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This paper describes various approaches to evaluating ecological risk in rivers affected by multiple chemical stressors, with emphasis on biofilm and invertebrate community responses. Metrics should be considered as different lines of evidence that, when weighted, form an advanced weight of evidence approach to establishing the environmental risk on a basin scale. Combination of field surveys to obtain observational data of communities, in situ experiments, toxicological sediment tests and a good chemical description of the medium (water and sediment) helps give an integrative view of the chemical and biological state of a river ecosystem. The greater and more distinct the variables used, the greater is our ability to identify the effects of major stressors impairing communities. Weight of evidence is an integrative methodology for tackling the challenge of determining causal relations and applying this knowledge in the decision-making processes of river management. more...

ABSTRACT Rivers are among the most diverse and threatened ecosystems on the Earth, but their conservation is a requisite for sustainable development. Conservation must consider both the structure and the functioning of the elements (usually species), as well as of their ecosystem. Therefore, successful river conservation must go beyond protecting species to protecting entire ecosystems and the processes that give each ecosystem its special characteristics. River conservation has to meet the legitimate aspirations of human populations for clean, readily available supply of water, without compromising the water needs of ecosystems and nature. Therefore, it is essential to take a landscape perspective that incorporates processes occurring in the riverine riparian areas as well as on connectivity with the land and across the river network. RESUMEN Los ríos son uno de los ecosistemas más diversos y amenazados de la Tierra, pero su conservación es esencial para un desarrollo sostenible. La conservación debe tener en cuenta tanto la estructura y el funcionamiento de los elementos (por lo general las especies), así como de su ecosistema. Por tanto, la conservación debe ir más allá de la protección de especies, para contemplar la protección de ecosistemas enteros y de los procesos que en ellos acontecen y les proporcionan sus especiales características. La conservación fluvial tiene que responder a las legítimas aspiraciones de las poblaciones humanas de un suministro limpio de agua fácilmente disponible, sin comprometer las necesidades de agua de los ecosistemas y la naturaleza. Por tanto, es fundamental adoptar una perspectiva del paisaje que incorpore procesos que ocurren en las áreas ribereñas fluviales, así como la conectividad con el ecosistema terrestre y toda la red fluvial. more...