Chironomid riverine assemblages at the regional temperate scale – compositional distance and species diversity

Abstract

Chironomids are the most common and abundant benthic invertebrate family in freshwater environments worldwide, but most studies on chironomid assemblages focus on presence/absence of species rather than abundance and community composition. This makes the assessment of chironomid assemblage composition and diversity limited in any physiographic zone and at any scale. This study enhances knowledge of chironomid abundance in rivers in Central Europe, which is typical part of the temperate climatic zone, and investigates chironomid (inter-)assemblage characteristics. Benthic assemblages of seven lowland rivers were sampled monthly over annual cycles with a total of 61 chironomid species detected. PCA was used to determine the environmental profile of the rivers at study sites, while cluster and ANOSIM analysis and univariate diversity indices were applied to the chironomid samples of the assemblages grouped at the river level to identify their similarities and differences. The environmental profile explained much of the cluster and ANOSIM-based patterns of the rivers’ compositional distances, and also some values of given univariate diversity indices. SIMPER analysis distinguished a group of 14 species that explained almost 60% of differences between the assemblages. The contribution of each species of the group was similar, ranging between 6.13% and 2.87%, yet on average several times greater than that of each of the remaining 47 species. Univariate diversity values differed from index to index and from river to river, and indicated that the application of few such indices, particularly one, may be misleading. The N 1 gamma diversity of the whole region (calculated from 82 samples) was 18.31 species, which was multiplicatively decomposed into the average alpha component of 4.04 species, and beta component of 4.53 assemblages.