Baltic Sea as species in 2005 and 2018 respectively, having formerly been confused with more widespread relatives. The tiny Copenhagen cockle ("Parvicardium hauniense"), a rare mussel, is sometimes considered endemic, but has now been recorded in the Mediterranean. However, some consider non-Baltic records to be misidentifications of juvenile lagoon cockles ("Cerastoderma glaucum"). Several widespread marine species have distinctive subpopulations in the Baltic Sea adapted to the low salinity, such as the Baltic Sea forms of the Atlantic herring and lumpsucker, which are smaller than the widespread forms in the North Atlantic. A peculiar feature of the fauna is that it contains a
History of the North Sea dumped in the Skagerrak and the Baltic, conventional weapons (grenades, mines, bazookas, and cartridges) were sunk in the German Bight. The estimates vary widely but it seems to be clear that more than a hundred thousand tons of munitions were sunk. The Maunsell Sea Forts were small fortified towers built in the Thames and Mersey estuaries during the Second World War to help defend the United Kingdom. One of which on HM Fort Roughs is now occupied by the controversial Principality of Sealand. Post Second World War period, the North Sea, bounded entirely by NATO allies became completely peaceful whilst