I'm wondering, why aren't oceans covered in photosynthesizing organisms, like land, or even some stationary ponds are? There's some algae of course but most sunlight seems "wasted". Is it really mechanical (waves break them all up)?
Maybe it's the other bits? Like sure a ton of photonic energy is available, but cyannobacteria need P, N, and other elements like Fe. In fact, I recall something about geohacking by just dumping a bunch of Fe into the ocean to do exactly what you're thinking...
