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.

Nitrogen dynamics in oak forest soils along a historical deposition gradient

Treesearch

Ralph E. J. Boerner; Elaine Kennedy Sutherland

1995-01-01

This study quantified soil nutrient status and N mineralization/nitrification potentials in soils of oakdominated, unmanaged forest stands in seven experimental forests ranging along a historical and current acidic deposition gradient from southern Illinois to central West Virginia, U.S.A. Among these seven sites (that spanned 8.5º of longitude) soil pH and Ca...

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.

The Role of Fine Root Dynamics in the N and P Cycles of Regenerating Upland Oak-Hickory Forests

Treesearch

Travis W. Idol; Phillip E. Pope; Jennifer Tucker; Felix, Jr. Ponder

1998-01-01

ln naturally regenerating hardwood forest stands, inputs of organic matter and nutrients from fine root turnover and decomposition are significant but not well-quantified. Four forest stands in southern Indiana-aged 6, 12, 31, and approximately 100 years since clearcutting at the time of the study-were chosen to represent the different developmental stages of upland...

Quantifying the Temporal Inequality of Nutrient Loads with a Novel Metric

NASA Astrophysics Data System (ADS)

Gall, H. E.; Schultz, D.; Rao, P. S.; Jawitz, J. W.; Royer, M.

2015-12-01

Inequality is an emergent property of many complex systems. For a given series of stochastic events, some events generate a disproportionately large contribution to system responses compared to other events. In catchments, such responses cause streamflow and solute loads to exhibit strong temporal inequality, with the vast majority of discharge and solute loads exported during short periods of time during which high-flow events occur. These periods of time are commonly referred to as "hot moments". Although this temporal inequality is widely recognized, there is currently no uniform metric for assessing it. We used a novel application of Lorenz Inequality, a method commonly used in economics to quantify income inequality, to quantify the spatial and temporal inequality of streamflow and nutrient (nitrogen and phosphorus) loads exported to the Chesapeake Bay. Lorenz Inequality and the corresponding Gini Coefficient provide an analytical tool for quantifying inequality that can be applied at any temporal or spatial scale. The Gini coefficient (G) is a formal measure of inequality that varies from 0 to 1, with a value of 0 indicating perfect equality (i.e., fluxes and loads are constant in time) and 1 indicating perfect inequality (i.e., all of the discharge and solute loads are exported during one instant in time). Therefore, G is a simple yet powerful tool for providing insight into the temporal inequality of nutrient transport. We will present the results of our detailed analysis of streamflow and nutrient time series data collected since the early 1980's at 30 USGS gauging stations in the Chesapeake Bay watershed. The analysis is conducted at an annual time scale, enabling trends and patterns to be assessed both temporally (over time at each station) and spatially (for the same period of time across stations). The results of this analysis have the potential to create a transformative new framework for identifying "hot moments", improving our ability to temporally and spatially target implementation of best management practices to ultimately improve water quality in the Chesapeake Bay. This method also provides insight into the temporal scales at which hydrologic and biogeochemical variability dominate nutrient export dynamics.

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

BELOWGROUND NITROGEN UPTAKE AND ALLOCATION ...

EPA Pesticide Factsheets

Anthropogenic nitrogen inputs coupled with rising sea level complicate predictions of marsh stability. As marsh stability is a function of its vegetation, it is important to understand the mechanisms that drive community dynamics. Many studies have examined aboveground dynamics and nutrient cycling, but few have studied the belowground uptake and allocation of nitrogen. Literature suggests that D. spicata may dominate the marsh platform in nutrient-rich conditions, though the mechanism driving the vegetation shift is unclear. Our study examines belowground nutrient uptake and allocation underlying these patterns. To determine whether D. spicata is a more efficient scavenger of nutrients than S. alterniflora we performed a 15N pulse-chase experiment. Tracer was added to mesocosms growing D. spicata and S. alterniflora in monoculture. After the initial pulse, a subset of pots were sacrificed weekly and partitioned into detailed depth intervals for 15N analysis of several belowground pools: live coarse and fine roots, live rhizomes, dead organic matter, and bulk sediment. Comparisons between D. spicata and S. alterniflora uptake and allocation can explain mechanisms of competitive advantage and predictions of D. spicata dominance. Additionally, we used denitrification enzyme assays (DEA) and greenhouse gas slurries to quantify denitrification rates and potentials. Initial results suggest that the vegetation types support similar N-relevant microbial communities. Th

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 field investigations show that ground-water discharge into the Lynch Cove area of Hood Canal is highly dynamic and strongly affected by the large tidal range. In areas with a steep shoreline and steep hydraulic gradient, ground-water discharge is spatially concentrated in or near the intertidal zone, with increased discharge during low tide. Topographically flat areas with weak hydraulic gradients had more spatial variability, including larger areas of seawater recirculation and more widely dispersed discharge. Measured total-dissolved-nitrogen concentrations in ground water ranged from below detection limits to 2.29 milligrams per liter and the total load entering Lynch Cove was estimated to be approximately 98 ? 10.3 metric tons per year (MT/yr). This estimate is based on net freshwater seepage rates from Lee-type seepage meter measurements and can be compared to estimates derived from geochemical tracer mass balance estimates (radon and radium) of 231 to 749 MT/yr, and previous water-mass-balance estimates (14 to 47 MT/ yr). Uncertainty in these loading estimates is introduced by complex biogeochemical cycles of relevant nutrient species, the representativeness of measurement sites, and by energetic dynamics at the coastal aquifer-seawater interface caused by tidal forcing.

Soil incorporation of logging residue affects fine-root and mycorrhizal root-tip dynamics of young loblolly pine clones

Treesearch

Seth G. Pritchard; Chris A. Maier; Kurt H. Johnsen; Andrea J. Grabman; Anne P. Chalmers

2010-01-01

Loblolly pine (Pinus taeda L.) plantations cover a large geographic area of the southeastern USA and supply a large proportion of the nation’s wood products. Research on management strategies designed to maximize wood production while also optimizing nutrient use efficiency and soil C sequestration is needed. We used minirhizotrons to quantify the effects of...

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.

Effects of Atrazine, Metolachlor, Carbaryl and Chlorothalonil on Benthic Microbes and Their Nutrient Dynamics

PubMed Central

Elias, Daniel; Bernot, Melody J.

2014-01-01

Atrazine, metolachlor, carbaryl, and chlorothalonil are detected in streams throughout the U.S. at concentrations that may have adverse effects on benthic microbes. Sediment samples were exposed to these pesticides to quantify responses of ammonium, nitrate, and phosphate uptake by the benthic microbial community. Control uptake rates of sediments had net remineralization of nitrate (−1.58 NO3 µg gdm−1 h−1), and net assimilation of phosphate (1.34 PO4 µg gdm−1 h−1) and ammonium (0.03 NH4 µg gdm−1 h−1). Metolachlor decreased ammonium and phosphate uptake. Chlorothalonil decreased nitrate remineralization and phosphate uptake. Nitrate, ammonium, and phosphate uptake rates are more pronounced in the presence of these pesticides due to microbial adaptations to toxicants. Our interpretation of pesticide availability based on their water/solid affinities supports no effects for atrazine and carbaryl, decreasing nitrate remineralization, and phosphate assimilation in response to chlorothalonil. Further, decreased ammonium and phosphate uptake in response to metolachlor is likely due to affinity. Because atrazine target autotrophs, and carbaryl synaptic activity, effects on benthic microbes were not hypothesized, consistent with results. Metolachlor and chlorothalonil (non-specific modes of action) had significant effects on sediment microbial nutrient dynamics. Thus, pesticides with a higher affinity to sediments and/or broad modes of action are likely to affect sediment microbes' nutrient dynamics than pesticides dissolved in water or specific modes of action. Predicted nutrient uptake rates were calculated at mean and peak concentrations of metolachlor and chlorothalonil in freshwaters using polynomial equations generated in this experiment. We concluded that in natural ecosystems, peak chlorothalonil and metolachlor concentrations could affect phosphate and ammonium by decreasing net assimilation, and nitrate uptake rates by decreasing remineralization, relative to mean concentrations of metolachlor and chlorothalonil. Our regression equations can complement models of nitrogen and phosphorus availability in streams to predict potential changes in nutrient dynamics in response to pesticides in freshwaters. PMID:25275369

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

The unseen iceberg: Plant roots in arctic tundra

USGS Publications Warehouse

Iverson, Colleen M.; Sloan, Victoria L.; Sullivan, Patrick F.; Euskirchen, E.S.; McGuire, A. David; Norby, Richard J.; Walker, Anthony P.; Warren, Jeffrey M.; Wullschleger, Stan D.

2015-01-01

Plant roots play a critical role in ecosystem function in arctic tundra, but root dynamics in these ecosystems are poorly understood. To address this knowledge gap, we synthesized available literature on tundra roots, including their distribution, dynamics and contribution to ecosystem carbon and nutrient fluxes, and highlighted key aspects of their representation in terrestrial biosphere models. Across all tundra ecosystems, belowground plant biomass exceeded aboveground biomass, with the exception of polar desert tundra. Roots were shallowly distributed in the thin layer of soil that thaws annually, and were often found in surface organic soil horizons. Root traits – including distribution, chemistry, anatomy and resource partitioning – play an important role in controlling plant species competition, and therefore ecosystem carbon and nutrient fluxes, under changing climatic conditions, but have only been quantified for a small fraction of tundra plants. Further, the annual production and mortality of fine roots are key components of ecosystem processes in tundra, but extant data are sparse. Tundra root traits and dynamics should be the focus of future research efforts. Better representation of the dynamics and characteristics of tundra roots will improve the utility of models for the evaluation of the responses of tundra ecosystems to changing environmental conditions.

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-free nutrient consumption free is shorter. Hence, stress,threshold depends directly on free. In other words, the threshold rate of stress-sensitive nutrient consumption is higher when the stress-free rate of nutrient consumption increases. Modulated rotation of the impeller, superimposed on steady shear, increases stress,threshold when free is constant, and stress,threshold depends directly on the amplitude A of these angular velocity modulations.

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 in the rapidly changing polar regions.

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.

Revisiting soil carbon and nitrogen sampling: quantitative pits versus rotary cores

USDA-ARS?s Scientific Manuscript database

Increasing atmospheric carbon dioxide and its feedbacks with global climate have sparked renewed interest in quantifying ecosystem carbon (C) budgets, including quantifying belowground pools. Belowground nutrient budgets require accurate estimates of soil mass, coarse fragment content, and nutrient ...

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.

Quantifying the Urban and Rural Nutrient Fluxes to Lake Erie Using a Paired Watershed Approach

NASA Astrophysics Data System (ADS)

Hopkins, M.; Beck, M.; Rossi, E.; Luh, N.; Allen-King, R. M.; Lowry, C.

2016-12-01

Excess nutrients have a detrimental impact on the water quality of Lake Erie, specifically nitrate and phosphate, which can lead to toxic algae blooms. Algae blooms have negatively impacted Lake Erie, which is the main source of drinking water for many coastal Great Lake communities. In 2014 the city of Toledo, Ohio was forced to shut down its water treatment plant due to these toxic algae blooms. The objective of this research is to quantify surface water nutrient fluxes to the eastern basin of Lake Erie using a paired watershed approach. Three different western New York watersheds that feed Lake Erie were chosen based on land use and areal extent: one small urban, one small rural, and one large rural. These paired watersheds were chosen to represent a range of sources of potential nutrient loading to the lake. Biweekly water samples were taken from the streams during the 2015-2016 winter to summer seasonal transition to quantify springtime snow melt effects on nutrient fluxes. These results were compared to the previous year samples, collected over the summer of 2015, which represented wetter conditions. Phosphorous levels were assessed using the ascorbic acid colorimetric assay, while nitrate was analyzed by anion-exchange chromatography. Stream gaging was used to obtain flow measurements and establish a rating curve, which was incorporated to quantify seasonal nutrient fluxes entering the lake. Patterns in the nutrient levels show higher level of nutrients in the rural watersheds with a decrease in concentration over the winter to spring transition. However, nutrient patterns in the urban stream show relatively constant patters of nutrient flux, which is independent of seasonal transition or stream discharge. A comparison of wet and dry seasons shows higher nutrient concentrations during summers with greater rainfall. By identifying the largest contributors of each nutrient, we can better allocate limited attenuation resources.

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.

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.

The unseen iceberg: plant roots in arctic tundra.

PubMed

Iversen, Colleen M; Sloan, Victoria L; Sullivan, Patrick F; Euskirchen, Eugenie S; McGuire, A David; Norby, Richard J; Walker, Anthony P; Warren, Jeffrey M; Wullschleger, Stan D

2015-01-01

Plant roots play a critical role in ecosystem function in arctic tundra, but root dynamics in these ecosystems are poorly understood. To address this knowledge gap, we synthesized available literature on tundra roots, including their distribution, dynamics and contribution to ecosystem carbon and nutrient fluxes, and highlighted key aspects of their representation in terrestrial biosphere models. Across all tundra ecosystems, belowground plant biomass exceeded aboveground biomass, with the exception of polar desert tundra. Roots were shallowly distributed in the thin layer of soil that thaws annually, and were often found in surface organic soil horizons. Root traits - including distribution, chemistry, anatomy and resource partitioning - play an important role in controlling plant species competition, and therefore ecosystem carbon and nutrient fluxes, under changing climatic conditions, but have only been quantified for a small fraction of tundra plants. Further, the annual production and mortality of fine roots are key components of ecosystem processes in tundra, but extant data are sparse. Tundra root traits and dynamics should be the focus of future research efforts. Better representation of the dynamics and characteristics of tundra roots will improve the utility of models for the evaluation of the responses of tundra ecosystems to changing environmental conditions. No claim to original US Government works New Phytologist © 2014 New Phytologist Trust.

Hyperspectral Remote Sensing of New England Coastal Waters to Predict Seagrass Distribution

EPA Science Inventory

The U.S. Environmental Protection Agency is working to improve its ability to quantify and predict aquatic (freshwater, estuarine, marine) ecosystem response and recovery to changing nutrient loads. The objective of this research is to quantify the relationship of nutrients with...

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.

Global changes in biogeochemical cycles in response to human activities

NASA Technical Reports Server (NTRS)

Moore, Berrien, III; Melillo, Jerry

1994-01-01

The main objective of our research was to characterize biogeochemical cycles at continental and global scales in both terrestrial and aquatic ecosystems. This characterization applied to both natural ecosystems and those disturbed by human activity. The primary elements of interest were carbon and nitrogen and the analysis sought to quantify standing stocks and dynamic cycling processes. The translocation of major nutrients from the terrestrial landscape to the atmosphere (via trace gases) and to fluvial systems (via leaching, erosional losses, and point source pollution) were of particular importance to this study. Our aim was to develop the first generation of Earth System Models. Our research was organized around the construction and testing of component biogeochemical models which treated terrestrial ecosystem processes, aquatic nutrient transport through drainage basins, and trace gas exchanges at the continental and global scale. A suite of three complementary models were defined within this construct. The models were organized to operate at a 1/2 degree latitude by longitude level of spatial resolution and to execute at a monthly time step. This discretization afforded us the opportunity to understand the dynamics of the biosphere down to subregional scales, while simultaneously placing these dynamics into a global context.

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.

Regulation of C:N:P stoichiometry of microbes and soil organic matter by optimizing enzyme allocation: an omics-informed model study

NASA Astrophysics Data System (ADS)

Song, Y.; Yao, Q.; Wang, G.; Yang, X.; Mayes, M. A.

2017-12-01

Increasing evidences is indicating that soil organic matter (SOM) decomposition and stabilization process is a continuum process and controlled by both microbial functions and their interaction with minerals (known as the microbial efficiency-matrix stabilization theory (MEMS)). Our metagenomics analysis of soil samples from both P-deficit and P-fertilization sites in Panama has demonstrated that community-level enzyme functions could adapt to maximize the acquisition of limiting nutrients and minimize energy demand for foraging (known as the optimal foraging theory). This optimization scheme can mitigate the imbalance of C/P ratio between soil substrate and microbial community and relieve the P limitation on microbial carbon use efficiency over the time. Dynamic allocation of multiple enzyme groups and their interaction with microbial/substrate stoichiometry has rarely been considered in biogeochemical models due to the difficulties in identifying microbial functional groups and quantifying the change in enzyme expression in response to soil nutrient availability. This study aims to represent the omics-informed optimal foraging theory in the Continuum Microbial ENzyme Decomposition model (CoMEND), which was developed to represent the continuum SOM decomposition process following the MEMS theory. The SOM pools in the model are classified based on soil chemical composition (i.e. Carbohydrates, lignin, N-rich SOM and P-rich SOM) and the degree of SOM depolymerization. The enzyme functional groups for decomposition of each SOM pool and N/P mineralization are identified by the relative composition of gene copy numbers. The responses of microbial activities and SOM decomposition to nutrient availability are simulated by optimizing the allocation of enzyme functional groups following the optimal foraging theory. The modeled dynamic enzyme allocation in response to P availability is evaluated by the metagenomics data measured from P addition and P-deficit soil samples in Panama sites.The implementation of dynamic enzyme allocation in response to nutrient availability in the CoMEND model enables us to capture the varying microbial C/P ratio and soil carbon dynamics in response to shifting nutrient constraints over time in tropical soils.

A new conceptual framework for unifying the heterogeneity of plant-microbe interactions in forests by linking belowground measurements with large-scale modeling and remote sensing

NASA Astrophysics Data System (ADS)

Brzostek, E. R.; Phillips, R.; Fisher, J. B.

2015-12-01

Recognition of the importance of rhizosphere interactions to ecosystem processes has led to efforts to integrate these dynamics into a conceptual framework that can be tested, refined and applied across spatial scales. A new view suggests that a plant's mycorrhizal association represents a "trait integrator" for a suite of aboveground and belowground functional traits involved in coupling C-nutrient cycles, since nearly all plants associate with a single type of mycorrhizal fungi. The MANE framework predicts that tree species that associate with arbuscular mycorrhizal (AM) fungi differ from trees that associate with ectomycorrhizal (ECM) fungi in a suite of functional traits, and that such differences contribute to unique "biogeochemical syndromes" in forests with varying abundances of AM- and ECM-associated trees. To date, we have found that relative to AM trees, the leaf litter of ECM trees decomposes nearly 50% more slowly; as such, the nutrient economy of ECM-dominated stands is driven by organic forms of N and P whereas the nutrient economy of AM-dominated stands in driven by inorganic forms of N and P. Moreover, differences in the nutrient economies between AM- and ECM-dominated stands can affect the carbon (C) cost of nutrient acquisition. For example, while ECM trees allocate 2-3-fold more C to fine roots and mycorrhizal fungi, this greater investment results in the enhanced activity of enzymes that mobilize nitrogen (N) and phosphorus (P) from soil organic matter, and ultimately the greater uptake of nutrients by plants. However, this enhanced uptake by ECM trees comes at a cost to soil organic C, which declines as a function of root-accelerated N mineralization. By incorporating these dynamics into a coupled nutrient acquisition-microbial decomposition model, and scaling these processes following development of a map of mycorrhizal associations, we are now quantifying how belowground processes shape ecosystem sensitivity to global changes (e.g., rising CO2, warming) at regional- and continental-scales.

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

Continuous Water Quality Monitoring in the Sacramento-San Joaquin Delta to support Ecosystem Science

NASA Astrophysics Data System (ADS)

Downing, B. D.; Bergamaschi, B. A.; Pellerin, B. A.; Saraceno, J.; Sauer, M.; Kraus, T. E.; Burau, J. R.; Fujii, R.

2013-12-01

Characterizing habitat quality and nutrient availability to food webs is an essential step for understanding and predicting the success of pelagic organisms in the Sacramento-San Joaquin Delta (Delta). The difficulty is that water quality and nutrient supply changes continuously as tidal and wind-driven currents move new water parcels to and from comparatively static geomorphic settings. Understanding interactions between nutrient cycling, suspended sediment, and plankton dynamics with flow and tidal range relative to position in the estuary is critical to predicting and managing bottom up effects on aquatic habitat in the Delta. Historically, quantifying concentrations and loads in the Delta has relied on water quality data collected at monthly intervals. Current in situ optical sensors for nutrients, dissolved organic matter (DOM) and algal pigments (chlorophyll-A, phycocyanin) allow for real-time, high-frequency measurements on time scales of seconds, and extending up to years. Such data is essential for characterizing changes in water quality over short and long term temporal scales as well as over broader spatial scales. High frequency water quality data have been collected at key stations in the Delta since 2012. Sensors that continuously measure nitrate, DOM, algal pigments and turbidity have been co-located at pre-existing Delta flow monitoring stations. Data from the stations are telemetered to USGS data servers and are designed to run autonomously with a monthly service interval, where sensors are cleaned and checked against calibration standards. The autonomous system is verified against discrete samples taken monthly and intensively over periodic ebb to flood tidal cycles. Here we present examples of how coupled optical and acoustic data from the sensor network to improve our understanding of nutrient and DOM dynamics and fluxes. The data offer robust quantitative estimates of concentrations and constituent fluxes needed to investigate biogeochemical processes in tidal reaches of the Delta. The data is available in real time on the web and has proven invaluable for anticipating interactions between nutrient supply and the Delta landscape, and is useful for continued research in aspects of pelagic habitat quality, algal productivity, and food web dynamics.

A method to quantify and value floodplain sediment and nutrient retention ecosystem services

USGS Publications Warehouse

Hopkins, Kristina G.; Noe, Gregory; Franco, Fabiano; Pindilli, Emily J.; Gordon, Stephanie; Metes, Marina J.; Claggett, Peter; Gellis, Allen; Hupp, Cliff R.; Hogan, Dianna

2018-01-01

Floodplains provide critical ecosystem services to local and downstream communities by retaining floodwaters, sediments, and nutrients. The dynamic nature of floodplains is such that these areas can both accumulate sediment and nutrients through deposition, and export material downstream through erosion. Therefore, estimating floodplain sediment and nutrient retention should consider the net flux of both depositional and erosive processes. An ecosystem services framework was used to quantify and value the sediment and nutrient ecosystem service provided by floodplains in the Difficult Run watershed, a small (151 km2) suburban watershed located in the Piedmont of Virginia (USA). A sediment balance was developed for Difficult Run and two nested watersheds. The balance included upland sediment delivery to streams, stream bank flux, floodplain flux, and stream load. Upland sediment delivery was estimated using geospatial datasets and a modified Revised Universal Soil Loss Equation. Predictive models were developed to extrapolate field measurements of the flux of sediment, sediment-bound nitrogen (N), and sediment-bound phosphorus (P) from stream banks and floodplains to 3232 delineated stream segments in the study area. A replacement cost approach was used to estimate the economic value of the sediment and nutrient retention ecosystem service based on estimated net stream bank and floodplain flux of sediment-bound N for all streams in the study area. Results indicated the net fluvial fluxes of sediment, sediment-bound N, and sediment-bound P were −10,439 Mg yr−1 (net export), 57,300 kg-N yr−1(net trapping), and 98 kg-P yr−1(net trapping), respectively. For sediment, floodplain retention was offset by substantial losses from stream bank erosion, particularly in headwater catchments, resulting in a net export of sediment. Nutrient retention in the floodplain exceeded that lost through stream bank erosion resulting in net retention of nutrients (TN and TP). Using a conservative cost estimate of $12.69 (USD) per kilogram of nitrogen, derived from wastewater treatment costs, the estimated annual value for sediment and nutrient retention on Difficult Run floodplains was $727,226 ± 194,220 USD/yr. Values and differences in floodplain nitrogen retention among stream reaches can be used to target areas for floodplain conservation and stream restoration. The methods presented are scalable and transferable to other areas if appropriate datasets are available for validation.

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...

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.

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 developing fundamental understanding of the influences of HEFs on water quality, nutrient dynamics, and ecosystem health in dynamic river corridor systems.

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.

Analysis of in situ manganese(II) oxidation in the Columbia River and offshore plume: Linking microbial community structure to active biogeochemical cycles

PubMed Central

Anderson, C. R.; Davis, R. E.; Bandolin, N. S.; Baptista, A. M.; Tebo, B. M.

2017-01-01

The Columbia River is a major source of dissolved nutrients and trace metals for the west coast of North America. A large proportion of these nutrients are sourced from the Columbia River Estuary where coastal and terrestrial waters mix and resuspend particulate matter within the water column. As estuarine water is discharged off the coast it transports the particulate matter, dissolved nutrients and microorganisms forming nutrient rich and metabolically dynamic plumes. In this study, bacterial manganese oxidation within the plume and estuary was investigated during spring and neap tides. The microbial community proteome was fractionated and assayed for Mn oxidation activity. Proteins from the outer membrane and the loosely bound outer membrane fractions were separated using size exclusion chromatography and Mn(II)-oxidizing eluates were analyzed with tandem mass spectrometry to identify potential Mn oxidase protein targets. Multi-copper oxidase (MCO) and heme-peroxidase enzymes were identified in active fractions. T-RFLP cluster analysis indicates that the organisms oxidizing the most Mn(II) were sourced from the Columbia River estuary and nearshore coastal ocean. These organisms are producing up to 10 fM MnO2 cell−1 day−1. Evidence for the presence of Mn(II)-oxidizing bacterial isolates from the genera Aurantimonas, Rhodobacter, Bacillus, and Shewanella was found in T-RFLP profiles. Q-PCR was used to quantify the gene copies of the heme-peroxidase, Aurantimonas SSU rRNA and total bacterial SSU rRNA gene copies. The probes used suggested that Aurantimonas could only account for 1.7% of heme-peroxidase genes quantified suggesting that peroxidase driven manganese oxidation capabilities are widespread throughout other organisms in this environment. PMID:21418498

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.

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 through this significant regional demonstration project make it a potentially powerful agent of change for advancing conservation success.

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 Dynamic Nutrient Budget of Subsystem Interactions in a Salt Marsh Estuary

NASA Astrophysics Data System (ADS)

Childers, Daniel L.; McKellar, Henry N.; Dame, Richard F.; Sklar, Fred H.; Blood, Elizabeth R.

1993-02-01

In tidal salt marsh estuaries, the different habitats of the ecosystem interact primarily through the tidal creek water column. These interactions include nutrient and materials exchanges with the salt marsh, oyster reefs, creek bottoms, and adjacent uplands. Nutrient budgets are often used to synthesize these kinds of subsystem exchange data, and are usually based on annual totals without accounting for nutrient variability at finer temporal resolutions. In this paper, we present a dynamic budget of carbon (C), nitrogen (N), and phosphorus (P) for the North Inlet estuary, South Carolina that synthesizes subsystem flux data in a new way. We have developed a dynamic budget that uses a tidal hydrology model to generate daily areas of inundated intertidal habitat (i.e. vegetated marsh and oyster reef) from tidal heights calculated hourly and combines them with flux data to determine a net daily input to, or removal from, the water column. Daily surpluses or deficits of each nutrient were compared with daily rates of change in observed tidally-averaged nutrient concentrations. Particular emphasis was placed on evaluating budget output from the intertidal subsystems. We compared our total annual budgets to values from syntheses of two North Inlet flux studies. Although areas of marsh inundated were 150-200 times greater than areas of oyster reef inundated, interactions per unit volume of estuarine water column were comparable in magnitude for soluble reactive P (SRP), particulate organic C (POC), and dissolved organic C (DOC). The marsh dominated the ammonium (NH +4) and nitrate + nitrite (NN) exchanges in the summer but the NH +4 and POC output were particularly sensitive to changes in oyster reef area. Winter and spring DOC release by the marsh coincided closely (in timing and magnitude) with the peak in DOC concentrations observed in the North Inlet estuary, suggesting that forest stream inputs of DOC are not nearly as important as has been hypothesized. Comparison of our budget predictions to a previous synthesis of the same subsytem flux data confirmed the power of using tidal hydrology to estimate subsystem interactions between sampling times. These comparisons also emphasized the importance of (1) water column processes to NH +4 dynamics (2) subtidal benthic fluxes to DOC dynamics, and (3) external inputs to NN dynamics. By incorporating our best current knowledge of estuary-wide subsystem areas, the dynamic budget also allowed us to link subsystem flux data to the results of a study quantifying exchanges between the estuary and the coastal ocean. That comparison indicated the shortcomings of any site-specific extrapolation to whole-system conclusions where a homogeneous ecosystem must be assumed. We used the differences between our total annual C, N, and P budgets and reported exports of those constituents from the system to generate hypotheses and suggest future research efforts both at North Inlet and southeastern salt marsh estuaries in general.

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 provide evidence for a proximate cause of the physiological trade-off between larval growth and development, and provide insight into the energetic and nutrient costs that shape fitness trade-offs across life stages. © 2017. Published by The Company of Biologists Ltd.

The economic cost of upland and gully erosion on subsistence agriculture for a watershed in the Ethiopian highlands

USDA-ARS?s Scientific Manuscript database

This paper quantifies the cost of erosion; it uses nutrient replacement cost to value topsoil nutrient depletion, daily wage rate to monetize the opportunity cost of labour due to gully erosion and local market price to quantify the lost animal and cash crop trees. Soil erosion rate is estimated fro...

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.

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...

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.

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.

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.

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...

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...

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...

"Land-Cover Conversion in Amazonia, The Role of ENV" Ironment and Substrate composition in Modifying SOI

NASA Technical Reports Server (NTRS)

Roberts, Dar A.; Chadwick, Oliver A.; Batista, Getulio T.

2003-01-01

LBA research from the first phase of LBA focused on three broad categories: 1) mapping land cover and quantifying rates of change, persistence of pasture, and area of recovering forest; 2) evaluating the role of environmental factors and land-use history on soil biogeochemistry; and 3) quantifying the natural and human controls on stream nutrient concentrations. The focus of the research was regional, concentrating primarily in the state of RondBnia, but also included land-cover mapping in the vicinity of Maraba, Para, and Manaus, Amazonas. Remote sensing analysis utilized Landsat Thematic Mapper (TM) and Multispectral Scanner (MS S) data to map historical patterns of land-cover change. Specific questions addressed by the remote sensing component of the research included: 1) what is the areal extent of dominant land-cover classes? 2) what are the rates of change of dominant land cover through processes of deforestation, disturbance and regeneration? and 3) what are the dynamic properties of each class that characterize temporal variability, duration, and frequency of repeat disturbance? Biogeochemical analysis focused on natural variability and impacts of land-use/land-cover changes on soil and stream biogeochemical properties at the regional scale. An emphasis was given to specific soil properties considered to be primary limiting factors regionally, including phosphorus, nitrogen, base cations and cation-exchange properties. Stream sampling emphasized the relative effects of the rates and timing of land-cover change on stream nutrients, demonstrating that vegetation conversion alone does not impact nutrients as much as subsequent land use and urbanization.

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....

Functional group-specific traits drive phytoplankton dynamics in the oligotrophic ocean.

PubMed

Alexander, Harriet; Rouco, Mónica; Haley, Sheean T; Wilson, Samuel T; Karl, David M; Dyhrman, Sonya T

2015-11-03

A diverse microbial assemblage in the ocean is responsible for nearly half of global primary production. It has been hypothesized and experimentally demonstrated that nutrient loading can stimulate blooms of large eukaryotic phytoplankton in oligotrophic systems. Although central to balancing biogeochemical models, knowledge of the metabolic traits that govern the dynamics of these bloom-forming phytoplankton is limited. We used eukaryotic metatranscriptomic techniques to identify the metabolic basis of functional group-specific traits that may drive the shift between net heterotrophy and autotrophy in the oligotrophic ocean. Replicated blooms were simulated by deep seawater (DSW) addition to mimic nutrient loading in the North Pacific Subtropical Gyre, and the transcriptional responses of phytoplankton functional groups were assayed. Responses of the diatom, haptophyte, and dinoflagellate functional groups in simulated blooms were unique, with diatoms and haptophytes significantly (95% confidence) shifting their quantitative metabolic fingerprint from the in situ condition, whereas dinoflagellates showed little response. Significantly differentially abundant genes identified the importance of colimitation by nutrients, metals, and vitamins in eukaryotic phytoplankton metabolism and bloom formation in this system. The variable transcript allocation ratio, used to quantify transcript reallocation following DSW amendment, differed for diatoms and haptophytes, reflecting the long-standing paradigm of phytoplankton r- and K-type growth strategies. Although the underlying metabolic potential of the large eukaryotic phytoplankton was consistently present, the lack of a bloom during the study period suggests a crucial dependence on physical and biogeochemical forcing, which are susceptible to alteration with changing climate.

Functional group-specific traits drive phytoplankton dynamics in the oligotrophic ocean

PubMed Central

Alexander, Harriet; Rouco, Mónica; Haley, Sheean T.; Wilson, Samuel T.; Karl, David M.; Dyhrman, Sonya T.

2015-01-01

A diverse microbial assemblage in the ocean is responsible for nearly half of global primary production. It has been hypothesized and experimentally demonstrated that nutrient loading can stimulate blooms of large eukaryotic phytoplankton in oligotrophic systems. Although central to balancing biogeochemical models, knowledge of the metabolic traits that govern the dynamics of these bloom-forming phytoplankton is limited. We used eukaryotic metatranscriptomic techniques to identify the metabolic basis of functional group-specific traits that may drive the shift between net heterotrophy and autotrophy in the oligotrophic ocean. Replicated blooms were simulated by deep seawater (DSW) addition to mimic nutrient loading in the North Pacific Subtropical Gyre, and the transcriptional responses of phytoplankton functional groups were assayed. Responses of the diatom, haptophyte, and dinoflagellate functional groups in simulated blooms were unique, with diatoms and haptophytes significantly (95% confidence) shifting their quantitative metabolic fingerprint from the in situ condition, whereas dinoflagellates showed little response. Significantly differentially abundant genes identified the importance of colimitation by nutrients, metals, and vitamins in eukaryotic phytoplankton metabolism and bloom formation in this system. The variable transcript allocation ratio, used to quantify transcript reallocation following DSW amendment, differed for diatoms and haptophytes, reflecting the long-standing paradigm of phytoplankton r- and K-type growth strategies. Although the underlying metabolic potential of the large eukaryotic phytoplankton was consistently present, the lack of a bloom during the study period suggests a crucial dependence on physical and biogeochemical forcing, which are susceptible to alteration with changing climate. PMID:26460011

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 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...

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...

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.

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.

Successional dynamics drive tropical forest nutrient limitation

NASA Astrophysics Data System (ADS)

Chou, C.; Hedin, L. O. O.

2017-12-01

It is increasingly recognized that nutrients such as N and P may significantly constrain the land carbon sink. However, we currently lack a complete understanding of these nutrient cycles in forest ecosystems and how to incorporate them into Earth System Models. We have developed a framework of dynamic forest nutrient limitation, focusing on the role of secondary forest succession and canopy gap disturbances as bottlenecks of high plant nutrient demand and limitation. We used succession biomass data to parameterize a simple ecosystem model and examined the dynamics of nutrient limitation throughout tropical secondary forest succession. Due to the patterns of biomass recovery in secondary tropical forests, we found high nutrient demand from rapid biomass accumulation in the earliest years of succession. Depending on previous land use scenarios, soil nutrient availability may also be low in this time period. Coupled together, this is evidence that there may be high biomass nutrient limitation early in succession, which is partially met by abundant symbiotic nitrogen fixation from certain tree species. We predict a switch from nitrogen limitation in early succession to one of three conditions: (i) phosphorus only, (ii) phosphorus plus nitrogen, or (iii) phosphorus, nitrogen, plus light co-limitation. We will discuss the mechanisms that govern the exact trajectory of limitation as forests build biomass. In addition, we used our model to explore scenarios of tropical secondary forest impermanence and the impacts of these dynamics on ecosystem nutrient limitation. We found that secondary forest impermanence exacerbates nutrient limitation and the need for nitrogen fixation early in succession. Together, these results indicate that biomass recovery dynamics early in succession as well as their connection to nutrient demand and limitation are fundamental for understanding and modeling nutrient limitation of the tropical forest carbon sink.

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.

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.

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.

NUTRIENT DYNAMICS IN RELATION TO GEOMORPHOLOGY OF RIVERINE WETLANDS

EPA Science Inventory

Variation in water depth and soil properties associated with geomorphic structures can affect riverine wetland nutrient dynamics by altering biogeochemical processes. We examined the seasonal influence of soils and geomorphology on nutrient forms and concentrations in riverine we...

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.

Predicting marine physical-biogeochemical variabilities in the Gulf of Mexico and southeastern U.S. shelf sea

NASA Astrophysics Data System (ADS)

He, R.; Zong, H.; Xue, Z. G.; Fennel, K.; Tian, H.; Cai, W. J.; Lohrenz, S. E.

2017-12-01

An integrated terrestrial-ocean ecosystem modeling system is developed and used to investigate marine physical-biogeochemical variabilities in the Gulf of Mexico and southeastern US shelf sea. Such variabilities stem from variations in the shelf circulation, boundary current dynamics, impacts of climate variability, as well as growing population and associated land use practices on transport of carbon and nutrients within terrestrial systems and their delivery to the coastal ocean. We will report our efforts in evaluating the performance of the coupled modeling system via extensive model and data comparisons, as well as findings from a suite of case studies and scenario simulations. Long-term model simulation results are used to quantify regional ocean circulation dynamics, nitrogen budget and carbon fluxes. Their corresponding sub-regional differences are also characterized and contrasted.

Hydrologic processes and nutrient dynamics in a pristine mountain catchment

USGS Publications Warehouse

F. Richard Hauer,; Fagre, Daniel B.; Stanford, Jack A.

2002-01-01

Nutrient dynamics in watersheds have been used as an ecosystem-level indicator of overall ecosystem function or response to disturbance (e.g. Borman.N et al. 1974, WEBSTER et al. 1992). The examination of nutrients has been evaluated to determine responses to logging practices or other changes in watershed land use. Nutrient dynamics have been related to changing physical and biological characteristics (Mulholl AND 1992, CHESTNUT & McDowell 2000). Herein, the concentrations and dynamics of nitrogen, phosphorus and particulate organic carbon were examined in a large pristine watershed because they are affected by changes in discharge directly from the catchment and after passage through a large oligotrophic lake. 

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...

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...

Mechanistic modeling of microbial interactions at pore to profile scale resolve methane emission dynamics from permafrost soil

NASA Astrophysics Data System (ADS)

Ebrahimi, Ali; Or, Dani

2017-05-01

The sensitivity of polar regions to raising global temperatures is reflected in rapidly changing hydrological processes associated 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 stimulation of other soil-borne greenhouse gas emissions such as methane. Soil methanotrophic and methanogenic microbial communities rapidly adjust their activity and spatial organization in response to permafrost thawing and other environmental factors. Soil structural elements such as aggregates and layering affect oxygen and nutrient diffusion processes thereby contributing to methanogenic activity within temporal anoxic niches (hot spots). We developed a mechanistic individual-based model to quantify microbial activity dynamics in soil pore networks considering transport processes and enzymatic activity associated with methane production in soil. The model was upscaled from single aggregates to the soil profile where freezing/thawing provides macroscopic boundary conditions for microbial activity at different soil depths. The model distinguishes microbial activity in aerate bulk soil from aggregates (or submerged profile) for resolving methane production and oxidation rates. Methane transport pathways by diffusion and ebullition of bubbles vary with hydration dynamics. 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 and enzyme activity) on long-term methane emissions and carbon decomposition rates in the rapidly changing polar regions.

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.

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 ...

Identifying ecological "sweet spots" underlying cyanobacteria functional group dynamics from long-term observations using a statistical machine learning approach

NASA Astrophysics Data System (ADS)

Nelson, N.; Munoz-Carpena, R.; Phlips, E. J.

