Quantifying uncertainty in carbon and nutrient pools of coarse woody debris

NASA Astrophysics Data System (ADS)

See, C. R.; Campbell, J. L.; Fraver, S.; Domke, G. M.; Harmon, M. E.; Knoepp, J. D.; Woodall, C. W.

2016-12-01

Woody detritus constitutes a major pool of both carbon and nutrients in forested ecosystems. Estimating coarse wood stocks relies on many assumptions, even when full surveys are conducted. Researchers rarely report error in coarse wood pool estimates, despite the importance to ecosystem budgets and modelling efforts. To date, no study has attempted a comprehensive assessment of error rates and uncertainty inherent in the estimation of this pool. Here, we use Monte Carlo analysis to propagate the error associated with the major sources of uncertainty present in the calculation of coarse wood carbon and nutrient (i.e., N, P, K, Ca, Mg, Na) pools. We also evaluate individual sources of error to identify the importance of each source of uncertainty in our estimates. We quantify sampling error by comparing the three most common field methods used to survey coarse wood (two transect methods and a whole-plot survey). We quantify the measurement error associated with length and diameter measurement, and technician error in species identification and decay class using plots surveyed by multiple technicians. We use previously published values of model error for the four most common methods of volume estimation: Smalian's, conical frustum, conic paraboloid, and average-of-ends. We also use previously published values for error in the collapse ratio (cross-sectional height/width) of decayed logs that serves as a surrogate for the volume remaining. We consider sampling error in chemical concentration and density for all decay classes, using distributions from both published and unpublished studies. Analytical uncertainty is calculated using standard reference plant material from the National Institute of Standards. Our results suggest that technician error in decay classification can have a large effect on uncertainty, since many of the error distributions included in the calculation (e.g. density, chemical concentration, volume-model selection, collapse ratio) are decay

Global dynamics in a stoichiometric food chain model with two limiting nutrients.

PubMed

Chen, Ming; Fan, Meng; Kuang, Yang

2017-07-01

Ecological stoichiometry studies the balance of energy and multiple chemical elements in ecological interactions to establish how the nutrient content affect food-web dynamics and nutrient cycling in ecosystems. In this study, we formulate a food chain with two limiting nutrients in the form of a stoichiometric population model. A comprehensive global analysis of the rich dynamics of the targeted model is explored both analytically and numerically. Chaotic dynamic is observed in this simple stoichiometric food chain model and is compared with traditional model without stoichiometry. The detailed comparison reveals that stoichiometry can reduce the parameter space for chaotic dynamics. Our findings also show that decreasing producer production efficiency may have only a small effect on the consumer growth but a more profound impact on the top predator growth. Copyright © 2017 Elsevier Inc. All rights reserved.

DYNAMICS OF NUTRIENTS AND HYDROLOGY IN A LAKE SUPERIOR COASTAL WETLAND

EPA Science Inventory

Coastal wetlands are hydrologically complex ecosystems situated at the interface of upland catchments and oligotrophic Lake Superior. Little is known about nutrient dynamics within coastal wetlands or their role in modifying or contributing to nutrient fluxes from watersheds to ...

Flow Dynamics and Nutrient Reduction in Rain Gardens

EPA Science Inventory

The hydrological dynamics and changes in stormwater nutrient concentrations within rain gardens were studied by introducing captured stormwater runoff to rain gardens at EPA’s Urban Water Research Facility in Edison, New Jersey. The runoff used in these experiments was collected...

Dynamic shear-stress-enhanced rates of nutrient consumption in gas-liquid semi-continuous-flow suspensions

NASA Astrophysics Data System (ADS)

Belfiore, Laurence A.; Volpato, Fabio Z.; Paulino, Alexandre T.; Belfiore, Carol J.

2011-12-01

The primary objective of this investigation is to establish guidelines for generating significant mammalian cell density in suspension bioreactors when stress-sensitive kinetics enhance the rate of nutrient consumption. Ultra-low-frequency dynamic modulations of the impeller (i.e., 35104 Hz) introduce time-dependent oscillatory shear into this transient analysis of cell proliferation under semi-continuous creeping flow conditions. Greater nutrient consumption is predicted when the amplitude A of modulated impeller rotation increases, and stress-kinetic contributions to nutrient consumption rates increase linearly at higher modulation frequency via an application of fluctuation-dissipation response. Interphase mass transfer is required to replace dissolved oxygen as it is consumed by aerobic nutrient consumption in the liquid phase. The theory and predictions described herein could be important at small length scales in the creeping flow regime where viscous shear is significant at the interface between the nutrient medium and isolated cells in suspension. Two-dimensional flow around spherically shaped mammalian cells, suspended in a Newtonian culture medium, is analyzed to calculate the surface-averaged magnitude of the velocity gradient tensor and modify homogeneous rates of nutrient consumption that are stimulated by viscous shear, via the formalism of stress-kinetic reciprocal relations that obey Curie's theorem in non-equilibrium thermodynamics. Time constants for stress-free free and stress-sensitive stress nutrient consumption are defined and quantified to identify the threshold (i.e., stress,threshold) below which the effect of stress cannot be neglected in accurate predictions of bioreactor performance. Parametric studies reveal that the threshold time constant for stress-sensitive nutrient consumption stress,threshold decreases when the time constant for stress

Vegetation composition, nutrient, and sediment dynamics along a floodplain landscape

USGS Publications Warehouse

Rybicki, Nancy B.; Noe, Gregory; Hupp, Cliff R.; Robinson, Myles

2015-01-01

Forested floodplains are important landscape features for retaining river nutrients and sediment loads but there is uncertainty in how vegetation influences nutrient and sediment retention. In order to understand the role of vegetation in nutrient and sediment trapping, we quantified species composition and the uptake of nutrients in plant material relative to landscape position and ecosystem attributes in an urban, Piedmont watershed in Virginia, USA. We investigated in situ interactions among vegetative composition, abundance, carbon (C), nitrogen (N) and phosphorus (P) fluxes and ecosystem attributes such as water level, shading, soil nutrient mineralization, and sediment deposition. This study revealed strong associations between vegetation and nutrient and sediment cycling processes at the plot scale and in the longitudinal dimension, but there were few strong patterns between these aspects at the scale of geomorphic features (levee, backswamp, and toe-slope). Patterns reflected the nature of the valley setting rather than a simple downstream continuum. Plant nutrient uptake and sediment trapping were greatest at downstream sites with the widest floodplain and lowest gradient where the hydrologic connection between the floodplain and stream is greater. Sediment trapping increased in association with higher herbaceous plant coverage and lower tree canopy density that, in turn, was associated with a more water tolerant tree community found in the lower watershed but not at the most downstream site in the watershed. Despite urbanization effects on the hydrology, this floodplain functioned as an efficient nutrient trap. N and P flux rates of herbaceous biomass and total litterfall more than accounted for the N and P mineralization flux rate, indicating that vegetation incorporated nearly all mineralized nutrients into biomass.

Aggregated filter-feeding consumers alter nutrient limitation: consequences for ecosystem and community dynamics.

PubMed

Atkinson, Carla L; Vaughn, Caryn C; Forshay, Kenneth J; Cooper, Joshua T

2013-06-01

Nutrient cycling is a key process linking organisms in ecosystems. This is especially apparent in stream environments in which nutrients are taken up readily and cycled through the system in a downstream trajectory. Ecological stoichiometry predicts that biogeochemical cycles of different elements are interdependent because the organisms that drive these cycles require fixed ratios of nutrients. There is growing recognition that animals play an important role in biogeochemical cycling across ecosystems. In particular, dense aggregations of consumers can create biogeochemical hotspots in aquatic ecosystems via nutrient translocation. We predicted that filter-feeding freshwater mussels, which occur as speciose, high-biomass aggregates, would create biogeochemical hotspots in streams by altering nutrient limitation and algal dynamics. In a field study, we manipulated nitrogen and phosphorus using nutrient-diffusing substrates in areas with high and low mussel abundance, recorded algal growth and community composition, and determined in situ mussel excretion stoichiometry at 18 sites in three rivers (Kiamichi, Little, and Mountain Fork Rivers, south-central United States). Our results indicate that mussels greatly influence ecosystem processes by modifying the nutrients that limit primary productivity. Sites without mussels were N-limited with -26% higher relative abundances of N-fixing blue-green algae, while sites with high mussel densities were co-limited (N and P) and dominated by diatoms. These results corroborated the results of our excretion experiments; our path analysis indicated that mussel excretion has a strong influence on stream water column N:P. Due to the high N:P of mussel excretion, strict N-limitation was alleviated, and the system switched to being co-limited by both N and P. This shows that translocation of nutrients by mussel aggregations is important to nutrient dynamics and algal species composition in these rivers. Our study highlights the

Legacy nutrient dynamics and patterns of catchment response under changing land use and management

NASA Astrophysics Data System (ADS)

Attinger, S.; Van, M. K.; Basu, N. B.

2017-12-01

Watersheds are complex heterogeneous systems that store, transform, and release water and nutrients under a broad distribution of both natural and anthropogenic controls. Many current watershed models, from complex numerical models to simpler reservoir-type models, are considered to be well-developed in their ability to predict fluxes of water and nutrients to streams and groundwater. They are generally less adept, however, at capturing watershed storage dynamics. In other words, many current models are run with an assumption of steady-state dynamics, and focus on nutrient flows rather than changes in nutrient stocks within watersheds. Although these commonly used modeling approaches may be able to adequately capture short-term watershed dynamics, they are unable to represent the clear nonlinearities or hysteresis responses observed in watersheds experiencing significant changes in nutrient inputs. To address such a lack, we have, in the present work, developed a parsimonious modeling approach designed to capture long-term catchment responses to spatial and temporal changes in nutrient inputs. In this approach, we conceptualize the catchment as a biogeochemical reactor that is driven by nutrient inputs, characterized internally by both biogeochemical degradation and residence or travel time distributions, resulting in a specific nutrient output. For the model simulations, we define a range of different scenarios to represent real-world changes in land use and management implemented to improve water quality. We then introduce the concept of state-space trajectories to describe system responses to these potential changes in anthropogenic forcings. We also increase model complexity, in a stepwise fashion, by dividing the catchment into multiple biogeochemical reactors, coupled in series or in parallel. Using this approach, we attempt to answer the following questions: (1) What level of model complexity is needed to capture observed system responses? (2) How can we

Real-time monitoring of nutrients in the Changjiang Estuary reveals short-term nutrient-algal bloom dynamics

NASA Astrophysics Data System (ADS)

Wang, Kui; Chen, Jianfang; Ni, Xiaobo; Zeng, Dingyong; Li, Dewang; Jin, Haiyan; Glibert, Patricia M.; Qiu, Wenxian; Huang, Daji

2017-07-01

The Changjiang Estuary is a large-river estuary ecosystem in the East China Sea, and its plume, the Changjiang Diluted Water (CDW), transports a large mass of nutrients (NO3- + NO2-, PO43-, SiO32-) to the shelf sea, leading to substantial eutrophication; the CDW also supports high primary production. However, relationships between nutrient delivery and phytoplankton responses have been difficult to establish, as many nutrient delivery events and algal blooms are episodic, and the CDW may expand or become detached with changing winds. To study the relationship between nutrient delivery events, algal blooms and estuarine metabolism dynamics, a buoy system was deployed in the CDW from 9 September to 10 October 2013, with measurements of chlorophyll a and dissolved nutrients. Day-to-day nutrient increases covaried with salinity decreases, regulated by both the spring-neap tidal cycle and wind events. Several specific nutrient injection periods were detected, each followed by nutrient drawdown and chlorophyll a accumulation (algal blooms). Each algal bloom had its own unique pattern of nutrient uptake based on change in nutrient ratios (ΔN:ΔP; ΔN:ΔSi) and appeared to be dominated by different algal groups. These events occurred under weak wind and stable hydrodynamic conditions. Ecosystem metabolism based on net community production (NCP) showed that the upper estuarine ecosystem was autotrophic when chlorophyll a accumulated, but heterotrophic when wind-induced mixing strengthened, and upwelling brought organic-rich water to the near surface. In spite of several short-lived algal blooms, the average NCPdaily was negative during the observation period, indicating a net source of CO2 to the atmosphere.

Fine-root growth in a forested bog is seasonally dynamic, but shallowly distributed in nutrient-poor peat

DOE PAGES

Iversen, Colleen M.; Childs, Joanne; Norby, Richard J.; ...

2017-03-30

Fine roots contribute to ecosystem carbon, water, and nutrient fluxes through resource acquisition, respiration, exudation, and turnover, but are understudied in peatlands. Here, we aimed to determine how the amount and timing of fine-root growth in a forested, ombrotrophic bog varied across gradients of vegetation density, peat microtopography, and changes in environmental conditions across the growing season and throughout the peat profile. We quantified fine-root peak standing crop and growth using non-destructive minirhizotron technology over a two-year period, focusing on the dominant woody species in the bog: Picea mariana, Larix laricina, Rhododendron groenlandicum, and Chamaedaphne calyculata. The fine roots ofmore » trees and shrubs were concentrated in raised hummock microtopography, with more tree roots associated with greater tree densities and a unimodal peak in shrub roots at intermediate tree densities. Fine-root growth tended to be seasonally dynamic, but shallowly distributed, in a thin layer of nutrient-poor, aerobic peat above the growing season water table level. Finally, the dynamics and distribution of fine roots in this forested ombrotrophic bog varied across space and time in response to biological, edaphic, and climatic conditions, and we expect these relationships to be sensitive to projected environmental changes in northern peatlands.« less

Fine-root growth in a forested bog is seasonally dynamic, but shallowly distributed in nutrient-poor peat

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iversen, Colleen M.; Childs, Joanne; Norby, Richard J.

Fine roots contribute to ecosystem carbon, water, and nutrient fluxes through resource acquisition, respiration, exudation, and turnover, but are understudied in peatlands. Here, we aimed to determine how the amount and timing of fine-root growth in a forested, ombrotrophic bog varied across gradients of vegetation density, peat microtopography, and changes in environmental conditions across the growing season and throughout the peat profile. We quantified fine-root peak standing crop and growth using non-destructive minirhizotron technology over a two-year period, focusing on the dominant woody species in the bog: Picea mariana, Larix laricina, Rhododendron groenlandicum, and Chamaedaphne calyculata. The fine roots ofmore » trees and shrubs were concentrated in raised hummock microtopography, with more tree roots associated with greater tree densities and a unimodal peak in shrub roots at intermediate tree densities. Fine-root growth tended to be seasonally dynamic, but shallowly distributed, in a thin layer of nutrient-poor, aerobic peat above the growing season water table level. Finally, the dynamics and distribution of fine roots in this forested ombrotrophic bog varied across space and time in response to biological, edaphic, and climatic conditions, and we expect these relationships to be sensitive to projected environmental changes in northern peatlands.« less

Consumer-driven nutrient dynamics in freshwater ecosystems: from individuals to ecosystems.

PubMed

Atkinson, Carla L; Capps, Krista A; Rugenski, Amanda T; Vanni, Michael J

2017-11-01

The role of animals in modulating nutrient cycling [hereafter, consumer-driven nutrient dynamics (CND)] has been accepted as an important influence on both community structure and ecosystem function in aquatic systems. Yet there is great variability in the influence of CND across species and ecosystems, and the causes of this variation are not well understood. Here, we review and synthesize the mechanisms behind CND in fresh waters. We reviewed 131 articles on CND published between 1973 and 1 June 2015. The rate of new publications in CND has increased from 1.4 papers per year during 1973-2002 to 7.3 per year during 2003-2015. The majority of investigations are in North America with many concentrating on fish. More recent studies have focused on animal-mediated nutrient excretion rates relative to nutrient demand and indirect impacts (e.g. decomposition). We identified several mechanisms that influence CND across levels of biological organization. Factors affecting the stoichiometric plasticity of consumers, including body size, feeding history and ontogeny, play an important role in determining the impact of individual consumers on nutrient dynamics and underlie the stoichiometry of CND across time and space. The abiotic characteristics of an ecosystem affect the net impact of consumers on ecosystem processes by influencing consumer metabolic processes (e.g. consumption and excretion/egestion rates), non-CND supply of nutrients and ecosystem nutrient demand. Furthermore, the transformation and transport of elements by populations and communities of consumers also influences the flow of energy and nutrients across ecosystem boundaries. This review highlights that shifts in community composition or biomass of consumers and eco-evolutionary underpinnings can have strong effects on the functional role of consumers in ecosystem processes, yet these are relatively unexplored aspects of CND. Future research should evaluate the value of using species traits and abiotic

Nutrient supply and mercury dynamics in marine ecosystems: a conceptual model.

PubMed

Driscoll, Charles T; Chen, Celia Y; Hammerschmidt, Chad R; Mason, Robert P; Gilmour, Cynthia C; Sunderland, Elsie M; Greenfield, Ben K; Buckman, Kate L; Lamborg, Carl H

2012-11-01

There is increasing interest and concern over the impacts of mercury (Hg) inputs to marine ecosystems. One of the challenges in assessing these effects is that the cycling and trophic transfer of Hg are strongly linked to other contaminants and disturbances. In addition to Hg, a major problem facing coastal waters is the impacts of elevated nutrient, particularly nitrogen (N), inputs. Increases in nutrient loading alter coastal ecosystems in ways that should change the transport, transformations and fate of Hg, including increases in fixation of organic carbon and deposition to sediments, decreases in the redox status of sediments and changes in fish habitat. In this paper we present a conceptual model which suggests that increases in loading of reactive N to marine ecosystems might alter Hg dynamics, decreasing bioavailabilty and trophic transfer. This conceptual model is most applicable to coastal waters, but may also be relevant to the pelagic ocean. We present information from case studies that both support and challenge this conceptual model, including marine observations across a nutrient gradient; results of a nutrient-trophic transfer Hg model for pelagic and coastal ecosystems; observations of Hg species, and nutrients from coastal sediments in the northeastern U.S.; and an analysis of fish Hg concentrations in estuaries under different nutrient loadings. These case studies suggest that changes in nutrient loading can impact Hg dynamics in coastal and open ocean ecosystems. Unfortunately none of the case studies is comprehensive; each only addresses a portion of the conceptual model and has limitations. Nevertheless, our conceptual model has important management implications. Many estuaries near developed areas are impaired due to elevated nutrient inputs. Widespread efforts are underway to control N loading and restore coastal ecosystem function. An unintended consequence of nutrient control measures could be to exacerbate problems associated with Hg

Nutrient supply and mercury dynamics in marine ecosystems: A conceptual model

PubMed Central

Chen, Celia Y.; Hammerschmidt, Chad R.; Mason, Robert P.; Gilmour, Cynthia C.; Sunderland, Elsie M.; Greenfield, Ben K.; Buckman, Kate L.; Lamborg, Carl H.

2013-01-01

There is increasing interest and concern over the impacts of mercury (Hg) inputs to marine ecosystems. One of the challenges in assessing these effects is that the cycling and trophic transfer of Hg are strongly linked to other contaminants and disturbances. In addition to Hg, a major problem facing coastal waters is the impacts of elevated nutrient, particularly nitrogen (N), inputs. Increases in nutrient loading alter coastal ecosystems in ways that should change the transport, transformations and fate of Hg, including increases in fixation of organic carbon and deposition to sediments, decreases in the redox status of sediments and changes in fish habitat. In this paper we present a conceptual model which suggests that increases in loading of reactive N to marine ecosystems might alter Hg dynamics, decreasing bioavailabilty and trophic transfer. This conceptual model is most applicable to coastal waters, but may also be relevant to the pelagic ocean. We present information from case studies that both support and challenge this conceptual model, including marine observations across a nutrient gradient; results of a nutrient-trophic transfer Hg model for pelagic and coastal ecosystems; observations of Hg species, and nutrients from coastal sediments in the northeastern U.S.; and an analysis of fish Hg concentrations in estuaries under different nutrient loadings. These case studies suggest that changes in nutrient loading can impact Hg dynamics in coastal and open ocean ecosystems. Unfortunately none of the case studies is comprehensive; each only addresses a portion of the conceptual model and has limitations. Nevertheless, our conceptual model has important management implications. Many estuaries near developed areas are impaired due to elevated nutrient inputs. Widespread efforts are underway to control N loading and restore coastal ecosystem function. An unintended consequence of nutrient control measures could be to exacerbate problems associated with Hg

Sediment and nutrient budgets are inherently dynamic: evidence from a long-term study of two subtropical reservoirs

NASA Astrophysics Data System (ADS)

O'Brien, Katherine R.; Weber, Tony R.; Leigh, Catherine; Burford, Michele A.

2016-12-01

Accurate reservoir budgets are important for understanding regional fluxes of sediment and nutrients. Here we present a comprehensive budget of sediment (based on total suspended solids, TSS), total nitrogen (TN) and total phosphorus (TP) for two subtropical reservoirs on rivers with highly intermittent flow regimes. The budget is completed from July 1997 to June 2011 on the Somerset and Wivenhoe reservoirs in southeast Queensland, Australia, using a combination of monitoring data and catchment model predictions. A major flood in January 2011 accounted for more than half of the water entering and leaving both reservoirs in that year, and approximately 30 % of water delivered to and released from Wivenhoe over the 14-year study period. The flood accounted for an even larger proportion of total TSS and nutrient loads: in Wivenhoe more than one-third of TSS inputs and two-thirds of TSS outputs between 1997 and 2011 occurred during January 2011. During non-flood years, mean historical concentrations provided reasonable estimates of TSS and nutrient loads leaving the reservoirs. Calculating loads from historical mean TSS and TP concentrations during January 2011, however, would have substantially underestimated outputs over the entire study period, by up to a factor of 10. The results have important implications for sediment and nutrient budgets in catchments with highly episodic flow. First, quantifying inputs and outputs during major floods is essential for producing reliable long-term budgets. Second, sediment and nutrient budgets are dynamic, not static. Characterizing uncertainty and variability is therefore just as important for meaningful reservoir budgets as accurate quantification of loads.

Urbanization Changes the Temporal Dynamics of Nutrients and Water Chemistry

NASA Astrophysics Data System (ADS)

Steele, M.; Badgley, B.

2017-12-01

Recent studies find that urban development alters the seasonal dynamics of nutrient concentrations, where the highest concentrations of nitrogen occurred during the winter in urban watersheds, rather than the summer. However, the effects of urbanization on the seasonal concentrations of other nutrients and chemical components is unknown. Therefore, to determine how urbanization changes the seasonal dynamics, once a week we measured concentrations of dissolved organic carbon (DOC), nutrients (NO3, DON, TN, PO4), base cations (Ca, Mg, Na, K), anions (F, Cl, SO4), pH, sediment, temperature, conductivity, and dissolved oxygen (DO) of nine urban, agricultural, and minimally developed watersheds in southwest Virginia, USA. We found that urbanization disrupted the seasonal dynamics of all metrics, except DON, PO4, Ca, sediment, and DO, where some shifted to high concentrations during the winter (Cl, conductivity), highs during late winter or spring (DOC, Na), a season low (TN, SO4, NO3) or high (NH4) during the summer, or remained more constant throughout the year compared to the reference watersheds (Mg, K, pH). The complex changes in seasonal dynamics coincide with a decoupling of common correlations between constituents; for example, DO and NO3 are negatively correlated in reference watersheds (NO3 increases, DO decreases), but positively correlated in urban watersheds. These results suggest that as watersheds become more intensely developed, the influence of natural drivers like temperature and vegetation become steadily overcome by the influence of urban drivers like deicing salts and wastewater leakage, which exert increasing control of seasonal water quality and aquatic habitat.

Animal pee in the sea: consumer-mediated nutrient dynamics in the world's changing oceans.

PubMed

Allgeier, Jacob E; Burkepile, Deron E; Layman, Craig A

2017-06-01

Humans have drastically altered the abundance of animals in marine ecosystems via exploitation. Reduced abundance can destabilize food webs, leading to cascading indirect effects that dramatically reorganize community structure and shift ecosystem function. However, the additional implications of these top-down changes for biogeochemical cycles via consumer-mediated nutrient dynamics (CND) are often overlooked in marine systems, particularly in coastal areas. Here, we review research that underscores the importance of this bottom-up control at local, regional, and global scales in coastal marine ecosystems, and the potential implications of anthropogenic change to fundamentally alter these processes. We focus attention on the two primary ways consumers affect nutrient dynamics, with emphasis on implications for the nutrient capacity of ecosystems: (1) the storage and retention of nutrients in biomass, and (2) the supply of nutrients via excretion and egestion. Nutrient storage in consumer biomass may be especially important in many marine ecosystems because consumers, as opposed to producers, often dominate organismal biomass. As for nutrient supply, we emphasize how consumers enhance primary production through both press and pulse dynamics. Looking forward, we explore the importance of CDN for improving theory (e.g., ecological stoichiometry, metabolic theory, and biodiversity-ecosystem function relationships), all in the context of global environmental change. Increasing research focus on CND will likely transform our perspectives on how consumers affect the functioning of marine ecosystems. © 2017 John Wiley & Sons Ltd.

Quantifying uncertainty in forest nutrient budgets

Treesearch

Ruth D. Yanai; Carrie R. Levine; Mark B. Green; John L. Campbell

2012-01-01

Nutrient budgets for forested ecosystems have rarely included error analysis, in spite of the importance of uncertainty to interpretation and extrapolation of the results. Uncertainty derives from natural spatial and temporal variation and also from knowledge uncertainty in measurement and models. For example, when estimating forest biomass, researchers commonly report...

Quantifying nutrient sources in an upland catchment using multiple chemical and isotopic tracers

NASA Astrophysics Data System (ADS)

Sebestyen, S. D.; Boyer, E. W.; Shanley, J. B.; Doctor, D. H.; Kendall, C.; Aiken, G. R.

2006-12-01

To explore processes that control the temporal variation of nutrients in surface waters, we measured multiple environmental tracers at the Sleepers River Research Watershed, an upland catchment in northeastern Vermont, USA. Using a set of high-frequency stream water samples, we quantified the variation of nutrients over a range of stream flow conditions with chemical and isotopic tracers of water, nitrate, and dissolved organic carbon (DOC). Stream water concentrations of nitrogen (predominantly in the forms of nitrate and dissolved organic nitrogen) and DOC reflected mixing of water contributed from distinct sources in the forested landscape. Water isotopic signatures and end-member mixing analysis revealed when solutes entered the stream from these sources and that the sources were linked to the stream by preferential shallow subsurface and overland flow paths. Results from the tracers indicated that freshly-leached, terrestrial organic matter was the overwhelming source of high DOC concentrations in stream water. In contrast, in this region where atmospheric nitrogen deposition is chronically elevated, the highest concentrations of stream nitrate were attributable to atmospheric sources that were transported via melting snow and rain fall. These findings are consistent with a conceptual model of the landscape in which coupled hydrological and biogeochemical processes interact to control stream solute variability over time.

Upland and in-stream controls on baseflow nutrient dynamics in tile-drained agroecosystem watersheds

USDA-ARS?s Scientific Manuscript database

Controls on baseflow nutrient concentrations in agroecosystems are poorly characterized in comparison with storm events. However, in landscapes with low residence times (e.g., rivers and reservoirs), baseflow nutrient concentration dynamics during sensitive timeframes can drive deleterious environm...

User-inspired Research Quantifies How Floodplain Restoration Paired With Cover Crops Reduces Nutrient Export From an Agricultural Catchment Translating to Conservation Success in the Midwestern Cornbelt.

NASA Astrophysics Data System (ADS)

Tank, J. L.; Hanrahan, B.; Christopher, S. F.; Mahl, U. H.; Royer, T. V.

2017-12-01

The Midwestern US has undergone extensive land use change as forest, wetlands, and prairies have been converted to agroecosystems. Today, excess fertilizer nutrients from farm fields enter agricultural streams, which degrades both local and downstream water quality. We are quantifying the nutrient reduction benefits of two conservation practices implemented at the catchment scale. In partnership with The Nature Conservancy, in a small Indiana catchment, we have quantified how 600m of floodplain restoration (i.e., a two-stage ditch) increased nitrate-N removal via denitrification and reduced sediment export, but impacts on stream nutrient concentrations were negligible due to very high catchment loading relative to the short implementation reach. Requests from state and federal partners led to development and parameterization of a new two-stage ditch module in the SWAT model to determine the potential catchment-scale benefits when implementation lengths were extended. More recently, in partnership with state SWCD managers, we have added a landscape practice to quantify how winter cover crops reduce nutrient loss from fields, sampling year-round nutrient fluxes from multiple subsurface tile drains and longitudinally along the stream channel. Nitrate-N and dissolved P fluxes were significantly lower in tiles draining fields with cover crops compared to those without. At the urging of farmers and federal NRCS partners, we also linked tile drain nutrient reductions to changes in soil chemistry. Both soil nitrate-N and dissolved P were lower in cover cropped fields, and we found significant correlations between soil and tile drain nutrients, which may encourage future adoption of the conservation practice as soil health benefits appeal to farmers. As biogeochemists, this research has provided valuable insights on how floodplains and land cover change can alter patterns of catchment-scale nutrient export. The translation of successful soil and water quality outcomes

Stoichiometry and climatic stress drive respiration and nutrient dynamics of beech litter decomposition

NASA Astrophysics Data System (ADS)

Keiblinger, Katharina Maria; Hämmerle, Ieda; Zechmeister-Boltenstern, Sophie

2010-05-01

Little is known about how the variance in resources in terms of carbon (C), nitrogen (N), phosphorus (P) ratios affects respiration and nutrient dynamics. To elucidate how resource quantity and stoichiometry affect the decomposition process of beech (Fagus sylvatica) litter a terrestrial microcosm experiment was conducted. Our aim was to follow changes of beech litter stoichiometry and biogeochemical processes, and to quantify element losses as affected by temperature and moisture extremes. In addition to gaseous element losses (CO2) we examined the release of nutrients prone to leaching and the importance of environmental controls. We addressed mechanisms and pathways of carbon, nitrogen and phosphorus losses. In our experiment sterilised dried leaves were inoculated with a litter-soil suspension from a beech forest in order to ensure similar starting conditions. Beech litter from different Austrian sites covering C:N ratios from 45 to 66 and C:P ratios from 652 to 1467 were incubated at 15°C for six months. The water content was adjusted to 60% at regular intervals to keep the moisture constant. To monitor transient and persistent influences of environmental stress, the microcosms were subject to extreme changes in temperature (+30°C and -20°C) and moisture (draught) after an incubation time of three months. Litter stoichiometries (C:N, C:P) turned out to be strong predictors for respiration, and nitrogen, and phosphorous losses. (i) Litter with narrow litter C:nutrient ratios decomposed faster than litter with wider litter C:nutrient ratios; and therefore showed higher respiration rates. (ii) Increased nutrient losses as leachates were observed for high quality leaf litter i.e. inorganic nitrogen losses for sites with narrow litter C:N ratios and phosphate was released more quickly in sites with narrow C:P ratios. There was a strong functional response of the microbial community to environmental extremes. Respiration increased upon temperature extremes

Spatio-temporal dynamics in phytobenthos structural properties reveal insights into agricultural catchment dynamics and nutrient fluxes

NASA Astrophysics Data System (ADS)

Reaney, S. M.; Snell, M. A.; Barker, P. A.; Aftab, A.; Barber, N. J.; Benskin, C.; Burke, S.; Cleasby, W.; Haygarth, P.; Jonczyk, J. C.; Owen, G. J.; Perks, M. T.; Quinn, P. F.; Surridge, B.

2016-12-01

Low order streams are spatially extensive, temporally dynamic, systems within the agricultural landscape. This dynamism extends to the aquatic communities within these streams, including the phytobentos, which demonstrates considerable resilience to diffuse anthropogenic nutrient pressures and changing climate dynamics. The phytobenthos community can substantially contribute to the food web, in particular diatoms, which dominate photo-autotrophic assemblages in low order streams. Diatoms are widely used in ecological monitoring because of their high sensitivity to environmental condition, but knowledge is limited on the ecological effects of winter disturbances and variance introduced by multiple and interacting pressures (N, P, sediment), introducing bias in understanding temporal dynamics in benthic diatom communities. Using the environmental time series data from long term monitoring within the River Eden Demonstration Test Catchment programme, we assess the impact of multiple hydro-chemical stressors on phytobenthic community resilience, and synthesize the impact of an extreme winter event. Monthly data from diatom communities collected in the Eden DTC from March 2011 to present show that river flow, strongly coupled to precipitation, is a key driver of these communities. Discharge has a direct effect on communities through scouring, but is also tightly correlated to nutrient delivery, such that 80% of the annual TP load arrives in 10% of the time. Trophic Diatom Index (TDI) values demonstrated considerable resilience by the stability of inter-monthly TDI scores over 5 seasonal cycles against the characterised highly variable hydrological regime. This research demonstrates that well characterised winter disturbances are critical to understanding drivers of aquatic dynamics. This has implications for catchment diffuse pollution policy, farm management and economics, given the climate projections of increases in frequency and intensity of extreme winter events

Quantification of Shallow Groundwater Nutrient Dynamics in Septic Areas

Treesearch

Ying Ouyang; Jia-En Zhang

2012-01-01

Of all groundwater pollution sources, septic systems are the second largest source of groundwater nitrate contamination in USA. This study investigated shallow groundwater (SGW) nutrient dynamics in septic areas at the northern part of the Lower St. Johns River Basin, Florida, USA. Thirty-five SGW-monitoring wells, located at nine different urban areas served by septic...

Consistent nutrient storage and supply mediated by diverse fish communities in coral reef ecosystems.

PubMed

Allgeier, Jacob E; Layman, Craig A; Mumby, Peter J; Rosemond, Amy D

2014-08-01

Corals thrive in low nutrient environments and the conservation of these globally imperiled ecosystems is largely dependent on mitigating the effects of anthropogenic nutrient enrichment. However, to better understand the implications of anthropogenic nutrients requires a heightened understanding of baseline nutrient dynamics within these ecosystems. Here, we provide a novel perspective on coral reef nutrient dynamics by examining the role of fish communities in the supply and storage of nitrogen (N) and phosphorus (P). We quantified fish-mediated nutrient storage and supply for 144 species and modeled these data onto 172 fish communities (71 729 individual fish), in four types of coral reefs, as well as seagrass and mangrove ecosystems, throughout the Northern Antilles. Fish communities supplied and stored large quantities of nutrients, with rates varying among ecosystem types. The size structure and diversity of the fish communities best predicted N and P supply and storage and N : P supply, suggesting that alterations to fish communities (e.g., overfishing) will have important implications for nutrient dynamics in these systems. The stoichiometric ratio (N : P) for storage in fish mass (~8 : 1) and supply (~20 : 1) was notably consistent across the four coral reef types (but not seagrass or mangrove ecosystems). Published nutrient enrichment studies on corals show that deviations from this N : P supply ratio may be associated with poor coral fitness, providing qualitative support for the hypothesis that corals and their symbionts may be adapted to specific ratios of nutrient supply. Consumer nutrient stoichiometry provides a baseline from which to better understand nutrient dynamics in coral reef and other coastal ecosystems, information that is greatly needed if we are to implement more effective measures to ensure the future health of the world's oceans. © 2014 John Wiley & Sons Ltd.

Contrasting patterns of nutrient dynamics during different storm events in a semi-arid catchment of northern China.

PubMed

Du, Xinzhong; Li, Xuyong; Hao, Shaonan; Wang, Huiliang; Shen, Xiao

2014-01-01

Nutrient discharge during storm events is a critical pathway for nutrient export in semi-arid catchments. We investigated nutrient dynamics during three summer storms characterized by different rainfall magnitude in 2012 in a semi-arid catchment of northern China. The results showed that, in response to storm events, nutrient dynamics displayed big variation in temporal trends of nutrient concentration and in nutrient concentration-flow discharge relationships. Nutrient concentrations had broader fluctuations during an extreme storm than during lesser storms, whereas the concentration ranges of the a moderate storm were no broader than those of a smaller one. The different concentration fluctuations were caused by storm magnitude and intensity coupled with the antecedent rainfall amount and cumulative nutrients. Correlation coefficients between nutrient concentrations and flow discharge varied from positive to negative for the three different events. There were no consistent hysteresis effects for the three different events, and no hysteresis effects were observed for any of the variables during the moderate storm (E2). Our findings provide useful information for better understanding nutrient loss mechanisms during storm events in semi-arid areas of a monsoon climate region.

Effect of the alien invasive bivalve Corbicula fluminea on the nutrient dynamics under climate change scenarios

NASA Astrophysics Data System (ADS)

Coelho, J. P.; Lillebø, A. I.; Crespo, D.; Leston, S.; Dolbeth, M.

2018-05-01

The main aim of this study was to evaluate the impact of the alien invasive bivalve Corbicula fluminea (Müller, 1774) in the nutrient dynamics of temperate estuarine systems (oligohaline areas) under climate change scenarios. The scenarios simulated shifts in climatic conditions, following salinity (0 or 5) and temperature (24 or 30 °C) changes, usual during drought and heat wave events. The effect of the individual size/age (different size classes with fixed biomass) and density (various densities of <1 cm clams) on the bioturbation-associated nutrient dynamics were also evaluated under an 18-day laboratory experimental setup. Results highlight the significant effect of C. fluminea on the ecosystem nutrient dynamics, enhancing the efflux of both phosphate and dissolved inorganic nitrogen (DIN) from the sediments to the water column. Both drought and heat wave events will have an impact on the DIN dynamics within C. fluminea colonized systems, favouring a higher NH4-N efflux. The population structure of C. fluminea will have a decisive role on the impact of the species, with stronger nutrient effluxes associated with a predominantly juvenile population structure.

Accounting for heterogeneity of nutrient dynamics in riverscapes through spatially distributed models

NASA Astrophysics Data System (ADS)

Wollheim, W. M.; Stewart, R. J.

2011-12-01

Numerous types of heterogeneity exist within river systems, leading to hotspots of nutrient sources, sinks, and impacts embedded within an underlying gradient defined by river size. This heterogeneity influences the downstream propagation of anthropogenic impacts across flow conditions. We applied a river network model to explore how nitrogen saturation at river network scales is influenced by the abundance and distribution of potential nutrient processing hotspots (lakes, beaver ponds, tributary junctions, hyporheic zones) under different flow conditions. We determined that under low flow conditions, whole network nutrient removal is relatively insensitive to the number of hotspots because the underlying river network structure has sufficient nutrient processing capacity. However, hotspots become more important at higher flows and greatly influence the spatial distribution of removal within the network at all flows, suggesting that identification of heterogeneity is critical to develop predictive understanding of nutrient removal processes under changing loading and climate conditions. New temporally intensive data from in situ sensors can potentially help to better understand and constrain these dynamics.

Quantifying chaotic dynamics from integrate-and-fire processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pavlov, A. N.; Saratov State Technical University, Politehnicheskaya Str. 77, 410054 Saratov; Pavlova, O. N.

2015-01-15

Characterizing chaotic dynamics from integrate-and-fire (IF) interspike intervals (ISIs) is relatively easy performed at high firing rates. When the firing rate is low, a correct estimation of Lyapunov exponents (LEs) describing dynamical features of complex oscillations reflected in the IF ISI sequences becomes more complicated. In this work we discuss peculiarities and limitations of quantifying chaotic dynamics from IF point processes. We consider main factors leading to underestimated LEs and demonstrate a way of improving numerical determining of LEs from IF ISI sequences. We show that estimations of the two largest LEs can be performed using around 400 mean periodsmore » of chaotic oscillations in the regime of phase-coherent chaos. Application to real data is discussed.« less

Long-term MODIS observations of cyanobacterial dynamics in Lake Taihu: Responses to nutrient enrichment and meteorological factors

PubMed Central

Shi, Kun; Zhang, Yunlin; Zhou, Yongqiang; Liu, Xiaohan; Zhu, Guangwei; Qin, Boqiang; Gao, Guang

2017-01-01

We developed and validated an empirical model for estimating chlorophyll a concentrations (Chla) in Lake Taihu to generate a long-term Chla and algal bloom area time series from MODIS-Aqua observations for 2003 to 2013. Then, based on the long-term time series data, we quantified the responses of cyanobacterial dynamics to nutrient enrichment and climatic conditions. Chla showed substantial spatial and temporal variability. In addition, the annual mean cyanobacterial surface bloom area exhibited an increasing trend across the entire lake from 2003 to 2013, with the exception of 2006 and 2007. High air temperature and phosphorus levels in the spring can prompt cyanobacterial growth, and low wind speeds and low atmospheric pressure levels favor cyanobacterial surface bloom formation. The sensitivity of cyanobacterial dynamics to climatic conditions was found to vary by region. Our results indicate that temperature is the most important factor controlling Chla inter-annual variability followed by phosphorus and that air pressure is the most important factor controlling cyanobacterial surface bloom formation followed by wind speeds in Lake Taihu. PMID:28074871

Advances in the understanding of nutrient dynamics and management in UK agriculture.

PubMed

Dungait, Jennifer A J; Cardenas, Laura M; Blackwell, Martin S A; Wu, Lianhai; Withers, Paul J A; Chadwick, David R; Bol, Roland; Murray, Philip J; Macdonald, Andrew J; Whitmore, Andrew P; Goulding, Keith W T

2012-09-15

Current research on macronutrient cycling in UK agricultural systems aims to optimise soil and nutrient management for improved agricultural production and minimise effects on the environment and provision of ecosystem services. Nutrient use inefficiencies can cause environmental pollution through the release of greenhouse gases into the atmosphere and of soluble and particulate forms of N, P and carbon (C) in leachate and run-off into watercourses. Improving nutrient use efficiencies in agriculture calls for the development of sustainable nutrient management strategies: more efficient use of mineral fertilisers, increased recovery and recycling of waste nutrients, and, better exploitation of the substantial inorganic and organic reserves of nutrients in the soil. Long-term field experimentation in the UK has provided key knowledge of the main nutrient transformations in agricultural soils. Emerging analytical technologies, especially stable isotope labelling, that better characterise macronutrient forms and bioavailability and improve the quantification of the complex relationships between the macronutrients in soils at the molecular scale, are augmenting this knowledge by revealing the underlying processes. The challenge for the future is to determine the relationships between the dynamics of N, P and C across scales, which will require both new modelling approaches and integrated approaches to macronutrient cycling. Copyright © 2012 Elsevier B.V. All rights reserved.

Quantifying cadherin mechanotransduction machinery assembly/disassembly dynamics using fluorescence covariance analysis.

PubMed

Vedula, Pavan; Cruz, Lissette A; Gutierrez, Natasha; Davis, Justin; Ayee, Brian; Abramczyk, Rachel; Rodriguez, Alexis J

2016-06-30

Quantifying multi-molecular complex assembly in specific cytoplasmic compartments is crucial to understand how cells use assembly/disassembly of these complexes to control function. Currently, biophysical methods like Fluorescence Resonance Energy Transfer and Fluorescence Correlation Spectroscopy provide quantitative measurements of direct protein-protein interactions, while traditional biochemical approaches such as sub-cellular fractionation and immunoprecipitation remain the main approaches used to study multi-protein complex assembly/disassembly dynamics. In this article, we validate and quantify multi-protein adherens junction complex assembly in situ using light microscopy and Fluorescence Covariance Analysis. Utilizing specific fluorescently-labeled protein pairs, we quantified various stages of adherens junction complex assembly, the multiprotein complex regulating epithelial tissue structure and function following de novo cell-cell contact. We demonstrate: minimal cadherin-catenin complex assembly in the perinuclear cytoplasm and subsequent localization to the cell-cell contact zone, assembly of adherens junction complexes, acto-myosin tension-mediated anchoring, and adherens junction maturation following de novo cell-cell contact. Finally applying Fluorescence Covariance Analysis in live cells expressing fluorescently tagged adherens junction complex proteins, we also quantified adherens junction complex assembly dynamics during epithelial monolayer formation.

Nutrient chemotaxis suppression of a diffusive instability in bacterial colony dynamics

NASA Astrophysics Data System (ADS)

Arouh, Scott; Levine, Herbert

2000-07-01

Bacteria grown on a semisolid agar surface have been observed to form branching patterns as the colony envelope propagates outward. The fundamental cause of this instability relates to the need for limited nutrient to diffuse towards the colony. Here, we investigate the effect on this instability of allowing the bacteria to move chemotactically in response to the nutrient gradient. Our results show that this additional effect has a tendency to suppress the instability. Our calculations are done within the context of a simple ``cutoff'' model of colony dynamics, but presumably remain valid for more complex and hence more realistic approaches.

Relations between phytoplankton growth rates and nutrient dynamics in Lake Norman, North Carolina. Technical report series

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodriguez, M.S.

A baseline study of phytoplankton production and nutrient dynamics was conducted on Lake Norman, NC, a 13000-ha, warm-monomictic reservoir, prior to the initiation of thermal inputs from an 1180-MW nuclear electric generation facility. The objective of the study was to identify the major physical, chemical and biological processes controlling nutrient dynamics in Lake Norman, with specific reference to the impact of phytoplankton production on the cycling of carbon, nitrogen and phosphorus.

Nutrient budget for Saguling Reservoir, West Java, Indonesia.

PubMed

Hart, Barry T; van Dok, Wendy; Djuangsih, Nani

2002-04-01

A preliminary nutrient budget for Saguling Reservoir is reported as a first attempt to quantify the behaviour of nutrients entering this reservoir. This work is part of a larger Indonesia-Australia collaborative research and training project, involving Padjadjaran University and Monash University, established to study nutrient dynamics in Saguling Reservoir. Saguling Reservoir, the first of a chain of three large reservoirs (Saguling, Cirata and Jatilahur), built on the Citarum River in central Java, was completed in 1985. It has already become highly polluted, particularly with domestic and industrial effluent (organic matter, nutrients, heavy metals) from the urban areas of Bandung (population 2 million). The reservoir experiences major water quality problems, including excessive growths of floating plants, toxic cyanobacterial blooms and regular fish-kills. The work reported in this paper shows that Saguling receives a very large nutrient load from the city of Bandung and because of this, is highly eutrophic. It is unlikely that the water quality of Saguling will improve until a substantial part of Bandung is sewered and adequate discharge controls are placed on the many industries in the region upstream of the reservoir.

Impact of Seasonal Variability in Water, Plant and Soil Nutrient Dynamics in Agroecosystems

NASA Astrophysics Data System (ADS)

Pelak, N. F., III; Revelli, R.; Porporato, A. M.

2017-12-01

Agroecosystems cover a significant fraction of the Earth's surface, making their water and nutrient cycles a major component of global cycles across spatial and temporal scales. Most agroecosystems experience seasonality via variations in precipitation, temperature, and radiation, in addition to human activities which also occur seasonally, such as fertilization, irrigation, and harvesting. These seasonal drivers interact with the system in complex ways which are often poorly characterized. Crop models, which are widely used for research, decision support, and prediction of crop yields, are among the best tools available to analyze these systems. Though normally constructed as a set of dynamical equations forced by hydroclimatic variability, they are not often analyzed using dynamical systems theory and methods from stochastic ecohydrology. With the goal of developing this viewpoint and thus elucidating the roles of key feedbacks and forcings on system stability and on optimal fertilization and irrigation strategies, we develop a minimal dynamical system which contains the key components of a crop model, coupled to a carbon and nitrogen cycling model, driven by seasonal fluctuations in water and nutrient availability, temperature, and radiation. External drivers include seasonally varying climatic conditions and random rainfall forcing, irrigation and fertilization as well as harvesting. The model is used to analyze the magnitudes and interactions of the effects of seasonality on carbon and nutrient cycles, crop productivity, nutrient export of agroecosystems, and optimal management strategies with reference to productivity, sustainability and profitability. The impact of likely future climate scenarios on these systems is also discussed.

Variation in wood nutrients along a tropical soil fertility gradient.

PubMed

Heineman, Katherine D; Turner, Benjamin L; Dalling, James W

2016-07-01

Wood contains the majority of the nutrients in tropical trees, yet controls over wood nutrient concentrations and their function are poorly understood. We measured wood nutrient concentrations in 106 tree species in 10 forest plots spanning a regional fertility gradient in Panama. For a subset of species, we quantified foliar nutrients and wood density to test whether wood nutrients scale with foliar nutrients at the species level, or wood nutrient storage increases with wood density as predicted by the wood economics spectrum. Wood nutrient concentrations varied enormously among species from fourfold in nitrogen (N) to > 30-fold in calcium (Ca), potassium (K), magnesium (Mg) and phosphorus (P). Community-weighted mean wood nutrient concentrations correlated positively with soil Ca, K, Mg and P concentrations. Wood nutrients scaled positively with leaf nutrients, supporting the hypothesis that nutrient allocation is conserved across plant organs. Wood P was most sensitive to variation in soil nutrient availability, and significant radial declines in wood P indicated that tropical trees retranslocate P as sapwood transitions to heartwood. Wood P decreased with increasing wood density, suggesting that low wood P and dense wood are traits associated with tree species persistence on low fertility soils. Substantial variation among species and communities in wood nutrient concentrations suggests that allocation of nutrients to wood, especially P, influences species distributions and nutrient dynamics in tropical forests. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Spatial dynamics of a nutrient-phytoplankton system with toxic effect on phytoplankton.

PubMed

Chakraborty, Subhendu; Tiwari, P K; Misra, A K; Chattopadhyay, J

2015-06-01

The production of toxins by some species of phytoplankton is known to have several economic, ecological, and human health impacts. However, the role of toxins on the spatial distribution of phytoplankton is not well understood. In the present study, the spatial dynamics of a nutrient-phytoplankton system with toxic effect on phytoplankton is investigated. We analyze the linear stability of the system and obtain the condition for Turing instability. In the presence of toxic effect, we find that the distribution of nutrient and phytoplankton becomes inhomogeneous in space and results in different patterns, like stripes, spots, and the mixture of them depending on the toxicity level. We also observe that the distribution of nutrient and phytoplankton shows spatiotemporal oscillation for certain toxicity level. Copyright © 2015 Elsevier Inc. All rights reserved.

A suite of microplate reader-based colorimetric methods to quantify ammonium, nitrate, orthophosphate and silicate concentrations for aquatic nutrient monitoring.

PubMed

Ringuet, Stephanie; Sassano, Lara; Johnson, Zackary I

2011-02-01

A sensitive, accurate and rapid analysis of major nutrients in aquatic systems is essential for monitoring and maintaining healthy aquatic environments. In particular, monitoring ammonium (NH(4)(+)) concentrations is necessary for maintenance of many fish stocks, while accurate monitoring and regulation of ammonium, orthophosphate (PO(4)(3-)), silicate (Si(OH)(4)) and nitrate (NO(3)(-)) concentrations are required for regulating algae production. Monitoring of wastewater streams is also required for many aquaculture, municipal and industrial wastewater facilities to comply with local, state or federal water quality effluent regulations. Traditional methods for quantifying these nutrient concentrations often require laborious techniques or expensive specialized equipment making these analyses difficult. Here we present four alternative microcolorimetric assays that are based on a standard 96-well microplate format and microplate reader that simplify the quantification of each of these nutrients. Each method uses small sample volumes (200 µL), has a detection limit ≤ 1 µM in freshwater and ≤ 2 µM in saltwater, precision of at least 8% and compares favorably with standard analytical procedures. Routine use of these techniques in the laboratory and at an aquaculture facility to monitor nutrient concentrations associated with microalgae growth demonstrates that they are rapid, accurate and highly reproducible among different users. These techniques offer an alternative to standard nutrient analyses and because they are based on the standard 96-well format, they significantly decrease the cost and time of processing while maintaining high precision and sensitivity.

Quantifying dynamic characteristics of human walking for comprehensive gait cycle.

PubMed

Mummolo, Carlotta; Mangialardi, Luigi; Kim, Joo H

2013-09-01

Normal human walking typically consists of phases during which the body is statically unbalanced while maintaining dynamic stability. Quantifying the dynamic characteristics of human walking can provide better understanding of gait principles. We introduce a novel quantitative index, the dynamic gait measure (DGM), for comprehensive gait cycle. The DGM quantifies the effects of inertia and the static balance instability in terms of zero-moment point and ground projection of center of mass and incorporates the time-varying foot support region (FSR) and the threshold between static and dynamic walking. Also, a framework of determining the DGM from experimental data is introduced, in which the gait cycle segmentation is further refined. A multisegmental foot model is integrated into a biped system to reconstruct the walking motion from experiments, which demonstrates the time-varying FSR for different subphases. The proof-of-concept results of the DGM from a gait experiment are demonstrated. The DGM results are analyzed along with other established features and indices of normal human walking. The DGM provides a measure of static balance instability of biped walking during each (sub)phase as well as the entire gait cycle. The DGM of normal human walking has the potential to provide some scientific insights in understanding biped walking principles, which can also be useful for their engineering and clinical applications.

Quantifying suspended sediment dynamics in mega deltas using remote sensing data: A case study of the Mekong floodplains

NASA Astrophysics Data System (ADS)

Dang, Thanh Duc; Cochrane, Thomas A.; Arias, Mauricio E.

2018-06-01

Temporal and spatial concentrations of suspended sediment in floodplains are difficult to quantify because in situ measurements can be logistically complex, time consuming and costly. In this research, satellite imagery with long temporal and large spatial coverage (Landsat TM/ETM+) was used to complement in situ suspended sediment measurements to reflect sediment dynamics in a large (70,000 km2) floodplain. Instead of using a single spectral band from Landsat, a Principal Component Analysis was applied to obtain uncorrelated reflectance values for five bands of Landsat TM/ETM+. Significant correlations between the scores of the 1st principal component and the values of continuously gauged suspended sediment concentration, shown via high coefficients of determination of sediment rating curves (R2 ranging from 0.66 to 0.92), permit the application of satellite images to quantify spatial and temporal sediment variation in the Mekong floodplains. Estimated suspended sediment maps show that hydraulic regimes at Chaktomuk (Cambodia), where the Mekong, Bassac, and Tonle Sap rivers diverge, determine the amount of seasonal sediment supplies to the Mekong Delta. The development of flood prevention systems to allow for three rice crops a year in the Vietnam Mekong Delta significantly reduces localized flooding, but also prevents sediment (source of nutrients) from entering fields. A direct consequence of this is the need to apply more artificial fertilizers to boost agricultural productivity, which may trigger environmental problems. Overall, remote sensing is shown to be an effective tool to understand temporal and spatial sediment dynamics in large floodplains.

Contribution of seawater recirculation to submarine groundwater discharge and related nutrient fluxes in two tropical bays

NASA Astrophysics Data System (ADS)

Vautier, Camille; Dulaiova, Henrietta

2017-04-01

Hawaiian coastal waters suffer from excess terrestrial nutrient loading, most of which comes from submarine groundwater discharge (SGD). This study quantifies and distinguishes the role of the fresh terrestrial and tidally pumped salt water components of SGD into the nearshore zone of two reefs on the island of Oahu: Maunalua Bay and Kāneohe Bay. The two components of SGD are characterized using isotopic techniques, and the study mainly focuses on the less understood recirculation component. A two-step approach is implemented: first, a conceptual model of groundwater circulation is established; second, nutrient fluxes associated with seawater recirculation are quantified. Groundwater circulation through the beach berm is quantified and characterized using 222Rn and 224Ra activity measurements. Nutrient fluxes are obtained by coupling nutrient concentration measurements and discharge estimates. The isotopic signatures inform us about the influence of the tidal cycle on groundwater circulation. 222Rn, 224Ra, and δ18O isotopes are used to derive apparent ages of the infiltrated seawater and allow us to quantify recirculation rates. The method is also complemented with the use of silicate concentration as tracers of the recirculation process. The trends in apparent ages observed in pore water in Maunalua match previously published conceptual groundwater circulation models and show a sequentially aging pore water circulation loop. However, the ages obtained in Kāneohe suggest a different tidal pumping dynamic that lacks a circulation loop, perhaps resulting from the absence of freshwater discharge. Derived nutrient fluxes show that the autochthonous production of inorganic nitrogen and phosphorus that occurs during seawater recirculation has a significant impact on nutrient cycles in the nearshore areas of the bays. This result suggests that seawater recirculation should be taken into account in biogeochemical studies of coastal areas.

Impacts of Modernizing Urban Stormwater Systems on Nutrient and Carbon Dynamics

NASA Astrophysics Data System (ADS)

Filippelli, G. M.; Jacinthe, P. A.; Druschel, G.

2015-12-01

Over 200 cities throughout the U.S. are undergoing the painful and expensive transition from Combined Sewer Outflows (CSOs) to modern stormwater systems. The infrastructure of CSOs is frequently a century old, with a design adapted to stormwater conditions of smaller, more pervious cities. Normal rainfall events of less 1 cm per hour can now exceed the CSO capacities in many urban sub-watersheds, leading to streamwater conditions that exceed human health standards for pathogens. Although much focus has been placed on the plumbing aspects of urban stormwater modernization, less has been focused on local, and indeed regional, implications of nutrient and carbon dynamic changes. Indianapolis, Indiana, with a metropolitan population of over 1 million, is a case study of CSO modernization. Most CSO systems in the city were built almost 100 years ago, and the city has experienced classic patterns of growth of impervious surface area, population growth, and enhanced use of chemical fertilizers. The result of these changes has been frequent failure of the CSO system, and release of sewage water into suburban and urban streams, rivers and reservoirs. Driven largely by modern environmental regulations, the city is now "footing the bill" for a century of poor planning and growth, with the real costs seen by ratepayers in the form of steeply growing wastewater fees. The mitigation approach to this problem is largely one of subsurface engineering on a mega scale, with less attention (i.e., money) placed on complementary land-use and nutrient management efforts on the surface. Several examples illustrate the relatively straightforward nature of changing plumbing, in contrast to the complex result of these changes on nutrient pathways, and the implications that this has on oxygenation, nutrient cycling, and carbon release/sequestration dynamics in riparian and urban reservoir systems.

Coordinated Approaches to Quantify Long-Term Ecosystem dynamics in Response to Global Change

USDA-ARS?s Scientific Manuscript database

Climate change and its impact on ecosystems are usually assessed at decadal and century time scales. Ecological responses to climate change at those scales are strongly regulated by long-term processes, such as changes in species composition, carbon dynamics in soil and by big trees, and nutrient r...

Nutrient dynamics across a dissolved organic carbon and burn gradient in central Siberia

NASA Astrophysics Data System (ADS)

Rodriguez-Cardona, B.; Coble, A. A.; Prokishkin, A. S.; Kolosov, R.; Spencer, R. G.; Wymore, A.; McDowell, W. H.

2016-12-01

In stream ecosystems, dissolved organic carbon (DOC) and nitrogen (N) processing are tightly linked. In temperate streams, greater DOC concentrations and higher DOC:NO3- ratios promote the greatest nitrate (NO3-) uptake. However, less is known about this relationship in other biomes including the arctic which is undergoing changes due to climate change contributing to thawing of permafrost and alterations in biogeochemical cycles in soils and streams. Headwater streams draining into the N. Tunguska River in the central Siberian plateau are affected by forest fires but little is known about the aquatic biogeochemical implications in both a thawing and burning landscape. There are clear patterns between carbon concentration and fire history where generally DOC concentration in streams decrease after fires and older burn sites have shown greater DOC concentrations and more bioavailable DOC that could promote greater heterotrophic uptake of NO3-. However, the relationship between nutrient dynamics, organic matter composition, and fire history in streams is not very clear. In order to assess the influence of organic matter composition and DOC concentration on nutrient uptake in arctic streams, we conducted a series of short-term nutrient addition experiments following the tracer addition for spiraling curve characterization (TASCC) method, consisting of NO3- and NH4++PO43- additions, across 4 streams that comprise a fire gradient that spans 3- >100 years since the last burn with DOC concentrations ranging between 12-23 mg C/L. We hypothesized that nutrient uptake would be greatest in older burn sites due to greater DOC concentrations and availability. We will specifically examine how nutrient uptake relates to DOC concentration and OM composition (analyzed via FTICR-MS) across the burn gradient. Across the four sites DOC concentration and DOC:NO3- ratios decreased from old burn sites to recently burned sites. Results presented here can elucidate on the potential impacts

Proximate and ultimate controls on carbon and nutrient dynamics of small agricultural catchments

NASA Astrophysics Data System (ADS)

Thomas, Zahra; Abbott, Benjamin W.; Troccaz, Olivier; Baudry, Jacques; Pinay, Gilles

2016-03-01

Direct and indirect effects from human activity have dramatically increased nutrient loading to aquatic inland and estuarine ecosystems. Despite an abundance of studies investigating the impact of agricultural activity on water quality, our understanding of what determines the capacity of a watershed to remove or retain nutrients remains limited. The goal of this study was to identify proximate and ultimate controls on dissolved organic carbon and nutrient dynamics in small agricultural catchments by investigating the relationship between catchment characteristics, stream discharge, and water chemistry. We analyzed a 5-year, high-frequency water chemistry data set from three catchments in western France ranging from 2.3 to 10.8 km2. The relationship between hydrology and solute concentrations differed between the three catchments and was associated with hedgerow density, agricultural activity, and geology. The catchment with thicker soil and higher surface roughness had relatively invariant carbon and nutrient chemistry across hydrologic conditions, indicating high resilience to human disturbance. Conversely, the catchments with smoother, thinner soils responded to both intra- and interannual hydrologic variation with high concentrations of phosphate (PO43-) and ammonium (NH4+) in streams during low flow conditions and strong increases in dissolved organic carbon (DOC), sediment, and particulate organic matter during high flows. Despite contrasting agricultural activity between catchments, the physical context (geology, topography, and land-use configuration) appeared to be the most important determinant of catchment solute dynamics based on principle components analysis. The influence of geology and accompanying topographic and geomorphological factors on water quality was both direct and indirect because the distribution of agricultural activity in these catchments is largely a consequence of the geologic and topographic context. This link between inherent

Biomass and nutrient dynamics associated with slash fires in neotropical dry forests

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kauffman, J.B.; Cummings, D.L.; Sanford, R.L. Jr.

1993-01-01

Unprecedented rates of deforestation and biomass burning in tropical dry forests are dramatically influencing biogeochemical cycles, resulting in resource depletion, declines in biodiversity, and atmospheric pollution. We quantified the effects of deforestation and varying levels of slash-fire severity on nutrient losses and redistribution in a second-growth tropical dry forest ([open quotes]Caatinga[close quotes]) near Serra Talhada, Pernambuco, Brazil. Total aboveground biomass prior to burning was [approx]74 Mg/ha. Nitrogen and phosphorus concentrations were highest in litter, leaves attached to slash, and fine wood debris (

Coordinated approaches to quantify long-term ecosystem dynamics in response to global change

Treesearch

Yiqi Luo; Jerry Melillo; Shuli Niu; Claus Beier; James S. Clark; Aime E.T. Classen; Eric Dividson; Jeffrey S. Dukes; R. Dave Evans; Christopher B. Field; Claudia I. Czimczik; Michael Keller; Bruce A. Kimball; Lara M. Kueppers; Richard J. Norby; Shannon L. Pelini; Elise Pendall; Edward Rastetter; Johan Six; Melinda Smith; Mark G. Tjoelker; Margaret S. Torn

2011-01-01

Many serious ecosystem consequences of climate change will take decades or even centuries to emerge. Long-term ecological responses to global change are strongly regulated by slow processes, such as changes in species composition, carbon dynamics in soil and by long-lived plants, and accumulation of nutrient capitals. Understanding and predicting these processes...

The Nutrient Density of Snacks: A Comparison of Nutrient Profiles of Popular Snack Foods Using the Nutrient-Rich Foods Index.

PubMed

Hess, Julie; Rao, Goutham; Slavin, Joanne

2017-01-01

Background: Although Americans receive almost a quarter of their daily energy from snacks, snacking remains a poorly defined and understood eating occasion. However, there is little dietary guidance about choosing snacks. Families, clinicians, and researchers need a comprehensive approach to assessing their nutritional value. Objective: To quantify and compare the nutrient density of commonly consumed snacks by their overall nutrient profiles using the Nutrient-Rich Foods (NRF) Index 10.3. Methods: NRF Index scores were calculated for the top 3 selling products (based on 2014 market research data) in different snack categories. These NRF scores were averaged to provide an overall nutrient-density score for each category. Results: Based on NRF scores, yogurt (55.3), milk (52.5), and fruit (30.1) emerged as the most nutrient-dense snacks. Ice cream (-4.4), pies and cakes (-11.1), and carbonated soft drinks (-17.2) emerged as the most nutrient-poor snacks. Conclusions: The NRF Index is a useful tool for assessing the overall nutritional value of snacks based on nutrients to limit and nutrients to encourage.

Early-stage changes in natural (13)C and (15)N abundance and nutrient dynamics during different litter decomposition.

PubMed

Gautam, Mukesh Kumar; Lee, Kwang-Sik; Song, Byeong-Yeol; Lee, Dongho; Bong, Yeon-Sik

2016-05-01

Decomposition, nutrient, and isotopic (δ(13)C and δ(15)N) dynamics during 1 year were studied for leaf and twig litters of Pinus densiflora, Castanea crenata, Erigeron annuus, and Miscanthus sinensis growing on a highly weathered soil with constrained nutrient supply using litterbags in a cool temperate region of South Korea. Decay constant (k/year) ranged from 0.58 to 1.29/year, and mass loss ranged from 22.36 to 58.43 % among litter types. The results demonstrate that mass loss and nutrient dynamics of decomposing litter were influenced by the seasonality of mineralization and immobilization processes. In general, most nutrients exhibited alternate phases of rapid mineralization followed by gradual immobilization, except K, which was released throughout the field incubation. At the end of study, among all the nutrients only N and P showed net immobilization. Mobility of different nutrients from decomposing litter as the percentage of initial litter nutrient concentration was in the order of K > Mg > Ca > N ≈ P. The δ(13)C (0.32-6.70 ‰) and δ(15)N (0.74-3.90 ‰) values of residual litters showed nonlinear increase and decrease, respectively compared to initial isotopic values during decomposition. Litter of different functional types and chemical quality converged toward a conservative nutrient use strategy through mechanisms of slow decomposition and slow nutrient mobilization. Our results indicate that litter quality and season, are the most important regulators of litter decomposition in these forests. The results revealed significant relationships between litter decomposition rates and N, C:N ratio and P, and seasonality (temperature). These results and the convergence of different litters towards conservative nutrient use in these nutrient constrained ecosystems imply optimization of litter management because litter removal can have cascading effects on litter decomposition and nutrient availability in these systems.

Calculating radiation exposures during use of (14)C-labeled nutrients, food components, and biopharmaceuticals to quantify metabolic behavior in humans.

PubMed

Kim, Seung-Hyun; Kelly, Peter B; Clifford, Andrew J

2010-04-28

(14)C has long been used as a tracer for quantifying the in vivo human metabolism of food components, biopharmaceuticals, and nutrients. Minute amounts (< or =1 x 10 (-18) mol) of (14)C can be measured with high-throughput (14)C-accelerator mass spectrometry (HT (14)C-AMS) in isolated chemical extracts of biological, biomedical, and environmental samples. Availability of in vivo human data sets using a (14)C tracer would enable current concepts of the metabolic behavior of food components, biopharmaceuticals, or nutrients to be organized into models suitable for quantitative hypothesis testing and determination of metabolic parameters. In vivo models are important for specification of intake levels for food components, biopharmaceuticals, and nutrients. Accurate estimation of the radiation exposure from ingested (14)C is an essential component of the experimental design. Therefore, this paper illustrates the calculation involved in determining the radiation exposure from a minute dose of orally administered (14)C-beta-carotene, (14)C-alpha-tocopherol, (14)C-lutein, and (14)C-folic acid from four prior experiments. The administered doses ranged from 36 to 100 nCi, and radiation exposure ranged from 0.12 to 5.2 microSv to whole body and from 0.2 to 3.4 microSv to liver with consideration of tissue weighting factor and fractional nutrient. In comparison, radiation exposure experienced during a 4 h airline flight across the United States at 37000 ft was 20 microSv.

Linking runoff and erosion dynamics to nutrient fluxes in a degrading dryland landscape

NASA Astrophysics Data System (ADS)

Michaelides, Katerina; Lister, Debbie; Wainwright, John; Parsons, Anthony J.

2012-12-01

Current theories of land degradation assume that shifts in vegetation communities result in changes to the rates and patterns of water and sediment movement, which are vectors of nutrient redistribution. This nutrient redistribution is hypothesized to reinforce, through positive feedbacks, progressive vegetation changes toward a more degraded ecosystem. A key component of this theory, which is currently poorly resolved, is the relative role of runoff and erosion in driving nutrient fluxes from different vegetation types. We address this gap through a series of field-based, rainfall-simulation experiments designed to explore plant-level dynamics of runoff- and erosion-driven nutrient fluxes of N, P and K species. Our results highlight important linkages between physical and biogeochemical processes that are controlled by plant structure. We found that: 1) the magnitude of sediment-bound nutrient export is determined by the grain-size distribution of the eroded sediment and the total sediment yield; 2) the partitioning of nutrients in dissolved and sediment-bound form is determined by the availability and concentration of different nutrient species in the soil or rainfall; 3) these processes varied according to vegetation type and resulted in stark differences between degrading and invading plant communities. Specifically, we observed that grassland areas consistently exported the highest yields of sediment-bound N, P and K despite producing similar erosion rates to shrub and intershrub areas. Our results have implications for better understanding how grassland areas are being replaced by shrubs and provide insights into the mechanisms of continuing land degradation in drylands.

