Le peuplement des Crustacés du sous-écoulement du ruisseau de Lachein (Pyrénées) a été étudié sur un site de 75 m2 et à une profondeur de 0,60 m.Les écoulements de surface déterminent quatre zones principales, deux bancs de graviers, un chenal et une zone d'eau morte. La porosité (20 à 30 %), plus élevée dans les bancs de graviers que dans le chenal, est également plus forte à l'amont des bancs qu'à l'aval. La granulométrie diffère selon les zones, les bancs de graviers étant caractérisés par une plus forte abondance des éléments mesurant 1 à 8 mm. Les caractéristiques chimiques du sous-écoulement, toujours proches de celles du cours subaérien, évoluent de façon identique à ces dernières au cours des saisons. Les valeurs de l'O2 dissous, proches de la saturation en surface, sont comprises entre 0,02 % et 84,7 % dans le sous-écoulement où leur distribution dépend très directement de la dynamique des écoulements de surface. Les teneurs en matière organique particulaire, comprises entre 4 et 13,6 %, subissent une évolution saisonnière. Les valeurs moyennes les plus basses caractérisent le chenal.Les Crustacés, représentés par 50 espèces et sous-espèces. dont 22 taxons stygobies, montrent une forte similitude faunistique avec ceux colonisant le système karstique du Baget dont le ruisseau de Lachein est issu. Ils sont caractérisés par une organisation stable dans le temps, dominée par les Copépodes et, notamment, par les Harpacticides qui constituent 60 % du peuplement. Leur densité moyenne est de 369 individus/10 l. La répartition spatiale des Malacostracés comme des Harpacticides est très variable, avec des espèces eurytopes (formes épigées) et sténotopes (formes hypogées) ; parmi ces dernières, les unes sont inféodées aux zones les plus oxygénées, d'autres au contraire, sont limitées aux zones les moins oxygénées. Chez les Harpacticides, les densités comme les pourcentages des formes hypogées sont très directement liés aux différentes zones définies par les écoulements de surface.

The spatial and temporal distribution patterns of benthic macroinvertebrates were studied in an intermittent river in Algeria (Chelif wadi, North Africa), by using the self-organizing map (SOM), an unsupervised artificial neural network. The samples were collected monthly at 8 sampling sites (630 to 20 m above sea level) and community variation was analysed in space and time. Overall, the study sites showed a very poor macroinvertebrate fauna: more than 60% of samples contained less than 11 species, and 99% had less than 30 species. Furthermore, most species displayed very low abundance: 66% of the species were represented by less than 20 individuals (abundance). Among the identified taxa, Chironomidae was the dominant taxon at all sampling sites except at the most upstream site (630 m a.s.l.) where it was replaced by Coleoptera. Concerning monthly changes, the species richness was very low in August and October. Through the learning process of the SOM, samples were classified into four clusters by the SOM, and the classification was mainly related to the location of the sampling sites. Benthic macroinvertebrates were divided into four classes, which revealed the influence of pollution on their longitudinal distribution in this stream. According to the distribution gradients of the environmental variables on the SOM map, their influence on the classification of the sampling sites could be assessed effectively.

Diatoms are good environmental indicators and are often the main component of phytobenthos, one of the key groups of organismsrecommended by the Water Framework Directive (W.F.D.) for the assessment of ecological status of surface waters.Although diatoms are regularly used as indicators in rivers and in lakes, less is known about the benthic diatom communities inwetland systems, especially in Italy. The main aim of the project was to provide a contribution to the knowledge on distribution,composition and structure of benthic diatom communities in wetland systems in Italy. In 2005, we investigated the benthic diatomcommunities and their relationships to water variables of nine ponds and wetlands along the Tyrrhenian coast near Rome.Furthermore, a first application of seven European diatom-based indices on this type of water body was undertaken. A total of225 species and varieties belonging to 54 genera were identified. The Canonical Correspondence Analysis indicated that certainspecies were closely associated with each wetland type and their distribution mainly depended on nutrient and chloride contents:pollution tolerant species (i. e. Luticola goeppertiana, Mayamaea atomus, Navicula subminuscula) in the wetlands connected toriver mouths, halophilous species and also marine littoral species (i. e. Nitzschia elegantula, Amphora coffeaeformis, Achnanthesbrevipes var. intermedia, Epithemia adnata var. porcellus) in the coastal brackish ponds and wetlands, and less eutrophic species(i. e. Achnanthidium minutissimum, A. biasolettianum) in the lowland freshwater wetland. In general, the indices classifiedmost of the studied water bodies as bad, poor and moderate status; few sites were classified into a good class, even for at leastin one sampling occasion. Eutrophication and Pollution Index (EPI-D), Trophic Diatom Index (TDI), Taxa Pollution Tolerant(%PT), Pollution Sensitivity Index (IPS) and Generic Diatom Index (IDG) were significantly correlated to nutrient contents inthe studied wetlands. Our preliminary data set illustrated the potential of the use of these benthic algae as bioindicators in wetlands.

