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Freshwater Ecoregions

Some of the most diverse vertebrate assemblages on Earth occur in freshwater communities of the Amazon and the Orinoco River basins. Over 3000 species of fish are estimated to occur in the Amazon Basin alone.
Small river basins are represented by 21 ecoregions, large lakes by 4 ecoregions, small lakes by 7, xeric basins by 3 ecoregions, large river headwaters by 5, large river deltas by 6 ecoregions, and large rivers by 7 ecoregions.