Tropical oceans have the greatest biodiversity, but they have the least biomass -- they have less total life but more kinds of life.
This is because tropical oceans are warmer and do not have as much oxygen or carbon dioxide in the water as colder areas do. This means that fewer microorganisms can grow and therefore there is less food for larger animals.
At the same time, though, there are more different kinds of animals that are exploiting different little niches in the biome so that they can survive even in the absense of abundant nutrients.
Since the Pacific Ocean is spread over 135,663 kms of coastlines of North and South America, Asia, Australia, we can say that this is the ocean that represents the most the biodiversity of ocean and marine life.
We can find in here, from the greatest coral reefs of the world to the famous whales (blue whale, humpback) and ferocious predators, the fierce sharks.
There are various speciesof fish, crustaceans and plankton, some of them being in danger of extinction.