Broken Ring and Atmosphere

If the Ring is broken how does it maintain its atmosphere? There are some animals in the gameplay demo and I wonder how they would survive without it. Has it been described in the EU?

we’ve seen from the control room that each region of the ring can be controlled in Halo 2 where they literally space an entire region. I imagine a lot of the ring in still perfect and working order i would think that we’d see a different landscape when/if we go nearer to the actual damaged part of the ring.