Size‐based differences in isotopic niche width (δ13C and δ15N) of green turtles (Chelonia mydas) nesting on Príncipe Island,Gulf of Guinea

Within the same population, nesting green turtles (Chelonia mydas) might exploit different niches by exhibiting polymorphic foraging strategies and/or inhabiting geographically distinct foraging areas. This is crucial information for the conservation of this species. Here, we used stable carbon and nitrogen isotope ratios (δ¹³C and δ¹⁵N) to test for differences in a population of green turtles nesting on Príncipe Island (1°37′N; 7°24?′E), Central Africa. A total of 60 nesting females were sampled on the two main nesting beaches of the island in December 2012. Minimum curved carapace length (CCL) was recorded, and δ¹³C and δ¹⁵N values were measured in the epidermis of each individual. Overall, CCL varied from 87.0 to 108.0 cm (mean ± SD =100.0 ± 5.1), δ¹³C values from ?19.4 to ?8.6‰ (?17.3 ± 1.8) and δ¹⁵N values from 7.9 to 17.3‰ (13.6 ± 1.5). Despite the large variation in both isotopic ratios, their distributions were unimodal, showing an absence of polymorphic foraging strategies and isotopically distinct foraging areas. However, smaller females (< median, 100.8 cm) occupied a much larger isotopic niche (i.e., four times greater) than larger females. These results suggest that nesting green turtles may forage opportunistically on the resources available in each of their foraging home ranges, with smaller females venturing to more isotopic‐diversified areas and/or exhibiting broader foraging strategies than larger females. In addition, and in accordance with other studies, findings suggest that the foraging grounds used by the Príncipe green turtle nesting females are distributed mainly throughout the Gulf of Guinea.     

Quantifying the effects of Eucalyptus plantations and management on water resources at plot and catchment scales

Our aim was to quantify the effects of forest plantation and management (clear cut or 30% partial harvest) in relation to pasture, on catchment discharge in southeast Rio Grande do Sul state, Brazil. A paired‐catchment approach was implemented in two regions (Eldorado do Sul and São Gabriel municipalities) where discharge was measured for 4 years at three catchments in each region, two of which were predominantly eucalypt plantation (mainly Eucalyptus saligna, rotation of approximately 7–9 years) with native forest and grass in streamside zones. The third catchment was covered with grazed pasture. Weather, soils, canopy interception, groundwater level, tree growth, and leaf area index were also measured. The 3‐PG process‐based forest productivity model was adapted to predict spatial daily plantation and pasture water balance including precipitation interception, soil evaporation, transpiration, soil moisture, drainage, discharge, and monthly plantation growth. The TOPMODEL framework was used to simulate water pools and fluxes in the catchments. Discharge was higher under pasture than pre‐harvesting plantation and increased for 1–2 years after complete plantation harvest; this change was less pronounced in the catchments under partial harvest. The ratio of discharge to precipitation before harvesting varied from 7% to 13% in the eucalypt catchments and 28% to 29% under pasture. The ratio increases to 23–24% after total harvest, and to 17% after partial harvesting. The ratio under pasture also increases during this period (to 32–44%) owing to increased precipitation. The baseflow, in relation to total discharge, varied from 28% to 62% under Eucalyptus and from 38% to 43% in the pasture catchments. Hence, eucalypt plantations in these regions can be expected to influence discharge regimes when compared with pasture land use, and modelling suggests that partial harvesting would moderate the magnitude of discharge variation compared with a full catchment plantation harvesting. The model efficiency coefficient (Nash–Sutcliffe model efficiency coefficient) varied from 0.665 to 0.799 for the total period of the study. Simulation of alternative harvesting scenarios suggested that at least 20% of the catchment planted area must be harvested to increase discharge. This model could be a useful practical tool in various plantation forestry contexts around the world. Copyright © 2016 John Wiley & Sons, Ltd.     

Analysis of the reliability of a statistical oil spill response model

A statistical oil spill response model is developed and validated by means of actual oil slick observations reported during the Prestige accident and trajectories of drifter buoys. The model is based on the analysis of a database of hypothetical oil spill scenarios simulated by means of a Lagrangian transport model. To carry out the simulations, a re-analysis database consisting of 44-year hindcast dataset of wind and waves and climatologic daily mean surface currents is used. The number of scenarios required to obtain statistically reliable results is investigated, finding that 200 scenarios provide an optimal balance between the accuracy of the results and the computational effort. The reliability of the model was analyzed by comparing the actual data with the numerical results. The agreement found between actual and numerical data shows that the developed statistical oil spill model is a valuable tool to support spill response planning.     