2017-12-01

Diversity in the eco-physiological adaptations of cyanobacteria genera creates challenges for water managers who are tasked with developing appropriate actions for controlling not only the intensity and frequency of cyanobacteria blooms, but also reducing the potential for blooms of harmful taxa (e.g., toxin producers, N2 fixers). Compounding these challenges, the efficacy of nutrient management strategies (phosphorus-only versus nitrogen-and-phosphorus) for cyanobacteria bloom abatement is the subject of an ongoing debate, which increases uncertainty associated with bloom mitigation decision-making. In this work, we analyze a unique long-term (17-year) dataset composed of monthly observations of cyanobacteria genera abundances, zooplankton abundances, water quality, and flow from Lake George, a bloom-impacted flow-through lake of the St. Johns River (FL, USA). Using the Random Forests machine learning algorithm, an assumption-free ensemble modeling approach, the dataset was evaluated to quantify and characterize relationships between environmental conditions and seven cyanobacteria groupings: five genera (Anabaena, Cylindrospermopsis, Lyngbya, Microcystis, and Oscillatoria) and two functional groups (N2 fixers and non-fixers). Results highlight the selectivity of nitrogen in describing genera and functional group dynamics, and potential for physical effects to limit the efficacy of nutrient management as a mechanism for cyanobacteria bloom mitigation.

Nutrient dynamics in streams and the role of J-NABS

Treesearch

Patrick J. Mulholland; Jackson R. Webster

2010-01-01

Nutrient dynamics in streams has been an important topic of research since the 1960s. Here we review this topic and the significant role played by J-NABS in its development. We limit this review almost exclusively to studies of N and P because these elements have been shown to limit productivity in streams. We use the expression nutrient dynamics for studies that...

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.

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...

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.

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...

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.

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.

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 quality. Climate and land uses change scenarios are incorporated into the model to explain how nutrient export will vary across the catchment in 30, 60 and 90 years from now. Uncertainty of nutrient predictions is also assesses in order to determine the degree of reliability of the estimates.

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 quality. Climate and land uses change scenarios are incorporated into the model to explain how nutrient export will vary across the catchment in 30, 60 and 90 years from now. Uncertainty of nutrient predictions is also assesses in order to determine the degree of reliability of the estimates.

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 ...

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.

Biogeochemistry from Gliders at the Hawaii Ocean Times-Series

NASA Astrophysics Data System (ADS)

Nicholson, D. P.; Barone, B.; Karl, D. M.

2016-02-01

At the Hawaii Ocean Time-series (HOT) autonomous, underwater gliders equipped with biogeochemical sensors observe the oceans for months at a time, sampling spatiotemporal scales missed by the ship-based programs. Over the last decade, glider data augmented by a foundation of time-series observations have shed light on biogeochemical dynamics occuring spatially at meso- and submesoscales and temporally on scales from diel to annual. We present insights gained from the synergy between glider observations, time-series measurements and remote sensing in the subtropical North Pacific. We focus on diel variability observed in dissolved oxygen and bio-optics and approaches to autonomously quantify net community production and gross primary production (GPP) as developed during the 2012 Hawaii Ocean Experiment - DYnamics of Light And Nutrients (HOE-DYLAN). Glider-based GPP measurements were extended to explore the relationship between GPP and mesoscale context over multiple years of Seaglider deployments.

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.

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.

Comparing Measures of Estuarine Ecosystem Production in a Temperate New England Estuary

EPA Science Inventory

Anthropogenic nutrient enrichments and concerted efforts at nutrient reductions, compounded with the influences of climate change, are likely changing the net ecosystem production (NEP) of our coastal systems. To quantify these changes, scientists monitor a range of physical, che...

Food selection in larval fruit flies: dynamics and effects on larval development

NASA Astrophysics Data System (ADS)

Schwarz, Sebastian; Durisko, Zachary; Dukas, Reuven

2014-01-01

Selecting food items and attaining a nutritionally balanced diet is an important challenge for all animals including humans. We aimed to establish fruit fly larvae ( Drosophila melanogaster) as a simple yet powerful model system for examining the mechanisms of specific hunger and diet selection. In two lab experiments with artificial diets, we found that larvae deprived of either sucrose or protein later selectively fed on a diet providing the missing nutrient. When allowed to freely move between two adjacent food patches, larvae surprisingly preferred to settle on one patch containing yeast and ignored the patch providing sucrose. Moreover, when allowed to move freely between three patches, which provided either yeast only, sucrose only or a balanced mixture of yeast and sucrose, the majority of larvae settled on the yeast-plus-sucrose patch and about one third chose to feed on the yeast only food. While protein (yeast) is essential for development, we also quantified larval success on diets with or without sucrose and show that larvae develop faster on diets containing sucrose. Our data suggest that fruit fly larvae can quickly assess major nutrients in food and seek a diet providing a missing nutrient. The larvae, however, probably prefer to quickly dig into a single food substrate for enhanced protection over achieving an optimal diet.

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.

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 explain different patterns of nonlinearity in watershed nutrient dynamics? And finally, how does the accumulation of nutrient legacies within watersheds impact current and future water quality?

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.

Plant functional traits and canopy structure control the relationship between photosynthetic CO2 uptake and far-red sun-induced fluorescence in a Mediterranean grassland under different nutrient availability.

PubMed

Migliavacca, Mirco; Perez-Priego, Oscar; Rossini, Micol; El-Madany, Tarek S; Moreno, Gerardo; van der Tol, Christiaan; Rascher, Uwe; Berninger, Anna; Bessenbacher, Verena; Burkart, Andreas; Carrara, Arnaud; Fava, Francesco; Guan, Jin-Hong; Hammer, Tiana W; Henkel, Kathrin; Juarez-Alcalde, Enrique; Julitta, Tommaso; Kolle, Olaf; Martín, M Pilar; Musavi, Talie; Pacheco-Labrador, Javier; Pérez-Burgueño, Andrea; Wutzler, Thomas; Zaehle, Sönke; Reichstein, Markus

2017-05-01

Sun-induced fluorescence (SIF) in the far-red region provides a new noninvasive measurement approach that has the potential to quantify dynamic changes in light-use efficiency and gross primary production (GPP). However, the mechanistic link between GPP and SIF is not completely understood. We analyzed the structural and functional factors controlling the emission of SIF at 760 nm (F 760 ) in a Mediterranean grassland manipulated with nutrient addition of nitrogen (N), phosphorous (P) or nitrogen-phosphorous (NP). Using the soil-canopy observation of photosynthesis and energy (SCOPE) model, we investigated how nutrient-induced changes in canopy structure (i.e. changes in plant forms abundance that influence leaf inclination distribution function, LIDF) and functional traits (e.g. N content in dry mass of leaves, N%, Chlorophyll a+b concentration (Cab) and maximum carboxylation capacity (V cmax )) affected the observed linear relationship between F 760 and GPP. We conclude that the addition of nutrients imposed a change in the abundance of different plant forms and biochemistry of the canopy that controls F 760 . Changes in canopy structure mainly control the GPP-F 760 relationship, with a secondary effect of Cab and V cmax . In order to exploit F 760 data to model GPP at the global/regional scale, canopy structural variability, biodiversity and functional traits are important factors that have to be considered. © 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.

Submarine groundwater discharge into typical tropical lagoons: A case study in eastern Hainan Island, China

NASA Astrophysics Data System (ADS)

Wang, Xilong; Du, Jinzhou

2016-11-01

Assessing submarine groundwater discharge (SGD) into lagoons and bays can be helpful to understand biogeochemical processes, especially nutrient dynamics. In the present paper, radium (Ra) isotopes were used to quantify SGD in two typical tropical lagoons (Laoye Lagoon (LY Lagoon) and Xiaohai Lagoon (XH Lagoon)) of eastern Hainan Island, China. The Ra mass balance model provided evidence that SGD plays an important role in the hydrology of the LY Lagoon and the XH Lagoon, delivering average SGD fluxes of 1.7 × 106 (94 L m-2 d-1) and 1.8 × 106 (41 L m-2 d-1) m3 d-1, respectively. Tidal pumping was one of the important driving forces for SGD fluxes in the LY and the XH Lagoons. Tidal-driven SGD into the tidal channels of both lagoons can account for approximately 10% of the total SGD flux into the lagoons. In addition, the dissolved inorganic nutrient budgets were reassessed in the LY Lagoon and the XH Lagoon, which showed that SGD was the major source of nutrients entering the LY Lagoon and that the LY Lagoon behaved as a source for dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) and as a sink for dissolved silicate (DSi). Nutrient loads in the XH Lagoon were mainly derived from riverine inputs and SGD, and the XH Lagoon behaved as a source for DIP, but a sink for DIN and DSi.

Graph Theory Approach for Studying Food Webs

NASA Astrophysics Data System (ADS)

Longjas, A.; Tejedor, A.; Foufoula-Georgiou, E.

2017-12-01

Food webs are complex networks of feeding interactions among species in ecological communities. Metrics describing food web structure have been proposed to compare and classify food webs ranging from food chain length, connectance, degree distribution, centrality measures, to the presence of motifs (distinct compartments), among others. However, formal methodologies for studying both food web topology and the dynamic processes operating on them are still lacking. Here, we utilize a quantitative framework using graph theory within which a food web is represented by a directed graph, i.e., a collection of vertices (species or trophic species defined as sets of species sharing the same predators and prey) and directed edges (predation links). This framework allows us to identify apex (environmental "source" node) to outlet (top predators) subnetworks and compute the steady-state flux (e.g., carbon, nutrients, energy etc.) in the food web. We use this framework to (1) construct vulnerability maps that quantify the relative change of flux delivery to the top predators in response to perturbations in prey species (2) identify keystone species, whose loss would precipitate further species extinction, and (3) introduce a suite of graph-theoretic metrics to quantify the topologic (imposed by food web connectivity) and dynamic (dictated by the flux partitioning and distribution) components of a food web's complexity. By projecting food webs into a 2D Topodynamic Complexity Space whose coordinates are given by Number of alternative paths (topologic) and Leakage Index (dynamic), we show that this space provides a basis for food web comparison and provide physical insights into their dynamic behavior.

Influence of plant invasion on seed chemistry of winterfat, green rabbitbrush, freckled milkvetch, indian ricegrass and cheatgrass

USDA-ARS?s Scientific Manuscript database

Plant invasions have proven detrimental to numerous ecosystem processes; however, limited information exists on how plant invasions affect seed nutrients. We quantified nutrients in seeds of Indian ricegrass (Achnatherum hymenoides), green rabbitbrush (Chrysothamnus viscidiflorus), winterfat (Krasch...

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.

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.

USE OF ELECTRICAL RESISTIVITY PROBE WITH MODFLOW FOR SCREENING LEVEL DETERMINATION OF PARAFLUVIAL HYPORHEIC FLOW

EPA Science Inventory

The hyporheic zone can provide significant nutrient attenuation in watersheds. Conceptual models describe the behavior of nutrients and biota for the hyporheic ecotone, but site characterization is needed to quantify these effects at the restoration reach scale (hundreds of meter...

Hydrology and Water Quality from Managed Turf

USDA-ARS?s Scientific Manuscript database

Quantification of nutrient and pesticide losses from managed turf systems (golf courses) is scant. A study was initiated at Northland Country Club in Duluth, MN, in 2003 to quantify nutrient and pesticide losses in surface and subsurface discharge waters. Based on the four years of data collected at...

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...

Positive responses of coastal dune plants to soil conditioning by the invasive Lupinus nootkatensis

NASA Astrophysics Data System (ADS)

Hanslin, Hans Martin; Kollmann, Johannes

2016-11-01

Invasive nitrogen-fixing plants drive vegetation dynamics and may cause irreversible changes in nutrient-limited ecosystems through increased soil resources. We studied how soil conditioning by the invasive alien Lupinus nootkatensis affected the seedling growth of co-occurring native plant species in coastal dunes, and whether responses to lupin-conditioned soil could be explained by fertilisation effects interacting with specific ecological strategies of the native dune species. Seedling performance of dune species was compared in a greenhouse experiment using field-collected soil from within or outside coastal lupin stands. In associated experiments, we quantified the response to nutrient supply of each species and tested how addition of specific nutrients affected growth of the native grass Festuca arundinacea in control and lupin-conditioned soil. We found that lupin-conditioned soil increased seedling biomass in 30 out of 32 native species; the conditioned soil also had a positive effect on seedling biomass of the invasive lupin itself. Increased phosphorus mobilisation by lupins was the major factor driving these positive seedling responses, based both on growth responses to addition of specific elements and analyses of plant available soil nutrients. There were large differences in growth responses to lupin-conditioned soil among species, but they were unrelated to selected autecological indicators or plant strategies. We conclude that Lupinus nootkatensis removes the phosphorus limitation for growth of native plants in coastal dunes, and that it increases cycling of other nutrients, promoting the growth of its own seedlings and a wide range of dune species. Finally, our study indicates that there are no negative soil legacies that prevent re-establishment of native plant species after removal of lupins.

Uptake of dissolved inorganic and organic nitrogen by the benthic toxic dinoflagellate Ostreopsis cf. ovata.

PubMed

Jauzein, Cécile; Couet, Douglas; Blasco, Thierry; Lemée, Rodolphe

2017-05-01

Environmental factors that shape dynamics of benthic toxic blooms are largely unknown. In particular, for the toxic dinoflagellate Ostreopsis cf. ovata, the importance of the availability of nutrients and the contribution of the inorganic and organic pools to growth need to be quantified in marine coastal environments. The present study aimed at characterizing N-uptake of dissolved inorganic and organic sources by O. cf. ovata cells, using the 15 N-labelling technique. Experiments were conducted taking into account potential interactions between nutrient uptake systems as well as variations with the diel cycle. Uptake abilities of O. cf. ovata were parameterized for ammonium (NH 4 + ), nitrate (NO 3 - ) and N-urea, from the estimation of kinetic and inhibition parameters. In the range of 0 to 10μmolNL -1 , kinetic curves showed a clear preference pattern following the ranking NH 4 + >NO 3 - >N-urea, where the preferential uptake of NH 4 + relative to NO 3 - was accentuated by an inhibitory effect of NH 4 + concentration on NO 3 - uptake capabilities. Conversely, under high nutrient concentrations, the preference for NH 4 + relative to NO 3 - was largely reduced, probably because of the existence of a low-affinity high capacity inducible NO 3 - uptake system. Ability to take up nutrients in darkness could not be defined as a competitive advantage for O. cf. ovata. Species competitiveness can also be defined from nutrient uptake kinetic parameters. A strong affinity for NH 4 + was observed for O. cf. ovata cells that may partly explain the success of this toxic species during the summer season in the Bay of Villefranche-sur-mer (France). Copyright © 2017 Elsevier B.V. All rights reserved.

Iron control on global productivity: an efficient inverse model of the ocean's coupled phosphate and iron cycles.

NASA Astrophysics Data System (ADS)

Pasquier, B.; Holzer, M.; Frants, M.

2016-02-01

We construct a data-constrained mechanistic inverse model of the ocean's coupled phosphorus and iron cycles. The nutrient cycling is embedded in a data-assimilated steady global circulation. Biological nutrient uptake is parameterized in terms of nutrient, light, and temperature limitations on growth for two classes of phytoplankton that are not transported explicitly. A matrix formulation of the discretized nutrient tracer equations allows for efficient numerical solutions, which facilitates the objective optimization of the key biogeochemical parameters. The optimization minimizes the misfit between the modelled and observed nutrient fields of the current climate. We systematically assess the nonlinear response of the biological pump to changes in the aeolian iron supply for a variety of scenarios. Specifically, Green-function techniques are employed to quantify in detail the pathways and timescales with which those perturbations are propagated throughout the world oceans, determining the global teleconnections that mediate the response of the global ocean ecosystem. We confirm previous findings from idealized studies that increased iron fertilization decreases biological production in the subtropical gyres and we quantify the counterintuitive and asymmetric response of global productivity to increases and decreases in the aeolian iron supply.

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 recently disturbed forests.

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 ...

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...

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...

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...

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 ...

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...

Quantifying spatial differences in metabolism in headwater streams

Treesearch

Ricardo González-Pinzón; Roy Haggerty; Alba Argerich

2014-01-01

Stream functioning includes simultaneous interaction among solute transport, nutrient processing, and metabolism. Metabolism is measured with methods that have limited spatial representativeness and are highly uncertain. These problems restrict development of methods for up-scaling biological processes that mediate nutrient processing. We used the resazurin–resorufin (...

Monitoring the Productivity of Coastal Systems Using PH: When Simpler is Better

EPA Science Inventory

The impact of nutrient inputs to the eutrophication of coastal ecosystems has been one of the great themes of coastal ecology. There have been countless studies devoted to quantifying how human sources of nutrients, in particular nitrogen (N), effect coastal water bodies. These s...

Monitoring the Productivity of Coastal Systems Using PH: When Simpler is Better (NEERS)

EPA Science Inventory

The impact of nutrient inputs to the eutrophication of coastal ecosystems has been one of the great themes of coastal ecology. There have been countless studies devoted to quantifying how human sources of nutrients, in particular nitrogen (N), effect coastal water bodies. These s...

Monitoring the Productivity of Coastal Systems Using PH: When Simpler is Better.

EPA Science Inventory

The impact of nutrient inputs to the eutrophication of coastal ecosystems has been one of the great themes of coastal ecology. There have been countless studies devoted to quantifying how human sources of nutrients, in particular nitrogen (N), effect coastal water bodies. These s...

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...

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...

Phosphorous bioavailability along a soil chronosequence

NASA Astrophysics Data System (ADS)

Roberts, K.; Vokhshoori, N. L.; Rosenthanl, A.; Turner, B. L.; Condron, L.; Paytan, A.

2011-12-01

In humid environments, as soils age nutrient loss through leaching and chemical trasformations affect the succession and composition of the biological communities. In particular phosphorus (P), often a limiting nutrient in terrestrial systems, tends to evolve into less bio-available forms over time, compounding loss through leaching. Thus P availability has the potential to strongly affect community productivity and structure. Low standing stock of P may not necessarily imply P limitation as the bio-available P pool is continuously recycled and re-utilized. Thus extensive recycling can reduce to varying extents the effect of P limitation. The bio-availability and recycling rates of P are difficult to measure; multiple sequential extraction processes have been developed to try to define and quantify the bio-availability of both inorganic and organic forms of P. In this preliminary study, we will present results of P concentrations in different soil fractions and oxygen isotopes in phosphate. These data together increase our understanding of P dynamics as soils age. The work is being done with a well characterized and dated chronosequence from the west coast of the South Island of New Zealand near the Haast River.

Quantification and bioaccessibility of California pistachio bioactives

USDA-ARS?s Scientific Manuscript database

The content of carotenoids, chlorophylls, phenolics, and tocols in pistachios (Pistacia vera L.) has not been methodically quantified. The objective of this study was to first optimize extraction protocols for lipophilic nutrients and then quantify the content of two phenolic acids, nine flavonoids,...

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, especially in the litter with highest C:P ratio. A persistent effect of temperature extremes on NH4 and NO3 concentrations was observed for three months after stress application. However, the effect on PO4 concentrations was only transient. Environmental conditions had a strong affect on nutrient losses but only a minor affect on microbial carbon Cmic and microbial nitrogen Nmic. The impact of environmental stress (heat or freezing) on microbes in terms of Cmic, Nmic and C:Nmic was strongest in sites with narrow litter C:N ratios. Our results indicate a similar stoichiometric demand of microbes, with temporal changes which results in differences in nutrient cycling on substrates with different C:N:P ratios.

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.

Simulating the impacts of disturbances on forest carbon cycling in North America: Processes, data, models, and challenges

USGS Publications Warehouse

Liu, Shuguang; Bond-Lamberty, Ben; Hicke, Jeffrey A.; Vargas, Rodrigo; Zhao, Shuqing; Chen, Jing; Edburg, Steven L.; Hu, Yueming; Liu, Jinxun; McGuire, A. David; Xiao, Jingfeng; Keane, Robert; Yuan, Wenping; Tang, Jianwu; Luo, Yiqi; Potter, Christopher; Oeding, Jennifer

2011-01-01

Forest disturbances greatly alter the carbon cycle at various spatial and temporal scales. It is critical to understand disturbance regimes and their impacts to better quantify regional and global carbon dynamics. This review of the status and major challenges in representing the impacts of disturbances in modeling the carbon dynamics across North America revealed some major advances and challenges. First, significant advances have been made in representation, scaling, and characterization of disturbances that should be included in regional modeling efforts. Second, there is a need to develop effective and comprehensive process‐based procedures and algorithms to quantify the immediate and long‐term impacts of disturbances on ecosystem succession, soils, microclimate, and cycles of carbon, water, and nutrients. Third, our capability to simulate the occurrences and severity of disturbances is very limited. Fourth, scaling issues have rarely been addressed in continental scale model applications. It is not fully understood which finer scale processes and properties need to be scaled to coarser spatial and temporal scales. Fifth, there are inadequate databases on disturbances at the continental scale to support the quantification of their effects on the carbon balance in North America. Finally, procedures are needed to quantify the uncertainty of model inputs, model parameters, and model structures, and thus to estimate their impacts on overall model uncertainty. Working together, the scientific community interested in disturbance and its impacts can identify the most uncertain issues surrounding the role of disturbance in the North American carbon budget and develop working hypotheses to reduce the uncertainty

Viral control of phytoplankton populations--a review.

PubMed

Brussaard, Corina P D

2004-01-01

Phytoplankton population dynamics are the result of imbalances between reproduction and losses. Losses include grazing, sinking, and natural mortality. As the importance of microbes in aquatic ecology has been recognized, so has the potential significance of viruses as mortality agents for phytoplankton. The field of algal virus ecology is steadily changing and advancing as new viruses are isolated and new methods are developed for quantifying the impact of viruses on phytoplankton dynamics and diversity. With this development, evidence is accumulating that viruses can control phytoplankton dynamics through reduction of host populations, or by preventing algal host populations from reaching high levels. The identification of highly specific host ranges of viruses is changing our understanding of population dynamics. Viral-mediated mortality may not only affect algal species succession, but may also affect intraspecies succession. Through cellular lysis, viruses indirectly affect the fluxes of energy, nutrients, and organic matter, especially during algal bloom events when biomass is high. Although the importance of viruses is presently recognized, it is apparent that many aspects of viral-mediated mortality of phytoplankton are still poorly understood. It is imperative that future research addresses the mechanisms that regulate virus infectivity, host resistance, genotype richness, abundance, and the fate of viruses over time and space.

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 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

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.

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 significantly reduce annual watershed-scale nutrient export. Moreover, successful outcomes highlighted through demonstration projects may facilitate widespread adoption, making them powerful agents of change for advancing conservation success.

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 projected. These results suggest that the clay content of soils could be a good indicator of the sensitivity of catchments to climatic input, and reinforces calls for catchment-specific management plans.

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 increases, were projected. These results suggest that the clay content of soils could be a good indicator of the sensitivity of catchments to climatic input, and reinforces calls for catchment-specific management plans.

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...

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...

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 importance of consumers and this imperiled faunal group on nutrient cycling and community dynamics in aquatic ecosystems.

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-host virus growth and alterations of plant traits. A deeper understanding of the differential effects of environmental nutrient supplies on virus epidemiology and ecology is particularly relevant given the rapid increase of nutrients flowing into Earth's ecosystems as a result of human activities. PMID:29163408

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.

Ovarian follicle dynamics of female Greater Scaup during egg production

USGS Publications Warehouse

Gorman, Kristen B.; Flint, Paul L.; Esler, Daniel N.; Williams, T.D.

2007-01-01

Studies of female waterfowl nutrient reserve use during egg production require a precise understanding of ovarian follicle dynamics to correctly interpret breeding status, and, therefore, derive proper inference. Concerns over numerical declines of North American scaup have increased the need to better understand the role of female condition in reproductive performance. We quantified ovarian follicle dynamics of female Greater Scaup (Aythya marila) breeding on the Yukon–Kuskokwim Delta, Alaska, using a method that accounts for within day variation in follicle size. We considered several models for describing changes in follicle growth with the best supported model estimating the duration of rapid follicle growth (RFG) to be 5.20 ± 0.52 days (±95% confidence intervals) for each developing follicle. Average diameter and dry mass of preovulatory follicles were estimated to be 9.36 mm and 0.26 g, respectively, at the onset of RFG, and these follicle characteristics were 41.47 mm and 15.57 g, respectively, at ovulation. The average diameter of postovulatory follicles immediately following ovulation was estimated to be 17.35 mm, regressing quickly over several days. In addition, we derived predictive equations using diameter and dry mass to estimate the number of days before, and after, ovulation for pre- and postovulatory follicles, as well as an equation to estimate dry mass of damaged follicles. Our results allow precise definition of RFG and nest initiation dates, clutch size, and the daily energetic and nutritional demands of egg production at the individual level. This study provides the necessary foundation for additional work on Greater Scaup reproductive energetics and physiology, and offers an approach for quantifying ovarian follicle dynamics in other species.

Dissolved oxygen and its response to eutrophication in a tropical black water river.

PubMed

Rixen, Tim; Baum, Antje; Sepryani, Harni; Pohlmann, Thomas; Jose, Christine; Samiaji, Joko

2010-08-01

The Siak is a typical, nutrient-poor, well-mixed, black water river in central Sumatra, Indonesia, which owes its brown color to dissolved organic matter (DOM) leached from surrounding, heavily disturbed peat soils. We measured dissolved organic carbon (DOC) and oxygen concentrations along the river, carried out a 36-h experiment in the province capital Pekanbaru and quantified organic matter and nutrient inputs from urban wastewater channels into the Siak. In order to consider the complex dynamic of oxygen in rivers, a box-diffusion model was used to interpret the measured data. The results suggest that the decomposition of soil derived DOM was the main factor influencing the oxygen concentration in the Siak which varied between approximately 100 and 140 micromol l(-1). Additional DOM input caused by wastewater discharges appeared to reduce the oxygen concentrations by approximately 20 micromol l(-1) during the peak-time in household water use in the early morning and in the early evening. Associated enhanced nutrient inputs appear to reduce the impact of the anthropogenic DOM by favoring the photosynthetic production of oxygen in the morning. A reduction of 20 micromol l(-1), which although perhaps not of great significance in Pekanbaru, has strong implications for wastewater management in the fast developing areas downstream Pekanbaru where oxygen concentrations rarely exceed 20 micromol l(-1). Copyright 2010 Elsevier 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

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.

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...

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-...

Long-Term Time Series of Remote Sensing Observations for Development of Regulatory Water Quality Standards

NASA Technical Reports Server (NTRS)

Blonski, Slawomir; Spiering, Bruce A.; Holekamp, Kara L.

2010-01-01

Water quality standards in the U.S. consist of: designated uses (the services that a water body provides; e.g., drinking water, aquatic life, harvestable species, recreation) . criteria that define the environmental conditions that must be maintained to support the uses For estuaries and coastal waters in the Gulf of Mexico, there are no numeric (quantitative) criteria to protect designated uses from effects of nutrients. This is largely due to the absence of adequate data that would quantitatively link biological conditions to nutrient concentrations. The Gulf of Mexico Alliance, an organization fostering collaboration between the Gulf States and U.S. Federal agencies, has identified the development of the numeric nutrient criteria as a major step leading to reduction in MODIS Products Figure 6. Map of the Mobile Bay with a yellow patch indicating the Bon Secour Bay area selected in this study for averaging water clarity parameters retrieved from MODIS datasets. nutrient inputs to coastal ecosystems. Nutrient enrichment in estuaries and coastal waters can be quantified based on response variables that measure phytoplankton biomass and water clarity. Long-term, spatially and temporally resolved measurements of chlorophyll a concentration, total concentration of suspended solids, and water clarity are needed to establish reference conditions and to quantify stressor-response relationships.

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...

Enhancement of phytoplankton chlorophyll by submesoscale frontal dynamics in the North Pacific Subtropical Gyre.

PubMed

Liu, Xiao; Levine, Naomi M

2016-02-28

Subtropical gyres contribute significantly to global ocean productivity. As the climate warms, the strength of these gyres as a biological carbon pump is predicted to diminish due to increased stratification and depleted surface nutrients. We present results suggesting that the impact of submesoscale physics on phytoplankton in the oligotrophic ocean is substantial and may either compensate or exacerbate future changes in carbon cycling. A new statistical tool was developed to quantify surface patchiness from sea surface temperatures. Chlorophyll concentrations in the North Pacific Subtropical Gyre were shown to be enhanced by submesoscale frontal dynamics with an average increase of 38% (maximum of 83%) during late winter. The magnitude of this enhancement is comparable to the observed decline in chlorophyll due to a warming of ~1.1°C. These results highlight the need for an improved understanding of fine-scale physical variability in order to predict the response of marine ecosystems to projected climate changes.

Enhancement of phytoplankton chlorophyll by submesoscale frontal dynamics in the North Pacific Subtropical Gyre

NASA Astrophysics Data System (ADS)

Liu, Xiao; Levine, Naomi M.

2016-02-01

Subtropical gyres contribute significantly to global ocean productivity. As the climate warms, the strength of these gyres as a biological carbon pump is predicted to diminish due to increased stratification and depleted surface nutrients. We present results suggesting that the impact of submesoscale physics on phytoplankton in the oligotrophic ocean is substantial and may either compensate or exacerbate future changes in carbon cycling. A new statistical tool was developed to quantify surface patchiness from sea surface temperatures. Chlorophyll concentrations in the North Pacific Subtropical Gyre were shown to be enhanced by submesoscale frontal dynamics with an average increase of 38% (maximum of 83%) during late winter. The magnitude of this enhancement is comparable to the observed decline in chlorophyll due to a warming of ~1.1°C. These results highlight the need for an improved understanding of fine-scale physical variability in order to predict the response of marine ecosystems to projected climate changes.

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 ...

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...

Partitioning the Relative Importance of Phylogeny and Environmental Conditions on Phytoplankton Fatty Acids

PubMed Central

Galloway, Aaron W. E.; Winder, Monika

2015-01-01

Essential fatty acids (EFA), which are primarily generated by phytoplankton, limit growth and reproduction in diverse heterotrophs. The biochemical composition of phytoplankton is well-known to be governed both by phylogeny and environmental conditions. Nutrients, light, salinity, and temperature all affect both phytoplankton growth and fatty acid composition. However, the relative importance of taxonomy and environment on algal fatty acid content has yet to be comparatively quantified, thus inhibiting predictions of changes to phytoplankton food quality in response to global environmental change. We compiled 1145 published marine and freshwater phytoplankton fatty acid profiles, consisting of 208 species from six major taxonomic groups, cultured in a wide range of environmental conditions, and used a multivariate distance-based linear model to quantify the total variation explained by each variable. Our results show that taxonomic group accounts for 3-4 times more variation in phytoplankton fatty acids than the most important growth condition variables. The results underscore that environmental conditions clearly affect phytoplankton fatty acid profiles, but also show that conditions account for relatively low variation compared to phylogeny. This suggests that the underlying mechanism determining basal food quality in aquatic habitats is primarily phytoplankton community composition, and allows for prediction of environmental-scale EFA dynamics based on phytoplankton community data. We used the compiled dataset to calculate seasonal dynamics of long-chain EFA (LCEFA; ≥C20 ɷ-3 and ɷ-6 polyunsaturated fatty acid) concentrations and ɷ-3:ɷ-6 EFA ratios in Lake Washington using a multi-decadal phytoplankton community time series. These analyses quantify temporal dynamics of algal-derived LCEFA and food quality in a freshwater ecosystem that has undergone large community changes as a result of shifting resource management practices, highlighting diatoms, cryptophytes and dinoflagellates as key sources of LCEFA. Moreover, the analyses indicate that future shifts towards cyanobacteria-dominated communities will result in lower LCEFA content in aquatic ecosystems. PMID:26076015

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.

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.

The biological pump and lower trophic level controls on carbon cycling in Lake Superior: Insights from a multi-pronged study

NASA Astrophysics Data System (ADS)

Schreiner, K. M.; Bramburger, A.; Ozersky, T.; Sheik, C.; Steinman, B. A.

2016-02-01

Lake Superior is the largest freshwater lake in the world, supporting economically important fisheries and providing drinking water to hundreds of thousands of people. In recent decades, summer surface water temperature and the intensity and duration of water column stratification in the lake has increased steadily. These physical changes have resulted in significant perturbations to lower trophic level ecosystem characteristics. Recent observations of Great Lakes plankton assemblages have revealed multi-decadal patterns of community reorganization, with increased relative abundance of taxa characteristic of warmer waters. These changes, coupled with changing nutrient concentrations and colonization by non-native taxa, threaten to shift trophic structure and carbon dynamics at the bottom of the food web. To this end, this study seeks to quantify the impacts of this ecosystem shift on carbon fixation, the biological pump, and organic carbon cycling in Lake Superior. Utilizing a combined sampling approach, in the summer of 2015 we collected water, sediment, and biological samples across a nearshore-to-offshore gradient in the western arm of Lake Superior. Analyses included the community composition of bacteria, archaea, phytoplankton, and zooplankton; water column carbon and nutrient speciation; algal pigments and pigment degradation products; and net primary productivity. The collection of surface sediments allowed for additional assessment of benthic-pelagic coupling. The novel combination of this wide-ranging set of analyses to a locally and globally important water body like Lake Superior allowed us to fully assess the interactions between lower trophic level biology and carbon and nutrient cycling throughout the water column. Preliminary data indicates that microbial community composition was variable across the western arm of Lake Superior and showed signs of stratification at individual stations (>100 m deep). Sample collection occurred soon after lake stratification in July 2015, and the presence of a deep chlorophyll maximum was noted. The results shed light on the functioning of the biological pump and nutrient and carbon dynamics in a changing ecosystem and provides insight on how further change in Lake Superior and other aquatic systems will affect ecosystem function and services.

Imaging complex nutrient dynamics in mycelial networks.

PubMed

Fricker, M D; Lee, J A; Bebber, D P; Tlalka, M; Hynes, J; Darrah, P R; Watkinson, S C; Boddy, L

2008-08-01

Transport networks are vital components of multi-cellular organisms, distributing nutrients and removing waste products. Animal cardiovascular and respiratory systems, and plant vasculature, are branching trees whose architecture is thought to determine universal scaling laws in these organisms. In contrast, the transport systems of many multi-cellular fungi do not fit into this conceptual framework, as they have evolved to explore a patchy environment in search of new resources, rather than ramify through a three-dimensional organism. These fungi grow as a foraging mycelium, formed by the branching and fusion of threadlike hyphae, that gives rise to a complex network. To function efficiently, the mycelial network must both transport nutrients between spatially separated source and sink regions and also maintain its integrity in the face of continuous attack by mycophagous insects or random damage. Here we review the development of novel imaging approaches and software tools that we have used to characterise nutrient transport and network formation in foraging mycelia over a range of spatial scales. On a millimetre scale, we have used a combination of time-lapse confocal imaging and fluorescence recovery after photobleaching to quantify the rate of diffusive transport through the unique vacuole system in individual hyphae. These data then form the basis of a simulation model to predict the impact of such diffusion-based movement on a scale of several millimetres. On a centimetre scale, we have used novel photon-counting scintillation imaging techniques to visualize radiolabel movement in small microcosms. This approach has revealed novel N-transport phenomena, including rapid, preferential N-resource allocation to C-rich sinks, induction of simultaneous bi-directional transport, abrupt switching between different pre-existing transport routes, and a strong pulsatile component to transport in some species. Analysis of the pulsatile transport component using Fourier techniques shows that as the colony forms, it self-organizes into well demarcated domains that are identifiable by differences in the phase relationship of the pulses. On the centimetre to metre scale, we have begun to use techniques borrowed from graph theory to characterize the development and dynamics of the network, and used these abstracted network models to predict the transport characteristics, resilience, and cost of the network.

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.

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...

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.

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 forests.

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.

Phosphorus retention and internal loading in the Bay of Quinte, Lake Ontario, using diagenetic modelling.

PubMed

Doan, Phuong T K; Watson, Sue B; Markovic, Stefan; Liang, Anqi; Guo, Jay; Mugalingam, Shan; Stokes, Jonathan; Morley, Andrew; Zhang, Weitao; Arhonditsis, George B; Dittrich, Maria

2018-04-24

Internal phosphorus (P) loading significantly contributes to hysteresis in ecosystem response to nutrient remediation, but the dynamics of sediment P transformations are often poorly characterized. Here, we applied a reaction-transport diagenetic model to investigate sediment P dynamics in the Bay of Quinte, a polymictic, spatially complex embayment of Lake Ontario, (Canada). We quantified spatial and temporal variability of sediment P binding forms and estimated P diffusive fluxes and sediment P retention in different parts of the bay. Our model supports the notion that diagenetic recycling of redox sensitive and organic bound P forms drive sediment P release. In the recent years, summer sediment P diffusive fluxes varied in the range of 3.2-3.6 mg P m -2  d -1 in the upper bay compared to 1.5 mg P m -2  d -1 in the middle-lower bay. Meanwhile sediment P retention ranged between 71% and 75% in the upper and middle-lower bay, respectively. The reconstruction of temporal trends of internal P loading in the past century, suggests that against the backdrop of reduced external P inputs, sediment P exerts growing control over the lake nutrient budget. Higher sediment P diffusive fluxes since mid-20th century with particular increase in the past 20 years in the shallower upper basins, emphasize limited sediment P retention potential and suggest prolonged ecosystem recovery, highlighting the importance of ongoing P control measures. Copyright © 2018 Elsevier B.V. All rights reserved.

High-latitude dust in the Earth system

USGS Publications Warehouse

Bullard, Joanna E; Baddock, Matthew; Bradwell, Tom; Crusius, John; Darlington, Eleanor; Gaiero, Diego; Gasso, Santiago; Gisladottir, Gudrun; Hodgkins, Richard; McCulloch, Robert; NcKenna Neuman, Cheryl; Mockford, Tom; Stewart, Helena; Thorsteinsson, Throstur

2016-01-01

Natural dust is often associated with hot, subtropical deserts, but significant dust events have been reported from cold, high latitudes. This review synthesizes current understanding of high-latitude (≥50°N and ≥40°S) dust source geography and dynamics and provides a prospectus for future research on the topic. Although the fundamental processes controlling aeolian dust emissions in high latitudes are essentially the same as in temperate regions, there are additional processes specific to or enhanced in cold regions. These include low temperatures, humidity, strong winds, permafrost and niveo-aeolian processes all of which can affect the efficiency of dust emission and distribution of sediments. Dust deposition at high latitudes can provide nutrients to the marine system, specifically by contributing iron to high-nutrient, low-chlorophyll oceans; it also affects ice albedo and melt rates. There have been no attempts to quantify systematically the expanse, characteristics, or dynamics of high-latitude dust sources. To address this, we identify and compare the main sources and drivers of dust emissions in the Northern (Alaska, Canada, Greenland, and Iceland) and Southern (Antarctica, New Zealand, and Patagonia) Hemispheres. The scarcity of year-round observations and limitations of satellite remote sensing data at high latitudes are discussed. It is estimated that under contemporary conditions high-latitude sources cover >500,000 km2 and contribute at least 80–100 Tg yr−1 of dust to the Earth system (~5% of the global dust budget); both are projected to increase under future climate change scenarios.

Assessing digestibility of Hadza tubers using a dynamic in-vitro model.

PubMed

Schnorr, Stephanie L; Crittenden, Alyssa N; Venema, Koen; Marlowe, Frank W; Henry, Amanda G

2015-11-01

Bioaccessibility is a useful measure for assessing the biological value of a particular nutrient from food, especially foods such as tubers. The wild tubers exploited by Hadza foragers in Tanzania are of interest because they are nontoxic, consumed raw or briefly roasted, and entail substantial physical barriers to consumers. In this study, we attempted to elucidate the biological value of Hadza tubers by measuring the absorption of glucose through in-vitro digestion. We quantified digestibility using data from 24 experimental trials on four species of Hadza tuber using a dynamic in-vitro model that replicates digestion in the stomach and small intestine. Analysis of glucose in the input meal and output dialysate revealed the accessible glucose fraction. We also conducted assays for protein, vitamin, and mineral content on whole tubers and meal fractions. Bioaccessibility of glucose varies depending on tuber species. Holding effects of chewing constant, brief roasting had negligible effects, but high intraspecific variation precludes interpretive power. Overall, Hadza tubers are very resistant to digestion, with between one- and two-thirds of glucose absorbed on average. Glucose absorption negatively correlated with glucose concentration of the tubers. Roasting may provide other benefits such as ease of peeling and chewing to extract edible parenchymatous tissue. A powerful factor in glucose acquisition is tuber quality, placing emphasis on the skill of the forager. Other nutrient assays yielded unexpectedly high values for protein, iron, and iodine, making tubers potentially valuable resources beyond caloric content. © 2015 Wiley Periodicals, Inc.

