Impacts of macroalgal spores on the dynamics of adult macroalgae in a eutrophic estuary: high versus low hydrodynamic seasons and long-term simulations for global warming scenarios     

Martins I  Marcotegui A  Marques JC 《Marine pollution bulletin》2008,56(5):984-998

A model describing macroalgal early life stages and adult dynamics was used to quantify the effects of non-adult forms on the productivity of adult macroalgae in a eutrophic estuary. Predictions indicate that during years with mild winters and low rainfall, spring blooms will occur at the expense of the growth and reproduction of overwintering adults and without the contribution of the spore bank. In these circumstances, there is a positive correlation between the intensity of the blooms and the biomass of overwintering adults until a maximum threshold value. On the contrary, in years with high rainfall and low or inexistent biomass of overwintering adults, the onset of adult’s growth depends on the biomass of viable dormant spores, the growing season occurs later and adult productivity is very limited. Long-term predictions for climate change scenarios suggest that, in general, global warming will have adverse affects on Ulva intestinalis productivity, with the adults being more affected than the early life stages.  相似文献   

Mesocosm experiments identifying hotspots of groundwater upwelling in a water column by fibre optic distributed temperature sensing          下载免费PDF全文

Amaya Irene Marruedo Arricibita  Stefan Krause  Jesus Gomez‐Velez  David M. Hannah  Jörg Lewandowski 《水文研究》2018,32(2):185-199

Lacustrine groundwater discharge (LGD) can substantially impact ecosystem characteristics and functions. Fibre optic distributed temperature sensing (FO‐DTS) has been successfully used to locate groundwater discharge into lakes and rivers at the sediment–water interface, but locating groundwater discharge would be easier if it could be detected from the more accessible water surface. So far, it is not clear if how and under which conditions the LGD signal propagates through the water column to the water surface–atmosphere interface, and what perturbations and signal losses occur along this pathway. In the present study, LGD was simulated in a mesocosm experiment. Under winter conditions, water with temperatures of 14 to 16 °C was discharged at the bottom of a 10 × 2.8‐m mesocosm. Water within this mesocosm ranged from 4.0 to 7.4 °C. Four layers (20, 40, 60, and 80 cm above the sediment) of the 82 cm deep mesocosm were equipped with FO‐DTS for tracing thermal patterns in the mesocosm. Aims are (a) to test whether the positive buoyancy of relatively warm groundwater imported by LGD into shallow water bodies allows detection of LGD at the lake's water surface–atmosphere interface by FO‐DTS, (b) to analyse the propagation of the temperature signal from the sediment‐water interface through the water column, and (c) to learn more about detectability of the signal under different discharge rates and weather conditions. The experiments supported the benchmarking of scale dependencies and robustness of FO‐DTS applications for measuring upwelling into aquatic environments and revealed that weather conditions can have important impacts on the detection of upwelling at water surface–atmosphere interfaces at larger scales.  相似文献   

Dynamics and patterns of land levelling for agricultural reclamation of erosional badlands in Chambal Valley (Madhya Pradesh,India)          下载免费PDF全文

