I've been thinking about this image since I first saw it. You may have seen the photo of the reflection in a pond that I posted the other day. When I saw the slight ripple in the water in your image, it reminded me of mine. That made me wonder if these images would have benefited from a longer exposure to smooth out the water. A look at the exif for my photo shows that the lighting was too bright to slow the exposure enough to make a difference. Your night shot, however, would work well. The exif on your photo of the bridge shows f/4, 1/2 second, ISO 800. You could slow the shutter by three stops by setting the ISO to 100 and another four stops by going to f/16. That would get your shutter speed all the way to 60 seconds, which would probably be longer than needed and probably longer than your camera can do. Using a slow shutter speed to flatten out ripples is something I've never done with a shot like this, but I think it would be interesting to try.