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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jbusres.2006.09.017 Byline: Gregory J. Whitwell (a), Bryan A. Lukas (a), Paul Hill (b) Keywords: Marketing; Intangible assets; Stock analysts; Shareholder value Abstract: Marketing decisions create intangible assets. In the absence of formal intangible asset value reporting structures, the stock analyst acts as an independent valuation source who provides seemingly objective assessments of the shareholder value of a firm's intangible assets. Drawing on qualitative data from in-depth interviews with stock analysts, the authors investigate a series of antecedent factors that affect the accuracy of the stock analyst's assessment of intangible assets. The study collates these observations into several propositions that may serve as a basis for further research. Author Affiliation: (a) Department of Management and Marketing, University of Melbourne, Parkville, VIC 3010, Australia (b) Hansen Corporation Pty Ltd, 2 Frederick Street, Doncaster, VIC 3108, Australia Article History: Received 1 November 2005; Revised 1 April 2006; Accepted 1 September 2006

Previous research has shown that the destruction of large aggregate particles plays several important roles in the sea. However, the incorporation of this process into existing models of aggregate dynamics has not been possible because of the lack of a rigorous method to facilitate such incorporation. To remedy this problem, the population-balance approach to modelling floc breakage is used to model the effect of aggregation on particle-size distributions.

Purpose: The aim of this study was to evaluate the effect of Pennsylvania Act 112 notification reading level and presentation on patient understanding and anxiety.Methods: Four notifications were developed by alternating 12th grade and 6th grade reading level Act 112 language with letters or infographics. Using Amazon Mechanical Turk, 909 US adult volunteers were randomly assigned to one notification followed by a survey. Participants who answered all 12 survey questions on understanding, anxiety, and sociodemographics were paid $0.10. Chi-square analysis and multivariate regression were used to determine the impact of notification type and sociodemographic data on understanding of communicated information and anxiety.Results: Sixty percent of participants (489 of 821) correctly understood all three questions directly answered within notifications regarding Act 112 subject, next steps, and process for obtaining reports. Approximately half of respondents understood that notifications indirectly conveyed "definitely" or "possibly" abnormal test results (344 of 821 [42%] and 99 of 821 [12%], respectively). Compared with the 12th grade letter, correct understanding of all directly communicated information was lower with the 12th grade infographic after adjustment (odds ratio, 0.61; 95% confidence interval, 0.39-0.95; P = .028) and equivalent with the 6th grade infographic and letter (P = .744 and P = .316). Correct indirect understanding of abnormal test results was not associated with notification type after adjustment but was associated with higher anxiety (odds ratio, 2.86; 95% confidence interval, 0.57-1.35; P < .001).Conclusions: Layperson understanding of information directly and indirectly communicated in Pennsylvania Act 112 is suboptimal, regardless of reading level or presentation. New Act 112 language is needed to improve patient understanding, which would ideally be coproduced with Pennsylvania patients, policymakers, and other relevant stakeholders. [ABSTRACT FROM AUTHOR]

• Retrieval gating allows retrieved content to be aligned with a retrieval goal. • Younger adults show retrieval gating as operationalized by cortical reinstatement. • Older adults failed to demonstrate evidence of retrieval gating. • Scene reinstatement correlated with memory performance in younger adults only. Retrieval gating refers to the ability to modulate the retrieval of features of a single memory episode according to behavioral goals. Recent findings demonstrate that younger adults engage retrieval gating by attenuating the representation of task-irrelevant features of an episode. Here, we examine whether retrieval gating varies with age. Younger and older adults incidentally encoded words superimposed over scenes or scrambled backgrounds that were displayed in one of three spatial locations. Participants subsequently underwent fMRI as they completed two memory tasks: the background task, which tested memory for the word's background, and the location task, testing memory for the word's location. Employing univariate and multivariate approaches, we demonstrated that younger, but not older adults, exhibited attenuated reinstatement of scene information when it was goal-irrelevant (during the location task). Additionally, in younger adults only, the strength of scene reinstatement in the parahippocampal place area during the background task was related to item and source memory performance. Together, these findings point to an age-related decline in the ability to engage retrieval gating. [ABSTRACT FROM AUTHOR]

Current descriptions of ultrasound evaluations, including use of the term "point-of-care ultrasound" (POCUS), are imprecise because they are predicated on distinctions based on the device used to obtain images, the location where the images were obtained, the provider who obtained the images, or the focus of the examination. This is confusing because it does not account for more meaningful distinctions based on the setting, comprehensiveness, and completeness of the evaluation. In this article, the Society of Radiologists in Ultrasound and the members of the American College of Radiology Ultrasound Commission articulate a map of the ultrasound landscape that divides sonographic evaluations into four distinct categories on the basis of setting, comprehensiveness, and completeness. Details of this classification scheme are elaborated, including important clarifications regarding what ensures comprehensiveness and completeness. Practical implications of this framework for future research and reimbursement paradigms are highlighted. [ABSTRACT FROM AUTHOR]

Pennsylvania (PA) Act 112, which became law on October 24, 2018, requires diagnostic imaging entities in the Commonwealth of Pennsylvania to notify patients directly of abnormal imaging results. Relevant outpatient examinations are additionally flagged so that the coordinator can fill required patient and examination information into a PA Act 112 patient notification letter template (M. Adeb, personal communication, August 20, 2019). Ultimately, data are needed to determine whether PA Act 112 improves patient follow-up of abnormal imaging findings within 3 months and, ultimately, improves patient outcomes. [Extracted from the article]

