The effects of modifying the level of taxonomic resolution used in biological water quality assessments, and of accounting for exotic species' invasions, were studied for the case of the Belgian ...Biotic Index (BBI) method of water quality assessment. Most indices only require identification to the genus or family level, but this can bias the assessment scores toward certain stream types. Changes in taxonomic classification over time also can affect the assessment outcome if tolerant/sensitive taxa are involved. Addition of invasive species to index calculations also affects the outcome. For example, Corbicula is invading Belgian rivers and streams in increasing numbers, but the BBI does not define a tolerance class for Corbicula, so inconsistencies may arise in calculating the BBI. To eliminate such problems, a semi-fixed list of taxa is used that incorporates a tolerance class for each taxon.
This study aimed at analysing the relationship between river characteristics and abundance of Gammarus pulex. To this end, four methods which can identify the relative contribution and/or the ...contribution profile of the input variables in neural networks describing the habitat preferences of this species were compared: (i) the ‘PaD‘ (‘Partial Derivatives‘) method consists of a calculation of the partial derivatives of the output in relation to the input variables; (ii) the ‘Weights‘method is a computation using the connection weights of the backpropagation Artificial Neural Networks; (iii) the ‘Perturb‘method analyses the effect of a perturbation of the input variables on the output variable; (iv) the ‘Profile‘ method is a successive variation of one input variable while the others are kept constant at a fixed set of values. The dataset consisted of 179 samples, collected over a three-year period in the Zwalm river basin in Flanders, Belgium. Twenty-four environmental variables as well as the log-transformed abundance of Gammarus pulex were used in this study. The different contribution methods gave similar results concerning the order of importance of the input variables. Moreover, the stability of the methods was confirmed by gradually removing variables. Only in a limited number of cases a shift in the relative importance of the remaining input variables could be observed. Nevertheless, differences in sensitivity and stability of the methods were detected, probably as a result of the different calculation procedures. In this respect, the ‘PaD‘method made a more severe discrimination between minor and major contributing environmental variables in comparison to the ‘Weights‘, ‘Profile‘ and ‘Perturb‘ methods. From an ecological point of view, the input variables ‘Ammonium‘ and to a smaller extent ‘COD‘, were selected by these methods as dominant river characteristics for the prediction of the abundance of Gammarus pulex in this study area.
tIn this study, we assessed the relationship between the occurrence of the invasive water hyacinth (Eichhornia crassipes) and water quality properties as well as macroinvertebrate diversity in a ...tropical reservoir, situated in western Ecuador. Macroinvertebrates and physico-chemical water quality variables were sampled at 32 locations (during the dry season of 2013) in both sites covered and non-covered by water hyacinth in the Daule-Peripa reservoir. The results indicated that, in terms of water quality, only turbidity was significantly different between sampling sites with and without water hyacinth (Mann-Whitney U-test, p < 0.01). The habitat suitability model showed that water hyacinth was present at sites with alow turbidity. The percentage water hyacinth cover increased with decreasing turbidity. The Biological Monitoring Working Party-Colombia score and the Margalef diversity index were significantly higher(Mann-Whitney U-test, p < 0.01) at sampling sites where water hyacinth was present compared to water hyacinth absent sites. However, there were no significant differences in the Shannon-Wiener index, Evenness index and Simpson index between the sampling sites with and without water hyacinth. Our results suggest that water hyacinth cover was an important variable affecting the diversity of macroinver-tebrates in the Daule-Peripa reservoir, with intermediate levels of water hyacinth cover having a positive effect on the diversity of macroinvertebrates. Information on the habitat suitability of water hyacinth and its effect on the physico-chemical water quality and the macroinvertebrate community are essential to develop conservation and management programs for large tropical reservoirs such as the Daule-Peripa reservoir and the Guayas river basin, where water resources are being at high risk due to expansion of agricultural and industrial development activities.
Macroinvertebrates were sampled from summer 2006 until spring 2008 in the Du River basin in subtropical northern Vietnam. Seventy taxa were identified, which were dominated by aquatic insects, with ...Diptera, Hemiptera, Ephemeroptera, and Odonata being the orders with the highest diversities. Overall, macroinvertebrate diversity was higher during the wet season at upstream sites, while wide river sites downstream showed a higher diversity during the dry season. Spatial and temporal variations in the macroinvertebrate communities were driven by hydromorphological characteristics and especially by water quality issues reflecting anthropogenic impacts in the river basin. Multivariate analyses using canonical correspondence analysis discriminated between pristine and impacted sites. The caddisfly family Hydropsychidae, the mayfly family Caenidae, and the dobsonfly family Corydalidae were reliable indicators of sites with good ecological status. A relatively small temporal variation was detected in the macroinvertebrate community composition.
