screening large numbers of environmental samples.
Role of photoreactions in the formation of biologically labile compounds from dissolved organic matter
Authors: Moran Mary Ann , Zepp Richard G.
Published: May 2010

Dissolved organic matter (DOM) can be degraded by sunlight into a variety of photoproducts that stimulate the growth and activity of microorganisms in aquatic environments. All biologically labile photoproducts identified to date fall into one of four categories: (1) low‐molecular‐weight (MW) organic compounds (carbonyl compounds with MW of <200); (2) carbon gases (primarily CO); (3) unidentified bleached organic matter; and (4) nitrogen‐ and phosphorus‐rich compounds (including NH4+ and PO43−). A number of laboratory studies using bacterial bioassay approaches have shown that the photochemical breakdown of DOM can stimulate biomass production or activity by 1.5‐ to 6‐fold. Results of photochemical studies, extrapolated to estimate formation rates of biologically available photoproducts from DOM in surface waters, also predict important biological roles for these compounds. In a continental shelf system, for example, full exposure of surface seawater to sunlight for one summer day can produce DOM photodegradation products equivalent to >20% of the bacterial carbon demand. Likewise, 30% of the bacterial nitrogen demand can be met by photodegradation of the nitrogen components of DOM, a process likely to be of particular importance in nitrogen‐limited systems. When considered on a depth‐integrated basis around the globe, at least 1.0 × 1015 g C and 0.15 × 1015 g N are estimated to be available annually for utilization by planktonic microorganisms through the conversion of light‐absorbing fractions of DOM to more biologically labile compounds. By comparison, direct photochemical mineralization of DOM is estimated to convert 12−16 × 1015 g C to CO2 annually.
Nitrogen and phosphorus excretion by detritivorous gizzard shad in a reservoir ecosystem
Authors: Schaus M. H. , Vanni M. J. , Wissing T. E. , Bremigan M. T. , Garvey J. E. , Stein R. A.
Published: May 2010

The detritivorous fish, gizzard shad (Dorosoma cepedianum), provides nutrients to phytoplankton in reservoirs by ingesting organic detritus associated with sediments and excreting substantial quantities of nutrients such as N and P in soluble forms that are highly available to phytoplankton. We estimated nutrient excretion by gizzard shad in a eutrophic reservoir (Acton Lake, Ohio) during April–October 1994 by measuring N and P excretion of field‐caught fish (n = 135). Excretion rates were then extrapolated to nutrient release by the gizzard shad population using quadrat rotenone biomass estimates, electrofishing surveys, and historic seasonal trends. N and P excretion were positively correlated with fish wet mass and temperature, but mass‐specific excretion declined with increasing fish mass. Lakewide gizzard shad biomass in July 1994 was 417 kg ha−1. Our estimates of nutrient excretion by the gizzard shad population ranged from 0.487 to 0.769 µmol NH3‐N liter−1 d−1 and 0.022 to 0.057 µmol soluble reactive phosphorus liter−1 d−1, with the highest excretion occurring during mid‐summer through early fall. The low N : P ratio at which gizzard shad excrete [mean molar N : P= 16.75 (±0.89 SE)] may alter phytoplankton community composition, favoring cyanobacteria. Our results indicate that nutrient excretion by detritivorous fish can be an important source of nutrients to open waters, especially when other sources of nutrients are reduced.
Partial characterization of the dissolved organic phosphorus pool in the oligotrophic North Pacific Ocean
Authors: Karl David M. , Yanagi Katsumi
Published: May 2010

The combined application of two independent methods for phosphorus (P i determination in seawater, continuous‐flow UV photodecomposition and magnesium‐induced coprecipitation (MAGIC), was used to provide a partial characterization of the dissolved P pools at Sta. ALOHA (22°45′N, 158°W) in tl e oligotrophic subtropical North Pacific Ocean. Comprehensive laboratory analyses of the UV light‐induced photodecomposition of a variety of specific organic P compounds dissolved in seawater confirmed that submicromolar concentrations of monophosphate compounds could be analytically separated from nucleotide di‐ and triphosphates based upon a previously described temperature‐controlled low‐pressure, mercury vapor UV irradiation treatment. When combined with a recently described high‐precision P‐detection system, the total dissolved phosphorus (TDP) in seawater could be reproducibly subdivided into three chemically distinct pools: soluble reactive phosphorus (SRP; presumably dominated by orthophosphate), UVlabile phosphorus (PUV‐L; containing primarily monophosphate esters), and UV‐stable phosphorus (PUV‐S; containing primarily nucleotide di‐ and triphosphates, nucleic acids, and other compounds that are resistant to the UV treatment). Field application of these procedures to samples collected at Sta. ALOHA during the period September 1991 to March 1992 (HOT‐30 to HOT‐35) revealed the presence of all three operationally defined pools. In the upper portion of the water column (0–100 m) the TDP pool (29.26 ± 2.32 mmol P m−2) contained, on average, 23% SRP, 26% PUV‐S, and 51% With increasing depth, the concentration of P decreased while that of the PUV‐S pool increased; the PUVL,: PUV‐S ratios decreased from values of 2–5 in the upper water column to ≤ 1.0 at 200 m.
Dynamics of UV‐driven hydrogen peroxide formation on an intertidal sandflat
Authors: Abele‐Oeschger Doris , Tüg Helmut , Röttgers Rüdiger
Published: May 2010