Nutrient dynamics and decomposition of riparian Arundinaria gigantea (Walt.)Muhl. leaves in southern Illinois

USDA-ARS?s Scientific Manuscript database

Leaf litter quality and quantity can influence soil nutrient dynamics and stream productivity through decomposition and serving as allochthonous stream inputs. Leaf deposition, nitrogen (N)-resorption efficiency and proficiency, and decomposition rates were analyzed in riparian stands of Arundinaria...

Dynamics of Inorganic Nutrients in Intertidal Sediments: Porewater, Exchangeable, and Intracellular Pools

PubMed Central

Garcia-Robledo, Emilio; Bohorquez, Julio; Corzo, Alfonso; Jimenez-Arias, Juan L.; Papaspyrou, Sokratis

2016-01-01

The study of inorganic nutrients dynamics in shallow sediments usually focuses on two main pools: porewater (PW) nutrients and exchangeable (EX) ammonium and phosphate. Recently, it has been found that microphytobenthos (MPB) and other microorganisms can accumulate large amounts of nutrients intracellularly (IC), highlighting the biogeochemical importance of this nutrient pool. Storing nutrients could support the growth of autotrophs when nutrients are not available, and could also provide alternative electron acceptors for dissimilatory processes such as nitrate reduction. Here, we studied the magnitude and relative importance of these three nutrient pools (PW, IC, and EX) and their relation to chlorophylls (used as a proxy for MPB abundance) and organic matter (OM) contents in an intertidal mudflat of Cadiz Bay (Spain). MPB was localized in the first 4 mm of the sediment and showed a clear seasonal pattern; highest chlorophylls content was found during autumn and lowest during spring-summer. The temporal and spatial distribution of nutrients pools and MPB were largely correlated. Ammonium was higher in the IC and EX fractions, representing on average 59 and 37% of the total ammonium pool, respectively. Similarly, phosphate in the IC and EX fractions accounted on average for 40 and 31% of the total phosphate pool, respectively. Nitrate in the PW was low, suggesting low nitrification activity and rapid consumption. Nitrate accumulated in the IC pool during periods of moderate MPB abundance, being up to 66% of the total nitrate pool, whereas it decreased when chlorophyll concentration peaked likely due to a high nitrogen demand. EX-Nitrate accounted for the largest fraction of total sediment nitrate, 66% on average. The distribution of EX-Nitrate was significantly correlated with chlorophyll and OM, which probably indicates a relation of this pool to an increased availability of sites for ionic adsorption. This EX-Nitrate pool could represent an alternative nitrate

Dynamics of Inorganic Nutrients in Intertidal Sediments: Porewater, Exchangeable, and Intracellular Pools.

PubMed

Garcia-Robledo, Emilio; Bohorquez, Julio; Corzo, Alfonso; Jimenez-Arias, Juan L; Papaspyrou, Sokratis

2016-01-01

The study of inorganic nutrients dynamics in shallow sediments usually focuses on two main pools: porewater (PW) nutrients and exchangeable (EX) ammonium and phosphate. Recently, it has been found that microphytobenthos (MPB) and other microorganisms can accumulate large amounts of nutrients intracellularly (IC), highlighting the biogeochemical importance of this nutrient pool. Storing nutrients could support the growth of autotrophs when nutrients are not available, and could also provide alternative electron acceptors for dissimilatory processes such as nitrate reduction. Here, we studied the magnitude and relative importance of these three nutrient pools (PW, IC, and EX) and their relation to chlorophylls (used as a proxy for MPB abundance) and organic matter (OM) contents in an intertidal mudflat of Cadiz Bay (Spain). MPB was localized in the first 4 mm of the sediment and showed a clear seasonal pattern; highest chlorophylls content was found during autumn and lowest during spring-summer. The temporal and spatial distribution of nutrients pools and MPB were largely correlated. Ammonium was higher in the IC and EX fractions, representing on average 59 and 37% of the total ammonium pool, respectively. Similarly, phosphate in the IC and EX fractions accounted on average for 40 and 31% of the total phosphate pool, respectively. Nitrate in the PW was low, suggesting low nitrification activity and rapid consumption. Nitrate accumulated in the IC pool during periods of moderate MPB abundance, being up to 66% of the total nitrate pool, whereas it decreased when chlorophyll concentration peaked likely due to a high nitrogen demand. EX-Nitrate accounted for the largest fraction of total sediment nitrate, 66% on average. The distribution of EX-Nitrate was significantly correlated with chlorophyll and OM, which probably indicates a relation of this pool to an increased availability of sites for ionic adsorption. This EX-Nitrate pool could represent an alternative nitrate

Effects of changes in nutrient loading and composition on hypoxia dynamics and internal nutrient cycling of a stratified coastal lagoon

NASA Astrophysics Data System (ADS)

Zhu, Yafei; McCowan, Andrew; Cook, Perran L. M.

2017-10-01

The effects of changes in catchment nutrient loading and composition on the phytoplankton dynamics, development of hypoxia and internal nutrient dynamics in a stratified coastal lagoon system (the Gippsland Lakes) were investigated using a 3-D coupled hydrodynamic biogeochemical water quality model. The study showed that primary production was equally sensitive to changed dissolved inorganic and particulate organic nitrogen loads, highlighting the need for a better understanding of particulate organic matter bioavailability. Stratification and sediment carbon enrichment were the main drivers for the hypoxia and subsequent sediment phosphorus release in Lake King. High primary production stimulated by large nitrogen loading brought on by a winter flood contributed almost all the sediment carbon deposition (as opposed to catchment loads), which was ultimately responsible for summer bottom-water hypoxia. Interestingly, internal recycling of phosphorus was more sensitive to changed nitrogen loads than total phosphorus loads, highlighting the potential importance of nitrogen loads exerting a control over systems that become phosphorus limited (such as during summer nitrogen-fixing blooms of cyanobacteria). Therefore, the current study highlighted the need to reduce both total nitrogen and total phosphorus for water quality improvement in estuarine systems.

Modeling brine and nutrient dynamics in Antarctic sea ice: the case of dissolved silica

NASA Astrophysics Data System (ADS)

Vancoppenolle, M.; Goosse, H.; de Montety, A.; Fichefet, T.; Tremblay, B.; Tison, J.

2009-12-01

Sea ice ecosystems are characterized by micro-algae living in brine inclusions. The growth rate of ice algae depends on light and nutrient supply. Here, the interactions between nutrients and brine dynamics under the influence of algae are investigated using a one-dimensional model. The model includes snow and ice thermodynamics with brine physics and an idealized sea ice biological component, characterized by one nutrient, namely dissolved silica (DSi). In the model, DSi follows brine motion and is consumed by ice algae. Depending on physical ice characteristics, the brine flow is either advective, diffusive or turbulent. The vertical profiles of ice salinity and DSi concentration are solutions of advection-diffusion equations. The model is configured to simulate the typical thermodynamic regimes of first-year Antarctic pack ice. The simulated vertical profiles of salinity and DSi qualitatively reproduce observations. Analysis of results highlights the role of convection in the lowermost 5-10 cm of ice. Convection mixes saline, nutrient-poor brine with comparatively fresh, nutrient-rich seawater. This implies a rejection of salt to the ocean and a flux of DSi to the ice. In presence of growing algae, the simulated ocean-to-ice DSi flux increases by 0-115% compared to an abiotic situation. In turn, primary production and brine convection act in synergy to form a nutrient pump. The other important processes are the flooding of the surface by seawater and the percolation of meltwater. The former refills nutrients near the ice surface in spring. The latter, if present, tends to expell nutrients from the ice in summer. Sketch of salt (left) and nutrient (right) exchanges at the ice-ocean interface proposed in this paper.

Dynamics of nutrient cycling and related benthic nutrient and oxygen fluxes during a spring phytoplankton bloom in South San Francisco Bay (USA)

USGS Publications Warehouse

Grenz, C.; Cloern, J.E.; Hager, S.W.; Cole, B.E.

2000-01-01

Benthic oxygen uptake and nutrient releases of N, P and Si were measured weekly at 2 sites in South San Francisco Bay around the 1996 spring bloom. Exchanges across the sediment-water interface were estimated from whole core incubations performed in the laboratory at in situ temperature and in dark. Fluxes changed significantly on a weekly time scale. Over a period of 15 wk the fluxes of dissolved inorganic N, P and Si ranged from -40 to +200, 0 to 13 and from 30 to 400 ??mol m-2 h-1 respectively. Sediment oxygen demand increased from 10 before to 64 mg O2 m-2 h-1 just after the bloom period. During the bloom, nutrient fluxes represented about 20, 16 and 9% of the Si, P and N requirements for primary production. Before and after the bloom period, Si fluxes contributed up to 30 and > 100% of this requirement and P and N fluxes up to 15 and 50% respectively. Simple empirical models explain most of the spatial-temporal variability of benthic fluxes of Si, P and NH4 (but not NO3) from 3 predictor variables: sediment porosity, nutrient concentration in bottom waters and chlorophyll content of surficial sediments. These models show that algal blooms influence benthic-pelagic nutrient exchange through 2 processes: (1) depletion of nutrients from the water column (which enhances gradient-driven transports across the sediment-water interface) and (2) sedimentation of labile phytodetritus (which promotes remineralization in or on the surficial sediments). Rates and patterns of nutrient cycling were very different at the shallow and deep study sites, illustrating the challenge of extrapolating measurements of coupled algae-nutrient dynamics to whole ecosystems.

Modeling brine and nutrient dynamics in Antarctic sea ice: The case of dissolved silica

NASA Astrophysics Data System (ADS)

Vancoppenolle, Martin; Goosse, Hugues; de Montety, Anne; Fichefet, Thierry; Tremblay, Bruno; Tison, Jean-Louis

2010-02-01

Sea ice ecosystems are characterized by microalgae living in brine inclusions. The growth rate of ice algae depends on light and nutrient supply. Here, the interactions between nutrients and brine dynamics under the influence of algae are investigated using a one-dimensional model. The model includes snow and ice thermodynamics with brine physics and an idealized sea ice biological component, characterized by one nutrient, namely, dissolved silica (DSi). In the model, DSi follows brine motion and is consumed by ice algae. Depending on physical ice characteristics, the brine flow is either advective, diffusive, or turbulent. The vertical profiles of ice salinity and DSi concentration are solutions of advection-diffusion equations. The model is configured to simulate the typical thermodynamic regimes of first-year Antarctic pack ice. The simulated vertical profiles of salinity and DSi qualitatively reproduce observations. Analysis of results highlights the role of convection in the lowermost 5-10 cm of ice. Convection mixes saline, nutrient-poor brine with comparatively fresh, nutrient-rich seawater. This implies a rejection of salt to the ocean and a flux of DSi to the ice. In the presence of growing algae, the simulated ocean-to-ice DSi flux increases by 0-115% compared to an abiotic situation. In turn, primary production and brine convection act in synergy to form a nutrient pump. The other important processes are the flooding of the surface by seawater and the percolation of meltwater. The former refills nutrients near the ice surface in spring. The latter, if present, tends to expell nutrients from the ice in summer.

Annual litterfall dynamics and nutrient deposition depending on elevation and land use at Mt. Kilimanjaro

NASA Astrophysics Data System (ADS)

Becker, J.; Pabst, H.; Mnyonga, J.; Kuzyakov, Y.

2015-10-01

Litterfall is one of the major pathways connecting above- and below-ground processes. The effects of climate and land-use change on carbon (C) and nutrient inputs by litterfall are poorly known. We quantified and analyzed annual patterns of C and nutrient deposition via litterfall in natural forests and agroforestry systems along the unique elevation gradient of Mt. Kilimanjaro. Tree litter in three natural (lower montane, Ocotea and Podocarpus forests), two sustainably used (homegardens) and one intensively managed (shaded coffee plantation) ecosystems was collected on a biweekly basis from May 2012 to July 2013. Leaves, branches and remaining residues were separated and analyzed for C and nutrient contents. The annual pattern of litterfall was closely related to rainfall seasonality, exhibiting a large peak towards the end of the dry season (August-October). This peak decreased at higher elevations with decreasing rainfall seasonality. Macronutrients (N, P, K) in leaf litter increased at mid elevation (2100 m a.s.l.) and with land-use intensity. Carbon content and micronutrients (Al, Fe, Mn, Na) however, were unaffected or decreased with land-use intensity. While leaf litterfall decreased with elevation, total annual input was independent of climate. Compared to natural forests, the nutrient cycles in agroforestry ecosystems were accelerated by fertilization and the associated changes in dominant tree species.

Tidal Pumping-Induced Nutrients Dynamics and Biogeochemical Implications in an Intertidal Aquifer

NASA Astrophysics Data System (ADS)

Liu, Yi; Jiao, Jiu Jimmy; Liang, Wenzhao; Luo, Xin

2017-12-01

Tidal pumping is a major driving force affecting water exchange between land and sea, biogeochemical reactions in the intertidal aquifer, and nutrient loading to the sea. At a sandy beach of Tolo Harbour, Hong Kong, the nutrient (NH4+, NO2-, NO3-, and PO43-) dynamic in coastal groundwater mixing zone (CGMZ) is found to be fluctuated with tidal oscillation. Nutrient dynamic is mainly controlled by tidal pumping-induced organic matter that serves as a reagent of remineralization in the aquifer. NH4+, NO2-, and PO43- are positively correlated with salinity. Both NH4+ and PO43- have negative correlations with oxidation/reduction potential. NH4+ is the major dissolved inorganic nitrogen species in CGMZ. The adsorption of PO43- onto iron oxides occurs at the deep transition zone with a salinity of 5-10 practical salinity unit (psu), and intensive N-loss occurs in near-surface area with a salinity of 10-25 psu. The biogeochemical reactions, producing PO43- and consuming NH4+, are synergistic effect of remineralization-nitrification-denitrification. In CGMZ, the annual NH4+ loss is estimated to be 4.32 × 105 mol, while the minimum annual PO43- production is estimated to be 2.55 × 104 mol. Applying these rates to the entire Tolo Harbour, the annual NH4+ input to the harbor through the remineralization of organic matters is estimated to be 1.02 × 107 mol. The annual NH4+ loss via nitrification is 1.32 × 107 mol, and the annual PO43- production is 7.76 × 105 mol.

Use of a multi-isotope and multi-tracer approach including organic matter isotopes for quantifying nutrient contributions from agricultural vs wastewater sources

NASA Astrophysics Data System (ADS)

Kendall, C.; Silva, S. R.; Young, M. B.

2013-12-01

While nutrient isotopes are a well-established tool for quantifying nutrients inputs from agricultural vs wastewater treatment plant (WWTP) sources, we have found that combining nutrient isotopes with the C, N, and S isotopic compositions of dissolved and particulate organic matter, as part of a comprehensive multi-isotope and multi-tracer approach, is a much more diagnostic approach. The main reasons why organic matter C-N-S isotopes are a useful adjunct to studies of nutrient sources and biogeochemical processes are that the dissolved and particulate organic matter associated with (1) different kinds of animals (e.g., humans vs cows) often have distinctive isotopic compositions reflecting the different diets of the animals, and (2) the different processes associated with the different land uses (e.g., in the WWTP or associated with different crop types) often result in significant differences in the isotopic compositions of the organics. The analysis of the δ34S of particulate organic matter (POM) and dissolved organic matter (DOM) has been found to be especially useful for distinguishing and quantifying water, nutrient, and organic contributions from different land uses in aquatic systems where much of the organic matter is aquatic in origin. In such environments, the bacteria and algae incorporate S from sulfate and sulfide that is isotopically labeled by the different processes associated with different land uses. We have found that there is ~35 permil range in δ34S of POM along the river-estuary continuum in the San Joaquin/Sacramento River basin, with low values associated with sulfate reduction in the upstream wetlands and high values associated with tidal inputs of marine water into the estuary. Furthermore, rice agriculture results in relatively low δ34S values whereas WWTP effluent in the Sacramento River produces distinctly higher values than upstream of the WWTP, presumably because SO2 is used to treat chlorinated effluent. The fish living

Flamingos and drought as drivers of nutrients and microbial dynamics in a saline lake.

PubMed

Batanero, Gema L; León-Palmero, Elizabeth; Li, Linlin; Green, Andy J; Rendón-Martos, Manuel; Suttle, Curtis A; Reche, Isabel

2017-09-22

Waterbird aggregations and droughts affect nutrient and microbial dynamics in wetlands. We analysed the effects of high densities of flamingos on nutrients and microbial dynamics in a saline lake during a wet and a dry hydrological year, and explored the effects of guano on prokaryotic growth. Concentrations of dissolved organic carbon, total phosphorus and total nitrogen in the surface waters were 2-3 fold higher during the drought and were correlated with salinity. Flamingos stimulated prokaryotic heterotrophic production and triggered cascading effects on prokaryotic abundance, viruses and dissolved nitrogen. This stimulus of heterotrophic prokaryotes was associated with soluble phosphorus inputs from guano, and also from sediments. In the experiments, the specific growth rate and the carrying capacity were almost twice as high after guano addition than in the control treatments, and were coupled with soluble phosphorus assimilation. Flamingo guano was also rich in nitrogen. Dissolved N in lake water lagged behind the abundance of flamingos, but the causes of this lag are unclear. This study demonstrates that intense droughts could lead to increases in total nutrients in wetlands; however, microbial activity is likely constrained by the availability of soluble phosphorus, which appears to be more dependent on the abundance of waterbirds.

Differential effects of canopy trimming and litter deposition on litterfall and nutrient dynamics in a wet subtropical forest

Treesearch

W.L. Silver; S.J. Hall; Grizelle Gonzalez

2014-01-01

Humid tropical forests have the highest rates of litterfall production globally, which fuels rapid nutrient recycling and high net ecosystem production. Severe storm events significantly alter patterns in litterfall mass and nutrient dynamics through a combination of canopy disturbance and litter deposition. In this study, we used a large-scale long-term manipulation...

Imaging Nutrient Distribution in the Rhizosphere Using FTIR Imaging

DOE PAGES

Victor, Tiffany; Delpratt, Natalie; Cseke, Sarah Beth; ...

2017-03-06

Symbiotic associations in the rhizosphere between plants and microorganisms lead to efficient changes in the distribution of nutrients that promote growth and development for each organism involved. Understanding these nutrient fluxes provides insight into the molecular dynamics involved in nutrient transport from one organism to the other. Here, to study such a nutrient flow, a new application of Fourier transform infrared imaging (FTIRI) was developed that entailed growing Populus tremulodes seedlings on a thin, nutrient-enriched Phytagel matrix that allows pixel to pixel measurement of the distribution of nutrients, in particular, nitrate, in the rhizosphere. The FTIR spectra collected from ammoniummore » nitrate in the matrix indicated the greatest changes in the spectra at 1340 cm -1 due to the asymmetric stretching vibrations of nitrate. For quantification of the nitrate concentration in the rhizosphere of experimental plants, a calibration curve was generated that gave the nitrate concentration at each pixel in the chemical image. These images of the poplar rhizosphere showed evidence for symbiotic sharing of nutrients between the plant and the fungi, Laccaria bicolor, where the nitrate concentration was five times higher near mycorrhizal roots than further out into the rhizosphere. This suggested that nitrates are acquired and transported from the media toward the plant root by the fungi. Similarly, the sucrose used in the growth media as a carbon source was depleted around the fungi, suggesting its uptake and consumption by the system. In conclusion, this study is the first of its kind to visualize and quantify the nutrient availability associated with mycorrhizal interactions, indicating that FTIRI has the ability to monitor nutrient changes with other microorganisms in the rhizosphere as a key step for understanding nutrient flow processes in more diverse biological systems.« less

Imaging Nutrient Distribution in the Rhizosphere Using FTIR Imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Victor, Tiffany; Delpratt, Natalie; Cseke, Sarah Beth

Symbiotic associations in the rhizosphere between plants and microorganisms lead to efficient changes in the distribution of nutrients that promote growth and development for each organism involved. Understanding these nutrient fluxes provides insight into the molecular dynamics involved in nutrient transport from one organism to the other. Here, to study such a nutrient flow, a new application of Fourier transform infrared imaging (FTIRI) was developed that entailed growing Populus tremulodes seedlings on a thin, nutrient-enriched Phytagel matrix that allows pixel to pixel measurement of the distribution of nutrients, in particular, nitrate, in the rhizosphere. The FTIR spectra collected from ammoniummore » nitrate in the matrix indicated the greatest changes in the spectra at 1340 cm -1 due to the asymmetric stretching vibrations of nitrate. For quantification of the nitrate concentration in the rhizosphere of experimental plants, a calibration curve was generated that gave the nitrate concentration at each pixel in the chemical image. These images of the poplar rhizosphere showed evidence for symbiotic sharing of nutrients between the plant and the fungi, Laccaria bicolor, where the nitrate concentration was five times higher near mycorrhizal roots than further out into the rhizosphere. This suggested that nitrates are acquired and transported from the media toward the plant root by the fungi. Similarly, the sucrose used in the growth media as a carbon source was depleted around the fungi, suggesting its uptake and consumption by the system. In conclusion, this study is the first of its kind to visualize and quantify the nutrient availability associated with mycorrhizal interactions, indicating that FTIRI has the ability to monitor nutrient changes with other microorganisms in the rhizosphere as a key step for understanding nutrient flow processes in more diverse biological systems.« less

Influence of Organic Amendment and Compaction on Nutrient Dynamics in a Saturated Saline-Sodic Soil from the Riparian Zone.

PubMed

Miller, J J; Bremer, E; Curtis, T

2016-07-01

Cattle grazing in wet riparian pastures may influence nutrient dynamics due to nutrient deposition in feces and urine, soil compaction, and vegetation loss. We conducted a lab incubation study with a saline-sodic riparian soil to study nutrient (N, P, S, Fe, Mn, Cu, and Zn) dynamics in soil pore water using Plant Root Simulator (PRS) probes and release of nutrients into the overlying ponded water during flooding. The treatment factors were organic amendment (manure, roots, and unamended control), compaction (compacted, uncompacted), and burial time (3, 7, and 14 d). Amendment treatment had the greatest impact on nutrient dynamics, followed by burial time, whereas compaction had little impact. The findings generally supported our hypothesis that organic amendments should first increase nitrate loss, then increase Mn mobility, then Fe mobility and associated release of P, and finally increase sulfate loss. Declines in nitrate due to amendment addition were small because nitrate was at low levels in all treatments due to high denitrification potential instead of being released to soil pore water or overlying water. Addition of organic amendment strongly increased Mn and Fe concentrations in overlying water and of adsorbed Fe on PRS probes but only increased Mn on PRS probes on Day 3 due to subsequent displacement from ion exchange membranes. Transport of P to overlying water was increased by organic amendment addition but less so for manure than roots despite higher P on PRS probes. The findings showed that saline-sodic soils in riparian zones are generally a nutrient source for P and are a nutrient sink for N as measured using PRS probes after 3 to 7 d of flooding. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Impacts of Cover Crops on Water and Nutrient Dynamics in Agroecosystems

NASA Astrophysics Data System (ADS)

Williard, K.; Swanberg, S.; Schoonover, J.

2013-05-01

Intensive cropping systems of corn (Zea Mays L.) and soybeans (Glycine max) are commonly leaky systems with respect to nitrogen (N). Reactive N outputs from agroecosystems can contribute to eutrophication and hypoxic zones in downstream water bodies and greenhouse gas (N2O) emissions. Incorporating cover crops into temperate agroecosystem rotations has been promoted as a tool to increase nitrogen use efficiency and thus limit reactive N outputs to the environment. Our objective was determine how cereal rye (Secale cereal L.) and annual ryegrass (Lolium multiflorum) cover crops impact nutrient and soil water dynamics in an intensive corn and soybean cropping rotation in central Illinois. Cover crops were planted in mid to late October and terminated in early April prior to corn or soybean planting. In the spring just prior to cover crop termination, soil moisture levels were lower in the cover crop plots compared to no cover plots. This can be a concern for the subsequent crop in relatively dry years, which the Midwestern United States experienced in 2012. No cover plots had greater nutrient leaching below the rooting zone compared to cover crop areas, as expected. The cover crops were likely scavenging nutrients during the fall and early spring and should provide nutrients to the subsequent crop via decomposition and mineralization of the cover crop residue. Over the long term, cover crop systems should produce greater inputs and cycling of carbon and N, increasing the productivity of crops due to the long-term accumulation of soil organic matter. This study demonstrates that there may be short term trade-offs in reduced soil moisture levels that should be considered alongside the long term nutrient scavenging and recycling benefits of cover crops.

STABLE ISOTOPES AS INDICATORS OF SOIL WATER DYNAMICS IN WATERSHEDS

EPA Science Inventory

Stream water quality and quantity depend on discharge rates of water and nutrients from soils. However, soil-water storage is very dynamic and strongly influenced by plants. We analyzed stable isotopes of oxygen and hydrogen to quantify spatial and temporal changes in evaporati...

Internal cycling, not external loading, decides the nutrient limitation in eutrophic lake: A dynamic model with temporal Bayesian hierarchical inference.

PubMed

Wu, Zhen; Liu, Yong; Liang, Zhongyao; Wu, Sifeng; Guo, Huaicheng

2017-06-01

Lake eutrophication is associated with excessive anthropogenic nutrients (mainly nitrogen (N) and phosphorus (P)) and unobserved internal nutrient cycling. Despite the advances in understanding the role of external loadings, the contribution of internal nutrient cycling is still an open question. A dynamic mass-balance model was developed to simulate and measure the contributions of internal cycling and external loading. It was based on the temporal Bayesian Hierarchical Framework (BHM), where we explored the seasonal patterns in the dynamics of nutrient cycling processes and the limitation of N and P on phytoplankton growth in hyper-eutrophic Lake Dianchi, China. The dynamic patterns of the five state variables (Chla, TP, ammonia, nitrate and organic N) were simulated based on the model. Five parameters (algae growth rate, sediment exchange rate of N and P, nitrification rate and denitrification rate) were estimated based on BHM. The model provided a good fit to observations. Our model results highlighted the role of internal cycling of N and P in Lake Dianchi. The internal cycling processes contributed more than external loading to the N and P changes in the water column. Further insights into the nutrient limitation analysis indicated that the sediment exchange of P determined the P limitation. Allowing for the contribution of denitrification to N removal, N was the more limiting nutrient in most of the time, however, P was the more important nutrient for eutrophication management. For Lake Dianchi, it would not be possible to recover solely by reducing the external watershed nutrient load; the mechanisms of internal cycling should also be considered as an approach to inhibit the release of sediments and to enhance denitrification. Copyright © 2017 Elsevier Ltd. All rights reserved.

Changes in nutrient dynamics of midcontinent greater white-fronted geese during spring migration

USGS Publications Warehouse

Pearse, Aaron T.; Alisauskas, Ray T.; Krapu, Gary L.; Cox, Robert R.

2011-01-01

Waterfowl and other migratory birds commonly store nutrients at traditional staging areas during spring for later use during migration and reproduction. We investigated nutrient-storage dynamics in the midcontinent population of greater white-fronted geese (Anser albifrons; hereafter white-fronted geese) at spring staging sites in the Rainwater Basin of Nebraska during February-April and in southern Saskatchewan during April-May, 1998 and 1999. In Nebraska, lipid content of white-fronted geese did not increase, and protein content changed little over time for most age and sex categories. In Saskatchewan, lipids increased 11.4 g/day (SE = 1.7) and protein content increased 1.6 g/day (SE = 0.6) in the sample of adult geese collected over a 3-week period. A study conducted during 1979-1980 in the Rainwater Basin reported that white-fronted geese gained 8.8-17.7 g of lipids per day during spring, differing greatly from our results 2 decades later. In addition, lipid levels were less in the 1990s compared to spring 1980 for adult geese nearing departure from staging sites in Saskatchewan. This shift in where geese acquired nutrient stores from Nebraska to more northern staging sites coincided with a decrease in availability of waste corn in Nebraska, their primary food source while staging at that stopover site, and an increase in cultivation of high-energy pulse crops in Saskatchewan. White-fronted geese exhibited flexibility in nutrient dynamics during spring migration, likely in response to landscape-level variation in food availability caused by changes in agricultural trends and practices. Maintaining a wide distribution of wetlands in the Great Plains may allow springstaging waterfowl to disperse across the region and facilitate access to high-energy foods over a larger cropland base.

Urbanization effects on leaf litter decomposition, foliar nutrient dynamics and aboveground net primary productivity in the subtropics

Treesearch

Heather A. Enloe; B. Graeme Lockaby; Wayne C. Zipperer; Greg L. Somers

2015-01-01

Urbanization can alter nutrient cycling. This research evaluated how urbanization affected nutrient dynamics in the subtropics. We established 17–0.04 ha plots in five different land cover types—slash pine (Pinus elliottii) plantations (n=3), rural natural pine forests (n= 3), rural natural oak forests (n=4), urban pine forests (n=3) and urban oak forests (n=4) in the...

Introducing Co-Activation Pattern Metrics to Quantify Spontaneous Brain Network Dynamics

PubMed Central

Chen, Jingyuan E.; Chang, Catie; Greicius, Michael D.; Glover, Gary H.

2015-01-01

Recently, fMRI researchers have begun to realize that the brain's intrinsic network patterns may undergo substantial changes during a single resting state (RS) scan. However, despite the growing interest in brain dynamics, metrics that can quantify the variability of network patterns are still quite limited. Here, we first introduce various quantification metrics based on the extension of co-activation pattern (CAP) analysis, a recently proposed point-process analysis that tracks state alternations at each individual time frame and relies on very few assumptions; then apply these proposed metrics to quantify changes of brain dynamics during a sustained 2-back working memory (WM) task compared to rest. We focus on the functional connectivity of two prominent RS networks, the default-mode network (DMN) and executive control network (ECN). We first demonstrate less variability of global Pearson correlations with respect to the two chosen networks using a sliding-window approach during WM task compared to rest; then we show that the macroscopic decrease in variations in correlations during a WM task is also well characterized by the combined effect of a reduced number of dominant CAPs, increased spatial consistency across CAPs, and increased fractional contributions of a few dominant CAPs. These CAP metrics may provide alternative and more straightforward quantitative means of characterizing brain network dynamics than time-windowed correlation analyses. PMID:25662866

Quantifying nutrient uptake as driver of rock weathering in forest ecosystems by magnesium stable isotopes

NASA Astrophysics Data System (ADS)

Uhlig, David; Schuessler, Jan A.; Bouchez, Julien; Dixon, Jean L.; von Blanckenburg, Friedhelm

2017-04-01

Plants and soil microbiota play an active role in rock weathering and potentially couple weathering at depth with erosion at the soil surface. The nature of this coupling is still unresolved because we lacked means to quantify the passage of chemical elements from rock through higher plants. In a temperate forested landscape of the Southern Sierra Critical Zone Observatory (SSCZO), California, we measured magnesium (Mg) stable isotopes that are sensitive indicators of Mg utilisation by biota. We find that Mg is highly bio-utilised: 50-100 % of the Mg released by chemical weathering is taken up by forest trees. To estimate the tree uptake of other bio-utilised elements (K, Ca, P and Si) we compared the dissolved fluxes of these elements and Mg in rivers with their solubilisation fluxes from rock (rock dissolution flux minus secondary mineral formation flux). We find a deficit in the dissolved fluxes throughout, that we attribute to the nutrient uptake by forest trees. Therefore, both the Mg isotopes and the flux comparison suggests that a substantial part of the major element weathering flux is consumed by the tree biomass. This isotopic and elemental compartment separation is preserved only if the mineral nutrients contained in biomass are prevented from re-dissolution after litter fall, showing that these nutrients have been removed as "solid" biomass. The enrichment of 26Mg over 24Mg in tree trunks relative to leaf litter suggests that this removal occurs mainly in coarse woody debris (CWD). Today, CWD is exported from the ecosystem by tree logging. Over pre-anthropogenic weathering time scales, a similar removal flux might have been in operation in the form of natural erosion of CWD. Regardless of the removal mechanism, our data provides the first direct quantification of biogenic uptake following weathering. We find that Mg and other bio-elements are taken up by trees at up to 7 m depth, and surface recycling of all bio-elements but P is minimal. Thus, in the

Nutrient dynamics and plant assemblages of Macrotermes falciger mounds in a savanna ecosystem

NASA Astrophysics Data System (ADS)

Muvengwi, Justice; Ndagurwa, Hilton G. T.; Nyenda, Tatenda; Mbiba, Monicah

2016-10-01

Termites through mound construction and foraging activities contribute significantly to carbon and nutrient fluxes in nutrient-poor savannas. Despite this recognition, studies on the influence of termite mounds on carbon and nitrogen dynamics in sub-tropical savannas are limited. In this regard, we examined soil nutrient concentrations, organic carbon and nitrogen mineralization in incubation experiments in mounds of Macrotermes falciger and surrounding soils of sub-tropical savanna, northeast Zimbabwe. We also addressed whether termite mounds altered the plant community and if effects were similar across functional groups i.e. grasses, forbs or woody plants. Mound soils had significantly higher silt and clay content, pH and concentrations of calcium (Ca), magnesium (Mg), potassium (K), organic carbon (C), ammonium (NH4+) and nitrate (NO3-) than surrounding soils, with marginal differences in phosphorus (P) and sodium (Na) between mounds and matrix soils. Nutrient enrichment increased by a factor ranging from 1.5 for C, 4.9 for Mg up to 10.3 for Ca. Although C mineralization, nitrification and nitrification fraction were similar between mounds and matrix soils, nitrogen mineralization was elevated on mounds relative to surrounding matrix soils. As a result, termite mounds supported unique plant communities rich and abundant in woody species but less diverse in grasses and forbs than the surrounding savanna matrix in response to mound-induced shifts in soil parameters specifically increased clay content, drainage and water availability, nutrient status and base cation (mainly Ca, Mg and Na) concentration. In conclusion, by altering soil properties such as texture, moisture content and nutrient status, termite mounds can alter the structure and composition of sub-tropical savanna plant communities, and these results are consistent with findings in other savanna systems suggesting that increase in soil clay content, nutrient status and associated changes in the plant

Nitrogen limitation of growth and nutrient dynamics in a disturbed mangrove forest, Indian River Lagoon, Florida

USGS Publications Warehouse

Feller, Ilka C.; Whigham, D.F.; McKee, K.L.; Lovelock, C.E.

2003-01-01

The objectives of this study were to determine effects of nutrient enrichment on plant growth, nutrient dynamics, and photosynthesis in a disturbed mangrove forest in an abandoned mosquito impoundment in Florida. Impounding altered the hydrology and soil chemistry of the site. In 1997, we established a factorial experiment along a tree-height gradient with three zones, i.e., fringe, transition, dwarf, and three fertilizer treatment levels, i.e., nitrogen (N), phosphorus (P), control, in Mosquito Impoundment 23 on the eastern side of Indian River. Transects traversed the forest perpendicular to the shoreline, from a Rhizophora mangle-dominated fringe through an Avicennia germinans stand of intermediate height, and into a scrub or dwarf stand of A. germinans in the hinterland. Growth rates increased significantly in response to N fertilization. Our growth data indicated that this site is N-limited along the tree-height gradient. After 2 years of N addition, dwarf trees resembled vigorously growing saplings. Addition of N also affected internal dynamics of N and P and caused increases in rates of photosynthesis. These findings contrast with results for a R. mangle-dominated forest in Belize where the fringe is N-limited, but the dwarf zone is P-limited and the transition zone is co-limited by N and P. This study demonstrated that patterns of nutrient limitation in mangrove ecosystems are complex, that not all processes respond similarly to the same nutrient, and that similar habitats are not limited by the same nutrient when different mangrove forests are compared.

Protein-DNA binding dynamics predict transcriptional response to nutrients in archaea.

PubMed

Todor, Horia; Sharma, Kriti; Pittman, Adrianne M C; Schmid, Amy K

2013-10-01

Organisms across all three domains of life use gene regulatory networks (GRNs) to integrate varied stimuli into coherent transcriptional responses to environmental pressures. However, inferring GRN topology and regulatory causality remains a central challenge in systems biology. Previous work characterized TrmB as a global metabolic transcription factor in archaeal extremophiles. However, it remains unclear how TrmB dynamically regulates its ∼100 metabolic enzyme-coding gene targets. Using a dynamic perturbation approach, we elucidate the topology of the TrmB metabolic GRN in the model archaeon Halobacterium salinarum. Clustering of dynamic gene expression patterns reveals that TrmB functions alone to regulate central metabolic enzyme-coding genes but cooperates with various regulators to control peripheral metabolic pathways. Using a dynamical model, we predict gene expression patterns for some TrmB-dependent promoters and infer secondary regulators for others. Our data suggest feed-forward gene regulatory topology for cobalamin biosynthesis. In contrast, purine biosynthesis appears to require TrmB-independent regulators. We conclude that TrmB is an important component for mediating metabolic modularity, integrating nutrient status and regulating gene expression dynamics alone and in concert with secondary regulators.

Annual litterfall dynamics and nutrient deposition depending on elevation and land use at Mt. Kilimanjaro

NASA Astrophysics Data System (ADS)

Becker, J.; Pabst, H.; Mnyonga, J.; Kuzyakov, Y.

2015-07-01

Litterfall is one of the major pathways connecting above- and belowground processes. The effects of climate and land-use change on carbon (C) and nutrient inputs by litterfall are poorly known. We quantified and analyzed annual patterns of C and nutrient deposition via litterfall in natural forests and agroforestry systems along the unique elevation gradient of Mt. Kilimanjaro. Tree litter in three natural (lower montane, Ocotea and Podocarpus forests), two sustainably used (homegardens) and one intensively managed (shaded coffee plantation) was collected on a biweekly basis from May 2012 to July 2013. Leaves, branches and remaining residues were separated and analyzed for C and nutrient contents. The annual pattern of litterfall was closely related to rainfall seasonality, exhibiting a large peak towards the end of the dry season (August-October). This peak decreased at higher elevations with decreasing rainfall seasonality. Macronutrients (N, P, K) in leaf litter increased at mid elevation (2100 m a.s.l.) and with land-use intensity. Carbon content and micronutrients (Al, Fe, Mn, Na) however, were unaffected or decreased with land-use intensity. On the southern slope of Mt. Kilimanjaro, the annual pattern of litterfall depends on seasonal climatic conditions. While leaf litterfall decreased with elevation, total annual input was independent of climate. Compared to natural forests, the nutrient cycles in agroforestry ecosystems were accelerated by fertilization and the associated changes in dominant tree species.

Is nitrogen transfer among plants enhanced by contrasting nutrient-acquisition strategies?

PubMed

Teste, François P; Veneklaas, Erik J; Dixon, Kingsley W; Lambers, Hans

2015-01-01

Nitrogen (N) transfer among plants has been found where at least one plant can fix N2 . In nutrient-poor soils, where plants with contrasting nutrient-acquisition strategies (without N2 fixation) co-occur, it is unclear if N transfer exists and what promotes it. A novel multi-species microcosm pot experiment was conducted to quantify N transfer between arbuscular mycorrhizal (AM), ectomycorrhizal (EM), dual AM/EM, and non-mycorrhizal cluster-rooted plants in nutrient-poor soils with mycorrhizal mesh barriers. We foliar-fed plants with a K(15) NO3 solution to quantify one-way N transfer from 'donor' to 'receiver' plants. We also quantified mycorrhizal colonization and root intermingling. Transfer of N between plants with contrasting nutrient-acquisition strategies occurred at both low and high soil nutrient levels with or without root intermingling. The magnitude of N transfer was relatively high (representing 4% of donor plant N) given the lack of N2 fixation. Receiver plants forming ectomycorrhizas or cluster roots were more enriched compared with AM-only plants. We demonstrate N transfer between plants of contrasting nutrient-acquisition strategies, and a preferential enrichment of cluster-rooted and EM plants compared with AM plants. Nutrient exchanges among plants are potentially important in promoting plant coexistence in nutrient-poor soils. © 2014 John Wiley & Sons Ltd.

Long-term soil nutrient dynamics comparison under smallholding land and farmland policy in northeast of China.

PubMed

Ouyang, Wei; Wei, Xinfeng; Hao, Fanghua

2013-04-15

There are two kinds of land policies, the smallholding land policy (SLP) and the farmland policy (FLP) in China. The farmland nutrient dynamics under the two land policies were analysed with the soil system budget method. The averaged nitrogen (N) input of the SLP and the FLP over sixteen years increased about 23.9% and 33.3%, respectively and the phosphorus (P) input climbed about 39.1% and 42.3%, respectively. The statistical analysis showed that the land policies had significant impacts on N and P input from fertilizer and manure, but did not obviously affect the N input from seeds and biological N fixation. The efficiency percentage of N of the SLP and the FLP climbed about 54.5% and 59.4%, respectively, and the P efficiency improved by 52.7% and 82.6%, respectively. About the nutrient output, the F-test analysis indicated that the land polices had remarkable impacts on N output by crop uptake, ammonia volatilisation, denitrification, leaching and runoff, and P output by uptake, runoff, and leach. The balance showed that the absolute loss of N from land deceased about 43.6% and 46.0%, respectively, in the SLP and the FLP, and P discharge reduced about 34.2% and 75.2%, respectively. The F-test analysis of N and P efficiency and balance of between two polices both indicated that the FLP had significant impact on nutrient dynamic. With the Mitscherlich model, the correlations between nutrient input and crop uptake, usage efficiency and loss were analysed and showed that was a threshold value for the optimal nutrient input with the highest efficiency rate. For the optimal nutrient efficiency, the space for extra P addition was bigger than the N input. The FLP have more advantage than the SLP on the crop yield, nutrient efficiency and environmental discharge. Copyright © 2013 Elsevier B.V. All rights reserved.

Quantifying Information Gain from Dynamic Downscaling Experiments

NASA Astrophysics Data System (ADS)

Tian, Y.; Peters-Lidard, C. D.

2015-12-01

Dynamic climate downscaling experiments are designed to produce information at higher spatial and temporal resolutions. Such additional information is generated from the low-resolution initial and boundary conditions via the predictive power of the physical laws. However, errors and uncertainties in the initial and boundary conditions can be propagated and even amplified to the downscaled simulations. Additionally, the limit of predictability in nonlinear dynamical systems will also damper the information gain, even if the initial and boundary conditions were error-free. Thus it is critical to quantitatively define and measure the amount of information increase from dynamic downscaling experiments, to better understand and appreciate their potentials and limitations. We present a scheme to objectively measure the information gain from such experiments. The scheme is based on information theory, and we argue that if a downscaling experiment is to exhibit value, it has to produce more information than what can be simply inferred from information sources already available. These information sources include the initial and boundary conditions, the coarse resolution model in which the higher-resolution models are embedded, and the same set of physical laws. These existing information sources define an "information threshold" as a function of the spatial and temporal resolution, and this threshold serves as a benchmark to quantify the information gain from the downscaling experiments, or any other approaches. For a downscaling experiment to shown any value, the information has to be above this threshold. A recent NASA-supported downscaling experiment is used as an example to illustrate the application of this scheme.

The Nutrient Density of Snacks

PubMed Central

Hess, Julie; Rao, Goutham; Slavin, Joanne

2017-01-01

Background: Although Americans receive almost a quarter of their daily energy from snacks, snacking remains a poorly defined and understood eating occasion. However, there is little dietary guidance about choosing snacks. Families, clinicians, and researchers need a comprehensive approach to assessing their nutritional value. Objective: To quantify and compare the nutrient density of commonly consumed snacks by their overall nutrient profiles using the Nutrient-Rich Foods (NRF) Index 10.3. Methods: NRF Index scores were calculated for the top 3 selling products (based on 2014 market research data) in different snack categories. These NRF scores were averaged to provide an overall nutrient-density score for each category. Results: Based on NRF scores, yogurt (55.3), milk (52.5), and fruit (30.1) emerged as the most nutrient-dense snacks. Ice cream (−4.4), pies and cakes (−11.1), and carbonated soft drinks (−17.2) emerged as the most nutrient-poor snacks. Conclusions: The NRF Index is a useful tool for assessing the overall nutritional value of snacks based on nutrients to limit and nutrients to encourage. PMID:28491924

Interspecific divergence in foliar nutrient dynamics and stem growth in a temperate forest in response to chronic nitrogen inputs

Treesearch

Jeffrey D. May; Sarah Beth Burdette; Frank S. Gilliam; Mary Beth Adams

2005-01-01

We studied the effects of excessive nitrogen (N) fertilization on foliar nutrient dynamics and stem growth in three important tree species in a mixed-deciduous forest. Stem diameter growth, foliar N concentrations, nitrogen-phosphorus (NIP) ratios, and nutrient resorption were determined for Acer rubrum L. (ACRU), Liriodendron tulipifera L. (LITU), and Prunas serotina...

Nutrient dynamics in shallow lakes of Northern Greece.

PubMed

Petaloti, Christina; Voutsa, Dimitra; Samara, Constantini; Sofoniou, Mihalis; Stratis, Ioannis; Kouimtzis, Themistocles

2004-01-01

GOAL, SCOPE, BACKGROUND: Shallow lakes display a number of features that set them apart from the more frequently studied deeper systems. The majority of lakes in Northern Greece are small to moderate in size with a relatively low depth and are considered as sites of high value of the wetland habitat. However, the water quality of these lakes has only been evaluated segmentally and occasionally. The objectives of this study were to thoroughly investigate nitrogen and phosphorus speciation in lakes of a high ecological significance located in N. Greece, in order to evaluate their eutrophication status and possible nutrient limitation factors, and to investigate the main factors/sources that affect the water quality of these systems. An extensive survey was carried out during the period from 1998-1999. Water samples were collected on a monthly basis from lakes Koronia, Volvi, Doirani, Mikri Prespa and Megali Prespa located in N. Greece. Water quality parameters (temperature, dissolved oxygen, pH and conductivity), organic indices (COD, BOD5), and N- and P-species (NO3(-), NO2(-), NH4(+), and PO4(3-), Kieldahl nitrogen and acid-hydrolysable phosphorus) were determined according to standard methods for surface water. Statistical treatment of the data was employed. The physicochemical parameters determined in the lakes studied revealed a high temporal variation. The trophic state of the lakes ranged from meso- to hypertrophic. The nutrient limiting factor varied among lakes suggesting either P-limitation conditions or mixed conditions changing from P- to N-limitation throughout the year. Urban/industrial activities and agricultural runoff are the major factors affecting all lakes, although with a varying contribution. This lake-specific research offers valuable information about water quality and nutrient dynamics in lakes of significant ecological value located in N. Greece that can be useful for an effective pollution control/management of these systems. Due to the

Nutrient cycle benchmarks for earth system land model

NASA Astrophysics Data System (ADS)

Zhu, Q.; Riley, W. J.; Tang, J.; Zhao, L.

2017-12-01

Projecting future biosphere-climate feedbacks using Earth system models (ESMs) relies heavily on robust modeling of land surface carbon dynamics. More importantly, soil nutrient (particularly, nitrogen (N) and phosphorus (P)) dynamics strongly modulate carbon dynamics, such as plant sequestration of atmospheric CO2. Prevailing ESM land models all consider nitrogen as a potentially limiting nutrient, and several consider phosphorus. However, including nutrient cycle processes in ESM land models potentially introduces large uncertainties that could be identified and addressed by improved observational constraints. We describe the development of two nutrient cycle benchmarks for ESM land models: (1) nutrient partitioning between plants and soil microbes inferred from 15N and 33P tracers studies and (2) nutrient limitation effects on carbon cycle informed by long-term fertilization experiments. We used these benchmarks to evaluate critical hypotheses regarding nutrient cycling and their representation in ESMs. We found that a mechanistic representation of plant-microbe nutrient competition based on relevant functional traits best reproduced observed plant-microbe nutrient partitioning. We also found that for multiple-nutrient models (i.e., N and P), application of Liebig's law of the minimum is often inaccurate. Rather, the Multiple Nutrient Limitation (MNL) concept better reproduces observed carbon-nutrient interactions.

Habitat-specific nutrient removal and release in Oregon salt marshes

EPA Science Inventory

Wetlands can be sources, sinks and transformers of nutrients, although it is their role in nutrient removal that is valued as a water purification ecosystem service. In order to quantify that service for any wetland, it is important to understand the drivers of nutrient removal w...

A comparison of nutrient density scores for 100% fruit juices.

PubMed

Rampersaud, G C

2007-05-01

The 2005 Dietary Guidelines for Americans recommend that consumers choose a variety of nutrient-dense foods. Nutrient density is usually defined as the quantity of nutrients per calorie. Food and nutrition professionals should be aware of the concept of nutrient density, how it might be quantified, and its potential application in food labeling and dietary guidance. This article presents the concept of a nutrient density score and compares nutrient density scores for various 100% fruit juices. One hundred percent fruit juices are popular beverages in the United States, and although they can provide concentrated sources of a variety of nutrients, they can differ considerably in their nutrient profiles. Six methodologies were used to quantify nutrient density and 7 100% fruit juices were included in the analysis: apple, grape, pink grapefruit, white grapefruit, orange, pineapple, and prune. Food composition data were obtained from the USDA National Nutrient Database for Standard Reference, Release 18. Application of the methods resulted in nutrient density scores with a range of values and magnitudes. The relative scores indicated that citrus juices, particularly pink grapefruit and orange juice, were more nutrient dense compared to the other nonfortified 100% juices included in the analysis. Although the methods differed, the relative ranking of the juices based on nutrient density score was similar for each method. Issues to be addressed regarding the development and application of a nutrient density score include those related to food fortification, nutrient bioavailability, and consumer education and behavior.

Quantifying Aggregation Dynamics during Myxococcus xanthus Development▿†

PubMed Central

Zhang, Haiyang; Angus, Stuart; Tran, Michael; Xie, Chunyan; Igoshin, Oleg A.; Welch, Roy D.

2011-01-01

Under starvation conditions, a swarm of Myxococcus xanthus cells will undergo development, a multicellular process culminating in the formation of many aggregates called fruiting bodies, each of which contains up to 100,000 spores. The mechanics of symmetry breaking and the self-organization of cells into fruiting bodies is an active area of research. Here we use microcinematography and automated image processing to quantify several transient features of developmental dynamics. An analysis of experimental data indicates that aggregation reaches its steady state in a highly nonmonotonic fashion. The number of aggregates rapidly peaks at a value 2- to 3-fold higher than the final value and then decreases before reaching a steady state. The time dependence of aggregate size is also nonmonotonic, but to a lesser extent: average aggregate size increases from the onset of aggregation to between 10 and 15 h and then gradually decreases thereafter. During this process, the distribution of aggregates transitions from a nearly random state early in development to a more ordered state later in development. A comparison of experimental results to a mathematical model based on the traffic jam hypothesis indicates that the model fails to reproduce these dynamic features of aggregation, even though it accurately describes its final outcome. The dynamic features of M. xanthus aggregation uncovered in this study impose severe constraints on its underlying mechanisms. PMID:21784940

A combinatorial framework to quantify peak/pit asymmetries in complex dynamics.

PubMed

Hasson, Uri; Iacovacci, Jacopo; Davis, Ben; Flanagan, Ryan; Tagliazucchi, Enzo; Laufs, Helmut; Lacasa, Lucas

2018-02-23

We explore a combinatorial framework which efficiently quantifies the asymmetries between minima and maxima in local fluctuations of time series. We first showcase its performance by applying it to a battery of synthetic cases. We find rigorous results on some canonical dynamical models (stochastic processes with and without correlations, chaotic processes) complemented by extensive numerical simulations for a range of processes which indicate that the methodology correctly distinguishes different complex dynamics and outperforms state of the art metrics in several cases. Subsequently, we apply this methodology to real-world problems emerging across several disciplines including cases in neurobiology, finance and climate science. We conclude that differences between the statistics of local maxima and local minima in time series are highly informative of the complex underlying dynamics and a graph-theoretic extraction procedure allows to use these features for statistical learning purposes.

Quantifying nutrient uptake as driver of rock weathering in forest ecosystems by magnesium stable isotopes

NASA Astrophysics Data System (ADS)

Uhlig, David; Schuessler, Jan A.; Bouchez, Julien; Dixon, Jean L.; von Blanckenburg, Friedhelm

2017-06-01

Plants and soil microbiota play an active role in rock weathering and potentially couple weathering at depth with erosion at the soil surface. The nature of this coupling is still unresolved because we lacked means to quantify the passage of chemical elements from rock through higher plants. In a temperate forested landscape characterised by relatively fast (˜ 220 t km-2 yr-1) denudation and a kinetically limited weathering regime of the Southern Sierra Critical Zone Observatory (SSCZO), California, we measured magnesium (Mg) stable isotopes that are sensitive indicators of Mg utilisation by biota. We find that Mg is highly bio-utilised: 50-100 % of the Mg released by chemical weathering is taken up by forest trees. To estimate the tree uptake of other bio-utilised elements (K, Ca, P and Si) we compared the dissolved fluxes of these elements and Mg in rivers with their solubilisation fluxes from rock (rock dissolution flux minus secondary mineral formation flux). We find a deficit in the dissolved fluxes throughout, which we attribute to the nutrient uptake by forest trees. Therefore both the Mg isotopes and the flux comparison suggest that a substantial part of the major element weathering flux is consumed by the tree biomass. The enrichment of 26Mg over 24Mg in tree trunks relative to leaves suggests that tree trunks account for a substantial fraction of the net uptake of Mg. This isotopic and elemental compartment separation is prevented from obliteration (which would occur by Mg redissolution) by two potential effects. Either the mineral nutrients accumulate today in regrowing forest biomass after clear cutting, or they are exported in litter and coarse woody debris (CWD) such that they remain in solid biomass. Over pre-forest-management weathering timescales, this removal flux might have been in operation in the form of natural erosion of CWD. Regardless of the removal mechanism, our approach provides entirely novel means towards the direct

Climate forcing for dynamics of dissolved inorganic nutrients at Palmer Station, Antarctica: An interdecadal (1993-2013) analysis

NASA Astrophysics Data System (ADS)

Kim, Hyewon; Doney, Scott C.; Iannuzzi, Richard A.; Meredith, Michael P.; Martinson, Douglas G.; Ducklow, Hugh W.

2016-09-01

We analyzed 20 years (1993-2013) of observations of dissolved inorganic macronutrients (nitrate, N; phosphate, P; and silicate, Si) and chlorophyll a (Chl) at Palmer Station, Antarctica (64.8°S, 64.1°W) to elucidate how large-scale climate and local physical forcing affect the interannual variability in the seasonal phytoplankton bloom and associated drawdown of nutrients. The leading modes of nutrients (N, P, and Si empirical orthogonal functions 1, EOF1) represent overall negative anomalies throughout growing seasons, showing a mixed signal of variability in the initial levels and drawdown thereafter (low-frequency dynamics). The second most common seasonal patterns of nitrate and phosphate (N and P EOF2) capture prolonged drawdown events during December-March, which are correlated to Chl EOF1. Si EOF2 captures a drawdown event during November-December, which is correlated to Chl EOF2. These different drawdown patterns are shaped by different sets of physical and climate forcing mechanisms. N and P drawdown events during December-March are influenced by the winter and spring Southern Annular Mode (SAM) phase, where nutrient utilization is enhanced in a stabilized upper water column as a consequence of SAM-driven winter sea ice and spring wind dynamics. Si drawdown during November-December is influenced by early sea ice retreat, where ice breakup may induce abrupt water column stratification and a subsequent diatom bloom or release of diatom cells from within the sea ice. Our findings underscore that seasonal nutrient dynamics in the coastal WAP are coupled to large-scale climate forcing and related physics, understanding of which may enable improved projections of biogeochemical responses to climate change.

Quantifying the effect of hydrogen on dislocation dynamics: A three-dimensional discrete dislocation dynamics framework

NASA Astrophysics Data System (ADS)

Gu, Yejun; El-Awady, Jaafar A.

2018-03-01

We present a new framework to quantify the effect of hydrogen on dislocations using large scale three-dimensional (3D) discrete dislocation dynamics (DDD) simulations. In this model, the first order elastic interaction energy associated with the hydrogen-induced volume change is accounted for. The three-dimensional stress tensor induced by hydrogen concentration, which is in equilibrium with respect to the dislocation stress field, is derived using the Eshelby inclusion model, while the hydrogen bulk diffusion is treated as a continuum process. This newly developed framework is utilized to quantify the effect of different hydrogen concentrations on the dynamics of a glide dislocation in the absence of an applied stress field as well as on the spacing between dislocations in an array of parallel edge dislocations. A shielding effect is observed for materials having a large hydrogen diffusion coefficient, with the shield effect leading to the homogenization of the shrinkage process leading to the glide loop maintaining its circular shape, as well as resulting in a decrease in dislocation separation distances in the array of parallel edge dislocations. On the other hand, for materials having a small hydrogen diffusion coefficient, the high hydrogen concentrations around the edge characters of the dislocations act to pin them. Higher stresses are required to be able to unpin the dislocations from the hydrogen clouds surrounding them. Finally, this new framework can open the door for further large scale studies on the effect of hydrogen on the different aspects of dislocation-mediated plasticity in metals. With minor modifications of the current formulations, the framework can also be extended to account for general inclusion-induced stress field in discrete dislocation dynamics simulations.

Nutrient Budgets Calculated in Floodwaters Using a Whole-Ecosystem Experimental Manipulation

NASA Astrophysics Data System (ADS)

Talbot, C. J.; Paterson, M. J.; Xenopoulos, M. A.

2017-12-01

Flooding provides pathways for nutrients to move into surface waters and alter nutrient concentrations, therefore influencing downstream ecosystems and increasing events of eutrophication. Nutrient enrichment will likely affect water quality, primary production, and overall ecosystem function. Quantifying nutrient movement post-flood will help evaluate the risks or advantages that flooding will have on ecosystem processes. Here we constructed nutrient budgets using data collected as part of the Flooded Upland Dynamics Experiment (FLUDEX) at the Experimental Lakes Area (ELA) in northwestern Ontario. Three experimental reservoirs with varying amounts of stored carbon were created by flooding forested land from May through September annually from 1999 to 2003. Organic matter became a significant source of nutrients under flooded conditions and elevated reservoir total nitrogen (TN) and total phosphorus (TP) concentrations within one week of flooding. The highest TN (2.6 mg L-1) and TP (579 µg L-1) concentrations throughout the entire flooding experiment occurred in the medium carbon reservoir within the first two weeks of flooding in 1999. TN and TP fluxes were positive in all years of flooding. TP fluxes decreased after each flooding season therefore, TP production may be less problematic in floodplains subject to frequent repeated flooding. However, TN fluxes remained large even after repeated flooding. Therefore, flooding, whether naturally occurring or from anthropogenic flow alteration, may be responsible for producing significant amounts of nitrogen and phosphorus in aquatic ecosystems.

Nutrient dynamics in tropical rivers, estuarine-lagoons, and coastal ecosystems along the eastern Hainan Island

NASA Astrophysics Data System (ADS)

Li, R. H.; Liu, S. M.; Li, Y. W.; Zhang, G. L.; Ren, J. L.; Zhang, J.

2013-06-01

Nutrient dynamics were studied along the eastern Hainan Island based on field observations during 2006-2009, to understand nutrient biogeochemical processes and to have an overview of human perturbations on coastal ecosystems in this tropical region. The concentrations of nutrients in the rivers had seasonal variations enriched with dissolved inorganic nitrogen (DIN). High riverine concentrations of nitrate were mainly originated from agricultural fertilizer input. The ratios of DIN : PO43- ranged from 37 to 1063, suggesting preferential PO43- relative to nitrogen in the rivers. The areal yields of dissolved silicate (DSi) varied from 76 to 448 × 103 mol km-2 yr-1 due to erosion over the drainage area, inducing high levels of DSi among worldwide tropical systems. Aquaculture ponds contained high concentrations of NH4+ (up to 157 μM) and DON (up to 130 μM). Particulate phosphorus concentrations (0.5 ∼1.4 μM) were in lower level comparied with estuaries around the world. Particulate silicate levels in rivers and lagoons were lower than global average level. Nutrient biogeochemistry in coastal areas were affected by human activities (e.g. aquaculture, agriculture), as well as natural events such as typhoon. Nutrient concentrations were low because open sea water dispersed land-derived nutrients. Nutrient budgets were built based on a steady-state box model, which showed that riverine fluxes would be magnified by estuarine processes (e.g. regeneration, desorption) in the Wenchanghe/Wenjiaohe Estuary, Wanquan River estuary, and the Laoyehai Lagoon except in the Xiaohai Lagoon. Riverine and groundwater input were the major sources of nutrients to the Xiaohai Lagoon and the Laiyehai Lagoon, respectively. Riverine input and aquaculture effluent were the major sources of nutrients to the eastern coastal of Hainan Island. Nutrient inputs to the coastal ecosystem can be increased by typhoon-induced runoff of rainwater, and phytoplankton bloom in the sea would be

Nutrient dynamics in tropical rivers, lagoons, and coastal ecosystems of eastern Hainan Island, South China Sea

NASA Astrophysics Data System (ADS)

Li, R. H.; Liu, S. M.; Li, Y. W.; Zhang, G. L.; Ren, J. L.; Zhang, J.

2014-01-01

Nutrient dynamics based on field observations made along the eastern Hainan Island during the period 2006-2009 were investigated to understand nutrient biogeochemical processes, and to provide an overview of human perturbations of coastal ecosystems in this tropical region. The rivers showed seasonal variations in nutrient concentrations, with enrichment of dissolved inorganic nitrogen and dissolved silicate, and depletion of PO43-. High riverine concentrations of nitrate mainly originated from agricultural fertilizer inputs. The DIN : PO43- ratios ranged from 37 to 1063, suggesting preferential depletion of PO43- relative to nitrogen in rivers. Chemical weathering in the drainage area might explain the high levels of dissolved silicate. Aquaculture ponds contained high concentrations of NH4+ and dissolved organic nitrogen. The particulate phosphorus concentrations in the study area were lower than those reported for estuaries worldwide. The particulate silicate levels in rivers and lagoons were lower than the global average level. Nutrient biogeochemistry in coastal areas was affected by human activities (e.g., aquaculture, agriculture), and by natural phenomena including typhoons. The nutrient concentrations in coastal waters were low because of dispersion of land-derived nutrients in the sea. Nutrient budgets were built based on a steady-state box model, which showed that riverine fluxes are magnified by estuarine processes (e.g., regeneration, desorption) in estuaries and Laoyehai Lagoon, but not in Xiaohai Lagoon. Riverine and groundwater inputs were the major sources of nutrients to Xiaohai and Laoyehai lagoons, respectively, and riverine inputs and aquaculture effluents were the major sources for the eastern coast of Hainan Island. Nutrient inputs to the coastal ecosystem increased with typhoon-induced runoff of rainwater, elucidating the important influence of typhoons on small tropical rivers.

Hydrochemical controls on reservoir nutrient and phytoplankton dynamics under storms.

PubMed

Chen, Nengwang; Mo, Qiongli; Kuo, Yi-Ming; Su, Yuping; Zhong, Yanping

2018-04-01

Eutrophication and undesired algal blooms in surface water are common and have been linked to increasing nutrient loading. Effects of extreme events such as storms on reservoir nutrient and phytoplankton remain unclear. Here we carried out continuous high-frequency measurements in a long and narrow dam reservoir in southeast China during a storm period in June-July 2015. Our results show a strong nutrient-phytoplankton relationship as well as a very rapid response to storm runoff. We observed an increase in total suspended matter (TSM), ammonium (NH 4 -N), and dissolved reactive phosphate (DRP), with a sharp decline in chlorophyll-a (Chl-a) in the high flow periods. Afterward, Chl-a, total phytoplankton abundance and Cyanophyta fraction elevated gradually. Nitrate was diluted at first with increasing discharge before concentration increased, likely following a delayed input of groundwater. Physiochemical parameters and Chl-a were evenly distributed in the water column during the flooding period. However, 10% of NH 4 -N and 25% of DRP were removed in surface water (0-1m) when an algal bloom (Chl-a>30μgL -1 ) occurred 10days after peak discharge. Conversely, total particulate P (TPP) of surface water was 58% higher than in the deeper water. Dynamic factor analysis (DFA) revealed that TSM, NH 4 -N, DRP, total P and discharge significantly explain Chl-a variations following storms (C eff =0.89). These findings highlight that the reservoir ecosystem was vulnerable to pulse input from storm runoff and the Cyanophyta bloom was likely fueled by phosphate and ammonium rather than nitrate. Copyright © 2017 Elsevier B.V. All rights reserved.

Quantifying sleep architecture dynamics and individual differences using big data and Bayesian networks

PubMed Central

Shelton, Christian; Mednick, Sara C.

2018-01-01

The pattern of sleep stages across a night (sleep architecture) is influenced by biological, behavioral, and clinical variables. However, traditional measures of sleep architecture such as stage proportions, fail to capture sleep dynamics. Here we quantify the impact of individual differences on the dynamics of sleep architecture and determine which factors or set of factors best predict the next sleep stage from current stage information. We investigated the influence of age, sex, body mass index, time of day, and sleep time on static (e.g. minutes in stage, sleep efficiency) and dynamic measures of sleep architecture (e.g. transition probabilities and stage duration distributions) using a large dataset of 3202 nights from a non-clinical population. Multi-level regressions show that sex effects duration of all Non-Rapid Eye Movement (NREM) stages, and age has a curvilinear relationship for Wake After Sleep Onset (WASO) and slow wave sleep (SWS) minutes. Bayesian network modeling reveals sleep architecture depends on time of day, total sleep time, age and sex, but not BMI. Older adults, and particularly males, have shorter bouts (more fragmentation) of Stage 2, SWS, and they transition less frequently to these stages. Additionally, we showed that the next sleep stage and its duration can be optimally predicted by the prior 2 stages and age. Our results demonstrate the potential benefit of big data and Bayesian network approaches in quantifying static and dynamic architecture of normal sleep. PMID:29641599

Quantifying sleep architecture dynamics and individual differences using big data and Bayesian networks.

PubMed

Yetton, Benjamin D; McDevitt, Elizabeth A; Cellini, Nicola; Shelton, Christian; Mednick, Sara C

2018-01-01

The pattern of sleep stages across a night (sleep architecture) is influenced by biological, behavioral, and clinical variables. However, traditional measures of sleep architecture such as stage proportions, fail to capture sleep dynamics. Here we quantify the impact of individual differences on the dynamics of sleep architecture and determine which factors or set of factors best predict the next sleep stage from current stage information. We investigated the influence of age, sex, body mass index, time of day, and sleep time on static (e.g. minutes in stage, sleep efficiency) and dynamic measures of sleep architecture (e.g. transition probabilities and stage duration distributions) using a large dataset of 3202 nights from a non-clinical population. Multi-level regressions show that sex effects duration of all Non-Rapid Eye Movement (NREM) stages, and age has a curvilinear relationship for Wake After Sleep Onset (WASO) and slow wave sleep (SWS) minutes. Bayesian network modeling reveals sleep architecture depends on time of day, total sleep time, age and sex, but not BMI. Older adults, and particularly males, have shorter bouts (more fragmentation) of Stage 2, SWS, and they transition less frequently to these stages. Additionally, we showed that the next sleep stage and its duration can be optimally predicted by the prior 2 stages and age. Our results demonstrate the potential benefit of big data and Bayesian network approaches in quantifying static and dynamic architecture of normal sleep.

Cooperation through Competition-Dynamics and Microeconomics of a Minimal Nutrient Trade System in Arbuscular Mycorrhizal Symbiosis.

PubMed

Schott, Stephan; Valdebenito, Braulio; Bustos, Daniel; Gomez-Porras, Judith L; Sharma, Tripti; Dreyer, Ingo

2016-01-01

In arbuscular mycorrhizal (AM) symbiosis, fungi and plants exchange nutrients (sugars and phosphate, for instance) for reciprocal benefit. Until now it is not clear how this nutrient exchange system works. Here, we used computational cell biology to simulate the dynamics of a network of proton pumps and proton-coupled transporters that are upregulated during AM formation. We show that this minimal network is sufficient to describe accurately and realistically the nutrient trade system. By applying basic principles of microeconomics, we link the biophysics of transmembrane nutrient transport with the ecology of organismic interactions and straightforwardly explain macroscopic scenarios of the relations between plant and AM fungus. This computational cell biology study allows drawing far reaching hypotheses about the mechanism and the regulation of nutrient exchange and proposes that the "cooperation" between plant and fungus can be in fact the result of a competition between both for the same resources in the tiny periarbuscular space. The minimal model presented here may serve as benchmark to evaluate in future the performance of more complex models of AM nutrient exchange. As a first step toward this goal, we included SWEET sugar transporters in the model and show that their co-occurrence with proton-coupled sugar transporters results in a futile carbon cycle at the plant plasma membrane proposing that two different pathways for the same substrate should not be active at the same time.

