bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microphotometric characterization of phytoplankton and detrital absorption properties in the Sargasso Sea
Authors: Iturriaga Rodolfo , Siegel David A. 
Published: April 2010

Microphotometric techniques were used to characterize the spectral absorption properties of individual phytoplankton cells and detrital particles from two sites in the Sargasso Sea during spring 1985. Direct determinations of the absorption efficiency factor, Qa(λ), geometric cross‐sectional area, G, and particle type were made for about 50 individual particles for each water sample analyzed. Large intrasample and intersample variations of Qa(λ) spectra for both phytoplankton and detrital particles were observed. For the mesotrophic northern station, mean values of Qa(λ) and G for phytoplankton cells showed insignificant vertical variations. For detrital particles, however, the mean geometric cross‐sectional area decreased with depth while their mean Qa(λ) values increased. For the oligotrophic southern station these same relationships were observed, although more small‐scale variability was apparent.The statistical comparison of the mean Qa(λ) values with the total particulate absorption coefficient spectrum, ap(λ), enabled quantification of the contributions phytoplankton and detrital materials made to ap(λ). Results showed that phytoplankton abundances accounted for ∼50–70% of the particulate absorption at 440 nm, although instances were observed where phytoplankton cells accounted for >90% of ap(440 nm). The reconstructed particulate absorption spectrum, âp(λ), compared favorably with the total ap(λ) indicating that nearly all of the optically relevant absorbing particulate material was sampled with the microphotometric technique.
Molybdenum and sulfate as controls on the abundance of nitrogen‐fixing cyanobacteria in saline lakes in Alberta
Authors: Marino Roxanne , Howarth Robert W. , Shamess Jennifer , Prepas Ellie 
Published: April 2010

We studied 13 saline lakes in Alberta to test the hypothesis that molybdenum availability influences the abundance of planktonic, N‐fixing cyanobacteria in saline ecosystems. Our earlier work in oxic seawater showed that the availability of Mo is controlled in part by the ratio of sulfate to molybdenum because sulfate inhibits the assimilation of molybdate. The SO42−: Mo ratio in seawater is very high relative to most freshwater lakes—a finding that is consistent with the scarcity of planktonic, N‐fixing cyanobacteria in coastal marine ecosystems. This ratio is constant in seawater, however, limiting a test of our hypothesis in marine systems. These Alberta salt lakes provide a more robust test in saline systems.The ratio of sulfate to molybdenum within any given saline lake was relatively constant over a summer season, but the ratio between lakes varied and ranged from values typical of freshwater lakes to values higher than in seawater. N‐fixing cyanobacteria are significant fractions of the plankton in six of the 13 lakes we studied and are rare or absent in the others. The SO42−: Mo ratio was a strong predictor of the abundance of planktonic, N‐fixing cyanobacteria. Sulfate or Mo concentrations alone, however, were not. This finding is consistent with our hypothesis that sulfate can control Mo availability in oxic waters.Phosphorus concentrations, and the ratio of N to P, were not good predictors of the abundance of N‐fixing cyanobacteria in these saline lakes, as they often are in freshwater lakes. The differences between predictions from a freshwater, P regression model and actual abundances of N‐fixing cyanobacteria in the saline lakes were best explained by the SO42−: Mo ratio.
Estimation of ammonification and ammonium assimilation in surficial coastal and estuarine sediments
Authors: Sumi Takayuki , Koike Isao 
Published: April 2010

Ammonification and NH4+ assimilation in slurries of surface sediments from Japanese coastal and estuarine areas were studied with 15NH4+ tracers. In completely aerobic sediments, where NO3− reduction is negligible, the Blackburn 15NH4+ dilution model can be applied to estimate the ammonification rate after a correction for nitrification is made. In semiaerobic sediments, where significant NO3− reduction occurs, a mathematical model based on the change of 15NH4+ and 15NO3− with time was successfully applied to estimate the ammonification rate. The rate of NH4+ assimilation can be obtained directly from the incorporation of 15NH4+ into particles in the sediments after correcting for 15NH4+ dilution during incubation.The rate of ammonification ranged from 5.8 to 220 ng‐atoms N (g sediment)−1 h−1 and that of NH,,’ assimilation ranged from 6.2 to 114, indicating both large seasonal and local variations. We found, however, that both NH4+ assimilation and ammonification were significantly correlated with ATP biomass, NH4+, and organic N contents in sediments. Several lines of evidence also suggested that NH4+ assimilation is primarily an aerobic microbial process.
Microbial biomass in the coastal plume of Chesapeake Bay: Phytoplankton‐bacterioplankton relationships
Authors: Malone Thomas C. , Ducklow Hugh W. 
Published: April 2010