Photochemically produced H2O2 was found to accumulate at micromolar concentrations in intertidal Wadden Sea areas. Annual amplitudes of solar radiation lead to variations of the intertidal H2O2 accumulation with concentrations between 1 and 4 µmol liter−1 during summer, while winter concentrations were mostly <0.5 µmol liter−1. Diurnal variations of H2O2 accumulation over daily low‐tide periods in intertidal environments are determined by the incident solar radiation, the concentration of UV‐absorbing dissolved organic carbon in the water, as well as the concomitant biological and chemical H2O2 degradation within the sediment surface. The efficiency of photosynthetic available radiation (PAR), UVA and UVB photons for photochemical H2O2 production was assessed using cut‐off filters in the UVB and in different UVA ranges. UVB photons (295–320 nm) displayed an 11‐fold higher efficiency compared to UVA (335–370 nm) and a 340‐fold higher efficiency compared to PAR photons (>400 nm). A 10% ozone reduction leads to a doubling of UVB surface irradiance at 300 nm, which entails a 30 and 40% increase of the apparent intertidal H2O2 concentrations. Progressive stratospheric ozone depletion via UVB‐induced H2O2 formation will have yet unpredictable effects on boreal and Antarctic intertidal ecosystems.
Local differences in macrozoobenthic response to enhanced food supply caused by mild eutrophication in a Wadden Sea area. Food is only locally a limiting factor
Authors: Beukema J. J. , Cadée G. C.
Published: May 2010

In the late 1970s food supply to herbivores suddenly doubled in the western half of the Dutch Wadden Sea probably as a consequence of increased nutrient concentrations. The response of zoobenthos was studied during 1970–1990 as part of a long‐term monitoring program, including annual sampling at 15 fixed stations with very different environmental conditions (elevation, sediment grain size) on Balgtand, a 50‐km2 tidal flat area. The total zoobenthic stock in the affected area roughly doubled within 2 yr after the doubling of the stock of planktonic algae. However, the magnitude of the response differed from station to station. We tested the hypothesis that a strong positive response would occur particularly at stations where food could be limiting, i.e. where zoobenthic food demand was high relative to food supply. Biomass increases of zoobenthos in the order of a doubling were indeed restricted to the part of Balgzand characterized already in the 1970s by high biomass values. The zoobenthic biomass hardly increased in two areas of Balgzand with relatively low values for zoobenthic biomass and species richness. In these impoverished areas environmental conditions are harsh and the benthic communities are dominated by small opportunistic species. One of these areas is characterized by a high intertidal elevation (short daily inundation periods) combined with a sheltered location near the coast (resulting in muddy sediments), the other by severe exposure to currents and wind (rasultinh in mobile sands with silt and organic‐matter contents) due to its offshore position. We conclude that food limitation only existed in the midshore communities living under relatively mild abiotic conditions. Apparently, the benthic consumer populations benefitted from eutrophication‐induced enhancement of their food supply by enlargement of their stocks only where they were not too stressed by unfavorable abiotic conditions.
Effects of darkness on multi‐excitation in vivo fluorescence and survival in a marine diatom
Authors: Murphy Alice M. , Cowles Timothy J.
Published: May 2010

Surveys of the California Current System in 1993 revealed high concentrations of photosynthetic pigment biomass at ∼200‐m depth, well below the euphotic zone. The deep fluorescence feature contained an estimated 2.2 × 104 metric tons of carbon and contained ∼2.5 times the amount of chlorophyll observed in surface waters directly above it. Deep phytoplankton assemblages may be a signature of water mass subduction, suggesting the possibility of using phytoplankton as water mass tracers. These field observations led to a laboratory study of the fluorescence characteristics of autotrophic cells as possible indices of acclimation to extended periods of darkness. In vivo multiexcitation Chl a fluorescence of the diatom Thalassiosira weissflogii was monitored for 2 months of total darkness. Numbers of living and dead cells were determined using the vital stain fluorescein diacetate (FDA). By the end of the dark incubation period, in vivo Chl a fluorescence and fluorescence per cell had leveled off to ∼45% and 65% of initial values, respectively. The contribution of accessory pigments to Chl a fluorescence, expressed as multiexcitation fluorescence ratios, was higher in the dark than prior to transfer to darkness but showed no significant changes during 2 months of darkness. The FDA assay indicated that ∼85% of the cells were alive for at least the first 3 weeks during the first dark experiment and for the entire 2 months of second dark incubation. Cell numbers decreased to 65% of initial values and then grew exponentially upon reexposure to a light: dark photoperiod. Our results for T. weissflogii suggest that extended light limitation of photosynthesis does not preclude the survival of subducted phytoplankton assemblages and the consequent accumulation of Chl a at depths below the euphotic zone. If these results extend to natural assemblages, it is not possible to estimate advective time scales based on a maximum persistence time of pigment fluorescence below the euphotic zone. Nevertheless, the deep phytoplankton assemblage we observed provides evidence for water mass subduction and suggests that large, intermittent pulses of phytoplankton carbon are a part of cross‐shelf exchange and vertical flux from surface waters to depth in this region.
Isotopic compositions of lipid biomarker compounds in estuarine plants and surface sediments
Authors: Canuel Elizabeth A. , Freeman Katherine H. , Wakeham Stuart G.
Published: May 2010

