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,
Migration of marine species in the Northern Atlantic Ocean as black carbon also catalyze the warming effect as they are unreflective and absorb energy from the sun supplementing greenhouse gases in the warming effect. These combined factors are warming the Earth's land as well as the oceans. Many fish species possess a certain range of water temperature that they are able to tolerate which is causing species to migrate to different areas where the water temperature is livable. The warming of the Atlantic Ocean is causing many fish species to shift north towards once cooler waters so they can live within their temperature range. Tropical species are being found