The case for "subsidizing" shellfish

I've seen quite a few articles like this one titled "Who Should Clean Up Big Ag's Mess?" which look at the problems associated with farm waste contaminating local ecosystems and also causing problems for downstream human use of the water. Apply Coasian economics and it seems to me that there's a decent case for charging agricultural operations for the harmful effects of their runoff and using this to subsidize the production of shellfish. Shellfish operate as filter feeders, and the difference that they can make to water quality is quite apparent and can be seen in the following timelapse recorded over a 90 minute interval:

This cleaning process can happen with "no demonstrable negative impacts on the bay's ecosystem, harbor seals or native eelgrass" as concluded by a National Research Council report on one project. It's worth noting that the same can be said also of seaweed.

Is more shellfish and seaweed how your diet is likely to change in years ahead. I'm a lot more positive about their potential than I am about some of the fish species currently being farmed - this solution can even be applied to fish farm waste.