Fig. 1
Schematic drawing of the laboratory tidal micro-ecosystem. The tank was filled with 20 l artificial seawater. Petri dishes containing Wadden Sea sediment were placed onto a rake which was moved down into or out of the seawater by a timer-controlled motor. The Petri dishes were notched so that the water could drain off completely. Low intensity white light with a photon-fluence rate of 10 µmol m−2 s−1 was provided from above