plants for a niche; a duck greywater marsh

I am thinking about building a modified greywater marsh for some ducks. ( There would be NO GREYWATER ENTERING THE MARSH. It would just be filtering duck manure.) The marsh would be built as usual, but in one part, the gravel would be scooped away, making a little pond for the ducks. Part of the marsh would be fenced off limits to the ducks. Overflow from the marsh would flow into swales to fertilize and irrigate the garden, but first it might flow into a small duck free pond. The whole thing would be in the shade of a tree, and I am in zone five.

So, I would need various types of plants:

Plants to live in with the ducks in the marsh. They would have to survive ferocious plant eating bills, (perhaps by growing up, and the raining down edible fruit, leaves, or seeds on the ducks below?), like growing in the shade, and be able to grow in gravel topped with wood chips, with nitrogen rich water underneath. Ideal, they would be very multifunctional.

Plants to live in the marsh without the ducks. Would need to cope with all of the above, except the ducks.

And, floating plants in the small pond to harvest nitrogen and turn it into duck feed. I am thinking duckweed for this, but can it stand some shade?

Remember that this is Colorado, and our intense sun makes shade a rather different proposition from other areas.

Any plant ideas are welcome.

How big are we talking?

Small duck ponds can be shaded fairly easily if you don't care how it looks--a mesh landscapers tarp and a couple tarp poles or hoophouse hoops. You can buy one of those triangular shadeclothes if you want it a little prettier. You can shade a corner of a larger pond the same way.