We examined the isotopic compositions of fatty acids, sterols, and hydrocarbons isolated from three coastal macrophytes (Zostera marina, Spartina alterniflora, and Juncus roemerianus) in order to investigate the relative contribution of these vascular plants as sources of organic matter in coastal sediments such as Cape Lookout Bight, North Carolina. On average, lipid biomarker compounds extracted from the plants were depleted in 13C by 3–5‰ relative to δ13C total organic carbon (TOC). However, individual compounds within each lipid class varied by up to 5.6‰. Trends in the isotopic compositions of lipids were consistent with δ13CTOC; compounds obtained from Z. marina were the most enriched in 13C and those from J. roemerianus were the most depleted. The range in isotopic abundances and molecular compositions of the sediments was greater than that obtained from the plants, indicating that additional, presently unidentified sources of organic matter contribute to the Cape Lookout Bight sediments. Similarity between the signatures for suspended particulate matter and the sediments indicates that much of the sedimentary organic matter is derived from algal and bacterial sources. Bacterial sources of organic matter are likely greater during summer/early fall, and incorporation of 13C‐enriched bacterial biomass may contribute to observed seasonal shifts in δ13CTOC in the surficial sediments.
An autonomous. bottom‐transecting vehicle for making long time‐series measurements of sediment community oxygen consumption to abyssal depths
Authors: Smith K. L. , Glatts R. C. , Baldwin R. J. , Beaulieu S. E. , Uhlman A. H. , Horn R. C. , Reimers C. E.
Published: May 2010

We have developed and successfully collected data with a unique, bottom‐transecting vehicle (ROVER) that permits the first long time‐series measurements of sediment community oxygen consumption (SCOC). This instrument has the following capabilities: (1) it operates as an autonomous, free vehicle on the sea floor to 6,000‐m depth for periods up to 6 months; (2) it transits across the sea floor, minimizing the impact that a long‐term, free‐vehicle structure would have on measurement sites; (3) it measures SCOC by using duplicate benthic chambers at up to 30 different sites over a single deployment period; (4) it measures sediment porewater oxygen concentration as an independent measure of SCOC by using a microprofiler at up to 30 different sites over a single deployment period; (5) it has an incubation period of programmable duration for each SCOC measurement; (6) it monitors operation of instruments and the surrounding area with time‐lapse still and video cameras; (7) it has the flexibility to be used as an autonomous programmable platform for a wide variety of benthic boundary‐layer measurements; and (8) it collects a water sample for oxygen and other analyses at the end of the deployment. The ROVER resembles a small forklift with a forward‐mounted instrument assembly, a current meter, double‐tread propulsion system, central battery and controller electronics, flotation, acoustic releases, and disposable ballast. The ROVER was deployed for a 4‐month period (January–May 1996) to measure SCOC at 4,100‐m depth in the eastern North Pacific. During this deployment the ROVER occupied 17 sites with each benthic chamber incubation lasting 152.3 h and a 17‐h interval between incubations for repositioning and transit. SCOC ranged from 0.50 to 0.91 mmol O2 n−2 d−1, generally declining from January until the end of February and then increasing irregularly to the end of the deployment in late May. These measurements show good agreement with those made at the same site with another autonomous instrument, the free‐vehicle grab respirometer, at the beginning and end of the ROVER deployment.
Rapid fluorometric assay of bacterial density in lake water and seawater
Authors: Tranvik Lars J.
Published: May 2010

This paper describes a rapid fluorometric method for the determination of bacterial densities ranging from 105 to 107 ml−1 by using the double‐stranded DNA stain PicoGreen. Reagents are added to water samples (200 µl) without concentration of the bacteria or laborious extraction of bacterial DNA. The method works well both in lake water, including humic water with high background fluorescence, and in seawater. The PicoGreen assay successfully replaces time‐consuming microscopy for counts of bacterial cultures and can be used in natural water samples as well. In samples from 12 lakes representing a wide range of bacterial and algal concentrations, DNA content was closely correlated with bacterial numbers (r = 0.96).
Comparison of the phytoplankton species composition and structure in the Climax area (1973–1985) with that of station ALOHA (1994)
Authors: Venrick E. L.
Published: May 2010