Turnover rate of suspended organic matter (POC) increased seasonally with temperature as the proportions of POC accounted for by bacterioplankton increased relative to phytoplankton. The proportion of phytoplankton productivity that cycled through bacterioplankton averaged 13% and showed little seasonal variability. These results imply changes in the pathways and rates by which phytoplankton and bacterioplankton production were consumed or exported from the plume.Time series of 1–3 d next to surface drifters within the plume provided some insight into the nature of these changes. In February when the turnover rate of POC was low, phytoplankton biomass declined relative to bacterioplankton due to sedimentation of large diatoms. Low bacterioplankton biomass was associated with high rates of predation by heterotrophic microflagellates. In August when POC was turning over rapidly, phytoplankton biomass declined relative to bacterioplankton due to selective grazing by copepods. High bacterioplankton biomass appeared to be a consequence of enhanced DOC flux associated with high copepod grazing and POC turnover rates as well as with low predation by heterotrophic microflagellates.
Biogeochemistry of carbon in the Amazon River
Authors: Richey Jeffrey E. , Hedges John I. , Devol Allan H. , Quay Paul D. , Victoria Reynaldo , Martinelli Luiz , Forsberg Bruce R. 
Published: April 2010

Depth‐integrated, discharge‐weighted water samples were collected over 1,800 km of the Amazon River on eight cruises at different stages of the hydrograph, 1982–1984. Fine (FPOC, <63 µm) and coarse (CPOC, >63 µm) particulate organic carbon as weight percentage of suspended sediment varied between 0.9–1.5% for FPOC and 0.5–3.4% for CPOC. Concentrations of FPOC ranged from 5 mg liter−1 upriver to 2 mg liter−1 downriver in the mainstem and from 6 mg liter−1 in the Rio Madeira to <1 in the Rio Negro. CPOC had similar distribution patterns, but with concentrations 15–30% those of FPOC. Dissolved organic carbon (DOC) averaged 4–6 mg liter−1 in the mainstem and up to 12 mg liter−1 in the Rio Negro. Upriver dissolved inorganic carbon (DIC) concentrations of about 1,200 µM were diluted by tributaries and floodplain drainage to 600 µM at the most downriver site. Evasion of CO2, invasion of O2, and in situ oxidation were of comparable magnitude, 3–8 µmol m−2 s−1.The average export of total organic carbon (TOC) was 36.1 Tg yr−1 (8.5 g m−2 yr−1), of which 62% was DOC, 34% was FPOC, and 4% was CPOC. TOC inputs were insufficient to support in situ oxidation by a factor of at least two. A relatively small, rapidly cycling pool of labile organic matter may coexist with a much larger pool of more refractory material.
Fluxes and transformations of aquatic pigments in Lake Mendota, Wisconsin
Authors: Hurley James P. , Armstrong David E. 
Published: April 2010

Concentrations and fluxes of chlorophyll and carotenoid pigments were measured in suspended and settling particulate matter and in surface sediments in Lake Mendota. Flux comparisons were used to calculate the extent of alteration or degradation within the water column and at the sediment surface. Losses within the water column for specific time intervals ranged from almost negligible for diatoxanthin to 96% for peridinin. The extent of loss was influenced by pigment type and transport process.Surface sediment diagenesis in Lake Mendota resulted in differential degradation rates among chlorophyll and carotenoid constituents. Deposition of pheophorbide a—a grazing indicator—was most important during late spring, as zooplankton populations increased and chlorophyll levels in the water column dropped below 1 nmol liter−1. The ability to trace the magnitude of this annual event through the sedimentary record was obscured by selective degradation of pheophorbide relative to chlorophyll and pheophytin. Similarly, carotenoid composition was dramatically altered both within the water column and at the sediment surface. Fucoxanthin and peridinin, major water‐column carotenoids, were degraded extensively before incorporation in the sediments.
The vertical flux of metazoans (holoplankton, meiofauna, and larval invertebrates) due to their association with marine snow
Authors: Shanks Alan L. , Edmondson Elizabeth W. 
Published: April 2010

