Fine Sediment Input and Benthic Fauna Interactions at the Confluence of Two Large Rivers

BLETTER, MARTIN; AMSLER, MARIO L.; EZCURRA DE DRAGO; DRAGO, E; PAIRA, ALDO; ESPINOLA, LUIS; EBERLE, L.; SZUPIANY, RICARDO N.

INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH

UNIV TEHRAN

Lugar: Tehran; Año: 2016 vol. 10 p. 65 - 76

1735-6865

Several studies suggest thatinvertebrate abundance and richness are disrupted and reset at confluences.Thus, junctions contribute disproportionately to the overall aquaticbiodiversity of the river. In general terms, authors have reported highabundance and diversity due to the major physical heterogeneity at junctions.However, data are still scarce and uncertainties are plentiful. The impact of agreat input of fine sediments on the distribution patterns of benthicinvertebrates at a river confluence was quantitatively analyzed herein. Thejunction of the subtropical Bermejo River (high suspended sediment load) withthe large Paraguay River is the selected study area to achieve this aim. Whilediversity increased slightly downstream the junction (from 0.21 to 0.36),density and richness of the macroinvertebrate assemblage significantlydiminished downstream the confluence (from 29050 to 410 ind/m2; p< 0.05) dueto the input of fine sediment from the Bermejo River (mean fine sedimentincreased downstream from 6.3 to 10.2 mg/L), causing a negatively impact oninvertebrate assemblage. This study highlights the ecological importance of thesediment input effects on benthic invertebrates, a topic still poorly exploredin river ecology. It is speculated that the spatial extent of the impact wouldbe dependent upon the hydrological and sedimentological context, highly unequalbetween both rivers. New hypotheses should be tested through new studiesconsidering different hydrological stages.