bluuebunny/crossref_metadata_2025 huggingface dataset:
Sources of nitrogen used for denitrification and nitrous oxide formation in sediments of the hypernutrified Colne, the nutrified Humber, and the oligotrophic Conwy estuaries, United Kingdom
Authors: Dong Liang F. , Nedwell David B. , Stott Andrew
Published: July 2010

Rates of denitrification and nitrous oxide (N2O) formation, and the sources of N2 and N2O, were examined by the isotope‐pairing technique in three U.K. estuaries (Colne, Humber, Conwy), which ranged from extremely nutrified to oligotrophic. Nitrous oxide concentrations were supersaturated throughout the year with annual averages of 603% in the Colne, 158% in the Humber, and 133% in the Conwy, indicating that the estuaries were sources of atmospheric N2O. Denitrification and N2O formation were from benthic processes, and not from water‐column processes. Generally, both denitrification and N2O formation decreased down the estuary as nitrate concentrations lowered. The proportion of N2 and N2O derived from nitrate in the overlying water column (Dw) also decreased with nitrate concentration, while that from benthic coupled nitrification—denitrification (Dn) increased. Scaled to the total estuary area, in the hypernutrified Colne, water‐column nitrate was the main source of N2 and N2O; in the moderately nutrified Humber, Dw and Dn contributed approximately equally, while in the oligotrophic Conwy, coupled nitrification—denitrification (Dn) was the main source of N2 and N2O. For the first time, the formation of N2O from either the nitrification or denitrification steps of Dn was also determined. In the Colne, that from the nitrification step predominated at the top of the estuary but decreased down the estuary, while in the Humber that from denitrification dominated at the top and decreased down the estuary. In the oligotrophic Conwy, there were approximately equal contributions.
Effect of eutrophication on the distribution and ecophysiology of the mussel Mytilus trossulus (Bivalvia) in southern Baltic Sea (the Gulf of Gdańsk)
Authors: Wołowicz Maciej , Sokołowski Adam , Bawazir Abdullah Salem , Lasota Rafał
Published: July 2010

The effect of eutrophication on benthos is usually reported as negative. In the case of the Gulf of Gdansk, eutrophication has increased the availability of food resources to filter feeders such as mussels, affecting their physiology and vertical distribution. Comparative studies of the mussel Mytilus trossulus from two depth zones (10 m and 40 m) over a seasonal cycle revealed ecophysiologic differences between deep‐ and shallow‐water animals. For the same shell length, the shallow‐water mussels were heavier (dry weight = 0.004L2.297) and showed a higher weight index (dry weight/volume), averaging 3.8 ± 1.9 mg cm−3, than the deep‐water mussels (dry weight = 0.0002L1.726 and 2.5 ± 1.1 mg cm−3), primarily because of a nearly twofold greater carbohydrate store. In the shallow zone, females contained more carbohydrates (on average 5.8% dry weight) than males (3.8% dry weight) because females conserve energy for reproduction. Differences in physiologic variables, and subsequently physiologic performance of the mussels, were related to different nutritional conditions in the ambient water. The deep habitat had lower Chl a, averaging 1.1 mg L−1, total particulate matter (TPM) 4.3 mg L−1 and particulate organic matter (POM) 1.1% of TPM as compared with the shallow habitat, with average Chl a 2.5 mg L−1, TPM 4.9 mg L−1, and POM 1.5%. The eutrophication of the Gulf of Gdańsk has led to an increase in the food availability in the water column, which allowed efficient colonization of the deep zone by the mussels; however, the dominance of males over females (~3 : 1) suggests that the food sustains only spawning‐related metabolic demands and is not sufficient for energy conservation in this zone. Starch gel electrophoresis of eight enzyme loci showed no statistical differences in the allele and genotype frequencies between the shallow‐ and deep‐water mussels; thus, the differences in ecophysiologic traits between depths are due to acclimatization.
Relating precipitation and water management to nutrient concentrations in the oligotrophic “upside‐down” estuaries of the Florida Everglades
Authors: Childers Daniel L. , Boyer Joseph N. , Davis Stephen E. , Madden Christopher J. , Rudnick David T. , Sklar Fred H.
Published: July 2010

We present 8 yr of long‐term water quality, climatological, and water management data for 17 locations in Everglades National Park, Florida. Total phosphorus (P) concentration data from freshwater sites (typically <0.25 µmol L−1, or 8 µg L−1) indicate the oligotrophic, P‐limited nature of this large freshwater—estuarine landscape. Total P concentrations at estuarine sites near the Gulf of Mexico (average ~0.5 µmol L−1) demonstrate the marine source for this limiting nutrient. This “upside down” phenomenon, with the limiting nutrient supplied by the ocean and not the land, is a defining characteristic of the Everglade landscape. We present a conceptual model of how the seasonality of precipitation and the management of canal water inputs control the marine P supply, and we hypothesize that seasonal variability in water residence time controls water quality through internal biogeochemical processing. Low freshwater inflows during the dry season increase estuarine residence times, enabling local processes to control nutrient availability and water quality. El Ni#x00F1;o—Southern Oscillation (ENSO) events tend to mute the seasonality of rainfall without altering total annual precipitation inputs. The Niño3 ENSO index (which indicates an ENSO event when positive and a La Niña event when negative) was positively correlated with both annual rainfall and the ratio of dry season to wet season precipitation. This ENSO‐driven disruption in seasonal rainfall patterns affected salinity patterns and tended to reduce marine inputs of P to Everglades estuaries. ENSO events also decreased dry season residence times, reducing the importance of estuarine nutrient processing. The combination of variable water management activities and interannual differences in precipitation patterns has a strong influence on nutrient and salinity patterns in Everglades estuaries.
Trends in the nutrient enrichment of U.S. rivers during the late 20th century and their relation to changes in probable stream trophic conditions
Authors: Alexander Richard B. , Smith Richard A.
Published: July 2010

