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Biogeochemical Cycles (biogeochemical + cycle)
Kinds of Biogeochemical Cycles Selected AbstractsInteractions of the Major Biogeochemical Cycles: Global Change and Human ImpactsAUSTRAL ECOLOGY, Issue 3 2005JOSHUA MACKIE No abstract is available for this article. [source] Retention of chloride in soil and cycling of organic matter-bound chlorineHYDROLOGICAL PROCESSES, Issue 11 2005G. Öberg Abstract Chloride (Clinorg) is generally considered to be a hydrologically and chemically inert substance. Past research suggests that Clinorg participates in a complex biogeochemical cycle involving the formation of organically bound chlorine (Clorg). The present study examines whether Clorg cycling is sufficiently extensive as to influence the geochemical cycling of Clinorg. Undisturbed soil cores were collected in a coniferous forest soil in SE Sweden. The cores were stored in climate chambers for three months, irrigated with artificial rain, and the leachate was collected and analysed. The water balance of the lysimeters could be well described, and we found that 20,50% of the chlorine leached from the lysimeters was organically bound and that the amounts lost did not decrease with time. This strongly suggests that a substantial amount of Clorg forms in topsoil, and that subsequent leaching to deeper layers causes a considerable withdrawal of Clinorg. The concentration of both organic carbon and Clorg in the leachate was considerably higher than concentrations observed in the runoff in the actual catchment, suggesting that organic matter precipitates or is mineralized on its way through the soil. Copyright © 2005 John Wiley & Sons, Ltd. [source] When to say when: can excessive drinking explain silicon uptake in diatoms?BIOESSAYS, Issue 3 2009Kimberlee Thamatrakoln Abstract Diatoms are the single most important drivers of the oceanic silicon biogeochemical cycle. Due to their considerable promise in nanotechnology, there is tremendous interest in understanding the mechanism by which they produce their intricately and ornately decorated silica-based cell wall. Although specific proteins have been implicated in some of the key steps of silicification, the exact mechanisms are poorly understood. Silicon transporters, identified in both diatoms and silicoflagellates, are hypothesized to mediate silicon uptake. Recently, macropinocytosis, the non-specific engulfment of extracellular fluid, was proposed as a more energetically favorable uptake mechanism, which can also explain the long-observed effect of salinity on frustule morphology. We explore the bioenergetic, membrane recycling, and vacuolar volume requirements that must be satisfied for pinocytosis-mediated silicon uptake. These calculated requirements contrast starkly with existing data on diatom physiology, uptake kinetics, growth, and ultrastructure, leading us to conclude that pinocytosis cannot be the primary mechanism of silicon uptake. [source] Aqueous films limit bacterial cell motility and colony expansion on partially saturated rough surfacesENVIRONMENTAL MICROBIOLOGY, Issue 5 2010Gang Wang Summary Bacterial motility is a key mechanism for survival in a patchy environment and is important for ecosystem biodiversity maintenance. Quantitative description of bacterial motility in soils is hindered by inherent heterogeneity, pore-space complexity and dynamics of microhydrological conditions. Unsaturated conditions result in fragmented aquatic habitats often too small to support full bacterial immersion thereby forcing strong interactions with mineral and air interfaces that significantly restrict motility. A new hybrid model was developed to study hydration effects on bacterial motility. Simulation results using literature parameter values illustrate sensitivity of colony expansion rates to hydration conditions and are in general agreement with measured values. Under matric potentials greater than ,0.5 kPa (wet), bacterial colonies grew fast at colony expansion rates exceeding 421 ± 94 µm h,1; rates dropped significantly to 31 ± 10 µm h,1 at ,2 kPa; as expected, no significant colony expansion was observed at ,5 kPa because of the dominance of capillary pinning forces in the submicrometric water film. Quantification of hydration-related constraints on bacterial motion provides insights into optimal conditions for bacterial dispersion and spatial ranges of resource accessibility important for bioremediation and biogeochemical cycles. Results define surprisingly narrow range of hydration conditions where motility confers ecological advantage on natural surfaces. [source] Dynamics of marine bacterial and phytoplankton populations using multiplex liquid bead array technologyENVIRONMENTAL MICROBIOLOGY, Issue 4 2010Xavier Mayali Summary Heterotrophic bacteria and phytoplankton dominate the biomass and play major roles in the biogeochemical cycles of the surface ocean. Here, we designed and tested a fast, high-throughput and multiplexed hybridization-based