Original paper

The distribution of chironomid larvae and oligochaetes within a stony-bottomed river stretch: the role of substrate and hydraulic characteristics

Syrovátka, Vít Schenková; Brabec, Karel


The taxonomic and functional structure of oligochaete and chironomid communities in a stony-bottomed river reach was investigated with respect to substrate and hydraulic conditions. Combined oligochaete and chironomid data were analyzed to search for main gradients and the separate data sets were analyzed to identify the most important variables determining the structure of the communities. Preferences for particular hydraulic conditions, expressed as Froude number, were calculated for 29 most abundant taxa. The results of Correspondence Analysis (CA) indicated that the main gradient in the data could be explained by hydraulic conditions and, inversely, by the amount of sedimented particulate organic matter (POM). The second CA axis probably reflected the quantity of the available food and space resources. Canonical Correspondence Analysis (CCA) showed the amount of sedimented POM as the most important variable explaining 21 and 24 % of the variance in the oligochaete and chironomid data, respectively. Among the other variables, the occurrence of aquatic vegetation, variability of near-bottom current velocity and substrate roughness were the most important. In the case of chironomids, the proportions of functional feeding strategies changed along the gradient of hydraulic conditions: the proportions of predators, active filter-feeders and collectors/gatherers decreased with the increasing hydraulic stress, while the proportion of grazers/scrapers increased. Nevertheless, in the case of oligochaetes, the proportions of functional feeding strategies did not follow the gradient of hydraulic conditions. Although the total abundance of both oligochaetes and chironomids was independent of hydraulic conditions, only few oligochaete taxa were able to succeed in hydraulically rough conditions and most oligochaete taxa were found only in pools. On the other hand, chironomids showed high taxa richness, which seemed to be limited by the quantity of the available food and space resources rather than hydraulic stress.


chironomidaeoligochaetadistributionsubstratehydraulic conditionsstream