Lister Tief, the Heverstrom, the Purrenstrom, the Wesselburener Loch or the Piep. Outside the mudflat area runs a constantly strong current from south to north, coming from the southern North Sea and going on to the Norwegian Trench. Owing to the river mouths of several big European waters (like the Rhine or Elbe), the current´s salinity of 20–30 psu lies below that of the ocean, and above that of the river mouths. Since inhabited regions are not part of the national park, the land areas are nearly completely covered with salt marshes and a small part contains sandbars and dunes. The salt marshes cover over 10.000 ha, of which 70% developed on land protected by breakwaters, 10% are situated on the downwind side of the islands and the remainder formed around the Hallig Islands. Between 1988 and 2001 the area of the salt marshes expanded about 700 ha. Widely natural and use-free salt marshes can be found around the islands and ashore around Schobüll and St. Peter-Ording. The whole Wadden Sea is ruled by an Atlantic climate. Strong westerlies and the heat storage capacity are determining factors which often generate strong winds, but at the same time balance the temperatures. Thus occur cold summers (July: 14,5 °C) and mild winters (January: 1,8 °C). Flora and fauna Saltwater, tide and strong winds characterize the environment in the Wadden Sea area. Only extremely specialized organisms can cope with the conditions. Fishes, breeding birds and most of the marine mammals living in the Wadden Sea use it as nursery. Besides that, giant flocks of migratory birds visit the Wadden Sea regularly in spring and fall using it as a food source. In the Wadden Sea of Schleswig-Holstein you can find about 700 plant and 2500 animal species, of which 10% are endemic. Plants Eelgrass is the only flowering plant in the Wadden Sea which is capable of living under water. In 1930 most of the eelgrass in the Atlantic Ocean was killed by an epidemic. The eelgrass stocks haven't regenerated since. The plants are mainly located in the northern part of Schleswig-Holstein’s Wadden Sea and cover an area of 6000 ha. Compared to 705 ha in Lower Saxony and 130 ha in the Netherlands, it is quite large. Also in contrast to the worldwide trend of decreasing eelgrass stocks, the stocks in the Frisian Wadden Sea area are increasing. During the maximum spatial