Prediction and uncertainty source analysis of the spatial and temporal disturbance from off-road vehicular traffic in a complex ecosystem

Vehicle use during military training activities results in soil disturbance and vegetation loss. The capacity of lands to sustain training is a function of the sensitivity of lands to vehicle use and the pattern of land use. The sensitivity of land to vehicle use has been extensively studied. Less well understood are the spatial patterns of vehicle disturbance. Since disturbance from off-road vehicular traffic moving through complex landscapes varies spatially, a spatially explicit nonlinear regression model (disturbance model) was used to predict the pattern of vehicle disturbance across a training facility. An uncertainty analysis of the model predictions assessed the spatial distribution of prediction uncertainty and the contribution of different error sources to that uncertainty.For the most part, this analysis showed that mapping and modeling process errors contributed more than 95% of the total uncertainty of predicted disturbance, while satellite imagery error contributed less than 5% of the uncertainty. When the total uncertainty was larger than a threshold, modeling error contributed 60% to 90% of the prediction uncertainty. Otherwise, mapping error contributed about 10% to 50% of the total uncertainty. These uncertainty sources were further partitioned spatially based on other sources of uncertainties associated with vehicle moment, landscape characterization, satellite imagery, etc.     

Maternal exposure to specific perfluoroalkyl substances is associated with increasing blood glucose in pregnant women

正Imagine if a group of toxic substances that increase oxidative stress and disrupt glucose and lipid metabolism have been broadly used worldwide for applications such as repellent,food packaging,and non-stick frying pan coatings.Now imagine if some of these substances have half-lives as long as 3-8 years.This is an environmental reality that has come to light with perfluoroalkyl and polyfluoroalkyl substances(PFASs)–high     

Causes of habitat divergence in two species of agamid lizards in arid central Australia

The deserts of central Australia contain richer communities of lizards than any other arid regions, with the highest diversity occurring in sand dune habitats dominated by hummock-forming spinifex grasses. To investigate the mechanisms that permit coexistence, we studied two species of coexisting agamid lizards that exhibit striking divergence in their use of habitat in the Simpson Desert of central Australia. Here, the military dragon Ctenophorus isolepis is restricted primarily to sites providing > 30% cover of hard spinifex Triodia basedowii, whereas the central netted dragon C. nuchalis occurs in areas with much sparser (< 10%) cover. We constructed four mechanistic models to explain this pattern and then derived hypotheses to test them. One hypothesis, that competition restricts each species to its preferred habitat, was rejected after dyad encounters in field enclosures failed to elicit any habitat shift or any overt interactions between the species. Our next hypotheses were that each species exhibits preferences for different thermal environments or different prey types and that each selects the habitats that maximize access to them. Both were supported. C. isolepis preferred lower temperatures when active and specialized in eating ants < 5 mm long and selected spinifex-dominated areas where these requirements were met. In contrast, C. nuchalis preferred higher temperatures and a diversity of prey, both of which were available mostly in open areas. Finally, we used plasticine models to test the hypothesis that each species faced lower risk of predation in its selected habitat. This was partly supported, as models of both species were attacked more often in the open than under spinifex cover. The results show that habitat divergence occurs along several, probably covarying, niche axes. We suggest that different levels of spinifex cover provide the template for a broad range of ecological interactions, allowing lizard species to partition biotic and abiotic resources and achieve the extraordinarily high levels of local diversity that are observed.     

Limited salvage logging effects on forest regeneration after moderate-severity windthrow.

Recent conceptual advances address forest response to multiple disturbances within a brief time period, providing an ideal framework for examining the consequences of natural disturbances followed by anthropogenic management activities. The combination of two or more disturbances in a short period may produce "ecological surprises," and models predict a threshold of cumulative disturbance severity above which forest composition will be drastically altered and regeneration may be impaired. Salvage logging (the harvesting of timber after natural disturbances; also called "salvaging" or "sanitary logging") is common, but there have been no tests of the manner in which salvaging after natural wind disturbance affects woody plant regeneration. Here we present findings from three years after a moderate-severity wind disturbance in west-central Tennessee, USA. We compare two unsalvaged sites and two sites that had intermediate-intensity salvaging. Our approach demonstrates the calculation of cumulative severity measures, which combine natural windthrow severity and anthropogenic tree cutting and removal, on a plot-by-plot basis. Seedling/sapling density and species richness were not influenced by cumulative disturbance severity, but species diversity showed a marginal increase with increasing cumulative severity. The amount of compositional change (from predisturbance trees to post-disturbance seedlings/saplings) increased significantly with cumulative severity of disturbance but showed no evidence of thresholds within the severity range examined. Overall, few deleterious changes were evident in these sites. Moderate-severity natural disturbances followed by moderate-intensity salvaging may have little detrimental effect on forest regeneration and diversity in these systems; the ecological surprises and threshold compositional change are more likely after combinations of natural and anthropogenic disturbances that have a much greater cumulative severity.     

Budgets of turbulent kinetic energy,Reynolds stresses,and dissipation in a turbulent round jet discharged into a stagnant ambient

Environmental Fluid Mechanics - This paper presents a set of stereoscopic particle image velocimetry (SPIV) measurements of a turbulent round water jet (jet exit Reynolds number $$Re = 2679$$ and...     

