Food sources of macrobenthos in an estuarine seagrass habitat (Zostera noltii) as revealed by dual stable isotope signatures

Stable carbon and nitrogen isotope analysis was used to examine the resources and position of macrobenthos in an estuarine seagrass food web in two sampling moments, during summer and winter. The contribution of each food source to the carbon requirements of consumers was estimated by a mixing model. The used carbon sources were largely seagrass associated, although seagrass tissues were utilized by only few species, and equally contributed to microphytobenthos and suspended particulate organic matter. Based on isotopic data, Lucinidae bivalves have an alternative trophic pathway via symbiosis with chemoautotrophic bacteria. Resource utilization inside and adjacent to seagrass beds did not differ significantly, implying that seagrass-associated inputs extend well beyond the borders of the vegetation patches.     

Bioaccumulation and adverse effects of trace metals and polycyclic aromatic hydrocarbons in the common onion Allium cepa as a model in ecotoxicological bioassays

The common onion Allium cepa can be easily used in ecotoxicological bioassays to evaluate the bioavailability and adverse effects of pollutants and complex mixtures like waste, industrial effluent or coal-mining drainage that contain elevated levels of trace metals and polycyclic aromatic hydrocarbons (PAHs). In this study, onions were exposed for 7 days to individual metals (1?µg?mL^?1), i.e., aluminium, copper, iron and manganese, or PAHs (1.5?ng?mL^?1), i.e., benzo[a]antracene and benzo[a]pirene. Biological effects, measured as growth inhibition of roots and leaves, were integrated with analysis of bioaccumulation in roots, bulbs and leaves. Copper, iron and benzo[a]pirene caused a significant inhibition in root development of newly formed tissues, whereas only slight variations were caused by other chemicals; the number of new root filaments and the length of the leaves did not show significant variations, thus not representing sensitive parameters to evaluate adverse effects of pollutants in A. cepa. Chemicals bioaccumulation was always significant in roots, whereas levels in bulbs and leaves exhibited increased levels only for manganese, and a decrease for aluminium. The overall results confirmed the sensitivity of the bioassays with A. cepa, suggesting their utility for future applications to evaluate the adverse effects of complex mixtures containing metals or PAHs.     

A model based on molecular structure descriptors for predicting mutagenicity of organic compounds

A model predictive of the potential mutagenicity of organic compounds was devised by relating mutagenicity data obtained in the Ames reversion test to molecular structure parameters describing their hydrophobic, topological, steric and electronic properties. These included second order valence molecular connectivity index, parachor, molar refraction and polarizability of electrons. A classification rule was calculated, by means of discriminant analysis, using a training set of 117 compounds of various chemical classes. There was agreement between experimental data and theoretical expectations for the majority of compounds (70.9%), with homogeneous figures among the different chemical classes under scrutiny. An exception was represented by halogenated aliphatics with up to 3 C atoms, the mutagenicity of which was poorly predicted by the structural analysis model.     

Chromate reduction by Serratia marcescens immobilized on activated carbon

Serratia marcescens, isolated from tannery effluents, was resistant to chromate (0.5 mM) under both aerobic and anaerobic conditions. A stable biofilm was developed, using activated carbon as a support. Extracellular precipitate suggests that insoluble chromium hydroxide was formed. The strain showed an enhanced cell growth in an aerobic culture medium, although under anaerobic conditions chromate reduction was carried out more efficiently. About 95% of chromate was reduced in 4 days.     

Evaluation of the sustainable land use status of the North China Plain

The North China Plain is one of the most important production areas for wheat and maize in China, and also has the densest agricultural population in China. How to use and develop the limited land resources reasonably, and improve and protect them, have become issues of major concern. This paper is based on sustainability theory, reviewing the fundamental principles of sustainability, and developing an index system with which to evaluate the sustainability status of land use. We also use this method to evaluate the land-use status of the North China Plain and to analyze current factors affecting sustainable land use in this area. In addition, we propose a specific method for evaluating sustainable land use.     

Isotopic fractionation between seawater and the shell of <Emphasis Type="Italic">Scrobicularia plana</Emphasis> (Bivalvia) and its application for age validation

This study analyzed the isotopic profiles of four aragonitic shells of Scrobicularia plana in conjunction with measured seawater temperatures and salinities. Comparison of δ¹⁸O_SHELL with expected values revealed fractionation of δ¹⁸O in near equilibrium with the ambient environment. Growth cessation occurred between November and March. Carbonate deposition stopped when temperatures were <12°C. Analysis of δ¹³C_SHELL values suggested that carbon in the shell does not reflect the DIC in ambient water, likely due to the incorporation of metabolic carbon. An ontogenetic trend of increasing δ¹³C values over time was observed, likely related to changes in metabolic activity. Annual growth patterns were inferred from δ¹⁸O_SHELL profiles and compared with internal and external growth lines. Estimations of age based on external lines were unreliable, resulting in overestimation of age and underestimation of growth rates, likely due to the disturbance lines being wrongly identified as annual. Analysis of internal lines may lead to over- or underestimation of age and was more reliable in recent portions of the shell.     

Exploring community assembly through an individual-based model for trophic interactions

Traditionally, the dynamics of community assembly has been analyzed by means of deterministic models of differential equations. Despite the theoretical advances provided by such models, they are restricted to questions about community-wide features. The individual-based modeling offers an opportunity to link bionomic features to patterns at the community scale, allowing us to understand how trait-based assembly rules can arise by dynamical processes. The present paper introduces an individual-based model of community assembly, and discusses some of the major advantages and drawbacks of this approach. The model was framed to deal with predation among size-structured populations, incorporating allometric constraints to energetic requirements, movement, life-history features and interaction relationships among individuals. A protocol of assembly procedure is proposed, in which a period of intense species introductions is followed by a period without introductions. The resultant communities did not present any pattern of trait over-dispersion, meaning that the multivariate distances of bionomic features among co-occurring species were neither larger nor more regular than expected in a random collection of species. It suggests a weak influence of interspecific interactions in the model environment and individualistic rules of coexistence, driven mainly by the spatial structure. This highlights that trait over-dispersion and resource partitioning should not be considered a necessary condition for coexistence, even in communities entirely structured by internal processes like predation and competition.     