We investigated the association of meiofauna (nematodes and harpactacoid copepods), larval polychaetes, and holoplankton with marine snow. Using a sediment trap equipped with a time‐lapse camera, we measured the vertical flux of these organisms due to their association with marine snow. On average, 83 and 74% of the nematodes and competent larval polychaetes were on marine snow as were only 15 and 9% of the harpacticoid copepods and precompetent larval polychaetes. On average, 94, 80, and 25% of the vertical fluxes of nematodes, competent larval polychaetes, and harpacticoid copepods were due to individuals on marine snow. The vertical flux of precompetent larval polychaetes was negligible. By inhabiting passively sinking aggregates, nematodes and competent larval polychaetes would deposit on the seabed according to the hydrodynamical processes controlling marine snow deposition.Of the holoplankton (calanoid and cyclopoid copepods, nauplii, and larvaceans), <2% was on marine snow. Vertical fluxes of calanoid copepods and nauplii were negligible. The vertical fluxes of cyclopoid copepods and larvaceans were large, but ony 3% was due to individuals on marine snow.
Spectral absorption coefficients of living phytoplankton and nonalgal biogenous matter: A comparison between the Peru upwelling areaand the Sargasso Sea
Authors: Bricaud Annick , Stramski Dariusz 
Published: April 2010

Absorption coefficients of total particulate (biogenous) matter were determined in the mesotrophic waters of the Peruvian upwelling and the oligotrophic waters of the Sargasso Sea. A method based on spectral criteria was used to partition these coefficients into absorption by living algal cells and by nonalgal (mainly detrital) material. This method was tested by independently measuring absorption by nonalgal material for samples from the Sargasso Sea.The average Chl‐specific absorption coefficients measured in the Sargasso Sea are significantly higher than in the Peruvian upwelling and also higher in the surface layer than in the deep Chl maximum layer. These systematic variations appear to be mainly due to differences in sizes and intracellular pigment concentrations of the cells, inducing differences in the amplitude of the package effect.
lron transport in marine phytoplankton: Kinetics of cellular and medium coordination reactions
Authors: Hudson Robert J. M. , Morel FraÇois M. M. 
Published: April 2010

Iron is taken up via specific sites on the cell surface in two coastal phytoplankters—the coccolithophorid Pleurochrysis carterae and the diatom Thalassiosira weissflogii. Direct uptake from the cell surface of ∼ 10−17 mol Fe cell−1 was observed in pulse‐chase experiments with cells grown under Fe limitation. This quantity corresponds to the theoretical number of transport sites needed by each cell given the slow coordination kinetics and the low seawater concentrations of Fe. The observed turnover time of Fe in the sites—6–20 min—the observed half‐saturation constants for uptake—0.7 and 3.1 nM for P. carterae and T. weissflogii—and maximal Fe complexation rates are consistent with a standard model for carrier‐mediated transport. Analysis of the reaction kinetics indicates that the sites are not at equilibrium with dissolved Fe species. Iron uptake rates are thus controlled by the complex formation kinetics of the transport site with monomeric ferric hydroxide species.Fe‐limited P. carterae and T. weissflogii can take up Fe at rates up to 14–20% of the maximum rate at which dissolved inorganic Fe can diffuse to the cell. Since oceanic phytoplankters must also be subject to the same strongly size‐dependent limit on uptake rates imposed by diffusion, large species are more likely to experience growth rate limitation under low‐Fe conditions in the ocean.
Mass flux estimation and mass transport mechanism in estuaries
Authors: Park J. K. , James A. 
Published: April 2010

