How to work on quicksand?

Working on a novel ecosystem such as the Marker Wadden can be very adventurous: the soil is sometimes so soft you can’t walk there. Getting stuck in the quick sand is a returning theme. So how are we working there? An overview of our struggles and solutions 🙂

Not being able to walk and not being able to swim: working on quick sand as soft as yoghurt:

  • Using an inflatable boat – some water on top required! Con: the boat is punctured often.
  • Using a specially designed mud sleigh. It must be operated by a couple of people – the best role is obviously sitting in the sleigh.  
  • Moving on floating insulation materials/ body boards – not very stable, but you can move through the whole research plot!

When the soil is a bit more consolidated, you can often walk at places and then suddenly sink into the mud. How to prevent this or handle when this happens?

  • Using snow shoes
  • Making board walks if you constantly have to walk along the same route
  • Or when the damage is done and you got stuck: Crawling through the mud!

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.

Estimating emergence of aquatic insects from different habitats

In April 2019, 18 emergence traps where placed at Marker Wadden to estimate the amount of aquatic insects emerging from aquatic, semi-aquatic habitats. In particular, we are interested in the amount of nutrients and energy transported between water and land and how it changes over the season.
Already in 2018, huge amounts of flying insects could be observed at Marker Wadden. The most dominant species belong to the family of non-biting midges (Chironomidae). Both larvae and adult animals, representing an important food source for different bird species, as well as for fish, spiders, beetles and other insects.

In charge of this Project is Yvonne Kahlert, University of Groningen.

Emergence traps (white tent) on shallow water.
Students from the University of Groningen placing an emergence trap in vegetated areas of Marker Wadden.

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