Shredders play a major ecological role in temperate streams, but their numerical importance is highly variable within the tropics. Detailed studies on the diets of tropical stream invertebrates are advisable to be able to better describe and understand this variation. Here, we examined the diets of invertebrates collected from the leaf litter of three tropical streams in Colombia, using gut content analysis. Fine and coarse particulate organic matter were the main food resources for invertebrates, which could be divided into four main dietary groups: predators, shredders, specialist collectors and generalist collectors. While the specialist collectors were the most numerically abundant group (54%), shredder biomass accounted for 63% of total invertebrate biomass, suggesting that shredders play a significant ecological role in the study streams. We describe the diets of 12 out of 47 taxa that were previously unknown, which indicates that knowledge about the feeding ecology of tropical stream invertebrates is still incipient.

This study evaluated the status of the Asian clam Corbicula fluminea (Müller, 1774) in the River Lima estuary (Portugal),which it first invaded in 2002. During the summers of 2004 and 2005, spatial and temporal variations in the abundance, biomassand population structure of C. fluminea were investigated in this estuary. This species was present in a limited intertidal area ofthe estuary and was rarely found in the subtidal zone. Its abundance and biomass were considerably lower than those found inother estuarine systems. Based on these studies it appears that salinity fluctuations and possibly other factors such as nutrientsand environmental contaminants are keeping this invasive species from reaching its full potential. Given the lower abundanceand biomass recorded and the restrict distribution of the species in this estuary, the eradication of this nonindigenous invasivespecies is still possible. The findings of this study may be useful for the management of this species not only in the River Limaestuary but also in other locations it may invade.

La mise au point d'une technique originale nous a permis d'obtenir un électrocardiogramme (E.C.G.), chez les poissons évoluant "librement" dans leur milieu. Semblable à celui des autres vertébrés (ondes pentaphasiques), l'E.C.G. des poissons est surtout caractérisé, à l'image du métabolisme myocardique, par la durée de l'onde T. La fréquence cardiaque est généralement marquée par une arythmie d'origine vagale. En effet, la structure simple et l'innervation uniquement parasympathique du coeur, chez les poissons, se prêtent tout particulièrement aux recherches sur l'influence vagale. Nous avons pu ainsi effectuer l'étude de deux réflexes cardiaques importants. D'une part, un mécanisme vago-humoral a été mis en évidence dans le " réflexe d'approche ", ce qui nous a permis de confirmer, par des injections intra-cardiaques, le rôle chronotrope négatif de l'adrénaline sur le coeur des téléostéens mis en expériences. D'autre part, une augmentation de la pression sanguine au niveau du sinus, a provoqué une tachycardie caractéristique du réflexe " baro-sinusal ", antagoniste d'une inhibition cardiaque d'origine vagale.

Ainsi, la connaissance et l'étude de ces réflexes, nous ont permis de confirmer l'existence d'une évolution neuro-humorale de la régulation cardiaque, qui s'effectuerait parallèlement à une évolution anatomique et cytophysiologique du coeur, depuis les cyclostomes jusqu'aux mammifères.

L'obtention d'un E.C.G. net et stable dans le temps, nous a servi de référence biologique, au cours de l'étude des variations de quelques facteurs écologiques importants. Pour cela, nous avons essayé de mettre en évidence les effets de la lumière, de la salinité, de la température, de l'oxygénation et de la pression du milieu extérieur, sur la fréquence cardiaque des poissons.

