Effects of chlorpyrifos on cholinesterase activity and stress markers in the tropical reef fish Acanthochromis polyacanthus

Tropical coastal ecosystems, including the Great Barrier Reef (GBR) of Australia are increasingly threatened by pollution; yet few studies have investigated the sensitivity of GBR species to these pollutants. Here we exposed juveniles of the tropical reef fish Acanthochromis polyacanthus (spiny damselfish) to three concentrations of the insecticide chlorpyrifos (CPF) and measured (i) muscle cholinesterase (ChE) activity; (ii) hepatic glutathione-S-transferase (GST) activity; and (iii) coenzyme Q (CoQ) redox balance, after 6h and 96h of exposure. After 96h, muscle ChE activity was significantly inhibited by 26%, 49% and 53% when fish were exposed to 1, 10 or 100μg/L CPF, respectively. Muscle ChE characterization revealed three types of ChEs, including two atypical forms. Hepatic CoQ antioxidant form significantly increased at 10μg/L after 6h of exposure, potentially demonstrating an early response to CPF-induced oxidative stress in liver. Hepatic GST was not affected by CPF exposure.     

Formation of drying crack patterns in soils: a deterministic approach

Soils, as well as most of deformable multiphase porous materials, are likely to suffer from desiccation cracking, leading to the formation of regular crack patterns affecting their permeability. The ensuing crack spacing has often been related to a concept sometimes called “sequential infilling”: it is assumed that desiccation cracks are formed by successive generations. However, such a concept does not consider the pattern of a simultaneous crack formation at a given moment. Using our desiccation cracking test results and their numerical simulation, we propose a consistent explanation for the formation of desiccation crack patterns in soils. We show that the “sequential infilling” concept is suitable only when the position of the crack(s) clearly stems from the stress field. To derive an estimate of the desiccation crack spacing, the overall energy of the system needs to be considered. Statistical variability should be superimposed on the mean deterministic conditions discussed here.     

Soil moisture from operational meteorological satellites

In recent years, unforeseen advances in monitoring soil moisture from operational satellite platforms have been made, mainly due to improved geophysical retrieval methods. In this study, four recently published soil-moisture datasets are compared with in-situ observations from the REMEDHUS monitoring network located in the semi-arid part of the Duero basin in Spain. The remotely sensed soil-moisture products are retrieved from (1) the Advanced Microwave Scanning Radiometer (AMSR-E), which is a passive microwave sensor on-board NASA’s Aqua satellite, (2) European Remote Sensing satellite (ERS) scatterometer, which is an active microwave sensor on-board the two ERS satellites and (3) visible and thermal images from the METEOSAT satellite. Statistical analysis indicates that three satellite datasets contribute effectively to the monitoring of trends in surface soil-moisture conditions, but not to the estimation of absolute soil-moisture values. These sensors, or rather their successors, will be flown on operational meteorological satellites in the near future. With further improvements in processing techniques, operational meteorological satellites will increasingly deliver high-quality soil-moisture data. This may be of particular interest for hydrogeological studies that investigate long-term processes such as groundwater recharge.     

Paleoenvironmental dynamics in central-eastern Brazil during the last 23 000 years: tropical peatland record in the Cerrado biome

The Cerrado biome is the second largest in Brazil, but the evolution of the Cerrado during the late Quaternary is not yet fully known. This study identifies paleoenvironmental changes during the last 23 000 years, based on a tropical mountain peatland record, in the Serra do Espinhaço Meridional in central-eastern Brazil. A multi-proxy approach was used that involved palynological analysis, stable isotopes (δ¹³C, δ¹⁵N), geochemistry, radiocarbon dating and multivariate statistics derived from a peatland core from Rio Preto (Minas Gerais state). The study reveals a very humid and cold climate during the late Pleistocene, with an increase in temperature and decrease in humidity at the Pleistocene–Holocene transition. During this period there was strong instability in the landscape (episodes of erosion). At the beginning of the Holocene there was a reduction in humidity with greater landscape stability. The current sub-humid climatic conditions seem to have been established in the mid-/late Holocene, with periods of landscape instability. Our findings agree with other Cerrado records that contradict previously established hypotheses, such as the Amazonian Refuge and the Pleistocene Arc.     

Early to mid‐Holocene climate change at Lago dell'Accesa (central Italy): climate signal or anthropogenic bias?

