Variation in water colour is a remarkable characteristic of Amazonian rivers and reflects their limnological properties and the geomorphology of sub-basins. We present here a literature-based study to examine the relationships between fish species turnover and abiotic properties of Amazonian rivers with contrasting water colours. We analysed fish records and water physicochemical properties (pH, colour, turbidity, dissolved oxygen, ammonia and suspended solids) of eight Amazonian rivers with white-, black- and clearwaters. Rivers with similar water colour shared more fish species than those that contrasted in colour. Increased differences in abiotic parameters imply an increased dissimilarity in fish species composition. Species composition is also related to distance among rivers with high dissimilarity observed in rivers distant to each other. The fish species turnover could be ultimately driven by the geological history of rivers which provides different opportunities to speciation and biotic interchange. Water types likely influence species turnover by selecting fishes with different limits of physiological tolerance and specialized use of different habitat types. Our findings suggest that river water colours are reliable proxies for historical and ecological mechanisms affected fish species distribution. Antropic disturbances of Amazonian rivers with distinct water colours could threaten unique fish assemblages.

We employed X-ray diffraction methods to quantify clay mineral assemblages in the Indus Delta and flood plains since ~ 14 ka, spanning a period of strong climatic change. Assemblages are dominated by smectite and illite, with minor chlorite and kaolinite. Delta sediments integrate clays from across the basin and show increasing smectite input between 13 and 7.5 ka, indicating stronger chemical weathering as the summer monsoon intensified. Changes in clay mineralogy postdate changes in climate by 5–3 ka, reflecting the time needed for new clay minerals to form and be transported to the delta. Samples from the flood plains in Punjab show evidence for increased chemical weathering towards the top of the sections (6–≪ 4 ka), counter to the trend in the delta, at a time of monsoon weakening. Clay mineral assemblages within sandy flood-plain sediment have higher smectite/(illite + chlorite) values than interbedded mudstones, suggestive of either stronger weathering or more sediment reworking since the Mid Holocene. We show that marine records are not always good proxies for weathering across the entire flood plain. Nonetheless, the delta record likely represents the most reliable record of basin-wide weathering response to climate change.

The Chironomidae fauna of ten large European rivers (Rhine, Elbe, Oder, Danube, Loire, Pripjat, Po, Maas, Garonne and Rhône) were investigated by analysing their ecological traits (longitudinal zonation pattern, saprobiological affinities, feeding types) using one-dimensional and multivariate methods. The results confirm the geomorphological differentiation of these rivers in two main types, i.e. gravel-type and sand-type rivers. The analyses of the Chironomidae traits also showed that transition zones separate the two main types of rivers.

Une série de dragages effectués dans la Saône au niveau de 13 stations réparties sur 377 km de rivière montre que le macrobenthos du chenal de cette rivière est, dans les stations les moins dégradées, largement dominé par les Ephéméroptères fouisseurs (Ephoron virgo et Ephemera lineata). La comparaison avec le macrobenthos du Haut-Rhône indique que ce dernier, qui présente des caractéristiques mésologiques et hydrologiques similaires, se situe typologiquement plus à l'amont que la Saône. La durée et l'importance de l'étiage combinées avec les différences de pente, cette dernière influençant la vitesse du courant et la granulométrie, sont probablement les facteurs essentiels qui structurent les peuplements macrobenthiques de ces deux cours d'eau.

L'échantillonnage des rives aquatiques du Rhône, en amont de Lyon, fournit une approche faunistique nouvelle du milieulotique. Les rives sont définies avec précision : la zone prospectée correspond à la frange supérieure de la rive immergée.Une mosaïque complexe de microhabitats constitue la rive ; une liste non exhaustive en est proposée. Une descriptiondes techniques de prélèvement de chaque microhabitat est également fournie. Enfin une Analayse des Correspondancessur la matrice 35 relevés × 80 taxons montre que les microhabitats abritent des communautés faunistiques effectivement différentes et caractéristiques des trois milieux d'érosion, de sédimentation et de végétation. La définition a priori des microhabitats est donc validée par la distribution des macroinvertébrés. Quelques exemples de taxons caractéristiques des différents microhabitats sont donnés : Trichoptères Leptoceridae en microhabitats d'érosion, Hydropsyche sp. dans les racines ou Oligochètes en microhabitat de sédimentation.