Abstract The frequency and intensity of extreme weather events (e.g. flood, drought) are predicted to increase for the foreseeable future and it is expected that these will negatively impact upon agroecosystem functioning. Our understanding of how grassland ecosystems respond to extreme weather events occurring at different times of the year, however, is lacking. To better understand the seasonal response of grassland to flooding, we subjected an agricultural grassland to an 8-week extreme flood event at three different temperatures (5 °C-winter, 15 °C-spring/autumn and 25°C-summer) and then followed its subsequent recovery for 9 weeks after floodwater removal. We focused on key indicators of ecosystem functioning including primary production, nutrient cycling, greenhouse gas (GHG) emissions, ammonia (NH 3) volatilization, and soil microbial communities. The experiment used intact soil mesocosms (1 kg) with indigenous vegetation collected from a grassland with no previous history of flooding. Flooding reduced biomass production by 18% at 5 °C, 50% at 15 °C and 95% at 25 °C. Flooding also significantly disrupted elemental cycling (nitrogen, phosphorus and carbon) as evidenced by an increased release of P, Fe and NH 4 + into the soil and overlying floodwater and large amounts of CH 4 and NH 3 released to the atmosphere (mainly during the flooding). These effects were more pronounced at higher temperatures (e.g. 45–700 kg CH 4 C ha−1 and 1–5 kg NH 3 N ha−1 at 15 and 25 °C, respectively). In addition, after floodwater removal this NH 4 + was rapidly nitrified leading to large losses of N 2 O (1.0–14.2 kg N 2 O N ha−1 at 5–25 °C, respectively). Especially at higher temperatures, flooding resulted in a reduction in soil microbial biomass (more than 58% of the equivalent unflooded treatment at 25 °C) and changes in microbial community structure (assessed by PLFAs). Further, some of these changes persisted after flood removal including a loss of actinomycetes, arbuscular mycorrhizal fungi and fungi. Overall, we conclude that ecosystem responses to extreme weather events are critically dependent on temperature with those occurring at higher temperatures having a greater negative impact than those at the lowest temperature (5 °C). The large potential release of CH 4 and N 2 O also suggests that flood events should be considered as a potential source of GHGs when comparing top-down and bottom-up calculations of national inventories, and that further work is needed to better refine GHG emission estimates for these events. Highlights • Flooding induced a rapid release of nutrients, especially at higher temperatures. • 700 kg CH 4 C ha−1 and 5 kg NH 3 N ha−1 were released in the flood phase at 25 °C. • During soil recovery, nitrification led to 1.0–14.2 kg N 2 O N ha−1 losses at 5–25 °C. • Flooding reduced soil microbial biomass, actinomycetes and arbuscular mycorrhiza. • Flooding reduced biomass production by 18% at 5 °C, 50% at 15 °C and 95% at 25 °C. [ABSTRACT FROM AUTHOR]

Abstract Soils around the world are being exposed to weather events which are unprecedented in recent history. To maintain the delivery of soil-related ecosystem services and to promote greater soil resilience it is essential to understand how plant-soil systems respond to these extreme events. In this study we replicated a recent period of extreme rainfall and prolonged spring flooding in a temperate grassland which had no previous history of flooding. Intact soil mesocosms (Eutric Cambisol) 1 kg weight were subjected to a simulated long-term spring flood (15 °C, 2 months) and maintained in the light with above ground indigenous vegetation (Lolium perenne L.) or dark with and without indigenous vegetation to simulate different flood typologies. In comparison to a no-flood control treatment, nutrient cycling, water quality, air quality (greenhouse gas emissions), habitat provision and biological population regulation shifts were evaluated. Flooding induced a rapid release of nutrients into the soil solution and overlying floodwater, resulting in potential nutrient losses up to 15 mg Fe, 16 mg NH 4 +, 360 mg DOC and 28 mg DON, per mesocosm. The presence of plants increased the rate of nutrient release (especially P), with the effects magnified when light transmission through the floodwater was restricted (1.3 mg P vs 0.2 mg P, per mesocosm). Flooding induced a rapid decline in redox potential and subsequent production of CH 4 , especially in the darkened treatments (10 and between 11 and 16 times higher than the control, without and with light restrictions, respectively). Upon removal of the floodwater, the accumulated NH 4 + was nitrified leading to a shift in greenhouse gas emissions, from CH 4 to N 2 O emissions. N 2 O was only significantly produced in the mesocosms kept under light restrictions (13 times higher than in other two treatments). Flooding eliminated earthworms, reduced grass production after soil recovery (from 28 g for control mesocosms to 11 g and <1 g for flooded mesocosms without and with light restrictions, respectively). Soil microbial biomass was also reduced (up to a 22–27% of the total PLFAs) and flooding induced shifts in microbial community structure, particularly a loss of soil fungi. The soil fungi content quickly recovered (4 weeks) when light was not restricted during the flood period, however, no such recovery was seen in the darkened treatments. Overall, we conclude that extreme flood events cause rapid and profound changes in soil function. Both the impact of the flooding and the time to recover is exacerbated when light is restricted (e.g. in sediment laden floodwater). In addition, our results suggest that the presence of flood-resilient plants can mitigate against some of the negative impacts of flooding on soil functioning. Highlights • Flooding eliminated earthworms and altered soil microbial community structure. • Flooding reduced the size of the microbial biomass and fungal content. • Vegetation played a vital role in preserving soil quality during flooding. • Decomposition of vegetation induced P loss in light restricted floodwater. • Impact of flooding was greater under light restricted floodwater conditions. [ABSTRACT FROM AUTHOR]

