How would a world entirely covered in oceans get the nutrients to support life? On earth nutrients flow from the land to the ocean. Life on oceans need those nutrients to trive.  

I was trying to think how an ocean world might support life if there was no land to provide the necessary bootstapping nutrients.

Any thoughts?
If the planet is geologically/volcanically active hydrothermal vents are a way by which nutrients, in the way of minerals and chemicals, can enter the ocean.

Certain types of bacteria can consume the minerals and such bacteria form the base of a food chain. Also, the heat from the hot water can provide energy to life forms.