Without decomposers, dead leaves, dead insects, and dead animals would pile up everywhere. Imagine what the world would look like! More importantly, decomposers make vital nutrients available to an ecosystem's primary producers—usually plants and algae.
Interactions may be commensalism, mutualism, or parasitism.
They are warned about contracting Toxoplasma.
I'm not completely sure but I came up with Carbon dioxide, methane, water vapor, and nitrous oxide. I hope this is right and maybe helps you. Good luck!!