Irene Marzolff  Padmini Pani 《地球表面变化过程与地形》2018,43(2):524-542

Gully and badland erosion constitute important land‐degradation processes with severe on‐site and off‐site effects above all in sedimentary deposits and alluvial soils of the arid and semi‐arid regions. Agricultural use of the affected land is impeded both by the irreversible loss of topsoil and the morphological dissection of the terrain. In various badland regions around the world, a solution to the latter problem is attempted by infilling of gullies and levelling of badland topography in order restore a morphology suitable for agricultural cultivation. Gully and badland levelling for agricultural reclamation has been conducted for decades in the large ravine lands of India. This study aims at analysing the distribution and dynamics of land levelling within the Chambal badlands in Morena district, Madhya Pradesh, between 1971 and 2015. Using high to medium resolution satellite images from the Corona, Landsat, Aster and RapidEye missions and a multi‐temporal classification approach, we have mapped and quantified areas that were newly levelled within eight observation periods. We analysed the spatial relation of levelled land to several physical and socio‐economic factors that potentially influence the choice of reclamation site by employing geographic information system (GIS) analysis methods and results from focus‐group discussions in selected villages. Results show that nearly 38 km² or 23% of the badlands in the study area have been levelled within 45 years. The levelling rate generally increases during the observation period, but the annual variability is high. We have found spatial relationships to badland morphology, vicinity of existing cropland and proximity to villages and drainage lines. From a socio‐economic point of view, availability of financial and technical means, access rights to the badland and ownership issues play an important role. Considering studies on soil degradation caused by levelling of badlands in other regions, the sustainability of the newly reclaimed fields in the Chambal badlands is questionable. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Relative quantification of wind erosion in argan woodlands in the Souss Basin,Morocco     

Miriam Marzen  Mario Kirchhoff  Irene Marzolff  Ali Aït Hssaine  Johannes B. Ries 《地球表面变化过程与地形》2020,45(15):3808-3823

The endemic argan woodlands cover large parts of South Morocco and create a characteristic landscape with areas of sparsely vegetated and bare soil surfaces between single trees. This unique ecosystem has been under extensive agrosilvopastoral management for centuries and is now at risk of degradation caused by overgrazing and increasing scarcity and variability of rainfall. To investigate susceptibility to wind erosion, we conducted an experimental–empirical study including wind tunnel tests and a drone-generated digital elevation model and quantified wind-erodible material on five different associated surface types by means of sediment catchers. The highest emission flux was measured on freshly ploughed surfaces (1875 g m^–2 h^–1), while older ploughed areas with a re-established crust produced a much lower emission flux (795 g m^–2 h^–1). Extensive tillage may have been a sustainable practice for generations, but increasing drought and uncertainty of rainfall now lead to an acute risk of severe soil erosion and dust production. The typical crusted surfaces characterized by residual rock fragment accumulation and wash processes produced the second highest emission flux (1,354 g m^–2 h^–1). Material collected from tree-shaded areas (933 g m^–2 h^–1) was revealed to be a considerable source of organic material, possibly affecting substrate conditions positively on a larger regional scale. The lowest flux was measured on rock fragment-covered surfaces (301 g m^–2 h^–1). The data show that open argan woodland may be a considerable source for wind erosion and dust production, depending on surface characteristics strongly related to management. An adapted management must include the conservation of argan trees to offer a promising approach to prevent severe wind erosion and dust production and mitigate possible impacts of land-use change and climate change related shifts in wind and rainfall patterns. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd  相似文献   

Geomasking sensitive health data and privacy protection: an evaluation using an E911 database   总被引：2，自引：0，他引：2  

Allshouse WB  Fitch MK  Hampton KH  Gesink DC  Doherty IA  Leone PA  Serre ML  Miller WC 《国际地球制图》2010,25(6):443-452

Geomasking is used to provide privacy protection for individual address information while maintaining spatial resolution for mapping purposes. Donut geomasking and other random perturbation geomasking algorithms rely on the assumption of a homogeneously distributed population to calculate displacement distances, leading to possible under-protection of individuals when this condition is not met. Using household data from 2007, we evaluated the performance of donut geomasking in Orange County, North Carolina. We calculated the estimated k-anonymity for every household based on the assumption of uniform household distribution. We then determined the actual k-anonymity by revealing household locations contained in the county E911 database. Census block groups in mixed-use areas with high population distribution heterogeneity were the most likely to have privacy protection below selected criteria. For heterogeneous populations, we suggest tripling the minimum displacement area in the donut to protect privacy with a less than 1% error rate.  相似文献   

Using multivariate statistical analysis of groundwater major cation and trace element concentrations to evaluate groundwater flow in a regional aquifer     