In August 1994, water samples were collected from seven depths on each of two casts at the Hawaiian Ocean Time‐series station (ALOHA; 22°45′N, 158°W). These samples allowed a comparison between the larger phytoplankton taxa at ALOHA and those in the Climax area (near 28°N, 155°W) that were collected during summers between 1973 and 1985. Of the 142 species found at ALOHA, all but 6 have been seen in the Climax area. The two‐layered structure that is typical of the Climax area was also found at station ALOHA, where the break between shallow and deep associations occurred between 100‐ and 135‐m depth. However, abundances of the deep species at ALOHA were lower than in the Climax area. The correlations between the rank order of abundances of phytoplankton from Sta. ALOHA and from the Climax area fell within the spectrum of correlations between pairs of stations from the Climax area. These results indicate that in August 1994 the phytoplankton at Sta. ALOHA was indistinguishable from that in the Climax area between 1973 and 1985. Nevertheless, many additional studies are needed before results from the Climax area or results from the Hawaiian Ocean Time‐series program can be unconditionally generalized.
Measurement and prediction of mass transfer to experimental coral reef communities
Authors: Baird M. E. , Atkinson M. J.
Published: May 2010

The uptake of nutrients (N and P) into coral reef communities is proposed to be limited by diffusion through concentration‐depleted boundary layers between the water and organisms, or what is termed “mass transfer limitation.” The mass transfer rate is a physical limit to the rate of nutrient uptake. Maximum uptake rates by highly rough biological surfaces have not yet been evaluated. Engineering correlations indicate that increased surface roughness should increase mass transfer, although it has been difficult to quantify roughness of living corals. In this paper, the effects of highly rough coral surfaces on mass transfer were investigated by using dissolution of gypsum (plaster‐of‐paris) from flat smooth surfaces and coral skeletons. The gypsum dissolution rates were measured as an increase in concentration of calcium ions in freshwater recirculating over experimental surfaces. Stanton numbers (Stm, a dimensionless number giving the ratio of uptake rate per unit area to the rate of advection of the substance past the uptake surface) of experimental smooth surfaces ranged from 2.6 to 3.5 × 10−5 and were the same as values in the engineering literature for smooth surfaces. Stm for coral‐shaped surfaces ranged from 70 × 10−5 at 0.03 m s−1 to 17 × 10−5 at velocities up to 0.50 m s−1 and were in general 9 ± 1 times that of smooth surfaces. The measured Stm for each coral‐shaped surface was the same as the predicted Stm (±10%) calculated from measured friction and roughness using a correlation of heat transfer. Stm for ammonia uptake on living coral reef communities show the same relationship between mass transfer, friction, and roughness as the coral‐shaped gypsum surfaces. The transport rates of nutrients to reef surfaces are controlled by large‐scale roughness, typically associated with coral heads, and not small‐scale roughness elements on the organisms, nor biological alterations of diffusive boundary layers. Nutrient uptake and possibly other metabolic exchange rates arc governed by concentration, water velocity, and friction dissipated over the reef, denoting that coral reef community metabolism is physically forced.
Silica cycling within marine snow
Authors: Brzezinski Mark A. , Alldredge Alice L. , O'Bryan Linda M.
Published: May 2010

The silica cycle within particles of marine snow from coastal waters off central California was examined. The ratios of biogenic silica to particulate organic nitrogen and to particulate org.anic carbon in aggregates were significantly greater than Redfield ratios, suggesting a large detrital silica component within the particles. Silicic acid concentrations within aggregates were ∼10‐fold greater on average than those in the surrounding seawater, with interstitial concentrations up to 305 µM Si(OH)4. Silica production rates within aggregates were sufficient to deplete the interstitial silicic acid in 0.3–4.0 h, suggesting rapid cycling of Si within the aggregates. Efflux of Si(OH)4 from the aggregates predicted from molecular diffusion theory was 20‐fold greater than the known maximum possible rates of silica dissolution could support. Congruence between efflux rates predicted by diffusion theory and dissolution kinetics requires the diffusion coefficient for Si(OH)4 in marine snow to be 2 orders of magnitude less than in pure seawater. Experimental determination of the concentration dependence of silicic acid use by diatoms in aggregates and by those in the surrounding seawater indicated that assemblages from both environments would experience Si‐replete conditions within marine snow. Aggregation of diatoms following silicic acid depletion at the end of blooms may provide Si‐replete microhabitats suitable for the formation of the heavily silicified resting spores that are central to the life‐history of many species.
Production of bromoform and dibromomethane by Giant Kelp: Factors affecting release and comparison to anthropogenic bromine sources
Authors: Goodwin Kelly D. , North Wheeler J. , Lidstrom Mary E.
Published: May 2010

