INALI   02622
INSTITUTO NACIONAL DE LIMNOLOGIA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Morpho-hydrodynamic conditions along meander bends control the distribution of benthic fauna in a large river (Paraguay River, Argentina-Paraguay).
Autor/es:
BLETTLER, M.C.M.; EZCURRA DE DRAGO, I.; AMSLER, M.L.; DRAGO, E.
Lugar:
Columbus, OH
Reunión:
Congreso; EcoSummit 2012 - Ecological Sustainability. Restoring the Planet’s Ecosystem Services.; 2012
Institución organizadora:
Ohio State University, Mid-Ohio Regional Planning Commission (MORPC), Society of Ecological Restoration, Ecological Society of America, The International Association for Ecolgy.
Resumen:
The Paraguay River is a meandering large river (mean discharge= 4000 m3 s-1, drainage basin area= 1095000 km2). Changes in morpho- and hydrodynamic conditions influence benthic invertebrates, however, there are few studies linking morphological features and sedimentological characteristics, closely related to hydraulic conditions, and the ecological patterns of benthic invertebrates along meanders. We have selected two meander bends of the Paraguay River. One of them is located downstream of the Bermejo River outlet, a tributary which supplies a huge amount of fine sediments (mainly in suspension) to the Paraguay. These particles in suspension are Precambrian and Paleozoic sediments transported from the Andean headwaters. The other bend is located upstream of this tributary and consequently, the sediment load is significantly lower and coarser. The results reveal that at meander scale, average bed hydraulic conditions are most intense in the downstream meander and the concentration of suspended sediments is higher (125 mg l-1), leading to low mean density of invertebrates (960 ind. m2). Moreover, the upstream meander presents lower average values of hydraulic stresses and suspended sediments (56.5 mg l-1), prompting larger benthic densities (15600 ind. m2). Besides of the bed hydraulic conditions, the suspended fine sediments would have strong ecological implications. A fraction of these suspended sediment particles cover the interstitial spaces between sand bed grains, i.e. the sites where the invertebrates live, preventing their development. At a riffle-pool scale the density of organisms decrease significantly on the scour hole of the upstream meander, where the bed stresses are higher. Nevertheless, this relation was not clear on the downstream meander. It could be generated by the high sediment inputs from the Bermejo River, which would reduce the importance of the hydrodynamic role on the invertebrate densities and structure. All above facts have obvious implications for habitat assessments and rehabilitation design.