I was reading a news article today (http://www.wvec.com/news/topstories/stories/wvec_local_011808_oyster_gardening.342f7936.html) about a kind of gardening I've never encountered before. Oyster gardening is good for the environment and apparently, not that complicated. Oysters will help filter the bays mentioned in the article, improving overall water quality. It's $25 to get a bag of oysters and the article states that it takes one tiny bag to grow a trillion oysters in a year!
My in-laws have been doing this for a bazillion years! They live on the Patapsco River in Maryland, prime oyster land. They also use the shells for compost. I think some areas around here also use ground oyster shells in making pavements. We are having a real oyster shortage, though. Also, it's a weird thing... they have discovered that natural (not farm raised) oysters seem to like the MOST polluted areas of Norfork, Virginia! So, they are thriving there, but you can't eat them! A little Darwinism, anyone?