assay to detect populations of marine heterotrophic bacteria and phytoplankton based on their small subunit ribosomal DNA sequences. The assay is based on established liquid bead array technology, an approach that is gaining acceptance in biomedical research but remains underutilized in ecology. End-labelled PCR products are hybridized to taxon-specific oligonucleotide probes attached to fluorescently coded beads followed by flow cytometric detection. We used ribosomal DNA environmental clone libraries (a total of 450 clones) and cultured isolates to design and test 26 bacterial and 10 eukaryotic probes specific to various ribotypes and genera of heterotrophic bacteria and eukaryotic phytoplankton. Pure environmental clones or cultures were used as controls and demonstrated specificity of the probes to their target taxa. The quantitative nature of the assay was demonstrated by a significant relationship between the number of target molecules and fluorescence signal. Clone library sequencing and bead array fluorescence from the same sample provided consistent results. We then applied the assay to a 37-day time series of coastal surface seawater samples from the Southern California Bight to examine the temporal dynamics of microbial communities on the scale of days to weeks. As expected, several bacterial phylotypes were positively correlated with total bacterial abundances and chlorophyll a concentrations, but others were negatively correlated. Bacterial taxa belonging to the same broad taxonomic groups did not necessarily correlate with one another, confirming recent results suggesting that inferring ecological role from broad taxonomic identity may not always be accurate. [source] Uptake and elimination of hydrophobic organic contaminants in estuarine copepods: An experimental studyENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2009Kévin Cailleaud Abstract Polycyclic aromatic hydrocarbons (PAHs) are considered to be rapidly biotransformed by organisms, whereas poly-chlorinated biphenyls (PCBs) are strongly bioaccumulated. In the present study, the estuarine copepod Eurytemora affinis was exposed in a continuous flow-through system to dissolved PAH (500 ng/L) and PCB (300 ng/L) mixtures for 86 h, whereas control groups were placed in a continuous flow-through system with clean water. Both PCB and PAH body residues were measured and compared in exposed and in nonexposed copepods to assess the uptake and the elimination of these two contaminant classes in this copepod species. After the exposure, exposed copepods exhibited concentration factors, based on a dry-weight basis, of 25, 750, and 1,200, respectively, for total PCBs and PAHs. The lower concentrations of PAHs in the nonexposed versus exposed copepods in contrast to small differences for PCBs suggest a higher rate of metabolism of PAHs compared with PCBs and could explain the differences observed in the accumulation. Furthermore, uptake as well as elimination of both PCBs and PAHs were compound selective in E. affinis. Therefore, higher-molecular-weight PCBs and PAHs were preferentially accumulated, while lower-molecular-weight compounds were preferentially eliminated. These results suggest the importance of copepods in the biogeochemical cycles of hydrophobic organic contaminants in estuarine ecosystems. [source] Prediction of uptake dynamics of persistent organic pollutants by bacteria and phytoplanktonENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2002Sabino Del Vento Abstract Phytoplankton and bacteria play an important role on the biogeochemical cycles of persistent organic pollutants (POPs). However, experimental data and quantitative knowledge of the kinetics of uptake and depuration of most POPs by bacteria and phytoplankton are scarce. In the present paper, a procedure to predict the sorption kinetics to bacteria and phytoplankton is developed. The prediction method is the combination of a mechanistic model for sorption and quantitative structure,activity relationships relating bioconcentration factors and membrane permeability to the chemical physical-chemical properties. The model consists of two compartments where the first compartment is the cellular surface and the second compartment is the cell biomass or matrix. Equations for estimating uptake and depuration rate constants into the matrix and adsorption and desorption rate constants onto the surface are obtained. These expressions depend on the physical-chemical properties of the chemical, the environmental temperature, the microorganism size, and species-specific quality of organic matter. While microorganism shape has a secondary influence on uptake dynamics, microorganism size and chemical hydrophobicity arise as the key factors controlling the kinetics of POP incorporation into bacteria and plankton. Uptake, depuration, adsorption, and desorption rate constants are reported for POPs such as polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated dioxins and furans (PCDD/Fs), and POPs of emerging concern, such as polybrominated diphenyl ethers (PBDEs). Finally, implications of uptake and depuration dynamics on the biogeochemical cycling of POPs are discussed. [source] Linking the global carbon cycle to individual metabolismFUNCTIONAL ECOLOGY, Issue 2 2005A. P. ALLEN Summary 1We present a model that yields ecosystem-level predictions of the flux, storage and turnover of carbon in three important pools (autotrophs, decomposers, labile soil C) based on the constraints of body size and temperature on individual metabolic rate. 2The model predicts a 10 000-fold increase in C turnover rates moving from tree- to phytoplankton-dominated ecosystems due to the size dependence of photosynthetic rates. 