We estimated trends in concentrations of total phosphorus (TP) and total nitrogen (TN) and the related change in the probabilities of trophic conditions from 1975 to 1994 at 250 nationally representative riverine monitoring locations in the U.S. with drainage areas larger than about 1,000 km2. Statistically significant (p < 0.05) declines were detected in TP and TN concentrations at 44% and 37% of the monitoring sites, and significant increases were detected at 3% and 9% of the sites, respectively. We used a statistical model to assess changes in the probable trophic‐state classification of the sites after adjusting for climate‐related variability in nutrient concentrations. The probabilistic assessment accounts for current knowledge of the trophic response of streams to nutrient enrichment, based on a recently proposed definition of “eutrophic,” “mesotrophic,” and “oligotrophic” conditions in relation to total nutrient concentrations. Based on these trophic definitions, we found that the trophic state improved at 25% of the monitoring sites and worsened at fewer than 5% of the sites; about 70% of the sites were unchanged. Improvements in trophic‐state related to declines in TP were more common in predominantly forested and shrub—grassland watersheds, whereas the trophic state of predominantly agricultural sites was unchanged. Despite the declines in TP concentrations at many sites, about 50% of all monitoring sites, and more than 60% of the sites in predominantly agricultural and urban watersheds, were classified as eutrophic in 1994 based on TP concentrations. Contemporaneous reductions in major nutrient sources to streams, related to wastewater treatment upgrades, phosphate detergent bans, and declines in some agricultural sources, may have contributed to the declines in riverine nutrient concentrations and associated improvements in trophic conditions.
Potamoplankton size structure and taxonomic composition: Influence of river size and nutrient concentrations
Authors: Chételat John , Pick Frances R. , Hamilton Paul B.
Published: July 2010

We measured the size structure and taxonomic composition of phytoplankton in temperate rivers during base flows of summer to investigate the influence of river size, ambient nutrient concentration, and light availability on potamoplankton community structure. Algal biomass was measured in three size classes (2–20, 20–64, and >64 µm) by microscope enumeration of water samples collected in 31 rivers and by chlorophyll a in water samples collected in 46 rivers in another year across Ontario and western Quebec. Nanoplankton dominated the potamoplankton biomass across the range of river nutrient concentrations (total phosphorus 5–280 µg P L−1), water residence times (1–39 d), and light regimes (euphotic zone to mixing depth ratio 0.1–33). Both nanoplankton (2–20 µm) and total potamoplankton biomass were significantly correlated with water column total phosphorus concentrations and were not related to water residence time or light availability. On average, diatoms contributed the largest percentage of the total biomass, followed by cryptophytes and an equal percentage of chlorophytes and chrysophytes. The contribution of any one division to total biomass was not significantly correlated with nutrients, water residence time, or light regime. In contrast to temperate lake systems, both the proportion of biomass in larger size classes and the contribution of cyanobacteria did not change significantly as a function of nutrient concentrations. However, community size structure varied in relation to river size: netplankton (>64 µm) contributed slightly more to total biomass at sites with both shorter (<2 d) and longer (>10 d) water residence times. These results point to differences between the phytoplankton of lakes and rivers in response to eutrophication.
Plankton food web structure in a eutrophic polymictic lake with a history of toxic cyanobacterial blooms
Authors: Moustaka-Gouni Maria , Vardaka Elisabeth , Michaloudi Evangelia , Kormas Konstantinos Ar. , Tryfon Eleni , Mihalatou Helen , Gkelis Spyros , Lanaras Tom
Published: July 2010

We studied the seasonal dynamics of phytoplankton, bacterioplankton, heterotrophic nanoflagellates, ciliates, and metazoan plankton in the highly eutrophic polymictic Lake Kastoria (Greece), which has a history of toxic cyanobacterial blooms. An acute increase in the flushing rate of the lake during spring inhibited cyanobacterial biomass accumulation. During this transient oligotrophic period, which was characterized by abundant lake snow particles, the plankton food web was an inverted biomass pyramid (low autotrophic biomass and high heterotrophic biomass). Prokaryotes played a key role in these changes (cyanobacteria during periods of autotrophy and bacteria during periods of heterotrophy). In summer and autumn, toxic cyanobacterial blooms developed, and the microbial loop was weak. The microbial loop was weak because the heterotrophic nanoflagellates and nanociliates decreased to undetectable densities during the summer, when larger bacterivores (rotifers and small cladocera) were abundant. Toxic blooms may have a dual effect on heterotrophic nanoplankton: negative during the first bloom and postbloom period and positive during a following toxic bloom. Different species (Cylindrospermopsis raciborskii, Aphanizomenon spp., and Microcystis aeruginosa) and succession phases of toxic blooms may differentially affect the microbial food web structure.
Changes in whitefish scales δ13C during eutrophication and reoligotrophication of subalpine lakes
Authors: Gerdeaux Daniel , Perga Marie-Elodie
Published: July 2010

