Their survival was somewhat of a surprise. Some coastal species, like mussels, barnacles, and anemones, clearly need to latch on to a surface as part of their normal life cycle, and so find the open ocean inhospitable. Other species that stick near land, while mobile, may rely on nutrients or prey that is limited to coastal waters. But there are several other potential barriers, such as nutrient availability, that could limit species' survival in the deep ocean and thus provide a barrier that separates species on opposite shores of the ocean.