Les poissons se montrent très sensibles à un vif éclairement, parce qu'ils sont généralement lucifuges. En particulier, des stimulations lumineuses au niveau des globes oculaires, provoquent un réflexe d'inhibition cardio-respiratoire. Ce réflexe, d'origine vagale, est particulièrement intense chez les soles et les flets. Cependant, ces pleuronectes sont plus sensibles aux stimulations visuelles mobiles (réflexe d'approche) qu'aux stimulations visuelles fixes (lumière).

La salinité, autre facteur important du milieu, joue un rôle primordial dans les phénomènes d'osmorégulation. Si les anguilles (euryhalines) s'adaptent bien aux brusques variations de salinité du milieu, leur fréquence cardiaque restant relativement stable, nous avons constaté, au contraire, une importante tachycardie chez les muges (mésohalins), ainsi que chez les grisets (sténohalins). Cette tachycardie, provoquée surtout par une pléthore sanguine (troubles de l'osmorégulation), nous a amené à soupçonner l'existence du réflexe " baro-sinusal ". Cependant, les variations rapides de la salinité du milieu, déterminent aussi une anoxie, dont les effets viennent accentuer les réactions cardiaques et respiratoires des poissons sténohalins.

Aussi, ne faut-il pas s'étonner du rôle primordial joué dans l'écologie piscicole, par l'oxygène dissous dans le milieu. Nous avons analysé les modalités des réponses cardiaques, chez trois espèces de téléostéens soumis à différents degrés d'anoxie. Nous avons montré que la bradycardie anoxique, d'origine surtout vagale chez les poissons adaptés à des milieux pauvres en oxygène (carpes), est à prédominance métabolique chez des sujets plus exigeants (barbeaux). Les phénomènes déterminés par l'ensablement chez la sole, sont un exemple d'anoxie éthologique rappelant le cas des vertébrés aériens plongeurs.

Parmi les poïkilothermes, les poissons paraissent avoir le mode d'existence le plus étroitement lié à la température de leur biotope. Chez la carpe, l'étude des variations thermiques lentes du milieu, bien plus que celle de ses variations rapides, nous montre l'existence d'une zone critique aux environs de 10°C. Au-dessous de cette température, la sensibilité du poisson est fortement diminuée (état semi-léthargique), alors qu'au-dessus le poisson réagit bien. Il est fondamental de constater que, chez la plupart des téléostéens dulçaquicoles, ce ne sont pas les variations thermiques en valeur absolue qui sont les plus importantes, mais surtout la place de ces variations par rapport à la zone de leur température critique. Le système parasympathique cardiaque ne semble efficace que pour des adaptations thermiques lentes.

Enfin, si les variations thermiques interviennent dans le cas des eaux superficielles, un facteur semble dominer tous les autres, dans les eaux profondes : la pression. Il ressort de nos expériences, que la carpe et la perche sont très sensibles aux fortes variations de la pression. Ces poissons répondent par une tachycardie, dont l'importance est proportionnelle à la pression exercée, jusqu'à un maximum de 30 atmosphères (300 m de profondeur). Chez la carpe (physostome), une adaptation vagale se produit peu de temps après la réaction à la pression, alors que chez la perche (physocliste) un tel phénomène adaptatif n'apparaît pas, du moins dans les délais impartis à notre expérimentation.

Les poissons cystectomisés ou vagotomisés, ne présentent plus de réactions cardiaques à l'augmentation de la pression. Le relâchement de l'inhibition vagale cardiaque qui se manifeste chez les poissons intacts, peut donc être vraisemblablement assimilé à une baronarcose localisée au niveau des terminaisons nerveuses du parasympathique, dans les parois de la vessie natatoire. Au contraire, les faibles dépressions agissent sur les carpes comme un excitant du système nerveux vagal cardiaque, cette réaction bradycardique n'apparaissant pas chez les sujets vagotomisés.

Les corrélations entre les centres cardiaques et les centres respiratoires, chez les poissons, montrent qu'il existe entre eux une relative indépendance.

