From Marine Biodiversity Wiki
Species diversity is a measure of the number and frequency of species in a community. Biodiversity is most commonly described in terms of species diversity, and particularly in terms of species richness (the number of species in a given habitat). In the ocean, there is a plenty of information on marine mammals (seals, whales, dolphins, porpoises) and fish, while only recently are scientists beginning to understand the extreme diversity present in micro-organisms such as bacteria and phytoplankton.
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