We measured the isotope composition of whitefish (Coregonus lavaretus) scales from 50‐yr collections to determine the pattern of change of δ13C during the eutrophication and reoligotrophication of two subalpine lakes: Lakes Constance and Geneva. The isotope composition of scales from Lake Annecy, a subalpine lake that has been protected from eutrophication, was also determined, to provide a control value for modifications in the values of whitefish scale δ13C in the absence of any significant changes in the trophic status of the lake. In Lakes Constance and Geneva, changes in whitefish scales δ13C were closely correlated with those in the mean annual phosphorus concentrations and, to a lesser extent, also reflected the efficiency of winter mixing in Lake Geneva. In contrast, in Lake Annecy, whitefish δ13C exhibited only minor changes during the survey. Changes in whitefish scale δ13C with the trophic status of Lakes Geneva and Constance were not linked to either a shift in whitefish feeding behavior or to alterations in the length of the pelagic trophic chain. Hence, the pattern of variation of whitefish δ13C during the last decades mirrored the lakes' trophic history. The responses of the Lakes Geneva and Constance to changes in Ptot were strictly synchronous and parallel, with a response during restoration that may have been the result of the antagonism between the effects of the falling phosphorus concentration and increasing temperature.
The effect of seawater CO2 concentration on growth of a natural phytoplankton assemblage in a controlled mesocosm experiment
Authors: Kim Ja-Myung , Lee Kitack , Shin Kyoungsoon , Kang Jung-Hoon , Lee Hyun-Woo , Kim Miok , Jang Pung-Guk , Jang Min-Chul
Published: July 2010

We examine the effects of seawater pCO2 concentration of 25, 41, and 76 kPa (250, 400, and 750 matm) on the growth rate of a natural assemblage of mixed phytoplankton obtained from a carefully controlled, 14‐d mesocosm experiment. Throughout the experiment period, in all enclosures, two phytoplankton taxa (microflagellates and cryptomonads) and two diatom species (Skeletonema costatum and Nitzschia spp.) account for approximately 90% of the phytoplankton community. During the nutrient‐replete period from day 9 to day 14 populations of Skeletonema costatum and Nitzschia spp. increased substantially; however, only Skeletonema costatum showed an increase in growth rate with increasing seawater pCO2. Not all diatom species in Korean coastal waters are sensitive to seawater pCO2 under nutrient‐replete conditions.
Spatial variation of nitrogen fixation in lakes of the northern Great Plains
Authors: Patoine Alain , Graham Mark D. , Leavitt Peter R.
Published: July 2010

Cyanobacterial blooms are a regular feature of lakes in central North America, but little is known of their importance to the nitrogen (N) cycle and nutrition of aquatic food webs. We hypothesized that N2‐fixing cyanobacteria constitute a significant source of N to prairie lakes, that fixed N is effectively transferred to primary and secondary consumers, and that the importance of fixed N is structured on a landscape scale due to spatial gradients of lake chemistry and catchment characteristics. These hypotheses were tested using stable isotope analyses and mass budgets in six chained lakes of the northern Great Plains that were sampled biweekly during summers of 1994‐2004. Mean annual N isotope signatures of particulate organic matter (δ15N‐POM) were highly correlated to the abundance of N2‐fixing cyanobacteria (r2 = 0.75, p , 0.001), but exhibited no marked spatial organization. Instead, the temporal variability of δ15N‐POM was greatest in downstream lakes where N2‐fixing cyanobacteria were abundant. Furthermore, seasonal declines in δ15N‐POM were correlated with reductions in δ15N of individual zooplankton taxa (Daphnia spp., Diacyclops thomasi, Leptodiaptomus siciloides, Leptodora kindtii), especially in downstream eastern lakes. N mass balances revealed that the importance of biological N2 fixation relative to total N inputs (up to 77%) and initial N standing stock (up to 201%) were significantly linearly correlated with landscape position (0.59 ≤ r2 ≤ 0.83, p ≤ 0.07) and effective drainage area (0.61 ≤ r2 ≤ 0.98, p ≤ 0.07), as were volumetric and areal estimates of N2 fixation during summer (r2 ≥ 0.87, p ≤ 0.007). These patterns demonstrate that fixed N is spatially structured, highly predictable based on landscape position, and readily assimilated into aquatic food webs.
The FeL model of iron acquisition: Nondissociative reduction of ferric complexes in the marine environment
Authors: Salmon Tim P. , Rose Andrew L. , Neilan Brett A. , Waite T. David
Published: July 2010

Recently there has been recognition of the importance of reductive processes in the acquisition of iron by microorganisms in marine environments with Fe(III) reduction induced by either membrane‐bound reductases or by superoxide, a powerful Fe(III) reducing agent generated either by photochemical or biological means. We have measured the relative rates of iron uptake achieved by the cyanobacterium L. majuscula in the presence of a variety of model‐ and naturally‐derived organic ligands exhibiting a broad range of conditional ferric and ferrous stability constants. Additionally, we have investigated the effect upon iron uptake rate of varying the concentration of both iron and the iron‐binding ligands. We have reconciled this data with previous work in which we measured rates of reduction by exogenous superoxide of Fe(III) bound to these same complexes. We show that the rate of formation of ferrous iron and the rate of uptake of iron by Lyngbya majuscula are each independent of the concentration of Fe' and demonstrate that this is consistent with our previous finding that this organism acquires iron via nondissociative reduction of ferric complexes. We also show that the rate of reoxidation of organically complexed Fe(II) is a critical determinant of the subsequent bioavailability of iron, a feature not previously addressed in the literature. In view of the central importance of the complexation and redox behavior of the iron‐ organic complexes to iron uptake rate, we propose a new kinetic model of iron acquisition, termed the FeL model, that is consistent with presented and previously published data and which describes processes both in natural and artificial conditions.
Community dominance by a canopy species controls the relationship between macroalgal production and species richness
Authors: Eriksson Britas Klemens , Rubach Anja , Hillebrand Helmut
Published: July 2010