Quantifying stochasticity in the dynamics of delay-coupled semiconductor lasers via forbidden patterns.

PubMed

Tiana-Alsina, Jordi; Buldú, Javier M; Torrent, M C; García-Ojalvo, Jordi

2010-01-28

We quantify the level of stochasticity in the dynamics of two mutually coupled semiconductor lasers. Specifically, we concentrate on a regime in which the lasers synchronize their dynamics with a non-zero lag time, and the leader and laggard roles alternate irregularly between the lasers. We analyse this switching dynamics in terms of the number of forbidden patterns of the alternate time series. The results reveal that the system operates in a stochastic regime, with the level of stochasticity decreasing as the lasers are pumped further away from their lasing threshold. This behaviour is similar to that exhibited by a single semiconductor laser subject to external optical feedback, as its dynamics shifts from the regime of low-frequency fluctuations to coherence collapse. This journal is © 2010 The Royal Society

Quantifying Km-scale Hydrological Exchange Flows under Dynamic Flows and Their Influences on River Corridor Biogeochemistry

NASA Astrophysics Data System (ADS)

Chen, X.; Song, X.; Shuai, P.; Hammond, G. E.; Ren, H.; Zachara, J. M.

2017-12-01

Hydrologic exchange flows (HEFs) in rivers play vital roles in watershed ecological and biogeochemical functions due to their strong capacity to attenuate contaminants and process significant quantities of carbon and nutrients. While most of existing HEF studies focus on headwater systems with the assumption of steady-state flow, there is lack of understanding of large-scale HEFs in high-order regulated rivers that experience high-frequency stage fluctuations. The large variability of HEFs is a result of interactions between spatial heterogeneity in hydrogeologic properties and temporal variation in river discharge induced by natural or anthropogenic perturbations. Our 9-year spatially distributed dataset (water elevation, specific conductance, and temperature) combined with mechanistic hydrobiogeochemical simulations have revealed complex spatial and temporal dynamics in km-scale HEFs and their significant impacts on contaminant plume mobility and hyporheic biogeochemical processes along the Hanford Reach. Extended multidirectional flow behaviors of unconfined, river corridor groundwater were observed hundreds of meters inland from the river shore resulting from discharge-dependent HEFs. An appropriately sized modeling domain to capture the impact of regional groundwater flow as well as knowledge of subsurface structures controlling intra-aquifer hydrologic connectivity were essential to realistically model transient storage in this large-scale river corridor. This work showed that both river water and mobile groundwater contaminants could serve as effective tracers of HEFs, thus providing valuable information for evaluating and validating the HEF models. Multimodal residence time distributions with long tails were resulted from the mixture of long and short exchange pathways, which consequently impact the carbon and nutrient cycling within the river corridor. Improved understanding of HEFs using integrated observational and modeling approaches sheds light on

A comparative analysis of alternative approaches for quantifying nonlinear dynamics in cardiovascular system.

PubMed

Chen, Yun; Yang, Hui

2013-01-01

Heart rate variability (HRV) analysis has emerged as an important research topic to evaluate autonomic cardiac function. However, traditional time and frequency-domain analysis characterizes and quantify only linear and stationary phenomena. In the present investigation, we made a comparative analysis of three alternative approaches (i.e., wavelet multifractal analysis, Lyapunov exponents and multiscale entropy analysis) for quantifying nonlinear dynamics in heart rate time series. Note that these extracted nonlinear features provide information about nonlinear scaling behaviors and the complexity of cardiac systems. To evaluate the performance, we used 24-hour HRV recordings from 54 healthy subjects and 29 heart failure patients, available in PhysioNet. Three nonlinear methods are evaluated not only individually but also in combination using three classification algorithms, i.e., linear discriminate analysis, quadratic discriminate analysis and k-nearest neighbors. Experimental results show that three nonlinear methods capture nonlinear dynamics from different perspectives and the combined feature set achieves the best performance, i.e., sensitivity 97.7% and specificity 91.5%. Collectively, nonlinear HRV features are shown to have the promise to identify the disorders in autonomic cardiovascular function.

Inter-individual variation in nutrient balancing in the honeybee (Apis mellifera).

PubMed

Reade, Abbie J; Naug, Dhruba

2016-12-01

The Geometric Framework approach in nutritional ecology postulates that animals attempt to balance the consumption of different nutrients rather than simply maximizing energetic gain. The intake target with respect to each nutrient maximizes fitness in a specific dimension and any difference between individuals in intake target therefore represents alternative behavioral and fitness maximization strategies. Nutritional interactions are a central component of all social groups and any inter-individual variation in intake target should therefore have a significant influence on social dynamics. Using the honeybee colony as an experimental model, we quantified differences in the carbohydrate intake target of individual foragers using a capillary feeder (CAFE) assay. Our results show that the bees did not simply maximize their net energetic gain, but combined sugar and water in their diet in a way that brought them to an intake target equivalent to a 33% sucrose solution. Although the mean intake target with respect to the nutrients sucrose and water was the same under different food choice regimens, there was significant inter-individual variation in intake target and the manner in which individuals reached this target, a variation which suggests different levels of tolerance to nutrient imbalance. We discuss our results in the context of how colony performance may be influenced by the different nutrient balancing strategies of individual members and how such nutritional constraints could have contributed to the evolution of sociality. Copyright © 2016 Elsevier Ltd. All rights reserved.

Loblolly pine needle decomposition and nutrient dynamics as affected by irrigation, fertilization, and substrate quality

Treesearch

Felipe G. Sanchez

2001-01-01

This study examined the effects of initial litter quality and irrigation and fertilization treatments on litter decomposition rates and nutrient dynamics (N, Ca, K, Mg, and P) of loblolly (Pinus taeda L.) pine needles in the North Carolina Sand Hills over 3 years. Litter quality was based on the initial C/N ratios, with the high-quality litter having...

Nutrient Dynamics of Estuarine Invertebrates Are Shaped by Feeding Guild Rather than Seasonal River Flow

PubMed Central

Ortega-Cisneros, Kelly; Scharler, Ursula M.

2015-01-01

This study aimed to determine the variability of carbon and nitrogen elemental content, stoichiometry and diet proportions of invertebrates in two sub-tropical estuaries in South Africa experiencing seasonal changes in rainfall and river inflow. The elemental ratios and stable isotopes of abiotic sources, zooplankton and macrozoobenthos taxa were analyzed over a dry/wet seasonal cycle. Nutrient content (C, N) and stoichiometry of suspended particulate matter exhibited significant spatio-temporal variations in both estuaries, which were explained by the variability in river inflow. Sediment particulate matter (%C, %N and C:N) was also influenced by the variability in river flow but to a lesser extent. The nutrient content and ratios of the analyzed invertebrates did not significantly vary among seasons with the exception of the copepod Pseudodiaptomus spp. (C:N) and the tanaid Apseudes digitalis (%N, C:N). These changes did not track the seasonal variations of the suspended or sediment particulate matter. Our results suggest that invertebrates managed to maintain their stoichiometry independent of the seasonality in river flow. A significant variability in nitrogen content among estuarine invertebrates was recorded, with highest % N recorded from predators and lowest %N from detritivores. Due to the otherwise general lack of seasonal differences in elemental content and stoichiometry, feeding guild was a major factor shaping the nutrient dynamics of the estuarine invertebrates. The nutrient richer suspended particulate matter was the preferred food source over sediment particulate matter for most invertebrate consumers in many, but not all seasons. The most distinct preference for suspended POM as a food source was apparent from the temporarily open/closed system after the estuary had breached, highlighting the importance of river flow as a driver of invertebrate nutrient dynamics under extreme events conditions. Moreover, our data showed that estuarine

Nutrient Dynamics of Estuarine Invertebrates Are Shaped by Feeding Guild Rather than Seasonal River Flow.

PubMed

Ortega-Cisneros, Kelly; Scharler, Ursula M

2015-01-01

This study aimed to determine the variability of carbon and nitrogen elemental content, stoichiometry and diet proportions of invertebrates in two sub-tropical estuaries in South Africa experiencing seasonal changes in rainfall and river inflow. The elemental ratios and stable isotopes of abiotic sources, zooplankton and macrozoobenthos taxa were analyzed over a dry/wet seasonal cycle. Nutrient content (C, N) and stoichiometry of suspended particulate matter exhibited significant spatio-temporal variations in both estuaries, which were explained by the variability in river inflow. Sediment particulate matter (%C, %N and C:N) was also influenced by the variability in river flow but to a lesser extent. The nutrient content and ratios of the analyzed invertebrates did not significantly vary among seasons with the exception of the copepod Pseudodiaptomus spp. (C:N) and the tanaid Apseudes digitalis (%N, C:N). These changes did not track the seasonal variations of the suspended or sediment particulate matter. Our results suggest that invertebrates managed to maintain their stoichiometry independent of the seasonality in river flow. A significant variability in nitrogen content among estuarine invertebrates was recorded, with highest % N recorded from predators and lowest %N from detritivores. Due to the otherwise general lack of seasonal differences in elemental content and stoichiometry, feeding guild was a major factor shaping the nutrient dynamics of the estuarine invertebrates. The nutrient richer suspended particulate matter was the preferred food source over sediment particulate matter for most invertebrate consumers in many, but not all seasons. The most distinct preference for suspended POM as a food source was apparent from the temporarily open/closed system after the estuary had breached, highlighting the importance of river flow as a driver of invertebrate nutrient dynamics under extreme events conditions. Moreover, our data showed that estuarine

Dissolved Nutrient Retention Dynamics in River Networks: A Modeling Investigation of Transient Flow and Scale Effects

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ye, Sheng; Covino, Timothy P.; Sivapalan, Murugesu

In this paper, we use a dynamic network flow model, coupled with a transient storage zone biogeochemical model, to simulate dissolved nutrient removal processes at the channel network scale. We have explored several scenarios in respect of the combination of rainfall variability, and the biological and geomorphic characteristics of the catchment, to understand the dominant controls on removal and delivery of dissolved nutrients (e.g., nitrate). These model-based theoretical analyses suggested that while nutrient removal efficiency is lower during flood events compared to during baseflow periods, flood events contribute significantly to bulk nutrient removal, whereas bulk removal during baseflow periods ismore » less. This is due to the fact that nutrient supply is larger during flood events; this trend is even stronger in large rivers. However, the efficiency of removal during both periods decreases in larger rivers, however, due to (i) increasing flow velocities and thus decreasing residence time, and (ii) increasing flow depth, and thus decreasing nutrient uptake rates. Besides nutrient removal processes can be divided into two parts: in the main channel and in the hyporheic transient storage zone. When assessing their relative contributions the size of the transient storage zone is a dominant control, followed by uptake rates in the main channel and in the transient storage zone. Increasing size of the transient storage zone with downstream distance affects the relative contributions to nutrient removal of the water column and the transient storage zone, which also impacts the way nutrient removal rates scale with increasing size of rivers. Intra-annual hydrologic variability has a significant impact on removal rates at all scales: the more variable the streamflow is, compared to mean discharge, the less nutrient is removed in the channel network. A scale-independent first order uptake coefficient, ke, estimated from model simulations, is highly dependent on

Quantifying Temperature Effects on Snow, Plant and Streamflow Dynamics in Headwater Catchments

NASA Astrophysics Data System (ADS)

Wainwright, H. M.; Sarah, T.; Siirila-Woodburn, E. R.; Newcomer, M. E.; Williams, K. H.; Hubbard, S. S.; Enquist, B. J.; Steltzer, H.; Carroll, R. W. H.

2017-12-01

Quantifying Temperature Effects on Snow, Plant and Streamflow Dynamics in Headwater Catchments Snow-dominated headwater catchments are critical for water resource throughout the world; particularly in Western US. Under climate change, temperature increases are expected to be amplified in mountainous regions. We use a data-driven approach to better understand the coupling among inter-annual variability in temperature, snow and plant community dynamics and stream discharge. We apply data mining methods (e.g., principal component analysis, random forest) to historical spatiotemporal datasets, including the SNOTEL data, Landsat-based normalized difference vegetation index (NDVI) and airborne LiDAR-based snow distribution. Although both snow distribution and NDVI are extremely heterogeneous spatially, the inter-annual variability and temporal responses are spatially consistent, providing an opportunity to quantify the effect of temperature in the catchment-scale. We demonstrate our approach in the East River Watershed of the Upper Colorado River Basin, including Rocky Mountain Biological Laboratory, where the changes in plant communities and their dynamics have been extensively documented. Results indicate that temperature - particularly spring temperature - has a significant control not only on the timing of snowmelt, plant NDVI and peak flow but also on the magnitude of peak NDVI, peak flow and annual discharge. Monthly temperature in spring explains the variability of snowmelt by the equivalent standard deviation of 3.4-4.4 days, and total discharge by 10-11%. In addition, the high correlation among June temperature, peak NDVI and annual discharge suggests a primary role of spring evapotranspiration on plant community phenology, productivity, and streamflow volume. On the other hand, summer monsoon precipitation does not contribute significantly to annual discharge, further emphasizing the importance of snowmelt. This approach is mostly based on a set of datasets

Cooperation through Competition—Dynamics and Microeconomics of a Minimal Nutrient Trade System in Arbuscular Mycorrhizal Symbiosis

PubMed Central

Schott, Stephan; Valdebenito, Braulio; Bustos, Daniel; Gomez-Porras, Judith L.; Sharma, Tripti; Dreyer, Ingo

2016-01-01

In arbuscular mycorrhizal (AM) symbiosis, fungi and plants exchange nutrients (sugars and phosphate, for instance) for reciprocal benefit. Until now it is not clear how this nutrient exchange system works. Here, we used computational cell biology to simulate the dynamics of a network of proton pumps and proton-coupled transporters that are upregulated during AM formation. We show that this minimal network is sufficient to describe accurately and realistically the nutrient trade system. By applying basic principles of microeconomics, we link the biophysics of transmembrane nutrient transport with the ecology of organismic interactions and straightforwardly explain macroscopic scenarios of the relations between plant and AM fungus. This computational cell biology study allows drawing far reaching hypotheses about the mechanism and the regulation of nutrient exchange and proposes that the “cooperation” between plant and fungus can be in fact the result of a competition between both for the same resources in the tiny periarbuscular space. The minimal model presented here may serve as benchmark to evaluate in future the performance of more complex models of AM nutrient exchange. As a first step toward this goal, we included SWEET sugar transporters in the model and show that their co-occurrence with proton-coupled sugar transporters results in a futile carbon cycle at the plant plasma membrane proposing that two different pathways for the same substrate should not be active at the same time. PMID:27446142

Predictive modeling of transient storage and nutrient uptake: Implications for stream restoration

USGS Publications Warehouse

O'Connor, Ben L.; Hondzo, Miki; Harvey, Judson W.

2010-01-01

This study examined two key aspects of reactive transport modeling for stream restoration purposes: the accuracy of the nutrient spiraling and transient storage models for quantifying reach-scale nutrient uptake, and the ability to quantify transport parameters using measurements and scaling techniques in order to improve upon traditional conservative tracer fitting methods. Nitrate (NO3–) uptake rates inferred using the nutrient spiraling model underestimated the total NO3– mass loss by 82%, which was attributed to the exclusion of dispersion and transient storage. The transient storage model was more accurate with respect to the NO3– mass loss (±20%) and also demonstrated that uptake in the main channel was more significant than in storage zones. Conservative tracer fitting was unable to produce transport parameter estimates for a riffle-pool transition of the study reach, while forward modeling of solute transport using measured/scaled transport parameters matched conservative tracer breakthrough curves for all reaches. Additionally, solute exchange between the main channel and embayment surface storage zones was quantified using first-order theory. These results demonstrate that it is vital to account for transient storage in quantifying nutrient uptake, and the continued development of measurement/scaling techniques is needed for reactive transport modeling of streams with complex hydraulic and geomorphic conditions.

Tidal pumping drives nutrient and dissolved organic matter dynamics in a Gulf of Mexico subterranean estuary

NASA Astrophysics Data System (ADS)

Santos, Isaac R.; Burnett, William C.; Dittmar, Thorsten; Suryaputra, I. G. N. A.; Chanton, Jeffrey

2009-03-01

We hypothesize that nutrient cycling in a Gulf of Mexico subterranean estuary (STE) is fueled by oxygen and labile organic matter supplied by tidal pumping of seawater into the coastal aquifer. We estimate nutrient production rates using the standard estuarine model and a non-steady-state box model, separate nutrient fluxes associated with fresh and saline submarine groundwater discharge (SGD), and estimate offshore fluxes from radium isotope distributions. The results indicate a large variability in nutrient concentrations over tidal and seasonal time scales. At high tide, nutrient concentrations in shallow beach groundwater were low as a result of dilution caused by seawater recirculation. During ebb tide, the concentrations increased until they reached a maximum just before the next high tide. The dominant form of nitrogen was dissolved organic nitrogen (DON) in freshwater, nitrate in brackish waters, and ammonium in saline waters. Dissolved organic carbon (DOC) production was two-fold higher in the summer than in the winter, while nitrate and DON production were one order of magnitude higher. Oxic remineralization and denitrification most likely explain these patterns. Even though fresh SGD accounted for only ˜5% of total volumetric additions, it was an important pathway of nutrients as a result of biogeochemical inputs in the mixing zone. Fresh SGD transported ˜25% of DOC and ˜50% of total dissolved nitrogen inputs into the coastal ocean, with the remainder associated with a one-dimensional vertical seawater exchange process. While SGD volumetric inputs are similar seasonally, changes in the biogeochemical conditions of this coastal plain STE led to higher summertime SGD nutrient fluxes (40% higher for DOC and 60% higher for nitrogen in the summer compared to the winter). We suggest that coastal primary production and nutrient dynamics in the STE are linked.

NITRATE RELEASE BY SALT MARSH PLANTS: AN OVERLOOKED NUTRIENT FLUX MECHANISM

EPA Science Inventory

Salt marshes provide water purification as an important ecosystem service in part by storing, transforming and releasing nutrients. This service can be quantified by measuring nutrient fluxes between marshes and surface waters. Many processes drive these fluxes, including photosy...

Laser activation of a nutrient medium and antibiotic solutions and its estimation by of bacteria growth dynamics

NASA Astrophysics Data System (ADS)

Malov, Alexander N.; Neupokoeva, Anna V.; Kokorina, Lubov A.; Simonova, Elena V.

2016-11-01

A laser photomodifacation of nutrient mediums and antibiotics results at the microbiological supervision of bacteria colonies growth are discussed. It is experimentally shown, that on the irradiated media there is a delay of bacterial colonies growth number. Influence of laser radiation on activity of an antibiotic also is experimentally studied. It is revealed, that laser photomodifacation increases antimicrobic activity of a preparation. The mechanism of biological solutions activation is connected with the phenomenon laser nanoclusterization. Parameters of bacteria growth bacteria growth dynamics allow to numerically estimate degree of laser activation of nutrient mediums and pharmaceutical preparations.

Nutrient and algal responses to winterkilled fish-derived nutrient subsidies in eutrophic lakes

USGS Publications Warehouse

Schoenebeck, Casey W.; Brown, Michael L.; Chipps, Steven R.; German, David R.

2012-01-01

Fishes inhabiting shallow, glacial lakes of the Prairie Pothole Region in the United States and Canada periodically experience hypoxia in severe winters that can lead to extensive fish mortality resulting in high biomasses of dead fish. However, the role of carcass-derived nutrient subsidies in shallow, eutrophic lakes translocated to pelagic primary producers is not well documented. This study quantified the influence of winterkill events on nutrient contributions from decaying fish carcasses of common carp (Cyprinus carpio) and the phytoplankton response among pre- and postwinterkill years and compared seasonal patterns of nutrient limitation and phytoplankton community composition between winterkill and nonwinterkill lakes. We found that fish carcasses contributed an estimated 2.5–4.3 kg/ha of total (Kjeldahl) nitrogen (N) and 0.3–0.5 kg/ha of total phosphorus (P) to lakes that experienced winterkill conditions. Nutrient bioassays showed that winterkill lakes were primarily N limited, congruent with the low N:P ratios produced by fish carcasses corrected for the disproportionate release of N and P (8.6). Nutrient subsidies translocated from decomposed fish to pelagic primary producers seemed to have little immediate influence on the seasonal phytoplankton community composition, but total N and subsequent chlorophyll-a increased the year following the winterkill event. Cyanobacteria density varied seasonally but was higher in winterkill lakes, presumably due to the integration of nutrients released from fish decomposition. This study provides evidence that large inputs of autochthonous fish-derived nutrients contribute to nutrient availability within winterkilled systems and increase the maximum attainable biomass of the phytoplankton community.

Soil Organic Carbon and Nutrient Dynamics in Reclaimed Appalachian Mine Soil

NASA Astrophysics Data System (ADS)

Acton, P.; Fox, J.; Campbell, J. E.; Rowe, H. D.; Jones, A.

2011-12-01

Past research has shown that drastically disturbed and degraded soils can offer a high potential for soil organic carbon and aboveground carbon sequestration. Little work has been done on both the functioning of soil carbon accumulation and turnover in reclaimed surface mining soils. Reclamation practices of surface coal mine soils in the Southern Appalachian forest region of the United States emphasizes heavy compaction of surface material to provide slope stability and reduce surface erosion, and topsoil is not typically added. An analysis of the previously collected data has provided a 14 year chronosequence of SOC uptake and development in the soil column and revealed that these soils are sequestering carbon at a rate of 1.3 MgC ha-1 yr-1, which is 1.6 to 3 times less than mining soils reported for other regions. Results of bulk density analysis indicate a contrast between 0 - 10 cm (1.51 g cm-3) and 10 - 50 cm (2.04 g cm-3) depth intervals. Aggregate stability was also quantified as well as dynamic soil texture measurements. With this analysis, it has been established that these soils are well below their potential in terms of the ability to store and cycle carbon and other nutrients as well their ability to sustain a fully-functioning forested ecosystem typical for the region. We are taking an integrated approach that relies on ecological observations for present conditions combined with computational modeling to understand long-term soil organic carbon (SOC) accumulation and turnover in regards to SOC sequestration potential and quantification of specific processes by which these soils develop. A dual-isotope end-member model, utilizing the carbon 13 and nitrogen 15 stable isotopes, is being developed to provide greater input into the mathematical separation of organic carbon derived from new soil inputs and existing coal carbon. Soils from the study sites have been isolated into three distinct size pools, and elemental and isotopic analysis of these samples

Decomposition of sea lamprey Petromyzon marinus carcasses: temperature effects, nutrient dynamics, and implications for stream food webs

USGS Publications Warehouse

Weaver, Daniel M.; Coghlan, Stephen M.; Zydlewski, Joseph D.; Hogg, Robert S.; Canton, Michael

2015-01-01

Anadromous fishes serve as vectors of marine-derived nutrients into freshwaters that are incorporated into aquatic and terrestrial food webs. Pacific salmonines Oncorhynchus spp. exemplify the importance of migratory fish as links between marine and freshwater systems; however, little attention has been given to sea lamprey (Petromyzon marinus Linnaeus, 1758) in Atlantic coastal systems. A first step to understanding the role of sea lamprey in freshwater food webs is to characterize the composition and rate of nutrient inputs. We conducted laboratory and field studies characterizing the elemental composition and the decay rates and subsequent water enriching effects of sea lamprey carcasses. Proximate tissue analysis demonstrated lamprey carcass nitrogen:phosphorus ratios of 20.2:1 (±1.18 SE). In the laboratory, carcass decay resulted in liberation of phosphorus within 1 week and nitrogen within 3 weeks. Nutrient liberation was accelerated at higher temperatures. In a natural stream, carcass decomposition resulted in an exponential decline in biomass, and after 24 days, the proportion of initial biomass remaining was 27% (±3.0% SE). We provide quantitative results as to the temporal dynamics of sea lamprey carcass decomposition and subsequent nutrient liberation. These nutrient subsidies may arrive at a critical time to maximize enrichment of stream food webs.

Decay and nutrient dynamics of coarse woody debris in the Qinling Mountains, China

PubMed Central

Yuan, Jie; Hou, Lin; Wei, Xin; Shang, Zhengchun; Cheng, Fei; Zhang, Shuoxin

2017-01-01

As an ecological unit, coarse woody debris (CWD) plays an essential role in productivity, nutrient cycling, carbon sequestration, community regeneration and biodiversity. However, thus far, the information on quantification the decomposition and nutrient content of CWD in forest ecosystems remains considerably limited. In this study, we conducted a long-term (1996–2013) study on decay and nutrient dynamics of CWD for evaluating accurately the ecological value of CWD on the Huoditang Experimental Forest Farm in the Qinling Mountains, China. The results demonstrated that there was a strong correlation between forest biomass and CWD mass. The single exponential decay model well fit the CWD density loss at this site, and as the CWD decomposed, the CWD density decreased significantly. Annual temperature and precipitation were all significantly correlated with the annual mass decay rate. The K contents and the C/N ratio of the CWD decreased as the CWD decayed, but the C, N, P, Ca and Mg contents increased. We observed a significant CWD decay effect on the soil C, N and Mg contents, especially the soil C content. The soil N, P, K, Ca and Mg contents exhibited large fluctuations, but the variation had no obvious regularity and changed with different decay times. The results showed that CWD was a critical component of nutrient cycling in forest ecosystems. Further research is needed to determine the effect of diameter, plant tissue components, secondary wood compounds, and decomposer organisms on the CWD decay rates in the Qinling Mountains, which will be beneficial to clarifying the role of CWD in carbon cycles of forest ecosystems. PMID:28384317

Enzyme-mediated Nutrient Regeneration Following Lysis of Synechococcus WH7803

NASA Astrophysics Data System (ADS)

Mine, A. H.; Coleman, M.; Colman, A. S.

2016-02-01

Phosphate availability plays a pivotal role in limiting primary production in large regions of the oceans. In order to meet their metabolic needs, microbes use a variety of strategies to overcome phosphate stress. Expression of enzymes such as alkaline phosphatase (APase) allows cells to hydrolyze and use certain ambient dissolved organic phosphorus (DOP) compounds to meet their P demand. Cell lysis releases a range of nutrient forms and enzymes into the ambient environment and is an essential component of the microbial loop. Yet very few studies have attempted to characterize both the immediate and sustained nutrient remineralization linked to the milieu of organophosphorus compounds and enzymatic activity in lysate. We conducted experiments using Synechococcus WH7803 grown under nutrient replete and starved conditions to quantify the release of phosphate during viral lysis and lysis by lysozyme treatment. Dissolved inorganic and organic phosphorus concentrations and APase activity were monitored over time following lysis. We observed a significant initial release of orthophosphate that accompanies lysis. Following lysis, phosphate concentrations continue to rise for a period of hours to days as organophosphorus compounds continue to hydrolyze. Our observations suggest this is due to a combination of direct hydrolysis of DOP released during lysis, solubilization of POP followed by hydrolysis, and possibly polyphosphate decomposition. Size fractionated enzymatic assays suggest cellular debris associated enzymes and dissolved fractions are both important in DOP hydrolysis in the viral lysate, whereas particle associated APase activity dominates in the lysozyme treatments. Moreover, nutrient status prior to lysis has important controls on the initial nutrient release and subsequent regenerative flux. These findings underscore the significance of lysis and subsequent enzyme-mediated hydrolysis in nutrient regeneration and biogeochemical dynamics in marine ecosystems.

An immunological approach to quantifying the saprotrophic growth dynamics of Trichoderma species during antagonistic interactions with Rhizoctonia solani in a soil-less mix.

PubMed

Thornton, Christopher R

2004-04-01

Studies of the saprotrophic growth dynamics of Trichoderma species and their fungal hosts during antagonistic interactions are severely hampered by the absence of methods that allow the unambiguous identification and quantification of individual genera in complex environments such as soil or compost containing mixed populations of fungi. Furthermore, methods are required that allow discrimination between active hyphal growth and other components of fungal biomass such as quiescent spores that are produced in large numbers by Trichoderma species. This study details the use of monoclonal antibodies to quantify the saprotrophic growth dynamics of the soil-borne plant pathogen Rhizoctonia solani and biological control strains of Trichoderma asperellum and Trichoderma harzianum during antagonistic interactions in peat-based microcosms. Quantification was based on the immunological detection of constitutive, extracellular antigens that are secreted from the growing tip of Rhizoctonia and Trichoderma mycelium and, in the case of Trichoderma harzianum, from quiescent phialoconidia also. The Trichoderma-specific monoclonal antibody (MF2) binds to a protein epitope of the enzyme glucoamylase, which was shown by immunofluorescence and immunogold electron gold microscopy studies of Trichoderma virens in vitro to be produced at the origin of germ tube emergence in phialoconidia and from the growing tip of germ tubes. In addition, a non-destructive immunoblotting technique showed that the enzyme was secreted during active growth of Trichoderma asperellum mycelium in peat. The Rhizoctonia solani-specific monoclonal antibody (EH2) similarly binds to a protein epitope of a glycoprotein that is secreted during active mycelial growth. Extracts derived from lyophilized mycelium were used as a quantifiable and repeatable source of antigens for construction of calibration curves. These curves were used to convert the absorbance values obtained in ELISA tests of peat extracts to biomass

Diagnosing the Dynamics of Observed and Simulated Ecosystem Gross Primary Productivity with Time Causal Information Theory Quantifiers

DOE PAGES

Sippel, Sebastian; Lange, Holger; Mahecha, Miguel D.; ...

2016-10-20

Data analysis and model-data comparisons in the environmental sciences require diagnostic measures that quantify time series dynamics and structure, and are robust to noise in observational data. This paper investigates the temporal dynamics of environmental time series using measures quantifying their information content and complexity. The measures are used to classify natural processes on one hand, and to compare models with observations on the other. The present analysis focuses on the global carbon cycle as an area of research in which model-data integration and comparisons are key to improving our understanding of natural phenomena. We investigate the dynamics of observedmore » and simulated time series of Gross Primary Productivity (GPP), a key variable in terrestrial ecosystems that quantifies ecosystem carbon uptake. However, the dynamics, patterns and magnitudes of GPP time series, both observed and simulated, vary substantially on different temporal and spatial scales. Here we demonstrate that information content and complexity, or Information Theory Quantifiers (ITQ) for short, serve as robust and efficient data-analytical and model benchmarking tools for evaluating the temporal structure and dynamical properties of simulated or observed time series at various spatial scales. At continental scale, we compare GPP time series simulated with two models and an observations-based product. This analysis reveals qualitative differences between model evaluation based on ITQ compared to traditional model performance metrics, indicating that good model performance in terms of absolute or relative error does not imply that the dynamics of the observations is captured well. Furthermore, we show, using an ensemble of site-scale measurements obtained from the FLUXNET archive in the Mediterranean, that model-data or model-model mismatches as indicated by ITQ can be attributed to and interpreted as differences in the temporal structure of the respective ecological

Diagnosing the Dynamics of Observed and Simulated Ecosystem Gross Primary Productivity with Time Causal Information Theory Quantifiers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sippel, Sebastian; Lange, Holger; Mahecha, Miguel D.

Data analysis and model-data comparisons in the environmental sciences require diagnostic measures that quantify time series dynamics and structure, and are robust to noise in observational data. This paper investigates the temporal dynamics of environmental time series using measures quantifying their information content and complexity. The measures are used to classify natural processes on one hand, and to compare models with observations on the other. The present analysis focuses on the global carbon cycle as an area of research in which model-data integration and comparisons are key to improving our understanding of natural phenomena. We investigate the dynamics of observedmore » and simulated time series of Gross Primary Productivity (GPP), a key variable in terrestrial ecosystems that quantifies ecosystem carbon uptake. However, the dynamics, patterns and magnitudes of GPP time series, both observed and simulated, vary substantially on different temporal and spatial scales. Here we demonstrate that information content and complexity, or Information Theory Quantifiers (ITQ) for short, serve as robust and efficient data-analytical and model benchmarking tools for evaluating the temporal structure and dynamical properties of simulated or observed time series at various spatial scales. At continental scale, we compare GPP time series simulated with two models and an observations-based product. This analysis reveals qualitative differences between model evaluation based on ITQ compared to traditional model performance metrics, indicating that good model performance in terms of absolute or relative error does not imply that the dynamics of the observations is captured well. Furthermore, we show, using an ensemble of site-scale measurements obtained from the FLUXNET archive in the Mediterranean, that model-data or model-model mismatches as indicated by ITQ can be attributed to and interpreted as differences in the temporal structure of the respective ecological

Diagnosing the Dynamics of Observed and Simulated Ecosystem Gross Primary Productivity with Time Causal Information Theory Quantifiers

PubMed Central

Sippel, Sebastian; Mahecha, Miguel D.; Hauhs, Michael; Bodesheim, Paul; Kaminski, Thomas; Gans, Fabian; Rosso, Osvaldo A.

2016-01-01

Data analysis and model-data comparisons in the environmental sciences require diagnostic measures that quantify time series dynamics and structure, and are robust to noise in observational data. This paper investigates the temporal dynamics of environmental time series using measures quantifying their information content and complexity. The measures are used to classify natural processes on one hand, and to compare models with observations on the other. The present analysis focuses on the global carbon cycle as an area of research in which model-data integration and comparisons are key to improving our understanding of natural phenomena. We investigate the dynamics of observed and simulated time series of Gross Primary Productivity (GPP), a key variable in terrestrial ecosystems that quantifies ecosystem carbon uptake. However, the dynamics, patterns and magnitudes of GPP time series, both observed and simulated, vary substantially on different temporal and spatial scales. We demonstrate here that information content and complexity, or Information Theory Quantifiers (ITQ) for short, serve as robust and efficient data-analytical and model benchmarking tools for evaluating the temporal structure and dynamical properties of simulated or observed time series at various spatial scales. At continental scale, we compare GPP time series simulated with two models and an observations-based product. This analysis reveals qualitative differences between model evaluation based on ITQ compared to traditional model performance metrics, indicating that good model performance in terms of absolute or relative error does not imply that the dynamics of the observations is captured well. Furthermore, we show, using an ensemble of site-scale measurements obtained from the FLUXNET archive in the Mediterranean, that model-data or model-model mismatches as indicated by ITQ can be attributed to and interpreted as differences in the temporal structure of the respective ecological time

THE COMPARISON OF TWO WATERSHEDS USING A WATERSHED NUTRIENT LOADING MODEL

EPA Science Inventory

Monitoring data, collected from the Yaquina River, Oregon, from 1999 through 2002 were used as the basis for developing the nutrient flux model as part of a larger agency program for quantifying nutrient processes. The PNWL nitrate loading model indicates that the nitrate load is...

Stormflow influence on nutrient dynamics in micro-catchments under contrasting land use in the Cerrado and Amazon Biomes, Brazil

NASA Astrophysics Data System (ADS)

Edelmann, Katharina; Nóbrega, Rodolfo L. B.; Gerold, Gerhard

2017-04-01

The Amazon and Cerrado biomes in Brazil have been under intense land-use change during the past few decades. The conversion of native vegetation to pastures and croplands has caused impacts on hydrological processes in these biomes, resulting in increased streamflow and nutrient fluxes. Our aim was to compare the nutrient dynamics during stormflow events in two pairs of adjacent micro-catchments with similar physical characteristics under contrasting land use, i.e. native vegetation (rainforest or cerrado) and pasture. One pair of catchments was located in the Amazon and the other in the Cerrado, both on the Amazon Agricultural Frontier in the Brazilian states of Mato Grosso and Pará. We collected hydrological and hydrochemical data on 50 stormflow events on a sub-hourly resolution during the wet seasons of 2013 and 2014. We compared the dynamics of total inorganic carbon (TIC), total organic carbon (TOC), dissolved organic carbon (DOC), nitrate (NO3), calcium (Ca), potassium (K), and magnesium (Mg) in different hydrograph parts, i.e. rising limb, peak and recession limb, between the catchments within the same biome. For the Cerrado biome, our findings show that the nutrient concentrations in the stormflows were higher in the pasture catchment than in the cerrado catchment. In the Amazon biome, we found an inverse relationship with higher concentrations in the forest catchment than in the pasture catchment, except for TIC and K. Most nutrients in the cerrado catchment had the highest concentrations in the rising limb. Mg, however, reached highest concentrations during peak discharge, and lowest in the recession limb. In the adjacent pasture catchment, in contrast, the highest nutrient concentrations were observed during the peak discharge (TIC, TOC, Ca) or the recession limb (DOC, NO3, K, Mg) with lowest in the rising limb, except for NO3, which showed the lowest concentrations during peak discharge. In the Amazon forest catchment, the peak discharge showed the

Drug-nutrient interactions in transplant recipients.

PubMed

Chan, L N

2001-01-01

Drug-nutrient interaction refers to an alteration of kinetics or dynamics of a drug or a nutritional element, or a compromise in nutritional status as a result of the addition of a drug. The potentials for drug-nutrient interaction increase with the number of drugs taken by the patient. Organ transplant recipients are therefore at high risk for drug-nutrient interactions because multiple medications are used to manage graft rejection, opportunistic infections, and other associated complications. Unrecognized or unmanaged drug-nutrient interactions in this patient population can have an adverse impact on their outcomes. This paper reviews the importance of recognizing drug-nutrient interaction when using cyclosporine-based regimens.

The dynamics of food chains under climate change and nutrient enrichment.

PubMed

Binzer, Amrei; Guill, Christian; Brose, Ulrich; Rall, Björn C

2012-11-05

Warming has profound effects on biological rates such as metabolism, growth, feeding and death of organisms, eventually affecting their ability to survive. Using a nonlinear bioenergetic population-dynamic model that accounts for temperature and body-mass dependencies of biological rates, we analysed the individual and interactive effects of increasing temperature and nutrient enrichment on the dynamics of a three-species food chain. At low temperatures, warming counteracts the destabilizing effects of enrichment by both bottom-up (via the carrying capacity) and top-down (via biological rates) mechanisms. Together with increasing consumer body masses, warming increases the system tolerance to fertilization. Simultaneously, warming increases the risk of starvation for large species in low-fertility systems. This effect can be counteracted by increased fertilization. In combination, therefore, two main drivers of global change and biodiversity loss can have positive and negative effects on food chain stability. Our model incorporates the most recent empirical data and may thus be used as the basis for more complex forecasting models incorporating food-web structure.

Nutrient sequestration in Aquitaine lakes (SW France) limits nutrient flux to the coastal zone

NASA Astrophysics Data System (ADS)

Buquet, Damien; Anschutz, Pierre; Charbonnier, Céline; Rapin, Anne; Sinays, Rémy; Canredon, Axel; Bujan, Stéphane; Poirier, Dominique

2017-12-01

Oligotrophic coastal zones are disappearing from increased nutrient loading. The quantity of nutrients reaching the coast is determined not only by their original source (e.g. fertilizers used in agriculture, waste water discharges) and the land use, but also by the pathways through which nutrients are cycled from the source to the river mouth. In particular, lakes sequester nutrients and, hence, reduce downstream transfer of nutrients to coastal environments. Here, we quantify the impact of Aquitaine great lakes on the fluxes of dissolved macro-nutrients (N, P, Si) to the Bay of Biscay. For that, we have measured nutrient concentrations and fluxes in 2014 upstream and downstream lakes of Lacanau and Carcans-Hourtin, which belongs to the catchment of the Arcachon Bay, which is the largest coastal lagoon of the Bay of Biscay French coast. Data were compared to values obtained from the Leyre river, the main freshwater and nutrient source for the lagoon. Results show that processes in lakes greatly limit nutrient flux to the lagoon compared to fluxes from Leyre river, although the watershed is similar in terms of land cover. In lakes, phosphorus and silicon are trapped for long term in the sediment, silicon as amorphous biogenic silica and phosphorus as organic P and P associated with Fe-oxides. Nitrogen that enters lakes mostly as nitrate is used for primary production. N is mineralized in the sediment; a fraction diffuses as ammonium. N2 production through benthic denitrification extracts only 10% of dissolved inorganic nitrogen from the aquatic system. The main part is sequestered in organic-rich sediment that accumulates below 5 m depth in both lakes.

Exogenous stress hormones alter energetic and nutrient costs of development and metamorphosis.

PubMed

Kirschman, Lucas J; McCue, Marshall D; Boyles, Justin G; Warne, Robin W

2017-09-15

Variation in environmental conditions during larval life stages can shape development during critical windows and have lasting effects on the adult organism. Changes in larval developmental rates in response to environmental conditions, for example, can trade off with growth to determine body size and condition at metamorphosis, which can affect adult survival and fecundity. However, it is unclear how use of energy and nutrients shape trade-offs across life-stage transitions because no studies have quantified these costs of larval development and metamorphosis. We used an experimental approach to manipulate physiological stress in larval amphibians, along with respirometry and 13 C-breath testing to quantify the energetic and nutritional costs of development and metamorphosis. Central to larval developmental responses to environmental conditions is the hypothalamic-pituitary-adrenal/interrenal (HPA/I) axis, which regulates development, as well as energy homeostasis and stress responses across many taxa. Given these pleiotropic effects of HPA/I activity, manipulation of the HPA/I axis may provide insight into costs of metamorphosis. We measured the energetic and nutritional costs across the entire larval period and metamorphosis in a larval amphibian exposed to exogenous glucocorticoid (GC) hormones - the primary hormone secreted by the HPA/I axis. We measured metabolic rates and dry mass across larval ontogeny, and quantified lipid stores and nutrient oxidation via 13 C-breath testing during metamorphosis, under control and GC-exposed conditions. Changes in dry mass match metamorphic states previously reported in the literature, but dynamics of metabolism were influenced by the transition from aquatic to terrestrial respiration. GC-treated larvae had lower dry mass, decreased fat stores and higher oxygen consumption during stages where controls were conserving energy. GC-treated larvae also oxidized greater amounts of 13 C-labelled protein stores. These results

Quantifying ocean and ice sheet contributions to nutrient fluxes in Sermilik Fjord, Southeast Greenland

NASA Astrophysics Data System (ADS)

Cape, M. R.; Straneo, F.; Beaird, N.; Bundy, R.; Charette, M. A.

2016-12-01

Meltwater discharged at the margins of the Greenland Ice Sheet (GrIS) represents a potential source of nutrients to biological communities downstream. In Greenland's glacial fjords, this discharge occurs at depth below and along the face of deeply grounded marine-terminating glaciers. This process drives vigorous circulation and mixing between melt and ambient waters at the ice-ocean margins, giving rise to a new glacially modified water mass (GMW) which constitutes the primary vehicle for transport of meltwater in the marine environment. While previous field studies have noted nutrient enrichment in GMW with respect to unmodified waters along the shelf, the source of this enrichment, whether due to entrainment of deep ambient waters or input by meltwater, remains poorly understood. This knowledge is however critical in order to evaluate the current and future contributions of the GrIS to marine biogeochemical cycling. Here we shed light on the distribution, composition, and properties of GMW along the GrIS margin by analyzing integrated physical and chemical measurements collected in August 2015 in Sermilik Fjord, a major glacial freshwater export pathway. Our results document up to a doubling of nutrient concentrations (nitrate, silicate, phosphate, and iron) in GMW, which is distributed in the top 300 m of the water column throughout the fjord. Partitioning of ocean and ice sheet contributions to GMW nutrient load demonstrates that upwelled waters are the primary source of macro-nutrients to GMW. We expand on these results to discuss the magnitude of fluxes in context of previous observations along the GrIS margins, export pathways of GMW to the shelf, and knowledge gaps needed to be addressed to better constrain ice sheet contributions to marine ecosystem processes.

Sewage-derived nutrient dynamics in highly urbanized coastal rivers, western Japan

NASA Astrophysics Data System (ADS)

Onodera, S. I.; Saito, M.; Jin, G.; Taniguchi, M.

2016-12-01

Water pollution by domestic sewage is one of the critical environmental problems in the early stage of urbanization with significant growth of population. In case of Osaka metropolitan area in Japan, the pollution was significant until 1970s, while it has been improved by the development of sewage treatment systems. However, removal of nitrogen needs the advanced process therefore relatively large part of dissolved inorganic nitrogen (DIN) is usually discharged by treated sewage effluent. Besides, increase of sewage-derived pollutant loads through the combined sewage systems during rainfall events is recognized as a new problem in recent years. However, the impacts of sewage-derived loads on the water environment of river and coastal area have not been fully evaluated in previous studies. In the present research, we aimed to examine the dynamics of sewage-derived nutrients in highly urbanized coastal rivers. Study area is located on the coastal area of Osaka bay in Seto Inland Sea, western Japan. Treated sewage effluent is discharged from three sewage treatment plants (KH, SU and SA) to a river and channels. Water and sediment samples were collected and electric conductivity (EC), chlorophyll-a (Chl.-a) and dissolved oxygen concentration (DO) were measured from the discharging points to few kilometers offshore at 100-300 m intervals. Nutrients (nitrogen, phosphorus and silica), nitrogen and carbon contents and stable isotope ratios (δ15N and δ13C) of particulate organic matter (POM) and sediment, nitrogen and oxygen stable isotope ratios (δ15N and δ18O) in nitrate (NO3-) were measured. Nitrate-nitrogen (NO3-N) concentration were significantly high near the discharging point then it decreased to offshore suggesting that impact zone of sewage effluent is about 1 km from the discharging point. Significant NO3-N uptake by phytoplankton as well as dilution process were suggested in the area. However, the impact zone expanded more than twofold during the rainfall

Phytoplankton and nutrient dynamics in Winyah Bay, SC.

NASA Astrophysics Data System (ADS)

Boneillo, G. E.; Brooks, S. S.; Brown, S. L.; Woodford, K. M.; Wright, C. R.

2016-02-01

Winyah Bay is a coastal plain estuary located in South Carolina that has been classified for a moderate risk of Eutrophication by NOAA. Winyah Bay receives freshwater input from four rivers, the Waccamaw, Sampit, Black, and Pee Dee Rivers. The Waccamaw, Sampit and Black River are blackwater systems that discharge elevated amounts of colored dissolved organic matter. During the summer and fall of 2015, bioassay experiments were performed to simultaneously examine both light and nutrient (nitrogen & phosphate) limitation throughout Winyah Bay. Sampling stations near the mouth of the Waccamaw and Sampit Rivers showed that phytoplankton were light limited in the late summer instead of nutrient limited. These stations were located in the industrialized area of the bay and typically had the highest nutrient concentrations and highest turbidity, with Secchi depths typically less than 0.5 meters. Results indicated that phytoplankton may be nitrogen limited near the mouth of Winyah Bay, where nutrient concentrations and turbidity were observed to be lower than locations further upstream. There was also an observed dissolved oxygen and pH gradient during the summer of 2015. Dissolved oxygen levels less than 4.0 mg/L were routinely observed near the industrialized head of the estuary and corresponded with lower pH values.

Estimates of Nutrient Loading by Ground-Water Discharge into the Lynch Cove Area of Hood Canal, Washington

USGS Publications Warehouse

Simonds, F. William; Swarzenski, Peter W.; Rosenberry, Donald O.; Reich, Christopher D.; Paulson, Anthony J.

2008-01-01

Low dissolved oxygen concentrations in the waters of Hood Canal threaten marine life in late summer and early autumn. Oxygen depletion in the deep layers and landward reaches of the canal is caused by decomposition of excess phytoplankton biomass, which feeds on nutrients (primarily nitrogen compounds) that enter the canal from various sources, along with stratification of the water column that prevents mixing and replenishment of oxygen. Although seawater entering the canal is the largest source of nitrogen, ground-water discharge to the canal also contributes significant quantities, particularly during summer months when phytoplankton growth is most sensitive to nutrient availability. Quantifying ground-water derived nutrient loads entering an ecologically sensitive system such as Hood Canal is a critical component of constraining the total nutrient budget and ultimately implementing effective management strategies to reduce impacts of eutrophication. The amount of nutrients entering Hood Canal from ground water was estimated using traditional and indirect measurements of ground-water discharge, and analysis of nutrient concentrations. Ground-water discharge to Hood Canal is variable in space and time because of local geology, variable hydraulic gradients in the ground-water system adjacent to the shoreline, and a large tidal range of 3 to 5 meters. Intensive studies of ground-water seepage and hydraulic-head gradients in the shallow, nearshore areas were used to quantify the freshwater component of submarine ground-water discharge (SGD), whereas indirect methods using radon and radium geochemical tracers helped quantify total SGD and recirculated seawater. In areas with confirmed ground-water discharge, shore-perpendicular electrical resistivity profiles, continuous electromagnetic seepage-meter measurements, and continuous radon measurements were used to visualize temporal variations in ground-water discharge over several tidal cycles. The results of these

Can uptake length in strams be determined by nutrient addition experiments? Results from an interbiome comparison study

Treesearch

P. J Mulholland; J. L. Tanks; J. R. Webster; W. B. Bowden; W. K Dodds; S. V. Gregory; N. B Grimm; J. L. Meriam; J. L. Meyer; B. J. Peterson; H. M. Valett; W. M. Wollheim

2002-01-01

Nutrient uptake length is an important parnmeter tor quantifying nutrient cycling in streams. Although nutrient tracer additions are the preierred method for measuring uptake length under ambient nutrient concentrations, short-term nutrient addition experiments have more irequently been used to estimate uptake length in streams. Theoretical analysis of the relationship...

Implementation of sediment dynamics in a global integrated assessment model for an improved simulation of nutrient retention and transfers in surface freshwaters

NASA Astrophysics Data System (ADS)

Vilmin, L.; Beusen, A.; Mogollón, J.; Bouwman, L.

2017-12-01

Sediment dynamics play a significant role in river biogeochemical functioning. They notably control the transfer of particle-bound nutrients, have a direct influence on light availability for primary production, and particle accumulation can affect oxic conditions of river beds. In the perspective of improving our current understanding of large scale nutrient fluxes in rivers, it is hence necessary to include these dynamics in global models. In this scope, we implement particle accumulation and remobilization in a coupled global hydrology-nutrient model (IMAGE-GNM), at a spatial resolution of 0.5°. The transfer of soil loss from natural and agricultural lands is simulated mechanistically, from headwater streams to estuaries. First tests of the model are performed in the Mississippi river basin. At a yearly time step for the period 1978-2000, the average difference between simulated and measured suspended sediment concentrations at the most downstream monitoring station is 25%. Sediment retention is estimated in the different Strahler stream orders, in lakes and reservoirs. We discuss: 1) the distribution of sediment loads to small streams, which has a significant effect on transfers through watersheds and larger scale river fluxes and 2) the potential effect of damming on the fate of particle-bound nutrients. These new developments are crucial for future assessments of large scale nutrient and carbon fluxes in river systems.

Energy and nutrient flows connecting coastal wetland food webs to land and lake

EPA Science Inventory

Both landscape character and hydrologic forces (principally, tributary discharge and seiches) can influence utilization of externally-derived energy and nutrients in coastal wetland food webs. We quantified the contribution of internal vs external energy and nutrients among wetla...

Dynamic investigation of nutrient consumption and injection strategy in microbial enhanced oil recovery (MEOR) by means of large-scale experiments.

PubMed

Song, Zhiyong; Zhu, Weiyao; Sun, Gangzheng; Blanckaert, Koen

2015-08-01

Microbial enhanced oil recovery (MEOR) depends on the in situ microbial activity to release trapped oil in reservoirs. In practice, undesired consumption is a universal phenomenon but cannot be observed effectively in small-scale physical simulations due to the scale effect. The present paper investigates the dynamics of oil recovery, biomass and nutrient consumption in a series of flooding experiments in a dedicated large-scale sand-pack column. First, control experiments of nutrient transportation with and without microbial consumption were conducted, which characterized the nutrient loss during transportation. Then, a standard microbial flooding experiment was performed recovering additional oil (4.9 % Original Oil in Place, OOIP), during which microbial activity mostly occurred upstream, where oil saturation declined earlier and steeper than downstream in the column. Subsequently, more oil remained downstream due to nutrient shortage. Finally, further research was conducted to enhance the ultimate recovery by optimizing the injection strategy. An extra 3.5 % OOIP was recovered when the nutrients were injected in the middle of the column, and another additional 11.9 % OOIP were recovered by altering the timing of nutrient injection.

Soil Properties, Nutrient Dynamics, and Soil Enzyme Activities Associated with Garlic Stalk Decomposition under Various Conditions

PubMed Central

Han, Xu; Cheng, Zhihui; Meng, Huanwen

2012-01-01

The garlic stalk is a byproduct of garlic production and normally abandoned or burned, both of which cause environmental pollution. It is therefore appropriate to determine the conditions of efficient decomposition, and equally appropriate to determine the impact of this decomposition on soil properties. In this study, the soil properties, enzyme activities and nutrient dynamics associated with the decomposition of garlic stalk at different temperatures, concentrations and durations were investigated. Stalk decomposition significantly increased the values of soil pH and electrical conductivity. In addition, total nitrogen and organic carbon concentration were significantly increased by decomposing stalks at 40°C, with a 5∶100 ratio and for 10 or 60 days. The highest activities of sucrase, urease and alkaline phosphatase in soil were detected when stalk decomposition was performed at the lowest temperature (10°C), highest concentration (5∶100), and shortest duration (10 or 20 days). The evidence presented here suggests that garlic stalk decomposition improves the quality of soil by altering the value of soil pH and electrical conductivity and by changing nutrient dynamics and soil enzyme activity, compared to the soil decomposition without garlic stalks. PMID:23226411

Nutrient dynamics in five off-stream reservoirs in the lower South Platte River basin, March-September 1995

USGS Publications Warehouse

Sprague, Lori A.

2002-01-01

In 1995, the U.S. Geological Survey conducted a study to characterize nutrient concentrations in five off-stream reservoirs in the lower South Platte River Basin?Riverside, Jackson, Prewitt, North Sterling, and Julesburg. These reservoirs are critical sources of irrigation water for agricultural areas, and several also are used for fishing, boating, swimming, hunting, and camping. Data collected for this study include depth profiles of water temperature, dissolved oxygen, pH, and specific conductance; nutrient species concentrations in the water column, bottom sediment, and inflow and outflow canals; and chlorophyll-a concentrations in the water column. Data were collected during the irrigation season from March through September 1995 at five sites each in Riverside, Jackson, Prewitt, and Julesburg Reservoirs and at six sites in North Sterling Reservoir. The five reservoirs studied are located in similar geographic, climatic, and land-use areas and, as a result, have a number of similarities in their internal nutrient dynamics. Nitrogen concentrations in the reservoirs were highest in March and decreased through September as a result of dilution from river inflows and biological activity. From March through June, decreases in nitrogen concentrations in the river and biological activity contributed to decreases in reservoir concentrations. From July through September, inflows from the river were cut off, and biological activity in the reservoirs led to further decreases in nitrate concentrations, which fell to near or below detectable levels. Phosphorus concentrations in the reservoirs did not show the same consistent decrease from March through September. Phosphorus likely was recycled continuously back to algae during the study period through processes such as excretion from fish, decay of aquatic plants and animals, and release of orthophosphate from bottom sediment during periods of low oxygen. With the exception of phosphorus in Jackson Reservoir, the

Nutrient dynamics and budget with the surface water-groundwater interaction in the tidal river in Japan

NASA Astrophysics Data System (ADS)

Onodera, S.; Saito, M.; Maruyama, Y.; Jin, G.; Miyaoka, K.; Shimizu, Y.

2013-12-01

In coastal megacities, sever groundwater depression and water pollution occurred. These impacts affected to river environment change. Especially, the river mouth area has been deposited the polluted matters. These areas have characteristics of water level fluctuation which causes river water-groundwater interaction and the associated change in dynamics of nutrients. However, these effects on the nutrient transport in tidal reaches and nutrient load to the sea have not been fully evaluated in previous studies. Therefore, we aimed to clarify the characteristics of the nutrient transport with the river water-groundwater interaction in the tidal river of Osaka metropolitan city. We conducted the field survey from the river mouth to the 7km upstream area of Yamato River, which has a length of 68km and a watershed area of 1070 km2. Spatial variations in radon (222Rn) concentrations and the difference of hydraulic potential between river waters and the pore waters suggest that the groundwater discharges to the river channel in the upstream area. In contrast, the river water recharged into the groundwater near the river mouth area. It may be caused by the lowering of groundwater level associated with the excess abstraction of groundwater in the urban area. The result also implies the seawater intrusion would accelerate the salinization of groundwater. The spatial and temporal variations in nutrient concentrations indicate that nitrate-nitrogen (NO3-N) concentrations changed temporally and it negative correlated with dissolved organic nitrogen (DON) concentrations. Inorganic phosphorous (PO4-P) concentrations showed the increasing trend with the increase of the river water level. Based on the mass balance, nutrient reproduction from the river bed was suggested in tidal reach. That was estimated to be 10 % of total nitrogen and 3% of phosphorus loads from the upstream.

Relationship of nutrient dynamics and bacterial community structure at the water-sediment interface using a benthic chamber experiment.

PubMed

Ki, Bo-Min; Huh, In Ae; Choi, Jung-Hyun; Cho, Kyung-Suk

2018-04-16

The relationships between nutrient dynamics and the bacterial community at the water-sediment interface were investigated using the results of nutrient release fluxes, bacterial communities examined by 16S rRNA pyrosequencing and canonical correlation analysis (CCA) accompanied by lab-scale benthic chamber experiment. The nutrient release fluxes from the sediments into the water were as follows: -3.832 to 12.157 mg m -2 d -1 for total phosphorus, 0.049 to 9.993 mg m -2 d -1 for PO 4 -P, -2.011 to 41.699 mg m -2 d -1 for total nitrogen, -7.915 to -0.074 mg m -2 d -1 for NH 3 -N, and -17.940 to 1.209 mg m -2 d -1 for NO 3 -N. To evaluate the relationship between the bacterial communities and environmental variables, CCA was conducted in three representative conditions: in the overlying water, in the sediment at a depth of 0-5 cm, and in the sediment at a depth of 5-15 cm. CCA results showed that environmental variables such as nutrient release fluxes (TN, NH 4 , NO 3 , TP, and PO 4 ) and water chemical parameters (pH, DO, COD, and temperature) were highly correlated with the bacterial communities. From the results of the nutrient release fluxes and the bacterial community, this study proposed the hypothesis for bacteria involved in the nutrient dynamics at the interface between water and sediment. In the sediment, sulfate-reducing bacteria (SRB) such as Desulfatibacillum, Desulfobacterium, Desulfomicrobium, and Desulfosalsimonas are expected to contribute to the decomposition of organic matter, and release of ammonia (NH 4 + ) and phosphate (PO 4 3- ). The PO 4 3- released into the water layer was observed by the positive fluxes of PO 4 3- . The NH 4 + released from the sediment was rapidly oxidized by the methane-oxidizing bacteria (MOB). This study observed in the water layer dominantly abundant MOB of Methylobacillus, Methylobacter, Methylocaldum, and Methylophilus. The nitrate (NO 3 - ) accumulation caused by the oxidation environment of the water layer

Biomass and nutrient mass of Acacia dealbata and Eucalyptus globulus bioenergy plantations

Treesearch

Timothy J. Albaugh; Rafael A. Rubilar; Chris A. Maier; Eduardo A. Acuña; Rachel L. Cook

2017-01-01

We quantified biomass and nutrient accumulation of Acacia dealbata Link and Eucalyptus globulus Labill. planted at stem densities of 5000 and 15000 ha-1 in a bioenergy plantation in Chile. We tested the hypotheses that species and stocking will not affect biomass or nutrient accumulation. Species and...

Quantifying Periphyton Community Responses to Nutrients in a Southeast Coastal Plain Watershed using a Molecular Approach

EPA Science Inventory

Nutrient (nitrogen and phosphorus) pollution is a water quality issue in the US, including within the southeastern states that comprise US EPA Region 4. Biotic condition of southeastern streams with respect to nutrients has been evaluated using biological indicators based on mac...

The Impact of High-Turbidity Water's Seasonal and Decadal Variations on Offshore Phytoplankton and Nutrients Dynamics around The Changjiang Estuary

NASA Astrophysics Data System (ADS)

Ge, J.; Torres, R.; Chen, C.; Bellerby, R. G. J.

2017-12-01

The Changjiang Estuary is characterized as strong river discharge into the inner shelf of the East China Sea with abundant sediment load, producing significant high-turbidity water coverage from river mouth to deep region. The growth of offshore phytoplankton is dynamically controlled by river flushed low-salinity and high-turbidity water, and salter water from inner shelf of East China Sea. During last decade, the sediment and nutrients from the Changjiang River has significantly changed, which lead to the variation of offshore phytoplankton dynamics. The variations of sediment, nutrients, and their influenced phytoplankton has been simulated through a comprehensive modeling system, which integrated a multi-scale current-wave-sediment FVCOM model and generic marine biogeochemistry and ecosystem ERSEM model through The Framework for Aquatic Biogeochemical Models (FABM). This model system has successfully revealed the seasonal and decadal variations of sediment, nutrients transport around the inner shelf of the East China Sea. The spring and autumn peaks of phytoplankton growth were correctly captured by simulation. The modeling results, as well as MODIS and GOCI remote sensing, shows a strong sediment decreasing from northern to southern region, which creates different patterns of Chlorophyll-a distribution and seasonal variations. These results indicate the high-turbidity water in northern region strongly influenced the light attenuation in the water column and limits the phytoplankton growth in this relatively higher-nutrient area, especially in the wintertime. The relatively low-turbidity southern region has significant productivity of phytoplankton, even during low-temperature winter. The phytoplankton growth increased in the northern region from 2005 to 2010, with the increase of the nutrient load during this period. Then it became a decreasing trend after 2010.

Sequential nutrient uptake as a potential mechanism for phytoplankton to maintain high primary productivity and balanced nutrient stoichiometry

NASA Astrophysics Data System (ADS)

Yin, Kedong; Liu, Hao; Harrison, Paul J.

2017-05-01

We hypothesize that phytoplankton have the sequential nutrient uptake strategy to maintain nutrient stoichiometry and high primary productivity in the water column. According to this hypothesis, phytoplankton take up the most limiting nutrient first until depletion, continue to draw down non-limiting nutrients and then take up the most limiting nutrient rapidly when it is available. These processes would result in the variation of ambient nutrient ratios in the water column around the Redfield ratio. We used high-resolution continuous vertical profiles of nutrients, nutrient ratios and on-board ship incubation experiments to test this hypothesis in the Strait of Georgia. At the surface in summer, ambient NO3- was depleted with excess PO43- and SiO4- remaining, and as a result, both N : P and N : Si ratios were low. The two ratios increased to about 10 : 1 and 0. 45 : 1, respectively, at 20 m. Time series of vertical profiles showed that the leftover PO43- continued to be removed, resulting in additional phosphorus storage by phytoplankton. The N : P ratios at the nutricline in vertical profiles responded differently to mixing events. Field incubation of seawater samples also demonstrated the sequential uptake of NO3- (the most limiting nutrient) and then PO43- and SiO4- (the non-limiting nutrients). This sequential uptake strategy allows phytoplankton to acquire additional cellular phosphorus and silicon when they are available and wait for nitrogen to become available through frequent mixing of NO3- (or pulsed regenerated NH4). Thus, phytoplankton are able to maintain high productivity and balance nutrient stoichiometry by taking advantage of vigorous mixing regimes with the capacity of the stoichiometric plasticity. To our knowledge, this is the first study to show the in situ dynamics of continuous vertical profiles of N : P and N : Si ratios, which can provide insight into the in situ dynamics of nutrient stoichiometry in the water column and the inference of

Linkages between nutrients and assemblages of macroinvertebrates and fish in wadeable streams: Implication to nutrient criteria development

USGS Publications Warehouse

Wang, L.; Robertson, Dale M.; Garrison, P.J.

2007-01-01

We sampled 240 wadeable streams across Wisconsin for different forms of phosphorus and nitrogen, and assemblages of macroinvertebrates and fish to (1) examine how macroinvertebrate and fish measures correlated with the nutrients; (2) quantify relationships between key biological measures and nutrient forms to identify potential threshold levels of nutrients to support nutrient criteria development; and (3) evaluate the importance of nutrients in influencing biological assemblages relative to other physicochemical factors at different spatial scales. Twenty-three of the 35 fish and 18 of the 26 macroinvertebrate measures significantly correlated (P < 0.05) with at least one nutrient measure. Percentages of carnivorous, intolerant, and omnivorous fishes, index of biotic integrity, and salmonid abundance were fish measures correlated with the most nutrient measures and had the highest correlation coefficients. Percentages of Ephemeroptera-Plecoptera-Trichoptera individuals and taxa, Hilsenhoff biotic index, and mean tolerance value were macroinvertebrate measures that most strongly correlated with the most nutrient measures. Selected biological measures showed clear trends toward degradation as concentrations of phosphorus and nitrogen increased, and some measures showed clear thresholds where biological measures changed drastically with small changes in nutrient concentrations. Our selected environmental factors explained 54% of the variation in the fish assemblages. Of this explained variance, 46% was attributed to catchment and instream habitat, 15% to nutrients, 3% to other water quality measures, and 36% to the interactions among all the environmental variables. Selected environmental factors explained 53% of the variation in macroinvertebrate assemblages. Of this explained variance, 42% was attributed to catchment and instream habitat, 22% to nutrients, 5% to other water quality measures, and 32% to the interactions among all the environmental variables. ?? 2006

Linkages Between Nutrients and Assemblages of Macroinvertebrates and Fish in Wadeable Streams: Implication to Nutrient Criteria Development

NASA Astrophysics Data System (ADS)

Wang, Lizhu; Robertson, Dale M.; Garrison, Paul J.

2007-02-01

We sampled 240 wadeable streams across Wisconsin for different forms of phosphorus and nitrogen, and assemblages of macroinvertebrates and fish to (1) examine how macroinvertebrate and fish measures correlated with the nutrients; (2) quantify relationships between key biological measures and nutrient forms to identify potential threshold levels of nutrients to support nutrient criteria development; and (3) evaluate the importance of nutrients in influencing biological assemblages relative to other physicochemical factors at different spatial scales. Twenty-three of the 35 fish and 18 of the 26 macroinvertebrate measures significantly correlated ( P < 0.05) with at least one nutrient measure. Percentages of carnivorous, intolerant, and omnivorous fishes, index of biotic integrity, and salmonid abundance were fish measures correlated with the most nutrient measures and had the highest correlation coefficients. Percentages of Ephemeroptera-Plecoptera-Trichoptera individuals and taxa, Hilsenhoff biotic index, and mean tolerance value were macroinvertebrate measures that most strongly correlated with the most nutrient measures. Selected biological measures showed clear trends toward degradation as concentrations of phosphorus and nitrogen increased, and some measures showed clear thresholds where biological measures changed drastically with small changes in nutrient concentrations. Our selected environmental factors explained 54% of the variation in the fish assemblages. Of this explained variance, 46% was attributed to catchment and instream habitat, 15% to nutrients, 3% to other water quality measures, and 36% to the interactions among all the environmental variables. Selected environmental factors explained 53% of the variation in macroinvertebrate assemblages. Of this explained variance, 42% was attributed to catchment and instream habitat, 22% to nutrients, 5% to other water quality measures, and 32% to the interactions among all the environmental variables.

Quantifying the dynamics of emotional expressions in family therapy of patients with anorexia nervosa.

PubMed

Pezard, Laurent; Doba, Karyn; Lesne, Annick; Nandrino, Jean-Louis

2017-07-01

Emotional interactions have been considered dynamical processes involved in the affective life of humans and their disturbances may induce mental disorders. Most studies of emotional interactions have focused on dyadic behaviors or self-reports of emotional states but neglected the dynamical processes involved in family therapy. The main objective of this study is to quantify the dynamics of emotional expressions and their changes using the family therapy of patients with anorexia nervosa as an example. Nonlinear methods characterize the variability of the dynamics at the level of the whole therapeutic system and reciprocal influence between the participants during family therapy. Results show that the variability of the dynamics is higher at the end of the therapy than at the beginning. The reciprocal influences between therapist and each member of the family and between mother and patient decrease with the course of family therapy. Our results support the development of new interpersonal strategies of emotion regulation during family therapy. The quantification of emotional dynamics can help understanding the emotional processes underlying psychopathology and evaluating quantitatively the changes achieved by the therapeutic intervention. Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.

Invasive fishes generate biogeochemical hotspots in a nutrient-limited system.

