Which trophic level of a marine food chain breaks down organisms from all of the other levels?

Decomposers break down the dead decaying body parts of all other organisms. They are also known as saprophytes. Apart from this, the top consumers like sharks, dolphin etc. eat away the smaller trophic organisms like squids, fishes etc,. But after the death of the tertiary consumers, they are also decomposed by the decomposers.