Purplish-red almandine garnets with alexandrite-like effect: causes of colors and color-enhancing treatments

Fine gem-quality, purplish-red garnets from the Tocantins State, Brazil, were investigated for their crystal chemistry and optical properties by several spectroscopic techniques, including electron microprobe analysis, Mössbauer, Raman spectroscopy and optical absorption. Although most garnets are purplish-red, some specimens show color zoning, with deep red color in the core and purple in the outer parts. Electron microprobe analysis showed that these garnets are principally almandine–pyrope solid solution at the rim. However, at the red core, they contain also up to 7 % of spessartine. Mössbauer spectroscopy reveals that the iron content is predominantly Fe²⁺ (>99 %) in the natural garnets. The optical absorption spectra are dominated by spin-allowed and unusual high-intense spin-forbidden transitions from eightfold coordinated Fe(II) in the near infrared and visible spectral region, respectively. For the red core, in addition, three sharp bands centered in the blue part of the visible spectral range and a broad charge transfer band in the near-UV region are observed. All garnets with purplish colors show also a remarkable color-changing effect from purple in daylight light to red in incandescent light called alexandrite-like effect. Heat treatments in the 700–900 °C temperature range in oxidizing and reducing atmospheres lead to reversible and irreversible color changes which are discussed based on the microscopic changes in the Fe ion coordination and valence states.     

Monthly streamflow forecasting using neuro-wavelet techniques and input analysis

ABSTRACT

Combinations of low-frequency components (also known as approximations) resulting from the wavelet decomposition are tested as inputs to an artificial neural network (ANN) in a hybrid approach, and compared to classical ANN models for flow forecasting for 1, 3, 6 and 12 months ahead. In addition, the inputs are rewritten in terms of the flow, revealing what type of information was being provided to the network, in order to understand the effect of the approximations on the forecasting performance. The results show that the hybrid approach improved the accuracy of all tested models, especially for 1, 3 and 6 months ahead. The input analyses show that high-frequency components are more important for shorter forecast horizons, while for longer horizons, they may worsen the model accuracy.     

Criteria for recognizing shelf-slope clinoforms in outcrop; Jurassic Lajas and Los Molles formations,S. Neuquén Basin,Argentina

Seismic-reflection data show that most deepwater (>200 m water depth) basins are filled by sand and mud dispersed across clinoformal geometries characterized by gently dipping topsets, steeper foresets and gently dipping bottomsets. However, the entire geometry of these ubiquitous clinoforms is not always recognized in outcrops. Sometimes the infill is erroneously interpreted as “layer cake” or “ramp” stratigraphy because the topset-foreset-bottomset clinoforms are not well exposed. Regional 2-D seismic lines show clinoforms in the Lower to Middle Jurassic Challaco, Lajas, and Los Molles formations in S. Neuquén Basin in Argentina. Time equivalent shelf, slope and basin-floor segments of clinoforms are exposed, and can be walked out in hundreds of metres thick and kilometres-wide outcrops. The studied margin-scale clinoforms are not representing a continental-margin but a deepwater shelf margin that built out in a back-arc basin. Lajas-Los Molles clinoforms have been outcrop-mapped by tracing mudstones interpreted as flooding surfaces on the shelf and abandonment surfaces (low sedimentation rate) in the deepwater basin. The downslope and lateral facies variability in the outcrops is also consistent with a clinoform interpretation. The Lajas topset (shelf) is dominated by fluvial and tidal deposits. The shelf-edge rollover zone is occasionally occupied by a 40–50-m-thick coarse-grained shelf-edge delta, sometimes incising into the underlying slope mudstones, producing oblique clinoforms expressing toplap erosion on seismic. A muddy transgressive phase capping the shelf-edge deltas contains tidal sandbodies. Shelf-edge deltas transition downslope into turbidite- and debris flow-filled channels that penetrate down the mud-prone Los Molles slope. At the base-of-slope, some 300m below the shelf edge, there are basin-floor fan deposits (>200 m thick) composed of sandy submarine-fan lobes separated by muddy abandonment intervals. The large-scale outcrop correlation between topset–foreset–bottomset allows facies and depositional interpretation and sets outcrop criteria recognition for each clinoform segment.     

Strutted Excavation in Soft Soil Incorporating a Jet-Grout Base Slab: Analysis Considering the Consolidation Effect

The influence of the consolidation on a strutted excavation in soft soil is analysed using a computer code based on the finite element method. A base jet-grout slab is considered in order to improve stability against bottom heave failure and minimize wall displacements. The numerical model incorporates the Biot consolidation theory (coupled formulation of the flow and equilibrium equations) with soil constitutive relations simulated by the p–q–θ critical state model. Special emphasis is given to the analysis, during and after the construction period, of the pore pressures, shear stresses, stress levels and displacements in the ground, as well as strut compression loads, wall displacements and bending moments, earth pressures on the wall faces and compression loads and bending moments on the jet-grout slab. The safety factor against bottom heave is also evaluated from the finite element analysis considering formulations of the critical state soil mechanics, and also compared to values obtained with traditional methods that use limit equilibrium approach and bearing capacity fundamentals.