High Latitude Dust in the Earth System

NASA Technical Reports Server (NTRS)

Bullard, Joanna E.; Baddock, Matthew; Bradwell, Tom; Crusius, John; Darlington, Eleanor; Gaiero, Diego; Gasso, Santiago; Gisladottir, Gudrun; Hodgkins, Richard; McCulloch, Robert;

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...

Adaptive dynamics of competition for nutritionally complementary resources: character convergence, displacement, and parallelism.

PubMed

Vasseur, David A; Fox, Jeremy W

2011-10-01

Consumers acquire essential nutrients by ingesting the tissues of resource species. When these tissues contain essential nutrients in a suboptimal ratio, consumers may benefit from ingesting a mixture of nutritionally complementary resource species. We investigate the joint ecological and evolutionary consequences of competition for complementary resources, using an adaptive dynamics model of two consumers and two resources that differ in their relative content of two essential nutrients. In the absence of competition, a nutritionally balanced diet rarely maximizes fitness because of the dynamic feedbacks between uptake rate and resource density, whereas in sympatry, nutritionally balanced diets maximize fitness because competing consumers with different nutritional requirements tend to equalize the relative abundances of the two resources. Adaptation from allopatric to sympatric fitness optima can generate character convergence, divergence, and parallel shifts, depending not on the degree of diet overlap but on the match between resource nutrient content and consumer nutrient requirements. Contrary to previous verbal arguments that suggest that character convergence leads to neutral stability, coadaptation of competing consumers always leads to stable coexistence. Furthermore, we show that incorporating costs of consuming or excreting excess nonlimiting nutrients selects for nutritionally balanced diets and so promotes character convergence. This article demonstrates that resource-use overlap has little bearing on coexistence when resources are nutritionally complementary, and it highlights the importance of using mathematical models to infer the stability of ecoevolutionary dynamics.

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...

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...

Evaluation of new alternatives in wastewater treatment plants based on dynamic modelling and life cycle assessment (DM-LCA).

PubMed

Bisinella de Faria, A B; Spérandio, M; Ahmadi, A; Tiruta-Barna, L

2015-11-01

With a view to quantifying the energy and environmental advantages of Urine Source-Separation (USS) combined with different treatment processes, five wastewater treatment plant (WWTP) scenarios were compared to a reference scenario using Dynamic Modelling (DM) and Life Cycle Assessment (LCA), and an integrated DM-LCA framework was thus developed. Dynamic simulations were carried out in BioWin(®) in order to obtain a realistic evaluation of the dynamic behaviour and performance of plants under perturbation. LCA calculations were performed within Umberto(®) using the Ecoinvent database. A Python™ interface was used to integrate and convert simulation data and to introduce them into Umberto(®) to achieve a complete LCA evaluation comprising foreground and background processes. Comparisons between steady-state and dynamic simulations revealed the importance of considering dynamic aspects such as nutrient and flow peaks. The results of the evaluation highlighted the potential of the USS scenario for nutrient recovery whereas the Enhanced Primary Clarification (EPC) scenario gave increased biogas production and also notably decreased aeration consumption, leading to a positive energy balance. Both USS and EPC scenarios also showed increased stability of plant operation, with smaller daily averages of total nitrogen and phosphorus. In this context, USS and EPC results demonstrated that the coupled USS + EPC scenario and its combinations with agricultural spreading of N-rich effluent and nitritation/anaerobic deammonification could present an energy-positive balance with respectively 27% and 33% lower energy requirements and an increase in biogas production of 23%, compared to the reference scenario. The coupled scenarios also presented lesser environmental impacts (reduction of 31% and 39% in total endpoint impacts) along with effluent quality well within the specified limits. The marked environmental performance (reduction of global warming) when nitrogen is used in agriculture shows the importance of future research on sustainable solutions for nitrogen recovery. The contribution analysis of midpoint impacts also showed hotspots that it will be important to optimize further, such as plant infrastructure and direct N2O emissions. Copyright © 2015 Elsevier Ltd. All rights reserved.

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.

Kinetics, bioavailability, and metabolism of RRR-alpha-tocopherol in humans supports lower requirement for vitamin E

USDA-ARS?s Scientific Manuscript database

Kinetic models enable nutrient needs and kinetic behaviors to be quantified and provide mechanistic insights into metabolism. Therefore, we modeled and quantified the kinetics, bioavailability and metabolism of RRR-alpha-tocopherol in 12 healthy adults. Six men and six women, aged 27 ± 6 y, each i...

Evaluation of the effectiveness of riparian zone restoration in the southern Appalachians by assessing soil microbial populations

Treesearch

Guanglong Tian; James M. Vose; David C. Coleman; Christopher D. Geron; John T. Walker

2004-01-01

Microbial biomass, nitrifiers and denitrifiers in surface soil (0-10 cm) were quantified in a riparian zone restoration project at Coweeta, North Carolina, USA. Four treatments are included in this study: ( I ) a degraded (+N) riparian zone with continued compaction, vegetation removal, and nutrient addition (mow, roll, and nutrient addition);(2) a degraded (-N)...

Mineral cycling in soil and litter arthropod food chains. Three-year progress report, February 1, 1984-January 31, 1987

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

Crossley, D.A. Jr.

1986-08-29

This report summarizes progress in a three-year research project on the influence of soil arthropods (mites, collembolans, insects, millipedes and others) upon decomposition rates and nutrient dynamics in decaying vegetable matter. Research has concentrated on two aspects of elemental dynamics in decomposing organic matter: Effects of arthropods on rates of decomposition and nutrient loss (mineralization of carbon and other elements), and arthropod stimulation of microbial immobilization of nutrient elements during decomposition.

The ebb and flood of Silica: Quantifying dissolved and biogenic silica fluxes from a temperate salt marsh

NASA Astrophysics Data System (ADS)

Vieillard, Amanda M.; Fulweiler, Robinson W.; Hughes, Zoe J.; Carey, Joanna C.

2011-12-01

Salt marshes are widely studied due to the broad range of ecosystem services they provide including serving as crucial wildlife habitat and as hotspots for biogeochemical cycling. Nutrients such as nitrogen (N), phosphorus (P), and carbon (C) are well studied in these systems. However, salt marshes may also be important environments for the cycling of another key nutrient, silica (Si). Found at the land-sea interface, these systems are silica replete with large stocks in plant biomass, sediments, and porewater, and therefore, have the potential to play a substantial role in the transformation and export of silica to coastal waters. In an effort to better understand this role, we measured the fluxes of dissolved (DSi) and biogenic (BSi) silica into and out of two tidal creeks in a temperate, North American (Rowley, Massachusetts, USA) salt marsh. One of the creeks has been fertilized from May to September for six years allowing us to examine the impacts of nutrient addition on silica dynamics within the marsh. High-resolution sampling in July 2010 showed no significant differences in Si concentrations between the fertilized and reference creeks with dissolved silica ranging from 0.5 to 108 μM and biogenic from 2.0 to 56 μM. Net fluxes indicated that the marsh is a point source of dissolved silica to the estuary in the summer with a net flux of approximately 169 mol h -1, demonstrating that this system exports DSi on the same magnitude as some nearby, mid-sized rivers. If these findings hold true for all salt marshes, then these already valuable regions are contributing yet another ecosystem service that has been previously overlooked; by exporting DSi to coastal receiving waters, salt marshes are actively providing this important nutrient for coastal primary productivity.

Soil Biogeochemistry in a Changing Climate: Effect of Snow Removal

NASA Astrophysics Data System (ADS)

Patel, K.; Tatariw, C.; Fernandez, I. J.; Macrae, J. D.; Ohno, T.

2016-12-01

Winter snowpack plays an important role in ecosystem functioning, thermally insulating the subnivean soil from freezing temperatures. Wintertime microbial mineralization of organic material results in accumulation of nutrients under the snowpack, which are available post-melt for plant root uptake. The northeastern United States has experienced declining snow accumulation, and climate models project this trend will continue in the future. Intermittent and reduced snow cover increases soil freezing and frost damage, which can have implications on spring nutrient availability and forest productivity. We conducted a 2-year snow removal experiment in the Dwight B. DeMeritt Forest at the University of Maine to study subnivean winter processes, and to examine the effect of a decreased snowpack on soil winter and spring biogeochemistry. Surface organic soils were collected during winter and spring of 2015 and 2016, years with sharply contrasting snow accumulation, to track temporal changes in nutrient dynamics as the system evolved from under the snowpack. Laboratory extractions and incubations were performed to quantify the inorganic available nitrogen, dissolved organic carbon (DOC), and potential net N-mineralization (PNNM) in field moist soils. Snow removal resulted in decreased winter soil temperatures (2-8°C colder than the reference plots). There was an increased incidence of rain-on-soil events in the winter, forming concrete frost. Freeze-thaw cycles in the treatment plots resulted in higher NH4-N and DOC concentrations, but lower PNNM, compared to the reference plots. Treatment effects on DOC and NH4-N concentrations were not seen in the spring, although the effects on PNNM persisted. Our findings demonstrated that freeze-thaw cycles play an important role in the timing and magnitude of soil nutrient availability during the vernal transition. Understanding these processes becomes increasingly important when defining forest ecosystem response to a changing climate.

The importance of benthic-pelagic coupling for marine ecosystem functioning in a changing world.

PubMed

Griffiths, Jennifer R; Kadin, Martina; Nascimento, Francisco J A; Tamelander, Tobias; Törnroos, Anna; Bonaglia, Stefano; Bonsdorff, Erik; Brüchert, Volker; Gårdmark, Anna; Järnström, Marie; Kotta, Jonne; Lindegren, Martin; Nordström, Marie C; Norkko, Alf; Olsson, Jens; Weigel, Benjamin; Žydelis, Ramunas; Blenckner, Thorsten; Niiranen, Susa; Winder, Monika

2017-06-01

Benthic-pelagic coupling is manifested as the exchange of energy, mass, or nutrients between benthic and pelagic habitats. It plays a prominent role in aquatic ecosystems, and it is crucial to functions from nutrient cycling to energy transfer in food webs. Coastal and estuarine ecosystem structure and function are strongly affected by anthropogenic pressures; however, there are large gaps in our understanding of the responses of inorganic nutrient and organic matter fluxes between benthic habitats and the water column. We illustrate the varied nature of physical and biological benthic-pelagic coupling processes and their potential sensitivity to three anthropogenic pressures - climate change, nutrient loading, and fishing - using the Baltic Sea as a case study and summarize current knowledge on the exchange of inorganic nutrients and organic material between habitats. Traditionally measured benthic-pelagic coupling processes (e.g., nutrient exchange and sedimentation of organic material) are to some extent quantifiable, but the magnitude and variability of biological processes are rarely assessed, preventing quantitative comparisons. Changing oxygen conditions will continue to have widespread effects on the processes that govern inorganic and organic matter exchange among habitats while climate change and nutrient load reductions may have large effects on organic matter sedimentation. Many biological processes (predation, bioturbation) are expected to be sensitive to anthropogenic drivers, but the outcomes for ecosystem function are largely unknown. We emphasize how improved empirical and experimental understanding of benthic-pelagic coupling processes and their variability are necessary to inform models that can quantify the feedbacks among processes and ecosystem responses to a changing world. © 2017 The Authors. Global Change Biology Published by John Wiley & Sons Ltd.

Bioreactor-based bone tissue engineering: The influence of dynamic flow on osteoblast phenotypic expression and matrix mineralization

PubMed Central

Yu, Xiaojun; Botchwey, Edward A.; Levine, Elliot M.; Pollack, Solomon R.; Laurencin, Cato T.

2004-01-01

An important issue in tissue engineering concerns the possibility of limited tissue ingrowth in tissue-engineered constructs because of insufficient nutrient transport. We report a dynamic flow culture system using high-aspect-ratio vessel rotating bioreactors and 3D scaffolds for culturing rat calvarial osteoblast cells. 3D scaffolds were designed by mixing lighter-than-water (density, <1g/ml) and heavier-than-water (density, >1g/ml) microspheres of 85:15 poly(lactide-co-glycolide). We quantified the rate of 3D flow through the scaffolds by using a particle-tracking system, and the results suggest that motion trajectories and, therefore, the flow velocity around and through scaffolds in rotating bioreactors can be manipulated by varying the ratio of heavier-than-water to lighter-than-water microspheres. When rat primary calvarial cells were cultured on the scaffolds in bioreactors for 7 days, the 3D dynamic flow environment affected bone cell distribution and enhanced cell phenotypic expression and mineralized matrix synthesis within tissue-engineered constructs compared with static conditions. These studies provide a foundation for exploring the effects of dynamic flow on osteoblast function and provide important insight into the design and optimization of 3D scaffolds suitable in bioreactors for in vitro tissue engineering of bone. PMID:15277663

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 equivalents, which allowed comparisons of the saprotrophic growth dynamics of the pathogen and antagonists to be made in single or mixed species microcosms. Trichoderma species were able to compete successfully with R. solani for nutrients and to prevent saprotrophic growth of the pathogen. Specificity of the Trichoderma quantitative assay was tested in non-sterile soil-based microcosms artificially inoculated with T. asperellum. The assay was highly specific and only detected T. asperellum population dynamics. No cross-reactivity was found with extracts from soil samples containing contaminant fungi.

Adaptation of pancreatic islet cyto-architecture during development

NASA Astrophysics Data System (ADS)

Striegel, Deborah A.; Hara, Manami; Periwal, Vipul

2016-04-01

Plasma glucose in mammals is regulated by hormones secreted by the islets of Langerhans embedded in the exocrine pancreas. Islets consist of endocrine cells, primarily α, β, and δ cells, which secrete glucagon, insulin, and somatostatin, respectively. β cells form irregular locally connected clusters within islets that act in concert to secrete insulin upon glucose stimulation. Varying demands and available nutrients during development produce changes in the local connectivity of β cells in an islet. We showed in earlier work that graph theory provides a framework for the quantification of the seemingly stochastic cyto-architecture of β cells in an islet. To quantify the dynamics of endocrine connectivity during development requires a framework for characterizing changes in the probability distribution on the space of possible graphs, essentially a Fokker-Planck formalism on graphs. With large-scale imaging data for hundreds of thousands of islets containing millions of cells from human specimens, we show that this dynamics can be determined quantitatively. Requiring that rearrangement and cell addition processes match the observed dynamic developmental changes in quantitative topological graph characteristics strongly constrained possible processes. Our results suggest that there is a transient shift in preferred connectivity for β cells between 1-35 weeks and 12-24 months.

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 shallower layers, where their effect on plant growth was temporarily most pronounced. At final harvest (21 DAS) however, effects of nitrification inhibitors on plant height were visible only in deeper layers. Furthermore, the statistically significant interaction between the factors time x layer depths x nitrification inhibitors underlined the dynamic influence of nitrification inhibitors on plant growth over time and across rooting depths. This study offers insights into optimizing nutrient uptake and plant productivity by (re-) using residues from the biogas industry. It is among the first to monitor and try to explain the dynamics of nitrification inhibitors on root system architecture over time. A modified N-fertilization application scheme might also serve as a promising tool in optimizing phytoremediation and phytomining techniques through predictably altering root structure in fertilized layers. References: Nagel, K. A. ; Putz, A. ; Gilmer, F. ; Heinz, K. ; Fischbach, A. ; Pfeifer, J. ; Faget, M. ; Blossfeld, S. ; Ernst, M. ; Dimaki, C. ; Kastenholz, B. ; Kleinert, A.-K. ; Galinski, A. ; Scharr, H. ; Fiorani, F. ; Schurr, U. (2012): GROWSCREEN-Rhizo is a novel phenotyping robot enabling simultaneous measurements of root and shoot growth for plants grown in soil-filled rhizotrons.
Functional plant biology 39(11), 891-904.

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

Soil quality succession of mudflat in coastal area of China under different types of man-made land uses

NASA Astrophysics Data System (ADS)

Lu, Haiying; Shao, Hongbo; Xu, Zhaolong; Peng, Cheng

2017-04-01

Marshy reclamation in coastal area is becoming an important strategy for food safety security and economic development in China. After the reclamation of mudflat, the nutrient concentration in soil is one of the dominated factors restricting the development of marshy agriculture. However, little information is available for soil nutrient dynamics and its driving mechanisms under different types of man-made land uses. In this review, we summarized the soil nutrient dynamics under different types of man-made land uses (bare mudflat soil, rice-wheat rotation soil, aquaculture soil, and forest soil), including the change of physical and chemical features of the reclaimed soil; ii) the dynamics of soil organic matters and its driving mechanism in marshy land; iii) the migration of N, P, and K in marshy soil; and iv) the oriented cultivation and improvement for soil nutrient in marshy soil. This study contributes not only to understanding the soil nutrient cycling in marshy land, but also to providing valuable information for the sustainable development of salt-soil agriculture in marshy land along seaside cities of China.

Optimal N:P ratios of growth media: quantification of nutrient-replete growth rates in five ion hyperspace for Chlorella vulgaris (Dinophyceae) and Peridinium cinctum (Dinophyceae).

USDA-ARS?s Scientific Manuscript database

In this study our principal goal was to quantify the main effects and interactions of several primary nutrient and bulk solution ions. The total ion concentration range chosen spans fresh to brackish waters (1-30 milliMolar) and explores most of the hypervolume delineated by the five ion/concentrat...

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.

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 used worldwide in other semi-arid regions requiring irrigation for agriculture as well as urban areas in developing countries with inadequate sanitation infrastructure. Copyright © 2015 Elsevier Ltd. All rights reserved.

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.

Litter decomposition, N2-fixer abundance, and microbial dynamics govern tropical dry forest recovery to land use change

NASA Astrophysics Data System (ADS)

Trierweiler, A.; Powers, J. S.; Xu, X.; Gei, M. G.; Medvigy, D.

2017-12-01

As one of the most threatened tropical biomes, Seasonal Dry Tropical Forests (TDF) have undergone extensive land-use change. However, some areas are undergoing recovery into secondary forests. Despite their broad distribution (42% of tropical forests), they are under-studied compared to wet tropical forests and our understanding of their biogeochemical cycling and belowground processes are limited. Here, we use models along with field measurements to improve our understanding of nutrient cycling and limitation in secondary TDFs. We ask (1) Is there modeling evidence that tropical dry forests can become nutrient limited? (2) What are the most important mechanisms employed to avoid nutrient limitation? (3) How might climate change alter biogeochemical cycling and nutrient limitation in recovering TDF? We use a new version of the Ecosystem Demography (ED2) model that has been recently parameterized for TDFs and incorporates a range of plant functional groups (including deciduousness and N2-fixation) and multiple resource constraints (carbon, nitrogen, phosphorus, and water). In the model, plants then can dynamically adjust their carbon allocation and nutrient acquisition strategies using N2-fixing bacteria and mycorrhizal fungi according to the nutrient limitation status. We ran the model for a nutrient gradient of field sites in Costa Rica and explored the sensitivity of nutrient limitation to key mechanisms including litter respiration, N resorption, N2-fixation, and overflow respiration. Future runs will evaluate how CO2 and climate change affect recovering TDFs. We found increasing nutrient limitation across the nutrient gradient of sites. Nitrogen limitation dominated the nutrient limitation signal. In the model, forest litter accumulation was negatively correlated with site fertility in Costa Rican forests. Our sensitivity analyses indicate that N2-fixer abundance, decomposition rates, and adding more explicit microbial dynamics are key factors in overcoming this limitation. These insights improve our understanding of how TDFs function and are especially relevant to the management of recovering secondary TDFs by highlighting potential bottlenecks in the recovery process.

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 contamination. Additional focused research and monitoring are needed to critically examine the link between nutrient supply and Hg contamination of marine waters. PMID:22749872

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 contamination. Additional focused research and monitoring are needed to critically examine the link between nutrient supply and Hg contamination of marine waters. Copyright © 2012 Elsevier Inc. All rights reserved.

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 pathways will show changes under different LULC conditions even if the slope remains the same. The graphical approach provides the statistics of connected and disconnected graph elements (edges, nodes) and graph components, thereby allowing the quantification of structural connectivity. This approach also quantifies the dynamic connectivity by allowing the measurement of the fluxes (e.g. via hydrographs or sedimentographs) at any node as well as at any system outlet. The contribution of any sub-system can be understood by removing the remaining sub-systems which can be conveniently achieved by masking associated graph elements.

Toward an integrated monitoring framework to assess the effects of tropical forest degradation and recovery on carbon stocks and biodiversity.

PubMed

Bustamante, Mercedes M C; Roitman, Iris; Aide, T Mitchell; Alencar, Ane; Anderson, Liana O; Aragão, Luiz; Asner, Gregory P; Barlow, Jos; Berenguer, Erika; Chambers, Jeffrey; Costa, Marcos H; Fanin, Thierry; Ferreira, Laerte G; Ferreira, Joice; Keller, Michael; Magnusson, William E; Morales-Barquero, Lucia; Morton, Douglas; Ometto, Jean P H B; Palace, Michael; Peres, Carlos A; Silvério, Divino; Trumbore, Susan; Vieira, Ima C G

2016-01-01

Tropical forests harbor a significant portion of global biodiversity and are a critical component of the climate system. Reducing deforestation and forest degradation contributes to global climate-change mitigation efforts, yet emissions and removals from forest dynamics are still poorly quantified. We reviewed the main challenges to estimate changes in carbon stocks and biodiversity due to degradation and recovery of tropical forests, focusing on three main areas: (1) the combination of field surveys and remote sensing; (2) evaluation of biodiversity and carbon values under a unified strategy; and (3) research efforts needed to understand and quantify forest degradation and recovery. The improvement of models and estimates of changes of forest carbon can foster process-oriented monitoring of forest dynamics, including different variables and using spatially explicit algorithms that account for regional and local differences, such as variation in climate, soil, nutrient content, topography, biodiversity, disturbance history, recovery pathways, and socioeconomic factors. Generating the data for these models requires affordable large-scale remote-sensing tools associated with a robust network of field plots that can generate spatially explicit information on a range of variables through time. By combining ecosystem models, multiscale remote sensing, and networks of field plots, we will be able to evaluate forest degradation and recovery and their interactions with biodiversity and carbon cycling. Improving monitoring strategies will allow a better understanding of the role of forest dynamics in climate-change mitigation, adaptation, and carbon cycle feedbacks, thereby reducing uncertainties in models of the key processes in the carbon cycle, including their impacts on biodiversity, which are fundamental to support forest governance policies, such as Reducing Emissions from Deforestation and Forest Degradation. © 2015 John Wiley & Sons Ltd.

Dengue Virus Inhibition of Autophagic Flux and Dependency of Viral Replication on Proteasomal Degradation of the Autophagy Receptor p62

PubMed Central

Metz, Philippe; Chiramel, Abhilash; Chatel-Chaix, Laurent; Alvisi, Gualtiero; Bankhead, Peter; Mora-Rodríguez, Rodrigo; Long, Gang; Hamacher-Brady, Anne

2015-01-01

ABSTRACT Autophagic flux involves formation of autophagosomes and their degradation by lysosomes. Autophagy can either promote or restrict viral replication. In the case of Dengue virus (DENV), several studies report that autophagy supports the viral replication cycle, and describe an increase of autophagic vesicles (AVs) following infection. However, it is unknown how autophagic flux is altered to result in increased AVs. To address this question and gain insight into the role of autophagy during DENV infection, we established an unbiased, image-based flow cytometry approach to quantify autophagic flux under normal growth conditions and in response to activation by nutrient deprivation or the mTOR inhibitor Torin1. We found that DENV induced an initial activation of autophagic flux, followed by inhibition of general and specific autophagy. Early after infection, basal and activated autophagic flux was enhanced. However, during established replication, basal and Torin1-activated autophagic flux was blocked, while autophagic flux activated by nutrient deprivation was reduced, indicating a block to AV formation and reduced AV degradation capacity. During late infection AV levels increased as a result of inefficient fusion of autophagosomes with lysosomes. In addition, endolysosomal trafficking was suppressed, while lysosomal activities were increased. We further determined that DENV infection progressively reduced levels of the autophagy receptor SQSTM1/p62 via proteasomal degradation. Importantly, stable overexpression of p62 significantly suppressed DENV replication, suggesting a novel role for p62 as a viral restriction factor. Overall, our findings indicate that in the course of DENV infection, autophagy shifts from a supporting to an antiviral role, which is countered by DENV. IMPORTANCE Autophagic flux is a dynamic process starting with the formation of autophagosomes and ending with their degradation after fusion with lysosomes. Autophagy impacts the replication cycle of many viruses. However, thus far the dynamics of autophagy in case of Dengue virus (DENV) infections has not been systematically quantified. Therefore, we used high-content, imaging-based flow cytometry to quantify autophagic flux and endolysosomal trafficking in response to DENV infection. We report that DENV induced an initial activation of autophagic flux, followed by inhibition of general and specific autophagy. Further, lysosomal activity was increased, but endolysosomal trafficking was suppressed confirming the block of autophagic flux. Importantly, we provide evidence that p62, an autophagy receptor, restrict DENV replication and was specifically depleted in DENV-infected cells via increased proteasomal degradation. These results suggest that during DENV infection autophagy shifts from a proviral to an antiviral cellular process, which is counteracted by the virus. PMID:26018155

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...

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.

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 respiration, respectively. Root exudation and carbon export to mycorrhizal represent about 7% of plant Net Primary Production. The model allows exploring the temporal dynamics of respiration fluxes from the different ecosystem components and designing virtual experiments on the controls exerted by environmental variables and/or soil microbes and mycorrhizal associations on soil carbon storage, plant growth, and nutrient leaching.

FACTORS INFLUENCING CARBON, NITROGEN, AND PHOSPHORUS CONTENT OF FISH FROM A LAKE SUPERIOR COASTAL WETLAND: LIFE HISTORY VERSUS MORPHOMETRICS.

EPA Science Inventory

The narrow fish nutrient ranges (C, 42.8-48.4%; N. 9.6-12.7%; P, 1.91-2.74%) in this study suggest that overall mean values are adequate for quantifying movement of C, N, or P as part of fish-mediated nutrient transport. We measured C, N, or P in 20 species of Lake Superior coas...

FACTORS INFLUENCING CARBON, NITROGEN, AND PHOSPHORUS CONTENT OF FISH FROM A LAKE SUPERIOR COASTAL WETLAND: LIFE HISTORY VERSUS MORPHOMETRICS

EPA Science Inventory

The narrow fish nutrient ranges (C, 42.8-48.4%; N, 9.6-12.7%; P, 1.91-2.74%) in this study suggest that overall mean values are adequate for quantifying movement of C, N, or P as part of fish-mediated nutrient transport. We measured C, N, and P in 20 species of Lake Superior coa...

Aggregating land use quantity and intensity to link water quality in upper catchment of Miyun Reservoir

NASA Astrophysics Data System (ADS)

Xu, E.

2015-12-01

Land use is closely related to hydrological and biochemical processes influencing the water quality. Quantifying relationship between both of them can help effectively manage land use to improve water quality. Previous studies majorly utilized land use quantity as an indicator to link water quality parameters, which lacked an insight to the influence of land use intensity. Taking upper catchment of Miyun Reservoir as a case study, we proposed a method of aggregating land use quantity and intensity to build a new land use indicator and investigated its explanation empower on water quality. Six nutrient concentrations from 52 sub-watersheds covering the whole catchment were used to characterize spatial distributions of water eutrophication. Based on spatial techniques and empirical conversion coefficients, combined remote sensing with socio-economic statistical data, land use intensity was measured and mapped visually. Then the new land use indicator was calculated and linked to nutrient concentrations by Pearson correlation coefficients. Results demonstrated that our new land use indicator incorporating intensity information can quantify the potential different nutrients exporting abilities from land uses. Comparing to traditional indicators only characterized by land use quantity, most Pearson correlation coefficients between new indicator and water nutrient concentrations increased. New information enhanced the explanatory power of land use on water nutrient concentrations. Then it can help better understand the impact of land use on water quality and guide land use management for supporting decision making.

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.

Microbial processes in marine ecosystem models: state of the art and future prospective

NASA Astrophysics Data System (ADS)

Polimene, L.; Butenschon, M.; Blackford, J.; Allen, I.

2012-12-01

Heterotrophic bacteria play a key role in the marine biogeochemistry being the main consumer of dissolved organic matter (DOM) and the main producer of carbon dioxide (CO2) by respiration. Quantifying the carbon and energy fluxes within bacteria (i.e. production, respiration, overflow metabolism etc.) is therefore crucial for the assessment of the global ocean carbon and nutrient cycles. Consequently, the description of bacteria dynamic in ecosystem models is a key (although challenging) issue which cannot be overlooked if we want to properly simulate the marine environment. We present an overview of the microbial processes described in the European Sea Regional Ecosystem Model (ERSEM), a state of the art biogeochemical model resolving carbon and nutrient cycles (N, P, Si and Fe) within the low trophic levels (up to mesozooplankton) of the marine ecosystem. The description of the theoretical assumptions and philosophy underpinning the ERSEM bacteria sub-model will be followed by the presentation of some case studies highlighting the relevance of resolving microbial processes in the simulation of ecosystem dynamics at a local scale. Recent results concerning the implementation of ERSEM on a global ocean domain will be also presented. This latter exercise includes a comparison between simulations carried out with the full bacteria sub-model and simulations carried out with an implicit parameterization of bacterial activity. The results strongly underline the importance of explicitly resolved bacteria in the simulation of global carbon fluxes. Finally, a summary of the future developments along with issues still open on the topic will be presented and discussed.

Post-Fire Spatial Patterns of Soil Nitrogen Mineralization and Microbial Abundance

PubMed Central

Smithwick, Erica A. H.; Naithani, Kusum J.; Balser, Teri C.; Romme, William H.; Turner, Monica G.

2012-01-01

Stand-replacing fires influence soil nitrogen availability and microbial community composition, which may in turn mediate post-fire successional dynamics and nutrient cycling. However, fires create patchiness at both local and landscape scales and do not result in consistent patterns of ecological dynamics. The objectives of this study were to (1) quantify the spatial structure of microbial communities in forest stands recently affected by stand-replacing fire and (2) determine whether microbial variables aid predictions of in situ net nitrogen mineralization rates in recently burned stands. The study was conducted in lodgepole pine (Pinus contorta var. latifolia) and Engelmann spruce/subalpine fir (Picea engelmannii/Abies lasiocarpa) forest stands that burned during summer 2000 in Greater Yellowstone (Wyoming, USA). Using a fully probabilistic spatial process model and Bayesian kriging, the spatial structure of microbial lipid abundance and fungi-to-bacteria ratios were found to be spatially structured within plots two years following fire (for most plots, autocorrelation range varied from 1.5 to 10.5 m). Congruence of spatial patterns among microbial variables, in situ net N mineralization, and cover variables was evident. Stepwise regression resulted in significant models of in situ net N mineralization and included variables describing fungal and bacterial abundance, although explained variance was low (R2<0.29). Unraveling complex spatial patterns of nutrient cycling and the biotic factors that regulate it remains challenging but is critical for explaining post-fire ecosystem function, especially in Greater Yellowstone, which is projected to experience increased fire frequencies by mid 21st Century. PMID:23226324

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...

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 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

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 regeneration and mineralization are minimized. In summary, the transport-based, time-series approach provides a means of estimating traditional measures of nutrient uptake (SW, V?? U) while providing additional information on the location and magnitude of uptake (main channel versus storage zone). Application of the transport-based approach to time-series data from Green Creek, Antarctica, indicates that the bulk of nitrate uptake (???74% to 100%) occurred within the main channel where benthic uptake by algal mats is a likely process. Substantial uptake (???26%) also occurred in the storage zone of one reach, where uptake is attributed to the microbial community.

ESTUARINE-OCEAN EXCHANGE IN A NORTH PACIFIC ESTUARY: COMPARISON OF STEADY STATE AND DYNAMIC MODELS

EPA Science Inventory

Nutrient levels in coastal waters must be accurately assessed to determine the nutrient effects of increasing populations on coastal ecosystems. To accomplish this goal, in-field data with sufficient temporal resolution are required to define nutrient sources and sinks, and to ul...

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 ...

Nonlinear and Synchronous Dissolved Organic Matter Dynamics in Streams Across an Agriculture Land Use and Climate Setting

NASA Astrophysics Data System (ADS)

Xenopoulos, M. A.; Vogt, R. J.

2014-12-01

There is now increasing evidence that non-linearity is a common response in ecological systems to pressures caused by human activities. There is also increasing evidence that exogenous environmental drivers, such as climate, induce spatial and temporal synchrony in a wide range of ecological variables. Using Moran's I and Pearson's correlation, we quantified the synchrony of dissolved organic carbon concentration (DOC) and quality (DOM; e.g., specific UV absorbance, Fluorescence Index, PARAFAC), nutrients, discharge and temperature in 40 streams that span an agriculture gradient (0 to >70% cropland), over 10 years. We then used breakpoint regression, 2D-Kolmogorov-Smirnov test and significant zero crossings (SiZer) analyses to quantify the prevalence of nonlinearity and ecological thresholds (breakpoints) where applicable. There was a high degree of synchrony in DOM quality (r > 0.7) but not DOC (r < 0.4). The degree of synchrony was driven in part by the catchment's land use. With respect to the nonlinear analyses we found non-linearity in ~50% of bivariate datasets analyzed. Non-linearity was also driven in part by the catchment's land use. Breakpoints defined different DOM properties. Nonlinearity and synchronous behaviour in DOM are intimately linked to land use.

Quantification of the inevitable: the influence of soil macrofauna on soil water movement in rehabilitated open-cut mine land

NASA Astrophysics Data System (ADS)

Arnold, S.; Williams, E. R.

2015-08-01

Recolonisation of soil by macrofauna (especially ants and termites) in rehabilitated open-cut mine sites is inevitable. In these highly disturbed landscapes, soil invertebrates play a major role in soil development (macropore configuration, nutrient cycling, bioturbation, etc.) and can influence hydrological processes such as infiltration and seepage. Understanding and quantifying these ecosystem processes is important in rehabilitation design, establishment and subsequent management to ensure progress to the desired end-goal, especially in waste cover systems designed to prevent water reaching and transporting underlying hazardous waste materials. However, soil macrofauna are typically overlooked during hydrological modelling, possibly due to uncertainties on the extent of their influence, which can lead to failure of waste cover systems or rehabilitation activities. We propose that scientific experiments under controlled conditions are required to quantify (i) macrofauna - soil structure interactions, (ii) functional dynamics of macrofauna taxa, and (iii) their effects on macrofauna and soil development over time. Such knowledge would provide crucial information for soil water models, which would increase confidence in mine waste cover design recommendations and eventually lead to higher likelihood of rehabilitation success of open-cut mining land.

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.

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 conditions to predict and understand the effects of consumers on ecosystem-level nutrient dynamics across temporal and spatial scales. Moreover, new work in CND should strive to integrate knowledge from disparate fields of ecology and environmental science, such as physiology and ecosystem ecology, to develop a comprehensive and mechanistic understanding of the functional role of consumers. Comparative and experimental studies that develop testable hypotheses to challenge the current assumptions of CND, including consumer stoichiometric homeostasis, are needed to assess the significance of CND among species and across freshwater ecosystems. © 2016 Cambridge Philosophical Society.

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.

Riparian zone hydrology and biogeochemistry as a function of stream evolution stage in glaciated landscapes of the US Northeast

NASA Astrophysics Data System (ADS)

Rook, S. P.; Vidon, P.; Walter, M. T.

2011-12-01

The management of riparian buffer strips is often regarded as one of the most economical and sustainable methods of managing non-point source pollution and water quality. However, current riparian management often follows a 'one size fits all' design, which fails to recognize the complexity of the many biogeochemical processes that regulate pollutant transformation and retention in these systems. This study addresses two critical gaps in knowledge: (1) How carbon, nitrogen, phosphorous, and iron cycles interact with one another (rather than individually). (2) How stream channel geometry and evolution regulate these nutrient cycles and greenhouse gas (GHG) dynamics in the near stream zone. This project specifically explores the hydrological and biogeochemical functioning of riparian zones across a gradient of stream meander evolution stages, with the primary goal of understanding and predicting potential interactions between nutrient dynamics in these systems. Key research questions include: (1) How does stream meander curvature affect riparian zone hydrology? (2) How does stream meander curvature influence riparian zone biogeochemistry? (3) What relationships exist among N, P, Fe, and GHG dynamics? We instrumented three riparian sites near Ithaca, NY, with a dense network of wells, piezometers, and static chambers. These sites represent three riparian zones along three evolution stages of stream meanders: an inner meander, a straight stream section, and an outer bend of the stream with an oxbow lake formation. In spring through fall 2011, water samples and gas samples were collected at a tri-weekly bases at each of the three sites. Water samples were analyzed for oxidation-reduction potential, dissolved oxygen, temperature, FeII/FeIII, nutrients (NO3-, NH4+, PO43-) and dissolved organic carbon (DOC). GHG fluxes at the soil-atmosphere interface were measured for N2O, CO2, and CH4 gases. We predict that stream curvature will significantly affect groundwater flow direction in the riparian zones. Owing to more prolonged saturation, we expect that the oxbow setting will exhibit anoxic conditions, and associated biogeochemistry. Finally, we hypothesize clear relationships among N, P, Fe, and GHG dynamics. In areas of significant denitrification, we expect to see an increase in Fe reduction, PO43- release, N2O emission, and CH4 emission, and a decrease in CO2 emission. Quantifying these interactions will enhance our ability to model riparian biogeochemical processes, promote water quality, and comprehend to what extent the promotion of riparian zones for nitrate removal is done at the expense of air quality (with respect to GHG emissions) and/or water quality (with respect to P).

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.

Integration of Carbon, Nitrogen, and Oxygen Metabolism in Escherichia coli--Final Report

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

Rabinowitz, Joshua D; Wingreen, Ned s; Rabitz, Herschel A

2012-10-22

A key challenge for living systems is balancing utilization of multiple elemental nutrients, such as carbon, nitrogen, and oxygen, whose availability is subject to environmental fluctuations. As growth can be limited by the scarcity of any one nutrient, the rate at which each nutrient is assimilated must be sensitive not only to its own availability, but also to that of other nutrients. Remarkably, across diverse nutrient conditions, E. coli grows nearly optimally, balancing effectively the conversion of carbon into energy versus biomass. To investigate the link between the metabolism of different nutrients, we quantified metabolic responses to nutrient perturbations usingmore » LC-MS based metabolomics and built differential equation models that bridge multiple nutrient systems. We discovered that the carbonaceous substrate of nitrogen assimilation, -ketoglutarate, directly inhibits glucose uptake and that the upstream glycolytic metabolite, fructose-1,6-bisphosphate, ultrasensitively regulates anaplerosis to allow rapid adaptation to changing carbon availability. We also showed that NADH controls the metabolic response to changing oxygen levels. Our findings support a general mechanism for nutrient integration: limitation for a nutrient other than carbon leads to build-up of the most closely related product of carbon metabolism, which in turn feedback inhibits further carbon uptake.« less

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

Early warning indicators for river nutrient and sediment loads in tropical seagrass beds: a benchmark from a near-pristine archipelago in Indonesia.

