Spatial and temporal changes in estuarine water quality during a post-flood hypoxic event     

Vanessa N.L. Wong  Scott G. Johnston  Richard T. Bush  Leigh A. Sullivan  Christina Clay  Edward D. Burton  Peter G. Slavich 《Estuarine, Coastal and Shelf Science》2010

A major fish kill occurred in the Richmond River estuary in January 2008 due to oxygen depletion following extensive overbank flooding. This paper examines spatial and temporal changes in the chemistry of main channel waters, thereby identifying the primary sources of deoxygenating water. Over 40 km of the mid- to lower estuary main channel was deoxygenated within seven days of the flood peak. Hypoxia was confined to downstream of the confluences with mid-estuary backswamp basins and occurred during the later phase of the flood recession. Water chemistry at key locations in the estuary indicated elevated concentrations of redox sensitive species associated with acid sulfate soils (ASS) during the hypoxic period. Peak concentrations of Fe²⁺ up to 18.2 μmol L⁻¹, dissolved Mn up to 4.3 μmol L⁻¹, chemical oxygen demand (COD) up to 2052 μmol L⁻¹, dissolved organic carbon (DOC) up to 960 μmol L⁻¹ and elemental S⁰ up to 4.7 μmol L⁻¹ were found in the backswamp discharge confluences and mid-estuary main channel locations. The geochemical signature of main channel floodwaters identifies anaerobic decomposition of floodplain vegetation in ASS backswamps as a primary process leading to generation of hypoxic waters. The transport of these hypoxic floodwaters to the estuary has been accelerated and prolonged by extensive floodplain drainage, thereby enhancing the magnitude and duration of estuarine deoxygenation.  相似文献   

“Convoluted Journeys”: Integrating Nonprofit Organizations and University Science     

Vanessa Crossgrove Fry  Jen Schneider  Sally Sargeant-Hu  Carl Anderson  Erik Olson 《社会与自然资源》2019,32(3):239-254

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Decoupling of nutrient and grazer impacts on a benthic estuarine diatom assemblage     

Anna R. Armitage  Vanessa L. Gonzalez  Peggy Fong   《Estuarine, Coastal and Shelf Science》2009,84(3):375-380

Strong interactions between top-down (consumptive) and bottom-up (resource supply) trophic factors occur in many aquatic communities, but these forces can act independently in some microphytobenthic communities. Within benthic estuarine diatom assemblages, the dynamics of these interactions and how they vary with abiotic environmental conditions are not well understood. We conducted a field experiment at two sites with varying habitat characteristics to investigate the interactive effects of grazers and nutrients on benthic estuarine diatoms. We crossed snail (Cerithidea californica) and nutrient (nitrogen and phosphorus) addition treatments in enclosures on a restored tidal sandflat and a reference tidal mudflat in Mugu Lagoon, southern California. We repeated the study in summer 2000 and spring 2001 to assess temporal variation in the interactions. Snails caused a large decrease in diatom relative abundance and biomass (estimated as surface area); nutrients increased diatom abundance but did not alter diatom biomass. Snails and nutrients both reduced average diatom length, although the nutrient effect was weaker and temporally variable, occurring in the reference mudflat in the spring. There were few interactions between snail and nutrient addition treatments, suggesting that links between top-down and bottom-up forces on the diatom community were weak. There were no consistent differences in diatom assemblage characteristics between the two study sites, despite marked differences in sediment grain size and other abiotic characteristics between the sites. The strong diatom response to herbivores and weaker responses to enrichment differed from the previous studies where cyanobacteria increased in response to nutrient enrichment, further dissolving the “black box” perception of microphytobenthic communities.  相似文献   

Reconstructing Phreatic Palaeogroundwater Levels in a Geoarchaeological Context: A Case Study in Flanders,Belgium     

