INALI   02622
INSTITUTO NACIONAL DE LIMNOLOGIA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Hydrological processes and ecological patterns in a large river system
Autor/es:
BLETTLER, MARTIN
Lugar:
Stellenbosch
Reunión:
Conferencia; Guest Seminar; 2014
Institución organizadora:
University of Stellenbosch and CSIR-Council for Scientific and Industrial Research
Resumen:
Drawing from our own research's results and field expertise, this lecture offers an overview of the ecological, hydrological and morphological relationships of a very complex and sensitive large South-American watershed: the Paraná River system. This is a large and very dynamic fluvial system attractive for human settlement, characterized by several river-floodplain interactions due to the flood/flow pulse regime. Specific examples of macroinvertebrates and fish assemblages, deeply analyzed, we herein considered in order to understand physical-biotic interactions and to be aware of the extreme complexity and fragility of this kind of ecosystems. As it is relatively well known, physical habitat features are greatly responsible for spatial and temporal ecological patterns. Therefore, hydrological and morphological conditions are stream features which affect the benthic and fish assemblage composition and distribution. Nevertheless, we indentified specific ecological patterns of fauna distribution at morphological units like mobile underwater dunes, meander bends (crossing-pool sequences) and large confluences (including scour holes). Turbulent flows as well as sediment dynamics over these units are strongly associated to invertebrate ecology (at different spatial scales) and therefore they may be considered as hydrologic biotopes. Invertebrate species inhabiting over those units are forced to develop body and behavioral adaptations to face the prevailing strong bed hydrodynamic forces. On the other hand, we detected and described remarkable different invertebrate assemblages between the main channel, banks and floodplain secondary channels, revealing higher diversity and richness in the floodplain habitats. We found that the main channel assemblage is very sensitive to environmental pollution, showing a great potential to be used as bioindicator. Regarding the hydrodynamics of the system, we found that the flow/flood pulses of distinct magnitude and duration (including ENSO phenomenon) determine great changes in benthic and fish assemblage structure. Summer floods determine fish recruitments. Indeed, long-distance migratory fishes need flood pulses associated with high water temperatures to trigger migration for reproduction. Also, sedentary fishes require high floodplain connectivity during summer for juvenile development. Finally, we remark that linking physical processes to ecological patterns, considering different temporal and spatial scales, is particularly useful to aid the understanding of the ecological legacy of anthropogenic modification and natural evolution on river systems.