Vistula Lagoon million. However, major ecological considerations stand in the way. For example, mammal migration along the lagoon could be disrupted. Also, the inflow of brackish waters from the Baltic sea could result in serious unbalancing of the lagoon's freshwater ecosystem. From 1772 until 1918, the lagoon was part of the Kingdom of Prussia, which had become part of the German Empire in 1871. Between 1920 and 1946 it was split between Germany and the Free City of Danzig. At present state since 1945 its eastern part belongs to Russia (formerly USSR), Poland has 43.8% of its area at lagoon's western side.
Muthupet Lagoon can be observed well with the exposure of oyster beds and roots during low tide. The tidal fluctuations are playing a major role in dispersing the mangrove seeds. Dense mangroves mostly cover the lagoon shore. The islets are found on western side which are submerged during high tide. The salinity is the major environmental factor, controlling zonation of Muthupet mangrove forest. Avicennia marina is the conqueror of the forest which is found as a single dominant species. Southern side (mud flat) separates the lagoon from adjacent sea that also leaves a permanent mouth of lagoon with seasonally opened shallow waterways.