The impact of significant input of fine sediment on benthic fauna at tributary junctions: a case study of the Bermejo-Paraguay River confluence, Argentina

BLETTLER MCM, AMSLER M, EZCURRA DE DRAGO I, ESPINOLA L, EBERLE E, PAIRA A, BEST J, PARSONS D, DRAGO E.

ECOHYDROLOGY

JOHN WILEY & SONS INC

Lugar: New York; Año: 2014 vol. 8 p. 340 - 352

1936-0584

This study examines the morphological features, suspended sediment inputs and hydraulic conditions within a large river in association with ecological patterns before and after a tributary confluence. In order to investigate these effects, it is investigates herein the macroinvertebrate distributions from three reaches of the Paraguay and Bermejo rivers (Paraguay-Argentina). The Bermejo River is a tributary that supplies significant quantities of fine sediment to the Paraguay River, primarily in suspension. Two reaches were examined on the Paraguay River, upstream and downstream of the Bermejo River junction, with a third study reach located on the Bermejo River, upstream of the confluence with the Paraguay River. The results provide clear evidence that a significantly increased loading of fine sediment at a river confluence has an effect on the distribution and potential movement of benthic invertebrates in the lotic environment by representing physical barriers at affected sites. These effects may be important at both local and regional scales and such increases in suspended sediment (especially associated with anthropogenic change) may thus pose a major threat to ecosystem integrity that has been historically underestimated.