Nos expériences viennent ainsi confirmer l'existence d'un tonus vagal permanent chez les poissons. Cette vagotonicité semble jouer un rôle important dans les adaptations aux variations lentes des différents facteurs du biotope. Les variations rapides sont assez mal supportées chez ces vertébrés. Le plus souvent, les facteurs du milieu aquatique évoluent en effet de façon relativement lente. Il en est tout autrement dans le milieu aérien, du moins en ce qui concerne la température, qui reste l'un des principaux facteurs intéressant les poïkilothermes terrestres. Aussi, pour effectuer ce grand pas évolutif qu'est le passage du milieu aquatique au milieu aérien, on peut penser que les vertébrés ont dû attendre la différenciation d'un système antagoniste du parasympathique cardiaque. L'innervation sympathique, par son mécanisme plus souple, a pu permettre des adaptations circulatoires plus rapides, indispensables à la vie terrestre.

A simple procedure is described in order to estimate the biodegradable fraction of dissolved organic carbon (DOC), particulate organic carbon (POC) and total organic carbon (TOC) in water samples. Methodological improvements of the method which includes aerobic incubation in batch and carbon measurements are presented. First applications to natural and waste water samples show the usefulness of the method in the field of water treatment and management of surface water.

Les durées de développement embryonnaire (De), post-embryonnaire (Dp) et le temps de génération (Tg) sont déterminées à différentes températures (de 10 à 23° C) chez 12 espèces de Rotifères planctoniques ou périphytes : Asplanchna brightwelli, Brachionus calyciflorus, Epiphanes brachionus, Euchlanis dilatata, Keratella quadrata, K. valga, Notholca acuminata, Notommata collaris, N. copeus, Polyarthra dolichoptera, Synchaeta pectinata et Conochiloides natans.

Taux de développement et température sont le plus souvent liés par une relation linéaire (1/D — aθ + b). Les valeurs des constantes a et b dépendent de l'adaptation des espèces, voire des races, à la température dans leur milieu. L'étude est complétée par quelques remarques sur le rapport Dp/De (approximativement constant), le Q10 et les facteurs de conversion.

Aquatic plants play a substantial role in almost all freshwater habitats throughout the world. Even though submerged aquatic plants dominantly spread by the dispersal of vegetative plant fragments, most aquatic plant species show a broad distribution range. Here we studied the differences in the regeneration capacity and the regeneration type of fragments (by root and/or shoot growth) of eight submerged plant species (Ceratophyllum demersum, Egeria najas, Elodea canadensis, Elodea nuttallii, Hydrilla verticillata, Myriophyllum aquaticum, Myriophyllum heterophyllum and Myriophyllum spicatum) under different water nutrients in sediment-free conditions. Overall, M. spicatum showed the highest regeneration (82±2%) in this study, followed by C. demersum (73±2%) and M. aquaticum (47±4%), whereas M. heterophyllum showed the lowest (1±1%). The shoot fragments of E. canadensis, H. verticillata, E. najas and E. nuttallii regenerated by 40±2, 23±2, 16±2 and 7±1%. The nitrate concentration affected the regeneration capacities of E. najas (P=0.05), M. spicatum (P=0.013) and C. demersum (P=0.001), whereas phosphate had no significant effect. Additionally, the different nutrient concentrations had a significant effect on the portion of the regeneration types within E. canadensis, E. nuttallii and H. verticillata. Summarizing, submerged plants differ significantly in their regeneration capacity, and water nutrients have a potential effect on the regeneration of submerged plant fragments. This might influence the further colonization and spread of the species under field conditions.

In order to determine the influence of lentic habitats and macrophyte stands on the plankton development and seston flux, an investigation of zooplankton was carried out in the karst Jankovac flow-through system (Papuk Nature Park, Croatia). The system was characterized by low abundance (1–116 ind.L−1) and high diversity of identified zooplankton. Eighty-six taxa were recorded, comprising 57 rotifers, 15 cladocerans, 8 copepods and 6 members of other groups of organisms. The spatial oscillations of environmental parameters and biocoenosis assemblage revealed statistically significant differences between lotic and lentic habitats, as well as between vegetated and non-vegetated stations. These differences mainly respond to higher concentration of food resources and zooplankton/zooseston abundance and biomass in lentic, especially vegetated, habitats. This is also proved by results of principal component analysis (PCA), which suggested that the main drivers of development of the planktonic community were the food resources and the avoidance of flow velocity. Accordingly, shoreline areas with submerged macrophyte stands of Hippuris vulgaris L. were the most productive parts, represented by highest zooplankton abundance, biomass and biodiversity. Flow velocity significantly affected crustaceans assemblage, so that higher abundances of the larger cladocerans and copepods were achieved in vegetated stations with low flow velocity, while rotifers showed to be rheotolerance organisms. On the other hand, the longitudinal discontinuum of the stream channel by two man-made reservoirs could offer new habitats to enrich seston with organic particles and bioseston. The results of our study pronounce the need for further monitoring of this hydrosystem, especially considering biodiversity and microhabitats conservation.