Macrocystis pyrifera (Giant Kelp), a dominant macroalgal species in southern California, produced 171 ng per g fresh wt (gfwt) per day of CHBr3 and 48 ng gfwt−1 d−1 of CH2Br2 during laboratory incubations of whole blades. Comparable rates were measured during in situ incubations of intact fronds. Release of CHBr3 and CH2Br2 by M. pyrifera was affected by light and algal photosynthetic activity, suggesting that environmental factors influencing kelp physiology can affect halomethane release to the atmosphere. Data from H2O2 additions suggest that brominated methane production during darkness is limited by bromide oxidant supply. A bromine budget constructed for a region of southern California indicated that bromine emitted from the use of CH3Br as a fumigant (1 × 108 g Br yr−1) dominates macroalgal sources (3 × 106 g Br yr−1). Global projections, however, suggest that combined emissions of marine algae (including microalgae) contribute substantial amounts of bromine to the global cycle, perhaps on the same order of magnitude as anthropogenic sources.
Physicochemical variations in DOM‐synchronous fluorescence: Implications for mixing studies
Authors: Pullin Michael J. , Cabaniss Stephen E.
Published: May 2010

Synchronous fluorescence (SF) spectra of dissolved organic matter (DOM) show promise for mixing studies and can resolve multiple river inputs to large water masses in a single fast measurement. This study examines the effects of physicochemical variables on DOM SF, independent of mixing. Our results show that changes in the pH and metal ion concentration do not affect SF in the alkaline Cuyahoga‐Erie system. The effect of temperature is small and correctable. Model predictions suggest that photobleaching of DOM SF can limit the use of this method to short periods (3–7 d, depending on conditions). SF spectra are sensitive enough to detect 1% river water mixed in Lake Erie water.
Improvements in the profiles and distributions of nitric acid and nitrogen dioxide with the LIMS version 6 dataset
Authors: Remsberg E. , Natarajan M. , Marshall B. T. , Gordley L. L. , Thompson R. E. , Lingenfelser G.
Published: May 2010

Abstract. The quality of the Nimbus 7 Limb Infrared Monitor of the Stratosphere (LIMS) nitric acid (HNO3) and nitrogen dioxide (NO2) profiles and distributions of 1978/1979 are described after their processing with an updated, Version 6 (V6) algorithm and subsequent archival in 2002. Estimates of the precision and accuracy of both of those species are developed and provided herein. The character of the V6 HNO3 profiles is relatively unchanged from that of the earlier LIMS Version 5 (V5) profiles, except in the upper stratosphere where the interfering effects of CO2 are accounted for better with V6. The accuracy of the retrieved V6 NO2 is also significantly better in the middle and upper stratosphere, due to improvements in its spectral line parameters and in the reduced biases for the accompanying V6 temperature and water vapor profiles. As a result of these important updates, there is better agreement with theoretical calculations for profiles of the HNO3/NO2 ratio, day-to-night NO2 ratio, and with estimates of the production of NO2 in the mesosphere and its descent to the upper stratosphere during polar night. In particular, the findings for middle and upper stratospheric NO2 should also be more compatible with those obtained from more recent satellite sensors because the effects of the spin-splitting of the NO2 lines are accounted for now with the LIMS V6 algorithm. The improved precisions and more frequent retrievals of the LIMS profiles along their orbit tracks provide for better continuity and detail in map analyses of these two species on pressure surfaces. It is judged that the chemical effects of the oxides of nitrogen on ozone can be studied quantitatively throughout the stratosphere with the LIMS V6 data.
The PreVOCA experiment: modeling the lower troposphere in the Southeast Pacific
Authors: Wyant M. C. , Wood R. , Bretherton C. S. , Mechoso C. R. , Bacmeister J. , Balmaseda M. A. , Barrett B. , Codron F. , Earnshaw P. , Fast J. , Hannay C. , Kaiser J. W. , Kitagawa H. , Klein S. A. , Köhler M. , Manganello J. , Pan H.-L. , Sun F. , Wang S. , Wang Y.
Published: May 2010

Abstract. The Preliminary VOCALS Model Assessment (PreVOCA) aims to assess contemporary atmospheric modeling of the subtropical South East Pacific, with a particular focus on the clouds and the marine boundary layer (MBL). Models results from fourteen modeling centers were collected including operational forecast models, regional models, and global climate models for the month of October 2006. Forecast models and global climate models produced daily forecasts, while most regional models were run continuously during the study period, initialized and forced at the boundaries with global model analyses. Results are compared in the region from 40° S to the equator and from 110° W to 70° W, corresponding to the Pacific coast of South America. Mean-monthly model surface winds agree well with QuikSCAT observed winds and models agree fairly well on mean weak large-scale subsidence in the region next to the coast. However they have greatly differing geographic patterns of mean cloud fraction with only a few models agreeing well with MODIS observations. Most models also underestimate the MBL depth by several hundred meters in the eastern part of the study region. The diurnal cycle of liquid water path is underestimated by most models at the 85° W 20° S stratus buoy site compared with satellite, consistent with previous modeling studies. The low cloud fraction is also underestimated during all parts of the diurnal cycle compared to surface-based climatologies. Most models qualitatively capture the MBL deepening around 15 October 2006 at the stratus buoy, associated with colder air at 700 hPa.
CCN predictions using simplified assumptions of organic aerosol composition and mixing state: a synthesis from six different locations
Authors: Ervens B. , Cubison M. J. , Andrews E. , Feingold G. , Ogren J. A. , Jimenez J. L. , Quinn P. K. , Bates T. S. , Wang J. , Zhang Q. , Coe H. , Flynn M. , Allan J. D.
Published: May 2010