PubMed

Capps, Krista A; Flecker, Alexander S

2013-01-01

Fishes can play important functional roles in the nutrient dynamics of freshwater systems. Aggregating fishes have the potential to generate areas of increased biogeochemical activity, or hotspots, in streams and rivers. Many of the studies documenting the functional role of fishes in nutrient dynamics have focused on native fish species; however, introduced fishes may restructure nutrient storage and cycling freshwater systems as they can attain high population densities in novel environments. The purpose of this study was to examine the impact of a non-native catfish (Loricariidae: Pterygoplichthys) on nitrogen and phosphorus remineralization and estimate whether large aggregations of these fish generate measurable biogeochemical hotspots within nutrient-limited ecosystems. Loricariids formed large aggregations during daylight hours and dispersed throughout the stream during evening hours to graze benthic habitats. Excretion rates of phosphorus were twice as great during nighttime hours when fishes were actively feeding; however, there was no diel pattern in nitrogen excretion rates. Our results indicate that spatially heterogeneous aggregations of loricariids can significantly elevate dissolved nutrient concentrations via excretion relative to ambient nitrogen and phosphorus concentrations during daylight hours, creating biogeochemical hotspots and potentially altering nutrient dynamics in invaded systems.

Invasive Fishes Generate Biogeochemical Hotspots in a Nutrient-Limited System

PubMed Central

Capps, Krista A.; Flecker, Alexander S.

2013-01-01

Fishes can play important functional roles in the nutrient dynamics of freshwater systems. Aggregating fishes have the potential to generate areas of increased biogeochemical activity, or hotspots, in streams and rivers. Many of the studies documenting the functional role of fishes in nutrient dynamics have focused on native fish species; however, introduced fishes may restructure nutrient storage and cycling freshwater systems as they can attain high population densities in novel environments. The purpose of this study was to examine the impact of a non-native catfish (Loricariidae: Pterygoplichthys) on nitrogen and phosphorus remineralization and estimate whether large aggregations of these fish generate measurable biogeochemical hotspots within nutrient-limited ecosystems. Loricariids formed large aggregations during daylight hours and dispersed throughout the stream during evening hours to graze benthic habitats. Excretion rates of phosphorus were twice as great during nighttime hours when fishes were actively feeding; however, there was no diel pattern in nitrogen excretion rates. Our results indicate that spatially heterogeneous aggregations of loricariids can significantly elevate dissolved nutrient concentrations via excretion relative to ambient nitrogen and phosphorus concentrations during daylight hours, creating biogeochemical hotspots and potentially altering nutrient dynamics in invaded systems. PMID:23342083

Healthy Snacks: Using Nutrient Profiling to Evaluate the Nutrient-Density of Common Snacks in the United States.

PubMed

Hess, Julie M; Slavin, Joanne L

2017-09-01

To quantify and compare the nutrient-density of commonly consumed snacks using two nutrient-density measures, Nutrient Rich Foods Indices 9.3 (NRF 9.3) and 15.3 (NRF 15.3). Identify commonly consumed categories of snacks and individual snack foods, calculate NRF 9.3 and 15.3 scores, rank snacks by category and by individual food based on nutrient density, compare and contrast scores generated by the two NRF Indices. NRF 9.3 and 15.3 scores. Averages and standard deviations of nutrient-density scores for each snack category. Vegetables and coffee/tea received the highest category scores on both indices. Cakes/cookies/pastries and sweets had the lowest category scores. NRF 9.3 scores for individual snacks ranged from -46 (soda) to 524 (coffee). NRF 15.3 scores ranged from -45 (soda) to 736 (coffee). If added to food labels, NRF scores could help consumers identify more nutritious choices. The differences between NRF 9.3 and 15.3 scores generated for the same foods and the limitations of these indices highlight the need for careful consideration of which nutrient-density measure to include on food labels as well as consumer education. © 2017 Institute of Food Technologists®.

Analyzing complex networks evolution through Information Theory quantifiers

NASA Astrophysics Data System (ADS)

Carpi, Laura C.; Rosso, Osvaldo A.; Saco, Patricia M.; Ravetti, Martín Gómez

2011-01-01

A methodology to analyze dynamical changes in complex networks based on Information Theory quantifiers is proposed. The square root of the Jensen-Shannon divergence, a measure of dissimilarity between two probability distributions, and the MPR Statistical Complexity are used to quantify states in the network evolution process. Three cases are analyzed, the Watts-Strogatz model, a gene network during the progression of Alzheimer's disease and a climate network for the Tropical Pacific region to study the El Niño/Southern Oscillation (ENSO) dynamic. We find that the proposed quantifiers are able not only to capture changes in the dynamics of the processes but also to quantify and compare states in their evolution.

Nutrient production from dairy cattle manure and loading on arable land

PubMed Central

You, Byung-Gu; Choi, Yoon-Seok; Ra, Changsix

2017-01-01

Objective Along with increasing livestock products via intensive rearing, the accumulation of livestock manure has become a serious issue due to the fact that there is finite land for livestock manure recycling via composting. The nutrients from livestock manure accumulate on agricultural land and the excess disembogues into streams causing eutrophication. In order to systematically manage nutrient loading on agricultural land, quantifying the amount of nutrients according to their respective sources is very important. However, there is a lack of research concerning nutrient loss from livestock manure during composting or storage on farms. Therefore, in the present study we quantified the nutrients from dairy cattle manure that were imparted onto agricultural land. Methods Through investigation of 41 dairy farms, weight reduction and volatile solids (VS), total nitrogen (TN), and total phosphorus (TP) changes of dairy cattle manure during the storage and composting periods were analyzed. In order to support the direct investigation and survey on site, the three cases of weight reduction during the storing and composting periods were developed according to i) experiment, ii) reference, and iii) theoretical changes in phosphorus content (ΔP = 0). Results The data revealed the nutrient loading coefficients (NLCs) of VS, TN, and TP on agricultural land were 1.48, 0.60, and 0.66, respectively. These values indicated that the loss of nitrogen and phosphorus was 40% and 34%, respectively, and that there was an increase of VS since bedding materials were mixed with excretion in the barn. Conclusion As result of nutrient-footprint analyses, the amounts of TN and TP particularly entered on arable land have been overestimated if applying the nutrient amount in fresh manure. The NLCs obtained in this study may assist in the development of a database to assess the accurate level of manure nutrient loading on soil and facilitate systematic nutrient management. PMID:27492346

Nutrient production from dairy cattle manure and loading on arable land.

PubMed

Won, Seunggun; Shim, Soo-Min; You, Byung-Gu; Choi, Yoon-Seok; Ra, Changsix

2017-01-01

Along with increasing livestock products via intensive rearing, the accumulation of livestock manure has become a serious issue due to the fact that there is finite land for livestock manure recycling via composting. The nutrients from livestock manure accumulate on agricultural land and the excess disembogues into streams causing eutrophication. In order to systematically manage nutrient loading on agricultural land, quantifying the amount of nutrients according to their respective sources is very important. However, there is a lack of research concerning nutrient loss from livestock manure during composting or storage on farms. Therefore, in the present study we quantified the nutrients from dairy cattle manure that were imparted onto agricultural land. Through investigation of 41 dairy farms, weight reduction and volatile solids (VS), total nitrogen (TN), and total phosphorus (TP) changes of dairy cattle manure during the storage and composting periods were analyzed. In order to support the direct investigation and survey on site, the three cases of weight reduction during the storing and composting periods were developed according to i) experiment, ii) reference, and iii) theoretical changes in phosphorus content (ΔP = 0). The data revealed the nutrient loading coefficients (NLCs) of VS, TN, and TP on agricultural land were 1.48, 0.60, and 0.66, respectively. These values indicated that the loss of nitrogen and phosphorus was 40% and 34%, respectively, and that there was an increase of VS since bedding materials were mixed with excretion in the barn. As result of nutrient-footprint analyses, the amounts of TN and TP particularly entered on arable land have been overestimated if applying the nutrient amount in fresh manure. The NLCs obtained in this study may assist in the development of a database to assess the accurate level of manure nutrient loading on soil and facilitate systematic nutrient management.

Subterranean Groundwater Nutrient Input to Coastal Oceans and Coral Reef Sustainability

NASA Astrophysics Data System (ADS)

Paytan, A.; Street, J. H.

2003-12-01

Coral reefs are often referred to as the tropical rain forests of the oceans because of their high productivity and biodiversity. Recent observations in coral reefs worldwide have shown clear degradation in water quality and coral reef health and diversity. The implications of this are severe, including tremendous economic losses mostly though fishing and tourism. Nutrient loading has been implicated as one possible cause for the ecosystem decline. A previously unappreciated potential source of nutrient loading is submarine ground water discharge (SGW). Ground water in many cases has high nutrient content from sewage pollution and fertilizer application for agriculture and landscaping. To better understand the effect of this potential source of nutrient input and degrading water quality, we are exploring the contribution of SGW to the nutrient levels in coral reefs. A key to this approach is determining the amount and source of SGW that flows into the coast as well as its nutrient concentrations. The SGW flux and associated input of chemical dissolved load (nutrient, DOC, trace elements and other contaminants) is quantified using naturally occurring Ra isotopes. Radium isotopes have been shown to be excellent tracers for SGW inputs into estuaries and coastal areas (Moore, 1996; Hussain et al., 1999; Kerst et al., 2000). Measurements of Ra activity within the coral reef, the lagoons and the open waters adjacent to the reef provide valuable information regarding the input of Ra as well as nutrients and possibly pollutant from groundwater discharge. Through this analysis the effect of SGD on the delicate carbon and nutrient balance of the fragile coral reef ecosystem could be evaluated. In addition to quantifying the contribution of freshwater to the nutrient mass balance in the reef, information regarding the length of time a water parcel has remained in the near-shore region over the reef can be estimated using the Ra isotope quartet.

Recovery dynamics of evapotranspiration, flow, sediment and nutrients following severe wildfire in eucalypt forests

NASA Astrophysics Data System (ADS)

Lane, P. N.; Sheridan, G. J.; Nyman, P.; Nolan, R.; Nokse, P. J.

2013-12-01

Wildfire is a particularly significant disturbance event in forested landscapes. Around 40,000 km2 of largely forested land has been burnt in south eastern Australia in the past decade. Fire effects on erosion and water quality have been widely reported and studied in many environments, but nutrient dynamics and evapotranspiration (ET) and streamflow are also of significant concern or interest. However the hydrologic response and recovery trajectories of the majority of eucalypt forests has been poorly known. Likewise, the coupling of ET response with sediment and nutrient dynamics has not been explored widely. Our research over the past decade into sediment, nutrients and ET/flow dynamics in differing forest types has led to new insights into this resilience/recovery question in eucalypt forests. This research has encompassed scales from the point to large catchment, identified the driving processes, and led to models that deal with discrete events and risk/probability frameworks. Broadly, we suggest there are two distinct 'sets' of responses and recovery trajectories depending on forest type. (1) wet eucalypt stands of E. regnans and E. delegatensis and associated 'ash' stands; and (2) the drier 'mixed-species' forests. The hydrologic responses of (1) may be summarized as: (i) Widespread mortality of trees exposed to moderate-hot fire, leading to dense single-age regeneration. ET is suppressed for 1-3 years, then increases to exceed that of a stands > 30 years old, with a concomitant inverse effect on flow. This recovery trajectory may play out until forests reach maturity (~100 years) or are re-burnt (ii) Sediment and nutrients (P and N principally) exports can increase by 1-2 orders of magnitude, but export rates recover with 2 years of the fire. Erosion processes are largely non-rill. Water quality issues (per event) are relatively short term (days) For case (2): (i) These stands are fire-resistant and show low (~10 %) rates of mortality. Leaf are recovery

Time-scale Dependence of Response of an Estuarine Water Quality Model to Nutrient Loading

EPA Science Inventory

We describe calibration and evaluation of a water quality model being implemented for Narragansett Bay to quantify the response of concentrations of nutrients, phytoplankton chlorophyll a and dissolved oxygen in the Bay to loading rates of nutrients and other boundary conditions....

Upland and in-stream controls on baseflow nutrient dynamics in tile-drained agroecosystem watersheds

NASA Astrophysics Data System (ADS)

Ford, William I.; King, Kevin; Williams, Mark R.

2018-01-01

In landscapes with low residence times (e.g., rivers and reservoirs), baseflow nutrient concentration dynamics during sensitive timeframes can contribute to deleterious environmental conditions downstream. This study assessed upland and in-stream controls on baseflow nutrient concentrations in a low-gradient, tile-drained agroecosystem watershed. We conducted time-series analysis using Empirical mode decomposition of seven decade-long nutrient concentration time-series in the agricultural Upper Big Walnut Creek watershed (Ohio, USA). Four tributaries of varying drainage areas and three main-stem sites were monitored, and nutrient grab samples were collected weekly from 2006 to 2016 and analyzed for dissolved reactive phosphorus (DRP), nitrate-nitrogen (NO3-N), total nitrogen (TN), and total phosphorus (TP). Statistically significant seasonal fluctuations were compared with seasonality of baseflow, watershed characteristics (e.g., tile-drain density), and in-stream water quality parameters (pH, DO, temperature). Findings point to statistically significant seasonality of all parameters with peak P concentrations in summer and peak N in late winter-early spring. Results suggest that upland processes exert strong control on DRP concentrations in the winter and spring months, while coupled upland and in-stream conditions control watershed baseflow DRP concentrations during summer and early fall. Conversely, upland flow sources driving streamflow exert strong control on baseflow NO3-N, and in-stream attenuation through transient and permanent pathways impacts the magnitude of removal. Regarding TN and TP, we found that TN was governed by NO3-N, while TP was governed by DRP in summer and fluvial erosion of P-rich benthic sediments during higher baseflow conditions. Findings of the study highlight the importance of coupled in-stream and upland management for mitigating eutrophic conditions during environmentally sensitive timeframes.

Nematodes enhance plant growth and nutrient uptake under C and N-rich conditions.

PubMed

Gebremikael, Mesfin T; Steel, Hanne; Buchan, David; Bert, Wim; De Neve, Stefaan

2016-09-08

The role of soil fauna in crucial ecosystem services such as nutrient cycling remains poorly quantified, mainly because of the overly reductionistic approach adopted in most experimental studies. Given that increasing nitrogen inputs in various ecosystems influence the structure and functioning of soil microbes and the activity of fauna, we aimed to quantify the role of the entire soil nematode community in nutrient mineralization in an experimental set-up emulating nutrient-rich field conditions and accounting for crucial interactions amongst the soil microbial communities and plants. To this end, we reconstructed a complex soil foodweb in mesocosms that comprised largely undisturbed native microflora and the entire nematode community added into defaunated soil, planted with Lolium perenne as a model plant, and amended with fresh grass-clover residues. We determined N and P availability and plant uptake, plant biomass and abundance and structure of the microbial and nematode communities during a three-month incubation. The presence of nematodes significantly increased plant biomass production (+9%), net N (+25%) and net P (+23%) availability compared to their absence, demonstrating that nematodes link below- and above-ground processes, primarily through increasing nutrient availability. The experimental set-up presented allows to realistically quantify the crucial ecosystem services provided by the soil biota.

Nematodes enhance plant growth and nutrient uptake under C and N-rich conditions

NASA Astrophysics Data System (ADS)

Gebremikael, Mesfin T.; Steel, Hanne; Buchan, David; Bert, Wim; de Neve, Stefaan

2016-09-01

The role of soil fauna in crucial ecosystem services such as nutrient cycling remains poorly quantified, mainly because of the overly reductionistic approach adopted in most experimental studies. Given that increasing nitrogen inputs in various ecosystems influence the structure and functioning of soil microbes and the activity of fauna, we aimed to quantify the role of the entire soil nematode community in nutrient mineralization in an experimental set-up emulating nutrient-rich field conditions and accounting for crucial interactions amongst the soil microbial communities and plants. To this end, we reconstructed a complex soil foodweb in mesocosms that comprised largely undisturbed native microflora and the entire nematode community added into defaunated soil, planted with Lolium perenne as a model plant, and amended with fresh grass-clover residues. We determined N and P availability and plant uptake, plant biomass and abundance and structure of the microbial and nematode communities during a three-month incubation. The presence of nematodes significantly increased plant biomass production (+9%), net N (+25%) and net P (+23%) availability compared to their absence, demonstrating that nematodes link below- and above-ground processes, primarily through increasing nutrient availability. The experimental set-up presented allows to realistically quantify the crucial ecosystem services provided by the soil biota.

Watershed-Scale Cover Crops Reduce Nutrient Export From Agricultural Landscapes.

NASA Astrophysics Data System (ADS)

Tank, J. L.; Hanrahan, B.; Christopher, S. F.; Trentman, M. T.; Royer, T. V.; Prior, K.

2016-12-01

The Midwestern US has undergone extensive land use change as forest, wetlands, and prairies have been converted to agroecosystems. Today, excess fertilizer nutrients from farm fields enter Midwestern agricultural streams, which degrades both local and downstream water quality, resulting in algal blooms and subsequent hypoxic "dead zones" far from the nutrient source. We are quantifying the benefits of watershed-scale conservation practices that may reduce nutrient runoff from adjacent farm fields. Specifically, research is lacking on whether the planting of winter cover crops in watersheds currently dominated by row-crop agriculture can significantly reduce nutrient inputs to adjacent streams. Since 2013, farmers have planted cover crops on 70% of croppable acres in the Shatto Ditch Watershed (IN), and "saturation level" implementation of this conservation practice has been sustained for 3 years. Every 14 days, we have quantified nutrient loss from fields by sampling nutrient fluxes from multiple subsurface tile drains and longitudinally along the stream channel throughout the watershed. Cover crops improved stream water quality by reducing dissolved inorganic nutrients exported downstream; nitrate-N and DRP concentrations and fluxes were significantly lower in tiles draining fields with cover crops compared to those without. Annual watershed nutrient export also decreased, and reductions in N and P loss ( 30-40%) exceeded what we expected based on only a 6-10% reduction in runoff due to increased watershed water holding capacity. We are also exploring the processes responsible for increased nutrient retention, where they are occurring (terrestrial vs. aquatic) and when (baseflow vs. storms). For example, whole-stream metabolism also responded to cover crop planting, showing reduced variation in primary production and respiration in years after watershed-scale planting of cover crops. In summary, widespread land cover change, through cover crop planting, can

Dynamics of indigenous bacterial communities associated with crude oil degradation in soil microcosms during nutrient-enhanced bioremediation.

PubMed

Chikere, Chioma B; Surridge, Karen; Okpokwasili, Gideon C; Cloete, Thomas E

2012-03-01

Bacterial population dynamics were examined during bioremediation of an African soil contaminated with Arabian light crude oil and nutrient enrichment (biostimulation). Polymerase chain reaction followed by denaturing gradient gel electrophoresis (DGGE) were used to generate bacterial community fingerprints of the different treatments employing the 16S ribosomal ribonucleic acid (rRNA) gene as molecular marker. The DGGE patterns of the nutrient-amended soils indicated the presence of distinguishable bands corresponding to the oil-contaminated-nutrient-enriched soils, which were not present in the oil-contaminated and pristine control soils. Further characterization of the dominant DGGE bands after excision, reamplification and sequencing revealed that Corynebacterium spp., Dietzia spp., Rhodococcus erythropolis sp., Nocardioides sp., Low G+C (guanine plus cytosine) Gram positive bacterial clones and several uncultured bacterial clones were the dominant bacterial groups after biostimulation. Prominent Corynebacterium sp. IC10 sequence was detected across all nutrient-amended soils but not in oil-contaminated control soil. Total heterotrophic and hydrocarbon utilizing bacterial counts increased significantly in the nutrient-amended soils 2 weeks post contamination whereas oil-contaminated and pristine control soils remained fairly stable throughout the experimental period. Gas chromatographic analysis of residual hydrocarbons in biostimulated soils showed marked attenuation of contaminants starting from the second to the sixth week after contamination whereas no significant reduction in hydrocarbon peaks were seen in the oil-contaminated control soil throughout the 6-week experimental period. Results obtained indicated that nutrient amendment of oil-contaminated soil selected and enriched the bacterial communities mainly of the Actinobacteria phylogenetic group capable of surviving in toxic contamination with concomitant biodegradation of the hydrocarbons. The

Evidence for self-organization in determining spatial patterns of stream nutrients, despite primacy of the geomorphic template

PubMed Central

Dong, Xiaoli; Grimm, Nancy B.

2017-01-01

Nutrients in freshwater ecosystems are highly variable in space and time. Nevertheless, the variety of processes contributing to nutrient patchiness, and the wide range of spatial and temporal scales at which these processes operate, obfuscate how this spatial heterogeneity is generated. Here, we describe the spatial structure of stream nutrient concentration, quantify the relative importance of the physical template and biological processes, and detect and evaluate the role of self-organization in driving such patterns. We examined nutrient spatial patterns in Sycamore Creek, an intermittent desert stream in Arizona that experienced an ecosystem regime shift [from a gravel/algae-dominated to a vascular plant-dominated (hereafter, “wetland”) system] in 2000 when cattle grazing ceased. We conducted high-resolution nutrient surveys in surface water along a 10-km stream reach over four visits spanning 18 y (1995–2013) that represent different successional stages and prewetland stage vs. postwetland state. As expected, groundwater upwelling had a major influence on nutrient spatial patterns. However, self-organization realized by the mechanism of spatial feedbacks also was significant and intensified over ecosystem succession, as a resource (nitrogen) became increasingly limiting. By late succession, the effects of internal spatial feedbacks and groundwater upwelling were approximately equal in magnitude. Wetland establishment influenced nutrient spatial patterns only indirectly, by modifying the extent of surface water/groundwater exchange. This study illustrates that multiple mechanisms interact in a dynamic way to create spatial heterogeneity in riverine ecosystems, and provides a means to detect spatial self-organization against physical template heterogeneity as a dominant driver of spatial patterns. PMID:28559326

Evidence for self-organization in determining spatial patterns of stream nutrients, despite primacy of the geomorphic template.

PubMed

Dong, Xiaoli; Ruhí, Albert; Grimm, Nancy B

2017-06-13

Nutrients in freshwater ecosystems are highly variable in space and time. Nevertheless, the variety of processes contributing to nutrient patchiness, and the wide range of spatial and temporal scales at which these processes operate, obfuscate how this spatial heterogeneity is generated. Here, we describe the spatial structure of stream nutrient concentration, quantify the relative importance of the physical template and biological processes, and detect and evaluate the role of self-organization in driving such patterns. We examined nutrient spatial patterns in Sycamore Creek, an intermittent desert stream in Arizona that experienced an ecosystem regime shift [from a gravel/algae-dominated to a vascular plant-dominated (hereafter, "wetland") system] in 2000 when cattle grazing ceased. We conducted high-resolution nutrient surveys in surface water along a 10-km stream reach over four visits spanning 18 y (1995-2013) that represent different successional stages and prewetland stage vs. postwetland state. As expected, groundwater upwelling had a major influence on nutrient spatial patterns. However, self-organization realized by the mechanism of spatial feedbacks also was significant and intensified over ecosystem succession, as a resource (nitrogen) became increasingly limiting. By late succession, the effects of internal spatial feedbacks and groundwater upwelling were approximately equal in magnitude. Wetland establishment influenced nutrient spatial patterns only indirectly, by modifying the extent of surface water/groundwater exchange. This study illustrates that multiple mechanisms interact in a dynamic way to create spatial heterogeneity in riverine ecosystems, and provides a means to detect spatial self-organization against physical template heterogeneity as a dominant driver of spatial patterns.

Comparison of Habitat-Specific Nutrient Removal and Release in Pacific NW Salt Marshes at Multiple Spatial Scales

EPA Science Inventory

Wetlands can be sources, sinks and transformers of nutrients, although it is their role in nutrient removal that is valued as a water purification ecosystem service. In order to quantify that service for any wetland, it is important to understand the drivers of nutrient removal w...

Nutrients in waters on the inner shelf between Cape Charles and Cape Hatteras

NASA Technical Reports Server (NTRS)

Wong, G. T. F.; Todd, J. F.

1981-01-01

The distribution of nutrients in the shelf waters of the southern tip of the Middle Atlantic Bight was investigated. It is concluded that the outflow of freshwater from the Chesapeake Bay is a potential source of nutrients to the adjacent shelf waters. However, a quantitative estimation of its importance cannot yet be made because (1) there are other sources of nutrients to the study area and these sources cannot yet be quantified and (2) the concentrations of nutrients in the outflow from Chesapeake Bay exhibit significant short-term and long-term temporal variabilities.

Effects of nutrient enrichment on Prymnesium parvum population dynamics and toxicity: Results from field experiments, Lake Possum Kingdom, USA

USGS Publications Warehouse

Roelke, D.L.; Errera, R.M.; Riesling, R.; Brooks, B.W.; Grover, J.P.; Schwierzke, L.; Urena-Boeck, F.; Baker, J.; Pinckney, J.L.

2007-01-01

Large fish kills associated with toxic populations of the haptophyte Prymnesium parvum occur worldwide. In the past 5 yr, incidences of P. parvum blooms in inland water bodies of Texas (USA) have increased dramatically, where cell densities in excess of 1 ?? 107 cells l-1 are typically observed. We conducted field experiments (Lake Possum Kingdom) during the fall and early spring of 28 d duration using 24 enclosures of 1.57 m 3 each. The experiments investigated the effect of nutrient enrichment, immigration of P. parvum and addition of barley straw extract on phytoplankton biomass and assemblage structure, P. parvum population density, zooplankton biomass and assemblage structure, bacteria, and toxicity. Nutrient enrichment stimulated P. parvum population growth beyond bloom proportions (>1 ?? 107 cells l-1). However, P. parvum did not dominate the assemblage under these conditions, as it does during natural blooms. Instead, euglenophytes and chlorophytes dominated. Toxicity, estimated using fish (Pimephales promelas) and cladoceran (Daphnia magna) bioassays and which is linked to P. parvum's allelopathic and mixotrophic effectiveness, was greatly reduced (eliminated in many cases) under conditions of nutrient enrichment. The suppression of toxicity by nutrient addition suggested that targeted and time-limited nutrient manipulations might be used to mitigate the effects of P. parvum blooms. Immigration of P. parvum into natural assemblages and addition of barley straw extract had no significant effect on plankton dynamics. ?? Inter-Research 2007.

The impact of an underground cut-off wall on nutrient dynamics in groundwater in the lower Wang River watershed, China.

PubMed

Kang, Pingping; Xu, Shiguo

2017-03-01

Underground cut-off walls in coastal regions are mainly used to prevent saltwater intrusion, but their impact on nutrient dynamics in groundwater is not clear. In this study, a combined analysis of multiple isotopes ([Formula: see text]) and nitrogen and phosphorus concentrations is used in order to assess the impact of the underground cut-off walls on the nutrient dynamics in groundwater in the lower Wang River watershed, China. Compared with the nitrogen and phosphorus concentrations in groundwater downstream of the underground cut-off walls, high [Formula: see text] and total dissolved nitrogen concentrations and similar concentration levels of [Formula: see text] and total dissolved phosphorus are found in groundwater upstream of the underground cut-off walls. The isotopic data indicated the probable occurrence of denitrification and nitrification processes in groundwater upstream, whereas the fingerprint of these processes was not shown in groundwater downstream. The management of fertilizer application is critical to control nitrogen concentrations in groundwater restricted by the underground cut-off walls.

Reducing runoff and nutrient loss from agricultural land in the Lower Mississippi River Basin

NASA Astrophysics Data System (ADS)

Reba, M. L.; Bouldin, J.; Teague, T.; Choate, J.

2011-12-01

The Lower Mississippi River Basin (LMRB) yields suspended sediment, total phosphorus, total nitrogen and silicate that are disproportionately high for the area. In addition, groundwater pumping of the alluvial aquifer has been deemed unsustainable under current practices. Much of the LMRB is used for large-scale agricultural production of primarily cotton, soybeans and rice. The incorporation of conservation practices may improve nutrient use efficiency and reduce runoff from agricultural fields. Three paired fields have been instrumented at the edge-of-field to quantify nutrients and runoff. The fields are located in northeastern Arkansas in the Little River Ditches and St. Francis watersheds. Nutrient use efficiency will be gained by utilizing variable rate fertilizer application technology. Reduced runoff will be gained through improved irrigation management. This study quantifies the runoff and nutrient loss from the first year of a 5-year study and will serve as a baseline for a comparative study of conservation practices employed on the paired fields.

The influence of nutrient and water availability on carbohydrate storage in loblolly pine

Treesearch

K.H. Ludovici; H.L. Allen; T.J. Albaugh; P.M. Dougherty

2002-01-01

We quantified the effects of nutrient and water availability on monthly whole-tree carbohydrate budgets and determined allocation patterns of storage carbohydrates in loblolly pine (Pinus taeda) to test site resource impacts on internal carbon (C) storage. A factorial combination of two nutrient and two irrigation treatments were imposed on a 7-year...

Litterfall dynamics and nutrient deposition at different elevation and land use levels on Mt. Kilimanjaro, Tanzania

NASA Astrophysics Data System (ADS)

Becker, Joscha; Pabst, Holger; Mnyonga, James; Kuzyakov, Yakov

2014-05-01

One of the major pathways that connect above- and belowground nutrient and carbon stocks in forest ecosystems is litterfall. Depending on climate, tree species composition and stand structure it varies considerably between different ecosystems. Another driving factor that is known to affect ecosystem cycles is the level of anthropogenic disturbance such as land use. In case of tropical regions this is often present as the transformation from rainforests to plantation economy and sustainable agroforestry. The objective of this study was to quantify and determine patterns of carbon and nutrient deposition via tree litterfall in natural and anthropogenically affected forest ecosystems along an elevation gradient of Mt. Kilimanjaro. Tree litter of three natural (lower montane forest), two sustainably used (home gardens) and one intensively managed (shaded coffee plantation) ecosystem was collected on a biweekly basis from May 2012 to July 2013. Samples were separated into leaves, branches and remaining residues, dried and weighted. Carbon and nutrient content were measured in leave samples. We found that the overall annual pattern of litterfall was closely related to rainfall exhibiting a large peak during the dry season. Albeit visible on all plots, this characteristic decreased with elevation. No consistent patterns were found for other components than leaves. Total annual litter mainly consisted of leaf litter and ranges from 4639 kg/ha to 10673 kg/ha for all vegetation types. Flowers, fruits, etc. make up roughly 20% of total litter. Highest and lowest values occurred at home gardens and could not be significantly related to land use or elevation levels. Chemistry though differed between natural and used forest plots. N, P and K contents increased significantly with usage intensity while Mn decreased and C is more or less unaffected. We conclude that on the southern slope of Mt. Kilimanjaro, short term variations in litterfall are related to seasonal climatic

Faunal isotope records reveal trophic and nutrient dynamics in twentieth century Yellowstone grasslands.

PubMed

Fox-Dobbs, Kena; Nelson, Abigail A; Koch, Paul L; Leonard, Jennifer A

2012-10-23

Population sizes and movement patterns of ungulate grazers and their predators have fluctuated dramatically over the past few centuries, largely owing to overharvesting, land-use change and historic management. We used δ(13)C and δ(15)N values measured from bone collagen of historic and recent gray wolves and their potential primary prey from Yellowstone National Park to gain insight into the trophic dynamics and nutrient conditions of historic and modern grasslands. The diet of reintroduced wolves closely parallels that of the historic population. We suggest that a significant shift in faunal δ(15)N values over the past century reflects impacts of anthropogenic environmental changes on grassland ecosystems, including grazer-mediated shifts in grassland nitrogen cycle processes.

Progress and limitations on quantifying nutrient and carbon loading to coastal waters

NASA Astrophysics Data System (ADS)

Stets, E.; Oelsner, G. P.; Stackpoole, S. M.

2017-12-01

Riverine export of nutrients and carbon to estuarine and coastal waters are important determinants of coastal ecosystem health and provide necessary insight into global biogeochemical cycles. Quantification of coastal solute loads typically relies upon modeling based on observations of concentration and discharge from selected rivers draining to the coast. Most large-scale river export models require unidirectional flow and thus are referenced to monitoring locations at the head of tide, which can be located far inland. As a result, the contributions of the coastal plain, tidal wetlands, and concentrated coastal development are often poorly represented in regional and continental-scale estimates of solute delivery to coastal waters. However, site-specific studies have found that these areas are disproportionately active in terms of nutrient and carbon export. Modeling efforts to upscale fluxes from these areas, while not common, also suggest an outsized importance to coastal flux estimates. This presentation will focus on illustrating how the problem of under-representation of near-shore environments impacts large-scale coastal flux estimates in the context of recent regional and continental-scale assessments. Alternate approaches to capturing the influence of the near-coastal terrestrial inputs including recent data aggregation efforts and modeling approaches will be discussed.

Comparison of Habitat-Specific Nutrient Removal and Release in Pacific NW Salt Marshes at Multiple Spatial Scales - CERF

EPA Science Inventory

Wetlands can be sources, sinks and transformers of nutrients, although it is their role in nutrient removal that is valued as a water purification ecosystem service. In order to quantify that service for any wetland, it is important to understand the drivers of nutrient removal w...

Quantifying the effects of overgrazing on mountainous watershed vegetation dynamics under a changing climate.

PubMed

Hao, Lu; Pan, Cen; Fang, Di; Zhang, Xiaoyu; Zhou, Decheng; Liu, Peilong; Liu, Yongqiang; Sun, Ge

2018-10-15

Grazing is a major ecosystem disturbance in arid regions that are increasingly threatened by climate change. Understanding the long-term impacts of grazing on rangeland vegetation dynamics in a complex terrain in mountainous regions is important for quantifying dry land ecosystem services for integrated watershed management and climate change adaptation. However, data on the detailed long-term spatial distribution of grazing activities are rare, which prevents trend detection and environmental impact assessments of grazing. This study quantified the impacts of grazing on vegetation dynamics for the period of 1983-2010 in the Upper Heihe River basin, a complex multiple-use watershed in northwestern China. We also examined the relative contributions of grazing and climate to vegetation change using a dynamic grazing pressure method. Spatial grazing patterns and temporal dynamics were mapped at a 1 km × 1 km pixel scale using satellite-derived leaf area index (LAI) data. We found that overgrazing was a dominant driver for LAI reduction in alpine grasslands and shrubs, especially for the periods of 1985-1991 and 1997-2004. Although the recent decade-long active grazing management contributed to the improvement of LAI and partially offset the negative effects of increased livestock, overgrazing has posed significant challenges to shrub-grassland ecosystem recovery in the eastern part of the study basin. We conclude that the positive effects of a warming and wetting climate on vegetation could be underestimated if the negative long-term grazing effects are not considered. Findings from the present case study show that assessing long-term climate change impacts on watersheds must include the influences of human activities. Our study provides important guidance for ecological restoration efforts in locating vulnerable areas and designing effective management practices in the study watershed. Such information is essential for natural resource management that aims

Linking nutrient inputs, phytoplankton composition, zooplankton dynamics and the recruitment of pink snapper, Chrysophrys auratus, in a temperate bay

NASA Astrophysics Data System (ADS)

Black, Kerry P.; Longmore, Andrew R.; Hamer, Paul A.; Lee, Randall; Swearer, Stephen E.; Jenkins, Gregory P.

2016-12-01

Survival of larval fish is often linked to production of preferred prey such as copepods, both inter- and intra-annually. In turn, copepod production depends not only the quantity of food, but also on the nutritional quality, edibility and/or toxicity of their micro-algal food. Hence, larval fish survival can become de-coupled from levels of nutrient input depending on the resulting composition of the plankton. Here we use a plankton dynamics model to study nutrient input, phytoplankton composition and copepod, Paracalanus, production in relation to interannual variation in recruitment of snapper, Chrysophrys auratus, in Port Phillip Bay, Australia. The model was able to simulate the ratio of diatoms to flagellates in the plume of the main river entering Port Phillip Bay. Interannual variability in the copepod, Paracalanus, abundance during the C. auratus spawning period over 5 years was accurately predicted. The seasonal peak in Paracalanus production depended on the timing and magnitude (match-mismatch) of nutrient inputs and how these were reflected in temporal change in the diatom:flagellate ratio. In turn, the model-predicted Paracalanus abundance was strongly related to inter-annaul variability in abundance of snapper, C. auratus, larvae over 7 years. Years of highest larval C. auratus abundance coincided with a matching of the spawning period with the peak in Paracalanus abundance. High freshwater flows and nutrient inputs led to an early seasonal dominance of diatoms, and consequently reduced abundances of copepods over the C. auratus spawning period with correspondingly low abundances of larvae. Conversely years of very low rainfall and nutrient input also led to low phytoplankton and copepod concentrations and larval C. auratus abundances. Highest abundances of larval C. auratus occurred in years of low to intermediate rainfall and nutrient inputs, particularly when pulses of nutrients occurred in the spring period, the latter supporting the match

Impact of hydrochar application on soil nutrient dynamics and plant availability

NASA Astrophysics Data System (ADS)

Bargmann, I.; Greef, J. M.; Kücke, M.

2012-04-01

In order to investigate potentials for the use of HTC-products (hydrochar) in agriculture, the influence of soil application of different hydrochars on soil nutrient dynamics as well as on plant growth and plant nutrient uptake was determined. Hydrochars were produced from sugar beet pulps and brewer's grains by carbonization at 190°C for 4 respectively 12 hours each. Incubation experiments with two soil types showed an increase of soil pH by 0.5 to 2.5 pH units, depending on the amount of hydrochar added and the process conditions (i.e. addition of calcium carbonate during production). The application of HTC to soil decreased the plant available nitrogen to almost zero in the first week after HTC-addition, followed by a slow re-release of nitrate in the following weeks. A similar immobilization of soluble phosphate was observed for one soil type, although to a lower extent. The plant availability of phosphorus in hydrochars and biochars is subject of current trials. Furthermore it is actually investigated to what extend the N immobilization is related to soil microbial activity. Germination tests with barley showed toxic effects of hydrochar application on germination, both by direct contact of grains with HTC as well as by release of gaseous compounds from HTC. Effects differ significantly for different parent materials and pretreatments (washing, drying, storage). The influence of HTC-addition to soil on plant growth and nutrient uptake was investigated in pot experiments with various crop species (barley, phaseolus bean, leek), comparing HTC from different parent materials and process parameters such as carbonization time. With increasing addition of HTC, the N availability was decreased and N contents in the plant were significantly lower compared with the untreated control. The plant growth response was different for each tested crop. On barley, leaf tip necroses were observed, but not on phaseolus. Biomass yield of barley and beans was generally increased

Managing urban nutrient biogeochemistry for sustainable urbanization.

PubMed

Lin, Tao; Gibson, Valerie; Cui, Shenghui; Yu, Chang-Ping; Chen, Shaohua; Ye, Zhilong; Zhu, Yong-Guan

2014-09-01

Urban ecosystems are unique in the sense that human activities are the major drivers of biogeochemical processes. Along with the demographic movement into cities, nutrients flow towards the urban zone (nutrient urbanization), causing the degradation of environmental quality and ecosystem health. In this paper, we summarize the characteristics of nutrient cycling within the urban ecosystem compared to natural ecosystems. The dynamic process of nutrient urbanization is then explored taking Xiamen city, China, as an example to examine the influence of rapid urbanization on food sourced nitrogen and phosphorus metabolism. Subsequently, the concept of a nutrient footprint and calculation method is introduced from a lifecycle perspective. Finally, we propose three system approaches to mend the broken biogeochemical cycling. Our study will contribute to a holistic solution which achieves synergies between environmental quality and food security, by integrating technologies for nutrient recovery and waste reduction. Copyright © 2014 Elsevier Ltd. All rights reserved.

Monitoring Physicochemical and Nutrient Dynamics Along a Development Gradient in Maine Ephemeral Wetlands

NASA Astrophysics Data System (ADS)

Podzikowski, L. Y.; Capps, K. A.; Calhoun, A.

2014-12-01

Vernal pools are ephemeral wetlands in forested landscapes that fill with snowmelt, precipitation, and/or groundwater in the spring, and characteristically dry down through the summer months. Typically, vernal pool research has focused on the population and community ecology of pool-breeding organisms (amphibians and macroinvertebrates) conducted during their relatively short breeding season. Yet, little is known about the temporal variability of biogeochemical processes within and among vernal pools in urbanizing landscapes. In this study, we monitored physicochemical characteristics and nutrient dynamics in 22 vernal pools in central Maine post thaw in 2014. Four pristine pools were sampled weekly in five locations within the pool for ambient nutrient concentrations (SRP, NH4, NOx) and at three locations for physicochemical characteristics (DO, pH, temperature, conductivity). In the remaining 18 pools, we sampled one location for nutrients and three locations for physicochemical characteristics at least monthly to estimate the influence of increasing urbanization on the physical and chemical environment. Our data suggest most pools found in urbanizing areas have higher conductivity (developed sites ranging 18.52 - 1238 μS cm-1 compared to pristine between 14.08 - 58.4 μS cm-1). Previous work suggests forested pools exhibit dystrophic conditions with high coloration from DOC limiting primary production due to increased light attenuation in pools. However, both pristine and urban pools experienced spikes in DO (>100% saturation) throughout the day, suggesting that high productivity is not a reliable indicator of the effects of urbanization on vernal pools. We argue that continued monitoring of vernal pools along a gradient of urbanization could give insight into the role of ephemeral wetlands as potential biogeochemical hotspots and may also indicate how human development may alter biogeochemical cycling in ephemeral wetlands.

Short-term effect of nutrient availability and rainfall distribution on biomass production and leaf nutrient content of savanna tree species.

PubMed

Barbosa, Eduardo R M; Tomlinson, Kyle W; Carvalheiro, Luísa G; Kirkman, Kevin; de Bie, Steven; Prins, Herbert H T; van Langevelde, Frank

2014-01-01

Changes in land use may lead to increased soil nutrient levels in many ecosystems (e.g. due to intensification of agricultural fertilizer use). Plant species differ widely in their response to differences in soil nutrients, and for savannas it is uncertain how this nutrient enrichment will affect plant community dynamics. We set up a large controlled short-term experiment in a semi-arid savanna to test how water supply (even water supply vs. natural rainfall) and nutrient availability (no fertilisation vs. fertilisation) affects seedlings' above-ground biomass production and leaf-nutrient concentrations (N, P and K) of broad-leafed and fine-leafed tree species. Contrary to expectations, neither changes in water supply nor changes in soil nutrient level affected biomass production of the studied species. By contrast, leaf-nutrient concentration did change significantly. Under regular water supply, soil nutrient addition increased the leaf phosphorus concentration of both fine-leafed and broad-leafed species. However, under uneven water supply, leaf nitrogen and phosphorus concentration declined with soil nutrient supply, this effect being more accentuated in broad-leafed species. Leaf potassium concentration of broad-leafed species was lower when growing under constant water supply, especially when no NPK fertilizer was applied. We found that changes in environmental factors can affect leaf quality, indicating a potential interactive effect between land-use changes and environmental changes on savanna vegetation: under more uneven rainfall patterns within the growing season, leaf quality of tree seedlings for a number of species can change as a response to changes in nutrient levels, even if overall plant biomass does not change. Such changes might affect herbivore pressure on trees and thus savanna plant community dynamics. Although longer term experiments would be essential to test such potential effects of eutrophication via changes in leaf nutrient concentration

[Nutrient dynamics in forest plantations of Azadirachta indica (Meliaceae) established for restoration of degraded lands in Colombia].

PubMed

Flórez-Flórez, Claudia Patricia; León-Peláez, Juan Diego; Osorio-Vega, Nelson Walter; Restrepo-Llano, Manuel Fernando

2013-06-01

Nutrient dynamics in forest plantations of Azadirachta indica (Meliaceae) established for restoration of degraded lands in Colombia. Azadirachta indica is a tree species which use is steadily increasing for restoration of tropical and subtropical arid and degraded lands throughout the world. The objective of this research study was to evaluate the potential of these plantations as an active restoration model for the recovery of soils under desertification in arid lands of Colombia. Litter traps and litter-bags were installed in twenty 250m2 plots. Green leaves and soil samples inside and outside this species plantations were taken, and their elemental concentrations were determined. Litterfall, leaf litter decomposition and foliar nutrient resorption were monitored for one year. The annual contributions of organic material, such as fine litterfall, represented 557.54kg/ha, a third of which was A. indica leaves. The greatest potential returns of nutrients per foliar litterfall were from Ca (4.6kg/ha) and N (2.4kg/ha), and the smallest potential returns came from P (0.06kg/ha). A total of 68% of the foliar material deposited in litter-bags disappeared after one year. The greatest release of nutrients was that of K (100%), and the least was that of N (40%). P was the most limiting nutrient, with low edaphic availability and high nutrient use efficiency from Vitousek's index (IEV = 3176) and foliar nutrient resorption (35%). Despite these plantations are young, and that they have not had forestry management practices, as an active restoration model, they have revitalized the biogeochemical cycle, positively modifying the edaphic parameters according to the increases in organic material, P and K of 72%, 31% and 61%, respectively. Furthermore, they improved the stability of aggregates and the microbe respiration rates. The forest plantation model with exotic species has been opposed by different sectors; however, it has been acknowledged that these projects derive many

The 'fine structure' of nutrient dynamics in rivers: ten years of study using high-frequency monitoring

NASA Astrophysics Data System (ADS)

Jordan, Phil; Melland, Alice; Shore, Mairead; Mellander, Per-Erik; Shortle, Ger; Ryan, David; Crockford, Lucy; Macintosh, Katrina; Campbell, Julie; Arnscheidt, Joerg; Cassidy, Rachel

2014-05-01

A complete appraisal of material fluxes in flowing waters is really only possibly with high time resolution data synchronous with measurements of discharge. Defined by Kirchner et al. (2004; Hydrological Processes, 18/7) as the high-frequency wave of the future and with regard to disentangling signal noise from process pattern, this challenge has been met in terms of nutrient flux monitoring by automated bankside analysis. In Ireland over a ten-year period, time-series nutrient data collected on a sub-hourly basis in rivers have been used to distinguish fluxes from different catchment sources and pathways and to provide more certain temporal pictures of flux for the comparative definition of catchment nutrient dynamics. In catchments where nutrient fluxes are particularly high and exhibit a mix of extreme diffuse and point source influences, high time resolution data analysis indicates that there are no satisfactory statistical proxies for seasonal or annual flux predictions that use coarse datasets. Or at least exposes the limits of statistical approaches to catchment scale and hydrological response. This has profound implications for catchment monitoring programmes that rely on modelled relationships. However, using high resolution monitoring for long term assessments of catchment mitigation measures comes with further challenges. Sustaining continuous wet chemistry analysis at river stations is resource intensive in terms of capital, maintenance and quality assurance. Furthermore, big data capture requires investment in data management systems and analysis. These two institutional challenges are magnified when considering the extended time period required to identify the influences of land-based nutrient control measures on water based systems. Separating the 'climate signal' from the 'source signal' in river nutrient flux data is a major analysis challenge; more so when tackled with anything but higher resolution data. Nevertheless, there is scope to lower

Dynamics of microorganism populations in recirculating nutrient solutions

NASA Technical Reports Server (NTRS)

Strayer, R. F.

1994-01-01

This overview covers the basic microbial ecology of recirculating hydroponic solutions. Examples from NASA and Soviet CELSS tests and the commercial hydroponic industry will be used. The sources of microorganisms in nutrient solutions include air, water, seeds, plant containers and plumbing, biological vectors, and personnel. Microbial fates include growth, death, and emigration. Important microbial habitats within nutrient delivery systems are root surfaces, hardware surfaces (biofilms), and solution suspension. Numbers of bacteria on root surfaces usually exceed those from the other habitats by several orders of magnitude. Gram negative bacteria dominate the microflora with fungal counts usually much lower. Trends typically show a decrease in counts with increasing time unless stressed plants increase root exudates. Important microbial activities include carbon mineralization and nitrogen transformations. Important detrimental interactions include competition with plants, and human and plant pathogenesis.

Marine fisheries declines viewed upside down: human impacts on consumer-driven nutrient recycling.

PubMed

Layman, Craig A; Allgeier, Jacob E; Rosemond, Amy D; Dahlgren, Craig P; Yeager, Lauren A

2011-03-01

We quantified how two human impacts (overfishing and habitat fragmentation) in nearshore marine ecosystems may affect ecosystem function by altering the role of fish as nutrient vectors. We empirically quantified size-specific excretion rates of one of the most abundant fishes (gray snapper, Lutjanus griseus) in The Bahamas and combined these with surveys of fish abundance to estimate population-level excretion rates. The study was conducted across gradients of two human disturbances: overfishing and ecosystem fragmentation (estuaries bisected by roads), to evaluate how each could result in reduced population-level nutrient cycling by consumers. Mean estimated N and P excretion rates for gray snapper populations were on average 456% and 541% higher, respectively, in unfished sites. Ecosystem fragmentation resulted in significant reductions of recycling rates by snapper, with degree of creek fragmentation explaining 86% and 72% of the variance in estimated excretion for dissolved N and P, respectively. Additionally, we used nutrient limitation assays and primary producer nutrient content to provide a simple example of how marine fishery declines may affect primary production. This study provides an initial step toward integrating marine fishery declines and consumer-driven nutrient recycling to more fully understand the implications of human impacts in marine ecosystems.

Comparison of export dynamics of nutrients and animal-borne estrogens from a tile-drained Midwestern agroecosystem.

PubMed

Gall, Heather E; Sassman, Stephen A; Jenkinson, Byron; Lee, Linda S; Jafvert, Chad T

2015-04-01

Concentrated animal feeding operations (CAFOs) are known to be a source of nutrients and hormones found in surface water bodies around the world. While the fate and transport of nutrients have been studied for decades, much less research has been conducted on the fate and transport of hormones. To facilitate a comparison of nutrient and hormone export dynamics from farm fields, nitrate + nitrite (N), dissolved reactive phosphorus (DRP), 17α- and 17β-estradiol (E2), estrone (E1), and estriol (E3) were monitored in a tile drain and receiving ditch for one year on a working farm in north central Indiana. Repeated animal waste applications led to high frequency detection of hormones (>50% in tile drain; >90% in the ditch) and nutrients (>70% for DRP; 100% for N). Hydrologic variability was found to be a dominant factor controlling export of N, DRP, and E1 to the drain and ditch. Of the estrogens, the temporal trend in E1 export was most similar to that of DRP. Differences in temporal export between P and the other estrogens likely were due to differences in the biogeochemical processes that affect their fate and transport within the agroecosystem. During short periods when the flowrate exceeded the 80(th) percentile for the year, over 70% of the total mass export of DRP and E1 occurred for the year in both the tile drain and ditch, demonstrating the importance of high-flow events. Therefore, best management practices must be effective during large flow events to substantially reduce transport to downstream locations. Copyright © 2014 Elsevier Ltd. All rights reserved.

Faunal isotope records reveal trophic and nutrient dynamics in twentieth century Yellowstone grasslands

PubMed Central

Fox-Dobbs, Kena; Nelson, Abigail A.; Koch, Paul L.; Leonard, Jennifer A.

2012-01-01

Population sizes and movement patterns of ungulate grazers and their predators have fluctuated dramatically over the past few centuries, largely owing to overharvesting, land-use change and historic management. We used δ13C and δ15N values measured from bone collagen of historic and recent gray wolves and their potential primary prey from Yellowstone National Park to gain insight into the trophic dynamics and nutrient conditions of historic and modern grasslands. The diet of reintroduced wolves closely parallels that of the historic population. We suggest that a significant shift in faunal δ15N values over the past century reflects impacts of anthropogenic environmental changes on grassland ecosystems, including grazer-mediated shifts in grassland nitrogen cycle processes. PMID:22675135

Nutrient enrichment alters storage and fluxes of detritus in a headwater stream ecosystem

Treesearch

Jonathan P. Benstead; Amy D. Rosemond; Wyatt F. Cross; J. Bruce Wallace; Susan L. Eggert; Keller Suberkropp; Vladislav Gulis; Jennifer L. Greenwood; Cynthia J. Tant

2009-01-01

Responses of detrital pathways to nutrients may differ fundamentally from pathways involving living plants: basal carbon resources can potentially decrease rather than increase with nutrient enrichment. Despite the potential for nutrients to accelerate heterotrophic processes and fluxes of detritus, few studies have examined detritus-nutrient dynamics at whole-...

INFLUENCES OF HYDROLOGY ON NUTRIENT DYNAMICS IN LAKE SUPERIOR COASTAL WETLANDS

EPA Science Inventory

Little is known about the role of the coastal wetlands (CWs) of Lake Superior in modifying or contributing to nutrient fluxes from watersheds to the lake. We are studying factors controlling nutrient retention and transformation of CWs in Western Lake Superior. CWs may be unique ...

Quantifying the size-resolved dynamics of indoor bioaerosol transport and control.

PubMed

Kunkel, S A; Azimi, P; Zhao, H; Stark, B C; Stephens, B

2017-09-01

Understanding the bioaerosol dynamics of droplets and droplet nuclei emitted during respiratory activities is important for understanding how infectious diseases are transmitted and potentially controlled. To this end, we conducted experiments to quantify the size-resolved dynamics of indoor bioaerosol transport and control in an unoccupied apartment unit operating under four different HVAC particle filtration conditions. Two model organisms (Escherichia coli K12 and bacteriophage T4) were aerosolized under alternating low and high flow rates to roughly represent constant breathing and periodic coughing. Size-resolved aerosol sampling and settle plate swabbing were conducted in multiple locations. Samples were analyzed by DNA extraction and quantitative polymerase chain reaction (qPCR). DNA from both organisms was detected during all test conditions in all air samples up to 7 m away from the source, but decreased in magnitude with the distance from the source. A greater fraction of T4 DNA was recovered from the aerosol size fractions smaller than 1 μm than E. coli K12 at all air sampling locations. Higher efficiency HVAC filtration also reduced the amount of DNA recovered in air samples and on settle plates located 3-7 m from the source. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Dynamic control of nutrient-removal from industrial wastewater in a sequencing batch reactor, using common and low-cost online sensors.

PubMed

Dries, Jan

2016-01-01

On-line control of the biological treatment process is an innovative tool to cope with variable concentrations of chemical oxygen demand and nutrients in industrial wastewater. In the present study we implemented a simple dynamic control strategy for nutrient-removal in a sequencing batch reactor (SBR) treating variable tank truck cleaning wastewater. The control system was based on derived signals from two low-cost and robust sensors that are very common in activated sludge plants, i.e. oxidation reduction potential (ORP) and dissolved oxygen. The amount of wastewater fed during anoxic filling phases, and the number of filling phases in the SBR cycle, were determined by the appearance of the 'nitrate knee' in the profile of the ORP. The phase length of the subsequent aerobic phases was controlled by the oxygen uptake rate measured online in the reactor. As a result, the sludge loading rate (F/M ratio), the volume exchange rate and the SBR cycle length adapted dynamically to the activity of the activated sludge and the actual characteristics of the wastewater, without affecting the final effluent quality.

Whole-system nutrient enrichment increases secondary production in a detritus-based ecosystem

Treesearch

W.F. Cross; J.B. Wallace; A.D. Rosemond; S.L. Eggert

2006-01-01

Although the effects of nutrient enrichment on consumer-resource dynamics are relatively well studied in ecosystems based on living plants, little is known about the manner in which enrichment influences the dynamics and productivity of consumers and resources in detritus-based ecosystems. Because nutrients can stimulate loss of carbon at the base of detrital food webs...

Dynamics of microorganism populations in recirculating nutrient solutions

NASA Technical Reports Server (NTRS)

Strayer, R. F.

1994-01-01

This overview covers the basic microbial ecology of recirculating hydroponic solutions. Examples from NASA and Soviet Controlled Ecological Life Support Systems (CELSS) tests and the commercial hydroponic industry will be used. The sources of microorganisms in nutrient solutions include air, water, seeds, plant containers and plumbing, biological vectors, and personnel. Microbial fates include growth, death, and emigration. Important microbial habitats within nutrient delivery systems are root surfaces, hardware surfaces (biofilms), and solution suspension. Numbers of bacteria on root surfaces usually exceed those from the other habitats by several orders of magnitude. Gram negative bacteria dominate the microflora with fungal counts usually much lower. Trends typically show a decrease in counts with increasing time unless stressed plants increase root exudates. Important microbial activities include carbon mineralization and nitrogen transformations. Important detrimental interactions include competition with plants, and human and plant pathogenesis.

Contribution of Wastewater Treatment Plant Effluents to Nutrient Dynamics in Aquatic Systems: A Review

NASA Astrophysics Data System (ADS)

Carey, Richard O.; Migliaccio, Kati W.

2009-08-01

Excessive nutrient loading (considering nitrogen and phosphorus) is a major ongoing threat to water quality and here we review the impact of nutrient discharges from wastewater treatment plants (WWTPs) to United States (U.S.) freshwater systems. While urban and agricultural land uses are significant nonpoint nutrient contributors, effluent from point sources such as WWTPs can overwhelm receiving waters, effectively dominating hydrological characteristics and regulating instream nutrient processes. Population growth, increased wastewater volumes, and sustainability of critical water resources have all been key factors influencing the extent of wastewater treatment. Reducing nutrient concentrations in wastewater is an important aspect of water quality management because excessive nutrient concentrations often prevent water bodies from meeting designated uses. WWTPs employ numerous physical, chemical, and biological methods to improve effluent water quality but nutrient removal requires advanced treatment and infrastructure that may be economically prohibitive. Therefore, effluent nutrient concentrations vary depending on the particular processes used to treat influent wastewater. Increasingly stringent regulations regarding nutrient concentrations in discharged effluent, along with greater freshwater demand in populous areas, have led to the development of extensive water recycling programs within many U.S. regions. Reuse programs provide an opportunity to reduce or eliminate direct nutrient discharges to receiving waters while allowing for the beneficial use of reclaimed water. However, nutrients in reclaimed water can still be a concern for reuse applications, such as agricultural and landscape irrigation.

Composting and gypsum amendment of broiler litter to reduce nutrient leaching loss

USDA-ARS?s Scientific Manuscript database

Relative to fresh broiler litter, little is known about the dynamics of composted litter derived-nutrient in the ecosystem. In this study, the potential leaching losses of nutrients from compost relative to fresh broiler litter along with flue gas desulfurization (FGD gypsum), as a nutrient immobil...

Dynamics of Nutrients Transport in Onsite Wastewater Treatment Systems

NASA Astrophysics Data System (ADS)

Toor, G.; De, M.

2013-05-01

Domestic wastewater is abundant in nutrients¬ that originate from various activities in the households. In developed countries, wastewater is largely managed by (1) centralized treatment where wastewater from large population is collected, treated, and discharged and (2) onsite treatment where wastewater is collected from an individual house, treated, and dispersed onsite; this system is commonly known as septic system or onsite wastewater treatment system (OWTS) and consist of a septic tank (collects wastewater) and drain-field (disperses wastewater in soil). In areas with porous sandy soils, the transport of nutrients from drain-field to shallow groundwater is accelerated. To overcome this limitation, elevated disposal fields (commonly called mounds) on top of the natural soil are constructed to provide unsaturated conditions for wastewater treatment. Our objective was to study the dynamics of nitrogen (N) and phosphorus (P) transport in the vadose zone and groundwater in traditional and advanced OWTS. Soil water samples were collected from the vadose zone by using suction cup lysimeters and groundwater samples were collected by using piezometers. Collected samples (wastewater, soil-water, groundwater) were analyzed for various water quality parameters. The pH (4.39-4.78) and EC (0.28-0.34 dS/m) of groundwater was much lower than both wastewater and soil-water. In contrast to >50 mg/L of ammonium-N in wastewater, concentrations in all lysimeters (0.02-0.81 mg/L) and piezometers (0.01-0.82 mg/L) were <1 mg/L; suggesting that >99% disappeared (primarily nitrified) in the vadose zone (<1.05-m soil profile depth). In the vadose zone of advanced system, heterotrophic and autrotrophic denitrification reduced nitrate-N concentrations to <0.12 mg/L, compared with >20 mg/L in the vadose zones of traditional systems (drip dispersal and gravel trench). Concentrations of chloride showed a distinct pattern of nitrate-N breakthrough in vadose zone and groundwater; the

Quantifying the impacts of vegetation changes on catchment storage-discharge dynamics using paired-catchment data

NASA Astrophysics Data System (ADS)

Cheng, Lei; Zhang, Lu; Chiew, Francis H. S.; Canadell, Josep G.; Zhao, Fangfang; Wang, Ying-Ping; Hu, Xianqun; Lin, Kairong

2017-07-01

It is widely recognized that vegetation changes can significantly affect the local water availability. Methods have been developed to predict the effects of vegetation change on water yield or total streamflow. However, it is still a challenge to predict changes in base flow following vegetation change due to limited understanding of catchment storage-discharge dynamics. In this study, the power law relationship for describing catchment storage-discharge dynamics is reformulated to quantify the changes in storage-discharge relationship resulting from vegetation changes using streamflow data from six paired-catchment experiments, of which two are deforestation catchments and four are afforestation catchments. Streamflow observations from the paired-catchment experiments clearly demonstrate that vegetation changes have led to significant changes in catchment storage-discharge relationships, accounting for about 83-128% of the changes in groundwater discharge in the treated catchments. Deforestation has led to increases in groundwater discharge (or base flow) but afforestation has resulted in decreases in groundwater discharge. Further analysis shows that the contribution of changes in groundwater discharge to the total changes in streamflow varies greatly among experimental catchments ranging from 12% to 80% with a mean of 38 ± 22% (μ ± σ). This study proposed a new method to quantify the effects of vegetation changes on groundwater discharge from catchment storage and will improve our predictability about the impacts of vegetation changes on catchment water yields.

Estimating uncertainty in ambient and saturation nutrient uptake metrics from nutrient pulse releases in stream ecosystems

DOE PAGES

Brooks, Scott C.; Brandt, Craig C.; Griffiths, Natalie A.

2016-10-07

Nutrient spiraling is an important ecosystem process characterizing nutrient transport and uptake in streams. Various nutrient addition methods are used to estimate uptake metrics; however, uncertainty in the metrics is not often evaluated. A method was developed to quantify uncertainty in ambient and saturation nutrient uptake metrics estimated from saturating pulse nutrient additions (Tracer Additions for Spiraling Curve Characterization; TASCC). Using a Monte Carlo (MC) approach, the 95% confidence interval (CI) was estimated for ambient uptake lengths (S w-amb) and maximum areal uptake rates (U max) based on 100,000 datasets generated from each of four nitrogen and five phosphorous TASCCmore » experiments conducted seasonally in a forest stream in eastern Tennessee, U.S.A. Uncertainty estimates from the MC approach were compared to the CIs estimated from ordinary least squares (OLS) and non-linear least squares (NLS) models used to calculate S w-amb and U max, respectively, from the TASCC method. The CIs for Sw-amb and Umax were large, but were not consistently larger using the MC method. Despite the large CIs, significant differences (based on nonoverlapping CIs) in nutrient metrics among seasons were found with more significant differences using the OLS/NLS vs. the MC method. Lastly, we suggest that the MC approach is a robust way to estimate uncertainty, as the calculation of S w-amb and U max violates assumptions of OLS/NLS while the MC approach is free of these assumptions. The MC approach can be applied to other ecosystem metrics that are calculated from multiple parameters, providing a more robust estimate of these metrics and their associated uncertainties.« less

Estimating uncertainty in ambient and saturation nutrient uptake metrics from nutrient pulse releases in stream ecosystems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brooks, Scott C.; Brandt, Craig C.; Griffiths, Natalie A.

Nutrient spiraling is an important ecosystem process characterizing nutrient transport and uptake in streams. Various nutrient addition methods are used to estimate uptake metrics; however, uncertainty in the metrics is not often evaluated. A method was developed to quantify uncertainty in ambient and saturation nutrient uptake metrics estimated from saturating pulse nutrient additions (Tracer Additions for Spiraling Curve Characterization; TASCC). Using a Monte Carlo (MC) approach, the 95% confidence interval (CI) was estimated for ambient uptake lengths (S w-amb) and maximum areal uptake rates (U max) based on 100,000 datasets generated from each of four nitrogen and five phosphorous TASCCmore » experiments conducted seasonally in a forest stream in eastern Tennessee, U.S.A. Uncertainty estimates from the MC approach were compared to the CIs estimated from ordinary least squares (OLS) and non-linear least squares (NLS) models used to calculate S w-amb and U max, respectively, from the TASCC method. The CIs for Sw-amb and Umax were large, but were not consistently larger using the MC method. Despite the large CIs, significant differences (based on nonoverlapping CIs) in nutrient metrics among seasons were found with more significant differences using the OLS/NLS vs. the MC method. Lastly, we suggest that the MC approach is a robust way to estimate uncertainty, as the calculation of S w-amb and U max violates assumptions of OLS/NLS while the MC approach is free of these assumptions. The MC approach can be applied to other ecosystem metrics that are calculated from multiple parameters, providing a more robust estimate of these metrics and their associated uncertainties.« less

Biochar as carrier for plant nutrients and microorganisms - techniques of agro-activation

NASA Astrophysics Data System (ADS)

Schmidt, H.-P.

2012-04-01

The soil enhancing qualities of biochar are strongly linked to its influence on nutrient cycling dynamics, sorption dynamics and to changing habitat condition for soil fauna. But as shown in multiple studies, the addition of pure biochar to agricultural soils may provoke reduced plant growth caused by the immobilisation of plant nutrients. The very potent sorption dynamics of biochar makes it an effective carrier for plant nutrients and plant-root symbiotic microorganisms. At the Delinat-Institute, we tried sundry methods of charging biochars with organic and mineral plant nutrients as well as with microorganisms. This includes the use of biochar as bulk agent in aerobic composting, in malolactic fermentation and as treatment for liquid manure, but also formulations of mineral carbon-fertilizers. Those biochar products are tested in pot and also large scale field trials. Results and experiences of these trials as well as different activation methods will be explained. A short overview of industrial designing of biochar based products will be given.

Effects of elevated atmospheric Co2 and tropospheric O3 on nutrient dynamics: decomposition of leaf litter in trembling aspen and paper birch communities. Plant Soil. 299:65–82.

Treesearch

Lingli Liu; John S. King; Christian P. Giardina

2007-01-01

Atmospheric changes could strongly influence how terrestrial ecosystems function by altering nutrient cycling. We examined how the dynamics of nutrient release from leaf litter responded to two important atmospheric changes: rising atmospheric Co2 and tropospheric O3. We evaluated the independent and combined effects of...

Emergence of nutrient limitation in tropical dry forests: hypotheses from simulation models

NASA Astrophysics Data System (ADS)

Medvigy, D.; Waring, B. G.; Xu, X.; Trierweiler, A.; Werden, L. K.; Wang, G.; Zhu, Q.; Powers, J. S.

2017-12-01

It is unclear to what extent tropical dry forest productivity may be limited by nutrients. Direct assessment of nutrient limitation through fertilization experiments has been rare, and paradigms pertaining to other ecosystems may not extend to tropical dry forests. For example, because dry tropical forests have a lower water supply than moist tropical forests, dry forests can have lower decomposition rates, higher soil carbon and nitrogen concentrations, and a more open nitrogen cycle than moist forests. We used a mechanistic, numerical model to generate hypotheses about nutrient limitation in tropical dry forests. The model dynamically couples ED2 (vegetation dynamics), MEND (biogeochemistry), and N-COM (plant-microbe competition for nutrients). Here, the MEND-component of the model has been extended to include nitrogen (N) and phosphorus (P) cycles. We focus on simulation of sixteen 25m x 25m plots in Costa Rica where a fertilization experiment has been underway since 2015. Baseline simulations are characterized by both nitrogen and phosphorus limitation of vegetation. Fertilization with N and P increased vegetation biomass, with N fertilization having a somewhat stronger effect. Nutrient limitation was also sensitive to climate and was more pronounced during drought periods. Overflow respiration was identified as a key process that mitigated nutrient limitation. These results suggest that, despite often having richer soils than tropical moist forests, tropical dry forests can also become nutrient-limited. If the climate becomes drier in the next century, as is expected for Central America, drier soils may decrease microbial activity and exacerbate nutrient limitation. The importance of overflow respiration underscores the need for appropriate treatment of microbial dynamics in ecosystem models. Ongoing and new nutrient fertilization experiments will present opportunities for testing whether, and how, nutrient limitation may indeed be emerging in tropical dry

Quantifying uncertainty due to fission-fusion dynamics as a component of social complexity.

PubMed

Ramos-Fernandez, Gabriel; King, Andrew J; Beehner, Jacinta C; Bergman, Thore J; Crofoot, Margaret C; Di Fiore, Anthony; Lehmann, Julia; Schaffner, Colleen M; Snyder-Mackler, Noah; Zuberbühler, Klaus; Aureli, Filippo; Boyer, Denis

2018-05-30

Groups of animals (including humans) may show flexible grouping patterns, in which temporary aggregations or subgroups come together and split, changing composition over short temporal scales, (i.e. fission and fusion). A high degree of fission-fusion dynamics may constrain the regulation of social relationships, introducing uncertainty in interactions between group members. Here we use Shannon's entropy to quantify the predictability of subgroup composition for three species known to differ in the way their subgroups come together and split over time: spider monkeys ( Ateles geoffroyi ), chimpanzees ( Pan troglodytes ) and geladas ( Theropithecus gelada ). We formulate a random expectation of entropy that considers subgroup size variation and sample size, against which the observed entropy in subgroup composition can be compared. Using the theory of set partitioning, we also develop a method to estimate the number of subgroups that the group is likely to be divided into, based on the composition and size of single focal subgroups. Our results indicate that Shannon's entropy and the estimated number of subgroups present at a given time provide quantitative metrics of uncertainty in the social environment (within which social relationships must be regulated) for groups with different degrees of fission-fusion dynamics. These metrics also represent an indirect quantification of the cognitive challenges posed by socially dynamic environments. Overall, our novel methodological approach provides new insight for understanding the evolution of social complexity and the mechanisms to cope with the uncertainty that results from fission-fusion dynamics. © 2017 The Author(s).

