Benthos of the lotic environments in the middle Paraná River system: transverse zonation

Abstract

This study synthesizes the results from ten years (1978)(1979)(1980)(1981)(1982)(1983)(1984)(1985)(1986)(1987)(1988) of research in lotic environments of the middle Parana River . We elucidate the important environmental factors that determine differences in quality and structure of the benthos among the main channel, secondary channels and tributaries, and we determine species or descriptive associations of the different types of environment .The results of a principal components analysis reveal a transverse gradient from the main channel through the secondary channels of progressively decreasing size. The gradient shows decreasing depth, current velocity, discharge, sand, oxygen, and density of the benthos, and increasing transparency, pH, conductivity, temperature, silt, clay, sediment, organic matter and species richness and diversity of the benthos .The centre of the river channels was found to be the zone of greatest descriptive and representative value for the characterization of the benthos .In relation to the transverse gradient, the following succession of benthic fauna associations was observed in the center of channels from the main channel to the anabranches : 1 -Narapa bonettoi + Haplotaxis aedeochaeta + Microstomum? sp . 2 -N. bonettoi + H. aedeochaeta + Microstomum? sp . + Parachironomus sp . 3 -Parachironomus sp . + Xenochironomus sp . + Cryptochironomus sp . + Coelotanypus sp . + Limnodrilus hoffmeisteri + Paranadrilus descolei + Campsurus sp . + Pisidium sp .

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

“…Three samples of bottom sediments for benthic invertebrates and one sample for benthic organic matter and granulometric analysis were collected for each sampling date and site using a Tamura grab (319 cm 2 ) in the main channel and an Ekman grab (225 cm 2 ) in the connection channel and in the lake. The Tamura grab is most effective in deep, fast-flowing sandy bottom rivers (Marchese and Ezcurra de Drago, 1992), whereas the Ekman grab is widely used in lakes with silt-clay sediments.…”

Development of fauna of water beetles (Coleoptera) in waters bodies of a river valley – habitat factors, landscape and geomorphology

“…This observation is also confirmed in the results of studies on Hydrachnidae . This may be convincingly explained when considering the smaller than expected hydrological contact between the water bodies resulting from the valley's topography, and only rare flooding which does not reach many of the water bodies, especially those located away from the main riverbed (Marchese and Ezcurra de Drago, 1992;Smock, 1994;Ward et al, 2002;Biesiadka and Pakulnicka, 2004a;Pakulnicka and Nowakowski, 2012). Decreased hydrological contact between the valley's individual ecosystems and the main riverbed typically results in modification of their fauna (Castella et al, 1984;Van den Brink et al, 1996;Biesiadka and Pakulnicka, 2004a;Costea et al, 2013).…”

“…The local habitat conditions of these varied types of waters have with no doubt a strong impact on the characteristics of the beetle clusters inhabiting them. Such environmental factors as water periodicity, water flow speed, water body size, type of bottom, degree to which they are overgrown with vegetation, are indicated as key factors shaping the faunistic relations of beetles inhabiting the flooded valley of the river Niemen (Pakulnicka and Nowakowski, 2012); this is true also for other types of landscapes with numerous bodies of water (Koch, 1989;Marchese and Ezcurra de Drago, 1992;Winfield Fairchild et al, 2000;Lundkvist et al, 2001;Oertli et al, 2002;Pakulnicka, 2008;Giora, 2014;Pakulnicka et al, 2015a, b).…”

“…On one hand, this contributes to their eutrophication (unfortunately also of oxbows) as well as their individualism. On the other hand, the lack of flooding reduces the drift of organisms from hatching habitats, which, in turn, reduces the river's species richness (Marchese and Ezcurra de Drago, 1992;Biesiadka and Pakulnicka, 2004a;Pakulnicka and Nowakowski, 2012). …”

“…Biesiadka and Pakulnicka (2004a) point out that for water beetles, which are usually perfect fliers and are characterized with high biological dispersal (Bilton, 1994;Lundkvist et al, 2002), faunistic integration between the river and the water bodies located on the floodplain is influenced by two mechanisms: active overflights and migration of beetles in the floodplain area in time of spate. Despite this, water environments comprising the cohesive hydrological system may still be distinguished by a certain degree of individualism (Marchese and Ezcurra de Drago, 1992;Pakulnicka and Nowakowski, 2012;Costea et al, 2013;Biesiadka and Pakulnicka, 2004a). These individual features are the result of internal environmental (site) factors, such as type of water body, type of substrate, extent of vegetation, area, age, permanence and water flow speed (Castella et al, 1991;Marchese and Ezcurra de Drago, 1992;Winfield Fairchild et al, 2000;Lundkvist et al, 2001;Oertli et al, 2002;Pakulnicka, 2008;Pakulnicka and Nowakowski, 2012;Pakulnicka et al, 2015a,b).…”