Biodiversity of the oceans
Most of the biodiversity (number of species) of the oceans still remains a mystery. It is believed that less than 0.1% of bacterial plankton diversity has been documented. The deep-sea sediments are considered to be yet another source of undiscovered biodiversity. While the diversity of species is greater on land, the number of phyla is greater in the sea.
The sheer size and volume of the oceans makes it a major player in the global climate, and much of this can be attributed to its biology. Carbon dioxide is the major reenhouse gas and photosynthesis is the fundamental mechanism by which it is sequestered in tissues of living organisms and their dead matter. The oceans contain about 38 x 1012 tons of soluble carbon dioxide, which is ~60 times more than that in the atmosphere. The magnitude of primary production, export to the deep sea, and the production of calcium carbonate by marine organisms are the major biological factors in determining the role of the oceans in the global carbon cycle. Understanding details of these processes remains a major challenge in biological oceanography.