Hydrodynamic surveys were conducted in a partially stratified estuary. Longitudinal salt fluxes through a cross‐section were measured and the optimal number of lateral and vertical points for observation and estimation of fluxes of pollutants found. The hydrodynamic data were decomposed to investigate the mechanism of instantaneous and tidally averaged mass fluxes.The decomposition method developed showed that instantaneous salt flux arose principally from the combination of velocity fluctuation with the tidal mean salinity. The error analysis showed that the estimate of mass flux was sensitive to the error inherent in the velocity data and the error range was within ±10% of the total flux. Seven depth and four width points gave acceptable estimates of the water flux, salt flux, and longitudinal dispersion.
The physical strength of marine snow and its implications for particle disaggregation in the ocean
Authors: Alldredge Alice L. , Granata Timothy C. , Gotschalk Chris C. , Dickey Tommy D. 
Published: April 2010

Abiotic fragmentation of large, rapidly sinking aggregates into smaller, suspended particles by fluid shear has been suggested as an important process governing the particle size spectrum in the ocean and as one explanation for the exponential decrease of particulate flux with depth below the euphotic zone. We investigated this process by quantifying the small‐scale energy dissipation rates required to disaggregate marine snow settling through a gradient of turbulent kinetic energy in a laboratory tank.Aggregates of detrital debris, gelatinous houses of larvacean tunicates, and aggregates of living bacteria did not break apart even at energy dissipation rates ≫1 cm2 s−3. The rate of energy dissipation required to disaggregate fragile diatom flocs up to 25 mm long ranged from 10−3 to > 1 cm2 s−3 and increased exponentially with decreasing maximum aggregate diameter. Aged diatom aggregates were significantly stronger than otherwise identical but unaged particles. These results indicate that only the highest shears associated with storm events or flows in tidal channels would be able to fragment even the most fragile organic aggregates in the upper ocean. Biological processes of disaggregation, such as animal grazing, appear far more likely to mediate the size spectrum of aggregated particulate matter in the ocean than abiotic fragmentation due to fluid motion.
Modeling spectral diffuse attenuation, absorption, and scattering coefficients in a turbid estuary
Authors: Gallegos Charles L. , Correll David L. , Pierce J. W. 
Published: April 2010

Spectral diffuse attenuation coefficients were measured in the Rhode River and Chesapeake Bay, Maryland, on 28 occasions in 1988 and 1989. The model of Kirk was used to extract scattering and absorption coefficients from the measurements in waters considerably more turbid than those in which the model was previously applied. Estimated scattering coefficients were linearly related to mineral suspended solids. Estimates of total absorption coefficients were decomposed as the sum of contributions by water, dissolved organic matter, phytoplankton chlorophyll, and particulate detritus, each having a characteristic spectral shape. The 1988 data were used to develop a model of scattering and absorption coefficients based on the specific curves regressed against water‐quality parameters. Diffuse attenuation coefficients in the 1989 data ranging from 1 to 10 m−1 and photic depths ranging from <1 to 4.5 m were predicted with a C.V. of about 25%.The problem of estimating concentrations of water‐quality constituents from optical measurements was indeterminate due to the similarity in shape of the specific curves of dissolved substances and depigmented particulates. Chlorophyll concentration could be estimated because it was strongly related to water‐corrected absorption in the 670‐nm waveband, but several outliers occurred due to biological variability in specific absorption of pigments.
The effect of food concentration, body size, and environmental oxygen tension on the growth of the deposit‐feeding polycheate, Capitella species 1
Authors: Forbes Thomas L. , Lopez Glenn R. 
Published: April 2010

This study investigates the separate and interactive effects of food concentration, environmental oxygen level, and body size on the growth rates of Capitella species 1 individuals. Reduction of environmental pO2 or food concentration decreased the volume‐specific growth rates of both large (>1.3 mm3; >1.6 mg wet wt, WW) and small (<1.0 mm3; <1.1 mg WW) worms. Within the high‐food treatments a reduction in environmental pO2 from ∼130 to 35 mm of Hg decreased the growth rates of worms by up to 36% d− 1.Growth of large worms decreased in response to reductions in either pO2 or food concentration. The growth rates of small worms decreased significantly only in response to reductions in environmental pO2 levels. Reductions in either food concentration or environmental oxygen level alone decreased the growth of large worms to the same extent as a concomitant decrease in both. When worms were fed 100% natural sediment, a reduction in average O2 tension from 38 to 21 mm of Hg decreased the growth of large worms from 2% d−1 to −25% d−1. The growth rates of small individuals were unaffected (−4 to −3% d−1).We predict that under conditions of near‐bottom hypoxia or food limitation (e.g. complete pelletization of ingestible sediment) populations of Capitella sp. 1 will experience size‐dependent growth with large animals (>1.6 mg WW) experiencing the greatest decline in growth rate.
Foster Care and Health in Medicaid-Enrolled Children Experiencing Parental Opioid Use Disorder
Authors: Meinhofer Angélica , Chandra Nisha , Byanova Desislava , Keyes Katherine M. 
Published: May 2024

