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 outside their normal range and into more northern waters causing an array of ecological, economic, and fishery management problems. William Cheung, a professor at the University of East Anglia, in the Sea Around Us Project at the University of British Columbia concluded that the oceans were warming at an average of per decade and at per decade in tropical waters. However, the north-east Atlantic has been warming at a rate of per decade. Cheung and his colleagues were able to get these estimates by using the mean temperature of catch. They used data from 990 species within 52 marine ecosystems