Improved methodology for measuring pore patterns in the benthic foraminiferal genus Ammonia

Benthic foraminiferal pores are considered to play an important role in facilitating the gas exchange between the organism and the environment, with pore size and density supposed to be related to gas exchange intensity. Recent studies have therefore attempted to establish relationships between pore patterns and redox conditions, such as bottom water oxygen and nitrate concentrations. However, a prerequisite for such an attempt is the development of a practical and reliable methodology for measuring pore patterns. The aim of this study is to present a semi-automated pore measurement method for Ammonia, a dominant taxon of temperate coastal environments that are increasingly affected by seasonal hypoxia (bottom water oxygen concentration < 63 μM). The approach is based on image analyses of a measurement frame positioned on SEM images with 1000 × magnification. Statistical analyses show that the surface area of the pores in the frame has a normal distribution. Therefore, a mean pore surface area can be used to describe the pores in the measurement frame. We observed small but significant ontogenetic changes in pore density (number of pores per frame) and pore surface area. Accordingly, it seems preferable to limit pore measurements to size windows on chambers representing the same ontogenetic stage. In order to demonstrate the efficiency of the method, we applied it in two case studies. Firstly, a study of living Ammonia in Lake Grevelingen (Netherlands) revealed a clear difference in pore patterns between three studied stations characterised by different seasonal bottom water oxygenation patterns. Secondly, a sediment core from the same site clearly showed the presence of two morphotypes of Ammonia; one with numerous, small pores and the other with fewer but much larger pores, resulting in a higher porosity (larger part of the test covered by pores). Since the man-made closure of Lake Grevelingen in 1971, the latter morphotype has progressively replaced the former one. Finally, a summary of the measurements on 870 specimens with both pore patterns shows a strong relationship between pore density and pore surface area, suggesting a physical control of the interaction between these two parameters

Parasitism of Lepidopterous Stem Borers in Cultivated and Natural Habitats

Plant infestation, stem borer density, parasitism, and parasitoid abundance were assessed during two years in two host plants, Zea mays (L.) (Cyperales: Poaceae) and Sorghum bicolor (L.) (Cyperales: Poaceae), in cultivated habitats. The four major host plants (Cyperus spp., Panicum spp., Pennisetum spp., and Sorghum spp.) found in natural habitats were also assessed, and both the cultivated and natural habitat species occurred in four agroecological zones in Kenya. Across habitats, plant infestation (23.2%), stem borer density (2.2 per plant), and larval parasitism (15.0%) were highest in maize in cultivated habitats. Pupal parasitism was not higher than 4.7% in both habitats, and did not vary with locality during each season or with host plant between each season. Cotesia sesamiae (Cameron) and C. flavipes Cameron (Hymenoptera: Braconidae) were the key parasitoids in cultivated habitats (both species accounted for 76.4% of parasitized stem borers in cereal crops), but not in natural habitats (the two Cotesia species accounted for 14.5% of parasitized stem borers in wild host plants). No single parasitoid species exerted high parasitism rates on stem borer populations in wild host plants. Low stem borer densities across seasons in natural habitats indicate that cereal stem borer pests do not necessarily survive the non-cropping season feeding actively in wild host plants. Although natural habitats provided refuges for some parasitoid species, stem borer parasitism was generally low in wild host plants. Overall, because parasitoids contribute little in reducing cereal stem borer pest populations in cultivated habitats, there is need to further enhance their effectiveness in the field to regulate these pests

Flow-bearing structures of fractured rocks: Insights from hydraulic property scalings revealed by a pumping test

