To encounter invasive species, visit the Mediterranean. It had the most alien species among the 25 regions surveyed, with over 600 (4 percent of all the species inventoried), most of which arrived from the Red Sea via the Suez Canal.
Relative to their volume of water, the Baltic Sea and South China Sea were particularly diverse in species. Relative to their seabed area, South Korea, China and South Africa had the most sea species.
Fish made up 28 percent of species in the Tropical West Atlantic and the Southeast United States, but only 3 percent to 6 percent for the Arctic, Antarctica, Baltic and Mediterranean.
Plants and algae (mostly algae) contributed about one third of species in the Baltic, Arctic, Atlantic Ocean around Europe, and the seas off Western Canada, but accounted for relatively few of the species in the seas around Antarctica, the Caribbean, China's waters, the Humboldt Sea, the upwelling of cold, nutrient-rich water along the Peruvian and Chilean coast, the Tropical Eastern Pacific, and the Tropical Western Atlantic.
The number of unique "endemic" species provides another measure of biodiversity. The relatively isolated regions of Australia, New Zealand, Antarctica and South Africa had the most endemic species. They may have suffered fewer extinctions from climate cooling thousands of years ago during glaciation events. Or species from regions that escaped glaciers may have reached them more easily when the glaciers melted.