Abstract. An accurate but simple quantification of the fraction of aerosol particles that can act as cloud condensation nuclei (CCN) is needed for implementation in large-scale models. Data on aerosol size distribution, chemical composition, and CCN concentration from six different locations have been analyzed to explore the extent to which simple assumptions of composition and mixing state of the organic fraction can reproduce measured CCN number concentrations. Fresher pollution aerosol as encountered in Riverside, CA, and the ship channel in Houston, TX, cannot be represented without knowledge of more complex (size-resolved) composition. For aerosol that has experienced processing (Mexico City, Holme Moss (UK), Point Reyes (CA), and Chebogue Point (Canada)), CCN can be predicted within a factor of two assuming either externally or internally mixed soluble organics although these simplified compositions/mixing states might not represent the actual properties of ambient aerosol populations, in agreement with many previous CCN studies in the literature. Under typical conditions, a factor of two uncertainty in CCN concentration due to composition assumptions translates to an uncertainty of ~15% in cloud drop concentration, which might be adequate for large-scale models given the much larger uncertainty in cloudiness.
Response of the auroral electrojet indices to abrupt southward IMF turnings
Authors: Gjerloev J. W. , Hoffman R. A. , Ohtani S. , Weygand J. , Barnes R.
Published: May 2010

Abstract. We present results from a study of the behavior of the auroral electrojet indices following abrupt southward turnings of the IMF Bz. The auroral electrojet indices are calculated from observations made by more than 100 ground based stations provided by the SuperMAG collaborators. Based on three simple criteria we selected 73 events. In each event the interval of analysis started at the time of the IMF Bz southward turning and ended 45 minutes later or at the onset of any abrupt energy unloading event in the magnetosphere, regardless of size. We refer to this period as the "pre-unloading phase". To isolate the dependence of the auroral electrojets on the solar induced ionospheric conductivity during this phase we separated the standard AU/AL indices into two new sets of indices defined by the upper and lower envelope of the north-south component for all sunlit stations (AUs/ALs) and for all stations in darkness (AUd/ALd). Based on events and statistical analyses we can conclude that following a southward turning of the IMF Bz the AUd/ALd indices show no measurable response while the AUs/ALs indices clearly intensify. The intensifications of AUs/ALs are dependent on the intensity of the solar wind driver (as measured by IMF Bz or the Akasofu ε parameter). The lack of AUd/ALd response does not depend on the intensity of any subsequent substorm. We find that during these isolated events the ionospheric current system is primarily confined to the sunlit ionosphere. This truncated version of the classical global DP-2 current system suggests that auroral electrojet continuity is not maintained across the terminator. Because of its conductivity dependence on the solar zenith angle, this truncated global current pattern is expected to be highly dependent on UT and season and thus can be asymmetric between hemispheres. Thus we argue that the global two-cell DP-2 current system is not a consequence only of a southward turning of the IMF but requires also the reduction of the conductivity gradient at the terminator.
Flow tilt angles near forest edges – Part 1: Sonic anemometry
Authors: Dellwik E. , Mann J. , Larsen K. S.
Published: May 2010

Abstract. An analysis of flow tilt angles from a fetch-limited beech forest site with clearings is presented in the context of vertical advection of carbon dioxide. Flow angles and vertical velocities from two sonic anemometers by different manufacturers were analyzed. Instead of using rotations, where zero-flow angles were assumed for neutral flow, the data was interpreted in relation to upstream and downstream forest edges. Uncertainties caused by flow distortion, vertical misalignment and limited sampling time (statistical uncertainty) were evaluated and found to be highly significant. Since the attack angle distribution of the wind on the sonic anemometer is a function of atmospheric stratification, an instrumental error caused by imperfect flow distortion correction is also a function of the atmospheric stratification. In addition, it is discussed that the sonic anemometers have temperature dependent off-sets. These features of the investigated sonic anemometers make them unsuitable for measuring vertical velocities over highly turbulent forested terrain. By comparing the sonic anemometer results to that of a conically scanning Doppler lidar (Dellwik et al., 2010b), sonic anemometer accuracy for measuring mean flow tilt angles was estimated to between 2° and 3°. Use of planar fit algorithms, where the mean vertical velocity is calculated as the difference between the neutral and non-neutral flow, does not solve this problem of low accuracy and is not recommended. Because of the large uncertainties caused by flow distortion and vertical alignment, it was only possible to a limited extent to relate sonic anemometer flow tilt angles to upwind forest edges, but the results by the lidar indicated that an internal boundary layer affect flow tilt angles at 21m above the forest. This is in accordance with earlier studies at the site. Since the mean flow tilt angles do not follow the terrain, an estimate of the vertical advection term for near-neutral conditions was calculated using profile measurements of carbon dioxide. The estimated advection term is large, but it is not recommended to include it in the surface carbon balance, unless all terms in the carbon dioxide conservation equation can be precisely estimated.
Climate and carbon-cycle variability over the last millennium
Authors: Jungclaus J. H. , Lorenz S. J. , Timmreck C. , Reick C. H. , Brovkin V. , Six K. , Segschneider J. , Giorgetta M. A. , Crowley T. J. , Pongratz J. , Krivova N. A. , Vieira L. E. , Solanki S. K. , Klocke D. , Botzet M. , Esch M. , Gayler V. , Haak H. , Raddatz T. J. , Roeckner E. , Schnur R. , Widmann H. , Claussen M. , Stevens B. , Marotzke J.
Published: May 2010

