Effect of flooding by fresh and brackish water on earthworm communities along Matsalu Bay and the Kasari River

The continuum of Matsalu Bay and the Kasari River located on the east coast of the Baltic Sea represents a complex mosaic of marine, coastal and inland wetlands (shallow sea waters, estuarine waters, coastal lagoons, an inland delta and flooded meadows). Earthworm communities were studied at five sites on the southern shore of Matsalu Bay and the banks of the Kasari River under different salt water regimes (brackish or fresh water). Sample sites were located along a flooding gradient (distance from the sea). Flooding duration appears to have the strongest negative impact on the abundance of earthworm communities, which largely depends on species' tolerance of high moisture content and low soil aeration. The brackish conditions of the Baltic Sea create special habitat conditions; the sea water salinity and periodic flooding have a significant negative impact on earthworm communities.

► The water salinity and periodical flooding create specific habitats for earthworms. ► Low salinity decreased the abundance and diversity of earthworms. ► Epigeic species were more tolerant to the limiting effect of flooding and salinity. ► Endogeic species were more sensitive to submersion.