3The model predicts a 16-fold increase in rates controlled by respiration (e.g. decomposition, turnover of labile soil C and microbial biomass) over the temperature range 0,30 °C due to the temperature dependence of ATP synthesis in respiratory complexes. 4The model predicts only a fourfold increase in rates controlled by photosynthesis (e.g. net primary production, litter fall, fine root turnover) over the temperature range 0,30 °C due to the temperature dependence of Rubisco carboxylation in chloroplasts. 5The difference between the temperature dependence of respiration and photosynthesis yields quantitative predictions for distinct phenomena that include acclimation of plant respiration, geographic gradients in labile C storage, and differences between the short- and long-term temperature dependence of whole-ecosystem CO2 flux. 6These four sets of model predictions were tested using global compilations of data on C flux, storage and turnover in ecosystems. 7Results support the hypothesis that the combined effects of body size and temperature on individual metabolic rate impose important constraints on the global C cycle. The model thus provides a synthetic, mechanistic framework for linking global biogeochemical cycles to cellular-, individual- and community-level processes. [source] Mass-independent fractionation of sulfur isotopes in sulfides from the pre-3770 Ma Isua Supracrustal Belt, West GreenlandGEOBIOLOGY, Issue 4 2006D. PAPINEAU ABSTRACT Redox chemistry of the coupled atmosphere,hydrosphere system has coevolved with the biosphere, from global anoxia in the Archean to an oxygenated Proterozoic surface environment. However, to trace these changes to the very beginning of the rock record presents special challenges. All known Eoarchean (c. 3850,3600 Ma) volcanosedimentary successions (i.e. supracrustal rocks) are restricted to high-grade gneissic terranes that seldom preserve original sedimentary structures and lack primary organic biomarkers. Although complicated by metamorphic overprinting, sulfur isotopes from Archean supracrustal rocks have the potential to preserve signatures of both atmospheric chemistry and metabolic fractionation from the original sediments. We present a synthesis of multiple sulfur isotope measurements (32S, 33S and 34S) performed on sulfides from amphibolite facies banded iron-formations (BIFs) and ferruginous garnet-biotite (metapelitic) schists from the pre-3770 Ma Isua Supracrustal Belt (ISB) in West Greenland. Because these data come from some of the oldest rocks of interpretable marine sedimentary origin, they provide the opportunity to (i) explore for possible biosignatures of sulfur metabolisms in early life; (ii) assess changes in atmospheric redox chemistry from ,3.8 Ga; and (iii) lay the groundwork to elucidate sulfur biogeochemical cycles on the early Earth. We find that sulfur isotope results from Isua do not unambiguously indicate microbially induced sulfur isotopic fractionation at that time. A significantly expanded data set of ,33S analyses for Isua dictates that the atmosphere was devoid of free oxygen at time of deposition and also shows that the effects of post-depositional metamorphic remobilization and/or dilution can be traced in mass-independently fractionated sulfur isotopes. [source] The evolution of, and revolution in, land surface schemes designed for climate modelsINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 5 2003A. J. Pitman Abstract The land surface is a key component of climate models. It controls the partitioning of available energy at the surface between sensible and latent heat, and it controls the partitioning of available water between evaporation and runoff. The land surface is also the location of the terrestrial carbon sink. Evidence is increasing that the influence of the land surface is significant on climate and that changes in the land surface can influence regional- to global-scale climate on time scales from days to millennia. Further, there is now a suggestion that the terrestrial carbon sink may decrease as global temperatures increase as a consequence of rising CO2 levels. This paper provides the theoretical background that explains why the land surface should play a central role in climate. It also provides evidence, sourced from climate model experiments, that