ImportanceThe burden of the US opioid crisis has fallen heavily on children, a vulnerable population increasingly exposed to parental opioid use disorder (POUD) in utero or during childhood. A paucity of studies have investigated foster care involvement among those experiencing parental opioid use during childhood and the associated health and health care outcomes.ObjectiveTo examine the health and health care outcomes of children experiencing POUD with and without foster care involvement.Design, Setting, and ParticipantsThis population-based cohort study used nationwide Medicaid claims data from January 1, 2014, to December 31, 2020. Participants included Medicaid-enrolled children experiencing parental opioid use–related disorder during ages 4 to 18 years. Data were analyzed between January 2023 and February 2024.ExposurePerson-years with (exposed) and without (nonexposed) foster care involvement, identified using Medicaid eligibility, procedure, and diagnostic codes.Main Outcomes and MeasuresThe main outcomes included physical and mental health conditions, developmental disorders, substance use, and health care utilization. The Pearson χ2 test, the t test, and linear regression were used to compare outcomes in person-years with (exposed) and without (nonexposed) foster care involvement. An event study design was used to examine health care utilization patterns before and after foster care involvement.ResultsIn a longitudinal sample of 8 939 666 person-years from 1 985 180 Medicaid-enrolled children, 49% of children were females and 51% were males. Their mean (SD) age was 10 (4.2) years. The prevalence of foster care involvement was 3% (276 456 person-years), increasing from 1.5% in 2014 to 4.7% in 2020. Compared with those without foster care involvement (8 663 210 person-years), foster care involvement was associated with a higher prevalence of developmental delays (12% vs 7%), depression (10% vs 4%), trauma and stress (35% vs 7%), and substance use–related disorders (4% vs 1%; P &amp;lt; .001 for all). Foster children had higher rates of health care utilization across a wide array of preventive services, including well-child visits (64% vs 44%) and immunizations (41% vs 31%; P &amp;lt; .001 for all). Health care utilization increased sharply in the first year entering foster care but decreased as children exited care.Conclusions and RelevanceIn this cohort study of Medicaid-enrolled children experiencing parental opioid use–related disorder, foster care involvement increased significantly between 2014 and 2020. Involvement was associated with increased rates of adverse health outcomes and health care utilization. These findings underscore the importance of policies that support children and families affected by opioid use disorder, as well as the systems that serve them.
Ethylene Glycol Co‐Solvent Enables Stable Aqueous Ammonium‐Ion Batteries with Diluted Electrolyte
Authors: Fei Huifang , Yang Fuhua , Jusys Zenonas , Passerini Stefano , Varzi Alberto 
Published: May 2024

AbstractAqueous ammonium‐ion batteries (AAIBs) are considered as one of the most promising technologies for large scale energy storage applications, due to their intrinsic safety, environmental friendliness and low cost. Nevertheless, the practical application of AAIBs is impeded by hydrogen evolution reaction (HER) occurring in diluted aqueous electrolyte. Highly concentrated electrolytes can improve electrochemical stability but lead to higher costs and increased hydrolysis of NH4+. In this work ethylene glycol (EG) is proposed as co‐solvent, which can act as H‐bond modulating agent, to increase the stability of AAIBs with diluted electrolytes. The perturbation of water H‐bond network regulated by EG is proved by spectroscopic methods, while the suppressed HER is confirmed by differential electrochemical mass spectrometry (DEMS) results. As a result, full cells with 3,4,9,10‐perylenebis(dicarboximide) (PTCDI) anode and FeFe(CN)6 (FeHCF) cathode and EG‐added electrolyte exhibit stable cycling performance with capacity retention of 77% after 1950 cycles.