Ann Zwertvaegher  Peter Finke  Jeroen De Reu  Alexander Vandenbohede  Luc Lebbe  Machteld Bats  Wim De Clercq  Philippe De Smedt  Vanessa Gelorini  Joris Sergant  Marc Antrop  Jean Bourgeois  Philippe De Maeyer  Marc Van Meirvenne  Jacques Verniers  Philippe Cromb 《Geoarchaeology》2013,28(2):170-189

The complex debate on prehistoric settlement decisions is no longer tackled from a purely archaeological perspective but from a more landscape‐oriented manner combined with archaeological evidence. Therefore, reconstruction of several components of the former landscape is needed. Here, we focus on the reconstruction of the groundwater table based on modeling. The depth of the phreatic aquifer influences, for example, soil formation processes and vegetation type. Furthermore, it directly influences settlement by the wetness of a site. Palaeogroundwater modeling of the phreatic aquifer was carried out to produce a series of full‐coverage maps of the mean water table depth between 12.7 ka and the middle of the 20th century (1953) in Flanders, Belgium. The research focuses on the reconstruction of the input data and boundary conditions of the model and the model calibration. The model was calibrated for the 1924–1953 time period using drainage class maps. Archaeological site data and podzol occurrence data act as proxies for local drainage conditions over periods in the past. They also served as a control on the simulated phreatic palaeogroundwater levels. Model quality testing on an independent validation data set showed that the model predicts phreatic water table levels at the time of soil mapping well (mean error of 1.8 cm; root mean square error of 65.6 cm). Simulated hydrological conditions were in agreement with the occurrence of archaeological sites of Mesolithic to Roman age at 96% of the validation locations, and also with the occurrence of well‐drained podzols at 97% of the validation locations.  相似文献   

Review of tufa deposition and palaeohydrological conditions in the White Peak,Derbyshire, UK: implications for Quaternary landscape evolution     

Vanessa J. Banks  Peter F. Jones  David J. Lowe  Jonathan R. Lee  Jeremy Rushton  Michael A. Ellis 《Proceedings of the Geologists' Association. Geologists' Association》2012,123(1):117-129

This review considers the geological and geomorphological context of tufa barrages that occupy buried valley settings in the Wye catchment, Derbyshire. It describes the potential relationship of the tufa with locations of hypothesised river captures and inception horizon-guided groundwater flow paths. Tufa barrage development is associated with steps in the bedrock, which may be related to knick-point recession during river capture. Broad estimates of valley incision have been calculated from previously dated deposits. These support current interpretations of particularly significant effective base-level lowering during the Anglian and Devensian stages of the Quaternary and have the potential to add to the knowledge of regional uplift histories.  相似文献   

Continental-scale comparisons of terrestrial carbon sinks estimated from satellite data and ecosystem modeling 1982–1998     

Christopher Potter  Steven Klooster  Ranga Myneni  Vanessa Genovese  Pang-Ning Tan  Vipin Kumar 《Global and Planetary Change》2003,39(3-4):201-213

A simulation model based on satellite observations of monthly vegetation cover was used to estimate monthly carbon fluxes in terrestrial ecosystems from 1982 to 1998. The NASA–CASA model was driven by vegetation properties derived from the Advanced Very High Resolution Radiometer (AVHRR) and radiative transfer algorithms that were developed for Moderate Resolution Imaging Spectroradiometer (MODIS). For the terrestrial biosphere, predicted net ecosystem production (NEP) flux for atmospheric CO₂ has varied widely between an annual source of −0.9 Pg C per year and a sink of +2.1 Pg C per year. The southern hemisphere tropical zones (SHT, between 0° and 30°S) have a major influence over the predicted global trends in interannual variability of NEP. In contrast, the terrestrial NEP sink for atmospheric CO₂ on the North American (NA) continent has been fairly consistent between +0.2 and +0.3 Pg C per year, except during relatively cool annual periods when continental NEP fluxes are predicted to total to nearly zero. The predicted NEP sink for atmospheric CO₂ over Eurasia (EA) increased notably in the late 1980s and has been fairly consistent between +0.3 and +0.55 Pg C per year since 1988. High correlations can be detected between the El Niño Southern Oscillation (ENSO) and predicted NEP fluxes on the EA continent and for the SHT latitude zones, whereas NEP fluxes for the North American continent as a whole do not correlate strongly with ENSO events over the same time series since 1982. These observations support the hypothesis that regional climate warming has had notable but relatively small-scale impacts on high latitude ecosystem (tundra and boreal) sinks for atmospheric CO₂.  相似文献   

