Compared with an average seabed, the tidal flat comprises ten-times more animals by weight. With its total area of 4,700 km2, the tidal flat forms a gigantic food basket. The conditions for the rich animal life are primarily caused by the tidal waters, which bring nutrient-rich waters into the shallow Wadden Sea twice a day. The foundation for life is high occurrences of microscopic algae, especially diatoms, that comprise the first link in the food chain. The diatoms appear floating in the water, on the surface of the tidal flat and buried below the mud. The diatoms give the tidal flat its brown colour.
Varied seabed creates life
Most life in the Wadden Sea is buried below the tidal silt. However, there has to be the right mixture of sand and clay in order to create the silt. The largest quantity of animals is found in places where silt constitutes one-fifth of the seabed. If the seabed consists of pure sand or pure silt, there are only few animals. Most of the animals in the tidal flat are very small, but they often appear in huge quantities. One cubic centimetre of the tidal flat may contain more than 100 roundworms. Above the surface of the tidal flat, we find the laver spire shell snail (hydrobia ulvae) which is only a few millimetres in length and is therefore often overlooked. However, there are huge populations of these small snails. Almost 120,000 snails can live on just one square metre.
The builders of the tidal flat
One of the most numerous species of the tidal flat is the small mud shrimp, which is found in populations of almost 100,000 individuals per square metre. The mud shrimp lives in burrows in the seabed and eats decomposed plant material and bacteria, which it filters from the water or collects from the seabed. The digging