By field manipulations of nutrients, propagules, and canopy cover in a shallow rocky subtidal, we show that dominance by a leathery macrophyte (Fucus vesiculosus) controls net production and the propagation of nutrient effects on understory algal species richness. On substrates with propagules, canopy cover prevented a significant loss of diversity from nutrient enrichment demonstrated outside canopy cover. On sterile substrates, negative canopy effects on diversity were counteracted by nutrient enrichment. Experimental manipulations produced a significant hump‐shaped relationship between species richness and log net production, with low richness at low or high biomass production and highest richness at intermediate biomass production. By strong control of net primary production, canopy cover changed the algal understory community to an alternative production state and thereby generated a switch in the relationship between net primary production and species richness from negative outside canopy cover to positive inside. This demonstrates that species contributing to biological structure and habitat diversity can determine the responses of a coastal ecosystem to resource loading.
Evaluating hypolimnetic diffusion parameters in thermally stratified lakes
Authors: Rimmer Alon , Eckert Werner , Nishri Aminadav , Agnon Yehuda
Published: July 2010

The vertical transport of solutes in the anoxic hypolimnion of thermally stratified lakes can be described by a one‐dimensional diffusion model. Using ammonium and dissolved methane as inert tracers, the model was solved, both analytically and numerically, for Lake Kinneret while taking into account sedimentary release, hypolimnetic transport, and the deepening of the thermocline depth. An average seasonal turbulent diffusion coefficient in the hypolymnion of 1.5 ± 0.5 m2 d−1 was confirmed independently by both tracers. In all cases, the modeled hypolimnetic distribution pattern was highly correlated with the actual measurements.
Effects of cyanobacterial toxicity and morphology on the population growth of freshwater zooplankton: Meta‐analyses of laboratory experiments
Authors: Wilson Alan E. , Sarnelle Orlando , Tillmanns Angeline R.
Published: July 2010

We synthesized data from 66 published laboratory studies, representing 597 experimental comparisons, examining the effects of cyanobacterial toxicity and morphology on the population growth rate and survivorship of 17 genera (34 species) of freshwater, herbivorous zooplankton. Two meta‐analyses were conducted with these data. The primary analysis compared herbivore population growth rates for grazers fed treatment diets containing cyanobacteria versus control diets comprising phytoplankton that are generally considered to be nutritious for zooplankton (chlorophytes and/or flagellates). This analysis confirmed that cyanobacteria were poor foods relative to small chlorophytes and flagellates. More importantly, filamentous cyanobacteria were found to be significantly better foods for grazers than single‐celled cyanobacteria over all studies. Surprisingly, the presence or absence of commonly‐measured toxic compounds (microcystins in 70% of the cases) in the diet had no overall influence on grazer population growth relative to control diets. A secondary analysis compared survival rates for grazers fed cyanobacteria versus no food. In contrast to the primary analysis, grazer survival was more negatively affected by toxic cyanobacteria than non‐toxic cyanobacteria, relative to starvation. However, this difference was attributable to the effects of a single Microcystis strain, PCC7820. Thus, though some cyanobacterial strains appear to be toxic to some strains of zooplankton, the overall role of commonly‐assayed cyanobacterial toxins as a determinant of food quality may be less than widely assumed. We suggest that more attention be focused on nutritional deficiencies, morphology, and the toxicity of undescribed cyanobacterial compounds as mediators of the poor food quality of cyanobacteria for zooplankton.
Molecular analysis of photosynthetic picoeukaryote community structure along an Arabian Sea transect
Authors: Fuller Nicholas J. , Tarran Glen A. , Cummings Denise G. , Woodward E. Malcolm S. , Orcutt Karen M. , Yallop Marian , Le Gall Florence , Scanlan David J.
Published: July 2010

We developed oligonucleotide probes, based on plastid 16S ribosomal DNA (rDNA) sequences, to target 10 different algal classes (Chlorarachniophyceae, Chrysophyceae, Cryptophyceae, Eustigmatophyceae, Pavlovophyceae, Pelagophyceae, Pinguiophyceae, Prasinophyceae [clade VI], Prymnesiophyceae, and Trebouxiophyceae), for use with dot blot hybridization technology. These class‐specific probes were then used to investigate the community structure of photosynthetic picoeukaryotes (≪3 µm) along a transect in the Arabian Sea during September 2001, using hybridization to plastid 16S rDNA polymerase chain reaction amplicons. The transect ranged from oligotrophic open‐ocean waters, just south of the Equator, through mesotrophic and eutrophic waters toward the north coast of Oman, crossing a region of monsoonal upwelling off the Omani northeast coast. Photosynthetic picoeukaryotes in the surface‐mixed layer (SML) and deep chlorophyll maximum ranged from 1.0 x 103 cells mL‐1 in southern oligotrophic waters to almost 30 x 103 cells mL‐1 at the region of upwelling. Chrysophytes were abundant along most of the transect throughout much of the euphotic zone. Prymnesiophytes were abundant in surface waters along much of the transect. By contrast, trebouxiophytes were confined to deeper waters, below the SML. Pelagophytes were found in surface waters that were more mesotrophic, whereas cryptophytes were only detected in the more nutrient‐rich waters at the northern end of the transect, between depths of 20‐30 m. Pinguiophytes were also detected, but only in the warm surface waters off the north coast of Oman. Chlorarachniophytes, eustigmatophytes, pavlovophytes, and clade VI prasinophytes were essentially below detection limits for the entire transect.
Major contribution from littoral crustaceans to zooplankton species richness in lakes
Authors: Walseng Bjørn , Hessen Dag O. , Halvorsen Gunnar , Schartau Ann Kristin
Published: July 2010

