engleski

Siltation disturbance in a mountain stream: aspect of functional composition of benthic community

Background and purpose Siltation is a recognized stress for the benthic community. It may cause changes in structure of habitat substrate and water physical and chemical properties. The aim of this study was to ascertain the effects of siltation on the function of a mountain stream benthic community, specifically in respect to availability of food resources. Materials and methods The study was carried out at Bistra Stream on Medvednica Mountain in NW Croatia. Siltation was caused by quarrying. Samples were taken at a control (unsilted) site and three impact sites on four dates during the spring of 2006. Turbidity, water temperature, pH, oxygen content, conductivity and COD were measured and triplicate benthos samples were taken using a 30×30 cm Surber sampler on each sampling date. Impact of siltation on functional feeding guilds was analyzed. Results and conclusions Turbidity, pH and temperature increased significantly downstream of siltation source. Total number of individuals decreased by 85%, number of taxa by 60% and the Shannon’s diversity index followed accordingly (by 56%). The grazers and the detritivores were proven to be most sensitive to the disturbance. The disturbance did not strongly affect shredders whereas predators’ abundance increased. We conclude that the change in food availability is a crucial aspect of the siltation disturbance and that allogenic siltation is more devastating because of the additional chemical changes not noted during natural siltation.

fine sediment; stress; FFG; benthos; macroinvertebrates; quarrying; mining; Croatia

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