Seasonal development, long-term changes and effect of extreme events on macrozoobenthos of acidified brooks in headwater catchments of Litavka, the Brdy Mountains

This Master thesis was focused on seasonal development of macrozoobenthos for season 2009-2010, its long-term changes and effects of extreme events on acidified brooks in headwater catchments of the Litavka river in the Brdy Mountains (the Czech Republic). The extreme events are considered: drought, floods and deforestation. Changes in composition of macrozoobenthos were compared with the previous research, which was provided there for season 1999-2000. Headwater catchment of the Litavka river consist of two streams: strongly acidified Litavka-krmelec (LK) and slightly acidified Litavka-hlavní (LH), which is taken as a reference stream. Measured pH levels of LK were in range of 4,00-4,22 (with median 4,10) and concentration of reactive aluminium (R-Al) were in range of 1381-2187 µg.L-1 (with median 1692 µg.L-1 ). Measured pH levels of LH were in range of 4,74-6,22 (with median 5,62) and concentration of reactive aluminium (R-Al) were in range of 8-400 µg.L-1 (with median 33 µg.L-1 ). Concentrations of R-Al are observed due to toxic forms of Al3+ ions on aquatic organisms. The significant differences in composition of macrozoobenthos were also observed. On strongly acidified study site LK were not present acidosensitive groups, such as mayflies, molluscs and some species of caddisflies. All of these..