A first pioneer-species survival experiment was carried out by planting relative large Spartina and Scirpus seedlings (11 weeks old) in July 2015 at the 15 locations where we monitor the abiotic sediment properties in Perkpolder (see: Sediment properties: figure 1). That is at each of these 15 locations, two plots of 1m2 each were established: in one of the plots five Spartina seedlings were planted; in the other plot five Scirpus seedlings. Their survival over time was subsequently measured. The survival curves show that Scirpus seedlings died much faster than the Spartina seedlings (figure 1). It has not been possible to explain spatial variability in Spartina seedling mortality (data not shown).