Despite the high potential of pollen records for climate reconstruction, pollen–climate relationships may be biased due to past and present human activities on the landscape. We use (i) transfer functions based on modern pollen–climate relationships to infer seasonal temperature and summer precipitation for the period 11 500–4500 cal. a BP and (ii) lake‐level change records based on different sedimentary proxies in multiple cores that are mainly indicative for summer hydrology at Lago dell'Accesa (central Italy). Quantitative reconstructions indicate lowest summer precipitation during two phases (8500–7700 cal. a BP and after 6000 cal. a BP) and a gradual winter temperature increase from 11 500 to ca. 8000 cal. a BP. Lowest summer precipitation was reconstructed during these phases characterised by vegetation shifts from open forests dominated by summergreen oaks (Quercus) to forests dominated by evergreen oaks (Quercus ilex), which are at present most abundant where summer drought is stronger. Similarly, the lake‐level record indicates two long‐lasting low summer precipitation phases (8800–7700 and 6400–4400 cal. a BP) that were interrupted by short‐term high summer precipitation events. Based on the broad agreement between the pollen‐inferred summer precipitation and the low‐frequency lake‐level changes, we suggest that the duration of the high summer precipitation events may have been too short to maintain drought‐sensitive trees, which may have been affected by high mortality rates when summer dry conditions returned. Although past and modern pollen–climate relationships may very likely have been affected by human activities since the Neolithic (i.e. when exploitation of the landscape started), we reject the hypothesis of a significant anthropogenic bias in the pollen‐based climate reconstruction. In addition, we suggest that pollen‐based and lake‐level reconstructions may have different inherent abilities of capturing high‐ and low‐frequency precipitation signals. Copyright © 2010 John Wiley & Sons, Ltd.     

An Elliptical Model for Deformation Due to Groundwater Fluctuations

Historically, surface subsidence as a result of subsurface groundwater fluctuations have produced important and, at times, catastrophic effects, whether natural or anthropogenic. Over the past 30?years, numerical and analytical techniques for the modeling of this surface deformation, based upon elastic and poroelastic theory, have been remarkably successful in predicting the magnitude of that deformation (Le Mouélic and Adragna in Geophys Res Lett 29:1853, 2002). In this work we have extended the formula for a circular-shaped aquifer (Geertsma in J Petroleum Tech 25:734–744, 1973) to a more realistic elliptical shape. We have improved the accuracy of the approximation by making use of the cross terms of the expansion for the elliptic coordinates in terms of the eccentricity, e, and the mean anomaly angle, M, widely used in astronomy. Results of a number of simulations, in terms of e and M developed from the transcendental Kepler equation, are encouraging, giving realistic values for the elliptical approximation of the vertical deformation due to groundwater change. Finally, we have applied the algorithm to modeling of groundwater in southern California.     

The rise of the diptera‐microbial mat interactions during the Cenozoic: consequences for the sedimentary record of saline lakes

Shoreline gypsiferous sediments of an inland lake in central Spain furnishes valuable insight into reconstructions of early sedimentary changes related to shore fly–microbial mat interactions in fossil gypsum precipitating saline lake systems. The association of adult and larval forms of Ephydra (Diptera) with microbial matgrounds overlying the lake margin results in the formation of gypsiferous meniscate back‐filled burrows that provide an analogue for recurring, extensively developed trace fossils that occur in Cenozoic, but not older, lacustrine gypsum rocks. In this setting, sediment burrowing by ephydridae hinders significant preservation of microbialites. The overwhelming rise of Diptera at the onset of the Cenozoic resulted in extensive feeding and dwelling activity and contributed to reshape the saline aquatic habitat where microbial mats thrived, thus leading to the formation of specific trace fossils that are illustrative of the existence of microbes in the paleoenvironment.     

Initial assessment of the infiltration and overland flow for different rainfall events in land constituted of sandstones of the Botucatu Formation (Guarani Aquifer), State of São Paulo, Brazil

This study was carried out in the Córrego do Vaçununga basin constituted of eolic sandstones of Botucatu Formation and residual unconsolidated materials (>90%), considered the most important unconfined aquifer in Brazil, in the city of Luiz Antonio, State of São Paulo, Brazil. Laboratory and in situ tests were performed to characterize the unconsolidated materials in terms of basic physical properties, potential infiltration rate, suction and hydraulic conductivity. The results for infiltration and overland flow depths were obtained according to Morel-Seytoux and Khanji (Water Resour Res 10(4):795–800, 1976) and Chu (Water Resour Res 14(3):461–466, 1978) adaptation of the Green and Ampt [J Agr Sci 4(Part 1):1–24, 1911] model for steady and transient rainfalls, respectively. Rainfall data were collected from January of 2000 to December of 2002, and 12 scenarios were defined considering the intensity and durations. Rather than high homogeneity in terms of the texture of unconsolidated materials, the infiltration and overland flow ratio depends on the type of land use and associated management practices. The results showed that rainfall with high intensity and short duration do not produce high overland flow ratio as we have observed for transient scenarios with long duration and low intensities.