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

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.     

Effects of CO2 on benthic biota: An in situ benthic chamber experiment in Storfjorden (Norway)

Carbon capture and storage (CCS) methods, either sub-seabed or in ocean depths, introduces risk of CO₂ leakage and subsequent interaction with the ecosystem. It is therefore important to obtain information on possible effects of CO₂. In situ CO₂ exposure experiments were carried out twice for 10 days during 2005 using a Benthic Chamber system at 400 m depth in Storfjorden, Norway. pCO₂ in the water above the sediment in the chambers was controlled at approximately 500, 5000 and 20,000 μatm, respectively. This article describes the experiment and the results from measured the biological responses within the chamber sediments. The results show effects of elevated CO₂ concentrations on biological processes such as increased nanobenthos density. Methane production and sulphate reduction was enhanced in the approximately 5000 μatm chamber.     

A simple model accounting for the uptake,transport, and deposition of wind‐eroded mineral particles in the hyperarid coastal Atacama Desert of northern Chile

As previously observed in marine sediments collected downwind of African or South American continental sources, recent studies of sediment cores collected at the bottom of Mejillones Bay in north Chile (23°S) show a laminated structure in which the amount of particles of aeolian origin and their size create significant differences between the layers. This suggests inter‐annual to inter‐decadal variations in the strength of the local southerly winds responsible for (1) the erosion of the adjacent hyperarid surface of the Mejillones Pampa, and (2) the subsequent transport of the eroded particles towards the bay. A simple model accounting for the vertical uptake, transport, and deposition of the particles initially set into motion by wind at the surface of the pampa is proposed. This model, which could be adapted to other locations, assumes that the initial rate of (vertical) uptake is proportional to the (horizontal) saltation flux quantified by means of White's equation, that particles are lifted to a height (H), increasing with the magnitude of turbulence, and that sedimentation progressively removes the coarsest particles from the air column as it moves towards the bay. In this model, the proportionality constant (A) linking the vertical flux of particles with the horizontal flux, and the injection height (H) control the magnitude and size distribution of the deposition flux in the bay. Their values are determined using the wind speed measured over the pampa and the size distribution of particles collected in sediment traps deployed in the bay as constraints. After calibration, the model is used to assess the sensitivity of the deposition flux to the wind intensity variations. The possibility of performing such quantitative studies is necessary for interpreting precisely the variability of the aeolian material in the sediment cores collected at the bottom of Mejillones Bay. Copyright © 2010 John Wiley & Sons, Ltd.     

Indirect Boundary Element Method applied to fluid–solid interfaces

In this paper scattering of elastic waves in fluid–solid interfaces is investigated. We use the Indirect Boundary Element Method to study this wave propagation phenomenon in 2D models. Three models are analyzed: a first one with an interface between two half-spaces, one fluid on the top part and the other solid in the bottom; a second model including a fluid half-space above a layered solid; and finally, a third model with a fluid layer bounded by two solid half-spaces. The source, represented by Hankel's function of the second kind, is always applied in the fluid. This indirect formulation can give to the analyst a deep physical insight on the generated diffracted waves because it is closer to the physical reality and can be regarded as a realization of Huygens' principle. In any event, mathematically it is fully equivalent to the classical Somigliana's representation theorem. In order to gauge accuracy we test our method by comparing with an analytical solution known as Discrete Wave Number. A near interface pulse generates scattered waves that can be registered by receivers located in the fluid and it is possible to infer wave velocities of solids. Results are presented in both time and frequency domain, where several aspects related to the different wave types that emerge from this kind of problems are pointed out.     

