Blog entry by Rémon Saaltink - PhD student
Already six months ago, I posted that I successfully collected 1500 liters of mud and clay from the lake’s bed of Markermeer. I used this mud and clay for my first “pilot” experiment. The experiment is now running for five months and will end in January. The results of this experiment will enable me to choose which direction of research is most fruitful for the remainder of the project and what type of research questions are important for the Marker Wadden itself. I can tell you that a lot of interesting findings resulted from this experiment. But before I go in to (modest) detail, just a little recap. What was my research about anyway?
To explore which processes are important, a small-scale pilot experiment was conducted where I tested many treatments and measured a lot of variables. Because the water chemistry of lake Markermeer is rather unique in terms of metals and nutrients compared to other lakes in the Netherlands, I tested a groundwater fed system (Markermeer water) and a rainwater fed system. I constructed two basins filled with these two types of water. In these basins, I placed pots filled with three types of sediment: 1) fluffy mud, 2) fluffy mud mixed with sand and 3) underlying Southern Sea deposit. The pots were perforated at the bottom so that water could penetrate into the sediment. Reed seedlings (Phragmites australis) were planted in half of these pots. At two different depths in the pot, I installed rhizons to extract porewater: 1 cm (oxic) and 11 cm (anoxic) depth. With this design I could monitor the effects of porewater-, soil- and plant quality through time and determine important biogeochemical processes. Especially when this mud is desiccating and oxidizing.
Especially in the first few months, the reed was growing pretty fast (see Figure below). It appears that reed is growing faster on fluffy mud than on the other sediment treatments. The growing speed of plants is important as it is indirectly linked to soil formation and consolidation on the future islands.