Shrublands cover a large proportion of the world’s land surface, yet they remain poorly studied in comparison to other ecosystems. Within shrublands, soil organic matter (SOM) is replenished from inputs of both above- and below-ground plant litter, however, their relative importance depends on their respective turnover rates. To critically address this, we measured the biodegradation rates of the soluble and insoluble components of 14 C-labelled above- and below-ground plant litter in soil. During the 150 day incubation, the amount of plant-derived soluble-C lost as 14 CO 2 was similar for the different plant parts being 64.7 ± 2.3% for roots, 72.1 ± 7.4% for stems, and 72.4 ± 1.8% for leaves. In comparison, the turnover of the insoluble fraction was much slower. However, again little difference in mineralisation was seen for the different plant parts with the total losses being 21.1 ± 0.9% for roots, 19.5 ± 1.6% for stems, and 19.6 ± 1% for leaves. A double exponential first order kinetic model fitted well to the experimental data. It also allowed the partitioning of C between microbial anabolic and catabolic processes for the soluble C component. Using this model, we deduced that the soluble fraction turns over ca. 40 times annually, whereas it takes ca. 2.5 years to turnover the insoluble fraction. For the soluble plant component, the overall microbial carbon use efficiency (CUE) was estimated to be greater for root-derived C in comparison to that derived from aboveground (no difference was observed for the insoluble component). From this, we tentatively suggest that C sourced from belowground plant components may persist longer in soil than C derived from aboveground plant components. [ABSTRACT FROM AUTHOR]

Recent modifications in the metrics for reimbursement have reinforced the importance of radiology service-delivery experiences of patients. Evaluating current radiology practices calls for reflection on the various touch points with patients, as well as their overall satisfaction. If problems occur during encounters, service failure, or lack of satisfactory medical experiences can be transformed through service recovery, whereby patients-as-customers are given chances to voice their concerns, and health care providers across the spectrum can work together to resolve problematic issues. This paper takes a systemic view of the patient experience as embedded in the care continuum, recognizing that different beliefs, attitudes, and behaviors of members of the health care team can negatively affect or sabotage patient satisfaction. Although radiologists are only one of many roles in the care continuum, recommendations are discussed for how they can integrate service satisfaction as a pervasive communal goal among all health care team members. [ABSTRACT FROM AUTHOR]

Size-specific sediment retention by diatom biofilms was measured by eroding intertidal muds at increasing shear stresses (0.01–0.60 Pa) using a Gust microcosm. The grain sizes eroded from biofilm-covered sediment were compared to those from control cores from which the biofilms were destroyed using bleach. Biofilms were quantified using carbohydrate measurements. Cores from an intertidal mud flat in the Minas Basin of the Bay of Fundy (Canada) showed biofilms preferentially retained clays and very fine silts relative to fine and medium silts. In contrast, prior field observations on an intertidal sand flat indicated that fine and medium silts were preferentially retained by biofilms relative to clays and very fine silts. These contrasting results suggest a link between size-specific sediment retention and sediment texture, where sand biofilms retain coarser, non-cohesive sediment grains, while mud biofilms retain finer, cohesive sediment grains. This relationship implies that biofilms could contribute to a positive feedback that would preserve existing sediment texture. [ABSTRACT FROM AUTHOR]

In this study, we first determined the low molecular weight dissolved organic carbon (LMW DOC) concentration-dependent kinetics of soil respiration in a temperate grassland soil sampled on successive occasions. We then used the established relationship to estimate in situ LMW DOC concentrations from basal respiration measurements. 14C-labelled glucose was used as a model substrate and was added to soil over a wide range of concentrations (0.05-4000 μg C g−1 DW soil; equivalent to ca. 2.5 μM-200 mM glucose-C). The time-dependent loss of 14C-glucose to 14CO2 was similar to previous assessments. The Michaelis-Menten parameter Vmax varied between 17 (September 2010) and 42 (October 2010) μg CO2-C g−1 h−1 (corresponding to 1.4-3.5 µmol CO2 g−1 h−1), while Km varied between 893 (September 2010) and 1990 (October 2010) μg glucose-C g−1 (41-92 mM glucose), thus within the span previously reported for soils, albeit in the higher end of the range. However, the estimates were 6 orders-of-magnitude greater than those found in previous studies in natural waters. A possible methodological reason for this difference was an induced multiphasic concentration dependence, biasing Km and Vmax with high concentrations of LMW DOC. By combining the established concentration dependences with measurements of basal respiration, we estimated in situ concentrations of LMW DOC of 131 (October 2010), 112 (January 2011) and 270 (September 2010) μg LMW DOC g−1, far exceeding the total DOC concentration in the soil (17-20 μg DOC g−1 soil), thus invalidating our approach. We propose a way forward, and suggest that although current estimates of LMW DOC cycling need revision, there is evidence for a rapidly cycling pool of LMW DOC, possibly turning over >30 times per day, that warrants further attention. [ABSTRACT FROM AUTHOR]