The role of antecedent groundwater heads in controlling transient aquifer storage and flood peak attenuation in karst watersheds

Transient storage of floodwaters in aquifers is known to attenuate peak flows in rivers and drive subsurface dissolution. Transient aquifer storage could be enhanced in watersheds overlying karst aquifers where caves facilitate surface and groundwater exchange. Few studies, however, have examined controls on, or magnitudes of, transient aquifer storage or flood peak attenuation in karstic watersheds. Here we evaluate flood peak attenuation with multiple linear regression analyses of 10 years of river and groundwater data from the Suwannee River, which flows over the karstic upper Floridan aquifer in north-central Florida and experiences frequent flooding. Regressions show antecedent river stage exerts the dominant control on magnitudes of transient aquifer storage, with recharge and time to peak having secondary controls. Specifically, low antecedent stages result in larger magnitudes of transient aquifer storage and thus greater flood attenuation than conditions of elevated antecedent stage. These findings suggest subsurface weathering, including cave formation and enlargement, caused by transient aquifer storage could occur on a more frequent basis in aquifers where groundwater table elevation is lowered due to anthropogenic or climatic influences. Our work also shows that measures of groundwater table elevation prior to an event could be used to improve predictive flood models. © 2018 John Wiley & Sons, Ltd.     

Effects of organochlorine compounds on cytochrome P450 aromatase activity in an immortal sea turtle cell line

Many classes of environmental contaminants affect the reproductive function of animals through interactions with the endocrine system. The primary components affected by endocrine active compounds (EACs) are the steroid receptors and the enzymes responsible for steroidogenesis. This study sought to develop an in vitro model for assessing EAC effects in sea turtles by examining their ability to alter cytochrome P450 aromatase (CYP19) activity. Aromatase is the enzyme responsible for the conversion of testosterone to estradiol. This enzyme is critical in the sexual differentiation of reptiles which demonstrate temperature-dependent sex determination. An immortal testis cell line GST-TS from a green sea turtle was grown in culture at 30 degrees C in RPMI 1640 media. The cells were exposed to three known aromatase inducers; dexamethasone (Dex), 8Br-cyclic AMP, or human chronic gonadotropin (HCG) and one aromatase inhibitor 4-androstenol-dione (4-OHA). In addition, the GST-TS cells were exposed to 0.1-30 microM atrazine and 3-100 microM 4,4'-DDE. The inducing compounds that have been shown to increase aromatase activity in other systems failed to induce aromatase activity in the GST-TS cells, yet exposure to the inhibiting compound, 4-OHA, did result in a significant reduction. Atrazine (0.1, 1.0 and 10 microM) significantly induced aromatase activity following a 24 h exposure, and 4,4'-DDE inhibited the activity but only at cytotoxic concentrations (100 microM). Based on these results, this in vitro model can be useful in examining the endocrine effects of EACs in sea turtles.     

Otolith shape as a stock discrimination tool for ling (Genypterus blacodes) in the fjords of Chilean Patagonia

ABSTRACT

Genypterus blacodes, in terms of its fishing history and local economic importance, is an emblematic species harvested in Chilean Patagonia (41°00’–57°00’S). Most of the current fisheries and biological knowledge of this species come from the open ocean, whereas information about the species in fjords and inner channels is fragmentary. In 2018, two research surveys targeting G. blacodes were conducted in the fjords and inner channels of Chilean Patagonia. A total of 253 pairs of sagittal otoliths were sampled at three different localities, and their contours were modelled using wavelet analysis as a tool for stock discrimination. Contours were compared using canonical analysis, and classification was performed using linear discriminant and Random Forest analyses. The results indicated that the wavelet method is efficient in modelling otolith contours, and the discriminant analyses showed differences among fishing grounds across the latitudinal gradient, thus confirming the hypothesis that G. blacodes conform to at least two separate stock units in Chilean Patagonia. Fishing grounds that were closer in space showed higher levels of misclassification. The discussion focuses on how environmental variables and the geography of fjords shape stock differences and how this information can be used for the sustainable management of G. blacodes.     

The Cepheid period–luminosity zero-point from radial velocities and Hipparcos proper motions

A value for the zero-point (ρ) of the Cepheid period–luminosity relation, <  M _V  >= 2.81 log P  + ρ, is deduced by comparing the value of the Oort constant, A , derived from radial velocities with that derived from Hipparcos proper motions. We find in this way that ρ =−1.47 ± 0.13, in excellent agreement with the value derived from Hipparcos trigonometrical parallaxes, ρ = −1.43 ± 0.10, by Feast &38; Catchpole in a recent paper.