Anthropogenic land use within watersheds has substantial effects on aquatic habitats and biological communities. From September 2006 to December 2008, we investigated the effects of land use on benthic macroinvertebrate communities by comparing Song Stream and Odae Stream, two adjacent mountain streams in Korea whose watersheds have different land use patterns. Song Stream is significantly disturbed by agricultural activities in the watershed, whereas Odae Stream is relatively undisturbed and is surrounded by a well-conserved forest area. Song Stream had significantly higher levels of all nutrients and sediment-related factors due to the adjacent agricultural area. As a result, Song Stream had markedly lower species community indices, such as taxa richness and abundance. In Song Stream, macroinvertebrate scrapers and predators were most adversely affected, whereas collector-gatherers became a dominant group. Based on correlation and multivariate analyses, total dissolved solids had the strongest negative relationship with macroinvertebrate assemblages, followed by electrical conductivity, total nitrogen, and pH. The proportion of cobble in stream substrate was positively related to the richness and abundance of macroinvertebrates. Our results indicate that disturbances caused by agricultural land use, particularly sand deposition, had significant adverse effects on macroinvertebrate habitats and on the biotic integrity of benthic macroinvertebrate communities.

We characterized the responses of benthic macroinvertebrates to heavy metals released from mines in high mountain streams of the Gangqu River in the Shangrila Gorge, China. Benthic macroinvertebrates were collected with a kick-net at 32 sampling sites. In addition, 25 environmental variables including heavy metal concentrations were measured at each sampling site. Although the concentrations of heavy metals were not seriously high, their effects were reflected in the changes of community composition of benthic macroinvertebrates. Total abundance and species richness decreased with increasing heavy metal concentrations. Species richness of Plecoptera and Trichoptera, Margalef richness index, and percentage of scrapers in functional feeding groups were negatively correlated with heavy metal concentrations. A high variation was observed in the response of different taxa to heavy metals. Heavy metals mainly affected the sensitive taxa of Plecoptera, Ephemeroptera, and Trichoptera. However, some tolerant taxa were observed in Trichoptera (such as Hydropsyche sp.) and Dugesia sp. Cluster analysis and a non-metric multidimensional scaling analysis were applied to characterize specific macroinvertebrate taxa composition. The analyses revealed the effects of different environmental factors such as geographical, hydromorphological, physical, and chemical factors including heavy metals on the distribution of benthic macroinvertebrates in high mountain streams. Although the effects were compounded with different factors such as altitude, temperature, stream width, turbidity, and heavy metals, the influence of heavy metals on benthic macroinvertebrate communities was clearly identified (decreased species richness, changes in species composition). Even though the contamination of heavy metals was low in the sampling area, the consequences were clear, indicating that long-term exposure to heavy metals could seriously impact aquatic communities in high mountain streams.

The impact of Elodea canadensis on aquatic macrophyte biodiversity in (Lake) Steinsfjord has been studied through extensive lake-wide surveys and photographic sampling. E. canadensis greatly expanded in Steinsfjord since its appearance in 1978 and still dominated the macrophyte community in 2004. The areal distribution of E. canadensis peaked within 6 years from invasion and has remained relatively stable since; however, stands no longer reach the water surface. E. canadensis significantly increased its depth range, but the cover-weighted mean depth remained unchanged, suggesting that 3–4 m is its optimal depth in Steinsfjord. Species richness has not changed significantly since the earliest survey in 1936–38. However, species composition has changed remarkably, from isoetid dominance in 1936–38 to a diverse community dominated by Najas flexilis in 1979–80 to a less diverse community dominated by E. canadensis in 2004, with Potamogeton berchtoldii and Myriophyllum alterniflorum as lake-wide subdominants. Regardless of their abundance at the onset of the E. canadensis invasion, taxa whose cover-weighted mean depth overlapped with E. canadensis's in 1979–80 greatly reduced their abundance in 2004, shifted to deeper or shallow water or disappeared from sampling stations. Our survey indicates that E. canadensis may be the reason for the decrease of N. flexilis, likely through depletion of CO2 in the water column and reduced nutrients in sediments. The abilities to survive and grow in periodically exposed shallow areas, combined with minor herbivory by waterfowl, are likely important factors for the increase of M. alterniflorum in Steinsfjord's shallow waters.