the land surface is of central importance. This paper then reviews the development of land surface models designed for climate models from the early, very simple models through to recent efforts, which include a coupling of biophysical processes to represent carbon exchange. It is pointed out that significant problems remain to be addressed, including the difficulties in parameterizing hydrological processes, root processes, sub-grid-scale heterogeneity and biogeochemical cycles. It is argued that continued development of land surface models requires more multidisciplinary efforts by scientists with a wide range of skills. However, it is also argued that the framework is now in place within the international community to build and maintain the latest generation of land surface models. Further, there should be considerable optimism that consolidating the recent rapid advances in land surface modelling will enhance our capability to simulate the impacts of land-cover change and the impacts of increasing CO2 on the global and regional environment. Copyright © 2003 Royal Meteorological Society [source] Two-way interactions between ocean biota and climate mediated by biogeochemical cyclesISRAEL JOURNAL OF CHEMISTRY, Issue 1 2002Hezi Gildor Some of the two-way interactions between ocean biota and climate are mediated by biogeochemical cycles that link the different components of the climate system. As suggested by proxy records extracted from ice and ocean cores, by recent measurements, and by numerical models, such two-way interactions were likely major players in past climate variability on glacial,interglacial timescales, and may act to amplify or moderate an anthropogenically induced climate change in the near future. At present, our lack of understanding of these interactions hampers our ability to anticipate the consequences of possible anthropogenic climate change. In this article, we highlight some of the possible feedbacks between ocean biota and climate, reviewing some key biogeochemical processes and discussing mechanisms of two-way interactions. We also outline the need and strategies for continuing research aimed at advancing our understanding of these feedbacks and discuss their significance. [source] Large-scale ecology and hydrology: an introductory perspective from the editors of the Journal of Applied EcologyJOURNAL OF APPLIED ECOLOGY, Issue 2000S.J. Ormerod 1. Five key features characterize large-scale factors in ecology: (a) they incorporate some of the most major of all ecological phenomena , the ranges of organisms, patterns of diversity, variations in ecosystem character and environmental processes such as climate, biogeochemical cycles, dispersal and migration; (b) they involve interactions across scales through both top-down and bottom-up processes; (c) they are multifaceted, and hence require an interdisciplinary perspective; (d) they reflect the cumulative effects of anthropogenic change across all scales, and so have direct relevance to environmental management; (e) they invariably exceed the range of classical ecological experiments, and so require alternative approaches to hypothesis testing. 2. Against this background, a recent research initiative on large-scale ecology and hydrology was funded jointly by the Natural Environment Research Council (NERC) and the Scottish Executive Rural Affairs Department (SERAD). Outputs from this programme are reported in this special issue of the Journal of Applied Ecology, and they illustrate some of the ecological research that is currently in progress in the UK at large spatio-temporal scales. 3. The spatial scales investigated in the papers range from hectares to whole continents, and much of the work reported here involves modelling. Although the model outputs are intrinsically valuable, several authors express the need for improved validation and testing. We suggest that this is an area requiring much development, and will need considerable innovation due to the difficulties at the scales involved (see 1d). Possible methods include: model applications to new circumstances; large-scale environmental manipulations; large-scale surveys that mimic experimental protocols; support from process studies at smaller scales. These alternatives are not mutually exclusive, and all can allow robust hypothesis testing. 4. Much of the work reported here is interdisciplinary linking, for example, geographical, mathematical, hydrological, hydrochemical and ecological concepts (see 1c). We suggest that even stronger links between environmental disciplines will further aid large-scale ecological research. 5. Most important in the context of the Journal of Applied Ecology, the work reported in this issue reveals that large-scale ecology already has applied value. Sectors benefiting include the conservation of biodiversity, the control of invasive species, and the management of land and water resources. 