Fauna of Europe of the Baltic Sea has led to the evolution of many slightly divergent species, such as the Baltic Sea herring, which is a smaller variant of the Atlantic herring. The most frequent benthic species are "Saduria entomon" and "Monoporeia affinis", which is originally a freshwater species. A great part of its bottom is anoxic and without animal life. The Baltic Sea and North Sea are also home to a variety of marine mammals (common seals, grey seals). Europe contains several important freshwater ecoregions, including the heavily developed rivers of Europe, the rivers of Russia, which flow into the Arctic, Baltic,
History of the North Sea Danelaw, carving out his own kingdom. Harthacanute of Denmark and England was the last Viking king to rule over a territory spanning the North Sea. After Harthacanute's death, the kingdom broke apart. With the rise of William the Conqueror the North Sea began to lose its significance as an invasion route. The new order oriented most of England and Scandinavia's trade south, toward the Mediterranean and the Orient. The Baltic Sea became increasingly important for northern Germany and Scandinavia as well as the powerful Hanseatic League began to rise. Though the Hanseatic League was centered in the Baltic, it also