Amino acid and oligopeptide-nitrogen (N) forms only a minor component of the total dissolved N pool in grassland soils, yet the importance of these N-pools for plant productivity will ultimately depend on the rate at which these pools turnover. Fluxes of dissolved organic matter (DOM) through the soil solution are frequently estimated from measurements of respiration, but this method fails to consider any delay between microbial substrate acquisition and mineralization. Here, we added 14C-labelled alanine and tri-alanine (10 μM) to 4 soils collected from a natural grassland productivity gradient and then measured substrate depletion from the soil solution and the subsequent production of 14CO2 resulting from mineralization at 1-60 min. There was a considerable delay between microbial 14C removal from the soil solution, which occurred extremely rapidly (up to 96% of added substrate depleted within a minute), and 14CO2 evolution resulting from the fast turnover of the alanine and tri-alanine. This indicates that amino acid and peptide longevity in the soil solution of the soils in this grassland productivity gradient has been greatly overestimated from measurements of mineralization alone. Rates of substrate uptake and mineralization by microbes declined in less productive, N-limited grassland soils with lower levels of microbial biomass, suggesting that the availability of organic N for plant uptake is likely to be controlled by soil microbial activity. We estimate that amino acid and peptide pools occurring in the most productive grassland soils may turnover at a rate of up to 20 times a minute, representing a very considerable flux of N through the soil. [ABSTRACT FROM AUTHOR]

Highlights: [•] Enumerated microplastics in intertidal sediment, fecal matter, and Mytilus edulis. [•] Extracted microplastics >0.8μm via floatation in saline solution and filtration. [•] Accumulation at high tide of exposed beach and low tide of protected beaches. [•] Similar concentrations in polychaete fecal matter and low tide sediments. [•] Higher concentrations observed in farmed blue mussels compared to wild mussels. [Copyright &y& Elsevier]

Abstract: In natural plant–soil systems and following incorporation into plants in agricultural systems, most nitrogen enters soil as protein or other biological polymers. Before this nitrogen can be taken up by soil microorganisms or plants, it must be cleaved to a form which can be transported into the organism. It is well known that soil microorganisms and many plants can utilise l-amino acids and a growing body of evidence shows that short l-peptides can be taken up without further modification. However, there has been very little empirical investigation of rates of uptake in soil. d-amino acids and their peptides are less abundant in soil than their l-enantiomeric counterparts, but do occur in significant quantities. To date their potential rate of cycling in the soil solution remains virtually unknown. We directly measured rates of uptake of 14C-labelled l- and d-alanine and their di- and tripeptides in a temperate agricultural soil. All were taken up extremely rapidly by soil microorganisms. Half-times for l-enantiomers and the d-amino acid monomer were all less than 1 min, with l-peptides accounting for the highest potential fluxes (9 nmol N g−1 DW soil min−1), more than double that of the amino acid monomer. Uptake of d-peptides was slowest with half-times in soil solution of 10 and 36 min (di- and tripeptide, respectively). Availability of l-peptides had a much stronger effect on the rate of uptake of the amino acid monomer than the amino acid monomer had on the uptake of the peptides, suggesting a microbial preference for peptides. We suggest that very high potential N fluxes and an apparent microbial preference for l-peptides indicates that most N is cycled through the soil solution as l-peptides early in protein degradation, and that this is the site of fiercest competition for soil N. [Copyright &y& Elsevier]

Abstract: Most nitrogen (N) enters many Arctic and Antarctic soil ecosystems as protein. Soils in these polar environments frequently contain large stocks of proteinaceous organic matter, which has decomposed slowly due to low temperatures. In addition to proteins, considerable quantities of d-amino acids and their peptides enter soil from bacteria and lengthy residence times can lead to racemisation of l-amino acids in stored proteins. It has been predicted that climate warming in polar environments will lead to increased rates of soil organic N turnover (i.e. amino acids and peptides of both enantiomers). However, our understanding of organic N breakdown in these soils is very limited. To address this, we tested the influence of chain length and enantiomeric composition on the rate of breakdown of amino acids and peptides in three contrasting tundra soils formed under the grass, moss or lichen-dominated primary producer communities of Signy Island in the South Orkney Islands. Both d- and l-enantiomers of the amino acid monomer were rapidly mineralized to CO2 at rates in line with those found for l-amino acids in many other terrestrial ecosystems. In all three soils, l-peptides were decomposed faster than their amino acid monomer, suggesting a different route of microbial assimilation and catabolism. d-peptides followed the same mineralization pattern as l-peptides in the two contrasting soils under grass and lichens, but underwent relatively slow decomposition in the soil underneath moss, which was similar to the soil under the grass. We conclude that the decomposition of peptides of l-amino acids may be widely conserved amongst soil microorganisms, whereas the decomposition of peptides of d-amino acids may be altered by subtle differences between soils. We further conclude that intense competition exists in soil microbial communities for the capture of both peptides and amino acids produced from protein breakdown. [Copyright &y& Elsevier]