Quantifying nonergodicity in nonautonomous dissipative dynamical systems: An application to climate change

NASA Astrophysics Data System (ADS)

Drótos, Gábor; Bódai, Tamás; Tél, Tamás

2016-08-01

In nonautonomous dynamical systems, like in climate dynamics, an ensemble of trajectories initiated in the remote past defines a unique probability distribution, the natural measure of a snapshot attractor, for any instant of time, but this distribution typically changes in time. In cases with an aperiodic driving, temporal averages taken along a single trajectory would differ from the corresponding ensemble averages even in the infinite-time limit: ergodicity does not hold. It is worth considering this difference, which we call the nonergodic mismatch, by taking time windows of finite length for temporal averaging. We point out that the probability distribution of the nonergodic mismatch is qualitatively different in ergodic and nonergodic cases: its average is zero and typically nonzero, respectively. A main conclusion is that the difference of the average from zero, which we call the bias, is a useful measure of nonergodicity, for any window length. In contrast, the standard deviation of the nonergodic mismatch, which characterizes the spread between different realizations, exhibits a power-law decrease with increasing window length in both ergodic and nonergodic cases, and this implies that temporal and ensemble averages differ in dynamical systems with finite window lengths. It is the average modulus of the nonergodic mismatch, which we call the ergodicity deficit, that represents the expected deviation from fulfilling the equality of temporal and ensemble averages. As an important finding, we demonstrate that the ergodicity deficit cannot be reduced arbitrarily in nonergodic systems. We illustrate via a conceptual climate model that the nonergodic framework may be useful in Earth system dynamics, within which we propose the measure of nonergodicity, i.e., the bias, as an order-parameter-like quantifier of climate change.

Environmental Nutrient Supply Directly Alters Plant Traits but Indirectly Determines Virus Growth Rate

PubMed Central

Lacroix, Christelle; Seabloom, Eric W.; Borer, Elizabeth T.

2017-01-01

Ecological stoichiometry and resource competition theory both predict that nutrient rates and ratios can alter infectious disease dynamics. Pathogens such as viruses hijack nutrient rich host metabolites to complete multiple steps of their epidemiological cycle. As the synthesis of these molecules requires nitrogen (N) and phosphorus (P), environmental supply rates, and ratios of N and P to hosts can directly limit disease dynamics. Environmental nutrient supplies also may alter virus epidemiology indirectly by changing host phenotype or the dynamics of coinfecting pathogens. We tested whether host nutrient supplies and coinfection control pathogen growth within hosts and transmission to new hosts, either directly or through modifications of plant tissue chemistry (i.e., content and stoichiometric ratios of nutrients), host phenotypic traits, or among-pathogen interactions. We examined two widespread plant viruses (BYDV-PAV and CYDV-RPV) in cultivated oats (Avena sativa) grown along a range of N and of P supply rates. N and P supply rates altered plant tissue chemistry and phenotypic traits; however, environmental nutrient supplies and plant tissue content and ratios of nutrients did not directly alter virus titer. Infection with CYDV-RPV altered plant traits and resulted in thicker plant leaves (i.e., higher leaf mass per area) and there was a positive correlation between CYDV-RPV titer and leaf mass per area. CYDV-RPV titer was reduced by the presence of a competitor, BYDV-PAV, and higher CYDV-RPV titer led to more severe chlorotic symptoms. In our experimental conditions, virus transmission was unaffected by nutrient supply rates, co-infection, plant stoichiometry, or plant traits, although nutrient supply rates have been shown to increase infection and coinfection rates. This work provides a robust test of the role of plant nutrient content and ratios in the dynamics of globally important pathogens and reveals a more complex relationship between within

Influences of historical and projected changes in climate and land management practices on nutrient fluxes in the Mississippi River Basin, 1948-2100

NASA Astrophysics Data System (ADS)

Spak, S.; Ward, A. S.; Li, Y.; Dalrymple, K. E.

2016-12-01

Nitrogen fertilization is central to contemporary row crop production in the U.S., but resultant nitrate transport leads to eutrophication, hypoxia, and algal blooms throughout the Mississippi River Basin and in coastal waters of the Gulf of Mexico. Effective basin-scale nutrient management requires a comprehensive understanding of the dynamics of nitrate transport in this large river catchment and the roles of individual management practices, that must then be operationalized to optimize management for both local geophysical and agricultural conditions and in response to decadal and inter-annual variations in local and regional climate. Here, we apply ensemble simulations with Agro-IBIS and THMB using spatially and temporally specific land cover, soil, agricultural, topographic, and climate data to simulate the individual and combined effects of land management and climate on historical (1948-2007) nitrate concentrations and transport in the Mississippi River Basin. We further identify sensitivities of in-stream nitrate dynamics to local and regional applications of Best Management Practices. The ensemble resolves the effects of techniques recommended in the Iowa Nutrient Reduction Strategy, including crop rotations, fertilizer management, tillage and residue management, and cover crops. Analysis of the nitrate transport response surfaces identifies non-linear effects of combined nutrient management tactics, and quantifies the stationarity of the relative and absolute influences of land management and climate during the 60-year study period.

Microbial dynamics and enzyme activities in tropical Andosols depending on land use and nutrient inputs

NASA Astrophysics Data System (ADS)

Mganga, Kevin; Razavi, Bahar; Kuzyakov, Yakov

2015-04-01

Microbial decomposition of soil organic matter is mediated by enzymes and is a key source of terrestrial CO2 emissions. Microbial and enzyme activities are necessary to understand soil biochemical functioning and identify changes in soil quality. However, little is known about land use and nutrients availability effects on enzyme activities and microbial processes, especially in tropical soils of Africa. This study was conducted to examine how microbial and enzyme activities differ between different land uses and nutrient availability. As Andosols of Mt. Kilimanjaro are limited by nutrient concentrations, we hypothesize that N and P additions will stimulate enzyme activity. N and P were added to soil samples (0-20 cm) representing common land use types in East Africa: (1) savannah, (2) maize fields, (3) lower montane forest, (4) coffee plantation, (5) grasslands and (6) traditional Chagga homegardens. Total CO2 efflux from soil, microbial biomass and activities of β-glucosidase, cellobiohydrolase, chitinase and phosphatase involved in C, N and P cycling, respectively was monitored for 60 days. Total CO2 production, microbial biomass and enzyme activities varied in the order forest soils > grassland soils > arable soils. Increased β-glucosidase and cellobiohydrolase activities after N addition of grassland soils suggest that microorganisms increased N uptake and utilization to produce C-acquiring enzymes. Low N concentration in all soils inhibited chitinase activity. Depending on land use, N and P addition had an inhibitory or neutral effect on phosphatase activity. We attribute this to the high P retention of Andosols and low impact of N and P on the labile P fractions. Enhanced CO2 production after P addition suggests that increased P availability could stimulate soil organic matter biodegradation in Andosols. In conclusion, land use and nutrients influenced soil enzyme activities and microbial dynamics and demonstrated the decline in soil quality after landuse

San Francisco Bay nutrients and plankton dynamics as simulated by a coupled hydrodynamic-ecosystem model

NASA Astrophysics Data System (ADS)

Liu, Qianqian; Chai, Fei; Dugdale, Richard; Chao, Yi; Xue, Huijie; Rao, Shivanesh; Wilkerson, Frances; Farrara, John; Zhang, Hongchun; Wang, Zhengui; Zhang, Yinglong

2018-06-01

An open source coupled physical-biogeochemical model is developed for San Francisco Bay (SFB) to study nutrient cycling and plankton dynamics as well as to assist ecosystem based management and risk assessment. The biogeochemical model in this study is based on the Carbon, Silicate and Nitrogen Ecosystem (CoSiNE) model, and coupled to the unstructured grid, Semi-Implicit Cross-scale Hydroscience Integrated System Model (SCHISM). The SCHISM-CoSiNE model reproduces the spatial and temporal variability in nutrients and plankton biomass, and its physical and biogeochemical performance is successfully tested using comparisons with shipboard and fixed station observations. The biogeochemical characteristics of the SFB during wet and dry years are investigated by changing the input of the major rivers. River discharges from the Sacramento and San Joaquin Rivers affect the phytoplankton biomass in North SFB through both advection and dilution of nutrient (including ammonium, NH4) concentrations in the river. The reduction in residence time caused by increased inflows can result in decreased biomass accumulation, while the corresponding reduction in NH4 concentration favors the growth of biomass. In addition, the model is used to make a series of sensitivity experiments to examine the response of SFB to changes in 1) nutrient loading from rivers and wastewater treatment plants (WWTPs), 2) a parameter (ψ) defining NH4 inhibition of nitrate (NO3) uptake by phytoplankton, 3) bottom grazing and 4) suspended sediment concentration. The model results show that changes in NH4 input from rivers or WWTPs affect the likelihood of phytoplankton blooms via NH4 inhibition and that the choice of ψ is critical. Bottom grazing simulated here as increased plankton mortality demonstrates the potential for bivalve reduction of chlorophyll biomass and the need to include bivalve grazing in future models. Furthermore, the model demonstrates the need to include sediments and their contribution

Decomposition drives convergence of forest litter nutrient stoichiometry following phosphorus addition

USGS Publications Warehouse

van Huysen, Tiff L.; Perakis, Steven; Harmon, Mark E.

2016-01-01

We conclude that litter P concentrations and to some extent soil P may influence litter nutrient dynamics during decomposition, resulting in a convergence of element ratios that reflect the balance of substrate decomposition and microbial nutrient stoichiometry.

Nutrient availability at Mer Bleue bog measured by PRSTM probes

NASA Astrophysics Data System (ADS)

Wang, M.; Moore, T. R.; Talbot, J.

2015-12-01

Bogs, covering ~0.7 million km2 in Canada, store a large amount of C and N. As nutrient deficient ecosystems, it's critical to examine the nutrient availabilities and seasonal dynamics. We used Plant Root Simulators (PRSTM) at Mer Bleue bog to provide some baseline data on nutrient availability and its variability. In particular, we focused on ammonium, nitrate, phosphate, calcium, magnesium and potassium, iron, sulphate and aluminum. We placed PRS probes at a depth of 5 - 15 cm in pristine plots and plots with long term N, P and K fertilization for 4 weeks and determined the availability of these nutrients, from spring through to fall. Probes were also placed beneath the water table in hummock and hollow microtopography and along a transect including part of the bog which had been drained through the creation of a ditch 80 years ago. The result showed that there was limited available ammonium, nitrate and phosphate in the bog, the seasonal variation of nutrient availabilities probably due to mineralization, an increase in the availability of some nutrients between different water table depths or as a result of drainage, and the relative availability of nutrients compared to the input from fertilization. We suggest that PRS probes could be a useful tool to examine nutrient availability and dynamics in wetlands, with careful consideration of installing condition, for example, proper exposure period, depth relative to water table etc.

Quantifying Factors That Impact Riverbed Dynamic Permeability at a Riverbank Filtration Facility

NASA Astrophysics Data System (ADS)

Ulrich, C.; Hubbard, S. S.; Florsheim, J. L.; Rosenberry, D. O.; Borglin, S. E.; Zhang, Y.; Seymour, D.; Trotta, M.

2012-12-01

Previous modeling studies of the Wohler riverbank filtration system on the Russian River, California suggested that riverbed and aquifer permeability both influence the development of a pumping-induced unsaturated zone below the riverbed, which affects water produced through large radial water-supply collector wells that extend beneath and adjacent to the river. In particular, previous work suggests that riverbed permeability is influenced by interaction between pumping and river stage that is controlled by a downstream temporary inflatable dam during the summer low flow period. We hypothesize that raising the dam may instead lead to deposition of fine-grained sediment and/or accumulation of biota, both of which decrease riverbed permeability in the vicinity of the collector wells. To test this hypothesis, we are monitoring streambed permeability and seepage as a function of river stage and dam operation. We are using multiple methods to monitor the hydrological, sedimentological and geomorphic dynamics, including: seepage meters, sediment traps, cryogenic coring, ground penetrating radar, electrical resistance tomography, riverbed topography, piezometers, and thermistors. Here we discuss the use of this novel suite of methods to quantify dynamic riverbed permeability, how it relates to dam operation, and determine the key controls on permeability (i.e., biotic or abiotic). These results are expected to improve the overall understanding of riverbed permeability dynamics associated with Riverbank filtration. The results are also expected to be transferable to the project sponsors, the Sonoma County Water Agency, toward the development of an optimal pumping and dam operation schedule.

Nutrient Dynamics in Flooded Wetlands. II: Model Application

EPA Science Inventory

In this paper we applied and evaluated the wetland nutrient model described in an earlier paper. Hydrologic and water quality data from a small restored wetland located on Kent Island, Maryland, which is part of the Delmarva Peninsula on the Eastern shores of the Chesapeake Bay...

Plant response to nutrient availability across variable bedrock geologies

USGS Publications Warehouse

Castle, S.C.; Neff, J.C.

2009-01-01

We investigated the role of rock-derived mineral nutrient availability on the nutrient dynamics of overlying forest communities (Populus tremuloides and Picea engelmanni-Abies lasiocarpa v. arizonica) across three parent materials (andesite, limestone, and sandstone) in the southern Rocky Mountains of Colorado. Broad geochemical differences were observed between bedrock materials; however, bulk soil chemistries were remarkably similar between the three different sites. In contrast, soil nutrient pools were considerably different, particularly for P, Ca, and Mg concentrations. Despite variations in nutrient stocks and nutrient availability in soils, we observed relatively inflexible foliar concentrations and foliar stoichiometries for both deciduous and coniferous species. Foliar nutrient resorption (P and K) in the deciduous species followed patterns of nutrient content across substrate types, with higher resorption corresponding to lower bedrock concentrations. Work presented here indicates a complex plant response to available soil nutrients, wherein plant nutrient use compensates for variations in supply gradients and results in the maintenance of a narrow range in foliar stoichiometry. ?? 2008 Springer Science+Business Media, LLC.

Dissolved Nutrient Removal in River Networks: When and Where

NASA Astrophysics Data System (ADS)

Ye, S.; Ran, Q.

2017-12-01

Along the river network, water, sediment, and nutrients are transported, cycled, and altered by coupled hydrological and biogeochemical processes. Due to increasing human activities such as urbanization, and fertilizer application associated with agricultural land use, nitrogen and phosphorus inputs to aquatic ecosystems have increased dramatically since the beginning of the 20th century. Meanwhile, our current understanding of the rates and processes controlling the cycling and removal of dissolved inorganic nutrients in river networks is still limited due to a lack of empirical measurements, especially in large rivers. Here, based on the simulation of a coupled hydrological and biogeochemical process model, we track the nutrient uptake at the network scale. The model was parameterized with literature values from headwater streams and empirical measurements made in 15 rivers with varying hydrological, biological, and topographic characteristics. We applied the coupled model to an agricultural catchment in the Midwest to estimate the residence time, reaction time and travel distance of the nutrient exported from different places across watershed. In this work, we explore how to use these temporal and spatial characteristics to quantify the nutrient removal across the river network. We then further investigate the impact of heterogeneous lateral input on network scale nutrient removal. Whether or not this would influence the overall nutrient removal in the watershed, if so, to what extent would this have significant impact?

Roots bridge water to nutrients: a study of utilizing hydraulic redistribution through root systems to extract nutrients in the dry soils

NASA Astrophysics Data System (ADS)

Yan, J.; Ghezzehei, T. A.

2017-12-01

The rhizosphere is the region of soil that surrounds by individual plant roots. While its small volume and narrow region compared to bulk soil, the rhizosphere regulates numerous processes that determine physical structure, nutrient distribution, and biodiversity of soils. One of the most important and distinct functions of the rhizosphere is the capacity of roots to bridge and redistribute soil water from wet soil layers to drier layers. This process was identified and defined as hydraulic lift or hydraulic redistribution, a passive process driven by gradients in water potentials and it has attracted much research attention due to its important role in global water circulation and agriculture security. However, while previous studies mostly focused on the hydrological or physiological impacts of hydraulic redistribution, limited research has been conducted to elucidate its role in nutrient cycling and uptake. In this study, we aim to test the possibility of utilizing hydraulic redistribution to facilitate the nutrient movement and uptake from resource segregated zone. Our overarching hypothesis is that plants can extract nutrients from the drier but nutrient-rich regions by supplying sufficient amounts of water from the wet but nutrient-deficient regions. To test our hypothesis, we designed split-root systems of tomatoes with unequal supply of water and nutrients in different root compartments. More specifically, we transplanted tomato seedlings into sand or soil mediums, and grew them under conditions with alternate 12-h lightness and darkness. We continuously monitored the temperature, water and nutrient content of soils in these separated compartments. The above and below ground biomass were also quantified to evaluate the impacts on the plant growth. The results were compared to a control with evenly supply of water and nutrients to assess the plant growth, nutrient leaching and uptake without hydraulic redistribution.

Response of Periphyton to Seasonal Changes in Nutrient Concentrations in Central Illinois Agricultural Streams

NASA Astrophysics Data System (ADS)

Kirkham, K. G.; Perry, W. L.

2005-05-01

Headwater streams in central Illinois have been dredged and channelized to drain surrounding agricultural fields and has led to extensive erosion and eutrophication. Restoration of these systems through farmer implementation of Best Management Practices (BMPs) may be one solution. Examination of algal population dynamics may be useful in assessment of BMP effectiveness. We have monitored two small headwater streams, Bray Creek and Frog Alley, for a suite of physicochemical parameters focusing on dissolved oxygen, nitrogen, and phosphorus for three years. Nutrient concentrations suggested potential nutrient limitation by nitrates during late summer and phosphorus limitation in early summer. To determine seasonal algal dynamics with seasonally varying nutrient limitation in agricultural headwater streams, we used nutrient diffusing substrata (NDS). NDS with agar (controls) or amended with either nitrogen, phosphorus, or both were deployed for 21-24 days in both streams each month for a year. Slight nutrient limitation was observed in Bray Creek during August and November while phosphorus was limiting in September (P<0.05). We suggest agricultural streams are more dynamic than previously thought and algal populations may be seasonally nutrient limited and with consequent effects on dissolved oxygen concentrations.

Proximate and Ultimate Limiting Nutrients in the Mississippi River Plume: Implications for Hypoxia Reduction Through Nutrient Management

NASA Astrophysics Data System (ADS)

Fennel, K.; Laurent, A.

2016-02-01

A large hypoxic area (15,000 km2 on average) forms every summer over the Texas-Louisiana shelf in the northern Gulf of Mexico due to decay of organic matter that is primarily derived from nutrient inputs from the Mississippi/Atchafalaya River System. Efforts are underway to reduce the extent of hypoxic conditions through nutrient management in the watershed; for example, an interagency Hypoxia Task Force is developing Action Plans with input from various stakeholders that set out targets for hypoxia reduction. An open question is by how much nutrient loads would have to be decreased in order to produce the desired reductions in hypoxia and when these would be measurable over natural variability. We have performed a large number of multi-year nutrient load reduction scenarios with a regional biogeochemical model for the region. The model is based on the Regional Ocean Modeling System (ROMS), explicitly includes nitrogen (N) and phosphorus (P) species as inorganic nutrients, and has been shown to realistically reproduce the key processes responsible for hypoxia generation. We have quantified the effects of differential reductions in river N and P loads on hypoxic extent. An assessment of the effects of N versus P reductions is important because, thus far, nutrient management efforts have focused on N, yet P is known to limit primary production in spring and early summer. A debate is ongoing as to whether targets for P reductions should be set and whether nutrient reduction efforts should focus solely on P, which results primarily from urban and industrial point sources and is uncoupled from agricultural fertilizer application. Our results strongly indicate that N is the `ultimate' limiting nutrient to primary production determining the areal extent and duration of hypoxic conditions in a cumulative sense, while P is temporarily limiting in spring. Although reductions in river P load would decrease hypoxic extent in early summer, they would have a much smaller effect

Repeat synoptic sampling reveals drivers of change in carbon and nutrient chemistry of Arctic catchments

NASA Astrophysics Data System (ADS)

Zarnetske, J. P.; Abbott, B. W.; Bowden, W. B.; Iannucci, F.; Griffin, N.; Parker, S.; Pinay, G.; Aanderud, Z.

2017-12-01

Dissolved organic carbon (DOC), nutrients, and other solute concentrations are increasing in rivers across the Arctic. Two hypotheses have been proposed to explain these trends: 1. distributed, top-down permafrost degradation, and 2. discrete, point-source delivery of DOC and nutrients from permafrost collapse features (thermokarst). While long-term monitoring at a single station cannot discriminate between these mechanisms, synoptic sampling of multiple points in the stream network could reveal the spatial structure of solute sources. In this context, we sampled carbon and nutrient chemistry three times over two years in 119 subcatchments of three distinct Arctic catchments (North Slope, Alaska). Subcatchments ranged from 0.1 to 80 km2, and included three distinct types of Arctic landscapes - mountainous, tundra, and glacial-lake catchments. We quantified the stability of spatial patterns in synoptic water chemistry and analyzed high-frequency time series from the catchment outlets across the thaw season to identify source areas for DOC, nutrients, and major ions. We found that variance in solute concentrations between subcatchments collapsed at spatial scales between 1 to 20 km2, indicating a continuum of diffuse- and point-source dynamics, depending on solute and catchment characteristics (e.g. reactivity, topography, vegetation, surficial geology). Spatially-distributed mass balance revealed conservative transport of DOC and nitrogen, and indicates there may be strong in-stream retention of phosphorus, providing a network-scale confirmation of previous reach-scale studies in these Arctic catchments. Overall, we present new approaches to analyzing synoptic data for change detection and quantification of ecohydrological mechanisms in ecosystems in the Arctic and beyond.

Differences in ecosystem carbon distribution and nutrient cycling linked to forest tree species composition in a mid-successional boreal forest

USGS Publications Warehouse

Melvin, April M.; Mack, Michelle C.; Johnstone, Jill F.; McGuire, A. David; Genet, Helene; Schuur, Edward A.G.

2015-01-01

In the boreal forest of Alaska, increased fire severity associated with climate change is expanding deciduous forest cover in areas previously dominated by black spruce (Picea mariana). Needle-leaf conifer and broad-leaf deciduous species are commonly associated with differences in tree growth, carbon (C) and nutrient cycling, and C accumulation in soils. Although this suggests that changes in tree species composition in Alaska could impact C and nutrient pools and fluxes, few studies have measured these linkages. We quantified C, nitrogen, phosphorus, and base cation pools and fluxes in three stands of black spruce and Alaska paper birch (Betula neoalaskana) that established following a single fire event in 1958. Paper birch consistently displayed characteristics of more rapid C and nutrient cycling, including greater aboveground net primary productivity, higher live foliage and litter nutrient concentrations, and larger ammonium and nitrate pools in the soil organic layer (SOL). Ecosystem C stocks (aboveground + SOL + 0–10 cm mineral soil) were similar for the two species; however, in black spruce, 78% of measured C was found in soil pools, primarily in the SOL, whereas aboveground biomass dominated ecosystem C pools in birch forest. Radiocarbon analysis indicated that approximately one-quarter of the black spruce SOL C accumulated prior to the 1958 fire, whereas no pre-fire C was observed in birch soils. Our findings suggest that tree species exert a strong influence over C and nutrient cycling in boreal forest and forest compositional shifts may have long-term implications for ecosystem C and nutrient dynamics.

Toward a transport-based analysis of nutrient spiraling and uptake in streams

USGS Publications Warehouse

Runkel, Robert L.

2007-01-01

Nutrient addition experiments are designed to study the cycling of nutrients in stream ecosystems where hydrologic and nonhydrologic processes determine nutrient fate. Because of the importance of hydrologic processes in stream ecosystems, a conceptual model known as nutrient spiraling is frequently employed. A central part of the nutrient spiraling approach is the determination of uptake length (SW), the average distance traveled by dissolved nutrients in the water column before uptake. Although the nutrient spiraling concept has been an invaluable tool in stream ecology, the current practice of estimating uptake length from steady-state nutrient data using linear regression (called here the "SW approach") presents a number of limitations. These limitations are identified by comparing the exponential SW equation with analytical solutions of a stream solute transport model. This comparison indicates that (1) SW, is an aggregate measure of uptake that does not distinguish between main channel and storage zone processes, (2) SW, is an integrated measure of numerous hydrologie and nonhydrologic processes-this process integration may lead to difficulties in interpretation when comparing estimates of SW, and (3) estimates of uptake velocity and areal uptake rate (Vf and U) based on S W, are not independent of system hydrology. Given these findings, a transport-based approach to nutrient spiraling is presented for steady-state and time-series data sets. The transport-based approach for time-series data sets is suggested for future research on nutrient uptake as it provides a number of benefits, including the ability to (1) separately quantify main channel and storage zone uptake, (2) quantify specific hydrologic and nonhydrologic processes using various model parameters (process separation), (3) estimate uptake velocities and areal uptake rates that are independent of hydrologic effects, and (4) use short-term, non-plateau nutrient additions such that the effects of

Exploring bamboo leaf nutrient value in the US NPGS germplasm collection

USDA-ARS?s Scientific Manuscript database

Bamboo shoots and leaves are nutritious, providing food for both human and animal consumption. But their nutrient value may depend on the bamboo species, harvesting season, and growing location. Leaf crude protein content, amino acid composition, and mineral element concentration were quantified fro...

Boosted Regression Tree Models to Explain Watershed Nutrient Concentrations and Biological Condition

EPA Science Inventory

Boosted regression tree (BRT) models were developed to quantify the nonlinear relationships between landscape variables and nutrient concentrations in a mesoscale mixed land cover watershed during base-flow conditions. Factors that affect instream biological components, based on ...

The effect of herbicide application on rangeland soil nutrient availability

USDA-ARS?s Scientific Manuscript database

Very sparse literature exists on the effect of soil active herbicides on nutrient availability. As part of a larger rangeland rehabilitation project, on four sites in northern Nevada, we quantified the effect of the herbicides Landmark®, Perspective®, and Plateau® relative to controls on surface soi...

Proposal for a method to estimate nutrient shock effects in bacteria

PubMed Central

2012-01-01

Background Plating methods are still the golden standard in microbiology; however, some studies have shown that these techniques can underestimate the microbial concentrations and diversity. A nutrient shock is one of the mechanisms proposed to explain this phenomenon. In this study, a tentative method to assess nutrient shock effects was tested. Findings To estimate the extent of nutrient shock effects, two strains isolated from tap water (Sphingomonas capsulata and Methylobacterium sp.) and two culture collection strains (E. coli CECT 434 and Pseudomonas fluorescens ATCC 13525) were exposed both to low and high nutrient conditions for different times and then placed in low nutrient medium (R2A) and rich nutrient medium (TSA). The average improvement (A.I.) of recovery between R2A and TSA for the different times was calculated to more simply assess the difference obtained in culturability between each medium. As expected, A.I. was higher when cells were plated after the exposition to water than when they were recovered from high-nutrient medium showing the existence of a nutrient shock for the diverse bacteria used. S. capsulata was the species most affected by this phenomenon. Conclusions This work provides a method to consistently determine the extent of nutrient shock effects on different microorganisms and hence quantify the ability of each species to deal with sudden increases in substrate concentration. PMID:22873690

Evaluating Aquatic Life Benefits of Reducing Nutrient Loading ...

EPA Pesticide Factsheets

Theoretical linkages between excess nutrient loading, nutrient-enhanced community metabolism (i.e., production and respiration), and hypoxia in estuaries are well-understood. In seasonally-stratified estuaries and coastal systems (e.g., Chesapeake Bay, northern Gulf of Mexico), hypoxia is predominantly seasonal, such that the spatial extent indicates potential aquatic life impacts. However, in relatively small and shallow Gulf of Mexico bays and bayous, hypoxia frequently occurs episodically or on a diel basis. This study utilized continuous DO monitoring and 3-D hydrodynamic (Environmental Fluid Dynamics Code) and water quality (Water Quality Analysis Simulation Program) models to examine physical and biological controls on DO dynamics and ecosystem metabolism in Weeks Bay, AL. Observed vertical DO gradients varied on a diel basis, with larger amplitude variations at depth relative to the surface, underscoring the importance of benthic production and respiration as a driver of ecosystem metabolism in shallow estuaries. Hydrodynamic and water quality models simulated seasonal and event-driven dynamics, but struggled to resolve the amplitude of daily DO fluctuations, particularly in bottom waters. Using these data in conjunction with the 10-year continuous O2 record from Weeks Bay, we applied empirical relationships and simple scaling relations to predict how reducing nutrient loading may affect the frequency, severity and duration of hypoxia. We further applied

The afterlife of interspecific indirect genetic effects: genotype interactions alter litter quality with consequences for decomposition and nutrient dynamics.

PubMed

Genung, Mark A; Bailey, Joseph K; Schweitzer, Jennifer A

2013-01-01

Aboveground-belowground linkages are recognized as divers of community dynamics and ecosystem processes, but the impacts of plant-neighbor interactions on these linkages are virtually unknown. Plant-neighbor interactions are a type of interspecific indirect genetic effect (IIGE) if the focal plant's phenotype is altered by the expression of genes in a neighboring heterospecific plant, and IIGEs could persist after plant senescence to affect ecosystem processes. This perspective can provide insight into how plant-neighbor interactions affect evolution, as IIGEs are capable of altering species interactions and community composition over time. Utilizing genotypes of Solidago altissima and Solidago gigantea, we experimentally tested whether IIGEs that had affected living focal plants would affect litter decomposition rate, as well as nitrogen (N) and phosphorous (P) dynamics after the focal plant senesced. We found that species interactions affected N release and genotype interactions affected P immobilization. From a previous study we knew that neighbor genotype influenced patterns of biomass allocation for focal plants. Here we extend those previous results to show that these changes in biomass allocation altered litter quality, that then altered rates of decomposition and nutrient cycling. Our results provide insights into above- and belowground linkages by showing that, through their effects on plant litter quality (e.g., litter lignin:N), IIGEs can have afterlife effects, tying plant-neighbor interactions to ecosystem processes. This holistic approach advances our understanding of decomposition and nutrient cycling by showing that evolutionary processes (i.e., IIGEs) can influence ecosystem functioning after plant senescence. Because plant traits are determined by the combined effects of genetic and environmental influences, and because these traits are known to affect decomposition and nutrient cycling, we suggest that ecosystem processes can be described as gene

The Afterlife of Interspecific Indirect Genetic Effects: Genotype Interactions Alter Litter Quality with Consequences for Decomposition and Nutrient Dynamics

PubMed Central

Genung, Mark A.; Bailey, Joseph K.; Schweitzer, Jennifer A.

2013-01-01

Aboveground-belowground linkages are recognized as divers of community dynamics and ecosystem processes, but the impacts of plant-neighbor interactions on these linkages are virtually unknown. Plant-neighbor interactions are a type of interspecific indirect genetic effect (IIGE) if the focal plant’s phenotype is altered by the expression of genes in a neighboring heterospecific plant, and IIGEs could persist after plant senescence to affect ecosystem processes. This perspective can provide insight into how plant-neighbor interactions affect evolution, as IIGEs are capable of altering species interactions and community composition over time. Utilizing genotypes of Solidago altissima and Solidago gigantea, we experimentally tested whether IIGEs that had affected living focal plants would affect litter decomposition rate, as well as nitrogen (N) and phosphorous (P) dynamics after the focal plant senesced. We found that species interactions affected N release and genotype interactions affected P immobilization. From a previous study we knew that neighbor genotype influenced patterns of biomass allocation for focal plants. Here we extend those previous results to show that these changes in biomass allocation altered litter quality, that then altered rates of decomposition and nutrient cycling. Our results provide insights into above- and belowground linkages by showing that, through their effects on plant litter quality (e.g., litter lignin:N), IIGEs can have afterlife effects, tying plant-neighbor interactions to ecosystem processes. This holistic approach advances our understanding of decomposition and nutrient cycling by showing that evolutionary processes (i.e., IIGEs) can influence ecosystem functioning after plant senescence. Because plant traits are determined by the combined effects of genetic and environmental influences, and because these traits are known to affect decomposition and nutrient cycling, we suggest that ecosystem processes can be described as

Hillslope nutrient dynamics following upland riparian vegetation disturbance

Treesearch

J. Alan Yeakley; David C. Coleman; Bruce L. Haines; Brian D. Kloeppel; Judy L. Meyer; Wayne T. Swank; Barry W. Argo; James M. Deal; Sharon F. Taylor

2003-01-01

We investigated the effects of removing nearstream Rhododendron and of the natural blowdown of canopy trees on nutrient export to streams in the southern Appalachians. Transects were instrumented on adjacent hillslopes in a first-order watershed at the Coweeta Hydrologic Laboratory (35°03'N, 83°25'W). Dissolved organic carbon (DOC), K+...

Spatiotemporal associations of reservoir nutrient characteristics and the invasive, harmful alga Prymnesium parvum in West Texas

USGS Publications Warehouse

VanLandeghem, Matthew M.; Farooqi, Mukhtar; Southard, Greg M.; Patino, Reynaldo

2015-01-01

Golden alga (Prymnesium parvum) is a harmful alga that has caused ecological and economic harm in freshwater and marine systems worldwide. In inland systems of North America, toxic blooms have nearly eliminated fish populations in some systems. Modifying nutrient profiles through alterations to land or water use may be a viable alternative for golden alga control in reservoirs. The main objective of this study was to improve our understanding of the nutrient dynamics that influence golden alga bloom formation and toxicity in west Texas reservoirs. We examined eight sites in the Upper Colorado River basin, Texas: three impacted reservoirs that have experienced repeated golden alga blooms; two reference reservoirs where golden alga is present but nontoxic; and three confluence sites downstream of the impacted and reference sites. Total, inorganic, and organic nitrogen and phosphorus and their ratios were quantified monthly along with golden alga abundance and ichthyotoxicity between December 2010 and July 2011. Blooms persisted for several months at the impacted sites, which were characterized by high organic nitrogen and low inorganic nitrogen. At impacted sites, abundance was positively associated with inorganic phosphorus and bloom termination coincided with increases in inorganic nitrogen and decreases in inorganic phosphorus in late spring. Management of both inorganic and organic forms of nutrients may create conditions in reservoirs unfavorable to golden alga.

Proximate versus ultimate limiting nutrients in the Mississippi River Plume and Implications for Hypoxia Reductions through Nutrient Management

NASA Astrophysics Data System (ADS)

Fennel, Katja; Laurent, Arnaud

2016-04-01

A large hypoxic area (15,000 km2 on average) forms every summer over the Texas-Louisiana shelf in the northern Gulf of Mexico due to decay of organic matter that is primarily derived from nutrient inputs from the Mississippi/Atchafalaya River System. Efforts are underway to reduce the extent of hypoxic conditions through nutrient management in the watershed; for example, an interagency Hypoxia Task Force is developing Action Plans with input from various stakeholders that set out targets for hypoxia reduction. An open question is how far nutrient loads would have to be decreased in order to produce the desired reductions in hypoxia and when these would be measurable given significant natural variability. We have simulated a large number of multi-year nutrient load reduction scenarios with a regional biogeochemical model for the region. The model is based on the Regional Ocean Modeling System (ROMS), explicitly includes nitrogen (N) and phosphorus (P) species as inorganic nutrients, and has been shown to realistically reproduce the key processes responsible for hypoxia generation. We have quantified the effects of differential reductions in river N and P loads on hypoxic extent. An assessment of the effects of N versus P reductions is important because, thus far, nutrient management efforts have focused on N, yet P is known to limit primary production in spring and early summer. A debate is ongoing as to whether targets for P reductions should be set and whether nutrient reduction efforts should focus solely on P, which results primarily from urban and industrial point sources and is uncoupled from agricultural fertilizer application. Our results strongly indicate that N is the 'ultimate' limiting nutrient to primary production determining the areal extent and duration of hypoxic conditions in a cumulative sense, while P is temporarily limiting in spring. Although reductions in river P load would decrease hypoxic extent in early summer, they would have a much

Monitoring TASCC Injections Using A Field-Ready Wet Chemistry Nutrient Autoanalyzer

NASA Astrophysics Data System (ADS)

Snyder, L. E.; Herstand, M. R.; Bowden, W. B.

2011-12-01

Quantification of nutrient cycling and transport (spiraling) in stream systems is a fundamental component of stream ecology. Additions of isotopic tracer and bulk inorganic nutrient to streams have been frequently used to evaluate nutrient transfer between ecosystem compartments and nutrient uptake estimation, respectively. The Tracer Addition for Spiraling Curve Characterization (TASCC) methodology of Covino et al. (2010) instantaneously and simultaneously adds conservative and biologically active tracers to a stream system to quantify nutrient uptake metrics. In this method, comparing the ratio of mass of nutrient and conservative solute recovered in each sample throughout a breakthrough curve to that of the injectate, a distribution of spiraling metrics is calculated across a range of nutrient concentrations. This distribution across concentrations allows for both a robust estimation of ambient spiraling parameters by regression techniques, and comparison with uptake kinetic models. We tested a unique sampling strategy for TASCC injections in which samples were taken manually throughout the nutrient breakthrough curves while, simultaneously, continuously monitoring with a field-ready wet chemistry autoanalyzer. The autoanalyzer was programmed to measure concentrations of nitrate, phosphate and ammonium at the rate of one measurement per second throughout each experiment. Utilization of an autoanalyzer in the field during the experiment results in the return of several thousand additional nutrient data points when compared with manual sampling. This technique, then, allows for a deeper understanding and more statistically robust estimation of stream nutrient spiraling parameters.

The micro and macro of nutrients across biological scales.

PubMed

Warne, Robin W

2014-11-01

During the past decade, we have gained new insights into the profound effects that essential micronutrients and macronutrients have on biological processes ranging from cellular function, to whole-organism performance, to dynamics in ecological communities, as well as to the structure and function of ecosystems. For example, disparities between intake and organismal requirements for specific nutrients are known to strongly affect animal physiological performance and impose trade-offs in the allocations of resources. However, recent findings have demonstrated that life-history allocation trade-offs and even microevolutionary dynamics may often be a result of molecular-level constraints on nutrient and metabolic processing, in which limiting reactants are routed among competing biochemical pathways. In addition, recent work has shown that complex ecological interactions between organismal physiological states such as exposure to environmental stressors and infectious pathogens can alter organismal requirements for, and, processing of, nutrients, and even alter subsequent nutrient cycling in ecosystems. Furthermore, new research is showing that such interactions, coupled with evolutionary and biogeographical constraints on the biosynthesis and availability of essential nutrients and micronutrients play an important, but still under-studied role in the structuring and functioning of ecosystems. The purpose of this introduction to the symposium "The Micro and Macro of Nutrient Effects in Animal Physiology and Ecology" is to briefly review and highlight recent research that has dramatically advanced our understanding of how nutrients in their varied forms profoundly affect and shape ecological and evolutionary processes. © The Author 2014. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.

Shrub canopies influence soil temperatures but not nutrient dynamics: An experimental test of tundra snow–shrub interactions

PubMed Central

Myers-Smith, Isla H; Hik, David S

2013-01-01

Shrubs are the largest plant life form in tundra ecosystems; therefore, any changes in the abundance of shrubs will feedback to influence biodiversity, ecosystem function, and climate. The snow–shrub hypothesis asserts that shrub canopies trap snow and insulate soils in winter, increasing the rates of nutrient cycling to create a positive feedback to shrub expansion. However, previous work has not been able to separate the abiotic from the biotic influences of shrub canopies. We conducted a 3-year factorial experiment to determine the influences of canopies on soil temperatures and nutrient cycling parameters by removing ∼0.5 m high willow (Salix spp.) and birch (Betula glandulosa) shrubs, creating artificial shrub canopies and comparing these manipulations to nearby open tundra and shrub patches. Soil temperatures were 4–5°C warmer in January, and 2°C cooler in July under shrub cover. Natural shrub plots had 14–33 cm more snow in January than adjacent open tundra plots. Snow cover and soil temperatures were similar in the manipulated plots when compared with the respective unmanipulated treatments, indicating that shrub canopy cover was a dominant factor influencing the soil thermal regime. Conversely, we found no strong evidence of increased soil decomposition, CO2 fluxes, or nitrate or ammonia adsorbtion under artificial shrub canopy treatments when compared with unmanipulated open tundra. Our results suggest that the abiotic influences of shrub canopy cover alone on nutrient dynamics are weaker than previously asserted. PMID:24198933

Shrub canopies influence soil temperatures but not nutrient dynamics: An experimental test of tundra snow-shrub interactions.

PubMed

Myers-Smith, Isla H; Hik, David S

2013-10-01

Shrubs are the largest plant life form in tundra ecosystems; therefore, any changes in the abundance of shrubs will feedback to influence biodiversity, ecosystem function, and climate. The snow-shrub hypothesis asserts that shrub canopies trap snow and insulate soils in winter, increasing the rates of nutrient cycling to create a positive feedback to shrub expansion. However, previous work has not been able to separate the abiotic from the biotic influences of shrub canopies. We conducted a 3-year factorial experiment to determine the influences of canopies on soil temperatures and nutrient cycling parameters by removing ∼0.5 m high willow (Salix spp.) and birch (Betula glandulosa) shrubs, creating artificial shrub canopies and comparing these manipulations to nearby open tundra and shrub patches. Soil temperatures were 4-5°C warmer in January, and 2°C cooler in July under shrub cover. Natural shrub plots had 14-33 cm more snow in January than adjacent open tundra plots. Snow cover and soil temperatures were similar in the manipulated plots when compared with the respective unmanipulated treatments, indicating that shrub canopy cover was a dominant factor influencing the soil thermal regime. Conversely, we found no strong evidence of increased soil decomposition, CO2 fluxes, or nitrate or ammonia adsorbtion under artificial shrub canopy treatments when compared with unmanipulated open tundra. Our results suggest that the abiotic influences of shrub canopy cover alone on nutrient dynamics are weaker than previously asserted.

Stream-subsurface nutrient dynamics in a groundwater-fed stream

NASA Astrophysics Data System (ADS)

Rezanezhad, F.; Niederkorn, A.; Parsons, C. T.; Van Cappellen, P.

2015-12-01

The stream-riparian-aquifer interface plays a major role in the regional flow of nutrients and contaminants due to a strong physical-chemical gradient that promotes the transformation, retention, elimination or release of biogenic elements. To better understand the effect of the near-stream zones on stream biogeochemistry, we conducted a field study on a groundwater-fed stream located in the rare Charitable Research Reserve, Cambridge, Ontario, Canada. This study focused on monitoring the spatial and temporal distributions of nutrient elements within the riparian and hyporheic zones of the stream. Several piezometer nests and a series of passive (diffusion) water samplers, known as peepers, were installed along longitudinal and lateral transects centered on the stream to obtain data on the groundwater chemistry. Groundwater upwelling along the stream resulted in distinctly different groundwater types and associated nitrate concentrations between small distances in the riparian zone (<4m). After the upstream source of the stream surface water, concentrations of nutrients (NO3-, NH4+, SO42- and carbon) did not significantly change before the downstream outlet. Although reduction of nitrate and sulphate were found in the riparian zone of the stream, this did not significantly influence the chemistry of the adjacent stream water. Also, minimal retention in the hyporheic zones limited reduction of reactive compounds (NO3- and SO42-) within the stream channel. The results showed that the dissolved organic carbon (DOC) and residence time of water in the hyporheic zone and in surface water limited denitrification.

Effects of nutrient availabiiity on biomass allocation as well as constitutive and rapid induced herbivore resistance in poplar

Treesearch

Carolyn Glynn; Daniel A. Herms; Marie Egawa; Robert Hansen; William J. Mattson

2003-01-01

Many studies have examined effects of nutrient availability on constitutive herbivore resistance of plants, but few have addressed effects on expression of rapid induced resistance (RIR). We quantified effects of two levels of nutrient availability on growth, biomass allocation, photosynthesis, and constitutive secondary metabolism of black poplar (>i>Populus...

Improving Lowland Rice (O. sativa L. cv. MR219) Plant Growth Variables, Nutrients Uptake, and Nutrients Recovery Using Crude Humic Substances.

PubMed

Palanivell, Perumal; Ahmed, Osumanu Haruna; Ab Majid, Nik Muhamad; Jalloh, Mohamadu Boyie; Susilawati, Kasim

2015-01-01

High cation exchange capacity and organic matter content of crude humic substances from compost could be exploited to reduce ammonia loss from urea and to as well improve rice growth and soil chemical properties for efficient nutrients utilization in lowland rice cultivation. Close-dynamic air flow system was used to determine the effects of crude humic substances on ammonia volatilization. A pot experiment was conducted to determine the effects of crude humic substances on rice plant growth, nutrients uptake, nutrients recovery, and soil chemical properties using an acid soil mixed with three rates of crude humic substances (20, 40, and 60 g pot(-1)). Standard procedures were used to evaluate rice plant dry matter production, nutrients uptake, nutrients recovery, and soil chemical properties. Application of crude humic substances increased ammonia volatilization. However, the lowest rate of crude humic substances (20 g pot(-1)) significantly improved total dry matter, nutrients uptake, nutrients recovery, and soil nutrients availability compared with crude humic substances (40 and 60 g pot(-1)) and the normal fertilization. Apart from improving growth of rice plants, crude humic substances can be used to ameliorate acid soils in rice cultivation. The findings of this study are being validated in our ongoing field trials.

Improving Lowland Rice (O. sativa L. cv. MR219) Plant Growth Variables, Nutrients Uptake, and Nutrients Recovery Using Crude Humic Substances

PubMed Central

Palanivell, Perumal; Ahmed, Osumanu Haruna; Ab Majid, Nik Muhamad; Jalloh, Mohamadu Boyie; Susilawati, Kasim

2015-01-01

High cation exchange capacity and organic matter content of crude humic substances from compost could be exploited to reduce ammonia loss from urea and to as well improve rice growth and soil chemical properties for efficient nutrients utilization in lowland rice cultivation. Close-dynamic air flow system was used to determine the effects of crude humic substances on ammonia volatilization. A pot experiment was conducted to determine the effects of crude humic substances on rice plant growth, nutrients uptake, nutrients recovery, and soil chemical properties using an acid soil mixed with three rates of crude humic substances (20, 40, and 60 g pot−1). Standard procedures were used to evaluate rice plant dry matter production, nutrients uptake, nutrients recovery, and soil chemical properties. Application of crude humic substances increased ammonia volatilization. However, the lowest rate of crude humic substances (20 g pot−1) significantly improved total dry matter, nutrients uptake, nutrients recovery, and soil nutrients availability compared with crude humic substances (40 and 60 g pot−1) and the normal fertilization. Apart from improving growth of rice plants, crude humic substances can be used to ameliorate acid soils in rice cultivation. The findings of this study are being validated in our ongoing field trials. PMID:25977938

Efficiencies of forestry best management practices for reducing sediment and nutrient losses in the eastern United States

Treesearch

Pamela Edwards; Karl W.J. Williard

2010-01-01

Quantifying the effects of forestry best management practices (BMPs) on sediment and nutrient loads is a critical need. Through an exhaustive literature search, three paired forested watershed studies in the eastern United States were found that permitted the calculation of BMP efficiencies--the percent reduction in sediment or nutrients achieved by BMPs. For sediment...

Influence of different forest system management practices on leaf litter decomposition rates, nutrient dynamics and the activity of ligninolytic enzymes: a case study from central European forests.

PubMed

Purahong, Witoon; Kapturska, Danuta; Pecyna, Marek J; Schulz, Elke; Schloter, Michael; Buscot, François; Hofrichter, Martin; Krüger, Dirk

2014-01-01

Leaf litter decomposition is the key ecological process that determines the sustainability of managed forest ecosystems, however very few studies hitherto have investigated this process with respect to silvicultural management practices. The aims of the present study were to investigate the effects of forest management practices on leaf litter decomposition rates, nutrient dynamics (C, N, Mg, K, Ca, P) and the activity of ligninolytic enzymes. We approached these questions using a 473 day long litterbag experiment. We found that age-class beech and spruce forests (high forest management intensity) had significantly higher decomposition rates and nutrient release (most nutrients) than unmanaged deciduous forest reserves (P<0.05). The site with near-to-nature forest management (low forest management intensity) exhibited no significant differences in litter decomposition rate, C release, lignin decomposition, and C/N, lignin/N and ligninolytic enzyme patterns compared to the unmanaged deciduous forest reserves, but most nutrient dynamics examined in this study were significantly faster under such near-to-nature forest management practices. Analyzing the activities of ligninolytic enzymes provided evidence that different forest system management practices affect litter decomposition by changing microbial enzyme activities, at least over the investigated time frame of 473 days (laccase, P<0.0001; manganese peroxidase (MnP), P = 0.0260). Our results also indicate that lignin decomposition is the rate limiting step in leaf litter decomposition and that MnP is one of the key oxidative enzymes of litter degradation. We demonstrate here that forest system management practices can significantly affect important ecological processes and services such as decomposition and nutrient cycling.

Investigating Stream Metabolism and Nutrient Dynamics in Contrasting Ecosystems: The Role of Hydrologic Compartments

NASA Astrophysics Data System (ADS)

Gonzalez-Pinzon, R.; Riveros-Iregui, D. A.; Covino, T. P.

2015-12-01

The interactions between mobile and less mobile hydrologic compartments affect the quality and quantity of water in streams and aquifers, and the cycling of dissolved carbon and nutrients. As new laboratory and field techniques become available, new questions and challenges emerge, including: What do we measure, where, and for how long to fully characterize a system? and, What is the ideal cost-maintenance-benefit relationship that we should strive for to maximize knowledge gained in different field settings? We recently performed a series of field experiments to measure aquatic metabolism and nutrient dynamics in two highly contrasting hydrologic systems, i.e., 1) a wetland-stream alpine, tropical system in Colombia (South America) and 2) a dryland river continuum (1st - 5th stream orders) in New Mexico. In this presentation we discuss how multiple lines of evidence can support the analysis of key aquatic processes and how co-interpretation provides a more complete picture of stream complexity. For this analysis, we deployed YSI EXO2 and 6920 sondes, Turner Designs C-sense and C6 sensors, and Onset HOBO water quality data loggers. Parameters measured by these instruments include conductivity, temperature, dissolved oxygen, pH, turbidity, pCO2, chlorophyll-a, phycocyanin, fluorescein, CDOM, brighteners and water depth. We also injected conservative tracers (i.e., NaCl and NaBr) and the bioreactive tracer resazurin in both experimental sites, and NO3 in the dryland river continuum. NO3 was measured in-situ with Satlantic Submersible Ultraviolet Nitrate Analyzers (SUNA) sensors and in the laboratory using Ion Chromatograph techniques using stream grab samples. Our results highlight the role of both residence times and chemical fluxes in regulating the effective processing of carbon and nutrients. Our results also demonstrate that stream stimuli from controlled experiments are ideal for maximizing the information content derived from short (hours to days) and mid

Quantifying geomorphic controls on riparian forest dynamics using a linked physical-biological model: implications for river corridor conservation

NASA Astrophysics Data System (ADS)

Stella, J. C.; Harper, E. B.; Fremier, A. K.; Hayden, M. K.; Battles, J. J.

2009-12-01

In high-order alluvial river systems, physical factors of flooding and channel migration are particularly important drivers of riparian forest dynamics because they regulate habitat creation, resource fluxes of water, nutrients and light that are critical for growth, and mortality from fluvial disturbance. Predicting vegetation composition and dynamics at individual sites in this setting is challenging, both because of the stochastic nature of the flood regime and the spatial variability of flood events. Ecological models that correlate environmental factors with species’ occurrence and abundance (e.g., ’niche models’) often work well in infrequently-disturbed upland habitats, but are less useful in river corridors and other dynamic zones where environmental conditions fluctuate greatly and selection pressures on disturbance-adapted organisms are complex. In an effort to help conserve critical riparian forest habitat along the middle Sacramento River, CA, we are taking a mechanistic approach to quantify linkages between fluvial and biotic processes for Fremont cottonwood (Populus fremontii), a keystone pioneer tree in dryland rivers ecosystems of the U.S. Southwest. To predict the corridor-wide population effects of projected changes to the disturbance regime from flow regulation, climate change, and landscape modifications, we have coupled a physical model of channel meandering with a patch-based population model that incorporates the climatic, hydrologic, and topographic factors critical for tree recruitment and survival. We employed these linked simulations to study the relative influence of the two most critical habitat types--point bars and abandoned channels--in sustaining the corridor-wide cottonwood population over a 175-year period. The physical model uses discharge data and channel planform to predict the spatial distribution of new habitat patches; the population model runs on top of this physical template to track tree colonization and survival on

The stoichiometry of nutrient release by terrestrial herbivores and its ecosystem consequences

NASA Astrophysics Data System (ADS)

Sitters, Judith; Bakker, Elisabeth S.; Veldhuis, Michiel P.; Veen, G. F.; Olde Venterink, Harry; Vanni, Michael J.

2017-04-01

It is widely recognized that the release of nutrients by herbivores via their waste products strongly impacts nutrient availability for autotrophs. The ratios of nitrogen (N) and phosphorus (P) recycled through herbivore release (i.e., waste N:P) are mainly determined by the stoichiometric composition of the herbivore’s food (food N:P) and its body nutrient content (body N:P). Waste N:P can in turn impact autotroph nutrient limitation and productivity. Herbivore-driven nutrient recycling based on stoichiometric principles is dominated by theoretical and experimental research in freshwater systems, in particular interactions between algae and invertebrate herbivores. In terrestrial ecosystems, the impact of herbivores on nutrient cycling and availability is often limited to studying carbon (C ):N and C:P ratios, while the role of terrestrial herbivores in mediating N:P ratios is also likely to influence herbivore-driven nutrient recycling. In this review, we use rules and predictions on the stoichiometry of nutrient release originating from algal-based aquatic systems to identify the factors that determine the stoichiometry of nutrient release by herbivores. We then explore how these rules can be used to understand the stoichiometry of nutrient release by terrestrial herbivores, ranging from invertebrates to mammals, and its impact on plant nutrient limitation and productivity. Future studies should focus on measuring both N and P when investigating herbivore-driven nutrient recycling in terrestrial ecosystems, while also taking the form of waste product (urine or feces) and other pathways by which herbivores change nutrients into account, to be able to quantify the impact of waste stoichiometry on plant communities.

Effect of soil in nutrient cycle assessment at dairy farms

NASA Astrophysics Data System (ADS)

van Leeuwen, Maricke; de Boer, Imke; van Dam, Jos; van Middelaar, Corina; Stoof, Cathelijne

2016-04-01

Annual farm nutrient cycle assessments give valuable insight in the nutrient cycles and nutrient losses at dairy farms. It describes nutrient use efficiencies for the entire farm and for the underlying components cattle, manure, crops and soil. In many modelling studies, soil is kept as a constant factor, while soil quality is vital for soil functioning of the ecosystem. Improving soil quality will improve the nutrient cycle, and will also have positive effect on the soil functions crop production, water cycling and greenhouse gas mitigation. Spatial variation of soil properties within a farm, however, are not included in annual nutrient cycle assessments. Therefore it is impossible to identify fields where most profit can be gained by improving farm management at field level, and it is not possible to identify and to quantify nutrient flow path ways. The aim of this study is to develop a framework to improve the annual nutrient cycle assessment at Dutch dairy farms, by including soil properties and their spatial variation within farms. Soil type and soil quality will be described by visual soil assessment of soil quality characteristics. The visual observations will be linked to the nutrient cycle assessment, using soil-hydrological model SWAP. We will demonstrate how soil quality at field level can impact on crop production, eutrophication potential and greenhouse gas potential at farm level. Also, we will show how this framework can be used by farmers to improve their farm management. This new approach is focusing on annual nutrient cycle assessment, but could also be used in life cycle assessment. It will improve understanding of soil functioning and dairy farm management.

Carbon and nutrients recycling when leaves falling off: mycorrhizal association matters

NASA Astrophysics Data System (ADS)

Zhang, H., II; Lü, X. T.; Hartmann, H.; Han, X.; Trumbore, S.

2016-12-01

Root-associated mycorrhizal fungi is being increasingly recognized for their roles in influencing soil carbon (C) storage, plant growth and nutrient cycling, whereas mycorrhizae-mediated C dynamics and nutrient acquisition strategy strongly different. Because of a reinforcing feedback from belowground, how different mycorrhizal plants differ in aboveground nutrient status and recycle from senesced to green leaves remains unknown. Based on a global database of C and nutrients concentrations in plant green and senesced leaves, we further identified plant mycorrhizal types (here focus on arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) plants) for woody species and tested whether mycorrhizal types showing consistent effects in plant nutrient status and recycle. Generally, nutrient resorptions from senesced to green leaves for ECM plants are more conservative, balanced and sensitive to climate compare to AM plants. Specifically, we first found lower nutrients concentrations in green and senesced leaves whereas greater nutrient resorption efficiency (NuR) for ECM vs. AM plants. However, C concentration in green and senesced leaves were significant greater while NuR was lower for ECM plants. Second, compare to that for AM plants, we found a general balanced N:P resorption ratio ( 1) for ECM plants, indicating ECM plants had greater ability to balance their N and P resorption simultaneously. Third, we found NuR in N, P and K (potassium) for ECM plants were sensitive to the variation of MAT and MAP while these for AM plants showed no clear trend. Our results suggested that accounting for the influence of mycorrhizae on C and nutrient dynamics in vegetation models will be critical for predicting ecosystem responses and feedbacks to climate change.

Nutrient depletion from rhizosphere solution by maize grown in soil with long-term compost amendment

USDA-ARS?s Scientific Manuscript database

Improved understanding of rhizosphere chemistry will enhance our ability to model nutrient dynamics and on a broader scale, to develop effective management strategies for applied plant nutrients. With a controlled-climate study, we evaluated in situ changes in macro-nutrient concentrations in the rh...

Plasticity of the Arabidopsis Root System under Nutrient Deficiencies1[C][W][OPEN

PubMed Central

Gruber, Benjamin D.; Giehl, Ricardo F.H.; Friedel, Swetlana; von Wirén, Nicolaus

2013-01-01

Plant roots show a particularly high variation in their morphological response to different nutrient deficiencies. Although such changes often determine the nutrient efficiency or stress tolerance of plants, it is surprising that a comprehensive and comparative analysis of root morphological responses to different nutrient deficiencies has not yet been conducted. Since one reason for this is an inherent difficulty in obtaining nutrient-deficient conditions in agar culture, we first identified conditions appropriate for producing nutrient-deficient plants on agar plates. Based on a careful selection of agar specifically for each nutrient being considered, we grew Arabidopsis (Arabidopsis thaliana) plants at four levels of deficiency for 12 nutrients and quantified seven root traits. In combination with measurements of biomass and elemental concentrations, we observed that the nutritional status and type of nutrient determined the extent and type of changes in root system architecture (RSA). The independent regulation of individual root traits further pointed to a differential sensitivity of root tissues to nutrient limitations. To capture the variation in RSA under different nutrient supplies, we used principal component analysis and developed a root plasticity chart representing the overall modulations in RSA under a given treatment. This systematic comparison of RSA responses to nutrient deficiencies provides a comprehensive view of the overall changes in root plasticity induced by the deficiency of single nutrients and provides a solid basis for the identification of nutrient-sensitive steps in the root developmental program. PMID:23852440

Quantifying and comparing dynamic predictive accuracy of joint models for longitudinal marker and time-to-event in presence of censoring and competing risks.

PubMed

Blanche, Paul; Proust-Lima, Cécile; Loubère, Lucie; Berr, Claudine; Dartigues, Jean-François; Jacqmin-Gadda, Hélène

2015-03-01

Thanks to the growing interest in personalized medicine, joint modeling of longitudinal marker and time-to-event data has recently started to be used to derive dynamic individual risk predictions. Individual predictions are called dynamic because they are updated when information on the subject's health profile grows with time. We focus in this work on statistical methods for quantifying and comparing dynamic predictive accuracy of this kind of prognostic models, accounting for right censoring and possibly competing events. Dynamic area under the ROC curve (AUC) and Brier Score (BS) are used to quantify predictive accuracy. Nonparametric inverse probability of censoring weighting is used to estimate dynamic curves of AUC and BS as functions of the time at which predictions are made. Asymptotic results are established and both pointwise confidence intervals and simultaneous confidence bands are derived. Tests are also proposed to compare the dynamic prediction accuracy curves of two prognostic models. The finite sample behavior of the inference procedures is assessed via simulations. We apply the proposed methodology to compare various prediction models using repeated measures of two psychometric tests to predict dementia in the elderly, accounting for the competing risk of death. Models are estimated on the French Paquid cohort and predictive accuracies are evaluated and compared on the French Three-City cohort. © 2014, The International Biometric Society.

Impacts of climate and land use changes on regional nutrient export in the South Saskatchewan River catchment

NASA Astrophysics Data System (ADS)

Morales-Marin, L. A.; Wheater, H. S.; Lindenschmidt, K. E.

2016-12-01

Climate and land use changes modify the physical functioning of river catchments and, in particular, influence the transport of nutrients from land to water. In large-scale catchments, where a variety of climates, topographies, soil types and land uses co-exist to form a highly heterogeneous environment, a more complex nutrient dynamic is imposed by climate and land use changes. This is the case of the South Saskatchewan River (SSR) that, along with the North Saskatchewan River, forms the largest river system in western Canada. In the past years changes in the land use and new industrial developments in the SSR area have heightened serious concerns about the future of water quality in the catchment and downstream waters. Agricultural activities have increased the supply of manure and fertilizer for cropping. Oil and gas exploitation has also increased the risk of surface water and groundwater contamination. The rapid population growth not only leads to increments in water consumption and wastewater, but in the construction of roads, railways and the expansion of new urban developments that impose hydraulic controls on the catchment hydrology and therefore the sediment and nutrient transport. Consequences of the actual anthropogenic changes have been notorious in reservoirs where algal blooms and signs of eutrophication have become common during certain times of the year. Although environmental agencies are constantly improving the mechanisms to reduce nutrient export into the river and ensure safe water quality standards, further research is needed in order to identify major nutrient sources and quantify nutrient export and also, to assess how nutrients are going to vary as a result of future climate and land use change scenarios. The SPAtially Referenced Regression On Watershed (SPARROW) model is therefore implemented to assess water quality regionally, in order to describe spatial and temporal patterns to identify those factors and processes that affect water

Impacts of climate and land use changes on regional nutrient export in the South Saskatchewan River catchment

NASA Astrophysics Data System (ADS)

Morales-Marin, L. A.; Wheater, H. S.; Lindenschmidt, K. E.

2015-12-01

Climate and land use changes modify the physical functioning of river catchments and, in particular, influence the transport of nutrients from land to water. In large-scale catchments, where a variety of climates, topographies, soil types and land uses co-exist to form a highly heterogeneous environment, a more complex nutrient dynamic is imposed by climate and land use changes. This is the case of the South Saskatchewan River (SSR) that, along with the North Saskatchewan River, forms the largest river system in western Canada. In the past years changes in the land use and new industrial developments in the SSR area have heightened serious concerns about the future of water quality in the catchment and downstream waters. Agricultural activities have increased the supply of manure and fertilizer for cropping. Oil and gas exploitation has also increased the risk of surface water and groundwater contamination. The rapid population growth not only leads to increments in water consumption and wastewater, but in the construction of roads, railways and the expansion of new urban developments that impose hydraulic controls on the catchment hydrology and therefore the sediment and nutrient transport. Consequences of the actual anthropogenic changes have been notorious in reservoirs where algal blooms and signs of eutrophication have become common during certain times of the year. Although environmental agencies are constantly improving the mechanisms to reduce nutrient export into the river and ensure safe water quality standards, further research is needed in order to identify major nutrient sources and quantify nutrient export and also, to assess how nutrients are going to vary as a result of future climate and land use change scenarios. The SPAtially Referenced Regression On Watershed (SPARROW) model is therefore implemented to assess water quality regionally, in order to describe spatial and temporal patterns to identify those factors and processes that affect water

AGGREGATED FILTER-FEEDING CONSUMERS ALTER NUTRIENT LIMITATION: CONSEQUENCES FOR ECOSYSTEM AND COMMUNITY DYNAMICS

EPA Science Inventory

Nutrient cycling is a key process that ties all organisms together. This is especially apparent in stream environments in which nutrients are taken up readily and cycled through the system in a downstream trajectory. Ecological stoichiometry predicts that biogeochemical cycles of...

Native Mussels Alter Nutrient Availability and Reduce Blue ...

EPA Pesticide Factsheets

Nutrient cycling is a key process that ties all organisms together. This is especially apparent in stream environments in which nutrients are taken up readily and cycled through the system in a downstream trajectory. Ecological stoichiometry predicts that biogeochemical cycles of different elements are interdependent because the organisms that drive these cycles require fixed ratios of nutrients. There is growing recognition that animals play an important role in biogeochemical cycling across ecosystems. In particular, dense aggregations of consumers can create biogeochemical hotspots in aquatic ecosystems via nutrient translocation. We predicted that filter-feeding freshwater mussels, which occur as speciose, high biomass aggregates, would create biogeochemical hotspots in streams by altering nutrient limitation and algal dynamics. In a field study, we manipulated nitrogen and phosphorus using nutrient-diffusing substrates in areas with high and low mussel abundance, recorded algal growth and community composition, and determined in situ mussel excretion stoichiometry at 18 sites in 3 rivers (Kiamichi, Little, and Mt. Fork rivers, southcentral U.S.). Our results indicate that mussels greatly influence ecosystem processes by modifying the nutrients that limit primary productivity. Sites without mussels were N-limited with ~26% higher abundances of N-fixing blue-green algae, while sites with high mussel densities were co-limited (N and P) and dominated by diatoms

Low latitude ionospheric TEC responses to dynamical complexity quantifiers during transient events over Nigeria

NASA Astrophysics Data System (ADS)

Ogunsua, Babalola

2018-04-01

In this study, the values of chaoticity and dynamical complexity parameters for some selected storm periods in the year 2011 and 2012 have been computed. This was done using detrended TEC data sets measured from Birnin-Kebbi, Torro and Enugu global positioning system (GPS) receiver stations in Nigeria. It was observed that the significance of difference (SD) values were mostly greater than 1.96 but surprisingly lower than 1.96 in September 29, 2011. The values of the computed SD were also found to be reduced in most cases just after the geomagnetic storm with immediate recovery a day after the main phase of the storm while the values of Lyapunov exponent and Tsallis entropy remains reduced due to the influence of geomagnetic storms. It was also observed that the value of Lyapunov exponent and Tsallis entropy reveals similar variation pattern during storm period in most cases. Also recorded surprisingly were lower values of these dynamical quantifiers during the solar flare event of August 8th and 9th of the year 2011. The possible mechanisms responsible for these observations were further discussed in this work. However, our observations show that the ionospheric effects of some other possible transient events other than geomagnetic storms can also be revealed by the variation of chaoticity and dynamical complexity.

Carbohydrate and nutrient composition of corn stover from three Southeastern USA locations

USDA-ARS?s Scientific Manuscript database

Corn (Zea mays L.) stover has been identified as an important feedstock for bioenergy and bio-product production. Our objective was to quantify nutrient removal, carbohydrate composition, theoretical ethanol yield (TEY) for various stover fractions. In 2009, 2010, and 2011, whole-plant samples were ...

Long-term nutrient reductions lead to the unprecedented recovery of a temperate coastal region.

PubMed

Lefcheck, Jonathan S; Orth, Robert J; Dennison, William C; Wilcox, David J; Murphy, Rebecca R; Keisman, Jennifer; Gurbisz, Cassie; Hannam, Michael; Landry, J Brooke; Moore, Kenneth A; Patrick, Christopher J; Testa, Jeremy; Weller, Donald E; Batiuk, Richard A

2018-04-03

Humans strongly impact the dynamics of coastal systems, yet surprisingly few studies mechanistically link management of anthropogenic stressors and successful restoration of nearshore habitats over large spatial and temporal scales. Such examples are sorely needed to ensure the success of ecosystem restoration efforts worldwide. Here, we unite 30 consecutive years of watershed modeling, biogeochemical data, and comprehensive aerial surveys of Chesapeake Bay, United States to quantify the cascading effects of anthropogenic impacts on submersed aquatic vegetation (SAV), an ecologically and economically valuable habitat. We employ structural equation models to link land use change to higher nutrient loads, which in turn reduce SAV cover through multiple, independent pathways. We also show through our models that high biodiversity of SAV consistently promotes cover, an unexpected finding that corroborates emerging evidence from other terrestrial and marine systems. Due to sustained management actions that have reduced nitrogen concentrations in Chesapeake Bay by 23% since 1984, SAV has regained 17,000 ha to achieve its highest cover in almost half a century. Our study empirically demonstrates that nutrient reductions and biodiversity conservation are effective strategies to aid the successful recovery of degraded systems at regional scales, a finding which is highly relevant to the utility of environmental management programs worldwide.