PubMed

van Katwijk, M M; van der Welle, M E W; Lucassen, E C H E T; Vonk, J A; Christianen, M J A; Kiswara, W; al Hakim, I Inayat; Arifin, A; Bouma, T J; Roelofs, J G M; Lamers, L P M

2011-07-01

In remote, tropical areas human influences increase, potentially threatening pristine seagrass systems. We aim (i) to provide a bench-mark for a near-pristine seagrass system in an archipelago in East Kalimantan, by quantifying a large spectrum of abiotic and biotic properties in seagrass meadows and (ii) to identify early warning indicators for river sediment and nutrient loading, by comparing the seagrass meadow properties over a gradient with varying river influence. Abiotic properties of water column, pore water and sediment were less suitable indicators for increased sediment and nutrient loading than seagrass properties. Seagrass meadows strongly responded to higher sediment and nutrient loads and proximity to the coast by decreasing seagrass cover, standing stock, number of seagrass species, changing species composition and shifts in tissue contents. Our study confirms that nutrient loads are more important than water nutrient concentrations. We identify seagrass system variables that are suitable indicators for sediment and nutrient loading, also in rapid survey scenarios with once-only measurements. Copyright © 2011 Elsevier Ltd. All rights reserved.

From theory to field experiments

NASA Astrophysics Data System (ADS)

de Vos, Bram

2016-04-01

Peter Raats' achievements in Haren (NL) 1986-1997 were based on a solid theoretical insight in hydrology and transport process in soil. However, Peter was also the driving force behind many experimental studies and applied research. This will be illustrated by a broad range of examples ranging from the dynamics of composting processes of organic material; modelling and monitoring nutrient leaching at field-scale; wind erosion; water and nutrient dynamics in horticultural production systems; oxygen diffusion in soils; and processes of water and nutrient uptake by plant roots. Peter's leadership led to may new approaches and the introduction of innovative measurement techniques in Dutch research; ranging from TDR to nutrient concentration measurements in closed fertigation systems. This presentation will give a brief overview how Peter's theoretical and mathematical insights accelerated this applied research.

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.

Flow Partitioning in Fully Saturated Soil Aggregates

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

Yang, Xiaofan; Richmond, Marshall C.; Scheibe, Timothy D.

2014-03-30

Microbes play an important role in facilitating organic matter decomposition in soils, which is a major component of the global carbon cycle. Microbial dynamics are intimately coupled to environmental transport processes, which control access to labile organic matter and other nutrients that are needed for the growth and maintenance of microorganisms. Transport of soluble nutrients in the soil system is arguably most strongly impacted by preferential flow pathways in the soil. Since the physical structure of soils can be characterized as being formed from constituent micro aggregates which contain internal porosity, one pressing question is the partitioning of the flowmore » among the “inter-aggregate” and “intra-aggregate” pores and how this may impact overall solute transport within heterogeneous soil structures. The answer to this question is particularly important in evaluating assumptions to be used in developing upscaled simulations based on highly-resolved mechanistic models. We constructed a number of diverse multi-aggregate structures with different packing ratios by stacking micro-aggregates containing internal pores and varying the size and shape of inter-aggregate pore spacing between them. We then performed pore-scale flow simulations using computational fluid dynamics methods to determine the flow patterns in these aggregate-of-aggregates structures and computed the partitioning of the flow through intra- and inter-aggregate pores as a function of the spacing between the aggregates. The results of these numerical experiments demonstrate that soluble nutrients are largely transported via flows through inter-aggregate pores. Although this result is consistent with intuition, we have also been able to quantify the relative flow capacity of the two domains under various conditions. For example, in our simulations, the flow capacity through the aggregates (intra-aggregate flow) was less than 2% of the total flow when the spacing between the aggregates was larger than 18 micron. Inter-aggregate pores continued to be the dominant flow pathways even at much smaller spacing; intra-aggregate flow was less than 10% of the total flow when the inter- and intra-aggregate pore sizes were comparable. Such studies are making it possible to identify which model upscaling assumptions are realistic and what computational methods are required for detailed numerical investigation of microbial carbon cycling dynamics in soil systems.« less

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.

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.

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.

Pesticide and nitrate transport in an agriculturally influenced stream in Indiana.

PubMed

Elias, Daniel; Bernot, Melody J

2017-04-01

Agrochemicals can be transported from agricultural fields into streams where they might have adverse effects on water quality and ecosystems. Three enrichment experiments were conducted in a central Indiana stream to quantify pesticide and nitrogen transport dynamics. In an enrichment experiment, a compound solution is added at a constant rate into a stream to increase compound background concentration. A conservative tracer (e.g., bromide) is added to determine discharge. Water and sediment samples are taken at several locations downstream to measure uptake metrics. We assessed transport of nitrate, atrazine, metolachlor, and carbaryl through direct measurement of uptake length (S w ), uptake velocity (V f ), and areal uptake (U). S w measures the distance traveled by a nutrient along the stream reach. V f measures the velocity a nutrient moves from the water column to immobilization sites. U represents the amount of nutrient immobilized in an area of streambed per unit of time. S w varied less than one order of magnitude across pesticides. The highest S w for atrazine suggests greater transport to downstream ecosystems. Across compounds, pesticide S w was longest in August relative to October and July. V f varied less than one order of magnitude across pesticides with the highest V f for metolachlor. U varied three orders of magnitude across pesticides with the highest U associate with sediment-bound carbaryl. Increasing nitrate S w suggests a lower nitrate demand of biota in this stream. Overall, pesticide transport was best predicted by compound solubility which can complement and improve models of pesticide abundance used by water quality programs and risk assessments.

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...

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.

Production regimes in four eastern boundary current systems

NASA Technical Reports Server (NTRS)

Carr, M. E.; Kearns, E. J.

2003-01-01

High productivity (maxima 3 g C m(sup -2)day(sup -1)) of the Eastern Boundary Currents (EBCs), i.e. the California, Peru-Humboldt, Canary and Benguela Currents, is driven by a combination of local forcing and large-scale circulation. The characteristics of the deep water brought to the surface by upwelling favorable winds depend on the large-scale circulation patterns. Here we use a new hydrographic and nutrient climatology together with satellite measurements ofthe wind vector, sea-surface temperature (SST), chlorophyll concentration, and primary production modeled from ocean color to quantify the meridional and seasonal patterns of upwelling dynamics and biological response. The unprecedented combination of data sets allows us to describe objectively the variability for small regions within each current and to characterize the governing factors for biological production. The temporal and spatial environmental variability was due in most regions to large-scale circulation, alone or in combination with offshore transport (local forcing). The observed meridional and seasonal patterns of biomass and primary production were most highlycorrelated to components representing large-scale circulation. The biomass sustained by a given nutrient concentration in the Atlantic EBCs was twice as large as that of the Pacific EBCs. This apparent greater efficiency may be due toavailability of iron, physical retention, or differences in planktonic community structure.

PHYSICAL AND BIOLOGICAL CONTROLS ON DISSOLVED OXYGEN DYNAMICS IN A NORTHEASTERN GULF OF MEXICO ESTUARY

EPA Science Inventory

Nutrient over-enrichment is one of the most often cited causes of 305b impairment in coastal waters. Excessive nutrients affect designated uses of the nation's aquatic resources, and pose risks to human health and the environment. The process of developing nutrient criteria for e...

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.

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.

Decomposition and nitrogen dynamics of 15N-labeled leaf, root, and twig litter in temperate coniferous forests

USGS Publications Warehouse

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

2013-01-01

Litter nutrient dynamics contribute significantly to biogeochemical cycling in forest ecosystems. We examined how site environment and initial substrate quality influence decomposition and nitrogen (N) dynamics of multiple litter types. A 2.5-year decomposition study was installed in the Oregon Coast Range and West Cascades using 15N-labeled litter from Acer macrophyllum, Picea sitchensis, and Pseudotsuga menziesii. Mass loss for leaf litter was similar between the two sites, while root and twig litter exhibited greater mass loss in the Coast Range. Mass loss was greatest from leaves and roots, and species differences in mass loss were more prominent in the Coast Range. All litter types and species mineralized N early in the decomposition process; only A. macrophyllum leaves exhibited a net N immobilization phase. There were no site differences with respect to litter N dynamics despite differences in site N availability, and litter N mineralization patterns were species-specific. For multiple litter × species combinations, the difference between gross and net N mineralization was significant, and gross mineralization was 7–20 % greater than net mineralization. The mineralization results suggest that initial litter chemistry may be an important driver of litter N dynamics. Our study demonstrates that greater amounts of N are cycling through these systems than may be quantified by only measuring net mineralization and challenges current leaf-based biogeochemical theory regarding patterns of N immobilization and mineralization.

Dynamics of multiple elements in fast decomposing vegetable residues.

PubMed

Cao, Chun; Liu, Si-Qi; Ma, Zhen-Bang; Lin, Yun; Su, Qiong; Chen, Huan; Wang, Jun-Jian

2018-03-01

Litter decomposition regulates the cycling of nutrients and toxicants but is poorly studied in farmlands. To understand the unavoidable in-situ decomposition process, we quantified the dynamics of C, H, N, As, Ca, Cd, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, Pb, and Zn during a 180-d decomposition study in leafy lettuce (Lactuca sativa var. longifoliaf) and rape (Brassica chinensis) residues in a wastewater-irrigated farmland in northwestern China. Different from most studied natural ecosystems, the managed vegetable farmland had a much faster litter decomposition rate (half-life of 18-60d), and interestingly, faster decomposition of roots relative to leaves for both the vegetables. Faster root decomposition can be explained by the initial biochemical composition (more O-alkyl C and less alkyl and aromatic C) but not the C/N stoichiometry. Multi-element dynamics varied greatly, with C, H, N, K, and Na being highly released (remaining proportion<20%), Ca, Cd, Cr, Mg, Ni, and Zn released, and As, Cu, Fe, Hg, Mn, and Pb possibly accumulated. Although vegetable residues serve as temporary sinks of some metal(loid)s, their fast decomposition, particularly for the O-alkyl-C-rich leafy-lettuce roots, suggest that toxic metal(loid)s can be released from residues, which therefore become secondary pollution sources. Copyright © 2017 Elsevier B.V. All rights reserved.

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.

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.

Methyl-Donor and Cofactor Nutrient Intakes in the First 2–3 Years and Global DNA Methylation at Age 4: A Prospective Cohort Study

PubMed Central

Taylor, Rachael M.; Smith, Roger; Collins, Clare E.; Mossman, David; Wong-Brown, Michelle W.; Chan, Eng-Cheng; Evans, Tiffany-Jane; Attia, John R.; Smith, Tenele; Butler, Trent

2018-01-01

Background: During the early postnatal period, the impact of nutrition on DNA methylation has not been well studied in humans. The aim was to quantify the relationship between one-carbon metabolism nutrient intake during the first three years of life and global DNA methylation levels at four years. Design: Childhood dietary intake was assessed using infant feeding questionnaires, food frequency questionnaires, 4-day weighed food records and 24-h food records. The dietary records were used to estimate the intake of methionine, folate, vitamins B2, B6 and B12 and choline. The accumulative nutrient intake specific rank from three months to three years of age was used for analysis. Global DNA methylation (%5-methyl cytosines (%5-mC)) was measured in buccal cells at four years of age, using an enzyme-linked immunosorbent assay (ELISA) commercial kit. Linear regression models were used to quantify the statistical relationships. Results: Data were collected from 73 children recruited from the Women and their Children’s Health (WATCH) study. No association was found between one-carbon metabolism nutrient intake and global DNA methylation levels (P 0.05). Global DNA methylation levels in males were significantly higher than in females (median %5-mC: 1.82 vs. 1.03, males and females respectively, (P 0.05)). Conclusion: No association was found between the intake of one-carbon metabolism nutrients during the early postnatal period and global DNA methylation levels at age four years. Higher global DNA methylation levels in males warrants further investigation. PMID:29495543

An In situ Study of Seasonal Dissolved Organic Carbon and Nutrient Fluxes from a Spartina alterniflora Salt Marsh in North Carolina

NASA Astrophysics Data System (ADS)

Detweiler, D. J.; Loh, A. N.

2016-02-01

Spartina alterniflora salt marshes are among the most productive and biogeochemically active ecosystems on Earth. While they have been shown to be sources of dissolved organic carbon (DOC) and nutrient export to the coastal ocean via tidal processes, it has not been well quantified experimentally. The purpose of this study was to quantify DOC and nutrient fluxes from a fringing S. alterniflora salt marsh in North Carolina. The experiment was conducted using in situ benthic microcosm chambers filled with seawater during a flooding tide; the chambers were then plugged, and samples were collected during an ebbing tide over the course of 270 minutes while simulating light and dark conditions. Water samples were filtered and analyzed for DOC and nutrient concentrations over time and used to calculate fluxes from vegetated (S. alterniflora) and non-vegetated marsh sediments. Preliminary daily flux calculations show that fluxes from vegetated sediments have a higher magnitude when compared to fluxes from non-vegetated sediments. Daily flux calculations also suggest that vegetated sediments act as a DOC source while non-vegetated sediments act as a DOC sink. Additional flux data for dissolved inorganic and organic nitrogen (DIN, DON) and dissolved inorganic and organic phosphorus (DIP, DOP) as well as marsh sediment characterization will also be presented. Ultimately, these data will provide seasonal daily flux calculations for S. alterniflora salt marshes and insight as to how changing environmental conditions such as wetland modification, wetland destruction, nutrient input, and climate change are affecting coastal biogeochemical cycles.

Importance of terrestrial arthropods as subsidies in lowland Neotropical rain forest stream ecosystems

USGS Publications Warehouse

Small, Gaston E.; Torres, Pedro J.; Schwizer, Lauren M.; Duff, John H.; Pringle, Catherine M.

2013-01-01

The importance of terrestrial arthropods has been documented in temperate stream ecosystems, but little is known about the magnitude of these inputs in tropical streams. Terrestrial arthropods falling from the canopy of tropical forests may be an important subsidy to tropical stream food webs and could also represent an important flux of nitrogen (N) and phosphorus (P) in nutrient-poor headwater streams. We quantified input rates of terrestrial insects in eight streams draining lowland tropical wet forest in Costa Rica. In two focal headwater streams, we also measured capture efficiency by the fish assemblage and quantified terrestrially derived N- and P-excretion relative to stream nutrient uptake rates. Average input rates of terrestrial insects ranged from 5 to 41 mg dry mass/m2/d, exceeding previous measurements of aquatic invertebrate secondary production in these study streams, and were relatively consistent year-round, in contrast to values reported in temperate streams. Terrestrial insects accounted for half of the diet of the dominant fish species, Priapicthys annectens. Although terrestrially derived fish excretion was found to be a small flux relative to measured nutrient uptake rates in the focal streams, the efficient capture and processing of terrestrial arthropods by fish made these nutrients available to the local stream ecosystem. This aquatic-terrestrial linkage is likely being decoupled by deforestation in many tropical regions, with largely unknown but potentially important ecological consequences.

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.

Mitochondrial Dynamics Mediated by Mitofusin 1 Is Required for POMC Neuron Glucose-Sensing and Insulin Release Control.

PubMed

Ramírez, Sara; Gómez-Valadés, Alicia G; Schneeberger, Marc; Varela, Luis; Haddad-Tóvolli, Roberta; Altirriba, Jordi; Noguera, Eduard; Drougard, Anne; Flores-Martínez, Álvaro; Imbernón, Mónica; Chivite, Iñigo; Pozo, Macarena; Vidal-Itriago, Andrés; Garcia, Ainhoa; Cervantes, Sara; Gasa, Rosa; Nogueiras, Ruben; Gama-Pérez, Pau; Garcia-Roves, Pablo M; Cano, David A; Knauf, Claude; Servitja, Joan-Marc; Horvath, Tamas L; Gomis, Ramon; Zorzano, Antonio; Claret, Marc

2017-06-06

Proopiomelanocortin (POMC) neurons are critical sensors of nutrient availability implicated in energy balance and glucose metabolism control. However, the precise mechanisms underlying nutrient sensing in POMC neurons remain incompletely understood. We show that mitochondrial dynamics mediated by Mitofusin 1 (MFN1) in POMC neurons couple nutrient sensing with systemic glucose metabolism. Mice lacking MFN1 in POMC neurons exhibited defective mitochondrial architecture remodeling and attenuated hypothalamic gene expression programs during the fast-to-fed transition. This loss of mitochondrial flexibility in POMC neurons bidirectionally altered glucose sensing, causing abnormal glucose homeostasis due to defective insulin secretion by pancreatic β cells. Fed mice lacking MFN1 in POMC neurons displayed enhanced hypothalamic mitochondrial oxygen flux and reactive oxygen species generation. Central delivery of antioxidants was able to normalize the phenotype. Collectively, our data posit MFN1-mediated mitochondrial dynamics in POMC neurons as an intrinsic nutrient-sensing mechanism and unveil an unrecognized link between this subset of neurons and insulin release. Copyright © 2017 Elsevier Inc. All rights reserved.

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.

Significant Findings: Seasonal Distributions of Global Ocean Chlorophyll and Nutrients With a Coupled Ocean General Circulation, Biogeochemical, and Radiative Model. 2; Comparisons With Satellite and In Situ Data

NASA Technical Reports Server (NTRS)

Gregg, Watson W.; Busalacchi, Antonio (Technical Monitor)

2000-01-01

A coupled ocean general circulation, biogeochemical, and radiative model was constructed to evaluate and understand the nature of seasonal variability of chlorophyll and nutrients in the global oceans. Biogeochemical processes in the model were determined from the influences of circulation and turbulence dynamics, irradiance availability, and the interactions among three functional phytoplankton groups (diatoms, chlorophytes, and picoplankton) and three nutrients (nitrate, ammonium, and silicate). Basin scale (>1000 km) model chlorophyll seasonal distributions were statistically positively correlated with CZCS chlorophyll in 10 of 12 major oceanographic regions, and with SeaWiFS in all 12. Notable disparities in magnitudes occurred, however, in the tropical Pacific, the spring/summer bloom in the Antarctic, autumn in the northern high latitudes, and during the southwest monsoon in the North Indian Ocean. Synoptic scale (100-1000 km) comparisons of satellite and in situ data exhibited broad agreement, although occasional departures were apparent. Model nitrate distributions agreed with in situ data, including seasonal dynamics, except for the equatorial Atlantic. The overall agreement of the model with satellite and in situ data sources indicated that the model dynamics offer a reasonably realistic simulation of phytoplankton and nutrient dynamics on basin and synoptic scales.

The roles of resuspension, diffusion and biogeochemical processes on oxygen dynamics offshore of the Rhône River, France: a numerical modeling study

NASA Astrophysics Data System (ADS)

Moriarty, Julia M.; Harris, Courtney K.; Fennel, Katja; Friedrichs, Marjorie A. M.; Xu, Kehui; Rabouille, Christophe

2017-04-01

Observations indicate that resuspension and associated fluxes of organic material and porewater between the seabed and overlying water can alter biogeochemical dynamics in some environments, but measuring the role of sediment processes on oxygen and nutrient dynamics is challenging. A modeling approach offers a means of quantifying these fluxes for a range of conditions, but models have typically relied on simplifying assumptions regarding seabed-water-column interactions. Thus, to evaluate the role of resuspension on biogeochemical dynamics, we developed a coupled hydrodynamic, sediment transport, and biogeochemical model (HydroBioSed) within the Regional Ocean Modeling System (ROMS). This coupled model accounts for processes including the storage of particulate organic matter (POM) and dissolved nutrients within the seabed; fluxes of this material between the seabed and the water column via erosion, deposition, and diffusion at the sediment-water interface; and biogeochemical reactions within the seabed. A one-dimensional version of HydroBioSed was then implemented for the Rhône subaqueous delta in France. To isolate the role of resuspension on biogeochemical dynamics, this model implementation was run for a 2-month period that included three resuspension events; also, the supply of organic matter, oxygen, and nutrients to the model was held constant in time. Consistent with time series observations from the Rhône Delta, model results showed that erosion increased the diffusive flux of oxygen into the seabed by increasing the vertical gradient of oxygen at the seabed-water interface. This enhanced supply of oxygen to the seabed, as well as resuspension-induced increases in ammonium availability in surficial sediments, allowed seabed oxygen consumption to increase via nitrification. This increase in nitrification compensated for the decrease in seabed oxygen consumption due to aerobic remineralization that occurred as organic matter was entrained into the water column. Additionally, entrainment of POM into the water column during resuspension events, and the associated increase in remineralization there, also increased oxygen consumption in the region of the water column below the pycnocline. During these resuspension events, modeled rates of oxygen consumption increased by factors of up to ˜ 2 and ˜ 8 in the seabed and below the pycnocline, respectively. When averaged over 2 months, the intermittent cycles of erosion and deposition led to a ˜ 16 % increase of oxygen consumption in the seabed, as well as a larger increase of ˜ 140 % below the pycnocline. These results imply that observations collected during quiescent periods, and biogeochemical models that neglect resuspension or use typical parameterizations for resuspension, may underestimate net oxygen consumption at sites like the Rhône Delta. Local resuspension likely has the most pronounced effect on oxygen dynamics at study sites with a high oxygen concentration in bottom waters, only a thin seabed oxic layer, and abundant labile organic matter.

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 light of improved data, particularly in the representation of storm driven flow pathways. Hence the aggregation and the impact of any management or mitigation will rely on having confidence that local activities are beneficial, that a basket of measures merit pursuing, and are worthy of funding. A novel set of data driven risk-based indices, impact models and new experiments are needed to show the worth of catchment scale management. The high frequency data have been useful to build knowledge but a quantifiable cause and effect remains an elusive goal at the catchment scale.

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...

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, which may alter instream nutrient fluxes.

Benthic exchange and biogeochemical cycling in permeable sediments.

PubMed

Huettel, Markus; Berg, Peter; Kostka, Joel E

2014-01-01

The sandy sediments that blanket the inner shelf are situated in a zone where nutrient input from land and strong mixing produce maximum primary production and tight coupling between water column and sedimentary processes. The high permeability of the shelf sands renders them susceptible to pressure gradients generated by hydrodynamic and biological forces that modulate spatial and temporal patterns of water circulation through these sediments. The resulting dynamic three-dimensional patterns of particle and solute distribution generate a broad spectrum of biogeochemical reaction zones that facilitate effective decomposition of the pelagic and benthic primary production products. The intricate coupling between the water column and sediment makes it challenging to quantify the production and decomposition processes and the resultant fluxes in permeable shelf sands. Recent technical developments have led to insights into the high biogeochemical and biological activity of these permeable sediments and their role in the global cycles of matter.

Virocell Metabolism: Metabolic Innovations During Host-Virus Interactions in the Ocean.

PubMed

Rosenwasser, Shilo; Ziv, Carmit; Creveld, Shiri Graff van; Vardi, Assaf

2016-10-01

Marine viruses are considered to be major ecological, evolutionary, and biogeochemical drivers of the marine environment, responsible for nutrient recycling and determining species composition. Viruses can re-shape their host's metabolic network during infection, generating the virocell-a unique metabolic state that supports their specific requirement. Here we discuss the concept of 'virocell metabolism' and its formation by rewiring of host-encoded metabolic networks, or by introducing virus-encoded auxiliary metabolic genes which provide the virocell with novel metabolic capabilities. The ecological role of marine viruses is commonly assessed by their relative abundance and phylogenetic diversity, lacking the ability to assess the dynamics of active viral infection. The new ability to define a unique metabolic state of the virocell will expand the current virion-centric approaches in order to quantify the impact of marine viruses on microbial food webs. Copyright © 2016. Published by Elsevier Ltd.

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.

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 conditions whereas the total annual sum is not climatically dependent. Nutrient cycles of Kilimanjaro forest ecosystems are significantly altered by land use and the associated changes of dominant tree species.

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

Effects of increased biomass removal on the biogeochemistry of two Norwegian forest ecosystems

NASA Astrophysics Data System (ADS)

Lange, H.; Clarke, N.; Kjønaas, O. J.; Aas, W.; Andreassen, K.; Børja, I.; Bratli, H.; Eich-Greatorex, S.; Eldhuset, T.; Holt-Hanssen, K.

2009-04-01

Increased removal of biomass from forested ecosystems for use as an alternative source of energy is an option in several countries. E.g., it is planned to double the use of bioenergy from all sources until 2020 in Norway. A large fraction of this increase is coming from forest resources, e.g. by removing harvest residues like branches and tops. This removal will reduce the supply of nutrients and organic matter to the forest soil, and may in the longer term increase the risk for future nutrient imbalance, soil erosion on steep slopes, reduced forest production, and changes in biodiversity and ground vegetation species composition. However, field experiments so far have found contrasting results in this respect. Soil effects of increased biomass removal will be closely related to soil organic matter (SOM) dynamics, litter quality, and turnover rates. Harvest intensity may affect the decomposition of existing SOM as well as the build-up of new SOM from litter and forest residues, by changing factors like soil temperature and moisture as well as amount and type of litter input. Changes in input of litter with different nutrient concentrations and decomposition patterns along with changes in SOM decomposition will affect the total storage of carbon, nitrogen and other vital nutrients in the soil. In the context of a Norwegian research project started in 2009, we will quantify how different harvesting regimes lead to different C addition to soil, and determine which factors have the greatest effect on decomposition of SOM under different environmental conditions. Two Norway spruce forest ecosystems will be investigated, one in eastern and one in western Norway, representing different climatic conditions and landscape types. At each location, two treatment regimes will be tested: (1) conventional harvesting (CH), with residues left on-site, and (2) aboveground whole-tree harvest (WTH), with branches, needles, and tops removed. Input of different forest residues will be quantified post harvest. Soil water at 30 cm soil depth will be analysed for nutrients, and element fluxes will be estimated to provide information about nutrient leaching. Soil respiration will be measured, along with lab decomposition studies under different temperature and moisture regimes. Long term in situ decomposition studies will be carried out in the WTH plots using three different tree compartments (needles, coarse twigs, fine roots) decomposing in litter bags, in order to determine their limit value. The structure of the fungal community will be determined by soil core sampling and molecular techniques. Understory vegetation will be sampled to determine its biomass, and the frequency of all vascular plants, bryophytes and lichens will be estimated. After harvesting, replanting will be carried out. Seedling survival, causes of mortality and potential damage, growth, and needle nutrients will be monitored. Results from these studies will be used to identify key processes explaining trends observed in two series of ongoing long-term whole-tree thinning trials. We shall combine knowledge obtained using field experiments with results of modelling and data from the Norwegian Monitoring Programme for Forest Damage and the National Forest Inventory. The overall project aim is to predict and map the ecologically most suitable areas for increased harvesting of branches and tops on a regional scale, and to identify uncertainties and additional knowledge needed to improve current predictions.

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 significance of GW-SW interactions for biogeochemical processes in sandy streambeds

NASA Astrophysics Data System (ADS)

Arnon, Shai; De Falco, Natalie; Fox, Aryeh; Laube, Gerrit; Schmidt, Christian; Fleckenstein, Jan; Boano, Fulvio

2015-04-01

Stream-groundwater interactions have a major impact on hyporheic exchange fluxes in sandy streambeds. However, the physical complexity of natural streams has limited our ability to study these types of interactions systematically, and to evaluate their importance to biogeochemical processes and nutrient cycling. In this work we were able to quantify the effect of losing and gaining fluxes on hyporheic exchange and nutrient cycling in homogeneous and heterogeneous streambeds by combining experiments in laboratory flumes and modeling. Tracer experiments for measuring hyporheic exchange were done using dyes and NaCl under various combinations of overlying water velocity and losing or gaining fluxes. Nutrient cycling experiments were conducted after growing a benthic biofilm by spiking with Sodium Benzoate (as a source of labile dissolved organic carbon, DOC) and measuring DOC and oxygen dynamics. The combination of experimental observations and modeling revealed that interfacial transport increases with the streambed hydraulic conductivity and proportional to the square of the overlying water velocity. Hyporheic exchange fluxes under losing and gaining flow conditions were similar, and became smaller when the losing or gaining flux increases. Increasing in streambed hydraulic conductivity led to higher hyporheic fluxes and reduction in the effects of losing and gaining flow conditions to constrain exchange. Despite the evident effect of flow conditions on hyporheic exchange, labile DOC uptake was positively linked to increasing overlying water velocity but was not affected by losing and gaining fluxes. This is because microbial aerobic activity was taking place at the upper few millimeters of the streambed as shown by local oxygen consumption rates, which was measured using microelectrodes. Based on modeling work, it is expected that GW-SW interaction will be more significant for less labile DOC and anaerobic processes. Our results enable us to study systematically the coupling between flow conditions and biogeochemical processes under highly controlled physical and chemical conditions and are expected to improve our understanding of nutrient cycling in streams.

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.

Indirect quantification of fine root production in a near tropical wet mountainous region

NASA Astrophysics Data System (ADS)

Lu, X.; Zhang, J.; Huang, C.

2016-12-01

The main functions of fine root (defined as diameter <= 2 mm) are water and nutrient transports. Besides being a carbon (C) storage pool, it also provides a C flux pathway through soil and plant. Fine root takes up a small portion, normally 5%, of biomass in forest ecosystems, but 30% to 70% of total net primary production. Therefore, quantifying fine root productivity is important to study the forest C budget. Presumably, belowground growth can be indirectly estimated by the more accessible aboveground vegetation structure dynamics. To verify the relationship with fine root productivity, we take internal (floristic) and external (environmental) factors into account, including litter production, canopy density (leaf area index), leaf nutrients (N, K, Ca, Mg, P), weather and/or soil physical conditions (air temperature, humidity, precipitation, solar radiation and soil moisture). The study was conducted in near tropical broadleaf (700 m asl) and conifer (1700 m asl) forests in northeastern Taiwan, generally receiving more than 4000 mm of precipitation per year. For each site, 16 50-cm long minirhizotron tubes were installed. Fine root images were acquired every three weeks. Growth and decline, newly presence and absence of fine roots were delineated by image processing algorithms to derive fine-root productivity through time. Aforementioned internal and external attributes were simultaneously collected as well. Some of these variables were highly correlated and were detrended using principal component analysis. We found that these transformed variables (mainly associated with litter production, precipitation and solar radiation) can delineate the spatiotemporal dynamics of root production well (r2 = 0.87, p = 0.443). In conclusion, this study demonstrated the feasibility of utilized aboveground variables to indirectly assess fine root growth, which could be further developed for the regional scale mapping with aid of remote sensing.

Remote Sensing Marine Ecology: Wind-driven algal blooms in the open oceans and their ecological impacts

NASA Astrophysics Data System (ADS)

Tang, DanLing

2016-07-01

Algal bloom not only can increase the primary production but also could result in negative ecological consequence, e.g., Harmful Algal Blooms (HABs). According to the classic theory for the formation of algal blooms "critical depth" and "eutrophication", oligotrophic sea area is usually difficult to form a large area of algal blooms, and actually the traditional observation is only sporadic capture to the existence of algal blooms. Taking full advantage of multiple data of satellite remote sensing, this study: 1), introduces "Wind-driven algal blooms in open oceans: observation and mechanisms" It explained except classic coastal Ekman transport, the wind through a variety of mechanisms affecting the formation of algal blooms. Proposed a conceptual model of "Strong wind -upwelling-nutrient-phytoplankton blooms" in Western South China Sea (SCS) to assess role of wind-induced advection transport in phytoplankton bloom formation. It illustrates the nutrient resources that support long-term offshore phytoplankton blooms in the western SCS; 2), Proposal of the theory that "typhoons cause vertical mixing, induce phytoplankton blooms", and quantify their important contribution to marine primary production; Proposal a new ecological index for typhoon. Proposed remote sensing inversion models. 3), Finding of the spatial and temporaldistributions pattern of harmful algal bloom (HAB)and species variations of HAB in the South Yellow Sea and East China Sea, and in the Pearl River estuary, and their oceanic dynamic mechanisms related with monsoon; The project developed new techniques and generated new knowledge, which significantly improved understanding of the formation mechanisms of algal blooms. 1), It proposed "wind-pump" mechanism integrates theoretical system combing "ocean dynamics, development of algal blooms, and impact on primary production", which will benefit fisheries management. 2), A new interdisciplinary subject "Remote Sensing Marine Ecology"(RSME) has been developed via these achievements.

Selected achievements, science directions, and new opportunities for the WEBB small watershed research program

USGS Publications Warehouse

Glynn, Pierre D.; Larsen, Matthew C.; Greene, Earl A.; Buss, Heather L.; Clow, David W.; Hunt, Randall J.; Mast, M. Alisa; Murphy, Sheila F.; Peters, Norman E.; Sebestyen, Stephen D.; Shanley, James B.; Walker, John F.

2009-01-01

Over nearly two decades, the Water, Energy, and Biogeochemical Budgets (WEBB) small watershed research program of the U.S. Geological Survey (USGS) has documented how water and solute fluxes, nutrient, carbon, and mercury dynamics, and weathering and sediment transport respond to natural and humancaused drivers, including climate, climate change, and atmospheric deposition. Together with a continued and increasing focus on the effects of climate change, more investigations are needed that examine ecological effects (e.g., evapotranspiration, nutrient uptake) and responses (e.g., species abundances, biodiversity) that are coupled with the physical and chemical processes historically observed in the WEBB program. Greater use of remote sensing, geographic modeling, and habitat/watershed modeling tools is needed, as is closer integration with the USGS-led National Phenology Network. Better understanding of process and system response times is needed. The analysis and observation of land-use and climate change effects over time should be improved by pooling data obtained by the WEBB program during the last two decades with data obtained earlier and (or) concurrently from other research and monitoring studies conducted at or near the five WEBB watershed sites. These data can be supplemented with historical and paleo-environmental information, such as could be obtained from tree rings and lake cores. Because of the relatively pristine nature and small size of its watersheds, the WEBB program could provide process understanding and basic data to better characterize and quantify ecosystem services and to develop and apply indicators of ecosystem health. In collaboration with other Federal and State watershed research programs, the WEBB program has an opportunity to contribute to tracking the short-term dynamics and long-term evolution of ecosystem services and health indicators at a multiplicity of scales across the landscape. 

Increasing metabolic rate despite declining body weight in an adult parasitoid wasp.

PubMed

Casas, Jérôme; Body, Mélanie; Gutzwiller, Florence; Giron, David; Lazzari, Claudio R; Pincebourde, Sylvain; Richard, Romain; Llandres, Ana L

2015-08-01

Metabolic rate is a positive function of body weight, a rule valid for most organisms and the basis of several theories of metabolic ecology. For adult insects, however, the diversity of relationships between body mass and respiration remains unexplained. The aim of this study is to relate the respiratory metabolism of a parasitoid with body weight and foraging activity. We compared the metabolic rate of groups of starving and host-fed females of the parasitoid Eupelmus vuilleti recorded with respirometry for 7days, corresponding to the mean lifetime of starving females and over half of the lifetime of foraging females. The dynamics of carbohydrate, lipid and protein in the body of foraging females were quantified with biochemical techniques. Body mass and all body nutrients declined sharply from the first day onwards. By contrast, the CO2 produced and the O2 consumed increased steadily. Starving females showed the opposite trend, identifying foraging as the reason for the respiration increase of feeding females. Two complementary physiological processes explain the unexpected relationship between increasing metabolic rate and declining body weight. First, host hemolymph is a highly unbalanced food, and the excess nutrients (protein and carbohydrate) need to be voided, partially through excretion and partially through respiration. Second, a foraging young female produces eggs at an increasing rate during the first half of its lifetime, a process that also increases respiration. We posit that the time-varying metabolic rate contributions of the feeding and reproductive processes supplements the contribution of the structural mass and lead to the observed trend. We extend our explanations to other insect groups and discuss the potential for unification using Dynamic Energy Budget theory. Copyright © 2015 Elsevier Ltd. All rights reserved.

Role of model structure on the response of soil biogeochemistry to hydro-climatic fluctuations

NASA Astrophysics Data System (ADS)

Manzoni, S.; Porporato, A.

2005-05-01

Soil carbon and nutrient cycles are strongly affected by hydro-climatic variability, which interacts with the internal ecosystem structure. Here we test the implications of biogeochemical model structure on such dynamics by extending an existing model by the authors and coworkers. When forced by hydro-climatic fluctuations, the different model structures induce specific preferential nutrient paths among the soil pools, which in turn affect nutrient distribution and availability to microbes and plants. In particular, if it is assumed that microbes can directly assimilate organic nitrogen, plants tend to be inferior competitors for nutrients even in well-watered conditions, while if a certain amount of organic nitrogen is assumed to be mineralized without being first incorporated into microbial cells, vegetation can be advantaged over a wide range of soil moisture values. We also investigate the intensification of competition for nutrients (e.g., nitrogen) between plant and soil microbial communities under extreme hydrologic conditions, such as droughts and intense storms. Frequent rainfall events may determine ideal soil moisture conditions for plant uptake, enhancing nitrogen leaching while lowering oxygen concentration and inhibiting microbial activity. During droughts, the soil water potential often drops to the point of hampering the plant nutrient uptake while still remaining high enough for microbial decomposition and nitrogen immobilization. The interplay of microbe and vegetation water stress is investigated in depth as it controls the ability of one community (e.g., plants or soil microbes) to establish competitive advantage on the other. The long-term effects of these dynamics of competition and nutrient allocation are explored under steady-state and stochastic soil moisture conditions to analyze the feedbacks between soil organic matter and vegetation dynamics.

The relationship between Gross Primary Productivity and Sun-Induced Fluorescence in a nutrient manipulated Mediterranean grassland is controlled primarily by canopy structure

NASA Astrophysics Data System (ADS)

Migliavacca, Mirco

2017-04-01

Recent studies have shown how human induced N/P imbalances affect essential ecosystem processes, and might be particularly important in water-limited ecosystems. Hyperspectral information can be used to directly infer nutrient-induces variation in structural and functional changes of vegetation under different nutrient availability. Among those, sun-induced fluorescence in the far-red region provides a new non-invasive measurement approach that has the potential to quantify dynamic changes in light-use efficiency and photosynthetic carbon dioxide uptake (Gross Primary Production, GPP). However, the mechanistic link between GPP and sun-induced fluorescence under different environmental conditions is not completely understood. In this contribution we investigated the structural and functional factors controlling the emission of SIF at 760 nm in a Mediterranean grassland with different levels of nutrient availability (Nitrogen (N), Phosphorous (P), and Nitrogen and Phosphorous (NP)). We showed how nutrient-induced changes in canopy structure (i.e. changes in plant forms abundance that influence leaf inclination distribution function, LIDF) and functional traits (e.g. nitrogen content per dry mass of leaves, N%, Chlorophyll ab concentration - Cab, and maximum carboxylation capacity, Vcmax) affected the observed relationship between SIF and GPP. Simultaneous measurements of canopy scale GPP and SIF were conducted with transparent transient-state canopy chambers and narrow-band spectrometers, respectively. To disentangle the main drivers of the GPP-SIF relationship we performed a factorial modeling exercise with the Soil-Canopy Observation of Photosynthesis and Energy (SCOPE) model. We conclude that the addition of nutrients imposed a change in the abundance of different plant forms and biochemistry of the canopy. This lead to changes in canopy structure (leaf area index, leaf inclinaton distribution function LIDF parameters) and functional traits (N%, P%, Cab and Vcmax) that eventually controlled the spatial patterns of SIF. Changes in LIDF mainly control the GPP-SIF relationship, with a secondary control of Cab and Vcmax. In order to exploit SIF data to model GPP at global/regional scale canopy structural variability, plant community, and plant functional traits are important confounding factors that have to be considered to correct the plant-functional type specific relationship between sun-induced fluorescence and GPP.