Competing Place Meanings in Complex Landscapes: A Social–Ecological Approach to Unpacking Community Conservation Outcomes on the Wild Coast,South Africa     

Vanessa Masterson  Maria Tengö  Marja Spierenburg 《社会与自然资源》2017,30(12):1442-1457

Despite a general awareness of the social–ecological complexities within which conservation interventions are embedded, approaches to understanding a diversity of local perspectives of heterogeneous landscapes and how they matter for the outcomes of these interventions are seldom demonstrated. We apply a social–ecological approach to exploring the multiple place meanings related to key landscape elements around a proposed community conservation intervention on the Wild Coast, South Africa, by identifying and analyzing three narratives about this impending change. These narratives mobilize competing meanings of the landscape to argue for or against the conservation project. By linking place meanings to locally defined landscape units (ecotopes), we engage multiple interpretations of the heterogeneous and changing landscape to gain a holistic and more inclusive picture of social–ecological landscape processes such as increasing woodlands and field abandonment. The obstruction of this particular intervention indicates the importance of engaging with multiple cultural values of nature.  相似文献   

A Chart for Judging Optimal Sample Spacing for Ore Grade Estimation     

Vanessa Cerqueira Koppe  Ricardo Hundelshaussen Rubio  João Felipe Coimbra Leite Costa 《Natural Resources Research》2017,26(2):191-199

Mineral deposit grades are usually estimated using data from samples of rock cores extracted from drill holes. Commonly, mineral deposit grade estimates are required for each block to be mined. Every estimated grade has always a corresponding error when compared against real grades of blocks. The error depends on various factors, among which the most important is the number of correlated samples used for estimation. Samples may be collected on a regular sampling grid and, as the spacing between samples decreases, the error of grade estimated from the data generally decreases. Sampling can be expensive. The maximum distance between samples that provides an acceptable error of grade estimate is useful for deciding how many samples are adequate. The error also depends on the geometry of a block, as lower errors would be expected when estimating the grade of large-volume blocks, and on the variability of the data within the region of the blocks. Local variability is measured in this study using the coefficient of variation (CV). We show charts analyzing error in block grade estimates as a function of sampling grid (obtained by geostatistical simulation), for various block dimensions (volumes) and for a given CV interval. These charts show results for two different attributes (Au and Ni) of two different deposits. The results show that similar errors were found for the two deposits, although they share similar features: sampling grid, block volume, CV, and continuity model. Consequently, the error for other attributes with similar features could be obtained from a single chart.  相似文献   

Erratum to: An investigation of future fuel load and fire weather in Australia     

Hamish Clarke  Andrew J. Pitman  Jatin Kala  Claire Carouge  Vanessa Haverd  Jason P. Evans 《Climatic change》2016,139(3-4):607-607

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Analyzing Uncertainty in Multibeam Bathymetric Data and the Impact on Derived Seafloor Attributes   总被引：2，自引：0，他引：2  

Vanessa Lucieer  Zhi Huang  Justy Siwabessy 《Marine Geodesy》2016,39(1):32-52

Multibeam bathymetric data provide critical information for the modeling of seabed geology and benthic biodiversity. The accuracy of these models depends on the accuracy of the bathymetric data, which contain uncertainties that are stochastic at individual soundings but exhibit a distinct spatial distribution with increasing magnitude from nadir to the outer beams. A restricted spatial randomness method that simulates both the stochastic and spatial characteristics of the data uncertainty performed better than a complete spatial randomness method in analyzing the impact of bathymetric data uncertainty on derived seafloor attributes.  相似文献