6. Large-scale issues continue to affect many applied ecologists, with roughly 30,40% of papers published in the Journal of Applied Ecology typically confronting such problems. This special issue adds to the growing body of seminal contributions that will add impetus to further large-scale work. Moreover, occurring in a period when other areas of biology are increasingly reductionist, this collection illustrates that, at least with respect to large-scale environmental problems, ecology still holds centre ground. [source] Earliest rooting system and root : shoot ratio from a new Zosterophyllum plantNEW PHYTOLOGIST, Issue 1 2010Shougang Hao Summary ,,The enhanced chemical weathering by rooted vascular plants during the Silurian,Devonian period played a crucial role in altering global biogeochemical cycles and atmospheric environments; however, the documentation of early root morphology and physiology is scarce because the existing fossils are mostly incomplete. ,,Here, we report an entire, uprooted specimen of a new Zosterophyllum Penhallow, named as Z. shengfengense, from the Early Devonian Xitun Formation (Lochkovian, c. 413 Myr old) of Yunnan, south China. This plant has the most ancient known record of a rooting system. ,,The plant consists of aerial axes of 98 mm in height, showing a tufted habit, and a rhizome bearing a fibrous-like rooting system, c. 20 mm in length. The rhizome shows masses of branchings, which produce upwardly directed aerial axes and downwardly directed root-like axes. ,,The completeness of Z. shengfengense made it possible to estimate the biomass allocation and root : shoot ratio. The root : shoot ratio of this early plant is estimated at a mean value of 0.028, and the root-like axes constitute only c. 3% of the total biomass. Zosterophyllum shengfengense was probably a semi-aquatic plant with efficient water use or a strong uptake capacity of the root-like axes. [source] Toward a stoichiometric framework for evolutionary biologyOIKOS, Issue 1 2005Adam D. Kay Ecological stoichiometry, the study of the balance of energy and materials in living systems, may serve as a useful synthetic framework for evolutionary biology. Here, we review recent work that illustrates the power of a stoichiometric approach to evolution across multiple scales, and then point to important open questions that may chart the way forward in this new field. At the molecular level, stoichiometry links hereditary changes in the molecular composition of organisms to key phenotypic functions. At the level of evolutionary ecology, a simultaneous focus on the energetic and material underpinnings of evolutionary tradeoffs and transactions highlights the relationship between the cost of resource acquisition and the functional consequences of biochemical composition. At the macroevolutionary level, a stoichiometric perspective can better operationalize models of adaptive radiation and escalation, and elucidate links between evolutionary innovation and the development of global biogeochemical cycles. Because ecological stoichiometry focuses on the interaction of energetic and multiple material currencies, it should provide new opportunities for coupling evolutionary dynamics across scales from genomes to the biosphere. [source] Long-term growth of soybean at elevated [CO2] does not cause acclimation of stomatal conductance under fully open-air conditionsPLANT CELL & ENVIRONMENT, Issue 9 2006ANDREW D. B. LEAKEY ABSTRACT Accurately predicting plant function and global biogeochemical cycles later in this century will be complicated if stomatal conductance (gs) acclimates to growth at elevated [CO2], in the sense of a long-term alteration of the response of gs to [CO2], humidity (h) and/or photosynthetic rate (A). If so, photosynthetic and stomatal models will require parameterization at each growth [CO2] of interest. Photosynthetic acclimation to long-term growth at elevated [CO2] occurs frequently. Acclimation of gs has rarely been examined, even though stomatal density commonly changes with growth [CO2]. Soybean was grown under field conditions at ambient [CO2] (378 µmol mol,1) and elevated [CO2] (552 µmol mol,1) using free-air [CO2] enrichment (FACE). This study tested for stomatal acclimation by parameterizing and validating the widely used Ball et al. model (1987, Progress in Photosynthesis Research, vol IV, 221,224) with measurements of leaf gas exchange. The dependence of gs on A, h and [CO2] at the leaf surface was unaltered by long-term growth at elevated [CO2]. This suggests that the commonly observed decrease in gs under elevated [CO2] is due entirely to the direct instantaneous effect of [CO2] on gs and that there is no longer-term acclimation of gs independent of photosynthetic acclimation. The model accurately predicted gs for soybean growing under ambient and elevated [CO2] in the field. Model parameters under ambient and elevated [CO2] were indistinguishable, demonstrating that stomatal function under ambient and elevated [CO2] could be modelled without the need for parameterization at each growth [CO2]. [source] | |||||||||||||||||||||||||