A Coupled Ocean General Circulation, Biogeochemical, and Radiative Model of the Global Oceans: Seasonal Distributions of Ocean Chlorophyll and Nutrients

NASA Technical Reports Server (NTRS)

Gregg, Watson W.; Busalacchi, Antonio (Technical Monitor)

2000-01-01

A coupled ocean general circulation, biogeochemical, and radiative model was constructed to evaluate and understand the nature of seasonal variability of chlorophyll and nutrients in the global oceans. Biogeochemical processes in the model are determined from the influences of circulation and turbulence dynamics, irradiance availability. and the interactions among three functional phytoplankton groups (diatoms. chlorophytes, and picoplankton) and three nutrients (nitrate, ammonium, and silicate). Basin scale (greater than 1000 km) model chlorophyll results are in overall agreement with CZCS pigments in many global regions. Seasonal variability observed in the CZCS is also represented in the model. Synoptic scale (100-1000 km) comparisons of imagery are generally in conformance although occasional departures are apparent. Model nitrate distributions agree with in situ data, including seasonal dynamics, except for the equatorial Atlantic. The overall agreement of the model with satellite and in situ data sources indicates that the model dynamics offer a reasonably realistic simulation of phytoplankton and nutrient dynamics on synoptic scales. This is especially true given that initial conditions are homogenous chlorophyll fields. The success of the model in producing a reasonable representation of chlorophyll and nutrient distributions and seasonal variability in the global oceans is attributed to the application of a generalized, processes-driven approach as opposed to regional parameterization and the existence of multiple phytoplankton groups with different physiological and physical properties. These factors enable the model to simultaneously represent many aspects of the great diversity of physical, biological, chemical, and radiative environments encountered in the global oceans.

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.

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.

Enzyme Sorption onto Soil and Biocarbon Amendments Alters Catalytic Capacity and Depends on the Specific Protein and pH

NASA Astrophysics Data System (ADS)

Foster, E.; Fogle, E. J.; Cotrufo, M. F.

2017-12-01

Enzymes catalyze biogeochemical reactions in soils and play a key role in nutrient cycling in agricultural systems. Often, to increase soil nutrients, agricultural managers add organic amendments and have recently experimented with charcoal-like biocarbon products. These amendments can enhance soil water and nutrient holding capacity through increasing porosity. However, the large surface area of the biocarbon has the potential to sorb nutrients and other organic molecules. Does the biocarbon decrease nutrient cycling through sorption of enzymes? In a laboratory setting, we compared the interaction of two purified enzymes β-glucosidase and acid phosphatase with a sandy clay loam and two biocarbons. We quantified the sorbed enzymes at three different pHs using a Bradford protein assay and then measured the activity of the sorbed enzyme via high-throughput fluorometric analysis. Both sorption and activity depended upon the solid phase, pH, and specific enzyme. Overall the high surface area biocarbon impacted the catalytic capacity of the enzymes more than the loam soil, which may have implications for soil nutrient management with these organic amendments.

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.

Uncovering the Nutritional Landscape of Food

PubMed Central

Kim, Seunghyeon; Sung, Jaeyun; Foo, Mathias; Jin, Yong-Su; Kim, Pan-Jun

2015-01-01

Recent progresses in data-driven analysis methods, including network-based approaches, are revolutionizing many classical disciplines. These techniques can also be applied to food and nutrition, which must be studied to design healthy diets. Using nutritional information from over 1,000 raw foods, we systematically evaluated the nutrient composition of each food in regards to satisfying daily nutritional requirements. The nutrient balance of a food was quantified and termed nutritional fitness; this measure was based on the food’s frequency of occurrence in nutritionally adequate food combinations. Nutritional fitness offers a way to prioritize recommendable foods within a global network of foods, in which foods are connected based on the similarities of their nutrient compositions. We identified a number of key nutrients, such as choline and α-linolenic acid, whose levels in foods can critically affect the nutritional fitness of the foods. Analogously, pairs of nutrients can have the same effect. In fact, two nutrients can synergistically affect the nutritional fitness, although the individual nutrients alone may not have an impact. This result, involving the tendency among nutrients to exhibit correlations in their abundances across foods, implies a hidden layer of complexity when exploring for foods whose balance of nutrients within pairs holistically helps meet nutritional requirements. Interestingly, foods with high nutritional fitness successfully maintain this nutrient balance. This effect expands our scope to a diverse repertoire of nutrient-nutrient correlations, which are integrated under a common network framework that yields unexpected yet coherent associations between nutrients. Our nutrient-profiling approach combined with a network-based analysis provides a more unbiased, global view of the relationships between foods and nutrients, and can be extended towards nutritional policies, food marketing, and personalized nutrition. PMID:25768022

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...

Amounts of calcium and magnesium cycled and its release kinetics in a long-term no-till integrated crop-livestock system with varying grazing intensities in subtropical region

USDA-ARS?s Scientific Manuscript database

Under an integrated crop-livestock production system, plant and animal residues become an important nutrient stock. Grazing management could affect both plant and animal residue amount and quality, thereby influencing nutrient dynamics through modifications in nutrient release rates. The objective o...

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...

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.

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.

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®.

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.

Nutrient composition of plants consumed by black and white ruffed lemurs, Varecia variegata, in the Betampona Natural Reserve, Madagascar.

PubMed

Schmidt, Debra A; Iambana, R Bernard; Britt, Adam; Junge, Randall E; Welch, Charles R; Porton, Ingrid J; Kerley, Monty S

2010-01-01

The purpose of this study was to quantify the concentrations of crude protein, fat, ash, neutral detergent fiber, acid detergent fiber, lignin, nonstructural carbohydrates, and gross energy in plant foods consumed by wild black and white ruffed lemurs (Varecia variegata). Calcium, phosphorous, magnesium, potassium, sodium, iron, zinc, copper, manganese, molybdenum, and selenium concentrations were also determined. A total of 122 samples from 33 plant families and more than 60 species were collected and analyzed for their nutritional content. The specific nutrient needs of black and white ruffed lemurs are unknown, but quantifying the nutritional composition of the foods they consume in the wild will help nutritionists and veterinarians formulate more appropriate diets for captive ruffed lemurs. This information will also supply information on how man-induced habitat changes affect the nutritional composition of foods consumed by free-ranging lemurs. (c) 2009 Wiley-Liss, Inc.

The influence of subsurface porosity and bedrock composition on ecosystem productivity and drought resilience in the Sierra Nevada Batholith, California

NASA Astrophysics Data System (ADS)

Riebe, C. S.; Callahan, R. P.; Goulden, M.; Pasquet, S.; Flinchum, B. A.; Taylor, N. J.; Holbrook, W. S.

2017-12-01

The availability of water and nutrients in soil and weathered rock influences the distribution of Earth's terrestrial life and regulates ecosystem vulnerability to land use and climate change. We explored these relationships by combining geochemical and geophysical measurements at three mid-elevation sites in the Sierra Nevada, California. Forest cover correlates strongly with bedrock composition across the sites, implying strong lithologic control on the ecosystem. We evaluated two hypotheses about bedrock-ecosystem connections: 1) that bedrock composition influences vegetation by moderating plant-essential nutrient supply; and 2) that bedrock composition influences the degree of subsurface weathering, which influences vegetation by controlling subsurface water-storage capacity. To quantify subsurface water-holding capacity, we used seismic refraction surveys to infer gradients in P and S-wave velocity structure, which reveal variations in porosity when coupled together in a Hertz-Mindlin rock-physics model. We combined the geophysical data on porosity with bedrock bulk geochemistry measured in previous work to evaluate the influence of water-holding capacity and nutrient supply on ecosystem productivity, which we quantified using remote sensing. Our results show that more than 80% of the variance in ecosystem productivity can be explained by differences in bedrock phosphorus concentration and subsurface porosity, with phosphorus content being the dominant explanatory variable. This suggests that bedrock composition exerts a strong bottom-up control on ecosystem productivity through its influence on nutrient supply and weathering susceptibility, which in turn influences porosity. We show that vegetation vulnerability to drought stress and mortality can be explained in part by variations in subsurface water-holding capacity and rock-derived nutrient supply.

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, our findings provide important insights that can help guide management plans that aim to preserve savanna biodiversity.

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.

Modeling Hydrologic Transport through the Critical Zone: Lessons from Catchment-Scale and Lysimeter Studies

NASA Astrophysics Data System (ADS)

Benettin, P.; Queloz, P.; Bailey, S. W.; McGuire, K. J.; Rinaldo, A.; Botter, G.

2015-12-01

Water age distributions can be used to address a number of environmental challenges, such as modeling the dynamics of river water quality, quantifying the interactions between shallow and deep flow systems and understanding nutrient loading persistence. Moreover, as the travel time of a water particle is the time available for biogeochemical reactions, it can be explicitly used to predict the concentration of non-conservative solutes, as e.g. those derived by mineral weathering. In recent years, many studies acknowledged the dynamic nature of streamflow age and linked it to observed variations in stream water quality. In this new framework, water stored within a catchment can be seen as a pool that is selectively "sampled" by streams and vegetation, determining the chemical composition of discharge and evapotranspiration. We present results from a controlled lysimeter experiment and real-world catchments, where the theoretical framework has been used to reproduce water quality datasets including conservative tracers (e.g. chloride and water stable isotopes) and weathering-derived solutes (like silicon and sodium). The approach proves useful to estimate the catchment water storage involved in solute mixing and sheds light on how solutes and water of different ages are selectively removed by vegetation and soil drainage.

Memory and obesity affect the population dynamics of asexual freshwater planarians

NASA Astrophysics Data System (ADS)

Dunkel, Jörn; Talbot, Jared; Schötz, Eva-Maria

2011-04-01

Asexual reproduction in multicellular organisms is a complex biophysical process that is not yet well understood quantitatively. Here, we report a detailed population study for the asexual freshwater planarian Schmidtea mediterranea, which can reproduce via transverse fission due to a large stem cell contingent. Our long-term observations of isolated non-interacting planarian populations reveal that the characteristic fission waiting time distributions for head and tail fragments differ significantly from each other. The stochastic fission dynamics of tail fragments exhibits non-negligible memory effects, implying that an accurate mathematical description of future data should be based on non-Markovian tree models. By comparing the effective growth of non-interacting planarian populations with those of self-interacting populations, we are able to quantify the influence of interactions between flatworms and physical conditions on the population growth. A surprising result is the non-monotonic relationship between effective population growth rate and nutrient supply: planarians exhibit a tendency to become 'obese' if the feeding frequency exceeds a critical level, resulting in a decreased reproduction activity. This suggests that these flatworms, which possess many genes homologous to those of humans, could become a new model system for studying dietary effects on reproduction and regeneration in multicellular organisms.

Effectiveness of SWAT in characterizing the watershed hydrology in the snowy-mountainous Lower Bear Malad River (LBMR) watershed in Box Elder County, Utah

NASA Astrophysics Data System (ADS)

Salha, A. A.; Stevens, D. K.

2015-12-01

Distributed watershed models are essential for quantifying sediment and nutrient loads that originate from point and nonpoint sources. Such models are primary means towards generating pollutant estimates in ungaged watersheds and respond well at watershed scales by capturing the variability in soils, climatic conditions, land uses/covers and management conditions over extended periods of time. This effort evaluates the performance of the Soil and Water Assessment Tool (SWAT) model as a watershed level tool to investigate, manage, and characterize the transport and fate of nutrients in Lower Bear Malad River (LBMR) watershed (Subbasin HUC 16010204) in Utah. Water quality concerns have been documented and are primarily attributed to high phosphorus and total suspended sediment concentrations caused by agricultural and farming practices along with identified point sources (WWTPs). Input data such as Digital Elevation Model (DEM), land use/Land cover (LULC), soils, and climate data for 10 years (2000-2010) is utilized to quantify the LBMR streamflow. Such modeling is useful in developing the required water quality regulations such as Total Maximum Daily Loads (TMDL). Measured concentrations of nutrients were closely captured by simulated monthly nutrient concentrations based on the R2 and Nash- Sutcliffe fitness criteria. The model is expected to be able to identify contaminant non-point sources, identify areas of high pollution risk, locate optimal monitoring sites, and evaluate best management practices to cost-effectively reduce pollution and improve water quality as required by the LBMR watershed's TMDL.

Hydrological regulation drives regime shifts: evidence from paleolimnology and ecosystem modeling of a large shallow Chinese lake.

PubMed

Kong, Xiangzhen; He, Qishuang; Yang, Bin; He, Wei; Xu, Fuliu; Janssen, Annette B G; Kuiper, Jan J; van Gerven, Luuk P A; Qin, Ning; Jiang, Yujiao; Liu, Wenxiu; Yang, Chen; Bai, Zelin; Zhang, Min; Kong, Fanxiang; Janse, Jan H; Mooij, Wolf M

2017-02-01

Quantitative evidence of sudden shifts in ecological structure and function in large shallow lakes is rare, even though they provide essential benefits to society. Such 'regime shifts' can be driven by human activities which degrade ecological stability including water level control (WLC) and nutrient loading. Interactions between WLC and nutrient loading on the long-term dynamics of shallow lake ecosystems are, however, often overlooked and largely underestimated, which has hampered the effectiveness of lake management. Here, we focus on a large shallow lake (Lake Chaohu) located in one of the most densely populated areas in China, the lower Yangtze River floodplain, which has undergone both WLC and increasing nutrient loading over the last several decades. We applied a novel methodology that combines consistent evidence from both paleolimnological records and ecosystem modeling to overcome the hurdle of data insufficiency and to unravel the drivers and underlying mechanisms in ecosystem dynamics. We identified the occurrence of two regime shifts: one in 1963, characterized by the abrupt disappearance of submerged vegetation, and another around 1980, with strong algal blooms being observed thereafter. Using model scenarios, we further disentangled the roles of WLC and nutrient loading, showing that the 1963 shift was predominantly triggered by WLC, whereas the shift ca. 1980 was attributed to aggravated nutrient loading. Our analysis also shows interactions between these two stressors. Compared to the dynamics driven by nutrient loading alone, WLC reduced the critical P loading and resulted in earlier disappearance of submerged vegetation and emergence of algal blooms by approximately 26 and 10 years, respectively. Overall, our study reveals the significant role of hydrological regulation in driving shallow lake ecosystem dynamics, and it highlights the urgency of using multi-objective management criteria that includes ecological sustainability perspectives when implementing hydrological regulation for aquatic ecosystems around the globe. © 2016 John Wiley & Sons Ltd.

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.

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.

Invasive aquarium fish transform ecosystem nutrient dynamics

PubMed Central

Capps, Krista A.; Flecker, Alexander S.

2013-01-01

Trade of ornamental aquatic species is a multi-billion dollar industry responsible for the introduction of myriad fishes into novel ecosystems. Although aquarium invaders have the potential to alter ecosystem function, regulation of the trade is minimal and little is known about the ecosystem-level consequences of invasion for all but a small number of aquarium species. Here, we demonstrate how ecological stoichiometry can be used as a framework to identify aquarium invaders with the potential to modify ecosystem processes. We show that explosive growth of an introduced population of stoichiometrically unique, phosphorus (P)-rich catfish in a river in southern Mexico significantly transformed stream nutrient dynamics by altering nutrient storage and remineralization rates. Notably, changes varied between elements; the P-rich fish acted as net sinks of P and net remineralizers of nitrogen. Results from this study suggest species-specific stoichiometry may be insightful for understanding how invasive species modify nutrient dynamics when their population densities and elemental composition differ substantially from native organisms. Risk analysis for potential aquarium imports should consider species traits such as body stoichiometry, which may increase the likelihood that an invasion will alter the structure and function of ecosystems. PMID:23966642

Tracing C Fluxes From Leaf Litter To Microbial Respired CO2 And Specific Soil Compounds

NASA Astrophysics Data System (ADS)

Rubino, M.; Lubritto, C.; D'Onofrio, A.; Gleixner, G.; Terrasi, F.; Cotrufo, F. M.

2004-12-01

Despite litter decomposition is one of the major process controlling soil C stores and nutrient cycling, yet C dynamics during litter decay are poorly understood and quantified. Here we report the results of a laboratory experiment where 13C depleted leaf litter was incubated on a 13C enriched soil with the aims to: i) partition the C loss during litter decay into microbial respired-CO2 and C input into the soil; ii) identify the soil compounds where litter derived C is retained; iii) assess whether litter quality is a determinant of both the above processes. Three 13C-depleted leaf litter(delta13C ca. -43), differing in their degradability, were incubated on C4 soil (delta13C ca. -18) under laboratory controlled conditions for 8 months, with litter respiration and delta13C-CO2 being measured at regular intervals. At harvest, Compound Specific Isotope Analyses was performed on soil and litter samples in order to follow the fate of litter-derived C compounds in the various pools of SOMƒn The delta13C of soils carbohydrates, alkanes and Phospho Lipids Fatty Acids (PLFA) were measured, and the mixing model approach used to quantify the contribution of litter derived C to the specific compounds.

Quantification of the inevitable: the influence of soil macrofauna on soil water movement in rehabilitated open-cut mined lands

NASA Astrophysics Data System (ADS)

Arnold, S.; Williams, E. R.

2016-01-01

Recolonisation of soil by macrofauna (especially ants, termites and earthworms) in rehabilitated open-cut mine sites is inevitable and, in terms of habitat restoration and function, typically of great value. In these highly disturbed landscapes, soil invertebrates play a major role in soil development (macropore configuration, nutrient cycling, bioturbation, etc.) and can influence hydrological processes such as infiltration, seepage, runoff generation and soil erosion. Understanding and quantifying these ecosystem processes is important in rehabilitation design, establishment and subsequent management to ensure progress to the desired end goal, especially in waste cover systems designed to prevent water reaching and transporting underlying hazardous waste materials. However, the soil macrofauna is typically overlooked during hydrological modelling, possibly due to uncertainties on the extent of their influence, which can lead to failure of waste cover systems or rehabilitation activities. We propose that scientific experiments under controlled conditions and field trials on post-mining lands are required to quantify (i) macrofauna-soil structure interactions, (ii) functional dynamics of macrofauna taxa, and (iii) their effects on macrofauna and soil development over time. Such knowledge would provide crucial information for soil water models, which would increase confidence in mine waste cover design recommendations and eventually lead to higher likelihood of rehabilitation success of open-cut mining land.

Challenges and opportunities for quantifying roots and rhizosphere interactions through imaging and image analysis.

PubMed

Downie, H F; Adu, M O; Schmidt, S; Otten, W; Dupuy, L X; White, P J; Valentine, T A

2015-07-01

The morphology of roots and root systems influences the efficiency by which plants acquire nutrients and water, anchor themselves and provide stability to the surrounding soil. Plant genotype and the biotic and abiotic environment significantly influence root morphology, growth and ultimately crop yield. The challenge for researchers interested in phenotyping root systems is, therefore, not just to measure roots and link their phenotype to the plant genotype, but also to understand how the growth of roots is influenced by their environment. This review discusses progress in quantifying root system parameters (e.g. in terms of size, shape and dynamics) using imaging and image analysis technologies and also discusses their potential for providing a better understanding of root:soil interactions. Significant progress has been made in image acquisition techniques, however trade-offs exist between sample throughput, sample size, image resolution and information gained. All of these factors impact on downstream image analysis processes. While there have been significant advances in computation power, limitations still exist in statistical processes involved in image analysis. Utilizing and combining different imaging systems, integrating measurements and image analysis where possible, and amalgamating data will allow researchers to gain a better understanding of root:soil interactions. © 2014 John Wiley & Sons Ltd.

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.

Species traits and environmental conditions govern the relationship between biodiversity effects across trophic levels

USGS Publications Warehouse

Spooner, D.E.; Vaughn, C.C.; Galbraith, H.S.

2012-01-01

Changing environments can have divergent effects on biodiversity-ecosystem function relationships at alternating trophic levels. Freshwater mussels fertilize stream foodwebs through nutrient excretion, and mussel species-specific excretion rates depend on environmental conditions. We asked how differences in mussel diversity in varying environments influence the dynamics between primary producers and consumers. We conducted field experiments manipulating mussel richness under summer (low flow, high temperature) and fall (moderate flow and temperature) conditions, measured nutrient limitation, algal biomass and grazing chironomid abundance, and analyzed the data with non-transgressive overyielding and tripartite biodiversity partitioning analyses. Algal biomass and chironomid abundance were best explained by trait-independent complementarity among mussel species, but the relationship between biodiversity effects across trophic levels (algae and grazers) depended on seasonal differences in mussel species' trait expression (nutrient excretion and activity level). Both species identity and overall diversity effects were related to the magnitude of nutrient limitation. Our results demonstrate that biodiversity of a resource-provisioning (nutrients and habitat) group of species influences foodweb dynamics and that understanding species traits and environmental context are important for interpreting biodiversity experiments. ?? 2011 Springer-Verlag.

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.

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...

Amino acids rather than glucose account for the majority of cell mass in proliferating mammalian cells

PubMed Central

Hosios, Aaron M.; Hecht, Vivian C.; Danai, Laura V.; Johnson, Marc O.; Rathmell, Jeffrey C.; Steinhauser, Matthew L.; Manalis, Scott R.; Vander Heiden, Matthew G.

2016-01-01

Cells must duplicate their mass in order to proliferate. Glucose and glutamine are the major nutrients consumed by proliferating mammalian cells, but the extent to which these and other nutrients contribute to cell mass is unknown. We quantified the fraction of cell mass derived from different nutrients and find that the majority of carbon mass in cells is derived from other amino acids, which are consumed at much lower rates than glucose and glutamine. While glucose carbon has diverse fates, glutamine contributes most to protein, and this suggests that glutamine’s ability to replenish TCA cycle intermediates (anaplerosis) is primarily used for amino acid biosynthesis. These findings demonstrate that rates of nutrient consumption are indirectly associated with mass accumulation and suggest that high rates of glucose and glutamine consumption support rapid cell proliferation beyond providing carbon for biosynthesis. PMID:26954548

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.

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.

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.

Evolution and Termination of Oceanic Anoxic Event 2: Testing the impact of organic matter sulfurization on benthic-pelagic coupling during OAE2

NASA Astrophysics Data System (ADS)

Hülse, D.; Arndt, S.; Ridgwell, A.

2016-12-01

Oceanic Anoxic Events (OAEs) represent severe disturbances of the global carbon, oxygen and nutrient cycles of the ocean. The archetypal example is OAE2 ( 93.5 Ma), which is characterized by widespread bottom water anoxia and photic zone euxinia. One way to explain these conditions is via increased oxygen demand in the water column resulting from enhanced primary productivity (PP), itself fuelled by increased nutrient availability for instance from the sediments as the burial efficiency of phosphorus declines when bottom waters become anoxic. The recovery from OAE like conditions is thought to involve the permanent removal of excess CO2 from the atmosphere and ocean by burying carbon in the form of organic matter (OM) in marine sediments, which is consistent with the geological record of widespread black shale formation. A number of possible controls on enhanced OM burial have previously been proposed and assessed, such as elevated depositional fluxes, higher clay mineral availability, or reduced oxygenation. Here we explore a 4th possible mechanism - organic matter sulfurization. During sulfurization, reduced inorganic sulfur species (e.g. H2S) react with OM, resulting in the formation of organic sulfur compounds which are less prone to bacterial degradation. Although studies indicate the global significance of this process for OAE2, its implications on Cretaceous benthic-pelagic coupling and thus OAE2 evolution and recovery has not yet been quantified and tested with a 3D Earth system model. The major hurdle is the high computational cost of simulating the essential redox reactions in marine sediments, which are critical to quantify the burial of OM and benthic recycling fluxes of chemical compounds. In order to close this knowledge gap, we developed a new, mechanistic representation of OM preservation in marine sediments (OMEN-SED) and coupled it to a 3D Earth system model (cGENIE). Using this new model we explore the impact of organic matter sulfurization on benthic nutrient fluxes, ocean oxygenation and PP during OAE2 for the first time in a fully coupled 3D-ocean-sediment model. We investigate the role of sulfurization in Earth's recovery dynamics from OAE2 by comparing our results with multiple geochemical proxies for seafloor anoxia and photic zone euxinia.

UNCERTAINTIES IN NITROGEN MASS LOADINGS IN COASTAL WATERSHEDS

EPA Science Inventory

With the increasing reduction of nutrients for coastal eutrophication control, the importance of well defined nitrogen mass balance becomes paramount. imited number of attempts have been made to quantify inputs and outputs within major coastal ecosystems including its watersheds....

Oregon Salt Marshes: How Blue are They?

EPA Science Inventory

Two important ecosystem services of wetlands are carbon sequestration and filtration of nutrients and particulates. We quantified the carbon and nitrogen accumulation rates in salt marshes at 135 plots distributed across eight estuaries located in Oregon, USA. Net carbon and ...

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.

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 downstream of these different land uses become isotopically labeled by the environments, making δ34S a useful tracer of fish derived from these different environments. This presentation will use examples from several large-scale river and wetlands studies to demonstrate useful applications of POM and DOM isotopes for environmental monitoring studies, and will discuss the relative merits of different methods for the collection and analysis of POM and DOM samples for C, N, and S isotopes.

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 the transient status of phytoplankton nutrient stoichiometry in the coastal ocean.

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

Microbial response to environmental gradients in a ceramic-based diffusion system.

PubMed

Wolfaardt, G M; Hendry, M J; Birkham, T; Bressel, A; Gardner, M N; Sousa, A J; Korber, D R; Pilaski, M

2008-05-01

A solid, porous matrix was used to establish steady-state concentration profiles upon which microbial responses to concentration gradients of nutrients or antimicrobial agents could be quantified. This technique relies on the development of spatially defined concentration gradients across a ceramic plate resulting from the diffusion of solutes through the porous ceramic matrix. A two-dimensional, finite-element numerical transport model was used to predict the establishment of concentration profiles, after which concentration profiles of conservative tracers were quantified fluorometrically and chemically at the solid-liquid interface to verify the simulated profiles. Microbial growth responses to nutrient, hypochloride, and antimicrobial concentration gradients were then quantified using epifluorescent or scanning confocal laser microscopy. The observed microbial response verified the establishment and maintenance of stable concentration gradients along the solid-liquid interface. These results indicate the ceramic diffusion system has potential for the isolation of heterogeneous microbial communities as well as for testing the efficacy of antimicrobial agents. In addition, the durability of the solid matrix allowed long-term investigations, making this approach preferable to conventional gel-stabilized systems that are impeded by erosion as well as expansion or shrinkage of the gel. Copyright 2008 Wiley Periodicals, Inc.

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 global biogeochemical cycles. Cross-fed nutrients within these systems can be either waste products valued by only one partner or nutrients valued by both partners. Here, we explored how interpartner competition for a communally valuable cross-fed nutrient impacts mutualism dynamics. We discovered that mutualism stability necessitates that the recipient have a competitive advantage against the producer in obtaining the cross-fed nutrient, provided that the nutrient is generated intracellularly. We propose that the requirement for recipient-biased competition is a general rule for mutualistic coexistence based on the transfer of intracellularly generated, communally valuable resources.« less

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 global biogeochemical cycles. Cross-fed nutrients within these systems can be either waste products valued by only one partner or nutrients valued by both partners. Here, we explored how interpartner competition for a communally valuable cross-fed nutrient impacts mutualism dynamics. We discovered that mutualism stability necessitates that the recipient have a competitive advantage against the producer in obtaining the cross-fed nutrient, provided that the nutrient is generated intracellularly. We propose that the requirement for recipient-biased competition is a general rule for mutualistic coexistence based on the transfer of intracellularly generated, communally valuable resources.« less

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 cycles. Cross-fed nutrients within these systems can be either waste products valued by only one partner or nutrients valued by both partners. Here, we explored how interpartner competition for a communally valuable cross-fed nutrient impacts mutualism dynamics. We discovered that mutualism stability necessitates that the recipient have a competitive advantage against the producer in obtaining the cross-fed nutrient, provided that the nutrient is generated intracellularly. We propose that the requirement for recipient-biased competition is a general rule for mutualistic coexistence based on the transfer of intracellularly generated, communally valuable resources. Copyright © 2017 McCully et al.

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.

Seasonal Distributions of Global Ocean Chlorophyll and Nutrients: Analysis with a Coupled Ocean General Circulation Biogeochemical, and Radiative Model

NASA Technical Reports Server (NTRS)

Gregg, Watson W.

1999-01-01

A coupled general ocean circulation, biogeochemical, and radiative model was constructed to evaluate and understand the nature of seasonal variability of chlorophyll and nutrients in the global oceans. The model is driven by climatological meteorological conditions, cloud cover, and sea surface temperature. Biogeochemical processes in the model are determined from the influences of circulation and turbulence dynamics, irradiance availability, and the interactions among three functional phytoplankton groups (diatoms, chorophytes, and picoplankton) and three nutrient groups (nitrate, ammonium, and silicate). Phytoplankton groups are initialized as homogeneous fields horizontally and vertically, and allowed to distribute themselves according to the prevailing conditions. Basin-scale model chlorophyll results are in very good agreement with CZCS pigments in virtually every global region. Seasonal variability observed in the CZCS is also well represented in the model. Synoptic scale (100-1000 km) comparisons of imagery are also in good conformance, although occasional departures are apparent. Agreement of nitrate distributions with in situ data is even better, including seasonal dynamics, except for the equatorial Atlantic. The good agreement of the model with satellite and in situ data sources indicates that the model dynamics realistically simulate phytoplankton and nutrient dynamics on synoptic scales. This is especially true given that initial conditions are homogenous chlorophyll fields. The success of the model in producing a reasonable representation of chlorophyll and nutrient distributions and seasonal variability in the global oceans is attributed to the application of a generalized, processes-driven approach as opposed to regional parameterization, and the existence of multiple phytoplankton groups with different physiological and physical properties. These factors enable the model to simultaneously represent the great diversity of physical, biological, chemical, and radiative environments encountered in the global oceans.

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.

Instream Attenuation of Nitrogen and Phosphorus in Non-Point Source Dominated Streams: Hydrologic and Biogeochemical Controls

NASA Astrophysics Data System (ADS)

Bray, E. N.; Chen, X.; Keller, A. A.

2010-12-01

Non-point source inputs of total nitrogen (TN) and total phosphorus (TP) in rivers are the leading causes of water quality degradation in the United States (Turner and Rabalais, 2003; Broussard and Turner, 2009). Yet it remains a challenge to adequately quantify the relative role and influence of physical hydrological processes versus biogeochemical processes on the attenuation of TN and TP for individual river reaches. A watershed-scale study of instream dynamics and attenuation of TN and TP in northeastern U.S. headwater streams demonstrates that physical and hydrological processes exert greater control over nutrient removal than biogeochemical processes. To explore these interactions under various attenuation scenarios, we developed the watershed-scale model (WARMF) for 97 catchments to simulate watershed processes, hydrology, and diffuse source loads of nutrients. We simulated a hypothetical nutrient release at a rate of 1 kg/d of TN (50% as ammonium and 50% as nitrate) and TP (100% as phosphate) to predict response lengths of downstream catchments. Resulting attenuation factors are presented as the change in mean load at a given location, normalized to the change in the catchment in which the load is applied. Results indicate that for most catchments, the TN and TP load increase is attenuated from the stream within a few tens of kilometers. Fifty percent attenuation occurs across length scales ranging from a few hundreds of meters to kilometers if the load is introduced in the headwaters, indicating the most rapid nutrient removal occurs in the smallest headwater streams but generally decreases with distance downstream. There are some differences in the attenuation factors for TN and TP, although the pattern of attenuation is the same. Sensitivity analyses highlight five hydrological parameters of paramount importance to concentrations of N and P, namely precipitation, evaporation coefficients (magnitude and skewness), soil layer thickness, soil saturated moisture and soil hydraulic conductivity. These model parameters have a significant effect on the concentrations of nutrients, with TN exhibiting greater sensitivity. Further, attenuation results suggest that stream depth, flow regime, and density of agriculture in small headwater streams are potentially important controls to nutrient uptake and removal; i.e. during periods of low flow, dilution is reduced, attenuation length increases, and removal processes may be dominated by settling as opposed to biogeochemistry. Instream attenuation and model results can be used to assess 1) the scale and nature of best management practices which must be adopted to result in nutrient reductions, 2) the downstream distance at which load reductions will be effective, and 3) the hydrological characteristics of the river network which exert considerable influence on attenuation lengths and nutrient removal.

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.

The effect of elevated atmospheric CO2 concentration on gross nitrogen and carbon dynamics in a permanent grassland: A field pulse-labeling study

NASA Astrophysics Data System (ADS)

Moser, Gerald; Gorenflo, André; Keidel, Lisa; Brenzinger, Kristof; Elias, Dafydd; McNamara, Niall; Maček, Irena; Vodnik, Dominik; Braker, Gesche; Schimmelpfennig, Sonja; Gerstner, Judith; Müller, Christoph

2014-05-01

To predict ecosystem reactions to elevated atmospheric CO2 (eCO2) it is essential to understand the interactions between plant carbon input, microbial community composition and activity and associated nutrient dynamics. Long-term observations (> 14 years) within the Giessen Free Air Carbon dioxide Enrichment (Giessen FACE) study on permanent grassland showed next to an enhanced biomass production an unexpected strong positive feedback effect on ecosystem respiration and nitrous oxide (N2O) production. The overall goal of this study is to understand the long-term effects of eCO2 and carbon input on microbial community composition and activity as well as the associated nitrogen dynamics, N2O production and plant N uptake in the Giessen FACE study on permanent grassland. A combination of 13CO2 pulse labelling with 15N tracing of 15NH4+ and 15NO3- was carried out in situ. Different fractions of soil organic matter (recalcitrant, labile SOM) and the various mineral N pools in the soil (NH4+, NO3-), gross N transformation rates, pool size dependent N2O and N2 emissions as well as N species dependent plant N uptake rates and the origin of the CO2 respiration have been quantified. Microbial analyses include exploring changes in the composition of microbial communities involved in the turnover of NH4+, NO3-, N2O and N2, i.e. ammonia oxidizing, denitrifying, and microbial communities involved in dissimilatory nitrate reduction to ammonia (DNRA). mRNA based analyses will be employed to comparably evaluate the long-term effects of eCO2 on the structure and abundance of these communities, while transcripts of these genes will be used to target the fractions of the communities which actively contribute to N transformations. We quantified the contribution of mycorrhizae on N2O emissions and observed the phenological development of the mycorrhizae after the labeling.

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.

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 Springer Science+Business Media, Inc.

Quantification of brain macrostates using dynamical nonstationarity of physiological time series.

PubMed

Latchoumane, Charles-Francois Vincent; Jeong, Jaeseung

2011-04-01

The brain shows complex, nonstationarity temporal dynamics, with abrupt micro- and macrostate transitions during its information processing. Detecting and characterizing these transitions in dynamical states of the brain is a critical issue in the field of neuroscience and psychiatry. In the current study, a novel method is proposed to quantify brain macrostates (e.g., sleep stages or cognitive states) from shifts of dynamical microstates or dynamical nonstationarity. A ``dynamical microstate'' is a temporal unit of the information processing in the brain with fixed dynamical parameters and specific spatial distribution. In this proposed approach, a phase-space-based dynamical dissimilarity map (DDM) is used to detect transitions between dynamically stationary microstates in the time series, and Tsallis time-dependent entropy is applied to quantify dynamical patterns of transitions in the DDM. We demonstrate that the DDM successfully detects transitions between microstates of different temporal dynamics in the simulated physiological time series against high levels of noise. Based on the assumption of nonlinear, deterministic brain dynamics, we also demonstrate that dynamical nonstationarity analysis is useful to quantify brain macrostates (sleep stages I, II, III, IV, and rapid eye movement (REM) sleep) from sleep EEGs with an overall accuracy of 77%. We suggest that dynamical nonstationarity is a useful tool to quantify macroscopic mental states (statistical integration) of the brain using dynamical transitions at the microscopic scale in physiological data.

The activated sludge ecosystem contains a core community of abundant organisms

PubMed Central

Saunders, Aaron M; Albertsen, Mads; Vollertsen, Jes; Nielsen, Per H

2016-01-01

Understanding the microbial ecology of a system requires that the observed population dynamics can be linked to their metabolic functions. However, functional characterization is laborious and the choice of organisms should be prioritized to those that are frequently abundant (core) or transiently abundant, which are therefore putatively make the greatest contribution to carbon turnover in the system. We analyzed the microbial communities in 13 Danish wastewater treatment plants with nutrient removal in consecutive years and a single plant periodically over 6 years, using Illumina sequencing of 16S ribosomal RNA amplicons of the V4 region. The plants contained a core community of 63 abundant genus-level operational taxonomic units (OTUs) that made up 68% of the total reads. A core community consisting of abundant OTUs was also observed within the incoming wastewater to three plants. The net growth rate for individual OTUs was quantified using mass balance, and it was found that 10% of the total reads in the activated sludge were from slow or non-growing OTUs, and that their measured abundance was primarily because of immigration with the wastewater. Transiently abundant organisms were also identified. Among them the genus Nitrotoga (class Betaproteobacteria) was the most abundant putative nitrite oxidizer in a number of activated sludge plants, which challenges previous assumptions that Nitrospira (phylum Nitrospirae) are the primary nitrite-oxidizers in activated sludge systems with nutrient removal. PMID:26262816

Evaluating hillslope and riparian contributions to dissolved nitrogen (N) export from a boreal forest catchment

NASA Astrophysics Data System (ADS)

Blackburn, M.; Ledesma, José L. J.; Näsholm, Torgny; Laudon, Hjalmar; Sponseller, Ryan A.

2017-02-01

Catchment science has long held that the chemistry of small streams reflects the landscapes they drain. However, understanding the contribution of different landscape units to stream chemistry remains a challenge which frequently limits our understanding of export dynamics. For limiting nutrients such as nitrogen (N), an implicit assumption is that the most spatially extensive landscape units (e.g., uplands) act as the primary sources to surface waters, while near-stream zones function more often as sinks. These assumptions, based largely on studies in high-gradient systems or in regions with elevated inputs of anthropogenic N, may not apply to low-gradient, nutrient-poor, and peat-rich catchments characteristic of many northern ecosystems. We quantified patterns of N mobilization along a hillslope transect in a northern boreal catchment to assess the extent to which organic matter-rich riparian soils regulate the flux of N to streams. Contrary to the prevailing view of riparian functioning, we found that near-stream, organic soils supported concentrations and fluxes of ammonium (NH4+) and dissolved organic nitrogen that were much higher than the contributing upslope forest soils. These results suggest that stream N chemistry is connected to N mobilization and mineralization within the riparian zone rather than the wider landscape. Results further suggest that water table fluctuation in near-surface riparian soils may promote elevated rates of net N mineralization in these landscapes.

Modelling field scale spatial variation in water run-off, soil moisture, N2O emissions and herbage biomass of a grazed pasture using the SPACSYS model.

PubMed

Liu, Yi; Li, Yuefen; Harris, Paul; Cardenas, Laura M; Dunn, Robert M; Sint, Hadewij; Murray, Phil J; Lee, Michael R F; Wu, Lianhai

2018-04-01

In this study, we evaluated the ability of the SPACSYS model to simulate water run-off, soil moisture, N 2 O fluxes and grass growth using data generated from a field of the North Wyke Farm Platform. The field-scale model is adapted via a linked and grid-based approach (grid-to-grid) to account for not only temporal dynamics but also the within-field spatial variation in these key ecosystem indicators. Spatial variability in nutrient and water presence at the field-scale is a key source of uncertainty when quantifying nutrient cycling and water movement in an agricultural system. Results demonstrated that the new spatially distributed version of SPACSYS provided a worthy improvement in accuracy over the standard (single-point) version for biomass productivity. No difference in model prediction performance was observed for water run-off, reflecting the closed-system nature of this variable. Similarly, no difference in model prediction performance was found for N 2 O fluxes, but here the N 2 O predictions were noticeably poor in both cases. Further developmental work, informed by this study's findings, is proposed to improve model predictions for N 2 O. Soil moisture results with the spatially distributed version appeared promising but this promise could not be objectively verified.

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.

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.

Propagation of hydroclimatic variability through the critical zone

NASA Astrophysics Data System (ADS)

Porporato, A. M.; Calabrese, S.; Parolari, A.

