Springtails of flooded meadows along Matsalu Bay and the Kasari River, Estonia

The brackish conditions of the Baltic Sea create special habitats in coastal meadow soils surrounding Matsalu Bay. The floodplains of the Kasari River are periodically flooded by fresh water. In the eastern part of Matsalu Bay and in the delta of the river, brackish and fresh water can be mixed due to strong winds from the west or due to exceptionally large amounts of fresh water flowing from the river in the spring. The aim of this study was to find out how flood and habitat soil salinity influence the abundance and diversity of springtail communities on flooded meadows. The studied meadows were grouped to four types by distance of study sites from the open sea and by soil electroconductivity: fresh floodplain, wet floodplain, transitional and coastal grasslands. Springtail communities on temporarily flooded meadows along Matsalu Bay and the Kasari River consist of 20 − 30 species per meadow type, species Metaphorura affinis, Willemia anophthalma, Brachystomella parvula, Folsomia quadrioculata were abundant in soil of all types of meadows. Our results confirmed that flooding is an important factor in shaping soil communities. Long-term flood had strong negative effect on springtail communities' abundance and diversity. However, there was no such negative effect of flood on meadows with shorter flooding period, for several species the flood was positive factor increasing the abundance. Flooding brackish sea water is the reason for higher electroconductivity of meadow soils negatively influencing the diversity of springtail communities. The abundance of several species was the highest in soil of coastal grasslands (Agrenia bidenticulata, Folsomia sexoculata, Podura aquatica, Sminthurides schoetti) despite the higher salinity of soil. The impact of flood duration on the composition of communities by life forms seemed to be less important than the impact of soil salinity, saline soil was not a suitable habitat for euedaphic springtails.