Abstract: Understanding the fate and turnover of the pools that comprise dissolved organic nitrogen (DON) in soil is key to determining its role in ecosystem functioning. We investigated seasonal changes of dissolved organic carbon (DOC) and nitrogen (DON) concentrations within four molecular weight (MW) size fractions across an altitudinal gradient (from lowland to montane systems), and quantified individual amino acids and amino acid constituents of oligopeptidic-N, as well as nitrate and ammonium. We tested two ideas: first, that DON is more abundant than DIN in low-productivity relative to high-productivity grassland ecosystems; and second, that the abundance of peptides and amino acids is likewise greater in low- than high-productivity grassland. The most productive site had a history of inorganic fertiliser application, and hence in this site alone DIN was more abundant than DON. Plant productivity varied 3-fold between the other sites, and DON was generally at higher concentrations in the sites of lower productivity both in absolute terms as well as relative to DIN, with a large increase observed in spring. The fraction containing the highest concentration of the DON had a MW of >100 kDa, and in summer and autumn this fraction was more abundant at the lowest productivity site. We conclude that relationships between the abundance of DON relative to DIN and ecosystem productivity is dependent on season, and hence more complex than previously suggested, and that peptides are a dynamic and potentially nutritionally significant component of DON. [Copyright &y& Elsevier]

Abstract: Distinguishing between root and non-root derived CO2 efflux is important when determining rates of soil organic matter turnover, however, in practice they remain difficult to separate. Our aim was to evaluate two methods for determining the component of below-ground respiration not dependent on plant roots (i.e., basal soil respiration; R b). The first approach estimated R b indirectly from the y-intercept of linear regressions between below-ground respiration (BGR) and root biomass. The second approach involved direct measurements of soil respiration from bare plots. To compare the contrasting approaches, BGR and crop biomass measurements were collected throughout the year in a range of agricultural systems. We found that both methods were very closely correlated with each other. Values of R b determined by the intercept approach, however, were slightly higher than those determined by measurement of bare plots. Both approaches showed a seasonal trend with estimates of R b lowest in winter months at 0.02 t C ha−1 month−1 for the y-intercept approach and 0.11 t C ha−1 month−1 for the bare plots approach, even after the data had been corrected for the influence of soil temperature. Highest rates of R b occurred from the height to the end of the crop growing season (0.8–1.5 t C ha−1 month−1). The annual CO2 efflux due to R b was estimated to be 8.1 t C ha−1 y−1 from the y-intercept approach and 6.8 t C ha−1 y−1 from bare plots. Annual BGR was 12.1 t C ha−1 y−1. We conclude that both methods provide similar estimates of R b, however, logistically the bare plots approach is much easier to undertake than the y-intercept approach. [Copyright &y& Elsevier]

Abstract: The rate of organic matter turnover in soil is a critical component of the terrestrial carbon cycle and is frequently estimated from measurements of respiration. For estimates to be reliable requires that isotopically labelled substrate uptake into the soil microbial biomass and its subsequent mineralization occurs almost simultaneously (i.e. no time delay). Here we investigated this paradigm using glucose added to an agricultural soil. Immediately after collection from the field, various concentrations of 14C-labeled glucose (1μM to 10mM) were added to soil and the depletion from the soil solution measured at 1–60min after substrate addition. 14CO2 production from the mineralization of glucose was simultaneously measured. The microbial uptake of glucose from soil solution was concentration-dependent and kinetic analysis suggests the operation of at least two distinct glucose transport systems of differing affinity. At glucose concentrations reflecting those naturally present in the soil solution (54±10μM), the half-time (t 1/2) of exogenous glucose was extremely rapid at ca. 30s. At higher glucose concentrations (100μM to 10mM), the t 1/2 values for the high-affinity carrier were altered little, but increasing proportions of glucose were taken up by the low affinity transport system. Glucose mineralization by the soil microbial community showed a significant delay after its uptake into the microbial biomass suggesting a decoupling of glucose uptake and subsequent respiration, possibly by dilution of glucose in labile metabolite pools. By fitting a double first order kinetic equation to the mineralization results we estimated the t 1/2 for the first rapid phase of respiration at natural soil solution glucose concentrations to be 6–8min, but at least 87% of the added glucose was retained in the microbial biomass prior to mineralization. Our results suggest that in this soil the soil solution glucose pool turns over 100–1000 times each day, an order of magnitude faster than when determined from measurements of mineralization. These results imply that traditional isotopic based measurements of substrate turnover measured using CO2 may vastly underestimate their rate of cycling in soil. [Copyright &y& Elsevier]

Abstract: Large amounts of low molecular weight (LMW;<250Da) carbon (C) are lost from roots into the rhizosphere as a consequence of root turnover and exudation. Their rates of turnover after release into the soil remain poorly understood. We extracted soil solution from a temperate grassland Eutric Cambisol, isotopically labeled the glucose and amino acid components, and then re-injected the solution back into the soil. We followed the subsequent evolution of 14CO2 and incorporation of the LMW C into the soil microbial biomass or grasses for 48h. The experiments were performed both on grazed and un-grazed swards in the field, and in the laboratory. In the field, we showed that glucose and amino acids had short half-lives (t 1/2) in soil solution (t 1/2=20–40min), but that they persisted in soil microbes for much longer. A first-order double exponential model fitted the experimental data well and gave rate constant (k) values of 1.21–2.14h−1 for k 1 and 0.0025–0.0048h−1 for k 2. Only small amounts of the added 14C were recovered in plant biomass (<5% of total added to soil) indicating that plant roots are poor competitors for LMW dissolved organic C (DOC) in comparison to soil microorganisms. The first phase of glucose and amino acid mineralization in the laboratory was slower (t 1/2=40–60min) than measured in the field reinforcing the importance of making flux measurements in situ. Whilst grazing stimulated below-ground respiration, it exerted only a small influence on the turnover of LMW DOC suggesting that the increase in respiration was due to increased root respiration and not turnover of soil organic matter (SOM). Our results suggest that some components of the LMW DOC pool are turned over extremely rapidly (ca. 4000 times annually). [Copyright &y& Elsevier]