A study of pelagic and littoral species richness among microcrustaceans in 2,466 Norwegian lakes recorded 120 crustacean species: 77 cladocerans, 31 cyclopoids, and 12 calanoids, respectively. Very few species were strictly pelagic, and the pelagic crustacean zooplankton species were by far outnumbered by their littoral counterparts. More than two‐thirds of the total crustacean species numbers in lakes were accounted for by species with a littoral preference. A considerable number of species occurred with low frequency, and the median total number of crustacean species in the lakes was only 14. A majority of littoral species also occurred commonly in pelagic samples, and vice versa. Some species are truly both littoral and pelagic, and nearly all species occurring in pelagic samples were also common in littoral samples. A high proportion of the common littoral species was only recorded occasionally in pelagic samples, and should thus be considered strictly littoral. There was no significant correlation between lake area and species richness for pelagic or littoral species. Our findings demonstrate the importance of including littoral species when assessing microcrustacean diversity in lakes, and we question the practice of considering species as either pelagic or littoral, because a majority of the recorded species was common in both habitats. It calls for a further discussion of the term "planktonic", since most of the species are at least partly "semiplanktonic."
Zooplankton retention in the estuarine transition zone of the St. Lawrence Estuary
Authors: Simons Rachel D. , Monismith Stephen G. , Johnson Ladd E. , Winkler Gesche , Saucier François J.
Published: July 2010

We used a three‐dimensional physical‐biological model consisting of a Eulerian circulation model and a Lagrangian particle‐tracking model, which included vertical sinking and swimming, to explore zooplankton retention in the estuarine transition zone of the St. Lawrence Estuary (SLETZ). To test the accuracy of the model, the results were temporally and spatially compared to a passive scalar released simultaneously in the circulation model and to field data for zebra mussel veligers. The model was then used to study the effects of baroclinic density‐driven flow, vertical sinking and swimming, and tidal vertical migration on retention of simulated zooplankton. Baroclinic flow, created by longitudinal and lateral salinity gradients, was a critical part of retention in the SLETZ. In the presence of baroclinic flow, vertical sinking and swimming speeds of $0.2 mm s21 had a large effect on the residence time of the simulated zooplankton as a result of gravitational circulation. Tidal vertical migration—a pattern of upward movement on flood and downward movement on ebb—was a viable retention mechanism for the SLETZ, and its effectiveness was amplified by baroclinic flow. As the speed of tidal vertical migration increased, the simulated zooplankton were concentrated in smaller areas of the SLETZ and moved further upstream.
Mesoscale variability in the metabolic balance of the Sargasso Sea
Authors: Mouriño-Carballido Beatriz , McGillicuddy Dennis J.
Published: July 2010

Net community production (NCP) experiments based on in vitro changes in dissolved oxygen were carried out in three mesoscale eddies investigated in the Sargasso Sea in the summer of 2004. NCP estimates ranged from negative to positive values, and the age and type of the sampled eddy were important factors responsible for this variability. Positive rates occurred in younger cyclones and in areas of eddy‐eddy interactions, whereas negative NCP rates were observed in anticyclones and older cyclone features that were decaying. This information was combined with a nine‐year data set from the BATS program and satellite altimeter data to assess the role of mesoscale eddies in the metabolic balance of the Sargasso Sea. Indirect NCP estimates (NCPe) were obtained by calculating the difference between 14C phytoplankton production and bacterial carbon demand rates. The results showed highly variable NCPe rates that spanned the range of direct NCP observations.
Irradiance and the elemental stoichiometry of marine phytoplankton
Authors: Finkel Z. V. , Quigg A. , Raven J. A. , Reinfelder J. R. , Schofield O. E. , Falkowski P. G.
Published: July 2010

We analyzed the elemental composition (C, N, P, S, K, Mg, Ca, Sr, Fe, Mn, Zn, Cu, Co, Mo, and Ni) of five marine phytoplankton species representing the four major marine phyla grown over a range of growth irradiances. We found substantial variability in the elemental composition between different species, which is consistent with previously reported differences associated with evolutionary history. We found that many elements (Fe, Mn, Zn, Cu, Co, and Mo) are enriched relative to phosphorus by about two to three orders of magnitude under irradiances that are limiting for growth, and net steady‐state uptake of element : P is often elevated under lower irradiances. For most elements, the variability in element : P due to irradiance is comparable to the variability due to phylogenetic differences at any irradiance, but often the interaction between genetic differences and the phenotypic response to irradiance amplifies the differences in elemental composition between species. The fractionation of trace elements relative to phosphorus into phytoplankton biomass under low light is consistent with depleted levels of Cu2+ and Mn2+ in deep chlorophyll maxima, suggesting that the export of lowlight‐ acclimated phytoplankton is a major source of trace element flux to the deep ocean and an important factor in the biogeochemical cycles of many of the biologically limiting elements in the oceans.
The effect of hydrodynamics on the mass transfer of dissolved inorganic carbon to the freshwater macrophyte Vallisneria americana
Authors: Nishihara Gregory N. , Ackerman Josef D.
Published: July 2010

