In broad terms, habitats in the ocean can be split in two, the seabed and the water column

This is where primary production takes place (plant growth in the form of plankton and algae), and where one finds fish and other animals that are either herbivores or carnivores. 

The seabed is rich in life, and the Mareano survey project has provided new knowledge about the seabed. Significant biological production also occurs in the water column. One example is the annual herring spawning (in Norwegian), often termed “the greatest adventure of spring.” Combined, life on the seabed and in the water column comprise the ocean's ecosystem (in Norwegian).