Based on a literature survey and the identifi cation of all available collection material from Flanders, a checklist is presented, distribution maps are plotted and the relationship between the ...occurrence of the different species and water characteristics is analysed. Of the sixteen stonefly species that have been recorded, three are now extinct in Flanders (Isogenus nubecula, Taeniopteryx nebulosa and T. schoenemundi), while the remaining species are rare. The occurrence of stoneflies is almost restricted to small brooks, while observations in larger watercourses are almost lacking. Although a few records may indicate that some larger watercourses have recently been recolonised, these observations consisted of single specimens and might be due to drift. Most stonefly population are strongly isolated and therefore extremely vulnerable. Small brooks in the Campine region (northeast Flanders), which are characterised by a lower pH and a lower conductivity, contained a different stonefly community than the small brooks in the rest of Flanders. Leuctra pseudosignifera, Nemoura marginata and Protonemura intricata are mainly found in small brooks in the loamy region, Amphinemura standfussi, Isoperla grammatica, Leuctra fusca, L. hippopus, N. avicularis and P. meyeri mainly occur in small Campine brooks, while L. nigra, N. cinerea and Nemurella pictetii can be found in both types. Nemoura dubitans can typically be found in stagnant water fed with freatic water. Sustainable populations of these stonefly species can only be achieved when their present habitats are adequately protected and in addition, measures should be taken to connect and enlarge the remaining populations.
During the summer of 1999, two automated water quality measurement stations were installed along the Dender river in Belgium. The variables dissolved oxygen, temperature, conductivity, pH, ...rain-intensity, flow and solar radiation were measured continuously. In this paper these on-line measurement series are presented and interpreted using also additional measurements and ecological expert-knowledge. The purpose was to demonstrate the variability in time and space of the aquatic processes and the consequences of conducting and interpreting discrete measurements for river quality assessment and management. The large fluctuations of the data illustrated the importance of continuous measurements for the complete description and modelling of the biological processes in the river.
The European Water Framework Directive prescribes that the development of a river assessment system should be based on an ecological typology taking the biological reference conditions of each river ...type as a starting point. Aside from this assessment, water managers responsible for river restoration actions also need to know the steering environmental factors to meet these reference conditions for biological communities in each ecological river type. As such, an ecological typology based on biological communities is a necessity for efficient river management. In this study, different clustering techniques including the Sørensen similarity ratio, ordination analysis and self-organizing maps were applied to come to an ecological classification of a river. For this purpose, a series of sites within the Zwalm river basin (Flanders, Belgium) were monitored. These river sites were then characterized in terms of biotic (macroinvertebrates), physical–chemical and habitat variables. The cluster analysis resulted in a series of characteristic biotic communities that are found under certain environmental conditions, natural as well as human-influenced. The use of multiple clustering techniques can be of advantage to draw more straightforward and robust conclusions with regard to the ecological classification of river sites. The application of the clustering techniques on the Zwalm river basin, allowed for distinguishing five mutually isolated clusters, characterized by their natural typology and their pollution status. On the basis of this study, one may conclude that river management could benefit from the use of clustering methods for the interpretation of large quantities of data. Furthermore, the clustering results might enable the development of a cenotypology useful for efficiently steering river restoration and enabling river managers to meet a good ecological status in most of the rivers as set by the European Water Framework Directive.
Integrated ecological models are of great potential as predictive tools in decision support of river management. Such models need to be transparent and consistent with the existing expert knowledge, ...and give the river manager adequate information regarding their inherent uncertainty. One way to fulfil these needs is through the use of Bayesian Belief Networks (BBNs). Such networks represent cause-and-effect assumptions between system variables in a graphical structure. To establish the potential of Bayesian Belief Networks in river management, a small-scale study was performed with the aim of assessing the success of prediction of macroinvertebrate taxa in rivers by means of a selected number of environmental variables. Gammaridae and Asellidae were chosen because of their high relative abundances in small and large brooks in contrast to other macroinvertebrate taxa. Based on one-layered BBN networks, the predictive capacity of the models was assessed by means of the number of Correctly Classified Instances (CCI) and Cohen’s Kappa (K). The performance of these models was moderate to good for presence/absence classifications but showed a low to moderate performance when predicting abundance classes. When extending the former BBN network to a two-layered one, enhancing the number of links and variables, no obvious improvement in model performance was detected. The results indicate that thoughtful input variable selection as well as sensitivity analysis will improve the models for practical use in river restoration management.
Modelling has become an interesting tool to support decision making in water management. River ecosystem modelling methods have improved substantially during recent years. New concepts, such as ...artificial neural networks, fuzzy logic, evolutionary algorithms, chaos and fractals, cellular automata, etc., are being more commonly used to analyse ecosystem databases and to make predictions for river management purposes. In this context, artificial neural networks were applied to predict macroinvertebrate communities in the Zwalm River basin (Flanders, Belgium). Structural characteristics (meandering, substrate type, flow velocity) and physical and chemical variables (dissolved oxygen, pH) were used as predictive variables to predict the presence or absence of macroinvertebrate taxa in the headwaters and brooks of the Zwalm River basin. Special interest was paid to the frequency of occurrence of the taxa as well as the selection of the predictors and variables to be predicted on the prediction reliability of the developed models. Sensitivity analyses allowed us to study the impact of the predictive variables on the prediction of presence or absence of macroinvertebrate taxa and to define which variables are the most influential in determining the neural network outputs.
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