The combined effects of water velocity (U) and dissolved inorganic carbon (DIC) concentration on photosynthesis rates of Vallisneria americana were investigated. The net photosynthesis rate or O2 flux (Jobs) from leaves increased with U from 0.20 ± 0.01 (mean ± standard error) µmol m‐2 s‐1 at U = 0 m s‐1 (i.e., in stagnant water) to 2.1 ± 0.07 µmol m‐2 s‐1 at U = 0.066 m s‐1. The velocity where Jobs was saturated (Usat) was inversely proportional to the DIC concentration ([DIC]) and decreased monotonically from 0.04 ± 0.01 m s‐1 at 0.46 mol m‐3 to 0.006 ± 0.004 m s‐1 at 4.8 mol m‐3. If the net photosynthesis rate and DIC uptake are equal, HCO3‐ uptake rates contributed ≫90% of DIC uptake at all [DIC] at U = 0.005 m s‐1 and contributed less at higher velocities. The proportion of HCO3‐ uptake to DIC uptake decreased linearly with increasing [DIC]. The measured local Sherwood numbers (Shx) and the parameter a (2.24 ± 1.32) for O2 of the equation, Shx = a Rebx Sc0.33 were higher than predicted for a laminar flat plate boundary layer, indicating that physicochemical activity, such as photosynthesis, influenced Shx. The thickness of the measured concentration boundary layer (ΔCBL) and the diffusive sublayer (ΔDSL) were 63% and 70% smaller, respectively, than theoretical values based on hydrodynamic theory. Theoretical hydrodynamic predictions of mass transfer need to account for biological reactions.
Assessment of the processes controlling the seasonal variations of dissolved inorganic carbon in the North Sea
Authors: Bozec Yann , Thomas Helmuth , Schiettecatte Laure-Sophie , Borges Alberto V. , Elkalay Khalid , de Baar Hein J. W.
Published: July 2010

We used a seasonal North Sea data set comprising dissolved inorganic carbon (DIC), partial pressure of CO2 (pCO2), and inorganic nutrients to assess the abiotic and biological processes governing the monthly variations of DIC. During winter, advection and air‐sea exchange of CO2 control and increase the DIC content in the surface and deeper layers of the northern and central North Sea, with the atmosphere supplying CO2 on the order of 0.2 mol C m−2 month−1 to these areas. From February to July, net community production (NCP) controls the seasonal variations of DIC in the surface waters of the entire North Sea, with a net uptake ranging from 0.5 to 1.4 mol C m−2 month−1. During the August‐December period, NCP controls the seasonal variations of DIC in the southern North Sea, with a net release ranging from 0.5 to 0.8 mol C m−2 month−1. Similarly, during the April‐August period in the deeper layer of the northern North Sea, the NCP was the main factor controlling DIC concentrations, with a net release ranging from 0.5 to 5.5 mol C m−2 month−1. In the surface layer of the North Sea, NCP on the basis of DIC was 4.3 ± 0.4 mol C m−2 yr−1, whereas, NCP on the basis of nitrate was 1.6 ± 0.2 mol C m−2 yr−1. Under nutrient‐depleted conditions, preferential recycling (extracellular) of nutrients and intracellular mechanisms occurred and were responsible for the non‐Redfield uptake of DIC versus nitrate and phosphate.
Long‐term changes in legacy trace organic contaminants and mercury in Lake Ontario salmon in relation to source controls, trophodynamics, and climatic variability
Authors: French Todd D. , Campbell Linda M. , Jackson Donald A. , Casselman John M. , Scheider Wolfgang A. , Hayton Al
Published: July 2010

We used long‐term (20+ yr) datasets to determine how the sum of 209 polychlorinated biphenyl congeners ([ΣPCB]), dodecachloropentacyclodecane ([mirex]), para‐para dichlorodiphenyltrichloroethane ([ p,p'‐DDT]), and total mercury ([Tot‐Hg]) concentrations have changed in Lake Ontario chinook salmon (Oncorhynchus tshawytscha, 1983‐2003) and coho salmon (Oncorhynchus kisutch, 1976‐2003). Exponential decay models best describe temporal reductions of persistent organic pollutant concentrations [POPs], including [ΣPCB], [mirex], and [p,p'‐DDT], in chinook (r2 = 0.68‐0.77, p < 0.001) and coho (r2 = 0.68‐0.87, p < 0.001) salmon over the record. In comparison, declines in [Tot‐Hg] were slight, with linear models best describing trends (r2 = 0.49‐0.50, p = <0.001‐0.001). Rapid declines of [POPs] from the mid‐1970s through the early 1980s were attributed mostly to Canada‐United States bans on usage and sedimentation; subsequent concentration oscillations were linked to salmonine stocking and nutrient abatement programs, climatic cycles, and alewife (Alosa pseudoharengus) population dynamics.
Factors controlling seasonal variations in stable isotope composition of particulate organic matter in a softwater eutrophic lake
Authors: Gu Binhe , Chapman Andrew D. , Schelske Claire L.
Published: July 2010

