Macrophytes were studied downstream of the Roph&#xE9;mel hydroelectric dam on the River Rance (C&#xF4;tes d&#x2019;Armor Department, western France) to assess the effects of hydroelectric functioning on river macrophyte communities. We studied ten representative sections of the hydro-peaking channel on five occasions in 1995 and 1996, on a 15-km stretch of river. Floristic surveys were carried out on sections 50 m in length, and genera of macroalgae, species of bryophyta, hydrophytes, and emergent rhizophytes were identified. For the aquatic bryophytes and spermatophytes section of our study, we compared our results with 19th century floristic surveys, before the dam was built. During the vegetative growth period, the hydro-peaking frequency was low. The plant richness was highest near the dam. The macrophyte communities were highly modified according to the distance to the dam. The frequency and magnitude of hydro-peaking was related to the aquatic macrophyte richness in an Intermediate Disturbance Hypothesis position. However, the results of the eco-historical comparison with 19th century floristic surveys point to the original nature of the flora found at the site. Some floral patterns, seen during both periods and at an interval of 133 years, were indicative of the ubiquity of the aquatic flora and of the plants&#x2019; adaptability. This demonstrates the importance of taking river basin history into account in such biological surveys.

Ivan Bernez

Jacques Haury

Maria Teresa Ferreira

Downstream Effects of a Hydroelectric Reservoir on Aquatic Plant Assemblages

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.

Andy P. Dedecker

Peter L.M. Goethals

Niels De Pauw

Comparison of Artificial Neural Network (ANN) Model Development Methods for Prediction of Macroinvertebrate Communities in the Zwalm River Basin in Flanders, Belgium

The Dender basin in Flanders (Belgium) was used as a case study to implement the European Union (EU) Water Framework Directive. During the last 5 years, ample research on pollution loads and ecological water quality has been done on the Dender River. In addition to biological sampling of macroinvertebrates and fish, automated measurement stations were also used to investigate the spatial-temporal variability of the physical-chemical water quality. This research revealed that the pollution of the Dender River is highly variable. The high nutrient loads result in severe algae blooms during summer, leading to very complex diurnal processes. In this paper, the monitoring strategy for the assessment of the biological water quality in the Dender basin has been reviewed in relation to the EU Water Framework Directive. For this, seasonal macroinvertebrate data were collected and assessed. General trends and hidden structures in these data were analysed by means of classification trees, using different inputs (seasons, river types, and subbasins). Validation of the results was obtained by applying statistical methods. Analysis about the presence and abundance of the macroinvertebrates revealed that there is a distinct difference between the biological water quality in the Dender stem river and its tributaries. There are also seasonal differences between the macroinvertebrate communities when the Dender and its tributaries are examined separately. An optimised monitoring strategy is proposed based on these results and the EU Water Framework Directive. This includes two monitoring campaigns in summer and winter every 3 years. Furthermore, a cyclic monitoring scheme was developed to minimise sampling efforts.

Tom P. D&#x2019;heygere

Optimisation of the Monitoring Strategy of Macroinvertebrate Communities in the River Dender, in Relation to the EU Water Framework Directive

