Decomposers break down dead plants or animals and return back the nutrients to the ground. You might say "Ewww", but you know what they keep the Earth clean. In the ocean they can help prevent water pollution. So they are helpful a lot to the Earth. When organisms die in the ocean, the decomposers will decompose or break down it, then it will return the nutrients to the ground. Then can a new food chain start? The answer is yes, it starts a new food chain. Look at the picture below.