2016-12-01

The interaction between soil moisture dynamics and mineral-weathering reactions (e.g., ion exchange, precipitation-dissolution) affects the availability of nutrients to plants, composition of soils, soil acidification, as well as CO2 sequestration. Across the critical zone (CZ), this interaction is responsible for propagating hydroclimatic fluctuations to deeper soil layers, controlling weathering rates via leaching events which intermittently alter the alkalinity levels. In this contribution, we analyze these dynamics using a stochastic modeling approach based on spatially lumped description of soil hydrology and chemical weathering reactions forced by multi-scale temporal hydrologic variability. We quantify the role of soil moisture dynamics in filtering the rainfall fluctuations through its impacts on soil water chemistry, described by a system of ordinary differential equations (and algebraic equations, for the equilibrium reactions), driving the evolution of alkalinity, pH, the chemical species of the soil solution, and the mineral-weathering rate. A probabilistic description of the evolution of the critical zone is thus obtained, allowing us to describe the CZ response to long-term climate fluctuations, ecosystem and land-use conditions, in terms of key variables groups. The model is applied to the weathering rate of albite in the Calhoun CZ observatory and then extended to explore similarities and differences across other CZs. Typical time scales of response and degrees of sensitivities of CZ to hydroclimatic fluctuations and human forcing are also explored.

Composition and dynamics of biostimulated indigenous oil-degrading microbial consortia from the Irish, North and Mediterranean Seas: a mesocosm study.

PubMed

Gertler, Christoph; Näther, Daniela J; Cappello, Simone; Gerdts, Gunnar; Quilliam, Richard S; Yakimov, Michail M; Golyshin, Peter N

2012-09-01

Diversity of indigenous microbial consortia and natural occurrence of obligate hydrocarbon-degrading bacteria (OHCB) are of central importance for efficient bioremediation techniques. To investigate the microbial population dynamics and composition of oil-degrading consortia, we have established a series of identical oil-degrading mesocosms at three different locations, Bangor (Menai Straits, Irish Sea), Helgoland (North Sea) and Messina (Messina Straits, Mediterranean Sea). Changes in microbial community composition in response to oil spiking, nutrient amendment and filtration were assessed by ARISA and DGGE fingerprinting and 16Sr RNA gene library analysis. Bacterial and protozoan cell numbers were quantified by fluorescence microscopy. Very similar microbial population sizes and dynamics, together with key oil-degrading microorganisms, for example, Alcanivorax borkumensis, were observed at all three sites; however, the composition of microbial communities was largely site specific and included variability in relative abundance of OHCB. Reduction in protozoan grazing had little effect on prokaryotic cell numbers but did lead to a decrease in the percentage of A. borkumensis 16S rRNA genes detected in clone libraries. These results underline the complexity of marine oil-degrading microbial communities and cast further doubt on the feasibility of bioaugmentation practices for use in a broad range of geographical locations. © 2012 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

WATER COLUMN DATA AND SPECTRAL IRRADIANCE MODEL

EPA Science Inventory

Water samples collected monthly, for 18 months, from six sites in the Laguna Madre were analyzed to identify and quantify phytopigments using High Performance Liquid Chromatography (HPLC). In addition, water column pigment and nutrient data were acquired at 12 stations in Upper ...

Estimating Air-Manganese Exposures in Two Ohio Towns

EPA Science Inventory

Manganese (Mn), a nutrient required for normal metabolic function, is also a persistent air pollutant and a known neurotoxin at high concentrations. Elevated exposures can result in a number of motor and cognitive deficits. Quantifying chronic personal exposures in residential po...

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.

Comparing Measures of Estuarine Ecosystem Production in a ...

EPA Pesticide Factsheets

Anthropogenic nutrient enrichments and concerted efforts at nutrient reductions, compounded with the influences of climate change, are likely changing the net ecosystem production (NEP) of our coastal systems. To quantify these changes, scientists monitor a range of physical, chemical, and biological parameters sampled at various frequencies. Water column chlorophyll concentrations are arguably the most commonly used indicator of net phytoplankton production, as well as a coarse indicator of NEP. We compared parameters that estimate production, including chlorophyll, across an experimental nutrient gradient and in situ in both well-mixed and stratified estuarine environments. Data from an experiment conducted in the early 1980s in mesocosms designed to replicate a well-mixed mid-Narragansett Bay (Rhode Island) water column were used to correlate changes in chlorophyll concentrations, pH, dissolved oxygen (O2), dissolved inorganic nitrogen, phosphate, and silicate concentrations, cell counts, and 14C carbon uptake measurements across a range of nutrient enrichments. The pH, O2, nutrient, and cell count measurements reflected seasonal cycles of spring blooms followed by late summer/early fall respiration periods across nutrient enrichments. Chlorophyll concentrations were more variable and rates of 14C productivity were inconsistent with observed trends in nutrient concentrations, pH, and O2 concentrations. Similar comparisons were made using data from a well-mixe

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.

Soil C dynamics under intensive oil palm plantations in poor tropical soils

NASA Astrophysics Data System (ADS)

Guillaume, Thomas; Ruegg, Johanna; Quezada, Juan Carlos; Buttler, Alexandre

2017-04-01

Oil palm cultivation mainly takes place on heavily-weathered tropical soils where nutrients are limiting factors for plant growth and microbial activity. Intensive fertilization and changes of C input by oil palms strongly affects soil C and nutrient dynamics, challenging long-term soil fertility. Oil palm plantations management offers unique opportunities to study soil C and nutrients interactions in field conditions because 1) they can be considered as long-term litter manipulation experiments since all aboveground C inputs are concentrated in frond pile areas and 2) mineral fertilizers are only applied in specific areas, i.e. weeded circle around the tree and interrows, but not in harvest paths. Here, we determined impacts of mineral fertilizer and organic matter input on soil organic carbon dynamics and microbial activity in mature oil palm plantation established on savanna grasslands. Rates of savanna-derived soil organic carbon (SOC) decomposition and oil palm-derived SOC net stabilization were determined using changes in isotopic signature of in C input following a shift from C4 (savanna) to C3 (oil palm) vegetation. Application of mineral fertilizer alone did not affect savanna-derived SOC decomposition or oil palm-derived SOC stabilization rates, but fertilization associated with higher C input lead to an increase of oil palm-derived SOC stabilization rates, with about 50% of topsoil SOC derived from oil palm after 9 years. High carbon and nutrients inputs did not increase microbial biomass but microorganisms were more active per unit of biomass and SOC. In conclusion, soil organic matter decomposition was limited by C rather than nutrients in the studied heavily-weathered soils. Fresh C and nutrient inputs did not lead to priming of old savanna-derived SOC but increased turnover and stabilization of new oil palm-derived SOC.

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

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.

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.

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?

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.

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.

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.

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 caused.

Predictive Understanding of Mountainous Watershed Hydro-Biogeochemical Function and Response to Perturbations

NASA Astrophysics Data System (ADS)

Hubbard, S. S.; Williams, K. H.; Agarwal, D.; Banfield, J. F.; Beller, H. R.; Bouskill, N.; Brodie, E.; Maxwell, R. M.; Nico, P. S.; Steefel, C. I.; Steltzer, H.; Tokunaga, T. K.; Wainwright, H. M.; Dwivedi, D.; Newcomer, M. E.

2017-12-01

Recognizing the societal importance, vulnerability and complexity of mountainous watersheds, the `Watershed Function' project is developing a predictive understanding of how mountainous watersheds retain and release downgradient water, nutrients, carbon, and metals. In particular, the project is exploring how early snowmelt, drought, floods and other disturbances will influence mountainous watershed dynamics at seasonal to decadal timescales. Located in the 300km2 East River headwater catchment of the Upper Colorado River Basin, the project is guided by several constructs. First, the project considers the integrated role of surface and subsurface flow and biogeochemical reactions - from bedrock to the top of the vegetative canopy, from terrestrial through aquatic compartments, and from summit to receiving waters. The project takes a system-of-systems perspective, focused on developing new methods to quantify the cumulative watershed hydrobiogeochemical response to perturbations based on information from select subsystems within the watershed, each having distinct vegetation-subsurface biogeochemical-hydrological characteristics. A `scale-adaptive' modeling capability, in development using adaptive mesh refinement methods, serves as the organizing framework for the SFA. The scale-adaptive approach is intended to permit simulation of system-within-systems behavior - and aggregation of that behavior - from genome through watershed scales. This presentation will describe several early project discoveries and advances made using experimental, observational and numerical approaches. Among others, examples may include:quantiying how seasonal hydrological perturbations drive biogeochemical responses across critical zone compartments, with a focus on N and C transformations; metagenomic documentation of the spatial variability in floodplain meander microbial ecology; 3D reactive transport simulations of couped hydrological-biogeochemical behavior in the hyporheic zone; and new characterization and inversion approaches to quantify co-variability between above and below ground dynamics and the susceptibility of vegetation to drought stress. More information is provided at: Watershed.lbl.gov

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 of permafrost thawing and forest fires on nutrient dynamics in arctic streams.

Coastal groundwater dynamics off Santa Barbara, California: combining geochemical tracers, electromagnetic seepmeters, and electrical resistivity

USGS Publications Warehouse

Swarzenski, Peter W.; Izbicki, John A.

2009-01-01

This paper presents repeat field measurements of 222Rn and 223,224,226,228Ra, electromagnetic seepage meter-derived advective fluxes, and multi-electrode, stationary and continuous marine resistivity surveys collected between November 2005 and April 2007 to study coastal groundwater dynamics within a marine beach in Santa Barbara, California. The study provides insight into magnitude and dynamics of submarine groundwater discharge (SGD) and associated nutrient loadings into near-shore coastal waters, where the predominant SGD drivers can be both spatially and temporally separated. Rn-222 and 223,224,226,228Ra were utilized to quantify the total and saline contribution, respectively, of SGD. The two short-lived 224,223Ra isotopes provided an estimate of apparent near-shore water mass age, as well as an estimate of the Ra-derived eddy diffusion coefficient, Kh (224Ra = 2.86 ?? 0.7 m2 s-1; 223Ra = 1.32 ?? 0.5 m2 s-1). Because 222Rn (t1/2 = 3.8 day) and 224Ra (t1/2 = 3.66 day) have comparable half-lives and production terms, they were used in concert to examine respective water column removal rates. Electromagnetic seepage meters recorded the physical, bi-directional exchange across the sediment/water interface, which ranged from -6.7 to 14.5 cm day-1, depending on the sampling period and position relative to the low tide line. Multi-day time-series 222Rn measurements in the near-shore water column yielded total (saline + fresh) SGD rates that ranged from 3.1 ?? 2.6 to 9.2 ?? 0.8 cm day-1, depending on the sampling season. Offshore 226Ra (t1/2 = 1600 year) and 222Rn gradients were used with the calculated Kh values to determine seabed flux estimates (dpm m-2 day-1), which were then converted into SGD rates (7.1 and 7.9 cm day-1, respectively). Lastly, SGD rates were used to calculate associated nutrient loads for the near-shore coastal waters off Santa Barbara. Depending on both the season and the SGD method utilized, the following SGD-derived nutrient inputs were computed (mol per day per meter of shoreline): NH4+ = 0.06-0.29 mol day-1 m-1; SiO4 = 0.22-0.29 mol day-1 m-1; PO43-= 0.04-0.17 mol day-1 m-1; [NO2- + NO3-] = 0-0.52 mol day-1 m-1; dissolved inorganic nitrogen (DIN) = 0.01-0.17 mol day-1 m-1, and dissolved organic nitrogen (DON) = 0.08-0.09 mol day-1 m-1. Compared to the ephemeral nature of fluvial and marine inputs into this region, such SGD-derived loadings can provide a sustained source of select nutrients to the coastal waters off Santa Barbara, California that should be accounted for in mass balance estimates.

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.

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.

Influence of Watershed Characteristics on Wetland Hydrology (Tampa, FL)

EPA Science Inventory

The availability of oxygen in wetland soils is a major driver of rate changes for several important ecological functions (e.g. nutrient processing, carbon sequestration) that the Tampa Bay Ecosystem Services Research Program (TB-ESRP) is quantifying to estimate ecosystem services...

Soil carbon sequestration: Quantifying this ecosystem service

EPA Science Inventory

Soils have a crucial role in supplying many goods and services that society depends upon on a daily basis. These include food and fiber production, water cleansing and supply, nutrient cycling, waste isolation and degradation. Soils also provide a significant amount of carbon s...

Quantifying and characterizing dissolved carbon and nitrogen leaching from litter: a comparison of methods

USDA-ARS?s Scientific Manuscript database

Litter decomposition has a fundamental role in ecosystem functioning. It recycles energy, carbon and nutrients, supporting ecosystem productivity and soil organic matter formation. Litter decomposition occurs through leaching, fragmentation, and catabolism. Leaching is, arguably, the least studie...

Meet EPA Ecologist Michael Murrell, Ph.D.

EPA Pesticide Factsheets

Michael Murrel, Ph.D., is a EPA research ecologist working on the Gulf of Mexico Hypoxia Project, helping develop models of the northern Gulf to quantify the links between freshwater flowing into the Gulf from the land, nutrients, and hypoxia—“dead zones”

Development of a multispectral sensor for crop canopy temperature measurement

USDA-ARS?s Scientific Manuscript database

Quantifying spatial and temporal variability in plant stress has precision agriculture applications in controlling variable rate irrigation and variable rate nutrient application. One approach to plant stress detection is crop canopy temperature measurement by the use of thermographic or radiometric...

Carbon and Nitrogen Accumulation Rates in Salt Marshes in Oregon, USA

EPA Science Inventory

Two important ecosystem services of wetlands are carbon sequestration and filtration of nutrients and particulates. We quantified the carbon and nitrogen accumulation rates in salt marshes at 135 plots distributed across eight estuaries located in Oregon, USA. Net carbon and ...

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

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.

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.

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

Jellyfish modulate bacterial dynamic and community structure.

PubMed

Tinta, Tinkara; Kogovšek, Tjaša; Malej, Alenka; Turk, Valentina

2012-01-01

Jellyfish blooms have increased in coastal areas around the world and the outbreaks have become longer and more frequent over the past few decades. The Mediterranean Sea is among the heavily affected regions and the common bloom-forming taxa are scyphozoans Aurelia aurita s.l., Pelagia noctiluca, and Rhizostoma pulmo. Jellyfish have few natural predators, therefore their carcasses at the termination of a bloom represent an organic-rich substrate that supports rapid bacterial growth, and may have a large impact on the surrounding environment. The focus of this study was to explore whether jellyfish substrate have an impact on bacterial community phylotype selection. We conducted in situ jellyfish-enrichment experiment with three different jellyfish species. Bacterial dynamic together with nutrients were monitored to assess decaying jellyfish-bacteria dynamics. Our results show that jellyfish biomass is characterized by protein rich organic matter, which is highly bioavailable to 'jellyfish-associated' and 'free-living' bacteria, and triggers rapid shifts in bacterial population dynamics and composition. Based on 16S rRNA clone libraries and denaturing gradient gel electrophoresis (DGGE) analysis, we observed a rapid shift in community composition from unculturable Alphaproteobacteria to culturable species of Gammaproteobacteria and Flavobacteria. The results of sequence analyses of bacterial isolates and of total bacterial community determined by culture independent genetic analysis showed the dominance of the Pseudoalteromonadaceae and the Vibrionaceae families. Elevated levels of dissolved proteins, dissolved organic and inorganic nutrient release, bacterial abundance and carbon production as well as ammonium concentrations characterized the degradation process. The biochemical composition of jellyfish species may influence changes in the amount of accumulated dissolved organic and inorganic nutrients. Our results can contribute insights into possible changes in bacterial population dynamics and nutrient pathways following jellyfish blooms which have important implications for ecology of coastal waters.

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

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...

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.

Quantifying the Recreational Value of an Estuary: A Transferable Method

EPA Science Inventory

Coastal water quality impairment (excess bacteria and nutrients) due to failed septic systems and cesspools is a major concern for Cape Cod, Massachusetts because of its waters’ high economic and social value. High bacteria levels can lead to closures at bathing beaches. Nu...

Does livestock grazing influence spatial patterns of woody plant proliferation?

USDA-ARS?s Scientific Manuscript database

Patterns of woody plant proliferation in grasslands and savannas influence rates of erosion, spread of disturbance, and nutrient pools.  Spatial pattern is the outcome of plant dispersal, recruitment, competition/facilitation, and disturbance. We quantified effects of livestock grazing, a widely cit...

NITRATE VARIABILITY ALONG THE OREGON COAST: ESTUARINE-COASTAL EXCHANGE

EPA Science Inventory

Coastal upwelling along the Eastern Pacific provides a major source of nutrients to nearby bays and estuaries during the summer months. To quantify the coastal ocean nitrogen input to Yaquina Bay, Oregon, nitrate concentrations were measured hourly from a moored sensor during sum...

The dark side of suibsidies: quantifying contaminant exposure to riparian predators via stream insects

EPA Science Inventory

Aquatic insects provide a critical nutrient subsidy to riparian food webs, yet their role as vectors of contaminants to terrestrial ecosystems is poorly understood. We investigated relationships between aquatic (resource utilization) and contaminant exposure for a riparian invert...

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.

Carbon dynamics of contrasting agricultural practices

NASA Astrophysics Data System (ADS)

Ghee, Claire; Hallett, Paul; Neilson, Roy; Robinson, David; Paterson, Eric

2013-04-01

Application of organic amendments can improve soil quality and provide crop nutrients. To optimise these agricultural benefits from organic applications, the capacity of microbe-driven nutrient and carbon cycling must be understood and exploited. Consideration is therefore required of the complex interactions between the rhizosphere, microbial biomass and organic amendment. We hypothesise that the labile C present in root exudates of plants increases the mineralisation of organic matter in soil, constituting a mechanism to promote nutrient acquisition. This mechanism is known as the 'priming effect', but is poorly understood in the context of agricultural carbon and nutrient management. Field data from the Centre of Sustainable Cropping (CSC) research platform (Dundee, Scotland, UK) are utilised to build an understanding of soil C and N fluxes between contrasting agricultural practices. The field site uses a split-plot design to compare (i) compost amended soils with reduced tillage and chemical inputs and (ii) conventionally managed soils, reflective of current UK commercial arable practice. Significant differences (p= <0.001) were identified between compost amended and conventionally managed soils at field-scale with respect to soil microbial biomass (SMB), total organic carbon (TOC) and mineral nitrogen. Investigation into the priming effect within compost amended soils was subsequently undertaken under laboratory conditions. Stable isotope analysis and measurements of soil biotic parameters were used to quantify priming resulting from Spring Barley (Hordeum vulgare cv. Optic) cultivation for (i) unamended and (ii) municipal compost incorporated soils. Compost treatments comprised amendments of 25, 50 and 150 t/Ha and planted soils were compared with unplanted controls. Soil mesocosms were maintained under controlled environmental conditions within labelling chambers supplied continuously with 13C-depleted CO2. Throughout a 41-day incubation period, soil CO2 efflux and dissolved organic carbon (DOC) was collected for quantification and 13C analysis. Following the incubation period, soils and plant material were harvested for nitrogen, carbon and δ13C analyses. Isotopic analyses allowed partitioning of the contributions of plant- and soil-derived organic matter sources to SMB, DOC and soil respiration. The results demonstrate a strong influence of plant-microbe interactions in mediating the mobilisation and mineralisation of stabilised organic fractions in soil, constituting a significant feedback to crop productivity through increased nutrient cycling.

Functional traits and structural controls on the relationship between photosynthetic CO2 uptake and sun-induced fluorescence in a Mediterranean grassland under different nutrient availability

NASA Astrophysics Data System (ADS)

Migliavacca, Mirco

2016-04-01

Recent studies have shown how human induced nitrogen (N) and phosphorous (P) imbalances affect essential ecosystem processes, and might be particularly important in water-limited ecosystems. Hyperspectral information can be used to directly infer nutrient-induced variation in structural and functional changes of vegetation under different nutrient availability. However, several uncertainties still hamper the direct link between photosynthetic CO2 uptake (gross primary productivity, GPP) and hyperspectral reflectance. Sun-induced fluorescence (SIF) provides a new non-invasive measurement approach that has the potential to quantify dynamic changes in light use efficiency and photosynthetic CO2 uptake. In this contribution we will present an experiment conducted in a Mediterranean grassland, where 16 plots of 8x8 meters were manipulated by adding nutrient (N, P, and NP). Almost simultaneous estimates of canopy scale GPP and SIF were conducted with transparent transient-state canopy chambers and high resolution spectrometers, respectively. We investigated the response of GPP and SIF to different nutrient availability and plant stoichiometry. The second objective was to identify how structural (LAI, leaf angle distribution, and biodiversity) and canopy biochemical properties (e.g. N and chlorophyll content - Chl) control the functional relationship between GPP and SIF. To test the different hypotheses the SCOPE radiative transfer model was used. We ran a factorial experiment with SCOPE to disentangle the main drivers (structure vs biochemistry) of the relationship GPP-SIF. The results showed significant differences in GPP values between N and without N addition plots. We also found that vegetation indices sensitive to pigment variations and physiology (such as photochemical reflectance index PRI) and SIF showed differences between different treatments. SCOPE showed very good agreement with the observed data (R2=0.71). The observed variability in SIF was mainly related to changes in functional traits of the vegetation (changes in N and P content and Chl). However, beside changes in functional traits, changes in canopy structure (and in particular variation in plant forms abundance after fertilization) controlled the GPP-SIF relationship. According to these results, plant N/P stoichiometry and structure should be considered when modelling GPP assuming a linear relationship with SIF at grasslands sites.

Impact of Multiple Environmental Stresses on Wetland Vegetation Dynamics

NASA Astrophysics Data System (ADS)

Muneepeerakul, C. P.; Tamea, S.; Muneepeerakul, R.; Miralles-Wilhelm, F. R.; Rinaldo, A.; Rodriguez-Iturbe, I.

2009-12-01

This research quantifies the impacts of climate change on the dynamics of wetland vegetation under the effect of multiple stresses, such as drought, water-logging, shade and nutrients. The effects of these stresses are investigated through a mechanistic model that captures the co-evolving nature between marsh emergent plant species and their resources (water, nitrogen, light, and oxygen). The model explicitly considers the feedback mechanisms between vegetation, light and nitrogen dynamics as well as the specific dynamics of plant leaves, rhizomes, and roots. Each plant species is characterized by three independent traits, namely leaf nitrogen (N) content, specific leaf area, and allometric carbon (C) allocation to rhizome storage, which govern the ability to gain and maintain resources as well as to survive in a particular multi-stressed environment. The modeling of plant growth incorporates C and N into the construction of leaves and roots, whose amount of new biomass is determined by the dynamic plant allocation scheme. Nitrogen is internally recycled between pools of plants, litter, humus, microbes, and mineral N. The N dynamics are modeled using a parallel scheme, with the major modifications being the calculation of the aerobic and anoxic periods and the incorporation of the anaerobic processes. A simple hydrologic model with stochastic rainfall is used to describe the water level dynamics and the soil moisture profile. Soil water balance is evaluated at the daily time scale and includes rainfall, evapotranspiration and lateral flow to/from an external water body, with evapotranspiration loss equal to the potential value, governed by the daily average condition of atmospheric water demand. The resulting feedback dynamics arising from the coupled system of plant-soil-microbe are studied in details and species’ fitnesses in the 3-D trait space are compared across various rainfall patterns with different mean and fluctuations. The model results are then compared with those from experiments and field studies reported in the literature, providing insights about the physiological features that enable plants to thrive in different wetland environments and climate regimes.

COUPLING BETWEEN THE COASTAL OCEAN AND YAQUINA BAY, OREGON: THE IMPORTANCE OF OCEANIC INPUTS RELATIVE TO OTHER NITROGEN SOURCES

EPA Science Inventory

Understanding of the role of oceanic input in nutrient loadings is important for understanding nutrient and phytoplankton dynamics in estuaries adjacent to coastal upwelling regions as well as determining the natural background conditions. We examined the nitrogen sources to Yaqu...

Elevated enzyme activities in soils under the invasive nitrogen-fixing tree Falcataria moluccana

Treesearch

Steven D. Allison; Caroline Nielsen; R. Flint Hughes

2006-01-01

Like other N-fixing invasive species in Hawaii, Falcataria moluccana dramatically alters forest structure, litterfall quality and quantity, and nutrient dynamics. We hypothesized that these biogeochemical changes would also affect the soil microbial community and the extracellular enzymes responsible for carbon and nutrient mineralization. Across...

Dynamics of plant nutrients, utilization and uptake, and soil microbial community in crops under ambient and elevated carbon dioxide

USDA-ARS?s Scientific Manuscript database

In natural settings such as under field conditions, the plant available soil nutrients in conjunction with other environmental factors such as, solar radiation, temperature, precipitation, and atmospheric carbon dioxide (CO2) concentration determine crop adaptation and productivity. Therefore, crop...

SIMULATING TEMPORAL VARIATIONS IN NUTRIENT, PHYTOPLANKTON, AND ZOOPLANKTON ON THE INNER OREGON SHELF

EPA Science Inventory

The objective of this study is to use a numerical model to examine the linkages between physical processes and temporal variability in the plankton dynamics in a coastal upwelling system. We used a nutrient-phytoplankton-zooplankton model coupled to a two-dimensional circulation...

PHYTOPLANKTON DYNAMICS IN A GULF OF MEXICO ESTUARY: THE POTENTIAL USE OF PHOTO-PHYSIOLOGY AND ALGAL PHOSPHATASE ACTIVITY TO PREDICT NUTRIENT STATUS.

EPA Science Inventory

Development of rapid techniques to determine in situ phytoplankton nutrient status could facilitate understanding of phytoplankton growth and species succession. Variable fluorescence parameters of phytoplankton communities can be easily and rapidly measured, and changes in param...

Nitrogen retention in salt marsh systems across nutrient-enrichment, elevation, and precipitation regimes: a multiple stressor experiment

EPA Science Inventory

In the Northeastern U.S., multiple anthropogenic stressors, including changing nutrient loads, accelerated sea-level rise, and altered climactic patterns are co-occurring, and are likely to influence salt marsh nitrogen (N) dynamics. We conducted a multiple stressor mesocosm expe...

Large-scale suspended sediment transport and sediment deposition in the Mekong Delta

NASA Astrophysics Data System (ADS)

Manh, N. V.; Dung, N. V.; Hung, N. N.; Merz, B.; Apel, H.

2014-08-01

Sediment dynamics play a major role in the agricultural and fishery productivity of the Mekong Delta. However, the understanding of sediment dynamics in the delta, one of the most complex river deltas in the world, is very limited. This is a consequence of its large extent, the intricate system of rivers, channels and floodplains, and the scarcity of observations. This study quantifies, for the first time, the suspended sediment transport and sediment deposition in the whole Mekong Delta. To this end, a quasi-2D hydrodynamic model is combined with a cohesive sediment transport model. The combined model is calibrated using six objective functions to represent the different aspects of the hydraulic and sediment transport components. The model is calibrated for the extreme flood season in 2011 and shows good performance for 2 validation years with very different flood characteristics. It is shown how sediment transport and sediment deposition is differentiated from Kratie at the entrance of the delta on its way to the coast. The main factors influencing the spatial sediment dynamics are the river and channel system, dike rings, sluice gate operations, the magnitude of the floods, and tidal influences. The superposition of these factors leads to high spatial variability of sediment transport, in particular in the Vietnamese floodplains. Depending on the flood magnitude, annual sediment loads reaching the coast vary from 48 to 60% of the sediment load at Kratie. Deposited sediment varies from 19 to 23% of the annual load at Kratie in Cambodian floodplains, and from 1 to 6% in the compartmented and diked floodplains in Vietnam. Annual deposited nutrients (N, P, K), which are associated with the sediment deposition, provide on average more than 50% of mineral fertilizers typically applied for rice crops in non-flooded ring dike floodplains in Vietnam. Through the quantification of sediment and related nutrient input, the presented study provides a quantitative basis for estimating the benefits of annual Mekong floods for agriculture and fishery, and is an important piece of information with regard to the assessment of the impacts of deltaic subsidence and climate-change-related sea level rise on delta morphology.

STAND, A DYNAMIC MODEL FOR SEDIMENT TRANSPORT AND WATER QUALITY. (R825758)

EPA Science Inventory

We introduce a new model–STAND (Sediment-Transport-Associated Nutrient Dynamics)–for simulating stream flow, sediment transport, and the interactions of sediment with other attributes of water quality. In contrast to other models, STAND employs a fully dynamic ba...

Variations in the chemical composition of cassava ( Manihot esculenta Crantz) leaves and roots as affected by genotypic and environmental variation.

PubMed

Burns, Anna Elizabeth; Gleadow, Roslyn Margaret; Zacarias, Anabela M; Cuambe, Constantino Estevão; Miller, Rebecca Elizabeth; Cavagnaro, Timothy Richard

2012-05-16

The purpose of this study was to assess the quality of cassava cultivars, in terms of cyanogenic potential and composition of macro- and micronutrients, sampled from different locations in rural Mozambique. Total cyanide concentrations in fresh cassava tissues were measured using portable cyanide testing kits, and elemental nutrients were later analyzed from dried plant tissue. Variation in cyanogenic potential and nutrient composition occurred both among cultivars and across locations. The majority of cultivars contained >100 ppm total cyanide, fresh weight, and are therefore considered to be dangerously poisonous unless adequately processed before consumption. Leaf cyanogenic and nutrient content varied with plant water status, estimated using carbon isotope discrimination (δ(13)C). The colonization of roots of all cultivars by arbuscular mycorrhizal fungi was also quantified and found to be high, indicating that mycorrhizas could play a key role in plant nutrient acquisition in these low-input farming systems.

Low-Reynolds-number swimming at pycnoclines.

PubMed

Doostmohammadi, Amin; Stocker, Roman; Ardekani, Arezoo M

2012-03-06

Microorganisms play pivotal functions in the trophic dynamics and biogeochemistry of aquatic ecosystems. Their concentrations and activities often peak at localized hotspots, an important example of which are pycnoclines, where water density increases sharply with depth due to gradients in temperature or salinity. At pycnoclines organisms are exposed to different environmental conditions compared to the bulk water column, including reduced turbulence, slow mass transfer, and high particle and predator concentrations. Here we show that, at an even more fundamental level, the density stratification itself can affect microbial ecology at pycnoclines, by quenching the flow signature, increasing the energetic expenditure, and stifling the nutrient uptake of motile organisms. We demonstrate this through numerical simulations of an archetypal low-Reynolds-number swimmer, the "squirmer." We identify the Richardson number--the ratio of buoyancy forces to viscous forces--as the fundamental parameter that quantifies the effects of stratification. These results demonstrate an unexpected effect of buoyancy on low-Reynolds-number swimming, potentially affecting a broad range of abundant organisms living at pycnoclines in oceans and lakes.

Measurements, patterns, and controls of nitrogen flux in a cranberry bed during the harvest flood

NASA Astrophysics Data System (ADS)

Kennedy, C. D.

2012-12-01

Nitrogen (N) is an essential nutrient for cranberry production but also a source of freshwater eutrophication in southeastern Massachusetts. Surface application of N fertilizer is pervasive throughout the cranberry industry, accounting for 93% of total annual N export from farms. The agricultural practice of "wet harvesting", involving the flooding of farms with ~1 ft of water, may promote the vertical transport and transformation of nitrogen in cranberry beds. A cranberry bed at the University of Massachusetts Cranberry Station (East Wareham, MA) has been instrumented with a network of hydrological monitoring equipment for quantifying patterns and controls of nitrogen dynamics during the harvest flood. Here, data of (1) hydraulic head gradient between floodwater and groundwater (J), (2) hydraulic conductivity (K), and (3) N concentration in groundwater (C) collected from multiple points on the cranberry bed will be presented, and used to evaluate the patterns and controls N fluxes (f = JKC) in the cranberry bed.

Status of faecal pollution in ports: A basin-wide investigation in the Adriatic Sea.

PubMed

Luna, Gian Marco; Manini, Elena; Turk, Valentina; Tinta, Tinkara; D'Errico, Giuseppe; Baldrighi, Elisa; Baljak, Vanja; Buda, Donatella; Cabrini, Marina; Campanelli, Alessandra; Cenov, Arijana; Del Negro, Paola; Drakulović, Dragana; Fabbro, Cinzia; Glad, Marin; Grilec, Dolores; Grilli, Federica; Jokanović, Sandra; Jozić, Slaven; Kauzlarić, Vesna; Kraus, Romina; Marini, Mauro; Mikuš, Josip; Milandri, Stefania; Pećarević, Marijana; Perini, Laura; Quero, Grazia Marina; Šolić, Mladen; Lušić, Darija Vukić; Zoffoli, Silvia

2018-04-07

Ports are subject to a variety of anthropogenic impacts, and there is mounting evidence of faecal contamination through several routes. Yet, little is known about pollution in ports by faecal indicator bacteria (FIB). FIB spatio-temporal dynamics were assessed in 12 ports of the Adriatic Sea, a semi-enclosed basin under strong anthropogenic pressure, and their relationships with environmental variables were explored to gain insight into pollution sources. FIB were abundant in ports, often more so than in adjacent areas; their abundance patterns were related to salinity, oxygen, and nutrient levels. In addition, a molecular method, quantitative (q)PCR, was used to quantify FIB. qPCR enabled faster FIB determination and water quality monitoring that culture-based methods. These data provide robust baseline evidence of faecal contamination in ports and can be used to improve the management of routine port activities (dredging and ballast water exchange), having potential to spread pathogens in the sea. Copyright © 2018 Elsevier Ltd. All rights reserved.

Regulation of Aedes aegypti Population Dynamics in Field Systems: Quantifying Direct and Delayed Density Dependence

PubMed Central

Walsh, Rachael K.; Aguilar, Cristobal L.; Facchinelli, Luca; Valerio, Laura; Ramsey, Janine M.; Scott, Thomas W.; Lloyd, Alun L.; Gould, Fred

2013-01-01

Transgenic strains of Aedes aegypti have been engineered to help control transmission of dengue virus. Although resources have been invested in developing the strains, we lack data on the ecology of mosquitoes that could impact the success of this approach. Although studies of intra-specific competition have been conducted using Ae. aegypti larvae, none of these studies examine mixed age cohorts at densities that occur in the field, with natural nutrient levels. Experiments were conducted in Mexico to determine the impact of direct and delayed density dependence on Ae. aegypti populations. Natural water, food, and larval densities were used to estimate the impacts of density dependence on larval survival, development, and adult body size. Direct and delayed density-dependent factors had a significant impact on larval survival, larval development, and adult body size. These results indicate that control methods attempting to reduce mosquito populations may be counteracted by density-dependent population regulation. PMID:23669230

High Latitude Dust Sources, Transport Pathways and Impacts

NASA Astrophysics Data System (ADS)

Bullard, J. E.; Baddock, M. C.; Darlington, E.; Mockford, T.; Van-Soest, M.

2017-12-01

Estimates from field studies, remote sensing and modelling all suggest around 5% of global dust emissions originate in the high latitudes (≥50°N and ≥40°S), a similar proportion to that from the USA (excluding Alaska) or Australia. This paper identifies contemporary sources of dust within the high latitudes and their role within local, regional and hemispherical environmental systems. Field data and remote sensing analyses are used to identify the environmental and climatic conditions that characterize high latitude dust sources in both hemispheres. Examples from Arctic and sub-Arctic dust sources are used to demonstrate and explain the different regional relationships among dust emissions, glacio-fluvial dynamics and snow cover. The relative timing of dust input to high latitude terrestrial, cryospheric and marine systems determines its short to medium term environmental impact. This is highlighted through quantifying the importance of locally-redistributed dust as a nutrient input to high latitude soils and lakes in West Greenland.

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.

Algal Turf Recruitment and Early Growth did not Differ Across Sites that Varied Greatly in Herbivore and Coral Community Structure.

NASA Astrophysics Data System (ADS)

Gaynus, C.

2016-02-01

Worldwide losses of coral with accompanying phase shifts to algae have been attributed to human alterations of major ecological processes, especially top down (herbivory) and bottom up (nutrients) forces. While positive effects on macroalgae have received some attention, less is known about turf algae. Closely cropped turf algae (< 1cm) are a major component of pristine coral reefs, providing trophic support, aiding in nutrient cycling, and providing high rates of photosynthesis. We hypothesized that enhanced nutrient supplies from developed watersheds and reduced herbivory from overfishing would result in longer turf, and possibly development of macroalgae. The goals of this study were to quantify top down and bottom up forces in conjunction with assessments of turf algae recruitment and growth on a fringing reef in Mo'orea French Polynesia. While this study will continue for 2 years, data here are for 5 weeks. We chose 3 sites in Cooks Bay that likely varied in nutrients and 3 along the north shore, presumably higher in herbivory. At each site 10 recruitment tiles were deployed. Turf communities accumulated over five-weeks while benthic and herbivorous fish communities were quantified at each site. Herbivorous fish communities consisted of juveniles and adults from the families Acanthuridae and Scaridae with both adult and juvenile acanthurids, comprising > 50% of all herbivorous fish. Sites within the bay, however, contained at least 66.7% less fish than sites along the north shore. In contrast benthic surveys portrayed little difference between sites, with turf making up > 70% of total hard bottom cover. Similarly, there was little difference among sites in the recruitment and growth rate ( 0.2-0.3 mm/week) of turf on tiles. While turf recruitment and early development appeared to be unaffected by herbivory or nutrients over the short time, we predict that longer-term effects will occur as this community develops.

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

Root Cortical Senescence Improves Growth under Suboptimal Availability of N, P, and K1[OPEN

PubMed Central

Schneider, Hannah M.

2017-01-01

Root cortical senescence (RCS) in Triticeae reduces nutrient uptake, nutrient content, respiration, and radial hydraulic conductance of root tissue. We used the functional-structural model SimRoot to evaluate the functional implications of RCS in barley (Hordeum vulgare) under suboptimal nitrate, phosphorus, and potassium availability. The utility of RCS was evaluated using sensitivity analyses in contrasting nutrient regimes. At flowering (80 d), RCS increased simulated plant growth by up to 52%, 73%, and 41% in nitrate-, phosphorus-, and potassium-limiting conditions, respectively. Plants with RCS had reduced nutrient requirement of root tissue for optimal plant growth, reduced total cumulative cortical respiration, and increased total carbon reserves. Nutrient reallocation during RCS had a greater effect on simulated plant growth than reduced respiration or nutrient uptake. Under low nutrient availability, RCS had greater benefit in plants with fewer tillers. RCS had greater benefit in phenotypes with fewer lateral roots at low nitrate availability, but the opposite was true in low phosphorus or potassium availability. Additionally, RCS was quantified in field-grown barley in different nitrogen regimes. Field and virtual soil coring simulation results demonstrated that living cortical volume per root length (an indicator of RCS) decreased with depth in younger plants, while roots of older plants had very little living cortical volume per root length. RCS may be an adaptive trait for nutrient acquisition by reallocating nutrients from senescing tissue and secondarily by reducing root respiration. These simulated results suggest that RCS merits investigation as a breeding target for enhanced soil resource acquisition and edaphic stress tolerance. PMID:28667049

Spatial and temporal variability in the water column nutrients and pesticides of Jobos Bay

USDA-ARS?s Scientific Manuscript database

The Conservation Effects Assessment Project (CEAP) is a national, multi-agency effort to quantify the environmental benefits of best management practices used by agricultural producers participating in selected U.S. Department of Agriculture (USDA) conservation programs, including programs such as t...

Water Chemistry of Ephemeral Streams

Treesearch

J.L. Michael; W.P. Fowler; H.L. Gibbs; J.B. Fischer

1994-01-01

Four individual, but related, studies are currently being conducted to determine the effects of clearcut and seed tree reproduction cutting methods on stream chemistry, sedimentation, and bedload movement by monitoring herbicide and nutrient movement in stemflow, overland flow, streamflow, and zonal subsurface flow. Sediment movement is being quantified for...

Hydrologic and Water Quality Assessment from Managed Turf

USDA-ARS?s Scientific Manuscript database

The potential for nutrients and pesticides to be transported to surface water from turf systems (especially golf courses) is often debated because of limited information on water quality exiting these systems. This four year study quantified the amount and quality of water draining from part of Nort...