Weekly water samples were taken to measure stable isotope composition (δ13C and δ15N) of particulate organic matter (POM) in Lake Wauberg, Florida, from June 1994 to May 1995. The average δ13C of POM was ‐19.3%, consistent with an autochthonous origin from phytoplankton production, and exhibited a seasonal pattern that coincided with changes in water temperature, pH, CO2 concentration, and phytoplankton biomass in the surface water. The 13C enrichment in POM was attributed to reduced isotope fractionation due to carbon (C) limitation and the use of an isotopically heavy dissolved inorganic carbon pool supported mainly by atmospheric invasion and anaerobic respiration. Intermittent declines in δ13C of POM were related to the frequent collapses of phytoplankton blooms and increases in CO2 concentration resulting from both increased community respiration and terrestrial loading. Average δ15N of POM was 1.3% and varied within a narrow range (20.1% to 2.5%). No significant correlation between phytoplankton biovolume and the δ15N of POM was found. The low δ15N is indicative of strong N2 fixation, which is in line with the low concentration of dissolved inorganic nitrogen and the presence of high biovolume of N2‐fixing cyanobacteria in the surface water. This study suggests that stable C isotopes are good proxies for surface water CO2 concentration and primary production, while stable N isotopes can be used to indicate N2 fixation.
Modelling the chemically aged and mixed aerosols over the eastern central Atlantic Ocean – potential impacts
Authors: Astitha M. , Kallos G. , Spyrou C. , O'Hirok W. , Lelieveld J. , Denier van der Gon H. A. C.
Published: July 2010

Abstract. Detailed information on the chemical and physical properties of aerosols is important for assessing their role in air quality and climate. This work explores the origin and fate of continental aerosols transported over the Central Atlantic Ocean, in terms of chemical composition, number and size distribution, using chemistry-transport models, satellite data and in situ measurements. We focus on August 2005, a period with intense hurricane and tropical storm activity over the Atlantic Ocean. A mixture of anthropogenic (sulphates, nitrates), natural (desert dust, sea salt) and chemically aged (sulphate and nitrate on dust) aerosols is found entering the hurricane genesis region, most likely interacting with clouds in the area. Results from our modelling study suggest rather small amounts of accumulation mode desert dust, sea salt and chemically aged dust aerosols in this Atlantic Ocean region. Aerosols of smaller size (Aitken mode) are more abundant in the area and in some occasions sulphates of anthropogenic origin and desert dust are of the same magnitude in terms of number concentrations. Typical aerosol number concentrations are derived for the vertical layers near shallow cloud formation regimes, indicating that the aerosol number concentration can reach several thousand particles per cubic centimetre. The vertical distribution of the aerosols shows that the desert dust particles are often transported near the top of the marine cloud layer as they enter into the region where deep convection is initiated. The anthropogenic sulphate aerosol can be transported within a thick layer and enter the cloud deck through multiple ways (from the top, the base of the cloud, and by entrainment). The sodium (sea salt related) aerosol is mostly found below the cloud base. The results of this work may provide insights relevant for studies that consider aerosol influences on cloud processes and storm development in the Central Atlantic region.
Twin Doppler Rayleigh/Mie/Raman lidar for wind and temperature measurements in the middle atmosphere up to 80 km
Authors: Baumgarten G.
Published: July 2010

Abstract. A direct detection Doppler shift system for measuring wind speed in the middle atmosphere up to 80 km with 2 h resolution was implemented in the ALOMAR Rayleigh/Mie/Raman lidar (69° N, 16° E). The statistical uncertainty of the line of sight wind is about 0.6 m/s and 10 m/s at 49 km and 80 km, respectively. We use a Doppler Rayleigh Iodine Spectrometer (DoRIS) at the iodine line 1109 (~532.260 nm). DoRIS uses two branches of intensity cascaded channels to cover the dynamic range from 10 to 100 km altitude. The wind detection system was designed to extend the existing multi-color observations of aerosol and temperature. The lidar uses two lasers with a mean power of 14 W at 532 nm each and two 1.8 m diameter tiltable telescopes. Below about 49 km altitude the accuracy and time resolution is limited by the maximum count rate of the detectors used and not by the number of photons available. We report about the first simultaneous Rayleigh temperature and wind measurements by lidar in the strato- and mesosphere on 17 and 23 January 2009.
Oxygenation variability off Northern Chile during the last two centuries
Authors: Díaz-Ochoa J. A. , Pantoja S. , De Lange G. J. , Lange C. B. , Sánchez G. E. , Acuña V. R. , Muñoz P. , Vargas G.
Published: July 2010

Abstract. The Peru Chile Current ecosystem is characterized by high biological productivity and important fisheries. Although this system is likely to be severely affected by climate change, its response to current global warming is still uncertain. In this paper we analyze 10–166 year old sediments in two cores collected in Mejillones Bay, an anoxic sedimentary setting favorable for preservation of proxies. Based on a 166 year chronology we used indicators of bottom water oxygenation proxies (Mo, V, S, and the (lycopane+n-C35)/n-C31) ratio) and surface water productivity (biogenic opal, counts of diatom valves, biogenic Ba, organic carbon and chlorins) to reconstruct environmental variations in Mejillones Bay. We find that at decadal scales, and during the last two centuries, a shift in the coastal marine ecosystem off Northern Chile took place which was characterized by intense ENSO-like activity and large fluctuations in biological export productivity, in bottom water oxygenation, and increased eolic activity (inferred from Ti/Al and Zr/Al). On top of this short-term variability, a gradual increase of sulfidic conditions has occurred being even more intensified since the early 1960s.
Power law relationship between parameters of earthquakes and precursory electrical phenomena revisited II
Authors: Dologlou E.
Published: July 2010