Photocatalytic degradation of polybrominated diphenyl ethers in pure water system

Due to the low water solubility of polybrominated diphenyl ethers, organic solvent is usually added into the oxidation system to enhance the removal efficiency. In this study the photocatalytic degradation of decabromodiphenyl ether (BDE209), a type of polybrominated diphenyl ether used throughout the world, in pure water without the addition of organic solvent was investigated. In the pure water system, BDE209 was not dissolved but dispersed as nano-scale particles with a mean diameter of 166 nm. Most of BDE209 (>98%) were removed within 4 h and the final debromination ratio was greater than 80%. Although the addition of organic solvent (tetrahydrofuran, THF) could lead to a relatively high BDE209 degradation rate, the final debromination ratio (<50%) was much lower than that in pure water system. Major oxidation intermediates of tetrahydrofuran, including tetrahydro-2-furanol and γ-butyrolactone, were detected indicating the engagement of THF in the BDE209 degradation process. The photocatalytic degradation of BDE209 in the pure water system followed first-order kinetics. The BDE209 degradation rate constant increased from 0.0011 to 0.0023 min⁻¹ as the pH increased from 3 to 9.     

A farewell to Dr Thomas Knacker (* 29.04.1951 – ? 30.10.2011): scientific contributions and personal memories

Background

The bioaccumulation potential of chemical substances is commonly determined in flow-through fish tests according to the Organization for Economic Cooperation and Development (OECD) technical guideline (TG) 305, aiming at the determination of bioconcentration factors (BCF). Investigations on aquatic organisms have shown a significant positive correlation between the accumulation of a chemical and the lipid content of organisms. Residue levels can thus differ between individuals, species, and size groups depending on their lipid content. BCF values can be normalized by lipid content; however, this requires the use of appropriate extraction techniques to ensure the complete extraction of total lipids from fish/tissue samples. The OECD TG 305 is currently under revision. A literature review was carried out to select preferred methods which shall be included in the updated OECD TG 305 along with a sampling schedule for lipid measurement in fish.

Results

An overview and appraisal of a broad range of lipid extraction methods is presented. Extraction procedures applied in bioaccumulation studies described in the literature and procedures currently used for such studies by governmental, academic, and industrial labs are surveyed. Possible impacts of unsuitable extraction techniques on lipid normalized BCF results were assessed. Default values for BCF normalization commonly used in bioaccumulation studies are described. The effect of differences in residue distribution over different organs and/or lipids on the normalization of BCF values is discussed.

Conclusions

A broad range of procedures for lipid extraction are available. However, only the use of suitable extraction techniques guarantees the complete extraction of total lipids from fish samples in bioaccumulation studies which is required to ensure the correct lipid normalization of BCF values. Preferred methods for inclusion in the updated OECD 305 test guideline as well as a standard schedule for lipid measurements are suggested.     

Multi-scale marine biodiversity patterns inferred efficiently from habitat image processing

Cost-effective proxies of biodiversity and species abundance, applicable across a range of spatial scales, are needed for setting conservation priorities and planning action. We outline a rapid, efficient, and low-cost measure of spectral signal from digital habitat images that, being an effective proxy for habitat complexity, correlates with species diversity and requires little image processing or interpretation. We validated this method for coral reefs of the Great Barrier Reef (GBR), Australia, across a range of spatial scales (1 m to 10 km), using digital photographs of benthic communities at the transect scale and high-resolution Landsat satellite images at the reef scale. We calculated an index of image-derived spatial heterogeneity, the mean information gain (MIG), for each scale and related it to univariate (species richness and total abundance summed across species) and multivariate (species abundance matrix) measures of fish community structure, using two techniques that account for the hierarchical structure of the data: hierarchical (mixed-effect) linear models and distance-based partial redundancy analysis. Over the length and breadth of the GBR, MIG alone explained up to 29% of deviance in fish species richness, 33% in total fish abundance, and 25% in fish community structure at multiple scales, thus demonstrating the possibility of easily and rapidly exploiting spatial information contained in digital images to complement existing methods for inferring diversity and abundance patterns among fish communities. Thus, the spectral signal of unprocessed remotely sensed images provides an efficient and low-cost way to optimize the design of surveys used in conservation planning. In data-sparse situations, this simple approach also offers a viable method for rapid assessment of potential local biodiversity, particularly where there is little local capacity in terms of skills or resources for mounting in-depth biodiversity surveys.     

Flux by fin: fish-mediated carbon and nutrient flux in the northeastern Gulf of Mexico

Seagrass meadows are among the most productive ecosystems in the marine environment. It has been speculated that much of this production is exported to adjacent ecosystems via the movements of organisms. Our study utilized stable isotopes to track seagrass-derived production into offshore food webs in the northeastern Gulf of Mexico. We found that gag grouper (Myctereoperca microlepis) on reefs as far as 90 km from the seagrass beds incorporate a significant portion of seagrass-derived biomass. The muscle tissue of gag grouper, a major fisheries species, was composed on average of 18.5–25% seagrass habitat-derived biomass. The timing of this annual seagrass subsidy appears to be important in fueling gag grouper egg production. The δ³⁴S values of gag grouper gonad tissues varied seasonally and were δ³⁴S depleted during the spawning season indicating that gag utilize the seagrass-derived biomass to support reproduction. If such large scale trophic subsidies are typical of temperate seagrass systems, then loss of seagrass production or habitat would result in a direct loss of offshore fisheries productivity.