Abstract: Across a limited depth range (5–10m) on many continental shelves, the dominant sediment size changes from sand to mud. This important boundary, called the sand–mud transition (SMT), separates distinct benthic habitats, causes a significant change in acoustic backscatter, represents a key facies change, and delimits more surface-reactive mud from less surface-reactive sand. With the goal of improving dynamical understanding of the SMT, surficial sediments were characterized across two SMTs on the Adriatic continental shelf of Italy. Geometric mean diameter, specific surface area (SSA), mud fraction (<63μm) and heavy metal concentrations were all measured. The SMT related to the Tronto River is identified between 15 and 20m water depth while the SMT associated with the Pescara River varies between 15 and 25m water depth. The sediment properties correlate with a new, process-based sedimentological parameter that quantifies the fraction of the sediment in the seabed that was delivered as flocs. These correlations suggest that floc dynamics exert strong influence over sediment textural properties and metal concentrations. Relative constancy in the depth of the SMT along this portion of the margin and its lack of evolution over a period during which sediment input to the margin has dramatically decreased suggest that on the Adriatic continental shelf energy is the dominant control on the depth of the SMT. [Copyright &y& Elsevier]

Abstract: Measurements of floc sizes, floc settling velocities and effective floc densities were obtained at three locations on the inner Adriatic shelf (Italy) in February and May/June 2003 using the in situ size and settling column tripod INSSECT (Mikkelsen et al., 2004. INSSECT—an instrument platform for investigating floc properties close to the seabed. Limnology and Oceanography: Methods 2, 226–236). Measurements were carried out in a water depth of 8–12m and the final data set comprised 2491 flocs. Relationships of observed floc size vs. floc settling velocity and floc size vs. effective floc density were similar to those observed by other authors working in similar settings. The raw data showed significant scatter around mean trends, indicating that only a relatively small fraction of variability in floc settling velocity and effective floc density was explained by floc size. For bin-averaged data, however, much of the variability in settling velocity and density was explained by floc size. On the Adriatic shelf mean floc settling velocities varied from 0.48 to 1.35mms−1, while mean effective floc densities varied from 8.1 to 27.5kgm−3; within the range reported by other authors. Analysis of variance showed significant differences in floc settling velocities, effective floc densities and floc size in space and time (seasons). Thus, floc settling velocities, effective floc densities and floc size on the inner Adriatic shelf could not be characterized by a common mean, but were more appropriately characterized by a range of values, varying in time and space. [Copyright &y& Elsevier]

Abstract: The deficit of 234Th relative to its radioactive parent 238U in the surface ocean can yield reliable estimates of vertical Particulate Organic Carbon (POC) fluxes to deeper waters, but only when coupled with an accurate ratio of POC concentration to activity of 234Th on sinking matter. Assuming a simple partitioning of suspended phytoplankton mass between single cells and flocs, we calculate the ratio of the POC flux estimated from 234Th deficit to the actual POC flux (p ratio, Smith, J.N., Moran, S.B., Speicher, E.A., in press. The p-ratio: a new diagnostic for evaluating the accuracy of upper ocean particulate organic carbon export fluxes estimated from 234Th/238U disequilibrium. Deep-Sea Research I.). The p ratios are calculated under the assumption that particle surface area is correlated with 234Th activity and particle volume is correlated with POC concentration. The value of the p ratio depends on the relative contributions of single cells and flocs to the vertical flux. When large single cells make up a significant fraction of the vertical flux, p ratios are less than one, meaning POC fluxes estimated from 234Th deficits underestimate actual POC fluxes. When large single cells are abundant but do not sink fast enough to contribute to vertical POC flux, p ratios are greater than one (up to 3× overestimate). Factor analysis of the model indicates that altering the extent of flocculation in suspension and changing the density and maximum size of phytoplankton cells have the greatest effects on the p ratio. Failure to measure the properties of flocs when characterizing the ratio of POC to thorium on sinking matter potentially leads to large overestimation of the POC flux (over 20×). Failure to characterize the POC to thorium ratio of large particles, by, for example, destruction of phytoplankton cells in pumps, can lead to underestimation of POC flux. Estimates of POC flux should be most reliable in highly flocculated suspensions populated by small cells and rapidly sinking flocs. These conditions are often associated with intense phytoplankton blooms. [Copyright &y& Elsevier]

Abstract: Controlled laboratory studies of the formation of oil–mineral aggregates (OMA) in seawater demonstrate that sediment concentration and sediment size are key variables for determining the quantity of oil droplets stabilised by OMA formation. Experiments with a single sediment size and a range of sediment concentrations show that as sediment concentration increases, the quantity of oil trapped in OMA increases abruptly. In experiments with a single sediment concentration and a range of sediment sizes, the quantity of oil trapped in OMA decreases as sediment size increases. These results provide direct support to the hypothesis that there is a critical sediment concentration for OMA formation. Below this concentration, stabilisation of oil droplets by OMA decreases rapidly, while above this concentration, stabilisation is extensive. The results also support simple geometric models of OMA formation that predict that the critical sediment mass concentration increases linearly with sediment particle diameter. These results will help to place quantitative constraint on predictions of where and when OMA formation will be a factor in the natural dispersal of oil accidentally spilled into the ocean. [Copyright &y& Elsevier]