Effect of interactions on the nutrient status of a tropical soil treated with green manures and inorganic phosphate fertilizers.

PubMed

Bah, Abdul R; Rahman, Zaharah A; Hussin, Aminuddin

2004-06-08

Integrated nutrient management systems using plant residues and inorganic P fertilizers have high potential for increasing crop production and ensuring sustainability in the tropics, but their adoption requires in-depth understanding of nutrient dynamics in such systems. This was examined in a highly weathered tropical soil treated with green manures (GMs) and P fertilizers in two experiments conducted in the laboratory and glasshouse. The treatments were factorial combinations of the GMs (Calopogonium caeruleum, Gliricidia sepium, and Imperata cylindrica) and P fertilizers (phosphate rocks [PRs] from North Carolina, China, and Algeria, and triple superphosphate) replicated thrice. Olsen P, mineral N, pH, and exchangeable K, Ca, and Mg were monitored in a laboratory incubation study for 16 months. The change in soil P fractions and available P was also determined at the end of the study. Phosphorus available from the amendments was quantified at monthly intervals for 5 months by 33P-32P double isotopic labeling in the glasshouse using Setaria sphacelata as test crop. The GMs were labeled with 33P to determine their contribution to P taken up by Setaria, while that from the P fertilizers was indirectly measured by labeling the soil with 32P. The P fertilizers hardly changed Olsen P and exchangeable cations during 16 months of incubation. The legume GMs and legume GM+P did not change Olsen P, lowered exchangeable Ca, and increased exchangeable K about threefold (4.5 cmol[+]kg(-1) soil) in the first 4 months, even as large amounts of NH4-N accumulated (approximately 1000 mg kg soil(-1)) and soil pH increased to more than 6.5. Afterwards, Olsen P and exchangeable Ca and Mg increased (threefold) as NH4+-N and soil pH declined. The legume GMs also augmented reversibly sorbed P in Al-P and Fe-P fractions resulting in high residual effect in the soil, while fertilizer-P was irreversibly retained. The GMs increased PR-P utilization by 40 to over 80%, mobilized soil P, and markedly enhanced uptake of N, K, Ca, and Mg. Thus GMs+PRs is an appropriate combination for correcting nutrient deficiencies in tropical soils.

Dynamic optimization of metabolic networks coupled with gene expression.

PubMed

Waldherr, Steffen; Oyarzún, Diego A; Bockmayr, Alexander

2015-01-21

The regulation of metabolic activity by tuning enzyme expression levels is crucial to sustain cellular growth in changing environments. Metabolic networks are often studied at steady state using constraint-based models and optimization techniques. However, metabolic adaptations driven by changes in gene expression cannot be analyzed by steady state models, as these do not account for temporal changes in biomass composition. Here we present a dynamic optimization framework that integrates the metabolic network with the dynamics of biomass production and composition. An approximation by a timescale separation leads to a coupled model of quasi-steady state constraints on the metabolic reactions, and differential equations for the substrate concentrations and biomass composition. We propose a dynamic optimization approach to determine reaction fluxes for this model, explicitly taking into account enzyme production costs and enzymatic capacity. In contrast to the established dynamic flux balance analysis, our approach allows predicting dynamic changes in both the metabolic fluxes and the biomass composition during metabolic adaptations. Discretization of the optimization problems leads to a linear program that can be efficiently solved. We applied our algorithm in two case studies: a minimal nutrient uptake network, and an abstraction of core metabolic processes in bacteria. In the minimal model, we show that the optimized uptake rates reproduce the empirical Monod growth for bacterial cultures. For the network of core metabolic processes, the dynamic optimization algorithm predicted commonly observed metabolic adaptations, such as a diauxic switch with a preference ranking for different nutrients, re-utilization of waste products after depletion of the original substrate, and metabolic adaptation to an impending nutrient depletion. These examples illustrate how dynamic adaptations of enzyme expression can be predicted solely from an optimization principle. Copyright © 2014 Elsevier Ltd. All rights reserved.

A nutritionally mediated risk effect of wolves on elk.

PubMed

Christianson, David; Creel, Scott

2010-04-01

Though it is widely argued that antipredator responses carry nutritional costs, or risk effects, these costs are rarely measured in wild populations. To quantify risk effects in elk, a species that strongly responds to the presence of wolves, we noninvasively monitored diet selection and nutrient balance in wintering elk in the Upper Gallatin, Montana, USA, over three winters while quantifying the local presence of wolves at a fine spatiotemporal scale. Standard nutritional indices based on the botanical and chemical composition of 786 fecal samples, 606 snow urine samples, and 224 forage samples showed that elk were generally malnourished throughout winter. Increased selection for dietary nitrogen within forage types (e.g., grasses) led to approximately 8% higher fecal nitrogen in the presence of wolves. However, urinary allantoin : creatinine and potassium : creatinine ratios decreased in the presence of wolves, suggesting large declines in energy intake, equal to 27% of maintenance requirements. Urinary nitrogen : creatinine ratios confirmed that deficiencies in nitrogen and/or energy were exacerbated in the presence of wolves, leading to increased endogenous protein catabolism. Overall, the nutritional effects of wolf presence may be of sufficient magnitude to reduce survival and reproduction in wintering elk. Nutritionally mediated risk effects may be important for understanding predator-prey dynamics in wild populations, but such effects could be masked as bottom-up forces if antipredator responses are not considered.

Root proliferation in decaying roots and old root channels: A nutrient conservation mechanism in oligotrophic mangrove forests?

USGS Publications Warehouse

McKee, K.L.

2001-01-01

1. In oligotrophic habitats, proliferation of roots in nutrient-rich microsites may contribute to overall nutrient conservation by plants. Peat-based soils on mangrove islands in Belize are characterized by the presence of decaying roots and numerous old root channels (0.1-3.5 cm diameter) that become filled with living and highly branched roots of Rhizophora mangle and Avicennia germinans. The objectives of this study were to quantify the proliferation of roots in these microsites and to determine what causes this response. 2. Channels formed by the refractory remains of mangrove roots accounted for only 1-2% of total soil volume, but the proportion of roots found within channels varied from 9 to 24% of total live mass. Successive generations of roots growing inside increasingly smaller root channels were also found. 3. When artificial channels constructed of PVC pipe were buried in the peat for 2 years, those filled with nutrient-rich organic matter had six times more roots than empty or sand-filled channels, indicating a response to greater nutrient availability rather than to greater space or less impedance to root growth. 4. Root proliferation inside decaying roots may improve recovery of nutrients released from decomposing tissues before they can be leached or immobilized in this intertidal environment. Greatest root proliferation in channels occurred in interior forest zones characterized by greater soil waterlogging, which suggests that this may be a strategy for nutrient capture that minimizes oxygen losses from the whole root system. 5. Improved efficiency of nutrient acquisition at the individual plant level has implications for nutrient economy at the ecosystem level and may explain, in part, how mangroves persist and grow in nutrient-poor environments.

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.

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.

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.

An individual-based modeling approach to simulate the effects of cellular nutrient competition on Escherichia coli K-12 MG1655 colony behavior and interactions in aerobic structured food systems.

PubMed

Tack, Ignace L M M; Logist, Filip; Noriega Fernández, Estefanía; Van Impe, Jan F M

2015-02-01

Traditional kinetic models in predictive microbiology reliably predict macroscopic dynamics of planktonically-growing cell cultures in homogeneous liquid food systems. However, most food products have a semi-solid structure, where microorganisms grow locally in colonies. Individual colony cells exhibit strongly different and non-normally distributed behavior due to local nutrient competition. As a result, traditional models considering average population behavior in a homogeneous system do not describe colony dynamics in full detail. To incorporate local resource competition and individual cell differences, an individual-based modeling approach has been applied to Escherichia coli K-12 MG1655 colonies, considering the microbial cell as modeling unit. The first contribution of this individual-based model is to describe single colony growth under nutrient-deprived conditions. More specifically, the linear and stationary phase in the evolution of the colony radius, the evolution from a disk-like to branching morphology, and the emergence of a starvation zone in the colony center are simulated and compared to available experimental data. These phenomena occur earlier at more severe nutrient depletion conditions, i.e., at lower nutrient diffusivity and initial nutrient concentration in the medium. Furthermore, intercolony interactions have been simulated. Higher inoculum densities lead to stronger intercolony interactions, such as colony merging and smaller colony sizes, due to nutrient competition. This individual-based model contributes to the elucidation of characteristic experimentally observed colony behavior from mechanistic information about cellular physiology and interactions. Copyright © 2014 Elsevier Ltd. All rights reserved.

Altered resource availability and the population dynamics of tree species in Amazonian secondary forests.

PubMed

Fortini, Lucas Berio; Bruna, Emilio M; Zarin, Daniel J; Vasconcelos, Steel S; Miranda, Izildinha S

2010-04-01

Despite research demonstrating that water and nutrient availability exert strong effects on multiple ecosystem processes in tropical forests, little is known about the effect of these factors on the demography and population dynamics of tropical trees. Over the course of 5 years, we monitored two common Amazonian secondary forest species-Lacistema pubescens and Myrcia sylvatica-in dry-season irrigation, litter-removal and control plots. We then evaluated the effects of altered water and nutrient availability on population demography and dynamics using matrix models and life table response experiments. Our results show that despite prolonged experimental manipulation of water and nutrient availability, there were nearly no consistent and unidirectional treatment effects on the demography of either species. The patterns and significance of observed treatment effects were largely dependent on cross-year variability not related to rainfall patterns, and disappeared once we pooled data across years. Furthermore, most of these transient treatment effects had little effect on population growth rates. Our results suggest that despite major experimental manipulations of water and nutrient availability-factors considered critical to the ecology of tropical pioneer tree species-autogenic light limitation appears to be the primary regulator of tree demography at early/mid successional stages. Indeed, the effects of light availability may completely override those of other factors thought to influence the successional development of Amazonian secondary forests.

Transport pathways of nitrogen and phosphorus in tile-drained cranberry farms

NASA Astrophysics Data System (ADS)

Kennedy, C. D.; Alversion, N.; Jeranyama, P.; DeMoranville, C.; Sandler, H.; Caruso, F.

2013-12-01

Rapid, controlled drainage of cranberry farms is critical to optimizing production in Massachusetts, where approximately 1/3 of the industry's crop is produced. Relatively new to cranberry farming, tile drainage has been billed as a low-cost drainage management option for reducing crop disease and weed infestations. Despite its well documented agronomic benefits, tile drainage may exacerbate nutrient loss and promote eutrophication in nearby ponds receiving cranberry drainage waters. In this study, a monitoring program was established on a Massachusetts cranberry bed to quantify (1) mass loss of nitrogen and phosphorous via tile drainage to a perimeter ditch surrounding the cranberry bed, (2) the attenuation of N and P in the ditch prior to discharge from the cranberry bed, and (3) and the component contributions of preferential vs. matrix transport of N and P in tile drainage. A combination of compound weirs, acoustic-velocity meters, propeller-driven flow meters, and rain gauges were installed to quantify drainage management characteristics of the cranberry bed. Automatic samplers were also installed to collect water samples at each monitoring site (i.e., four tile drains, an irrigation pond, and a flume used to control ditch height) for analysis of N and P concentrations and hydrogen and oxygen stable isotope ratios to estimate nutrient loss and transport pathways. These data will be used to develop a mechanistic synthesis of nutrient cycling in tile-drained cranberry beds.

Elucidating the nutritional dynamics of fungi using stable isotopes

Treesearch

Jordan R. Mayor; Edward A.G. Schuur; Terry W. Henkel

2009-01-01

Mycorrhizal and saprotrophic (SAP) fungi are essential to terrestrial element cycling due to their uptake of mineral nutrients and decomposition of detritus. Linking these ecological roles to specific fungi is necessary to improve our understanding of global nutrient cycling, fungal ecophysiology, and forest ecology. Using discriminant analyses of nitrogen and carbon...

Anaerobic soil disinfestation impact on soil nutrients dynamics and nitrous oxide emissions in fresh-market tomato

USDA-ARS?s Scientific Manuscript database

Anaerobic soil disinfestation (ASD) is proposed as a pre-plant, non-chemical soil disinfestation technique to control several soilborne phytosanitary issues. Limited information is available on the impact of ASD on soil fertility, plant growth, and potential nutrient loss. The objectives of the curr...

FOOD WEB AND COMMUNITY COMPOSITION CHANGES IN RESPONSE TO NUTRIENT LOADING IN FRESHWATER AND MARINE COASTAL SYSTEMS (ESTUARIES AND COASTAL WETLANDS)

EPA Science Inventory

Our research will investigate the mechanisms by which increased loading of nutrients to coastal waters alters the structure and dynamics of food webs, resulting in declines in populations of ecologically and commercially important organisms. Research across NHEERL Divisions will...

Tidal Mixing Box Submodel for Tampa Bay: Calibration of Tidal Exchange Flows with the Parameter Estimation Tool (PEST)

EPA Science Inventory

In the mid-1990s the Tampa Bay Estuary Program proposed a nutrient reduction strategy focused on improving water clarity to promote seagrass expansion within Tampa Bay. A System Dynamics Model is being developed to evaluate spatially and temporally explicit impacts of nutrient r...

Does cattle grazing of dual-purpose wheat accelerate the rate of stubble decomposition and nutrients released

USDA-ARS?s Scientific Manuscript database

Decomposition and nutrient release of winter annual forages in integrated crop-livestock systems could be affected by the resultant alterations in structure and quality of residues caused by grazing, but little information is available to test this hypothesis. Information on residue dynamics is need...

Conceptual design and quantification of phosphorus flows and balances at the country scale: The case of France

NASA Astrophysics Data System (ADS)

Senthilkumar, Kalimuthu; Nesme, Thomas; Mollier, Alain; Pellerin, Sylvain

2012-06-01

Global biogeochemical cycles have been deeply modified by human activities in recent decades. But detailed studies analyzing the influence of current economic and social organizations on global biogeochemical cycles within a system perspective are still required. Country level offers a relevant scale for assessing nutrient management and identifying key driving forces and possible leaks in the nutrient cycle. Conceptual modeling helps to quantify nutrient flows within the country and we developed such an approach for France. France is a typical Western European country with intensive agriculture, trade and an affluent diet, all of which may increase internal and external P flows. Phosphorus (P) was taken as a case study because phosphate rock is a non-renewable resource which future availability is becoming increasingly bleak. A conceptual model of major P flows at the country scale was designed. France was divided into agriculture, industry, domestic, import and export sectors, and each of these sectors was further divided into compartments. A total of 25 internal and eight external P flows were identified and quantified on a yearly basis for a period of 16 years (from 1990 to 2006) in order to understand long-term P flows. All the P flows were quantified using the substance flow analysis principle. The results showed that the industrial sector remained the largest contributor to P flows in France, followed by the agriculture and domestic sectors. Soil P balance was positive. However, a positive P balance of 18 kg P ha-1 in 1990 was reduced to 4 kg P ha-1 in 2006, mainly due to the reduced application of inorganic P fertilizer. The overall country scale P balance was positive, whereas half of this additional P was lost to the environment mainly through the landfilling of municipal and industrial waste, disposal of treated wastewater from which P was partially removed, and P losses from agricultural soils though erosion and leaching. Consequences for global P resources and soil and water compartments are discussed. Some opportunities to more effectively close the P cycle in France by both improving the intensity of P recycling and decreasing losses are quantified.

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 the relative size of the transient storage zone and how it changes in the downstream direction, as well as the nature of hydrologic variability.« less

Economic development influences on sediment-bound nitrogen and phosphorus accumulation of lakes in China.

PubMed

Ni, Zhaokui; Wang, Shengrui

2015-12-01

China has been confronted with serious water quality deterioration concurrent with rapid socioeconomic progress during the past 40 years. Consequently, knowledge about economic growth and lake water quality dynamics is important to understand eutrophication processes. Objectives were to (i) reconstruct historical nutrient accumulation and the basin economic progress on burial flux (BF); (ii) determine forms and structures of nitrogen (N) and phosphorus (P) in sediment and water using six cores in three of the most severely eutrophic lake areas in China (i.e., Eastern Plain, Yunnan-Guizhou Plain, and Inner Mongolia-Xinjiang regions). Results suggest that BFs of total nitrogen (TN) continued to increase in sediment, whereas total phosphorus (TP) levels were consistent or only slightly increased, except in highly polluted lakes during the past decades. Similar results were observed for concentrations of nutrients in water (i.e., increased N/P). This historical distribution pattern was correlated to long-term fertilization practices of farmers in the watershed (N fertilization exceeds that of P) and was contingent upon pollution control policies (e.g., emphasized P whereas N was ignored). Vertical profiles of BFs indicated that lake nutrient accumulation included three stages in China. Nutrient accumulation started in the 1980s, accelerated from the 1990s, and then declined after 2000. Before the 1980s, nutrients were relatively low and stable, with nutrient inputs being controlled by natural processes. Thereafter, N- and P-bound sediments dramatically increased due to the increasing influence of anthropogenic processes. Nutrients were primarily derived from industries and domestic sewage. After 2000, BFs of nutrients were steady and even decreased, owing to implementation of watershed load reduction policies. The decreasing NaOH-extracted P (Fe/Al-P) and increasing organic phosphorus (OP) indicated that the source of exogenous pollution underwent a shift. Inputs of nutrients were predominantly from agricultural and domestic sewage, whereas industrial pollution has been gradually controlled in most of the watersheds. Historical nutrient dynamics suggest that the economy of China is growing at the expense of its aquatic ecological environments. Therefore, more attention to nutrient export to groundwater resulting from economic development is important for further aquatic ecosystem deterioration and eutrophication in China.

Future changes in coastal upwelling ecosystems with global warming: The case of the California Current System.

PubMed

Xiu, Peng; Chai, Fei; Curchitser, Enrique N; Castruccio, Frederic S

2018-02-12

Coastal upwelling ecosystems are among the most productive ecosystems in the world, meaning that their response to climate change is of critical importance. Our understanding of climate change impacts on marine ecosystems is largely limited to the open ocean, mainly because coastal upwelling is poorly reproduced by current earth system models. Here, a high-resolution model is used to examine the response of nutrients and plankton dynamics to future climate change in the California Current System (CCS). The results show increased upwelling intensity associated with stronger alongshore winds in the coastal region, and enhanced upper-ocean stratification in both the CCS and open ocean. Warming of the open ocean forces isotherms downwards, where they make contact with water masses with higher nutrient concentrations, thereby enhancing the nutrient flux to the deep source waters of the CCS. Increased winds and eddy activity further facilitate upward nutrient transport to the euphotic zone. However, the plankton community exhibits a complex and nonlinear response to increased nutrient input, as the food web dynamics tend to interact differently. This analysis highlights the difficulty in understanding how the marine ecosystem responds to a future warming climate, given to range of relevant processes operating at different scales.

Analyzing the spatial patterns and drivers of ecosystem services in rapidly urbanizing Taihu Lake Basin of China

NASA Astrophysics Data System (ADS)

Ai, Junyong; Sun, Xiang; Feng, Lan; Li, Yangfan; Zhu, Xiaodong

2015-09-01

Quantifying and mapping the distribution patterns of ecosystem services can help to ascertain which services should be protected and where investments should be directed to improve synergies and reduce tradeoffs. Moreover, the indicators of urbanization that affect the provision of ecosystem services must be identified to determine which approach to adopt in formulating policies related to these services. This paper presents a case study that maps the distribution of multiple ecosystem services and analyzes the ways in which they interact. The relationship between the supply of ecosystem services and the socio-economic development in the Taihu Lake Basin of eastern China is also revealed. Results show a significant negative relationship between crop production and tourism income ( p<0.005) and a positive relationship between crop production, nutrient retention, and carbon sequestration ( p<0.005). The negative effects of the urbanization process on providing and regulating services are also identified through a comparison of the ecosystem services in large and small cities. Regression analysis was used to compare and elucidate the relative significance of the selected urbanization factors to ecosystem services. The results indicate that urbanization level is the most substantial factor inversely correlated with crop production ( R 2 = 0.414) and nutrient retention services ( R 2 = 0.572). Population density is the most important factor that negatively affects carbon sequestration ( R 2 = 0.447). The findings of this study suggest the potential relevance of ecosystem service dynamics to urbanization management and decision making.

New, national bottom-up estimate for tree-based biological nitrogen fixation in the US

EPA Science Inventory

Nitrogen is a limiting nutrient in many ecosystems, but is also a chief pollutant from human activity. Quantifying human impacts on the nitrogen cycle and investigating natural ecosystem nitrogen cycling both require an understanding of the magnitude of nitrogen inputs from biolo...

Managing the herbage utilisation and intake by cattle grazing rangelands

USDA-ARS?s Scientific Manuscript database

To be able to predict the performance of grazing cattle in extensive rangeland environments, herbage intake is paramount because it quantifies energy intake and performance. Nutrient demand of the animals is the major driver of herbage intake and characteristics of the sward dictate how this demand...

Some Challenges of an “Upside Down” Nitrogen Budget – Science and Management in Greenwich Bay, RI (USA)

EPA Science Inventory

When nutrients impact estuarine water quality, scientists and managers instinctively focus on quantifying and controlling land-based sources. However, in Greenwich Bay, RI, the estuary opens onto a larger and more intensively fertilized coastal water body (Narragansett Bay). Prev...

Regional effects of agricultural conservation practices on nutrient transport in the Upper Mississippi River Basin

USDA-ARS?s Scientific Manuscript database

Despite progress in the implementation of conservation practices, related improvements in water quality have been challenging to measure in larger river systems. In this paper we quantify these downstream effects by applying the empirical U.S. Geological Survey water-quality model SPARROW to inves...

Integrated crop-livestock system effects on soil N, P, and pH in a semiarid region

USDA-ARS?s Scientific Manuscript database

Integrated crop-livestock systems (ICLS) represent a potential means to sustainably intensify agriculture. Developing ICLS that concurrently achieve production and environmental goals is contingent upon efficiently managing plant nutrients in time and space. In this study, we sought to quantify re...

QUANTIFYING SEASONAL SHIFTS IN NITROGEN SOURCES TO OREGON ESTUARIES. PART I: EMPIRICAL 15N MACROALGAE DATA

EPA Science Inventory

“Green Tides” are typically considered to be a symptom of eutrophication associated with anthropogenic nutrient loading. In many estuaries along the Pacific Northwest (PNW), the seasonal development of macroalgal mats or “Green Tides” coincides with the initiation of coastal upw...

FUNCTIONAL OVERLAP OF ROOT SYSTEMS IN AN OLD-GROWTH FOREST INFERRED FROM TRACER 15N UPTAKE

EPA Science Inventory

Belowground competition for nutrients and water is considered a key factor affecting spatial organization and productivity of individual stems within forest stands, yet there are few data describing the lateral extent and overlap of competing root systems. We quantified the func...

Managing Saginaw Bay nutrient loading by surrounding watersheds through near real time hydrologic resource sheds

EPA Science Inventory

We can quantify source areas contributing material to a location during various time periods as resource sheds. Various kinds of resource sheds and their source material distributions are defined. For watershed hydrology, we compute resource sheds and their source material distri...

Reproductive allocation and nutrient relationships in Cuphea: A semi-domesticated oilseed crop

USDA-ARS?s Scientific Manuscript database

No information is available on allometric variations in C, N, and P in structural, reproductive and metabolic tissues and their ratios in Cuphea germplasm line PSR23, a semi-domesticated indeterminate and phenotypically plastic oilseed crop. The objectives of this study were to quantify the impact o...

Contrasting nutrient mitigation and denitrification potential of agricultural drainage environments with different emergent aquatic macrophytes.

USDA-ARS?s Scientific Manuscript database

Remediation of excess nitrogen (N) in agricultural runoff can be enhanced by establishing wetland vegetation but the role of denitrification in N removal is not well understood in drainage ditches. We quantified differences in N retention during experimental runoff events followed by stagnant period...

Leaf habit and woodiness regulate different leaf economy traits at a given nutrient supply.

PubMed

Ordoñez, Jenny C; van Bodegom, Peter M; Witte, Jan-Philip M; Bartholomeus, Ruud P; van Dobben, Han F; Aerts, Rien

2010-11-01

The large variation in the relationships between environmental factors and plant traits observed in natural communities exemplifies the alternative solutions that plants have developed in response to the same environmental limitations. Qualitative attributes, such as growth form, woodiness, and leaf habit can be used to approximate these alternative solutions. Here, we quantified the extent to which these attributes affect leaf trait values at a given resource supply level, using measured plant traits from 105 different species (254 observations) distributed across 50 sites in mesic to wet plant communities in The Netherlands. For each site, soil total N, soil total P, and water supply estimates were obtained by field measurements and modeling. Effects of growth forms, woodiness, and leaf habit on relations between leaf traits (SLA, specific leaf area; LNC, leaf nitrogen concentration; and LPC, leaf phosphorus concentration) vs. nutrient and water supply were quantified using maximum-likelihood methods and Bonferroni post hoc tests. The qualitative attributes explained 8-23% of the variance within sites in leaf traits vs. soil fertility relationships, and therefore they can potentially be used to make better predictions of global patterns of leaf traits in relation to nutrient supply. However, at a given soil fertility, the strength of the effect of each qualitative attribute was not the same for all leaf traits. These differences may imply a differential regulation of the leaf economy traits at a given nutrient supply, in which SLA and LPC seem to be regulated in accordance to changes in plant size and architecture while LNC seems to be primarily regulated at the leaf level by factors related to leaf longevity.

Biomass of Speckled Alder on an Air-Polluted Mountain Site and its Response to Fertilization

NASA Astrophysics Data System (ADS)

Kuneš, Ivan; Baláš, Martin; Koňasová, Tereza; Špulák, Ondřej; Balcar, Vratislav; Millerová, Kateřina Bednářová; Kacálek, Dušan; Jakl, Michal; Zahradník, Daniel; Vítámvás, Jan; Š´astná, Jaroslava; Jaklová Dytrtová, Jana

2014-12-01

The article summarizes outcomes of a biomass study conducted in a young speckled alder plantation on a cold mountain site. At this location, the previously existing old forest was clear felled because of damage from air pollution, and present-day surface humus is in need of restoration. The intention of this study was to quantify the biomass and nutrients accumulated by alders and their components and assess whether the initial fertilization resulted in increased biomass production and nutrient accumulation in the biomass. Besides the control, two fertilized treatments were installed. In the surface treatment (SUT), the amendment was applied as a base dressing in small circles around trees. In the planting-hole treatment (PHT), the amendment was incorporated into soil inside the planting holes. Five growth seasons after planting and fertilization, six alders from each treatment were harvested including roots. Their biomass was quantified and analyzed for macroelements. The greatest pool of dry mass (DM) was branches in the control and stem wood in the fertilized treatments. The greatest pools of macroelements were leaves and branches. The most pronounced effects of fertilization were recorded in the DM and consequently in the absolute quantities of nutrients. The DM of an average tree in the control, SUT, and PHT was 85, 226, and 231 g, respectively. The absolute contents of nutrients per tree in the fertilized treatments showed the following increases, as compared with the control: (N) 2.5-2.6 times; (P) 1.6-2.4 times; (K) 1.8-2.1 times; and (Mg) 1.8-2.0 times, respectively. Speckled alder responded positively to fertilization.

Rate dependent fractionation of sulfur isotopes in through-flowing systems

NASA Astrophysics Data System (ADS)

Giannetta, M.; Sanford, R. A.; Druhan, J. L.

2017-12-01

The fidelity of reactive transport models in quantifying microbial activity in the subsurface is often improved through the use stable isotopes. However, the accuracy of current predictions for microbially mediated isotope fractionations within open through-flowing systems typically depends on nutrient availability. This disparity arises from the common application of a single `effective' fractionation factor assigned to a given system, despite extensive evidence for variability in the fractionation factor between eutrophic environments and many naturally occurring, nutrient-limited environments. Here, we demonstrate a reactive transport model with the capacity to simulate a variable fractionation factor over a range of microbially mediated reduction rates and constrain the model with experimental data for nutrient limited conditions. Two coupled isotope-specific Monod rate laws for 32S and 34S, constructed to quantify microbial sulfate reduction and predict associated S isotope partitioning, were parameterized using a series of batch reactor experiments designed to minimize microbial growth. In the current study, we implement these parameterized isotope-specific rate laws within an open, through-flowing system to predict variable fractionation with distance as a function of sulfate reduction rate. These predictions are tested through a supporting laboratory experiment consisting of a flow-through column packed with homogenous porous media inoculated with the same species of sulfate reducing bacteria used in the previous batch reactors, Desulfovibrio vulgaris. The collective results of batch reactor and flow-through column experiments support a significant improvement for S isotope predictions in isotope-sensitive multi-component reactive transport models through treatment of rate-dependent fractionation. Such an update to the model will better equip reactive transport software for isotope informed characterization of microbial activity within energy and nutrient limited environments.

Effect of river flow fluctuations on riparian vegetation dynamics: Processes and models

NASA Astrophysics Data System (ADS)

Vesipa, Riccardo; Camporeale, Carlo; Ridolfi, Luca

2017-12-01

Several decades of field observations, laboratory experiments and mathematical modelings have demonstrated that the riparian environment is a disturbance-driven ecosystem, and that the main source of disturbance is river flow fluctuations. The focus of the present work has been on the key role that flow fluctuations play in determining the abundance, zonation and species composition of patches of riparian vegetation. To this aim, the scientific literature on the subject, over the last 20 years, has been reviewed. First, the most relevant ecological, morphological and chemical mechanisms induced by river flow fluctuations are described from a process-based perspective. The role of flow variability is discussed for the processes that affect the recruitment of vegetation, the vegetation during its adult life, and the morphological and nutrient dynamics occurring in the riparian habitat. Particular emphasis has been given to studies that were aimed at quantifying the effect of these processes on vegetation, and at linking them to the statistical characteristics of the river hydrology. Second, the advances made, from a modeling point of view, have been considered and discussed. The main models that have been developed to describe the dynamics of riparian vegetation have been presented. Different modeling approaches have been compared, and the corresponding advantages and drawbacks have been pointed out. Finally, attention has been paid to identifying the processes considered by the models, and these processes have been compared with those that have actually been observed or measured in field/laboratory studies.

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 source with significant concentrations available to the microbial community, deeper in the sediment below the oxic layer. PMID:27303370

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 source with significant concentrations available to the microbial community, deeper in the sediment below the oxic layer.

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.

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 catchment buffering capacity and the probability of human disturbance provides a useful perspective for evaluating vulnerability of aquatic ecosystems and for managing systems to maintain agricultural production while minimizing leakage of nutrients.

Carbon and nitrogen dynamics across a bedrock-regulated subarctic pH gradient

NASA Astrophysics Data System (ADS)

Tomczyk, N.; Heim, E. W.; Sadowsky, J.; Remiszewski, K.; Varner, R. K.; Bryce, J. G.; Frey, S. D.

2014-12-01

Bedrock geochemistry has been shown to influence landscape evolution due to nutrient limitation on primary production. There may also be less direct interactions between bedrock-derived chemicals and ecosystem function. Effects of calcium (Ca) and pH on soil carbon (C) and nitrogen (N) cycling have been shown in acid impacted forests o f North America. Understanding intrinsic factors that affect C and nutrient dynamics in subarctic ecosystems has implications for how these ecosystems will respond to a changing climate. How the soil microbial community allocates enzymes to acquire resources from the environment can indicate whether a system is nutrient or energy limited. This study examined whether bedrock geochemistry exerts pressure on nutrient cycles in the overlying soils. In thin, weakly developed soils, bedrock is the primary mineral material and is a source of vital nutrients. Nitrogen (N) and C are not derived from bedrock, but their cycling is still affected by reactions with geologically-derived chemicals. Our study sites near Abisko, Sweden (~68°N) were selected adjacent to five distinct bedrock outcrops (quartzite, slate, carbonate, and two different metasedimenty units). All sites were at a similar elevation (~700 m a.s.l.) and had similar vegetation (subarctic heath). Nutrient concentrations in bedrock and soils were measured in addition to soil microbial biomass and extracellular enzyme activity. We found a statistically significant correlation between soil Ca concentrations and soil pH (r = 0.88, p < 0.01). There were also significant relationships between soil pH and the ratio of C-acquiring to N-acquiring enzyme activity (r = -0.89, p < 0.01), soil pH and soil C-to-N ratio (r = -0.76, p < 0.01), and the ratio of C-acquiring to N-acquiring enzyme activity and soil C-to-N ratio (r = 0.78, p < 0.01). These results suggest that soil Ca concentrations influence C and N cycling dynamics in these soils through their effect on soil pH.

Wind-driven marine phytoplank blooms: Satellite observation and analysis

NASA Astrophysics Data System (ADS)

Tang, DanLing

2016-07-01

Algal bloom is defined as a rapid increase or accumulation in biomass in an aquatic system. It not only can increase the primary production but also could result in negative ecological consequence, e.g.,Harmful Algal Blooms (HABs). According to the classic theory for the formation of algal blooms "critical depth" and "eutrophication", oligotrophic sea area is usually difficult to form a large area of algal blooms, and actuallythe traditional observation is only sporadic capture to the existence of algal blooms.Taking full advantage of multiple data of satellite remote sensing , this study introduces "Wind-driven algal blooms in open oceans: observation and mechanisms" It explained except classic coastal Ekman transport, the wind through a variety of mechanisms affecting the formation of algal blooms. Proposed a conceptual model of "Strong wind -upwelling-nutrient-phytoplankton blooms" in Western South China Sea (SCS) to assess role of wind-induced advection transport in phytoplankton bloom formation. It illustrates the nutrient resources that support long-term offshore phytoplankton blooms in the western SCS; (2)Proposal of the theory that "typhoons cause vertical mixing, induce phytoplankton blooms", and quantify their important contribution to marine primary production; Proposal a new ecological index for typhoon. Proposed remote sensing inversion models. (3)Finding of the spatial and temporaldistributions pattern of harmful algal bloom (HAB)and species variations of HAB in the South Yellow Sea and East China Sea, and in the Pearl River estuary, and their oceanic dynamic mechanisms related with monsoon; The project developed new techniques and generated new knowledge, which significantly improved understanding of the formation mechanisms of algal blooms. The proposed "wind-pump" mechanism integrates theoretical system combined "ocean dynamics, development of algal blooms, and impact on primary production", which will benefit fisheries management. These achievements led to the development of a new interdisciplinary subject "Remote Sensing Marine Ecology"(RSME).

Unlocking the forest inventory data: relating individual tree performance to unmeasured environmental factors.

PubMed

Lichstein, Jeremy W; Dushoff, Jonathan; Ogle, Kiona; Chen, Anping; Purves, Drew W; Caspersen, John P; Pacala, Stephen W

2010-04-01

Geographically extensive forest inventories, such as the USDA Forest Service's Forest Inventory and Analysis (FIA) program, contain millions of individual tree growth and mortality records that could be used to develop broad-scale models of forest dynamics. A limitation of inventory data, however, is that individual-level measurements of light (L) and other environmental factors are typically absent. Thus, inventory data alone cannot be used to parameterize mechanistic models of forest dynamics in which individual performance depends on light, water, nutrients, etc. To overcome this limitation, we developed methods to estimate species-specific parameters (thetaG) relating sapling growth (G) to L using data sets in which G, but not L, is observed for each sapling. Our approach involves: (1) using calibration data that we collected in both eastern and western North America to quantify the probability that saplings receive different amounts of light, conditional on covariates x that can be obtained from inventory data (e.g., sapling crown class and neighborhood crowding); and (2) combining these probability distributions with observed G and x to estimate thetaG using Bayesian computational methods. Here, we present a test case using a data set in which G, L, and x were observed for saplings of nine species. This test data set allowed us to compare estimates of thetaG obtained from the standard approach (where G and L are observed for each sapling) to our method (where G and x, but not L, are observed). For all species, estimates of thetaG obtained from analyses with and without observed L were similar. This suggests that our approach should be useful for estimating light-dependent growth functions from inventory data that lack direct measurements of L. Our approach could be extended to estimate parameters relating sapling mortality to L from inventory data, as well as to deal with uncertainty in other resources (e.g., water or nutrients) or environmental factors (e.g., temperature).

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 highest nutrient concentrations, while concentrations in the recession limb were higher than in the rising limb. We also found that in this catchment K concentrations were lower in the recession limb than in the rising limb. In the Amazonian pasture catchment, the peak discharge showed the greatest concentrations for TIC, TOC, and Ca, and the rising limb the lowest. DOC and NO3 concentrations in this catchment were the highest in the rising and were lowest in peak discharge, while K increased over time. Based on that, we conclude that stormflow is an important driver of nutrients fluxes due to land-use change on the Amazon Agricultural Frontier, with significant increases and distinguished dynamics during the storm events, and higher nutrient concentrations in the catchments with pastures than in the ones with native vegetation, especially for TIC and K.

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.

Greenland's glacial fjords and their role in regional biogeochemical dynamics.

NASA Astrophysics Data System (ADS)

Crosby, J.; Arndt, S.

2017-12-01

Greenland's coastal fjords serve as important pathways that connect the Greenland Ice Sheet (GrIS) and the surrounding oceans. They export seasonal glacial meltwater whilst being significant sites of primary production. These fjords are home to some of the most productive ecosystems in the world and possess high socio-economic value via fisheries. A growing number of studies have proposed the GrIS as an underappreciated yet significant source of nutrients to surrounding oceans. Acting as both transfer routes and sinks for glacial nutrient export, fjords have the potential to act as significant biogeochemical processors, yet remain underexplored. Critically, an understanding of the quantitative contribution of fjords to carbon and nutrient budgets is lacking, with large uncertainties associated with limited availability of field data and the lack of robust upscaling approaches. To close this knowledge gap we developed a coupled 2D physical-biogeochemical model of the Godthåbsfjord system, a sub-Arctic sill fjord in southwest Greenland, to quantitatively assess the impact of nutrients exported from the GrIS on fjord primary productivity and biogeochemical dynamics. Glacial meltwater is found to be a key driver of fjord-scale circulation patterns, whilst tracer simulations reveal the relative nutrient contributions from meltwater-driven upwelling and meltwater export from the GrIS. Hydrodynamic circulation patterns and freshwater transit times are explored to provide a first understanding of the glacier-fjord-ocean continuum, demonstrating the complex pattern of carbon and nutrient cycling at this critical land-ocean interface.

Mixing and the dynamics of the deep chlorophyll maximum in Lake Tahoe

NASA Technical Reports Server (NTRS)

Abbott, M. R.; Denman, K. L.; Powell, T. M.; Richerson, P. J.; Richards, R. C.; Goldman, C. R.

1984-01-01

Chlorophyll-temperature profiles were measured across Lake Tahoe about every 10 days from April through July 1980. Analysis of the 123 profiles and associated productivity and nutrient data identified three important processes in the formation and dynamics of the deep chlorophyll maximum (DCM): turbulent diffusion, nutrient supply rate, and light availability. Seasonal variation in these three processes resulted in three regimes: a diffusion-dominated regime with a weak DCM, a variable-mixing regime with a pronounced, nutrient supply-dominated DCM, and a stable regime with a deep, moderate light availability-dominated DCM. The transition between the first two regimes occurred in about 10 days, the transition between the last two more gradually over about 3 weeks. The degree of spatial variability of the DCM was highest in the second regime and lowest in the third. These data indicate that the DCM in Lake Tahoe is constant in neither time nor space.

Quantification of the impact of macrophytes on oxygen dynamics and nitrogen retention in a vegetated lowland river

NASA Astrophysics Data System (ADS)

Desmet, N. J. S.; Van Belleghem, S.; Seuntjens, P.; Bouma, T. J.; Buis, K.; Meire, P.