Abstract. The credibility of the power law relation, reported by Dologlou (2009) between the stress drop of an earthquake and the lead time of the preceded Seismic Electric Signal, SES, has been checked through additional new data from 9 June 2008 to 7 April 2010. Three earthquakes with Mw≥5.5 have been found in Greece during this period. A critical exponent α (e.g. 0.328) has been obtained which compares very well with the one reported (α=0.332) by Dologlou (2009). The stability of this exponent might imply that critical dynamic processes, of mechanical (earthquakes) and also of electromagnetic (SES) sense dominate the pre focal area when the SES signal of the impending earthquake is emitted.
Rheological control on the dynamics of explosive activity in the 2000 summit eruption of Mt. Etna
Authors: Giordano D. , Polacci M. , Papale P. , Caricchi L.
Published: July 2010

Abstract. In the period from January to June 2000 Mt. Etna exhibited an exceptional explosive activity characterized by a succession of 64 Strombolian and fire-fountaining episodes from the summit South-East Crater. Textural analysis of the eruptive products reveals that the magma associated with the Strombolian phases had a much larger crystal content (>55 vol%) with respect to the magma discharged during the fire-fountain phases (~35 vol%). Rheological modelling shows that the crystal-rich magma falls in a region beyond a critical crystal content where small addition of solid particles causes an exponential increase of the effective magma viscosity. When implemented into the modeling of steady magma ascent dynamics (as assumed for the fire-fountain activity), a large crystal content as the one found for products of Strombolian eruption phases results in a one order of magnitude decrease of mass flow-rate, and in the onset of conditions where small heterogeneities in the solid fraction carried by the magma translate into highly unsteady eruption dynamics. We argue that crystallization on top of the magmatic column during the intermediate phases when magma was not discharged favoured conditions corresponding to Strombolian activity, with fire-fountain activity resuming after removal of the highly crystalline top. The numerical simulations also provide a consistent interpretation of the association between fire-fountain activity and emergence of lava flows from the crater flanks.
Electronic Circular Dichroism Spectroscopy
Authors: Zsila Ferenc
Published: June 2010

Electronic circular dichroism (ECD or CD) is the manifestation of the important property of chiral compounds to absorb left and right circularly polarized light to different extents. Electronic circular dichroism (CD) spectroscopy technique has been used for investigation of chiral drugs and other pharmaceutical preparations. This article focuses on basic features, instrumentation, advantages, limitations, and practical applications of electronic circular dichroism (CD) spectroscopy in pharmaceutical sciences.
Quality by Design for the Pharmaceutical Industry
Authors: McGrath Richard N. , Lin Dennis K.J.
Published: June 2010

Many industries have incorporated design of experiment (DoE) as an important tool for product and process improvement. DoE allows researchers to vary multiple factors at a time in a systematic fashion, in order to obtain more information for the same amount of resources. This article discusses the DoEs that are relevant to pharmaceutical industry.
Statistical Tools
Authors: Christensen Antje , Esbjerg Sille
Published: June 2010

To the practitioner, statistics is a tool to better understand the numerical data that are abundant in a modern production environment. It is a set of tools to distinguish the probable from improbable, and find the most appropriate explanation for observations. This article focuses on various statistical tools, including data, graphs, descriptive statistics, measures of location, measures of variation, outliers, distributions, sampling, statistical process control (SPC), hypothesis testing, ANOVA, linear regression, non‐linear regression, design of experiments, time series analysis, and multivariate analysis.
Graphene and Graphene Oxide: Synthesis, Properties, and Applications
Authors: Zhu Yanwu , Murali Shanthi , Cai Weiwei , Li Xuesong , Suk Ji Won , Potts Jeffrey R. , Ruoff Rodney S.
Published: June 2010

There is intense interest in graphene in fields such as physics, chemistry, and materials science, among others. Interest in graphene's exceptional physical properties, chemical tunability, and potential for applications has generated thousands of publications and an accelerating pace of research, making review of such research timely. Here is an overview of the synthesis, properties, and applications of graphene and related materials (primarily, graphite oxide and its colloidal suspensions and materials made from them), from a materials science perspective.
Experimental investigation of a circulating fluidized‐bed reactor to capture CO2 with CaO
Authors: Rodríguez N. , Alonso M. , Abanades J. C.
Published: June 2010

Calcium looping processes for capturing CO2 from large emissions sources are based on the use of CaO particles as sorbent in circulating fluidized‐bed (CFB) reactors. A continuous flow of CaO from an oxyfired calciner is fed into the carbonator and a certain inventory of active CaO is expected to capture the CO2 in the flue gas. The circulation rate and the inventory of CaO determine the CO2 capture efficiency. Other parameters such as the average carrying capacity of the CaO circulating particles, the temperature, and the gas velocity must be taken into account. To investigate the effect of these variables on CO2 capture efficiency, we used a 6.5 m height CFB carbonator connected to a twin CFB calciner. Many stationary operating states were achieved using different operating conditions. The trends of CO2 capture efficiency measured are compared with those from a simple reactor model. This information may contribute to the future scaling up of the technology. © 2010 American Institute of Chemical Engineers AIChE J, 57: 000–000, 2011