Mechanical properties of a mature biofilm from a wastewater system: from microscale to macroscale level

A fundamental understanding of biofilm mechanical stability is critical in order to describe detachment and develop biofouling control strategies. It is thus important to characterise the elastic deformation and flow behaviour of the biofilm under different modes of applied force. In this study, the mechanical properties of a mature wastewater biofilm were investigated with methods including macroscale compression and microscale indentation using atomic force microscopy (AFM). The mature biofilm was found to be mechanically isotropic at the macroscale level as its mechanical properties did not depend on the scales and modes of loading. However, the biofilm showed a tendency for mechanical inhomogeneity at the microscale level as indentation progressed deeper into the matrix. Moreover, it was observed that the adhesion force had a significant influence on the elastic properties of the biofilm at the surface, subjected to microscale tensile loading. These results are expected to inform a damage-based model for biofilm detachment.     

Landscape correlates of forest plant invasions: A high‐resolution analysis across the eastern United States

Aim

Invasive species occurrence is often related to the anthropogenic context of a given area. Quantifying the effects of roads is of particular interest as roads are a major vector for invasion. Our objective was to further quantify the effects of roads on forest plant invasion through a macroscale, high‐resolution investigation to assist effective invasion control and mitigation.

Location

Eastern United States.

Methods

Using invasive plant data from 23,039 forest inventory plots in 13 ecological provinces, we employed logistic regression to relate the odds of invasion to distance from a road, with adjustments for broadscale differences attributable to ecological provinces, and local scale differences in productivity, forest fragmentation and land use.

Results

The overall proportion (P) of invaded plots was 0.58 (0.65 for plots within 50 m of a road), and the highest odds (P/1 ? P) of invasion were found in relatively more productive, fragmented forest in landscapes with more than 10% agriculture or developed land cover. Wald chi‐square statistics indicated the best predictor of the odds of invasion was ecological province, followed by land use, productivity, forest fragmentation and distance from a road. Depending on the province, the adjusted odds of invasion decreased by up to 23% (typically 4%–10%) per 100 m distance from a road. The adjusted probability of invasion approached zero in only three provinces, for the least productive, least fragmented forest that was at least 2,000 m from a road in landscapes with less than 10% agricultural or developed land cover.

Main conclusions

In the eastern United States, the existence of a nearby road is less important than the landscape context associated with the road. A purely road‐mediated effect has little practical meaning because anthropogenic activities and roads are pervasive and confounded.

     

Evaluating the use of macroscale variables as proxies for local aquatic variables and to model stream fish distributions

相似文献   

Visualizing the macroscale spatial distributions of biofilms in complex flow channels using industrial computed tomography

Abstract

The presence of biofilms in enclosed pipelines can lead to numerous deleterious issues. To date, it has been difficult to use optical imaging techniques to monitor the macroscale spatial distributions of biofilms. To address this concern, a combination of industrial computed tomography (ICT) and a contrast agent was explored to noninvasively visualize biofilms in three types of drip irrigation emitters. The results showed that ICT successfully observed and quantified the macroscale spatial distributions of biofilms. The complex hydrodynamic characteristics in the emitter channels affected the local distributions of biofilms. Biofilms were mainly attached to the lateral and medial faces and biomass decreased along the flow directions. Based on the distributions of biofilms, some emitter structural design defects were further diagnosed. Applying ICT in combination with the contrast agent could potentially provide a visual and effective way to reveal the formation mechanisms of biofilms and to optimize flow channel structures to avoid biofilm accumulations.     

Spatial and temporal variation of ecosystem properties at macroscales

Although spatial and temporal variation in ecological properties has been well‐studied, crucial knowledge gaps remain for studies conducted at macroscales and for ecosystem properties related to material and energy. We test four propositions of spatial and temporal variation in ecosystem properties within a macroscale (1000 km's) extent. We fit Bayesian hierarchical models to thousands of observations from over two decades to quantify four components of variation – spatial (local and regional) and temporal (local and coherent); and to model their drivers. We found strong support for three propositions: (1) spatial variation at local and regional scales are large and roughly equal, (2) annual temporal variation is mostly local rather than coherent, and, (3) spatial variation exceeds temporal variation. Our findings imply that predicting ecosystem responses to environmental changes at macroscales requires consideration of the dominant spatial signals at both local and regional scales that may overwhelm temporal signals.     

The effect of environmental conditions on distribution,growth and life span of <Emphasis Type="Italic">Protothaca euglypta</Emphasis> (Mollusca: Bivalvia)

The distribution and growth of the bivalve mollusk Protothaca euglypta in Peter the Great Bay and at the northern boundary of its area were investigated. It is shown that in some biotopes P. euglypta biomass reaches 1–2 kg/m², which exceeds the estimated values of abundance obtained for most associated species of mollusks. It has been established that local variability of P. euglypta growth rates can be compared with latitudinal variability, and the life span increases from the southern part of the area towards its northern boundary. It has been concluded that P. euglypta occupies a more prominent position in the malacofauna of shallow waters in its abundance, than it was considered earlier.     

Fifteenth annual research symposium University of Glasgow, 1975

Background: All human land use (LU) affects the distribution of plant species; however, the impacts vary with the type/intensity of LU. For managing ecosystems, it is therefore essential to understand the effects of LU types on the distribution of plant species on a macroscale.

Aims: The objectives of our study were to quantify the effects of various LU types on the distribution of vascular plant species in Japan and to determine in particular the extent to which LU was an important factor for the distribution of common species.

Methods: Based on a logistic regression model and variation partitioning being applied to each plant species, we evaluated the partial deviance by six LU types, four climatic types and three topographic and geological factors for 647 plant species at 14,412 sites in Japan.

Results: The effect of LU was significant for species present at multiple sites. Of the six LU types, secondary vegetation and plantation were the most important factors determining species distribution for many species.

Conclusions: Our results suggest that distribution of the common species is largely affected by LU on macroscale. The design of LU relating to secondary vegetation and plantations will thus be important in determining changes in the vegetation composition within Japan.