Benthic invertebrate assemblages and species diversity patterns of the Upper Paraguay River

Abstract

This paper presents the first study of the benthic invertebrate assemblages of the upper section of the Paraguay River, a major tributary to the Pantanal wetland in Brazil. Thirty-eight sites were sampled along a 200 km section below the city of Cáceres in November 2000. Sixty-nine species and morphospecies were identified, which were dominated by Oligochaeta and Chironomidae. Mean density of benthic invertebrates varied between 72 and 10 354 m-2 in the meandering sector of the river, 3611-49 629 m-2 in the straight-transitional sectors, 682-5962 m-2 in the floodplain lakes, and 1704-2208 m-2 in floodplain channels. Highest densities were attained in sand-gravel sediments dominated by the psammophilous oligochaete Narapa bonettoi. The Shannon diversity index ranged from 0.75 to 2.08 and was highest in floodplain lakes. Statistical analysis (UPGMA and CCA) revealed that benthic assemblages in the floodplain habitats were clearly distinct from the riverine habitats. In the river channel, the habitats were distinguished by grain size while the floodplain habitats were mostly determined by current and silt-clay concentration (floodplain channels) or by organic matter concentration (floodplain lakes). Conservation efforts in the Upper Paraguay area should aim to maintain the flood pulse as a permanent source of spatial and temporal habitat heterogeneit

Bidirectional exchanges of benthic invertebrates in a large river–floodplain system (Paraná River, Argentina)

“…The chironomid Axarus sp. was dominant in riverine assemblages of Parana´River, and this finding was in accordance with other studies in large rivers, such as the Paraguay River (Takeda et al, 2000;Ezcurra de Drago et al, 2004;Marchese et al, 2005). 0.75*** 0.48* 0.74*** 0.50** *P < 0.05; **P < 0.01; ***P < 0.001.…”

Using oligochaeta assemblages as an indicator of environmental changes

“…) and the upper Paraguay River (22) (Marchese et al, 2005). The richness of Oligochaeta species recorded in this river is related to the environmental heterogeneity (several falls, rapids, pools and backwaters), since it cuts the three Paranaense plateaus formed by rocks from different geological times, besides altitude and anthropogenic activities, which were the main variables explaining the patterns found.…”

Relationships between the spatial distribution of oligochaetes (Annelida, Clitellata) and environmental variables in a temperate estuary system of South America (Río de la Plata, Argentina)

“…The species is usually associated with highly polluted environments (Marchese 1987;Montanholi-Martins & Takeda 1999;Takeda 1999;Ezcurra de Drago et al 2004;Marchese et al 2005). Other authors also recorded L. hoffmeisteri in the shallow organically enriched sediments of lakes (Casellato & Caneva 1994) as well as in estuaries, in both the freshwater and brackish sectors (Moroz 1994;Finogenova 1996;Seys et al 1999).…”

“…The macroinvertebrates in the Rı´o de la Plata River have been studied by a number of authors Darrigran & Lo´pez Armengol 1998;Rodrigues Capı´tulo et al 1998Ce´sar et al 2000;Cortelezzi et al 2007), while the species composition and ecological requirements of oligochaetes in particular have been analysed during recent years in other larger rivers in South America (Montanholi-Martins & Takeda 1999;Takeda 1999;Ezcurra de Drago et al 2004;Marchese et al 2005). Furthermore, in various parts of the world, studies on the oligochaete fauna from temperate estuaries subjected to anthropogenic impact have indicated that the most significant environmental factors affecting their distribution are the salinity, turbidity, discharge, trophic condition, sediment characteristics and general quality of the bodies of water in question (Moroz 1994;Finogenova 1996;Gonza´lez-Oreja & Saiz-Salinas 1999;Seys et al 1999).…”