Use of colonization baskets for the investigation of disturbance phenomena in streams under model conditions

AbstractSeminatural substrates were used to mimic conditions of a denuded stream bed after a substrate-moving spate. For this purpose gravel-filled wire baskets were placed on the sediment surface of the Ilm river (Thuringia, Germany). Invertebrates colonized these structures very rapidly. The results indicate that resilience of the stream benthos after physical disturbances, such as spates is high. Colonization patterns of numerous taxa differed significantly between summer and winter exposures. Seasonally varying colonization rates indicate that the disturbance response of taxa varies throughout the year and throughout the life cycle of lotic invertebrates. If these changes are correlated with seasonal discharge dynamics, they can be interpreted as an adjustment to the disturbance regime. Findings are discussed in regard to the practicability of small-scale experiments for the investigation of disturbance phenomena in streams