Abstract: A LISST-100 in situ laser particle sizer was deployed together with a digital floc camera during field work in the Newark Bay area (USA) and along the Apennine margin (the Adriatic Sea, Italy). The purpose of these simultaneous deployments was to investigate how well in situ particle (floc) sizes and volume concentrations from the two different instruments compared. In the Adriatic Sea the two instruments displayed the same temporal variation, but the LISST provided lower estimates of floc size by a factor of 2–3, compared to the DFC. In the Newark Bay area, the LISST provided higher values of floc size by up to a factor of 2. When floc size was computed using only the overlapping size bins from the two instruments the discrepancy disappeared. The reason for the discrepancy in size was found to be related to several issues: First, the LISST measured particles in the 2.5–500μm range, whereas the camera measured particles in the 135–9900μm range, so generally the LISST should provide lower estimates of floc size, as it measures the smaller particles. Second, in the Newark Bay area scattering from particles >500μm generally caused the LISST to overestimate the volume of particles in its largest size bin, thereby increasing apparent floc size. Relative to the camera, the LISST generally provided estimates of total floc volume that were lower by a factor of 3. Factors that could explain this discrepancy are errors arising from the accuracy of the LISST volume conversion coefficient and image processing. Regardless of these discrepancies, the shapes of the size spectra from the instruments were similar in the regions of overlap and could be matched by multiplying with an appropriate correction coefficient. This facilitated merging of the size spectra from the LISST and the DFC, yielding size spectra in the 2.5–9900μm range. The merged size spectra generally had one or more peaks in the coarse end of the spectrum, presumably due to the presence of flocs. The fine end (<100μm) of the spectrum displayed a flat tail with equal concentration of particles in all size classes. Size spectra with this shape indicate that the classical Junge model for description of in situ particle size spectra is reasonable for particles smaller than 100μm but not for larger particles. Floc fraction was computed for the merged spectra by using a diameter-to-mass conversion and found to vary between 0.34 and 0.95, within the range reported by other authors. [Copyright &y& Elsevier]

The relative influence of oil type and temperature on the characteristics of oil droplets stabilized by mineral particles (oil–mineral aggregates––OMA) was studied in the laboratory. OMA were generated by shaking eight different oils under two temperatures with natural mineral fines in seawater at a pre-defined energy level. Shape, mean and maximum sizes, size distribution and concentration of oil droplets forming negatively buoyant OMA were measured by image analysis using epi-fluorescence microscopy. Results showed that oil droplets are, on average, spherical regardless of oil composition and temperature. Non-spherical “elongated” oil droplets form more at 20 °C than at 0 °C. Droplet shape and size were not correlated to oil viscosity. The concentration of oil droplets decreased rapidly with oil viscosity, temperature and asphaltenes–resins content (ARC). When normalized with ARC, mass concentration of oil droplets correlates well with oil viscosity, regardless of experimental temperature. A model was proposed to calculate mass of oil dispersed by OMA as a function of oil viscosity and ARC. Size distributions of oil droplets follow similar trends, but their magnitudes depend on oil type and temperature. A function was derived that describes all the data when size distributions were presented in a normalized form N/Nt=f(D/D50), where N is number of droplets of diameter D, Nt is the total number of droplets and D50 the mean size of the droplets. [Copyright &y& Elsevier]

Small rivers (drainage basins <104 km2) discharging runoff from mountainous terrain are major contributors of mud to the marine environment. However, little understanding of the dispersal mechanisms and fate of discharged fine-grained sediments to the continental shelf is known due to the episodic and unpredictable nature of discharge from these rivers. This study used a helicopter-based sampling program to capture unprecedented measures of Eel River, northern California, flood plume events during 1997, 1998, and 1999. In situ measures of floc size and estimated floc fraction show no relationship with concentration, turbulent-kinetic-energy, time from river mouth, wind speed, wave height, or discharge. A relationship apparently does exist between effective settling velocity (bulk mean settling velocity) of plume sediments and wind speed/direction, as well as with tides. Results implicate the energetic nearshore as a source of suspended sediment resupply to the offshore region of the plume. Future studies focusing on surf zone suspended fine-grained sediment dynamics are needed in order to understand the fate of flood plume sediments discharged to exposed, energetic shelves, such as the Eel River margin. [Copyright &y& Elsevier]

Petroleum exploration on continental shelves raises concerns over potential impacts it may have on ecologically sensitive and valuable fishing grounds. Several studies demonstrate that drill mud discharged from platforms exhibit negative impacts on surrounding benthic communities. However, the dispersal and deposition mechanisms of such mud are poorly understood. This study investigates the evolution of disaggregated particle size distributions of bentonite enriched water-based drill mud in a suspension flowing over a flat sand bed using a laboratory flume. Observed size-specific decay rates of suspended sediment concentrations indicate that suspended grains deposit as single grains and flocs. A simple model that considers deposition of particles by gravitational settling of single grains and flocs yields estimates of decay rates in good agreement with the measurements. The proposed model provides a grain size-specific analysis of parameters characteristic of a poorly sorted aging suspension that have previously been undocumented. [Copyright &y& Elsevier]

