engleski

Substrate type and vegetation cover, factors influencing longitudinal distribution of simuliid larvae in a karstic river

Background and purpose: The spatial distribution of simuliid larvae on different substrate types associated with varying vegetation cover in the karstic river was investigated with a view to establish the longitudinal distribution and trophic importance of simuliid larvae in the functional organisation of benthic macroinvertebrate communities. Materials and methods: The investigation was done on karstic river Kupa, located in the NW area of the Dinaric mountains. The samples were collected using Surber sampler on 12 sampling stations. S&oslash ; renson’s similarity coefficient (SS) and MDS analysis were used as indices of community structure in order to establish the degree of similarity among five simuliid associations. Results: We found 14 simuliid species. The major species diversity and greatest population density were found on boulder (4 057 Ind. m-2) and cobble substrates (2 964 Ind. m-2) in the upper river area. In the headwater streams, on the same substrate type covered with moss, and on a gravel substrate covered with macrophytes in the lower river area, the percentage biomass of simuliid was less than 1%. Conclusions: Considering observed percentage share in the total collector-filterer biomass (from 70 % to 80 %, approximately), in the upper river section, we presumed that simuliid larvae could play a considerable role in the processing of sestonic particles only in habitats in this river section. According to our observation, current velocity, water depth, degree of organic load and the vegetation cover of the substrate in connection with food supply are the environmental determinants most responsible for the spatial distribution of simuliids along the physical continuum of karstic rivers.

simuliid larvae; karstic running waters; species composition

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