I
n order to evaluate the impact of pollution and sewage on the occurrence and
antibiotic resistance of mesophilic aeromonads in riverine freshwaters of
Marrakech, samples were collected from three rivers (Oukaimeden, Ourika, and
Tensift) upstream and downstream from the principal bordering villages. During a
2-year study, indicators of pollution increased dramatically in the downstream
waters. Bacterial indicators (faecal coliforms and faecal streptococci) correlated
with mesophilic aeromonads only in heavily polluted waters. In low and moderately
polluted sources, densities of mesophilic aeromonads were independent of
water quality indicators and did not correlate statistically with faecal indicators.
Average counts of Aeromonas in low and heavily polluted waters were 2.5 × 103
and 2.1 × 106 colony forming units per 100 ml, respectively. The biochemical
identification of 841 isolates indicated a predominance of A. caviae in heavily and
moderately polluted water and sediment. A. hydrophila was dominant only in low
polluted waters and when the temperature was below 12°C. High densities of A.
sobria were found in low, moderately polluted, or cleaned waters and when the
water temperature was above 18°C. All selected isolates (total = 841) were tested
for antibiotic susceptibility against 21 antibiotics. Antibiotic resistance frequencies
recorded were: ampicillin and amoxicillin, 100%; novobiocin, 96%; cefalotin,
81%; colistin, 72%; sulfamethoxazole, 40%; cefamandole, 37%; polymyxin B, 23%;
trimethoprim, 17%; erythromycin, 15%; streptomycin, 8%; amoxicillin-clavulanate,
5%. Resistance to cefotaxime, kanamycin, gentamycin, chloramphenicol,
tetracycline, oxytetracycline, nalidixic acid, rifampicin, or trimethoprim-sulfamethoxazole
was found to be &#x3C;5%. Antibiotic resistance rates did vary according to the
source of a strain’s isolation, and high numbers of antibiotic resistant strains
were recorded in polluted samples. Since no correlation between mesophilic
aeromonads and conventional faecal pollution indicators was observed in low or
moderately polluted waters, and since these freshwaters are used for domestic
supply, we propose the use of mesophilic aeromonads as complementary water
pollution indicators to ensure the safety of water.

Boujamaa Imziln

Occurrence and Antibiotic Resistance of Mesophilic Aeromonas in Three Riverine Freshwaters of Marrakech, Morocco

Relationships between land-use and river water quality assessed by means of biological and physical-chemical variables and habitat characteristics were analysed for the Zwalm River basin in Flanders (Belgium). The research focussed on three zones within this river basin, each characterized by different land uses, and consequently, different types of pollution, mainly of diffuse origin. Environmental data have been integrated within a Geographic Information System. Possible relationships between aquatic ecosystem and land-use variables were searched for by means of multivariate analysis.

Veronique Adriaenssens

Peter L. M. Goethals

Assessment of Land-Use Impact on Macroinvertebrate Communities in the Zwalm River Basin (Flanders, Belgium) Using Multivariate Analysis and Geographic Information Systems

A model of analysis and environmental evaluation was applied to 11 stretches of the Adige River, where an innovative procedure was carried out to interpret ecological results. Within each stretch, the most suitable methods were used to assess the quality and processes of flood plains, banks, water column, bed, and interstitial environment. Indices were applied to evaluate the wild state and ecological quality of the banks (wild state index, buffer strip index) and the landscape quality of wide areas of the fluvial corridor (environmental landscape index). The biotic components (i.e., macrozoobenthos, phytoplankton and zooplankton, interstitial hyporheic fauna, vegetation in the riparian areas) were analysed by both quantitative and functional methods (as productivity, litter &#x2013; processing and colonisation). The results achieved were then translated into five classes of functional evaluation. These qualitative assessments have thus preserved a high level of precision and sensitivity in quantifying both the quality of the environmental conditions and the integrity of the ecosystem processes. Read together with urban planning data, they indicate what actions are needed to restore and rehabilitate the Adige River corridor.

M.G. Braioni

G. Salmoiraghi

F. Bracco

M. Villani

A. Braioni

L. Girelli

Functional Evaluations in the Monitoring of the River Ecosystem Processes: The Adige River as a Case Stu

This paper presents an overview of the application of models on aquatic ecosystems. More than 17% of the models published in the focal journal in the field, Ecological Modelling, are aquatic ecosystem models. An increasing number of papers are dealing with the theoretical aspects of modeling &#x2013; new modeling approaches and techniques, how models can be used to reveal ecosystem properties, and how models can better reflect the properties of ecosystems. This development implies that today we have more types of models. The characteristics, the advantages, and the disadvantages of these model types are presented briefly. The selection criteria for the presented model types are discussed, and the application of these types to models for aquatic ecosystems is reviewed. A recent improvement in model calibration of particular interest for aquatic ecosystems is presented, and the perspectives resulting from this new calibration procedure and from possible hybrids of the presented model types are discussed.

S.E. Jorgensen

Recent Trends in the Development of Ecological Models Applied on Aquatic Ecosystems

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