The effect of riverbed management on the habitat structure and macroinvertebrate community of a ninth order river, the Danube in Austria.
Humpesch, Uwe H.; Fesl, Christian; Rüger, Horst
To overcome the problem of bed deepening of a river, one possibility is the addition of coarse material to form a cover layer. Therefore a field experiment in the River Danube was performed to evaluate this method and examine its effects on the macroinvertebrate community. The sediment parameters were Q1, Q2, Q3 particle size, the coefficients of sorting and skewness and the pore space. Those of the macroinvertebrate community were the total number of individuals, the Oligochaeta and the Hydracarina. After an initial increase of the sediment parameters Q2 and Q3 and a decrease of the coefficient of sorting in the top layer as consequence of the addition of the coarse material, the particle size in the top layer decreased and the coefficient of sorting increased at sampling date 3 (18 months after the sediment addition) and 4 (3 years after). The change of the sediment habitat structure, e.g. decrease of pore space, was followed by a change in the vertical distribution of the animals. While >90 % of the total number of individuals colonized the pore space between 0 and 90 cm on sampling date 1, the depth distribution changed between 50 and 40 cm at the other sampling dates. - The sediment addition did not achieve the desired outcome, and with the decreasing pore space the potential recolonization via hyporheic zone decreased.