Abstract. A long-standing task in climate research has been to distinguish between anthropogenic climate change and natural climate variability. A prerequisite for fulfilling this task is the understanding of the relative roles of external drivers and internal variability of climate and the carbon cycle. Here, we present the first ensemble simulations over the last 1200 years with a comprehensive Earth system model including a fully interactive carbon cycle. Applying up-to-date reconstructions of external forcing including the recent low-amplitude estimates of solar variations, the ensemble simulations reproduce temperature evolutions consistent with the range of reconstructions. The 20th-century warming trend stands out against all pre-industrial trends within the ensemble. Volcanic eruptions are necessary to explain variations in pre-industrial climate such as the Little Ice Age; yet only the strongest, repeated eruptions lead to cooling trends that stand out against the internal variability across all ensemble members. The simulated atmospheric CO2 concentrations exhibit a stable carbon cycle over the pre-industrial era with multi-centennial variations somewhat smaller than in the observational records. Early land-cover changes have modulated atmospheric CO2 concentrations only slightly. We provide a model-based quantification of the sensitivity (termed γ) of the global carbon cycle to temperature for a variety of climate and forcing conditions. The magnitude of γ agrees with a recent statistical assessment based on reconstruction data. We diagnose a distinct dependence of γ on the forcing strength and time-scales involved, thus providing an explanation for the systematic difference in the observational estimates for different segments of the last millennium.
Factors influencing chloride deposition in a coastal hilly area and application to chloride deposition mapping
Authors: Guan H. , Love A. J. , Simmons C. T. , Makhnin O. , Kayaalp A. S.
Published: May 2010

Abstract. Chloride is commonly used as an environmental tracer for studying water flow and solute transport in the environment. It is especially useful for estimating groundwater recharge based on the commonly used chloride mass balance (CMB) method. Strong spatial variability in chloride deposition in coastal areas is one difficulty encountered in appropriately applying the method. A high-resolution bulk chloride deposition map in the coastal region is thus needed. The aim of this study is to construct a chloride deposition map in the Mount Lofty Ranges (MLR), a coastal hilly area of approximately 9000 km2 spatial extent in South Australia. We examined geographic (related to coastal distance), orographic, and atmospheric factors that may influence chloride deposition, using partial correlation and regression analyses. The results indicate that coastal distance, elevation, as well as terrain aspect and slope, appear to be significant factors controlling chloride deposition in the study area. Coastal distance accounts for 70% of spatial variability in bulk chloride deposition, with elevation, terrain aspect and slope an additional 15%. The results are incorporated into a de-trended residual kriging model (ASOADeK) to produce a 1 km×1 km resolution bulk chloride deposition and concentration maps. The average uncertainty of the deposition map is about 20–30% in the western MLR, and 40–50% in the eastern MLR. The maps will form a useful basis for examining catchment chloride balance for the CMB application in the study area.
Future high-mountain hydrology: a new parameterization of glacier retreat
Authors: Huss M. , Jouvet G. , Farinotti D. , Bauder A.
Published: May 2010

Abstract. Global warming is expected to significantly affect the runoff regime of mountainous catchments. Simple methods for calculating future glacier change in hydrological models are required in order to reliably assess economic impacts of changes in the water cycle over the next decades. Models for temporal and spatial glacier evolution need to describe the climate forcing acting on the glacier, and ice flow dynamics. Flow models, however, demand considerable computational resources and field data input and are moreover not applicable on the regional scale. Here, we propose a simple parameterization for calculating the change in glacier surface elevation and area, which is mass conserving and suited for hydrological modelling. The Δh-parameterization is an empirical glacier-specific function derived from observations in the past that can easily be applied to large samples of glaciers. We compare the Δh-parameterization to results of a 3-D finite-element ice flow model. As case studies, the evolution of two Alpine glaciers of different size over the period 2008–2100 is investigated using regional climate scenarios. The parameterization closely reproduces the distributed ice thickness change, as well as glacier area and length predicted by the ice flow model. This indicates that for the purpose of transient runoff forecasts, future glacier geometry change can be approximated using a simple parameterization instead of complex ice flow modelling. Furthermore, we analyse alpine glacier response to 21st century climate change and consequent shifts in the runoff regime of a highly glacierized catchment using the proposed methods.
Suspended particles in the Canada Basin from optical and bottle data, 2003–2008
Authors: Jackson J. M. , Allen S. E. , Carmack E. C. , McLaughlin F. A.
Published: May 2010

