The temperature is favourable, and food is abundant. Life on the tidal flat follows the changing seasons. In the summer, there is a rich animal life on the tidal flat. The birds make a short stop to feed before they continue their journey, or they decide to stay in the area for the winter. 12 million birds pass through the Wadden Sea every year. The Wadden Sea is an important resting area for many species of birds migrating from their northern breeding grounds to southern wintering areas. The rich animal life on the tidal flat is a sumptuous feast for water birds.
The lugworm can survive losing its tail many times. The lugworm is ‘off the hook’, but has lost its tail. The fish take advantage, but if a fish gets a good bite on the lugworm’s tail, the tail will fall off. The lugworms deposit faecal mounds by sticking their tail out of their protective burrows, and when they do this, they are particularly exposed. Sole and herring also use the Wadden Sea as a kindergarten. Lugworms are an important source of food for the fish. From there, the fry flow with the current into the Wadden Sea, where they live for 2-3 years and grow bigger by gorging on the infinite supply of prey, before they move on to the North Sea. The plaice spawns during winter in the open waters south-west of the Wadden Sea. The Wadden Sea is a growing site for several species of fish. The lugworm’s burrows lead water into the sand, which makes it possible for many other organisms to have their habitat deep down in the seabed. It eats sand and exploits the microscopic algae found on the surface of the sand particles.
The lugworm lives in the tidal mud in a U-shaped tunnel. Evidence of its activity, the characteristic swirls of sand, can be found everywhere. The diggingīehaviour of the mud shrimp is important for the chemical decomposition of the tidal flat and the stability of the seabed. The lugworm is also important for the tidal flat. 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. 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. Almost 120,000 snails can live on just one square metre. However, there are huge populations of these small snails. 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. One cubic centimetre of the tidal flat may contain more than 100 roundworms. Most of the animals in the tidal flat are very small, but they often appear in huge quantities. If the seabed consists of pure sand or pure silt, there are only few animals. The largest quantity of animals is found in places where silt constitutes one-fifth of the seabed. However, there has to be the right mixture of sand and clay in order to create the silt. Most life in the Wadden Sea is buried below the tidal silt. 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. The foundation for life is high occurrences of microscopic algae, especially diatoms, that comprise the first link in the food chain. With its total area of 4,700 km 2, 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. Compared with an average seabed, the tidal flat comprises ten-times more animals by weight.
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