Expedition Marker Wadden

From the 13th till the 17thof May, a big biannual field campaign took place at the Marker Wadden. With a team of 6 researchers and students, a lot of measurements were taken to study the development of the marsh vegetation and the corresponding food web in two running experiments.

Students doing vegetation surveys

In one of these experiments, we are examining which bottlenecks we have to overcome when starting a novel ecosystem such as the Marker Wadden. Therefore, we planted tussocks of reed (the goal vegetation) last year inside and outside exclosures – these are cages where geese are prevented to enter. Besides, we created similar research areas where we let the vegetation develop from scratch. The reed beds are intensively grazed by geese: they prevent their favorite food to grow into the desired marshes! Besides the planted reed, up to 10 different plant species were found after 1 year of marsh development!

Left: an exclosure with planted reed. Right: open area where we also planted reed, but where all the plants are eaten by geese.

Next to identifying and classifying the vegetation types, we are also interested in how the foodweb develops in the reed marshes. Do we find similar species in different vegetation types? And how soon does which type of species arrive? To study this, we sampled the water fauna inside and outside the vegetation types and we placed emergent traps: small tents used to catch insects. Especially in the plots where we planted reed, many musquito’s, spiders and beetles were found. 

Catching some fauna!

Other measurements we did, were taking soil samples to look at the organic matter content, porewater samples to look at the nutrients in the soil and determining the height of the marsh with a very sensitive dGPS. The last was performed to get insight in the effect of marsh vegetation on the subsidence of the soil. Because the islands were built with very fine sediment, the soil will subsiding a lot the coming years. By measuring the effect of plants on the soil, we can improve the models to estimate the rate of soil subsidence and to incorporate this in future building activities. 

After a week of long field days, with a lot of work but also with a lot of fun, it is time to head home. The coming months, I will be busy with processing the many samples we took.

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