Protein represents a major input of organic matter to soil and is an important source of carbon (C) and nitrogen (N) for microorganisms. Therefore, determining which soil properties influence protein mineralisation in soil is key to understanding and modelling soil C and N cycling. However, the effect of different soil properties on protein mineralisation, and especially the interactions between soil properties, are poorly understood. We investigated how topsoil and subsoil properties affect protein mineralisation along a grassland altitudinal (catena) sequence that contained a gradient in soil type and primary productivity. We devised a schematic diagram to test the key edaphic factors that may influence protein mineralisation in soil (e.g. pH, microbial biomass, inorganic and organic N availability, enzyme activity and sorption). We then measured the mineralisation rate of 14C-labelled soluble plant-derived protein and amino acids in soil over a two-month period. Correlation analysis was used to determine the associations between rates of protein mineralisation and soil properties. Contrary to expectation, we found that protein mineralisation rate was nearly as fast as for amino acid turnover. We ascribe this rapid protein turnover to the low levels of protein used here, its soluble nature, a high degree of functional redundancy in the microbial community and microbial enzyme adaptation to their ecological niche. Unlike other key soil N processes (e.g. nitrification, denitrification), protease activity was not regulated by a small range of factors, but rather appeared to be affected by a wide range of interacting factors whose importance was dependent on altitude and soil depth [e.g. above-ground net primary productivity (NPP), soil pH, nitrate, cation exchange capacity (CEC), C:N ratio]. Based on our results, we hypothesise that differences in soil N cycling and the generation of ammonium are more related to the rate of protein supply rather than limitations in protease activity and protein turnover per se. • Protein mineralisation rates differed along a grassland altitudinal gradient. • Effect of soil parameters on protein breakdown rates were modelled. • Protein mineralisation rate was nearly as fast as for amino acid mineralisation. • Protein mineralisation had weak relationships with many interacting edaphic factors. • Interactions between edaphic factors are more important than individual effects on protein mineralisation. [ABSTRACT FROM AUTHOR]

Freeze-thaw and dry-wet cycles are common phenomena in temperate regions. Such events may have a significant influence on the functioning of the soil microbial community. Using non-targeted metabolomics, we compared the effects of a single freeze-thaw or dry-wet event on microbial metabolism in an agricultural soil with and without plants. We showed that a dry-wet cycle had a greater impact on solute and metabolite concentrations in the unplanted soil than a freeze-thaw cycle. Drying or freezing caused increases in dissolved organic C, sugars and polyols, suggesting enhanced microbial production to alleviate temperature or moisture stress. Increased nucleobase concentration in the unplanted soil after a dry-wet cycle, and increased amino acids following both stresses, suggested a breakdown of microbial DNA and proteins released from damaged cells. The impacts of stress on metabolites in the planted soil were less than in the unplanted soil. In conclusion, our findings indicate that the soil microbial community responds quickly to stress events by accumulating osmotic solutes (e.g. sugars and polyols) and that a freeze-thaw event causes less disruption than dry-rewetting, and that plants have a key role in the mitigation of the freezing or drying effects on soil microbial communities. Unlabelled Image • Soil with and without plants was subjected to dry-wet or freeze-thaw stress events. • A dry-wet event impacted solute and metabolite concentrations more than freeze-thaw. • Drying and freezing caused increases in sugars, polyols and amino acids. • Dry-wet induces free nucleobases indicating extensive cell lysis. [ABSTRACT FROM AUTHOR]

Soils support a wide range of ecosystem services that underpin Earth system functioning. It is therefore essential that we have robust approaches to evaluate how anthropogenic perturbation affects soil quality and the delivery of these services. Metabolomics, the large-scale study of low molecular weight organic compounds in soil, offers one potential approach to characterise soils and evaluate the metabolic status of the soil biological community. The aims of the present study were to 1) characterise the soil metabolome across a contrasting range of soil types, 2) understand the relationships between common chemical and physical soil quality indicators and its metabolome, and 3) evaluate the discriminatory power of soil metabolomics and its potential use as a soil quality indicator. Nine different topsoils with 5 replications were collected along an altitudinal primary productivity gradient encompassing a wide range of soil types and land uses. Metabolites were extracted from soil using 3:3:2 (v/v/v) acetonitrile:isopropanol:water and individual compounds identified using a gas chromatography-mass spectrometry (GC-MS) platform. Overall, 405 individual compounds were detected, of which 146 were positively identified, including sugars, amino acids, organic acids, nucleobases, sugar alcohols, lipids and a range of secondary metabolites. The concentration and profile of metabolites was found to vary greatly between the soil types. Further, the soils' metabolomic fingerprints correlated to a number of environmental factors, including pH, land-use, moisture and salinity. We also tentatively attributed soil-specific metabolites to potential functional pathways, although complementary proteomic, genomic and transcriptomic approaches would be needed to provide definitive supporting evidence. In conclusion, soil metabolomics offers the potential to reveal the complex molecular networks and metabolic pathways operating in the soil microbial community and a means of evaluating soil function. Further work is now required to benchmark soil metabolomes under a wide range of management regimes so that they can be used for the quantitative assessment of soil quality. Image 1 • Soil metabolites were extracted using acetonitrile, isopropanol and water. • Metabolites with contrasting chemical properties were detected using GC-MS. • Soils could be categorized into 4 distinct groups based on metabolite profiles. • Soil metabolomic fingerprints correlated to several environmental factors. • Potential functional pathways were indicated for exploration. [ABSTRACT FROM AUTHOR]