International audienceA long duration pumping test conducted over 151 days in a fractured sandstone and shale formation displays a nonstandard drawdown response and anomalous pressure diffusion, which cannot be properly interpreted using existing frameworks (e.g., homogeneous, double porosity, boundary conditions, and fractal models). An alternative framework with simple geometry and more complex hydraulic properties is thus proposed to interpret such kind of drawdown responses. The analytical development allows first to demonstrate all scaling relations in this interpretation framework. Then, and most importantly, the multi-scale hydraulic test provides consistent scalings of transmissivity, T, to storativity, S, over distances ranging from 83 to 383 m in a faulted area. Drawdown analysis in several monitoring wells shows persistent decrease of transmissivity in highly channelized fracture flow structures. In one structure, the cubic dependency of transmissivity to storativity identifies a well-defined fault and also demonstrates the validity of Poiseuille flow at a scale rarely investigated. In the other structure, the linear dependency of transmissivity to storativity indicates that the flow-bearing structure is the surrounding fracture network. Well-designed pumping tests combined with scaling analysis driven by geological evidence thus provide essential information on flow-bearing structures for site characterization and modeling tasks. At least for moderate to low permeable fractured rocks, the scaling of transmissivity to storativity appears to be more informative than any separate interpretation of hydraulic property scaling exponents

Clogging detection and productive layers identification along boreholes using Active Distributed Temperature Sensing

International audienceFiber-Optic Active Distributed Temperature Sensing (FO-ADTS) experiments were performed on an Aquifer Thermal Energy Storage system (ATES) site located on the university campus of Bordeaux, France. The experiments consisted in heating the steel core of the FO cable while monitoring the rate of temperature increase during the heating periods. The changes in temperature, that were monitored through time at every depth under various hydraulic conditions and in different boreholes, were used to evaluate both aquifer properties and wells conditions. A first ADTS experiment was conducted under cross borehole configuration using a pumping well and a monitoring well separated by a distance of 8.5 meters. Then, to check the reciprocity of the results, a second experiment was conducted by switching the monitoring and the pumping well. The results obtained through the use of analytical solutions for reproducing and interpreting the data lead to the following conclusions: (i) ADTS can be used to estimate both thermal conductivity and Darcy velocity distribution along boreholes, crucial properties for ATES performance. (ii) The proposed method is a promising tool to detect clogging locations in the boreholes when it occurs. This can be of great practical interest to maintain systems performance, since, once FO cables deployed, experiments could be easily repeated without opening boreholes and stop the system operation

European invasion of an Asian phylotype from a cryptic species of benthic foraminifera (Ammonia tepida)

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Impact of activated sludge acclimation on the biodegradation of toluene absorbed in a hydrophobic ionic liquid

International audienceClassical hydrophobic ionic liquids such as 3-butyl-1-methylimidazolium bis(trifluoroethylsulfonyl)imide or 3-butyl-1-methylimidazolium hexafluorophosphate application, as a non-aqueous liquid phase in a two-partitioning bioreactor to biodegrade hydrophobic volatile organic compounds by activated sludge, have been already reported in the literature, especially when the activated sludge was beforehand acclimated to the targeted volatile organic compound. In this study, four hydrophobic ionic liquids were used as non-aqueous liquid phase in a two-phase partitioning bioreactor to biodegrade toluene using non-acclimated activated sludge. The preliminarily results allowed to select two ionic liquids, 1-octylisoquinolinium bis(trifluoromethylsulfonyl)imide and allyl-diethylsulfonium bis(trifluoromethylsulfonyl)imide. The activated sludge was acclimated to both toluene and the considered ionic liquid. The results were compared to those obtained with non-acclimated activated sludge. The use of non-acclimated activated sludge for toluene biodegradation led to long lag times and low biodegradation rates. Thus, the acclimation to toluene improved the biodegradation rates; however, acclimation to both toluene and ionic liquid did not result in a significant improvement in the biodegradation rate compared to an acclimation to toluene alone. The activated sludge acclimation had a positive impact on toluene biodegradation and allowed to totally overcome the inhibitory effect of the presence of ionic liquid. The most relevant acclimation strategy seems to be a prior acclimation to toluene, whereas acclimation to the non-aqueous liquid phase can be achieved during the culture, namely by performing successive batches for instance, or a continuous operation. © 2017, Islamic Azad University (IAU)

A European perspective on the curry commission report

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