Prevalence-adjusted optimisation of fuzzy models for species distribution

Most performance criteria which have been applied to train ecological models focus on the accuracy of the model predictions. However, these criteria depend on the prevalence of the training set and often do not take into account ecological issues such as the distinction between omission and commission errors. Moreover, a previous study indicated that model training based on different performance criteria results in different optimised models. Therefore, model developers should train models based on different performance criteria and select the most appropriate model depending on the modelling objective. This paper presents a new approach to train fuzzy models based on an adjustable performance criterion, called the adjusted average deviation (aAD). This criterion was applied to develop a species distribution model for spawning grayling in the Aare River near Thun, Switzerland. To analyse the strengths and weaknesses of this approach, it was compared to model training based on other performance criteria. The results suggest that model training based on accuracy-based performance criteria may produce unrealistic models at extreme prevalences of the training set, whereas the aAD allows for the identification of more accurate and more reliable models. Moreover, the adjustable parameter in this criterion enables modellers to situate the optimised models in the search space and thus provides an indication of the ecological model relevance. Consequently, it may support modellers and river managers in the decision making process by improving model reliability and insight into the modelling process. Due to the universality and the flexibility of the approach, it could be applied to any other ecosystem or species, and may therefore be valuable to ecological modelling and ecosystem management in general.     

Environmental risk assessment of cobalt and manganese from industrial sources in an estuarine system

A total of 74 samples of soil, sediment, industrial sludge, and surface water were collected in a Mediterranean estuarine system in order to assess the potential ecological impact of elevated concentrations of Co and Mn associated with a Terephthalic (PTA) and Isophthalic (PIPA) acids production plant. Samples were analyzed for elemental composition (37 elements), pH, redox potential, organic carbon, and CaCO₃ content, and a group of 16 selected samples were additionally subjected to a Tessier sequential extraction. Co and Mn soil concentrations were significantly higher inside the industrial facility and around its perimeter than in background samples, and maximum dissolved Co and Mn concentrations were found in a creek near the plant’s discharge point, reaching values 17,700 and 156 times higher than their respective background concentrations. The ecological risk was evaluated as a function of Co and Mn fractionation and bioavailability which were controlled by the environmental conditions generated by the advance of seawater into the estuarine system during high tide. Co appeared to precipitate near the river mouth due to the pH increase produced by the influence of seawater intrusion, reaching hazardous concentrations in sediments. In terms of their bioavailability and the corresponding risk assessment code, both Co and Mn present sediment concentrations that result in medium to high ecological risk whereas water concentrations of both elements reach values that more than double their corresponding Secondary Acute Values.     

Characterisation of major component leaching and buffering capacity of RDF incineration and gasification bottom ash in relation to reuse or disposal scenarios

Thermal treatment of refuse derived fuel (RDF) in waste-to-energy (WtE) plants is considered a promising solution to reduce waste volumes for disposal, while improving material and energy recovery from waste. Incineration is commonly applied for the energetic valorisation of RDF, although RDF gasification has also gained acceptance in recent years. In this study we focused on the environmental properties of bottom ash (BA) from an RDF incineration (RDF-I, operating temperature 850-1000 °C) and a RDF gasification plant (RDF-G, operating temperature 1200-1400 °C), by evaluating the total composition, mineralogy, buffering capacity, leaching behaviour (both at the material’s own pH and as a function of pH) of both types of slag. In addition, buffering capacity results and pH-dependence leaching concentrations of major components obtained for both types of BA were analysed by geochemical modelling. Experimental results showed that the total content of major components for the two types of BA was fairly similar and possibly related to the characteristics of the RDF feedstock. However, significant differences in the contents of trace metals and salts were observed for the two BA samples as a result of the different operating conditions (i.e. temperature) adopted by the two RDF thermal treatment plants. Mineralogy analysis showed in fact that the RDF-I slag consisted of an assemblage of several crystalline phases while the RDF-G slag was mainly made up by amorphous glassy phases. The leached concentrations of major components (e.g. Ca, Si) at the natural pH of each type of slag did not reflect their total contents as a result of the partial solubility of the minerals in which these components were chemically bound. In addition, comparison of total contents with leached concentrations of minor elements (e.g. Pb, Cu) showed no obvious relationship for the two types of BA. According to the compliance leaching test results, the RDF-G BA would meet the limits of the Italian legislation for reuse and the European acceptance criteria for inert waste landfilling. RDF-I BA instead would meet the European acceptance criteria for non hazardous waste landfilling. A new geochemical modelling approach was followed in order to predict the leaching behaviour of major components and the pH buffering capacity of the two types of slags on the basis of independent mineralogical information obtained by XRD analysis and the bulk composition of the slag. It was found that the combined use of data regarding the mineralogical characterization and the buffering capacity of the slag material can provide an independent estimate of both the identity and the amount of minerals that contribute to the leaching process. This new modelling approach suggests that only a limited amount of the mineral phases that control the pH, buffering capacity and major component leaching from the solid samples is available for leaching, at least on the time scale of the applied standard leaching tests. As such, the presented approach can contribute to gain insights for the identification of the types and amounts of minerals that control the leaching properties and pH buffering capacity of solid residues such as RDF incineration and gasification bottom ash.