Klaus J. Stetzenbach  Irene M. Farnham  Vernon F. Hodge  Kevin H. Johannesson 《水文研究》1999,13(17):2655-2673

Groundwater samples were collected from 11 springs in Ash Meadows National Wildlife Refuge in southern Nevada and seven springs from Death Valley National Park in eastern California. Concentrations of the major cations (Ca, Mg, Na and K) and 45 trace elements were determined in these groundwater samples. The resultant data were subjected to evaluation via the multivariate statistical technique principal components analysis (PCA), to investigate the chemical relationships between the Ash Meadows and Death Valley spring waters, to evaluate whether the results of the PCA support those of previous hydrogeological and isotopic studies and to determine if PCA can be used to help delineate potential groundwater flow patterns based on the chemical compositions of groundwaters. The results of the PCA indicated that groundwaters from the regional Paleozoic carbonate aquifers (all of the Ash Meadows springs and four springs from the Furnace Creek region of Death Valley) exhibited strong statistical associations, whereas other Death Valley groundwaters were chemically different. The results of the PCA support earlier studies, where potentiometric head levels, δ¹⁸O and δD, geological relationships and rare earth element data were used to evaluate groundwater flow, which suggest groundwater flows from Ash Meadows to the Furnace Creek springs in Death Valley. The PCA suggests that Furnace Creek groundwaters are moderately concentrated Ash Meadows groundwater, reflecting longer aquifer residence times for the Furnace Creek groundwaters. Moreover, PCA indicates that groundwater may flow from springs in the region surrounding Scotty's Castle in Death Valley National Park, to a spring discharging on the valley floor. The study indicates that PCA may provide rapid and relatively cost‐effective methods to assess possible groundwater flow regimes in systems that have not been previously investigated. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Ecometrics and the paleoecological implications of Pleistocene faunas from the western coastal plains of the Cape Floristic Region,South Africa     

J. Tyler Faith  David R. Braun  Benjamin Davies  Larisa R. G. DeSantis  Matthew J. Douglass  Irene Esteban  Vincent Hare  Naomi E. Levin  Julie Luyt  Robyn Pickering  Mitchell J. Power  Judith Sealy  Deano Stynder 《第四纪科学杂志》2020,35(8):1007-1020

The Pleistocene ungulate communities from the western coastal plains of South Africa's Cape Floristic Region (CFR) are diverse and dominated by grazers, in contrast to the region's Holocene and historical faunas, which are relatively species-poor and dominated by small-bodied browsers and mixed feeders. An expansion of grassy habitats is clearly implied by the Pleistocene faunas, but the presence of ruminant grazers that cannot survive the summer dry season typical of the region today suggests other important paleoecological changes. Here we use dental ecometrics to explore the paleoecological implications of the region's Pleistocene faunas. We show that the dental traits (hypsodonty and occlusal topography) of the ungulates that occurred historically in the CFR track annual and summer aridity, and we use these relationships to reconstruct past aridity. Our results indicate that the Pleistocene faunas signal paleoenvironments that were on average less arid than today, including during the summer, consistent with other lines of evidence that suggest a higher water table and expansion of well-watered habitats. Greater water availability can be explained by lower temperature and reduced evapotranspiration during cooler phases of the Pleistocene, probably coupled with enhanced groundwater recharge due to increased winter precipitation.  相似文献   

Future emissions of marine halogenated very-short lived substances under climate change     

Franziska?Ziska  Birgit?QuackEmail author  Susann?Tegtmeier  Irene?Stemmler  Kirstin?Krüger 《Journal of Atmospheric Chemistry》2017,74(2):245-260

