Bodden

Bodden are briny bodies of water often forming lagoons, along the southwestern shores of the Baltic Sea, primarily in Germany's state of Mecklenburg-Vorpommern. These lagoons can be found especially around the island of Rügen, Usedom and the Fischland-Darss-Zingst peninsula. Some of them are protected reserves, forming the Western Pomerania Lagoon Area National Park.

They have a distinctive geological origin and are enclosed by peninsulae, spits and islands, leaving only narrow connections to adjacent bodden or the open sea. Freshwater inflow from the mainland and saltwater inflow from the open sea, which depends on wind direction and force as well as the proximity of the bodden to the sea, result in fluctuating salt gradients and distinctive ecosystems.

During the Littorina Sea transgression, an island archipelago was formed by the carving of narrow glacial basins and channels resulting from meltwater. Bodden were formed in a comparatively short period between spits and offshore sandbars. These shallow glacial scoops were then subjected to extensive sedimentation during the Holocene, resulting in lakes with depths of no more than 4–6 metres. Thermal and saline stratification is extremely unstable under these conditions, and bodden have the typical dynamics of small bodies of water with a sea connection, which is a rapid filling and draining due to tidal and wind action, and inflow of fresh water. The frequent movement of water can lead to a scouring effect, but can also with heavy pollution show a tendency toward eutrophication. Due to erosion of cliffs and sedimentary deposition, the shape of the bodden coasts remains unstable. Sudden changes have been caused by stormfloods, which repeatedly closed connections to the sea or opened new ones in the past.