Interesting idea. Meets the challenge and has two potentially great subjects. The composition is a bit off to me. Perhaps if you'd used the bubble like a lens so we could only see the tree through the bubble, that'd add another layer of interest. Also the focus is just not there.. Looks as though you were moving when the image was taken? Perhaps this is intentional but I don't think it does the image justice. The use of natural light is okay, its a little hard to tell since many of the details are blurred out. I like the idea behind it, I like the execution in general but the technical aspects are lacking. I think the border is a bit too much for this image too, nearly dominates. I gave a 4.
Please don't be offended by this comment. I am making an effort to comment on all images that I scored below a 4. Although your image meets the challenge requirements, I believe attention to the following might have served to make it work better for me:
I'm guessing that you were going for the motion effect with the blur; but with nothing in focus it kind of makes me dizzy.