Abstract. It is expected that coastal erosion, upwelling and increased river runoff from Arctic warming will increase the concentration of suspended particles in the Arctic Ocean. Here we analyze in situ transmissometer and fluorometer data from the summers of 2003 through 2008 and bottle-derived particulate organic carbon (POC) and total suspended solids (TSS) measurements sampled in the summers of 2006 and 2007 from the Canada Basin and surrounding shelves. By coupling these data sets, we explored the correlation of POC with beam attenuation coefficients to assess the viability of estimating POC concentrations from archived transmissometer data. We divided our study area into five regions to account for the significant spatial variability and found that POC (but not TSS) and attenuation were well-correlated over the Northwind Ridge, in the Canada Basin interior, and along the eastern shelf of the Canada Basin. We then estimated POC from attenuation for these regions and found that the average POC ranged from 16 to 37 μg C kg−1 within the upper 50 m and from 14 to 23 μg C kg−1 from 50–100 m. The strength of the chlorophyll maximum appeared to dominate the average POC values. In general, the eastern shelf was the least productive region in our study area. Neither TSS nor POC were well-correlated along the entire Beaufort shelf. Our interannual comparison from the summers of 2003 through 2008 found no evidence of increased particle concentrations over the Northwind Ridge, in the Canada Basin interior, or along the eastern shelf, however, this work provides a baseline of suspended POC concentrations.
Prognostic factors for the two‐year course of activity limitations in early osteoarthritis of the hip and/or knee
Authors: Holla Jasmijn F. M. , Steultjens Martijn P. M. , Roorda Leo D. , Heymans Martijn W. , ten Wolde Saskia , Dekker Joost
Published: May 2010

Objective

To predict the 2‐year course of activity limitations in patients with early knee and/or hip osteoarthritis (OA).

Methods

The Cohort Hip & Cohort Knee (CHECK) study is a prospective followup study. The CHECK cohort, comprising participants (n = 1,002) with early OA‐related knee and/or hip symptoms, was followed for 2 years. Participants completed questionnaires and underwent physical, laboratory, and radiographic examination. Regression models were used to examine whether baseline variables predicted the course of activity limitations as measured with the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Analyses were performed separately for participants with knee symptoms and participants with hip symptoms.

Results

After 2 years of followup, activity limitations slightly decreased. Large between‐subject variation was observed in WOMAC change scores. In participants with knee symptoms, young age, non‐Western ethnicity, bilateral hip pain, morning stiffness in the knee, high comorbidity count, high body mass index, high bodily pain, poor general health perception, and pain coping strategy were associated with a poor 2‐year outcome on activity limitations. In participants with hip symptoms, few activity limitations at baseline, bilateral hip pain, morning stiffness in the knee, high comorbidity count, low active hip flexion, poor general health perception, and pain coping strategy were associated with a poor 2‐year outcome on activity limitations.

Conclusion

After 2 years of followup, large between‐subject variation was observed in the course of activity limitations. The course of activity limitations is to some extent already predictable at an early stage of knee and hip OA.
Therapeutic Window for Bioactive Nanocomposites Fabricated by Laser Ablation in Polymer‐Doped Organic Liquids
Authors: Hahn Anne , Stöver Timo , Paasche Gerrit , Löbler Marian , Sternberg Katrin , Rohm Henning , Barcikowski Stephan
Published: May 2010

Polymeric nanomaterials are gaining increased interest in medical applications due to the sustained release of bioactive agents. Within this study nanomaterials are fabricated using laser ablation of silver and copper in polymer‐doped organic liquids thus allowing to produce customized drug release systems. A strategy is shown to determine the therapeutic window for cells relevant for cochlear implant electrodes, defined by the viability of L929 fibroblasts, PC12 neuronal cells, and spiral ganglion cells on different concentrations of silver and copper ions. The distribution of nanoparticles within the silicone polymer matrix is determined using transmission electron microscopy. Hexane doped with 1% silicone resin is found to be an appropriate liquid matrix to fabricate a nanocomposite with a constant ion release rate. Silver ions of 10 µmol L−1 or copper ions of 100 µmol L−1 cause a suppression of tissue growth without inhibiting neuronal cell growth. The copper nanoparticle content of 0.1 wt% of the silicone composite releases ion concentrations which fit the therapeutic window.
Heck reaction catalyzed by a recyclable palladium supported on shell powder
Authors: Shen Yong‐Miao , Du Yi‐Jun , Zeng Min‐Feng , Zhi Duo , Zhao Sheng‐Xian , Rong Lin‐Mei , Lv Shao‐Qin , Du Lin , Qi Chen‐Ze
Published: May 2010

A novel palladium catalyst supported on shell powder has been prepared, and its application to the Heck reaction of aryl iodides with olefins has been reported. The results showed that the novel catalyst had extremely high activities for the reactions with the average yield over 90%. Also, this catalyst showed excellent stability in Heck reactions, being reused three times. The catalyst was characterized by X‐ray powder diffraction and field‐emission scanned electron microscopy images, and the energy dispersive X‐ray analyzer. Copyright © 2010 John Wiley & Sons, Ltd.