When macrophytes are growing in the river, the vegetation induces substantial changes to the water quality. Some effects are the result of direct interactions, such as photosynthetic activity or nutrient uptake, whereas others may be attributed to indirect effects of the water plants on hydrodynamics and river processes. This research focused on the direct effect of macrophytes on oxygen dynamics and nutrient cycling. Discharge, macrophyte biomass density, basic water quality, dissolved oxygen and nutrient concentrations were in situ monitored throughout the year in a lowland river (Nete catchment, Belgium). In addition, various processes were investigated in more detail in multiple ex situ experiments. The field and aquaria measurement results clearly demonstrated that aquatic plants can exert considerable impact on dissolved oxygen dynamics in a lowland river. When the river was dominated by macrophytes, dissolved oxygen concentrations varied from 5 to 10 mg l -1. Considering nutrient retention, it was shown that the investigated in-stream macrophytes could take up dissolved inorganic nitrogen (DIN) from the water column at rates of 33-50 mg N kgdry matter-1 h. And DIN fluxes towards the vegetation were found to vary from 0.03 to 0.19 g N ha -1 h -1 in spring and summer. Compared to the measured changes in DIN load over the river stretch, it means that about 3-13% of the DIN retention could be attributed to direct nitrogen uptake from the water by macrophytes. Yet, the role of macrophytes in rivers should not be underrated as aquatic vegetation also exerts considerable indirect effects that may have a greater impact than the direct fixation of nutrients into the plant biomass.

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.

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.

Decomposition dynamic of two aquatic macrophytes Trapa bispinosa Roxb. and Nelumbo nucifera detritus.

PubMed

Zhou, Xiaohong; Feng, Deyou; Wen, Chunzi; Liu, Dan

2018-03-29

In freshwater ecosystems, aquatic macrophytes play significant roles in nutrient cycling. One problem in this process is nutrient loss in the tissues of untimely harvested plants. In this study, we used two aquatic species, Nelumbo nucifera and Trapa bispinosa Roxb., to investigate the decomposition dynamics and nutrient release from detritus. Litter bags containing 10 g of stems (plus petioles) and leaves for each species detritus were incubated in the pond from November 2016 to May 2017. Nine times litterbags were retrieved on days 6, 14, 25, 45, 65, 90, 125, 145, and 165 after the decomposition experiment for the monitoring of biomass loss and nutrient release. The results suggested that the dry masses of N. nucifera and T. bispinosa decomposed by 49.35-69.40 and 82.65-91.65%, respectively. The order of decomposition rate constants (k) is as follows: leaves of T. bispinosa (0.0122 day -1 ) > stems (plus petioles) of T. bispinosa (0.0090 day -1 ) > leaves of N. nucifera (0.0060 day -1 ) > stems (plus petioles) of N. nucifera (0.0030 day -1 ). Additionally, the orders of time for 50% dry mass decay, time for 95% dry mass decay, and turnover rate are as follows: leaves < stems (plus petioles) and T. bispinosa < N. nucifera, respectively. This result indicated that the dry mass loss, k values, and other parameters related to k values are significantly different in species- and tissue-specific. The C, N, and P concentration and the C/N, C/P, and N/P ratios presented the irregular temporal changes trends during the whole decay period. In addition, nutrient accumulation index (AI) was significantly changed depending on the dry mass remaining and C, N, and P concentration in detritus at different decomposition times. The nutrient AIs were 36.72, 8.08, 6.35, and 2.56% for N; 31.25, 9.85, 4.00, and 1.63% for P; 25.15, 16.96, 7.36, and 6.16% for C in the stems (plus petioles) of N. nucifera, leaves of N. nucifera, stems (plus petioles) of T. bispinosa, and leaves of T. bispinosa, respectively, at the day 165. These results indicated that 63.28-97.44% of N, 68.75-98.37% of P, and 74.85-93.84% of C were released from the plant detritus to the water at the day 165 of the decomposition period. The initial detritus chemistry, particularly the P-related parameters (P concentration and C/P and N/P ratios), strongly affected dry mass loss, decomposition rates, and nutrient released from detritus into water. Two-way ANOVA results also confirm that the effects on the species were significant for decomposition dynamics (dry mass loss), nutrient release (nutrient concentration, their ratios, and nutrient AI) (P < 0.01), and expected N concentration (P > 0.05). In addition, the decomposition time had also significant effects on the detritus decomposition dynamic and nutrient release. However, the contributors of species and decomposition time on detritus decomposition were significantly different on the basis of their F values of two-way ANOVA results. This study can provide scientific bases for the aquatic plant scientific management in freshwater ecosystems of the East region of China.

Evaluation of Daphnid Grazing on Microscopic Zoosporic Fungi by Using Comparative Threshold Cycle Quantitative PCR

PubMed Central

Maier, Michelle A.; Uchii, Kimiko; Peterson, Tawnya D.

2016-01-01

ABSTRACT Lethal parasitism of large phytoplankton by chytrids (microscopic zoosporic fungi) may play an important role in organic matter and nutrient cycling in aquatic environments by shunting carbon away from hosts and into much smaller zoospores, which are more readily consumed by zooplankton. This pathway provides a mechanism to more efficiently retain carbon within food webs and reduce export losses. However, challenges in accurate identification and quantification of chytrids have prevented a robust assessment of the relative importance of parasitism for carbon and energy flows within aquatic systems. The use of molecular techniques has greatly advanced our ability to detect small, nondescript microorganisms in aquatic environments in recent years, including chytrids. We used quantitative PCR (qPCR) to quantify the consumption of zoospores by Daphnia in laboratory experiments using a culture-based comparative threshold cycle (CT) method. We successfully quantified the reduction of zoospores in water samples during Daphnia grazing and confirmed the presence of chytrid DNA inside the daphnid gut. We demonstrate that comparative CT qPCR is a robust and effective method to quantify zoospores and evaluate zoospore grazing by zooplankton and will aid in better understanding how chytrids contribute to organic matter cycling and trophic energy transfer within food webs. IMPORTANCE The study of aquatic fungi is often complicated by the fact that they possess complex life cycles that include a variety of morphological forms. Studies that rely on morphological characteristics to quantify the abundances of all stages of the fungal life cycle face the challenge of correctly identifying and enumerating the nondescript zoospores. These zoospores, however, provide an important trophic link between large colonial phytoplankton and zooplankton: that is, once the carbon is liberated from phytoplankton into the parasitic zoospores, the latter are consumed by zooplankton and carbon is retained in the aquatic food web rather than exported from the system. This study provides a tool to quantify zoospores and evaluate the consumption of zoospores by zooplankton in order to further our understanding of their role in food web dynamics. PMID:27107112

Evaluation of Daphnid Grazing on Microscopic Zoosporic Fungi by Using Comparative Threshold Cycle Quantitative PCR.

PubMed

Maier, Michelle A; Uchii, Kimiko; Peterson, Tawnya D; Kagami, Maiko

2016-07-01

Lethal parasitism of large phytoplankton by chytrids (microscopic zoosporic fungi) may play an important role in organic matter and nutrient cycling in aquatic environments by shunting carbon away from hosts and into much smaller zoospores, which are more readily consumed by zooplankton. This pathway provides a mechanism to more efficiently retain carbon within food webs and reduce export losses. However, challenges in accurate identification and quantification of chytrids have prevented a robust assessment of the relative importance of parasitism for carbon and energy flows within aquatic systems. The use of molecular techniques has greatly advanced our ability to detect small, nondescript microorganisms in aquatic environments in recent years, including chytrids. We used quantitative PCR (qPCR) to quantify the consumption of zoospores by Daphnia in laboratory experiments using a culture-based comparative threshold cycle (CT) method. We successfully quantified the reduction of zoospores in water samples during Daphnia grazing and confirmed the presence of chytrid DNA inside the daphnid gut. We demonstrate that comparative CT qPCR is a robust and effective method to quantify zoospores and evaluate zoospore grazing by zooplankton and will aid in better understanding how chytrids contribute to organic matter cycling and trophic energy transfer within food webs. The study of aquatic fungi is often complicated by the fact that they possess complex life cycles that include a variety of morphological forms. Studies that rely on morphological characteristics to quantify the abundances of all stages of the fungal life cycle face the challenge of correctly identifying and enumerating the nondescript zoospores. These zoospores, however, provide an important trophic link between large colonial phytoplankton and zooplankton: that is, once the carbon is liberated from phytoplankton into the parasitic zoospores, the latter are consumed by zooplankton and carbon is retained in the aquatic food web rather than exported from the system. This study provides a tool to quantify zoospores and evaluate the consumption of zoospores by zooplankton in order to further our understanding of their role in food web dynamics. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

The Nutritional Geometry of Resource Scarcity: Effects of Lean Seasons and Habitat Disturbance on Nutrient Intakes and Balancing in Wild Sifakas

PubMed Central

Irwin, Mitchell T.; Raharison, Jean-Luc; Raubenheimer, David R.; Chapman, Colin A.; Rothman, Jessica M.

2015-01-01

Animals experience spatial and temporal variation in food and nutrient supply, which may cause deviations from optimal nutrient intakes in both absolute amounts (meeting nutrient requirements) and proportions (nutrient balancing). Recent research has used the geometric framework for nutrition to obtain an improved understanding of how animals respond to these nutritional constraints, among them free-ranging primates including spider monkeys and gorillas. We used this framework to examine macronutrient intakes and nutrient balancing in sifakas (Propithecus diadema) at Tsinjoarivo, Madagascar, in order to quantify how these vary across seasons and across habitats with varying degrees of anthropogenic disturbance. Groups in intact habitat experience lean season decreases in frugivory, amounts of food ingested, and nutrient intakes, yet preserve remarkably constant proportions of dietary macronutrients, with the proportional contribution of protein to the diet being highly consistent. Sifakas in disturbed habitat resemble intact forest groups in the relative contribution of dietary macronutrients, but experience less seasonality: all groups’ diets converge in the lean season, but disturbed forest groups largely fail to experience abundant season improvements in food intake or nutritional outcomes. These results suggest that: (1) lemurs experience seasonality by maintaining nutrient balance at the expense of calories ingested, which contrasts with earlier studies of spider monkeys and gorillas, (2) abundant season foods should be the target of habitat management, even though mortality might be concentrated in the lean season, and (3) primates’ within-group competitive landscapes, which contribute to variation in social organization, may vary in complex ways across habitats and seasons. PMID:26061401

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.

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.

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.

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.

Reliability and Validity of Food Frequency Questionnaire and Nutrient Biomarkers in Elders With and Without Mild Cognitive Impairment

PubMed Central

Bowman, Gene L.; Shannon, Jackilen; Ho, Emily; Traber, Maret G.; Frei, Balz; Oken, Barry S.; Kaye, Jeffery A.; Quinn, Joseph F.

2010-01-01

Introduction There is great interest in nutritional strategies for the prevention of age-related cognitive decline, yet the best methods for nutritional assessment in populations at risk for dementia are still evolving. Our study objective was to test the reliability and validity of two common nutritional assessments (plasma nutrient biomarkers and Food Frequency Questionnaire) in people at risk for dementia. Methods Thirty-eight elders, half with amnestic -Mild Cognitive Impairment and half with intact cognition were recruited. Nutritional assessments were collected together at baseline and again at 1 month. Intraclass and Pearson correlation coefficients quantified reliability and validity. Results Twenty-six nutrients were examined and reliability was very good or better for 77% (20/26, ICC ≥ .75) of the plasma nutrient biomarkers and for 88% of the FFQ estimates. Twelve of the plasma nutrient estimates were as reliable as the commonly measured plasma cholesterol (ICC=.92). FFQ and plasma long-chain fatty acids (docosahexaenoic acid, r =.39, eicosapentaenoic acid, r = .39) and carotenoids (α-carotene, r =.49; lutein + zeaxanthin, r = .48; β-carotene, r = .43; β-cryptoxanthin, r = .41) were correlated, but no other FFQ estimates correlated with respective nutrient biomarkers. Correlations between FFQ and plasma fatty acids and carotenoids were significantly stronger after removing subjects with MCI. Conclusion The reliability and validity of plasma and FFQ nutrient estimates vary according to the nutrient of interest. Memory deficit attenuates FFQ estimate validity and inflates FFQ estimate reliability. Many plasma nutrient biomarkers have very good reliability over 1-month regardless of memory state. This method can circumvent sources of error seen in other less direct methods of nutritional assessment. PMID:20856100

Fueling export production: nutrient return pathways from the deep ocean and their dependence on the Meridional Overturning Circulation

NASA Astrophysics Data System (ADS)

Palter, J. B.; Sarmiento, J. L.; Gnanadesikan, A.; Simeon, J.; Slater, R. D.

2010-11-01

In the Southern Ocean, mixing and upwelling in the presence of heat and freshwater surface fluxes transform subpycnocline water to lighter densities as part of the upward branch of the Meridional Overturning Circulation (MOC). One hypothesized impact of this transformation is the restoration of nutrients to the global pycnocline, without which biological productivity at low latitudes would be significantly reduced. Here we use a novel set of modeling experiments to explore the causes and consequences of the Southern Ocean nutrient return pathway. Specifically, we quantify the contribution to global productivity of nutrients that rise from the ocean interior in the Southern Ocean, the northern high latitudes, and by mixing across the low latitude pycnocline. In addition, we evaluate how the strength of the Southern Ocean winds and the parameterizations of subgridscale processes change the dominant nutrient return pathways in the ocean. Our results suggest that nutrients upwelled from the deep ocean in the Antarctic Circumpolar Current and subducted in Subantartic Mode Water support between 33 and 75% of global export production between 30° S and 30° N. The high end of this range results from an ocean model in which the MOC is driven primarily by wind-induced Southern Ocean upwelling, a configuration favored due to its fidelity to tracer data, while the low end results from an MOC driven by high diapycnal diffusivity in the pycnocline. In all models, nutrients exported in the SAMW layer are utilized and converted rapidly (in less than 40 years) to remineralized nutrients, explaining previous modeling results that showed little influence of the drawdown of SAMW surface nutrients on atmospheric carbon concentrations.

Fueling primary productivity: nutrient return pathways from the deep ocean and their dependence on the Meridional Overturning Circulation

NASA Astrophysics Data System (ADS)

Palter, J. B.; Sarmiento, J. L.; Gnanadesikan, A.; Simeon, J.; Slater, D.

2010-06-01

In the Southern Ocean, mixing and upwelling in the presence of heat and freshwater surface fluxes transform subpycnocline water to lighter densities as part of the upward branch of the Meridional Overturning Circulation (MOC). One hypothesized impact of this transformation is the restoration of nutrients to the global pycnocline, without which biological productivity at low latitudes would be catastrophically reduced. Here we use a novel set of modeling experiments to explore the causes and consequences of the Southern Ocean nutrient return pathway. Specifically, we quantify the contribution to global productivity of nutrients that rise from the ocean interior in the Southern Ocean, the northern high latitudes, and by mixing across the low latitude pycnocline. In addition, we evaluate how the strength of the Southern Ocean winds and the parameterizations of subgridscale processes change the dominant nutrient return pathways in the ocean. Our results suggest that nutrients upwelled from the deep ocean in the Antarctic Circumpolar Current and subducted in Subantartic Mode Water support between 33 and 75% of global primary productivity between 30° S and 30° N. The high end of this range results from an ocean model in which the MOC is driven primarily by wind-induced Southern Ocean upwelling, a configuration favored due to its fidelity to tracer data, while the low end results from an MOC driven by high diapycnal diffusivity in the pycnocline. In all models, the high preformed nutrients subducted in the SAMW layer are converted rapidly (in less than 40 years) to remineralized nutrients, explaining previous modeling results that showed little influence of the drawdown of SAMW surface nutrients on atmospheric carbon concentrations.

Effects of Land Use on Lake Nutrients: The Importance of Scale, Hydrologic Connectivity, and Region

PubMed Central

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. PMID:26267813

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+...

Nutrient Dynamics in Riparian Ecosystems. Chapter 6 in Riparian Ecosystems, Volume 1: Science Synthesis and Management Implications

EPA Science Inventory

This report will be a chapter in an updated Riparian BMP manual developed by the State of WA Fish and Wildlife Dept. Jana Compton and I were asked to contribute the chapter on nutrients in riparian ecosystems based on experience and research in riparian systems. The document is...

Reduction of soluble nitrogen and mobilization of plant nutrients in soils from U.S. northern Great Plains agroecosystems by phenolic compounds

USDA-ARS?s Scientific Manuscript database

Phenolic plant secondary metabolites actively participate in a broad range of important reactions that affect livestock, plants and soil. In soil, phenolic compounds can affect nutrient dynamics and mobility of metals but their role in northern Great Plains agroecosystems is largely unknown. We eval...

NUTRIENT FLUX AT THE SEDIMENT-WATER INTERFACE IN ESCAMBIA BAY, FL, A NORTHERN GULF OF MEXICO ESTUARY INVITED SEMINAR

EPA Science Inventory

(Abstract). Presented at the University of Texas Marine Science Institute, 30 April 2001, Port Aransas, TX. 1 p. (ERL,GB R841).

Nutrient flux at the sediment-water interface is an integral component of estuarine dynamics, and the benthos may represent a significant source ...

Evaluating topsoil depth effects on phosphorus and potassium nutrient dynamics of grain and switchgrass production systems

USDA-ARS?s Scientific Manuscript database

Understanding the effects of fertilizer addition and crop removal on long-term change in soil test phosphorus (STP) and soil test potassium (STK) is crucial for maximizing the use of grower inputs on claypan soils. Due to variable nutrient supply from subsoils and variable crop removal across fields...

Tree harvest in an experimental sand ecosystem: plant effects on nutrient dynamics and solute generation.

Treesearch

C. K. Keller; R. O' Brien; J. R. Havig; J. L. Smith; B. T. Bormann; D. Wang

2006-01-01

The hydrochemical signatures of forested ecosystems are known to be determined by a time-variant combination of physical-hydrologic, geochemical, and biologic processes. We studied subsurface potassium (K), calcium (Ca), and nitrate (NO3) in an experimental red-pine mesocosm to determine how trees affect the behavior of these nutrients in soil...

Origins and scales of hypoxia on the Louisiana shelf: importance of seasonal plankton dynamics and river nutrients and discharge

EPA Science Inventory

Management plans for the Mississippi River Basin call for reductions in nutrient concentrations up to 40% or more to reduce hypoxia in the Gulf of Mexico (GOM), while at the same time the government is considering new farm subsidies to promote development of biofuels from corn. T...

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

Treesearch

Colleen M. Iversen; Joanne Childs; Richard J. Norby; Todd A. Ontl; Randall K. Kolka; Deanne J. Brice; Karis J. McFarlane; Paul J. Hanson

2017-01-01

Background and aims. Fine roots contribute to ecosystem carbon, water, and nutrient fluxes through resource acquisition, respiration, exudation, and turnover, but are understudied in peatlands. 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...

Effects of dietary tannins on total and extractable nutrients from manure

USDA-ARS?s Scientific Manuscript database

The effects of condensed tannins on N dynamics in ruminants have been a topic of research for some time, but much less work has focused on their impacts on other nutrients in manure A 4 × 4 Latin square sheep trial was used to determine if intake of sericea lespedeza (Lespedeza cuneata; SL; a conde...

Discharge, water temperature, and selected meteorological data for Vancouver Lake, Vancouver, Washington, water years 2011-13

USGS Publications Warehouse

Foreman, James R.; Marshall, Cameron A.; Sheibley, Rich W.

2014-01-01

The U.S. Geological Survey partnered with the Vancouver Lake Watershed Partnership in a 2-year intensive study to quantify the movement of water and nutrients through Vancouver Lake in Vancouver, Washington. This report is intended to assist the Vancouver Lake Watershed Partnership in evaluating potential courses of action to mitigate seasonally driven blooms of harmful cyanobacteria and to improve overall water quality of the lake. This report contains stream discharge, lake water temperature, and selected meteorological data for water years 2011, 2012, and 2013 that were used to develop the water and nutrient budgets for the lake.

An investigation of submarine groundwater-borne nutrient fluxes to the west Florida shelf and recurrent harmful algal blooms

USGS Publications Warehouse

Smith, Christopher G.; Swarzenski, Peter W.

2012-01-01

A cross-shelf, water-column mass balance of radon-222 (222Rn) provided estimates of submarine groundwater discharge (SGD), which were then used to quantify benthic nutrient fluxes. Surface water and groundwater were collected along a shore-normal transect that extended from Tampa Bay, Florida, across the Pinellas County peninsula, to the 10-m isobath in the Gulf of Mexico. Samples were analyzed for 222Rn and radium-223,224,226 (223,224,226Ra) activities as well as inorganic and organic nutrients. Cross-shore gradients of 222Rn and 223,224,226Ra activities indicate a nearshore source for these isotopes, which mixes with water characterized by low activities offshore. Radon-based SGD rates vary between 2.5 and 15 cm d-1 proximal to the shoreline and decrease offshore. The source of SGD is largely shallow exchange between surface and pore waters, although deeper groundwater cycling may also be important. Enrichment of total dissolved nitrogen and soluble reactive phosphorus in pore water combined with SGD rates results in specific nutrient fluxes comparable to or greater than estuarine fluxes from Tampa Bay. The significance of these fluxes to nearshore blooms of Karenia brevis is highlighted by comparison with prescribed nutrient demands for bloom maintenance and growth. Whereas our flux estimates do not indicate SGD and benthic fluxes as the dominant nutrient source to the harmful algal blooms, SGD-derived loads do narrow the deficit between documented nutrient supplies and bloom demands.

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.

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.

Coupling of the spatial-temporal distributions of nutrients and physical conditions in the southern Yellow Sea

NASA Astrophysics Data System (ADS)

Wei, Qin-Sheng; Yu, Zhi-Gang; Wang, Bao-Dong; Fu, Ming-Zhu; Xia, Chang-Shui; Liu, Lu; Ge, Ren-Feng; Wang, Hui-Wu; Zhan, Run

2016-04-01

This study investigated the coupling of the spatial-temporal variations in nutrient distributions and physical conditions in the southern Yellow Sea (SYS) using data compiled from annual-cycle surveys conducted in 2006-2007 as well as satellite-derived sea-surface temperature (SST) images. The influence of physical dynamics on the distribution and transport of nutrients varied spatially and seasonally in the SYS. The Changjiang Diluted Water (CDW) plume (in summertime), the Subei Coastal Water (SCW) (year-round), and the Lubei Coastal Current (LCC) (in wintertime) served as important sources of nutrients in the inshore area in a dynamic environment. The saline Taiwan Warm Current (TWC) might transport nutrients to the northeast region of the Changjiang Estuary in the summer, and this nutrient source began to increase from spring to summer and decrease when autumn arrived. Three types of nutrient fronts, i.e., estuarine, offshore, and coastal, were identified. A circular nutrient front caused by cross-shelf transport of SCW in the southeast shelf bank area in the winter and spring was observed. The southeastward flow of western coastal cold water in the SYS might be an important conduit for cross-shelf nutrient exchange between the SYS and the East China Sea (ECS). The tongue-shaped low-nutrient region in the western study area in the wintertime was driven by the interaction of the southward Yellow Sea Western Coastal Current (YSWCC) and the biological activity. The vertically variable SCM (subsurface Chl-a maximum) in the central SYS was controlled by coupled physical-chemical processes that involved stratification and associated nutricline. The average nutrient fluxes into the euphotic zone due to upwelling near the frontal zone of the Yellow Sea Cold Water Mass (YSCWM) in the summer are estimated here for the first time: 1.4 ± 0.9 × 103 μmol/m2/d, 0.1 ± 0.1 × 103 μmol/m2/d, and 2.0 ± 1.3 × 103 μmol/m2/d for DIN, PO4-P, and SiO3-Si, respectively. The depletion of nutrients in the central SYS and the upwelled transport in the boundary of the YSCWM resulted in a spatial transfer of the high Chl-a zone, varying generally from the central SYS to the boundary of the YSCWM from spring to summer, and the nutrient flux associated with this upwelling could contribute significantly to local primary production. This study deepens our understanding of the mechanisms influencing the distribution and transport of nutrients in the SYS.

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 present study therefore demonstrated that the soil investigated harbours hydrocarbon-degrading bacterial populations which can be biostimulated to achieve effective bioremediation of oil-contaminated soil.

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.

Nutrient transport within and between habitats through seed dispersal processes by woolly monkeys in north-western Amazonia.

PubMed

Stevenson, Pablo R; Guzmán-Caro, Diana C

2010-11-01

The contribution of vertebrate animals to nutrient cycling has proven to be important in various ecosystems. However, the role of large bodied primates in nutrient transport in neotropical forests is not well documented. Here, we assess the role of a population of woolly monkeys (Lagothrix lagothricha lugens) as vectors of nutrient movement through seed dispersal. We estimated total seed biomass transported by the population within and between two habitats (terra firme and flooded forests) at Tinigua Park, Colombia, and quantified potassium (K), phosphorus (P) and nitrogen (N) content in seeds of 20 plant species from both forests. Overall, the population transported an estimated minimum of 11.5 (±1.2 SD) g of potassium, 13.2 (±0.7) g of phosphorus and 34.3 (±0.1) g nitrogen, within 22.4 (±2.0) kg of seeds ha(-1) y(-1). Approximately 84% of all nutrients were deposited in the terra firme forest mostly through recycling processes, and also through translocation from the flooded forest. This type of translocation represents an important and high-quality route of transport since abiotic mechanisms do not usually move nutrients upwards, and since chemical tests show that seeds from flooded forests have comparatively higher nutrient contents. The overall contribution to nutrient movement by the population of woolly monkeys is significant because of the large amount of biomass transported, and the high phosphorus content of seeds. As a result, the phosphorus input generated by these monkeys is of the same order of magnitude as other abiotic mechanisms of nutrient transport such as atmospheric deposition and some weathering processes. Our results suggest that via seed dispersal processes, woolly monkey populations can contribute to nutrient movement in tropical forests, and may act as important nutrient input vectors in terra firme forests. © 2010 Wiley-Liss, Inc.

Carbon Cycle in South China Sea: Flux, Controls and Global Implications

NASA Astrophysics Data System (ADS)

Dai, M.; Cao, Z.; Yang, W.; Guo, X.; Yin, Z.; Gan, J.

2016-12-01

The contemporary coastal ocean is generally seen as a significant CO2 sink of 0.2-0.4 Pg C/yr at the global scale. However, mechanistic understanding of the coastal ocean carbon cycle remains limited, leading to the unanswered question of why some coastal systems are sources while others are sinks of atmospheric CO2. As the largest marginal sea of Northern Pacific, the South China Sea (SCS) is a mini-ocean with wide shelves in both its southern and northern parts. Its northern shelf, which receives significant land inputs from the Pearl River, a world major river, can be categorized as a River-Dominated Margin (RioMar) during peak discharges, and is characterized as a CO2 sink to the atmosphere. The SCS basin is identified as an Ocean-Dominated Margin (OceMar) and a CO2 source. OceMar is characterized by exchange with the open ocean via a two-dimensional (at least) process, i.e., the horizontal intrusion of open ocean water and subsequent vertical mixing and upwelling. Depending on the different ratios of dissolved inorganic carbon (DIC) and nutrients from the source waters into the continental margins, the relative consumption or removal bwtween DIC and nutrients, when being transported into the euphotic zones where biogeochemical processes take over, determines the CO2 fluxes. Thus, excess DIC relative to nutrients existing in the upper layer will lead to CO2 degassing. The CO2 fluxes in both RioMars and OceMars can be quantified using a semi-analytical diagnostic approach by coupling the physical dynamics and biogeochemical processes. We extended our mechanistic studies in the SCS to other OceMars including the Caribbean Sea, the Arabian Sea, and the upwelling system off the Oregon-California coast, and RioMars including the East China Sea and Amazon River plume to demonstrate the global implications of our SCS carbon studies.

Feedbacks Between Bioclogging and Infiltration in Losing River Systems

NASA Astrophysics Data System (ADS)

Newcomer, M. E.; Hubbard, S. S.; Fleckenstein, J. H.; Schmidt, C.; Maier, U.; Thullner, M.; Ulrich, C.; Rubin, Y.

2014-12-01

Reduction in riverbed permeability due to biomass growth is a well-recognized yet poorly understood process associated with losing connected and disconnected rivers. Although several studies have focused on riverbed bioclogging processes at the pore-scale, few studies have quantified bioclogging feedback cycles at the scale relevant for water resources management, or at the meander-scale. At this scale, often competing hydrological-biological processes influence biomass dynamics and infiltration. Disconnection begins when declines in the water table form an unsaturated zone beneath the river maximizing seepage. Simultaneously, bioclogging reduces the point-scale infiltration flux and can either limit the nutrient flux and reduce bioclogging, or preferentially focus infiltration elsewhere and enhance bioclogging. These feedbacks are highly dependent on geomorphology and seasonal patterns of discharge and water temperature. To assess the mutual influences of disconnection, biomass growth, and temperature changes on infiltration in a geomorphologically complex river system, we built a 3D numerical model, conditioned on field data, using the reactive-transport simulator MIN3P. Results show that in disconnected regions of the river, biomass growth reduced vertical seepage downward and extended the unsaturated zone length; however these changes were contingent upon disconnection. Mid-way through the seasonal cycle, biomass declined in these same regions due to limited nutrient flux. Seepage and biomass continued to oscillate with a lag correlation of 1 month. Connected regions, however, showed the largest infiltration rates, nutrient fluxes, and concentrations of biomass. Despite the reduction in conductivity from biomass, flow remains high in connected regions because the feedback between bioclogging and infiltration is not as pronounced due to the sharpening hydraulic gradient. Bioclogging ultimately shapes the pattern of flow, however geomorphology dominates the strength of connection. Recognition of the feedbacks between geomorphological patterns and heterogeneous biomass on meander scale hydrological processes can lead to better estimates of local water volumes and capacities, especially when these systems are used as municipal and public water supply sources.

Modelling the effects and economics of managed realignment on the cycling and storage of nutrients, carbon and sediments in the Blackwater estuary UK

NASA Astrophysics Data System (ADS)

Shepherd, D.; Burgess, D.; Jickells, T.; Andrews, J.; Cave, R.; Turner, R. K.; Aldridge, J.; Parker, E. R.; Young, E.

2007-07-01

A hydrodynamic model is developed for the Blackwater estuary (UK) and used to estimate nitrate removal by denitrification. Using the model, sediment analysis and estimates of sedimentation rates, we estimate changes in estuarine denitrification and intertidal carbon and nutrient storage and associated value of habitat created under a scenario of extensive managed realignment. We then use this information, together with engineering and land costs, to conduct a cost benefit analysis of the managed realignment. This demonstrates that over a 50-100 year timescale the value of the habitat created and carbon buried is sufficient to make the large scale managed realignment cost effective. The analysis reveals that carbon and nutrient storage plus habitat creation represent major and quantifiable benefits of realignment. The methodology described here can be readily transferred to other coastal systems.

Nitrogen and phosphorus effluent loads from a paddy-field district adopting collective crop rotation.

PubMed

Hama, T; Aoki, T; Osuga, K; Sugiyama, S; Iwasaki, D

2012-01-01

Japanese paddy rice systems commonly adopt the rotation of vegetables, wheat and soybeans with paddy rice. Crop rotation may, however, increase the nutrient load in effluent discharged from the district because more fertilizer is applied to the rotation crops than is applied to paddy crops. We investigated a paddy-field district subject to collective crop rotation and quantified the annual nutrient load of effluent from the district in three consecutive years. The total annual exports of nitrogen and phosphorus over the investigation period ranged from 30.3 to 40.6 kg N ha(-1) and 2.62 to 3.13 kg P ha(-1). The results suggest that rotation cropping increases the effluent nutrient load because applied fertilizer is converted to nitrate, and surface runoff is increased due to the absence of shuttering boards at the field outlets.

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).

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

Nutrient Removal from Wastewater Using Microalgae: A Kinetic Evaluation and Lipid Analysis.

PubMed

Babu, Anjana; Katam, Keerthi; Gundupalli, Marttin Paulraj; Bhattacharyya, Debraj

2018-06-01

  The objective of this study was to examine the performance of mixed microalgal bioreactors in treating three different types of wastewaters-kitchen wastewater (KWW), palm oil mill effluent (POME), and pharmaceutical wastewater (PWW) in semi-continuous mode and to analyze the lipid content in the harvested algal biomass. The reactors were monitored for total nitrogen and phosphate removal at eight solid retention times (SRTs): 2, 4, 6, 8, 10, 12, 14, and 16 days. The nutrient uptake kinetic parameters were quantified using linearized Michaelis-Menten and Monod models at steady-state conditions. The nutrient removal efficiency and lipid production were found to be higher in KWW when compared with the other wastewaters. Saturated fatty acids (C16:0, C18:0, and C18:1) accounted for more than 60% of the algal fatty acids for all the wastewaters. The lipid is, therefore, considered suitable for synthesizing biodiesel.

Application of real-time PCR for total airborne bacterial assessment: Comparison with epifluorescence microscopy and culture-dependent methods

NASA Astrophysics Data System (ADS)

Rinsoz, Thomas; Duquenne, Philippe; Greff-Mirguet, Guylaine; Oppliger, Anne

Traditional culture-dependent methods to quantify and identify airborne microorganisms are limited by factors such as short-duration sampling times and inability to count non-culturable or non-viable bacteria. Consequently, the quantitative assessment of bioaerosols is often underestimated. Use of the real-time quantitative polymerase chain reaction (Q-PCR) to quantify bacteria in environmental samples presents an alternative method, which should overcome this problem. The aim of this study was to evaluate the performance of a real-time Q-PCR assay as a simple and reliable way to quantify the airborne bacterial load within poultry houses and sewage treatment plants, in comparison with epifluorescence microscopy and culture-dependent methods. The estimates of bacterial load that we obtained from real-time PCR and epifluorescence methods, are comparable, however, our analysis of sewage treatment plants indicate these methods give values 270-290 fold greater than those obtained by the "impaction on nutrient agar" method. The culture-dependent method of air impaction on nutrient agar was also inadequate in poultry houses, as was the impinger-culture method, which gave a bacterial load estimate 32-fold lower than obtained by Q-PCR. Real-time quantitative PCR thus proves to be a reliable, discerning, and simple method that could be used to estimate airborne bacterial load in a broad variety of other environments expected to carry high numbers of airborne bacteria.

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.

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.

Modelling of point and diffuse pollution: application of the Moneris model in the Ipojuca river basin, Pernambuco State, Brazil.

PubMed

de Lima Barros, Alessandra Maciel; do Carmo Sobral, Maria; Gunkel, Günter

2013-01-01

Emissions of pollutants and nutrients are causing several problems in aquatic ecosystems, and in general an excess of nutrients, specifically nitrogen and phosphorus, is responsible for the eutrophication process in water bodies. In most developed countries, more attention is given to diffuse pollution because problems with point pollution have already been solved. In many non-developed countries basic data for point and diffuse pollution are not available. The focus of the presented studies is to quantify nutrient emissions from point and diffuse sources in the Ipojuca river basin, Pernambuco State, Brazil, using the Moneris model (Modelling Nutrient Emissions in River Systems). This model has been developed in Germany and has already been implemented in more than 600 river basins. The model is mainly based on river flow, water quality and geographical information system data. According to the Moneris model results, untreated domestic sewage is the major source of nutrients in the Ipojuca river basin. The Moneris model has shown itself to be a useful tool that allows the identification and quantification of point and diffuse nutrient sources, thus enabling the adoption of measures to reduce them. The Moneris model, conducted for the first time in a tropical river basin with intermittent flow, can be used as a reference for implementation in other watersheds.

What is the role of fresh groundwater and recirculated seawater in conveying nutrients to the coastal ocean?

USGS Publications Warehouse

Weinstein, Y.; Yechieli, Y.; Shalem, Y.; Burnett, W.C.; Swarzenski, P.W.; Herut, B.

2011-01-01

Submarine groundwater discharge (SGD) is a major process operating at the land-sea interface. Quantifying the SGD nutrient loads and the marine/terrestrial controls of this transport is of high importance, especially in oligotrophic seas such as the eastern Mediterranean. The fluxes of nutrients in groundwater discharging from the seafloor at Dor Bay (southeastern Mediterranean) were studied in detail using seepage meters. Our main finding is that the terrestrial, fresh groundwater is the main conveyor of DIN and silica to the coastal water, with loads of 500 and 560 mol/yr, respectively, per 1 m shoreline. Conversely, recirculated seawater is nutrient-poor, and its role is mainly as a dilution agent. The nutrient loads regenerated in the subterranean estuary (sub-bay sediment) are relatively small, consisting mostly of ammonium (24 mol/yr). On the other hand, the subterranean estuary at Dor Bay sequesters as much as 100 mol N/yr per 1 m shoreline, mainly via denitrification processes. These, and observations from other SGD sites, imply that the subterranean estuary at some coastal systems may function more as a sink for nitrogen than a source. This further questions the extent of nutrient contributions to the coastal water by some subterranean estuaries and warrants systematic evaluation of this process in various hydrological and marine trophic conditions. ?? 2011 American Chemical Society.

Data-model integration to interpret connectivity between biogeochemical cycling, and vegetation phenology and productivity in mountainous ecosystems under changing hydrologic regimes

NASA Astrophysics Data System (ADS)

Brodie, E.; Arora, B.; Beller, H. R.; Bill, M.; Bouskill, N.; Chakraborty, R.; Conrad, M. E.; Dafflon, B.; Enquist, B. J.; Falco, N.; Henderson, A.; Karaoz, U.; Polussa, A.; Sorensen, P.; Steltzer, H.; Wainwright, H. M.; Wang, S.; Williams, K. H.; Wilmer, C.; Wu, Y.

2017-12-01

In mountainous systems, snow-melt is associated with a large pulse of nutrients that originates from under-snow microbial mineralization of organic matter and microbial biomass turnover. Vegetation phenology in these systems is regulated by environmental cues such as air temperature ranges and photoperiod, such that, under typical conditions, vegetation greening and nutrient uptake occur in sync with microbial biomass turnover and nutrient release, closing nutrient cycles and enhancing nutrient retention. However, early snow-melt has been observed with increasing frequency in the mountainous west and is hypothesized to disrupt coupled plant-microbial behavior, potentially resulting in a temporal discontinuity between microbial nutrient release and vegetation greening. As part of the Watershed Function Scientific Focus Area (SFA) at Berkeley Lab we are quantifying below-ground biogeochemistry and above-ground phenology and vegetation chemistry and their relationships to hydrologic events at a lower montane hillslope in the East River catchment, Crested Butte, CO. This presentation will focus on data-model integration to interpret connectivity between biogeochemical cycling of nitrogen and vegetation nitrogen demand. Initial model results suggest that early snow-melt will result in an earlier accumulation and leaching loss of nitrate from the upper soil depths but that vegetation productivity may not decline as traits such as greater rooting depth and resource allocation to stems are favored.

Prescribed fire and timber harvesting effects on soil carbon and nitrogen in a pine forest

USDA-ARS?s Scientific Manuscript database

Thinning and prescribed fire are common management tools used to eliminate thick fuel loads that could otherwise facilitate and encourage a more severe catastrophic wildfire. The objective of this study was to quantify the lasting effects of prescribed fire on forest floor and soil nutrients approxi...

Fertilizer recommendations for switchgrass: Quantifying economic effects on quality and yield

USDA-ARS?s Scientific Manuscript database

Switchgrass (Panicum virgatum L.) is a native, perennial warm season grass that is suited for biomass production for conversion to renewable fuels as well as feed production on marginal soils. Yield responses to macro nutrients of N, P and K, have shown N to be the major driver for capturing yield p...

Impact of nonnative feral pig removal on soil structure and nutrient availability in Hawaiian tropical montane wet forests

Treesearch

Michael S. Long; Creighton M. Litton; Christian P. Giardina; Jonathan Deenik; Rebecca J. Cole; Jed P. Sparks

2017-01-01

Conservation and restoration of ecosystems impacted by nonnative ungulates increasingly involves their removal and exclusion. While the influence of nonnative ungulate removal on plant communities is commonly monitored, impacts on underlying ecological processes are seldom quantified. Here we examined how nonnative feral pig (