engleski

Composition and depth distribution of oligochaete fauna of Mediterranean karstic lake (Lake Visovac, Croatia).

The depth distribution of oligochaetes was studied in Visovac lake (Croatia) along a transect from 1 to a maximum of 24 metres. In the material collected, 21 oligochaete species belonging to 4 families were identified, all of them more or less common in European lakes. The greatest diversity of oligochaetes was found at a depth of 4-6 m (18 taxa). On silty-sands covered by reed decay at a depth of 1 m oligochaetes comprised only 2% of the total benthic biomass. Oligochaeta densities increased with depth and at a depth of 22-24 m they represented 59% of the total biomass. Depth and bottom type were the impor- tant variables in defining species distribution. Only three oligochaete species were found at all of the investigated depths: Potaraothrix hammoniensis, Psarrsrrdoryct,ides 6ar6ntus and Lirnnodrilus hoffraeisteri. Aulodridus plvriseta was distributed only in the area of submerged macrophytes. The remaining species occurred less frequently, and mainly with restricted distribution.

Oligochaeta; depth distribution; karstic lake; Croatia

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