Effects of short-term flooding on aquatic and terrestrial microeukaryotic communities: a mesocosm approach

Freshwater and soil are not strictly isolated habitats. In particular, floods may facilitate the exchange of organisms and nutrients. Flooding can have both a stimulating and a harmful effect on the organisms of the respective habitats. The effects of short-term flooding on microeukaryotic communities in the aquatic and terrestrial habitat have so far been scarcely studied. Here, we investigated the effect of a 24 h artificial inundation on the microeukaryotic community composition in AquaFlow mesocosm systems. We investigated the shift of community composition based on molecular amplicon diversity both on soil and water during flooding and for a period of 12 d after flooding. Community composition was, as expected, strongly different between soil and water. Flooding had a significant effect on the freshwater community, whereas the soil community was hardly affected. In particular, we observed a transfer of nutrients from the terrestrial habitat into the aquatic habitat and identified similar to 50 taxa that were transferred by the flooding event. This effect of flooding was, however, overlaid by shifts of the communities with time, presumably reflecting an acclimatization to the conditions in the AquaFlow systems.