Temporal and spatial variation in the concentrations of intra- and extra-cellular microcystins were studied in a hypertrophiclake with bloom of Planktothrix agardhii (Gomont) Anagnostidis et Komarek. Concomitantly with increase in watertemperature (from 2 to 20 °C) abundance of P. agardhii increased from 1.9 x 105 to 4.3 x 107 trichomes L-1. In autumn, in spiteof temperature lower (14°C) than in summer it was still very high. Mass development of P. agardhii (to 6 x 106 L-1 and higher)caused a severe decrease in water transparency (to 0.5 - 0.2 m in summer/autumn). The cyanobacterium density was relativelyuniform within water column; only in summer (July) it was significantly higher (by about 30%) in surface than in bottom layer.From spring to autumn microcystins (MCs) were mainly biomass-bound (up to 90 μg MC-LR equiv. L-1), whereas the level ofextra-cellular toxins was much lower (up to 2 μg L-1) and relatively stable. Only in winter, high amounts of MCs (11.3 μg L-1)were released from decaying biomass into water. The increasing concentrations of biomass-bound microcystins in the lake waterpositively correlated (R2 = 0.9863; y = -0.1285x2 + 7.14x ) with the abundance of P. agardhii and the highest concentrations ofthe intracellular MC fraction were found during the exponential phase of P. agardhii growth. In addition, the surface-sampledbiomass of P. agardhii contained in autumn 2-fold more MCs (2.75 μg MC-LR equiv. per 106 P. agardhii trichomes) than thebottom-sampled one (1.41 μg MC-LR equiv. per 106 trichomes). This is the first report showing that despite the homogenousdistribution of P. agardhii in water column of a shallow lake, various seasonal and spatial distributions of both extra-cellularand intracellular fractions of microcystins occur.

We studied the spatiotemporal trends of Eragrostis curvula (Schrad.) Nees in a flood meadow of a regulated river. The response variables, including the abundance of colonies, colony sizes, flowering spikes, biomass and root structure were checked against a set of environmental variables. These variables included distance from the river, substrate conditions (stony to sandy), soil nutrients (total nitrogen, phosphorous and calcium) and soil moisture. Relationships were evidenced using redundancy analysis. Response variables were found to be distinctive and based on substrate conditions (i.e. stony or sandy). The variables ‘distance from the river’ and ‘soil phosphorous’ contributed significantly to the overall variance. Stony habitats were observed to have lower soil nutrient levels and were characterised by monospecific stands of E. curvula, while the high nutrient levels of sandy habitats promoted heterogeneous herbaceous vegetation growth. Primary production, especially belowground, was measured to be significantly higher (t-test, P<0.05) in stony habitats. Spatiotemporal trends suggested that, irrespective of the number of colonies, E. curvula demonstrated significant levels of adaptation to micro-environments through biomass allocation and the morphological plasticity of its roots. The study results suggest that river regulation and the subsequent reduction in the frequency of inundation, in addition to the reduction of nutrients and fine sediment supply downstream, give a competitive edge to E. curvula over other herbaceous species.

Based on field observations performed in 1999 and 2000, the exotic amphipod Dikerogammarus villosus is now well established throughout the navigable sector of the River Moselle in France. D. villosus co-occurs with Gammarus pulex, G. tigrinus and D. haemobaphes, another recent exotic species found in this tributary of the River Rhine. The maximal size of individuals of D. villosus collected (15.7 mm) is lower in the River Moselle than in other basins, where this species could reach up to 30 mm (Neseman et al. 1995). Nevertheless it represents the largest gammarids found in the French sector of the River Moselle. Other particular traits are its wide phenotypic plasticity, varying from a melanic to a striped form, and its predatory behavior. These particular traits may favour the establishment of this species on a recipient ecosystem. The occurrence of D. villosus was noted in the Alsace Canal and in the River Rhône, showing that its immigration across French hydrosystems is still in progress.

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.

