Dumb me! I deleted before I got the name of the writer. But someone wrote about introduced clams or oysters that could filter San Francisco bay every 24 hours. How many critters would it take to do the job? Six? Nineteen? several million? When SF is finally cleaned up, do they die or keep filtering? Could they do the same for Chesapeake Bay? If it can be done, why isn't it being done? The Question Man