The present thesis approaches the question about the role of soil fauna, in particular annelid worms (Oligochaeta: Lumbricidae, Enchytraeidae), on nutrient mobilisation during an inundation. Four laboratory experiments shed light on the annelids' impact on nutrient dynamics in floodwater. Terrestrial-aquatic microcosms were composed of undisturbed soil cores and river water from the field. These microcosms were inoculated with natural densities of earthworms and/or enchytraeids. A two-year field survey in three floodplain meadows in Northern Germany shows the strong dynamics of annelid populations with alternating hydrological extremes (floods and drought). A literature review compares survival strategies of soil invertebrates in flooded grassland.