Community diversity is expected to reflect variations in local conditions but, recently, ecologists have started to realize that local diversity is also under pressure from global processes. As a result, the traditional view of community structure based on local interspecific interactions was replaced by the idea that community structure is a result of multiple processes acting in different spatial scales. This study is aimed at quantifying the relative importance of spatial, environmental and spatially structured processes on Ephemeroptera community in Cerrado streams in Brazil. Thirty-four rivers and streams in the Brazilian state Mato Grosso were sampled. Ephemeroptera species composition, based on abundance and presence data, was evaluated in relation to niche and neutral predictors by using a partial redundancy analysis (pRDA). Results obtained through the pRDA indicated that both environmental and spatial processes influenced Ephemeroptera abundance. On the other hand, only environmental processes showed effects on community patterns when using species presence data from preserved, altered and large streams and also when looking only at the preserved sites. When streams larger than 20 m were excluded from analysis, both environmental and spatially processes showed influence on Ephemeroptera composition. Adjusted R2 values were higher for environmental than for spatial processes in all analyses. The relatively high influence of both environmental processes and stream width in the analyses highlights the sensitivity of mayflies assemblies to environmental variation, and emphasizes the importance of local processes, as predicted by niche theory, while neutral processes act to a lesser extent on the structure of the studied communities.

The Guadiana estuary (Iberian Peninsula, Europe) has low agriculture, industry and urban pressure, unlike other major Iberianestuaries; however, this situation is about to change. The Alqueva dam was constructed at 150 km from the river mouth, creatingone of the biggest artificial lakes in Europe, which will support 110 000 ha of irrigation areas. Moreover, the estuarine marginsare suffering increased human pressure. The risks that the Alqueva dam will pose to the downstream ecosystems, mainly to theestuary and adjacent coastal area, will be reviewed in this paper. Other issues are also analysed, as increased humandesertification in the Portuguese basin, real estate pressure and the impact of the construction of a public infrastructure in thePortuguese lower estuary. Increased problems of sediment load reduction, water quality deterioration and shifts in thedownstream fish populations are expected due to higher river flow reduction. Irreversible changes to estuarine margins andincreased risk of pollution in the estuary will result from the multiple urban pressures. Lack of forest management and increasedrisk of wildfires, leading to water quality degradation and increased soil erosion, are a result of human desertification in the upperPortuguese basin. Multiple solutions to tackle these problems have to be considered. Creating the International Natural Park ofthe Lower Guadiana would not be enough and tourism should not be regarded as the only way to develop such a poor region. Anecohydrological approach of the basin should be implemented, to establish scientific based solutions to help solving conflicts andtesting scenarios. Ultimately, the creation of a Portuguese-Spanish Basin Management Council for the lower Guadiana, involvingthose that are interested in the sustainable development of the Guadiana (local populations and associations, private stakeholders(dam managers, tourism entrepreneurs, farmers), local and national authorities, ENGO’s and scientists) is essential to produceecological and sustainable management decisions.

We report the results of a study carried out in 2002 on the main limnological characteristics and on the ostracod communities of 16 wetlands of the Parco Oglio Sud (Northern Italy). Physical and hydrochemical variables were measured and ostracod samples were collected in different seasons (April, June, August, and October). Most of the considered sites were characterised by high concentrations of nitrogenous compounds due to washing out from cultivated areas, intermittent river flooding and internal recycling. Observed differences in macrophyte communities were consistent with trophic status of waters, with pleustonic forms dominating most degraded areas. Both morphology of valves (by scanning electron microscopy) and anatomy of soft parts were analysed for ostracod species identification. Nineteen ostracod species in five families were found. Two species, Candona weltneri and Pseudocandona compressa, are new records for Italy. Cypria ophthalmica was collected from all sampling sites; other relatively common species were Cypridopsis vidua, Cyclocypris ovum, and Candona weltneri. No clear seasonality was observed in community structure; highest species diversity occurred in June in most of the studied wetlands. The maximum number of species per site was seven, and a maximum of six species was found in a single sample. Ostracod occurrence in relation to environmental factors was examined using Canonical correspondence analysis (CCA). Total alkalinity and pH were the most important variables structuring the species assemblages. The ostracod fauna found in this area was compared to the known distribution of recent non-marine ostracods in Italy, and the validity of published checklists is discussed.