Water reuse in industries: analysis of opportunities in the Paraíba do Sul river basin,a case study in Presidente Vargas Plant,Brazil

Environmental Science and Pollution Research - In recent years, the demand for clean water has been growing all over the world despite the different threats posed, including increasing pollution,...     

Scaling-up spatially-explicit ecological models using graphics processors

How the properties of ecosystems relate to spatial scale is a prominent topic in current ecosystem research. Despite this, spatially explicit models typically include only a limited range of spatial scales, mostly because of computing limitations. Here, we describe the use of graphics processors to efficiently solve spatially explicit ecological models at large spatial scale using the CUDA language extension. We explain this technique by implementing three classical models of spatial self-organization in ecology: a spiral-wave forming predator-prey model, a model of pattern formation in arid vegetation, and a model of disturbance in mussel beds on rocky shores. Using these models, we show that the solutions of models on large spatial grids can be obtained on graphics processors with up to two orders of magnitude reduction in simulation time relative to normal pc processors. This allows for efficient simulation of very large spatial grids, which is crucial for, for instance, the study of the effect of spatial heterogeneity on the formation of self-organized spatial patterns, thereby facilitating the comparison between theoretical results and empirical data. Finally, we show that large-scale spatial simulations are preferable over repetitions at smaller spatial scales in identifying the presence of scaling relations in spatially self-organized ecosystems. Hence, the study of scaling laws in ecology may benefit significantly from implementation of ecological models on graphics processors.     

Increase in membrane thickness during development compensates for eggshell thinning due to calcium uptake by the embryo in falcons

We compared membrane thickness of fully developed eggs with those of non-developed eggs in different endangered falcon taxa. To our knowledge, membrane thickness variation during development has never been examined before in falcons or any other wild bird. Yet, the egg membrane constitutes an important protective barrier for the developing embryo. Because eggshell thinning is a general process that occurs during bird development, caused by calcium uptake by the embryo, eggs are expected to be less protected and vulnerable to breakage near the end of development. Thus, egg membranes could play an important protective role in the later stages of development by getting relatively thicker. We used linear mixed models to explore the variation in membrane thickness (n = 378 eggs) in relation to developmental stage, taxon, female age, mass and identity (73 females), egg-laying sequence (105 clutches) and the study zone. Our results are consistent with the prediction that egg membranes are thicker in fully developed eggs than in non-developed eggs, suggesting that the increase in membrane thickness during development may compensate for eggshell thinning. In addition, our data shown that thicker membranes are associated with larger, heavier and relatively wider eggs, as well as with eggs that had thinner eggshells. Egg-laying sequence, female age and the study zone did not explain the observed variation of membrane thickness in the falcon taxa studied. As we provide quantitative data on membrane thickness variation during development in falcons not subjected to contamination or food limitation (i.e. bred under captive conditions), our data may be used as a reference for studies on eggs from natural populations. Considering the large variation in membrane thickness and the multiple factors affecting on it and its importance in the protection of the embryo, we encourage other researchers to include measurements on membranes in studies exploring eggshell thickness variation.     

Ecosystem approaches to environmental quality assessment

Environmental quality assessment has to focus more on the quality of whole ecosystems, instead of focusing on the direct effects of a specific stressor, because of a more integrated environmetal policy approach. Yet, how can the ecosystem quality be measured? Partly this is a normative question, a question of what is considered good and bad. At the same time, it is a scientific question, dealing with the problem of low the state of a system as complex as an ecosystem could be measured. Measuring all abiotic and biotic components, not to mention their many relationships, is not feasible. In this article we review several approaches dealing with this scientific question. Three approaches are distinguished; they differ in type of variable set and ecosystem model used. As a result of this, the information about the state of the ecosystem differs: ultimate breadth, comprising information about the whole ecosystem, is at the expense of detail, while ultimate detail is at the expense of breadth. We discuss whether the resultant quality assessments differ in character and are therefore suitable to answer different policy questions.     

Environmental monitoring of water resources around a municipal landfill of the Rio Grande do Sul state,Brazil

Environmental Science and Pollution Research - In Brazil, landfills are commonly used as a method for the final disposal of waste that is compliant with the legislation. This technique, however,...     

The fire frequency analysis branch of the pyrostatistics tree: sampling decisions and censoring in fire interval data

Statistical characterization of past fire regimes is important for both the ecology and management of fire-prone ecosystems. Survival analysis—or fire frequency analysis as it is often called in the fire literature—has increasingly been used over the last few decades to examine fire interval distributions. These distributions can be generated from a variety of sources (e.g., tree rings and stand age patterns), and analysis typically involves fitting the Weibull model. Given the widespread use of fire frequency analysis and the increasing availability of mapped fire history data, our goal has been to review and to examine some of the issues faced in applying these methods in a spatially explicit context. In particular, through a case study on the massive Cedar Fire in 2003 in southern California, we examine sensitivities of parameter estimates to the spatial resolution of sampling, point- and area-based methods for assigning sample values, current age surfaces versus historical intervals in generating distributions, and the inclusion of censored (i.e., incomplete) observations. Weibull parameter estimates were found to be roughly consistent with previous fire frequency analyses for shrublands (i.e., median age at burning of ~30–50 years and relatively low age dependency). Results indicate, however, that the inclusion or omission of censored observations can have a substantial effect on parameter estimates, far more than other decisions about specifics of sampling.

Determining shark size from forensic analysis of bite damage

Bite damage patterns have long been used to estimate shark species and body size, with somewhat limited success. The lack of fit between damage patterns and shark size is partially due to variation in tooth size and shape within an individual. The ability to accurately predict body size from bite patterns is important for better understanding the ecological and behavioral underpinnings of shark bites/attacks on marine organisms, humans, and submarine equipment. To this end, we measured interdental distance (IDD) between the most labial teeth in the first six tooth files on both the upper and lower jaws, as well as the circumference of the portion of each jaw that bears teeth, for prepared jaw sets from fourteen shark species and regressed these data against total length. IDD is allometric as well as an accurate predictor of total length in all species examined, except Carcharhinus acronotus. Tooth-bearing circumference is also allometric and predictive of total length in all species. Though considerable overlap exists in IDD and circumference ranges among species for the total length ranges examined, Carcharodon carcharias and Isurus sp. can be differentiated from Carcharhinus limbatus, Carcharhinus brevipinna, and C. acronotus based on these values alone. When combined with knowledge of species-specific feeding behavior, geographic distribution, and habitat preferences, these simple measures from bite damage patterns allow quick, accurate assessment of shark size and potential species.     

Measuring complexity in three-trophic level systems

This essay is a trial on measuring complexity in a three-trophic level system by using a convex function of the informational entropy. The complexity measure defined here is compatible with the fact that real complexity lies between ordered and disordered states. Applying this measure to the data collected for two three-trophic level systems some hints about their organization are obtained.     

A system dynamics model for the management of the Manila clam, Ruditapes philippinarum (Adams and Reeve, 1850) in the Bay of Arcachon (France)

The Manila clam Ruditapes philippinarum (Adams and Reeve, 1850) is one of the mollusc species that, driven mainly by the shellfish market industry, has extended throughout the world, far beyond the limits of its original habitat. The Manila clam was introduced into France for aquaculture purposes, between 1972 and 1975. In France, this venerid culture became increasingly widespread and, since 1988, this species has colonised most of the embayments along the French Atlantic coast. In 2004, this development resulted in a fishery of ca. 520 t in Arcachon Bay.