A conceptual model for quantifying connectivity using graph theory and cellular (per-pixel) approach

NASA Astrophysics Data System (ADS)

Singh, Manudeo; Sinha, Rajiv; Tandon, Sampat K.

2016-04-01

The concept of connectivity is being increasingly used for understanding hydro-geomorphic processes at all spatio-temporal scales. Connectivity is defined as the potential for energy and material flux (water, sediments, nutrients, heat, etc.) to navigate within or between the landscape systems and has two components, structural connectivity and dynamic connectivity. Structural connectivity is defined by the spatially connected features (physical linkages) through which energy and materials flow. Dynamic connectivity is a process defined connectivity component. These two connectivity components also interact with each other by forming a feedback system. This study attempts to explore a method to quantify structural and dynamic connectivity. In fluvial transport systems, sediment and water can flow in either a diffused manner or in a channelized way. At all the scales, hydrological and sediment fluxes can be tracked using a cellular (per-pixel) approach and can be quantified using graphical approach. The material flux, slope and LULC (Land Use Land Cover) weightage factors of a pixel together determine if it will contribute towards connectivity of the landscape/system. In a graphical approach, all the contributing pixels will form a node at their centroid and this node will be connected to the next 'down-node' via a directed edge with 'least cost path'. The length of the edge will depend on the desired spatial scale and its path direction will depend on the traversed pixel's slope and the LULC (weightage) factors. The weightage factors will lie in-between 0 to 1. This value approaches 1 for the LULC factors which promote connectivity. For example, in terms of sediment connectivity, the weightage could be RUSLE (Revised Universal Soil Loss Equation) C-factors with bare unconsolidated surfaces having values close to 1. This method is best suited for areas with low slopes, where LULC can be a deciding as well as dominating factor. The degree of connectivity and its

Blade motion and nutrient flux to the kelp, Eisenia arborea.

PubMed

Denny, Mark; Roberson, Loretta

2002-08-01

Marine algae rely on currents and waves to replenish the nutrients required for photosynthesis. The interaction of algal blades with flow often involves dynamic reorientations of the blade surface (pitching and flapping) that may in turn affect nutrient flux. As a first step toward understanding the consequences of blade motion, we explore the effect of oscillatory pitching on the flux to a flat plate and to two morphologies of the kelp Eisenia arborea. In slow flow (equivalent to a water velocity of 2.7 cm s(-1)), pitching increases the time-averaged flux to both kelp morphologies, but not to the plate. In fast flow (equivalent to 20 cm s(-1) in water), pitching has negligible effect on flux regardless of shape. For many aspects of flux, the flat plate is a reliable model for the flow-protected algal blade, but predictions made from the plate would substantially underestimate the flux to the flow-exposed blade. These measurements highlight the complexities of flow-related nutrient transport and the need to understand better the dynamic interactions among nutrient flux, blade motion, blade morphology, and water flow.

A 3D parameterization of nutrients atmospheric deposition to the global ocean

NASA Astrophysics Data System (ADS)

Myriokefalitakis, S.; Nenes, A.; Baker, A. R.; Mihalopoulos, N.; Kanakidou, M.

2016-12-01

Atmospheric deposition of trace constituents, both of natural and anthropogenic origin, can act as a nutrient source into the open ocean and affect marine ecosystem functioning and subsequently the exchange of CO2 between the atmosphere and the global ocean. Dust is known as a major source of nutrients (such as iron and phosphorus) to the global ocean, but only a fraction of these nutrients is released in soluble form that can be assimilated by the ecosystems. The global atmospheric iron (Fe) and phosphorus (P) cycles are here parameterized in a global 3-D chemical transport model. Both primary emissions of total and soluble Fe and P associated with dust and combustion processes are taken into account. The impact of atmospheric acidity on nutrient solubility is parameterised based on experimental findings and model results are evaluated by comparison with available observations. The effect of air-quality changes on soluble nutrient deposition is studied by performing sensitivity simulations using preindustrial, present and future emission scenarios. The link between the soluble Fe and P atmospheric deposition and anthropogenic sources is also investigated. Overall, the response of the chemical composition of nutrient-containing aerosols to environmental changes is demonstrated and quantified.

Influence of Different Forest System Management Practices on Leaf Litter Decomposition Rates, Nutrient Dynamics and the Activity of Ligninolytic Enzymes: A Case Study from Central European Forests

PubMed Central

Schulz, Elke; Schloter, Michael; Buscot, François; Hofrichter, Martin; Krüger, Dirk

2014-01-01

Leaf litter decomposition is the key ecological process that determines the sustainability of managed forest ecosystems, however very few studies hitherto have investigated this process with respect to silvicultural management practices. The aims of the present study were to investigate the effects of forest management practices on leaf litter decomposition rates, nutrient dynamics (C, N, Mg, K, Ca, P) and the activity of ligninolytic enzymes. We approached these questions using a 473 day long litterbag experiment. We found that age-class beech and spruce forests (high forest management intensity) had significantly higher decomposition rates and nutrient release (most nutrients) than unmanaged deciduous forest reserves (P<0.05). The site with near-to-nature forest management (low forest management intensity) exhibited no significant differences in litter decomposition rate, C release, lignin decomposition, and C/N, lignin/N and ligninolytic enzyme patterns compared to the unmanaged deciduous forest reserves, but most nutrient dynamics examined in this study were significantly faster under such near-to-nature forest management practices. Analyzing the activities of ligninolytic enzymes provided evidence that different forest system management practices affect litter decomposition by changing microbial enzyme activities, at least over the investigated time frame of 473 days (laccase, P<0.0001; manganese peroxidase (MnP), P = 0.0260). Our results also indicate that lignin decomposition is the rate limiting step in leaf litter decomposition and that MnP is one of the key oxidative enzymes of litter degradation. We demonstrate here that forest system management practices can significantly affect important ecological processes and services such as decomposition and nutrient cycling. PMID:24699676

Comparison of process-based models to quantify nutrient flows and greenhouse gas emissions of milk production

USDA-ARS?s Scientific Manuscript database

Assessing and improving the sustainability of dairy production systems is essential to secure future food production. This requires a holistic approach that reveals trade-offs between emissions of the different greenhouse gases (GHG) and nutrient-based pollutants and ensures that interactions betwee...

Modelling system dynamics and phytoplankton diversity at Ranchi lake using the carbon and nutrient mass balance equations.

PubMed

Mukherjee, B; Nivedita, M; Mukherjee, D

2014-05-01

Modelling system dynamics in a hyper-eutrophic lake is quite complex especially with a constant influx of detergents and sewage material which continually changes the state variables and interferes with the assessment of the chemical rhythm occurring in polluted conditions as compared to unpolluted systems. In this paper, a carbon and nutrient mass balance model for predicting system dynamics in a complex environment was studied. Studies were conducted at Ranchi lake to understand the altered environmental dynamics in hyper-eutrophic conditions, and its impact on the plankton community. The lake was monitored regularly for five years (2007 - 2011) and the data collected on the carbon flux, nitrates, phosphates and silicates was used to design a mass balance model for evaluating and predicting the system. The model was then used to correlate the chemical rhythm with that of the phytoplankton dynamics and diversity. Nitrates and phosphates were not limiting (mean nitrate and phosphate concentrations were 1.74 and 0.83 mgl⁻¹ respectively). Free carbon dioxide was found to control the system and, interacting with other parameters determined the diversity and dynamics of the plankton community. N/P ratio determined which group of phytoplankton dominated the community, above 5 it favoured the growth of chlorophyceae while below 5 cyanobacteria dominates. TOC/TIC ratio determined the abundance. The overall system was controlled by the availability of free carbon dioxide which served as a limiting factor.

Application of Hierarchy Theory to Cross-Scale Hydrologic Modeling of Nutrient Loads

EPA Science Inventory

We describe a model called Regional Hydrologic Modeling for Environmental Evaluation 16 (RHyME²) for quantifying annual nutrient loads in stream networks and watersheds. RHyME² is 17 a cross-scale statistical and process-based water-quality model. The model ...

Trophic dynamics of shrinking Subarctic lakes: naturally eutrophic waters impart resilience to rising nutrient and major ion concentrations.

PubMed

Lewis, Tyler L; Heglund, Patricia J; Lindberg, Mark S; Schmutz, Joel A; Schmidt, Joshua H; Dubour, Adam J; Rover, Jennifer; Bertram, Mark R

2016-06-01

Shrinking lakes were recently observed for several Arctic and Subarctic regions due to increased evaporation and permafrost degradation. Along with lake drawdown, these processes often boost aquatic chemical concentrations, potentially impacting trophic dynamics. In particular, elevated chemical levels may impact primary productivity, which may in turn influence populations of primary and secondary consumers. We examined trophic dynamics of 18 shrinking lakes of the Yukon Flats, Alaska, that had experienced pronounced increases in nutrient (>200 % total nitrogen, >100 % total phosphorus) and ion concentrations (>100 % for four major ions combined) from 1985-1989 to 2010-2012, versus 37 stable lakes with relatively little chemical change over the same period. We found that phytoplankton stocks, as indexed by chlorophyll concentrations, remained unchanged in both shrinking and stable lakes from the 1980s to 2010s. Moving up the trophic ladder, we found significant changes in invertebrate abundance across decades, including decreased abundance of five of six groups examined. However, these decadal losses in invertebrate abundance were not limited to shrinking lakes, occurring in lakes with stable surface areas as well. At the top of the food web, we observed that probabilities of lake occupancy for ten waterbird species, including adults and chicks, remained unchanged from the period 1985-1989 to 2010-2012. Overall, our study lakes displayed a high degree of resilience to multi-trophic cascades caused by rising chemical concentrations. This resilience was likely due to their naturally high fertility, such that further nutrient inputs had little impact on waters already near peak production.

Trophic dynamics of shrinking Subarctic lakes: naturally eutrophic waters impart resilience to rising nutrient and major ion concentrations

USGS Publications Warehouse

Lewis, Tyler; Lindberg, Mark S.; Heglund, Patricia J.; Schmutz, Joel A.; Schmidt, Joshua H.; Dubour, Adam J.; Rover, Jennifer R.; Bertram, Mark R.

2016-01-01

Shrinking lakes were recently observed for several Arctic and Subarctic regions due to increased evaporation and permafrost degradation. Along with lake drawdown, these processes often boost aquatic chemical concentrations, potentially impacting trophic dynamics. In particular, elevated chemical levels may impact primary productivity, which may in turn influence populations of primary and secondary consumers. We examined trophic dynamics of 18 shrinking lakes of the Yukon Flats, Alaska, that had experienced pronounced increases in nutrient (>200 % total nitrogen, >100 % total phosphorus) and ion concentrations (>100 % for four major ions combined) from 1985-1989 to 2010-2012, versus 37 stable lakes with relatively little chemical change over the same period. We found that phytoplankton stocks, as indexed by chlorophyll concentrations, remained unchanged in both shrinking and stable lakes from the 1980s to 2010s. Moving up the trophic ladder, we found significant changes in invertebrate abundance across decades, including decreased abundance of five of six groups examined. However, these decadal losses in invertebrate abundance were not limited to shrinking lakes, occurring in lakes with stable surface areas as well. At the top of the food web, we observed that probabilities of lake occupancy for ten waterbird species, including adults and chicks, remained unchanged from the period 1985-1989 to 2010-2012. Overall, our study lakes displayed a high degree of resilience to multi-trophic cascades caused by rising chemical concentrations. This resilience was likely due to their naturally high fertility, such that further nutrient inputs had little impact on waters already near peak production.

Hydrological heterogeneity, nutrient dynamics and water quality of a non-tidal lentic ecosystem (Lesina Lagoon, Italy)

NASA Astrophysics Data System (ADS)

Roselli, Leonilde; Fabbrocini, Adele; Manzo, Cristina; D'Adamo, Raffaele

2009-10-01

The dynamics of the Lesina coastal lagoon (Italy) in terms of nutrients, phytoplankton and chemical-physical parameters were evaluated, together with their functional relationships with freshwater inputs, in order to identify ecosystem responses to changes in driving forces in a Mediterranean non-tidal lentic environment. Lesina Lagoon is a shallow coastal environment characterised by limited exchange with coastal waters, which favours enrichment of nutrients and organic matter and benthic fluxes within the system. Lagoon-sea exchanges are influenced by human management. There is a steep salinity gradient from East to West. High nitrogen and silica values were found close to freshwater inputs, indicating wastewater discharges and agricultural runoff, especially in winter. Dissolved oxygen was well below saturation (65%) near sewage and runoff inputs in the western part of the lagoon during summer. Classification in accordance with EEA (2001) guidelines suggests the system is of "poor" or "bad" quality in terms of nitrogen concentrations in the eastern zone during the winter rainy period. In terms of phosphate concentrations, the majority of the stations fall into the "good" category, with only two stations (close to the sewage and runoff inputs) classed as "bad". In both cases, the raw nitrogen levels make the lagoon a P-limited system, especially in the eastern part. There was wide space-time variability in chlorophyll a concentrations, which ranged from 0.25 to 56 μg l -1. No relationships between chlorophyll a and nutrients were found, suggesting that autotrophic biomass may be controlled by a large number of internal and external forcing factors driving eutrophication processes. Water quality for this type of environment depends heavily on pressure from human activities but also on the management of sewage treatment plants, agricultural practices and the channels connecting the lagoon with the sea.

Wildfire Effects on In-stream Nutrient Processing and Hydrologic Transport

NASA Astrophysics Data System (ADS)

Rhea, A.; Covino, T. P.; Rhoades, C.; Fegel, T.

2017-12-01

In many forests throughout the Western U.S., drought, climate change, and growing fuel loads are contributing to increased fire frequency and severity. Wildfires can influence watershed nutrient retention as they fundamentally alter the biological composition and physical structure in upland landscapes, riparian corridors, and stream channels. While numerous studies have documented substantial short-term increases in stream nutrient concentrations and export (particularly reactive nitrogen, N) following forest fires, the long-term implications for watershed nutrient cycling remain unclear. For example, recent work indicates that nitrate concentrations and export can remain elevated for a decade or more following wildfire, yet the controls on these processes are unknown. In this research, we use empirical observations from nutrient tracer injections, nutrient diffusing substrates, and continuous water quality monitoring to isolate biological and physical controls on nutrient export across a burn-severity gradient. Tracer results demonstrate substantial stream-groundwater exchange, but little biological nutrient uptake in burned streams. This in part explains patterns of elevated nutrient export. Paired nutrient diffusing substrate experiments allow us to further investigate shifts in N, phosphorus, and carbon limitation that may suppress post-fire stream nutrient uptake. By isolating the mechanisms that reduce the capacity of fire-affected streams to retain and transform nutrient inputs, we can better predict dynamics in post-fire water quality and help prioritize upland and riparian restoration.

Using high-frequency sensors to identify hydroclimatological controls on storm-event variability in catchment nutrient fluxes and source zone activation

NASA Astrophysics Data System (ADS)

Blaen, Phillip; Khamis, Kieran; Lloyd, Charlotte; Krause, Stefan

2017-04-01

At the river catchment scale, storm events can drive highly variable behaviour in nutrient and water fluxes, yet short-term dynamics are frequently missed by low resolution sampling regimes. In addition, nutrient source contributions can vary significantly within and between storm events. Our inability to identify and characterise time dynamic source zone contributions severely hampers the adequate design of land use management practices in order to control nutrient exports from agricultural landscapes. Here, we utilise an 8-month high-frequency (hourly) time series of streamflow, nitrate concentration (NO3) and fluorescent dissolved organic matter concentration (FDOM) derived from optical in-situ sensors located in a headwater agricultural catchment. We characterised variability in flow and nutrient dynamics across 29 storm events. Storm events represented 31% of the time series and contributed disproportionately to nutrient loads (43% of NO3 and 36% of CDOM) relative to their duration. Principal components analysis of potential hydroclimatological controls on nutrient fluxes demonstrated that a small number of components, representing >90% of variance in the dataset, were highly significant model predictors of inter-event variability in catchment nutrient export. Hysteresis analysis of nutrient concentration-discharge relationships suggested spatially discrete source zones existed for NO3 and FDOM, and that activation of these zones varied on an event-specific basis. Our results highlight the benefits of high-frequency in-situ monitoring for characterising complex short-term nutrient dynamics and unravelling connections between hydroclimatological variability and river nutrient export and source zone activation under extreme flow conditions. These new process-based insights are fundamental to underpinning the development of targeted management measures to reduce nutrient loading of surface waters.

Analytic Models of Oxygen and Nutrient Diffusion, Metabolism Dynamics, and Architecture Optimization in Three-Dimensional Tissue Constructs with Applications and Insights in Cerebral Organoids

PubMed Central

2016-01-01

Diffusion models are important in tissue engineering as they enable an understanding of gas, nutrient, and signaling molecule delivery to cells in cell cultures and tissue constructs. As three-dimensional (3D) tissue constructs become larger, more intricate, and more clinically applicable, it will be essential to understand internal dynamics and signaling molecule concentrations throughout the tissue and whether cells are receiving appropriate nutrient delivery. Diffusion characteristics present a significant limitation in many engineered tissues, particularly for avascular tissues and for cells whose viability, differentiation, or function are affected by concentrations of oxygen and nutrients. This article seeks to provide novel analytic solutions for certain cases of steady-state and nonsteady-state diffusion and metabolism in basic 3D construct designs (planar, cylindrical, and spherical forms), solutions that would otherwise require mathematical approximations achieved through numerical methods. This model is applied to cerebral organoids, where it is shown that limitations in diffusion and organoid size can be partially overcome by localizing metabolically active cells to an outer layer in a sphere, a regionalization process that is known to occur through neuroglial precursor migration both in organoids and in early brain development. The given prototypical solutions include a review of metabolic information for many cell types and can be broadly applied to many forms of tissue constructs. This work enables researchers to model oxygen and nutrient delivery to cells, predict cell viability, study dynamics of mass transport in 3D tissue constructs, design constructs with improved diffusion capabilities, and accurately control molecular concentrations in tissue constructs that may be used in studying models of development and disease or for conditioning cells to enhance survival after insults like ischemia or implantation into the body, thereby providing a

Belowground Nutrient Dynamics Following Three Harvest Intensities on the Pearl River Floodplain, Mississippi

Treesearch

E.B. Schilling; B.G. Lockaby; Robert Rummer

1999-01-01

Abstract: The influence of clear and partial cut harvests on belowground nutrient cycling processes was examined on the Pearl River floodplain, Mississippi. Foci examined by this study included fine root biomass and detritus, fine root production, fine root nutrient contents, soil respiration rates, and microbial biomass C, N, and P during the first...

Nutrient limitation in tropical savannas across multiple scales and mechanisms.

PubMed

Pellegrini, Adam F A

2016-02-01

Nutrients have been hypothesized to influence the distribution of the savanna biome through two possible mechanisms. Low nutrient availability may restrict growth rates of trees, thereby allowing for intermittent fires to maintain low tree cover; alternatively, nutrient deficiency may even place an absolute constraint on the ability of forests to form, independent of fire. However, we have little understanding of the scales at which nutrient limitation operates, what nutrients are limiting, and the mechanisms that influence how nutrient limitation regulates savanna-forest transitions. Here, I review literature, synthesize existing data, and present a simple calculation of nutrient demand to evaluate how nutrient limitation may regulate the distribution of the savanna biome. The literature primarily supports the hypothesis that nutrients may interact dynamically with fire to restrict the transition of savanna into forest. A compilation of indirect metrics of nutrient limitation suggest that nitrogen and phosphorus are both in short supply and may limit plants. Nutrient demand calculations provided a number of insights. First, trees required high rates of nitrogen and phosphorus supply relative to empirically determined inputs. Second, nutrient demand increased as landscapes approached the transition point between savanna and forest. Third, the potential for fire-driven nutrient losses remained high throughout transitions, which may exaggerate limitation and could be a key feedback stabilizing the savanna biome. Fourth, nutrient limitation varied between functional groups, with fast-growing forest species having substantially greater nutrient demand and a higher susceptibility to fire-driven nutrient losses. Finally, African savanna trees required substantially larger amounts of nutrients supplied at greater rates, although this varied across plant functional groups. In summary, the ability of nutrients to control transitions emerges at individual and landscape

Assessment of nutrient loadings of a large multipurpose prairie reservoir

NASA Astrophysics Data System (ADS)

Morales-Marín, L. A.; Wheater, H. S.; Lindenschmidt, K. E.

2017-07-01

The relatively low water flow velocities in reservoirs cause them to have high capacities for retaining sediments and pollutants, which can lead to a reduction in downstream nutrient loading. Hence, nutrients can progressively accumulate in reservoirs, resulting in the deterioration of aquatic ecosystems and water quality. Lake Diefenbaker (LD) is a large multipurpose reservoir, located on the South Saskatchewan River (SSR), that serves as a major source of freshwater in Saskatchewan, Canada. Over the past several years, changes in land use (e.g. expansion of urban areas and industrial developments) in the reservoir's catchment have heightened concerns about future water quality in the catchment and in the reservoir. Intensification of agricultural activities has led to an increase in augmented the application of manure and fertilizer for crops and pasture. Although previous research has attempted to quantify nutrient retention in LD, there is a knowledge gap related to the identification of major nutrient sources and quantification of nutrient export from the catchment at different spatial scales. Using the SPAtially Referenced Regression On Watershed (SPARROW) model, this gap has been addressed by assessing water quality regionally, and identifying spatial patterns of factors and processes that affect water quality in the LD catchment. Model results indicate that LD retains about 70% of the inflowing total nitrogen (TN) and 90% of the inflowing total phosphorus (TP) loads, of which fertilizer and manure applied to agricultural fields contribute the greatest proportion. The SPARROW model will be useful as a tool to guide the optimal implementation of nutrient management plans to reduce nutrient inputs to LD.

Critical Zone Co-dynamics: Quantifying Interactions between Subsurface, Land Surface, and Vegetation Properties Using UAV and Geophysical Approaches

NASA Astrophysics Data System (ADS)

Dafflon, B.; Leger, E.; Peterson, J.; Falco, N.; Wainwright, H. M.; Wu, Y.; Tran, A. P.; Brodie, E.; Williams, K. H.; Versteeg, R.; Hubbard, S. S.

2017-12-01

Improving understanding and modelling of terrestrial systems requires advances in measuring and quantifying interactions among subsurface, land surface and vegetation processes over relevant spatiotemporal scales. Such advances are important to quantify natural and managed ecosystem behaviors, as well as to predict how watershed systems respond to increasingly frequent hydrological perturbations, such as droughts, floods and early snowmelt. Our study focuses on the joint use of UAV-based multi-spectral aerial imaging, ground-based geophysical tomographic monitoring (incl., electrical and electromagnetic imaging) and point-scale sensing (soil moisture sensors and soil sampling) to quantify interactions between above and below ground compartments of the East River Watershed in the Upper Colorado River Basin. We evaluate linkages between physical properties (incl. soil composition, soil electrical conductivity, soil water content), metrics extracted from digital surface and terrain elevation models (incl., slope, wetness index) and vegetation properties (incl., greenness, plant type) in a 500 x 500 m hillslope-floodplain subsystem of the watershed. Data integration and analysis is supported by numerical approaches that simulate the control of soil and geomorphic characteristic on hydrological processes. Results provide an unprecedented window into critical zone interactions, revealing significant below- and above-ground co-dynamics. Baseline geophysical datasets provide lithological structure along the hillslope, which includes a surface soil horizon, underlain by a saprolite layer and the fractured Mancos shale. Time-lapse geophysical data show very different moisture dynamics in various compartments and locations during the winter and growing season. Integration with aerial imaging reveals a significant linkage between plant growth and the subsurface wetness, soil characteristics and the topographic gradient. The obtained information about the organization and

Nutrients versus emerging contaminants-Or a dynamic match between subsidy and stress effects on stream biofilms.

PubMed

Aristi, I; Casellas, M; Elosegi, A; Insa, S; Petrovic, M; Sabater, S; Acuña, V

2016-05-01

Freshwater ecosystems are threatened by multiple anthropogenic stressors, which might be differentiated into two types: those that reduce biological activity at all concentrations (toxic contaminants), and those that subsidize biological activity at low concentrations and reduce it at high concentrations (assimilable contaminants). When occurring in mixtures, these contaminants can have either antagonistic, neutral or synergistic effects; but little is known on their joint effects. We assessed the interaction effects of a mixture of assimilable and toxic contaminants on stream biofilms in a manipulative experiment using artificial streams, and following a factorial design with three nutrient levels (low, medium or high) and either presence or absence of a mixture of emerging contaminants (ciprofloxacin, erythromycin, diclofenac, methylparaben, and sulfamethoxazole). We measured biofilm biomass, basal fluorescence, gross primary production and community respiration. Our initial hypotheses were that biofilm biomass and activity would: increase with medium nutrient concentrations (subsidy effect), but decrease with high nutrient concentrations (stress effect) (i); decrease with emerging contaminants, with the minimum decrease at medium nutrient concentrations (antagonistic interaction between nutrients subsidy and stress by emerging contaminants) and the maximum decrease at high nutrient concentrations (synergistic interaction between nutrients and emerging contaminants stress) (ii). All the measured variables responded linearly to the available nutrients, with no toxic effect at high nutrient concentrations. Emerging contaminants only caused weak toxic effects in some of the measured variables, and only after 3-4 weeks of exposure. Therefore, only antagonistic interactions were observed between nutrients and emerging contaminants, as medium and high nutrient concentrations partly compensated the harmful effects of emerging contaminants during the first weeks of the

Assessment of forest nutrient pools in view of biomass potentials - a case study from Austria oak stands

NASA Astrophysics Data System (ADS)

Yan, S.; Bruckman, V. J.; Glatzel, G.; Hochbichler, E.

2012-04-01

As one of the renewable energy forms, bio-energy could help to relieve the pressure which is caused by growing global energy demand. In Austria, large area of forests, traditional utilization of biomass and people's desire to live in a sound environment have supported the positive development of bio-energy. Soil nutrient status is in principle linked with the productivity of the aboveground biomass. This study focuses on K, Ca and Mg pools in soils and aboveground biomass in order to learn more on the temporal dynamics of plant nutrients as indicators for biomass potentials in Quercus dominated forests in northeastern Austria. Three soil types (according to WRB: eutric cambisol, calcic chernozem and haplic luvisol) were considered representative for the area and sampled. We selected nine Quercus petraea dominated permanent plots for this study. Exchangeable cations K, Ca and Mg in the soils were quantified in our study plots. Macronutrients pools of K, Ca and Mg in aboveground biomass were calculated according to inventory data and literature review. The exchangeable cations pool in the top 50 cm of the soil were 882 - 1,652 kg ha-1 for K, 2,661 to 16,510 kg ha-1 for Ca and 320 - 1,850 kg ha-1 for Mg. The nutrient pool in aboveground biomass ranged from 29 to 181 kg ha-1 for K, from 56 to 426 kg ha-1 for Ca and from 4 to 26 kg ha-1 for Mg. The underground exchangeable pools of K, Ca and Mg are generally 10, 22 and 58 times higher than aboveground biomass nutrient pools. Our results showed that the nutrient pools in the mineral soil are sufficient to support the tree growth. The levels of soil nutrients in particular K, Ca and Mg in our study areas are reasonably high and do not indicate the necessity for additional fertilization under current silvicultural practices and biomass extraction rate. The forest in our study areas is in favorable condition to supply biomass as raw material for energy utilization.

Quantifying Groundwater Nutrient Discharge to a Large Glacial Lake using a Watershed Loading Model

NASA Astrophysics Data System (ADS)

Schilling, K. E.

2015-12-01

Groundwater discharge to a lake is an important, if often neglected, component to water and nutrient budgets. Point measurements of groundwater discharge into a lake are prone to error, so in this study of 15.57 km2 West Lake Okoboji, Iowa, a watershed-based groundwater loading model was developed. Located in northwest Iowa, West Lake Okoboji is considered one of Iowa's premier tourist destinations but is threatened by eutrophication. A network of 21 observation wells was installed in the watershed to evaluate groundwater recharge and quality under representative land cover types in a range of landscape positions. Our objective was to develop typical groundwater responses from various land cover-landscape associations for scaling up to unmonitored areas in the watershed. Results indicated substantial variation in groundwater recharge and quality in the 3847 ha watershed. Recharge was similar among land covers under vegetation but was much lower under urban pavement. Nitrate-nitrogen concentrations were highest under cropped fields and lowest under perennial grassland and golf courses, whereas dissolved phosphorus was highest under residential and urban areas, including an engineered bioswale. A groundwater load allocation model indicated 91% of the nitrate load was from cropped areas and 7% from residential areas. In contrast, P loads were more equally divided among cropped fields (43%), perennial grass (36%) and residential (19%) areas. Based on the mass of nitrate and P in the lake, groundwater accounts for 71% and 18% of the nutrient inputs, respectively.

Association of arsenic with nutrient elements in rice plants.

PubMed

Duan, Guilan; Liu, Wenju; Chen, Xueping; Hu, Ying; Zhu, Yongguan

2013-06-01

Rice is the main cereal crop that feeds half of the world's population, and two thirds of the Chinese population. Arsenic (As) contamination in paddy soil and irrigation water elevates As concentration in rice grains, thus rice consumption is an important As intake route for populations in south and south-east Asia, where rice is the staple food. In addition to direct toxicity of As to human, As may limit the accumulation of micro-nutrients in rice grains, such as selenium (Se) and zinc (Zn). These micro-nutrients are essential for humans, while mineral deficiencies, especially iron (Fe) and Zn, are prevalent in China. Therefore, it is important to understand the interactions between As and micro-nutrients in rice plants, which is the principal source of these nutrients for people on rice diets. In addition, during the processes of As uptake, translocation and transformation, the status of macro-nutrients (e.g. silicon (Si), phosphors (P), sulfur (S)) are important factors affecting As dynamics in soil-plant systems and As accumulation in rice grains. Recently, synchrotron-based spectroscopic techniques have been applied to map the distribution of As and nutrient elements in rice plants, which will aid to understand how As are accumulated, complexed and transported within plants. This paper reviews the interactions between As and macro-nutrients, as well as micro-nutrients in rice plants.

Effects of Harvesting Intensity and Herbivory by White-tailed Deer on Vegetation and Nutrient Uptake in a Northern Hardwood Forest

NASA Astrophysics Data System (ADS)

Yorks, T. E.; Leopold, D. J.; Raynal, D. J.; Murdoch, P. S.; Burns, D. A.

2003-12-01

We quantified the response of vegetation and nutrient uptake in a northern hardwood forest in southeastern New York for three to four years after three intensities of harvesting: clearcutting, heavy timber stand improvement (TSI), light TSI (97, 29, and 10% basal area reductions, respectively). We also quantified effects of white-tailed deer (Odocoileus virginianus) herbivory on nutrient retention by vegetation. Total biomass and nutrient accumulation in vegetation was higher after TSI than clearcutting in the first two years but was highest in the fenced clearcut in subsequent years, indicating that TSI or partial harvesting is a viable management tool for harvesting timber while consistently maintaining high rates of nutrient retention. After clearcutting, biomass and nutrient retention were initially dominated by woody stems <1.4 m tall and herbaceous vegetation, but saplings 0.1-5.0 cm DBH became the most important contributors to biomass and nutrient accumulation within four years. However, after both intensities of TSI, trees >5.0 cm DBH continued to account for most biomass and nutrient accumulation whereas understory vegetation accumulated little biomass or nutrients. Heavy TSI resulted in increased regeneration of only two tree species (Acer pensylvanicum, Fagus grandifolia), but clearcutting allowed these two species, mature forest species (A. saccharum, Betula alleghaniensis), and the early successional Prunus pensylvanica to regenerate. Several early successional shrub and herbaceous species were also important to nutrient retention after clearcutting, including Polygonum cilinode, Rubus spp., and Sambucus racemosa. Herbivory by white-tailed deer dramatically reduced biomass and nutrient accumulation by woody stems <5 cm DBH after clearcutting (5.5 vs. 0.7 Mg biomass/ha and 30.4 vs. 6.3 kg N/ha on fenced and unfenced clearcut sites, respectively, after four years), indicating the important influence this herbivore can have on nutrient retention in

Nutrient Limitation Dynamics of a Coastal Cape Cod Pond: Seasonal Trends in Alkaline Phosphatase Activity

DTIC Science & Technology

2000-11-13

Collection and Nutrient Analyses Ashumet Pond water column profiles and samples were taken by the School for Marine Science and Technology (SMAST) at the...Collection & Analysis ........................................ .......... 77 4.3.1 SMAST Water Sampling Plan/Collection and Nutrient Analyses...suited as an indicator of phosphate limitation in natural waters . In this study alkaline phosphatase is used to understand the nutrient limitation

Nutrient enrichment and fish nutrient tolerance: Assessing biologically relevant nutrient criteria

USGS Publications Warehouse

Meador, Michael R.

2013-01-01

Relationships between nutrient concentrations and fish nutrient tolerance were assessed relative to established nutrient criteria. Fish community, nitrate plus nitrite (nitrate), and total phosphorus (TP) data were collected during summer low-flow periods in 2003 and 2004 at stream sites along a nutrient-enrichment gradient in an agricultural basin in Indiana and Ohio and an urban basin in the Atlanta, Georgia, area. Tolerance indicator values for nitrate and TP were assigned for each species and averaged separately for fish communities at each site (TIVo). Models were used to predict fish species expected to occur at a site under minimally disturbed conditions and average tolerance indicator values were determined for nitrate and TP separately for expected communities (TIVe). In both areas, tolerance scores (TIVo/TIVe) for nitrate increased significantly with increased nitrate concentrations whereas no significant relationships were detected between TP tolerance scores and TP concentrations. A 0% increase in the tolerance score (TIVo/TIVe = 1) for nitrate corresponded to a nitrate concentration of 0.19 mg/l (compared with a USEPA summer nitrate criterion of 0.17 mg/l) in the urban area and 0.31 mg/l (compared with a USEPA summer nitrate criterion of 0.86 mg/l) in the agricultural area. Fish nutrient tolerance values offer the ability to evaluate nutrient enrichment based on a quantitative approach that can provide insights into biologically relevant nutrient criteria.

Human waste: An underestimated source of nutrient pollution in coastal seas of Bangladesh, India and Pakistan.

PubMed

Amin, Md Nurul; Kroeze, Carolien; Strokal, Maryna

2017-05-15

Many people practice open defecation in south Asia. As a result, lot of human waste containing nutrients such as nitrogen (N) and phosphorus (P) enter rivers. Rivers transport these nutrients to coastal waters, resulting in marine pollution. This source of nutrient pollution is, however, ignored in many nutrient models. We quantify nutrient export by large rivers to coastal seas of Bangladesh, India and Pakistan, and the associated eutrophication potential in 2000 and 2050. Our new estimates for N and P inputs from human waste are one to two orders of magnitude higher than earlier model calculations. This leads to higher river export of nutrients to coastal seas, increasing the risk of coastal eutrophication potential (ICEP). The newly calculated future ICEP, for instance, Godavori river is 3 times higher than according to earlier studies. Our modeling approach is simple and transparent and can easily be applied to other data-poor basins. Copyright © 2017 Elsevier Ltd. All rights reserved.

Nutrient gradients in a granular activated carbon biofilter drives bacterial community organization and dynamics.

PubMed

Boon, Nico; Pycke, Benny F G; Marzorati, Massimo; Hammes, Frederik

2011-12-01

The quality of drinking water is ensured by hygienic barriers and filtration steps, such as ozonation and granular activated carbon (GAC) filtration. Apart from adsorption, GAC filtration involves microbial processes that remove biodegradable organic carbon from the ozonated ground or surface water and ensures biological stability of the treated water. In this study, microbial community dynamics in were monitored during the start-up and maturation of an undisturbed pilot-scale GAC filter at 4 depths (10, 45, 80 and 115 cm) over a period of 6 months. New ecological tools, based on 16S rRNA gene-DGGE, were correlated to filter performance and microbial activity and showed that the microbial gradients developing in the filter was of importance. At 10 cm from the top, receiving the freshly ozonated water with the highest concentration of nutrients, the microbial community dynamics were minimal and the species richness remained low. However, the GAC samples at 80-115 cm showed a 2-3 times higher species richness than the 10-45 cm samples. The highest biomass densities were observed at 45-80 cm, which corresponded with maximum removal of dissolved and assimilable organic carbon. Furthermore, the start-up period was clearly distinguishable using the Lorenz analysis, as after 80 days, the microbial community shifted to an apparent steady-state condition with increased evenness. This study showed that GAC biofilter performance is not necessarily correlated to biomass concentration, but rather that an elevated functionality can be the result of increased microbial community richness, evenness and dynamics. Copyright © 2011 Elsevier Ltd. All rights reserved.

Quantifying predictability variations in a low-order ocean-atmosphere model - A dynamical systems approach

NASA Technical Reports Server (NTRS)

Nese, Jon M.; Dutton, John A.

1993-01-01

The predictability of the weather and climatic states of a low-order moist general circulation model is quantified using a dynamic systems approach, and the effect of incorporating a simple oceanic circulation on predictability is evaluated. The predictability and the structure of the model attractors are compared using Liapunov exponents, local divergence rates, and the correlation and Liapunov dimensions. It was found that the activation of oceanic circulation increases the average error doubling time of the atmosphere and the coupled ocean-atmosphere system by 10 percent and decreases the variance of the largest local divergence rate by 20 percent. When an oceanic circulation develops, the average predictability of annually averaged states is improved by 25 percent and the variance of the largest local divergence rate decreases by 25 percent.

Seasonal variation in nutrient retention during inundation of a short-hydroperiod floodplain

USGS Publications Warehouse

Noe, G.B.; Hupp, C.R.

2007-01-01

Floodplains are generally considered to be important locations for nutrient retention or inorganic-to-organic nutrient conversions in riverine ecosystems. However, little is known about nutrient processing in short-hydroperiod floodplains or seasonal variation in floodplain nutrient retention. Therefore, we quantified the net uptake, release or transformation of nitrogen (N), phosphorus (P) and suspended sediment species during brief periods (1-2 days) of overbank flooding through a 250-m floodplain flowpath on the fourth-order Mattawoman Creek, Maryland U.S.A. Sampling occurred during a winter, two spring and a summer flood in this largely forested watershed with low nutrient and sediment loading. Concentrations of NO3- increased significantly in surface water flowing over the floodplain in three of the four floods, suggesting the floodplain was a source of NO3-. The upper portion of the floodplain flowpath consistently exported NH4+, most likely due to the hyporheic: flushing of floodplain soil NH4+, which was then likely nitrified to NO3- in floodwaters. The floodplain was a sink for particulate organic P (POP) during two floods and particulate organic N and inorganic suspended sediment (ISS) during one flood. Large releases of all dissolved inorganic N and P species occurred following a snowmelt and subsequent cold winter flood. Although there was little consistency in most patterns of nutrient processing among the different floods, this floodplain, characterized by brief inundation, low residence time and low nutrient loading, behaved oppositely from the conceptual model for most floodplains in that it generally exported inorganic nutrients and imported organic nutrients.

Quantifying temporal trends in fisheries abundance using Bayesian dynamic linear models: A case study of riverine Smallmouth Bass populations

USGS Publications Warehouse

Schall, Megan K.; Blazer, Vicki S.; Lorantas, Robert M.; Smith, Geoffrey; Mullican, John E.; Keplinger, Brandon J.; Wagner, Tyler

2018-01-01

Detecting temporal changes in fish abundance is an essential component of fisheries management. Because of the need to understand short‐term and nonlinear changes in fish abundance, traditional linear models may not provide adequate information for management decisions. This study highlights the utility of Bayesian dynamic linear models (DLMs) as a tool for quantifying temporal dynamics in fish abundance. To achieve this goal, we quantified temporal trends of Smallmouth Bass Micropterus dolomieu catch per effort (CPE) from rivers in the mid‐Atlantic states, and we calculated annual probabilities of decline from the posterior distributions of annual rates of change in CPE. We were interested in annual declines because of recent concerns about fish health in portions of the study area. In general, periods of decline were greatest within the Susquehanna River basin, Pennsylvania. The declines in CPE began in the late 1990s—prior to observations of fish health problems—and began to stabilize toward the end of the time series (2011). In contrast, many of the other rivers investigated did not have the same magnitude or duration of decline in CPE. Bayesian DLMs provide information about annual changes in abundance that can inform management and are easily communicated with managers and stakeholders.

A mobile water analysis laboratory for the study of stream nutrient and DOC dynamics

NASA Astrophysics Data System (ADS)

Echevarria Roman, Y.; Pullin, M. J.; Schwingle, R.; Gabrielsen, P. J.

2013-12-01

The dynamics of nutrient and dissolved organic carbon (DOC) quantity and composition in streams vary with season and in response to hydrologic events. Periodic grab sampling can capture some of this variation, but has also been shown to miss high flow events. Sampling during winter, during thunderstorms, and at night is difficult and sometimes hazardous. For these reasons, we have developed a mobile laboratory that autonomously determines pH, Eh, conductivity, dissolved oxygen, turbidity, nitrate, phosphate, DOC, DIC, as well as DOC fluorescence and absorbance continuously on a minutes timescale. The laboratory includes a Labview operated computer system that allows remote control and interaction with pumps, pressure, temperature, and flow sensors as well as the analytical instruments. Climate control allows for operation in winter. The design and operation of this laboratory will be presented. We will also discuss example data showing diurnal changes and responses to hydrologic events in DOC quantity and quality in the East Fork of the Jemez River, New Mexico.

Quantifying hyporheic exchange dynamics in a highly regulated large river reach

NASA Astrophysics Data System (ADS)

Zhou, T.; Bao, J.; Huang, M.; Hou, Z.; Arntzen, E.; Mackley, R.; Harding, S.; Crump, A.; Xu, Y.; Song, X.; Chen, X.; Stegen, J.; Hammond, G. E.; Thorne, P. D.; Zachara, J. M.

2016-12-01

Hyporheic exchange is an important mechanism taking place in riverbanks and riverbed sediments, where the river water and shallow groundwater mix and interact with each other. The direction and magnitude of hyporheic flux that penetrates the river bed and residence time of river water in the hyporheic zone are critical for biogeochemical processes such as carbon and nitrogen cycling, and biodegradation of organic contaminants. Hyporheic flux can be quantified using many direct and indirect measurements as well as analytical and numerical modeling tools. However, in a relatively large river, these methods can be limited by the accessibility, spatial constraints, complexity of geomorphologic features and subsurface properties, and computational power. In rivers regulated by hydroelectric dams, quantifying hyporheic fluxes becomes more challenging due to frequent hydropeaking events created by dam operations. In this study, we developed and validated methods that combined field measurements and numerical modeling for estimating hyporheic fluxes across the river bed in a 7-km long reach of the highly regulated Columbia River. The reach has a minimum width of about 800 meters and variations in river stage within a day could be up to two meters due to the upstream dam operations. In shallow water along the shoreline, vertical thermal profiles measured by self-recording thermistors were combined with time series of hydraulic gradient derived from river stage and water level at in-land wells to estimate the hyporheic flux rate. For the deep section, a high resolution computational fluid dynamics (CFD) modeling framework was developed to characterize the spatial distribution of flux rates at the river bed and the residence time of hyporheic flow at different river flow conditions. Our modeling results show that the rates of hyporheic exchange and residence time are controlled by (1) hydrostatic pressure induced by river stage fluctuations, and (2) hydrodynamic drivers

Nutrient budgets in the subtropical ocean gyres dominated by lateral transport

NASA Astrophysics Data System (ADS)

Letscher, Robert T.; Primeau, François; Moore, J. Keith

2016-11-01

Ocean circulation replenishes surface nutrients depleted by biological production and export. Vertical processes are thought to dominate, but estimated vertical nutrient fluxes are insufficient to explain observed net productivity in the subtropical ocean gyres. Lateral inputs help balance the North Atlantic nutrient budget, but their importance for other gyres has not been demonstrated. Here we use an ocean model that couples circulation and ecosystem dynamics to show that lateral transport and biological uptake of inorganic and organic forms of nitrogen and phosphorus from the gyre margins exceeds the vertical delivery of nutrients, supplying 24-36% of the nitrogen and 44-67% of the phosphorus required to close gyre nutrient budgets. At the Bermuda and Hawaii time-series sites, nearly half of the annual lateral supply by lateral transport occurs during the summer-to-fall stratified period, helping explain seasonal patterns of inorganic carbon drawdown and nitrogen fixation. Our study confirms the importance of upper-ocean lateral nutrient transport for understanding the biological cycles of carbon and nutrients in the ocean's largest biome.

Oceanic δ15N biogeography: a novel top-down approach to examine nutrient dynamics in the equatorial Pacific Ocean

NASA Astrophysics Data System (ADS)

Graham, B. S.; Fry, B.; Popp, B. N.; Allain, V.; Olson, R.; Galvan, F.

2010-12-01

By mapping the δ15N and δ13C values of three top-level pelagic predators, yellowfin (Thunnus albacares), bigeye (T. obesus), and skipjack (Katsuwonus pelamis) tuna throughout the equatorial Pacific Ocean, we demonstrated systematic geographic isotopic variation (up to ~12‰ for the δ15N values) that reflect nutrient dynamics that occur at the base of the food web. Remarkably the variation observed in the δ15N values of the tunas is geographically similar to δ15N values previously reported in surface particulate organic matter and deep-sea sediments in the tropical Pacific. We discuss the mechanisms occurring at the base of the food web that could produce the spatial variability observed in tropical tuna δ15N values. We present a simple Rayleigh fractionation model that can explain much of the spatial structure. We also discuss the temporal stability in the isotopic compositions at the base and top of the food web. Overall, this nitrogen isotope cartography or “isoscapes” suggests nitrogen is tightly retained in the marine food web, up to the top predators, and that the uptake of nitrate from the equatorial upwelling zone, denitrification in the oxygen minimum zones, and nitrogen fixation at the base of the food web play major roles in the observed geographical variation. In addition to providing insight into the nutrient dynamics of the open ocean, these predator isoscapes can begin to be used to characterize regional residency in tropical tunas, which is important for the successful management of tuna fisheries.

Real-time nutrient monitoring in rivers: adaptive sampling strategies, technological challenges and future directions

NASA Astrophysics Data System (ADS)

Blaen, Phillip; Khamis, Kieran; Lloyd, Charlotte; Bradley, Chris

2016-04-01

Excessive nutrient concentrations in river waters threaten aquatic ecosystem functioning and can pose substantial risks to human health. Robust monitoring strategies are therefore required to generate reliable estimates of river nutrient loads and to improve understanding of the catchment processes that drive spatiotemporal patterns in nutrient fluxes. Furthermore, these data are vital for prediction of future trends under changing environmental conditions and thus the development of appropriate mitigation measures. In recent years, technological developments have led to an increase in the use of continuous in-situ nutrient analysers, which enable measurements at far higher temporal resolutions than can be achieved with discrete sampling and subsequent laboratory analysis. However, such instruments can be costly to run and difficult to maintain (e.g. due to high power consumption and memory requirements), leading to trade-offs between temporal and spatial monitoring resolutions. Here, we highlight how adaptive monitoring strategies, comprising a mixture of temporal sample frequencies controlled by one or more 'trigger variables' (e.g. river stage, turbidity, or nutrient concentration), can advance our understanding of catchment nutrient dynamics while simultaneously overcoming many of the practical and economic challenges encountered in typical in-situ river nutrient monitoring applications. We present examples of short-term variability in river nutrient dynamics, driven by complex catchment behaviour, which support our case for the development of monitoring systems that can adapt in real-time to rapid environmental changes. In addition, we discuss the advantages and disadvantages of current nutrient monitoring techniques, and suggest new research directions based on emerging technologies and highlight how these might improve: 1) monitoring strategies, and 2) understanding of linkages between catchment processes and river nutrient fluxes.

Plants adapted to nutrient limitation allocate less biomass into stems in an arid-hot grassland.

PubMed

Yan, Bangguo; Ji, Zhonghua; Fan, Bo; Wang, Xuemei; He, Guangxiong; Shi, Liangtao; Liu, Gangcai

2016-09-01

Biomass allocation can exert a great influence on plant resource acquisition and nutrient use. However, the role of biomass allocation strategies in shaping plant community composition under nutrient limitations remains poorly addressed. We hypothesized that species-specific allocation strategies can affect plant adaptation to nutrient limitations, resulting in species turnover and changes in community-level biomass allocations across nutrient gradients. In this study, we measured species abundance and the concentrations of nitrogen and phosphorus in leaves and soil nutrients in an arid-hot grassland. We quantified species-specific allocation parameters for stems vs leaves based on allometric scaling relationships. Species-specific stem vs leaf allocation parameters were weighted with species abundances to calculate the community-weighted means driven by species turnover. We found that the community-weighted means of biomass allocation parameters were significantly related to the soil nutrient gradient as well as to leaf stoichiometry, indicating that species-specific allocation strategies can affect plant adaptation to nutrient limitations in the studied grassland. Species that allocate less to stems than leaves tend to dominate nutrient-limited environments. The results support the hypothesis that species-specific allocations affect plant adaptation to nutrient limitations. The allocation trade-off between stems and leaves has the potential to greatly affect plant distribution across nutrient gradients. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Quantifying terrestrial ecosystem carbon dynamics in the Jinsha watershed, Upper Yangtze, China from 1975 to 2000

USGS Publications Warehouse

Zhao, Shuqing; Liu, Shuguang; Yin, Runsheng; Li, Zhengpeng; Deng, Yulin; Tan, Kun; Deng, Xiangzheng; Rothstein, David; Qi, Jiaguo

2010-01-01

Quantifying the spatial and temporal dynamics of carbon stocks in terrestrial ecosystems and carbon fluxes between the terrestrial biosphere and the atmosphere is critical to our understanding of regional patterns of carbon budgets. Here we use the General Ensemble biogeochemical Modeling System to simulate the terrestrial ecosystem carbon dynamics in the Jinsha watershed of China’s upper Yangtze basin from 1975 to 2000, based on unique combinations of spatial and temporal dynamics of major driving forces, such as climate, soil properties, nitrogen deposition, and land use and land cover changes. Our analysis demonstrates that the Jinsha watershed ecosystems acted as a carbon sink during the period of 1975–2000, with an average rate of 0.36 Mg/ha/yr, primarily resulting from regional climate variation and local land use and land cover change. Vegetation biomass accumulation accounted for 90.6% of the sink, while soil organic carbon loss before 1992 led to a lower net gain of carbon in the watershed, and after that soils became a small sink. Ecosystem carbon sink/source patterns showed a high degree of spatial heterogeneity. Carbon sinks were associated with forest areas without disturbances, whereas carbon sources were primarily caused by stand-replacing disturbances. It is critical to adequately represent the detailed fast-changing dynamics of land use activities in regional biogeochemical models to determine the spatial and temporal evolution of regional carbon sink/source patterns.

Dynamic dual-tracer MRI-guided fluorescence tomography to quantify receptor density in vivo

PubMed Central

Davis, Scott C.; Samkoe, Kimberley S.; Tichauer, Kenneth M.; Sexton, Kristian J.; Gunn, Jason R.; Deharvengt, Sophie J.; Hasan, Tayyaba; Pogue, Brian W.

2013-01-01

The up-regulation of cell surface receptors has become a central focus in personalized cancer treatment; however, because of the complex nature of contrast agent pharmacokinetics in tumor tissue, methods to quantify receptor binding in vivo remain elusive. Here, we present a dual-tracer optical technique for noninvasive estimation of specific receptor binding in cancer. A multispectral MRI-coupled fluorescence molecular tomography system was used to image the uptake kinetics of two fluorescent tracers injected simultaneously, one tracer targeted to the receptor of interest and the other tracer a nontargeted reference. These dynamic tracer data were then fit to a dual-tracer compartmental model to estimate the density of receptors available for binding in the tissue. Applying this approach to mice with deep-seated gliomas that overexpress the EGF receptor produced an estimate of available receptor density of 2.3 ± 0.5 nM (n = 5), consistent with values estimated in comparative invasive imaging and ex vivo studies. PMID:23671066

Quantifying changes in spatial patterns of surface air temperature dynamics over several decades

NASA Astrophysics Data System (ADS)

Zappalà, Dario A.; Barreiro, Marcelo; Masoller, Cristina

2018-04-01

We study daily surface air temperature (SAT) reanalysis in a grid over the Earth's surface to identify and quantify changes in SAT dynamics during the period 1979-2016. By analysing the Hilbert amplitude and frequency we identify the regions where relative variations are most pronounced (larger than ±50 % for the amplitude and ±100 % for the frequency). Amplitude variations are interpreted as due to changes in precipitation or ice melting, while frequency variations are interpreted as due to a northward shift of the inter-tropical convergence zone (ITCZ) and to a widening of the rainfall band in the western Pacific Ocean. The ITCZ is the ascending branch of the Hadley cell, and thus by affecting the tropical atmospheric circulation, ITCZ migration has far-reaching climatic consequences. As the methodology proposed here can be applied to many other geophysical time series, our work will stimulate new research that will advance the understanding of climate change impacts.

Overview: Cross-habitat flux of nutrients and detritus

USGS Publications Warehouse

Vanni, M.J.; DeAngelis, D.L.; Schindler, D.E.; Huxel, G.R.; Polis, G.A.; Power, M.E.; Huxel, G.R.

2004-01-01

Ecologists have long known that all ecosystems receive considerable quantities of materials from outside their boundaries (e.g., Elton 1927), and quantifying the magnitude of such fluxes has long been a central tenet of ecosystem ecology (e.g., Odum 1971). Thus, one might think that the consequences of such fluxes for food webs would be well understood. However, food webs have traditionally been viewed as if they were isolated from surrounding habitats, a habit that has been particularly persistent in the modeling of food webs. When fluxes from the outside have been considered, they have largely been restricted to constant inputs directly affecting the base of the food web (e.g., solar energy or nutrients), and usually only such issues as their effects on equilibrium conditions have been considered (e.g., the well-known relationships between nutrient inputs and average densities of various food web members).

The influence of microtopography on soil nutrients in created mitigation wetlands

USGS Publications Warehouse

Moser, K.F.; Ahn, C.; Noe, G.B.

2009-01-01

This study explores the relationship between microtopography and soil nutrients (and trace elements), comparing results for created and reference wetlands in Virginia, and examining the effects of disking during wetland creation. Replicate multiscale tangentially conjoined circular transects were used to quantify microtopography both in terms of elevation and by two microtopographic indices. Corresponding soil samples were analyzed for moisture content, total C and N, KCl-extractable NH4-N and NO3-N, and Mehlich-3 extractable P, Ca, Mg, K, Al, Fe, and Mn. Means and variances of soil nutrient/element concentrations were compared between created and natural wetlands and between disked and nondisked created wetlands. Natural sites had higher and more variable soil moisture, higher extractable P and Fe, lower Mn than created wetlands, and comparatively high variability in nutrient concentrations. Disked sites had higher soil moisture, NH4-N, Fe, and Mn than did nondisked sites. Consistently low variances (Levene test for inequality) suggested that nondisked sites had minimal nutrient heterogeneity. Across sites, low P availability was inferred by the molar ratio (Mehlich-3 [P/(Al + Fe)] < 0.06); strong intercorrelations among total C, total N, and extractable Fe, Al, and P suggested that humic-metal-P complexes may be important for P retention and availability. Correlations between nutrient/element concentrations and microtopographic indices suggested increased Mn and decreased K and Al availability with increased surface roughness. Disking appears to enhance water and nutrient retention, as well as nutrient heterogeneity otherwise absent from created wetlands, thus potentially promoting ecosystem development. ?? 2008 Society for Ecological Restoration International.

Fire and nutrient cycling in shortgrass steppe of the southern Great Plains, USA

Treesearch

P.L. Ford; C.S. White

2005-01-01

Fire in semi-arid grasslands releases nutrients bound up in organic matter and accelerates the rate of decomposition in the soil. This research experimentally tested effects of season and frequency of fire on nutrient cycling dynamics in shortgrass steppe. The objective was to identify if fire treatments have the ability to increase potential grassland productivity...

Nutrient dynamics in two seagrass species, Posidonia coriacea and Zostera tasmanica, on Success Bank, Western Australia

NASA Astrophysics Data System (ADS)

Walker, D. I.; Campey, M. L.; Kendrick, G. A.

2004-06-01

Nutrient concentrations and seasonal differences in atomic ratios (N:P) in plant tissue of Posidonia coriacea Kuo and Cambridge and Zostera tasmanica Aschers (formerly Heterozostera tasmanica (Syst Bot 27 (2002) 468) were measured from multiple locations on Success Bank, southwestern Australia, and used to infer nutritional constraints on seagrass vegetative growth, particularly by phosphorus. Posidonia plant tissue at the west site had higher nitrogen than the east site in both summer and winter. Nitrogen concentrations increased in winter, particularly in sheath tissue, but there was little change in root nitrogen concentrations between sites or seasons. Nitrogen concentrations of leaf tissue were all less than median seagrass values reported by Duarte (Mar Ecol Prog Ser 67 (1990) 201). The seasonality in nutrient concentrations in plant tissues suggests greater nutritional constraints in summer, during periods of high growth. Vegetative growth of Posidonia coriacea was more nutrient limited than that of Zostera tasmanica. Translocation of nutrients along rhizomes to the apex may ensure that growing points are not nutrient limited and that growth can be maintained, and was more apparent in Z. tasmanica than P. coriacea. Sexual reproduction placed large demands on P. coriacea through the high investment of nutrients into fruit, resulting in reduced nutritional constraints on successful seedling recruitment by initially providing seedlings with nutrients.

Mitigating cyanobacterial harmful algal blooms in aquatic ecosystems impacted by climate change and anthropogenic nutrients.

PubMed

Paerl, Hans W; Gardner, Wayne S; Havens, Karl E; Joyner, Alan R; McCarthy, Mark J; Newell, Silvia E; Qin, Boqiang; Scott, J Thad

2016-04-01

Mitigating the global expansion of cyanobacterial harmful blooms (CyanoHABs) is a major challenge facing researchers and resource managers. A variety of traditional (e.g., nutrient load reduction) and experimental (e.g., artificial mixing and flushing, omnivorous fish removal) approaches have been used to reduce bloom occurrences. Managers now face the additional effects of climate change on watershed hydrologic and nutrient loading dynamics, lake and estuary temperature, mixing regime, internal nutrient dynamics, and other factors. Those changes favor CyanoHABs over other phytoplankton and could influence the efficacy of control measures. Virtually all mitigation strategies are influenced by climate changes, which may require setting new nutrient input reduction targets and establishing nutrient-bloom thresholds for impacted waters. Physical-forcing mitigation techniques, such as flushing and artificial mixing, will need adjustments to deal with the ramifications of climate change. Here, we examine the suite of current mitigation strategies and the potential options for adapting and optimizing them in a world facing increasing human population pressure and climate change. Copyright © 2015 Elsevier B.V. All rights reserved.

Polymorphisms in the yeast galactose sensor underlie a natural continuum of nutrient-decision phenotypes.

PubMed

Lee, Kayla B; Wang, Jue; Palme, Julius; Escalante-Chong, Renan; Hua, Bo; Springer, Michael

2017-05-01

In nature, microbes often need to "decide" which of several available nutrients to utilize, a choice that depends on a cell's inherent preference and external nutrient levels. While natural environments can have mixtures of different nutrients, phenotypic variation in microbes' decisions of which nutrient to utilize is poorly studied. Here, we quantified differences in the concentration of glucose and galactose required to induce galactose-responsive (GAL) genes across 36 wild S. cerevisiae strains. Using bulk segregant analysis, we found that a locus containing the galactose sensor GAL3 was associated with differences in GAL signaling in eight different crosses. Using allele replacements, we confirmed that GAL3 is the major driver of GAL induction variation, and that GAL3 allelic variation alone can explain as much as 90% of the variation in GAL induction in a cross. The GAL3 variants we found modulate the diauxic lag, a selectable trait. These results suggest that ecological constraints on the galactose pathway may have led to variation in a single protein, allowing cells to quantitatively tune their response to nutrient changes in the environment.

Transitional Benthic Boundary Layers and their Influence on Nutrient Flux in Tidal Estuaries

NASA Astrophysics Data System (ADS)

Koetje, K. M.; Foster, D. L.; Lippmann, T. C.; Kalnejais, L. H.

2016-12-01

Quantifying the coupled physical and geochemical processes in the fluid-sediment interface is critical to managing coastal resources. This is of particular importance during times of enhanced hydrodynamic forcing where extreme tide or wind events can have a significant impact on water quality. A combination of field and laboratory experiments were used to examine the relationship between large-scale fluid shear stresses and geochemical fluxes at the fluid-sediment interface in the Great Bay Estuary, New Hampshire. Sediment geochemical measurements paired with flow field observations along estuary-wide transects over several tidal cycles provide nutrient load estimates that can be scaled to represent the whole Bay. Three-dimensional flow field measurements collected using a maneuverable personal watercraft were used to determine the spatial and temporal variability of the shear stress throughout the Bay. High-resolution bottom boundary layer dynamics were observed using a suite of acoustic Doppler current profilers (ADCP) in order to improve the accuracy of diffusive flux estimates by directly measuring the thickness of the benthic boundary layer. Over the 2.5 m tidal range and at water depths ranging from 0.3 m to 1.5 m at mean lower low water, peak mean flows ranged from 0.2 m/s to 1 m/s at the sampling sites. The dominant contribution of hydrodynamic forcing to the Bay is due to tidal flows, which are largely unidirectional during flood tide. Sediment grain size analysis characterized the bed at sampling sites as fine-grained sandy mud (d50 = 47 μm). Sampling during typical tidal flow conditions, a smooth turbulent flow field was observed and the threshold of motion was not exceeded. Along with sediment characterization, porosity profiles and erosion chamber experiments were used to characterize nutrient release. This host of data provides shear stress estimates that can constrain nutrient loads under variable hydrodynamic conditions.

Quantifying ubiquitin signaling.

PubMed

Ordureau, Alban; Münch, Christian; Harper, J Wade

2015-05-21

Ubiquitin (UB)-driven signaling systems permeate biology, and are often integrated with other types of post-translational modifications (PTMs), including phosphorylation. Flux through such pathways is dictated by the fractional stoichiometry of distinct modifications and protein assemblies as well as the spatial organization of pathway components. Yet, we rarely understand the dynamics and stoichiometry of rate-limiting intermediates along a reaction trajectory. Here, we review how quantitative proteomic tools and enrichment strategies are being used to quantify UB-dependent signaling systems, and to integrate UB signaling with regulatory phosphorylation events, illustrated with the PINK1/PARKIN pathway. A key feature of ubiquitylation is that the identity of UB chain linkage types can control downstream processes. We also describe how proteomic and enzymological tools can be used to identify and quantify UB chain synthesis and linkage preferences. The emergence of sophisticated quantitative proteomic approaches will set a new standard for elucidating biochemical mechanisms of UB-driven signaling systems. Copyright © 2015 Elsevier Inc. All rights reserved.

Quantifying Ubiquitin Signaling

PubMed Central

Ordureau, Alban; Münch, Christian; Harper, J. Wade

2015-01-01

Ubiquitin (UB)-driven signaling systems permeate biology, and are often integrated with other types of post-translational modifications (PTMs), most notably phosphorylation. Flux through such pathways is typically dictated by the fractional stoichiometry of distinct regulatory modifications and protein assemblies as well as the spatial organization of pathway components. Yet, we rarely understand the dynamics and stoichiometry of rate-limiting intermediates along a reaction trajectory. Here, we review how quantitative proteomic tools and enrichment strategies are being used to quantify UB-dependent signaling systems, and to integrate UB signaling with regulatory phosphorylation events. A key regulatory feature of ubiquitylation is that the identity of UB chain linkage types can control downstream processes. We also describe how proteomic and enzymological tools can be used to identify and quantify UB chain synthesis and linkage preferences. The emergence of sophisticated quantitative proteomic approaches will set a new standard for elucidating biochemical mechanisms of UB-driven signaling systems. PMID:26000850

Quantifying consumption rates of dissolved oxygen along bed forms

NASA Astrophysics Data System (ADS)

Boano, Fulvio; De Falco, Natalie; Arnon, Shai

2016-04-01

Streambed interfaces represent hotspots for nutrient transformations because they host different microbial species, and the evaluation of these reaction rates is important to assess the fate of nutrients in riverine environments. In this work we analyze a series of flume experiments on oxygen demand in dune-shaped hyporheic sediments under losing and gaining flow conditions. We employ a new modeling code to quantify oxygen consumption rates from observed vertical profiles of oxygen concentration. The code accounts for transport by molecular diffusion and water advection, and automatically determines the reaction rates that provide the best fit between observed and modeled concentration values. The results show that reaction rates are not uniformly distributed across the streambed, in agreement with the expected behavior predicted by hyporheic exchange theory. Oxygen consumption was found to be highly influenced by the presence of gaining or losing flow conditions, which controlled the delivery of labile DOC to streambed microorganisms.

Productivity and nutrient cycling in bioenergy cropping systems

NASA Astrophysics Data System (ADS)

Heggenstaller, Andrew Howard

One of the greatest obstacles confronting large-scale biomass production for energy applications is the development of cropping systems that balance the need for increased productive capacity with the maintenance of other critical ecosystem functions including nutrient cycling and retention. To address questions of productivity and nutrient dynamics in bioenergy cropping systems, we conducted two sets of field experiments during 2005-2007, investigating annual and perennial cropping systems designed to generate biomass energy feedstocks. In the first experiment we evaluated productivity and crop and soil nutrient dynamics in three prototypical bioenergy double-crop systems, and in a conventionally managed sole-crop corn system. Double-cropping systems included fall-seeded forage triticale (x Triticosecale Wittmack), succeeded by one of three summer-adapted crops: corn (Zea mays L.), sorghum-sudangrass [Sorghum bicolor (L.) Moench], or sunn hemp (Crotalaria juncea L.). Total dry matter production was greater for triticale/corn and triticale/sorghum-sudangrass compared to sole-crop corn. Functional growth analysis revealed that photosynthetic duration was more important than photosynthetic efficiency in determining biomass productivity of sole-crop corn and double-crop triticale/corn, and that greater yield in the tiritcale/corn system was the outcome of photosynthesis occurring over an extended duration. Increased growth duration in double-crop systems was also associated with reductions in potentially leachable soil nitrogen relative to sole-crop corn. However, nutrient removal in harvested biomass was also greater in the double-crop systems, indicating that over the long-term, double-cropping would mandate increased fertilizer inputs. In a second experiment we assessed the effects of N fertilization on biomass and nutrient partitioning between aboveground and belowground crop components, and on carbon storage by four perennial, warm-season grasses: big bluestem

Quantifying terrestrial ecosystem carbon dynamics in the Jinsha watershed, Upper Yangtze, China from 1975 to 2000

USGS Publications Warehouse

Zhao, Shuqing; Liu, Shuguang; Yin, Runsheng; Li, Zhengpeng; Deng, Yulin; Tan, Kun; Deng, Xiangzheng; Rothstein, David; Qi, Jiaguo; Yin, Runsheng

2009-01-01

Quantifying the spatial and temporal dynamics of carbon stocks in terrestrial ecosystems and carbon fluxes between the terrestrial biosphere and the atmosphere is critical to our understanding of regional patterns of carbon storage and loss. Here we use the General Ensemble Biogeochemical Modeling System to simulate the terrestrial ecosystem carbon dynamics in the Jinsha watershed of China's upper Yangtze basin from 1975 to 2000, based on unique combinations of spatial and temporal dynamics of major driving forces, such as climate, soil properties, nitrogen deposition, and land use and land cover changes. Our analysis demonstrates that the Jinsha watershed ecosystems acted as a carbon sink during the period of 1975–2000, with an average rate of 0.36 Mg/ha/yr, primarily resulting from regional climate variation and local land use and land cover change. Vegetation biomass accumulation accounted for 90.6% of the sink, while soil organic carbon loss before 1992 led to lower net gain of carbon in the watershed, and after that soils became a small sink. Ecosystem carbon sinks/source pattern showed a high degree of spatial heterogeneity, Carbon sinks were associated with forest areas without disturbances, whereas carbon Sources were primarily caused by stand-replacing disturbances. This highlights the importance of land-use history in determining the regional carbon sinks/source pattern.

