I'm liking this idea, so I think I'll throw this in. I hope it's okay for me to mention some insects, since they're essential to the whole "reclaiming matter" thing. If it's a problem I can change it.

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Name: Sea Of Swarms

Geography: The Sea Of Swarms is a vast ocean, and what it lacks in solid land it makes up for in sheer expanse. Islands dot the waves, sandy beaches covering the vast structures of bone that exist to keep the sea's waters from flooding into the innards of the world. The water is not salty, but full of microscopic particles of bone shaved off over thousands of years. This gives the water a special nutrition to it, and the rivers that flow into the countless islands seed the land with nutrients. Within the center of the larger islands and dotting the seas are massive sinkholes that lead into the planet, allowing it to take advantage of the interesting land that has formed on it.

Method of Recycling Matter: Massive swarms of insects and tiny sea animals take any old matter their instincts choose to, then return to one of the many sinkholes to deliver the matter to the planet for consumption. Ocean sinkholes near constantly draw in water, allowing the planet to reclaim some of the bone the water has taken from it.