Halogenated Very Short-lived Substances (VSLS), such as bromoform, dibromomethane and methyl iodide, are naturally produced in the oceans and are involved in ozone depletion in the troposphere and the stratosphere. The effect of climate change on the oceanic emissions of these compounds is not well quantified. Based on present-day observed global oceanic and atmospheric concentrations, and historic and future data from three CMIP5 models, past and future sea-to-air fluxes of these VSLS are calculated. The simulations are used to infer possible effects of projected changes of physical forcing on emissions in different oceanic regimes. CMIP5 model output for 1979–2100 from the historical scenario and the RCP scenarios 2.6 and 8.5 are used as input data for the emission calculations. Of the parameters that have the main influence on the sea-to-air fluxes, the global sea surface temperatures show a steady increase during the twenty-first century, while the projected changes of sea surface wind speed is very small. The calculated emissions based on the historical CMIP5 model runs (1979–2005) increased over the 26 year period and agree well with the emissions based on ERA-Interim data. The future sea-to-air fluxes of VSLS generally increase during the twenty-first century under the assumption of constant concentration fields in the ocean and atmosphere. The multi-model mean global emissions of bromoform increase by 29.4% (9.0%) between 1986 and 2005 and 2081–2100 under RCP 8.5 (2.6) and dibromomethane and methyl iodide emissions increase by 23.3% (6.4%) and 5.5% (1.5%), respectively. Uncertainties of the future emission estimates, driven by ongoing environmental changes such as changing oceanic productivity (not considered in this study) are discussed.  相似文献   

DNA-based methods in paleolimnology: new opportunities for investigating long-term dynamics of lacustrine biodiversity   总被引：1，自引：0，他引：1  

Isabelle Domaizon  Amanda Winegardner  Eric Capo  Joanna Gauthier  Irene Gregory-Eaves 《Journal of Paleolimnology》2017,57(1):1-18

We reconstructed 150 years of ecological change in a shallow boreal lake located on the east shore of the Baltic Sea by integrating different types of environmental evidence: paleolimnological records (XRF-measured elements, fossil pigments and Cladocera assemblages), information from historical limnological surveys and archival maps. We assessed the role of biomanipulation by liming and fish-removal in the disappearance of submerged macrophytes, such as Lobelia dortmanna L., and their replacement by persistent cyanobacterial blooms. The combination of different strands of evidence revealed that the shift from macrophyte to cyanobacterial dominance was part of a long-term ecological response to eutrophication and increased sediment load from catchment disturbances. The findings demonstrate that a gradual loss of wetlands and increase of ditches in a catchment had a more significant effect on the lake ecosystem, compared to the direct, but short-term impact of biomanipulation. The study highlights the importance of catchment land-use and disturbance by ditches in changing the ecology of boreal water bodies. Also, it illustrates that a thorough understanding of the long-term ecosystem dynamics and differentiation among responses to multiple anthropogenic impacts are essential preconditions for addressing the deterioration of habitats and change in aquatic environments.  相似文献   

A two-temperature model for the flare of 5 September, 1973     

Irene R. Little-Marenin  J. K. Silk  A. S. Krieger 《Solar physics》1980,65(2):299-313

The energetics and mass transfer during the X-ray flare of 1831 GMT on 5 September, 1973 have been studied using the observations in the objective grating mode of the AS&E X-ray spectrographic telescope on Skylab. The flare was a moderately energetic one, Class M1 according to Solrad. In H, however, it was only a subflare of class - N. The data are approximately monochromatic images of the small X-ray source. They show a continued rise in the emission for several minutes followed by a decline. The size and temporal evolution are slightly different for ions associated with higher temperatures (Fe xxii, Si xiii) than with those of lower temperatures (Fe xvii, Mg xi). The time of maximum emission moves from one side of the flare to the other and peaks earlier for hotter temperature ions. The observations are analyzed using a two-temperature model in order to determine the changes in the distribution of emission measure and of the amount of material as a function of temperature. The development of the flare can be divided into three periods in each of which different mechanisms are operating. For the first 3–4 min, evaporation drives mass into the entire emitting region. Second, the evaporation ceases: Hot material loses energy, and we see a loss of hot material and a corresponding gain of cool material. Later, after 1838, we see a decline in the emission measure.  相似文献