ROLE OF OCEANIC AND RIVERINE SOURCES IN NUTRIENT AND PHYTOPLANKTON DYNAMICS IN YAQUINA BAY, OREGON

EPA Science Inventory

There is evidence that coastal ecosystems are experiencing environmental problems due to excess nutrients. The numerous sources, forms, and pathways of nutrients make it difficult to determine the effect of increases in anthropogenic loading. This is particularly evident in Pac...

Nutrient bioassimilation capacity of aquacultured oysters: quantification of an ecosystem service.

PubMed

Higgins, Colleen B; Stephenson, Kurt; Brown, Bonnie L

2011-01-01

Like many coastal zones and estuaries, the Chesapeake Bay has been severely degraded by cultural eutrophication. Rising implementation costs and difficulty achieving nutrient reduction goals associated with point and nonpoint sources suggests that approaches supplemental to source reductions may prove useful in the future. Enhanced oyster aquaculture has been suggested as one potential policy initiative to help rid the Bay waters of excess nutrients via harvest of bioassimilated nutrients. To assess this potential, total nitrogen (TN), total phosphorous (TP), and total carbon (TC) content were measured in oyster tissue and shell at two floating-raft cultivation sites in the Chesapeake Bay. Models were developed based on the common market measurement of total length (TL) for aquacultured oysters, which was strongly correlated to the TN (R2 = 0.76), TP (R2 = 0.78), and TC (R2 = 0.76) content per oyster tissue and shell. These models provide resource managers with a tool to quantify net nutrient removal. Based on model estimates, 10(6) harvest-sized oysters (76 mm TL) remove 132 kg TN, 19 kg TP, and 3823 kg TC. In terms of nutrients removed per unit area, oyster harvest is an effective means of nutrient removal compared with other nonpoint source reduction strategies. At a density of 286 oysters m(-2), assuming no mortality, harvest size nutrient removal rates can be as high as 378 kg TN ha(-1), 54 kg TP ha(-1), and 10,934 kg TC ha(-1) for 76-mm oysters. Removing 1 t N from the Bay would require harvesting 7.7 million 76-mm TL cultivated oysters.

Nutrient cycling associated with the seagrass Halophila ovalis in the Swan-Canning Estuary based on seasonal variations in biomass and tissue nutrients

NASA Astrophysics Data System (ADS)

Connell, E. L.; Walker, D. I.

2001-09-01

Halophila ovalis occupies about 20% (461 ha) of the Swan-Canning Estuary. To assess the role of this plant in the biogeochemical cycling of the estuary, its biomass, nutrient dynamics and oxygen release from its roots to the sediment were investigated. This paper describes a conceptual model developed to extrapolate these findings to the whole estuary.The model follows changes in H. ovalis meadows in the Swan-Canning Estuary on a seasonal basis over an annual cycle. Total maximum seagrass biomass was estimated as 346 t dry weight (DW) in summer, declining in winter. In spring, although H. ovalis biomass did not increase, tissue nutrient concentrations were higher when external nutrient concentrations were high. From spring to summer, when external nutrient concentrations in the water column were severely depleted, shoot to root-rhizome biomass ratios changed from 1 : 1 in winter to 1 : 1·5 in summer. Plant tissue nutrients also decreased in root-rhizomes and increased in shoots, indicating an allocation of internal nutrient resources to the shoots for growth. Despite depletion of nitrogen in the water column, ammonium was still available in the sediment. Ammonium concentrations in the sediment porewater decreased in summer, suggesting H. ovalis meadows were a sink for ammonium. With an increase in biomass in summer, including the density of roots, oxygen release from H. ovalis roots subsequently increased. H. ovalis meadows act as a substantial sink for nutrients in the Swan-Canning Estuary in spring and summer. In winter, when there are large losses of plant biomass, H. ovalis meadows become a source of nutrients to the estuary.

The effect of modifying rooting depths and nitrification inhibitors on nutrient uptake from organic biogas residues in maize

NASA Astrophysics Data System (ADS)

Dietrich, Charlotte C.; Koller, Robert; Nagel, Kerstin A.; Schickling, Anke; Schrey, Silvia D.; Jablonowski, Nicolai D.

2017-04-01

Optimizing the application of and nutrient uptake from organic nutrient sources, such as the nutrient-rich residues ("digestates") from the biogas industry, is becoming a viable option in remediating fertility on previously unsuitable soils for agricultural utilization. Proposedly, concurrent changes in root system architecture and functioning could also serve as the basis of future phytomining approaches. Herein, we evaluate the effect of spatial nutrient availability and nitrification on maize root architecture and nutrient uptake. We test these effects by applying maize-based digestate at a rate of 170 kg/ha in layers of varying depths (10, 25 and 40 cm) and through either the presence or absence of nitrification inhibitors. In order to regularly monitor above- and below-ground plant biomass production, we used the noninvasive phenotyping platform, GROWSCREEN-Rhizo at the Forschungszentrum Jülich, using rhizotrons (Nagel et al., 2012). Measured parameters included projected plant height and leaf area, as well as root length and spatial distribution. Additionally, root diameters were quantified after the destructive harvest, 21 days after sowing (DAS). Spatial nutrient availability significantly affected root system architecture, as for example root system size -the area occupied by roots- increased alongside nutrient layer depths. Fertilization also positively affected root length density (RLD). Within fertilized layers, the presence of nitrification inhibitors increased RLD by up to 30% and was most pronounced in the fine root biomass fraction (0.1 to 0.5mm). Generally, nitrification inhibitors promoted early plant growth by up to 45% across treatments. However, their effect varied in dependence of layer depths, leading to a time-delayed response in deeper layers, accounting for plants having to grow significantly longer roots in order to reach fertilized substrate. Nitrification inhibitors also initiated the comparatively early on-set of growth differences in

Diagnosis of nutrient imbalances with vector analysis in agroforestry systems.

PubMed

Isaac, Marney E; Kimaro, Anthony A

2011-01-01

Agricultural intensification has had unintended environmental consequences, including increased nutrient leaching and surface runoff and other agrarian-derived pollutants. Improved diagnosis of on-farm nutrient dynamics will have the advantage of increasing yields and will diminish financial and environmental costs. To achieve this, a management support system that allows for site-specific rapid evaluation of nutrient production imbalances and subsequent management prescriptions is needed for agroecological design. Vector diagnosis, a bivariate model to depict changes in yield and nutritional response simultaneously in a single graph, facilitates identification of nutritional status such as growth dilution, deficiency, sufficiency, luxury uptake, and toxicity. Quantitative data from cocoa agroforestry systems and pigeonpea intercropping trials in Ghana and Tanzania, respectively, were re-evaluated with vector analysis. Relative to monoculture, biomass increase in cocoa ( L.) under shade (35-80%) was accompanied by a 17 to 25% decline in P concentration, the most limiting nutrient on this site. Similarly, increasing biomass with declining P concentrations was noted for pigeonpea [ (L). Millsp.] in response to soil moisture availability under intercropping. Although vector analysis depicted nutrient responses, the current vector model does not consider non-nutrient resource effects on growth, such as ameliorated light and soil moisture, which were particularly active in these systems. We revisit and develop vector analysis into a framework for diagnosing nutrient and non-nutrient interactions in agroforestry systems. Such a diagnostic technique advances management decision-making by increasing nutrient precision and reducing environmental issues associated with agrarian-derived soil contamination. American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.

Spatially explicit modeling of particulate nutrient flux in Large global rivers

NASA Astrophysics Data System (ADS)

Cohen, S.; Kettner, A.; Mayorga, E.; Harrison, J. A.

2017-12-01

Water, sediment, nutrient and carbon fluxes along river networks have undergone considerable alterations in response to anthropogenic and climatic changes, with significant consequences to infrastructure, agriculture, water security, ecology and geomorphology worldwide. However, in a global setting, these changes in fluvial fluxes and their spatial and temporal characteristics are poorly constrained, due to the limited availability of continuous and long-term observations. We present results from a new global-scale particulate modeling framework (WBMsedNEWS) that combines the Global NEWS watershed nutrient export model with the spatially distributed WBMsed water and sediment model. We compare the model predictions against multiple observational datasets. The results indicate that the model is able to accurately predict particulate nutrient (Nitrogen, Phosphorus and Organic Carbon) fluxes on an annual time scale. Analysis of intra-basin nutrient dynamics and fluxes to global oceans is presented.

FISH-MEDIATED NUTRIENT AND ENERGY EXCHANGE BETWEEN A LAKE SUPERIOR COASTAL WETLAND AND ITS ADJACENT BAY

EPA Science Inventory

Little has been done to quantify fluxes of organisms, nutrients, and energy between freshwater coastal habitats and adjacent offshore waters or to evaluate the ecological implications of these exchanges on a whole-lake basis. To test the hypothesis that fish-mediated transport m...

Mathematical modelling of the influenced of diffusion rate on macro nutrient availability in paddy field

NASA Astrophysics Data System (ADS)

Renny; Supriyanto

2018-04-01

Nutrition is the chemical compounds that needed by the organism for the growth process. In plants, nutrients are organic or inorganic compounds that are absorbed from the roots of the soil. It consist of macro and micro nutrient. Macro nutrients are nutrition that needed by plants in large quantities, such as, nitrogen, calcium, pottacium, magnesium, and sulfur. The total soil nutrient is the difference between the input nutrient and the output nutrients. Input nutrients are nutrient that derived from the decomposition of organic substances. Meanwhile, the output nutrient consists of the nutrients that absorbed by plant roots (uptake), the evaporated nutrients (volatilized) and leached nutrients. The nutrient transport can be done through diffusion process. The diffusion process is essential in removing the nutrient from one place to the root surface. It will cause the rate of absorption of nutrient by the roots will be greater. Nutrient concept in paddy filed can be represented into a mathematical modelling, by making compartment models. The rate of concentration change in the compartment model forms a system of homogeneous linear differential equations. In this research, we will use Laplaces transformation to solve the compartment model and determined the dynamics of macro nutrition due to diffusion process.

Top-down effects of a terrestrial frog on forest nutrient dynamics.

Treesearch

Karen H. Beard; Kristiina A. Vogt; Andrew Kulmatiski

2002-01-01

Many studies have found top-down effects of predators on prey, but few studies have linked top-down effects of vertebrate predators to nutrient cycling rates in terrestrial systems. In this study, large and significant effects of a terrestrial frog, Eleutherodactylus coqui (coqu

Quantified Facial Soft-tissue Strain in Animation Measured by Real-time Dynamic 3-Dimensional Imaging.

PubMed

Hsu, Vivian M; Wes, Ari M; Tahiri, Youssef; Cornman-Homonoff, Joshua; Percec, Ivona

2014-09-01

The aim of this study is to evaluate and quantify dynamic soft-tissue strain in the human face using real-time 3-dimensional imaging technology. Thirteen subjects (8 women, 5 men) between the ages of 18 and 70 were imaged using a dual-camera system and 3-dimensional optical analysis (ARAMIS, Trilion Quality Systems, Pa.). Each subject was imaged at rest and with the following facial expressions: (1) smile, (2) laughter, (3) surprise, (4) anger, (5) grimace, and (6) pursed lips. The facial strains defining stretch and compression were computed for each subject and compared. The areas of greatest strain were localized to the midface and lower face for all expressions. Subjects over the age of 40 had a statistically significant increase in stretch in the perioral region while lip pursing compared with subjects under the age of 40 (58.4% vs 33.8%, P = 0.015). When specific components of lip pursing were analyzed, there was a significantly greater degree of stretch in the nasolabial fold region in subjects over 40 compared with those under 40 (61.6% vs 32.9%, P = 0.007). Furthermore, we observed a greater degree of asymmetry of strain in the nasolabial fold region in the older age group (18.4% vs 5.4%, P = 0.03). This pilot study illustrates that the face can be objectively and quantitatively evaluated using dynamic major strain analysis. The technology of 3-dimensional optical imaging can be used to advance our understanding of facial soft-tissue dynamics and the effects of animation on facial strain over time.

Nutrient availability and nutrient use efficiency in plants growing in the transition zone between land and water.

PubMed

Cavalli, G; Baattrup-Pedersen, A; Riis, T

2016-03-01

The transition zone between terrestrial and freshwater habitats is highly dynamic, with large variability in environmental characteristics. Here, we investigate how these characteristics influence the nutritional status and performance of plant life forms inhabiting this zone. Specifically, we hypothesised that: (i) tissue nutrient content differs among submerged, amphibious and terrestrial species, with higher content in submerged species; and (ii) PNUE gradually increases from submerged over amphibious to terrestrial species, reflecting differences in the availability of N and P relative to inorganic C across the land-water ecotone. We found that tissue nutrient content was generally higher in submerged species and C:N and C:P ratios indicated that content was limiting for growth for ca. 20% of plant individuals, particularly those belonging to amphibious and terrestrial species groups. As predicted, the PNUE increased from submerged over amphibious to terrestrial species. We suggest that this pattern reflects that amphibious and terrestrial species allocate proportionally more nutrients into processes of importance for photosynthesis at saturating CO2 availability, i.e. enzymes involved in substrate regeneration, compared to submerged species that are acclimated to lower availability of CO2 in the aquatic environment. Our results indicate that enhanced nutrient loading may affect relative abundance of the three species groups in the land-water ecotone of stream ecosystems. Thus, species of amphibious and terrestrial species groups are likely to benefit more from enhanced nutrient availability in terms of faster growth compared to aquatic species, and that this can be detrimental to aquatic species growing in the land-water ecotone, e.g. Ranunculus and Callitriche. © 2015 German Botanical Society and The Royal Botanical Society of the Netherlands.

Nutrient and phytoplankton analysis of a Mediterranean coastal area.

PubMed

Sebastiá, M T; Rodilla, M

2013-01-01

Identifying and quantifying the key anthropogenic nutrient input sources are essential to adopting management measures that can target input for maximum effect in controlling the phytoplankton biomass. In this study, three systems characterized by distinctive main nutrient sources were sampled along a Mediterranean coast transect. These sources were groundwater discharge in the Ahuir area, the Serpis river discharge in the Venecia area, and a submarine wastewater outfall 1,900 m from the coast. The study area includes factors considered important in determining a coastal area as a sensitive area: it has significant nutrient sources, tourism is a major source of income in the region, and it includes an area of high water residence time (Venecia area) which is affected by the harbor facilities and by wastewater discharges. We found that in the Ahuir and the submarine wastewater outfall areas, the effects of freshwater inputs were reduced because of a greater water exchange with the oligotrophic Mediterranean waters. On the other hand, in the Venecia area, the highest levels of nutrient concentration and phytoplankton biomass were attributed to the greatest water residence time. In this enclosed area, harmful dinoflagellates were detected (Alexandrium sp. and Dinophysis caudata). If the planned enlargement of the Gandia Harbor proceeds, it may increase the vulnerability of this system and provide the proper conditions of confinement for the dinoflagellate blooms' development. Management measures should first target phosphorus inputs as this is the most potential-limiting nutrient in the Venecia area and comes from a point source that is easier to control. Finally, we recommend that harbor environmental management plans include regular monitoring of water quality in adjacent waters to identify adverse phytoplankton community changes.

Seasonal regulation of herbivory and nutrient effects on macroalgal recruitment and succession in a Florida coral reef

PubMed Central

Collado-Vides, Ligia; Burkepile, Deron E.

2016-01-01

Herbivory and nutrient enrichment are drivers of benthic dynamics of coral reef macroalgae; however, their impact may vary seasonally. In this study we evaluated the effects of herbivore pressure, nutrient availability and potential propagule supply on seasonal recruitment and succession of macroalgal communities on a Florida coral reef. Recruitment tiles, replaced every three months, and succession tiles, kept in the field for nine months, were established in an ongoing factorial nutrient enrichment-herbivore exclusion experiment. The ongoing experiment had already created very different algal communities across the different herbivory and nutrient treatments. We tracked algal recruitment, species richness, and species abundance through time. Our results show seasonal variation in the effect of herbivory and nutrient availability on recruitment of coral reef macroalgae. In the spring, when there was higher macroalgal species richness and abundance of recruits, herbivory appeared to have more control on macroalgal community structure than did nutrients. In contrast, there was no effect of either herbivory or nutrient enrichment on macroalgal communities on recruitment tiles in cooler seasons. The abundance of recruits on tiles was positively correlated with the abundance of algal in the ongoing, established experiment, suggesting that propagule abundance is likely a strong influence on algal recruitment and early succession. Results of the present study suggest that abundant herbivorous fishes control recruitment and succession of macroalgae, particularly in the warm season when macroalgal growth is higher. However, herbivory appears less impactful on algal recruitment and community dynamics in cooler seasons. Ultimately, our data suggest that the timing of coral mortality (e.g., summer vs. winter mortality) and freeing of benthic space may strongly influence the dynamics of algae that colonize open space. PMID:27833810

Seasonal regulation of herbivory and nutrient effects on macroalgal recruitment and succession in a Florida coral reef.

PubMed

Duran, Alain; Collado-Vides, Ligia; Burkepile, Deron E

2016-01-01

Herbivory and nutrient enrichment are drivers of benthic dynamics of coral reef macroalgae; however, their impact may vary seasonally. In this study we evaluated the effects of herbivore pressure, nutrient availability and potential propagule supply on seasonal recruitment and succession of macroalgal communities on a Florida coral reef. Recruitment tiles, replaced every three months, and succession tiles, kept in the field for nine months, were established in an ongoing factorial nutrient enrichment-herbivore exclusion experiment. The ongoing experiment had already created very different algal communities across the different herbivory and nutrient treatments. We tracked algal recruitment, species richness, and species abundance through time. Our results show seasonal variation in the effect of herbivory and nutrient availability on recruitment of coral reef macroalgae. In the spring, when there was higher macroalgal species richness and abundance of recruits, herbivory appeared to have more control on macroalgal community structure than did nutrients. In contrast, there was no effect of either herbivory or nutrient enrichment on macroalgal communities on recruitment tiles in cooler seasons. The abundance of recruits on tiles was positively correlated with the abundance of algal in the ongoing, established experiment, suggesting that propagule abundance is likely a strong influence on algal recruitment and early succession. Results of the present study suggest that abundant herbivorous fishes control recruitment and succession of macroalgae, particularly in the warm season when macroalgal growth is higher. However, herbivory appears less impactful on algal recruitment and community dynamics in cooler seasons. Ultimately, our data suggest that the timing of coral mortality (e.g., summer vs. winter mortality) and freeing of benthic space may strongly influence the dynamics of algae that colonize open space.

Climate change impacts on the nutrient losses of two watersheds in the Great Lakes region

USDA-ARS?s Scientific Manuscript database

Non-point sources (NPS) of agricultural chemical pollution are one major reason for the degradation of water quality in the Great Lakes. This study focuses on quantifying the impacts of climate change on nutrient (Nitrogen and Phosphorus) losses from NPS in the Great Lakes region through the end of ...

Dynamics of reactive microbial hotspots in concentration gradients

NASA Astrophysics Data System (ADS)

Hubert, Antoine; Farasin, Julien; Tabuteau, Hervé; Méheust, Yves; Le Borgne, Tanguy

2017-04-01

In subsurface environments, bacteria play a major role in controlling the kinetics of a broad range of biogeochemical reactions. In such environments, nutrients fluxes and solute concentrations needed for bacteria metabolism may be highly variable in space and intermittent in time. This can lead to the formation of reactive hotspots where and when conditions are favorable to particular microorganisms, hence inducing biogeochemical reaction kinetics that differ significantly from those measured in homogeneous model environments. To investigate the impact of chemical gradients on the spatial structure and temporal dynamics of subsurface microorganism populations, we develop microfluidic cells allowing for a precise control of flow and chemical gradient conditions, as well as a quantitative monitoring of the bacteria's spatial distribution and biofilm development. Using the non-motile Escherichia coli JW1908-1 strain and Gallionella as model organisms, we investigate the behavior and development of bacteria over a range of single and double concentration gradients in the concentrations of nutrients, electron donors and electron acceptors. To quantify bacterial activity we use Fluorescein Diacetate (FDA) hydrolysis by bacterial enzymes which transforms FDA into Fluorescein, whose local concentration is measured optically. We thus measure bacterial activity locally from the time derivative of the measured fluorescence. This approach allows time-resolved monitoring of the location and intensity of reactive hotspots in micromodels as a function of the flow and chemical gradient conditions. We discuss consequences for the formation and temporal dynamics of biofilms in the subsurface.

RARE Grant- Atmospheric Dry Deposition: Quantification of Mercury and Nutrients using Novel Surrogate Surface Collector Techniques

EPA Science Inventory

This study will quantify the daily surrogate surface dry deposition of mercury and nutrient species, and evaluate its relative importance to wet deposition at two sites in Florida over a two-year period. It will identify the major sources contributing to the observed mercury and...

Oribatid mites and nutrient cycling. [Nutrient release by decomposition of leaf litter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crossley, D.A. Jr.

1976-08-01

Communities of oribatid mites (Cryptostigmata) in leaf litter and forest soils consist of an impressive number of individuals. Total populations of the order of 10/sup 5/ oribatids per square meter are commonly reported from forest floors. Because of their numbers, oribatids have been believed to be important contributors to the breakdown of organic detritus. Results are reported from studies of mineral or nutrient element cycling in forest floor ecosystems using radioisotopes as tracers. The phenomenon of cycling allows for the study of feedback loops among ecosystem processes, whereas energy flow is unidirectional. Evaluation of feedback loops can be a meansmore » of quantifying indirect effects of consumers. The availability of radioactive isotopes or radioactive analogs of mineral elements allows for the direct measurement of transfer rates. In decomposition studies applications of radioactive tracers have helped to identify pathways of transfer from microflora to oribatids.« less

A mechanistic soil biogeochemistry model with explicit representation of microbial and macrofaunal activities and nutrient cycles

NASA Astrophysics Data System (ADS)

Fatichi, Simone; Manzoni, Stefano; Or, Dani; Paschalis, Athanasios

2016-04-01

The potential of a given ecosystem to store and release carbon is inherently linked to soil biogeochemical processes. These processes are deeply connected to the water, energy, and vegetation dynamics above and belowground. Recently, it has been advocated that a mechanistic representation of soil biogeochemistry require: (i) partitioning of soil organic carbon (SOC) pools according to their functional role; (ii) an explicit representation of microbial dynamics; (iii) coupling of carbon and nutrient cycles. While some of these components have been introduced in specialized models, they have been rarely implemented in terrestrial biosphere models and tested in real cases. In this study, we combine a new soil biogeochemistry model with an existing model of land-surface hydrology and vegetation dynamics (T&C). Specifically the soil biogeochemistry component explicitly separates different litter pools and distinguishes SOC in particulate, dissolved and mineral associated fractions. Extracellular enzymes and microbial pools are explicitly represented differentiating the functional roles of bacteria, saprotrophic and mycorrhizal fungi. Microbial activity depends on temperature, soil moisture and litter or SOC stoichiometry. The activity of macrofauna is also modeled. Nutrient dynamics include the cycles of nitrogen, phosphorous and potassium. The model accounts for feedbacks between nutrient limitations and plant growth as well as for plant stoichiometric flexibility. In turn, litter input is a function of the simulated vegetation dynamics. Root exudation and export to mycorrhiza are computed based on a nutrient uptake cost function. The combined model is tested to reproduce respiration dynamics and nitrogen cycle in few sites where data were available to test plausibility of results across a range of different metrics. For instance in a Swiss grassland ecosystem, fine root, bacteria, fungal and macrofaunal respiration account for 40%, 23%, 33% and 4% of total belowground

Practical technique to quantify small, dense low-density lipoprotein cholesterol using dynamic light scattering

NASA Astrophysics Data System (ADS)

Trirongjitmoah, Suchin; Iinaga, Kazuya; Sakurai, Toshihiro; Chiba, Hitoshi; Sriyudthsak, Mana; Shimizu, Koichi

2016-04-01

Quantification of small, dense low-density lipoprotein (sdLDL) cholesterol is clinically significant. We propose a practical technique to estimate the amount of sdLDL cholesterol using dynamic light scattering (DLS). An analytical solution in a closed form has newly been obtained to estimate the weight fraction of one species of scatterers in the DLS measurement of two species of scatterers. Using this solution, we can quantify the sdLDL cholesterol amount from the amounts of the low-density lipoprotein cholesterol and the high-density lipoprotein (HDL) cholesterol, which are commonly obtained through clinical tests. The accuracy of the proposed technique was confirmed experimentally using latex spheres with known size distributions. The applicability of the proposed technique was examined using samples of human blood serum. The possibility of estimating the sdLDL amount using the HDL data was demonstrated. These results suggest that the quantitative estimation of sdLDL amounts using DLS is feasible for point-of-care testing in clinical practice.

Quantifying Proportional Variability

PubMed Central

Heath, Joel P.; Borowski, Peter

2013-01-01

Real quantities can undergo such a wide variety of dynamics that the mean is often a meaningless reference point for measuring variability. Despite their widespread application, techniques like the Coefficient of Variation are not truly proportional and exhibit pathological properties. The non-parametric measure Proportional Variability (PV) [1] resolves these issues and provides a robust way to summarize and compare variation in quantities exhibiting diverse dynamical behaviour. Instead of being based on deviation from an average value, variation is simply quantified by comparing the numbers to each other, requiring no assumptions about central tendency or underlying statistical distributions. While PV has been introduced before and has already been applied in various contexts to population dynamics, here we present a deeper analysis of this new measure, derive analytical expressions for the PV of several general distributions and present new comparisons with the Coefficient of Variation, demonstrating cases in which PV is the more favorable measure. We show that PV provides an easily interpretable approach for measuring and comparing variation that can be generally applied throughout the sciences, from contexts ranging from stock market stability to climate variation. PMID:24386334

Sediment type and benthic fauna control the nutrient release in a coastal bay

NASA Astrophysics Data System (ADS)

Voss, Maren; Thoms, Franziska; Dippner, Joachim; Bartl, Ines; Janas, Urzula; Hellemann, Dana; Hietanen, Susanna; Kendzierska, Halina

2017-04-01

Eutrophication of coastal seas is still a major problem that may even increase in the near future according to recent model studies. The catchment of the Baltic Sea with nine highly industrialized riparian countries is intensively used and only few major rivers are responsible for more than half of the riverine nutrient input to the coastal zones. It is hypothesized that these nutrient are the main drivers for large anoxic bottom waters in the central Baltic Sea and an increasing hypoxia problem in coastal waters. The sequestration of nutrients was therefore intensively studied in the Baltic Sea, however either in the water column or in the sediments. The role of the benthic pelagic coupling for the nutrient turnover was much less investigated especially due to technical challenges. We therefore used a lander system to quantify the nutrient release from sediments in a river impacted coastal Bay of Gdansk in the framework of the BONUS-COCOA project. Lander deployments and sediment coring were done simultaneously to measure nutrient fluxes over time and to characterize grain size, permeability, organic matter content, and benthic fauna. The benthic communities were analyzed to identify potential linkages between nutrient release and the species composition. Our study revealed close linkages between types/grain-size of sediment and the nutrient release. The activity of the animals in the sediment seems responsible for significant release of nutrients which is more pronounced than the diffusive nutrient release back to the water column. Rates from nineteen stations were used to draw a conclusive picture of the overall nutrient release from sediments and were set into a framework of a nutrient budget for the Bay of Gdansk considering the role of fauna. Moreover, we are able to identify a depth of roughly 50m as a border that separates the dominance of benthic recycling from deeper stations where mainly deposition or organic material takes place. Changes in properties of

Drug-nutrient interactions.

PubMed

Chan, Lingtak-Neander

2013-07-01

Drug-nutrient interactions are defined as physical, chemical, physiologic, or pathophysiologic relationships between a drug and a nutrient. The causes of most clinically significant drug-nutrient interactions are usually multifactorial. Failure to identify and properly manage drug-nutrient interactions can lead to very serious consequences and have a negative impact on patient outcomes. Nevertheless, with thorough review and assessment of the patient's history and treatment regimens and a carefully executed management strategy, adverse events associated with drug-nutrient interactions can be prevented. Based on the physiologic sequence of events after a drug or a nutrient has entered the body and the mechanism of interactions, drug-nutrient interactions can be categorized into 4 main types. Each type of interaction can be managed using similar strategies. The existing data that guide the clinical management of most drug-nutrient interactions are mostly anecdotal experience, uncontrolled observations, and opinions, whereas the science in understanding the mechanism of drug-nutrient interactions remains limited. The challenge for researchers and clinicians is to increase both basic and higher level clinical research in this field to bridge the gap between the science and practice. The research should aim to establish a better understanding of the function, regulation, and substrate specificity of the nutrient-related enzymes and transport proteins present in the gastrointestinal tract, as well as assess how the incidence and management of drug-nutrient interactions can be affected by sex, ethnicity, environmental factors, and genetic polymorphisms. This knowledge can help us develop a true personalized medicine approach in the prevention and management of drug-nutrient interactions.

Cool tadpoles from Arctic environments waste fewer nutrients - high gross growth efficiencies lead to low consumer-mediated nutrient recycling in the North.

PubMed

Liess, Antonia; Guo, Junwen; Lind, Martin I; Rowe, Owen

2015-11-01

Endothermic organisms can adapt to short growing seasons, low temperatures and nutrient limitation by developing high growth rates and high gross growth efficiencies (GGEs). Animals with high GGEs are better at assimilating limiting nutrients and thus should recycle (or lose) fewer nutrients. Longer guts in relation to body mass may facilitate higher GGE under resource limitation. Within the context of ecological stoichiometry theory, this study combines ecology with evolution by relating latitudinal life-history adaptations in GGE, mediated by gut length, to its ecosystem consequences, such as consumer-mediated nutrient recycling. In common garden experiments, we raised Rana temporaria tadpoles from two regions (Arctic/Boreal) under two temperature regimes (18/23 °C) crossed with two food quality treatments (high/low-nitrogen content). We measured tadpole GGEs, total nutrient loss (excretion + egestion) rates and gut length during ontogeny. In order to maintain their elemental balance, tadpoles fed low-nitrogen (N) food had lower N excretion rates and higher total phosphorous (P) loss rates than tadpoles fed high-quality food. In accordance with expectations, Arctic tadpoles had higher GGEs and lower N loss rates than their low-latitude conspecifics, especially when fed low-N food, but only in ambient temperature treatments. Arctic tadpoles also had relatively longer guts than Boreal tadpoles during early development. That temperature and food quality interacted with tadpole region of origin in affecting tadpole GGEs, nutrient loss rates and relative gut length, suggests evolved adaptation to temperature and resource differences. With future climate change, mean annual temperatures will increase. Additionally, species and genotypes will migrate north. This will change the functioning of Boreal and Arctic ecosystems by affecting consumer-mediated nutrient recycling and thus affect nutrient dynamics in general. Our study shows that evolved latitudinal adaption can

Including spatial data in nutrient balance modelling on dairy farms

NASA Astrophysics Data System (ADS)

van Leeuwen, Maricke; van Middelaar, Corina; Stoof, Cathelijne; Oenema, Jouke; Stoorvogel, Jetse; de Boer, Imke

2017-04-01

at Dutch dairy farms. We selected two dairy farms located on cover sands in the Netherlands. One farm was located on relatively homogeneous soil type, and one on many different soil types within the sandy soils. A full year of data of N and P inputs and outputs on farm and field level were provided by the farmers, including field level yields, yield composition, manure composition, degree of grazing and degree of mowing. Soil heterogeneity was defined as the number of soil units within the farm corrected for surface area, and quantified from the Dutch 1:50.000 soil map. N and P balances at farm and field level were determined, as well as differences in nutrient use efficiency, leaching, and N emission. We will present the effect of the spatial scale on nutrient balance analysis and discuss to which degree any differences are caused by within-farm land management and soil variation. This study highlights to which extent within-farm land management and soil variation should be taken into account when modelling nutrient flows and nutrient use efficiencies at farm level, to contribute to field-based decision making for improved land management.

Dynamics of barite growth in porous media quantified by in situ synchrotron X-ray tomography

NASA Astrophysics Data System (ADS)

Godinho, jose; Gerke, kirill

2016-04-01

Current models used to formulate mineral sequestration strategies of dissolved contaminants in the bedrock often neglect the effect of confinement and the variation of reactive surface area with time. In this work, in situ synchrotron X-ray micro-tomography is used to quantify barite growth rates in a micro-porous structure as a function of time during 13.5 hours with a resolution of 1 μm. Additionally, the 3D porous network at different time frames are used to simulate the flow velocities and calculate the permeability evolution during the experiment. The kinetics of barite growth under porous confinement is compared with the kinetics of barite growth on free surfaces in the same fluid composition. Results are discussed in terms of surface area normalization and the evolution of flow velocities as crystals fill the porous structure. During the initial hours the growth rate measured in porous media is similar to the growth rate on free surfaces. However, as the thinner flow paths clog the growth rate progressively decreases, which is correlated to a decrease of local flow velocity. The largest pores remain open, enabling growth to continue throughout the structure. Quantifying the dynamics of mineral precipitation kinetics in situ in 4D, has revealed the importance of using a time dependent reactive surface area and accounting for the local properties of the porous network, when formulating predictive models of mineral precipitation in porous media.

Classifying and quantifying basins of attraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sprott, J. C.; Xiong, Anda

2015-08-15

A scheme is proposed to classify the basins for attractors of dynamical systems in arbitrary dimensions. There are four basic classes depending on their size and extent, and each class can be further quantified to facilitate comparisons. The calculation uses a Monte Carlo method and is applied to numerous common dissipative chaotic maps and flows in various dimensions.

Using atmospheric fallout to date organic horizon layers and quantify metal dynamics during decomposition

NASA Astrophysics Data System (ADS)

Kaste, James M.; Bostick, Benjamin C.; Heimsath, Arjun M.; Steinnes, Eiliv; Friedland, Andrew J.

2011-03-01

High concentrations of metals in organic matter can inhibit decomposition and limit nutrient availability in ecosystems, but the long-term fate of metals bound to forest litter is poorly understood. Controlled experiments indicate that during the first few years of litter decay, Al, Fe, Pb, and other metals that form stable complexes with organic matter are naturally enriched by several hundred percent as carbon is oxidized. The transformation of fresh litter to humus takes decades, however, such that current datasets describing the accumulation and release of metals in decomposing organic matter are timescale limited. Here we use atmospheric 210Pb to quantify the fate of metals in canopy-derived litter during burial and decay in coniferous forests in New England and Norway where decomposition rates are slow and physical soil mixing is minimal. We measure 210Pb inventories in the O horizon and mineral soil and calculate a 60-630 year timescale for the production of mobile organo-metallic colloids from the decomposition of fresh forest detritus. This production rate is slowest at our highest elevation (˜1000 m) and highest latitude sites (>63°N) where decomposition rates are expected to be low. We calculate soil layer ages by assuming a constant supply of atmospheric 210Pb and find that they are consistent with the distribution of geochemical tracers from weapons fallout, air pollution, and a direct 207Pb application at one site. By quantifying a gradient of organic matter ages with depth in the O horizon, we describe the accumulation and loss of metals in the soil profile as organic matter transforms from fresh litter to humus. While decomposition experiments predict that Al and Fe concentrations increase during the initial few years of decay, we show here that these metals continue to accumulate in humus for decades, and that enrichment occurs at a rate higher than can be explained by quantitative retention during decomposition alone. Acid extractable Al and Fe

Oxygen Consumption Rates of Bacteria under Nutrient-Limited Conditions

PubMed Central

Riedel, Timothy E.; Nealson, Kenneth H.; Finkel, Steven E.

2013-01-01

Many environments on Earth experience nutrient limitation and as a result have nongrowing or very slowly growing bacterial populations. To better understand bacterial respiration under environmentally relevant conditions, the effect of nutrient limitation on respiration rates of heterotrophic bacteria was measured. The oxygen consumption and population density of batch cultures of Escherichia coli K-12, Shewanella oneidensis MR-1, and Marinobacter aquaeolei VT8 were tracked for up to 200 days. The oxygen consumption per CFU (QO2) declined by more than 2 orders of magnitude for all three strains as they transitioned from nutrient-abundant log-phase growth to the nutrient-limited early stationary phase. The large reduction in QO2 from growth to stationary phase suggests that nutrient availability is an important factor in considering environmental respiration rates. Following the death phase, during the long-term stationary phase (LTSP), QO2 values of the surviving population increased with time and more cells were respiring than formed colonies. Within the respiring population, a subpopulation of highly respiring cells increased in abundance with time. Apparently, as cells enter LTSP, there is a viable but not culturable population whose bulk community and per cell respiration rates are dynamic. This result has a bearing on how minimal energy requirements are met, especially in nutrient-limited environments. The minimal QO2 rates support the extension of Kleiber's law to the mass of a bacterium (100-fg range). PMID:23770901

Quantifying the aging response and nutrient composition for muscles of the beef round.

PubMed

Dixon, C L; Woerner, D R; Tokach, R J; Chapman, P L; Engle, T E; Tatum, J D; Belk, K E

2012-03-01

The objective of this study was to determine the optimal postmortem aging period and nutrient composition for Beef Value Cuts of the round. Forty USDA Select and 40 Premium USDA Choice beef carcasses were selected from a commercial beef packing plant in Colorado over a 12-wk period. The bottom and inside rounds were collected from both sides of each carcass for further fabrication into the following muscles: adductor, gastrocnemius, gracilis, pectineus, and superficial digital flexor. Each pair of muscles was cut into 7 steaks and randomly assigned to 1 of the following aging periods: 2, 4, 6, 10, 14, 21, and 28 d, and placed in refrigerated storage (2°C, never frozen). Upon completion of the designated aging period, steaks were removed from storage, cooked to a peak internal temperature of 72°C, and evaluated using Warner-Bratzler shear force (WBSF). A 2-way interaction was detected (P < 0.05) between individual muscle and postmortem aging period. The WBSF of all muscles except the superficial digital flexor decreased with increased time of postmortem aging. Quality grade did not affect (P > 0.05) WBSF values for the adductor, gastrocnemius, pectineus, and superficial digital flexor muscles. Exponential decay models were used to predict the change in WBSF from 2 to 28 d postmortem (aging response). The adductor, gastrocnemius, Select gracilis, Premium Choice gracilis, and pectineus required 21, 14, 23, 23, and 25 d, respectively, to complete the majority of the aging response. To determine the nutrient composition of the adductor, gastrocnemius, gracilis, pectineus, semimembranosus, and superficial digital flexor, bottom and inside rounds were collected from 10 USDA Select and 10 Premium USDA Choice carcasses and fabricated into the respective muscles, cut into 2.54-cm cubes, frozen (-20°C), and then homogenized. The adductor, gracilis, pectineus, semimembranosus, and superficial digital flexor were analyzed for DM, moisture, CP, and ash percentages. All

Distributions of Competing Container Mosquitoes Depend on Detritus Types, Nutrient Ratios, and Food Availability

PubMed Central

Murrell, Ebony G.; Damal, Kavitha; Lounibos, L. P.; Juliano, Steven A.

2012-01-01

Coexistence of competitors may result if resources are sufficiently abundant to render competition unimportant, or if species differ in resource requirements. Detritus type has been shown to affect interspecific competitive outcomes between Aedes albopictus (Skuse) and Aedes aegypti (L.) larvae under controlled conditions. We assessed the relationships among spatial distributions of detritus types, nutrients, and aquatic larvae of these species in nature. We collected mosquitoes, water, and detritus from artificial containers across 24 Florida cemeteries that varied in relative abundances of Ae. aegypti and Ae. albopictus.We measured nutrient content of fine particulate organic matter in water samples as total N, P, and C and ratios of these nutrients. We quantified food availability via a bioassay, raising individual Aedes larvae in the laboratory in standard volumes of field-collected, particulate-containing water from each cemetery. Quantities of detritus types collected in standard containers were significant predictors of nutrients and nutrient ratios. Nutrient abundances were significant predictors of relative abundance of Ae. aegypti, and of larval survival and development by both species in the bioassay. Survival and development of larvae reared in particulate-containing water from sites decreased with decreasing relative abundance of Ae. aegypti. These data suggest that N, P, and C availabilities are determined by detritus inputs to containers and that these nutrients in turn determine the feeding environment encountered by larvae, the intensity of interspecific competition among larvae, and subsequent relative abundances of species at sites. Detritus inputs, nutrients, and food availability thus seem to contribute to distributions of Ae. aegypti and Ae. albopictus in cemetery containers throughout Florida. PMID:22707761

Ecosystem Modeling Applied to Nutrient Criteria Development in Rivers

NASA Astrophysics Data System (ADS)

Carleton, James N.; Park, Richard A.; Clough, Jonathan S.

2009-09-01

Threshold concentrations for biological impairment by nutrients are difficult to quantify in lotic systems, yet States and Tribes in the United States are charged with developing water quality criteria to protect these ecosystems from excessive enrichment. The analysis described in this article explores the use of the ecosystem model AQUATOX to investigate impairment thresholds keyed to biological indexes that can be simulated. The indexes selected for this exercise include percentage cyanobacterial biomass of sestonic algae, and benthic chlorophyll a. The calibrated model was used to analyze responses of these indexes to concurrent reductions in phosphorus, nitrogen, and suspended sediment in an enriched upper Midwestern river. Results suggest that the indexes would respond strongly to changes in phosphorus and suspended sediment, and less strongly to changes in nitrogen concentration. Using simulated concurrent reductions in all three water quality constituents, a total phosphorus concentration of 0.1 mg/l was identified as a threshold concentration, and therefore a hypothetical water quality criterion, for prevention of both excessive periphyton growth and sestonic cyanobacterial blooms. This kind of analysis is suggested as a way to evaluate multiple contrasting impacts of hypothetical nutrient and sediment reductions and to define nutrient criteria or target concentrations that balance multiple management objectives concurrently.

Biomass and nutrients of Pinus massoniana plantations in southern China: simulations for different management practices.

Treesearch

Huixia Yang; Silong Wang; Jianwei Zhang; Bing Fan; Weidong Zhang

2011-01-01

We measured the dynamics of both biomass and nutrient pools on 7-, 17-, 31- and 51-year-old Pinus massoniana plantations in southern China. Using a chronosequence approach, we found that biomass of each component increased with aging while its proportion decreased except stem-wood. Nutrient pools varied with biomass pools except for foliage. For all harvest intensities...

Quantified Facial Soft-tissue Strain in Animation Measured by Real-time Dynamic 3-Dimensional Imaging

PubMed Central

Hsu, Vivian M.; Wes, Ari M.; Tahiri, Youssef; Cornman-Homonoff, Joshua

2014-01-01

Background: The aim of this study is to evaluate and quantify dynamic soft-tissue strain in the human face using real-time 3-dimensional imaging technology. Methods: Thirteen subjects (8 women, 5 men) between the ages of 18 and 70 were imaged using a dual-camera system and 3-dimensional optical analysis (ARAMIS, Trilion Quality Systems, Pa.). Each subject was imaged at rest and with the following facial expressions: (1) smile, (2) laughter, (3) surprise, (4) anger, (5) grimace, and (6) pursed lips. The facial strains defining stretch and compression were computed for each subject and compared. Results: The areas of greatest strain were localized to the midface and lower face for all expressions. Subjects over the age of 40 had a statistically significant increase in stretch in the perioral region while lip pursing compared with subjects under the age of 40 (58.4% vs 33.8%, P = 0.015). When specific components of lip pursing were analyzed, there was a significantly greater degree of stretch in the nasolabial fold region in subjects over 40 compared with those under 40 (61.6% vs 32.9%, P = 0.007). Furthermore, we observed a greater degree of asymmetry of strain in the nasolabial fold region in the older age group (18.4% vs 5.4%, P = 0.03). Conclusions: This pilot study illustrates that the face can be objectively and quantitatively evaluated using dynamic major strain analysis. The technology of 3-dimensional optical imaging can be used to advance our understanding of facial soft-tissue dynamics and the effects of animation on facial strain over time. PMID:25426394

Drug-nutrient interactions.

PubMed

Trovato, A; Nuhlicek, D N; Midtling, J E

1991-11-01

Drug-nutrient interactions are a commonly overlooked aspect of the prescribing practices of physicians. As more pharmaceutical agents become available, attention should be focused on interactions of drugs with foods and nutrients. Although drug-nutrient interactions are not as common as drug-drug interactions, they can have an impact on therapeutic outcome. Drugs can affect nutritional status by altering nutrient absorption, metabolism, utilization or excretion. Food, beverages and mineral or vitamin supplements can affect the absorption and effectiveness of drugs. Knowledge of drug-nutrient interactions can help reduce the incidence of these effects. Physicians should question patients about their dietary habits so that patients can be informed about possible interactions between a prescribed drug and foods and nutrients.

Nutrient Presses and Pulses Differentially Impact Plants, Herbivores, Detritivores and Their Natural Enemies

PubMed Central

Murphy, Shannon M.; Wimp, Gina M.; Lewis, Danny

2012-01-01

Anthropogenic nutrient inputs into native ecosystems cause fluctuations in resources that normally limit plant growth, which has important consequences for associated food webs. Such inputs from agricultural and urban habitats into nearby natural systems are increasing globally and can be highly variable, spanning the range from sporadic to continuous. Despite the global increase in anthropogenically-derived nutrient inputs into native ecosystems, the consequences of variation in subsidy duration on native plants and their associated food webs are poorly known. Specifically, while some studies have examined the effects of nutrient subsidies on native ecosystems for a single year (a nutrient pulse), repeated introductions of nutrients across multiple years (a nutrient press) better reflect the persistent nature of anthropogenic nutrient enrichment. We therefore contrasted the effects of a one-year nutrient pulse with a four-year nutrient press on arthropod consumers in two salt marshes. Salt marshes represent an ideal system to address the differential impacts of nutrient pulses and presses on ecosystem and community dynamics because human development and other anthropogenic activities lead to recurrent introductions of nutrients into these natural systems. We found that plant biomass and %N as well as arthropod density fell after the nutrient pulse ended but remained elevated throughout the nutrient press. Notably, higher trophic levels responded more strongly than lower trophic levels to fertilization, and the predator/prey ratio increased each year of the nutrient press, demonstrating that food web responses to anthropogenic nutrient enrichment can take years to fully manifest themselves. Vegetation at the two marshes also exhibited an apparent tradeoff between increasing %N and biomass in response to fertilization. Our research emphasizes the need for long-term, spatially diverse studies of nutrient enrichment in order to understand how variation in the duration

A framework to assess biogeochemical response to ecosystem disturbance using nutrient partitioning ratios

USGS Publications Warehouse

Kranabetter, J. Marty; McLauchlan, Kendra K.; Enders, Sara K.; Fraterrigo, Jennifer M.; Higuera, Philip E.; Morris, Jesse L.; Rastetter, Edward B.; Barnes, Rebecca; Buma, Brian; Gavin, Daniel G.; Gerhart, Laci M.; Gillson, Lindsey; Hietz, Peter; Mack, Michelle C.; McNeil, Brenden; Perakis, Steven

2016-01-01

Disturbances affect almost all terrestrial ecosystems, but it has been difficult to identify general principles regarding these influences. To improve our understanding of the long-term consequences of disturbance on terrestrial ecosystems, we present a conceptual framework that analyzes disturbances by their biogeochemical impacts. We posit that the ratio of soil and plant nutrient stocks in mature ecosystems represents a characteristic site property. Focusing on nitrogen (N), we hypothesize that this partitioning ratio (soil N: plant N) will undergo a predictable trajectory after disturbance. We investigate the nature of this partitioning ratio with three approaches: (1) nutrient stock data from forested ecosystems in North America, (2) a process-based ecosystem model, and (3) conceptual shifts in site nutrient availability with altered disturbance frequency. Partitioning ratios could be applied to a variety of ecosystems and successional states, allowing for improved temporal scaling of disturbance events. The generally short-term empirical evidence for recovery trajectories of nutrient stocks and partitioning ratios suggests two areas for future research. First, we need to recognize and quantify how disturbance effects can be accreting or depleting, depending on whether their net effect is to increase or decrease ecosystem nutrient stocks. Second, we need to test how altered disturbance frequencies from the present state may be constructive or destructive in their effects on biogeochemical cycling and nutrient availability. Long-term studies, with repeated sampling of soils and vegetation, will be essential in further developing this framework of biogeochemical response to disturbance.

Mechanistic modeling of thermo-hydrological processes and microbial interactions at pore to profile scales resolve methane emission dynamics from permafrost soil

NASA Astrophysics Data System (ADS)

Ebrahimi, Ali; Or, Dani

2017-04-01

The sensitivity of the Earth's polar regions to raising global temperatures is reflected in rapidly changing hydrological processes with pronounced seasonal thawing of permafrost soil and increased biological activity. Of particular concern is the potential release of large amounts of soil carbon and the stimulation of other soil-borne GHG emissions such as methane. Soil methanotrophic and methanogenic microbial communities rapidly adjust their activity and spatial organization in response to permafrost thawing and a host of other environmental factors. Soil structural elements such as aggregates and layering and hydration status affect oxygen and nutrient diffusion processes thereby contributing to methanogenic activity within temporal anoxic niches (hotspots or hot-layers). We developed a mechanistic individual based model to quantify microbial activity dynamics within soil pore networks considering, hydration, temperature, transport processes and enzymatic activity associated with methane production in soil. The model was the upscaled from single aggregates (or hotspots) to quantifying emissions from soil profiles in which freezing/thawing processes provide macroscopic boundary conditions for microbial activity at different soil depths. The model distinguishes microbial activity in aerate bulk soil from aggregates (or submerged parts of the profile) for resolving methane production and oxidation rates. Methane transport pathways through soil by diffusion and ebullition of bubbles vary with hydration dynamics and affect emission patterns. The model links seasonal thermal and hydrologic dynamics with evolution of microbial community composition and function affecting net methane emissions in good agreement with experimental data. The mechanistic model enables systematic evaluation of key controlling factors in thawing permafrost and microbial response (e.g., nutrient availability, enzyme activity, PH) on long term methane emissions and carbon decomposition rates

Ecology of duckweed ponds used for nutrient recovery from wastewater.

PubMed

Teles, C C; Mohedano, R A; Tonon, G; Filho, P Belli; Costa, R H R

2017-06-01

The microorganism community that grows under duckweed shelter can play an important role on treatment processes. Therefore, the present study aimed to assess the zooplankton dynamic and microbial community in duckweed ponds (DPs) applied for domestic wastewater treatment under open field conditions. A pilot system comprised of two DPs in series (DP1 and DP2), with 10 m 2 each, received domestic wastewater through a flow rate of 200 L·day -1 . Thus, the system was monitored during 314 days through samples collected and analysed weekly. Also, the zooplankton organisms were identified and quantified. DNA sequencing was performed in order to identify the bacterial populations. The findings showed a high efficiency of nutrient removal with 93% and 91% of total phosphorus and total nitrogen, respectively. A high density of microcrustaceans was observed in DP1 reaching 4,700 org.100 mL -1 and rotifers (over than 32,000 org.100 mL -1 ) in DP2, that could be related to the low suspended solids concentration (<30 mg·L -1 ) and turbidity (<10 NTU). The bacterial community showed a strong heterogeneity between samples collected along the seasons. Through these findings, it is possible to realise that the understanding of ecology could help to enhance the operation and designs of DPs.

Passive flux meter measurement of water and nutrient flux in saturated porous media: bench-scale laboratory tests.

PubMed

Cho, Jaehyun; Annable, Michael D; Jawitz, James W; Hatfield, Kirk

2007-01-01

The passive nutrient flux meter (PNFM) is introduced for simultaneous measurement of both water and nutrient flux through saturated porous media. The PNFM comprises a porous sorbent pre-equilibrated with a suite of alcohol tracers, which have different partitioning coefficients. Water flux was estimated based on the loss of loaded resident tracers during deployment, while nutrient flux was quantified based on the nutrient solute mass captured on the sorbent. An anionic resin, Lewatit 6328 A, was used as a permeable sorbent and phosphate (PO4(3-)) was the nutrient studied. The phosphate sorption capacity of the resin was measured in batch equilibration tests as 56 mg PO4(3-) g(-1), which was determined to be adequate capacity to retain PO4(3-) loads intercepted over typical PNFM deployment periods in most natural systems. The PNFM design was validated with bench-scale laboratory tests for a range of 9.8 to 28.3 cm d(-1) Darcy velocities and 6 to 43 h deployment durations. Nutrient and water fluxes measured by the PNFM averaged within 6 and 12% of the applied values, respectively, indicating that the PNFM shows promise as a tool for simultaneous measurement of water and nutrient fluxes.

Effects of Lipid Composition on Bilayer Membranes Quantified by All-Atom Molecular Dynamics.

PubMed

Ding, Wei; Palaiokostas, Michail; Wang, Wen; Orsi, Mario

2015-12-10

Biological bilayer membranes typically contain varying amounts of lamellar and nonlamellar lipids. Lamellar lipids, such as dioleoylphosphatidylcholine (DOPC), are defined by their tendency to form the lamellar phase, ubiquitous in biology. Nonlamellar lipids, such as dioleoylphosphatidylethanolamine (DOPE), prefer instead to form nonlamellar phases, which are mostly nonbiological. However, nonlamellar lipids mix with lamellar lipids in biomembrane structures that remain overall lamellar. Importantly, changes in the lamellar vs nonlamellar lipid composition are believed to affect membrane function and modulate membrane proteins. In this work, we employ atomistic molecular dynamics simulations to quantify how a range of bilayer properties are altered by variations in the lamellar vs nonlamellar lipid composition. Specifically, we simulate five DOPC/DOPE bilayers at mixing ratios of 1/0, 3/1, 1/1, 1/3, and 0/1. We examine properties including lipid area and bilayer thickness, as well as the transmembrane profiles of electron density, lateral pressure, electric field, and dipole potential. While the bilayer structure is only marginally altered by lipid composition changes, dramatic effects are observed for the lateral pressure, electric field, and dipole potential profiles. Possible implications for membrane function are discussed.

Simulating Food Web Dynamics along a Gradient: Quantifying Human Influence

PubMed Central

Jordán, Ferenc; Gjata, Nerta; Mei, Shu; Yule, Catherine M.

2012-01-01

Realistically parameterized and dynamically simulated food-webs are useful tool to explore the importance of the functional diversity of ecosystems, and in particular relations between the dynamics of species and the whole community. We present a stochastic dynamical food web simulation for the Kelian River (Borneo). The food web was constructed for six different locations, arrayed along a gradient of increasing human perturbation (mostly resulting from gold mining activities) along the river. Along the river, the relative importance of grazers, filterers and shredders decreases with increasing disturbance downstream, while predators become more dominant in governing eco-dynamics. Human activity led to increased turbidity and sedimentation which adversely impacts primary productivity. Since the main difference between the study sites was not the composition of the food webs (structure is quite similar) but the strengths of interactions and the abundance of the trophic groups, a dynamical simulation approach seemed to be useful to better explain human influence. In the pristine river (study site 1), when comparing a structural version of our model with the dynamical model we found that structurally central groups such as omnivores and carnivores were not the most important ones dynamically. Instead, primary consumers such as invertebrate grazers and shredders generated a greater dynamical response. Based on the dynamically most important groups, bottom-up control is replaced by the predominant top-down control regime as distance downstream and human disturbance increased. An important finding, potentially explaining the poor structure to dynamics relationship, is that indirect effects are at least as important as direct ones during the simulations. We suggest that our approach and this simulation framework could serve systems-based conservation efforts. Quantitative indicators on the relative importance of trophic groups and the mechanistic modeling of eco-dynamics

Recipient-Biased Competition for an Intracellularly Generated Cross-Fed Nutrient Is Required for Coexistence of Microbial Mutualists.

PubMed

McCully, Alexandra L; LaSarre, Breah; McKinlay, James B

2017-11-28

Many mutualistic microbial relationships are based on nutrient cross-feeding. Traditionally, cross-feeding is viewed as being unidirectional, from the producer to the recipient. This is likely true when a producer's waste, such as a fermentation product, has value only for a recipient. However, in some cases the cross-fed nutrient holds value for both the producer and the recipient. In such cases, there is potential for nutrient reacquisition by producer cells in a population, leading to competition against recipients. Here, we investigated the consequences of interpartner competition for cross-fed nutrients on mutualism dynamics by using an anaerobic coculture pairing fermentative Escherichia coli and phototrophic Rhodopseudomonas palustris In this coculture, E. coli excretes waste organic acids that provide a carbon source for R. palustris In return, R. palustris cross-feeds E. coli ammonium (NH 4 + ), a compound that both species value. To explore the potential for interpartner competition, we first used a kinetic model to simulate cocultures with varied affinities for NH 4 + in each species. The model predicted that interpartner competition for NH 4 + could profoundly impact population dynamics. We then experimentally tested the predictions by culturing mutants lacking NH 4 + transporters in both NH 4 + competition assays and mutualistic cocultures. Both theoretical and experimental results indicated that the recipient must have a competitive advantage in acquiring cross-fed NH 4 + to sustain the mutualism. This recipient-biased competitive advantage is predicted to be crucial, particularly when the communally valuable nutrient is generated intracellularly. Thus, the very metabolites that form the basis for mutualistic cross-feeding can also be subject to competition between mutualistic partners. IMPORTANCE Mutualistic relationships, particularly those based on nutrient cross-feeding, promote stability of diverse ecosystems and drive global biogeochemical

Recipient-Biased Competition for an Intracellularly Generated Cross-Fed Nutrient Is Required for Coexistence of Microbial Mutualists

DOE PAGES

McCully, Alexandra L.; LaSarre, Breah; McKinlay, James B.; ...

2017-11-28

ABSTRACT Many mutualistic microbial relationships are based on nutrient cross-feeding. Traditionally, cross-feeding is viewed as being unidirectional, from the producer to the recipient. This is likely true when a producer’s waste, such as a fermentation product, has value only for a recipient. However, in some cases the cross-fed nutrient holds value for both the producer and the recipient. In such cases, there is potential for nutrient reacquisition by producer cells in a population, leading to competition against recipients. Here, we investigated the consequences of interpartner competition for cross-fed nutrients on mutualism dynamics by using an anaerobic coculture pairing fermentative Escherichiamore » coli and phototrophic Rhodopseudomonas palustris . In this coculture, E. coli excretes waste organic acids that provide a carbon source for R. palustris . In return, R. palustris cross-feeds E. coli ammonium (NH 4 + ), a compound that both species value. To explore the potential for interpartner competition, we first used a kinetic model to simulate cocultures with varied affinities for NH 4 + in each species. The model predicted that interpartner competition for NH 4 + could profoundly impact population dynamics. We then experimentally tested the predictions by culturing mutants lacking NH 4 + transporters in both NH 4 + competition assays and mutualistic cocultures. Both theoretical and experimental results indicated that the recipient must have a competitive advantage in acquiring cross-fed NH 4 + to sustain the mutualism. This recipient-biased competitive advantage is predicted to be crucial, particularly when the communally valuable nutrient is generated intracellularly. Thus, the very metabolites that form the basis for mutualistic cross-feeding can also be subject to competition between mutualistic partners. IMPORTANCE Mutualistic relationships, particularly those based on nutrient cross-feeding, promote stability of diverse ecosystems and drive

Recipient-Biased Competition for an Intracellularly Generated Cross-Fed Nutrient Is Required for Coexistence of Microbial Mutualists

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCully, Alexandra L.; LaSarre, Breah; McKinlay, James B.

ABSTRACT Many mutualistic microbial relationships are based on nutrient cross-feeding. Traditionally, cross-feeding is viewed as being unidirectional, from the producer to the recipient. This is likely true when a producer’s waste, such as a fermentation product, has value only for a recipient. However, in some cases the cross-fed nutrient holds value for both the producer and the recipient. In such cases, there is potential for nutrient reacquisition by producer cells in a population, leading to competition against recipients. Here, we investigated the consequences of interpartner competition for cross-fed nutrients on mutualism dynamics by using an anaerobic coculture pairing fermentative Escherichiamore » coli and phototrophic Rhodopseudomonas palustris . In this coculture, E. coli excretes waste organic acids that provide a carbon source for R. palustris . In return, R. palustris cross-feeds E. coli ammonium (NH 4 + ), a compound that both species value. To explore the potential for interpartner competition, we first used a kinetic model to simulate cocultures with varied affinities for NH 4 + in each species. The model predicted that interpartner competition for NH 4 + could profoundly impact population dynamics. We then experimentally tested the predictions by culturing mutants lacking NH 4 + transporters in both NH 4 + competition assays and mutualistic cocultures. Both theoretical and experimental results indicated that the recipient must have a competitive advantage in acquiring cross-fed NH 4 + to sustain the mutualism. This recipient-biased competitive advantage is predicted to be crucial, particularly when the communally valuable nutrient is generated intracellularly. Thus, the very metabolites that form the basis for mutualistic cross-feeding can also be subject to competition between mutualistic partners. IMPORTANCE Mutualistic relationships, particularly those based on nutrient cross-feeding, promote stability of diverse ecosystems and drive

Importance of Nutrients and Nutrient Metabolism on Human Health

PubMed Central

Chen, Yiheng; Michalak, Marek; Agellon, Luis B.

2018-01-01

Nutrition transition, which includes a change from consumption of traditional to modern diets that feature high-energy density and low nutrient diversity, is associated with acquired metabolic syndromes. The human diet is comprised of diverse components which include both nutrients, supplying the raw materials that drive multiple metabolic processes in every cell of the body, and non-nutrients. These components and their metabolites can also regulate gene expression and cellular function via a variety of mechanisms. Some of these components are beneficial while others have toxic effects. Studies have found that persistent disturbance of nutrient metabolism and/or energy homeostasis, caused by either nutrient deficiency or excess, induces cellular stress leading to metabolic dysregulation and tissue damage, and eventually to development of acquired metabolic syndromes. It is now evident that metabolism is influenced by extrinsic factors (e.g., food, xenobiotics, environment), intrinsic factors (e.g., sex, age, gene variations) as well as host/microbiota interaction, that together modify the risk for developing various acquired metabolic diseases. It is also becoming apparent that intake of diets with low-energy density but high in nutrient diversity may be the key to promoting and maintaining optimal health.

Dispersion/dilution enhances phytoplankton blooms in low-nutrient waters

NASA Astrophysics Data System (ADS)

Lehahn, Yoav; Koren, Ilan; Sharoni, Shlomit; D'Ovidio, Francesco; Vardi, Assaf; Boss, Emmanuel

2017-03-01

Spatial characteristics of phytoplankton blooms often reflect the horizontal transport properties of the oceanic turbulent flow in which they are embedded. Classically, bloom response to horizontal stirring is regarded in terms of generation of patchiness following large-scale bloom initiation. Here, using satellite observations from the North Pacific Subtropical Gyre and a simple ecosystem model, we show that the opposite scenario of turbulence dispersing and diluting fine-scale (~1-100 km) nutrient-enriched water patches has the critical effect of regulating the dynamics of nutrients-phytoplankton-zooplankton ecosystems and enhancing accumulation of photosynthetic biomass in low-nutrient oceanic environments. A key factor in determining ecological and biogeochemical consequences of turbulent stirring is the horizontal dilution rate, which depends on the effective eddy diffusivity and surface area of the enriched patches. Implementation of the notion of horizontal dilution rate explains quantitatively plankton response to turbulence and improves our ability to represent ecological and biogeochemical processes in oligotrophic oceans.

Carbon and Nutrient Dynamics and Fluxes in the Northwest European Continental Shelf Sea

NASA Astrophysics Data System (ADS)

Humphreys, M. P.; Moore, M. M.; Achterberg, E. P.; Griffiths, A.; Smilenova, A.; Chowdhury, M. Z. H.; Kivimae, C.; Hartman, S. E.; Hopkins, J.; Woodward, M. S.

2016-02-01

Despite covering only about 5 % of the Earth's ocean surface area, shallow marginal seas support 15-20 % of global primary productivity, and are the key interface between the land and the open ocean. They are therefore of critical importance to marine biogeochemical cycles, and may have a significant role in ocean uptake and storage of anthropogenic carbon dioxide (CO2). However, their behaviour is significantly more complex than that of the open ocean, because of the greater heterogeneity of the underlying physical, chemical and biological processes acting upon them. Detailed case-studies of individual regions are therefore essential in order to accurately evaluate their net global influence. The Northwest European continental shelf, in particular the Celtic Sea, was the target of extensive hydrographic sampling from March 2014 to September 2015, as part of the UK Shelf Seas Biogeochemistry research programme (UK-SSB). Here, we use the UK-SSB carbonate chemistry and macronutrient measurements to describe the seasonal biogeochemical cycle in the Celtic Sea. The 100-200 m deep water column proceeds from vertically well mixed in winter to a strongly stratified two-layer structure over spring-summer. The associated seasonal cycle in near-surface biological activity removes dissolved inorganic carbon (DIC) and nutrients, some of which are then exported into the deeper layer. Calculating total inventories of the biogeochemical variables throughout the seasonal cycle, we determine seasonal net CO2 uptake and investigate whether non-Redfieldian macronutrient uptake and remineralisation processes occur. Combining these results with estimated water exchange across the shelf edge further allows us to quantify the strength of the `shelf pump' sink for atmospheric (and anthropogenic) CO2.

Municipal water reuse for urban agriculture in Namibia: Modeling nutrient and salt flows as impacted by sanitation user behavior.

PubMed

Woltersdorf, L; Scheidegger, R; Liehr, S; Döll, P

2016-03-15

Adequate sanitation, wastewater treatment and irrigation infrastructure often lacks in urban areas of developing countries. While treated, nutrient-rich reuse water is a precious resource for crop production in dry regions, excessive salinity might harm the crops. The aim of this study was to quantify, from a system perspective, the nutrient and salt flows a new infrastructure connecting water supply, sanitation, wastewater treatment and nutrient-rich water reuse for the irrigation of agriculture, from a system perspective. For this, we developed and applied a quantitative assessment method to understand the benefits and to support the management of the new water infrastructure in an urban area in semi-arid Namibia. The nutrient and salt flows, as affected by sanitation user behavior, were quantified by mathematical material flow analysis that accounts for the low availability of suitable and certain data in developing countries, by including data ranges and by assessing the effects of different assumptions in cases. Also the nutrient and leaching requirements of a crop scheme were calculated. We found that, with ideal sanitation use, 100% of nutrients and salts are reclaimed and the slightly saline reuse water is sufficient to fertigate 10 m(2)/cap/yr (90% uncertainty interval 7-12 m(2)/cap/yr). However, only 50% of the P contained in human excreta could be finally used for crop nutrition. During the pilot phase fewer sanitation users than expected used slightly more water per capita, used the toilets less frequently and practiced open defecation more frequently. Therefore, it was only possible to reclaim about 85% of nutrients from human excreta, the reuse water was non-saline and contained less nutrient so that the P was the limiting factor for crop fertigation. To reclaim all nutrients from human excreta and fertigate a larger agricultural area, sanitation user behavior needs to be improved. The results and the methodology of this study can be generalized and

Influence of submarine springs and wastewater on nutrient dynamics of Caribbean seagrass meadows

NASA Astrophysics Data System (ADS)

Carruthers, T. J. B.; van Tussenbroek, B. I.; Dennison, W. C.

2005-08-01

The east coast of the Yucatan Peninsula, Mexico, consists of highly permeable limestone, such that surface flow and rivers are absent in this region. Extensive underground cave systems connect sink holes (cenotes) to submarine springs (ojos de aqua), which vent into the seagrass meadows of the adjacent oligotrophic coastal lagoons. This study investigated the potential for these submarine springs to influence nutrient processes within seagrass meadows, by assessing nutrient status of Thalassia testudinum meadows in two contrasting coastal lagoons along the north eastern Yucatan peninsula. Tissue nutrient concentrations as well as δ 15N values of T. testudinum were surveyed in the Puerto Morelos Reef Lagoon and the Nichupte Lagoon System, Cancun Hotel Zone, during an extended dry period and again following heavy rainfall. After a period of heavy rainfall, T. testudinum near submarine springs in Puerto Morelos Reef Lagoon had exceptionally high leaf tissue phosphorus concentrations of 0.38±0.06%. These submarine springs may have been a direct source of phosphorus and/or a source of iron to this very iron limited carbonate system. Thalassia testudinum nutrient concentrations suggest that nitrogen loading to the Nichupte Lagoon System is regionally high and has increased over the past decade (mean leaf N: 2.04% N in 1991 to 2.71% N in 2002). Nitrogen content in leaf tissue of T. testudinum was significantly higher within the poorly flushed Nichupte Lagoon System (2.93±0.12% N) than in the well-flushed Puerto Morelos Reef Lagoon (1.80±0.07% N). Stable isotope ratios of nitrogen suggest that this high and increasing nitrogen loading within the Nichupte Lagoon System is a result of wastewater nitrogen (δ 15N 9.06±0.07 in northern Nichupte Lagoon System vs. 1.69±0.07 in Puerto Morelos Reef Lagoon).

Flow pathways and nutrient transport mechanisms drive hydrochemical sensitivity to climate change across catchments with different geology and topography

NASA Astrophysics Data System (ADS)

Crossman, J.; Futter, M. N.; Whitehead, P. G.; Stainsby, E.; Baulch, H. M.; Jin, L.; Oni, S. K.; Wilby, R. L.; Dillon, P. J.

2014-07-01

Hydrological processes determine the transport of nutrients and passage of diffuse pollution. Consequently, catchments are likely to exhibit individual hydrochemical responses (sensitivities) to climate change, which is expected to alter the timing and amount of runoff, and to impact in-stream water quality. In developing robust catchment management strategies and quantifying plausible future hydrochemical conditions it is therefore equally important to consider the potential for spatial variability in, and causal factors of, catchment sensitivity, as to explore future changes in climatic pressures. This study seeks to identify those factors which influence hydrochemical sensitivity to climate change. A perturbed physics ensemble (PPE), derived from a series of Global Climate Model (GCM) variants with specific climate sensitivities was used to project future climate change and uncertainty. Using the Integrated Catchment Model of Phosphorus Dynamics (INCA-P), we quantified potential hydrochemical responses in four neighbouring catchments (with similar land use but varying topographic and geological characteristics) in southern Ontario, Canada. Responses were assessed by comparing a 30 year baseline (1968-1997) to two future periods: 2020-2049 and 2060-2089. Although projected climate change and uncertainties were similar across these catchments, hydrochemical responses (sensitivity) were highly varied. Sensitivity was governed by soil type (influencing flow pathways) and nutrient transport mechanisms. Clay-rich catchments were most sensitive, with total phosphorus (TP) being rapidly transported to rivers via overland flow. In these catchments large annual reductions in TP loads were projected. Sensitivity in the other two catchments, dominated by sandy-loams, was lower due to a larger proportion of soil matrix flow, longer soil water residence times and seasonal variability in soil-P saturation. Here smaller changes in TP loads, predominantly increases, were

Flow pathways and nutrient transport mechanisms drive hydrochemical sensitivity to climate change across catchments with different geology and topography

NASA Astrophysics Data System (ADS)

Crossman, J.; Futter, M. N.; Whitehead, P. G.; Stainsby, E.; Baulch, H. M.; Jin, L.; Oni, S. K.; Wilby, R. L.; Dillon, P. J.

2014-12-01

Hydrological processes determine the transport of nutrients and passage of diffuse pollution. Consequently, catchments are likely to exhibit individual hydrochemical responses (sensitivities) to climate change, which are expected to alter the timing and amount of runoff, and to impact in-stream water quality. In developing robust catchment management strategies and quantifying plausible future hydrochemical conditions it is therefore equally important to consider the potential for spatial variability in, and causal factors of, catchment sensitivity, as it is to explore future changes in climatic pressures. This study seeks to identify those factors which influence hydrochemical sensitivity to climate change. A perturbed physics ensemble (PPE), derived from a series of global climate model (GCM) variants with specific climate sensitivities was used to project future climate change and uncertainty. Using the INtegrated CAtchment model of Phosphorus dynamics (INCA-P), we quantified potential hydrochemical responses in four neighbouring catchments (with similar land use but varying topographic and geological characteristics) in southern Ontario, Canada. Responses were assessed by comparing a 30 year baseline (1968-1997) to two future periods: 2020-2049 and 2060-2089. Although projected climate change and uncertainties were similar across these catchments, hydrochemical responses (sensitivities) were highly varied. Sensitivity was governed by quaternary geology (influencing flow pathways) and nutrient transport mechanisms. Clay-rich catchments were most sensitive, with total phosphorus (TP) being rapidly transported to rivers via overland flow. In these catchments large annual reductions in TP loads were projected. Sensitivity in the other two catchments, dominated by sandy loams, was lower due to a larger proportion of soil matrix flow, longer soil water residence times and seasonal variability in soil-P saturation. Here smaller changes in TP loads, predominantly

Urban Runoff and Nutrients Loading Control from Sustainable BMPs (Invited)

NASA Astrophysics Data System (ADS)

Xiao, Q.

2009-12-01

Climate change alters hydrodynamic and nutrient dynamic in both large and small geographic scales. These changes in our freshwater system directly affect drinking water, food production, business, and all aspects of our life. Along with climate change is increasing urbanization which alters natural landscape. Urban runoff has been identified as one of many potential drivers of the decline of pelagic fishes in san Francisco Bay-Delta region. Recent found of Pyrethroids in American River has increased scientists, public, and policy makers’ concern about our fresh water system. Increasing our understanding about the fundamental hydrodynamic, nutrient dynamics, and the transport mechanics of runoff and nutrients are important for future water resource and ecosystem management. Urbanization has resulted in significantly increasing the amount of impervious land cover. Most impervious land covers are hydrophobic that alters surface runoff because of the effects on surface retention storage, rainfall interception, and infiltration. Large volumes of excess storm runoff from urbanized areas cause flooding, water pollution, groundwater recharge deficits, destroyed habitat, beach closures, and toxicity to aquatic organisms. Parking lot alone accounts for more than 11% of these impervious surfaces. Contrast to impervious parking lot, turfgrass can accouter for 12% of urban land in California. Irrigated urban landscapes create considerable benefits to our daily living. However, the use of fertilizers and pesticides has caused environmental problems. Preventing fertilizers and pesticides from entering storm drains is an important goal for both landscape and storm runoff managers. Studies of urban runoff have found that the most fertilizers and pesticides are from dry weather runoff which conveys pollutants to sidewalks, streets, and storm drains. Controlling surface runoff is critical to preventing these pollutants from entering storm drains and water bodies. Large scale

Scaling Dissolved Nutrient Removal in River Networks: A Comparative Modeling Investigation

NASA Astrophysics Data System (ADS)

Ye, Sheng; Reisinger, Alexander J.; Tank, Jennifer L.; Baker, Michelle A.; Hall, Robert O.; Rosi, Emma J.; Sivapalan, Murugesu

2017-11-01

Along the river network, water, sediment, and nutrients are transported, cycled, and altered by coupled hydrological and biogeochemical processes. Our current understanding of the rates and processes controlling the cycling and removal of dissolved inorganic nutrients in river networks is limited due to a lack of empirical measurements in large, (nonwadeable), rivers. The goal of this paper was to develop a coupled hydrological and biogeochemical process model to simulate nutrient uptake at the network scale during summer base flow conditions. The model was parameterized with literature values from headwater streams, and empirical measurements made in 15 rivers with varying hydrological, biological, and topographic characteristics, to simulate nutrient uptake at the network scale. We applied the coupled model to 15 catchments describing patterns in uptake for three different solutes to determine the role of rivers in network-scale nutrient cycling. Model simulation results, constrained by empirical data, suggested that rivers contributed proportionally more to nutrient removal than headwater streams given the fraction of their length represented in a network. In addition, variability of nutrient removal patterns among catchments was varied among solutes, and as expected, was influenced by nutrient concentration and discharge. Net ammonium uptake was not significantly correlated with any environmental descriptor. In contrast, net daily nitrate removal was linked to suspended chlorophyll a (an indicator of primary producers) and land use characteristics. Finally, suspended sediment characteristics and agricultural land use were correlated with net daily removal of soluble reactive phosphorus, likely reflecting abiotic sorption dynamics. Rivers are understudied relative to streams, and our model suggests that rivers can contribute more to network-scale nutrient removal than would be expected based upon their representative fraction of network channel length.

Quantifying heterogeneity of lesion uptake in dynamic contrast enhanced MRI for breast cancer diagnosis

NASA Astrophysics Data System (ADS)

Karahaliou, A.; Vassiou, K.; Skiadopoulos, S.; Kanavou, T.; Yiakoumelos, A.; Costaridou, L.

2009-07-01

The current study investigates whether texture features extracted from lesion kinetics feature maps can be used for breast cancer diagnosis. Fifty five women with 57 breast lesions (27 benign, 30 malignant) were subjected to dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) on 1.5T system. A linear-slope model was fitted pixel-wise to a representative lesion slice time series and fitted parameters were used to create three kinetic maps (wash out, time to peak enhancement and peak enhancement). 28 grey level co-occurrence matrices features were extracted from each lesion kinetic map. The ability of texture features per map in discriminating malignant from benign lesions was investigated using a Probabilistic Neural Network classifier. Additional classification was performed by combining classification outputs of most discriminating feature subsets from the three maps, via majority voting. The combined scheme outperformed classification based on individual maps achieving area under Receiver Operating Characteristics curve 0.960±0.029. Results suggest that heterogeneity of breast lesion kinetics, as quantified by texture analysis, may contribute to computer assisted tissue characterization in DCE-MRI.

Novel fine-scale aerial mapping approach quantifies grassland weed cover dynamics and response to management.

PubMed

Malmstrom, Carolyn M; Butterfield, H Scott; Planck, Laura; Long, Christopher W; Eviner, Valerie T

2017-01-01

Invasive weeds threaten the biodiversity and forage productivity of grasslands worldwide. However, management of these weeds is constrained by the practical difficulty of detecting small-scale infestations across large landscapes and by limits in understanding of landscape-scale invasion dynamics, including mechanisms that enable patches to expand, contract, or remain stable. While high-end hyperspectral remote sensing systems can effectively map vegetation cover, these systems are currently too costly and limited in availability for most land managers. We demonstrate application of a more accessible and cost-effective remote sensing approach, based on simple aerial imagery, for quantifying weed cover dynamics over time. In California annual grasslands, the target communities of interest include invasive weedy grasses (Aegilops triuncialis and Elymus caput-medusae) and desirable forage grass species (primarily Avena spp. and Bromus spp.). Detecting invasion of annual grasses into an annual-dominated community is particularly challenging, but we were able to consistently characterize these two communities based on their phenological differences in peak growth and senescence using maximum likelihood supervised classification of imagery acquired twice per year (in mid- and end-of season). This approach permitted us to map weed-dominated cover at a 1-m scale (correctly detecting 93% of weed patches across the landscape) and to evaluate weed cover change over time. We found that weed cover was more pervasive and persistent in management units that had no significant grazing for several years than in those that were grazed, whereas forage cover was more abundant and stable in the grazed units. This application demonstrates the power of this method for assessing fine-scale vegetation transitions across heterogeneous landscapes. It thus provides means for small-scale early detection of invasive species and for testing fundamental questions about landscape dynamics.

Novel fine-scale aerial mapping approach quantifies grassland weed cover dynamics and response to management

PubMed Central

Butterfield, H. Scott; Planck, Laura; Long, Christopher W.; Eviner, Valerie T.

2017-01-01

Invasive weeds threaten the biodiversity and forage productivity of grasslands worldwide. However, management of these weeds is constrained by the practical difficulty of detecting small-scale infestations across large landscapes and by limits in understanding of landscape-scale invasion dynamics, including mechanisms that enable patches to expand, contract, or remain stable. While high-end hyperspectral remote sensing systems can effectively map vegetation cover, these systems are currently too costly and limited in availability for most land managers. We demonstrate application of a more accessible and cost-effective remote sensing approach, based on simple aerial imagery, for quantifying weed cover dynamics over time. In California annual grasslands, the target communities of interest include invasive weedy grasses (Aegilops triuncialis and Elymus caput-medusae) and desirable forage grass species (primarily Avena spp. and Bromus spp.). Detecting invasion of annual grasses into an annual-dominated community is particularly challenging, but we were able to consistently characterize these two communities based on their phenological differences in peak growth and senescence using maximum likelihood supervised classification of imagery acquired twice per year (in mid- and end-of season). This approach permitted us to map weed-dominated cover at a 1-m scale (correctly detecting 93% of weed patches across the landscape) and to evaluate weed cover change over time. We found that weed cover was more pervasive and persistent in management units that had no significant grazing for several years than in those that were grazed, whereas forage cover was more abundant and stable in the grazed units. This application demonstrates the power of this method for assessing fine-scale vegetation transitions across heterogeneous landscapes. It thus provides means for small-scale early detection of invasive species and for testing fundamental questions about landscape dynamics. PMID

Discontinuities in stream nutrient uptake below lakes in mountain drainage networks

USGS Publications Warehouse

Arp, C.D.; Baker, M.A.

2007-01-01

In many watersheds, lakes and streams are hydrologically linked in spatial patterns that influence material transport and retention. We hypothesized that lakes affect stream nutrient cycling via modifications to stream hydrogeomorphology, source-waters, and biological communities. We tested this hypothesis in a lake district of the Sawtooth Mountains, Idaho. Uptake of NO3- and PO4-3 was compared among 25 reaches representing the following landscape positions: lake inlets and outlets, reaches >1-km downstream from lakes, and reference reaches with no nearby lakes. We quantified landscape-scale hydrographic and reach-scale hydrogeomorphic, source-water, and biological variables to characterize these landscape positions and analyze relationships to nutrient uptake. Nitrate uptake was undetectable at most lake outlets, whereas PO4-3 uptake was higher at outlets as compared to reference and lake inlet reaches. Patterns in nutrient demand farther downstream were similar to lake outlets with a gradual shift toward reference-reach functionality. Nitrate uptake was most correlated to sediment mobility and channel morphology, whereas PO 4-3 uptake was most correlated to source-water characteristics. The best integrated predictor of these patterns in nutrient demand was % contributing area (the proportion of watershed area not routing through a lake). We estimate that NO3- and PO 4-3 demand returned to 50% of pre-lake conditions within 1-4-km downstream of a small headwater lake and resetting of nutrient demand was slower downstream of a larger lake set lower in a watershed. Full resetting of these nutrient cycling processes was not reached within 20-km downstream, indicating that lakes can alter stream ecosystem functioning at large spatial scales throughout mountain watersheds. ?? 2007, by the American Society of Limnology and Oceanography, Inc.

Quantifying microstructural dynamics and electrochemical activity of graphite and silicon-graphite lithium ion battery anodes

NASA Astrophysics Data System (ADS)

Pietsch, Patrick; Westhoff, Daniel; Feinauer, Julian; Eller, Jens; Marone, Federica; Stampanoni, Marco; Schmidt, Volker; Wood, Vanessa

2016-09-01

Despite numerous studies presenting advances in tomographic imaging and analysis of lithium ion batteries, graphite-based anodes have received little attention. Weak X-ray attenuation of graphite and, as a result, poor contrast between graphite and the other carbon-based components in an electrode pore space renders data analysis challenging. Here we demonstrate operando tomography of weakly attenuating electrodes during electrochemical (de)lithiation. We use propagation-based phase contrast tomography to facilitate the differentiation between weakly attenuating materials and apply digital volume correlation to capture the dynamics of the electrodes during operation. After validating that we can quantify the local electrochemical activity and microstructural changes throughout graphite electrodes, we apply our technique to graphite-silicon composite electrodes. We show that microstructural changes that occur during (de)lithiation of a pure graphite electrode are of the same order of magnitude as spatial inhomogeneities within it, while strain in composite electrodes is locally pronounced and introduces significant microstructural changes.

Quantifying and tuning entanglement for quantum systems

NASA Astrophysics Data System (ADS)

Xu, Qing

A 2D Ising model with transverse field on a triangular lattice is studied using exact diagonalization. The quantum entanglement of the system is quantified by the entanglement of formation. The ground state property of the system is studied and the quantified entanglement is shown to be closely related to the ground state wavefunction while the singularity in the entanglement as a function of the transverse field is a reasonable indicator of the quantum phase transition. In order to tune the entanglement, one can either include an impurity in the otherwise homogeneous system whose strength is tunable, or one can vary the external transverse field as a tuner. The latter kind of tuning involves complicated dynamical properties of the system. From the study of the dynamics on a comparatively smaller system, we provide ways to tune the entanglement without triggering any decoherence. The finite temperature effect is also discussed. Besides showing above physical results, the realization of the trace-minimization method in our system is provided; the scalability of such method to larger systems is argued.

Litter dynamics in two Sierran mixed conifer forests. II. Nutrient release in decomposing leaf litter

USGS Publications Warehouse

Stohlgren, Thomas J.

1988-01-01

The factors influencing leaf litter decomposition and nutrient release patterns were investigated for 3.6 years in two mixed conifer forests in the southern Sierra Nevada of California. The giant sequoia–fir forest was dominated by giant sequoia (Sequoiadendrongiganteum (Lindl.) Buchh.), white fir (Abiesconcolor Lindl. & Gord.), and sugar pine (Pinuslambertiana Dougl.). The fir–pine forest was dominated by white fir, sugar pine, and incense cedar (Calocedrusdecurrens (Torr.) Florin). Initial concentrations of nutrients and percent lignin, cellulose, and acid detergent fiber vary considerably in freshly abscised leaf litter of the studied species. Giant sequoia had the highest concentration of lignin (20.3%) and the lowest concentration of nitrogen (0.52%), while incense cedar had the lowest concentration of lignin (9.6%) and second lowest concentration of nitrogen (0.63%). Long-term (3.6 years) foliage decomposition rates were best correlated with initial lignin/N (r2 = 0.94, p r2 = 0.92, p r2 = 0.80, p < 0.05). Patterns of nutrient release were highly variable. Giant sequoia immobilized N and P, incense cedar immobilized N and to a lesser extent P, while sugar pine immobilized Ca. Strong linear or negative exponential relationships existed between initial concentrations of N, P, K, and Ca and percent original mass remaining of those nutrients after 3.6 years. This suggests efficient retention of these nutrients in the litter layer of these ecosystems. Nitrogen concentrations steadily increase in decomposing leaf litter, effectively reducing the C/N ratios from an initial range of 68–96 to 27–45 after 3.6 years.

Scale and legacy controls on catchment nutrient export regimes

NASA Astrophysics Data System (ADS)

Howden, N. J. K.; Burt, T.; Worrall, F.

2017-12-01

Nutrient dynamics in river catchments are complex: water and chemical fluxes are highly variable in low-order streams, but this variability declines as fluxes move through higher-order reaches. This poses a major challenge for process understanding as much effort is focussed on long-term monitoring of the main river channel (a high-order reach), and therefore the data available to support process understanding are predominantly derived from sites where much of the transient response of nutrient export is masked by the effect of averaging over both space and time. This may be further exacerbated at all scales by the accumulation of legacy nutrient sources in soils, aquifers and pore waters, where historical activities have led to nutrient accumulation where the catchment system is transport limited. Therefore it is of particular interest to investigate how the variability of nutrient export changes both with catchment scale (from low to high-order catchment streams) and with the presence of legacy sources, such that the context of infrequent monitoring on high-order streams can be better understood. This is not only a question of characterising nutrient export regimes per se, but also developing a more thorough understanding of how the concepts of scale and legacy may modify the statistical characteristics of observed responses across scales in both space and time. In this paper, we use synthetic data series and develop a model approach to consider how space and timescales combine with impacts of legacy sources to influence observed variability in catchment export. We find that: increasing space and timescales tend to reduce the observed variance in nutrient exports, due to an increase in travel times and greater mixing, and therefore averaging, of sources; increasing the influence of legacy sources inflates the variance, with the level of inflation dictated by the residence time of the respective sources.

The role of gap phase processes in the biomass dynamics of tropical forests

PubMed Central

Feeley, Kenneth J; Davies, Stuart J; Ashton, Peter S; Bunyavejchewin, Sarayudh; Nur Supardi, M.N; Kassim, Abd Rahman; Tan, Sylvester; Chave, Jérôme

2007-01-01

The responses of tropical forests to global anthropogenic disturbances remain poorly understood. Above-ground woody biomass in some tropical forest plots has increased over the past several decades, potentially reflecting a widespread response to increased resource availability, for example, due to elevated atmospheric CO2 and/or nutrient deposition. However, previous studies of biomass dynamics have not accounted for natural patterns of disturbance and gap phase regeneration, making it difficult to quantify the importance of environmental changes. Using spatially explicit census data from large (50 ha) inventory plots, we investigated the influence of gap phase processes on the biomass dynamics of four ‘old-growth’ tropical forests (Barro Colorado Island (BCI), Panama; Pasoh and Lambir, Malaysia; and Huai Kha Khaeng (HKK), Thailand). We show that biomass increases were gradual and concentrated in earlier-phase forest patches, while biomass losses were generally of greater magnitude but concentrated in rarer later-phase patches. We then estimate the rate of biomass change at each site independent of gap phase dynamics using reduced major axis regressions and ANCOVA tests. Above-ground woody biomass increased significantly at Pasoh (+0.72% yr−1) and decreased at HKK (−0.56% yr−1) independent of changes in gap phase but remained stable at both BCI and Lambir. We conclude that gap phase processes play an important role in the biomass dynamics of tropical forests, and that quantifying the role of gap phase processes will help improve our understanding of the factors driving changes in forest biomass as well as their place in the global carbon budget. PMID:17785266

The role of gap phase processes in the biomass dynamics of tropical forests.

PubMed

Feeley, Kenneth J; Davies, Stuart J; Ashton, Peter S; Bunyavejchewin, Sarayudh; Nur Supardi, M N; Kassim, Abd Rahman; Tan, Sylvester; Chave, Jérôme

2007-11-22

The responses of tropical forests to global anthropogenic disturbances remain poorly understood. Above-ground woody biomass in some tropical forest plots has increased over the past several decades, potentially reflecting a widespread response to increased resource availability, for example, due to elevated atmospheric CO2 and/or nutrient deposition. However, previous studies of biomass dynamics have not accounted for natural patterns of disturbance and gap phase regeneration, making it difficult to quantify the importance of environmental changes. Using spatially explicit census data from large (50 ha) inventory plots, we investigated the influence of gap phase processes on the biomass dynamics of four 'old-growth' tropical forests (Barro Colorado Island (BCI), Panama; Pasoh and Lambir, Malaysia; and Huai Kha Khaeng (HKK), Thailand). We show that biomass increases were gradual and concentrated in earlier-phase forest patches, while biomass losses were generally of greater magnitude but concentrated in rarer later-phase patches. We then estimate the rate of biomass change at each site independent of gap phase dynamics using reduced major axis regressions and ANCOVA tests. Above-ground woody biomass increased significantly at Pasoh (+0.72% yr(-1)) and decreased at HKK (-0.56% yr(-1)) independent of changes in gap phase but remained stable at both BCI and Lambir. We conclude that gap phase processes play an important role in the biomass dynamics of tropical forests, and that quantifying the role of gap phase processes will help improve our understanding of the factors driving changes in forest biomass as well as their place in the global carbon budget.

Resistance, resilience and recovery: aquatic bacterial dynamics after water column disturbance.

PubMed

Shade, Ashley; Read, Jordan S; Welkie, David G; Kratz, Timothy K; Wu, Chin H; McMahon, Katherine D

2011-10-01

For lake microbes, water column mixing acts as a disturbance because it homogenizes thermal and chemical gradients known to define the distributions of microbial taxa. Our first objective was to isolate hypothesized drivers of lake bacterial response to water column mixing. To accomplish this, we designed an enclosure experiment with three treatments to independently test key biogeochemical changes induced by mixing: oxygen addition to the hypolimnion, nutrient addition to the epilimnion, and full water column mixing. We used molecular fingerprinting to observe bacterial community dynamics in the treatment and control enclosures, and in ambient lake water. We found that oxygen and nutrient amendments simulated the physical-chemical water column environment following mixing and resulted in similar bacterial communities to the mixing treatment, affirming that these were important drivers of community change. These results demonstrate that specific environmental changes can replicate broad disturbance effects on microbial communities. Our second objective was to characterize bacterial community stability by quantifying community resistance, recovery and resilience to an episodic disturbance. The communities in the nutrient and oxygen amendments changed quickly (had low resistance), but generally matched the control composition by the 10th day after treatment, exhibiting resilience. These results imply that aquatic bacterial assemblages are generally stable in the face of disturbance. © 2011 Society for Applied Microbiology and Blackwell Publishing Ltd.

Mechanisms of nutrient retention and its relation to flow connectivity in river-floodplain corridors

USGS Publications Warehouse

Larsen, Laurel; Harvey, Judson; Maglio, Morgan M.

2015-01-01

Understanding heterogeneity or patchiness in the distribution of vegetation and retention of C and nutrients in river corridors is critical for setting priorities for river management and restoration. Several mechanisms of spatial differentiation in nutrient retention in river and floodplain corridors have been recognized, but few studies have distinguished their relative importance or established their role in long-term geomorphic change, nutrient retention, and connectivity with downstream systems. We evaluated the ability of 3 mechanisms (evapotranspiration focusing [EF], differential hydrologic exchange [DHE], and particulate nutrient redistribution [PNR]) to explain spatial patterns of P retention and function in the Everglades (Florida, USA). We used field measurements in sloughs and on slightly higher, more densely vegetated ridges to quantify P fluxes attributable to the 3 mechanisms. EF does not explain Everglades nutrient retention or P concentrations on ridges and in sloughs. However, DHE resulting from different periods of groundwater–surface-water connectivity across topographic elements is the primary cause of elevated P concentrations on ridges and completely explains interpatch differences in long-term P accumulation rates. With historical flow velocities, which were an order of magnitude higher than at present, PNR would have further increased the interpatch difference in long-term P retention rates nearly 2-fold. In conclusion, DHE and PNR are the dominant drivers of nutrient patchiness in the Everglades and are hypothesized to be important in P-limited river and floodplain corridors globally.

Nutrient reserve dynamics of breeding canvasbacks

USGS Publications Warehouse

Barzen, Jeb A.; Serie, Jerome R.

1990-01-01

We compared nutrients in reproductive and nonreproductive tissues of breeding Canvasbacks (Aythya valisineria) to assess the relative importance of endogenous reserves and exogenous foods. Fat reserves of females increased during rapid follicle growth and varied more widely in size during the early phase of this period. Females began laying with ca. 205 g of fat in reserve and lost 1.8 g of carcass fat for every 1 g of fat contained in their ovary and eggs. Females lost body mass (primarily fat) at a declining rate as incubation advanced. Protein reserves increased directly with dry oviduct mass during rapid follicle growth. This direct relationship was highly dependent upon data from 2 birds and likely biased by structural size. During laying, protein reserves did not vary with the combined mass of dry oviduct and dry egg protein. Between laying and incubation, mean protein reserves decreased by an amount equal to the protein found in 2.1 Canvasback eggs. Calcium reserves did not vary with the cumulative total of calcium deposited in eggs. Mean calcium reserve declined by the equivalent content of 1.2 eggs between laying and incubation. We believe that protein and calcium were stored in small amounts during laying, and that they were supplemented continually by exogenous sources. In contrast, fat was stored in large amounts and contributed significantly to egg production and body maintenance. Male Canvasbacks lost fat steadily-but not protein or calcium-as the breeding season progressed.

Seasonal and spatial dynamics of nutrients and phytoplankton biomass in Victoria Harbour and its vicinity before and after sewage abatement.

PubMed

Ho, Alvin Y T; Xu, Jie; Yin, Kedong; Yuan, Xiangcheng; He, Lei; Jiang, Yuelu; Lee, Joseph H W; Anderson, Donald M; Harrison, Paul J

2008-01-01

This study investigated the seasonal and spatial dynamics of nutrients and phytoplankton biomass at 12 stations in Hong Kong (HK) waters during a three year period from 2004 to 2006 after upgraded sewage treatment and compared these results to observations before sewage treatment. Pearl River estuary (PRE) discharge significantly increased NO(3) and SiO(4) concentrations, particularly in western and southern waters when rainfall and river discharge was maximal in summer. Continuous year round discharge of sewage effluent resulted in high NH(4) and PO(4) in Victoria Harbour (VH) and its vicinity. In winter, spring and fall, the water column at all stations was moderately mixed by winds and tidal currents, and phytoplankton biomass was relatively low compared to summer. In summer, the mean surface phytoplankton chl biomass was generally > 9 microL(-1) in most areas as a result of thermohaline stratification, and high nutrients, light, and water temperature. In summer, the potential limiting nutrient is PO(4) in the most productive southern waters and it seldom decreased to limiting levels ( approximately 0.1 microM), suggesting that phytoplankton growth may be only episodically limiting. The mean bottom dissolved oxygen (DO) remained > 3.5 mg L(-1) at most stations, indicating that the eutrophication impact in HK waters was not as severe as expected for such a eutrophic area. After the implementation of chemically enhanced primary sewage treatment in 2001, water quality in VH improved as indicated by a significant decrease in NH(4) and PO(4) and an increase in bottom DO. In contrast, there were an increase in chl a and NO(3), and a significant decrease in bottom DO in southern waters in summer, suggesting that hypoxic events are most likely to occur in this region if phytoplankton biomass and oxygen consumption keep increasing and exceed the buffering capacity of HK waters maintained by monsoon winds, tidal mixing and zooplankton grazing. Therefore, future studies on

Chemical characterization of biochar and assessment of the nutrient dynamics by means of preliminary plant growth tests.

PubMed

Prasad, Munoo; Tzortzakis, Nikos; McDaniel, Nicola

2018-06-15

Biochar can be produced from several organic sources with varying nutrients and metal concentrations. Four commercial grade biochars were evaluated as peat substitute. Biochars were characterised for plant nutrients and for biological stability. The results showed that there were negligible quantities of N and P and generally high levels of K and high biological stability. When these materials were mixed with peat at 10, 25 and 50% and nutrients were added to bring them to the same level of nutrients as in fertilized peat, it was found that biochar mixtures considerably reduced the levels of calcium chloride/DTPA (CAT) extractable N (including nitrate), P, and electrical conductivity- greater extent with higher rates of biochar addition except for K. The pH and K levels were increased with biochar addition. The drop in EC has important implications regarding the use of other materials used to dilute peat, for example, composted green waste, the rate of dilution is limited due to high EC and biochar addition gives the potential for higher peat dilution of these materials. Nitrate and phosphorus are very vulnerable to leaching of these nutrients in the environment in peat substrates and the binding of these by biochar has implication for leaching and nutrient application strategy. Root development using Cress test and tomato plant height and biomass using containers, were in some cases better than peat indicating that biochar could be used to dilute peat e.g. for seedling production where root development and rapid growth are very important. Application of biochars resulted in a marked reduction of N (and P) in the plant. There were significant correlation between CAT extractable N and P and corresponding plant concentration, indicating the standard growing media test, CAT, would be suitable for assessing the nutrient status of peat biochar mixes. Copyright © 2017 Elsevier Ltd. All rights reserved.

Solid or hollow: which core cultivation method is the most effective at reducing nutrient loss with runoff from turf?

USDA-ARS?s Scientific Manuscript database

Excess nutrients in surfaces waters can result in undesirable consequences. Experiments were designed to quantify phosphorus and nitrogen transport with runoff from plots maintained as a golf course fairway to identify which cultural practice, solid tine or hollow tine core cultivation, will maximiz...

Variation in nutrients formulated and nutrients supplied on 5 California dairies.

PubMed

Rossow, H A; Aly, S S

2013-01-01

Computer models used in ration formulation assume that nutrients supplied by a ration formulation are the same as the nutrients presented in front of the cow in the final ration. Deviations in nutrients due to feed management effects such as dry matter changes (i.e., rain), loading, mixing, and delivery errors are assumed to not affect delivery of nutrients to the cow and her resulting milk production. To estimate how feed management affects nutrients supplied to the cow and milk production, and determine if nutrients can serve as indexes of feed management practices, weekly total mixed ration samples were collected and analyzed for 4 pens (close-up cows, fresh cows, high-milk-producing, and low-milk-producing cows, if available) for 7 to 12 wk on 5 commercial California dairies. Differences among nutrient analyses from these samples and nutrients from the formulated rations were analyzed by PROC MIXED of SAS (SAS Institute Inc., Cary, NC). Milk fat and milk protein percentages did not vary as much [coefficient of variation (CV) = 18 to 33%] as milk yield (kg; CV = 16 to 47 %) across all dairies and pens. Variability in nutrients delivered were highest for macronutrient fat (CV = 22%), lignin (CV = 15%), and ash (CV = 11%) percentages and micronutrients Fe (mg/kg; CV = 48%), Na (%; CV = 42%), and Zn (mg/kg; CV = 38%) for the milking pens across all dairies. Partitioning of the variability in random effects of nutrients delivered and intraclass correlation coefficients showed that variability in lignin percentage of TMR had the highest correlation with variability in milk yield and milk fat percentage, followed by fat and crude protein percentages. But, variability in ash, fat, and lignin percentages of total mixed ration had the highest correlation with variability in milk protein percentage. Therefore, lignin, fat, and ash may be the best indices of feed management to include effects of variability in nutrients on variability in milk yield, milk fat, and milk

Water and nutrient budgets for Vancouver Lake, Vancouver, Washington, October 2010-October 2012

USGS Publications Warehouse

Sheibley, Rich W.; Foreman, James R.; Marshall, Cameron A.; Welch, Wendy B.

2014-01-01

Vancouver Lake, a large shallow lake in Clark County, near Vancouver, Washington, has been undergoing water-quality problems for decades. Recently, the biggest concern for the lake are the almost annual harmful cyanobacteria blooms that cause the lake to close for recreation for several weeks each summer. Despite decades of interest in improving the water quality of the lake, fundamental information on the timing and amount of water and nutrients entering and exiting the lake is lacking. In 2010, the U.S. Geological Survey conducted a 2-year field study to quantify water flows and nutrient loads in order to develop water and nutrient budgets for the lake. This report presents monthly and annual water and nutrient budgets from October 2010–October 2012 to identify major sources and sinks of nutrients. Lake River, a tidally influenced tributary to the lake, flows into and out of the lake almost daily and composed the greatest proportion of both the water and nutrient budgets for the lake, often at orders of magnitude greater than any other source. From the water budget, we identified precipitation, evaporation and groundwater inflow as minor components of the lake hydrologic cycle, each contributing 1 percent or less to the total water budget. Nutrient budgets were compiled monthly and annually for total nitrogen, total phosphorus, and orthophosphate; and, nitrogen loads were generally an order of magnitude greater than phosphorus loads across all sources. For total nitrogen, flow from Lake River at Felida, Washington, made up 88 percent of all inputs into the lake. For total phosphorus and orthophosphate, Lake River at Felida flowing into the lake was 91 and 76 percent of total inputs, respectively. Nutrient loads from precipitation and groundwater inflow were 1 percent or less of the total budgets. Nutrient inputs from Burnt Bridge Creek and Flushing Channel composed 12 percent of the total nitrogen budget, 8 percent of the total phosphorus budget, and 21 percent

Chemical evolution of the Salton Sea, California: Nutrient and selenium dynamics

USGS Publications Warehouse

Schroeder, R.A.; Orem, W.H.; Kharaka, Y.K.

2002-01-01

The Salton Sea is a 1000-km2 terminal lake located in the desert area of southeastern California. This saline (???44 000 mg l-1 dissolved solids) lake started as fresh water in 1905-07 by accidental flooding of the Colorado River, and it is maintained by agricultural runoff of irrigation water diverted from the Colorado River. The Salton Sea and surrounding wetlands have recently acquired substantial ecological importance because of the death of large numbers of birds and fish, and the establishment of a program to restore the health of the Sea. In this report, we present new data on the salinity and concentration of selected chemicals in the Salton Sea water, porewater and sediments, emphasizing the constituents of concern: nutrients (N and P), Se and salinity. Chemical profiles from a Salton Sea core estimated to have a sedimentation rate of 2.3 mm yr-1 show increasing concentrations of OC, N, and P in younger sediment that are believed to reflect increasing eutrophication of the lake. Porewater profiles from two locations in the Sea show that diffusion from bottom sediment is only a minor source of nutrients to the overlying water as compared to irrigation water inputs. Although loss of N and Se by microbial-mediated volatilization is possible, comparison of selected element concentrations in river inputs and water and sediments from the Salton Sea indicates that most of the N (from fertilizer) and virtually all of the Se (delivered in irrigation water from the Colorado River) discharged to the Sea still reside within its bottom sediment. Laboratory simulation on mixtures of sediment and water from the Salton Sea suggest that sediment is a potential source of N and Se to the water column under aerobic conditions. Hence, it is important that any engineered changes made to the Salton Sea for remediation or for transfer of water out of the basin do not result in remobilization of nutrients and Se from the bottom sediment into the overlying water.

Chemical evolution of the Salton Sea, California: nutrient and selenium dynamics

USGS Publications Warehouse

Schroeder, Roy A.; Orem, William H.; Kharaka, Yousif K.

2002-01-01

The Salton Sea is a 1000-km2 terminal lake located in the desert area of southeastern California. This saline (∼44 000 mg l−1 dissolved solids) lake started as fresh water in 1905–07 by accidental flooding of the Colorado River, and it is maintained by agricultural runoff of irrigation water diverted from the Colorado River. The Salton Sea and surrounding wetlands have recently acquired substantial ecological importance because of the death of large numbers of birds and fish, and the establishment of a program to restore the health of the Sea. In this report, we present new data on the salinity and concentration of selected chemicals in the Salton Sea water, porewater and sediments, emphasizing the constituents of concern: nutrients (N and P), Se and salinity. Chemical profiles from a Salton Sea core estimated to have a sedimentation rate of 2.3 mm yr−1 show increasing concentrations of OC, N, and P in younger sediment that are believed to reflect increasing eutrophication of the lake. Porewater profiles from two locations in the Sea show that diffusion from bottom sediment is only a minor source of nutrients to the overlying water as compared to irrigation water inputs. Although loss of N and Se by microbial-mediated volatilization is possible, comparison of selected element concentrations in river inputs and water and sediments from the Salton Sea indicates that most of the N (from fertilizer) and virtually all of the Se (delivered in irrigation water from the Colorado River) discharged to the Sea still reside within its bottom sediment. Laboratory simulation on mixtures of sediment and water from the Salton Sea suggest that sediment is a potential source of N and Se to the water column under aerobic conditions. Hence, it is important that any engineered changes made to the Salton Sea for remediation or for transfer of water out of the basin do not result in remobilization of nutrients and Se from the bottom sediment into the overlying water.

Response of non-added solutes during nutrient addition experiments in streams

NASA Astrophysics Data System (ADS)

Rodriguez-Cardona, B.; Wymore, A.; Koenig, L.; Coble, A. A.; McDowell, W. H.

2015-12-01

Nutrient addition experiments, such as Tracer Additions for Spiraling Curve Characterization (TASCC), have become widely popular as a means to study nutrient uptake dynamics in stream ecosystems. However, the impact of these additions on ambient concentrations of non-added solutes is often overlooked. TASCC addition experiments are ideal for assessing interactions among solutes because it allows for the characterization of multiple solute concentrations across a broad range of added nutrient concentrations. TASCC additions also require the addition of a conservative tracer (NaCl) to track changes in conductivity during the experimental manipulation. Despite its use as a conservative tracer, chloride (Cl) and its associated sodium (Na) might change the concentrations of other ions and non-added nutrients through ion exchange or other processes. Similarly, additions of biologically active solutes might change the concentrations of other non-added solutes. These methodological issues in nutrient addition experiments have been poorly addressed in the literature. Here we examine the response of non-added solutes to pulse additions (i.e. TASCC) of NaCl plus nitrate (NO3-), ammonium, and phosphate across biomes including temperate and tropical forests, and arctic taiga. Preliminary results demonstrate that non-added solutes respond to changes in the concentration of these added nutrients. For example, concentrations of dissolved organic nitrogen (DON) in suburban headwater streams of New Hampshire both increase and decrease in response to NO3- additions, apparently due to biotic processes. Similarly, cations such as potassium, magnesium, and calcium also increase during TASCC experiments, likely due to cation exchange processes associated with Na addition. The response of non-added solutes to short-term pulses of added nutrients and tracers needs to be carefully assessed to ensure that nutrient uptake metrics are accurate, and to detect biotic interactions that may

Nutrient Patterns and Their Association with Socio-Demographic, Lifestyle Factors and Obesity Risk in Rural South African Adolescents

PubMed Central

Pisa, Pedro T.; Pedro, Titilola M.; Kahn, Kathleen; Tollman, Stephen M.; Pettifor, John M.; Norris, Shane A.

2015-01-01

The aim of this study was to identify and describe the diversity of nutrient patterns and how they associate with socio-demographic and lifestyle factors including body mass index in rural black South African adolescents. Nutrient patterns were identified from quantified food frequency questionnaires (QFFQ) in 388 rural South African adolescents between the ages of 11–15 years from the Agincourt Health and Socio-demographic Surveillance System (AHDSS). Principle Component Analysis (PCA) was applied to 25 nutrients derived from QFFQs. Multiple linear regression and partial R2 models were fitted and computed respectively for each of the retained principal component (PC) scores on socio-demographic and lifestyle characteristics including body mass index (BMI) for age Z scores. Four nutrient patterns explaining 79% of the total variance were identified: PCI (26%) was characterized by animal derived nutrients; PC2 (21%) by vitamins, fibre and vegetable oil nutrients; PC3 (19%) by both animal and plant derived nutrients (mixed diet driven nutrients); and PC4 (13%) by starch and folate. A positive and significant association was observed with BMI for age Z scores per 1 standard deviation (SD) increase in PC1 (0.13 (0.02; 0.24); p = 0.02) and PC4 (0.10 (−0.01; 0.21); p = 0.05) scores only. We confirmed variability in nutrient patterns that were significantly associated with various lifestyle factors including obesity. PMID:25984738

Spatial and seasonal variation in the ecological significance of nutrient recycling by larval salamanders in Appalachian headwater streams

Treesearch

S. Conor Keitzer; Reuben R. Goforth

2013-01-01

Salamanders are abundant consumers in many temperate streams and may be important recyclers of biologically essential nutrients, but their ecological role is poorly understood. The ecological significance of nutrient recycling by salamanders may vary spatially and seasonally because of their potentially patchy distribution in streams and the dynamic nature of stream...

Simulation of Long-Term Carbon and Nitrogen Dynamics in Grassland-Based Dairy Farming Systems to Evaluate Mitigation Strategies for Nutrient Losses

PubMed Central

Shah, Ghulam Abbas; Groot, Jeroen C.J.; Shah, Ghulam Mustafa; Lantinga, Egbert A.

2013-01-01

Many measures have been proposed to mitigate gaseous emissions and other nutrient losses from agroecosystems, which can have large detrimental effects for the quality of soils, water and air, and contribute to eutrophication and global warming. Due to complexities in farm management, biological interactions and emission measurements, most experiments focus on analysis of short-term effects of isolated mitigation practices. Here we present a model that allows simulating long-term effects at the whole-farm level of combined measures related to grassland management, animal housing and manure handling after excretion, during storage and after field application. The model describes the dynamics of pools of organic carbon and nitrogen (N), and of inorganic N, as affected by farm management in grassland-based dairy systems. We assessed the long-term effects of delayed grass mowing, housing type (cubicle and sloping floor barns, resulting in production of slurry and solid cattle manure, respectively), manure additives, contrasting manure storage methods and irrigation after application of covered manure. Simulations demonstrated that individually applied practices often result in compensatory loss pathways. For instance, methods to reduce ammonia emissions during storage like roofing or covering of manure led to larger losses through ammonia volatilization, nitrate leaching or denitrification after application, unless extra measures like irrigation were used. A strategy of combined management practices of delayed mowing and fertilization with solid cattle manure that is treated with zeolite, stored under an impermeable sheet and irrigated after application was effective to increase soil carbon stocks, increase feed self-sufficiency and reduce losses by ammonia volatilization and soil N losses. Although long-term datasets (>25 years) of farm nutrient dynamics and loss flows are not available to validate the model, the model is firmly based on knowledge of processes and

Seasonal nutrient dynamics in the Anacostia River (D.C., USA): geochemistry and hydrocarbon biomarkers

NASA Astrophysics Data System (ADS)

Sarraino, S.; Frantz, D. E.; Macavoy, S. E.

2010-12-01

The seasonal biogeochemistry of the urban Anacostia River (Washington D.C. USA) was investigated. Chemical parameters examined include: inorganics (Ca, Mg, Na, S, K, P, NO3, NH4, PO4, B, Ba, Ni, Co); fatty acids and other hydrocarbons; C, N and S stable isotopes; and other water chemistry indicators (hardness, salinity, alkalinity, soluble salts, SAR, TDS). Between April and July 2010, water and sediment were sampled from three tidal freshwater sites along the Anacostia River (UP, MID, and DWN). Two of the selected sites, UP and DWN, are located next to a combined sewage outflow. Water column nutrient analysis shows increasing availability of ammonium (NH4) and nitrate (NO3) at all sites between April and July. At MID, the site showing the highest rates of nutrient growth over the sampling period, NH4 concentrations increase from 0.13 to 1.49 µg/L and NO3 concentrations increase from 0.71 to 2.88 mg/L. A marked NO3 pulse is observed at the DWN site in early May; NO3 concentrations jump from 0.68 to 3.36 mg/L between April 5 and May 6, decreasing to 1.22 mg/L by May 20. Unlike UP and MID, which show NH4 and NO3 increasing concurrently, this NO3 pulse at DWN is accompanied with a decline in NH4 levels, suggestive of an allochthonous NO3 source. Forthcoming stable isotope data are expected to characterize the source of such nitrogen inputs, as well as organic material, throughout the year. Preliminary GC-MS analysis of isolated fatty acids does not explicitly suggest bacterial or higher plant dominance in the spring; however, some notable compounds were identified, such as the PAH fluoranthene, naphthoquinone, and testosterone, as well as a number of cholesterols and other steroids. Higher proportions of bacterial fatty acid biomarkers are expected during the summer. Principle Component Analysis (PCA) of the chemistry data suggests geochemical variables, rather than nutrients, are the driving forces of observed trends. PCA, along with fatty acid characterization and

Effects of land use on lake nutrients: The importance of scale, hydrologic connectivity, and region

USGS Publications Warehouse

Soranno, Patricia A.; Cheruvelil, Kendra Spence; Wagner, Tyler; Webster, Katherine E.; Bremigan, Mary Tate

2015-01-01

Catchment land uses, particularly agriculture and urban uses, have long been recognized as major drivers of nutrient concentrations in surface waters. However, few simple models have been developed that relate the amount of catchment land use to downstream freshwater nutrients. Nor are existing models applicable to large numbers of freshwaters across broad spatial extents such as regions or continents. This research aims to increase model performance by exploring three factors that affect the relationship between land use and downstream nutrients in freshwater: the spatial extent for measuring land use, hydrologic connectivity, and the regional differences in both the amount of nutrients and effects of land use on them. We quantified the effects of these three factors that relate land use to lake total phosphorus (TP) and total nitrogen (TN) in 346 north temperate lakes in 7 regions in Michigan, USA. We used a linear mixed modeling framework to examine the importance of spatial extent, lake hydrologic class, and region on models with individual lake nutrients as the response variable, and individual land use types as the predictor variables. Our modeling approach was chosen to avoid problems of multi-collinearity among predictor variables and a lack of independence of lakes within regions, both of which are common problems in broad-scale analyses of freshwaters. We found that all three factors influence land use-lake nutrient relationships. The strongest evidence was for the effect of lake hydrologic connectivity, followed by region, and finally, the spatial extent of land use measurements. Incorporating these three factors into relatively simple models of land use effects on lake nutrients should help to improve predictions and understanding of land use-lake nutrient interactions at broad scales.

Mapping of macro and micro nutrients of mixed pastures using airborne AisaFENIX hyperspectral imagery

NASA Astrophysics Data System (ADS)

Pullanagari, R. R.; Kereszturi, Gábor; Yule, I. J.

2016-07-01

On-farm assessment of mixed pasture nutrient concentrations is important for animal production and pasture management. Hyperspectral imaging is recognized as a potential tool to quantify the nutrient content of vegetation. However, it is a great challenge to estimate macro and micro nutrients in heterogeneous mixed pastures. In this study, canopy reflectance data was measured by using a high resolution airborne visible-to-shortwave infrared (Vis-SWIR) imaging spectrometer measuring in the wavelength region 380-2500 nm to predict nutrient concentrations, nitrogen (N) phosphorus (P), potassium (K), sulfur (S), zinc (Zn), sodium (Na), manganese (Mn) copper (Cu) and magnesium (Mg) in heterogeneous mixed pastures across a sheep and beef farm in hill country, within New Zealand. Prediction models were developed using four different methods which are included partial least squares regression (PLSR), kernel PLSR, support vector regression (SVR), random forest regression (RFR) algorithms and their performance compared using the test data. The results from the study revealed that RFR produced highest accuracy (0.55 ⩽ R2CV ⩽ 0.78; 6.68% ⩽ nRMSECV ⩽ 26.47%) compared to all other algorithms for the majority of nutrients (N, P, K, Zn, Na, Cu and Mg) described, and the remaining nutrients (S and Mn) were predicted with high accuracy (0.68 ⩽ R2CV ⩽ 0.86; 13.00% ⩽ nRMSECV ⩽ 14.64%) using SVR. The best training models were used to extrapolate over the whole farm with the purpose of predicting those pasture nutrients and expressed through pixel based spatial maps. These spatially registered nutrient maps demonstrate the range and geographical location of often large differences in pasture nutrient values which are normally not measured and therefore not included in decision making when considering more effective ways to utilized pasture.

Dynamics of the biological properties of soil and the nutrient release of Amorpha fruticosa L. litter in soil polluted by crude oil.

PubMed

Zhang, Xiaoxi; Liu, Zengwen; Luc, Nhu Trung; Liang, Xiao; Liu, Xiaobo

2015-11-01

Litter from Amorpha fruticosa, a potential phytoremediating plant, was collected and used in a decomposition experiment that involved the litterbag in soil polluted by crude oil. The dynamics of the biological properties of soil and the nutrient release of the litter were detected. The results indicated that (1) in lightly polluted soil (LP, petroleum concentration was 15 g kg(-1)), the bacteria (including actinomycetes), and fungi populations were significant higher than those in unpolluted soil (CK) at the 1st month after pollution, and the bacteria (including actinomycetes) populations were higher than those in the CK at the 6th and 12th months. In moderately polluted soil (MP, 30 g kg(-1)), the bacteria (including actinomycetes) populations were higher than those in the CK at the 1st and 6th months, whereas only the actinomycetes population was greater than that in the CK at the 12th month. In seriously polluted soil (SP, 45 g kg(-1)), only the fungi population was higher than that in the CK at the 6th month. (2) The activities of soil protease, carboxymethyl cellulase, and sucrase were generally inhibited in polluted soil. Peroxidase activity was generally inhibited in the LP and MP soil, and polyphenol oxidase activity was inhibited in the SP soil at 6-12 months. (3) At the end of litter decomposition, the LP soil significantly increased the release rate of all nutrients, except for K. The MP soil reduced the release rate of Fe and Mn, whereas it increased that of C and Cu. The SP soil decreased the release rate of all nutrients except for Cu and Zn. In conclusion, SP by crude oil would lead to limitations in the release of nutrients from the litter and to decreases in the community stability of a phytoremediating plant. A. fruticosa could only be used in phytoremediation of polluted soil at concentrations below 45 g kg(-1) (crude).

Root cortical aerenchyma inhibits radial nutrient transport in maize (Zea mays).

PubMed

Hu, Bo; Henry, Amelia; Brown, Kathleen M; Lynch, Jonathan P

2014-01-01

Formation of root cortical aerenchyma (RCA) can be induced by nutrient deficiency. In species adapted to aerobic soil conditions, this response is adaptive by reducing root maintenance requirements, thereby permitting greater soil exploration. One trade-off of RCA formation may be reduced radial transport of nutrients due to reduction in living cortical tissue. To test this hypothesis, radial nutrient transport in intact roots of maize (Zea mays) was investigated in two radiolabelling experiments employing genotypes with contrasting RCA. In the first experiment, time-course dynamics of phosphate loading into the xylem were measured from excised nodal roots that varied in RCA formation. In the second experiment, uptake of phosphate, calcium and sulphate was measured in seminal roots of intact young plants in which variation in RCA was induced by treatments altering ethylene action or genetic differences. In each of three paired genotype comparisons, the rate of phosphate exudation of high-RCA genotypes was significantly less than that of low-RCA genotypes. In the second experiment, radial nutrient transport of phosphate and calcium was negatively correlated with the extent of RCA for some genotypes. The results support the hypothesis that RCA can reduce radial transport of some nutrients in some genotypes, which could be an important trade-off of this trait.

Physical determinants of phytoplankton production, algal stoichiometry, and vertical nutrient fluxes.

PubMed

Jäger, Christoph G; Diehl, Sebastian; Emans, Maximilian

2010-04-01

Most phytoplankters face opposing vertical gradients in light versus nutrient supplies but have limited capacities for vertical habitat choice. We therefore explored a dynamical model of negatively buoyant algae inhabiting a one-dimensional water column to ask how water column depth and turbulence constrain total (areal) phytoplankton biomass. We show that the population persistence boundaries in water column depth-turbulence space are set by sinking losses and light limitation but that nutrients are most limiting to total biomass in water columns that are neither too shallow or too weakly mixed (where sinking losses prevail) nor too deep and turbulent (where light limitation prevails). In shallow waters, the most strongly limiting process is nutrient influx to the bottom of the water column (e.g., from sediments). In deep waters, the most strongly limiting process is turbulent upward transport of nutrients to the photic zone. Consequently, the highest total biomasses are attained in turbulent waters at intermediate water column depths and in deep waters at intermediate turbulences. These patterns are insensitive to the assumption of fixed versus flexible algal carbon-to-nutrient stoichiometry, and they arise irrespective of whether the water column is a surface layer above a deep water compartment or has direct contact with sediments.

History of nutrient inputs to the northeastern United States, 1930-2000

NASA Astrophysics Data System (ADS)

Hale, Rebecca L.; Hoover, Joseph H.; Wollheim, Wilfred M.; Vörösmarty, Charles J.

2013-04-01

Humans have dramatically altered nutrient cycles at local to global scales. We examined changes in anthropogenic nutrient inputs to the northeastern United States (NE) from 1930 to 2000. We created a comprehensive time series of anthropogenic N and P inputs to 437 counties in the NE at 5 year intervals. Inputs included atmospheric N deposition, biological N2 fixation, fertilizer, detergent P, livestock feed, and human food. Exports included exports of feed and food and volatilization of ammonia. N inputs to the NE increased throughout the study period, primarily due to increases in atmospheric deposition and fertilizer. P inputs increased until 1970 and then declined due to decreased fertilizer and detergent inputs. Livestock consistently consumed the majority of nutrient inputs over time and space. The area of crop agriculture declined during the study period but consumed more nutrients as fertilizer. We found that stoichiometry (N:P) of inputs and absolute amounts of N matched nutritional needs (livestock, humans, crops) when atmospheric components (N deposition, N2 fixation) were not included. Differences between N and P led to major changes in N:P stoichiometry over time, consistent with global trends. N:P decreased from 1930 to 1970 due to increased inputs of P, and increased from 1970 to 2000 due to increased N deposition and fertilizer and decreases in P fertilizer and detergent use. We found that nutrient use is a dynamic product of social, economic, political, and environmental interactions. Therefore, future nutrient management must take into account these factors to design successful and effective nutrient reduction measures.

Microbial enzyme activity, nutrient uptake and nutrient limitation in forested streams

Treesearch

Brian H. Hill; Frank H. McCormick; Bret C. Harvey; Sherri L. Johnson; Melvin L. Warren; Colleen M. Elonen

2010-01-01

The flow of organic matter and nutrients from catchments into the streams draining them and the biogeochemical transformations of organic matter and nutrients along flow paths are fundamental processes instreams (Hynes,1975; Fisher, Sponseller & Heffernan, 2004). Microbial biofilms are often the primary interface for organic matter and nutrient uptake and...

Interactions among hydrogeomorphology, vegetation, and nutrient biogeochemistry in floodplain ecosystems

USGS Publications Warehouse

Noe, G.B.; Shroder, John F.

2013-01-01

Hydrogeomorphic, vegetative, and biogeochemical processes interact in floodplains resulting in great complexity that provides opportunities to better understand linkages among physical and biological processes in ecosystems. Floodplains and their associated river systems are structured by four-dimensional gradients of hydrogeomorphology: longitudinal, lateral, vertical, and temporal components. These four dimensions create dynamic hydrologic and geomorphologic mosaics that have a large imprint on the vegetation and nutrient biogeochemistry of floodplains. Plant physiology, population dynamics, community structure, and productivity are all very responsive to floodplain hydrogeomorphology. The strength of this relationship between vegetation and hydrogeomorphology is evident in the use of vegetation as an indicator of hydrogeomorphic processes. However, vegetation also influences hydrogeomorphology by modifying hydraulics and sediment entrainment and deposition that typically stabilize geomorphic patterns. Nitrogen and phosphorus biogeochemistry commonly influence plant productivity and community composition, although productivity is not limited by nutrient availability in all floodplains. Conversely, vegetation influences nutrient biogeochemistry through direct uptake and storage as well as production of organic matter that regulates microbial biogeochemical processes. The biogeochemistries of nitrogen and phosphorus cycling are very sensitive to spatial and temporal variation in hydrogeomorphology, in particular floodplain wetness and sedimentation. The least-studied interaction is the direct effect of biogeochemistry on hydrogeomorphology, but the control of nutrient availability over organic matter decomposition and thus soil permeability and elevation is likely important. Biogeochemistry also has the more documented but indirect control of hydrogeomorphology through regulation of plant biomass. In summary, the defining characteristics of floodplain ecosystems

Interactions among hydrogeomorphology, vegetation, and nutrient biogeochemistry in floodplain ecosystems

USGS Publications Warehouse

Noe, G.B.

2013-01-01

Hydrogeomorphic, vegetative, and biogeochemical processes interact in floodplains resulting in great complexity that provides opportunities to better understand linkages among physical and biological processes in ecosystems. Floodplains and their associated river systems are structured by four dimensional gradients of hydrogeomorphology: longitudinal, lateral, vertical, and temporal components. These four dimensions create dynamic hydrologic and geomorphologic mosaics that have a large imprint on the vegetation and nutrient biogeochemistry of floodplains. Plant physiology, population dynamics, community structure, and productivity are all very responsive to floodplain hydrogeomorphology. The strength of this relationship between vegetation and hydrogeomorphology is evident in the use of vegetation as an indicator of hydrogeomorphic processes. However, vegetation also influences hydrogeomorphology by modifying hydraulics and sediment entrainment and deposition that typically stabilize geomorphic patterns. Nitrogen and phosphorus biogeochemistry commonly influence plant productivity and community composition, although productivity is not limited by nutrient availability in all floodplains. Conversely, vegetation influences nutrient biogeochemistry through direct uptake and storage as well as production of organic matter that regulates microbial biogeochemical processes. The biogeochemistries of nitrogen and phosphorus cycling are very sensitive to spatial and temporal variation in hydrogeomorphology, in particular floodplain wetness and sedimentation. The least studied interaction is the direct effect of biogeochemistry on hydrogeomorphology, but the control of nutrient availability over organic matter decomposition and thus soil permeability and elevation is likely important. Biogeochemistry also has the more documented but indirect control of hydrogeomorphology through regulation of plant biomass. In summary, the defining characteristics of floodplain ecosystems

Soil nutrient availability and reproductive effort drive patterns in nutrient resorption in Pentachlethra macroloba

Treesearch

K. L. Tully; Tana Wood; A. M. Schwantes; D. Lawrence

2013-01-01

The removal of nutrients from senescing tissues, nutrient resorption, is a key strategy for conserving nutrients in plants. However, our understanding of what drives patterns of nutrient resorption in tropical trees is limited. We examined the effects of nutrient sources (stand-level and tree-level soil fertility) and sinks (reproductive effort) on nitrogen (N) and...

Significant drug-nutrient interactions.

PubMed

Kirk, J K

1995-04-01

Many nutrients substantially interfere with pharmacotherapeutic goals. The presence of certain nutrients in the gastrointestinal tract affects the bioavailability and disposition of many oral medications. Drug-nutrient interactions can also have positive effects that result in increased drug absorption or reduced gastrointestinal irritation. Knowing the significant drug-nutrient interactions can help the clinician identify the nutrients to avoid with certain medications, as well as the therapeutic agents that should be administered with food. This information can be used to educate patients and optimize pharmacotherapy.

The role of high frequency monitoring in understanding nutrient pollution processes to address catchment management issues

NASA Astrophysics Data System (ADS)

Quinn, Paul; Jonczyk, Jennine; Owen, Gareth; Barber, Nick; Adams, Russell; ODonnell, Greg; EdenDTC Team

2015-04-01

The process insights afforded to catchment scientists through the availability of high frequency time series of hydrological and nutrient pollution datasets are invaluable. However, the observations reveal both good and bad news for the WFD. Data for flow, N, P and sediment (taken at 30 min intervals) from the River Eden Demonstration Test Catchment and several other detailed UK studies, will be used to discuss nutrient fluxes in catchments between 1km2 and 10km2. Monitoring of the seasonal groundwater status and the forensic analysis of numerous storm events have identified dominant flow pathways and nutrient losses. Nonetheless, many of the management questions demanded by the WFD will not be resolved by collecting these datasets alone. Long term trends are unlikely to be determined from these data and even if trends are found they are unlikely to be accurately apportioned to the activities that have caused them. The impacts of where and when an action takes place will not be detected at the catchment scale and the cost effectiveness of any mitigation method is unlikely to be quantifiable. Even in small well instrumented catchments the natural variability in rainfall, antecedent patterns and the variability in farming practices will mask any identifiable catchment scale signal. This does not mean the cost of the data acquisition has been wasted, it just means that the knowledge and expertise gained from these data should be used in new novel ways. It will always be difficult to quantify the actual losses occurring at the farm or field scale, but the positive benefits of any mitigation may still be approximated. The evidence for the rate of nutrient removal from a local sediment trap, wetland and a pond can be shown with high resolution datasets. However, any quantifiable results are still highly localised and the transfer and upscaling of any findings must be done with care. Modelling these datasets is also possible and the nature of models have evolved in the

Nutrient and growth responses of Leersia oryzoides, rice cutgrass, to varying degrees of soil saturation and water nitrogen concentration

USDA-ARS?s Scientific Manuscript database

Leersia oryzoides (rice cutgrass) is an obligate wetland plant common to agricultural ditches. The objective of this greenhouse study was to quantify the allocation of nutrients and biomass to different plant components exposed to various soil moisture and aqueous N input regimes. Plants in the con...

A novel approach to selecting and weighting nutrients for nutrient profiling of foods and diets.

PubMed

Arsenault, Joanne E; Fulgoni, Victor L; Hersey, James C; Muth, Mary K

2012-12-01

Nutrient profiling of foods is the science of ranking or classifying foods based on their nutrient composition. Most profiling systems use similar weighting factors across nutrients due to lack of scientific evidence to assign levels of importance to nutrients. Our aim was to use a statistical approach to determine the nutrients that best explain variation in Healthy Eating Index (HEI) scores and to obtain β-coefficients for the nutrients for use as weighting factors for a nutrient-profiling algorithm. We used a cross-sectional analysis of nutrient intakes and HEI scores. Our subjects included 16,587 individuals from the National Health and Nutrition Examination Survey 2005-2008 who were 2 years of age or older and not pregnant. Our main outcome measure was variation (R(2)) in HEI scores. Linear regression analyses were conducted with HEI scores as the dependent variable and all possible combinations of 16 nutrients of interest as independent variables, with covariates age, sex, and ethnicity. The analyses identified the best 1-nutrient variable model (with the highest R(2)), the best 2-nutrient variable model, and up to the best 16-nutrient variable model. The model with 8 nutrients explained 65% of the variance in HEI scores, similar to the models with 9 to 16 nutrients, but substantially higher than previous algorithms reported in the literature. The model contained five nutrients with positive β-coefficients (ie, protein, fiber, calcium, unsaturated fat, and vitamin C) and three nutrients with negative coefficients (ie, saturated fat, sodium, and added sugar). β-coefficients from the model were used as weighting factors to create an algorithm that generated a weighted nutrient density score representing the overall nutritional quality of a food. The weighted nutrient density score can be easily calculated and is useful for describing the overall nutrient quality of both foods and diets. Copyright © 2012 Academy of Nutrition and Dietetics. Published by

Soluble dust as source of nutrients to the oceans and the role of humans

NASA Astrophysics Data System (ADS)

Tsigaridis, K.; Kanakidou, M.; Myriokefalitakis, S.; Nikolaou, P.; Daskalakis, N.; Theodosi, C.; Nenes, A.; Mihalopoulos, N.

2014-12-01

Atmospheric deposition of trace constituents, both of natural and anthropogenic origin, can act as a nutrient source into the open ocean and affect marine ecosystem functioning and subsequently the exchange of CO2 between the atmosphere and the global ocean. Dust is known as a major source of nutrients (Fe and P) into the atmosphere, but only a fraction of these nutrients is released in soluble form that can be assimilated by the ecosystems. Dust is also known to enhance N deposition by interacting with anthropogenic pollutants and neutralisation of part of the acidity of the atmosphere by crustal alkaline species. The link between the soluble iron (Fe) and phosphorus (P) atmospheric deposition and atmospheric acidity, as well as anthropogenic sources, is investigated. The global atmospheric Fe, P and N cycle are parameterized in the global 3-D chemical transport model TM4-ECPL. Both primary emissions of total and soluble Fe and P associated with dust and combustion processes are taken into account, as well as inorganic and organic N emissions. The impact of atmospheric acidity on nutrient solubility is parameterised based on experimental findings. The model results are evaluated by comparison with available observations. The impact of air-quality changes on soluble nutrient deposition is studied by performing sensitivity simulations using preindustrial, present and future emission scenarios. The response of the chemical composition of nutrient-containing aerosols to environmental changes is demonstrated and quantified. This work has been supported by ARISTEIA - PANOPLY grant co-financed by European Union (ESF) and Greek national funds NSRF.

Research to Inform Nutrient Thresholds and Prioritization of Watersheds for Nutrient Management

EPA Science Inventory

The information in this presentation focuses on SSWR's 4.02 project, which will advance the science needed to inform decisions to prioritize watersheds and nutrient sources for nutrient management and define appropriate nutrient levels for the nation’s waters, two importan...

Dynamics of Short-Term Phosphorus Uptake by Intact Mycorrhizal and Non-mycorrhizal Maize Plants Grown in a Circulatory Semi-Hydroponic Cultivation System.

PubMed

Garcés-Ruiz, Mónica; Calonne-Salmon, Maryline; Plouznikoff, Katia; Misson, Coralie; Navarrete-Mier, Micaela; Cranenbrouck, Sylvie; Declerck, Stéphane

2017-01-01

A non-destructive cultivation system was developed to study the dynamics of phosphorus (Pi) uptake by mycorrhizal and non-mycorrhizal maize plantlets. The system consisted of a plant container connected via silicon tubes to a glass bottle containing a nutrient solution supplemented with Pi. The nutrient solution is pumped with a peristaltic pump to the upper part of the container via the silicon tubes and the solution percolate through the plantlet container back into the glass bottle. Pi is sampled from the glass bottle at regular intervals and concentration evaluated. Maize plantlets were colonized by the AMF Rhizophagus irregularis MUCL 41833 and Pi uptake quantified at fixed intervals (9, 21, and 42 h) from the depletion of the Pi in the nutrient solution flowing through the plantlets containers. Plants and fungus grew well in the perlite substrate. The concentration of Pi in the bottles followed an almost linear decrease over time, demonstrating a depletion of Pi in the circulating solution and a concomitant uptake/immobilization by the plantlet-AMF associates in the containers. The Pi uptake rate was significantly increased in the AMF-colonized plantlets (at 9 and 21 h) as compared to non-colonized plantlets, although no correlation was noticed with plant growth or P accumulation in shoots. The circulatory semi-hydroponic cultivation system developed was adequate for measuring Pi depletion in a nutrient solution and by corollary Pi uptake/immobilization by the plant-AMF associates. The measurements were non-destructive so that the time course of Pi uptake could be monitored without disturbing the growth of the plant and its fungal associate. The system further opens the door to study the dynamics of other micro and macro-nutrients as well as their uptake under stressed growth conditions such as salinity, pollution by hydrocarbon contaminants or potential toxic elements.

A new theory of plant-microbe nutrient competition resolves inconsistencies between observations and model predictions.

PubMed

Zhu, Qing; Riley, William J; Tang, Jinyun

2017-04-01

Terrestrial plants assimilate anthropogenic CO 2 through photosynthesis and synthesizing new tissues. However, sustaining these processes requires plants to compete with microbes for soil nutrients, which therefore calls for an appropriate understanding and modeling of nutrient competition mechanisms in Earth System Models (ESMs). Here, we survey existing plant-microbe competition theories and their implementations in ESMs. We found no consensus regarding the representation of nutrient competition and that observational and theoretical support for current implementations are weak. To reconcile this situation, we applied the Equilibrium Chemistry Approximation (ECA) theory to plant-microbe nitrogen competition in a detailed grassland 15 N tracer study and found that competition theories in current ESMs fail to capture observed patterns and the ECA prediction simplifies the complex nature of nutrient competition and quantitatively matches the 15 N observations. Since plant carbon dynamics are strongly modulated by soil nutrient acquisition, we conclude that (1) predicted nutrient limitation effects on terrestrial carbon accumulation by existing ESMs may be biased and (2) our ECA-based approach may improve predictions by mechanistically representing plant-microbe nutrient competition. © 2016 by the Ecological Society of America.